带造型凹坑孔的平板气膜冷却特性研究

Investigation on the Film Cooling Efficiency on a Plain Surface with Hole Embedded in Contoured Crater

设计了一种造型凹坑冷却孔结构,采用数值求解雷诺平均Navier-Stokes方程的方法,研究了造型凹坑孔结构对平板气膜冷却性能的影响,并利用已有的实验数据考核了数值方法的有效性。通过计算得到了6种吹风比、3种凹坑深度条件下带造型凹坑孔的平板气膜冷却性能,并与常规圆孔进行了对比。研究结果表明:在考核的7种湍流模型中,Realizable k-ε湍流模型可以较好地模拟平板壁面的冷却性能;造型凹坑孔可以产生一对阻碍肾形涡发展的反向旋涡,降低冷却流体与高温主流的掺混作用,增加冷却流体在周向上的覆盖,从而提高气膜冷却效率;相比于常规圆孔结构,造型凹坑孔可以有效地提高轴向中心线及周向平均气膜冷却效率,在不同吹风比条件下,造型凹坑孔的气膜冷却效率在轴向长度为3倍孔径的区域提高了20%~200%,在3倍到10倍孔径的区域提高了10%~25%;在所研究的3种凹坑深度中,凹坑深度为圆孔直径的0.7倍时平板气膜冷却性能最优。

A contoured crater cooling hole was designed.With solutions of RANS(Reynolds-averaged Navier-Stokes)equations,the film cooling efficiency on a plain surface with cooling hole embedded in contoured crater was investigated.With the existing experimental data,the reliability of numerical methods was validated.Then,the influences of blowing ratio and crater depth on the cooling efficiency were studied.The numerical results for plain surface with cooling hole embedded in contoured crater were also compared with that of the conventional round hole configuration.The results show that,among all selected turbulence models,the Realizable k-εturbulence model has the superior accuracy in predicting the cooling efficiency on plain surface.The cooling hole embedded in contoured crater is able to generate a pair of reverse vortices that hinder the development of kidney vortices,reducing the mixing effect of coolant and high temperature mainstream.Correspondingly,the coverage of cooling flow on a plain surface in circumferential direction is increased significantly,thereby improving the film cooling efficiency on the plain surface.Compared with the conventional round hole configuration,the lateral-averaged film cooling efficiency on plain wall with contoured crater hole is increased by 20%-200%at the vicinity of cooling hole(X/D<3),and the cooling efficiency increased by 10%-25%downstream the cooling hole(3<X/D<10).Among three studied crater depths,the optimal film cooling efficiency on the plain wall is achieved with the crater depth of 0.7 D.