Springer Link: https://link.springer.com/journal/11630/volumes-and-issues/30-1
1. Liquid Air Energy Storage for Decentralized Micro Energy Networks with Combined Cooling, Heating, Hot Water and Power Supply
SHE Xiaohui, ZHANG Tongtong, PENG Xiaodong, WANG Li, TONG Lige, LUO Yimo, ZHANG Xiaosong, DING Yulong
Corresponding author: DING Yulong
E-mail: y.ding@bham.ac.uk
Journal of Thermal Science, 2021, 30(1): 1-17.
https://doi.org/10.1007/s11630-020-1396-x
Keywords: liquid air energy storage, cryogenic energy storage, micro energy grids, combined heating, cooling and power supply, heat pump
Open Access -Springer Link: https://link.springer.com/article/10.1007/s11630-020-1396-x
Abstract: Liquid air energy storage (LAES) has been regarded as a large-scale electrical storage technology. In this paper, we first investigate the performance of the current LAES (termed as a baseline LAES) over a far wider range of charging pressure (1 to 21 MPa). Our analyses show that the baseline LAES could achieve an electrical round trip efficiency (eRTE) above 60% at a high charging pressure of 19 MPa. The baseline LAES, however, produces a large amount of excess heat particularly at low charging pressures with the maximum occurred at ~1 MPa. Hence, the performance of the baseline LAES, especially at low charging pressures, is underestimated by only considering electrical energy in all the previous research. The performance of the baseline LAES with excess heat is then evaluated which gives a high eRTE even at lower charging pressures; the local maximum of 62% is achieved at ~4 MPa. As a result of the above, a hybrid LAES system is proposed to provide cooling, heating, hot water and power. To evaluate the performance of the hybrid LAES system, three performance indicators are considered: nominal-electrical round trip efficiency (neRTE), primary energy savings and avoided carbon dioxide emissions. Our results show that the hybrid LAES can achieve a high neRTE between 52% and 76%, with the maximum at ~5 MPa. For a given size of hybrid LAES (1 MW×8 h), the primary energy savings and avoided carbon dioxide emissions are up to 12.1 MWh and 2.3 ton, respectively. These new findings suggest, for the first time, that small-scale LAES systems could be best operated at lower charging pressures and the technologies have a great potential for applications in local decentralized micro energy networks.
2. Research Progress of Tip Winglet Technology in Compressor
ZHONG Jingjun, WU Wanyang, HAN Shaobing
Corresponding author: WU Wanyang
E-mail: wywu@shmtu.edu.cn
Journal of Thermal Science, 2021, 30(1): 18-31.
https://doi.org/10.1007/s11630-020-1402-3
Springer Link: https://link.springer.com/article/10.1007/s11630-020-1402-3
Keywords: blade tip winglet, compressor, tip leakage flow, tip leakage vortex
Abstract: In the present study, the research progress of tip winglets that control tip clearance leakage flow in compressors is reviewed. Firstly, the effects of tip leakage flow on the aerodynamic performance of the compressor are presented. Subsequently, the development of tip winglet technology is reviewed. Next, a series of studies on compressor tip winglet technology are conducted. Besides, the effects of tip winglets on the aerodynamic performance of rectangular cascades of low-speed and high-subsonic compressors, subsonic compressor rotor and transonic compressor rotor are discussed, respectively, and the control effect of tip winglet technology combined with tip groove design on tip leakage is investigated. Lastly, the subsequent development direction and research prospect of compressor tip winglet technology are presented.
3. Recent Advances in Closed Loop Spray Cooling and its Application in Airborne Systems
XU Xinjie, WANG Yu, JIANG Yanlong, LIU Jinxiang, YUAN Xiaolei
Corresponding author: WANG Yu
E-mail: yu-wang@njtech.edu.cn
Journal of Thermal Science, 2021, 30(1): 32-50.
https://doi.org/10.1007/s11630-020-1395-y
Springer Link: https://link.springer.com/article/10.1007/s11630-020-1395-y
Keywords: spray cooling, closed loop, heat transfer performance, influencing factor, correlations
Abstract: In recent years, the problem of heat dissipation in airborne directed energy weapons has attracted considerable research interest. Spray cooling can be applied to cool airborne directed energy weapons, owing to its several advantages such as a large heat transfer coefficient, absence of boiling hysteresis and uniform surface temperature. To examine the potential of an airborne spray cooling system, the typical high heat flux dissipation methods were compared, and the state of the art research on spray cooling was reviewed. This review was focused on studies related to the spray cooling hydrodynamic mechanism, experimental studies of closed loop spray cooling, numerical simulation studies about spray cooling and the identification of the factors influencing spray cooling systems, and investigations related to the multiple nozzle spray cooling technology and heat transfer correlation predictions. Overall, there is a need for further research to investigate the failure phenomenon after the critical state, matching operation of the total system and microscopic characteristics of airborne specific parameters.
4. Optimal Design of Distributed Energy Resource Systems under Uncertainties Based on Two-Stage Robust Optimization
LI Da, ZHANG Shijie
Corresponding author: ZHANG Shijie
E-mail: zhangsj@mail.etp.ac.cn
Journal of Thermal Science, 2021, 30(1): 51-63.
https://doi.org/10.1007/s11630-020-1397-9
Springer Link: https://link.springer.com/article/10.1007/s11630-020-1397-9
Keywords: distributed energy resource, optimal design, two-stage robust optimization, uncertainty, uncertainty set
Abstract: Distributed energy resource (DER) systems are widely used owing to their excellent economic and environmental performance. However, uncertainties in the system generate difficulties in the optimal design of DER systems. In practice, the distribution of uncertain parameters is generally unknown. In this work, a two-stage robust optimization (RO) model was proposed for the optimal design of DER systems considering uncertainties in renewable energy intensity, energy prices, and load demands. Three uncertainty sets (i.e., the box, ellipsoid, and convex-hull uncertainty sets) were adopted to describe the distribution of uncertain parameters, and the proposed two-stage RO problem was solved using affine decision rules. A typical hospital in Lianyungang, Jiangsu Province, China, was selected as the case study object, and the effectiveness of the model was verified. The case study results showed that uncertainties in energy prices and load demands have a significant impact on system configuration and economic performance, and mainly affect the installed capacities of gas boilers, absorption chillers, and storages. Uncertainty set will affect the optimization results and an appropriate uncertainty set should be adopted to describe uncertainties precisely and increase accuracy of results.
