Abstract: CFD is used to simulate the transient flow field of 5-blades vertical axis drag-type wind turbine (VAWT) with the rotor diameter of 4 m. Computational simulation on the change of moment coefficient of the wind turbine with time under different working conditions is used to analyze the dynamic characteristics of vertical axis wind turbines. The results show that the change of moment coefficient of flow field is cyclical, the average value and the cycle of moment coefficient decrease with the increase of rotational speed, while the amplitude increases. Its average value and amplitude rise sharply with the increase of wind speed. Meanwhile, its change is the periodic modulation wave. The wind speed has significant effect on the shape of moment coefficient curve. Moreover, the optimized rotational speed and the wind energy efficiency increase with the wind speed. As the wind speed increase from 7.5 to 9 m/s, the maximum wind energy efficiency increases from 23.2% to 25.8%, and the corresponding optimized rotational speed of wind turbine increases from 13 to 19 r/min.

Key words: vertical axis drag-type wind turbine, wind power, moment coefficient, periodicity, optimization

摘要： 采用CFD对风轮直径为4 m的垂直轴5叶片阻力型风力机的瞬态流场进行数值模拟. 通过对不同入口风速和风力机转速条件下风力机流场和力矩系数随时间的变化情况的计算模拟，分析了垂直轴5叶片阻力型风力机的动态特性. 结果表明，流场和力矩系数的变化具有周期性，随转速增加，力矩系数的均值和周期均减小，振荡幅度增大；随风速增加，力矩系数均值和振荡幅度均大幅上涨. 力矩系数呈调制波形式，风速对曲线形态有较大影响. 随风速增大，风力机的最佳转速和风能利用率逐渐增加. 当入口风速从7.5 m/s增加到9 m/s时，风力机的最佳转速和风力机的风能利用率最大值分别从13 r/min和23.2%增加到19 r/min和25.8%.

关键词: 垂直轴阻力型风力机, 风能, 力矩系数, 周期性, 优化