Title: Thermodynamic evaluation of a distributed energy system integrating a solar thermochemical process with a double-axis tracking parabolic trough collector
Abstract: A new distributed energy system integrating a solar thermochemical process with a double-axis tracking parabolic trough collector is proposed to address the challenges on large seasonal variations of solar-to-fuel efficiency and insufficient utilization of solar energy in exiting distributed energy systems. Low-energy level discontinuous solar energy is upgraded into the chemical energy of syngas via the solar thermochemical process, which is easy to be stored. The double-axis tracking parabolic trough collector is deployed to the solar thermochemical process to eliminate the cosine loss completely to increase the annual thermodynamic efficiency. With the consideration of the variation of solar energy, the coupling between user's loads and energy outputs in the proposed system is investigated, and the favorable on-design and off-design thermochemical performances are numerically validated. Results indicate that the solar fuel production and the solar power production in the proposed system increase approximately 27% annually as compared with the reference system.
ISSN: 1359-4311
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Record 2 of 233
Title: Compression performance optimization considering variable charge pressure in an adiabatic compressed air energy storage system
Source: ENERGY Volume: 165 Pages: 349-359 DOI: 10.1016/j.energy.2018.09.168 Part: B Published: DEC 15 2018
Abstract: In an adiabatic compressed air energy storage system (A-CAES), the storage pressure persistently increases during the energy storage process causing deteriorate of the charge performance under off design operating conditions. The compression performance with variable backpressure is essential for the energy storage efficiency and density of A-CAES. A thermodynamic model with energy loss analysis is built up to investigate the performance of a multi-stage centrifugal compressor used in an A-CAES (about 6.0 MW). By energy loss analysis, the blade inlet angle is first focused on to improve the disadvantages of narrow operating conditions and low efficiency at large mass flow rate of the original compressor. Then, the variable rotating speed study is applied on to increase the energy charge efficiency with a wide storage pressure range. Using the thermodynamic model, the available rotating speed is determined to be 0.85-1.05 of design value. Furthermore, the rotating speed is optimized to achieve the best efficiency under variable storage pressures and the corresponding correlation is fitted. Using the optimal rotating speed, the compression efficiency can be kept above 80% while the exergy efficiency is above 82% during the whole energy storage process with a wider storage pressure. (C) 2018 Elsevier Ltd. All rights reserved.
ISSN: 0360-5442
eISSN: 1873-6785
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Record 3 of 233
Title: Fusibility characteristic and flow properties of semi-char from industrial circulating fluidized bed gasification
Abstract: The carbon conversion of fluidized bed gasification (FBG) has been restricted by the entrainment of high-carbon-containing semi-chars. Thus, the concept of FBG combined with combustion melting system was proposed to make effective use of the gasified semi-char. However, long-term running of the melting furnace was confined by severe slag plugging. The objective of this research is to understand the ash fusibility and flow properties of the semi-char, and provide some guidance for the design and operation of the integrated system. Two typical semi-chars from industrial circulating fluidized bed gasifier were chosen as raw materials, and the major results are as follows. The ash fusion temperatures (AFTs) of Liaocheng semi-char (LCSC) are about 100 degrees C lower than Sugian semi-char (SQSC), mainly caused by its higher basic element content. As the particle size increases, the AFTs of SQSC ash first increase sharply, and then rise smoothly, whereas no obvious differences are found for LCSC ash. The effect of atmosphere on ash fusibility was also studied. The AFTs appear in the order of oxidizing > inert > reducing, which should be related to the variations in Fe2+/Fe3+ ratios under different atmospheres. The viscosity-temperature curves show that the LCSC ash tends to form glassy slag when completely melted, which turns out to be plastic slags for SQSC ash, probably resulting from mullite crystallization. Heating stage microscopy has been considered an effective way to in situ observe the melting and crystallization process of ashes. The preliminary results indicate that dendrite particles tend to strengthen internal bonding in the molten slags, promote the formation of solid phases, and accelerate the growth in viscosity.
ISSN: 0016-2361
eISSN: 1873-7153
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Record 4 of 233
Title: NO emissions under pulverized char MILD combustion in O-2/CO2 preheated by a circulating fluidized bed: Effect of oxygen-staging gas distribution
Abstract: MILD (moderate or intense low-oxygen dilution) combustion of pulverized char in O-2/CO2 was achieved by preheating fuel in a circulating fluidized bed (CFB). The purpose of this research was to study effects of oxygen-staging gas distribution on NO emissions under MILD combustion of pulverized char. First, the preheating characteristics were evaluated, including the conversion ratios of each fuel component and the composition of the coal gas. To calculate the nitrogen balance in the preheating process, the gas in the loop seal was changed to O-2/N-2. The results indicate that the conversion ratios of each component increased with the increasing oxygen concentration in the primary gas, and the conversion ratio of nitrogen was above 0.40. In addition, the reduced proportion of nitrogen increased with the increase of oxygen concentrations in the primary gas, surpassing 30.0%. The heating value of high-temperature coal gas also increased. Next, the effects of oxygen-staging gas distribution on NO emissions were investigated. Increasing oxygen concentrations in the primary gas and in the secondary gas as well as decreasing oxygen concentration in the tertiary gas all reduced NO emissions. The lowest NO emission was 26.8 mg/MJ, and the combustion efficiency was above 99.0%. These results demonstrate that the oxy-fuel preheating combustion technology with effective oxygen-staging gas distribution could achieve clean, efficient combustion of pulverized char.
ISSN: 0378-3820
eISSN: 1873-7188
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Record 5 of 233
Title: Experimental and theoretical study on acetone pyrolysis in a jet-stirred reactor
Author(s): Yu, D (Yu, Dan); Tian, ZY (Tian, Zhen-Yu); Wang, Z (Wang, Zhen); Liu, YX (Liu, Yue-Xi); Zhou, L (Zhou, Lei)
Abstract: Pyrolysis of acetone was investigated in a jet-stirred reactor coupled with on-line GC and GC-MS in the temperature range 700-1136 K at atmospheric pressure. Six species, namely 1-C4H8, iC(4)H(8), nC(4)H(10), iC(4)H(10), C5H6 and C6H6, were newly identified and quantified. A kinetic mechanism involving 296 species and 1836 reactions, including subsets of acetone and 2-butanone, was developed with reasonable predictions against the experimental data. C-C bond cleavage releasing CH3CO and CH3 radicals is the chain-initiation and the most intensively promoting reaction for the consumption of acetone. Its high-pressure limit rate constant was recalculated as k(1) = 1.12 x 106.T-3.84.exp(-78.6 kcal mol(-1)/RT) at the CBS-QB(3) level. Besides this step, H- and CH3-abstractions of acetone by CH3 radical, with the calculated high-pressure limit rate constant as k(4) = 1.38.T-3.49.exp(-8.58 kcal mol(-1)/RT) and k(7) = 5.70.T-3.96.exp(-41.7 kcal mol(-1)/RT), respectively, govern the major consumption routes of acetone. CH3 radicals contribute as the key species to the production of the major hydrocarbons such as CH4, C2H4 and C2H6, and minor branches to benzene and C2H5COCH3. Moreover, the present kinetic mechanism could predict fairly the mole fractions of the gas species in the high-temperature pyrolysis of acetone and the ignition delay times of acetone at different temperature and pressure region, which indicates the applicability of this model in a wide-range condition.
ISSN: 0016-2361
eISSN: 1873-7153
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Record 6 of 233
Title: Highly dispersed CuCo nanoparticles supported on reduced graphene oxide as high-activity catalysts for hydrogen evolution from ammonia borane hydrolysis
Author(s): Xu, M (Xu, Min); Huai, XL (Huai, Xiulan); Zhang, H (Zhang, Hang)
Source: JOURNAL OF NANOPARTICLE RESEARCH Volume: 20 Issue: 12 Article Number: 329 DOI: 10.1007/s11051-018-4429-6 Published: DEC 14 2018
Abstract: Hydrogen has been considered one of the best energy carriers to satisfy the increasing demand for clean and renewable energy supply. In this paper, a series of copper-based (CuCo, CuNi, and CuFe) nanoparticles supported on reduced graphene oxide (rGO) were synthesized via a facile one-pot chemical reduction route, and their catalytic performance on hydrogen evolution from ammonia borane (NH3BH3, AB) hydrolysis at room temperature was studied. The results revealed that the Cu0.2Co0.8 nanoparticles (2.1nm) on rGO exhibited the highest activity, and Co nanoparticles (3.9nm) on rGO also displayed the excellent performance. Among all the as-prepared Cu0.2Co0.8/rGO catalysts, Cu0.2Co0.8/rGO with 48wt% nanoparticles exhibits the highest activity with the initial hydrogen production rate values as high as 50.6mol H(2)mol(metal)(-1)min(-1), superior to the majority of Cu-based non-noble metal catalysts. The excellent performance could be attributed to the well dispersion of CuCo nanoparticles on reduced graphene oxide.
ISSN: 1388-0764
eISSN: 1572-896X
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Record 7 of 233
Title: Comparative study on the photoluminescence properties of monoclinic and cubic erbium oxide
Author(s): Yan, D (Yan, D.); Wu, P (Wu, P.); Zhang, SP (Zhang, S. -P.); Yang, JG (Yang, J. -G.); Li, YN (Li, Y. -N.); Wei, XC (Wei, X. -C.); Wang, L (Wang, L.); Huai, XL (Huai, X. -L.)
Source: SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY Volume: 205 Pages: 341-347 DOI: 10.1016/j.saa.2018.07.008 Published: DEC 5 2018
Abstract: As a heavy rare earth oxide, erbium oxide (Er2O3) has many attractive properties. Monoclinic Er2O3 has useful properties not found in stable cubic Er2O3, such as unique optical properties and high radiation damage tolerance. In this study, pure cubic and mixed phase of cubic and monoclinic Er2O3 coatings were prepared. Photoluminescence properties of these coatings were characterized by a confocal micro-Raman spectrometer equipped with 325, 473, 514, 532, 633 nm lasers, and the influence of microstructure on the fluorescence properties was analyzed in detail. The room temperature fluorescence peaks of cubic Er2O3 were assigned. Furthermore, a novel method for rapid phase identification of Er3+ doped cubic and monoclinic rare earth sesquioxides at room temperature was proposed. (C) 2018 Elsevier B.V. All rights reserved.
ISSN: 1386-1425
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Record 8 of 233
Title: Stochastic Dynamic Response Analysis of a 10 MW Tension Leg Platform Floating Horizontal Axis Wind Turbine
Author(s): Luo, T (Luo, Tao); Tian, D (Tian, De); Wang, RY (Wang, Ruoyu); Liao, CC (Liao, Caicai)
Abstract: The dynamic response of floating horizontal axis wind turbines (FHWATs) are affected by the viscous and inertia effects. In free decay motion, viscous drag reduces the amplitude of pitch and roll fluctuation, the quasi-static mooring system overestimates the resonant amplitude values of pitch and roll. In this paper, the quasi-static mooring system is modified by introducing linear damping and quadratic damping. The dynamic response characteristics of the FHAWT modified model of the DTU 10 MW tension leg platform (TLP) were studied. Dynamic response of the blade was mainly caused by wind load, while the wave increased the blade short-term damage equivalent load. The tower base bending moment was affected by inclination of the tower and the misaligned angle (wave) between wind and wave. Except the yaw motion, other degrees of freedom motions of the TLP were substantially affected by (wave). Ultimate tension of the mooring system was related to the displacement caused by pitch and roll motions, and standard deviation of the tension was significantly affected by the wave frequency response. Under the action of wave load, the viscous drag would stimulate the mooring system and increase the resonance of the platform motion.
ISSN: 1996-1073
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Record 9 of 233
Title: Integration of concentrating PVs in anaerobic digestion for biomethane production
Author(s): Hao, Y (Hao, Yong); Li, WJ (Li, Wenjia); Tian, ZY (Tian, Zhenyu); Campana, PE (Campana, Pietro Elia); Li, HL (Li, Hailong); Jin, HG (Jin, Hongguang); Yan, JY (Yan, Jinyue)
Source: APPLIED ENERGY Volume: 231 Pages: 80-88 DOI: 10.1016/j.apenergy.2018.09.119 Published: DEC 1 2018
Abstract: Biogas produced from anaerobic digestion processes is considered as an important alternative to natural gas and plays a key role in the emerging market for renewable energy. Aiming at achieving a more sustainable and efficient biomethane production, this work proposed a novel energy system, which integrates concentrating photovoltaic/thermal (C-PV/T) hybrid modules into a biogas plant with chemical absorption for biogas upgrading. The investigated energy system was optimized based on the data from an existing biogas plant, and its techno-economic feasibility was evaluated. Results show that about 7% of the heat consumption and 12% of the electricity consumption of the biogas plant can be covered by solar energy, by using the produced heat in a cascade way according to the operating temperature of different processes. The production of biomethane can also be improved by 25,800 N m(3)/yr (or 1.7%). The net present value of the integrated system is about 2.78 MSEK and the payback period is around 10 years. In order to further improve the economic performance, it is of great importance to lower the capital cost of the C-PV/T module.
ISSN: 0306-2619
eISSN: 1872-9118
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Record 10 of 233
Title: Droplet impact and LFP on wettability and nanostructured surface
Author(s): Kim, SH (Kim, Seol Ha); Jiang, YY (Jiang, Yuyan); Kim, H (Kim, Hyungmo)
Source: EXPERIMENTAL THERMAL AND FLUID SCIENCE Volume: 99 Pages: 85-93 DOI: 10.1016/j.expthermflusci.2018.07.029 Published: DEC 2018
Abstract: The Leidenfrost point (LFP) of a single deionized water droplet on various wettability surfaces was investigated by high-speed visualization. Manipulating both the chemical and geometric properties of a silicon wafer substrate, we prepared test samples with a wide range of wettabilities, from superhydrophilic (< 10 degrees) to superhydrophobic (> 165 degrees). Nanoscale wire or needle-shaped structures were fabricated by etching process on the silicon substrate. The effects of wettability on LFP were investigated by analyzing how the droplets rebound on the overheated surface. The results show that the more hydrophilic condition, the higher LFP. As the hydrophilic surface causes vigorous nucleate boiling and large viscous dissipation during the droplet contact, higher superheated condition of the substrate is required to trigger the rebounding dynamics and stable film boiling state. Furthermore, the superhydrophilic surface, which was assisted by nanostructures, contains many cavities and produces strong capillary wicking upon droplet contact; hence, explosive transition boiling in the droplet was observed. This study provides a detailed physical understanding of droplet dynamics on overheated nanostructures and its relation on LFP evaluation.
ISSN: 0894-1777
eISSN: 1879-2286
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Record 11 of 233
Title: Numerical prediction of thin liquid film near the solid wall for hydraulic cavitating flow in microchannel by a multiphase lattice Boltzmann model
Source: INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER Volume: 127 Pages: 107-115 DOI: 10.1016/j.ijheatmasstransfer.2018.06.146 Part: A Published: DEC 2018
Abstract: Based on a multiphase lattice Boltzmann (LB) model integrating body forces such as inter-particle interaction force and fluid-solid interaction force, a numerical prediction of thin liquid film near the solid wall for hydraulic cavitating flow in microchannel is conducted in the present work. The validity of model is tested by means of Laplace law and experimental result. On this basis, a full thin liquid film near the solid wall is successfully predicted, which proves that the single-component multiphase LB model integrated with various interaction forces is a good solution to this type of problem like hydraulic cavitating flow in microchannel. The further simulation indicates that the fluid-solid interaction strength (g(s)) has a significant effect on the formation of thin liquid film. A critical value (g(s) = -3.5) of fluid-solid interaction strength is found, and thin liquid film fails to be predicted at g(s) > 3.5. A simple simulation on the contact angle (theta) of droplet on the solid surface is conducted to analyze the reason for this phenomenon. It is found that a full thin liquid film could be successfully predicted only when the solid surface is fully wetted by liquid, i.e., theta = 0 degrees corresponding to g(s) <= -3.5. The current research provides a potential way for future investigation on heat transfer accompanied by hydraulic cavitating flow. (C) 2018 Elsevier Ltd. All rights reserved.
ISSN: 0017-9310
eISSN: 1879-2189
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Record 12 of 233
Title: Experimental investigation of geyser boiling in a two-phase closed loop thermosyphon with high filling ratios
Author(s): Liu, Y (Liu, Yun); Li, ZG (Li, Zhigang); Li, YH (Li, Yuhua); Kim, S (Kim, Seolha); Jiang, YY (Jiang, Yuyan)
Source: INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER Volume: 127 Pages: 857-869 DOI: 10.1016/j.ijheatmasstransfer.2018.07.018 Part: A Published: DEC 2018
Abstract: The geyser boiling instability in a two-phase closed loop thermosyphon (TPCLT) is experimentally investigated through flow visualization and simultaneous measurement of pressure and temperature fluctuations. Wide ranges of filling ratios of R134a fluid from 90% to 53%, and heat flux from 20 W cm(-2) to 220 W cm(-2) are examined. The Power Spectrum Density (PSD) method is applied to analyze the periodicity of geyser boiling, and the parameter Standard Deviation (SD) is used to characterize the oscillating amplitude. The effects of heat flux and filling ratio on the geyser boiling occurrence and the oscillation characteristics are discussed in detail. The results show that, the flow regimes experience the consecutive variation of single-phase flow, bubbly flow, churn flow, bubbly flow, and single-phase flow within each geyser boiling cycle, leading to the fluctuation of flow and heat transfer characteristics. The geyser boiling is more liable to occur in the conditions of higher filling ratio and moderate heat flux. The initiating heat flux for the onset of geyser boiling decreases with the increase of filling ratio, but the range of heat flux for the geyser boiling occurrence is narrow under the high filling ratio conditions. The frequency of geyser boiling increases with the increase of heat flux for a certain filling ratio. With the increase of filling ratio, the oscillating frequency firstly decreases and then increases. The minimum oscillating frequency occurs at the combination of filling ratio of 76% and heat flux of 90 W cm(-2) under the experimental conditions in this work. Both the fluctuation amplitude of pressure and temperature increase with the increase of heat flux, while decrease with the increase of filling ratio. Compared to R134a under the same filling ratio of 76%, the water has higher heat flux for geyser boiling occurrence, smaller oscillating amplitude of pressure, and lower oscillating frequency due to the difference in thermophysical properties. (C) 2018 Elsevier Ltd. All rights reserved.
ISSN: 0017-9310
eISSN: 1879-2189
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Record 13 of 233
Title: On the modeling of the filtered radiative transfer equation in large eddy simulations of lab-scale sooting turbulent diffusion flames
Source: JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER Volume: 221 Pages: 51-60 DOI: 10.1016/j.jqsrt.2018.09.020 Published: DEC 2018
Abstract: This study investigates the influence of some approximations on the modeling of the filtered absorption and emission terms in an ethylene/air turbulent jet flame. Filtered radiative quantities along characteristic diametric optical paths are computed from corresponding instantaneous radiative quantities obtained by using a stochastic space and time series model. Model results show that the subgrid-scale radiative absorption can be disregarded whatever the filter size. The effects of subgrid-scale fluctuations on the filtered emission term are dominated by the subgrid-scale absorption coefficient-blackbody intensity correlation and the subgrid-scale temperature self-correlation. The former reduces the filtered emission term in regions where soot radiation dominates and enhances it in regions where gas radiation prevails. The latter always increases the filtered emission term. For a filter size typical of engineering applications, model results suggest that the effects subgrid-scale fluctuations on the filtered emission term have to be modeled. (C) 2018 Elsevier Ltd. All rights reserved.
ISSN: 0022-4073
eISSN: 1879-1352
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Record 14 of 233
Title: Particle size-band gap energy-catalytic properties relationship of PSE-CVD-derived Fe3O4 thin films
Author(s): Kouotou, PM (Kouotou, Patrick Mountapmbeme); El Kasmi, A (El Kasmi, Achraf); Wu, LN (Wu, Ling-Nan); Waqas, M (Waqas, Muhammad); Tian, ZY (Tian, Zhen-Yu)
Source: JOURNAL OF THE TAIWAN INSTITUTE OF CHEMICAL ENGINEERS Volume: 93 Pages: 427-435 DOI: 10.1016/j.jtice.2018.08.014 Published: DEC 2018
Abstract: This study reports the control of catalytic properties of Fe3O4 thin films through adjusting the particles size and optical properties. Structure analysis of the obtained materials by X-ray diffraction indicated the formation of pure magnetite structure of Fe3O4. X-ray photoelectron spectroscopy showed that the surfaces of the samples were mainly composed of Feet, Fe3+, O2-, CO32- and OH-. Scanning electronic microscopy displayed a smooth films surface with an agglomerated crystallite grains. Both XRD and SEM exhibits particles size increases (similar to 40 to similar to 60 nm) with the substrate temperature (T-s), while micro-strain in the sample decreased. The correlation of the T-s with optical energy band gaps (Ee(OPt)) determined from UV visible (UV-vis) measurements indicated the increase of indirect (2.17 <= Eg(2) Opt <= 2.25 eV) and direct (2.78 <= Eg(1)(opt)< 2.95 eV) band gap of Fe3O4. Fe3O4 samples have been successfully tested towards the total oxidation of CO. While the change in E-g(OPt) of Fe3O4 has been explained on the basis of the variation in the grain size and likely adsorbed oxygen (O-Ads) with T-s, the catalytic performance was suggested to be strongly dependent on the films microstructure, catalysts surface composition and more importantly with the E-g. Pt and O-Ads variation. Moreover, theoretical calculations based on DFT method of CO oxidation over Fe3O4 film surface catalyst demonstrated that Om, was the most involved oxygen species during the catalytic process, revealing that the LH mechanism is the most appropriate route for the CO catalytic oxidation over MvK and ER mechanisms. This approach of highlighting the interplay among the particle size, optical and catalytic properties with DFT calculations can pave the way to better understand the catalytic behavior of other transition metal oxides. (C) 2018 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
ISSN: 1876-1070
eISSN: 1876-1089
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Record 15 of 233
Title: Coupled Heat Transfer Simulation of the Spiral Water Wall in a Double Reheat Ultra-supercritical Boiler
Source: JOURNAL OF THERMAL SCIENCE Volume: 27 Issue: 6 Pages: 592-601 DOI: 10.1007/s11630-018-1072-6 Published: DEC 2018
Abstract: This paper presented a coupled heat transfer model combining the combustion in the furnace and the ultra-supercritical (USC) heat transfer in the water wall tubes. The thermal analysis of the spiral water wall in a 1000 MW double reheat USC boiler was conducted by the coupled heat transfer simulations. The simulation results show that there are two peak heat flux regions on each wall of spiral water wall, where the primary combustion zone and burnt-out zone locate respectively. In the full load condition, the maximal heat flux of the primary combustion zone is close to 500 kW/m(2), which is higher than that in the conventional single reheat USC boilers. The heat flux along the furnace width presents a parabolic shape that the values in the furnace center are much higher than that in the corner regions. The distribution of water wall temperature has a perfect accordance with the heat flux distribution of the parabolic shape curves, which can illustrate the distribution of water wall temperature is mainly determined by heat flux on the water wall. The maximal water wall temperature occurs at the middle width of furnace wall and approaches 530 degrees C, which can be allowed by the metal material of water wall tube 12Cr1MoVG. In the primary combustion zone, the wall temperatures in half load are almost close to the values in 75% load condition, caused by the heat transfer deterioration of the subcritical pressure fluid under the high heat flux condition. The simulation results in this study are beneficial to the better design and operational optimization for the double reheat USC boilers.
ISSN: 1003-2169
eISSN: 1993-033X
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Record 16 of 233
Title: Evaluation of electrical resistance tomography with voltage excitation compared with electrical capacitance tomography
Author(s): Wang, RC (Wang, Ruican); Frias, MAR (Frias, Marco A. Rodriguez); Wang, HG (Wang, Haigang); Yang, WD (Yang, Wudiang); Ye, JM (Ye, Jiamin)
Source: MEASUREMENT SCIENCE AND TECHNOLOGY Volume: 29 Issue: 12 Article Number: 125401 DOI: 10.1088/1361-6501/aae8ff Published: DEC 2018
Abstract: Normally, a gas-solids flow should be non-conductive. With the increase in moisture content in a gas-solids flow, the non-conductive flow may become low-conductive. For the measurement of low-conductive materials, i.e. particles with high moisture content, in the pharmaceutical industry, both electrical capacitance tomography (ECT) and traditional electrical resistance tomography driven by current (ERTc) generate poor images. An ERT driven by voltage (ERTv) may be suitable for the measurement of materials with low- conductivity. In this research, ERTv is used for the measurement of a wet gas-solids flow with different moisture content and different flow patterns, as well as a gas-liquid flow with different flow patterns. In the meantime, ECT is also used for the same flow conditions for comparison. The measurement results of ERTv and ECT are evaluated by the correlation coefficient. The results show that ERTv is good for measurement of a gas-solids flow with high moisture content and a gas-liquid flow when the conductivity of the continuous phase is low or moderate, while ECT is suitable for the measurement of a dry gas-solids flow.
ISSN: 0957-0233
eISSN: 1361-6501
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Record 17 of 233
Title: Catalytic activity of flame-synthesized Pd/TiO2 for the methane oxidation following hydrogen pretreatments
Author(s): Wang, NF (Wang, Nafeng); Niu, F (Niu, Fang); Wang, SH (Wang, Shuhao); Huang, Y (Huang, Yun)
Abstract: A nanocatalyst composed of 10 wt% Pd supported on TiO2 was synthesized using one-step flame spray pyrolysis with a highly-quenched premixed stagnation flame. The as-prepared nanoparticles, having a mean diameter of approximately 10 nm, were then subjected to isothermal oxidation and reduction in a fixed bed reactor. The potential roles of Pd and PdO as well as possible synergistic effects between these two active species were explored during methane conversion. The lowest light-off temperature T-20 was obtained at a Pd ratio of 53% and this result can be reasonably explained based on a surface Pd-PdO site pair mechanism. Additionally, differences in the hysteresis behavior during methane oxidation were noted throughout a heating-cooling cycle over the temperature range of 200-600 degrees C, such that the degree of hysteresis was strongly correlated with the Pd ratio. (C) 2018 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.
ISSN: 1674-2001
eISSN: 2210-4291
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Record 18 of 233
Title: Mobilized thermal energy storage: Materials, containers and economic evaluation
Source: ENERGY CONVERSION AND MANAGEMENT Volume: 177 Pages: 315-329 DOI: 10.1016/j.enconman.2018.09.070 Published: DEC 1 2018
Abstract: The transportation of thermal energy is essential for users who are located far away from heat sources. The networks connecting them achieve the goal in efficient heat delivery and reasonable cost, especially for the users with large heat demands. However, it is difficult to satisfy the heat supply of the detached or emergent users with the existing pipelines. Therefore, a promising alternative, called mobilized thermal energy storage (M-TES), was proposed to deliver the heat flexibly without the restriction of networks. In this paper, a review of studies on M-TES is conducted in terms of materials, containers and economic evaluation. The potential candidates of materials, such as sugar alcohols, hydrated salts, alkalies and zeolite are reviewed and compared based on their thermophysical properties, price, advantages and disadvantages. Various containers, including the shell-and tube, encapsulated, direct-contact, detachable and sorptive types, are discussed from the aspects of configuration, performance and utilization. Furthermore, the studies on the economic evaluation of M-TES systems are summarized and discussed based on the analysis of the economic indicators, including initial cost, operating cost, revenue, subsidy and energy cost. Finally, the challenges and future perspectives for developing M-TES are presented.
ISSN: 0196-8904
eISSN: 1879-2227
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Record 19 of 233
Title: Microwave Doppler velocity measurement using tapered rectangular waveguide antenna with pattern offset correction
Source: MICROWAVE AND OPTICAL TECHNOLOGY LETTERS Volume: 60 Issue: 12 Pages: 3068-3072 DOI: 10.1002/mop.31431 Published: DEC 2018
Abstract: Rectangular waveguide antenna has been often used in velocity measurement based on microwave Doppler principle for its advantages of high directivity, high radiation efficiency, and reliability. In addition to a waveguide antenna with a straight aperture, a tapered waveguide antenna is frequently required in measuring flow velocities in a pipe. In the common sense, the maximum radiation direction is usually taken to be along the axial direction of the waveguide. This is well understood for a conventional straight open-ended waveguide antenna with an aperture perpendicular the axis of the waveguide. However, for a tapered rectangular waveguide antenna with an aperture at an angle to the axis of the waveguide, there exists an offset from the axial direction for the maximum radiation direction. In this paper, a tapered rectangular waveguide antenna with a tapering angle alpha is analyzed and studied experimentally. For alpha =45 degrees, the results show that the maximum radiation has an offset of 25.5 degrees in theory, 25 degrees in simulation and 30 degrees in measurement from the axial direction of the waveguide. The experimental study also shows that when this radiation pattern offset is taken into account, the velocities measured using the microwave Doppler principle agree well with the theoretically calculated free-fall velocity.
ISSN: 0895-2477
eISSN: 1098-2760
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Record 20 of 233
Title: Numerical Investigation on Film Cooling Performance of Fusiform Diffusion Holes
Author(s): An, BT (An, Bai-Tao); Liu, JJ (Liu, Jian-Jun)
Source: JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME Volume: 140 Issue: 12 Article Number: 122201 DOI: 10.1115/1.4041047 Published: DEC 2018
Abstract: This paper presents a numerical investigation of the film-cooling performance of a kind of diffusion hole with a fusiform cross section. Relative to the rectangular diffusion hole, the up- and/or downstream wall of the fusiform diffusion hole is outer convex. Under the same metering section area, six fusiform diffusion holes were divided into two groups with cross-sectional widths of W = 1.7D and W = 2.0D, respectively. Three fusiform: cross section shapes in each group included only downstream wall outer convex, only upstream wall outer convex, or a combination of both. Simulations were performed in a flat plate model using a 3D steady computational fluid dynamics method under an engine-representative condition. The simulation results showed that the fusiform diffusion hole with only an outer convex upstream wall migrates the coolant laterally toward the hole centerline, and then forms or enhances a tripeak effectiveness pattern. Conversely, the fusiform diffusion hole with an outer convex downstream wall intensely expands the coolant to the hole two sides, and results in a bipeak effectiveness pattern, regardless of the upstream wall shape. Compared with the rectangular diffusion holes, the fusiform diffusion holes with only an upstream wall outer convex significantly increase the overall effectiveness at high blowing ratios. The increased magnitude is approximately 20% for the hole of W = 1.7D at M = 2.5. Besides, the fusiform diffusion holes with an outer convex upstream wall increase the discharge coefficient about 5%, within the moderate to high blowing ratio range.
ISSN: 0022-1481
eISSN: 1528-8943
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Record 21 of 233
Title: Thermohydraulic performance of microchannel heat sinks with triangular ribs on sidewalls - Part 1: Local fluid flow and heat transfer characteristics
Author(s): Chai, L (Chai, Lei); Wang, L (Wang, Liang); Bai, X (Bai, Xin)
Source: INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER Volume: 127 Pages: 1124-1137 DOI: 10.1016/j.ijheatmasstransfer.2018.08.114 Part: C Published: DEC 2018
Abstract: Triangular ribs are mounted on the parallel sidewalls of microchannels in order to reinitialize the thermal boundary layer and improve the mixing of cold and hot fluids. This paper presents a detailed numerical study on local laminar fluid flow and heat transfer characteristics in microchannel heat sinks with tandem triangular ribs for Reynolds number of 443. Three-dimensional conjugate heat transfer models considering entrance effect, viscous heating, as well as temperature-dependent thermophysical properties are employed. Water and silicon are respectively used as fluid and solid for the computational domain. Triangular ribs are attached in microchannels with either aligned or offset arrangement. Four non-dimensional geometry parameters relative to the width, height, converging-diverging ratio and spacing of triangular ribs are proposed to investigate the influence on local fluid flow and heat transfer characteristics. Velocity contour, pressure and temperature distributions are examined to demonstrate the basic fluid flow and heat transfer mechanism. Local pressure and temperature profiles are studied to show the influence of the triangular ribs on fluid flow and heat transfer process. Local friction factor and Nusselt number for different non-dimensional geometry variables are further investigated to comprehensively indicate the impact of triangular ribs. Results shows that the triangular ribs can significantly reduce the temperature rise of the heat sink base and efficiently prevent the drop of local heat transfer coefficient along the flow direction, but also result in higher local friction factor than the straight microchannel. For the studied operation conditions and geometry parameters of flow passage, the heat sink base temperature varies in the range of from 301.90 to 32431 K, the computed pressure drop and heat transfer coefficient fluctuate from one triangular rib to the next and their amplitude and wavelength significantly depend on the geometry and arrangement of triangular ribs. Compared to the reference straight microchannel heat sink, a superior configuration considered in this paper can yield an improvement of up to 2.15 times higher of average Nusselt number. (C) 2018 Elsevier Ltd. All rights reserved.
ISSN: 0017-9310
eISSN: 1879-2189
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Record 22 of 233
Title: Quasiballistic Thermal Transport from Nanoscale Heaters and the Role of the Spatial Frequency
Author(s): Chen, XW (Chen, Xiangwen); Hua, CY (Hua, Chengyun); Zhang, H (Zhang, Hang); Ravichandran, NK (Ravichandran, Navaneetha K.); Minnich, AJ (Minnich, Austin J.)
Abstract: Quasiballistic heat conduction from nanoscale heat sources of size comparable to phonon mean free paths has recently become of intense interest both scientifically and for its applications. Prior work has established that, in the quasiballistic regime, the apparent thermal properties of materials depend both on intrinsic mechanisms and the characteristics of the applied thermal gradient. However, many aspects of this regime remain poorly understood. Here, we experimentally study the thermal response of crystals to large thermal gradients generated by optical heating of nanoline arrays. Our experiments reveal the key role of the spatial frequencies and Fourier series amplitudes of the heating profile for thermal transport in the quasiballistic regime, in contrast to the conventional picture that focuses on the geometric dimensions of the individual heaters. Our work provides the insight needed to rationally mitigate local hot spots in modern applications by manipulating the spatial frequencies of the heater patterns.
ISSN: 2331-7019
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Record 23 of 233
Title: Study on different heat supplementation strategies for a combined cooling, heating and power system
Author(s): Huan, L (Huan Lei); Han, DJ (Han Dongjiang); Yang, JF (Yang Jinfu); Tang, CL (Tang Changliang); Long, H (Long Hao)
Abstract: The small CCHP system is adopted by majority of office buildings and markets. The heat supplementation under partial load is a problem for CCHP systems. In this research, a partial load model of a combined cooling, heating and power (CCHP) system was established. The CCHP system's partial load analysis showed that the micro gas turbine (MGT) and the bottom absorption chiller were coupled by flue gas energy. Based on the coupling effects analysis, four different supplementary strategies (load adjustment method (LAM), mass flow first method (MFM), temperature first method (TFM) and maximum coefficient of performance (COP) method (MCOPM)) had been proposed and analyzed when flue gas heat was insufficient. The results showed that the CCHP system's supplemental fuels under MFM, TFM and MCOPM were all less than that under LAM. And the additional fuel under the TFM was the least among the four different strategies. The CCHP system's heating capacity under TFM was smaller than that under MFM and MCOPM, while the CCHP system's primary energy and exergy efficiencies under the TFM were larger than that under MFM and MCOPM, at the same cooling load, when supplement heat was needed. The CCHP system's total exergy destruction under TFM (106.236 kW) was smaller than that under the LAM (110.309 kW). So when the flue gas heat was insufficient, the TFM supplementation strategy was recommended.
ISSN: 1359-4311
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Record 24 of 233
Title: CVD synthesis of Cu-doped cobalt spinel thin film catalysts for kinetic study of propene oxidation
Author(s): Waqas, M (Waqas, Muhammad); El Kasmi, A (El Kasmi, Achraf); Wang, Y (Wang, Yu); Kouotou, PM (Kouotou, Patrick Mountapmbeme); Tian, ZY (Tian, Zhen-Yu)
Source: COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS Volume: 556 Pages: 195-200 DOI: 10.1016/j.colsurfa.2018.08.006 Published: NOV 5 2018
Abstract: A series of Co-Cu binary oxides dispersed homogenously on an inert support were prepared by pulsed-spray evaporation chemical vapor deposition for kinetic study of catalytic combustion. The physicochemical properties of the as-prepared samples were comprehensively characterized in terms of structure, morphology and composition. The results disclosed the formation of cubic binary oxides with amorphous surface. With the progressive introduction of copper into the cobalt spinel, the crystallite size tended to increase due to the incorporation of large Cu2+ ionic radius. Co3+, Co2+, Cu2+, lattice and adsorbed oxygen species were confirmed to co-exist at the surfaces of the binary oxides. The obtained samples exhibited excellent performance for C3H6 oxidation with a high gas hourly space velocity of 150,000 mL.g(-1).h(-1). The light-off curves shifted towards lower temperature with more Cu incorporation, which was linked to the increase in Co3+/Co2+, and the rearrangement and synergetic effects of Co, Cu and lattice oxygen. The reaction rate increases linearly with the increase in C3H6 concentration by following r=1.12*[C3H6](0.27), without reaching kinetic limitation stage. Moreover, an attractive durability of the binary oxides was observed in the C3H6 oxidation during 50 h. This work provides an inspiration and attractive strategy to develop efficient Co-Cu binary oxides for catalytic applications.
ISSN: 0927-7757
eISSN: 1873-4359
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Record 25 of 233
Title: Effect of Ti interlayer on interfacial thermal conductance between Cu and diamond
Abstract: Cu/Ti bilayers were magnetron sputtered onto a diamond substrate to simulate interfaces in diamond particles reinforced Cu matrix (Cu/diamond) composites. The Cu/Ti/diamond system was tuned to Cu/Ti/TiC/diamond and Cu/TiC/diamond structures by annealing the Ti interlayer at 1073 K. The interfacial thermal conductance (G) between Cu and diamond was experimentally measured by a time-domain thermoreflectance (TDTR) technique to investigate the dependence of the G on the Cu/interlayer/diamond structure. The Cu/TiC/diamond structure exhibits higher G of 76 MW m(-2)K(-1) than the Cu/Ti/TiC/diamond of 60 MW m(-2) K-1, the Cu/Ti/diamond of 30 MW m(-2) K-1, the as-deposited Cu/diamond of 66 MW M-2 K-1, and the annealed Cu/diamond of <1 MW m(-2) K-1. The measured G values are in broad agreement with the calculated values using an acoustic mismatch model (AMM). The results show that interfacial bonding is more critical than vibrational match of phonons in increasing the G between Cu and diamond as well as the thermal conductivity of Cu/diamond composites. A promising interlayer configuration is obtained as Cu/TiC/diamond, which provides an idea for design and preparation of high thermal conductivity Cu/diamond composites. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
ISSN: 1359-6454
eISSN: 1873-2453
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Record 26 of 233
Title: Assessment of a combined cooling, heating and power system by synthetic use of biogas and solar energy
Author(s): Su, BS (Su, Bosheng); Han, W (Han, Wei); Zhang, XS (Zhang, Xiaosong); Chen, Y (Chen, Yi); Wang, ZF (Wang, Zefeng); Jin, HG (Jin, Hongguang)
Source: APPLIED ENERGY Volume: 229 Pages: 922-935 DOI: 10.1016/j.apenergy.2018.08.037 Published: NOV 1 2018
Abstract: Anaerobic digesters should always be kept warm for a stable biogas yield. The conventional method for digester temperature maintenance results in a considerable waste of energy and pollution of the environment by directly firing biogas. Biogas-driven trigeneration systems can improve biogas utilization efficiency; however, the waste heat from the power engines is limited by the digester's thermal insulation, and additional fossil fuels are consumed to supplement the thermal power. To ease fossil fuel energy consumption and enhance the efficiency of biogas utilization, this paper presents a combined cooling heating and power (CCHP) system with synthetic use of biogas and solar energy. Solar energy is first transformed into syngas chemical energy through a chemical reaction called biogas steam reforming, and then the chemical energy is used for trigeneration in a conventional CCHP subsystem. Experimental research was conducted on the key process of biogas steam reforming to validate its feasibility. Hourly dynamic simulations of the proposed system were conducted by the mathematical models established using Lhasa, Tibet weather data. A biogas-fired CCHP system and a solar Dish/Stirling power system were adopted as reference systems, and a comparative analysis showed that the synthetic use of biogas and solar energy in the proposed system improves the annual electricity production by 8.70%, improves the refrigeration by 2.57%, and reduces the natural gas consumption by 8.66%. In addition, the direct CO2 footprint in the proposed system is 8.20% lower than that in the reference systems. Finally, an economic study was conducted to validate the technical feasibility of the new system. The study offers a new method of using biogas and solar energy for an improved integrated performance.
ISSN: 0306-2619
eISSN: 1872-9118
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Record 27 of 233
Title: Studies of low temperature oxidation of n-pentane with nitric oxide addition in a jet stirred reactor
Author(s): Zhao, H (Zhao, Hao); Wu, LN (Wu, Lingnan); Patrick, C (Patrick, Charles); Zhang, ZH (Zhang, Zunhua); Rezgui, Y (Rezgui, Yacine); Yang, XL (Yang, Xueliang); Wysocki, G (Wysocki, Gerard); Ju, YG (Ju, Yiguang)
Source: COMBUSTION AND FLAME Volume: 197 Pages: 78-87 DOI: 10.1016/j.combustflame.2018.07.014 Published: NOV 2018
Abstract: The low temperature oxidation of n-pentane with nitric oxide (NO) addition has been investigated at 500-800 K in an atmospheric jet stirred reactor (JSR). The molar fraction of NO in the mixture is varied between 0 to 1070 ppm to study its chemical sensitization effect on low temperature oxidation of both fuel lean and rich n-pentane/oxygen mixtures. N-pentane, O-2, CO, CO2, CH2O, C2H4, CH3CHO, NO, and NO2 are quantified simultaneously, in-situ by using an electron impact molecular beam mass spectrometer (MBMS), a micro-gas chromatograph (mu-GC), and a sensitive mid-IR dual-modulation faraday rotation spectrometer (DM-FRS). The experimental results reveal that NO addition delays the onset temperature of low temperature oxidation of n-pentane between 550-650K, but reduces the negative temperature coefficient (NTC) behavior in the NTC region (650-750K) and dramatically shifts the onset of high temperature fuel oxidation to an intermediate temperature (750-800 K). A recently developed n-pentane/NOx model by using Reaction Mechanism Generation (RMG) and a new n-pentane/NOx model in the present work were used to predict the experimental results. The results show that the three distinct temperature dependent characteristics of NO sensitized n-pentane oxidation are captured appropriately by these two models at both fuel rich and lean conditions, while the onset temperature of low temperature oxidation is not accurately predicted by these two models. It shows that the RMG model has a better prediction of the onset delay of n-pentane oxidation than Zhao's model, while Zhao's model performs better at NTC and intermediate temperature regions. Besides RO2 + NO, additional fuel/NOx reaction pathway, like R + NO2, RO + NO, and RO + NO2, and the interconversion reactions among NO, NO2, and HONO may need to be further studied. (C) 2018 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
ISSN: 0010-2180
eISSN: 1556-2921
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Record 28 of 233
Title: Heat transfer characteristics of a natural circulation separate heat pipe under various operating conditions
Author(s): Bai, Y (Bai, Ye); Wang, L (Wang, Liang); Zhang, S (Zhang, Shuang); Xie, NN (Xie, Ningning); Chen, HS (Chen, Haisheng)
Source: INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER Volume: 126 Pages: 191-200 DOI: 10.1016/j.ijheatmasstransfer.2018.04.130 Part: A Published: NOV 2018
Abstract: In order to determine the heat transfer performance and the mechanisms of separate heat pipe (SHP) under various operating conditions covering two-phase states and transcritical states, experimental investigation was carried out in this study. The effect of charging mass, cold bath temperature, heat load and height between evaporator and condenser on heat pipe was analyzed and the thermal resistance was calculated to characterize the heat transfer performance. Results showed that the increase of head load, the decrease of height difference and the increase of condenser temperature led to increases in thermal resistance. Appropriate charging mass was seen to be the most important factor in terms of optimum heat transfer performance, whereas too much or too little charging mass led to the subcooling or superheating in the evaporator, which was found to have a direct impact on heat transfer performance. (C) 2018 Elsevier Ltd. All rights reserved.
