低压透平叶片流动分离主动控制的数值研究

Numerical Study on Active Flow Separation Control for Low-Pressure Turbine Blade

基于Langtry-Menter转捩模型的Menter SST两方程模型,通过数值求解了三维非定常雷诺时均Navier-Stokes方程,研究了雷诺数(Re)和来流湍流强度(IFSTI)对Pak-B低压透平叶片吸力面流动分离的影响.计算结果表明:该湍流模型能够较好地预测低压透平叶栅内流动特性,并能有效捕捉到叶片吸力面上流动分离和再附位置;随着Re和IFSTI的增大,叶片吸力面流动分离均有大幅度的减少.在Re和IFSTI较低的条件下,数值分析了涡流发生器(VGJ)对低压透平叶片表面流动分离的控制效果,结果表明:VGJ的引入能够有效抑制甚至消除低Re条件下叶片吸力面上的流动分离,减小总压损失和尾迹宽度.在VGJ流动控制中,存在着最佳吹气比,由此可获得最佳的流动控制效果.吹气比太小,不能有效抑制流动分离;吹气比太大,射流与主流掺混加剧,流动损失增加.当VGJ吹气比为2时,流动控制效果最佳,相对于无VGJ控制时的总压损失减少了45%.

The three-dimensional viscous unsteady Reynolds-averaged Navier-Stokes equations were employed to investigate the effects of Reynolds numbers（Re）and freestream turbulence intensity（IFSTI）on the flow separation at the suction side of the Pak-B low-pressure turbine（LPT） blade on the basis of the Menter SST turbulence model coupled with the Langtry-Menter transition model.The numerical results indicate that the turbulence simulation can predict the flow characteristics inside the LPT cascade and capture the flow separation and reattachment location at the suction side of the blade effectively.The flow separation at the suction side of the blade decreases significantly with the increase in Re or IFSTI.The control effect of vortex generator jets（VGJs）on the flow separation at the suction side of the blade was numerically analyzed at the low Reand lowIFSTI.Applying VGJs can suppress the flow separation at the suction side of the blade and reduce the total pressure loss and wake width.There is an optimum blowing ratio（B）in the flow control by VGJs.The flow separation could not be suppressed effectively with a small Band the mixing loss of jet flow and main flow could rise with a large B.The total pressure loss decreases by 45%compared with that without the control by VGJs when Bof VGJs equals 2.