CALCULATING FOR AERODYNAMIC STABILITY RESPONSE OF WIND TURBINE BLADE IN FLAPWISE AND EDGEWISE DIRECTION

The measures of a force stoppage should be taken to avoid wind turbine blade damage under strong wind. The precondition for the flapwise and edgewise aeroelastic instability of a wind turbine blade on a non-rotating state was studied. Based on a simplified model, the natural frequency and vibration mode of a wind turbine blade were calculated by applying an iterative method. A modal superposition method was established, which could conveniently analyze the flapwise and edgewise vibration response of a wind turbine blade on a non-rotating state. The variation of flapwise and edgewise vibration response under different wind speed and attack angles and the distribution of a unstable wind attack angle were obtained. The results show that the response of the flapwise and edgewise vibration of a blade may be unstable even if wind speed is not too high in some attack angles, and it has great relationship with the inherent damping ratio of blades. Moreover, flapwise and edgewise instability will increase the wind load acting on blades significantly, and this kind of accretion may lead to failure of a wind turbine blade severely.