Performance Enhancement of HAWT Rotor Blades by Aerodynamic Shape Optimization

In the present study, an aerodynamic shape optimization framework has been developed to enhance the aerodynamic performance of horizontal-axis wind turbine rotor blades. The present optimization framework consists of two modules. The first module conducts 3-D coupled CFD-CSD analysis for the complete rotor blade configuration to evaluate the turbine performance, and also to extract the sectional flow conditions at selected design sections along the blade span. The second module performs 2-D shape optimization of blade airfoil sections to maximize the lift-to-drag ratio under the given sectional flow conditions. When the shape optimization is completed for all selected blade sections, the aerodynamic performance and the sectional flow characteristics of the new rotor blade reconfigured from the optimized airfoil sections are evaluated again by using the 3-D coupled CFD-CSD method. The above procedure is repeated until a satisfactory convergence in the shape optimization is obtained. For validation, the present methodology was applied to the NREL phase VI rotor blade under axial flow conditions, and the aerodynamic performance of the rotor blades before and after the optimization was compared. The optimization framework was also applied to the NREL 5MW reference rotor blade. The results showed that the present optimization framework is effective and efficient in enhancing the aerodynamic performance of HAWT rotor blades at the design operating condition, as well as at offdesign conditions.