后台阶三维缝隙气膜冷却的非稳态数值模拟

Unsteady numerical investigation of back-step three dimensional slots on film cooling effectiveness

为了进一步深入了解涡轮叶片尾缘冷却结构的气体流动情况及冷却特性,在原有稳态计算模型的基础上建立了非稳态的计算模型,研究了不同吹风比下(0.5,2.0)的出口壁面冷却效率的分布情况。计算结果表明:(1)非稳态效应使得出口下游的湍流度增大,非稳态时均冷却效率的计算结果比稳态的要低一些。(2)吹风比为2.0时,二次流对出口附近流动起决定作用,并且冷气的横向掺混充分,主流二次流的上下掺混缓慢;吹风比为0.5时,主流与二次流的上下掺混剧烈,非稳态的计算结果在出口肋后附近的冷却效率比稳态结果有所提高。(3)非稳态的计算结果比稳态的计算结果更接近实验结果。

Numerical investigation was carried out to study the aerodynamics and cooling effects of trailing edge. For understanding deeply and gaining more details, an unsteady numerical model has been proposed based on steady model. The unsteady numerical simulation was conducted under different blowing ratios （0. 5, 2. 0） to show their effects on film cooling effectiveness. The computational results show that the turbulence intensity in downstream region of the outlet of trailing edge tends to be enhanced by the unsteady flow effect. Film cooling effectiveness of unsteady model is weaker than that obtained by the steady model. When the blowing ration is 0. 5, the mixture and interaction of main flow and secondary flow are rapid and fierce ; with the increase of blowing ratio up to 2. 0, the secondary flow plays dominant role on the flow characteristics near the outlet of trailing edge. The mixture and interaction of main flow and secondary flow become smooth. The unsteady computational results agree better with the experiment results than that by steady computation.