5. Modelling and Thermodynamic Analysis of a Hot-Cold Conversion Pipe Using R134a-DMF-He as the Working Pair
LI Haiyu, LIN Peng, DU Shuai, WANG Liwei
Corresponding author: DU Shuai
E-mail: ds0108@sjtu.edu.cn
Journal of Thermal Science, 2021, 30(1): 64-75.
https://doi.org/10.1007/s11630-020-1243-0
Springer Link: https://link.springer.com/article/10.1007/s11630-020-1243-0
Keywords: diffusion absorption refrigeration, R134a-DMF-He, hot-cold conversion, waste heat recovery, thermodynamic analysis
Abstract: Based on the concept of a diffusion absorption system, a hot-cold conversion pipe utilizing 1,1,1,2-tetrafluoroethane (R134a)-dimethylformamide (DMF)-helium (He) as the working pair is presented with the aim of cooling output by recovering the low-grade waste heat. The model of the hot-cold conversion pipe is established, in which a heat pipe is used to transfer the waste heat as the heat input. The equations of the thermodynamic properties of the working pair are established by equation of state method (EOS). The model of the hot-cold conversion pipe is built based on the mass, species and energy balance equations of each component. The direct conversion of heat to cold is achieved by the desorption, absorption, condensation and diffusion evaporation processes of R134a. The hot-cold conversion pipe is cooled by natural convection, which can be enhanced by chimney effect. The thermodynamic analysis is carried out to analyze the effect of the boundary conditions, i.e. the heat source temperature, the refrigeration temperature, and the environmental temperature, on the system performance. This paper provides a theoretical basis for actual application of the hot-cold conversion pipe in waste heat recovery field.
6. Visualization Experiment and Numerical Analysis of Cavitation Flow Characteristics in Diesel Fuel Injector Control Valve with Different Structure Design
MA Haoyuan, ZHANG Tong, AN Qingsong, TAO Yuhao, XU Yue
Corresponding authors: MA Haoyuan; AN Qingsong
E-mail: mahaoyuan_2005@tju.edu.cn; anqingsong@tju.edu.cn
Journal of Thermal Science, 2021, 30(1): 76-87.
https://doi.org/10.1007/s11630-020-1301-7
Springer Link: https://link.springer.com/article/10.1007/s11630-020-1301-7
Keywords: diesel engine, fuel injector, control valve, cavitation
Abstract: Increasing the injection pressure has been proven an effective method to enhance performance and reduce pollutant of diesel engine. With the increase of the injection pressure, the cavitation damage problem inside common rail fuel injector is more significant, which has direct influences on reliability of diesel engine. While the most studies so far have focused on cavitation occurred in injector nozzle and its atomization characteristics, few researchers studied the cavitation phenomenon in fuel injector control valve. But due to the complexity of flow field and difficulty of experiment, the cavitation in control valve could not be fully described by existing theories. In this paper, the two-dimensional visualization experiment and numerical simulation of control valve was implemented to acquire the image of cavitation intuitively and validate the simulation method and model. Then a new structure design of control valve named convergent model was presented for comparison. The origin model and convergent model with different valve lifts were simulated in three dimensions. The results showed that the sheet cavitation occurred at the surface of seal cone and steel ball then turned to cloud cavitation in downstream area. The intensity of cavitation increased with the increase of valve lift. Convergent model could efficiently reduce the cavitation intensity near the seal area. This research could provide references for engineering optimization design of control valve.
7. Study of Unforced Unsteadiness in Centrifugal Pump at Partial Flow Rates
YANG Jun, XIE Tian, LIU Xiaohua, SI Qiaorui, LIU Jun
Corresponding author: SI Qiaorui
E-mail: siqiaorui@ujs.edu.cn
Journal of Thermal Science, 2021, 30(1): 88-99.
https://doi.org/10.1007/s11630-019-1241-2
Springer Link: https://link.springer.com/article/10.1007/s11630-019-1241-2
Keywords: centrifugal pumps, partial flow conditions, pressure pulsations, unforced unsteadiness, 2-D frequency domain visualization method
Abstract: In order to explore the unforced unsteadiness of centrifugal pumps, a 2-D frequency domain imaging display technology was used to study the development of these unsteady flow structures at partial flow conditions. The results showed that, the unsteady flow field was not only affected by rotor and stator interaction, but also appeared an unforced unsteadiness with fundamental frequency of St≈0.23 around the impeller throat area. Moreover, as the flow rates decreased, this unsteady flow structure gradually weakened and disappeared. When the flow rate was reduced to 0.6 times of design flow rate, another two unforced unsteady flow structures with characteristic frequencies of St≈0.0714 and St≈0.12 began to appear in the same area. Therefore, with the operating condition smaller than design flow rate, the internal flow became more and more complex. In addition to the forced unsteadiness, the unforced unsteadiness which is not connected with the blade passage frequency became more and more obvious.
8. Correlation Research between Turbulent Pressure Pulsation and Internal Sound Field Characteristics of Centrifugal Pump
CHENG Xiaorui, WANG Peng, ZHANG Shuyan
Journal of Thermal Science, 2021, 30(1): 100-110.
https://doi.org/10.1007/s11630-020-1253-y
Springer Link: https://link.springer.com/article/10.1007/s11630-020-1253-y
Keywords: centrifugal pump, pressure pulsation, internal sound field noise, frequency, simulation
Abstract: In order to study the correlation between the internal flow noise of the centrifugal pump and the turbulent pressure pulsation, a single-stage single-suction centrifugal pump was used as the research object by the combination of numerical calculation and experiment. Based on the RNG k-? model and the N-S equation, the model pump was simulated numerically by CFD. A dipole sound source was extracted by the turbulent pulse action of the volute wall surface according to the FW-H equation. The acoustic field of the model pump was solved on the basis of the boundary element method, and the sound pressure distribution of the internal flow field under the action of the dipole sound source of the volute wall and the frequency response of the inlet and outlet fields were obtained. The results show that the distribution of hydrodynamic noise inside the centrifugal pump is related to the pressure pulsation, presenting obvious dipole distribution and disturbance at the tongue. The sound pressure value of the field is mainly concentrated in the blade passing frequency and double frequency, in which the blade passing frequency is the strongest, and the sound pressure value decreases obviously under other double frequency. The main frequency of hydrodynamic noise is the blade passing frequency.
