扇形气膜孔几何参数对气膜冷却效率的影响

气膜冷却技术广泛应用于航空发动机火焰筒、涡轮叶片等热端部件的冷却。与常规圆柱形气膜孔相比，扇形气膜孔冷却效率更高。为更全面地掌握在典型大涵道比商用航空发动机燃烧室火焰筒工作环境下扇形气膜孔气膜冷却效率随几何参数和吹风比的变化规律，采用数值模拟方法研究了扇形气膜孔的流动和换热，分析并讨论了气膜孔板厚度、气膜孔出口宽度、气膜孔入口圆柱段长度、气膜孔倾斜角以及吹风比对扇形气膜孔下游流场和热侧面气膜冷却效率分布的影响。结果表明：在小吹风比条件下，几何参数的变化对冷却效率影响很小；而当吹风比较大时，冷却效率随几何参数的变化规律可能受其他几何参数的交叉影响；几何参数的变化将诱发不同的卵形涡结构，从而对气膜孔下游的冷却效率分布造成较大的影响。

Effect of Hole Geometry on the Film Cooling Effectiveness of Fan-shaped Cooling Holes

Film cooling technology is widely adopted in aero-engine to lower the temperature of hot components such as combustor liner and turbine blade. Compared with a conventional cylindrical hole, a fan-shaped hole is expected to be more advantageous with higher film cooling effectiveness. To gain a further understanding of the influence of the fan-shaped hole geometric parameters as well as blowing ratio at the typical combustor liner operating environment of a high bypass ratio commercial aero engine, the flow and heat transfer characteristics of fan-shaped holes are numerically investigated. The influences of the plate thickness, hole exit width, cylindrical inlet length and inclination angle on the downstream flow structure and film cooling effectiveness are investigated. It is shown that geometric parameters have little effect on cooling performance at small blowing ratio, while the changing tendency of the cooling effectiveness might vary due to the cross effect of different parameters at large blowing ratios. Several kidney vortex structures were observed at different geometric parameters, which were considered to greatly influence the distribution of film cooling effectiveness on the downstream part of the cooling hole.