ISSN: 0017-9310
eISSN: 1879-2189
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Record 29 of 233
Title: Hydrodynamic analysis of the advancing dynamic contact angle in microtube
Author(s): Kim, SH (Kim, Seol Ha); Wang, T (Wang, Tao); Zhang, L (Zhang, Lei); Jiang, YY (Jiang, Yuyan)
Source: JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Volume: 32 Issue: 11 Pages: 5305-5314 DOI: 10.1007/s12206-018-1029-4 Published: NOV 2018
Abstract: We explored the hydrodynamic features of dynamic wetting both theoretically and experimentally. We studied the triple-line motions of glycerol-water solutions of various viscosities (85-456 mPa center dot s) in microglass tubes (300, 500 and 1000 m in diameter). First, dynamic (advancing) contact angles were measured and compared with those of a well-known hydrodynamic model (O.V. Voinov, Hydrodynamics of Wetting, Fluid Dynamics (1976)). Second, the internal flow structures near moving menisci were visualized using micro-particle image velocimetry (mu-PIV). Several differences in flow shape (compared to those predicted by theory) were observed. Ultimately, we present a new method by which dynamic contact angles may be predicted, derived from analysis of wall shearing stress at the moving contact line to reflect on the liquid-solid interaction effect. Our analysis has the advantage of incorporating the effect of contact angle hysteresis on the dynamic contact angle. The modified approach yielded data in good agreement with our experimental results and other open-literature data. We thus fundamentally explored the hydrodynamic aspects of dynamic wetting.
ISSN: 1738-494X
eISSN: 1976-3824
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Record 30 of 233
Title: High-pressure ratio centrifugal compressor with two different fishtail pipe diffuser configurations
Source: PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART A-JOURNAL OF POWER AND ENERGY Volume: 232 Issue: 7 Pages: 785-798 DOI: 10.1177/0957650917753777 Published: NOV 2018
Abstract: To improve fishtail pipe diffuser outflow uniformity, deswirlers and splitters are added inside and after fishtail pipe diffuser passages for a compact centrifugal compressor. The influence of clocking effects between the deswirler and fishtail pipe diffuser passage is first studied to find the optimum clocking position. The performances of these two configurations are then compared, and their loss mechanisms are determined. Finally, the compressor exit flow conditions are estimated. Either adding the deswirler after the fishtail passages or adding splitters inside the fishtail passages tends to degrade the compressor performance. The intensity of the vortices in the fishtail passages is increased; therefore, losses are induced when a deswirler is added after the fishtail passage. As splitters are added inside the fishtail passages, flow separation is observed at the splitter suction side near the hub as a result of the large incidence angle near the splitter hub and results in large losses. Adding a deswirler after fishtail passages has a negative effect on the compressor outlet flow uniformity but can eliminate the residual swirl angle. Adding splitters in fishtail diffuser passages is recommended to decrease the compressor outlet non-uniformity and residual swirl angle. Through this work, physical insight into complex flows in these two configurations is obtained to provide guidelines on a diffusing system design with a fishtail pipe diffuser.
ISSN: 0957-6509
eISSN: 2041-2967
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Record 31 of 233
Title: Experimental and numerical study of the effect of main stage stratifier length on lean blow-out performance for a stratified partially premixed injector
Source: PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART A-JOURNAL OF POWER AND ENERGY Volume: 232 Issue: 7 Pages: 812-825 DOI: 10.1177/0957650918758227 Published: NOV 2018
Abstract: The lean blow-out performance of the pilot flame in a stratified partially premixed injector is studied in this work considering the influence of the main stage stratifier length. Particle image velocimetry and kerosene planar laser-induced fluorescence experiments at nonreacting conditions were carried out to give an explanation of the combustion performance. The evolutions of spray and velocity in space are discussed in detail to find out the inherent correlations of combustion stability, spray distribution, and flow structures. Moreover, special attentions are paid to the variation of primary recirculation zone with the increase of the stratifier length and its driving factors. Specifically, by lengthening the stratifier of the main stage, the primary recirculation zone is enlarged both axially and radially, and this creates an advantageous flow topology for the anchoring of the pilot flame. Finally, the dominating mechanisms for the primary recirculation zone that are responsible for the alteration of the primary recirculation zone size are pointed out with the assistance of computational fluid dynamics.
ISSN: 0957-6509
eISSN: 2041-2967
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Record 32 of 233
Title: Performance investigation of a new cooling, heating and power system with methanol decomposition based chemical recuperation process
Source: APPLIED ENERGY Volume: 229 Pages: 1152-1163 DOI: 10.1016/j.apenergy.2018.07.112 Published: NOV 1 2018
Abstract: A novel combined cooling, heating and power system, which mainly consists of an internal combustion engine power block with the capacity of 500 kW a chemical recuperation block, an absorption refrigeration block and a hot water supply block, is proposed to improve the energy conversion efficiency in this work. The high temperature exhaust gas from the internal combustion engine is first used to drive methanol decomposition to produce syngas of CO and H-2 via the chemical recuperation, and the produced syngas is fed into the ICE for power generation. The exit exhaust gas flows into a double-effect lithium bromide-water absorption refrigerator, and finally the rest of the gas sensible heat is used to generate hot water for district heating. The temperature of the exhaust gas reduces to approximately 280 degrees C by the chemical recuperation process, and the temperature difference between the heat resource and the absorption cooling requirement thereby decreases and leads to lower exergy loss. Numerical simulation results indicate that the developed combined cooling, heating and power system achieves favorable thermodynamic performances, and the matching characteristics between energy production and energy demand can be enhanced. The system annual averaged energy efficiency is increased to 58.05%, and the methanol consumption is reduced to 842.54 tons/year with an annual primary energy saving ratio of 9.75%. Additionally, the system achieves lower annual total cost, i.e., 538.95 k$. The research findings provide a promising method to improve the performances of the combined cooling, heating and power system.
Conference Title: 9th International Conference on Applied Energy (ICAE)
Conference Date: AUG 21-24, 2017
Conference Location: Cardiff, WALES
ISSN: 0306-2619
eISSN: 1872-9118
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Record 33 of 233
Title: Experimental Investigation of Asymmetric Vortex Breakdown Flow Control by Microperturbation over Highly Swept Wings
Author(s): Wu, GX (Wu, Guangxing)
Source: JOURNAL OF AEROSPACE ENGINEERING Volume: 31 Issue: 6 Article Number: 04018101 DOI: 10.1061/(ASCE)AS.1943-5525.0000922 Published: NOV 2018
Abstract: An experimental investigation on asymmetric vortex breakdown flow over three delta wings with sweep angle of 85 degrees, 80 degrees, and 70 degrees was carried out in a wind tunnel at high angles of attack and Reynolds number of 1.215x106 using particle image velocimetry and pressure measurement techniques. First, vortex breakdown flow over delta wings with different sweep angles was measured to confirm the asymmetric flow phenomenon and its formation conditions. Time-averaged vortex breakdown flow over the 70 degrees swept wing was found to be symmetric, whereas flow is asymmetric over the 80 degrees and 85 degrees swept wings. Instability due to crowding together of both leading-edge vortices is the cause of asymmetric vortex breakdown flow. Second, a special test that two nose sections with the same size and shape, named NT1 and NT2, was used to explore the effect of manufacturing imperfection of nose on the asymmetry of vortex breakdown flow was designed. Unpredictable manufacturing imperfection at the nose tip was found to be key natural perturbation of the instability, which led uncertain asymmetric vortex breakdown flow. Finally, the effects of an artificial spherical microperturbation with diameter of 0.2mm fixed at the nose tip were examined to confirm the nondeterminacy of natural perturbations. With artificial microperturbations, rolling moment induced by asymmetric vortex breakdown flow can be controlled in a skillfully deflected manner.
ISSN: 0893-1321
eISSN: 1943-5525
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Record 34 of 233
Title: Leakage and wear characteristics of finger seal in hot/cold state for aero-engine
Author(s): Li, GQ (Li Guoqing); Zhang, Q (Zhang Qian); Lei, G (Guo Lei); Yu, QP (Yu Qiangpeng); Xu, G (Xu Gang); Zhu, JQ (Zhu Junqiang)
Source: TRIBOLOGY INTERNATIONAL Volume: 127 Pages: 209-218 DOI: 10.1016/j.triboint.2018.06.008 Published: NOV 2018
Abstract: Experimental investigation has been done to approach the leakage and wear characteristics of finger seal in hot/cold state. The High-speed Sealing Test Rig was used in the study. Leakage measurements were done in terms of different working parameters. The pressure ratio changed from 1.1 to 1.8 and the rotating speed varied from 0 to 5000 rpm. The temperature altered from 283 K to 433 K to achieve the cold state and hot state, respectively. Two groups of durability tests were carried out in hot/cold state, separately. Each durability test lasted 300 h with two finger seals. An accurate optical measuring instrument was applied to record the wear growth of the finger seals. Results showed that the flow factor monotonously increases with the pressure ratio and decreases with the rotating speed. An attractive feature is firstly captured that the finger seal with double-laminate achieves lower leakage in cold state while the finger seal with triple-laminate behaves better in hot state. Full life-cycle theory was applied to analyse the wear of the finger seal. The wear growth curve exhibits a rule of SPSP (Sharp Wear, Progressive Wear, Stable Wear and Permanent Wear). Of particular interest is the wear comparison between hot state and cold state, which is firstly discussed in the study and shows that finger seals operating in hot state generate obviously more wear than those in cold state.
ISSN: 0301-679X
eISSN: 1879-2464
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Record 35 of 233
Title: Liquid metal nano/micro-channels as thermal interface materials for efficient energy saving
Author(s): Zhao, LY (Zhao, Liuying); Liu, HQ (Liu, Huiqiang); Chen, XC (Chen, Xuechen); Chu, S (Chu, Sheng); Liu, H (Liu, Han); Lin, ZY (Lin, Zuoye); Li, QG (Li, Qiuguo); Chu, G (Chu, Guang); Zhang, H (Zhang, Hang)
Source: JOURNAL OF MATERIALS CHEMISTRY C Volume: 6 Issue: 39 Pages: 10611-10617 DOI: 10.1039/c8tc03417f Published: OCT 21 2018
Abstract: Thermal interface material (TIMs) pads/sheets with both high elasticity and low thermal resistance are indispensable components for thermal management. In this paper, we propose a facile strategy for the fabrication of highly thermal conductive liquid metal (LM) nano/micro-channels embedded in an elastomeric matrix (polydimethylsiloxane, PDMS). The isolated LM micro-droplets were reshaped and became thermally connected upon applying stress to form conductive LM nano-channels, while improving the thermal conductivity (K) up to 8.3 W m(-1) K-1, which is greater than that of most commercial thermal silicone pads (<6 W m(-1) K-1). In addition, a series of experiments on a commercial smartphone were performed to evaluate the heat dissipation performance. The results proved that LM thermal pads could not only reduce the temperature of the CPU and the back cover, but could also save energy and enhance the battery running time by as much as 31%.
ISSN: 2050-7526
eISSN: 2050-7534
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Record 36 of 233
Title: Properties and reactivity of LaCuxNi1-xO3 perovskites in chemical-looping combustion for mid-temperature solar-thermal energy storage
Author(s): Jiang, QQ (Jiang, Qiongqiong); Zhang, H (Zhang, Hao); Deng, YN (Deng, Ya'nan); Kang, QL (Kang, Qilan); Hong, H (Hong, Hui); Jin, HG (Jin, Hongguang)
Source: APPLIED ENERGY Volume: 228 Pages: 1506-1514 DOI: 10.1016/j.apenergy.2018.07.028 Published: OCT 15 2018
Abstract: Solar-heat driven chemical-looping combustion (S-CLC) is an efficient method for storing solar energy. In the S-CLC process, solar heat is used to drive the endothermic reduction reaction between a hydrocarbon fuel and an oxygen carrier. The solar heat is converted into chemical energy and stored in the reduced oxygen carrier. Owing to their high reactivity at low reaction temperatures, perovskites are treated as promising oxygen carriers in S-CLC. Herein, the reactivity and regenerability of LaCuxN1-xO3 (x = 0.025, 0.050, 0.075, 0.1, 0.2, 0.3, 0.5) perovskites are studied using methane as the fuel gas. The experimental results show that LaCu0.1Ni0.9O3 has the highest reactivity and regenerability among the synthesized materials. At a reduction temperature of 350 degrees C, more than 46% of the LaCu0.1Ni0.9O3 is reduced in 5 min, much higher than the amount of other LaCuxN1-xO3 perovskites reduced under the same conditions. After 30 redox cycles, the reactivity and micrographs of LaCuxN1-xO3 are similar to those of fresh material, indicating thatLaCu(0.1)Ni(0.9)O(3) has a desirable regenerability. Furthermore, no carbon deposition is observed during the reduction reaction between CH4 and LaCuxN1-xO3. Our study is expected to provide a new method for storing mid-and-low temperature solar heat using this solid perovskite.
Conference Title: 4th International Conference on Advanced Electromaterials (ICAE) / Symposium 7 on Advanced Materials and Devices for Hydrogen Fuel Cell and Electrolysis Technologies
Conference Date: NOV 21-24, 2017
Conference Location: Jeju, SOUTH KOREA
ISSN: 0306-2619
eISSN: 1872-9118
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Record 37 of 233
Title: Isothermal versus two-temperature solar thermochemical fuel synthesis: A comparative study
Author(s): Kong, H (Kong, Hui); Hao, Y (Hao, Yong); Jin, HG (Jin, Hongguang)
Source: APPLIED ENERGY Volume: 228 Pages: 301-308 DOI: 10.1016/j.apenergy.2018.05.099 Published: OCT 15 2018
Abstract: Metal-oxide based, two-step thermochemical cycling is a promising means of harvesting solar energy, in which water or carbon dioxide is dissociated to synthesize fuels via successive reduction and oxidation half-reactions driven by concentrated solar heat. Isothermal thermochemical cycling has recently emerged as an important special case of two-step solar TC with distinct advantages of easier heat recovery and potentially high efficiencies, and criteria for the design of oxide materials of isothermal thermochemical cycling are talked about recently. However, the pros and cons of isothermal versus two-temperature (i.e. two-T) TC are under debate. In this work, the two approaches are compared by exploring the influence of temperature, reduction pressure and thermodynamic properties of materials on solar-to-fuel efficiencies. Through the analysis, isothermal cycling is shown to work much better on CO2 splitting for easily reducible materials than two-T cycling; even for materials conventionally considered good for two-T cycling, isothermal cycling could still excel (over two-T cycling) under certain operating conditions. General principles for materials screening are also explored. There are many factors that favour isothermal thermochemical cycling over two-T cycling, such as high temperature, high heat recovery rate, small reduction enthalpy or splitting of CO2 instead of water. In addition, materials with large specific heat, which are unfavorable for two-T cycling, may be suitable for isothermal cycling. At high temperatures or with high heat recovery rates, isothermal thermochemical cycling exhibits excellent performance even for H2O splitting. The theoretical solar-to-fuel efficiency of similar to 28% (for CO2 splitting at 1650 degrees C and pO(2) = 10(-5) atm, without heat recovery) of isothermal cycling may indicate a meaningful route to effective solar thermochemical fuel production.
Conference Title: 9th International Conference on Applied Energy (ICAE)
Conference Date: AUG 21-24, 2017
Conference Location: Cardiff, WALES
ISSN: 0306-2619
eISSN: 1872-9118
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Record 38 of 233
Title: Experimental performance of 300 kW(th) prototype of parabolic trough collector with rotatable axis and irreversibility analysis
Source: ENERGY Volume: 161 Pages: 595-609 DOI: 10.1016/j.energy.2018.07.136 Published: OCT 15 2018
Abstract: Parabolic trough collector (PTC) is the most mature concentrating solar thermal technology. Limited by the cosine effect, annual thermal efficiency of FTC is only 50%. To show the limitations of performance of PTC and find corresponding solutions, an irreversibility analysis of FTC is experimentally conducted. Global exergy destruction is divided into exergy destructions in concentrator and receiver according to process analysis. Experimental results shows that the exergy destruction in concentrator accounts for the largest share. It indicates the process that sunlight being concentrated onto receiver is the key limitation of the performance of FTC. Experiments of the PTC with rotatable axis tracking show that rotatable axis tracking could decrease the exergy destruction in concentrator obviously. The annual exergy efficiency would be expected to be improved by 3% points according to the experimental results. This indicates that rotatable axis tracking is a practical method to improve the performance of PTCs. The influences of azimuth angle of FTC and heat transfer fluid temperature on exergy destruction are also analysed based on experimental data. In this study, the key limitation of the performance of the FTC is revealed and practical methods to decrease the exergy destruction of the FTC are provided. (C) 2018 Published by Elsevier Ltd.
ISSN: 0360-5442
eISSN: 1873-6785
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Record 39 of 233
Title: Spectrally Resolved Specular Reflections of Thermal Phonons from Atomically Rough Surfaces
Author(s): Ravichandran, NK (Ravichandran, Navaneetha K.); Zhang, H (Zhang, Hang); Minnich, AJ (Minnich, Austin J.)
Source: PHYSICAL REVIEW X Volume: 8 Issue: 4 Article Number: 041004 DOI: 10.1103/PhysRevX.8.041004 Published: OCT 5 2018
Abstract: The reflection of waves from rough surfaces is a fundamental process that plays a role in diverse fields such as optics, acoustics, and seismology. While a quantitative understanding of the reflection process has long been established for many types of waves, the precise manner in which thermal phonons of specific wavelengths reflect from atomically rough surfaces remains unclear owing to limited control over terahertz-frequency phonon generation and detection. Knowledge of these processes is critical for many applications, however, and is particularly important for recent attempts to create novel materials by coherently interfering thermal phonons. Here, we report measurements of a key property for these efforts, the phonon-wavelength-dependent specularity parameter, which describes the probability of specular reflections of thermal phonons at a surface. Our experiments show evidence of specular surface reflections of terahertz thermal phonons in our samples around room temperature and indicate a sensitivity of these reflections to surface imperfections on the scale of just 2-3 atomic planes. Our work demonstrates a general route to probe the microscopic interactions of thermal phonons with surfaces that are typically inaccessible with traditional experiments.
ISSN: 2160-3308
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Record 40 of 233
Title: Quantitative Analysis by Thermogravimetry-Mass Spectrum Analysis for Reactions with Evolved Gases
Author(s): Li, RB (Li, Rongbin); Huang, Q (Huang, Qian); Wei, K (Wei, Kai); Xia, HD (Xia, Hongde)
Source: JOVE-JOURNAL OF VISUALIZED EXPERIMENTS Issue: 140 Article Number: e58233 DOI: 10.3791/58233 Published: OCT 2018
Abstract: During energy conversion, material production, and metallurgy processes, reactions often have the features of unsteadiness, multistep, and multi-intermediates. Thermogravimetry-mass spectrum (TG-MS) is seen as a powerful tool to study reaction features. However, reaction details and reaction mechanics have not been effectively obtained directly from the ion current of TG-MS. Here, we provide a method of an equivalent characteristic spectrum analysis (ECSA) for analyzing the mass spectrum and giving the mass flow rate of reaction gases as precise as possible. The ECSA can effectively separate overlapping ion peaks and then eliminate the mass discrimination and temperature-dependent effect. Two example experiments are presented: (1) the decomposition of CaCO3 with evolved gas of CO2 and the decomposition of hydromagnesite with evolved gas of CO2 and H2O, to evaluate the ECSA on single-component system measurement and (2) the thermal pyrolysis of Zhundong coal with evolved gases of inorganic gases CO, H-2, and CO2, and organic gases C2H4, C2H6, C3H8, C6H14, etc., to evaluate the ECSA on multi-component system measurement. Based on the successful calibration of the characteristic spectrum and relative sensitivity of specific gas and the ECSA on mass spectrum, we demonstrate that the ECSA accurately gives the mass flow rates of each evolved gas, including organic or inorganic gases, for not only single but multi-component reactions, which cannot be implemented by the traditional measurements.
ISSN: 1940-087X
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Record 41 of 233
Title: Thermodynamic investigations of the supercritical CO2 system with solar energy and biomass
Source: APPLIED ENERGY Volume: 227 Special Issue: SI Pages: 108-118 DOI: 10.1016/j.apenergy.2017.08.001 Published: OCT 1 2018
Abstract: In this work, a supercritical CO(2 )system integrating solar energy and biomass is proposed to mitigate the emission of the greenhouse gases, and realize the stable and efficient operation of the system. The proposed system mainly contains three parts, i.e., solar island, biomass burner and power block. With the consideration of the variations of the solar irradiation and the complementation of the biomass, the on-design and off-design thermodynamic performances of this system are numerically studied. Results indicate that the solar-to-electric efficiency of the system can reach to 27.85% at the design point, and the ratios of solar heat supply in the power cycle in four representative days are in the range of 15.7-36.4%. The exergy analyses are implemented to investigate the irreversible losses and the variation of the exergy destruction in the energy conversion process. The economic evaluations are carried out to illustrate the feasibility of the proposed system, and the LCOE of the system is 0.085 $/kW h. Theoretical results indicate that the supercritical CO2 system with multi-energies input is a promising option for the efficient utilization of the abundant solar and biomass resources in western China.
ISSN: 0306-2619
eISSN: 1872-9118
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Record 42 of 233
Title: Synthesis, Structure, and Properties of the Non-Centrosymmeteric Compound LiNaRbB5O8(OH)(2)
Author(s): Yang, Y (Yang, Yi); Qiu, Y (Qiu, Yi); Gong, PF (Gong, Pifu); Huang, Q (Huang, Qian); Zhao, SE (Zhao, Sangen); Luo, SY (Luo, Siyang); Sun, JL (Sun, Junliang); Lin, ZS (Lin, Zheshuai)
Abstract: A new non-centrosymmetric hydroxyl alkali metal borate LiNaRbB5O8(OH)(2) has been grown under mild hydrothermal conditions at 220 degrees C. LiNaRbB5O8(OH)(2) belongs to the orthorhombic space group Aba2, with a = 11.3017(5) angstrom, b = 10.9956(5) angstrom, c = 9.2860(4) angstrom, and Z = 2. The crystal structure of LiNaRbB5O8(OH)(2) consists of Li/Na-O, Rb-O polyhedra, and [B5O8(OH)(2)](3-) groups. The transmittance spectrum of the LiNaRbB5O8(OH)(2) exhibits an absorption edge less than 200 nm in the UV region. The powder second-harmonic generation coefficient in LiNaRbB5O8(OH)(2) is about one-third that of KH2PO4 (KDP) based the Kurtz-Perry method. First principle calculations based on band structure, density of states, and optical properties are used to better understand the relationship between electronic structure and optical properties.
ISSN: 1528-7483
eISSN: 1528-7505
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Record 43 of 233
Title: First principles calculation of boron diffusion in fcc-Fe
Author(s): Zhang, X (Zhang, Xin); Li, XL (Li, Xianglong); Wu, P (Wu, Ping); Chen, S (Chen, Sen); Zhang, SP (Zhang, Shiping); Chen, N (Chen, Ning); Huai, XL (Huai, Xiulan)
Source: CURRENT APPLIED PHYSICS Volume: 18 Issue: 10 Pages: 1108-1112 DOI: 10.1016/j.cap.2018.06.009 Published: OCT 2018
Abstract: The diffusion mechanism of boron in fcc-Fe was studied by first-principles calculations. The sites where B atoms tend to occupy and the diffusion behavior were calculated. Results indicated that the main mechanism of boron diffusion in fcc-Fe was the B-monovacancy complex mechanism instead of the interstitial mechanism. The diffusion coefficient D-1 of the B-monovacancy complex mechanism was calculated without considering the backward jump of the B atoms. The calculated D-1 = 1.26 x 10(-4) x exp((-)2.01eV/k(B)T) m(2).s(-1) is consistent with the reported results from experiments.
ISSN: 1567-1739
eISSN: 1878-1675
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Record 44 of 233
Title: Energy level difference graphic analysis method of combined cooling, heating and power systems
Source: ENERGY Volume: 160 Pages: 1069-1077 DOI: 10.1016/j.energy.2018.07.026 Published: OCT 1 2018
Abstract: In this research, an energy level difference graphic analysis method that describes the variation of the driving force for a thermodynamic process is proposed. This method is based on the average energy level difference, in which the contrastive analysis among energy transfer and conversion processes especially for off-design conditions is presented. The graphic analysis using this method is conducted on a combined cooling, heating and power (CCHP) system. At the design conditions, because the high energy level difference occurs in the combustor (COMB), the exergy destruction accounts for approximately 40% of the input fuel exergy, followed by the high-pressure generator (HPG). Moreover, this proposed method is introduced to evaluate the off-design performance of the CCHP system with the different operation method for the gas turbine. The energy level difference Delta A(COMB) under the inlet air throttling (LAT) operation method is decreased, which makes the less exergy destruction in the COMB compared with the reducing turbine inlet temperature (TIT) operation method. However, the opposite results are presented in the HPG. The proposed method may provide a new approach to reveal the energy-saving potential of the energy system. (C) 2018 Elsevier Ltd. All rights reserved.
ISSN: 0360-5442
eISSN: 1873-6785
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Record 45 of 233
Title: Efficient path of distributed solar energy system synergetically combining photovoltaics with solar-syngas fuel cell
Source: ENERGY CONVERSION AND MANAGEMENT Volume: 173 Pages: 704-714 DOI: 10.1016/j.enconman.2018.07.089 Published: OCT 1 2018
Abstract: Solar energy system is compatible with the ever-rising demands to switch from fossil fuels to renewable energy sources. Here, a concentrating solar power system integrating photovoltaics and a solar-syngas-fuelled solid oxide fuel cell is proposed. The concentrated sunlight is first absorbed by a spectrum selective nanofluid. The ultraviolet and infrared solar spectrum bands of the concentrated sunlight are absorbed and converted into solar syngas through a thermochemical reaction. The upgraded solar syngas is converted into electricity through solid oxide fuel cell. The visible and near-infrared sunlight band un-absorbed by nanofluid is transmitted and directly converted into electricity through concentrator photovoltaics. In contrast to individual concentrator photovoltaics, this solar hybrid system can convert the ultraviolet and infrared solar spectrum bands to solar syngas instead of waste heat. The nanofluid has the function of adjusting the output electricity share between the solid oxide fuel cell and the concentrator photovoltaics. The simulation method of this type of solar hybrid system is described. The conversion performance of the full spectrum solar energy converted into electricity is analysed for a typical system. In particular, the complementary feature of the spectrum response is disclosed for the selected nanofluid. The solar-to-electricity efficiency would be expected to be approximately 31.5% at a direct normal irradiation of 900 W/m(2). An optimal particle size and volume fraction of the nanofluid are provided. The results may provide a possibility of a new pathway to the high-efficiency of full solar spectrum utilization.
ISSN: 0196-8904
eISSN: 1879-2227
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Record 46 of 233
Title: Phosphorus Transformation from Municipal Sewage Sludge Incineration with Biomass: Formation of Apatite Phosphorus with High Bioavailability
Source: ENERGY & FUELS Volume: 32 Issue: 10 Pages: 10951-10955 DOI: 10.1021/acs.energyfuels.8b01915 Published: OCT 2018
Abstract: Phosphorus (P) is an essential and limited nutrient element for all life. The recovery and reuse of P from municipal sewage sludge (MSS) incineration fly ash are considered to be practical and economical. Addition of biomass into MSS was proposed to enhance the P bioavailability during incineration. The speciation conversion of P during MSS incineration with different types of biomass was studied in this work. The chemical reactions between P-containing model compound (AlPO4) and mineral model compounds in biomass (CaO and KCl) were investigated to simulate the conversion mechanism of nonapatite inorganic phosphorus (NAIP) to apatite phosphorus (AP) during MSS incineration with biomass. It is shown that the addition of biomass increases the P mass percentage and facilitates the transformation of NAIP to AP in fly ash. Cotton stalk has the most positive effect on the P transformation in the four biomass samples. Ca, Cl, K, and/or Mg compounds in biomass promote the conversion of NAIP (such as AlPO4) to AP (such as Ca2P2O7, Ca-5(PO4)(3)Cl, and Ca10K(PO4)(7)) during MSS incineration. Higher temperature stimulates the transformation of NAIP to stable AP. The primary reaction pathway between phosphorus and the main components in biomass is revealed. AlPO4 can react with CaO to form Ca2P2O7 and Ca-3(PO4)(2) at 900 degrees C, and two new P-containing compounds, Ca-5(PO4)(3)Cl and Ca10K(PO4)(7), are formed in the presence of KCl.
ISSN: 0887-0624
eISSN: 1520-5029
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Record 47 of 233
Title: Experimental and Numerical Investigations of Closed Radial Inflow Turbine With Labyrinth Seals
Source: JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME Volume: 140 Issue: 10 Article Number: 102502 DOI: 10.1115/1.4039804 Published: OCT 2018
Abstract: It is a common practice to use closed impeller in radial inflow turbine against the flow leakage from tip clearance of impellers, especially in small volume flow condition. It utilizes labyrinths between the shroud and the case to abate the higher pressure leakage. Experimental and computational investigations of shroud clearance flow in a radial inflow turbine with labyrinth seals are presented in this paper. Compared with the result without leakage, numerical computation result including the leakage of labyrinth seals agrees better with that of the experiment result, which indicates that the leakage of labyrinth seals cannot be neglected. Several geometrical arrangements with a series of different clearance of labyrinth seals are investigated experimentally and numerically, and the dimensionless shroud clearance is of 0%, 0.6%, 1.2%, 1.8%, 2.7%, 3.6%. Finally, the character of flow and loss is analyzed by computational fluid dynamics (CFD) tools. The results indicate that the labyrinth seal flow has no effect on the main flow passage and mainly causes different leakage mass flow.
ISSN: 0742-4795
eISSN: 1528-8919
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Record 48 of 233
Title: Numerical analysis of operating conditions for establishing high-density circulating fluidized bed by CPFD method
Abstract: The effects of operating conditions on the gas-solid hydrodynamics in a high-density CFB are numerically studied using the computational particle fluid dynamics approach. With the increase of standpipe bottom aeration rate, the solids circulation rate increases within the range of stable operation, while the packed bed height in the standpipe decreases. The same tendency is found for the standpipe aeration rate, however, it is more efficient than the bottom aeration rate to increase solids flux. With the increase of the solids inventory, the solids flux shows a parabolic relation with it, however, the standpipe pressure drop increases almost linearly under the fixed aeration conditions. The riser flowrate has only small effect on solids circulation behavior. The aeration distribution in the valve has little influence on solids flux, however, it affects significantly the valve pressure drop and transient flow behavior. The number of aeration ports on the standpipe does not influence solids flux much, but it affects the hydrodynamics stability of the standpipe. (C) 2018 Elsevier B.V. All rights reserved.
ISSN: 0032-5910
eISSN: 1873-328X
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Record 49 of 233
Title: Low NOx Emissions from Pulverized Coal Moderate or Intense Low-Oxygen Dilution Combustion in O-2/CO2 Preheated by a Circulating Fluidized Bed
Source: ENERGY & FUELS Volume: 32 Issue: 10 Pages: 10956-10963 DOI: 10.1021/acs.energyfuels.8b02000 Published: OCT 2018
Abstract: This work reports a newly preheated system with pulverized coal oxy-fuel moderate or intense low-oxygen dilution (MILD) combustion for low NOx emissions. During the experiment, high-temperature fuel preheated by a circulating fluidized bed unit would burn out in a down-fired combustor. This preheating process of pulverized coal tended to form a strong reducing atmosphere and promoted the fuel temperature above the ignition temperature, which contributed to NOx reduction and MILD combustion formation. During the oxy-fuel MILD combustion process, the CO2 concentration of flue gas reached approximately 95%, the NO2 and N2O emissions were nearly zero, and the NO emissions were 107.99 mg/MJ. The combustion efficiency was 98.21%, which indicates that the combustion efficiency would not decrease in MILD combustion. Also, NO emissions were further reduced to 37.25 mg/MJ through a rational arrangement of tertiary gas positions. For pulverized coal combustion, the accurate definition of MILD combustion should consider the disappearance of flame front besides the feature of temperature distribution.
ISSN: 0887-0624
eISSN: 1520-5029
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Record 50 of 233
Title: Study on the characteristics of the capillary wetting and flow in open rectangular microgrooves heat sink
Abstract: This study presents a computational model in terms of capillary wetting and flow occurring in open rectangular microgrooves heat sink. This specific microgrooves heat sink, used at inclined angle position applications, is characterized by high heat transfer coefficient. Based on classical conservation equations and the generalized relationships of liquid thickness and geometric structures of microgrooves, the radius of curvature, wetting cross-sectional area and average flow rate along with the wetting length (axial direction) are numerically solved. A range of parameters including inclined angles, microgrooves dimensions and contact angles are considered in this computational model. The calculated values are verified by the experimental data. The standard error of calculated values compared with the experimental data is 2.7 x 10(-4) and 1.405 x 10(-8) when calculating the radius of curvature and wetting cross-sectional area.
The modeling is sensitive to a variety of parameters. Both the radius of curvature and wetting cross-sectional area decrease with the increase of the axial distance, and approaches zero until the liquid film reaches the maximum wetting length (dryout point) in evaporative region. Less microgrooves dimensions lead to longer wetting length. The liquid wetting cross-sectional area decreases as inclined angles and contact angles increase. The average flow rate decreases with the increase of inclined angle for microgrooves under the same heat flux. It increases at first, and then decreases with the axial direction of the microgrooves.
ISSN: 1359-4311
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Record 51 of 233
Title: Operating technical characteristics on asymmetrical arrangement of six cyclones in a 600 MW supercritical CFB boiler
Author(s): Song, GL (Song, Guoliang); Yang, Z (Yang, Zhao); Zhou, T (Zhou, Tuo); Lyu, QG (Lyu, Qinggang)
Abstract: In order to obtain the operating characteristics of the first 600 MW supercritical circulating fluidized bed (CFB) boiler with six cyclones in an asymmetrical arrangement, the gas-solid flow information and temperature distribution of six circulating loops were measured and analyzed. The experimental results indicate that bed temperature in the furnace presents an S-type distribution pattern along the furnace height direction, for three cyclones of the same side, the temperature in the middle cyclone is high and the temperature on both side cyclones is low. At high boiler loads (450-600 MW), the temperature distribution of six cyclones and the gas solid flow uniformity along the furnace height direction is more uniform, the temperature distribution uniformity in dense phase zone of furnace and three circulating loops on the right side wall are superior to those of the left side wall. The calculation results indicate that the particle flow distribution of six cyclone inlets is relatively uniform, the calculated results are consistent with the test results. The gas-solid flow asymmetry phenomenon of six circulating loops on both sides of the furnace is found, and the relative standard deviation of six cyclones inlet temperature does not exceed 4.30%, the back pass structure needs further optimization.
ISSN: 1359-4311
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Record 52 of 233
Title: Experimental investigation and correlation development of jet impingement heat transfer with two rows of aligned jet holes on an internal surface of a wing leading edge
Author(s): Yu, J (Yu, Jia); Peng, L (Peng, Long); Bu, XQ (Bu, Xueqin); Shen, XB (Shen, Xiaobin); Lin, GP (Lin, Guiping); Bai, LZ (Bai, Lizhan)
Source: CHINESE JOURNAL OF AERONAUTICS Volume: 31 Issue: 10 Pages: 1962-1972 DOI: 10.1016/j.cja.2018.07.016 Published: OCT 2018
Abstract: Extensive experimental studies on the heat transfer characteristics of two rows of aligned jet holes impinging on a concave surface in a wing leading edge were conducted, where 50000 <= Re-j <= 90000, 1.74 <= H/d <= 27.5, 66 degrees <= alpha <= 90 degrees, and 13.2 <= r/d <= 42.03. The finding was that the heat transfer performance at the jet-impingement stagnation point with two rows of aligned jet holes was the same as that with a single row of jet holes or the middle row of three-row configurations when the circumferential angle of the two jet holes was larger than 30 degrees. The attenuation coefficient distribution of the jet impingement heat transfer in the chordwise direction was so complicated that two zones were divided for a better analysis. It indicated that: the attenuation coefficient curve in the jet impingement zone exhibited an approximate upside-down bell shape with double peaks and a single valley; the attenuation coefficient curve in the non-jet impingement zone was like a half-bell shape, which was similar to that with three rows of aligned jet holes; the factors, including Rej, H/d and r/d, affected the attenuation coefficient value at the valley significantly. When r/d was increased from 30.75 to 42.03, the attenuation rates of attenuation coefficient increased only by 1.8%. Consequently, experimental data-based correlation equations of the Nusselt number for the heat transfer at the jet-impingement stagnation point and the distribution of the attenuation coefficient in the chordwise direction were acquired, which play an important role in designing the wing leading edge anti-icing system with two rows of aligned jet holes. (C) 2018 Chinese Society of Aeronautics and Astronautics. Production and hosting by Elsevier Ltd.
ISSN: 1000-9361
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Record 53 of 233
Title: Post combustion CO2 capture in power plant using low temperature steam upgraded by double absorption heat transformer
Author(s): Wang, DD (Wang, Dandan); Li, S (Li, Sheng); Liu, F (Liu, Feng); Gao, L (Gao, Lin); Sui, J (Sui, Jun)
Source: APPLIED ENERGY Volume: 227 Special Issue: SI Pages: 603-612 DOI: 10.1016/j.apenergy.2017.08.009 Published: OCT 1 2018
Abstract: In CO2 capture retrofit unit of existing coal-fired power plants, energy level mismatch between extraction steam from turbines and CO2 regeneration process always results in large exergy destruction and low thermal efficiency. Thus, a new CO2 capture system driven by double absorption heat transformer is proposed. Through the absorption heat transformer, low-temperature steam is upgraded into a higher energy level to match the temperature of CO2 regeneration. Also, flue gas heat is partly recovered to preheat the circulating water from CO2 capture process to further decrease system energy penalty. Aspen Plus 11.0 is used to simulate the system and parameters of key processes are validated by experimental values. It is shown that with 90% CO2 capture, the thermal efficiency of the power plant with proposed CO2 capture system is enhanced by 1.25 percentage points compared with traditional method. And the efficiency enhancement of the proposed system has a trend of increase first and then decrease with CO2 capture rate growth. For a 350 MW coal-fired power plant, the optimum CO2 capture rate is 53.65% and the corresponding efficiency enhancement is 2.06 percentage points. Exergy analysis shows that the exergy destruction in CO2 separation and steam condensation process can decrease by 49.5% in the proposed system, and thereby the exergy efficiency is 1.85 percentage points higher than the conventional method. Furthermore, the cost of CO2 avoided and cost of electricity of the proposed system will be reduced by 10.7 $/t-CO2 and 1.9 $/MW h, respectively.
ISSN: 0306-2619
eISSN: 1872-9118
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Record 54 of 233
Title: Full-spectrum solar energy utilization integrating spectral splitting, photovoltaics and methane reforming
Source: ENERGY CONVERSION AND MANAGEMENT Volume: 173 Pages: 602-612 DOI: 10.1016/j.enconman.2018.06.012 Published: OCT 1 2018
Abstract: A spectral splitting photovoltaic-methane-steam-reforming hybrid system for heat and power cogeneration has been proposed. In the system, sunlight with wavelengths shorter than 870 nm is assigned to photovoltaic cells for direct power and heat cogeneration, while the rest of the solar spectrum is utilized by a methane-steam-reforming reactor via the route of solar thermal energy - chemical energy - heat and power. Analysis reveals that the hybrid system is characterized by high net solar-to-exergy efficiency (40%), high energy storage capability and low-emission energy supply (63% fossil energy saving and 77% carbon-dioxide emission reduction). Primary reasons underlying the excellent performance are full-spectrum optimized utilization of solar energy and comprehensive utilization among solar energy, thermal energy and chemical energy.
ISSN: 0196-8904
eISSN: 1879-2227
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Record 55 of 233
Title: Experimental study on combustion, flame and NOx emission of pulverized coal preheated by a preheating burner
Abstract: Experimental researches on combustion characteristics of pulverized Ningdong bitumite preheated by a preheating burner were carried out in a 0.2 MW coal preheating combustion test rig, and the effects of preheating temperature, secondary air equivalence ratio and the positions of tertiary air nozzles on combustion, flame and NOx emissions of preheated fuels were studied. The results showed that the 0.2 MW coal preheating combustion test rig can operate stably and the combustion efficiency can be higher than 97% while the NOx emissions are lower than 100 mg/Nm(3). With the increase of preheating temperature, NOx emissions increase, and the combustion efficiency does not change obviously. With the increase of secondary air equivalence ratio, the combustion efficiency increases, and NOx emissions increase as well. With the increase of the distance between the tertiary air nozzle and the preheated fuel nozzle, NOx emissions decrease, and the combustion efficiency decreases as well. The flame characteristic is not sensitive to preheating temperature, but closely related to the air distribution of down-fired combustor. With reasonable air supply positions, flameless combustion can be realized.
ISSN: 0378-3820
eISSN: 1873-7188
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Record 56 of 233
Title: Experimental study on the recovery of sodium in high sodium fly ash from thermochemical conversion of Zhundong coal
Abstract: Zhundong (ZD) coal gasification/combustion fly ash is a high Na content residual product and contains a large quantity of harmful elements, including as Cl, S, and Na that must be removed and recovered. Water-soluble Na is the predominant Na form in ZD coal fly ash, accounting for 34.7-92.8% of the total Na. The main minerals of Na identified were NaCl and Na2SO4. Most of the water-soluble Na in the ZD coal fly ash can be effectively removed by water washing, the removal yields have been found to be 31-93%. Increasing the washing time, water temperature, liquid-solid ratio and acid concentration can increase the Na removal yield. For the ZD coal combustion fly ash (SEHcf) and gasification fly ash (SEHf), NaCl particles are present on the fly ash surface, most water-soluble Na was washed by water in 5 min at 30 degrees C. However, the removal of Na by water washing was inhibited by the water insoluble calcium oxides and sulfides that covered the surface of the ZD coal gasification fly ashes (TCf and SHf), Na removal required higher wash water temperatures and longer washing times. It is feasible to recover Na from ZD coal fly ash by water washing, and the recovered Na products are primarily NaCl and Na2SO4. The recovery yields of Na in the SEHcf, SEHf and TCf were 49.4%, 81.2%, and 65.4%. But the recovery yield of Na in SHf was 16.6%. SEHcf, SEHf and TCf were more suitable for recovering Na. the recovery of Na from ZD coal fly ash is economically feasible.
ISSN: 0016-2361
eISSN: 1873-7153
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Record 57 of 233
Title: A new hybrid photovoltaic/thermal and liquid desiccant system for trigeneration application
Author(s): Su, BS (Su, Bosheng); Han, W (Han, Wei); Qu, WJ (Qu, Wanjun); Liu, CC (Liu, Changchun); Jin, HG (Jin, Hongguang)
Abstract: Conventional combined cooling, heating and power (CCHP) systems based on fossil fuels, with an acceptable energy performance, however, intensify the greenhouse effect worldwide. Using solar energy in distributed energy systems has the potential to further reduce fossil fuels consumption, and ease carbon emissions. This paper proposes a novel CCHP system by combining concentrated photovoltaic/thermal (PV/T) technology with an advanced air-handling process that realizes independent control of temperature and humidity. The heat produced from a PV/T collector is for desiccant regeneration in a two-stage liquid desiccant cycle in summer, and can be directly supplied to nearby users in winter. An office building under typical climate conditions of Beijing in 2002 was adopted to determine its various energy demands. Due to the efficient use of solar energy, annual energy saving ratio and CO2 emissions reduction ratio are predicted to be 73.28% and 74.55%, respectively. Two extreme conditions determining whether the excess heat from the PV/T collector is used were compared to demonstrate the top and bottom limitations of economic performance. The integrated performance, considering energy, environment and economic factors, reaches 37.48% when no excess heat from PV/T collector is used, and it can be further improved by thermal storage or recovering the excess heat to produce other products. This study provides a new solar utilization technology for trigeneration with advanced integrated performance.