9. Performance Study of a Hybrid Heat Pump Dryer based on Numerical Analysis and Experimental Set-up
SHAMSUDDEEN Mohamed Murshid, CHA Dong-An, KIM Seon-Chang, KANEMOTO Toshiaki, KIM Jin-Hyuk
Corresponding author: KIM Jin-Hyuk
E-mail: jinhyuk@kitech.re.kr
Journal of Thermal Science, 2021, 30(1): 111-122.
https://doi.org/10.1007/s11630-020-1384-1
Springer Link: https://link.springer.com/article/10.1007/s11630-020-1384-1
Keywords: heat pump, hybrid dryer, CFD, drying rate, sea cucumber, oyster
Abstract: Seafood, especially sea cucumbers and oysters are an expensive delicacy in several Asian countries. Traditional sun-drying of these products takes 3 to 4 days and fetches a lower market price. Modern industrial drying machines used for seafood drying are unable to dry sea cucumbers and oysters without texture and color degradation as they are delicate, temperature-sensitive and have longer drying time. An economical drying system that does not cause texture or color degradation is the heat pump drying system and is commonly applied for agriculture and fabric drying. In this study, the heat pump technology is applied to develop two hybrid dryer models (bottom discharge and front discharge) to dry shellfish and sea cucumbers in large scale for storage and transportation. Each model is tested in a laboratory-scale with wet sponges as input material for its dehumidification capacity and the power consumed to attain the target dryness. The front discharge model is found to have rapid drying capability and economy. Computational fluid dynamic tools are used to study the hot air flow behavior and flow uniformity inside the drying chamber. The front discharge model showed smooth uniform flow over the trays with fewer losses in the flow velocity. The front discharge model with higher drying rate, lower power consumption and uniform airflow distribution over the trays is chosen for the industrial-scale design.
10. General Design and Thermodynamic Analysis of a Supercritical Carbon Dioxide Cannon
ZHANG Fan, LIU Hongrui, WU You, LI Jiaqi, YU Huazhang, WANG Xiaoliang, GUO Baoting, YUAN Yixiang
Corresponding author: LIU Hongrui; E-mail: liuhongrui@iet.cn
YUAN Yixiang; yuanyixiang@iet.cn
Journal of Thermal Science, 2021, 30(1): 123-132.
https://doi.org/10.1007/s11630-020-1376-1
Springer Link: https://link.springer.com/article/10.1007/s11630-020-1376-1
Keywords: supercritical carbon dioxide (SCO2) cannon, state equation, thermodynamic analysis, field test
Abstract: This paper presents a new supercritical carbon dioxide (SCO2) cannon based on the carbon dioxide (CO2)’s thermodynamic cycle under constant volume. First, Virial equation and NIST database are applied to formulate SCO2’s property and analyze the thermodynamic cycle, which is aimed to get the optimization equation using the cannon’s exit velocity as objective function. Then the cannon’s structural parameters, such as diaphragm thickness and barrel length, and CO2’s filling mass, are optimized. Finally, the flow field and velocity’s change during the launch process is performed with FLUENT. In field test, the ultra-high pressure sensor and ultra-high speed camera are used to measure the pressure distribution along the barrel’s axial direction and the projectile’s exit velocity under different conditions. The results show that all the performance indexes meet the design requirement. The innovative SCO2 cannon in this paper has obvious advantages such as high safety, low cost and fast loading, which can be applied in many situations such as disaster relief, peacekeeping and anti-terrorism. Moreover, the unique energy storage method and thermodynamic design ensure its subsequent development.
11. Investigation on One-Dimensional Loss Models for Predicting Performance of Multistage Centrifugal Compressors in Supercritical CO2 Brayton Cycle
SHAO Wenyang, DU Juan, YANG Jinguang, WANG Xiaofang, LYU Guochuan
Corresponding author: YANG Jinguang
E-mail: jinguang_yang@dlut.edu.cn
Journal of Thermal Science, 2021, 30(1): 133-148.
https://doi.org/10.1007/s11630-020-1242-1
Springer Link: https://link.springer.com/article/10.1007/s11630-020-1242-1
Keywords: supercritical carbon dioxide Brayton cycle, centrifugal compressor, one-dimensional performance analysis, loss model, three-dimensional CFD simulation
Abstract: The main compressor in a supercritical carbon dioxide (SCO2) Brayton cycle works near the critical point where the physical properties of CO2 are far away from the ideal gas. To investigate the effectiveness of the conventional one-dimensional (1D) loss models for predicting the performance of compressors working in such nontraditional conditions, detailed comparisons of 1D predicted performance, experimental data and three- dimensional CFD results are made. A 1D analysis method with enthalpy and total pressure based loss system is developed for multistage SCO2 centrifugal compressors, and it is firstly validated against the experimental results of a single stage SCO2 centrifugal compressor from the Sandia National Laboratory. A good agreement of pressure ratios with experiments can be achieved by the 1D method. But the efficiency deviations reveal the potential deficiencies of the parasitic loss models. On the basis of the validation, a two-stage SCO2 centrifugal compressor is employed to do the evaluation. Three-dimensional CFD simulations are performed. Detailed comparisons are made between the CFD and the 1D results at different stations located in the compressor. The features of the deviations are analyzed in detail, as well as the reasons that might cause these deviations.
