Abstract: Based on the principle of maximum tangential force and Fourier function,it takes Darrieus vertical axis wind turbine of type H as the research object. In other words,the optimal angle of attack is determined based on the principle of maximum tangential force,and the theoretical curve of pitch variation is generated. Meanwhile,in order to ensure the periodicity and ease of implementation of the rule of pitch variation,the control points are discretized from the theoretical pitch curve, and Fourier function is used for quadratic optimization and fitting. Then,the influence of variable pitch rule on the aerodynamic performance of vertical axis wind turbines is studied from the aspects of static start-up performance and dynamic output performance by numerical simulation. The results show that the power coefficient of vertical axis wind turbines is significantly improved at different tip speed ratios,and the improvement effect is particularly significant when the tip speed ratio is low,and the peak power coefficient is increased by 13.5 % at the optimal tip speed ratio of 1.25. At the same time,the static starting performance of vertical wind turbine under each phase angle is greatly improved,and the maximum static torque coefficient is increased by 261.1 % compared with that before variable pitch. The research results can provide a reference for the optimization of aerodynamic performance of vertical wind turbines.

Key words: vertical axis wind turbine, variable pitch, power coefficient, starting performance