Conference Title: Conference on Renewable Energy Markets (REM)
Conference Date: OCT 22-24, 2017
Conference Location: New York, NY
ISSN: 0306-2619
eISSN: 1872-9118
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Record 58 of 233
Title: High-efficiency power generation system with integrated supercritical water gasification of coal
Author(s): Chen, ZW (Chen, Zhewen); Gao, L (Gao, Lin); Zhang, XS (Zhang, Xiaosong); Han, W (Han, Wei); Li, S (Li, Sheng)
Abstract: A novel power generation system with integrated supercritical water gasification (SCWG) of coal is proposed in this article. The gasification product directly enters the supercritical turbine to generate electricity. After pressure relief, the syngas separated from the unreacted water is transferred to the combined cycle. The influences of coal-water-slurry concentration (CWSC) and the outlet pressure (P-h) of the supercritical turbine on the system performances are studied. The results show that the thermal efficiency increases with increasing CWSC or decreasing P-h. The ultimate thermal efficiency of the system can be obtained when the CWSC is 25 wt% and P-h is 1 bar, which can approach 54.68%. The thermal efficiency of the novel system is higher than that of the power generation system with integrated SCWG of coal and parallel chemical heat recovery. (C) 2018 Elsevier Ltd. Ail rights reserved.
ISSN: 0360-5442
eISSN: 1873-6785
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Record 59 of 233
Title: A solar methane reforming reactor design with enhanced efficiency
Author(s): Jin, J (Jin, Jian); Wei, X (Wei, Xin); Liu, MK (Liu, Mingkai); Yu, YH (Yu, Yuhang); Li, WJ (Li, Wenjia); Kong, H (Kong, Hui); Hao, Y (Hao, Yong)
Abstract: We report an efficiency-enhanced solar methane reforming reactor design, featuring cutoff wavelength coating over quartz window for incident solar energy, a compound parabolic concentrator (CPC) device for thermochemical performance enhancement and reticulated porous ceramics (RPC) structure of Ni/CeO2-ZrO2 used as the catalyst. A numerical model combining Monte-Carlo ray-tracing (MCRT) method with finite-element method (FEM) is established to evaluate the effectiveness of this reactor design. The simulation results show that the cutoff wavelength coating (with threshold wavelength of 2400 nm) helps to reduce 80% radiation heat loss from within the reactor at the cost of only 1% incident sunlight loss during transmission at a typical reforming temperature of 850 degrees C. The performance of the reactor is numerically investigated under different reaction conditions with wide ranges of temperature, solar power input and steam-to-methane ratio. Results show that eta(solar-chemical) (solar-to-chemical efficiency) can reach 39.98% and 59.16% without and with 90% heat recovery, respectively, and X-CH4 (methane conversion) is 83.95% at reforming temperature of 850 degrees C and pressure of 1 atm. The new reactor design could considerably increase the utilization efficiency of solar energy.
Conference Title: 9th International Conference on Applied Energy (ICAE)
Conference Date: AUG 21-24, 2017
Conference Location: Cardiff, WALES
ISSN: 0306-2619
eISSN: 1872-9118
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Record 60 of 233
Title: A high-temperature hybrid absorption-compression heat pump for waste heat recovery
Author(s): Liu, CC (Liu, Changchun); Jiang, YC (Jiang, Yingchun); Han, W (Han, Wei); Kang, QL (Kang, Qilan)
Source: ENERGY CONVERSION AND MANAGEMENT Volume: 172 Pages: 391-401 DOI: 10.1016/j.enconman.2018.07.027 Published: SEP 15 2018
Abstract: An absorption-compression heat pump is a promising way to recover low-temperature waste heat efficiently in industrial applications. In this paper, an advanced ammonia-water absorption-compression heat pump is proposed to recover the sensible heat of flue gas below 150 degrees C to generate saturated steam at 0.5 MPa (151.8 degrees C). The sensible heat is cascade utilized in the hybrid heat pump system. The high-temperature waste heat is recovered to generate pure ammonia vapor in the rectifier, and the low-temperature heat is used to evaporate the ammonia liquid. In the ammonia vapor compression process, the gas compression process is combined with a liquid compression process, leading to the clear decrease in power consumption. The simulation results indicate that the coefficient of performance and exergy efficiency of the proposed system reaches 5.49 and 27.62%, which is almost two times and 4.69% higher than that of the reference system, respectively. Subsequently, a sensitivity analysis is conducted to optimizing the key parameters, and the optimums values are obtained. Finally, an economic analysis is adopted to evaluate the economic performance of the proposed system. The payback period of the proposed system is 6.26 years compared to the reference system. This study may provide a new way to produce saturated steam by efficiently using the low-temperature waste heat.
ISSN: 0196-8904
eISSN: 1879-2227
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Record 61 of 233
Title: Investigation on Pulverized Coal Char Oxy-Combustion Behavior at Moderate and High Temperatures: Experiments and a Novel Developed Kinetics Modeling
Abstract: In oxyfuel combustion with temperature higher than ash flowing temperature (FT), both chemical interactions between the char gasification reaction with carbon dioxide, that is, C+CO2 --> 2CO, and the char oxidation reaction with oxygen, that is, C + (2-f)/2O(2) --> fCO + (1-f)CO2, are needed for further investigation. Both experiments and a novel developed kinetics model compared with three previous kinetics models are implemented to investigate oxy- and air-char combustion behaviors. Results show that in high temperature the maximum burning rate ratio as 34.8% from gasification is smaller than that as 47.1% in moderate temperature for inner pore reduction induced by ash mineral melting. The char mean consumption rate of sole gasification with carbon dioxide in 1773 K is 1.25 times to that in 1273 K, but this burning rate under 27%O-2/CO2 is 0.69 times to that in 1273 K. The mean burning rate ratio of char gasification increases from 28.0% to 40.0% in 1273 K and 1773 K, respectively.
ISSN: 0888-5885
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Record 62 of 233
Title: A near-isothermal expander for isothermal compressed air energy storage system
Author(s): Zhang, XJ (Zhang, Xinjing); Xu, YJ (Xu, Yujie); Zhou, XZ (Zhou, Xuezhi); Zhang, Y (Zhang, Yi); Li, W (Li, Wen); Zuo, ZT (Zuo, Zhitao); Guo, H (Guo, Huan); Huang, Y (Huang, Ye); Chen, HS (Chen, Haisheng)
Abstract: Compressed air energy storage technology is considered as a promising method to improve the reliability and efficiency of the electricity transmission and distribution, especially with high penetration of renewable energy. Being a vital component, the expander takes an important role in compressed air energy storage operation. The specific work of an expander can be improved through an isothermal expansion compared with the adiabatic expansion process due to a nearly constant temperature which enables the expander to operate with a high pressure ratio. In this study, a specific reciprocating expander with a high pressure ratio was developed and its adiabatic expansion characteristics were measured. Numerical modelling was performed to simulate adiabatic expansion. This model was also validated by experimental results. Based on these findings, we propose a quasi isothermal expansion process using water injection into the expander cylinder. Modelling was also extended to simulate the quasi-isothermal process by introducing water-air direct heat transfer equations. Simulation results showed that when spraying tiny water droplets into the cylinder, the specific work generated was improved by 15.7% compared with that of the adiabatic expansion under the same air mass flowrate, whilst the temperature difference was only about 10% of that of the adiabatic process, and cylinder height was decreased by 8.7%. The influence of water/air mass flowrate ratio and the inlet temperature on the expander performance was also studied.
Conference Title: 9th International Conference on Applied Energy (ICAE)
Conference Date: AUG 21-24, 2017
Conference Location: Cardiff, WALES
ISSN: 0306-2619
eISSN: 1872-9118
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Record 63 of 233
Title: Investigation of wake characteristic of a 30 kW rated power Horizontal Axis Wind Turbine with wake model and field measurement
Author(s): Li, Q (Li, Qing'an); Maeda, T (Maeda, Takao); Kamada, Y (Kamada, Yasunari); Hiromori, Y (Hiromori, Yuto)
Abstract: A field measurement and wake model based on experimental data were introduced to investigate the wake characteristics of a HAWT (Horizontal Axis Wind Turbine) in a wind farm. In the present study, a HAWT generator of capacity 30 kW with the rotor diameter of 10.0 m was used. Firstly, the reference wind was measured with inflow measurement mast. And then, the wake flow was examined in the different tip speed ratios and pitch angles at the wind turbine wake position of x/D = 2.0 by ultrasonic anemometers, three-cup type anemometers and wind vane. Finally, the wake velocity distribution was predicted by the wake model with Gaussian function. As a result, the non-dimensional wind velocity ratio U-NR reached the minimum value around y/R = 0.50 and increased as it went laterally away from y/R = 0.50. Furthermore, the non-dimensional wind velocity ratio U-NR decreased with the increase of the pitch angle. When the pitch angles were 0(degrees), 2(degrees) and 4(degrees), the minimum U-NR were about 0.77, 0.78 and 0.84 at the horizontal position of y/R = 0.5. Meanwhile, the full wake widths at half maximum of 1.04, 0.98 and 1.09 were obtained at the pitch angle of 0(degrees). This study provided rich information for the prediction of annual power generation of the downstream wind turbine in wind farm.
ISSN: 0306-2619
eISSN: 1872-9118
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Record 64 of 233
Title: Deep Learning-Based Inversion Method for Imaging Problems in Electrical Capacitance Tomography
Source: IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT Volume: 67 Issue: 9 Pages: 2107-2118 DOI: 10.1109/TIM.2018.2811228 Published: SEP 2018
Abstract: Electrical capacitance tomography exhibits great potentials in the visualization measurement of industrial processes, and high-precision images are of great significance for the reliability and usefulness of measurement results. In this paper, we propose a deep learning-based inversion method to ameliorate the reconstruction accuracy. With the aid of the deep learning methodology, the prior from the images reconstructed by a certain imaging technique to the true images is abstracted and stored in the deep extreme learning machine. A new cost function is constructed to encapsulate the prior from the proposed deep learning model and the domain expertise about imaging targets, and the split Bregman algorithm and the fast iterative shrinkage thresholding technique are combined into a new numerical method to effectively solve it to get the final reconstruction. The numerical and experimental results validate that the inversion method proposed in this paper reduces the reconstruction artifacts and deformations and leads to the much improvement in the imaging quality.
ISSN: 0018-9456
eISSN: 1557-9662
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Record 65 of 233
Title: Improved particle swarm optimization of designing resonance fatigue tests for large-scale wind turbine blades
Source: JOURNAL OF RENEWABLE AND SUSTAINABLE ENERGY Volume: 10 Issue: 5 Article Number: 053303 DOI: 10.1063/1.5018227 Published: SEP 2018
Abstract: As the sizes of wind turbine blades increase, it is becoming more difficult for designing fatigue tests to meet the requirements of blades' certification. In order to design accurate fatigue tests for large-scale wind turbine blades, this paper proposes an improved optimization based on particle swarm optimization. The advantages of this optimization algorithm are its accuracy in predicting test moments and its ability in matching distributions of test moments. The shell model, which can model some special details of large-scale blades, is used to predict test moments instead of the beam model in the optimization algorithm. Besides, removing the blade tip is introduced in to enrich test methods, which enlarges the dimensions of variables in the optimization algorithm. Furthermore, moment errors are measured in both the absolute type and the relative type. Based on the study of these two types of moment errors, the objective function and constraints are designed to guide the decrease and distribution of moment errors. At last, edge-tests of a 38-m blade (shell and beam model), a 60-m blade (beam model), and a 38.75-m blade (beam model) are designed by this improved optimization, and the optimal test moments and distributions of moment errors prove the abilities of this improved optimization. Differences of the moment errors and test durations between the results designed by the standard testing method and those designed by the improved testing method demonstrate the advantages of improved optimization. Published by AIP Publishing.
ISSN: 1941-7012
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Record 66 of 233
Title: Flow characteristic of a multistage radial turbine for supercritical compressed air energy storage system
Author(s): Wang, X (Wang, Xing); Li, W (Li, Wen); Zhang, XH (Zhang, Xuehui); Zhu, YL (Zhu, Yangli); Qin, W (Qin, Wei); Chen, HS (Chen, Haisheng)
Source: PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART A-JOURNAL OF POWER AND ENERGY Volume: 232 Issue: 6 Pages: 622-640 DOI: 10.1177/0957650917743366 Published: SEP 2018
Abstract: Compressed air in supercritical compressed air energy storage system expand from supercritical to atmospheric conditions at lower inlet temperature (<500K) to generate MW scale power. Therefore, a new multistage radial turbine is adopted and the flow characteristic is investigated by numerical simulation. Effects of ideal gas model and tip clearance on the performance and flow field of the multistage turbine are revealed. Results show that ideal gas model can reveal flow pattern under supercritical condition correctly while leading to obvious deviation of isentropic enthalpy drop, entropy, and inlet-to-exit total temperature ratio. Relative differences for mass flow and efficiency are less than 2%, while the relative differences for output power reaches to 9.36%. For shrouded rotor, mixing of working fluid near hub, blade suction surface, and shroud is the main influencing factor of the flow loss in the rotor. For unshrouded rotor, leakage vortex promote mixture of the fluid deriving from the hub, shroud, and suction surface, and causes much higher flow loss in the channel of rotor. The rotors, which have higher blade height variation rate, present higher efficiency reduction when the tip clearance height is increased, which is because the proportion of tip clearance in blade inlet height increases with the increase of average aspect ratio, resulting in the increase of leakage flow at the leading edge of rotor blade. The pressure fluctuation near the tip clearance and efficiency reduction is also increased. The present study provides a reference for further design and optimization of the multistage radial turbines in compressed air energy storage.
ISSN: 0957-6509
eISSN: 2041-2967
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Record 67 of 233
Title: A hybrid energy storage system with optimized operating strategy for mitigating wind power fluctuations
Author(s): Zhang, Y (Zhang, Yi); Xu, YJ (Xu, Yujie); Guo, H (Guo, Huan); Zhang, XJ (Zhang, Xinjing); Guo, C (Guo, Cong); Chen, HS (Chen, Haisheng)
Abstract: A novel method based on hybrid energy storage system (HESS), composed of adiabatic compressed air energy storage (A-CAES) and flywheel energy storage system (FESS), to mitigate wind power fluctuations and augment wind power penetration is proposed in this paper. Wind power fluctuates in different frequencies, mainly divided into low and high frequency, which can be coped with by A-CAES and FESS respectively. To fit with low frequency fluctuation exhibiting large magnitude, A-CAES with multi operating strategies is first proposed to widen operational ranges. Mathematical model of key components' off-design performance is established. For a 49.5 MW wind farm in China, design and optimization of HESS are comprehensively investigated. More specifically, the selection of A-CAES system's key components, such as compressor and expander, and parameters of them are specified as well as the parameters of FESS. The key operating parameters of the HESS, when integrated with wind plant, are analyzed and the characteristics are revealed. The results indicate that by HESS, wind power with fluctuation within 0-49.5 MW (average 25.55 MW) can be stabilized to a steady electrical power output of 24.18 MW. The loss of wind power is 6.6%, far less than the wind power rejection rate 17.1% in China. (C) 2018 Elsevier Ltd. All rights reserved.
ISSN: 0960-1481
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Record 68 of 233
Title: Biomass and coal co-feed power and SNG polygeneration with chemical looping combustion to reduce carbon footprint for sustainable energy development: Process simulation and thermodynamic assessment
Author(s): Fan, JM (Fan, Junming); Hong, H (Hong, Hui); Jin, HG (Jin, Hongguang)
Abstract: In this paper, biomass and coal has been used as blending feedstock for synthetic natural gas (SNG) production to originally shift H-2/CO ratio in syngas during gasification step that benefits downstream methanation process. The recycling ratio of unreacted gas is controlled to avoid huge exergy destruction during methanation, thus providing opportunity for supplementary power generation. The remaining gas is directed to chemical looping combustion (CLC) for power generation, and carbon capture is inherently achieved. Besides capture and storage of photosynthetically-derived CO2 from biomass by means of CLC offers possibilities for negative greenhouse gas emissions. The energy efficiency and exergy efficiency of this proposed process are 53.19% and 50.81%, respectively. Meanwhile approximately 16.86% of energy consumption and 98.74% of carbon emissions have been reduced compared with standalone reference system. In terms with the captured CO2 quality, it meets the requirement of suggested restrictions at biomass share of 40% (wt, %). Within this biomass share, the oxygen-to-carbon ratio (O/C), steam-to-carbon ratio (S/C), and recycling ratio of unreacted gas (Ru) have been found to be optimum at 0.4, 0.5 and 0.7, respectively. (C) 2018 Published by Elsevier Ltd.
ISSN: 0960-1481
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Record 69 of 233
Title: Novel Coal-Steam Gasification With a Thermochemical Regenerative Process for Power Generation
Author(s): Wang, DD (Wang, Dandan); Li, S (Li, Sheng); Gao, L (Gao, Lin); Wu, HD (Wu, Handong); Jin, HG (Jin, Hongguang)
Source: JOURNAL OF ENERGY RESOURCES TECHNOLOGY-TRANSACTIONS OF THE ASME Volume: 140 Issue: 9 Article Number: 092203 DOI: 10.1115/1.4039978 Published: SEP 2018
Abstract: In this paper, a novel high-efficiency coal gasification technology is proposed in which a regenerative unit is applied to recover syngas sensible heat to generate steam; then, the high-temperature steam is used to gasify coke from a pyrolyzer. Through such a thermochemical regenerative unit, the sensible heat with a lower center dot energy level is upgraded into syngas chemical energy with a higher energy level; therefore, high cold gas efficiency (CGE) is expected from the proposed system. ASPEN PLUS software is selected to simulate the novel coal gasification system, and the key parameters are validated by experimentation. Then energy, exergy, and energy-utilization diagram (EUD) analyses are applied to disclose the plant performance enhancement mechanism. It is revealed that 83.2% of syngas sensible heat can be recovered into steam agent with the CGE upgraded to 90%. In addition, with the enhancement of CGE, the efficiency of an integrated gasification combined cycle (IGCC) based on the novel gasification system can be as high as 51.82%, showing a significant improvement compared to 45.2% in the general electric company (GE) gasification-based plant. In the meantime, the irreversible destruction of the gasification procedure is reduced to 25.7% through thermochemical reactions. The increase in the accepted energy level (A(ea)) and the decreases in the released energy level (A(ed)) and heat absorption (Delta H) contribute to the reduction in exergy destruction in the gasification process. Additionally, since the oxygen agent is no longer used in the IGCC, 34.5 MW exergy destruction in the air separation unit (ASU) is avoided.
ISSN: 0195-0738
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Record 70 of 233
Title: LES simulation and experimental validation of the unsteady aerodynamics of blunt wind turbine airfoils
Abstract: In order to investigate the unsteady performance of blunt wind turbine airfoils caused by boundary layer separation and wake eddies, this paper studies the aerodynamic performance by large eddy simulation (LES) and wind tunnel experiment at a Reynolds number of 2.62 x 10 boolean AND 5. The blunt airfoils are obtained by enlarging the trailing edge of the DU 91-W2-250 airfoil to 6% and 10% chords symmetrically on both pressure and suction sides of the airfoil. The simulation was carried out with the incompressible finite volume Navier-Stokes code EllipSys3D; and, the experiment was done in a wind tunnel with a crosssection of 0.5 m x 0.5 m by measuring the surface pressure and wake velocities using ESP-64HD pressure scanner and TSI hot-wire anemometer. The unsteady wake was captured by hot-wire in the wind tunnel, and LES with EllipSys3D. Both experiment and LES show that the spectrum of aerodynamic forces has a broadband nature which is in coincidence with the wake eddies, implying that the unsteady Karman vortex sheet is the driving mechanism of the force fluctuation. Moreover, the trailing edge size affects the separation bubbles and transition process in the boundary layer. It shows that the boundary layer near the leading edge is unstable in the spanwise direction, which is characterized by low frequency waves. (C) 2018 Elsevier Ltd. All rights reserved.
ISSN: 0360-5442
eISSN: 1873-6785
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Record 71 of 233
Title: Effect of the Addition of Biomass on the Fate and Speciation of Arsenic during Sewage Sludge Combustion
Abstract: Arsenic (As) emission during sewage sludge incineration is harmful to the ecology and environment. Adding biomass to sewage sludge was proposed to facilitate the conversion of As3+ to As5+ with low toxicity during combustion. In this study, co-firing tests of two sewage sludge samples and four biomass samples were carried out to determine the migration and transformation of arsenic. The results show that the addition of biomass to municipal sewage sludge (MSS) facilitates the fixation of As in bottom ash in the combustion process. During combustion of MSS with biomass, mineral compounds in biomass, such as CaO, Ca2SiO4, or CaSO4, can afford additional reactive sites for the oxidation of arsenic by producing multifarious arsenates, and the availability of mineral active sites in cotton stalk (CTS) and corn stalk (CRS) is higher than that in wood and wheat straw (WS). The inherent mineral compounds in industrial sewage sludge (ISS), such as CaO and Ca2SiO4, provide sufficient reactive sites for the complete oxidation of arsenic to As5+ during ISS combustion. The addition of CTS stimulates the migration of arsenic vapor into bottom ash and the stabilization of arsenic into aluminosilicates during ISS combustion.
ISSN: 0887-0624
eISSN: 1520-5029
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Record 72 of 233
Title: Characteristics of Fly Ash under Oxy-Fuel Circulating Fluidized Bed Combustion
Author(s): Li, W (Li, Wei); Liu, DB (Liu, Dianbin); Li, SY (Li, Shiyuan)
Abstract: The objective of the present paper is to study the physiochemical properties of fly ash under oxy-fuel circulating fluidized bed (CFB) combustion mode. Tests were conducted in a 50 kW oxy-fuel CFB combustor under both air and oxy-fuel combustion. The analyses of the collected fly ash samples included particle size analysis, N-2 adsorption analysis, char carbon, inductively coupled plasma optical emission spectrometry (ICP-OES), and X-ray diffraction (XRD). It was found that the d,o, d(50), and d(90) of fly ash under oxy-fuel combustion mode were larger than that under air combustion mode and increased with the rise of the inlet oxygen concentration. The Brunauer Emmett Teller (BET) surface area, pore volume, and pore size of fly ash under air combustion are almost the same with that at inlet oxygen concentration of 30%. The element mass concentrations were obviously different between the two combustion modes, but the main mineral phase was insignificantly different. Moreover, the inlet oxygen concentration has no significant effect on the element mass distribution in the fly ash, except for the alkaline earth metal under oxy-fuel combustion.
ISSN: 0887-0624
eISSN: 1520-5029
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Record 73 of 233
Title: Real-Time Variable Geometry Triaxial Gas Turbine Model for Hardware-in-the-Loop Simulation Experiments
Author(s): Wang, T (Wang, Tao); Tian, YS (Tian, Yong-Sheng); Yin, Z (Yin, Zhao); Zhang, DY (Zhang, Da-Yue); Ma, MZ (Ma, Ming-Ze); Gao, Q (Gao, Qing); Tan, CQ (Tan, Chun-Qing)
Source: JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME Volume: 140 Issue: 9 Article Number: 092603 DOI: 10.1115/1.4038992 Published: SEP 2018
Abstract: This paper proposes a hybrid method (HMRC) comprised of a radial basis function (RBF) neural net algorithm and component-level modeling method (CMM) as a real-time simulation model for triaxial gas turbines with variable power turbine guide vanes in MATLAB/SIMULINK. The sample size is decreased substantially after analyzing the relationship between high and low pressure shaft rotational speeds under dynamic working conditions, which reduces the computational burden of the simulation. The effects of the power turbine rotational speed on overall performance are also properly accounted for in the model. The RBF neural net algorithm and CMM are used to simulate the gas generator and power turbine working conditions, respectively, in the HMRC. The reliability and accuracy of both the traditional single CMM model (SCMM) and HMRC model are verified using gas turbine experiment data. The simulation models serve as a controlled object to replace the real gas turbine in a hardware-in-the-loop simulation experiment. The HMRC model shows better real-time performance than the traditional SCMM model, suggesting that it can be readily applied to hardware-in-the-loop simulation experiments.
ISSN: 0742-4795
eISSN: 1528-8919
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Record 74 of 233
Title: Effects of incidence angle on a low-pressure turbine blade boundary layer evolution through large eddy simulation
Source: PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART A-JOURNAL OF POWER AND ENERGY Volume: 232 Issue: 6 Pages: 722-734 DOI: 10.1177/0957650917752806 Published: SEP 2018
Abstract: The evolution mechanism of the boundary layer and coherent structures in a low-pressure turbine blade is discussed. Five different incidence angles over the T106A blade for a Mach number Ma=0.404 and Reynolds number Re=0.6x10(5) (based on the axial chord and outlet velocity) are performed using large eddy simulation method. The calculation results at +7.8 incidence angle are agreed well with the experimental and direct numerical simulation data. The influence of the incidence angle on the flow field is mainly shown at the front of the suction side and pressure side. As the incidence angle changes from positive to negative, the separation bubble near the leading edge disappears and the blade loading decreases gradually. When the incidence angle reduces to -5 degrees, separation bubble appears near the leading edge of the pressure side. At the case of incidence angle equaling -10 degrees, the length of time-averaged separation bubble on the pressure side grows to 39% axial chord and the evolution process of the coherent structures is extremely complex. The spanwise vortexes roll up near the leading edge and gradually evolve into streamwise vortexes. High-energy fluid in the main flow was driven to near-wall zone by the rotating effect of streamwise vortexes, which increases the fluid momentum inside the boundary layer. The streamwise vortexes are stretched by the strong acceleration of the flow until they transport to the trailing edge.
ISSN: 0957-6509
eISSN: 2041-2967
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Record 75 of 233
Title: Assessment of off-design performance of a combined cooling, heating and power system using exergoeconomic analysis
Author(s): Wang, ZF (Wang, Zefeng); Han, W (Han, Wei); Zhang, N (Zhang, Na); Su, BS (Su, Bosheng); Liu, M (Liu, Meng); Jin, HG (Jin, Hongguang)
Source: ENERGY CONVERSION AND MANAGEMENT Volume: 171 Pages: 188-195 DOI: 10.1016/j.enconman.2018.05.055 Published: SEP 1 2018
Abstract: This paper presents the exergy and exergoeconomic analyses of a typical combined cooling, heating and power (CCHP) system under off-design conditions. The exergoeconomic-related parameters and unit exergoeconomic cost of the flows are discussed using the exergy cost allocation method based on energy level (ECAEL). The absorption chiller is found to have an improved potential because of the highest relative cost difference and its continual increase with the decrease of the output power. According to the exergoeconomic factor analysis, the exergoeconomic performance of the turbine and combustor among all the components can be enhanced by decreasing the investment and destruction, respectively. Next, the unit energy costs of different products in the output power range (100-20%) including electricity, cooling and heating energy for users, are calculated. The results show that the electricity increases faster than that of other products from 0.537 to 1.077 Yuan/kWh. Finally, the sensitivity analyses for the unit energy cost of the products are presented with different influencing parameters, such as the natural gas price, service life and discount rate. This exergoeconomic analysis may provide guidance for evaluating the products in distributed energy systems for energy networks.
ISSN: 0196-8904
eISSN: 1879-2227
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Record 76 of 233
Title: Analysis of inlet air throttling operation method for gas turbine in performance of CCHP system under different operation strategies
Author(s): Wang, ZF (Wang, Zefeng); Han, W (Han, Wei); Zhang, N (Zhang, Na); Su, BS (Su, Bosheng); Li, M (Li, Meng); Jin, HG (Jin, Hongguang)
Source: ENERGY CONVERSION AND MANAGEMENT Volume: 171 Pages: 298-306 DOI: 10.1016/j.enconman.2018.05.072 Published: SEP 1 2018
Abstract: An appropriate operation strategy is the requirement to obtain high-efficiency performance of a combined cooling, heating and power (CCHP) system. In this paper, the inlet air throttling (IAT) operation method for gas turbine combined with following the electric load (FEL), following the thermal load (FTL) and following the hybrid electric-thermal load (FHL) operation strategies are employed to analyze the primary energy consumption (PEC), carbon dioxide emission (CDE) and operation cost (COST) with respect to a CCHP system in Beijing, China. The matching between the different operation strategies and the energy demands of the reference building are analyzed to reveal the energy saving mechanism. The results indicate that the CCHP system is superior to the separate system on annual evaluation regardless of which operation strategy is used. Moreover, the economic performances of different operation strategies are evaluated based on the payback period (PBP). Finally, the sensitivity analyses of main component parameters and economic factors are presented for the PEC and PBP of the CCHP system, respectively. This study may provide a guidance to utilize the IAT operation method economically and efficiently.
ISSN: 0196-8904
eISSN: 1879-2227
________________________________________
Record 77 of 233
Title: Performance optimization of a solar assisted CCHP based on biogas reforming
Author(s): Su, BS (Su, Bosheng); Han, W (Han, Wei); Chen, Y (Chen, Yi); Wang, ZF (Wang, Zefeng); Qu, WJ (Qu, Wanjun); Jin, HG (Jin, Hongguang)
Source: ENERGY CONVERSION AND MANAGEMENT Volume: 171 Pages: 604-617 DOI: 10.1016/j.enconman.2018.05.098 Published: SEP 1 2018
Abstract: Using renewable energy in the distributed energy systems has large potential to ease the excessive use of fossil fuels and the environmental problems. Selecting a new and efficient system scheme of utilizing the renewable energy to meet various user load is decisive to improve the technical, economical and environmental performances. This work presents a detailed research on a new CCHP based on synthetic utilization of biogas and solar energy. Unlike the conventional biogas-fired CCHP in which biogas is directly burned for utilization, biogas in the hybrid system is first transformed to the syngas via biogas reforming reaction which is assisted by the solar energy, and then used in an efficient tri-generation system. A system optimization model based on the comprehensive evaluation criteria is established under Lhasa Tibet weather data to optimize the key parameters of the CCHP following the electric load (FEL) by genetic algorithm (GA). The optimal engine capacity and hydraulic retention time are 1052 kW and 260.2 h, respectively. A biogas-fired CCHP and a solar Dish/Stirling power system are adopted as the reference systems, and the comparative analysis is presented to show the advanced annual efficiency of the hybrid CCHP. The saving ratios of natural gas and electricity from outside the system reach 3.3% and 77.8%, respectively. Moreover, a sensitivity analysis is carried out to indicate the effects of the prices of electricity, natural gas and refrigeration on the system dynamic operation performances. The electricity price has the biggest impact on the dynamic payback period of the proposed system. The research may provide a mutual beneficial way to use biogas and solar energy efficiently and economically.
ISSN: 0196-8904
eISSN: 1879-2227
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Record 78 of 233
Title: Solar-clean fuel distributed energy system with solar thermochemistry and chemical recuperation
Abstract: A new solar-hybrid fuel-fired distributed energy system incorporating thermochemical reaction driven by mid and low-temperature solar heat and exhaust heat is proposed, for increased solar energy utilization and exhaust heat recovery efficiency. Solar energy is upgraded to syngas (H-2 and CO) chemical energy via the solar thermochemical process of the methanol decomposition reaction, and the syngas drives the internal combustion engine to output power. Some of the exhaust heat is stored and drives the methanol decomposition reaction to supplement the syngas via the chemical recuperation process, enhancing the exergy efficiency of the exhaust heat recovery. The overall energy efficiency and net efficiency of solar energy to electricity conversion are improved by integrating solar thermochemistry and chemical recuperation, and excellent off-design thermodynamic performance under varying user loads and solar irradiation levels is achieved. The overall energy efficiency, exergy efficiency, and net solar-energy-to-electricity efficiency reach 80.55%, 42.18% and 24.66%, respectively. These research findings indicate that the proposed system embodies an efficient and stable approach towards utilization of solar energy and clean fuel in distributed energy systems.
Conference Title: 9th International Conference on Applied Energy (ICAE)
Conference Date: AUG 21-24, 2017
Conference Location: Cardiff, WALES
ISSN: 0306-2619
eISSN: 1872-9118
________________________________________
Record 79 of 233
Title: Online monitoring and characterization of dense phase pneumatically conveyed coal particles on a pilot gasifier by electrostatic-capacitance-integrated instrumentation system
Abstract: The transportation of pulverized coal in gasification system needs to be carefully monitored and regulated with respect to the operation stability, gas quality and energy efficiency. In this paper, an integrated instrumentation system is developed to continuously monitor the pulverized coal flow within a 30 mm horizontal pneumatic pipe on a pilot coal gasifier at low pressure. The instrumentation system calculates the mass flow rate of pulverized coal by measuring the particle mean velocity with two ring-shaped electrostatic sensors and particle concentration with a helical capacitance sensor. The system is calibrated and optimized before the field experiments, especially the optimal structure of the helical capacitance sensor with a homogeneous sensitivity distribution is achieved by static tests to minimize the influence of the uneven particle concentration distribution on the particle concentration measurement accuracy. Experiments are carried out under various operation conditions to characterize the flow of pulverized coal particles using the integrated instrumentation system. The regulating effects of the operation parameters of the pneumatic conveying system (the angle valve opening, the fluidized gas and supplement gas flow rates, the pressure within the feeding tank) on the particle velocity, concentration and mass flow rate are experimentally studied. Results demonstrate that the integrated instrumentation system can effectively monitor the dense phase pneumatically conveyed coal particles flow on the pilot coal gasifier. Both the angle valve and the pressure within the feeding tank are effective to control the mass flow rate via regulating the particle concentration. The supplement gas can regulate the particle velocity and concentration simultaneously.
ISSN: 0263-2241
eISSN: 1873-412X
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Record 80 of 233
Title: A concentrating photovoltaic/Kalina cycle coupled with absorption chiller
Source: APPLIED ENERGY Volume: 224 Pages: 481-493 DOI: 10.1016/j.apenergy.2018.04.093 Published: AUG 15 2018
Abstract: In this paper, we propose a concentrating photovoltaic/Kalina cycle having an absorption chiller. Here, the waste heat from photovoltaic cells can be recovered by an absorption chiller, and the produced cold energy is used to cool the turbine-outlet working fluid of the Kalina cycle. Compared with Kalina cycle without absorption chiller, output mechanical power from cycle can be increased due to the enhancement of turbine expansion ratio. A typical monocrystalline photovoltaic/Kalina cycle having absorption chiller is described. The influence of key parameters on the thermal performance is examined, such as photovoltaic temperature and direct normal irradiation. The results show that the waste heat with a temperature between 60 degrees C and 70 degrees C can be used for producing mechanical power by an efficiency among 4-5%. In comparison with the referenced Kalina cycle without further cooling the working fluid, the Kalina cycle having absorption chiller has a potential increase in the efficiency among 2-3%. As for the concentrating photovoltaics, the solar-to-electricity efficiency reaches about 24% while photovoltaic efficiency is about 4.2% without cooling. This work provides a new way to efficiently use the solar energy by combining photovoltaics and thermal cycles.
Conference Title: 9th International Conference on Applied Energy (ICAE)
Conference Date: AUG 21-24, 2017
Conference Location: Cardiff, WALES
ISSN: 0306-2619
eISSN: 1872-9118
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Record 81 of 233
Title: Atomic force microscopy for two-dimensional materials: A tutorial review (vol 406, pg 3, 2018)
Author(s): Zhang, H (Zhang, Hang); Huang, JX (Huang, Junxiang); Wang, YW (Wang, Yongwei); Liu, R (Liu, Rui); Huai, XL (Huai, Xiulan); Jiang, JJ (Jiang, Jingjing); Anfuso, C (Anfuso, Chantelle)
Abstract: This study focuses on the ultimate strength and failure response of composite box beams under three-point bending. The box beams consist of spar caps and shear webs and they are typically used in wind turbine blades as load-carrying members. Different spar cap configurations and loading directions are examined experimentally to investigate structural behavior associated with multiple nonlinearities leading to structural collapse. Global displacements, local strains and video images are recorded throughout the loading history to capture failure initiation, propagation and the strain state contributing to post-collapse characteristics. The failure mechanisms of the box beams involving geometric, material and contact nonlinearities are discussed in detail. The study shows that compressive crushing failure, driven by local buckling of shear webs, determines the ultimate strength of the box beams under flapwise loading, and adhesive joint debonding, initiated by local adhesive cracking and spar cap buckling, is the critical failure mode of the box beams under edgewise loading. The Brazier effect and shear nonlinearity contribute to the initial failure depending on the loading directions. Debonding rather than delamination characterizes post-collapse behavior of all box beams examined in this study.
ISSN: 0263-8223
eISSN: 1879-1085
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Record 83 of 233
Title: A review on the utilization of hybrid renewable energy
Source: RENEWABLE & SUSTAINABLE ENERGY REVIEWS Volume: 91 Pages: 1121-1147 DOI: 10.1016/j.rser.2018.04.105 Published: AUG 2018
Abstract: The utilization of renewable energy is significantly important for the world because global energy consumption is increasing, while conventional energy sources are no longer sufficient to meet the energy demand, triggering energy crises. However, variation in solar radiation and wind speed caused by climate and weather conditions restricts the stable operation of renewable energy systems, therefore, causing the output to fluctuate. A hybrid renewable energy (HRE) system can be highly efficient by combining multiple renewable energy sources and is regarded as a promising solution to the above issue. In this review, a comprehensive summary and discussion of the uses of HRE in terms of space heating, cooling, hot water usage, power generation, hydrogen production, drying and multi-generation are conducted. Hybrid system configurations, specific devices, application procedures, and performance are reviewed. Moreover, the challenges and outlook for HRE utilization are discussed, including the following points: proper use of the local sources in view of disperse and regional distribution of renewable energy; development of hybrid storage subsystems for HRE to improve the stability of the energy supply; further optimization of the operation strategy and system size to minimize the cost in order to promote the application; and, clear identification of the supporting local policies of renewable energy, especially considering HRE. Furthermore, the research potential is described for HRE utilization integrating direct CO2 reduction.
ISSN: 1364-0321
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Record 84 of 233
Title: Stethoscope-type 3 omega independent detector for fast measurement of material thermal conductivity
Author(s): Zheng, XH (Zheng, Xinghua); Yue, P (Yue, Peng); Li, S (Li, Shen); Wang, L (Wang, Liang); Yang, X (Yang, Xiao); Chen, HS (Chen, Haisheng)
Source: REVIEW OF SCIENTIFIC INSTRUMENTS Volume: 89 Issue: 8 Article Number: 084904 DOI: 10.1063/1.5035107 Published: AUG 2018
Abstract: As one of the most basic properties of materials, thermal conductivity is a key parameter to investigate the analysis and design of the particular thermal process, such as the analysis of the thermal/cool energy storage and release process, the thermal/cool energy storage system design, and so on. Also, it is the foundation of energy technology development. In order to overcome the problem that the measurement frequency of a polyimide substrate independent detector is lower and the measurement time is longer, based on the relationship among 3 omega detection frequency, thermal wave penetration depth, and thermal properties of the substrate material, this paper developed a stethoscope-type 3 omega independent detector based on a sapphire substrate for fast measurement of material thermal conductivity. Nickel, with a high resistance temperature coefficient, was used as the metal detector. The influence of the width of the nickel metal detector and the thickness of the sapphire substrate on the measurement accuracy was analyzed by introducing an effective heat flow ratio. The sapphire substrate independent detector was calibrated by using copper, aluminum, 304 stainless steel, quartz glass, ethylene glycol, and plexiglass with known thermal conductivities. The experiment shows that the measurement frequency of the stethoscope detector can be ten times higher than that of a Kapton film independent detector. Its measurement time is only one tenth of that of the Kapton film independent detector. Published by AIP Publishing.
ISSN: 0034-6748
eISSN: 1089-7623
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Record 85 of 233
Title: Monitoring a lab-scale wurster type fluidized bed process by electrical capacitance tomography
Author(s): Che, HQ (Che, H. Q.); Wu, M (Wu, M.); Ye, JM (Ye, J. M.); Yang, WQ (Yang, W. Q.); Wang, HG (Wang, H. G.)
Source: FLOW MEASUREMENT AND INSTRUMENTATION Volume: 62 Pages: 223-234 DOI: 10.1016/j.flowmeasinst.2017.09.005 Published: AUG 2018
Abstract: In this research, two types of electrical capacitance tomography (ECT) sensors, i.e. 12-4-8 combined electrodes and 8-8 dual planes sensors, were designed and used to monitor the gas-solids flow inside a Wurster type fluidized bed. For the 12-4-8 combined electrodes sensor, the measurement was conducted synchronously both inside and outside of the tube, i.e. coating zone and annulus zone, to achieve a fully understand the gas-solids flow characteristics in the bed. For the dual planes ECT sensor, the flow through the two cross-section areas inside the Wurster tube was measured and solids velocity was calculated based on cross-correlation method. A series of test were carried out by varying the operational parameters including the gap between the Wurster tube and air distributor, fluidization air velocity and materials loading. Different flow regimes as well as the flow stability were evaluated based on the ECT measurement results. To evaluate the flow characteristics inside the bed, power spectra density (PSD) and standard deviation (SD) were applied to investigate the fluctuation characteristics in the coating and annulus zones. Experiment results indicate that ECT technology is a powerful tool to monitor the Wurster type fluidized bed process and analysis the gas-solids flow characteristics inside the bed.
ISSN: 0955-5986
eISSN: 1873-6998
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Record 86 of 233
Title: Experimental and Modeling Study of Low Temperature Oxidation of Iso-propylbenzene with JSR
Source: ENERGY & FUELS Volume: 32 Issue: 8 Pages: 8781-8788 DOI: 10.1021/acs.energyfuels.8b01492 Published: AUG 2018
Abstract: Oxidation of iso-propylbenzene (IPB) has been studied over the temperature range from 700 to 1100 K in a jet stirred reactor (JSR) at low-temperature, which is operated at atmospheric pressure from fuel-lean to fuel-rich condition with residence time from 1.06 to 1.67 s. Reactants and 25 species were identified and quantified by online GC-MS and GC analysis. A new model involving 306 species and 1985 reactions for low-temperature oxidation of IPB was developed, whose predictions were in good agreement with the measured profiles of mole fraction. Sensitivity analysis indicates that the primary H atom abstraction from the side iso-propyl chain has significant promoting effect and H-abstraction from the tertiary site of side isopropyl tends to play an inhibiting effect under fuel-lean and fuel-rich cases. The predominant consumption pathway of IPB proceeds through primary benzylic H atom abstraction to form iso-phenylpropyl radicals for both fuel-lean and fuel-rich cases. However, compared to the fuel-rich condition, 1-iso-phenylpropyl is favorable kinetically under the fuel-lean condition. Both simulated and experimental results show that styrene and phenol are most abundant and stable monocyclic aromatic intermediates for IPB oxidation at low-temperature. These experimental and modeling works will expand the research area of low-temperature oxidation of IPB and provide insights on understanding the combustion mechanism of IPB.
ISSN: 0887-0624
eISSN: 1520-5029
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Record 87 of 233
Title: Alkali metal transformation and ash deposition performance of high alkali content Zhundong coal and its gasification fly ash under circulating fluidized bed combustion
Abstract: Alkali metal transformation and ash deposition during combustion of Zhundong (ZD) coal and its gasification fly ash (ZDf) were studied in a 0.4 t/d circulating fluidized bed. The Na in ZD coal was present primarily as Na2SO4. NaAlSi3O8 and KAlSi3O8 were the main compounds of Na and K in ZDf. Variation in the bed temperature had a significant effect on the transformation of Na, but it did not greatly affect the conversion of K. During combustion of the ZD coal, Na was mainly in flue gas, the Na in fly ash was mainly in the water soluble form, but in bottom ash it was mainly in the insoluble form. During combustion of the ZDf, Na was found mainly in the fly ash and flue gas, insoluble Na and K accounted for above 80.0% of Na and K in ashes. The release of Na during the ZDf combustion was less pronounced than that during the ZD coal combustion. The ash deposition during the ZD coal combustion occurred primarily as a result of the agglomeration and bonding of the ash particles that were rich in Na2SO4, and the deposition propensity was high. However, the ash deposition during the ZDf combustion was primarily caused by the accumulation of fine fly ash particles with a low Na content, the deposition propensity was low.
