V肋对尾缘劈缝气膜冷却特性的影响

Effect of V-shaped ribs on film cooling characteristics of trailing-edge cutback

采用压敏漆技术和瞬态热色液晶技术研究了V肋对尾缘劈缝表面气膜冷却特性的影响,获得了不同吹风比及V肋宽度下2种不同尾缘劈缝表面形状的气膜冷却效率和对流换热系数分布的试验数据,并采用净热流密度值评估对比了带有V肋的劈缝结构的综合冷却性能。试验结果表明:V肋的加入对未扩张型劈缝表面的气膜覆盖产生了不利影响,在小吹风比工况下,V肋宽度对面积平均气膜冷却效率无明显影响,相同V肋宽度结构下,未扩张型劈缝表面的气膜冷却效率始终高于扩张型劈缝表面的;V肋宽度对劈缝表面换热强度的影响不明显,V肋在未扩张劈缝表面结构上展现出的强换热性优于扩张型劈缝表面结构;带有V肋的尾缘劈缝冷却结构可有效增大6.9%~26.6%的净热流密度值,V肋宽度对其无明显影响,小吹风比工况下宜将V肋应用于未扩张的劈缝表面结构,大吹风比工况下无需考虑劈缝表面形状。

The influence of the V-shaped ribs on the film cooling characteristics of the trailing-edge cutback is studied using the pressure-sensitive paint technology and the transient thermochromic liquid-crystal technology.The distributions of the film cooling effectiveness and heat transfer coefficients on different cutback surfaces with varying V-shaped rib widths at varying blowing ratios are obtained.The heat flux ratio is adopted to evaluate and compare the overall cooling performance of the turbulated cutback surfaces with V-shaped ribs.The experimental results show that the addition of V-shaped ribs has an adverse effect on the film coverage on the unexpanded surface.At low blowing ratios,the rib width has no significant effect on the area-averaged film cooling effectiveness.For the cases with the same rib width,the film cooling effectiveness of the unexpanded surface is always higher than that of the expanded surface.The effect of the V-shaped rib width on the heat transfer enhancement of the trailing-edge cutback is not obvious.The V-shaped ribs exhibit a stronger heat transfer performance on the unexpanded surface than that on the expanded surface.Compared with the primeval trailing-edge cutback,the net heat flux reduction of the case with V-shaped ribs can significantly increase by a factor of 6.9%-26.6%,and the width has no significant effect on the wall heat flux.At low blowing ratios,it is advisable to use V-shaped ribs on the unexpanded surface,while unnecessary to consider the shape of the trailing-edge cutback at high blowing ratios.