偏航状态下水平轴风力机尾迹偏移及湍流特征分析

为探索水平轴风力机偏航状态下尾迹变化情况,采用数值模拟结合理论分析的方法对不同风速、不同偏航角工况下的S翼型水平轴风力机尾迹流场进行数值分析.首先分析偏航与风力机输出功率之间关系,在此基础上分析不同偏航角工况尾迹中心的偏移情况以及尾迹处湍流强度的变化情况.结果表明:随着偏航角的增大,叶片表面的压强差减小,方位角每隔120°,叶片表面正压和负压在数值上均达到一次峰值,能造成风力机输出功率有明显损失的恶劣偏航角临界值为10°~15°;随着偏航角增大,沿轴向在1.0D之前尾迹速度中心向X轴的负方向偏移的程度增大,在此之后偏航角小于15°时尾迹中心的偏移程度增大,偏航角大于15°时减小;随着偏航角的增大,尾迹湍流强度的最大值增大,尾迹湍流强度恢复加快,尾迹缩短;偏航下风力机尾迹上下侧湍流强度分布不对称,湍流强度变化不同,使风力机尾迹湍流环境更复杂.

Analysis on wake deviation and turbulence characteristics of horizontal-axis wind turbine under yawed condition

Numerical simulations combined with theoretical analysis were used to analyze the wake of a 300 W horizontal-axis wind turbine with S-shaped airfoil under different wind speeds and yaw angles to explore variation characteristics of the wake. At first, the relationship between yaw angle and wind turbine output power was derived; then the deviation of the wake center and the variation of turbulence intensity in the wake were analyzed at different yaw angles. The results show that the pressure difference across the airfoil surfaces decreases with increasing yaw angle. The positive and negative pressure peak on the blade surfaces occurs once at every 120° azimuth angle. The critical interval of adverse yaw angle, which can cause obvious loss of wind turbine output power, is 10°-15°. The deviation degree of wake velocity center towards the negative direction of the X-axis is intensified with increasing yaw angle when the axial length is less than 1D. As the axial length being longer than 1D, the deviation degree increasing when the yaw angle is smaller than 15°, and decreases when the angle is greater than 15°. As the yaw angle increases, the maximum turbulence intensity in the wake is increased, and the wake turbulence intensity is restored quickly, thus the wake is shortened. The turbulence intensity distribution on both sides of the wake is asymmetrical and shows different variation patterns with yaw angle, resulting in the wind turbine wake having a more complicated turbulence environment.