A Direct Approach of Design Optimization for Small Horizontal Axis Wind Turbine Blades

The performance of a wind turbine rotor depends on the wind characteristics of the site and the aerodynamic shape of the blades. The blade geometry determines the torque and the power generated by the rotor. From aerodynamic point of view, an economic and efficient blade design is attained by the maximization of rotor power coefficient. For small wind turbine blade design, there are some factors different from large blade. Such as, the small ones experience much lower Reynolds number flow than the large ones, thus large wind turbine airfoils may perform very poorly in small applications. The small turbines are self-started at lower wind speed, thus the hub and tip parts are vital for the starting-up torque which should be able to conquer the resistance of the generator and the mechanical system. This paper presents a direct method for small wind turbine blade design and optimization. A unique aerodynamic mathematical model was developed to obtain the optimal blade chord and twist angle distributions along the blade span. The airfoil profile analysis was integrated in this approach. The Reynolds number effects, tip and hub effects, and drag effects were all considered in the design optimization. The optimal chords and twist angles were provided with series of splines and points and three-dimensional blade models. This approach integrates blade design and airfoil analysis process, and enables seamless link with computational fluid dynamics analysis and CNC manufacturing.