不同横槽结构对气膜冷却效率影响的数值研究

Numerical investigation on the effect of different transverse trench configurations on film cooling effectiveness

在不同吹风比下,对几种带有横槽的离散孔气膜冷却结构的流动过程和气膜冷却效率进行了数值模拟,分析了在相同槽深的情况下,宽槽、窄槽和斜槽对冷却效率的影响;并将斜槽的模拟结果与异型孔的结果进行了对比.结果表明:在横槽的作用下,由于面积的突扩,使得气膜孔射流向主流的穿透能力有所降低;在横槽下游,二次流能够更好地贴附壁面,气膜冷却效率有一定的提高;在低吹风比下,斜槽冷却效果明显,而在高吹风比下,窄槽冷却效果较明显;斜槽的气膜孔冷却效果优于异型孔;宽槽内出现了横向涡,窄槽内出现了涡锥,斜槽内出现了反向涡对,槽下缘处的固壁对冷却气流的横向扩散有重要作用.

The flow fields and cooling effectiveness of the film cooling from a row of cylindrical angled holes embedded in different transverse slots configurations were investigated numerically in several blowing ratios, to reveal the effects of narrow trench, wide trench, and inclined trench with the same trench depth on the film cooling performance from the flowing mechanism. The simulation results of inclined trench model were compared with experimental data of shaped holes. It is found that, for the embedded holes, the jet injected into the slot loses momentum at the exit of the slot; the penetration of the film secondary flow into the cross flow is suppressed and the secondary flow is pushed downwards on to the surface, resulting in better coverage. At low blowing ratio, the inclined trench has superior cooling effect, while at high blowing ratio the narrow trench has superior cooling effect. A lateral vortex appears in the wide trench; a pair of taper vortex appear in the narrow trench; and a pair of counter rotating vortex appear in the inclined trench. The trailing edge wall of the trench plays an important role in the lateral diffusion of the cooling film.