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分别对收缩通道、扩张通道和直通道中亚声速主流条件下的气膜冷却进行数值模拟,对比分析了不同主流压力梯度、次流吹风比条件下的主流和次流流场、温度场特征。研究结果表明:引起气膜冷却效率变化和不同发展趋势的因素可归结为主流边界层厚度、主次流自由剪切混合程度、肾形涡的强度和位置等因素。相对于零压力梯度的主流条件,在吹风比较小(M=0.25)的情况下,主流的逆压力梯度一方面增厚边界层、增强了气膜射流对主流的穿透,另一方面减小了肾形涡的强度,综合作用的结果是气膜平均冷却效率提高了4.91%。在吹风比较大(M=2)的情况下,主流的顺压力梯度扼制主流边界层的发展、抑制气膜射流的穿透能力,降低肾形涡涡核的位置,从而提高气膜冷却效率达17.40%。
The numerical simulation of film cooling under the condition of sub-sonic main flow in the contraction channel, expansion channel and straight channel were carried out respectively. The flow field and temperature field under different mainstream pressure gradients and secondary flow were compared. The results show that the factors causing the change of film cooling efficiency and different development trends can be attributed to the thickness of the mainstream boundary layer, the degree of free shear mixing of primary and secondary streams, the strength and location of the kidney-shaped vortex, and other factors. Compared with the mainstream conditions of zero pressure gradient, in the case of a small blow ratio (M = 0.25), the mainstream reverse pressure gradient increases the boundary layer on the one hand and enhances the penetration of the gas film jet to the mainstream, on the other hand, The strength of the kidney-shaped vortex, the combined effect of the average film cooling efficiency increased by 4.91%. In the case of a large blower (M = 2), the mainstream of the pressure gradient to curb the development of the mainstream boundary layer, inhibit the penetration of the film jet, reduce the location of the kidney-shaped eddy vortex core, thereby enhancing the film cooling efficiency 17.40%.