12. Performance Improvement of Single Screw Compressor by Meshing Clearance Adjustment Used in Refrigeration System
LU Yuanwei, LIU Shanwei, WU Yuting, LEI Biao, ZHI Ruiping, WEN Qiangyu, MA Chongfang
Journal of Thermal Science, 2021, 30(1): 149-164.
https://doi.org/10.1007/s11630-020-1291-5
Springer Link: https://link.springer.com/article/10.1007/s11630-020-1291-5
Keywords: single screw compressor, leakage, performance improvement, meshing clearance height, refrigeration
Abstract: The single screw compressor (SSC) is widely used in air compression and refrigeration systems due to its many advantages. The meshing clearance between the screw groove and gate rotor teeth flank has a significant influence on the compressor performance. In this paper, mathematical calculation models describing the internal working process of the SSC are established in order to evaluate the thermal dynamic characteristics of the compressor under varying meshing clearance heights. The refrigerating capacity, volume efficiency and adiabatic efficiency of the SSC are calculated and discussed. Three prototypes, with different meshing clearance heights, were manufactured to study the internal influence mechanisms. The theoretical model was verified using experimental data and the calculation results strongly agreed with the experimental results. Results demonstrate that comparisons of volume efficiency and adiabatic efficiency between the measured and calculated results exhibited deviations of 3.64%?7.98% and 5.92%?9.4%, respectively. Based on the models, analysis under varying meshing clearance heights and working conditions was performed. Taking into account working performance, actual manufacturing conditions and manufacturing cost limitations, a meshing clearance height range from 0.01 mm to 0.08 mm is suggested. This study can provide important theoretical data and experimental support for the design, manufacturing and optimization of single screw compressors.
13. Phase Equilibrium Characteristics of CO2 and Ionic Liquids with [FAP]– Anion Used for Absorption-Compression Refrigeration Working Pairs
WU Weidong, WANG Li, LI Xiang, LIU Hui, ZHANG Hua, DOU Binlin
Corresponding author: WU Weidong; E-mail: usstwwd@163.com
ZHANG Hua, Zhanghua3000@163.com
Journal of Thermal Science, 2021, 30(1): 165-176.
https://doi.org/10.1007/s11630-020-1407-y
Springer Link: https://link.springer.com/article/10.1007/s11630-020-1407-y
Keywords: CO2, ionic liquids (ILs), absorption-compression, refrigeration working pair, phase equilibrium, tris(per?uoroalkyl)tri?uorophosphate anions ([FAP]–)
Abstract: The study of the phase equilibrium characteristics of CO2-ionic liquids (ILs) as new absorption-compression type refrigeration working pairs is of great importance. Three kinds of ILs, i.e., [emim][FAP], [bmim][FAP] and [hmim][FAP], were chosen as potential absorbents. The solubility of CO2 in these ILs was measured experimentally within 0 to 5.0 MPa at temperatures of 293.15 K to 333.15 K, and the effects of temperature, pressure, IL anion and cation structure and stirring action on CO2 solubility were also discussed and analyzed. The results showed that the longer alkyl chains in an identical IL family, the alkyl fluoride group in IL anions and the stirring action by a magnetic stirrer had positive effects on the solubility of CO2. In the three ILs, [hmim][FAP] possessed the best performance for CO2 absorption; the solubility of CO2 reached 0.7641 at a pressure of 5 MPa and temperature of 293.15 K, the maximum solubility measured in this work. The CO2-[hmim][FAP] binary mixture is recommended as a potentially applicable working pair for CO2 absorption-compression refrigeration systems.
14. Comparison of Conventional and Advanced Exergy Analysis for Dual-Loop Organic Rankine Cycle used in Engine Waste Heat Recovery
WANG Zhiqi, HU Yanhua, XIA Xiaoxia
Corresponding author: XIA xiaoxia
E-mail: xxx620@xtu.edu.cn
Journal of Thermal Science, 2021, 30(1): 177-190.
https://doi.org/10.1007/s11630-020-1299-x
Springer Link: https://link.springer.com/article/10.1007/s11630-020-1299-x
Keywords: advanced exergy analysis, conventional exergy analysis, dual-loop organic Rankine cycle (DORC), internal combustion engine, waste heat recovery (WHR)
Abstract: At present, the dual-loop organic Rankine cycle (DORC) is regarded as an important solution to engine waste heat recovery (WHR). Compared with the conventional exergy analysis, the advanced exergy analysis can better describe the interactions between system components and the irreversibility caused by economic or technical limitations. In order to systematically study the thermodynamic performance of DORC, the conventional and advanced exergy analyses are compared using an inline 6-cylinder 4-stroke turbocharged diesel engine. Meanwhile, the sensitivity analysis is implemented to further investigate the influence of operating parameters on avoidable-endogenous exergy destruction. The analysis result of conventional exergy analysis demonstrates that the priorities for the components that should be improved are in order of the high-temperature evaporator, the low-temperature turbine, the first low-temperature evaporator and the high-temperature condenser. The advanced exergy analysis result suggests that the avoidable exergy destruction values are the highest in the low-temperature turbine, the high-temperature evaporator and the high-temperature turbine because they have considerable endogenous-avoidable exergy destruction. The sensitivity analysis indicates that reducing the evaporation pinch point and raising the turbine efficiency can decrease the avoidable exergy destruction.
15. Reynolds-Averaged Navier-Stokes Equations Describing Turbulent Flow and Heat Transfer Behavior for Supercritical Fluid
YANG Zheng, CHENG Xu, ZHENG Xinghua, CHEN Haisheng
Corresponding author: CHEN Haisheng
E-mail: chen_hs@mail.etp.ac.cn
Journal of Thermal Science, 2021, 30(1): 191-200.
https://doi.org/10.1007/s11630-020-1339-6
Springer Link: https://link.springer.com/article/10.1007/s11630-020-1339-6
Keywords: SCF-RANS equations, supercritical fluid, turbulence, Reynolds-averaged, Navier-Stokes equations
Abstract: Supercritical fluid has been widely applied in many industrial applications. The traditional Reynolds-averaged Navier-Stokes (RANS) equations are directly applied for turbulent flow and heat transfer of the supercritical fluid, ignoring turbulent effect of the thermal physical properties due to the intense nonlinearity. This paper deduces a set of Reynolds-averaged Navier-Stokes equations for supercritical fluid (SCF-RANS equations) to depict turbulent flow and heat transfer of the supercritical fluid taking all the physical parameters as variables. The SCF-RANS equations include many new correlation terms due to fluctuation of the thermal physical properties. Model methods for the new correlation term have been discussed for closing the SCF-RANS equations. Some of them have relatively mature models, while others are completely new and need profound physical theoretical analysis for proposing reasonable models. This paper provides referable information for these new correlations as far as authors know. The SCF-RANS equations not only provide the formulation special for flow and heat transfer of the supercritical fluid, but also represent the most sophisticate form of the RANS equations, for every involved physical property has been considered as variable without any simplification.
