H型风力机新型变桨方案数值模拟

Numerical simulation of new variable-pitch strategy for H-type wind turbine

针对H型风力机叶片旋转至0°和180°方位角时攻角为0,力矩系数为负值且其附近较大区域也为负值或较小,由此对风力机整体气动性能产生较大负面影响这一问题,提出以改善小攻角区域性能为目标的新型变桨方案,在叶尖速比为4.5时设计桨距角变化曲线改变整机气动性能.采用动网格技术模拟叶片旋转,RNG k-ε模型模拟湍流影响,应用Fluent软件对变桨和定桨风力机进行数值模拟和分析比较.计算结果得出,变桨之后H型风力机叶片扭矩明显增大,最高提升幅度达14%;上盘面,30°~80°方位角叶片扭矩提升幅度较大;下盘面,除270°附近方位角处扭矩无明显变化外,其他方位角叶片扭矩均有较为明显的提升.变桨后风力机内流场变化也较为明显,流场内速度差异较大,内流场的低速区面积变大.从涡量云图也可得到变桨能有效地减小了叶片进入尾流区的概率,降低了尾流对整体风力机性能的影响.

When the blades of an H-type wind turbine rotate in a range of 0°-180° azimuth angles,the torque coefficient of the turbine is negative due to zero angle of attack,and the torque coefficient keeps negative or small value in the vicinity of these two azimuth angles.Therefore,the overall performance of wind turbine must suffer from a more significantly degraded effect.A new variable-pitch strategy was proposed and a pitch angle curve was designed at the tip speed ratio of 4.5 to improve the performance at small angle of attack.Additionally,the aerodynamics performance of the turbine with the new variable-pitch curve was simulated by using the sliding mesh technique and the RNG k-εturbulence model based on Fluent software,and compared with the performance of the turbine with fixed-pitch blades.The results show that the torque coefficient of the wind turbine with new variable-pitch blades increases obviously,and its increment can be as high as 14%.In the range of 30°-80° azimuth angles,the torque coefficient is improved greatly.The coefficient also exhibits a significant improvement when the azimuth angle is a range of 180°-360°（excluding 270°）.The flow field in the turbine with new variable-pitch shows a noticeable change in comparison with the turbine with fixed-pitch.Specially,the difference in velocity magnitude is larger and the low-velocity area becomes bigger in the new turbine.According to the vorticity contours,it is observed that the probability of one blade being in the wake of the other blade has been curtailed effectively by the proposed variable-pitch curve.As a result,the impact of wake on the overall performance of the turbine is relieved.