流动参数对合成射流控制叶栅流动分离的影响

采用大涡模拟方法、结构化网格建立了低压高负荷透平Pak B叶栅的非稳态数值分析模型,研究了不同流动参数对合成射流控制叶栅流动分离的影响.控制前随着雷诺数的减小和气流攻角的增大,叶栅流动分离区域变大,在气流攻角为5°下发生分离未在尾缘前再附的情况.合成射流控制后,不同流动参数下的流动分离都得到了有效的控制,并且在射流偏角为30°时,合成射流控制效果最好.合成射流使叶栅吸力面的流动分离位置推迟,再附位置前移,分离泡尺寸减小,叶栅吸力面的逆压梯度段缩短,吸力面边界层表面的剪切层在向下游迁移的过程中,没有发生充分的抬升,避免了大尺度涡旋的形成,并且很快地黏附于壁面,进而有效地控制了流动分离.

Influence of flow parameters on flow separation control of cascade with synthetic jet

With the application of large eddy simulation (LES) and structural hexahedral mesh, the unsteady numerical model of the low-pressure high-lift turbine Pak B cascade was established. The mechanism and influence of the flow separation control using synthetic jet were discussed in detail. The separation zone of flow becomes larger when Reynolds number decreases and angle of attack increases without synthetic jet. The separated flow has not reattached on the cascade when the angle of attack is 5°. After using synthetic jet control method, the flow separation under different flow parameters is controlled effectively. Meanwhile, the effects of synthetic jet control with different jet pitch angles were compared, and there exists an optimal jet pitch angle 30° which leads to the best flow control effect. The location of separation on the boundary layer of the cascade is delayed with synthetic jet, but the reattachment location moves forward and the size of separation bubble decreases. The adverse pressure gradient zone decreases evidently. The shear layer at the suction side moving downstream is not uplifted fully and it adheres to the wall of blade quickly, which avoids the formation of large scale vorticity and controls the flow separation.