16. Numerical Study of Dual Sweeping Jet Actuators for Corner Separation Control in Compressor Cascade
MENG Qinghe, DU Xin, CHEN Shaowen, WANG Songtao
Corresponding author: CHEN Shaowen
E-mail: cswemail@hit.edu.cn
Journal of Thermal Science, 2021, 30(1): 201-209.
https://doi.org/10.1007/s11630-019-1231-4
Springer Link: https://link.springer.com/article/10.1007/s11630-019-1231-4
Keywords: sweeping jet actuator, compressor cascade, active flow control, corner separation
Abstract: Unsteady behaviors are important issues in flow control of turbomachinery. Pulsed excitation or suction is widely investigated in compressor cascades. This paper presents a discussion on the unsteady flow control realized by dual sweeping jet actuator (SJA) located on the blade suction surface. The unsteady numerical simulations were utilized to study the effect of applying dual SJAs on controlling the corner separation. With the numerical results, the following conclusions could be drawn with current compressor cascade. A maximum total pressure loss coefficient reduction of 6.8% was obtained. The analysis of the flow field pointed out that the regulation mechanisms of the corner separation were different with each SJA. The SJA ahead achieved an interruption of the suction side boundary layer development and the rear SJA enhanced the interaction and entrainment between the excitation stream and the secondary flows. Meanwhile, the different unsteadiness structures of the flow field frequency spectrum compared with single SJA cases were identified. The first peak frequency corresponded to the difference of the two SJAs and the rest frequencies could be regulated to a base frequency and its harmonic frequencies.
17. Numerical Simulation Study on Cooling Characteristics of a New Type of Film Hole
GUO Chunhai, WANG Bin, KANG Zhenya, ZHANG Wenwu, ZHENG Huilong
Corresponding author: GUO Chunhai
E-mail: guochunhai@nimte.ac.cn
Journal of Thermal Science, 2021, 30(1): 210-219.
https://doi.org/10.1007/s11630-020-1288-0
Springer Link: https://link.springer.com/article/10.1007/s11630-020-1288-0
Keywords: film cooling, shaped hole, numerical simulation, optimal design, cooling efficiency
Abstract: A new type of film cooling hole with micro groove structure is presented in this paper. Based on the finite volume method and the Realizable k-ε model, the film cooling process of the hole in a flat plate structure is simulated. The surface temperature distribution and film cooling effect of different film cooling holes were analyzed. The effects of micro-groove structure on wall attachment and cooling efficiency of jet were discussed. The results show that under the same conditions, the transverse coverage width and overall protective area of the new micro-groove holes are larger than those of the ordinary cylindrical holes and special-shaped holes. Compared with ordinary holes, the new micro-groove holes can better form the film covering on the surface and enhance the overall film cooling efficiency of the wall. For example, when the blowing ratio M=1.5, the effective coverage ratio of micro-groove holes is 1.5 times the dustpan holes and is 8 times the traditional cylindrical holes. It provides reference data and experience rules for the optimization and selection of advanced cooling structure of high performance aero-gas engine hot-end components.
18. Near-Wall Flow in the Blade Cascades Representing Last Rotor Root Sections of Large Output Steam Turbines
?IMURDA David, FüRST Ji?í, HáLA Jind?ich, LUXA Martin, BOB?íK Marek, NOVáK Ond?ej, SYNá? Jaroslav
Corresponding author: ?IMURDA David
E-mail: simurda@it.cas.cz
Journal of Thermal Science, 2021, 30(1): 220-230.
https://doi.org/10.1007/s11630-020-1246-x
Springer Link: https://link.springer.com/article/10.1007/s11630-020-1246-x
Keywords: turbine blade cascade, secondary flow, near wall flow, supersonic flow, CFD, experiment
Abstract: This paper investigates the flow past two variants of root section profile cascades for a last stage rotor considering three-dimensional flow structures in the near-wall region. Analyses were drawn based on RANS numerical simulations of both variants and on the experimental data obtained by the 3D traversing in the exit flow field of one of the variants. Extent of 3D structures at two different regimes and its influence on aerodynamic characteristics of the blade cascades was assessed. The distributions of Mach number along the profiles were compared with 2D optical measurements and its distortion due to the presence of the sidewall was explored. The interaction between main vortical structures was described and its influence on the loading of the blades, mechanical energy losses and exit flow angle was discussed. The results showed that for a front loaded blade the vortical structures appeared earlier and at a larger extent than for an aft loaded variant. However, due to different Mach number distribution, contribution of end wall flow to the energy losses was lower in the case of the aft loaded variant. The influence of the near wall flow on the loading was found to be rather weak while the deviation of the exit flow angle appeared to be comparable for both of the variants.
19. Study on the Numerical Model of Transonic Wind Tunnel Test Section
LOUDA Petr, P?íHODA Jaromír
Journal of Thermal Science, 2021, 30(1): 231-241.
https://doi.org/10.1007/s11630-020-1277-3
Springer Link: https://link.springer.com/article/10.1007/s11630-020-1277-3
Keywords: perforated wall model, transonic wind tunnel, turbine blade cascade
Abstract: The authors consider numerical simulations of transonic flows through various turbine cascades in a confined channel which approximates boundaries of real wind tunnel. The boundaries of the wind tunnel are impermeable or there can be permeable tailboards to diminish shock wave reflections. The mathematical model is based on Favre-averaged Navier-Stokes equations closed by a turbulence model and model of transition to turbulence. The mathematical model is solved by an implicit finite volume method with multi-block grids. Several types of turbine blade cascades with subsonic or supersonic inlet are presented. The results are compared with optical measurements and simulations of periodic cascades. The validity of experimental reference flow parameters in relation to computed flow patterns is discussed.