ISSN: 1359-4311
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Record 88 of 233
Title: Experimental study on the heat transfer of gas with coagulative particles flowing through a packed granular bed filter
Abstract: An experimental study was carried out on heat transfer of gas with coagulative particles flowing through a packed granular bed. A logarithmic mean temperature difference (LMTD) method was used to obtain the overall heat transfer coefficient. An empirical formula was used to compare with the experimental results. The results show that the heat quantity released by the concretion of coagulative particles has an improved influence on the heat transfer when the inlet gas temperature of packed bed is above the melting point of the coagulative particles and outlet gas temperature is below the melting point. However, the heat quantity absorbed by the melting of coagulative particles can weaken the heat transfer when both the inlet and outlet gas temperature of the packed bed are above the melting point of coagulative particles. Two modified correlations are proposed to give the Nusselt number.
ISSN: 1359-4311
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Record 89 of 233
Title: The effect of temperature and pressure on n-heptane thermal cracking in regenerative cooling channel
Author(s): Wu, Y (Wu, Yong); Wang, XH (Wang, Xiaohan); Song, QS (Song, Qianshi); Zhao, LG (Zhao, Luoguang); Su, H (Su, Hang); Li, HH (Li, Haohan); Zeng, XJ (Zeng, Xiaojun); Zhao, DQ (Zhao, Daiqing); Xu, JZ (Xu, Jianzhong)
Source: COMBUSTION AND FLAME Volume: 194 Pages: 233-244 DOI: 10.1016/j.combustflame.2018.04.036 Published: AUG 2018
Abstract: A thermal cracking experimental equipment of hydrocarbon fuels was built to study n-heptane pyrolysis and the effect of reaction conditions on this reaction process. The main species were measured and the change rules were analyzed on the range of temperature 873-1073 K and pressure 0.1-3.5 MPa. The total content of alkenes products was more than alkanes on this pyrolysis process. Compared to alkenes with same number carbons, the alkanes were more easy to decompose with temperature but more conducive to formation with pressure increasing. The content of ethylene is usually the most on above reaction conditions, but its descent is also the fastest with pressure increasing. A mechanism model of n-heptane pyrolysis (44 species and 166 reactions) was constructed and validated by experiments on different conditions. Compared with n-heptane oxidation detailed model of Version 3.1 from Lawrence Livermore National Laboratory (LLNL), the pyrolysis model present a better accordant with experiment results on a range of temperature and pressure. The kinetic reaction of n-heptane pyrolysis was analyzed with present pyrolysis model, and the pyrolysis reaction pathway for the main products was obtained. The formation of alkenes are mainly through C-C bond dissociation reaction, especiallyp-C dissociation, and small alkanes are formed mainly by radical metathetical or synthesis reaction, the former are endothermic reactions, but the latter are mostly exothermal reactions. The properties of some main reactions have a critical role for the change of product content with temperature and pressure, which is the main reason for the variety of products selectivity under different conditions, Pressure increased the pyrolysis residence time and mass density but it does not significantly affect the reaction energy, so its contribution to conversion rate of fuels thermal cracking is limited, although it changes the reaction pathway greatly. However, the temperature can increase obviously the reaction activation energy, even though the residence time and concentration is decreased, the conversion rate of n-heptane pyrolysis still increased. (C) 2018 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
ISSN: 0010-2180
eISSN: 1556-2921
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Record 90 of 233
Title: Preheating Characteristics of Datong Coal in O-2/CO2 and Air Atmospheres
Author(s): Zhu, JG (Zhu Jianguo); Ma, HZ (Ma Hongzhou); Liu, DB (Liu Dianbin); Li, JR (Li Jiarong)
Source: JOURNAL OF THERMAL SCIENCE Volume: 27 Issue: 4 Pages: 341-348 DOI: 10.1007/s11630-018-1016-1 Published: AUG 2018
Abstract: Experimental studies were carried out to find the difference of preheating characteristics of Datong coal in O-2/CO2 and air atmospheres by a circulating fluidized bed. It is found that pulverized coal could be both steadily preheated to above 800A degrees C in the two different atmospheres, but the temperature distribution was more uniform along the riser in O-2/CO2 atmosphere. During the preheating, the content of CO in the flue gas can reach 12.32% under the O-2/CO2 atmosphere, far higher than that in air (5.94%). Simultaneously, the conversion rate of fixed carbon was higher in O-2/CO2 atmosphere compared with that in air. It can be inferred the higher oxygen concentration and higher partial pressure of CO2 have greatly accelerated the gasification reaction. The BET analysis indicated a number of large pores were transformed into micropores during the preheating progress, and the major contributors for overall pore volume of chars and specific surface area are the micro-pores and the mesopores with diameter ranging from 2 nm to 10 nm. The inner pore structure was more developed in O-2/CO2 atmosphere.
ISSN: 1003-2169
eISSN: 1993-033X
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Record 91 of 233
Title: Computational investigation of film cooling and secondary flow on turbine endwall with coolant injection from upstream interrupted slot
Author(s): Xu, QZ (Xu Qingzong); Du, Q (Du Qiang); Wang, P (Wang Pei); Liu, J (Liu Jun); Liu, G (Liu Guang)
Source: INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER Volume: 123 Pages: 285-296 DOI: 10.1016/j.ijheatmasstransfer.2018.01.117 Published: AUG 2018
Abstract: High pressure turbine vane surface and endwall regions are extensively cooled through discrete holes and leakage flow from combustor-turbine interface gap. For making better use of the limited amount of the leakage flow, this paper describes numerical investigation of endwall film cooling performance of a two-dimensional cascade with upstream interrupted slot injection. The geometry of the vane, size of the slot and mainstream parameters are all taken from a real engine high pressure turbine. The effects of varying blowing ratio, location of the upstream slot and coolant incidence angle on cooling effectiveness are studied. The ranges of the studied parameters are: blowing ratio 1.0, 1.7, 1.86; slot location Z/Cax = -0.1, -0.2, -0.3; coolant incidence angle -10 degrees, 10 degrees, 20 degrees. The calculations are completed by solving three-dimensional Reynolds-Averaged Navier-Stokes (RANS) equations with shear stress transport (SST) k-omega turbulence model, meanwhile, the turbulence model was validated by comparing the calculated results with the experiment data. The calculated results show an important influence of blowing ratio and axial position of the interrupted slot on film cooling effectiveness. Cooling Effectiveness is increased with increasing blowing ratio and decreasing distance between the slot and leading edge of the vane. To compare with BR =1.7 cooling effectiveness can be improved significantly in the condition of BR =1.86. Slot location of Z/Cax = -0.1 provides much higher cooling effectiveness than the rest two locations. The physical mechanism of the improvement is that in the condition of high blowing ratio high momentum coolant flow helps to reduce the strength of horseshoe vortex and therefore to limit its negative effect on the cooling effectiveness. The high momentum coolant jet impinges on leading edge of the vane and climbs the surface of it. The coverage of the coolant at the leading edge endwall and pressure side endwall junction becomes better. The contours of effectiveness for different slot location are similar to those of different blowing ratio. The momentum of the coolant jet increases with the slot moving close to the leading edge of the vane and creates similar effectiveness contour patterns of raising blowing ratio. The effect of varying coolant incidence angle on the cooling effectiveness is weaker than blowing ratio and slot location. Average cooling effectiveness is increased about 14% when the angle changed from 10 degrees to 20 degrees. (C) 2018 Elsevier Ltd. All rights reserved.
ISSN: 0017-9310
eISSN: 1879-2189
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Record 92 of 233
Title: DFT Study on CO Catalytic Oxidation Mechanism on the Defective Cu2O(111) Surface
Source: JOURNAL OF PHYSICAL CHEMISTRY C Volume: 122 Issue: 29 Pages: 16733-16740 DOI: 10.1021/acs.jpcc.8b03471 Published: JUL 26 2018
Abstract: Understanding the role of surface defects on the catalyst performance is of great significance for a good command of the catalytic mechanism on the real catalyst surface. This work reports the mechanistic study of CO oxidation on the defective Cu2O(111) surface using density functional theory calculations. The effect of surface defects on surface catalytic activity was investigated by creating surface-adsorbed O atoms and Cu vacancies on the perfect Cu2O(111) surface. Possible defective surface structures were found, and calculated results showed that Cu vacancy on the Cu2O(111) surface could promote CO oxidation in two ways by (I) promoting the reaction between CO and lattice O with the energy barrier of 1.316 eV following the Mars-van-Krevelen mechanism; (II) promoting the reaction between CO and adsorbed O atoms below 575 K. For the perfect Cu2O(111) surface, adding adsorbed O to the surface could either cause a strong surface reconstruction with the adsorbed O evolving into a lattice O or stay in the active state. The obtained results could explain the experimental observations that a higher O/Cu ratio on the Cu2O surface can improve the activity of Cu2O toward CO oxidation. Rate constants were provided according to harmonic transition state theory, which would be helpful for the kinetic modeling of CO catalytic oxidation on the real Cu2O surface.
ISSN: 1932-7447
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Record 93 of 233
Title: Performance analysis of a pre-cooled and fuel-rich pre-burned mixed-flow turbofan cycle for high speed vehicles
Abstract: A novel Pre-cooled and Fuel-rich Pre-burned Mixed-flow Turbofan (PFPMT) cycle is presented for reusable high speed vehicles based on practical technologies to reduce the travelling time of long distance flights. The motivation and the working principle of the PFPMT are explained in detail. A performance simulation model for the PFPMT cycle is established with the assumption of equilibrium fuel rich gas as the working fluid in the gas generator. Then parametric cycle studies are performed with the variation of bypass ratio, fuel/air ratio, core compressor pressure ratio and bypass fan pressure ratio at the flight Mach number of 0 and 5 respectively. The interrelationships between cycle parameters and their effects on cycle performance are discussed. Based on the parametric analysis, cycle parameters for a practical PFPMT engine are suggested for the flight speeds of Mach 0, 3 and 5 respectively. The predicted engine performance shows that the PFPMT concept exhibits a competitive specific impulse with respect to an ATR GG engine and an enhanced thrust to weight ratio with respect to an ATREX engine, and might be a promising propulsion system for high speed air-breathing flying vehicles. (C) 2018 Elsevier Ltd. All rights reserved.
ISSN: 0360-5442
eISSN: 1873-6785
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Record 94 of 233
Title: Mechanism of CO Oxidation on Cu2O (111) Surface: A DFT and Microkinetic Study
Source: INTERNATIONAL JOURNAL OF CHEMICAL KINETICS Volume: 50 Issue: 7 Pages: 507-514 DOI: 10.1002/kin.21176 Published: JUL 2018
Abstract: Catalytic oxidation has been recognized as one of the most efficient and promising techniques for the abatement of CO and volatile organic compounds. In the present work, the CO oxidation mechanism on perfect Cu2O (111) surface was investigated by using density functional theory (DFT) calculations with the periodic surface model. The unsaturated singly coordinated Cu+ site of Cu2O (111) surface could effectively adsorb gaseous CO molecule with a strong adsorption energy of -1.558 eV. The adsorbed O on Cu2O (111) surface is very active toward CO oxidation with only 0.269 eV energy barrier. The reaction between CO and lattice O is the rate-determining step of Mars-van-Krevelen (MvK) type CO oxidation with the energy barrier of 1.629 eV. The CO oxidation cycle initiated by the reaction between coadsorbed CO and O-2 at the Cu-I site has a relatively lower energy barrier of 1.082 eV and is, therefore, more likely to proceed compared with the MvK cycle. Microkinetic rate constants of elementary reaction steps based on the transition state theory were deduced, which could be helpful in the kinetic modeling of CO oxidation on Cu2O surface.
ISSN: 0538-8066
eISSN: 1097-4601
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Record 95 of 233
Title: A study of boiling on surfaces with temperature-dependent wettability by lattice Boltzmann method
Author(s): Zhang, L (Zhang, Lei); Wang, T (Wang, Tao); Jiang, YY (Jiang, Yuyan); Kim, S (Kim, SeolHa); Guo, CH (Guo, Chaohong)
Source: INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER Volume: 122 Pages: 775-784 DOI: 10.1016/j.ijheatmasstransfer.2018.02.026 Published: JUL 2018
Abstract: Effects of surface wettability have been the focus of boiling heat transfer research in recent years, due to its important role on boiling performance. It is reported that hydrophobic surface has higher boiling heat transfer coefficient while hydrophilic surface has higher critical heat flux. In this study, a surface with temperature-dependent wettability was proposed to take advantages of both hydrophilic and hydrophobic surfaces. A hybrid thermal lattice Boltzmann model with an improved forcing scheme was used to simulate and evaluate the effects of wettability control. First, single bubble dynamics on hydrophilic and hydrophobic surfaces were depicted to analyze the heat transfer features on both surfaces. Second, boiling curves for each condition have been obtained under stepwise heat flux control condition, and the controlled wettability surface shows higher boiling performance than both hydrophobic and hydrophilic surfaces. In addition, we found an optimal relation between temperature and surface wettability for heat transfer rate, and it is evaluated through the parameter test of the temperature-wettability relation. This research may provide a potential way of controlling surface wettability to improve boiling performance and also offer conceptual design of enhanced boiling surface. (C) 2018 Elsevier Ltd. All rights reserved.
ISSN: 0017-9310
eISSN: 1879-2189
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Record 96 of 233
Title: Effects of Inclination Angle, Orientation Angle, and Hole Length on Film Cooling Effectiveness of Rectangular Diffusion Holes
Source: JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME Volume: 140 Issue: 7 Article Number: 071003 DOI: 10.1115/1.4040101 Published: JUL 2018
Abstract: Film-cooling effectiveness of rectangular diffusion holes under an inclination angle alpha = 45 deg, an orientation angle beta = 45 deg, and a length-to-diameter ratio of L/D = 8.5 were, respectively, examined in a flat-plate experimental facility using the pressure sensitive paint (PSP) technique. Experiments were performed at a density ratio of DR = 1.38 and a mainstream turbulence intensity of Tu = 3.5%. The semicircle sidewall rectangular diffusion hole varied at three cross-sectional aspect ratios, i.e., AS = 3.4, 4.9, and 6.6. The tested results were compared with the baseline design with an inclination angle alpha = 30 deg, an orientation angle beta = 0 deg, and a length-to-diameter ratio L/D = 6. A three-dimensional (3D) numerical simulation method was employed to analyze the flow field. The experimental results showed that the increased inclination angle converted the bi- or tri-peak effectiveness pattern of the baseline design to a single-peak pattern, weakened the lateral diffusion of coolant, and consequently decreased cooling effectiveness obviously. The decreased magnitude amplified with the increase of cross-sectional aspect ratio and blowing ratio. The adding of orientation angle seriously weakened the cooling effectiveness of the baseline design, and the blowing ratio and cross-sectional aspect ratio had almost no effect on overall cooling effectiveness. The elongated hole length provided a uniform distribution of lateral cooling effectiveness, which produced differential effects on the bi- or tri-peak pattern. The elongated hole length decreased the cooling effectiveness on the near hole region, but had less effects on overall cooling effectiveness, except the high blowing ratio.
ISSN: 0889-504X
eISSN: 1528-8900
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Record 97 of 233
Title: Energy and, exergy analysis of a CCHP-ORC system based on MGT - ORC and absorption chiller
Author(s): Lei, H (Lei, Huan); Yang, JF (Yang, Jinfu); Tang, CL (Tang, Changliang); Han, DJ (Han, Dongjiang)
Abstract: A CCHP-ORC system consisting of a MGT, an ORC and an absorption refrigeration chiller was proposed in this study. A verified simulation model based on specific mass, energy conservation and exergy destruction was built. Thermodynamic analysis was applied to the system. A parametric study was carried out to investigate the impacts of the ORC's evaporating temperature and, turbine efficiency, and the ARC's generating temperature on the system's performance. Six different organic working fluids (R141b, Toluene, D4, n-Octane, n-Heptane and MM) were selected in this study, and their impact on the system's performance was also analyzed. The results showed that the CCHP-ORC system's primary energy efficiency and exergy efficiency could reach a maximum of 76.89% and 54.95% respectively, with toluene as the organic working fluid. The MGT accounted for a large part of exergy destruction in both the CCHP-ORC and reference system. Compared to the reference system, the total exergy destruction of the CCHP-ORC system decreased, for all six organic working fluids. The main exergy reduction occurred in the GEN, ABS and DHW. A T-Q diagram method was conducted to analyse the heat transfer process in the CCHP-ORC and reference system. The results showed that the CCHP-ORC system can significantly reduce the mean heat transfer temperature difference in the heat transfer process, which helps to decrease the exergy destruction in GEN, and improves the system's exergy efficiency. Hence, it is beneficial for the system's efficiency and exergy destruction to introduce ORC as a middle cycle into the CCHP system. (c) 2017 American Institute of Chemical Engineers Environ Prog, 37: 1513-1522, 2018
ISSN: 1944-7442
eISSN: 1944-7450
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Record 98 of 233
Title: Aerodynamic Performance of Wind Turbine Airfoil DU 91-W2-250 under Dynamic Stall
Author(s): Li, S (Li, Shuang); Zhang, L (Zhang, Lei); Yang, K (Yang, Ke); Xu, J (Xu, Jin); Li, X (Li, Xue)
Abstract: Airfoils are subjected to the 'dynamic stall' phenomenon in significant pitch oscillations during the actual operation process of wind turbines. Dynamic stall will result in aerodynamic fatigue loads and further cause a discrepancy in the aerodynamic performance between design and operation. In this paper, a typical wind turbine airfoil, DU 91-W2-250, is examined numerically using the transition shear stress transport (SST) model under a Reynolds number of 3 x 10(5). The influence of a reduced frequency on the unsteady dynamic performance of the airfoil model is examined by analyzing aerodynamic coefficients, pressure contours and separation point positions. It is concluded that an increasingly-reduced frequency leads to lower aerodynamic efficiency during the upstroke process of pitching motions. The results show the movement of the separation point and the variation of flow structures in a hysteresis loop. Additionally, the spectrum of pressure signals on the suction surface is analyzed, exploring the level of dependence of pressure fluctuation on the shedding vortex and oscillation process. It provides a theoretical basis for the understanding of the dynamic stall of the wind turbine airfoil.
ISSN: 2076-3417
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Record 99 of 233
Title: Effect of Air Distribution on NOx Emissions of Pulverized Coal and Char Combustion Preheated by a Circulating Fluidized Bed
Abstract: This study reports an experimental investigation on the nitrogen oxide (NOx) emissions in pulverized fuel (coal and char) combustion through preheating with a circulating fluidized bed. The high-temperature preheated fuel particles obtained from the circulating fluidized bed would be burned in the down-fired combustor. The focus of this research is the trend of NOx emissions with different air distribution through varying secondary air nozzle structures and air ratios as well as tertiary air positions along the down-fired combustor. Under stable operation, the burning temperature was uniform and the combustion efficiency was high. When the fuel was pulverized coal, the NOx emissions with the secondary air center nozzle structure were almost twice of that with ring nozzle Structure. Furthermore, the NOx emissions increased with an increase of secondary air ratio when the nozzle structure was in the center. However, there was a minimum NOx concentration when the nozzle structure was a ring. And, the lower NOx emissions were achieved through arranging the tertiary air distribution rationally. In addition, the trend in NOx concentration along the down-fired combustor was almost the same irrespective of the fuel (coal or char). But, the char combustion efficiency should be paid more attention when the tertiary air position changes.
ISSN: 0887-0624
eISSN: 1520-5029
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Record 100 of 233
Title: Stability Enhancement With Self-Recirculating Injection in Axial Flow Compressor
Author(s): Li, JC (Li, Jichao); Du, J (Du, Juan); Li, ZY (Li, Zhiyuan); Lin, F (Lin, Feng)
Source: JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME Volume: 140 Issue: 7 Article Number: 071001 DOI: 10.1115/1.4039806 Published: JUL 2018
Abstract: Self-recirculating injection, which bleeds air from the downstream duct of the last blade row and injects air as a wall jet upstream of the first rotor blade row, is experimentally investigated after the design of its structure in single-and three-stage axial flow compressors. External injection and outlet bleed air are selected for comparison. Results show that self-recirculating injection can improve the stall margin by 13.67% and 13% on the premise of no efficiency penalty in single-and three-stage axial flow compressors with only 0.7% and 4.2% of the total injected momentum ratio recirculated near stall, respectively. The self-recirculating injection is the best among all the three cases if the influence on pressure rise coefficient and efficiency is comprehensively considered. Moreover, findings indicate that the upstream injection plays an important role in terms of stability-enhancement. The details of the flow field are captured using a collection of pressure transducers on the casing with circumferential and chordwise spatial resolution. A detailed comparative analysis of the endwall flow indicates that the self-recirculating injection can postpone the occurrence of stalling in the proposed compressor by delaying the forward movement of the interface between the tip leakage flow (TLF) and main stream flow (MF), weakening the unsteadiness of TLF (UTLF), and sharply decreasing the circumferentially propagating speed dominated by the UTLF that triggers the spike-type stall inception. Finally, the stall control concept on the stage that first generates stall inception using self-recirculating injection is proposed. This study helps to guide the design of self-recirculating injection in actual application.
ISSN: 0889-504X
eISSN: 1528-8900
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Record 101 of 233
Title: Flow measurements near the open surfaces of single circumferential grooves in a low-speed axial compressor
Author(s): Le, L (Le, Liu); Xi, N (Xi, Nan); Feng, L (Feng, Lin)
Abstract: Circumferential grooves (CG) is an effective method to enhance the compressor stall margin with minor efficiency disturbances. The interaction between the groove and the blade passage is found to be responsible for the stall margin improvement (SMI) by many studies. The momentum transport across open surface of an individual groove could be an indicator to assess its effectiveness. These findings are all derived by numerical means. Two single grooves are chosen as the examples to demonstrate the needs of the experimental validation. In experiments, one groove, CG5 at 27% axial chord, produced less SMI than the other one, CG7 at 43% axial chord. Yet, many CFD simulations predicted just the opposite. In order to validate the numerical simulations, detailed flow structures are needed near the open surfaces of the casing grooves. However, such experimental results are still missing due to the difficulties of measurement, especially for the flow measurement inside the grooves. Aiming at providing reasonable experimental results for these casing grooves, a measuring technique is proposed in this paper. A special algorithm is utilized to obtain the time-averaged magnitudes of velocity components by using three hot-wire probes. The groove-passage interaction is recorded using the fluctuations of each velocity component and the frequency spectrum. Intensive interaction is detected for CG7. The experimental results demonstrate that the flow interaction between the groove and blade tip is crucial to the stability enhancement. (C) 2018 Elsevier Masson SAS. All rights reserved.
ISSN: 1270-9638
eISSN: 1626-3219
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Record 102 of 233
Title: Experimental study on NO emissions from pulverized char under MILD combustion in an O-2/CO2 atmosphere preheated by a circulating fluidized bed
Abstract: This study examined the combustion of pulverized char under an O-2/CO2 atmosphere to (1) attempt to achieve a moderate or intense low-oxygen dilution (MILD) combustion process and (2) investigate the effects of gas distribution modes on NO emissions. First, fuel was preheated in a circulating fluidized bed (CFB) and then high temperature preheated fuel from the CFB was burned in a down-fired combustor (DFC). The study was conducted with two secondary gas nozzle positions, three tertiary gas position arrangements, and four secondary oxygen ratios in the DFC. During the test process, the combustion temperature was uniform in the CFB and the CO2 concentration in the flue gas reached approximately 90%. MILD combustion was achieved when the secondary gas nozzle position was center and the char combustion reaction dispersed into the upper low-oxygen space in the DFC. The obvious flame front disappeared and the temperature profile in the DFC was more uniform which is also one of the important features of MILD combustion. This reduced NO emissions by around half while maintaining high combustion efficiency. NO emissions were further reduced by a particular arrangement of tertiary gas positions, but at the cost of reducing combustion efficiency.
ISSN: 0378-3820
eISSN: 1873-7188
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Record 103 of 233
Title: Numerical investigation on fluid-solid coupled heat transfer with variable properties in cross-wavy channels using half-wall thickness multi-periodic boundary conditions
Source: INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER Volume: 122 Pages: 1040-1052 DOI: 10.1016/j.ijheatmasstransfer.2018.02.055 Published: JUL 2018
Abstract: In the present work, based on half-wall thickness multi-periodic boundary conditions, a 3D fluid-solid coupled heat transfer model considering variable properties and mutual influence between high temperature hot gas and compressed cold air is established to predict the flow and heat transfer in the cross wavy (CW) channels. The present model is verified by comparing the Nusselt numbers of the numerical results with those of experimental results. On the base of model validation, the flow and heat transfer characteristics of the different CW channels are further investigated in a wide Reynolds number range (gas side: 100-2200; air side: 100-2800). The secondary flow which is responsible for the enhancement of heat transfer and the increase of the pressure loss is successfully captured, and its influence on the thermal and flow boundary layers is analyzed. By comparing the heat transfer and pressure loss of five configurations, the effecting law of geometrical parameters is revealed. Based on a large number of simulation results, the correlations of heat transfer and Fanning friction factor involving Reynolds number, Prandtl number and geometrical parameters are proposed using the least-squares method, which are helpful to the design of CW primary surface recuperator in the microturbine. (C) 2018 Elsevier Ltd. All rights reserved.
ISSN: 0017-9310
eISSN: 1879-2189
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Record 104 of 233
Title: An optimal design approach for the annular involute-profile cross wavy primary surface recuperator in microturbine and an application case study
Source: ENERGY Volume: 153 Pages: 80-89 DOI: 10.1016/j.energy.2018.04.016 Published: JUN 15 2018
Abstract: In this work, a computational model of heat transfer and pressure drop is established for the design optimization of the annular involute-profile cross wavy primary surface (CWPS) recuperator in micro turbine. The genetic algorithm method is employed to solve the optimization problem of annular CWPS recuperator with multiple design variables. Thus, an optimal design approach for this kind of recuperator is formulated. The validity of the computational model is checked by comparing the calculation results with the experimental data of C30 and C65 prototype recuperators (Capstone Turbine Corporation). With the total relative pressure loss as the optimization target, the developed method is applied to the optimal design of the recuperator in a 300 kW power-level microturbine. In comparison with the original design, the optimal design results in a significant reduction of the pressure loss in the case that all constraints are satisfied, which indicates the formulated optimal design approach is effective for the annular CWPS recuperator. By replacing the optimization target, the optimal design approach presented in this work can be also applied to the single-objective optimization for other targets (compactness, heat transfer area, weight, volume, effectiveness, etc.) and even the multi-objective optimization according to the particular requirements of different microturbines. (C) 2018 Elsevier Ltd. All rights reserved.
ISSN: 0360-5442
eISSN: 1873-6785
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Record 105 of 233
Title: Thermal performance of micro-channel heat sink with metallic porous/solid compound fin design
Author(s): Gong, L (Gong, Liang); Li, YT (Li, Yongtong); Bai, Z (Bai, Zhang); Xu, MH (Xu, Minghai)
Abstract: Rapid development of large-scale integrations of electronic circuits resulted in increasing requirements for chip power dissipation. In this study, a concept of micro-channel heat sink with the metallic porous/solid compound fin design was developed and numerically investigated. Computational investigations were carried out to analyze the effects of metallic porous fins on the hydraulic and thermal performances, and to determine the optimal dimensionless porous fin thickness for designing the porous/solid compound fins. The traditional solid fin heat sink is selected as the comparison model. The results indicate that the viscous shear stress is reduced at the fluid and porous fin interfaces, which leads to decreased pressure drop through the porous fin heat sink. Whereas, the heat transfer performance deteriorates when the solid fins are completely replaced by the porous fins. The novel design of porous/solid compound fin demonstrates more favorable in the hydraulic and thermal performances. Both the pressure drop and the overall thermal resistance are substantially decreased, and the optimal dimensionless porous fin thickness for the compound fin heat sink is approximately 0.2. The presented compound fin heat sink is capable of effectively enhancing the cooling performance for high-powered electronics.
ISSN: 1359-4311
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Record 106 of 233
Title: Advancement of distributed energy methods by a novel high efficiency solar-assisted combined cooling, heating and power system
Author(s): Zhang, N (Zhang, Na); Wang, ZF (Wang, Zefeng); Lior, N (Lior, Noam); Han, W (Han, Wei)
Source: APPLIED ENERGY Volume: 219 Pages: 179-186 DOI: 10.1016/j.apenergy.2018.03.050 Published: JUN 1 2018
Abstract: To improve the conversion efficiency of renewable energy use in high efficiency novel distributed energy systems, and the match between the energy donors and receivers in them, this paper proposes and analyzes a solar assisted combined cooling, heating and power system which supplies electricity, cooling and heat, with internal energy recovery and thermochemical upgrading, as their core component. The proposed system consists of a chemically recuperated gas turbine cycle, an absorption chiller and a heat exchanger, in which the reformer upgrades the absorbed turbine exhaust heat and solar heat into produced syngas chemical exergy, and rearranges the matches of energy donors and receivers both quantitatively and qualitatively. Based on well-established technologies including trigeneration, steam reforming and low/mid temperature solar heat collection, the system exhibits enhanced specific power generation and efficiency, and it commensurately reduces CO2 emissions and saves depletable fossil fuel. The net solar-to-electricity efficiency is predicted to be 26-29% for a turbine inlet temperature of 980 degrees C. Compared with the stand-alone power, cooling and heating generation system, the reduction potential of fossil fuel consumption has been demonstrated to be 30.4% with a solar thermal share of 26%. Moreover, this system produces 33% less CO2 emission than a conventional combined cooling, heating and power system with the same technology but without solar assistance. An excess electricity storage unit or storage of excess syngas can be considered to balance the difference between the supply and demand quantities.
ISSN: 0306-2619
eISSN: 1872-9118
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Record 107 of 233
Title: Propagation and failure mechanism of cylindrical detonation in free space
Source: COMBUSTION AND FLAME Volume: 192 Pages: 295-313 DOI: 10.1016/j.combustflame.2018.01.049 Published: JUN 2018
Abstract: Cylindrical detonations propagating in free space characterized by different activation energies were cornputationally studied. It is found that unstable detonations with the 2-D cellular structure have more velocity deficit than those without the cellular structure computed with the 1-D simulation. The weakening is due to lengthening of the detonation structure and the unreacted pocket behind the cylindrical front, while propagation sustenance depends strongly on the re-amplification and regeneration of transverse shocks and triple points. For low activation energies, cellular detonation can be initiated in free space through the subcritical initiation path due to absence of unreacted pockets, and the propagation is not very sensitive to the attenuation of transverse waves and triple points. However, for high activation energy the unreacted pocket aggravates initiation such that even a cellular detonation first established is prone to quench due to the lack of re-amplification of the transverse wave and the triple point. When considering confinement, it is demonstrated that a detonation that quenches in free space can be reinitiated in confined space. (C) 2018 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
ISSN: 0010-2180
eISSN: 1556-2921
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Record 108 of 233
Title: An experimental and modeling study on the low temperature oxidation of surrogate for JP-8 part I: Neat 1,3,5-trimethylbenzene
Source: COMBUSTION AND FLAME Volume: 192 Pages: 507-516 DOI: 10.1016/j.combustflame.2017.12.030 Published: JUN 2018
Abstract: This work describes the experimental and modeling study of low temperature oxidation of 1,3,5-trimethylbenzene (T135MB) in a jet-stirred reactor over the temperature range of 700-1100 K at atmospheric pressure under fuel-lean and stoichiometric conditions. 9 C-0-C-5 hydrocarbons, 6 oxygenated products and 6 aromatic compounds were identified and quantified using GC and GC-MS. A detailed kinetic based on T135MB model of Dievart et al. was proposed to simulate the low-temperature experimental results in the present work. Rate constants of T135MB decomposition and metatheses reactions were calculated with CBS-QB3 method implemented in Gaussian 09. The performance of proposed mechanism in reproducing the experimental data is reasonably good. Reaction flux analysis shows that dominant consumption channels for T135MB oxidation are H-abstraction reactions to form 3,5-dimethylbenzyl radicals, while reactions with O/OH radicals to generate 1,3,5-trimethylphenoxyl/1,3,5-trimethylphenyl and ipso-addition to form m-xylene play minor roles. Sensitivity analysis reveals that H-abstraction from side methyl groups of T135MB by OH radical is the most inhibiting reaction oxidation at Phi = 1.0, while it is a promoting reaction at Phi = 0.4. Moreover, current model were validated against experimental results on T135MB oxidation in flow reactor from Dievart et al. as well as global combustion property ignition delay times from Rao et al. and Dievart et al. with reasonable predictions. (C) 2018 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
ISSN: 0010-2180
eISSN: 1556-2921
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Record 109 of 233
Title: A Distributed Energy System with Advanced Utilization of Internal Combustion Engine Waste Heat
Author(s): Sui, J (Sui, Jun); Liu, H (Liu, Hao); Liu, F (Liu, Feng); Han, W (Han, Wei)
Source: CSEE JOURNAL OF POWER AND ENERGY SYSTEMS Volume: 4 Issue: 2 Pages: 257-262 DOI: 10.17775/CSEEJPES.2015.01260 Published: JUN 2018
Abstract: New trigeneration system consists of an internal combustion engine, a power and cooling cogeneration system and an absorption heat transformer system. The exhaust gas is recovered by the power and cooling cogeneration subsystem producing the cooling and power. The jacket water is recovered by the absorption heat transformer subsystem producing lowpressure steam. The exergy performance and the energy saving performance which is evaluated by the primary energy saving ratio of the new distributed energy system are analyzed. The effects of the ratio of the output power and cooling of the power and cooling cogeneration subsystem and the generator outlet temperature of the absorption heat transformer subsystem to the primary energy saving ratio are considered. The contributions of the subsystems to the primary energy saving ratio are quantified. The maximum primary energy saving ratio of the new distributed energy system is 15.8%, which is 3.9 percentage points higher than that of the conventional distributed energy system due to the cascade utilization of the waste heat from the internal combustion engine.
ISSN: 2096-0042
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Record 110 of 233
Title: Investigation of thermodynamic performances for two-stage recompression supercritical CO2 Brayton cycle with high temperature thermal energy storage system
Source: ENERGY CONVERSION AND MANAGEMENT Volume: 165 Pages: 477-487 DOI: 10.1016/j.enconman.2018.03.068 Published: JUN 1 2018
Abstract: The supercritical CO2 (S-CO2) Brayton cycle with high temperature thermal energy storage is proposed to efficiently utilize solar thermal energy. A molten halide salt (mixture of 8.1 wt.%NaCl + 31.3 wt.%KCl + 60.6 wt. %ZnCl2) that can operate at a relatively high temperature is selected as a heat transfer fluid (HTF) and a storage medium. The proposed two-stage recompression Brayton cycle is used as power block to make full use of high-level solar energy and reduce power consumption. The thermodynamic performances and economic assessments are investigated to illustrate the feasibility of the proposed system, and the comparison between halide salt and nitrate salt is conducted. Theoretical results show that the solar-to-electric efficiency in the system with halide salt reaches to 19.16-22.03% in four representative days, which is higher than existing concentrated solar power plants with the tower central receiver, and the monthly averaged solar-to-electric efficiency of the halide salt system is increased by 11% as compared with the nitrate salt system. Research findings introduce a promising approach for the efficient utilization of the abundant solar resources in western China.
ISSN: 0196-8904
eISSN: 1879-2227
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Record 111 of 233
Title: Numerical study on novel airfoil fins for printed circuit heat exchanger using supercritical CO2
Source: INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER Volume: 121 Pages: 354-366 DOI: 10.1016/j.ijheatmasstransfer.2018.01.015 Published: JUN 2018
Abstract: The Printed Circuit Heat Exchanger (PCHE) has attracted a lot of attentions recently due to its high efficiency and compactness, and the airfoil fin has excellent thermal-hydraulic performance compared with the zigzag channel in PCHE. Two novel fins were proposed in this study based on the configuration of NACA 0020 airfoil fin, in order to further improve the performance of airfoil fin PCHE. The thermal-hydraulic performance and the enhancement mechanism of the fins were numerically investigated using supercritical CO2 as the working fluid. The results showed that one of the novel fins has better comprehensive performance and less entransy dissipation than the NACA 0020 airfoil fin used in PCHE, since the j factor of this novel fin is 2.97-6.15% larger, and the pressure drop is 0-4.07% less than the NACA 0020 airfoil fin under the selected conditions. And the staggered arrangement and the proper shape of fins could reduce the effect of boundary layer and improve the thermal-hydraulic performance effectively. In addition, the enhancement mechanism of the novel fin PCHE could be explained with field synergy principle very well. (C) 2018 Elsevier Ltd. All rights reserved.
ISSN: 0017-9310
eISSN: 1879-2189
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Record 112 of 233
Title: Pinch point analysis of heat exchange for liquid nature gas (LNG) cryogenic energy using in air separation unit
Source: INTERNATIONAL JOURNAL OF REFRIGERATION-REVUE INTERNATIONALE DU FROID Volume: 90 Pages: 264-276 DOI: 10.1016/j.ijrefrig.2017.12.015 Published: JUN 2018
Abstract: Due to strong nonlinear variation of supercritical liquid nature gas (LNG) and nitrogen (N-2) isobaric heat capacity with temperature and pressure, pinch point analysis is conducted for heat exchange process between LNG and N-2 and its effect on the air separation unit cooled by LNG cryogenic energy (CEASU) is studied in the present study. The effect of pinch point value, temperature difference at the cold end and pressure of N-2 on mass flow ratio (N-2 to LNG), approach temperature difference, energy consumption of CEASU and cryogenic energy utilization rate are analyzed in detail. For the heat exchanger process between LNG and N-2, the different value of pinch point have little effect on its location, and increasing the temperature difference at the cold end effectively increases the mass flow ratio and decreases the approach temperature difference, while rising the pressure of N-2 leads to a valley value of the mass flow ratio, in contrast to a peak value in the approach temperature difference. For the energy consumption of CEASU, choosing the lower temperature difference at the cold end is good for the energy consumption and equivalent energy consumption per kilogram liquid production, but a large amount of LNG is needed and cryogenic energy could not be fully used; while the influence of pressure of N-2 on the energy consumption presents different variation trend. The result shows the energy consumption per kilogram liquid production of proposed CEASU is roughly 5-12% lower than that of convectional processes which the cryogenic energy is only used for cooling the nitrogen or the feed air. (C) 2017 Published by Elsevier Ltd.
ISSN: 0140-7007
eISSN: 1879-2081
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Record 113 of 233
Title: Combustion performance and slagging characteristics during co-combustion of Zhundong coal and sludge
Source: JOURNAL OF THE ENERGY INSTITUTE Volume: 91 Issue: 3 Pages: 397-410 DOI: 10.1016/j.joei.2017.02.002 Published: JUN 2018
Abstract: Zhundong coal (ZDc) with a very large reserve is faced with severe problems of slagging and fouling during combustion in boilers because of the high-Na content. Sludge, the by-product of urban sewage treatment, is also faced with the problem in utilization. In this study, the co-combustion of ZDc and sludge was investigated in a laboratory-scale experimental apparatus before further studies in larger-scale setups. The experimental results confirm an interaction between ZDc and sludge during co-combustion, which was mainly caused by the Na catalytic action and improved the combustion performance of the co-fuels. The catalytic effect was particularly significant at low sludge mixing ratios. The reactions between Na-based compounds in ZDc and Si/Al/P-rich minerals in sludge, forming high-melting-point phosphates and aluminosilicates, not only increased Na retention in residual ash reducing the risk of fouling on tail-heating surfaces in boilers, but also raised the ash fusibility of the co-fuels avoiding low-temperature sintering. Even so, to prevent slagging, the high combustion temperature above 900 degrees C should be avoided during co-combustion because of the high Na retention in residual ash. Moreover, the high heavy metal retention in residual ash decreased the pollution caused by heavy metal volatilization during sludge combustion. (C) 2017 Energy Institute. Published by Elsevier Ltd. All rights reserved.
ISSN: 1743-9671
eISSN: 1746-0220
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Record 114 of 233
Title: An improved model for tip clearance loss in transonic axial compressors
Source: PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART A-JOURNAL OF POWER AND ENERGY Volume: 232 Issue: 4 Pages: 295-314 DOI: 10.1177/0957650917736453 Published: JUN 2018
Abstract: An improved compressible model for estimating tip clearance loss in transonic compressors is presented with the emphasis on the effects of blade tip loading distribution and double leakage flow. Tip clearance flow is treated as three parts along the chord and the progressive relations from upstream to downstream part is revealed to be responsible for the formation of tip clearance flow. Control volume method is applied to simplify the mixing process and calculate the mixed-out loss for the three parts, separately. Computational study shows that mass flow of the incoming flow entering the control volume is consistent with that passing through an equivalent area of about half of tip leakage vortex region. The new model reveals that the second part of tip clearance flow has a larger mixed-out loss capacity than the two other parts. This difference is attributed to two factors: larger injection flow angle and more enrolled incoming flow, and both factors tend to increase the mixed-out loss. The success of the model implies that blade design or flow control strategies turning the tip clearance/main flow interface's arrival onto blade tip pressure side downstream and the shock's impingement point onto blade tip suction side upstream may be beneficial in desensitizing compressor performance to tip clearance size, without trading off pressure rise.
ISSN: 0957-6509
eISSN: 2041-2967
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Record 115 of 233
Title: Effect of Blade Pitch Angle on the Aerodynamic Characteristics of a Straight-bladed Vertical Axis Wind Turbine Based on Experiments and Simulations
Abstract: The blade pitch angle has a significant influence on the aerodynamic characteristics of horizontal axis wind turbines. However, few research results have revealed its impact on the straight-bladed vertical axis wind turbine (Sb-VAWT). In this paper, wind tunnel experiments and CFD simulations were performed at the Sb-VAWT to investigate the effect of different blade pitch angles on the pressure distribution on the blade surface, the torque coefficient, and the power coefficient. In this study, the airfoil type was NACA0021 with two blades. The Sb-VAWT had a rotor radius of 1.0 m with a spanwise length of 1.2 m. The simulations were based on the k- Shear Stress Transport (SST) turbulence model and the wind tunnel experiments were carried out using a high-speed multiport pressure device. As a result, it was found that the maximum pressure difference on the blade surface was obtained at the blade pitch angle of = 6 degrees in the upstream region. However, the maximum pressure coefficient was shown at the blade pitch angle of = 8 degrees in the downstream region. The torque coefficient acting on a single blade reached its maximum value at the blade pitch angle of = 6 degrees. As the tip speed ratio increased, the power coefficient became higher and reached the optimum level. Subsequently, further increase of the tip speed ratio only led to a quick reversion of the power coefficient. In addition, the results from CFD simulations had also a good agreement with the results from the wind tunnel experiments. As a result, the blade pitch angle did not have a significant influence on the aerodynamic characteristics of the Sb-VAWT.
