Optimized design of H-VAWT blade airfoils profile considering range of angle of attack

Abstract: Wind energy, as a green and renewable energy, has attracted increasing attention from all over the world. Currently, rapidly developed wind turbine can transfer wind energy into electricity power. A H-type vertical axis wind turbine (VAWT) has become a research focus to design new types of VAWT with high aerodynamic performance, due to its simple structure, easy installation, high adaptability, no need of yaw device, and feasible blade manufacturing. Therefore, H-type VAWT has become a focus on how to design new VAWT with high aerodynamic performance. The aerodynamic performance design of VAWT has very important influence on the power characteristics of wind station. Most previous studies on VAWTs were reported to predict accurately the energy efficiency and the effects of parameters, such as the number of blades, solidity, chord length, and pitch angle, on power coefficients using CFD simulation. As to the airfoil optimization design of H-type VAWT blade, most airfoils profile were designed based on an angle of attack or narrow range of angles of attack when determining the optimal angle of attack. In order to solve the problem that the airfoil profile of vertical axis wind turbine is designed under a single angle of attack, without considering the condition of large variation range of blade angle of attacks when the vertical axis wind turbine is working. In this study, an optimization design was proposed for the airfoil profile of VAWT blade under a certain angle of attacks. Firstly, the aerodynamic shape of blade airfoil in a VAWT was expressed in the combination of class function and B-spline function. As such, the optimal objective function of blade airfoil was set to the sum of tangential force coefficients under a certain angle of attacks. a NACA-0015 symmetric airfoil was chosen as the original airfoil when considering three ranges of angles of attack. Furthermore, the particle swarm optimization (PSO) and the aerodynamic performance prediction RFOIL software were used to optimize the aerodynamic shape of H-type VAWT blade. Finally, the optimized VAWT blade airfoil was addressed over the initial airfoil, particularly on the performance for utilization ratio of wind energy, torque coefficient, and vorticity distribution. The results showed that compared with the original vertical axis wind turbine, the new vertical axis wind turbine blade can effectively improve the torque coefficient and power coefficient of the vertical axis wind turbine. To be exactly, when the tip speed ratio is 1.9, the power coefficient reaches the peak which the maximum power coefficient of the new vertical axis wind turbine was 0.362 increased by 8.45% comparing to the original vertical axis wind turbine. In addition, the wake of the new H-type VAWT was effectively improved, which attributed to the new airfoil that could effectively suppressed the vortex shedding on the blade surface. This study has a good reference for how to the design the vertical axis wind turbine blade airfoil profile with high performance.