20. Measurements of Water-Air Flow Phenomena in a Chamber with a Rotating Shaft
TIUTIURSKI Pawe?, HERCEL Paulina, TELEGA Janusz, KARDA? Dariusz
Corresponding author: TIUTIURSKI Pawe?; ptiutiurski@imp.gda.pl
HERCEL Paulina; phercel@imp.gda.pl
Journal of Thermal Science, 2021, 30(1): 242-247.
https://doi.org/10.1007/s11630-020-1265-7
Springer Link: https://link.springer.com/article/10.1007/s11630-020-1265-7
Keywords: bearing chamber, measurements, fluid film velocity, two-phase flow
Abstract: The paper concerns the phenomena of the fluid film that occurs in the bearing chamber of an aircraft engine. The geometry of the system includes two concentric cylinders, between which there is a mixture of oil and air. The fluid circulates in a closed circuit. The rotary movement of the inner cylinder causes creation of the fluid film on the walls of the chamber. The article proposes a measurement method that is allowing observation of this fluid film and, in particular, analysis of the movement of the air bubbles occurring in the film. An own model of the bearing chamber with transparent walls was constructed for the research. For the investigation, water was used instead of oil. Observation of the behaviour of the flow was possible thanks to video recordings made with the use of a fast-capture camera. The results presented in the paper include velocity magnitudes of the air bubbles in the fluid film in dependence on the rotational speed of the shaft and water volume fraction and with a range from 0.37 to 0.91 m/s. The results presented in this article can be used for the bearing chamber numerical models validation.
21. Simulation and Experimental Study on Thermal Conductivity of Nano-Granule Porous Material Based on Lattice-Boltzmann Method
KAN Ankang, MAO Shang, WANG Ning, SHI Bingling
Corresponding author: KAN Ankang; ankang0537@126.com;
MAO Shang; ms802366@126.com
Journal of Thermal Science, 2021, 30(1): 248-256.
https://doi.org/10.1007/s11630-019-1218-1
Springer Link: https://link.springer.com/article/10.1007/s11630-019-1218-1
Keywords: effective thermal conductivity, mesoscopic scale, Lattice-Boltzmann method, aerogel, physics model
Abstract: Nano-porous materials have excellent thermal insulation performance, whose microstructure and physical properties, however, have great influence on the thermal conductivity. To accurately describe the stochastic phase distribution, a random internal morphology and structure generation-growth method, called the quartet structure generation set (QSGS), has been proposed in the present paper. The model was then imported into lattice Boltzmann algorithm as a fully resolved geometry and used to investigate the effects on heat transfer at the nanoscale. Furthermore, a three-dimensional Lattice Boltzmann method (LBM) D3Q15 was adopted to predict the nano-granule porous material effective thermal conductivity. This ideal method provided a significant advantage over similar porous media methods by directly controlling and adjusting of granule characteristics such as granule size, porosity and pore size distributions and studying their influence directly on thermal conductivity. To verify the accuracy of the proposed model, some experiments based on guarded hot plate meter (GHPM) were conducted. The results indicated that the simulation results agreed well with the experimental data and references values, which illustrated that this method was reliable to generate the microstructure of nano-granule. What’s more, the effects of pressure, core distribution probability, cd and density were investigated. There existed an optimal density (about 120 kg?m–3) making the effective thermal conductivity being minimum and an optimal core distribution probability about cd =0.1 making the uniformity being the best. In addition, the present approach is applicable in dealing with other porous materials as well.
22. Thermal Performance of Elliptical Fin-and-Tube Heat Exchangers with Vortex Generator under Various Inclination Angles
WANG Yucheng, ZHAO Wensheng, WANG Pengfei, JIANG Jin, LUO Xiangyu
Corresponding author: ZHAO Wensheng
E-mail: wenson.zhao@gmail.com
Springer Link: https://link.springer.com/article/10.1007/s11630-020-1305-3
Journal of Thermal Science, 2021, 30(1): 257-270.
https://doi.org/10.1007/s11630-020-1305-3
Keywords: heat exchanger, vortex generator, Colburn factor, friction factor, heat exchanger efficiency
Abstract: Elliptical fin-and-tube heat exchangers are commonly used in air conditioning, heating, refrigeration industries, and ventilation. This study numerically investigates the effect of vortex generators on the performance of elliptical fin-and-tube heat exchanger under different inclination angles. In this study, air flow that is in the transitional regime is selected as the working fluid. Reynolds numbers at the inlet are varied in a range of 1300 to 2100, and the shear stress transport k-ω turbulence model is selected to solve the non-closure of basic turbulence equations. The ellipticity ratios of the tubes which are used for the analysis are between 0.6 and 1.0, and the inclination angles are varied from 15° to 75°. The effects of different inclination angles of vortex generators on the Colburn factor j, friction factor f, and efficiency index j/f are analyzed. The friction and Colburn factors are observed to increase with increasing vortex generator inclination angles. It is found that the efficiency factors for a 15° vortex generator inclination angle at 0.6, 0.7, 0.8, and 0.9 ellipticity ratios improve compared to the corresponding cases with no vortex generator. However, the vortex generator cannot improve the efficiency factor of the circular tube heat exchanger. The 3D CFD method employed by this study has great potential for use in optimally designing the arrangement of the vortex generators to enhance the performance of heat exchangers.
23. Experimental Investigation of Microbial Fouling and Heat Mass Transfer Characteristics on Ni-P Modified Surface of Heat Exchanger
XU Zhiming, JIANG Xin, LIU Zuodong, HU Yinghong, LI Yanfeng
Corresponding author: LIU Zuodong
E-mail: liuzuodong@neepu.edu.cn
Journal of Thermal Science, 2021, 30(1): 271-278.
https://doi.org/10.1007/s11630-020-1304-4
Springer Link: https://link.springer.com/article/10.1007/s11630-020-1304-4
Keywords: heat exchanger, microbial fouling, Ni-P coating, surface modification
Abstract: Fouling deposition problem on heat transfer surface is widely distributed in the field of energy and chemical industry, and microbial fouling is a common fouling type in heat exchanger. In this article, the surface modification was used for inhibiting or mitigating the microbial fouling deposition on heat exchange surface. Firstly, the experimental system for real-time monitoring the fouling deposition process was built, and then the Ni-P modified surface was prepared. Further, the slime forming bacteria (SFB) microbial fouling characteristics and corresponding influencing factors on Ni-P modified surface were investigated experimentally. The results indicated that Ni-P modified surface had an excellent fouling inhibition property. Comparing with carbon steel, Ni-P modified surface reduced the fouling heat resistance by 80%. Accordingly, the influencing factors of microbial fouling deposition including temperature, flow rate and microbial concentrations were discussed. With cooling water temperature increasing given in the experiment arrangement, the microbial fouling resistance was increased first and then decreased, while with bacteria concentration and flow rate increasing, the fouling resistance was increased and decreased separately. The work can provide experimental reference for the fouling inhibition surface development and fouling inhibition mechanism study.
