考虑攻角范围的垂直轴风力机叶片翼型优化设计

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

    • 摘要: 为解决目前垂直轴风力机叶片翼型都是在单一攻角下进行设计而忽略运行时叶片攻角变化范围大的问题,该研究提出一定攻角范围下垂直轴风力机叶片翼型廓线优化方法。首先采用类函数与B样条函数相结合的方法来表征翼型气动外形,以一定攻角范围下的切向力系数之和作为叶片翼型优化的目标函数。进一步利用粒子群算法和翼型气动性能预测软件RFOIL对H型垂直轴风力机叶片翼型气动外形进行优化设计。最后从功率系数、力矩系数、涡量分布和速度分布这4个方面讨论优化翼型较初始翼型的优越性。结果表明:相比原始垂直轴风力机,优化后的垂直轴风力机翼型能有效提高风力机的力矩系数及功率系数,其最大功率系数为0.362,提高了8.45%。研究结果对于设计高性能垂直轴风力机翼型具有很好的借鉴意义。

       

      Abstract: 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.

       

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