心形孔气膜冷却特性的数值模拟

为进一步提高航空发动机热端部件的冷却效率,提出了心形气膜冷却孔结构,利用数值模拟分析心形孔的流场特性和冷却特性,并通过与常规圆形孔计算结果的对比,揭示心形气膜孔强化冷却的物理机制.计算结果表明:与圆形孔相比,心形孔能有效抑制反向旋转涡对的生成,冷却气流的贴壁效果得到明显提高,同时心形孔的扩展出口结构使得冷却气流在展向上的分布更为均匀,展向平均气膜冷却效率得到显著提高;在吹风比为0.5~2.0内,心形孔的全局平均冷却效率相对于圆形孔分别提高了70.93%,246.94%,598.9%和879.07%;从热流比分布来看,心形孔在吹风比为1.5下的热流比值最低,表征在吹风比为1.5下心形孔对壁面的保护效果最好. 

Numerical simulation on film cooling characteristics of heart shaped hole

A heart shaped film cooling hole was firstly presented to improve the cooling effectiveness of modern gas turbine. The flow field performance and cooling performance were analyzed through numerical simulation. The result of heart shaped film cooling hole was compared with that of cylindrical film cooling hole. The comparisons show that the heart shaped film cooling hole can reduce the strength of counter rotating vortex pair, thus the coolant-surface attachment is improved. For heart shaped film cooling hole, the expansion structure on the hole exit allows the coolant to flow along spanwise direction, resulting in a better spanwise averaged film cooling effectiveness than that of cylindrical hole. By comparing with cylindrical hole, the heart shaped hole increases the film cooling performance. The heart shaped film cooling hole shows enhancements of approximately 70.93%, 246.94%, 598.9% and 879.07% at blowing ratio of 0.5-2.0, respectively. In terms of heat-flux ratio, the hearted shaped hole shows the lowest heat-flux ratio at blowing ratio of 1.5, indicating that the hearted shaped hole provides the best film cooling performance at blowing ratio of 1.5.