考虑三维旋转和动态失速的风力机气动力建模

Aerodynamic Modelling of Wind Turbines Concerning Rotational Augmentation and Dynamic Stall

由于叶片流动分离和失速机理较为复杂,且缺乏深入理解,风力机非定常、非线性气动载荷难以准确预测。针对动态失速和三维旋转效应,基于Leishman-Beddoes模型和Bak模型,预测偏航条件下NREL Phase VI叶片的气动响应,并与实验值和二维数值模拟结果对比。考虑动态失速和三维旋转效应,有效提高叶片剖面升力的预测精度。但是,非线性段气动力的模型预测值与实验值偏差较大,表明三维旋转效应和动态失速耦合作用显著。从叶尖到叶根,局部入流迎角的平均值和幅值显著增加,气动力的非定常程度逐渐升高,因此耦合作用主要存在与叶根处。耦合作用改变了动态失速特性,使得30%剖面气动力迟滞环从二维的顺时针变为逆时针。二维和三维气动力的差别主要体现在下风侧,表明下风侧耦合作用大于上风侧。

Unsteady nonlinear aerodynamic loads of wind turbines are challenging to predict accurately,due to the complicated mechanism and poor understanding of flow separation and blade stall.This paper considered dynamic stall and rotational augmentation based on the Leishman-Beddoes model and Bak model,respectively.These models were used to predict the aerodynamic responses of NREL Phase VI blade undergoing yawed inflow.The predicted results were compared with the experimental data and two-dimensional numerical simulations.Considering both dynamic stall and rotational augmentation could effectively improve the predictive accuracy.However,the predicted results show a clear difference from the experimental data,implying a significant combined effect of rotational augmentation and dynamic stall.The mean value and amplitude of local angle of attack variation gradually increase from blade tip to blade root,thereby raising the unsteadiness in aerodynamic loads.This also manifests that the combined effect mainly exists on the inboard blade.The combined effect can change the direction of aerodynamic hysteresis loop from two-dimensional clockwise to anticlockwise at 30% span.The difference between two-dimensional and three-dimensional aerodynamic forces mainly lies on the downwind side,suggesting a stronger combined effect compared to the upwind side.