ISSN: 1996-1073
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Record 116 of 233
Title: Experimental Research on Flameless Combustion with Coal Preheating Technology
Source: ENERGY & FUELS Volume: 32 Issue: 6 Pages: 7132-7141 DOI: 10.1021/acs.energyfuels.8b00719 Published: JUN 2018
Abstract: As a novel combustion technology, flameless combustion is attractive to achieve highly efficient and low NOx utilization of fuels. In this paper, a new method to realize flameless combustion of pulverized coal based on coal preheating technology was adopted. Experimental research on flameless combustion was implemented with pulverized coal in a 30 kW coal preheating and combustion test rig. In the study, coal preheated characteristics, combustion behavior, and the formation mechanism of NOx are discussed. The results show that the temperature of pulverized coal can be preheated up to above 850 degrees C, and most of the volatiles are released during the preheating process. Only 33.90% of the fixed carbon in pulverized coal is converted into coal gas and most remains in the high temperature coal char, and 91.14% of the fuel-N released from pulverized coal is converted to N-2. Stable flameless combustion can be achieved with preheated fuels in the down-fired combustor, and no obvious flame front can be observed through the fire-observation windows, and the luminosity is uniform inside the down-fired combustor. The temperature profile in the combustion zone is uniform with normalized temperature fluctuation less than 10%. NOx is generated near the fuel nozzle and then reduced in the main combustion zone, and the NOx emission is 67 mg/Nm(3) (6% O-2). The formation of NOx is inhibited by rational air distribution, and the combustion efficiency reaches up to 96.4%.
ISSN: 0887-0624
eISSN: 1520-5029
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Record 117 of 233
Title: A novel antibiotic wastewater degradation technique combining cavitating jets impingement with multiple synergetic methods
Abstract: Antibiotics degradation remains a longstanding challenge in wastewater treatment. Towards this objective, we have developed a novel technique combining cavitating jets impingement with multiple synergetic methods, i.e., UV/Fenton, analogous Fenton, and photocatalytic oxidation in the present work. Three kinds of antibiotics namely amoxicillin, doxycycline and sulfadiazine sodium, are selected as model pollutants. Individual application of cavitating Jets impingement is firstly conducted to evaluate the effects of jets impinging forms and nozzle inlet pressure. The effects of impingement on promoting antibiotics degradation and weakening the coalescing effects of cavitation bubbles are confirmed. Perpendicular double cavitating jets impingement is proved to be the most effective impinging form and brought a COD (chemical oxidation demand) reduction of 30.04% with the impinging effect index 1.22 at Jet inlet pressure 10 MPa. Increasing the jet inlet pressure can improve the COD reduction and the effectiveness of impingement. Subsequently, UV/Fenton process is introduced to intensify the degradation process. The effects of important parameters are investigated by means of orthogonal experiments and the maximum COD reduction is up to 71.16% under the optimum conditions. Then, analogous Fenton process and photocatalytic oxidation are adopted for further enhancing the COD reduction. Different approaches used in the present work are assessed in view of multiple aspects. With COD reduction of 79.92%, the combination of cavitating jets impingement, UV/Fenton, analogous Fenton and photocatalytic oxidation is proved to be optimum method for antibiotic wastewater treatment.
ISSN: 1350-4177
eISSN: 1873-2828
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Record 118 of 233
Title: An experimental and modeling study on the low temperature oxidation of surrogate for JP-8 part II: Comparison between neat 1,3,5-trimethylbenzene and its mixture with n-decane
Source: COMBUSTION AND FLAME Volume: 192 Pages: 517-529 DOI: 10.1016/j.combustflame.2018.01.001 Published: JUN 2018
Abstract: The low temperature oxidation of neat 1,3,5-trimethylbenzene (T135MB) and n-decane/T135MB mixture as a surrogate for JP-8 has been investigated in a jet-stirred reactor over the temperature range of 500-1100K at atmospheric pressure under fuel-rich condition with residence time from 2.33 to 1.06s. Mole fraction profiles of 29 intermediates including light hydrocarbons, oxygenated and aromatic compounds were identified by gas chromatographic techniques. In general, the concentrations of intermediates tend to increase progressively with temperature from 925K in neat T135MB oxidation, while these species exhibit bimodal distributions from 550 K in the oxidation of n-decaneff135MB mixture (surrogate). By considering the calculated rate constants of T135MB and analogous coupling reactions between T135MB and n-decane, a detailed kinetic mechanism involving 910 species and 5329 reactions was established with a reasonable agreement with the experimental results. The low temperature chemistry of T135MB and surrogate was analyzed including the NTC behavior below 800K. The oxidation process of T135MB is occurring mainly by H-abstraction with OH radical and subsequent reactions. The difference is that in the NTC region H-abstraction by OH radicals is the major consumption pathway for T135MB in the surrogate. But for neat T135MB, the dominant channels change to the H-abstractions by H-atoms, OH and CH3 radicals. Addition of n-decane can promote the oxidation of T135MB by providing OH radicals in the low temperature oxidation of surrogate fuel. Moreover, the model was also validated against the experimental data on n-decane and JP-8 combustion, including species profiles in low temperature jet-stirred reactor oxidation and high temperature flow reactor pyrolysis as well as ignition delay times. These extended results yielded overall satisfactory agreement, and will benefit for further application of practical JP-8 fuels, particularly for their combustion properties at wide temperature range. (C) 2018 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
ISSN: 0010-2180
eISSN: 1556-2921
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Record 119 of 233
Title: Study on the limestone sulfation behavior under oxy-fuel circulating fluidized bed combustion condition
Author(s): Li, W (Li, Wei); Li, SY (Li, Shiyuan); Xu, MX (Xu, Mingxin); Wang, X (Wang, Xin)
Source: JOURNAL OF THE ENERGY INSTITUTE Volume: 91 Issue: 3 Pages: 358-368 DOI: 10.1016/j.joei.2017.02.005 Published: JUN 2018
Abstract: In order to investigate the behavior of limestone sulfation under oxy-fuel circulating fluidized bed (CFB) combustion condition, experiments were conducted in a 50 kW oxy-fuel CFB system under the O-2/CO2 and air combustion conditions. A small cage, containing limestone particles, was dipped into the dense zone of the CFB combustor during the experiments. The calcination of limestone, pore structure of the product layer, and calcium conversion were studied. It was found that the increasing of temperature would promote the calcination of limestone and the high concentration of CO2 would inhibit calcination of limestone. The formation process of the product layer was completely different between the direct and indirect sulfation, while it was almost the same during the indirect sulfation under the oxy-fuel and air combustion. However, both the temperature and gas compositions played important roles in determining the pore structures of the product layer during the limestone indirect sulfation process. Under the O-2/CO2 combustion condition, the calcium conversion of indirect sulfation was always higher than that of direct sulfation. The highest final calcium conversion after 60 min was found at 900 degrees C under the O-2/CO2 combustion condition. (C) 2017 Energy Institute. Published by Elsevier Ltd. All rights reserved.
ISSN: 1743-9671
eISSN: 1746-0220
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Record 120 of 233
Title: Influence of Reynolds Number on the Unsteady Aerodynamics of Integrated Aggressive Intermediate Turbine Duct
Author(s): Liu, HR (Liu, Hongrui); Liu, J (Liu, Jun); Ji, LC (Ji, Lucheng); Du, Q (Du, Qiang); Liu, G (Liu, Guang); Wang, P (Wang, Pei)
Source: JOURNAL OF THERMAL SCIENCE Volume: 27 Issue: 3 Pages: 294-303 DOI: 10.1007/s11630-018-1011-6 Published: JUN 2018
Abstract: The ultra-high bypass ratio turbofan engine attracts more and more attention in modern commercial engine due to advantages of high efficiency and low Specific Fuel Consumption (SFC). One of the characteristics of ultra-high bypass ratio turbofan is the intermediate turbine duct which guides the flow leaving high pressure turbine (HPT) to low pressure turbine (LPT) at a larger diameter, and this kind of design will lead to aggressive intermediate turbine duct (AITD) design concept. Thus, it is important to design the AITD without any severe loss. From the unsteady flow's point of view, in actual operating conditions, the incoming wake generated by HPT is unsteady which will take influence on boundary layer's transition within the ITD and LPT. In this paper, the three-dimensional unsteady aerodynamics of an AITD taken from a real engine is studied. The results of fully unsteady three-dimensional numerical simulations, performed with ANSYS-CFX (RANS simulation with transitional model), are critically evaluated against experimental data. After validation of the numerical model, the physical mechanisms inside the flow channel are analyzed, with an aim to quantify the sensitivities of different Reynolds number effect on both the ITD and LPT nozzle. Some general physical mechanisms can be recognized in the unsteady environment. It is recognized that wake characteristics plays a crucial role on the loss within both the ITD and LPT nozzle section, determining both time-averaged and time-resolved characteristics of the flow field. Meanwhile, particular attention needs to be paid to the unsteady effect on the boundary layer of LPT nozzle's suction side surface.
ISSN: 1003-2169
eISSN: 1993-033X
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Record 121 of 233
Title: Experimental study on the scattering and absorption coefficients of thermal barrier coatings at elevated temperatures
Source: INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER Volume: 121 Pages: 900-910 DOI: 10.1016/j.ijheatmasstransfer.2018.01.028 Published: JUN 2018
Abstract: The study on the scattering and absorption coefficients of thermal barrier coatings (TBCs) is becoming more and more important as the radiation heat transport through TBCs makes a greater contribution due to the continuous increase in turbine inlet temperature. The spectral reflectance and transmittance of the atmospheric plasma-sprayed 8 wt% yttria-stabilized zirconia (8YSZ) TBCs are measured by the two-substrate method at elevated temperatures from 850 to 1150 degrees C with the wavelength varying from 1.4 to 2.4 mu m. The reflectance decreases with increasing wavelength and temperature, while the transmittance has a reverse rule. The high reflectance and transmittance of the 8YSZ TBCs demonstrate that the 8YSZ TBCs have high scattering and low absorption coefficients. The scattering and absorption coefficients of the 8YSZ TBCs are determined by the four-flux model. The scattering coefficient decreases approximately from 820 to 460 cm(-1) as the wavelength increases with less temperature dependence. The absorption coefficient is extremely low (<0.1 cm(-1)), and it increases as the temperature increases with a little wavelength dependence. The transmittance of the 8YSZ TBCs cannot be simplified as a quasi-Beer's law or an exponential term of the thickness, because the scattering coefficient is too large and the condition that the thickness of 8YSZ TBCs is much larger than the effective attenuation length is not met. Due to the low absorption coefficient, the 8YSZ TBCs can be treated as the pure scattering coatings without the effect of absorption. The zero-absorption two-flux model is a simple and accurate model to predict the scattering coefficient of the 8YSZ TBCs approximately as the pure scattering material. (C) 2018 Elsevier Ltd. All rights reserved.
ISSN: 0017-9310
eISSN: 1879-2189
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Record 122 of 233
Title: Sodium nitrate - Diatomite composite materials for thermal energy storage (vol 146, pg 494, 2017)
Abstract: In this study, the nano/micro hierarchical structure effect of a nonwettable surface on droplet impact was investigated by high-speed visualization. A dual-scale structure of a superhydrophobic surface was designed for manipulating a wide range of capillary pressures (10(3)-10(6) Pa), and it was supposed to trigger a hierarchical effect on the droplet dynamics. Distilled water droplets of various sizes and initial velocity were subjected to the prepared samples, and the impact behavior, the spreading diameter, and contacted time, were quantitatively measured. The apparent maximum spreading and contact time of the low Weber number (We#) condition was less dependent on the microscaled design factor of the multiscale-fabricated surface. However, in the high We# condition, the wavy formation shape and the fragmented criteria of the droplet impact were affected by the configuration of the surface morphology. The hierarchical effect from the dual-scale structure on droplet spreading dynamics has been discussed through a balance between capillary pressure induced by the structure and the dynamic pressure of droplet impact.
ISSN: 0743-7463
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Record 124 of 233
Title: A review on heat transfer and hydrodynamic characteristics of nano/microencapsulated phase change slurry (N/MPCS) in mini/microchannel heat sinks
Author(s): Chai, L (Chai, Lei); Shaukat, R (Shaukat, Rabia); Wang, L (Wang, Liang); Wang, HS (Wang, Hua Sheng)
Abstract: Mini/microchannel heat sinks are currently widely used in a variety of thermal and energy applications with the advantages of compactness, light weight and higher heat transfer performance. In order to further improve the performance of such heat sink, many recent studies have introduced the nano/microencapsulated phase change slurry (N/MPCS) as the working fluid due to their high storage capacity during phase change. This paper concerns the channel with hydraulic diameter from 10 mu m to 3 mm, covering the range of microchannel and minichannel. Firstly, the existed review works relate to mini/microchannel heat sinks are summarized, with topics covering manufacturing processes and geometric designs, thermal and hydrodynamic performance with different working fluids, and their typical and potential applications. Then, the N/MPCS used in mini/microchannels from experimental and numerical simulation works are discussed, with focuses placed on the base fluid, core and shell materials, and thermophysical properties of slurry. Next, the local, average and overall heat transfer and hydrodynamic characteristics of mini/microchannel heat sinks with N/MPCS flowing inside are reviewed and analyzed, considering different flow conditions, material and dimension of test section, and composition and fraction of such slurry. Finally, the proposed heat transfer and pressure drop correlations in this research field are evaluated. The purpose of this review article is to provide exhaustive and comprehensive study of recent published works in this new area and supply useful information for the design of compact heat exchangers and thermal storage systems with N/MPCS as working fluid.
ISSN: 1359-4311
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Record 125 of 233
Title: Synthesis, crystal structure and characterizations of a new diphosphate Rb2CaP2O7
Source: JOURNAL OF ALLOYS AND COMPOUNDS Volume: 744 Pages: 370-374 DOI: 10.1016/j.jallcom.2018.02.113 Published: MAY 5 2018
Abstract: A new diphosphate Rb2CaP2O7 is synthesized by solid-states reaction. This compound crystallizes in the monoclinic space group of P2(1)/n, with unit cell parameters of a = 10.0238(9) angstrom, b = 5.7861(5) angstrom, c = 13.0654(11) angstrom and beta = 104.726 degrees. In this compound the [P2O7](4-) dimers and [CaO6](10-) units are interconnected by sharing the corner O atoms to form a 3D framework, with Rb+ cations filling in the interstices to balance the charge. The thermal property, IR and Raman spectra, UV-Vis-NIR diffuse reflectance spectrum and electronic band structure in Rb2CaP2O7 are determined, demonstrating its congruently melted characteristic and wide transparency down to the deep-ultraviolet region. Moreover, the replacement of Rb by K atoms in Rb2CaP2O7 can keep the compound structure unchanged, and the exemplified K1.85Rb0.15CaP2O7 exhibits almost the same fundamental physicochemical properties as Rb2CaP2O7. (c) 2018 Elsevier B.V. All rights reserved.
ISSN: 0925-8388
eISSN: 1873-4669
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Record 126 of 233
Title: Investigation on the mid-temperature solar thermochemical power generation system with methanol decomposition
Source: APPLIED ENERGY Volume: 217 Pages: 56-65 DOI: 10.1016/j.apenergy.2018.02.101 Published: MAY 1 2018
Abstract: A novel 1 MWe mid-temperature solar thermochemical power generation system is proposed to improve solar conversion efficiency in this work. The system consists of a parabolic trough solar collector, solar receiver/reactor, syngas storage tank, internal combustion engine (ICE) and heat exchange devices. The fed methanol is evaporated and flows into the solar receiver/reactor for decomposition and to produce syngas (H-2 and CO), with the required reaction heat provided by the parabolic trough collector. Different from typical solar power technologies, in the proposed system, solar thermal energy is converted to syngas as chemical energy, which can be stored or utilized efficiently by an ICE for power generation. The thermodynamic performance evaluation results indicate that the annual energy efficiency and solar-to-electric efficiency reach to 33.78% and 18.29%, respectively. A small-scale pilot system with the capacity of 20 kW(e) is constructed, and for the first time, an industrial-scale mid-temperature thermochemical power generation is realized, which experimentally validates the effectiveness of the novel solar power technology. The research findings provide an alternative means for improving solar conversion performances.
ISSN: 0306-2619
eISSN: 1872-9118
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Record 127 of 233
Title: Feasibility of a hybrid photovoltaic/thermal and liquid desiccant system for deep dehumidification
Author(s): Su, BS (Su, Bosheng); Qu, WJ (Qu, Wanjun); Han, W (Han, Wei); Jin, HG (Jin, Hongguang)
Source: ENERGY CONVERSION AND MANAGEMENT Volume: 163 Pages: 457-467 DOI: 10.1016/j.enconman.2018.02.018 Published: MAY 1 2018
Abstract: Air dehumidification is widely applied in the civilian and industrial use, however, conventional vapor compression air-conditioning system consumes substantial power. Using renewable energy in the air handling process has potential to further reduce the power consumption, meanwhile ease the carbon emission. This paper proposes a novel liquid desiccant system integrated with a concentrated photovoltaic/thermal collector for deep dehumidification. The generated electric power drives a vapor compression chiller for cooling the desiccant solution for a two-stage dehumidification, and the released heat from the collector is used for the desiccant regeneration. Simulation studies indicated the proposed system has a superior power saving ability of 55.65% comparing with the conventional one, besides the equivalent power generation efficiency reaches 8.7% in the base design condition. A comparative driven force analysis showed the two-stage dehumidification has a better match of driven force compared with the single-stage liquid desiccant dehumidification, thus leading to a reduced irreversible loss of 65.43%. Sensitivity analysis indicated that the dehumidification temperature has a decisive effect on the system performance. The exergy efficiency has a maximum value of 13% as the dehumidification temperature is 22.3 degrees C. The economic studies showed that the investment on the concentrated photovoltaic/thermal collector account for the largest share of the total initial investment, and has a significant effect on the payback period. The payback period would be reduced further if the benefit of the clean development mechanism (CDM) is considered.
ISSN: 0196-8904
eISSN: 1879-2227
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Record 128 of 233
Title: Numerical investigation of a highly loaded centrifugal compressor stage with a tandem bladed impeller
Source: PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART A-JOURNAL OF POWER AND ENERGY Volume: 232 Issue: 3 Pages: 240-253 DOI: 10.1177/0957650917725406 Published: MAY 2018
Abstract: This study numerically investigated a highly loaded centrifugal compressor stage with various tandem-designed impellers and a wedge diffuser using a state-of-the-art multi-block flow solver to better understand the fundamental mechanism of tandem impellers. The flow topologies in the impeller are analyzed in detail to identify the underlying physical mechanism of the effect of the tandem-impeller design on the performance of the compressor stage. Particular emphasis is placed on the evolution of the flow structure in the tandem bladed impeller by varying the inducer-exducer clocking arrangements. The results demonstrate that a tandem compressor design is more efficient than a conventional compressor design for the majority of the tested clocking configurations, and the tandem clocking friction significantly affects the impeller performance. For the tested centrifugal compressor stage, an approximately 1.4% increase in isentropic efficiency and 1.3% increase in stall margin are achieved with an inducer-exducer clocking fraction of 25%. The improvement in the primary centrifugal compressor stage performance by the tandem-impeller design is a result of the manipulation of the flow structure and the reduction in the highly distorted jet/wake exit flow pattern. Compared to the conventional impeller designs, the tandem-impeller clocking arrangement variation significantly affects the high-momentum flow along the exducer suction surface and inducer wake diffusion, inlet axial velocity, and flow angle of the exducer blade. Therefore, this variation is advantageous for shortening the length of the boundary layers on both parts of the blade and enables an intense mixing at the exducer passage to improve the flow uniformity of the impeller exit. As a result, the impeller efficiency, diffuser recovery, and stalling margin can be improved compared with the conventional design.
ISSN: 0957-6509
eISSN: 2041-2967
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Record 129 of 233
Title: A novel electrocoagulation process using insulated edges of Al electrodes for enhancement of urban wastewater treatment: Techno-economic study
Author(s): Elazzouzi, M (Elazzouzi, M.); El Kasmi, A (El Kasmi, A.); Haboubi, K (Haboubi, K.); Elyoubi, MS (Elyoubi, M. S.)
Source: PROCESS SAFETY AND ENVIRONMENTAL PROTECTION Volume: 116 Pages: 506-515 DOI: 10.1016/j.psep.2018.03.006 Published: MAY 2018
Abstract: A comparison between conventional process and novel process of insulated edges electrodes in a batch electrocoagulation (EC) reactor for the treatment of urban wastewater was undertaken to investigate the effect of current density, operating time and initial temperature on the treatment efficiency. The optimal experimental conditions are found to be: current density of 20 mA cm(-2), operating time of 6 min and initial temperature of 45 degrees C for phosphorous (P) and 55 degrees C for chemical oxygen demand (COD). The high removal efficiencies of COD and P using conventional electrodes system were found to be 89% and 99%, respectively. By comparison, the removal efficiencies using insulated edges of electrodes were achieved 91% for COD and 99.5% for P. The adsorption capacities of COD and P for conventional and novel processes were found to be 5930 mg COD kg(-1) and 80 mg P kg(-1), and 5860 mg COD kg(-1) and 77 mg P kg(-1), respectively. The sludge generated at optimum operating conditions using conventional and novel processes were calculated as 1.5 kg m(-3) and 1.8 kg m(-3), respectively. Also, insulated electrode process exhibited the ability to reduce the cost to 0.62 $ kg(-1) for COD and to 0.58 $ kg(-1) for P. The characterization study of produced sludge confirms that metal hydroxides and oxyhydroxides constitute the main components that contributed strongly to remove COD and P from urban wastewater. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
ISSN: 0957-5820
eISSN: 1744-3598
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Record 130 of 233
Title: Thermoelectric properties of lower concentration K-doped Ca3Co4O9 ceramics
Author(s): Li, YN (Li, Ya-Nan); Wu, P (Wu, Ping); Zhang, SP (Zhang, Shi-Ping); Chen, S (Chen, Sen); Yan, D (Yan, Dan); Yang, JG (Yang, Jin-Guang); Wang, L (Wang, Li); Huai, XL (Huai, Xiu-Lan)
Source: CHINESE PHYSICS B Volume: 27 Issue: 5 Article Number: 057201 DOI: 10.1088/1674-1056/27/5/057201 Published: MAY 2018
Abstract: The tuning of electron and phonon by ion doping is an effective method of improving the performances of thermoelectric materials. A series of lower concentration K-doped Ca3-xKxCo4O9 (x = 0, 0.05, 0.10, 0.15) polycrystalline ceramic samples are prepared by combining citrate acid sol-gel method with cold-pressing sintering method. The single-phase compositions and plate-like grain morphologies of all samples are confirmed by x-ray diffraction and field emission scanning electron microscope. The effects of lower concentration K doping on the thermoelectric properties of the material are evaluated systematically at high temperatures (300-1026 K). Low concentration K doping causes electrical conductivity to increase up to 23% with little effect on the Seebeck coefficient. Simultaneously, the thermal conductivity of K-doped sample is lower than that of the undoped sample, and the total thermal conductivity reaches a minimum value of approximately 1.30 W.m(-1).K-1 , which may be suppressed mainly by the phonon thermal conduction confinement. The dimensionless figure-of-merit ZT of Ca2.95K0.05CO4O9 is close to 0.22 at 1026 K, representing an improvement of about 36% compared with that of Ca3Co4O9 , suggesting that lower concentration K-doped Ca3Co4O9 series materials are promising thermoelectric oxides for high-temperature applications.
ISSN: 1674-1056
eISSN: 1741-4199
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Record 131 of 233
Title: Power Generation Based on Chemical Looping Combustion: Will It Qualify To Reduce Greenhouse Gas Emissions from Life-Cycle Assessment?
Author(s): Fan, JM (Fan, Junming); Hong, H (Hong, Hui); Jin, HG (Jin, Hongguang)
Abstract: The aim of this study is to disclose the relationship between the global warming impact (GWI) of chemical looping combustion (CLC) and four essential factors to investigate the environmental sustainability of this technology, namely, the types of oxygen carrier (OC), the lifetime of the OC, the global warming potential (GWP) of the OC, and thermodynamic performances of the CLC power facility. At designed conditions, the GWI of the CLC power plant is expected to be 63.4 kg of CO2 eq/(MW h) by using a Ni-based OC. The lifetime of the OC has a major influence on the GWI before it reaches 4000 h, and a further increment of OC lifetime presents a tender influence on reducing the GWI, whereas, at such a condition, the GWP of the OC presents obvious influences. A higher CLC system efficiency contributes to lower GWI; thus, integrating CLC with a more efficient combined cycle rather than the steam cycle and screening high-temperature resistance OCs should be focused on for future research needs.
ISSN: 2168-0485
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Record 132 of 233
Title: Numerical investigation of V-shaped riblets and an improved model of riblet effects
Author(s): Yu, Y (Yu Yang); Zhang, MM (Zhang Ming-Ming); Li, XS (Li Xue-Song)
Source: PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART C-JOURNAL OF MECHANICAL ENGINEERING SCIENCE Volume: 232 Issue: 9 Pages: 1622-1631 DOI: 10.1177/0954406217705907 Published: MAY 2018
Abstract: Symmetric V-shaped riblets are simulated by using the computational fluid dynamic method to understand the riblet effects on the turbulent boundary layer and the skin friction reduction. Three classical turbulence models, namely Spalart-Allmaras, shear stress transport, and re-normalization group k-epsilon models, are investigated under different grid densities. The re-normalization group model produces good results consistent with the experiment, as compared with the existing theoretical and experimental drag results of the flat plate and the V-shaped riblets with different sizes. Simulating V-shaped riblets yield the unexpected discovery that the shear stress transport model produces large errors, and the Spalart-Allmaras model even produces results of qualitative errors. Another finding is that von Karman's constants can no longer meet the requirement of describing velocity profiles in the logarithmic law layer. Aside from the traditional shift of the logarithmic law's intercept, the slope is also changed by riblet height and spacing. Therefore, an improved model of riblet effects is proposed by redefining von Karman's constants.
ISSN: 0954-4062
eISSN: 2041-2983
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Record 133 of 233
Title: A wide-range experimental and modeling study of oxidation and combustion of n-propylbenzene
Author(s): Liu, YX (Liu, Yue-Xi); Wang, BY (Wang, Bing-Yin); Weng, JJ (Weng, Jun-Jie); Yu, D (Yu, Dan); Richter, S (Richter, Sandra); Kick, T (Kick, Thomas); Naumann, C (Naumann, Clemens); Braun-Unkhoff, M (Braun-Unkhoff, Marina); Tian, ZY (Tian, Zhen-Yu)
Source: COMBUSTION AND FLAME Volume: 191 Pages: 53-65 DOI: 10.1016/j.combustflame.2017.12.029 Published: MAY 2018
Abstract: The oxidation of n-propylbenzene (NPB) was studied in a jet-stirred reactor (JSR) equipped with online GC and GC-MS for temperatures ranging between 700 and 1100 K, at phi = 0.4-2.0. In addition, laminar flame speeds were measured at p = 1, 3 and 6 bar at a preheat temperature of T = 473 K, and ignition delay times in a shock tube device behind reflected shock waves, for stoichiometric mixtures at around p = 16 bar. Mole fraction profiles of 25 intermediates including six species, namely 1-propenylbenzene, 2-propenylbenzene, alpha-methylstyrene, naphthalene, indene, and benzofuran were observed additionally. With phi increasing, NPB consumption shifts to higher temperatures, and the reaction temperature zone becomes broader. Based on the experimental measurements and on new calculations of the rate constants for the H-abstractions from NPB with OH, an updated kinetic model involving 292 species and 1919 reactions was developed with a reasonable agreement with the measured species profiles, flame speed values, and ignition delay times. Rate of production analysis reveals that NPB consumption is generally governed by C-H bond cleavage to form three AlC3H6 radicals, which mostly transform to styrene under rich condition and to benzaldehyde under lean condition. Compared to the aromatics formed in the oxidation of two other aromatic C9 fuels, 1,3,5-trimethylbenzene and 1,2,4-trimethylbenzene, NPB exhibits to be the most reactive fuel with the least aldehyde intermediates. Moreover, the present model gives a reasonable agreement with the literature-reported ignition delay times and JSR data. These results can improve the understanding of the oxidation and combustion of NPB as a surrogate fuel constituent for kerosene and diesel. (C) 2017 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
ISSN: 0010-2180
eISSN: 1556-2921
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Record 134 of 233
Title: Global Average Hydroxyl Radical Yield throughout the Lifetime of Cavitation Bubbles
Source: CHEMICAL ENGINEERING & TECHNOLOGY Volume: 41 Issue: 5 Pages: 1035-1042 DOI: 10.1002/ceat.201700153 Published: MAY 2018
Abstract: An improved model to predict OH center dot yield in hydrodynamic cavitation for wastewater treatment is developed. Relaxing the chemical equilibrium assumption, the model can estimate the global average OH center dot yield during the whole oscillation cycle of all bubbles by considering radicals diffusion, cavitation event rate, and bubble radius distribution. Reliability of the model is verified by comparing with experimental data from literature in terms of geometric and operating parameters. The results show that the maximum OH center dot yield is achieved at optimal upstream pressure of 3.6x10(5) Pa, while increasing downstream pressure always enhances OH center dot yield. Decreasing the hole and pipe diameters benefits the OH center dot yield. Finally, a relevant correlation is developed for the design of cavitation reactors.
ISSN: 0930-7516
eISSN: 1521-4125
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Record 135 of 233
Title: Overall design optimization of dedicated outboard airfoils for horizontal axis wind turbine blades
Author(s): Li, XX (Li, Xingxing); Yang, K (Yang, Ke); Liao, CC (Liao, Caicai); Bai, JY (Bai, Jingyan); Zhang, L (Zhang, Lei); Xu, JZ (Xu, Jianzhong)
Source: WIND ENERGY Volume: 21 Issue: 5 Pages: 320-337 DOI: 10.1002/we.2164 Published: MAY 2018
Abstract: Designing the primary airfoils for the outboard part of wind turbine blades is a complicated problem of balancing structural, aerodynamic, and acoustic requirements. This paper presents an optimization method for the overall performance of outboard wind turbine airfoils. Based on the complex flow characteristics of the rotor blades and the varying requirements along the span of a blade, the design principles of outboard airfoils were investigated. The requirements for improving the structural performance and reducing the aerodynamic noise were combined with the following aerodynamic design considerations: high efficiency, low extreme loads, stability, and a wide operating region. Thus, this paper proposes a new mathematical model for overall airfoil optimization using the airfoil performance evaluation indicators. Then, an integrated optimization design platform is established for outboard airfoils. Through 2 design cases, new airfoils with desirable aerodynamic characteristics and improved overall performance were obtained. Comparisons between the new airfoils and reference airfoils based on numerical predictions indicate that the proposed method with the newly established mathematical model can effectively balance the complex requirements of the airfoil and improve its overall performance. More notably, the design cases also indicate that the established optimization design method can be used to address special designs of outboard airfoils for different blade requirements.
ISSN: 1095-4244
eISSN: 1099-1824
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Record 136 of 233
Title: Co-producing electricity and solar syngas by transmitting photovoltaics and solar thermochemical process
Author(s): Qu, WJ (Qu, Wanjun); Hong, H (Hong, Hui); Li, Q (Li, Qiang); Xuan, YM (Xuan, Yimin)
Source: APPLIED ENERGY Volume: 217 Pages: 303-313 DOI: 10.1016/j.apenergy.2018.02.159 Published: MAY 1 2018
Abstract: In this paper, a solar co-producing electricity and solar syngas is originally proposed through synergistically combining a solar photovoltaic process and a solar thermochemical process. A transmitting photovoltaics is adopted and enables the ultraviolet and visible spectra to be converted into electricity. The infrared spectrum penetrates through the transmitting photovoltaics and is converted into high-grade chemical exergy of solar syngas through thermochemical reaction, rather than being converted into waste heat. The energy conversion models of the transmitting photovoltaics and solar thermochemical reactor are described. The total efficiency of solar-to-both electricity and solar syngas can be achieved to 55%. Furthermore, the influence of the key parameters on the solar cogeneration system performance is disclosed, such as the cut-off wavelength, solar cell types and production ratio. Our results would be expected to provide a new pathway of cascade utilization of the concentrating sunlight according to the spectrum distribution.
ISSN: 0306-2619
eISSN: 1872-9118
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Record 137 of 233
Title: Flameless combustion behaviour of preheated pulverized coal
Source: CANADIAN JOURNAL OF CHEMICAL ENGINEERING Volume: 96 Issue: 5 Pages: 1062-1070 DOI: 10.1002/cjce.23043 Published: MAY 2018
Abstract: A method for stable flameless combustion of pulverized coal based on coal preheating was recently proposed. The method involves the initial heating of pulverized coal to a temperature above 800 degrees C. The heated coal is then transferred into a combustion chamber, where it is mixed with secondary air injected at a high velocity to achieve flameless combustion. The flameless combustion behaviour of the preheated pulverized coal was experimentally investigated in a lab-scale test apparatus. The results showed that stable flameless combustion of bituminous coal and two different anthracite coals could be achieved. The temperature of the combustion chamber was also observed to be homogeneous. The peak temperature was below 1250 degrees C, while the average combustion temperature was about 1150 degrees C. The normalized root mean square temperature fluctuation over the combustion chamber is 7.0%, 6.7%, and 6.8% for the three different coals. The colour of the entire combustion chamber was a faint yellow with no obvious flame front surface observed. Fuel preheating was found to be effective for improving the combustion efficiency, with values of 99.2%, 98.3%, and 97.9% achieved for bituminous coal and two different anthracite coals, respectively. The experimental data further revealed that the NOX emissions for all the considered coals were very low compared to the corresponding cases of traditional combustion, with the values for the different coal types also significantly varying. The NOX emissions were determined to be 232, 187, and 165mg/Nm(3) (6% O-2) for bituminous coal and two different anthracite coals, respectively.
ISSN: 0008-4034
eISSN: 1939-019X
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Record 138 of 233
Title: A modified normal strain ratio fatigue life model based on the hybrid approach of critical plane and crystallographic slip theory
Author(s): Mu, LJ (Mu, L. J.); Dong, XZ (Dong, X. Z.); Gao, Q (Gao, Q.); Tan, CQ (Tan, C. Q.)
Source: FATIGUE & FRACTURE OF ENGINEERING MATERIALS & STRUCTURES Volume: 41 Issue: 5 Pages: 1032-1043 DOI: 10.1111/ffe.12749 Published: MAY 2018
Abstract: Based on the method combining the critical plane with crystallographic slip theory, an anisotropic low cycle fatigue life model is proposed to reflect the effects of orientation dependence and damage factors on fatigue life. According to this method, the crystallographic slip plane is adopted as the critical plane by searching for 30 potential slip systems. In addition, considering the effects of normal strain and strain ratio on fatigue failure, the normal strain ratio is introduced into model and regression model is obtained by fitting method. The proposed model is verified by estimating the low cycle fatigue lives of single crystal nickel-based superalloys PWA1480, CMSX-2 and DD3 for different loading conditions. The results show that the proposed model is applicable for more complicated loading situations and give a higher prediction accuracy compared to Sun's model.
ISSN: 8756-758X
eISSN: 1460-2695
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Record 139 of 233
Title: Enhanced irradiation resistance and thermal conductivity of SiC induced by the addition of carbon under Au2+ ion irradiation
Source: CERAMICS INTERNATIONAL Volume: 44 Issue: 7 Pages: 8521-8527 Published: MAY 2018
Abstract: A significant decrease in the thermal conductivity of SiC after irradiation has hindered its practical applications. To solve this problem, polymer-derived pure SiC and C-SiC composites were irradiated under 4 MeV Au2+ ions, and their thermal conductivity was evaluated. The time-domain thermoreflectance method was found to be effective and sensitive to obtain the thermal conductivity of the irradiated layer. In pure SiC, irradiation-induced complete amorphous SiC significantly decreased the thermal conductivity. However, in C-SiC composites, the heterogeneous interface between C and SiC probably increased the irradiation resistance, leaving residual crystallinity in both C and SiC phases and resulting in a higher thermal conductivity. The thermal conductivity of C-SiC composites was dominated by SiC matrix. The optimal thermal conductivity of SiC related composites after irradiation can be designed by controlling the distribution, size, content, interface, and degree of crystallinity of the two phases in the future.
ISSN: 0272-8842
eISSN: 1873-3956
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Record 140 of 233
Title: Thermal-hydraulic performance of interrupted microchannel heat sinks with different rib geometries in transverse microchambers
Author(s): Chai, L (Chai, Lei); Wang, L (Wang, Liang)
Source: INTERNATIONAL JOURNAL OF THERMAL SCIENCES Volume: 127 Pages: 201-212 DOI: 10.1016/j.ijthermalsci.2018.01.029 Published: MAY 2018
Abstract: The thermal-hydraulic performance of microchannel heat sinks with ribs in the interrupted transverse micro chambers is studied using a three-dimensional conjugated heat transfer model and considering entrance effect, viscous heating and temperature-dependent thermophysical properties. Five different configurations of ribs and four lengths along the flow direction for every rib configuration are selected to analyze the effects of rib geometry on the thermal-hydraulic performance. The five rib configurations are rectangular, backward triangular, diamond, forward triangular and ellipsoidal, and the rib geometry parameters include expansion-constriction profile, ratio and length. The effects of rib geometry on thermal-hydraulic performance are firstly examined by the variations of friction factor and Nusselt number with Reynolds number, and corresponding correlations are proposed. Then, the conductive, convective and fluid capacitive thermal resistances are analyzed to obtain some insight into the basic heat transfer mechanism. Next, the entropy generation rates due to heat transfer and fluid friction are investigated for the analysis of the lost available work and irreversibility in the heat transfer process. Finally, the performance evaluation criteria is calculated to comprehensively assess the performance of such interrupted microchannel heat sinks with different rib geometry. For the studied operation parameters and rib geometries, the interrupted microchannel heat sinks with ribs in the transverse microchambers show a 4-31% decrease in the total thermal resistance, a 4-26% decrease in the total entropy generation rates, the maximum value 1.39 in performance evaluation criteria, compared with the straight microchannel heat sink.
ISSN: 1290-0729
eISSN: 1778-4166
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Record 141 of 233
Title: The effects of nonuniform inlet fluid conditions on crossflow heat exchanger
Source: INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER Volume: 120 Pages: 807-817 DOI: 10.1016/j.ijheatmasstransfer.2017.12.084 Published: MAY 2018
Abstract: The influences of uneven inlet flow and temperature conditions on performance of crossflow heat exchanger using supercritical pressure CO2 (S-CO2) as working fluid were investigated from the viewpoint of distributed coordination. The inlet flow maldistribution and inlet temperature nonuniformity in either side of both fluids could deteriorate or enhance heat transfer, and the deterioration or enhancement effect of both fluids could be superimposed. The inlet conditions with enhancement effect eases the uneven distributions of heat transfer coefficient and temperature difference, and improves the distributed coordination between them, and eventually enhances the heat transfer. The total heat transfer rate depends not only on the values of heat transfer coefficient and temperature difference, but also on their coordination. The distributed coordination analysis indicates that the uneven inlet flow and temperature conditions could be used to enhance heat transfer using the special characteristics of S-CO2 without a significant increase of pressure drop. The present work may provide a new way to the optimization design of heat exchanger for the fluids with sharply variable properties. (C) 2017 Elsevier Ltd. All rights reserved.
ISSN: 0017-9310
eISSN: 1879-2189
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Record 142 of 233
Title: Application of microwave tomography to investigation the wet gas-solids flow hydrodynamic characteristics in a fluidized bed
Author(s): Che, HQ (Che, H. Q.); Wang, HG (Wang, H. G.); Ye, JM (Ye, J. M.); Yang, WQ (Yang, W. Q.); Wu, ZP (Wu, Z. P.)
Abstract: Fluidized beds are widely used in pharmaceutical industry for particles coating and granulation. Due to the complex gas solids flow process, it is extremely desirable that a real time monitoring and control system is used in the process in order to enable a bubbling stable fluidization and reduce the chance of defluidization due to agglomeration with high moisture contents particles. The microwave tomography (MWT) technology has been developed for more than twenty years and was mainly applied in medical sectors. MWT has a wide range of frequency (1-2.5 GHz) and can be used to measure materials with high permittivity and conductivity. Therefore, it is a good choice for the monitoring of fluidized bed coating and granulation processes. In this paper, a MWT system with 16 antennas was designed and applied for the monitoring of wetting and coating processes in a lab-scale fluidized bed with top-spray and bottom-spray system. The hydrodynamics characteristics of wet gas-solids flow with different moisture content were investigated by MWT technology. This is the first time that MWT was applied in a real dynamics gas-solids fluidized bed. Experiment result shows that the MWT is available for the online monitoring of the gas solids flow with different moisture content. Different flow regimes were revealed based on the MWT images combined with pressure signals. The results indicate that the MWT provides valuable information to identify the defluidization in the fluidized bed process with high moisture contents materials. It is evident that microwave tomography has clear advantages over single point based measurement technology for process fault diagnose. (C) 2018 Elsevier Ltd. All rights reserved.
Abstract: Temperature gradient is a significant problem for the practical application of solid oxide fuel cells (SOFCs), which may lead to low power density and the degradation of SOFCs. In order to equalize the temperature distribution and improve the electrochemical performance, the concept of a heat pipe with liquid sodium metal is introduced into the design of SOFCs. A highly thermal integrated heat pipe-solid oxide fuel cell (HP-SOFC) was fabricated and investigated. The HP-SOFC consists of a heat functional layer, a current-collecting layer, an anode layer, an electrolyte layer, and a cathode layer. For an extreme flame operation, the temperature gradient along the axis of the tubular SOFC decreases from 31 to 13 K/cm due to the high heat-transfer rate of the heat functional layer. For a single fuel cell, the power output is significantly improved by 65%, increasing from 73 to 120 mW/cm(2) at 0.6 V with a methane-rich flame at an equivalence ratio of 1.7. In addition, prospects for other possible applications of the HP-SOFC are discussed.
ISSN: 0306-2619
eISSN: 1872-9118
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Record 144 of 233
Title: Thermal performance of an active-passive ventilation wall with phase change material in solar greenhouses
Author(s): Chen, C (Chen, Chao); Ling, HS (Ling, Haoshu); Zhai, ZQ (Zhai, Zhiqiang (John)); Li, Y (Li, Yin); Yang, FG (Yang, Fengguang); Han, FT (Han, Fengtao); Wei, S (Wei, Shen)
Abstract: Using phase change material (PCM) in the north wall of solar greenhouses has been recommended as an efficient solution for promoting their indoor thermal environment. In this type of walls, however, there is always a thermal-stable layer, which would greatly decrease their heat storage capacity. To solve this problem, an active passive ventilation wall with PCM has been developed in this study, and a comparative study was carried out using both experimental and numerical methods to justify its advantages over conventional walls. Several important parameters have been monitored or calculated to reflect the contribution of the newly proposed method to the performance of the middle layer of the wall, the indoor thermal environment and the plants' growth. The obtained results confirmed the great effectiveness of the proposed wall in promoting the temperature of its middle layer and irradiated surface. In the newly proposed wall, there was no thermal-stable layer observed, resulting in a minimum temperature rise of 1.34 degrees C. The proposed solution also enhanced the wall's heat storage capacity by 35.27-47.89% and the heat release capacity by 49.93-60.21%, resulting in an average increase of indoor air temperature, daily effective accumulative temperature and soil temperature by 1.58-4.16 degrees C, 33.33-55.06% and 0.53-1.09 degrees C, respectively. The plant height, stem diameter and fruit yield have been increased by 30%, 25% and 28%, respectively.
ISSN: 0306-2619
eISSN: 1872-9118
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Record 145 of 233
Title: Application of process tomography in gas-solid fluidised beds in different scales and structures
Author(s): Wang, HG (Wang, H. G.); Che, HA (Che, H. A.); Ye, JM (Ye, J. M.); Tu, QY (Tu, Q. Y.); wu, ZP (wu, Z. P.); Yang, WQ (Yang, W. Q.); Ocone, R (Ocone, R.)
