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为了研究合成射流对低压高负荷透平叶片边界层流动分离进行控制的效果及机理,采用大涡模拟方法对利用合成射流控制低压高负荷透平Pak-B叶栅内的非稳态流动分离特性进行了研究.在合成射流控制下的结果表明:Pak-B叶栅吸力面流动分离位置变化不大,再附位置明显提前,叶栅吸力面尾缘区域逆压梯度明显减小,总压损失系数降低,分离泡尺寸缩小;叶栅吸力面大部分剪切层黏附于壁面,也未出现大尺度二维展向涡,静压脉动特征频率向高频转移,低频脉动幅值降低,大尺度涡旋结构发生变化.通过研究还发现:在吹气过程中,边界层外部高能流体被射流卷吸进入边界层内,边界层内流体能量增大进而抑制了分离;在吸气过程中,射流孔上游区域边界层厚度减小,流速增大,从而抑制了下游流动分离.
In order to study the effect and mechanism of the synthetic jet on the flow separation of low pressure and high load turbine blade boundary layer, a large eddy simulation method was used to control the unsteady flow separation characteristics of the low pressure and high load turbine Pak-B cascade Under the control of synthetic jet, the results show that the flow separation position of Pak-B cascade suction face is not changed much, the re-attachment position is obviously advanced, the reverse pressure gradient in the trailing edge region of suction cascade decreases obviously, and the total pressure loss The coefficient decreases and the size of the separation bubble shrinks; most of the shear layer on the suction side of the cascade adheres to the wall, nor does the large-scale two-dimensional vorticity vortex, the characteristic frequency of the hydrostatic pulsation transfer to the high frequency, the amplitude of the low frequency pulsation decreases, The results show that during the blowing process, the high-energy fluid outside the boundary layer is entrained into the boundary layer by the jet and the fluid energy in the boundary layer increases to restrain the separation. During the process of suction, The thickness of the boundary layer in the upper part of the pore decreases, and the velocity of flow increases, thus restraining downstream flow separation.