24. Critical Heat Flux (CHF) Correlations for Subcooled Water Flow Boiling at High Pressure and High Heat Flux
LIU Ping, GUO Yusheng, DING Wenlong, TANG Mingyun, SONG Yuntao, PENG Xuebing, JI Jiadong, CHEN Qinghua, MAO Xin
Corresponding author: SONG Yuntao
E-mail: songyt@ipp.ac.cn
Journal of Thermal Science, 2021, 30(1): 279-293.
https://doi.org/10.1007/s11630-021-1394-7
Springer Link: https://link.springer.com/article/10.1007/s11630-021-1394-7
Keywords: reactor divertor, correlations, subcooled water flow boiling, critical heat flux (CHF), high heat flux, high pressure
Abstract: The subcooled water flow boiling is beneficial for removing the high heat flux from the divertor in the fusion reactor, for which an accurate critical heat flux (CHF) correlation is necessary. Up to now, there are many CHF correlations mentioned for subcooled water flow boiling in the open literatures. However, the CHF correlations’ accuracies for the prediction of subcooled water flow boiling are not satisfactory at high heat flux and high pressure for reactor divertor. The present paper compiled 1356 CHF experimental data points from 15 independent open literatures and evaluated 10 existing CHF correlations in subcooled water flow boiling. From the evaluation, the W-2 CHF correlation performs best for the experimental CHF data in all existing critical heat flux correlations. However, the predicted mean absolute error (MAE) of the W-2 correlation is not very ideal for all database and the MAE of the W-2 correlation is from 30% to 50% for some database. In order to enhance the CHF prediction accuracy in subcooled water flow boiling at high heat flux and high pressure, the present paper developed a new CHF correlation. Compared with other existing CHF correlations, the new CHF correlation greatly enhances the prediction accuracy over a broad range of pressures and heat fluxes which are desired in the cooling of high heat flux devices, such as those in the fusion reactor divertor. The validation results show that the new correlation has a MAE of 10.05% and a root mean squared error (RMSE) of 16.61%, predicting 68.1% of the entire database within ±10% and 81.5% within ±15%. The MAE of the new CHF correlation is 7.4% less than that of the best existing one (W-2 correlation), further confirming its superior prediction accuracy and reliability. Besides, the new CHF correlation works well not only for a uniform power profile but also for a non-uniform power profile in subcooled water flow boiling at high pressure and high heat flux.
25. Experimental Investigation of Heat Transfer in Microchannel with Inlet Cavitation Structure
YUAN Junfei, WANG Lin, WANG Zhanwei, TAN Yingying
Corresponding author: WANG Lin
E-mail: wlhaust@163.com
Journal of Thermal Science, 2021, 30(1): 294-301.
https://doi.org/10.1007/s11630-019-1209-2
Springer Link: https://link.springer.com/article/10.1007/s11630-019-1209-2
Keywords: heat transfer, cavitation structure, flow pattern, pressure oscillation, microchannel
Abstract: Heat transfer of R134a through the microchannel with an inlet reentrant cavitation structure was investigated for high flux thermal management of electronic devices. The cavitating flow patterns, pressure, and heat transfer characteristics were studied in the range of effective heat fluxes from 0 to 138.4 W/cm2 with mass flow velocities from 2.12 to 5.23 m/s. A stable and ideal starting point of two phase flow and heat transfer was commendably provided by the inlet cavitation orifice. There existed an axis deviation liquid jet after the micro-orifice. The refrigeration vapor was generated from the cavitation structure but liquidized at the downstream of the channel. The wall temperature along flow orientation presented an opposite trend under the test states with or without heat input. The cavitation structure can significantly suppress the flow oscillation in microchannels and the outlet pressure fluctuation reduced about 72% compared with the fluctuation at the entrance. The heat transfer coefficient had been distinctly impacted by heat flux at lower heat input and then maintained the value nearly constant of 11.0 W/(cm2?K) with the critical heat flux of 88.4 W/cm2.
26. Numerical Study of Convective and Radiation Heat Transfer Characteristics in an Upward-Facing Cylindrical Cavity under Back-Side Windy Condition
WANG Zehui, WU Kefeng, WANG Ti, XIA Liangwei, YU Qiang, HUANG Ying, SUN Hao, WEI Guohua, GUAN Jingyu, YAN Yanfei
Corresponding author: GUAN Jingyu
E-mail: guanjy@hbc.com.cn
Journal of Thermal Science, 2021, 30(1): 302-312.
https://doi.org/10.1007/s11630-020-1309-z
Springer Link: https://link.springer.com/article/10.1007/s11630-020-1309-z
Keywords: upward-facing, cylindrical cavity, back-side wind, convective heat transfer, radiation heat transfer, numerical simulation
Abstract: Under the back-side windy condition, the convection and radiation heat transfer characteristics in an iso-flux upward-facing cylindrical cavity were studied by three-dimensional numerical simulation. The impacts of cavity tilt angle, wind incident angle and wind speed on convection and radiation heat transfer Nusselt number Nuc and Nur were analyzed, and the possible explanations for their impacts were presented. Results show that due to the disturbance of wind, the influence of cavity tilt angle becomes more complicated and is related to wind incident angle and wind speed. The variation of Nuc or Nur with wind incident angle is different for different cavity tilt angles. Despite of the changes of cavity tilt angle or wind incident angle, the Nuc increases with the wind speed while the Nur presents a declination with the increasing of wind speed. Hence, compared with cavity tilt angle and wind incident angle, wind speed may be the dominant factor affecting or controlling the convective and radiation heat transfer of cavity.
