主流马赫数对超声速气膜冷却流场特性及冷却效率的影响

Effect of mainstream Mach number on cooling flow field characteristics and cooling efficiency of supersonic air film

着眼于离散孔形式的气膜冷却在高超声速飞行器热防护中的应用,为更深入探究超声速气膜冷却流场结构特征以及激波对气膜冷却的耦合作用机理,采用三维可压缩RANS数值仿真方法,研究了不同主流马赫数条件下气膜冷却的流动和传热特性。结果表明,主流超声速条件下,冷却射流的阻碍作用使得气膜冷却孔上游出现激波,且随着主流马赫数的增大,激波强度增大;激波诱导主流沿展向偏转而远离气膜冷却孔中心区域,弱化了主流和冷却射流的相互作用,降低了冷却射流在展向的掺混耗散。因此,在主流超声速条件下气膜冷却覆盖效果更佳、距离更长,且整体气膜冷却效率随着主流马赫数的增大而提高。

With a view on the application of air film cooling in the form of discrete holes in hypersonic vehicle thermal protection,and in order to further understand the structural characteristics of supersonic air film cooling flow field and the coupling mechanism of shock waves on air film cooling,a 3D compressible RANS numerical simulation method was used to investigate the flow and heat transfer characteristics of air film cooling under different mainstream Mach numbers.The results show that,under mainstream supersonic conditions,the obstruction effect of the cooling jet causes shock waves to appear upstream of air film cooling holes,and the intensity of shock waves increases with the increase of mainstream Mach numbers.The shock wave induces the mainstream to deflect along the spanwise direction and move away from the central region of the air film cooling hole.Thus,the interaction between the mainstream and the cooling jet is weakened,and the mixing and dissipating strength of the cooling jet in the spanwise direction is reduced.Therefore,the coverage effect is better and the distance is longer for the air film cooling under supersonic mainstream conditions.In addition,the overall air film cooling efficiency increases with the increase of the mainstream Mach numbers.