合成射流控制下低压高负荷透平叶片边界层分离大涡模拟

Large-Eddy Simulation on Boundary Separation of High-Lift Low-Pressure Turbine Blade with Synthetic Jet Control

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 understand the effect and mechanism of controlling blade boundary flow separation using synthetic jets for a high-lift low-pressure turbine（LPT） cascade,the large-eddy simulation（LES） method was adopted to investigate the unsteady separation flow characteristics of the LPT Pak-B cascade with and without flow control using synthetic jets.The results indicate that the separation location in the controlled case changes slightly but the reattachment location moves upstream significantly on the suction surface of the Pak-B blade.The adverse pressure gradient,total pressure loss coefficient and the size of separation bubble near the cascade trailing edge all decrease remarkably.On the suction surface of the blade,the most part of the shear layer attaches to the wall and the large-scale two-dimensional vortex does not exist.The spectrums of static pressure in the trailing edge of the Pak-B cascade clearly show the conversion of characteristic frequency to high frequency,the decrease of low frequency domain and variation of the large-scale vortex structure.In addition,in the blowing stage,the fluid with high energy out of the boundary layer are entrained into the boundary layer and the energy of the fluid inside the boundary layer increases to inhibit the flow separation;in the suction stage,the boundary layer in the upstream domain of the jet hole becomes thinner and the flow rate rises,inhibiting the flow separation downstream.