不同等离子体激励强度下气膜冷却特性的大涡模拟研究

Large Eddy Simulation of Film Cooling Flow Characteristics under Different Plasma Actuation Strengths

关键词:  大涡模拟  气膜冷却  等离子体激励  平板  肾形涡对

Key words:  Large eddy simulation  Film cooling  Plasma actuation  Flat plate  Kidney shaped vortex

摘要:

为进一步改善燃气轮机叶片气膜冷却效果，采用大涡模拟(LES)方法对不同等离子体激励强度情况下的平板气膜冷却流场进行了数值模拟研究。结果表明:与无等离子体激励时相比，等离子体激励强度逐渐增至10时射流出口最大流向与法向速度分别增大了16%和7%左右，并移向气膜孔的尾缘，而气膜孔前缘附近的法向速度约减小了4%，从而减少了射流迎风面上冷、热气流的掺混；等离子体对气膜孔下游回流区的动量注入效应使得回流区内的流向速度增大，抑制了横流绕流分离旋涡的发展；等离子体气动激励削弱了肾形涡对的强度及其抬升冷却射流的能力，从而提高了气膜冷却效率，中心线气膜冷却效率随激励强度的增大而升高，当激励强度为10时中心线气膜冷却效率最大提高了55%。

Abstract:

In order to improve the film cooling efficiency of the gas turbine blade，effects of the strengths of the plasma actuation on the flat plate film cooling flow characteristics were conducted using large eddy simulation (LES). Results show that compared with the non-plasma actuation case，as the plasma actuation strength grows larger，the maximum jet exit streamwise and vertical velocities increase 16% and 7%，respectively，and shift to the trailing edge，but the vertical velocity near the leading edge decreases 4%，thus the mixing process between the jet and the crossflow at the upwind side of the jet is suppressed. Meanwhile，due to the momentum injection effect of the plasma actuation，the streamwise velocity in the reverse flow region is enhanced and the size of the crossflow separation vortex pair downstream of the cooling hole is reduced. Furthermore，the plasma actuation weakens the strength of the kidney shaped vortex and prevents the jet from lifting off the wall. Therefore，the centerline film cooling efficiency rises with increasing the plasma actuation strength，and it is improved by 55% at most when the plasma actuation strength is 10.