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 %.

Numerical simulation on flow field characteristics of a double-layer counter-rotating vertical axis wind turbine

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.