不同攻角下涡轮叶栅边界层分离再附的大涡模拟研究

Compressible LES of Unsteady Boundary Layer Separation and Reattachment in Turbines:Influence of Incidence Angle

本文采用三维可压缩N-S方程的大涡模拟方法,对低压涡轮叶栅T106A边界层的演化过程进行研究,分析攻角的变化对吸力面边界层的分离再附位置、分离泡长度等流动现象的影响。基于弦长和出口速度的雷诺数为1.1×10^5,出口马赫数为0.4。研究结果表明：来流攻角为＋7.8°时,叶栅表面静压系数、吸力面边界层分离和再附位置与实验结果吻合较好;边界层分离后在三维不稳定性作用下依次形成Λ涡、发卡涡等结构,最终发生转捩;当来流从正攻角向负攻角变化时,吸力面边界层的分离点向下游移动,分离泡长度逐渐减小。

In order to predict and analyze the phenomenon of separation,reattachment as well as separation bubble at different incidence angles.Self-developed large eddy simulation（LES） program of compressible N-S equations was used to simulate the flow field and the evolutionary process of the boundary layer in T106 A low-pressure turbine cascade.The outlet Mach number is 0.4 and the Reynolds number is 1.1×10^5 based on the exit isentropic velocity and the axial chord length.The computational results show the time-averaged pressure coefficient on the blade surface and the points of separation and reattachment at ＋7.8° incidence angle compare well with experiment data.The boundary layer separates from the suction side and the hairpin vortexes are formed in succession.The rapid growth of the hairpin vortex eventually leads to transition in boundary layer.As the incidence angle changes from positive to negative,the separation point on the suction side moves downstream and the length of the separation bubble is gradually shorter.