主流攻角对双射流孔气膜冷却特性的影响

应用压力敏感漆技术,在平板上测量了不同主流攻角(i=-30°,-20°,-10°,0°,10°,20°,30°)下双射流孔的气膜冷却效率,并利用计算流体动力学(CFD)计算得到的流场对气膜冷却效率的规律进行了解析。所研究的双射流孔结构的孔间无量纲横向距离为0.5,孔间无量纲流向距离为3;射流与主流密度比为1.0,吹风比分别为0.5、1.0、1.5、2.0。结果表明小的主流攻角(i=-10°,0°,10°)下,流场中存在反肾型涡对或挤压作用,气膜层与壁面贴附良好,气膜冷却效率最高;大正值攻角(i=20°,30°)下,虽然气膜覆盖面积大,但反肾型涡对退化,气膜冷却效率下降;大负值攻角(i=-20°,-30°)下,流场中有肾型涡对,且气膜横向覆盖受限,气膜冷却效率最低。

Effects of mainstream angles of attack on film cooling characteristics of double-jet film cooling holes

Film cooling effectiveness of double-jet film cooling holes was measured using pressure sensitive paint at various mainstream angles of attack (i=-30°, -20°, -10°, 0°, 10°, 20°, 30°) on a flat plate, and the flow field obtained by computational fluid dynamics (CFD) was used to analyze the film cooling effectiveness. The dimension less spanwise distance was 0.5, the dismension less streamwise distance was 3; the density ratio was 1.0, and the blowing ratio varied as 0.5, 1.0, 1.5, 2.0. The results showed that, at small mainstream angles of attack (i=-10°, 0°, 10°), the film layer attached well with wall because of the anti-kidney vortex pair or the pressing effect in the flow field, contributing to the highest film cooling effectiveness; at large positive angles of attack (i=20°, 30°), the anti-kidney vortex pair degenerated though the coverage area of film was the largest, the film cooling effectiveness became lower; at large negative angles of attack (i=-20°, -30°), there existed kidney vortex pair, the lateral coverage of the film was limited and the film cooling effectiveness was lowest.