27. Exergy Analysis of a Novel Chemical Looping Hydrogen Generation System Integrated with SOFC
ZHANG Xiaosong, CHEN Zhewen, CHEN Zhenbin, LI Jinsong
Corresponding author: ZHANG Xiaosong
E-mail: zhangxiaosong@hainanu.edu.cn
Journal of Thermal Science, 2021, 30(1): 313-323.
https://doi.org/10.1007/s11630-020-1404-1
Springer Link: https://link.springer.com/article/10.1007/s11630-020-1404-1
Keywords: chemical looping, fuel cell, exergy analysis
Abstract: In this paper, a novel system integrating chemical-looping hydrogen generation (CLH) system and solid oxide fuel cell (SOFC) has been proposed. This new methane-fuelled energy system was investigated with energy balance and exergy analysis. CLH produces the hydrogen as the fuel of the SOFC, and the FeO and Fe3O4 are selected as the looping material. Waste heat from the SOFC is absorbed by the CLH and converted to chemical energy through the reduction reaction of CLH. Owing to the cascade utilization of the fuel between the CLH and SOFC, the net efficiency of this novel system can achieve 62.8% considering CO2 separation, more than 10 percentage points higher than a methane reforming fuelled SOFC system. Meanwhile, by using the CLH to produce the hydrogen, the CO2 can be recovered without an energy penalty. Through the analysis of the graphical exergy, the cascade utilization of waste heat and the high-efficiency hydrogen production is the main reason of high performance. This novel system also has the advantage of CO2 capture without energy penalty, so this combined system is an advantaged method to accomplish the efficient utilization of methane.
28. Experimental Investigation on Flame Characterization and Temperature Profile of Single/Multiple Pool Fire in Cross Wind
CHEN Zhen, WEI Xiaolin, LI Teng
Corresponding author: WEI Xiaolin
E-mail: xlwei@imech.ac.cn
Journal of Thermal Science, 2021, 30(1): 324-332.
https://doi.org/10.1007/s11630-020-1335-x
Springer Link: https://link.springer.com/article/10.1007/s11630-020-1335-x
Keywords: pool fire, temperature profile, flame characteristic, kerosene, cross wind
Abstract: An experimental study was carried out to investigate the flame characterization and temperature profile for single and multiple pool fire with the influence of cross wind. There were 13 test cases in total, categorized into circle and rectangle fuel pans, with diameter (or equivalent diameter) ranged from 50 mm to 300 mm. Kerosene was used for the fuel of pool fire. Some K-type thermocouples were arranged around the flame to monitor the flame temperature, while the flame tilt angle was measured based on the photograph of flame for different case. Firstly, it can be found that there are three phases, including preheating, steady burning and extinguishing phase, during the flame evolution. The maximum temperature near the fuel surface is ~1040 K, which is higher than that of flame plume (~600 K), in the steady burning phase of circle single pool fire (D=300 mm), while the average burning rate is ~1.525 g/s. In addition, the burning rates of all cases were measured and compared with the current predicted method. Typically, the flame morphology of single/multiple pool fire at different cross wind speed (ranging from 0 to 3.5 m/s) was analyzed, and it is found that the results for single pool fire agree with Thomas model and AGA model well, which are not suitable for multiple pool fire. Finally, the temperature profile of different case was measured with various wind speed.
29. Gas Characteristics of Pine Sawdust Catalyzed Pyrolysis by Additives
YU Dongling, JIN Guang, PANG Yunji, CHEN Yisheng, GUO Shaopeng, SHEN Shengqiang
Corresponding author: PANG Yunji
E-mail: pangyunji2008@163.com
Journal of Thermal Science, 2021, 30(1): 333-342.
https://doi.org/10.1007/s11630-020-1244-z
Springer Link: https://link.springer.com/article/10.1007/s11630-020-1244-z
Keywords: pine sawdust, pyrolysis, additive, catalysis, gas analysis
Abstract: In order to effectively investigate the variation of gas production characteristics of biomass under normal-speed pyrolysis conditions, the gas production rate, gas production component yield and gas production calorific value of pine sawdust with adding Na2CO3, CaO and Fe2O3 were systematically analyzed. In the experiment, an improved tube furnace was used to research the pyrolysis process with the temperature from 350°C to 750°C. The results indicate that the gas yield rises with the increase of temperature without additives, reaching 19.59% at 750°C. The liquid yield reaches 59.38% at 450°C and then the yield change is small. CaO increases the calorific value of the pyrolysis product gas due to the adsorption of CO2. Na2CO3 is fused with inorganic substances in the biomass to form a char skeleton structure. The effect of Fe2O3 on H2 is more obvious at higher temperature. Na2CO3 has the most obvious effect on the pyrolysis of pine sawdust among the discussed additives, which effectively promotes the production of H2.
30. A Versatile Numerical Tool for Simulating Combustion Features at Small-Scales
KANG Xin, DENG Youcheng, WANG Jianyong, FAN Aiwu
Corresponding author: KANG Xin, xkang@whut.edu.cn;
FAN Aiwu, faw@hust.edu.cn
Journal of Thermal Science, 2021, 30(1): 343-361.
https://doi.org/10.1007/s11630-020-1300-8
Springer Link: https://link.springer.com/article/10.1007/s11630-020-1300-8
Keywords: micro-combustion, OpenFOAM, conjugate heat transfer, thermally orthotropic combustor, flame streets
Abstract: A versatile numerical tool based on the open-source framework OpenFOAM has been developed in this paper for modeling time-accurate, low-Mach number reacting flows, with a particular interest in small-scale flames. This tool consists of a gas-phase Navier-Stokes solver and a solid-wall heat conduction solver which can be implemented alone, or used together in a coupled means to reveal the small-scale combustion’s characteristics of significantly enhanced flame-wall thermal coupling. Validation works has proved that the tool is capable of reproducing experimental flames at various scales (from conventional to small scales), including well-recognized micro-flame features in literature such as three modes of premixed flame dynamics (weak flames, flames with repetitive extinction and ignition, and stable flames). Then, an experimentally-already-found but rarely-simulated unique phenomenon of diffusion flame street is successfully reproduced with well-captured flame structures. Moreover, the conjugate heat transfer model with the specific formulation of solid-wall heat conduction enables an attempt to simulate a novel, thermally-orthotropic combustor with its axial thermal conductivities superior to the transverse ones. Finally, computational performance of the developed OpenFOAM solver is compared to that of the previously-used compressible flow solver Eilmer. The OpenFOAM solver is found to show better wave-damping abilities for overcoming acoustic wave effects at the initial stage of simulations, and is much more efficient in terms of the computational cost.
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