Abstract: Within a circle of blade running, coefficient of torque looked like a wave line, where has two minim torque zones, performs as two brake toques. A new method to increase the performance of Φ-type wind turbine is put forward, by rebuilding the flow field at the minimal torque value area, through inducing a gust of interfere air. Based on multiply stream-tubes model, the effect of interfere air on attack angle of wind turbine in different rotation diameter R, 0.75R and 0.55R are studied, the results show that：The interfere air highly promote the attack angles in of blade element in different height and in minimal torque area, and a new maximum attack angle is created. Same time, at the optimum tip speed ratio, the performance coefficient is raised 10%.These prove that the new method positive effect on aerodynamic increasing and provide a new way for vertical axis wind turbine designing and application.The results of multiply stream tubes model are compared with the test results of reference, the two results show a good agreement, which means that the results of multiply stream tubes model has high accuracy.

Key words: attack angle, multiply stream-tubes model, performance promotion, vertical axis wind turbine