Abstract: Gas-solid fluidised beds are commonly used in particle-related processes, e.g. for coal combustion and gasification in the power industry, and the coating and granulation process in the pharmaceutical industry. Because the operation efficiency depends on the gas-solid flow characteristics, it is necessary to investigate the flow behaviour. This paper is about the application of process tomography, including electrical capacitance tomography (ECT) and microwave tomography (MWT), in multi-scale gas-solid fluidisation processes in the pharmaceutical and power industries. This is the first time that both ECT and MWT have been applied for this purpose in multi-scale and complex structure. To evaluate the sensor design and image reconstruction and to investigate the effects of sensor structure and dimension on the image quality, a normalised sensitivity coefficient is introduced. In the meantime, computational fluid dynamic (CFD) analysis based on a computational particle fluid dynamic (CPFD) model and a two-phase fluid model (TFM) is used. Part of the CPFD-TFM simulation results are compared and validated by experimental results from ECT and/or MWT. By both simulation and experiment, the complex flow hydrodynamic behaviour in different scales is analysed. Time-series capacitance data are analysed both in time and frequency domains to reveal the flow characteristics.
ISSN: 0957-0233
eISSN: 1361-6501
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Record 146 of 233
Title: Preliminary Design and Model Assessment of a Supercritical CO2 Compressor
Abstract: The compressor is a key component in the supercritical carbon dioxide (SCO2) Brayton cycle. In this paper, the authors designed a series of supercritical CO2 compressors with different parameters. These compressors are designed for 100 MWe, 10 MWe and 1 MWe scale power systems, respectively. For the 100 MWe SCO2 Brayton cycle, an axial compressor has been designed by the Smith chart to test whether an axial compressor is suitable for the SCO2 Brayton cycle. Using a specific speed and a specific diameter, the remaining two compressors were designed as centrifugal compressors with different pressure ratios to examine whether models used for air in the past are applicable to SCO2. All compressors were generated and analyzed with internal MATLAB programs coupled with the NIST REFPROP database. Finally, the design results are all checked by numerical simulations due to the lack of reliable experimental data. Research has found that in order to meet the de Haller stall criterion, axial compressors require a considerable number of stages, which introduces many additional problems. Thus, a centrifugal compressor is more suitable for the SCO2 Brayton cycle, even for a 100 MWe scale system. For the performance prediction model of a centrifugal compressor, the stall predictions are compared with steady numerical calculation, which indicates that past stall criteria may also be suitable for SCO2 compressors, but more validations are needed. However, the accuracy of original loss models is found to be inadequate, particularly for lower flow and higher pressure ratio cases. Deviations may be attributed to the underestimation of clearance loss according to the result of steady simulation. A modified model is adopted which can improve the precision to a certain extent, but more general and reasonable loss models are needed to improve design accuracy in the future.
ISSN: 2076-3417
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Record 147 of 233
Title: Exploration of effective bed material for use as slagging/agglomeration preventatives in circulating fluidized bed gasification of high-sodium lignite
Abstract: An effective bed material is crucial to remit slagging/agglomeration for high-sodium lignite during circulating fluidized bed (CFB) gasification. In this study, the exploration of effective bed material for use as slagging/agglomeration preventatives of high-sodium lignite mined from Zhundong district was conducted in a 0.4 T/D CFB test system. Three mineral materials, SiO2-based quartz sand, Al2O3-based corundum and CaO/Fe2O3-rich boiler ash collected from bottom ash of a CFB industrial boiler, were selected as the potential bed material. Their impacts on the de-fluidization tendency, transformation and migration of alkali metals, priority of reactions involving sodium-based species, formation of liquid slags and ash fusibility were investigated through the characterization of ash samples and thermodynamic equilibrium calculation by Factsage 6.1. The particle-size analysis results presented the improvement of three bed materials in the growth of ash particles followed the order of quartz sand > corundum > boiler ash. This order was ascribed to their reaction priority with sodium-based compounds in coal and the chemical property (mainly referring to ash fusibility) of corresponding products. Generally, reactions between sodium-based species and minerals (Al2O3 and SiO2) were the main way of sodium retention within the ash in gasifier. As boiler ash was used, however, Al2O3 and SiO2 preferentially reacted with the CaO enriched in boiler ash rather than sodium-based species in coal, resulting in very low sodium retention. Under such circumstances, computing results suggested the ash in gasifier could withstand higher gasification temperature, consistent with the measured results of ash fusibility. Additionally, the gasification temperature operating range could be largely widened by simply increasing CaO/Fe2O3 content in gasified ash. Therefore, boiler ash is an effective and low-cost bed material for use as the slagging/agglomeration preventative of high-sodium lignite during CFB gasification.
ISSN: 0016-2361
eISSN: 1873-7153
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Record 148 of 233
Title: Experimental study on combustion characteristics of pulverized coal preheated in a circulating fluidized bed
Abstract: A new technique to preheat pulverized coal in a circulating fluidized bed was adopted. This technique consists of two stages: the pulverized coal is first self-preheated in a circulating fluidized bed, and then the preheated fuel gas and char particles are burned out in a down-fired combustor under air-staging conditions. Experiments were conducted with two types of coals, two air ratios in the circulating fluidized bed and different air distributions in the combustor. The preheating and combustion processes ran stably under all experimental conditions. For both types of coals, the preheating temperatures in the circulating fluidized bed could be adjusted broadly within 800-950 degrees C, and the ratios of primary air could be lowered to 0.15. The combustion efficiency and nitrogen conversion were remarkably influenced by the air distribution, and were controlled above 98% and below 10% respectively, although the two targets could not be simultaneously achieved.
ISSN: 0378-3820
eISSN: 1873-7188
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Record 149 of 233
Title: Comprehensive assessment of line-/point-focus combined scheme for concentrating solar power system
Source: INTERNATIONAL JOURNAL OF ENERGY RESEARCH Volume: 42 Issue: 5 Pages: 1983-1998 DOI: 10.1002/er.3997 Published: APR 2018
Abstract: The line-/point-focus combined scheme for concentrating solar power (CSP) system is proposed. For solar field, the parabolic trough (PT) or linear Fresnel (LF) is used as the line-focus preheating and evaporation stages while the solar tower is used as the point-focus superheating and reheating stages. The combined schemes benefit from the high concentration ratio of point-focus technology and low cost of line-focus technology. Particularly, the combined scheme guarantees the concentrated solar thermal energy matching the temperature requirement of steam generation process with less exergy loss. Performance and economic assessments have been performed for 50MW(e) CSP system with two of the combined schemes, ie, PT (synthetic oil, SO)+Tower (molten salt, MS) and LF (direct steam generation, DSG)+Tower (DSG), as well as existing single schemes being the references, ie, PT (SO), LF (DSG), Tower (MS), and Tower (DSG). The comparative results show that the combined schemes are superior to liner-focus schemes in efficiency and to point-focus schemes in capital cost and scalability. Specifically, the PT (SO)+Tower (MS) system suggests the favorable potential in practical application with the highest annual net solar-to-electrical energy conversion efficiency of 16.07% and the reasonable levelized cost of electricity (LCOE) of 16.121 US cent/(kW<bold>h</bold>). This work provides an alternative guidance for future development of the CSP technology.
ISSN: 0363-907X
eISSN: 1099-114X
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Record 150 of 233
Title: Occurrence and Transformation Characteristics of Recoverable Soluble Sodium in High Alkali, High Carbon Fly Ash during Zhundong Coal Gasification in a Circulating Fluidized Bed
Abstract: In this reported study, the effects of bed temperature, air equivalence ratio (ER), heating surface wall temperature, and coal type on the occurrence and transformation of recoverable soluble Na in high alkali, high carbon fly ash during Zhundong (ZD) coal gasification were investigated in a 0.4 t/d circulating fluidized bed test system. The experimental results illustrated that the quantity of soluble Na in gasification fly ash of ZD coal was far greater than in the ZD coal. Na compounds in ZD coal gasification fly ash were present mainly as NaCl, with other compounds such as Na2SO4 and sodium aluminosilicates, including Na2SiO3 and NaAlSi3O8. The recoverable soluble Na accounted for 56-96.9% of the total Na in the ZD coal gasification fly ash. The proportion of soluble Na in ZD coal gasification fly ash was greatly affected by the gasification conditions. As the bed temperature was increased, the proportion of soluble Na decreased. As the ER was increased, the proportion of soluble Na increased, with the maximum proportion present at an ER of 0.50. Compared to the adiabatic condition, cooling of the heating surface increased the proportion of soluble Na. The soluble Na yield and the proportion of soluble Na were found to be high during gasification of Shaerhu (SEH) and Tianchi (TC) coals, which made them more suitable for recovery of soluble Na from their corresponding fly ashes: Shaerhu fly ash (SEHf) and Tianchi fly ash (TCf).
ISSN: 0887-0624
eISSN: 1520-5029
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Record 151 of 233
Title: Investigation of coating process in Wurster fluidised bed using electrical capacitance tomography
Author(s): Che, HQ (Che, H. Q.); Ye, JM (Ye, J. M.); Tu, QY (Tu, Q. Y.); Yang, WQ (Yang, W. Q.); Wang, HG (Wang, H. G.)
Source: CHEMICAL ENGINEERING RESEARCH & DESIGN Volume: 132 Pages: 1180-1192 DOI: 10.1016/j.cherd.2018.02.015 Published: APR 2018
Abstract: Wurster fluidised beds are used in the pharmaceutical industry for pellet coating. Due to Wurster tube in the chamber, the flow hydrodynamic characteristics are complex and difficult to measure. This paper presents a 12-4-8 electrode electrical capacitance tomography (ECT) sensor used for investigation of complex gas-solids flow characteristics in Wurster fluidised bed coating processes by visualising solids concentration and distribution both inside and outside of Wurster tube synchronously. It was revealed that there exist seven flow regimes, i.e. bubbling-core, intermittent-core, plug-core, plug-bubbling, bubbling-dispersed, intermittent-dispersed and defluidisation, in a coating process. Further analysis of capacitance and pressure drop signals using a continuous wavelet transform (CWT) method indicates that the characteristic frequencies for bubbling, intermittent and plug flow in the annular region are 2, 0-1 and 0 Hz, respectively. The influence of different operating parameters and flow regime on the coating quality, in particular agglomeration, is discussed. Experimental results indicate that ECT is an efficient process analytic technology (PAT) tool to monitor the pellets coating process in a Wurster fluidised bed. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
Conference Title: 8th International Granulation Workshop
Conference Date: JUN 26-30, 2017
Conference Location: Univ Sheffield, Sheffield, ENGLAND
Conference Host: Univ Sheffield
ISSN: 0263-8762
eISSN: 1744-3563
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Record 152 of 233
Title: Thermodynamic analysis for a concentrating photovoltaic-photothermochemical hybrid system
Abstract: In this paper, a novel model of a concentrating photovoltaic-photothermochemical (CPV/PTC) hybrid system is proposed. Solar spectrum is separated into several parts to enable photovoltaic (PV) and photothermochemical (PTC) conversion by utilizing the parabolic trough concentrator with a spectral beam splitter. The PV module converts a specific spectral range of solar radiation into electricity directly by the solar cells and the PTC module absorbs the rest solar energy to supply the reaction heat of methanol-steam reforming (MSR) that produces hydrogen for power generation. The energy and exergy analyses on the CPV/PTC hybrid system are carried out. The overall system efficiencies with different splitting wavebands, widths of the solar cells and heat transfer coefficients of the cooling system are investigated. Moreover, the CPV/PTC hybrid system is compared with a single PV or PTC system. The results indicate that the optimal splitting waveband, concentration ratio and heat transfer coefficient of the cooling system are 450 nm-870 nm, 7.9, and 1500 W/(m(2).K), respectively. With the optimization of the proposed CPV/PTC hybrid system, the overall power generation efficiency can reach 25.3%. (C) 2018 Elsevier Ltd. All rights reserved.
ISSN: 0360-5442
eISSN: 1873-6785
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Record 153 of 233
Title: Aerodynamic performance analysis and optimization of a turbine duct with low degree of partial admission
Source: PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART G-JOURNAL OF AEROSPACE ENGINEERING Volume: 232 Issue: 5 Pages: 988-1001 DOI: 10.1177/0954410017691068 Published: APR 2018
Abstract: A partial admission turbine duct with outlet-to-inlet area ratio greater than unity can increase the admission degree of the downstream turbine stage and, thus improve the performance of a multistage turbine with a low partial admission degree. However, the upstream flow structures of ducts, such as secondary flow, especially the circumferential nonuniformities originating from the effect of the partial admission, make the flow in ducts complex. The complexity of the flow has a negative impact on the performance of ducts. In the present investigation, numerical study of the flow behavior within ducts is done to evaluate the effect of the partial admission on the performance of the ducts. The study is carried out with regard to two cases, i.e. which are with the same duct geometry but are at different working conditions to highlight the impact of partial admission on the performance of ducts. Case 1 is used as baseline. It is designed based on circumferential mass-averaged flow conditions at ducts inlet. It causes the circumferential nonuniformities originating from the partial admission to have no impact on the performance of case 1. Case 2, which considers partial admission, is compared with case 1 to know the impact of the partial admission on the performance of ducts, and to give guidelines to design a duct for the partial admission turbines. Since the duct inlet conditions is a result of the interaction between partial admission turbine and duct, a straightforward way to consider the effect of the partial admission is to simulate the flows in ducts and upstream turbines contemporaneously. Comparative results indicate that the mixing of main flow in the admitted channel and the windage fluid from the unadmitted channel occurs at the duct inlet close to the duct circumferential wall. The adverse pressure gradient of case 2 in that region becomes larger than that of case 1. As a result, the flow separates at that region deteriorating the performance of ducts. Based on the simulation results of the previous cases, case 2's circumferential wall surface, which is along the gas swirling direction is shrunk to accelerate the flow and, thereby, overcome the adverse pressure gradient imposed by the effect of the partial admission. The results show that the separation is restrained and the decrease in total pressure loss is 52.9%.
ISSN: 0954-4100
eISSN: 2041-3025
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Record 154 of 233
Title: Effects of different alternative control methods for gas turbine on the off design performance of a trigeneration system
Author(s): Wang, ZF (Wang, Zefeng); Han, W (Han, Wei); Zhang, N (Zhang, Na); Su, BS (Su, Bosheng); Gan, ZX (Gan, Zhongxue); Jin, HG (Jin, Hongguang)
Abstract: Thermodynamic and economic performance of the combined cooling, heating and power system (CCHP) is mainly affected by its configuration and operation strategy. In this paper, the reducing turbine inlet temperature (TIT) and inlet air throttling (IAT) control methods for gas turbines following the electric load (FEL) are used to analyze the primary energy consumption (PEC), operational cost (COST) and carbon dioxide emission (CDE) in a case of a CCHP system that satisfies the cooling, heating and electric demands of a five-star hotel in Beijing, China. The results indicate that the CCHP system with both TIT and IAT control methods has better off-design performance than separate system except for transition seasons. Since the more production of high-temperature flue gas, the IAT control method significantly reduces the fuel consumption of the auxiliary boiler to satisfy the thermal demand of the reference building, especially in hot summer and cold winter. In January, the IAT control method can decrease fuel consumption by 7.53% compared with TIT control method. Moreover, it is found that improved energy saving performance and decreased operation cost and carbon dioxide emission of the CCHP system are presented with the IAT control method at the annual performance. Finally, the sensitivity analysis of the electric price and gas price is presented for the operation cost and shows that the gas price is the most sensitive variables for the operation cost of the CCHP system.
ISSN: 0306-2619
eISSN: 1872-9118
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Record 155 of 233
Title: One-dimensional model analysis and performance assessment of Tesla turbine
Abstract: Tesla turbine is characterized by the bladeless design that makes it easy to be manufactured and operated. It offers an attractive option for power output in small and micro scale systems if an efficient design can be achieved. One-dimensional model is useful as it can adequately represent the flow characteristics in the Tesla turbine and allow parametric exploration for early design analysis. This paper improves the one-dimensional model for Tesla turbine. The limit expansion ratio of the nozzle is introduced, which is related to the geometry angle and the working fluid properties. The flow loss in the nozzle is evaluated instead of assuming an empirical velocity coefficient. The flow is regarded as turbulence rather than laminar, and friction factor is determined by the Reynolds number based on Moody Figure. In the rotor, the governing equations for compressible flow between adjacent discs are used. In addition, the radial pressure gradient effect in the rotor gap spacing is considered. The improved model show better agreement with the experimental data than the original model. The flow characteristics in the Tesla turbine is analyzed and the streamline of the bulk flow in the rotor is derived based on the one-dimensional model. Tesla turbine can yield considerable efficiency and it can be regarded as a potential choice to be applied in small and micro scale systems.
ISSN: 1359-4311
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Record 156 of 233
Title: Heat Transfer and Entropy Generation Analysis of an Intermediate Heat Exchanger in ADS
Author(s): Wang, YW (Wang Yongwei); Huai, XL (Huai Xiulan)
Abstract: The intermediate heat exchanger for enhancement heat transfer is the important equipment in the usage of nuclear energy. In the present work, heat transfer and entropy generation of an intermediate heat exchanger (IHX) in the accelerator driven subcritical system (ADS) are investigated experimentally. The variation of entropy generation number with performance parameters of the IHX is analyzed, and effects of inlet conditions of the IHX on entropy generation number and heat transfer are discussed. Compared with the results at two working conditions of the constant mass flow rates of liquid lead-bismuth eutectic (LBE) and helium gas, the total pumping power all tends to reduce with the decreasing entropy generation number, but the variations of the effectiveness, number of transfer units and thermal capacity rate ratio are inconsistent, and need to analyze respectively. With the increasing inlet mass flow rate or LBE inlet temperature, the entropy generation number increases and the heat transfer is enhanced, while the opposite trend occurs with the increasing helium gas inlet temperature. The further study is necessary for obtaining the optimized operation parameters of the IHX to minimize entropy generation and enhance heat transfer.
ISSN: 1003-2169
eISSN: 1993-033X
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Record 157 of 233
Title: Thermodynamic characteristics of thermal power plant with hybrid (dry/wet) cooling system
Source: ENERGY Volume: 147 Pages: 729-741 DOI: 10.1016/j.energy.2018.01.074 Published: MAR 15 2018
Abstract: A hybrid cooling system (HCS) consisting of dry and wet sections is proposed as a means to conserve energy and water by combining the benefits of both dry and wet cooling modes. A thermodynamic model of a 660 MW thermal power plant with HCS is established, and the variations in thermodynamic characteristics with respect to dry bulb temperature (TA) and relative humidity (RH) are investigated using Ebsilon calculating code. Through comparison between the dry cooling system (DCS) and wet cooling system (WCS), HCS performance characteristics under different meteorological parameters are analyzed quantitatively. By comprehensively considering water and energy conservation indicators, the unique operation mode and ratio of the heat load shared by dry or wet sections are determined under various meteorological parameters. When TA exceeds a certain value or RH falls below a certain value, the HCS does not operate in a hybrid cooling mode. Instead, its operation is equivalent to that of a WCS. We suggest that the cooling load of the wet section in the HCS be designed with the peak cooling load of the condenser under the most inhospitable meteorological parameters of the year. The findings reported here may provide guidance for HCS thermodynamic design and operation regulations. (C) 2018 Elsevier Ltd. All rights reserved.
ISSN: 0360-5442
eISSN: 1873-6785
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Record 158 of 233
Title: The influence of pressure and temperature on gas-solid hydrodynamics for Geldart B particles in a high-density CFB riser
Abstract: The effects of operating pressure and temperature on the flow behavior in the riser of a high-density circulating fluidized bed have been numerically studied using the two-fluid model coupled with the EMMS-based drag model. When the operating pressure is below 0.4 MPa, the flow regime in the riser experiences the fluid dominated (FD) zone, the transition zone from FD to the particle-fluid compromising (PFC), and the PFC zone with the increase of solids circulating flux. Under the same solids circulating flux, the solids axial velocity increases while the solids volume fraction decreases with the increase of operating pressure. In terms of axial profiles of solids volume fraction and axial velocity, there exists a critical operating pressure, above which the axial profile changes little with further increase of operating pressure, while it is hard to find a critical pressure in terms of radial profiles. When the gas density is kept the same, the increase of gas viscosity caused by higher temperature has only minor effect on the axial profiles of solids volume fraction, but it makes the solids axial velocity increase in the core zone and decrease slightly near the wall. (C) 2017 Elsevier B.V. All rights reserved.
ISSN: 0032-5910
eISSN: 1873-328X
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Record 159 of 233
Title: Magnesium Oxide-Based Absorbents for CO2 Capture at Medium Temperature
Source: CURRENT POLLUTION REPORTS Volume: 4 Issue: 1 Pages: 13-22 DOI: 10.1007/s40726-018-0074-z Published: MAR 2018
Abstract: MgO-based absorbent has been recognized as a promisingCO(2) absorbent at intermediate temperature, though the carbonation performance of pure MgO is poor. Researchers have been devoted to optimize the CO2 absorption ability via introducing alkali metal carbonates or nitrates. In this paper. the absorption performance of MgO-based absorbents promoted by alkali metal carbonates or modified by alkali metal nitrates has been summarized, and the affecting mechanism has been concluded. Alkali metal nitrates are essential for high absorption ability, and alkali metal carbonates facilitate high-temperature carbonation. Effects of fuel gas conditions and absorbent pelletization are also mentioned for practical applications. H2O can accelerate the carbonation rate effectively, but the influencing mechanism of H2O and the CO(2 )absorption stability in presence of H2O was not clearly reported. Further investigations on pelletized MgO-based absorbents modified by alkali metal salts considering regeneration conditions of high CO2 concentration are proposed based on the recent research findings.
ISSN: 2198-6592
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Record 160 of 233
Title: Combination regularization reconstruction method for electrical capacitance tomography
Author(s): Lei, J (Lei, J.); Liu, QB (Liu, Q. B.); Wang, XY (Wang, X. Y.); Liu, S (Liu, S.)
Source: FLOW MEASUREMENT AND INSTRUMENTATION Volume: 59 Pages: 135-146 DOI: 10.1016/j.flowmeasinst.2017.12.010 Published: MAR 2018
Abstract: Two-dimensional or three-dimensional images from the electrical capacitance tomography (ECT) technology provide powerful evidences for revealing complicated mechanisms behind behaviors of tomographic objects. In order to satisfy the increasing demands of dynamic measurements in real-world industrial applications, in this paper a sequential dynamic imaging model is proposed to model the inverse problem with the focus on the ECT imaging, and a new cost function that encapsulates the temporal constraint, the reweighted L1 norm based spatial constraint and the reweighted nuclear norm based low rank constraint is constructed to convert the dynamic inversion problem into a minimization problem. A new algorithm that splits an intractable optimization problem into several simpler sub-problems is developed to solve the new cost function. Comprehensive evaluations of representative imaging targets and comparisons with state-of-the-art imaging algorithms demonstrate the superiorities of the imaging technique proposed in this study on improving the imaging quality and robustness.
ISSN: 0955-5986
eISSN: 1873-6998
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Record 161 of 233
Title: Regasification properties of industrial CFB-gasified semi-char
Source: JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY Volume: 131 Issue: 3 Pages: 3035-3046 DOI: 10.1007/s10973-017-6835-x Published: MAR 2018
Abstract: Fluidized bed (FB) gasification provides a promising way for the clean and effective utilization of low-rank coal. However, massive amounts of high-carbon-containing gasified semi-chars are produced, which greatly reduces its total carbon conversion. The disposal of the semi-char has become an intractable problem. Regasification of the semi-char is a possible way to realize further utilization of the residual carbon and achieve higher carbon conversion of coal gasification. In this paper, the regasification properties of the ultrafine semi-char, obtained from an industrial circulating fluidized bed gasifier, were investigated via thermogravimetric analysis and bench-scale study in a FB reactor. The kinetic parameters are derived by four different reaction models, namely homogeneous model (HM), shrinking core model, random pore model and modified random pore model (MRPM). Both non-isothermal and isothermal tests show that the chemical reactivity of the semi-char is poorer than the coal char. A higher temperature greatly favors regasification of the semi-char. For the studied reaction models, MRPM is the most favorable one for both coal char and semi-char. The activation energy of the semi-char is slightly higher than that of the coal char. Stable regasification of the semi-char in a FB reactor is achieved, and the residual carbon is further utilized. Increasing oxygen concentration could largely improve the heat value of the fuel gas, but slightly decrease the carbon conversion. Higher temperature operation greatly benefits the conversion of the residual carbon in the semi-char. Consequently, it will be considered feasible that the semi-chars are reclaimed and reused as feedstocks for gasification.
ISSN: 1388-6150
eISSN: 1588-2926
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Record 162 of 233
Title: Experimental research on combustion characteristics of coal gasification fly ash in a combustion chamber with a self-preheating burner
Abstract: Coal gasification fly ash (CGFA) is the by-product of coal gasification in a circulating fluidized bed (CFB) and is characterized by its low volatile-content, low carbon-content, and high ash-content, which can be used as a secondary fuel. In China, the annual output of CGFA is enormous; therefore, the realization of a highly efficient CGFA combustion method would be beneficial to achieve better overall coal utilization. Nevertheless, it is challenging to burn CGFA steadily with conventional technologies because of its low volatile content. However, the coal preheating combustion technique has been proven to be an effective method to burn semi-coke and anthracite, both of which are poorly flammable, and could also be applied to CGFA. We have used an advanced preheating combustion technique with a self-preheating burner and carried out experimental investigations into CGFA combustion in a 0.4-MW CGFA preheated combustion test rig. The results show that the preheated combustion system ran smoothly and the CGFA combustion efficiency reached 98.6% with NOX emissions of 155 mg/m(3) (6% O-2). Therefore, the highly efficient and clean combustion of CGFA was realized, and the combustion of poorly flammable fuels using a self-preheating burner was shown to be feasible. The effects of the primary air ratio, secondary air ratio, and the position of the tertiary air inlet on the combustion characteristics and NOX emissions of CGFA were also studied.
ISSN: 0016-2361
eISSN: 1873-7153
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Record 163 of 233
Title: Calcium sulfation characteristics at high oxygen concentration in a 1MW(th) pilot scale oxy-fuel circulating fluidized bed
Author(s): Li, W (Li, Wei); Xu, MX (Xu, Mingxin); Li, SY (Li, Shiyuan)
Abstract: In the present study, tests were conducted to investigate the behaviour of sulfur capture by calcium based sorbents during oxy-fuel circulating fluidized bed combustion at high oxygen concentrations via a 1MW(th) pilot scale oxy-fuel circulating fluidized bed facility. The effects of operating temperature, overall oxygen concentration, and Ca:S molar ratio were taken into consideration. It was determined that the efficiency of sulfur capture during oxy-fuel combustion was higher than that during air combustion. Meanwhile, with the increase of oxygen concentration, the efficiency of sulfur capture increased. Comparing with the optimum temperature for sulfur capture during air combustion, the optimum temperature during oxy-fuel circulating fluidized bed combustion was about 930 degrees C when the overall oxygen concentration was 50%. In addition, the optimal Ca:S molar ratio was similar to 3.0 during oxy-fuel combustion when various factors were all taken into consideration.
ISSN: 0378-3820
eISSN: 1873-7188
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Record 164 of 233
Title: Characteristics of a 10 kW honeycomb reactor for natural gas fueled chemical-looping combustion
Author(s): Zhang, H (Zhang, Hao); Liu, XY (Liu, Xiangyu); Hong, H (Hong, Hui); Jin, HG (Jin, Hongguang)
Source: APPLIED ENERGY Volume: 213 Pages: 285-292 DOI: 10.1016/j.apenergy.2018.01.037 Published: MAR 1 2018
Abstract: Chemical-looping combustion (CLC) is already treated as a promising way to capture CO2 in the utilization of fossil fuels. The most used reactors for the CLC are fluidized-beds, in which the fuel conversion and the conversion of fuel to CO2 is determined by the bed height. Here in this study, the CLC in an advanced 10 kW honeycomb reactor is studied by using, natural gas as the fuel and Fe2O3 as the oxygen carrier. In the honeycomb reactor, a honeycomb chamber consisted by the oxygen carrier is employed to enhance the contact area and the disturbance between the fuel gas and the oxygen carrier. Both of these two enhancement are benefit for achieving a high CH4 conversion and a high conversion of CH4 to CO2. The experiment results show that three stages of Fe2O3 to Fe3O4, Fe3O4 to FeO and FeO to Fe are occurred in sequence during the reduction reaction of Fe2O3 and CH4 in the honeycomb reactor. The behaviors and the relationships for these complicated reactions, the oxygen transfer rate, the CH4 conversion and the conversion of CH4 to CO2 at different stages are further experimentally studied. Additionally, to increasing the conversion of CH4 to CO2 in the continuous operation, the characteristics for the honeycomb reactor in redox cycles are also experimentally investigated. Our study here would be expected to provide a new method for developing the energy and environment compatible systems.
ISSN: 0306-2619
eISSN: 1872-9118
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Record 165 of 233
Title: Analysis of simplified heat transfer models for thermal property determination of nano-film by TDTR method
Source: MEASUREMENT SCIENCE AND TECHNOLOGY Volume: 29 Issue: 3 Article Number: 035902 DOI: 10.1088/1361-6501/aa9e18 Published: MAR 2018
Abstract: Heat transfer in nanostructures is of critical importance for a wide range of applications such as functional materials and thermal management of electronics. Time-domain thermoreflectance (TDTR) has been proved to be a reliable measurement technique for the thermal property determinations of nanoscale structures. However, it is difficult to determine more than three thermal properties at the same time. Heat transfer model simplifications can reduce the fitting variables and provide an alternative way for thermal property determination. In this paper, two simplified models are investigated and analyzed by the transform matrix method and simulations. TDTR measurements are performed on Al-SiO2-Si samples with different SiO2 thickness. Both theoretical and experimental results show that the simplified tri-layer model (STM) is reliable and suitable for thin film samples with a wide range of thickness. Furthermore, the STM can also extract the intrinsic thermal conductivity and interfacial thermal resistance from serial samples with different thickness.
ISSN: 0957-0233
eISSN: 1361-6501
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Record 166 of 233
Title: Experimental investigation and thermodynamic analysis of effective hydrogen production driven by mid- and low-temperature solar heat
Source: JOURNAL OF CLEANER PRODUCTION Volume: 176 Pages: 758-769 DOI: 10.1016/j.jclepro.2017.12.177 Published: MAR 1 2018
Abstract: To realize a shoft- and mid-term goal of sustainable development of solar fuel production, the possibility of effective hydrogen, generation via methanol steam reforming at temperatures of 200 degrees C-300 degrees C inside a novel solar collector/reactor was experimentally demonstrated. With solar irradiation of 1000 W/m(2), the solar collector-reactor achieved hydrogen generation rates up to 68.1 g/(m(2).h), with solar-to-hydrogen efficiencies up to 41.3% and total energetic efficiencies (considering solar and fuel inputs) up to 76.6%, which is competitive with other solar fuel production technologies using high-temperature solar heat. Furthermore, the mechanism of upgrading the energy level of solar heat at 200 degrees C-300 degrees C was revealed based on the second law of thermodynamics and experimental results, where the catalyst was found to play a key role by decreasing the reaction temperature. The results obtained here indicate the possibility of utilizing the mid- and low-temperature solar heat for hydrogen production with high efficiency by upgrading the energy level of solar heat, and provide an enhancement to solar fuel production technologies with the development of this low-grade solar thermochemical technology in the near future. (C) 2017 Published by Elsevier Ltd.
ISSN: 0959-6526
eISSN: 1879-1786
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Record 167 of 233
Title: Influence of the internal wall thickness of electrical capacitance tomography sensors on image quality
Author(s): Liang, SG (Liang, Shiguo); Ye, JM (Ye, Jiamin); Wang, HG (Wang, Haigang); Wu, M (Wu, Meng); Yang, WQ (Yang, Wuqiang)
Source: MEASUREMENT SCIENCE AND TECHNOLOGY Volume: 29 Issue: 3 Article Number: 035401 DOI: 10.1088/1361-6501/aaa0a1 Published: MAR 2018
Abstract: In the design of electrical capacitance tomography (ECT) sensors, the internal wall thickness can vary with specific applications, and it is a key factor that influences the sensitivity distribution and image quality. This paper will discuss the effect of the wall thickness of ECT sensors on image quality. Three flow patterns are simulated for wall thicknesses of 2.5 mm to 15 mm on eight-electrode ECT sensors. The sensitivity distributions and potential distributions are compared for different wall thicknesses. Linear back-projection and Landweber iteration algorithms are used for image reconstruction. Relative image error and correlation coefficients are used for image evaluation using both simulation and experimental data.
ISSN: 0957-0233
eISSN: 1361-6501
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Record 168 of 233
Title: Numerical simulation of multi-nozzle spray cooling heat transfer
Source: INTERNATIONAL JOURNAL OF THERMAL SCIENCES Volume: 125 Pages: 81-88 DOI: 10.1016/j.ijthermalsci.2017.11.011 Published: MAR 2018
Abstract: The aim of this paper is to study the spray cooling heat transfer characteristics using CFD method. The two phase mathematical model is established based on Euler-Lagrange approach. In this model, unsteady-state flow conditions are simulated. Heat and mass transfer between the vapor and the water droplet are computed. The averaged error of numerical results is 10% compared to experimental results in our previous papers. It is concluded that the heat flux and its distribution on heated surface are influenced by the heated surface temperature, mass flux, nozzle to surface distance and the number of nozzles. Furthermore, the heat flux distribution do not change obviously with the increasing of heated surface temperature, and the heat flux increases with the increasing of mass flux. Moreover, there is an optimal nozzle to surface distance while the spray impingement zone circumscribes in heated surface, and more nozzles lead to higher heat flux and better heat flux distribution on heated surface. Considering the disadvantage of manufacture difficulty and cost increase for more nozzles, there is an optimal nozzle number in certain space and heat dissipation requirement. The optimal number of nozzles is 8 in this article.
ISSN: 1290-0729
eISSN: 1778-4166
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Record 169 of 233
Title: Ni line pattern coarsening on zirconia substrates: Impact of initial dimensions
Author(s): Hao, Y (Hao, Yong); Ling, Y (Ling, Yunyi); Oh, TS (Oh, Tae-Sik)
Abstract: Long-term thermal stability of nickel line patterns was investigated. 5 mu m-wide patterns and 20 mu m-wide patterns were deposited with four different thicknesses, and their morphological change was compared after heat treatment. Displaced volume was calculated by post-annealing image analysis. Opposite coarsening trends were found for the two tested widths. 20 mu m-wide patterns show deviation from predictions of previous models, but they still behave as expected: thinner pattern shows higher mobility. This is reversed for 5 mu m-wide patterns. Surface tension at the metal-gas interface, the usual driving force behind coarsening, can still explain the unexpected displaced volume dependence on thickness. (C) 2017 Elsevier B.V. All rights reserved.
Abstract: Extending blades of wind turbine in service is the most effective method for increasing energy production. Adhesively bonding technology increases less mass and has simpler operation process, which is more suitable for extending blades in service. But unsteady aerodynamic loads on the blades due to stochastic turbulent inflow may lead to fatigue damage and even failure. This paper presented a study on strain response and fatigue life of adhesively bonded extended composite wind turbine blade suffering unsteady aerodynamic loads. Firstly, a loading method that applies periodic distributed aerodynamic loads on the blade was proposed to accurately simulate the unsteady distributed loads on the real extended blades in service. Secondly, strain response behaviors to unsteady aerodynamic loads and strain distribution behaviors in the adhesively bonded area were revealed. Finally, fatigue damage was predicted with unsteady aerodynamic load spectrums, rainflow cycle-counting algorithm, Goodman diagram and Miner's linear superposition principle. Based on the findings obtained from this study, the feasibility of adhesively bonding technology for extending blade was affirmed and a few potential future directions of study were addressed to reduce the risk of adhesively bonded structures.
ISSN: 1350-6307
eISSN: 1873-1961
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Record 171 of 233
Title: Investigation of ash deposition and corrosion during circulating fluidized bed combustion of high-sodium, high-chlorine Xinjiang lignite
Abstract: A high-sodium, high-chlorine Xinjiang lignite was used as fuel in a 0.4 t/d circulating fluidized bed (CFB) test system to investigate ash deposition and corrosion characteristics using an air-cooled stainless steel probe. Different wall temperatures of the probe, exposed to the similar flue gas environment for 8 h, were achieved by adjusting cooling air flow separately at 1.0 m(3)/h, 3.0 m(3)/h and 5.0 m(3)/h. The probe wall temperature variation was analyzed, and deposited ash was characterized via a series of analytical techniques. Experimental results confirmed the disturbance of ash deposition to the heat flux through the probe, and this disturbance was enhanced due to the faster ash deposition rate at lower wall temperature. The selective deposition of mineral species including Na-, Cl-, K- and Mg-species occurred, resulting in a larger ash deposition amount on the lower-temperature probe. The corrosion caused by NaCl-rich deposited ash was accompanied with the oxidation of metallic matrix. It is found that the antioxidation of metals was in the order of Ni > Cr > Fe. During corrosion, metal chlorides with strong volatility were the main corrosion products, resulting in the presence of voids in deposited ash because of their release. This corrosion was accelerated at high temperatures and had repeatability.
ISSN: 0016-2361
eISSN: 1873-7153
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Record 172 of 233
Title: Compressive mechanical behavior of multiple wire metal rubber
Abstract: This work presents the experimental characterization of multiple wire metal rubber material (MW-MR). MW-MR is a novel damping solid made of two kinds of coil entangled wires using a modified manufacturing process. Three batches of MW-MRs with different weight percentage ratios have been fabricated and tested under cyclic quasi-static loading and different maximum strains. Tangent modulus and loss factor are tested. The experimental results show that the weight percentage ratio can significantly affect the global mechanical compression properties. A microelement model of MW-MR was proposed for the first time, this model was based on the manufacturing process and then simplified by introducing the "equivalent factor" lambda, a qualitative analysis based on the microelement model of MW-MR about the test results was made. The conclusions derived from the tests provide a new way for designers to adjust the mechanical properties of metal rubber. (C) 2017 Published by Elsevier Ltd.
ISSN: 0264-1275
eISSN: 1873-4197
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Record 173 of 233
Title: Thermodynamic model development, experimental validation and performance analysis of a MW CCHP system integrated with dehumidification system
Author(s): Jiang, RH (Jiang, Runhua); Han, W (Han, Wei); Qin, FGF (Qin, Frank G. F.); Sui, J (Sui, Jun); Yin, HB (Yin, Huibin); Yang, ML (Yang, Minlin); Xu, YJ (Xu, Yongjun)
Source: ENERGY CONVERSION AND MANAGEMENT Volume: 158 Pages: 176-185 DOI: 10.1016/j.enconman.2017.12.060 Published: FEB 15 2018
Abstract: Combined cooling, heating and power (CCHP) systems, which have the advantages of energy saving and environmental protection, have attracted more and more attentions. Great deals of works have been done, but most of them are theoretical research. It is still lack of experimental research for large scale CCHP system in practical application, and an overall off-design thermodynamic model is also desired to simulate or exam the system performance. In this work, a novel CCHP system integrated with dehumidification system is proposed for further utilizing waste heat, in which an internal combustion engine (ICE) is used as prime mover, its heat of flue gas and the heat of jacket water above 81 degrees C are used to drive absorption chiller, and the heat of jacket water below 81 degrees C is used to drive absorption dehumidifier. A comprehensive off-design thermodynamic model and evaluation of the system is established. The tested results of a MW CCHP system integrated with dehumidification system are used to validate the model, and the thermodynamic performance analysis is also carried out. The thermodynamic performance comparison between the CCHP system integrated with dehumidification system and conventional CCHP system has been done. The results show that: the simulated values are basically in keeping with those experimental results; when the output power of ICE is 1200 kW, the primary energy rate of the MW CCHP system can go up to 84.0%, the primary energy saving ratio achieves 32.77%, and exergy efficiency is 42.45%; the thermodynamic performance of the proposed CCHP system is better than conventional CCHP system.
ISSN: 0196-8904
eISSN: 1879-2227
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Record 174 of 233
Title: Promotion of cotton stalk on bioavailability of phosphorus in municipal sewage sludge incineration ash
Abstract: Phosphorus (P) is a limited and non-regenerated resource that is an essential element for all living organisms. Municipal sewage sludge (MSS) incineration fly ash contains abundant phosphorus and can be used as a secondary resource of phosphorus. Adding cotton stalk (CS) into MSS was put forward to improve the bioavailability of phosphorus in the fly ash during incineration. The speciation transformation of phosphorus during co-firing of MSS with CS in a bench-scale bubbling fluidized bed was investigated. The results show that more phosphorus fraction was distributed in the fly ash during MSS incineration with more CS. Addition of CS into MSS was advantageous for the conversion of non-apatite inorganic phosphorus (NAIP) to apatite phosphorus (AP) in the fly ash. The Ca and Mg compounds in CS can provide chemical reactive sites for phosphorus to form Ca18Mg2H2(PO4)(14) and Ca2P2O7. The larger BET specific surface area and pore volume in fly ash offer a more reaction contact area for the transformation from NAIP to AP. The bioavailability of phosphorus in fly ash was greatly improved by MSS incineration with CS additive.
ISSN: 0016-2361
eISSN: 1873-7153
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Record 175 of 233
Title: Inlet and outlet boundary conditions for the discrete velocity direction model
Source: MODERN PHYSICS LETTERS B Volume: 32 Issue: 4 Article Number: 1850048 DOI: 10.1142/S0217984918500483 Published: FEB 10 2018
Abstract: The discrete velocity direction model is an approximate method to the Boltzmann equation, which is an optional kinetic method to microgas flow and heat transfer. In this paper, the treatment of the inlet and outlet boundary conditions for the model is proposed. In the computation strategy, the microscopic molecular speed distribution functions at inlet and outlet are indirectly determined by the macroscopic gas pressure, mass flux and temperature, which are all measurable parameters in microgas flow and heat transfer. The discrete velocity direction model with the pressure correction boundary conditions was applied into the plane Poiseuille flow in microscales and the calculations cover all flow regimes. The numerical results agree well with the data of the NS equation near the continuum regime and the date of linearized Boltzmann equation and the DSMC method in the transition regime and free molecular flow. The Knudsen paradox and the nonlinear pressure distributions have been accurately captured by the discrete velocity direction model with the present boundary conditions.
ISSN: 0217-9849
eISSN: 1793-6640
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Record 176 of 233
Title: Experimental research of heat transfer uniformity for fluidized bed heat exchangers in a 300 MW CFB boiler
Abstract: In order to investigate the heat transfer uniformity of fluidized bed heat exchangers (FBHEs), a series of experimental tests were carried out in a commercial 300 MW CFB boiler. The test results indicate that there is a good linear correspondence between the FBHEs conical valve openings and circulating ash flow rate, the average heat transfer coefficient of different heat exchangers takes on a monotonically increasing trend with the increase of the boiler loads. Moreover, there is a non-uniform heat transfer process between the different measuring points under the same load as well as the different loads for the same measuring points, the heat absorption proportion of two FBHEs (71# and 72#) on the left side is larger than that of two FBHEs (73# and 74#) on the right side of the furnace, there is a non-uniform heat transfer phenomena in the symmetrical arrangement of four FBHEs, the heating surface arrangement in the FBHEs must be adjusted from snake tube perpendicular to the ash flow direction to parallel to ash flow direction, the test results can provide a good reference for the optimized design and operation of 600 MW supercritical CFB boiler with the FBHEs in the future. (C) 2017 Elsevier Ltd. All rights reserved.
ISSN: 1359-4311
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Record 177 of 233
Title: Heat integration and optimization of direct-fired supercritical CO2 power cycle coupled to coal gasification process
Author(s): Zhao, YM (Zhao, Yongming); Yu, B (Yu, Bo); Wang, B (Wang, Bo); Zhang, SJ (Zhang, Shijie); Xiao, YH (Xiao, Yunhan)
Abstract: Supercritical carbon dioxide (sCO(2)) power cycle is a promising power cycle that has drawn much attention in recent years. Among various layouts, the direct-fired sCO(2) power cycle achieves not only high efficiency but also near zero emission. Coal gasification and air separation process are indispensable processes when coal is used as fuel. To explore the best cycle performance, the above two processes have to be tightly integrated with the sCO(2) power cycle in both mass and energy. Key parameters that govern the heat integration should also be optimized to achieve better performance. A two-stage method is applied for simultaneous optimization and heat integration of a direct-fired sCO(2) power cycle coupled to coal gasification process. First, boundary parameters of the heat integration process are optimized. Then the heat exchanger network, which reveals viable heat integration scheme, is designed to fulfill the optimized target. The result shows that the net efficiency reaches 39.29% when heat integration of ASU is not considered. If heat integration of ASU is considered, the net efficiency increases to 40.97%, showing an efficiency increment of 1.68%. When the CO2 turbine pressure ratio is also optimized, the net efficiency increases further to 41.41%. (C) 2017 Published by Elsevier Ltd.
