小孔辅助射流提高气膜冷却效率的机理分析

采用数值计算手段,模拟普通的圆柱形单孔结构和小孔辅助射流结构在不同吹风比下的流动和换热,侧重通过直观演示气膜孔下游反向对旋涡对(肾形涡)的生成、发展以及相互作用过程,揭示小孔辅助射流改善气膜冷却效果的机理.结果表明:与单孔结构相比,小孔辅助射流结构,由于小孔射流的干涉作用,主孔射流形成的肾形涡的尺度和强度均有较大程度的减小,冷气射流与主流的掺混减弱,对冷气的向上抬升作用减小,避免了冷气穿透主流脱离壁面,大大提高冷却效率.随着吹风比的增加,与圆柱形单孔相比,气膜冷却效果改善更加明显.

Analysis on improvement of film cooling effectiveness with small coolant jets

The primary focus of this paper is to further understand the flow and heat transfer characteristics of a special film cooling configuration where in the main film cooling hole is accompanied by two smaller jet holes.The adiabatic effectiveness and the interaction between the main hot stream and the coolant jets were simulated and analyzed by comparing with the standard single hole structure at different blowing ratios.It is found that the presence of smaller jets decreases the size and strength of the counter-rotating vortex pair of the main coolant jet and so does its mixing with the main hot stream.The coolant jets remain much closer to the surface.This avoids jets lift-off for the stand single hole structure at high blowing ratio.The surface adiabatic effectiveness value is enhanced as expected.A higher blowing ratio means more obvious improvement of film cooling effectiveness.