凹槽-襟翼对翼型动态失速特性影响研究

Effect of Trailing Edge Dimple-Flap on Dynamic Stall Characteristics of Airfoil

风力机复杂运行环境使叶片常处于失速环境,导致翼型升力骤降,严重影响风力机气动性能。为改善翼型流动分离,延缓失速,对凹槽-襟翼对翼型动态失速特性作用效果开展研究,并利用计算流体力学方法分析不同折合频率与翼型厚度时凹槽-襟翼对翼型气动性能的影响。结果表明:俯仰振荡过程中,凹槽-襟翼可有效提升翼型吸力面流速,降低失速攻角下逆压梯度,减缓流动分离;可提升尾缘吸力面流体下洗能力,抑制尾缘涡的形成,有效增加翼型失速攻角;同时避免翼型二次失速,翼型气动性能明显提高;较原始翼型,凹槽-襟翼翼型俯仰振荡平均升阻比增量随折合频率增加而增大,而平均升阻比提高百分率随翼型厚度增大呈整体减小趋势。

The complex operating environment of wind turbine often makes the blades in stall environment,which leads to the a sudden drop of airfoil lift and seriously affects the aerodynamic performance of wind turbine.In order to improve the flow separation of airfoil and delay the stall,the effect of dimple-flap on the dynamic stall characteristics of airfoil was studied in this paper,and the influence of dimple-flap on the aerodynamic performance of airfoil was analyzed by using computational fluid dynamics(CFD)method at different reduced frequencies and thickness of airfoil.Results show that in the pitching oscillation process,the dimple-flap can effectively improve flow rate on the suction side of the airfoil,reduce the adverse pressure gradient under the stall angle of attack,slow down the flow separation,improve fluid washing ability of the suction side of the trailing edge,inhibit the formation of the trailing edge vortex,effectively increase the airfoil stall angle of attack,avoid secondary stall at the same time,and improve airfoil aerodynamic performance significantly.Compared with the original airfoil,the average lift-drag ratio increment of dimple-flap airfoil pitching oscillation increases with the increase of reduced frequency,while the percentage increase of average lift-drag ratio decreases with the increase of airfoil thickness.