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Journal of ZheJiang University (Engineering Science)  2019, Vol. 53 Issue (11): 2223-2230    DOI: 10.3785/j.issn.1008-973X.2019.11.021
Energy Engineering     
Numerical simulation on flow field characteristics of a double-layer counter-rotating vertical axis wind turbine
Wen-hao XU(),Zhan QIU,Bo-ping YU,Fu-xin WANG*()
School of Aeronautics and Astronautics, Shanghai Jiao Tong University, Shanghai 200240, China
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Abstract  

Aiming at the low power coefficient problem caused by dynamic stall during the operation of vertical axis wind turbines (VAWTs), a double-layer counter-rotating VAWT was proposed. By setting the counter-rotating auxiliary blade in the inner of the traditional VAWT, the flow field of the VAWT is improved, thereby the power coefficient is increased. The computational fluid dynamics (CFD) numerical simulation of the proposed wind turbine and traditional VAWT has been carried out. The difference between the flow field characteristics of the two wind turbine configurations under different tip speed ratios (TSRs), and the influence of the initial operating phase difference between inner and outer layers of the double-layer wind turbine were studied. Results show that the time-averaged torque coefficient of the inner auxiliary blade is positive, and extra power input is not required. Results of the torque coefficient of the outer blade show that the arrangement of the proposed wind turbine improves the time-averaged power generation efficiency by reducing the peak value of torque coefficient of the main blade in the upstream, as well as greatly improving the torque coefficient of the main blade in the downstream. The vortex structure in the flow field was analysed, and the results indicates that the main reason for the increase of torque coefficient is that the inner auxiliary blades restrain the dynamic stall phenomenon of the main blade. Especially when the tip speed ratio was 1.85 and the phase difference was 90°, the time-averaged torque coefficient of the main blade of the proposed configuration was increased by 43.92%, compared with that of the traditional VAWT.



Key wordsvertical axis wind turbine      tip speed ratio      double-layer wind turbine      counter-rotating      dynamic stall      phase difference     
Received: 25 September 2018      Published: 21 November 2019
CLC:  TK 83  
Corresponding Authors: Fu-xin WANG     E-mail: 578009935@qq.com;fuxinwang@sjtu.edu.cn
Cite this article:

Wen-hao XU,Zhan QIU,Bo-ping YU,Fu-xin WANG. Numerical simulation on flow field characteristics of a double-layer counter-rotating vertical axis wind turbine. Journal of ZheJiang University (Engineering Science), 2019, 53(11): 2223-2230.

URL:

http://www.zjujournals.com/eng/10.3785/j.issn.1008-973X.2019.11.021     OR     http://www.zjujournals.com/eng/Y2019/V53/I11/2223


双层反转垂直轴风力机的流场特性数值模拟

针对由垂直轴风力机运行过程中的动态失速问题所导致的功率系数较低的问题,提出双层反转构型的垂直轴风力机. 通过在传统垂直轴风力机内侧设置反转向辅助叶片的方式,改善垂直轴风力机流场,从而提高其功率系数. 将该风力机与传统垂直轴风力机进行计算流体动力学数值模拟对比分析,研究不同叶尖速比情况下两者流场特性的差异以及双层风力机内外层风轮起始运转相位差的影响. 通过计算得到的内层辅助叶片的时均扭矩系数为正,不需要额外功率输入. 外层叶片的扭矩系数结果表明,采用这种构型会降低叶片上游区域扭矩系数的峰值,同时大幅提高下游区域扭矩系数,从而实现时均发电效率的提高. 对流场中涡系结构进行分析,结果表明,功率系数提升的原因是内层辅助叶片的反向旋转抑制了主叶片的动态失速. 特别是当叶尖速比为1.85时,在初始相位差为90°的对比算例中,与传统垂直轴风力机相比,新构型下的叶片时均扭矩系数提高了43.92 %.


关键词: 垂直轴风力机,  叶尖速比,  双层风轮,  反转,  动态失速,  相位差 
Fig.1 Schematic diagram of double-blades H-VAWTs
Fig.2 Schematic diagram of configuration of double-layer counter-rotating VAWTs and drive mechanism
网格名称 空间位置坐标/m
近场网格 最小值(?2.00,?2.00,?0.51);
最大值(4.00,2.00,0.51)
远场网格 最小值(?5.00,?5.00,?0.51);
最大值(15.00,5.00,0.51)
外层风轮网格 内层半径0.65;外层半径1.05
内层风轮网格 半径0.65
内层网格 半径0.65
Tab.1 Position of grid blocks
Fig.3 Computational domain and fine gird blocks
Fig.4 Comparison and validation of blade torque coefficient of single-layer configuration
Fig.5 Vorticity contours of single-layer configuration and double-layer configuration at phase angle of 0° in three kinds of tip speed ratios
Fig.6 Comparison of main blade torque coefficients of single-layer configuration and double-layer configuration in three kinds of tip speed ratios
Fig.7 Vorticity contours in different moments with phase differences between inner and outer blades of 0° and 90° respectively
Fig.8 Main blade torque coefficient curves with different configurations
Fig.9 Time-averaged torque coefficient of main blade with different tip speed ratios
Fig.10 Improvement percent of main blade torque coefficient in different tip speed ratios
Fig.11 Vorticity contours of four VAWT configurations with phase angle of 0°
Fig.12 Comparison diagram of instantaneous torque coefficient and time-averaged power coefficient
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