ISSN: 1359-4311
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Record 178 of 233
Title: Sodium transformation characteristic of high sodium coal in circulating fluidized bed at different air equivalence ratios
Abstract: Reacting atmosphere has great influence on sodium migration during high sodium coal thermal conversion, and influence the slagging and deposition characteristics further. The effect of different air equivalence ratios (ERs) on sodium migration and transformation during thermal conversion of high sodium Zhundong coal in circulating fluidized bed was investigated. The effect of ERs on the sodium content in circulating ash and bottom ash was similar. As the decrease of ER, the sodium content in the ashes increased due to the effect of carbon inhibition. Sodium in the bottom ash exists mainly as NaAlSiO4 and NaAlSi3O8, namely insoluble sodium. As to the fly ash, the sodium content decreased with the ER increase under reducing atmosphere, whereas the sodium content increased with the ER increase under oxidizing atmosphere. Sodium mainly exists as NaCl under reducing atmosphere and Na2SO4 was the main sodium existence under oxidizing atmosphere. The variety of sodium content in the ashes with the flue gas temperature was different under different reacting atmospheres. The ash fusion temperatures were also influenced by the atmosphere to a great extent. The fly ash fusion temperature was higher than that of bottom ash at the same ER. With lower ERs under reducing atmosphere and higher ERs under oxidizing atmosphere, the risk of slagging in the furnace and fouling in tail heating surface should be paid attention during the thermal conversion of high sodium coal. (C) 2017 Elsevier Ltd. All rights reserved.
ISSN: 1359-4311
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Record 179 of 233
Title: Study on pyrolysis characteristics of pretreated high-sodium (Na) Zhundong coal by skimmer-type interfaced TG-DTA-EI/PI-MS system
Abstract: Various pretreatment methods has been used to upgrade the high-Na Zhundong coal to solve the inherent problem with its thermal conversion. To provide a better understanding of pyrolysis characteristics of the pretreated high-Na Zhundong coal, a system of thermogravimetry-differential thermal analysis coupled with mass spectrometry equipped with skimmer-type interface and with electron ionization and photoionization capability (TG-DTA-EI/PI-MS system), was employed to analyze qualitatively the pyrolysis characteristics of the pretreated high-Na Zhundong coals. Three types of coal samples including the raw coal, H2O-washed coal, and HCl-washed coal were pyrolyzed in this study. The total pyrolysis yield, evolved volatile gases composition and individual gas evolving behavior were evaluated. It was shown that the pretreatments affected insignificantly the total yield but did significantly the volatile gases composition, the individual gas yield and production rate. The larger aromatic compounds of C7H8O (anisole), C9H12 (propylbenzene), and C10H14 (butylbenzene) disappeared gradually after the coals were pretreated. Especially, the HCl-washing pretreatment reduced greatly the yield and production rate of inorganic gases of H-2, CO, CO2, and aromatic compounds of C6H6O (phenol), Win (ethylbenzene), whereas improved greatly those of the smaller aliphatic compound of C3H6 (propene). It was believed that the absence of the NH4Ac-soluble Na species and HCl-soluble Na species was a main factor to affect the volatile gases composition, the individual gas yield and production rate, through altering the reaction routine of bond breaking and cross-linking during pyrolysis.
ISSN: 0378-3820
eISSN: 1873-7188
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Record 180 of 233
Title: Techno-economic study of compressed air energy storage systems for the grid integration of wind power
Author(s): Huang, Y (Huang, Y.); Keatley, P (Keatley, P.); Chen, HS (Chen, H. S.); Zhang, XJ (Zhang, X. J.); Rolfe, A (Rolfe, A.); Hewitt, NJ (Hewitt, N. J.)
Source: INTERNATIONAL JOURNAL OF ENERGY RESEARCH Volume: 42 Issue: 2 Pages: 559-569 DOI: 10.1002/er.3840 Published: FEB 2018
Abstract: Integrating variable renewable energy from wind farms into power grids presents challenges for system operation, control, and stability due to the intermittent nature of wind power. One of the most promising solutions is the use of compressed air energy storage (CAES). The main purpose of this paper is to examine the technical and economic potential for use of CAES systems in the grid integration. To carry out this study, 2 CAES plant configurations: adiabatic CAES (A-CAES) and diabatic CAES (D-CAES) were modelled and simulated by using the process simulation software ECLIPSE. The nominal compression and power generation of both systems were given at 100 and 140MWe, respectively. Technical results showed that the overall energy efficiency of the A-CAES was 65.6%, considerably better than that of the D-CAES at 54.2%. However, it could be seen in the economic analysis that the breakeven electricity selling price (BESP) of the A-CAES system was much higher than that of the D-CAES system at (sic)144/MWh and (sic)91/MWh, respectively. In order to compete with large-scale fossil fuel power plants, we found that a CO2 taxation scheme (with an assumed CO2-tax of (sic)20/tonne) improved the economic performance of both CAES systems significantly. This advantage is maximised if the CAES systems use low carbon electricity during its compression cycle, either through access to special tariffs at times of low carbon intensity on the grid, or by direct coupling to a clean energy source, for example a 100-MW class wind farm.
ISSN: 0363-907X
eISSN: 1099-114X
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Record 181 of 233
Title: A stress intensity factor estimation method for kinked crack
Abstract: A method for estimating the stress intensity factors (SIFs) of kinked crack with finite kink length is presented. This method is based on an estimation expression which is derived by He et al. according to the work of Cotterell and Rice from the stress field series of the original (unkinked) crack tip to the second order by using weight function (WF). In order to increase the estimation accuracy for the kinked crack with finite kink length, the third order coefficients of the stress field series of the original crack tip are introduced into this expression and these parameters can be obtained by a fitting procedure. Application of this modified expression to the cases of singly-kinked, edge kinked and doubly-kinked cracks reveals a good approximation with the finite element (FE) results of SIFs and showed that the accuracy is increased. (C) 2017 Elsevier Ltd. All rights reserved.
ISSN: 0013-7944
eISSN: 1873-7315
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Record 182 of 233
Title: Development of a chemical-looping combustion reactor having porous honeycomb chamber and experimental validation by using NiO/NiAl2O4
Author(s): Zhang, H (Zhang, Hao); Hong, H (Hong, Hui); Jiang, QQ (Jiang, Qiongqiong); Deng, YN (Deng, Ya'nan); Jin, HG (Jin, Hongguang); Kang, QL (Kang, Qilan)
Source: APPLIED ENERGY Volume: 211 Pages: 259-268 DOI: 10.1016/j.apenergy.2017.11.053 Published: FEB 1 2018
Abstract: Chemical-looping combustion (CLC) is already suggested as a promising approach for CO2 capture with a lower energy penalty. The appropriate reactor plays a paramount role in the application of CLC. Here, a fixed-bed honeycomb CLC reactor is proposed and its design methodology and procedure are given. The honeycomb chamber is a cylindrical monolithic block with a series of axial micro-channels. In this way, a sufficiently contact area and disturbance among reactants are provided for enhancing the reaction kinetics. The oxygen carrier not only consists of the supporting material of the honeycomb CLC reactor but also acts as reactants. A 10 kW prototype is manufactured by using NiO/NiAl2O4 as the oxygen carrier. The reactivity and redox stability of the honeycomb CLC reactor are experimentally examined by using the natural gas as the fuel gas. In the experiment, a CH4 conversion higher than 99% is obtained. By shortening the reduction time of the NiO/NiAl2O4, almost all the CH4 is converted into CO2 and CO emission is avoided. Additionally, the redox stability in the honeycomb CLC reactor is carried out for 150 h continuous operation. The test results show that the prototype reactor obtains a better reactivity and redox stability in contrast to the fixed-bed reactor without honeycomb chamber. Our results here would be expected to offer a new pathway for facilitating the progress of the CLC reactor.
ISSN: 0306-2619
eISSN: 1872-9118
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Record 183 of 233
Title: Combustion characteristics of well-dispersed boron submicroparticles and plasma effect
Author(s): Yu, D (Yu, Dan); Kong, CD (Kong, Chengdong); Zhuo, JK (Zhuo, Jiankun); Yao, Q (Yao, Qiang); Li, SQ (Li, Shuiqing); Wang, MZ (Wang, Mengze); Tian, ZY (Tian, Zhen-Yu)
Source: COMBUSTION AND FLAME Volume: 188 Pages: 94-103 DOI: 10.1016/j.combustflame.2017.09.022 Published: FEB 2018
Abstract: Boron is an attractive high-energy fuel additive. But it could not burn efficiently in practical systems due to its high ignition temperature and slow burning velocity. Finding methods to enhance the combustion of boron is desired. This work focused on the combustion characteristics of boron submicropartides with and without plasma discharges in a hot environment supported by CH4/N-2/O-2 flat flame based on the optical diagnostics. The boron submicroparticles were dispersed by the nebulization method to control the agglomeration. The well-dispersed boron flame exhibited two different burning modes, depending on the ambient temperature. As the ambient temperature was above 1520K, the boron flame showed definitely two-stage characteristics where the upstream of particle flow was yellow, corresponding to the first-stage flame, while the downstream was green and diffusive, corresponding to the second-stage flame. The first stage and second-stage burn times were respectively in the range of 0.46-1.08 ms and 0.92-4.87 ms, as the ambient temperature decreased from 1752K to 1520K. The chemical kinetics-controlled mechanism was confirmed by the nearly linear size dependence of the burn time (d(1) law). Nevertheless, as the ambient temperature was below 1520K, the boron submicropartides were partially burned or oxidized, exhibiting a mildly orange stream. This mild boron flame could be enhanced using a plasma discharge. The ignition delay time was shortened from 3.06 ms to 0.77 ms when the discharge was introduced at the ignition delay stage. The two-stage combustion characteristics occurred when the discharge was introduced at the combustion stage. (C) 2017 Published by Elsevier Inc. on behalf of The Combustion Institute.
ISSN: 0010-2180
eISSN: 1556-2921
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Record 184 of 233
Title: Performance optimization of low-temperature geothermal organic Rankine cycles using axial turbine isentropic efficiency correlation
Source: JOURNAL OF THE BRAZILIAN SOCIETY OF MECHANICAL SCIENCES AND ENGINEERING Volume: 40 Issue: 2 Article Number: UNSP 61 DOI: 10.1007/s40430-018-0996-9 Published: FEB 2018
Abstract: Present study deals with parametric optimization and performance evaluation of an air-cooled organic Rankine system for the low-temperature geothermal source, especially considering the effects of turbine isentropic efficiency. Turbine isentropic efficiency is predicted with turbine size parameter and volume ratio, using the well-known correlation for single-stage axial turbine. Optimal performances with the objective of maximizing system exergy efficiency are compared with the common used working fluid R245fa and two environmental friendly working fluids R1234ze(E) and R1234ze(Z). Highest turbine isentropic efficiency is achieved for working fluid R1234ze(Z). The optimal turbine inlet vapor is overheating for Working fluid R1234ze(E) with the limitation of allowable minimum geothermal brine reinjection temperature. Due to the influence of turbine isentropic efficiency, optimal system exergy efficiency for working fluid R1234ze(E) is 0.4576 for the 100 kg/s geothermal source, which is slightly higher than the value of 0.4487 for the 10 kg/s geothermal source.
ISSN: 1678-5878
eISSN: 1806-3691
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Record 185 of 233
Title: Influence of operating parameters on arsenic transformation during municipal sewage sludge incineration with cotton stalk
Abstract: Addition of cotton stalk (CS) has been proved to promote dramatically the transformation of toxic As3+ to less toxic As5+ in the fly ash during municipal sewage sludge (MSS) incineration. However, the fate of arsenic during co-firing of MSS and CS in different operating parameters was still unclear. In the present study, the effects of incineration temperatures and O-2 content in the flue gas on speciation transformation of arsenic during MSS and 70% MSS/30% CS incineration were investigated in a bubbling fluidized bed. The results show that less arsenic is distributed in bottom ash whereas more arsenic is migrated to the fly ash and flue gas, with the temperature increasing from 800 degrees C to 950 degrees C. The arsenic capture in fly ash is facilitated predominantly by the condensation and/or physical adsorption of As2O3(g) at the temperatures from 800 C to 900 degrees C. The chemical oxidation of As2O3(g) is favored by forming various arsenates (As5+) at 950 degrees C. At low O-2 content from 1% to 5%, some arsenic compounds in MSS such as As2S3 can react with O-2 to produce As2O3(g), and then more As2O3(g) is captured in the fly ash by the inherent mineral compounds like CaO through the condensation and/or physical adsorption. Further increasing O-2 content especially to 9% stimulates significantly the oxidation of As3+ to As5+ in the fly ash, which is mainly attributed to the chemical reactions between As2O3(g), various mineral compounds and sufficient O-2. (C) 2017 Elsevier Ltd. All rights reserved.
ISSN: 0045-6535
eISSN: 1879-1298
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Record 186 of 233
Title: The influence of wedge diffuser blade number and divergence angle on the performance of a high pressure ratio centrifugal compressor
Author(s): Wang, Y (Wang, Yi); Han, G (Han, Ge); Lu, XG (Lu, Xingen); Zhu, JQ (Zhu, Junqiang)
Source: JOURNAL OF THERMAL SCIENCE Volume: 27 Issue: 1 Pages: 17-24 DOI: 10.1007/s11630-018-0979-2 Published: FEB 2018
Abstract: Wedge diffuser is widely used in centrifugal compressors due to its high performance and compact size. This paper is aimed to research the influence of wedge diffuser blade number and divergence angle on centrifugal compressor performance. The impact of wedge diffuser blade number on compressor stage performance is investigated, and then the wedge diffusers with different divergence angle are studied by varying diffuser wedge angle and blade number simultaneously. It is found that wedge diffuser with 27 blades could have about 0.8% higher adiabatic efficiency and 0.14 higher total pressure ratio than the wedge diffuser with 19 blades and the best compressor performance is achieved when diffuser divergence angle is 8.3A degrees .These results could give some advices on centrifugal compressor design.
ISSN: 1003-2169
eISSN: 1993-033X
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Record 187 of 233
Title: A stress intensity factor estimation method for the kinked crack under anti-plane load
Source: THEORETICAL AND APPLIED FRACTURE MECHANICS Volume: 93 Pages: 319-325 DOI: 10.1016/j.tafmec.2017.10.003 Published: FEB 2018
Abstract: A method to estimate the mode III stress intensity factor (SIF) of kinked crack under anti-plane load is presented. The SIF of the kinked crack can be estimated by an expression derived from the stress field series of the original crack include first three order terms by the weight function (WE') method. The coefficients of the WFs were obtained by a fitting procedure based on the solutions of the weight function problem, which were solved by a conformal mapping method. The influence of the WFs in the estimation was evaluated as a function of the kink angle and the kink length ratio. The application to the case of a kinked crack shows good agreement with the analytical results.
ISSN: 0167-8442
eISSN: 1872-7638
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Record 188 of 233
Title: Novel air-cooled condenser with V-frame cells and induced axial flow fans
Author(s): Chen, L (Chen, Lei); Yang, LJ (Yang, Lijun); Du, XZ (Du, Xiaoze); Yang, YP (Yang, Yongping)
Source: INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER Volume: 117 Pages: 167-182 DOI: 10.1016/j.ijheatmasstransfer.2017.09.139 Published: FEB 2018
Abstract: The thermo-flow performances of air-cooled condensers (ACCs) are basically deteriorated under wind conditions, so it is of great concerns to propose the measures against the adverse wind effects on aircooled condensers. In this work, a novel reconstruction of ACCs combined the V-frame condenser cells with the induced axial flow fans, and a modified layout of the novel ACCs for a specific wind direction are proposed based on the direct dry cooling system in a 2 x 600 MW power plant. The CFD approach with a validation is applied to the performance investigation of the novel ACCs. The variable fields, mass flow rate, inlet air temperature and turbine back pressure for both the conventional and novel layouts of ACCs under different wind conditions are obtained and compared. The results show that the mass flow rates of the novel ACCs increase conspicuously compared with the conventional ACCs both in the absence and presence of winds. The flow distortions through the induced axial flow fans are greatly restrained and the inlet air temperature of the novel ACCs decreases, which lead to the improved thermo-flow performances of ACCs and reduced turbine back pressure of power generating unit. (C) 2017 Elsevier Ltd. All rights reserved.
ISSN: 0017-9310
eISSN: 1879-2189
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Record 189 of 233
Title: Data-driven reconstruction method for electrical capacitance tomography
Author(s): Lei, J (Lei, J.); Mu, HP (Mu, H. P.); Liu, QB (Liu, Q. B.); Wang, XY (Wang, X. Y.); Liu, S (Liu, S.)
Abstract: The appealing superiorities, including high-speed data acquisition, nonintrusive measurement, low cost, high safety and visual presentation, lead to the success of the electrical capacitance tomography (ECT) technique in the monitoring of industrial processes. High-accuracy tomographic images play a crucial role in the reliability of the ECT measurement results, which provide the powerful scientific evidences for investigating the complicated mechanisms behind the behaviors of the imaging objects (IOs). Beyond the existing numerical algorithms that are developed for the solution of the inverse problem in the ECT area, a data-driven two-stage reconstruction method is proposed to improve the reconstruction quality (RQ) in this paper. At the first stage, i.e., the learning stage, the regularized extreme learning machine (RELM) model solved by the split Bregman technique is developed to extract the mapping between the tomographic images reconstructed by the some algorithm and the true images according to a set of training samples. At the second stage, i.e., the prediction stage, a new IO is reconstructed by the same algorithm used in computing training samples, and then the imaging result is considered as an input of the trained RELM model to predict the final result. The performances of the proposed reconstruction method are compared and evaluated by the means of the numerical simulation approach using the clean and noisy capacitance data with different noise levels (NLs). Quantitative and qualitative comparison results validate the practicability and effectiveness of the proposed data-driven reconstruction method. Research findings provide a new insight for the improvement of the reconstruction accuracy and robustness in the ECT area. (C) 2017 Elsevier B.V. All rights reserved.
ISSN: 0925-2312
eISSN: 1872-8286
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Record 190 of 233
Title: Comprehensive evaluation for different modes of solar-aided coal-fired power generation system under common framework regarding both coal-savability and efficiency-promotability
Source: ENERGY Volume: 143 Pages: 151-167 DOI: 10.1016/j.energy.2017.10.085 Published: JAN 15 2018
Abstract: Solar-aided coal-fired power generation system (SCPGS) is a promising medium-term solution to reduce CO2 and PM2.5 emissions from numerous coal-fired power plants in China, yet lacking of unified theoretical guidance. In the present work, firstly, various specific integration schemes are reasonably generalized and unified by theoretical modelling. Secondly, the "superposition effect" has been revealed that the overall coal-savability of SCPGS is determined by not only the direct benefit due to local integration of solar energy but also the global effect of the integration on the system components in a superposition way. Meanwhile, the "promotion effect" has been revealed that the promotability of SCPGS on solar thermal exergy is primarily dependent on the higher-temperature Rankine cycle but sensitive to the energy level coupling between the solar thermal energy and the working fluid. Thirdly, the comprehensive evaluation factor (f), which serves as the common evaluation index between different SCPGSs considering both the coal-savability and efficiency-promotability, is proposed. Finally, with the help of the comprehensive evaluation factor, examples of application are given as demonstration for the comprehensive evaluations between 12 individual cases of SCPGS within a common framework. The present work is expected to fundamentally guide the future research and application of SCPGS. (C) 2017 Elsevier Ltd. All rights reserved.
ISSN: 0360-5442
eISSN: 1873-6785
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Record 191 of 233
Title: Corresponding-point methodology for physical energy storage system analysis and application to compressed air energy storage system
Source: ENERGY Volume: 143 Pages: 772-784 DOI: 10.1016/j.energy.2017.10.132 Published: JAN 15 2018
Abstract: In traditional thermodynamic analysis methods, the strong physical relationship between energy charge and discharge processes is usually underestimated, as well as being weak in exploring the energy transfer mechanism of physical energy storage (PES) systems. Aiming at this problem, a new method, corresponding-point methodology (CPM), for analyzing and optimizing PES systems is proposed on the basis of the correspondence of the system flow, and its application to compressed air energy storage (CAES) system is conducted in this paper. Meanwhile, a diagram of thermal exergy and mechanical exergy (E-th-E-mech diagram), which reflects not only energy loss but also the quantity of stored energy, is proposed in a complex plane. This method, along with E-th-E-mech diagram, focuses on analyzing the corresponding processes rather than the single process of the CAES. Some indicators of corresponding point separation, corresponding quotient, intersection angle and optimum object, are proposed, thereby making the analysis and optimization of the CAES system more efficient and explicit. For two typical corresponding processes, the relationship of thermal and mechanical exergy variations is revealed. Finally, CPM is used to analyze a supercritical compressed air energy storage system, and the system efficiency is improved by 9.2% points after CPM analysis and optimization. (C) 2017 Elsevier Ltd. All rights reserved.
ISSN: 0360-5442
eISSN: 1873-6785
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Record 192 of 233
Title: Feasibility of a two-stage liquid desiccant dehumidification system driven by low-temperature heat and power
Author(s): Su, BS (Su, Bosheng); Han, W (Han, Wei); Sui, J (Sui, Jun); Jin, HG (Jin, Hongguang)
Abstract: Liquid-desiccant dehumidification technology is a promising way to take advantage of low-grade energy to dry air for air conditioning and industrial applications. This paper proposed a two-stage liquid desiccant dehumidification system driven by low-temperature heat and electric power, which is integrated with a vapor compression refrigeration system that performs deep dehumidification. Air moisture is preliminarily removed by the desiccant solution at environmental temperature in a first-stage dehumidifier and then deeply removed by the desiccant solution cooled to 18 degrees C by a vapor compression refrigerator. Simulation results show that the new system can decrease power consumption by 30.63% compared with a conventional cooling dehumidification system. The equivalent power-generation efficiency of the proposed system can reach 2.91%. Finally, the power-saving mechanism of the proposed system was illuminated by conducting the exergy analysis and the study of the surface vapor partial pressure difference in the liquid desiccant dehumidifiers. (C) 2017 Elsevier Ltd. All rights reserved.
ISSN: 1359-4311
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Record 193 of 233
Title: Exergy analysis on the process with integrated supercritical water gasification of coal and syngas separation
Author(s): Chen, ZW (Chen, Zhewen); Zhang, XS (Zhang, Xiaosong); Han, W (Han, Wei); Gao, L (Gao, Lin); Li, S (Li, Sheng)
Abstract: Supercritical water gasification (SCWG) is a promising technology for clean and efficient coal utilization. The exergy analyses on the processes with integrated SCWG of coal and syngas separation are conducted for clear understanding about the exergy distributions in the processes. The energy level of the heat provided for the gasifier is upgraded to the energy level of the syngas, which is driven by the decrease of energy levels from the coal to the syngas. The minimum temperatures of the heat provided for the gasifier are obtained in different coal-water-slurry concentrations (CWSCs). The total exergy destruction firstly increases, and then decreases with increasing CWSC. The maximum total exergy destruction of the process is obtained when the CWSC is approximately 10%. The exergy efficiency of the process has a converse trend with the total exergy destruction. When the CWSC is in the range of 6% and 20%, the maximum exergy efficiency is 89.18%. The origins for the production of the exergy destruction are also studied. (C) 2017 Elsevier Ltd. All rights reserved.
ISSN: 1359-4311
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Record 194 of 233
Title: A Study on Steam Reforming of Methanol over a Novel Nanocatalyst of Compound Metal Oxides
Author(s): Zhang, YD (Zhang, Yidian); Zhao, YW (Zhao, Yawen); Hao, Y (Hao, Yong)
Edited by: Wang H; Wang X; Yan J; Wu J; Yang Y; Li H
Source: CLEANER ENERGY FOR CLEANER CITIES Book Series: Energy Procedia Volume: 152 Pages: 192-197 DOI: 10.1016/j.egypro.2018.09.087 Published: 2018
Abstract: The nanocatalysts of compound metal oxides ((La2Cu04)05(CNZ-1)05, denoted as LCO5-CNZ) composed of perovskite-like oxides La2CuO4 and CuO/ZnO/A1203 were prepared by co-precipitation and ball milling methods. The steam reforming of methanol (SRM) to H2 and CO2 over the nanocatalysts was experimentally studied at a molar ratio of 1.6 (H20/methanol). The methanol solution catalyzed by LCO5-CNZ can be completely converted into H2, CO2 and a small amount of CO at the reaction temperature of 270 C with a liquid hourly space velocity of 1.2 ml/(g.h). Simultaneously, under the same conditions, the catalysts of La2CuO4 and CuO/ZnO/A1203 were tested. Compared with the catalyst of pure La2CuO4, LCO5-CNZ showed higher methanol conversion rate and H2 yield. Compared with the conventional Cu-based catalyst of CuO/ZnO/A1203, LCO5-CNZ has both better CO selectivity and better H2 selectivity. It could be concluded that LCO5-CNZ with special structure has a significant improvement in catalyzing performance of SRM benefiting from the synergetic effect among perovskite-like La2CuO4 and Cu/Zn/A1 oxides. Copyright 2018 Elsevier Ltd. All rights reserved.
Conference Title: Applied Energy Symposium and Forum - Low-Carbon Cities and Urban Energy Systems (CUE)
Conference Date: JUN 05-07, 2018
Conference Location: Shanghai, PEOPLES R CHINA
ISSN: 1876-6102
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Record 195 of 233
Title: Thermodynamic and economic analysis of a solar-biomass gasification system with the production of methanol and electricity
Author(s): Bai, Z (Bai, Zhang); Liu, QB (Liu, Qibin); Gong, L (Gong, Liang); Lei, J (Lei, Jing)
Edited by: Wang H; Wang X; Yan J; Wu J; Yang Y; Li H
Source: CLEANER ENERGY FOR CLEANER CITIES Book Series: Energy Procedia Volume: 152 Pages: 1045-1050 DOI: 10.1016/j.egypro.2018.09.118 Published: 2018
Abstract: The thermodynamic and economic performances of a solar-biomass gasification polygeneration system are investigated in this work. In the system, the collected high-temperature concentrated solar energy with a new beam-down optical configuration is used to drive biomass gasification, the cotton stalk is selected as the feedstock, and the produced syngas is fed into a methanol synthesis reactor for methanol production. In addition, the un-reacted syngas and the system waste heat are efficiently utilized via a combined cycle to generate electricity. The designed methanol production and power capacities are 51.2 x 10(3) tons/year and 32.7 MWe, respectively. The numerical simulation of the polygeneration system is implemented. The on-design energy efficiency of the system reaches to 51.89% with the exergy efficiency of 51.23%. According to the system off-design evaluation within a typical year, the annual averaged system efficiency is up to 48.35% with the monthly efficiency in a range of 46.65%-49.05%, and the levelized cost of methanol is 361.88 $/ton. The solar-biomass gasification polygeneration system with methanol and electricity production achieve favorable thermodynamic and economic performances, which contributes to reducing CO2 emission and provides an alternative way for efficiently utilizing the abundant renewable energies of solar and biomass resources. Copyright (C) 2018 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the CUE2018-Applied Energy Symposium and Forum 2018: Low carbon cities and urban energy systems.
Conference Title: Applied Energy Symposium and Forum - Low-Carbon Cities and Urban Energy Systems (CUE)
Conference Date: JUN 05-07, 2018
Conference Location: Shanghai, PEOPLES R CHINA
ISSN: 1876-6102
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Record 196 of 233
Title: A distributed cogeneration system with a two-stage solar-driven biomass gasifier for heating, power and hydrogen in Northern China
Edited by: Wang H; Wang X; Yan J; Wu J; Yang Y; Li H
Source: CLEANER ENERGY FOR CLEANER CITIES Book Series: Energy Procedia Volume: 152 Pages: 1057-1062 DOI: 10.1016/j.egypro.2018.09.258 Published: 2018
Abstract: In this work, a cogeneration system with a two-stage solar-driven biomass gasifier is proposed to achieve the multiple outputs, i.e., generating power and heating during the heating period and producing hydrogen during the non heating period in Northern China The thermodynamic performances of the system under the design and off-design conditions are investigated. The solar-biomass gasification is divided into two stages, i.e., pyrolysis and gasification in sequence. The mid-temperature solar energy (around 673 K) from parabolic trough collectors is utilized to drive biomass pyrolysis, and the high-temperature solar energy (around 1150 K) from heliostats with point-focus solar collection technology is used to drive the gasification. In the heating period, the gasified syngas as a solar fuel is directly fed into a gas turbine for generating electricity, then a heat recovery steam generator (HRSG) is deployed to produce steams for heating. An energy storage module (i.e. gas tank) is introduced to offset heating at night. The primary energy efficiency of the system is 56.1%, while the rate of stored energy to the syngas based chemical energy is up to 35.66%. The energy storage module weakens the influence of time-varying solar irradiations on system performances, and the steady and efficient utilization of solar energy are achieved. In the non-heating period, the gasified syngas can be converted into hydrogen with the water-gas shift reaction. The above results indicate that the proposed system provides a promising complementary utilization approach of multiple energies (solar energy and biomass) in Northern China Copyright (C) 2018 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the CUE2018-Applied Energy Symposium and Forum 2018: Low carbon cities and urban energy systems.
Conference Title: Applied Energy Symposium and Forum - Low-Carbon Cities and Urban Energy Systems (CUE)
Conference Date: JUN 05-07, 2018
Conference Location: Shanghai, PEOPLES R CHINA
ISSN: 1876-6102
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Record 197 of 233
Title: A full-spectrum solar chemical energy storage system with photochemical process and thermochemical process
Edited by: Wang H; Wang X; Yan J; Wu J; Yang Y; Li H
Source: CLEANER ENERGY FOR CLEANER CITIES Book Series: Energy Procedia Volume: 152 Pages: 1063-1068 DOI: 10.1016/j.egypro.2018.09.120 Published: 2018
Abstract: A solar chemical energy storage system with photochemical process and thermochemical process is proposed to convert full spectrum solar energy into chemical energy. The ultraviolet and part of visible sunlight are firstly absorbed by norbomadiene derivatives, and the norbomadiene derivatives are converted into the related quadricyclane derivatives. When the quadricyclane derivatives are catalyzed, they are converted back to the norbomadiene derivatives for next cycle. The storage and releasing cycle are eco-friendly without CO2 emission. The rest of solar energy, which cannot be used in the solar photochemical process, are exploited by solar thermochemical process, providing heat for methanol decomposition. It is demonstrated that solar photochemical efficiency increases firstly and then it decreases with the increase of cut-off wavelength, while the solar thermochemical efficiency declines with the cut-off wavelength rising. In the hybrid system, the decrease of the solar thermochemical efficiency is balanced by an increase of the solar photochemical efficiency, and the maximum solar-to-chemical efficiency of the hybrid system reaches 68.7%. Copyright (C) 2018 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the CUE2018-Applied Energy Symposium and Forum 2018: Low carbon cities and urban energy systems.
Conference Title: Applied Energy Symposium and Forum - Low-Carbon Cities and Urban Energy Systems (CUE)
Conference Date: JUN 05-07, 2018
Conference Location: Shanghai, PEOPLES R CHINA
ISSN: 1876-6102
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Record 198 of 233
Title: NUMERICAL STUDY ON THE PERFORMANCE OF A CENTRIFUGAL IMPELLER WITH SELF-ADAPTIVE CASING TREATMENT
Author(s): Gong, MQ (Gong, M. Q.); Chen, HS (Chen, H. S.); Xu, YJ (Xu, Y. J.); Deng, JQ (Deng, J. Q.)
Book Group Author(s): ASME
Source: PROCEEDINGS OF THE ASME FLUIDS ENGINEERING DIVISION SUMMER MEETING, 2018, VOL 2 Book Series: ASME Fluids Engineering Division Summer Meeting Article Number: V002T09A011 Published: 2018
Abstract: The stall margin and choke margin of centrifugal compressor could be increased by using Self-Adaptive Casing Treatment (SA CT). The previous numerical research mainly focuses on making parametric optimization rather than the selection of turbulence model and flow field analysis of the compressor with SACT In this work, the 3D steady state simulations were carried out to obtain the performance and flow field of the Krain impeller with and without SACT by ANSY S-CFX. Four turbulence models including k-Epsilon turbulence model, RNG k-Epsilon turbulence model, Shear Stress Transport (SST) turbulence model and BSL Reynolds Stress (BSL) turbulence model were used to simulate the Krain impeller with a vaneless constant area diffuser. The numerical data were validated by the experimental data in reference. The results of this study showed that different turbulence models led to differences in performance predictions and flow field characteristics, and the overall performance and flow field features could be predicted more accurately by using SST turbulence model. The bypass flow and reinjected flow were respectively observed in the hole when the Krain impeller with SA CT worked at large and small mass flow rate conditions. And the stable working range of the Krain impeller was expanded by using SACT In addition, the development of the low-velocity fluid at the blade tip region was restrained with the application of SACT.
Source: PROCEEDINGS OF THE ASME TURBO EXPO: TURBOMACHINERY TECHNICAL CONFERENCE AND EXPOSITION, 2018, VOL 5A Article Number: UNSP V05AT12A018 Published: 2018
Abstract: This paper describes the numerical investigations on the aerodynamic and thermal performance of a rotor blade cascade with multiple film cooling rows in the passage. First, the experimental data on an annular cascade with upstream film cooling was compared with the numerical results to validate the numerical method. The CFD simulations of the models with a row of film holes at four different locations on the hub endwall were performed respectively. The aerodynamic and thermal performance under the interaction of the secondary flow and endwall film cooling are analyzed based on the CFD predicted streamlines of mainstream flow and film injection, the contours of total pressure loss on the sections located in the passage and at the blade exit, the pitch averaged film cooling effectiveness and film cooling effectiveness contours. The results show that film holes placed at low level of iso-Mach line tends to provide a better cooling with a smaller amount of coolant.
Conference Title: ASME Turbo Expo: Turbomachinery Technical Conference and Exposition
Conference Date: JUN 11-15, 2018
Conference Location: Oslo, NORWAY
ISBN: 978-0-7918-5108-1
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Record 200 of 233
Title: NUMERICAL INVESTIGATION OF THE COOLING PERFORMANCE ON THE ENDWALL WITH AND WITHOUT FILLET
Author(s): Xu, QZ (Xu, Qingzong); Du, Q (Du, Qiang); Wang, P (Wang, Pei); Liu, J (Liu, Jun); Liu, G (Liu, Guang)
Book Group Author(s): ASME
Source: PROCEEDINGS OF THE ASME TURBO EXPO: TURBOMACHINERY TECHNICAL CONFERENCE AND EXPOSITION, 2018, VOL 5A Article Number: UNSP V05AT12A016 Published: 2018
Abstract: High inlet temperature of turbine vane increases the demand of high film cooling effectiveness. Vane endwall region was extensively cooled due to the high and flat exit temperature distribution of combustor. Leakage flow from the combustor turbine gap was used to cool the endwall region except for preventing hot gas ingestion. Numerical predictions were conducted to investigate the flow structure and adiabatic film cooling effectiveness of endwall region in a linear cascade with vane-endwall junction fillet. The simulations were completed by solving the three-dimensional Reynolds-Averaged Navier-Stokes(RANS) equations with shear stress transport(SST) k-omega turbulence model, meanwhile, the computational method and turbulence model were validated by comparing computational result with the experiment. Three types of linear fillet with the length-to-height ratio of 0.5, 1 and 2, named fillet A, fillet B and fillet C respectively, were studied. In addition, circular fillet with radius of 2mm was compared with linear fillet B. The interrupted slot, produced by changing the way of junction of combustor and turbine vane endwall, is introduced at X/Cax = -0.2 upstream of the vane leading edge. Results showed that fillet can significantly affect the cooling performance on the endwall due to suppressing the strength of the secondary flow. Fillet C presented the best cooling performance comparing to fillet A and fillet B because a portion of the coolant which climbs to the fillet was barely affected by secondary flow. Results also showed the effect of fillet on the total pressure loss. The result indicated that only fillet A slightly decreases endwall loss.
Conference Title: ASME Turbo Expo: Turbomachinery Technical Conference and Exposition
Conference Date: JUN 11-15, 2018
Conference Location: Oslo, NORWAY
ISBN: 978-0-7918-5108-1
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Record 201 of 233
Title: THE BEHAVIOR OF THE CASING BOUNDARY LAYER WITH THE PRESENCE OF TIP LEAKAGE VORTEX
Author(s): Nan, X (Nan, Xi); Lin, F (Lin, Feng); Himeno, T (Himeno, Takehiro); Watanabe, T (Watanabe, Toshinori)
Book Group Author(s): ASME
Source: PROCEEDINGS OF THE ASME TURBO EXPO: TURBOMACHINERY TECHNICAL CONFERENCE AND EXPOSITION, 2018, VOL 2A Article Number: UNSP V02AT39A018 Published: 2018
Abstract: Casing boundary layer effectively places a limit on the pressure rise capability achievable by the compressor. The separation of the casing boundary layer not only produce flow loss but also closely related to the compressor rotating stall. The motivation of this paper is to present a viewpoint that the casing boundary layer should be paid attention to in parallel with other flow factors on rotating stall trigger. This paper illustrates the casing boundary layer behavior by displaying its separation phenomena with the presence of tip leakage vortex at different flow conditions. Skin friction lines and the corresponding absolute streamlines are used to demonstrate the three-dimensional flow patterns on and near the casing. The results depict a Saddle, a Node and several tufts of skin friction lines dividing the passage into four zones. The tip leakage vortex is enfolded within one of the zones by the separated flows. All the flows in each blade passage are confined within the passage as long as the compressor is stable. The casing boundary layer of a transonic compressor is also examined in the same way, which results in qualitatively similar zonal flows that enfolds the tip leakage vortex. This research develops a new way to study the casing boundary layer in rotating compressors. The results may provide a first-principle based explanation to stalling mechanisms for compressors that are casing sensitive.
Conference Title: ASME Turbo Expo: Turbomachinery Technical Conference and Exposition
Conference Date: JUN 11-15, 2018
Conference Location: Oslo, NORWAY
ISBN: 978-0-7918-5099-2
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Record 202 of 233
Title: EFFECTS OF CAVITY PURGE FLOW ON INTERMEDIATE TURBINE DUCT FLOWFIELD
Author(s): Liu, J (Liu, Jun); Du, Q (Du, Qiang); Liu, G (Liu, Guang); Wang, P (Wang, Pei); Liu, HR (Liu, Hongrui); Xu, QZ (Xu, Qingzong)
Book Group Author(s): ASME
Source: PROCEEDINGS OF THE ASME TURBO EXPO: TURBOMACHINERY TECHNICAL CONFERENCE AND EXPOSITION, 2018, VOL 2B Article Number: UNSP V02BT43A005 Published: 2018
Abstract: To increase the power output without adding additional stages, ultra-high bypass ratio engine, which has larger diameter low pressure turbine, attracts more and more attention because of its huge advantage. This tendency will lead to aggressive (high diffusion) intermediate turbine duct design. Much work has been done to investigate flow mechanisms in this kind of duct as well as its design criterion with numerical and experimental methods. Usually intermediate turbine duct simplified from real engine structure was adopted with upstream and downstream blades. However, cavity purge mass flow exists to disturb the duct flow field in real engine to change its performance. Naturally, the wall vortex pairs would develop in different ways. In addition to that, purge flow rate changes at different engine representative operating conditions. This paper deals with the influence of turbine purge flow on the aerodynamic performance of an aggressive intermediate turbine duct. The objective is to reveal the physical mechanism of purge flow ejected from the wheel-space and its effects on the duct flow field. Ten cases with and without cavity are simulated simultaneously. On one hand, the influence of cavity structure without purge flow on the flow field inside duct could be discussed. On the other hand, the effect of purge flow rate on flow field could be analyzed to investigate the mechanisms at different engine operating conditions. According to this paper, cavity structure is beneficial for pressure loss. And the influence concentrates near hub and duct inlet.
Conference Title: ASME Turbo Expo: Turbomachinery Technical Conference and Exposition
Conference Date: JUN 11-15, 2018
Conference Location: Oslo, NORWAY
ISBN: 978-0-7918-5100-5
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Record 203 of 233
Title: Numerical Investigation on Single-restricted Swirling Flows in an Innovative Combustor
Author(s): Hu, B (Hu, Bin); Zhang, JH (Zhang, JunHua); Deng, AM (Deng, AiMing); Zhao, W (Zhao, Wei); Zhao, QJ (Zhao, QingJun)
Book Group Author(s): ASME
Source: PROCEEDINGS OF THE ASME TURBO EXPO: TURBOMACHINERY TECHNICAL CONFERENCE AND EXPOSITION, 2018, VOL 4B Article Number: UNSP V04BT04A002 Published: 2018
Abstract: The size and fuel consumption as well as the pollutant emissions of gas turbine combustors have to be significantly reduced in the future, which brings new challenges to the design of combustors. An innovative gas turbine combustor, named Short Helical Combustor (SHC) has been proposed by B. Ariatabar et al. The major feature of SHC is that the swirling flow originated from a single swirler is only restricted by one side in circumferential direction which is greatly different than traditional combustors. The present work of this paper is to investigate the features of the single-restricted swirling flows in a model SHC by adjusting the axial distance (L) between adjacent swirlers. The relevant results show that, 1. In non reacting flows, with the increase of L, the flow field downstream the swirler successively presents four modes: traditional mode, single-vortex mode, critical mode and double-vortices mode. When L=0, a pair of counterrotating vortices exists in combustor. When 0.27H<L<0.67H, only one vortex exists downstream the swirler. When 0.68H <L<1.7 3H, another counter-rotating vortex gradually appears close to the unrestricted side. 2. With the increasing of L, the aerodynamic boundary is gradually formed on the unrestricted side in the reacting and non-reacting flows, which is the primary reason for the formation of vortex B. 3. The specific value of L of critical mode in reacting flows is larger than that in non-reacting flows because the gas expansion caused by combustion goes against the formation of aerodynamic boundary. 4. The velocity direction of the flows downstream the recirculation varies at different vortex modes in reacting and non-reacting flows. In non-reacting flows, the flow direction changes almost 180 degrees as L is increased from 0.27H-1.73H In reacting flows, the flow direction gradually varies from circumference to axis as L is increased from 0.27H-1.73H. The present work details the feature of the flow field in SHC, which is great meaningful to the design and improvement of the combustor.
Conference Title: ASME Turbo Expo: Turbomachinery Technical Conference and Exposition
Conference Date: JUN 11-15, 2018
Conference Location: Oslo, NORWAY
ISBN: 978-0-7918-5106-7
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Record 204 of 233
Title: EXPERIMENTAL INVESTIGATION OF SPRAY AND COMBUSTION PERFORMANCES OF A FUEL-STAGED LOW EMISSION COMBUSTOR PART II: EFFECTS OF VENTURI ANGLE
Source: PROCEEDINGS OF THE ASME TURBO EXPO: TURBOMACHINERY TECHNICAL CONFERENCE AND EXPOSITION, 2018, VOL 4B Article Number: UNSP V04BT04A025 Published: 2018
Abstract: In order to reduce NOx emissions, modern gas turbines are often equipped with lean burn combustion systems, where the high-velocity fuel-lean conditions that limit NOx formation in combustors also inhibit the ability of ignition, high altitude relight, and lean combustion stability. To face these issues, an internally staged scheme of fuel injection is proposed. The pilot and main fuel staging enable fuel distribution control and high turn-down ratio, multi-injections of main fuel leads to a fast and efficient fuel/air mixing. A fuel-staged low emission combustor in the framework of lean burn combustion is developed in the present study, the central pilot stage of fuel injector working singly at low power operating conditions is swirl-cup prefilming atomization and main stage is jet-incrossflow multi-injection atomization, a combination of pilot and main stage injection is provided for higher power operating conditions. A significant amount of the air mass flow utilised for fuel preparation and initiation is adverse to the operability specifications, such as ignition, lean blow-out, and high-altitude relight etc. The spray characteristics of pilot spray and flow field are one of the key factors affecting combustion operability. This work investigates the effects of the venturi angle on combustion operability, the ignition and lean blow-out performances were evaluated in a single dome rectangular combustor. Furthermore, the spray patterns and flow field are characterized by kerosene-planar laser induced fluorescence and particle image velocimetry to provide insight into the correlation between spray, flow field and combustion operability performances.
