Sectional wind turbine blades, by dividing an intact blade into multiple segments, have the advantage of being easy to handle and transport. To determine a suitable blade division location, this study was performed to clarify some crucial aspects and challenges for sectional blades. This paper proposes a method to estimate the effects of the location of the blade division on structural, manufacturing, and assembling performance of sectional blades. The advantage of this method is the ease of the assessment process, since it can be performed at an early stage of blade design, where only the aerodynamic profile, mass density and stiffness distribution, and service fatigue loads of original blades are essential. A case study with the proposed method was carried out based on a 38-meter commercial blade. Results show that the best position for the division of sectional blades is located 20% from the blade root by balancing the three aspects listed above. The key approaches to reduce additional increases in stiffness and weight of sectional blades are related to improving the fatigue strength and the choice of low-modulus materials for connecting bolts. The effects of the division location on assembling accessibility and natural frequencies of scaled sectional blades are consistent with the basic sectional blade. Unfavorable effects occur when up-scaling the diameter of the bolts; and, harsh external loads on the connections have negative effects on the application of sectional blades with larger wind turbines. In this regard, lightweight design is indispensable to reduce bolt stress.
The location of the division on sectional blades has significant influences on connection reliability, manufacturing accessibility, and structural dynamics. This paper proposed a method to evaluate the bolt strength, fabrication accessibility, and natural frequencies at different division locations based on the characterization of the axial bolts, practical requirements for bolt assembling, and stiffness and mass density variation after blade separation. Then, a case study on a 38-meter commercial blade, as a representative of structural and aerodynamic characteristics of the modern blade, was conducted to investigate the effects of the division location on the WT performance. Finally, upscaling studies were completed to address the challenges of large sectional blades according to the geometrical similarity rule. The conclusions drawn are as follows.
The beneficial interval of the division for sectional blades is located in the middle of the blades, when considering the manufacturing and assembling of the blade connection of current blades.
The optimal interval of the location for the division for sectional blades is situated at around 20% from the blade root, taking into consideration the connection strength and natural frequency variation of the sectional blade, as well as the convenience of manufacturing and assembly.
Key approaches to reduce additional increases in stiffness and weight are to improve fatigue strength and to choose low-modulus connection bolts.
Upscale-diameter connection bolts may be inadequate to meet the requirements for identical upscaled sectional blades due to the relatively low mechanical reliability of large diameter bolts. The lightweight design of blades is indispensable for extremely large sectional blades, especially to reduce bolt stress around the trailing and leading edges.
The effect of blade separation on the natural frequencies for scaled sectional blades is the same as that for the base sectional blade, and the assembling accessibility of the scaled sectional blade is consistent with that of the base blade.
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Determining Division Location for Sectional Wind Turbine Blades
Mar 18, 2019 / Author by Qin Zhiwen Text SizeDBSSectional wind turbine blades, by dividing an intact blade into multiple segments, have the advantage of being easy to handle and transport. To determine a suitable blade division location, this study was performed to clarify some crucial aspects and challenges for sectional blades. This paper proposes a method to estimate the effects of the location of the blade division on structural, manufacturing, and assembling performance of sectional blades. The advantage of this method is the ease of the assessment process, since it can be performed at an early stage of blade design, where only the aerodynamic profile, mass density and stiffness distribution, and service fatigue loads of original blades are essential. A case study with the proposed method was carried out based on a 38-meter commercial blade. Results show that the best position for the division of sectional blades is located 20% from the blade root by balancing the three aspects listed above. The key approaches to reduce additional increases in stiffness and weight of sectional blades are related to improving the fatigue strength and the choice of low-modulus materials for connecting bolts. The effects of the division location on assembling accessibility and natural frequencies of scaled sectional blades are consistent with the basic sectional blade. Unfavorable effects occur when up-scaling the diameter of the bolts; and, harsh external loads on the connections have negative effects on the application of sectional blades with larger wind turbines. In this regard, lightweight design is indispensable to reduce bolt stress.
The location of the division on sectional blades has significant influences on connection reliability, manufacturing accessibility, and structural dynamics. This paper proposed a method to evaluate the bolt strength, fabrication accessibility, and natural frequencies at different division locations based on the characterization of the axial bolts, practical requirements for bolt assembling, and stiffness and mass density variation after blade separation. Then, a case study on a 38-meter commercial blade, as a representative of structural and aerodynamic characteristics of the modern blade, was conducted to investigate the effects of the division location on the WT performance. Finally, upscaling studies were completed to address the challenges of large sectional blades according to the geometrical similarity rule. The conclusions drawn are as follows.
The beneficial interval of the division for sectional blades is located in the middle of the blades, when considering the manufacturing and assembling of the blade connection of current blades.
The optimal interval of the location for the division for sectional blades is situated at around 20% from the blade root, taking into consideration the connection strength and natural frequency variation of the sectional blade, as well as the convenience of manufacturing and assembly.
Key approaches to reduce additional increases in stiffness and weight are to improve fatigue strength and to choose low-modulus connection bolts.
Upscale-diameter connection bolts may be inadequate to meet the requirements for identical upscaled sectional blades due to the relatively low mechanical reliability of large diameter bolts. The lightweight design of blades is indispensable for extremely large sectional blades, especially to reduce bolt stress around the trailing and leading edges.
The effect of blade separation on the natural frequencies for scaled sectional blades is the same as that for the base sectional blade, and the assembling accessibility of the scaled sectional blade is consistent with that of the base blade.