凹槽状动叶顶部非定常气膜冷却性能的研究

Investigations of Unsteady Film Cooling Performance on Rotor Squealer Tip

采用数值求解三维(RANS)方程的方法,开展了燃气透平级在动静叶干涉下凹槽状动叶顶部定常和非定常气膜冷却性能的研究.定常计算结果表明:吹风比为1.0时的动叶顶部气膜冷却有效度优于吹风比为0.5和1.5的情况.在吹风比为1.5时,气膜冷却气流脱离槽底壁面并导致气膜冷却有效度降低.非定常计算结果表明:在动静干涉下凹槽状动叶顶部内流动和气膜冷却有效度具有高度的非定常特征;上游静叶尾迹和通道涡周期性地与动叶顶部间隙泄漏流相互作用,使得动叶顶部凹槽底部分离线发生变化,冷却气流覆盖槽底壁面的位置和面积也发生相应的改变,进而导致槽底和槽侧面的气膜冷却有效度发生变化;定常计算得到的凹槽底部气膜冷却有效度的预测值大于非定常计算的时均结果.

The steady and unsteady film cooling performance together with leakage flow and heat transfer characteristics for a typical gas turbine stage with a squealer tip is numerically investigated using the three-dimensional Reynolds-averaged Navier-Stokes（RANS）solutions.The influence of the film blowing ratio on the film cooling effectiveness in the squealer tip is discussed.The results calculated for the steady film cooling show that the film cooling effectiveness with a blowing ratio of 1.0 is greater than that of 0.5 or 1.5.However,the cooling gas will be separated at the adjacent downstream area of the film holes when the blowing ratio is 1.5.The results for the unsteady film cooling show that the flow and the film cooling effectiveness in the rotor squealer tip has significant unsteady characteristics under the interaction between the rotor/stator blade rows.The separation line at the bottom of the rotor squealer tip changes because the upstream wake and passage vortex interact periodically with the leakage flow in the rotor blade tip.The covering position and area of the film cooling vary accordingly.This unsteady flow behavior results in variation of the film cooling effectiveness at the bottom and sidewall of the rotor squealer tip.The film cooling effectiveness at the bottom of the rotor squealer tip achieved by the steady numerical prediction is greater than that by the unsteady numerical simulation.