Conference Title: ASME Turbo Expo: Turbomachinery Technical Conference and Exposition
Conference Date: JUN 11-15, 2018
Conference Location: Oslo, NORWAY
ISBN: 978-0-7918-5106-7
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Record 205 of 233
Title: INVESTIGATION OF H2/CH4-AIR FLAME CHARACTERISTICS OF A MICROMIX MODEL BURNER AT ATMOSPHERE PRESSURE CONDITION
Author(s): Liu, XW (Liu, Xunwei); Shao, WW (Shao, Weiwei); Tian, Y (Tian, Yong); Liu, Y (Liu, Yan); Yu, B (Yu, Bin); Zhang, ZD (Zhang, Zhedian); Xiao, YH (Xiao, Yunhan)
Book Group Author(s): ASME
Source: PROCEEDINGS OF THE ASME TURBO EXPO: TURBOMACHINERY TECHNICAL CONFERENCE AND EXPOSITION, 2018, VOL 4B Article Number: UNSP V04BT04A015 Published: 2018
Abstract: For high-hydrogen-content fuel, the Micromix Combustion Technology has been developed as a potential low NOx emission solution for gas turbine combustors, especially for advanced gas turbines with high turbine inlet temperature. Compared with conventional lean premixed flames, multiple distributed slim and micro flames could lead to a lower NOx emission performance for shortening residence time of high temperature flue gas and generally a more uniform temperature distribution.
This work aims at micromix flame characteristics of a model burner fueled with hydrogen blending with methane under atmosphere pressure conditions. The model burner assembly was designed to have six concentrically millimeter-sized premixed units around a same unit centrally. Numerical and experimental studies were conducted on mixing performance, flame stability, flame structure and CO/NOx emissions of the model burner. OH radical distribution by OH-PLIF and OH chemiluminescence (OH*) imaging were employed to analyze the turbulence-reaction interactions and characters of the reaction zone at the burner exit. Micromix flames fueled with five different hydrogen content H-2-CH4 (60/40, 50/50, 40/60, 30/70, 0/100 Vol.%) were investigated, along with the effects of equivalence ratio and heat load. Results indicated that low NOx emissions of less than 10 ppm (@15% O-2) below the exhaust temperature of 1920 K were obtained for all the different fuels. Combustion oscillation didn't occur for all the conditions. It was found that at a constant flame temperature, the higher the hydrogen content of the fuel, the higher the turbulent flame speed and the weaker the flame lift effect. Combustion noise and NOx emissions also increase with increasing hydrogen content. The OH/OH* signal distribution indicated that a pure methane micromix flame showed a lifted and weaken distributed feature.
Conference Title: ASME Turbo Expo: Turbomachinery Technical Conference and Exposition
Conference Date: JUN 11-15, 2018
Conference Location: Oslo, NORWAY
ISBN: 978-0-7918-5106-7
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Record 206 of 233
Title: Experimental Investigation of Ignition and LBO Characteristics of SPP Injector: The Effect of Pilot Stage Air Split Ratio
Source: PROCEEDINGS OF THE ASME TURBO EXPO: TURBOMACHINERY TECHNICAL CONFERENCE AND EXPOSITION, 2018, VOL 4B Article Number: UNSP V04BT04A017 Published: 2018
Abstract: The influence of PASR (Pilot stage Air Split Ratio) on the ignition and LBO (Lean Blow Out) performances is experimentally investigated for an SPP (Stratified Partially Premixed) injector in this paper. The pilot stage of the SPP injector comprises two axial air swirlers as well as an air blast prefilm atomizer for pilot fuel preparation. It is believed that the variation of the air split ratio between the outer swirler and the inner swirler of the pilot stage will transform the flow structure and fuel distribution of the local flame anchoring zone, and consequently improves or deteriorates the stability of the pilot flame. The ignition and LBO characteristics were measured for PASR=8:2, 7:3 and 6:4, and several inexplicable but interesting results are observed. In order to make out the underlying reasons for the differences of the obtained ignition and LBO data, the velocity field and spray concentration at the meridian plane were acquired experimentally with the help of optical diagnostics at isothermal conditions. It it concluded that two dominant mechanisms of flame stability exist depending on the range of the injector pressure drop (Delta P-sw/P-3t). At low pressure drop of the injector, the flame stability is mainly affected by the fuel distribution, however, the flow structure will play a more important role at high Delta P-sw/P-3t in that it can transform the local flow structures around the pilot flame root. The inherent correlations between the combustion stability and the flow structure as well as the fuel distribution are disscussed and conclusions are drawn for this research work in the end of this paper.
Conference Title: ASME Turbo Expo: Turbomachinery Technical Conference and Exposition
Conference Date: JUN 11-15, 2018
Conference Location: Oslo, NORWAY
ISBN: 978-0-7918-5106-7
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Record 207 of 233
Title: EXPERIMENTAL AND NUMERICAL INVESTIGATIONS OF MILD COMBUSTION IN A MODEL COMBUSTOR APPLIED FOR GAS TURBINE
Author(s): Zhang, H (Zhang, Huan); Zhang, ZD (Zhang, Zhedian); Xiong, Y (Xiong, Yan); Liu, Y (Liu, Yan); Xiao, YH (Xiao, Yunhan)
Book Group Author(s): ASME
Source: PROCEEDINGS OF THE ASME TURBO EXPO: TURBOMACHINERY TECHNICAL CONFERENCE AND EXPOSITION, 2018, VOL 4B Article Number: UNSP V04BT04A013 Published: 2018
Abstract: The Moderate or Intense Low-oxygen Dilution (MILD) combustion is characterized by low emission, stable combustion and low noise for various kinds of fuel. MILD combustion is a promising combustion technology for gas turbine. The model combustor composed of an optical quartz combustor liner, four jet nozzles and one pilot nozzle has been designed in this study. The four jet nozzles are equidistantly arranged in the combustor concentric circle and the high-speed jet flows from the nozzles will entrain amount of exhaust gas to make MILD combustion occur. The combustion characteristics of the model combustor under atmosphere pressure have been investigated through experiments and numerical simulations. The influence of equivalence ratio and jet velocity on flow pattern, combustion characteristics and exhaust emissions were investigated in detail, respectively.
Laser Doppler velocity (LDV) was utilized to measure the speed of a series of points in the model combustor. The measurement results show that a central recirculation existed in the combustion chamber. As the jet velocity of the nozzles increases, the amount of entrained mass by the jet increases simultaneously, however, the central recirculation zone is similar in shape and size. The recirculation of the model combustor will remain self-similar when the jet velocity varies in the range. The calculation model and method were verified through comparing with experimentally LDV data and be used to optimize the model combustor. Planar laser-induced fluorescence of hydroxyl radical (OH-PLIF) approaches were adopted to investigate the flame structure, the reaction zone and the OH distribution. OH distribution of the paralleled and crossed sections in the model combustor were measured, the whole reaction zone have been analyzed. The results show that the OH distribution was uniform in whole combustor. The exhaust gas composition of the combustor was measured by the "TESTO 350" Exhaust Gas Analyzer. All measurements emission results were corrected to 15% O-2 in volume. Experimental results showed that NOx and CO emissions were less than 10 ppm@15%O-2 when the equivalence ratio ranges from 0.63 to 0.8.
Conference Title: ASME Turbo Expo: Turbomachinery Technical Conference and Exposition
Conference Date: JUN 11-15, 2018
Conference Location: Oslo, NORWAY
ISBN: 978-0-7918-5106-7
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Record 208 of 233
Title: Measurement of External-Solids Circulation Flux in a Circulating Fluidized Bed by Electrical Capacitance Tomography and Microwave Doppler Radar
Author(s): Wang, HG (Wang, H. G.); Yang, WQ (Yang, W. Q.); Wu, ZP (Wu, Z. P.)
Book Group Author(s): IEEE
Source: 2018 IEEE INTERNATIONAL CONFERENCE ON IMAGING SYSTEMS AND TECHNIQUES (IST) Book Series: IEEE International Conference on Imaging Systems and Techniques Pages: 414-418 Published: 2018
Abstract: In a gas-solids circulating fluidized bed (CFB), the external-solids circulating flux (G(s)) has important effect on the mass and heat transfer inside the CFB system. To improve the process operation efficiency and reduce the emission of pollution, it is important to accurately measure G(s). In this paper, the authors proposed a new approach to measuring G(s) using electrical capacitance tomography (ECT) and microwave Doppler radar (MDR) velocity meter based on a lab-scale CFB system with multi-cyclone separators. The ECT sensor is used to get the solids volume fraction in the cross section of the standpipe and MDR is used to measure the averaged solids velocity along the standpipes. Based on those two values, G(s) can be addressed. Meanwhile, computation particle fluid dynamic (CPFD) is used to investigated the gas-solids flow hydrodynamic characteristics and verified the measurement results.
Conference Title: IEEE International Conference on Imaging Systems and Techniques (IST)
Conference Date: OCT 16-18, 2018
Conference Location: Krakow, POLAND
ISSN: 2471-6162
ISBN: 978-1-5386-6628-9
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Record 209 of 233
Title: Flow Physics behind the Effects of Leading-edge Protuberances on the Airfoil Aerodynamic Performance
Author(s): Zhao, M (Zhao, Ming); Zhang, MM (Zhang, Mingming); Xu, JZ (Xu, Jianzhong)
Book Group Author(s): IOP
Source: SCIENCE OF MAKING TORQUE FROM WIND (TORQUE 2018) Book Series: Journal of Physics Conference Series Volume: 1037 Article Number: UNSP 022035 DOI: 10.1088/1742-6596/1037/2/022035 Published: 2018
Abstract: This paper presents a numerical investigation of the flow physics behind the effects of leading-edge protuberances on the airfoil aerodynamic performance utilizing vortex dynamic method. An improved delayed detached eddy simulation (IDDES) method was adopted and validated through the comparisons with experimental results. Utilizing the IDDES scheme, together with vortex dynamic analysis, investigations were focused on the attached and post-stall regions, respectively. It was found that, within the attached region, the generation and development of the dominant diffused spanwise vortex rings over tubercled airfoil was responsible for the subsequent airfoil performance; within the post-stall region, the impaired flow detachment around both peak and trough sections of tubercles, due to the enhanced momentum injection by the strong streamwise vortices, resulted in better airfoil aerodynamic performance.
Conference Title: 7th Conference on Science of Making Torque from Wind (TORQUE)
Conference Date: JUN 20-22, 2018
Conference Location: Milan, ITALY
ISSN: 1742-6588
eISSN: 1742-6596
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Record 210 of 233
Title: An integrated numerical method for wind turbine flow simulation, sound generation and propagation
Source: SCIENCE OF MAKING TORQUE FROM WIND (TORQUE 2018) Book Series: Journal of Physics Conference Series Volume: 1037 Article Number: UNSP 022002 DOI: 10.1088/1742-6596/1037/2/022002 Published: 2018
Abstract: The scope of the paper is to present an efficient numerical method that predicts: (a) wind turbine aerodynamic loads and power; (b) wind turbine noise source; (c) long distance wind turbine noise source propagation. The numerical methods involved in this study are a combination of Computational Fluid Dynamics (CFD) and wind turbine aeroacoustic methods. The results from the CFD simulation provide necessary information of wind turbine power and thrust etc. The 2D Actuator Disc (AD) theory is applied for such a purpose. The computational efficiency becomes very high while using a steady 2D CFD approach. The flow geometry at each blade element is required for wind turbine noise source calculations. The predicted wind turbine noise source is the starting field for long distance noise propagation model which is based on solving the Parabolic Equations (PE) in the frequency domain. Results showed that the integrated wind turbine flow-acoustic prediction method is capable of calculating wind turbine aerodynamic, aerodynamic noise source and long range sound propagation.
Conference Title: 7th Conference on Science of Making Torque from Wind (TORQUE)
Conference Date: JUN 20-22, 2018
Conference Location: Milan, ITALY
ISSN: 1742-6588
eISSN: 1742-6596
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Record 211 of 233
Title: Loss Mechanism of Static Interstage Components of Multistage Centrifugal Compressors for Integrated Blade Design
Author(s): Ji, CJ (Ji, Chunjun); Li, CY (Li, Chunyang); Fang, JY (Fang, Junyi); Sun, Q (Sun, Qi)
Abstract: Although centrifugal compressors are widely used in construction, they consume a large amount of energy; in existing multistage centrifugal compressors, there is a serious pressure loss of 15.13% when gas flows through the diffuser, bend, and return channel. In this study, we analyze the loss mechanisms of these stages in detail, using computational fluid dynamics. Based on this analysis, we present a new type of integrated blade, connecting the diffuser, bend, and return channels, which can eliminate the airflow stall phenomenon. Through effective control of the airflow spreading process, we minimized losses in the component, which improved its efficiency by 4.39% and increased the pressure ratio by 2.86% relative to a compressor without the newly-designed integrated blade. The concepts used in the creation of this component can provide a reference for the future design of blades for flow through parts of multistage compressors.
ISSN: 1024-123X
eISSN: 1563-5147
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Record 212 of 233
Title: A power generation system with integrated supercritical water gasification of coal and CO2 capture
Author(s): Chen, ZW (Chen, Zhewen); Zhang, XS (Zhang, Xiaosong); Han, W (Han, Wei); Gao, L (Gao, Lin); Li, S (Li, Sheng)
Source: ENERGY Volume: 142 Pages: 723-730 DOI: 10.1016/j.energy.2017.10.077 Published: JAN 1 2018
Abstract: Supercritical water gasification (SCWG) is a promising clean coal technology. A new power generation system with integrated supercritical water gasification of coal and CO2 capture is proposed in this article. The gasification product consisted of H-2, CO, CO2, CH4, and unreacted supercritical water is directly combusted with pure O-2 to provide heat for other units of the system, and the combustion product is used for power generation in turbines. The combustion product consists only of CO2 and H2O. Thus, the CO2 can be easily captured under atmospheric condition. The thermal efficiency of the system can reach 38.31%, while the CO2 capture rate is 100%. The energy and exergic balances are conducted. The exergy efficiency of the system is 38.56%. The system has advantages over most coal-fired power plants with oxy-combustion or post-combustion technologies and IGCC systems with pre-combustion technologies. (C) 2017 Elsevier Ltd. All rights reserved.
ISSN: 0360-5442
eISSN: 1873-6785
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Record 213 of 233
Title: Hydrogen production by sorption-enhanced chemical looping steam reforming of ethanol in an alternating fixed-bed reactor: Sorbent to catalyst ratio dependencies
Source: ENERGY CONVERSION AND MANAGEMENT Volume: 155 Pages: 243-252 DOI: 10.1016/j.enconman.2017.10.075 Published: JAN 1 2018
Abstract: In this study, the effects of sorbent addition for in-situ CO2 removal on hydrogen production by sorption-enhanced chemical looping steam reforming (SE-CLSR) of ethanol have been evaluated in an alternating fixed-bed reactor using a mixture of NiO/Al(2)O(3)oxygen carrier catalyst (OC) and CaO based sorbent at moderate operating conditions (T: 600 degrees C, P: 1.0 atm and S:C: 3.0). The experimental data were compared with chemical equilibrium analysis based on the minimization of Gibbs free energy. The results demonstrated that NiO component in the OC was first reduced by ethanol and the reduced OC was responsible of catalytic steam reforming and water gas shift (WGS) for hydrogen production. The CO2 produced was efficiently removed by CaO based sorbent, also resulting in the process intensification considerably. It appears that the superior molar ratio of sorbent to OC (Ca/Ni) is to be 2.0-3.0 and the highest hydrogen selectivity and feeding conversion were obtained at 3.0 of Ca/Ni ratio. Hydrogen production was inhibited using further high Ca/Ni ratio due to the OC particles were surrounded and diluted by sorbent. The exothermic reactions also provided the heat to raise the temperature of the reactor. In-situ CO2 removal by solid sorbent promotes ethanol dehydration and C-C carbon bonds cleavage, and thus, the hydrogen production route of conventional CLSR is changed. Continuous high-purity hydrogen production was achieved by integrating the oxidization, steam reforming, WGS, and in situ CO2 capture in an alternating fixed-bed reactor.
ISSN: 0196-8904
eISSN: 1879-2227
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Record 214 of 233
Title: Models for Microbial Fuel Cells: A critical review
Source: JOURNAL OF POWER SOURCES Volume: 373 Pages: 119-131 DOI: 10.1016/j.jpowsour.2017.11.001 Published: JAN 1 2018
Abstract: Microbial fuel cells (MFCs) have been widely viewed as one of the most promising alternative sources of renewable energy. A recognition of needs of efficient development methods based on multidisciplinary research becomes crucial for the optimization of MFCs. Modeling of MFCs is an effective way for not only gaining a thorough understanding of the effects of operation conditions on the performance of power generation but also becomes of essential interest to the successful implementation of MFCs. The MFC models encompass the underlying reaction process and limiting factors of the MFC. The models come in various forms, such as the mathematical equations or the equivalent circuits. Different modeling focuses and approaches of the MFC have emerged. In this study, we present a state of the art of MFCs modeling; the past modeling methods are reviewed as well. Models and modeling methods are elaborated on based on the classification provided by Mechanism based models and Application-based models. Mechanisms, advantages, drawbacks, and application fields of different models are illustrated as well. We exhibit a complete and comprehensive exposition of the different models for MFCs and offer further guidance to promote the performance of MFCs.
ISSN: 0378-7753
eISSN: 1873-2755
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Record 215 of 233
Title: Atomic force microscopy for two-dimensional materials: A tutorial review
Author(s): Zhang, H (Zhang, Hang); Huang, JX (Huang, Junxiang); Wang, YW (Wang, Yongwei); Liu, R (Liu, Rui); Huai, XL (Huai, Xiulan); Jiang, JJ (Jiang, Jingjing); Anfuso, C (Anfuso, Chantelle)
Source: OPTICS COMMUNICATIONS Volume: 406 Special Issue: SI Pages: 3-17 DOI: 10.1016/j.optcom.2017.05.015 Published: JAN 1 2018
Abstract: Low dimensional materials exhibit distinct properties compared to their bulk counterparts. A plethora of examples have been demonstrated in two-dimensional (2-D) materials, including graphene and transition metal dichalcogenides (TMDCs). These novel and intriguing properties at the nano-, molecular-and even monatomic scales have triggered tremendous interest and research, from fundamental studies to practical applications and even device fabrication. The unique behaviors of 2-D materials result from the special structure-property relationships that exist between surface topographical variations and mechanical responses, electronic structures, optical characteristics, and electrochemical properties. These relationships are generally convoluted and sensitive to ambient and external perturbations. Characterizing these systems thus requires techniques capable of providing multidimensional information under controlled environments, such as atomic force microscopy (AFM). Today, AFM plays a key role in exploring the basic principles underlying the functionality of 2-D materials. In this tutorial review, we provide a brief introduction to some of the unique properties of 2-D materials, followed by a summary of the basic principles of AFM and the various AFM modes most appropriate for studying these systems. Following that, we will focus on five important properties of 2-D materials and their characterization in more detail, including recent literature examples. These properties include nanomechanics, nanoelectromechanics, nanoelectrics, nanospectroscopy, and nanoelectrochemistry. (C) 2017 Elsevier B.V. All rights reserved.
ISSN: 0030-4018
eISSN: 1873-0310
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Record 216 of 233
Title: CPFD study of a full-loop three-dimensional pilot-scale circulating fluidized bed based on EMMS drag model
Abstract: For the purpose of process optimization and scale-up, coupling energy-minimization multi-scale (EMMS) drag model with computational particle fluid dynamics (CPFD) is a good option for large scale three dimensional full-loop circulating fluidized bed (CFB) simulation. In this study, such integration is applied for a complex CFB with six cyclones, based on Barracuda platform, to investigate the gas-solids flow dynamic characteristics in scaled-up system, especially in the dense flow region, and to characterize different fluidization regimes. The simulation results are compared with those obtained from Wen-Yu model, in terms of axial pressure distribution, solid volume fraction, particle recirculation, etc., and are evaluated against available measurement data. The result demonstrates that EMMS drag model can predict the axial pressure distribution well, especially in the dense region, which gives an S-shape solid volume fraction in the axial direction and two-core-annulus structures ('M' shape) in the radial direction. Meanwhile, EMMS drag model provides smaller drag force between the gas phase and the solids that the particle recirculation fluxes inside and outside the riser is relatively smaller. With the increase of superficial gas velocity, three different fluidization regimes, including multiple bubble regime, exploding bubble regime and turbulent fluidization regime, are identified based on EMMS drag model. The results show that the dense region is clear at the multiple and exploding bubble regimes; while the particle volume fraction and mass flow rate in the riser top are larger than those in the middle at the turbulent fluidization regime, which gives a guidance that the riser height is limited that particles do not have enough space to distribute. (C) 2017 Elsevier B.V. All rights reserved.
ISSN: 0032-5910
eISSN: 1873-328X
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Record 217 of 233
Title: Simulation Study on Chemical Protection of a Certain Type of Transport Vehicle
Author(s): Zhu, XZ (Zhu, Xuezheng); Nie, KL (Nie, Kunlin); Tian, Y (Tian, Yong); Ma, ZJ (Ma, Zijing); Nie, XC (Nie, Xiaocong); Wang, ZJ (Wang, Zhijie)
Edited by: Zuo M
Source: PROCEEDINGS OF THE 2018 6TH INTERNATIONAL CONFERENCE ON MACHINERY, MATERIALS AND COMPUTING TECHNOLOGY (ICMMCT 2018) Book Series: AER-Advances in Engineering Research Volume: 152 Pages: 129-134 Published: 2018
Abstract: With the Fluent module of ANSYS software, simulation is conducted on the protection in contaminated areas for a certain type of transport vehicle encountering chemical attack. The distribution of contaminants in the vehicle is grasped, and the contamination of typical parts is analyzed to providence evidence for protection decisions.
A certain type of transport vehicle is used for combat, carry, and transportation with high speed and strong off-road performance. In the combat operations, there exists the threat of a chemical attack on a certain type of transport vehicle. Based on the application background, the protection of the contaminated area is simulated to provide a basis for protection decisions.
Conference Title: 6th International Conference on Machinery, Materials and Computing Technology (ICMMCT)
Conference Date: JUN 02-03, 2018
Conference Location: Jinan, PEOPLES R CHINA
ISSN: 2352-5401
ISBN: 978-94-6252-531-3
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Record 218 of 233
Title: The comparative analysis on thermal storage systems for solar power with direct steam generation
Source: RENEWABLE ENERGY Volume: 115 Pages: 217-225 DOI: 10.1016/j.renene.2017.08.046 Published: JAN 2018
Abstract: Two sensible heat storage systems and two latent heat storage systems, in which liquid lead-bismuth eutectic alloy (LBE) is selected as sensible heat storage medium and sodium nitrate is selected as phase change storage material, are investigated for concentrated solar power (CSP) with direct steam generation (DSG) in the present work. The temperature pinch point likely occurs in sensible heat storage system, which restricts the optimization space. The temperature difference distributes more uniformly in latent heat storage system than in sensible heat storage system, and the outlet temperature of steam is far higher in latent heat storage system than in sensible heat storage system. The exergy efficiency is more two times in latent heat storage system than in sensible heat storage system. The three-tank latent heat storage system has the most flexible and effective performance among the four storage systems. (C) 2017 Elsevier Ltd. All rights reserved.
ISSN: 0960-1481
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Record 219 of 233
Title: Performance analysis of a hybrid photovoltaic/thermal and liquid desiccant system
Author(s): Su, BS (Su, Bosheng); Qu, WJ (Qu, Wanjun); Han, W (Han, Wei); Jin, HG (Jin, Hongguang)
Edited by: Yan J; Wang C; Yu J; Jia H; Wu J; Xu T; Zhang Y
Source: RENEWABLE ENERGY INTEGRATION WITH MINI/MICROGRID Book Series: Energy Procedia Volume: 145 Pages: 116-121 DOI: 10.1016/j.egypro.2018.04.019 Published: 2018
Abstract: Air dehumidification is widely applied in the civilian and industrial use, however, conventional vapor compression air-conditioning system consumes substantial power. Using renewable energy in the air handling process has potential to further reduce the power consumption, meanwhile ease the carbon emission. This paper proposes a novel liquid desiccant system integrated with a photovoltaic/thermal collector for deep dehumidification. The generated electric power drives a vapor compression chiller for cooling the desiccant solution for a two-stage dehumidification, and the releasing heat from the collector is used for the desiccant regeneration. Simulation studies indicated the proposed system has a superior power saving ability of 55.65% comparing with the conventional one, besides the equivalent power generation efficiency reaches 8.7%. Copyright (C) 2018 The Authors. Published by Elsevier Ltd.
Conference Title: Applied Energy Symposium and Forum on Renewable Energy Integration with Mini/Microgrid Systems (REM)
Conference Date: OCT 18-20, 2017
Conference Location: Tianjin, PEOPLES R CHINA
ISSN: 1876-6102
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Record 220 of 233
Title: A mini smart solar driven hydrogen production process with chemical looping reforming for microgrids
Edited by: Yan J; Wang C; Yu J; Jia H; Wu J; Xu T; Zhang Y
Source: RENEWABLE ENERGY INTEGRATION WITH MINI/MICROGRID Book Series: Energy Procedia Volume: 145 Pages: 289-294 DOI: 10.1016/j.egypro.2018.04.053 Published: 2018
Abstract: Solar thermochemical production of hydrogen with methane reforming is a primary and appropriate strategy for a mini smart electricity system. Importantly, perovskite-type materials are state-of-the-art oxygen carriers (OCs) for solar methane reforming systems with hydrogen production and storage which exhibit thermal stability and prior physicochemical properties. A series of LaCuxNi1-xO3 materials are prepared by combustion methods and tested via BET, XRD, SEM and TGA. The redox performance of the LaCuxNi1-xO3 under different reducing and oxidizing atmospheres are discussed using thermogravimetric analysis. It is demonstrated that copper substitution facilitates the release of oxygen and the production of hydrogen along with solar-to-fuel efficiency. Copyright (C) 2018 The Authors. Published by Elsevier Ltd.
Conference Title: Applied Energy Symposium and Forum on Renewable Energy Integration with Mini/Microgrid Systems (REM)
Conference Date: OCT 18-20, 2017
Conference Location: Tianjin, PEOPLES R CHINA
ISSN: 1876-6102
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Record 221 of 233
Title: Integrating concentrating PVs in biogas upgrading
Author(s): Tian, ZY (Tian, Zhenyu); Hao, Y (Hao, Yong); Li, WJ (Li, Wenjia); Campana, PE (Campana, Pietro Elia); Li, HL (Li, Hailong); Yan, JY (Yan, Jinyue); Jin, HG (Jin, Hongguang)
Edited by: Yan J; Wang C; Yu J; Jia H; Wu J; Xu T; Zhang Y
Source: RENEWABLE ENERGY INTEGRATION WITH MINI/MICROGRID Book Series: Energy Procedia Volume: 145 Pages: 598-603 DOI: 10.1016/j.egypro.2018.04.089 Published: 2018
Abstract: Biogas produced from anaerobic digestion processes has been considered as an important alternative to natural gas and plays a key role in the emerging market for renewable energy. By removing CO2, biogas can be upgraded to vehicle fuel. Chemical absorption is one of the widely used upgrading technologies, which advantages include high purity and low loss of biomethane. However, chemical absorption usually suffers from the high consumption of thermal energy, which is required by the regeneration of the solvent. Aiming at achieving a more sustainable and efficient biomethane production, this work proposed a novel system, which integrate concentrating photovoltaic/thermal hybrid (C-PV/T) in the upgrading of biogas. Due to the ability to produce electricity and heat simultaneously and efficiently, C-PV/T can provide the demands of both the electricity and heat. By doing dynamic simulation of the energy production of C-PV/T, the technical feasibility of such a system is analyzed. Based on the design to meet the heat demand of solvent regeneration, without energy storage, the produced heat can cover 17% of the heat demand of the solvent regeneration, but 51.1% of the electricity demand; meanwhile, 140.3 MWh excess electricity can be sold for one year. Copyright (C) 2018 The Authors. Published by Elsevier Ltd.
Conference Title: Applied Energy Symposium and Forum on Renewable Energy Integration with Mini/Microgrid Systems (REM)
Conference Date: OCT 18-20, 2017
Conference Location: Tianjin, PEOPLES R CHINA
ISSN: 1876-6102
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Record 222 of 233
Title: A simplified model of local flame structure in thin reaction zones regime
Source: NUMERICAL HEAT TRANSFER PART B-FUNDAMENTALS Volume: 73 Issue: 6 Pages: 386-398 DOI: 10.1080/10407790.2018.1494935 Published: 2018
Abstract: In thin reaction zones regime, frequently localized flame quenching occurs, due to which a portion of reactant would mix with productions before burning. A simplified flame model, which takes account of this reactant-product mixing effect, was put forward. On the basis of this model, local flamelet characteristics were analyzed by both theoretical and numerical methods. The results show that flame structure and propagation could be notably influenced by reactant-product mixing. A thickened postflame high OH concentration zone and a double-peak profile of active radicals were predicted, which are in accordance with existing direct numerical simulation results but can't be reflected by traditional models.
ISSN: 1040-7790
eISSN: 1521-0626
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Record 223 of 233
Title: Dynamic Characteristics of Air Cycle Machine Rotor System
Author(s): Han, DJ (Han, Dongjiang); Hao, L (Hao, Long); Yang, JF (Yang, Jinfu)
Abstract: Parameters optimization in the critical speed region has the important influence on operational stability of an air cycle machine. Effects of bearing stiffness and unbalanced exciting force on critical speed and response characteristics are investigated by the modal method and harmonic response analysis. Resonance separation phenomenon in the critical speed region is analyzed in detail. When difference exists in the phase of unbalanced exciting force, resonance separation appears in the conical whirling speed region. The characteristics after resonance separation are closely related to the phase difference value and amplitude of unbalanced exciting force. The paper provides theoretical and experimental foundations for resonance separation analysis and also provides data support for dynamic balance and dynamic design of the rotor system.
ISSN: 1070-9622
eISSN: 1875-9203
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Record 224 of 233
Title: ANALYSIS OF THERMAL PERFORMANCE OF VOID CAVITY IN A PCM CANISTER UNDER MICROGRAVITY
Source: HEAT TRANSFER RESEARCH Volume: 49 Issue: 11 Special Issue: SI Pages: 1041-1057 DOI: 10.1615/HeatTransRes.2018016926 Published: 2018
Abstract: A physical model and a mathematical model of phase change during the process of heat transfer in a PCM (Phase Change Material) canister are suggested. Based on a theoretical analysis and calculation results of the PCM canister during the process of solidification, the model of improved void distribution in the PCM canister under microgravity is given. The phase change thermal storage process is numerically simulated with the use of the model of ignoring void cavity distribution, simple void cavity distribution, and improved void cavity distribution. The calculation results for three kinds of void distribution are compared and analyzed. The results show that the form of the void cavity distribution has a great effect on calculation results. The melting ratio of PCM has a great difference in the form of different void cavity distributions. The form of void distribution has a great effect on the process of phase change. Under the combined effects of local thermal resistance of void cavity and of the side wall of the PCM canister, it is the most difficult for them to melt during the period of sunlight.
Conference Title: 3rd International Workshop on Heat Transfer Advances for Energy Conservation and Pollution Control (IWHT)
Source: COMBUSTION THEORY AND MODELLING Volume: 22 Issue: 4 Pages: 694-713 DOI: 10.1080/13647830.2018.1447148 Published: 2018
Abstract: Large eddy simulations (LES) for turbulent flames with detailed kinetic mechanisms have received growing interest. However, a direct implementation of detailed kinetic mechanisms in LES modelling of turbulent combustion remains a challenge due to the requirement of huge computational resources. An on-the-fly mechanism reduction method named correlated dynamic adaptive chemistry (CoDAC) is proposed to overcome this issue. A LES was conducted for Sandia Flame-D, with the reaction mechanism of GRI-Mech 3.0 consisting of 53 species and 325 reactions. The reduction threshold used in LES was obtained a priori by using auto-ignition model and partially stirred reactor (PaSR) with pairwise mixing model. LES results with CoDAC are in good agreement with experimental data and those without reduction. The conditional mean of the number of selected species indicates that a large size of locally reduced mechanism is required in the reaction zone where CH4 is destructed. A computational time analysis shows that the PaSR model predicts better than the auto-ignition model on the wall time reduction with CoDAC in LES.
ISSN: 1364-7830
eISSN: 1741-3559
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Record 226 of 233
Title: Thermodynamic coupling characteristics in hybrid (dry/wet) cooling system
Source: INTERNATIONAL JOURNAL OF GREEN ENERGY Volume: 15 Issue: 9 Pages: 532-543 DOI: 10.1080/15435075.2018.1489253 Published: 2018
Abstract: A hybrid cooling system consisting of both a dry section and wet section is proposed in this paper as a means to conserving energy and water by combining the benefits of both dry and wet cooling modes. A new thermodynamic coupling characteristics computing model was established to identify the best combination of dry and wet cooling subsystems in the hybrid tower throughout year-round operation based on its air thermodynamic state under the no plume principle. A hybrid cooling tower in Inner Mongolia, China, consisting of an elliptical tube heat exchanger with rectangular fins and counter-flow wet packing, was designed as an example under the no plume principle. The minimum number of heat exchanger units in service and the corresponding thermodynamic operating parameters were obtained under a year-round operation. The tower exhibited notable advantages in regards to water conservation compared to the traditional evaporative cooling tower at an estimated yearly savings of 3.74x10(7)kg water.
ISSN: 1543-5075
eISSN: 1543-5083
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Record 227 of 233
Title: Numerical Computation for a Kind of Time Optimal Control Problem for the Tubular Reactor System
Abstract: This paper is devoted to the study of numerical computation for a kind of time optimal control problem for the tubular reactor system. This kind of time optimal control problem is aimed at delaying the initiation time tau of the active control as late as possible, such that the state governed by this controlled system can reach the target set at a given ending time T. To compute the time optimal control problem, we firstly approximate the original problem by finite element method and get a new approximation time optimal control problem governed by ordinary differential equations. Then, through the control parameterization method and time-scaling transformation, the approximation problem becomes an optimal parameter selection problem. Finally, we use Sequential Quadratic Program algorithm to solve the optimal parameter selection problem. A numerical simulation is given for illustration.
ISSN: 1024-123X
eISSN: 1563-5147
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Record 228 of 233
Title: An Improved Streamline Curvature Method for Centrifugal Compressor Performance
Source: PROCEEDINGS OF THE ASME GAS TURBINE INDIA CONFERENCE, 2017, VOL 1 Article Number: UNSP V001T01A005-1 Published: 2018
Abstract: This paper describes an improved throughflow calculation method on S2m based on streamline curvature method for predicting the performance of centrifugal compressor. A general method of specifying the empirical data provides separate treatment of blockage, deviation and losses. The spanwise and streamwise distribution laws of losses are described. The paper describes a new aspect of method about the mixing loss. Two-zone model considering the "jet and wake" can obtain the secondary flow width. For this reason, the improved prediction method combined with two-zone model is proposed to correct the mixing loss. Due to the average static pressure at outlet unknown, the secondary flow width is obtained by iterations.
This performance prediction method is validated with experimental and CFD data of three cases, including impeller(A), impeller(B) and impeller(C). The results show that the improved throughflow calculation method predicts the performance of centrifugal compressor more accurately than conventional throughflow calculation, with increased the accuracy of total pressure ratio and isentropic efficiency by about 3.18% and 1.30%.
Conference Title: 5th ASME Gas Turbine India Conference
Conference Date: DEC 07-08, 2017
Conference Location: Bangalore, INDIA
ISBN: 978-0-7918-5850-9
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Record 229 of 233
Title: Research on Model-Based Fault Diagnosis for a Gas Turbine Based on Transient Performance
Author(s): Zeng, DT (Zeng, Detang); Zhou, DJ (Zhou, Dengji); Tan, CQ (Tan, Chunqing); Jiang, BY (Jiang, Baoyang)
Abstract: It is essential to monitor and to diagnose faults in rotating machinery with a high thrust-weight ratio and complex structure for a variety of industrial applications, for which reliable signal measurements are required. However, the measured values consist of the true values of the parameters, the inertia of measurements, random errors and systematic errors. Such signals cannot reflect the true performance state and the health state of rotating machinery accurately. High-quality, steady-state measurements are necessary for most current diagnostic methods. Unfortunately, it is hard to obtain these kinds of measurements for most rotating machinery. Diagnosis based on transient performance is a useful tool that can potentially solve this problem. A model-based fault diagnosis method for gas turbines based on transient performance is proposed in this paper. The fault diagnosis consists of a dynamic simulation model, a diagnostic scheme, and an optimization algorithm. A high-accuracy, nonlinear, dynamic gas turbine model using a modular modeling method is presented that involves thermophysical properties, a component characteristic chart, and system inertial. The startup process is simulated using this model. The consistency between the simulation results and the field operation data shows the validity of the model and the advantages of transient accumulated deviation. In addition, a diagnostic scheme is designed to fulfill this process. Finally, cuckoo search is selected to solve the optimization problem in fault diagnosis. Comparative diagnostic results for a gas turbine before and after washing indicate the improved effectiveness and accuracy of the proposed method of using data from transient processes, compared with traditional methods using data from the steady state.
eISSN: 2076-3417
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Record 230 of 233
Title: A new approach of casing treatment design for high speed compressors running at partial speeds with low speed large scale test
Author(s): Xi, N (Xi, Nan); Ning, M (Ning, Ma); Feng, L (Feng, Lin); Takehiro, H (Takehiro, Himeno); Toshinori, W (Toshinori, Watanabe)
Source: AEROSPACE SCIENCE AND TECHNOLOGY Volume: 72 Pages: 104-113 DOI: 10.1016/j.ast.2017.10.032 Published: JAN 2018
Abstract: The instability problems tend to be more severe when high speed compressors operate at partial speeds. This paper proposes an economic approach for casing treatment design that suitable to this situation. Aiming at reducing the expensive and time-consuming high-speed casing treatment experiments, the idea of low-speed similitude of high-speed compressors, which was originally practiced in mid-1980 with the purpose of loss reduction, is now extended to simulate the stability enhancement with casing treatment in this paper. The core idea of this approach is to replace a large portion of design processes for the high-speed compressors (the Prototype) with their equivalent large scale model compressors (the Model). Two different transonic rotors with skewed slots and circumferential grooves casing treatments are conducted as examples to demonstrate this approach. Following the selected similarity rules, the Model is firstly acquired by modeling the near stall point of the Prototype. A variety of casing treatments are designed and assessed on the Model. Then a few more promising configurations can thus be selected via low speed experiments. They are believed to have similar tendency on stall margin improvement on the Prototype. Finally, the selected configurations are converted back to the Prototype with based on the rule of similarity and validated by experimental data. In this paper, principles that guarantee the similitude of the flow field at near stall condition and the effectiveness of the casing treatment are discussed. (C) 2017 Elsevier Masson SAS. All rights reserved.
ISSN: 1270-9638
eISSN: 1626-3219
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Record 231 of 233
Title: Analysis of carbon fines obtained from the off-gas dust of calcium carbide furnace
Source: JOURNAL OF MATERIAL CYCLES AND WASTE MANAGEMENT Volume: 20 Issue: 1 Pages: 614-621 DOI: 10.1007/s10163-017-0627-z Published: JAN 2018
Abstract: The off-gas dust of calcium carbide furnace is a hazardous waste of large quantities in China. It, however, contains valuable materials and should be recovered not only for environmental and safety reasons but also for economic reasons. This work examines carbon fines separated from the off-gas dust of a calcium carbide furnace by acid leaching using HCl and HF solutions. The carbon fines are characterized using various instrumental techniques. It is found that the carbon fines mainly consist of hollow spheres of 0.5-3.5 A mu m in size with multilayer graphitic shells, a BET surface area of 124.5 m(2)/g and a mean pore size of 4.0 nm. Some of the carbon fines enclosed smaller carbon spheres that are either hollow or enclosed with inorganic species, such as magnetic Fe3C, which can be separated magnetically. The carbon fines are good sorbent as demonstrated by quick adsorption of Congo Red in an aqueous solution to capacities of 216 or 296 mg/g with or without the magnetic separation, respectively. A mechanism for the formation of carbon spheres is proposed.
ISSN: 1438-4957
eISSN: 1611-8227
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Record 232 of 233
Title: Simultaneous Measurement of Thermal Conductivity and Specific Heat in a Single TDTR Experiment
Author(s): Sun, FY (Sun, Fangyuan); Wang, XW (Wang, Xinwei); Yang, M (Yang, Ming); Chen, Z (Chen, Zhe); Zhang, H (Zhang, Hang); Tang, DW (Tang, Dawei)
Source: INTERNATIONAL JOURNAL OF THERMOPHYSICS Volume: 39 Issue: 1 Article Number: 5 DOI: 10.1007/s10765-017-2328-1 Published: JAN 2018
Abstract: Time-domain thermoreflectance (TDTR) technique is a powerful thermal property measurement method, especially for nano-structures and material interfaces. Thermal properties can be obtained by fitting TDTR experimental data with a proper thermal transport model. In a single TDTR experiment, thermal properties with different sensitivity trends can be extracted simultaneously. However, thermal conductivity and volumetric heat capacity usually have similar trends in sensitivity for most materials; it is difficult to measure them simultaneously. In this work, we present a two-step data fitting method to measure the thermal conductivity and volumetric heat capacity simultaneously from a set of TDTR experimental data at single modulation frequency. This method takes full advantage of the information carried by both amplitude and phase signals; it is a more convenient and effective solution compared with the frequency-domain thermoreflectance method. The relative error is lower than 5% for most cases. A silicon wafer sample was measured by TDTR method to verify the two-step fitting method.
ISSN: 0195-928X
eISSN: 1572-9567
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Record 233 of 233
Title: Transient film thickness and microscale heat transfer during flow boiling in microchannels
Source: INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER Volume: 116 Pages: 458-470 DOI: 10.1016/j.ijheatmasstransfer.2017.09.027 Published: JAN 2018
Abstract: The underlying mechanism of heat transfer for several sub-processes that control a bubble growth cycle during flow boiling in microchannels is studied in this article by means of high frequency measurements of liquid film thickness and temperature accompanying synchronous visualization. The test section is made up of glass tube having an internal diameter of 0.94 mm with the Indium Tin Oxide (ITO) electrically conductive layer as heaters. The initial liquid film thickness formed by a boiling bubble slug agreed well with Taylor's law. For most cases of the liquid film thickness evolution, the thinning of the liquid film was found to be much quicker than the prediction when considering evaporation effect alone. A new model for predicting the liquid film thickness evolution under flow boiling condition was developed by inclusion of the combination effect of evaporation and shear stress. It was found that the sub-processes of a bubble growth cycle were dependent on heat flux. The cyclical fluctuation of the temperature was due to the different heat transfer capability of the sub-processes. The time ratio and relative importance of the different heat transfer mechanisms were quantitatively estimated by linking the transient temperature fluctuations with the liquid film thickness variations. (C) 2017 Elsevier Ltd. All rights reserved.
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