壁面换热条件下高负荷压气机叶片分离剪切层转捩机理研究

Numerical Investigations on the Transition Within Separated Shear Layers Over Highly Loaded Compressor Blades With Heat Transfer

本文采用大涡模拟(LES)方法研究了低雷诺数(Re=1.5×10^(5))下不同壁面条件(绝热壁和等温冷却壁)对两种不同负荷水平的压气机叶片(IET-ULF1和IET-ULF2)分离剪切层转捩特性的影响。研究表明:壁面冷却减小了近壁气流运动黏性,削弱湍流耗散对分离剪切层应起的稳定作用。对于压气机叶片IET-ULF1,壁面冷却诱发剪切层更快失稳,显著加速转捩过程;对于具有更高负荷水平的叶片IET-ULF2,壁面冷却对转捩的调控效果相对较弱。分离剪切层下方回流掺混、大尺度三维发卡涡破碎以及近壁低能流体的“上喷–下扫”过程决定了湍流脉动水平和气动损失。当存在壁面冷却时,分离剪切层转捩过程涡动力学强度受到抑制,湍流脉动产生速率减小,延缓了边界层发展,IET-ULF1和IET-ULF2叶型损失分别降低18.2%和22.1%。

Large eddy simulations(LESs)were conducted to investigate the effects of wall heat transfer on the transition process within separated shear layers over two highly loaded compressor blades(adiabatic and isothermal cooled wall conditions)at a Reynolds number(Re)of 1.5×10^(5).Results showed that wall cooling reduced the flow kinematic viscosity of the near-wall fow,which weakened the relative role of turbulent energy dissipation in suppressing the rapid amplification of amplifications.For the compressor blade IET-ULF1,the separated shear layers were more prone to being destabilized,and the transition process was accelerated.However,for the compressor blade IET-ULF2 with a higher loading level,the positive effect of wall cooling on promoting the transition process was much weaker.It was found that the reverse fow mixing,breakdown of large-scale threedimensional hairpin vortices,and the ejection-sweeping process of the near-wall fow determined the generation of turbulent fuctuations and the resulting loss.Compared with the adiabatic wall,the vortex dynamics on the cooled wall were weakened,and the generation rate of turbulent fuctuations declined.Thus,the growth rate of boundary layers was decreased,and the profile losses of the IET-ULF1 and IET-ULF2 were reduced by 18.2%and 22.1%,respectively.