纵向波纹隔热屏气膜冷却特性数值研究

Numerical Study on Film Cooling Characteristics for

关键词:  加力燃烧室  纵向波纹隔热屏  吹风比  气膜冷却  冷却效率

Key words:  Afterburner  Longitudinal ripple heat shield  Blowing ratio  Film cooling  Cooling efficiency

摘要:

以加力燃烧室纵向波纹隔热屏为研究对象，采用数值方法，对不同吹风比、不同展向间距以及不同流向间距的纵向波纹隔热屏进行计算，获得了纵向波纹隔热屏流场流动特征和气膜冷却效率的变化。结果表明:纵向波纹隔热屏气膜冷却与常规的平板气膜冷却有着本质的区别，表现出气膜射流脱离壁面、较小吹风比下的冷却效率受结构影响大等特征；较低吹风比(M<1.3)下气膜冷却效率沿着流向呈现出起伏变化，较高吹风比(M≥1.3)下的气膜冷却效率沿程逐渐增加，最终趋于平缓；对于几何结构，吹风比约为2.5时效率达到最大值；随着展向间距的减小，气膜冷却效率逐渐增加，但增加较为缓慢；气膜冷却效率并不是一直随流向间距的减小而增加，当流向间距从4.2倍孔径减小到3.25倍孔径时，在第二周期波峰区域，冷却效率反而降低，随着流向间距进一步减小，局部冷却效率降低的区域甚至扩大，并占据了波纹隔热屏的第二个波峰。

Abstract:

Aiming at the?afterburner?longitudinal wave?heat shiled，numerical simulations were performed on different blowing ratio，different?span-wise and different flow-wise of longitudinal wave?model to?obtain?the film cooling efficiency and the flow characteristics of the?longitudinal wave heat shiled. The results show that the film cooling characteristics of the longitudinal ripple heat shield has essential difference with that of the conventional plane，performance gas jet out of the wall and the geometrical structure has more effect on the cooling efficiency of a smaller blowing ratio. Under the low blowing ratio of(M<1.3)，the film cooling efficiency fluctuates with the longitudinal wave. Under the high blowing ratio of(M≥1.3)，the film cooling efficiency increases gradually along the flow，eventually flatten out. For the geometry structure mentioned in this article，the film cooling efficiency increases with the increase of blowing ratio. When the blow ratio is about to 2.5，the film cooling efficiency reaches to the maximum. With the decrease of the span-wise spacing，the film cooling efficiency increases gradually，but the increase is relatively mild. The film cooling efficiency does not always increase with the decrease of the flow distance. When the flow distance reduces from 4.2 times the aperture to 3.25 times the aperture，at the second cycle peaks area，the cooling efficiency reduces oppositely. As the flow distance reduces further，the area，where the cooling efficiency reduces，enlarges and even occupies the second-peak of the ripple heat shield.