EFFECTS OF BEND-TWIST COUPLING DEFORMATION ON THE AERODYNAMIC PERFORMANCE OF A WIND TURBINE BLADE

Abstract

Comprehensive research exists on passive pitch control of wind turbines using bend-twist coupling property of composite materials. Blades with bend-twist coupling deformation can increase energy capture, improve dynamic stability, or reduce aerodynamic loads. The objectives of this work are to apply bend-twist coupling into an existing blade design and to investigate the resulting aerodynamic performance. The 41.25-meter blade was based on GE 1.5 GLX wind turbine. Aerodynamic loads were calculated using Blade Element Momentum (BEM) theory and Computational Fluid Dynamics (CFD) simulation. The resultant thrust and torque from both methods agree well. However, only the CFD can provide details of pressure distribution over the complex blade surface. Three levels of bend-twist coupling were designed for the Glass/Epoxy blade skins i.e. no coupling, low coupling, and high coupling. From Finite Element Analysis (FEA), the deflections of the three blades were slightly different while the twist angles were considerably different. The deformed geometries of the blades were then used to produce new three dimensional (3D) models for the prediction of the power coefficient (CP) by CFD. The results show that the proper bend-twist coupling laminate can improve the performance of the blade. At low wind speed, the CP is higher than the baseline blade. At wind speed greater than rated speed, however, the blades twist two much and the CP decreases below the baseline blade. Simulation of 3D blade models can help in the design of a bend-twist coupling level suitable to the blade shape and wind speed.