主流马赫数对气膜冷却效率与掺混损失的影响

Effect of Mainstream Mach Number on Film Cooling Effectiveness and Mixing Loss

本文采用数值模拟的方法,研究了主流马赫数(Ma_(m))对双射流孔与收缩型双射流孔气膜冷却效率与掺混损失的影响机理。结果表明:随着Ma_(m)增大,冷气贴壁性能增强,近气膜孔区域横向平均冷却效率增大。两种气膜孔结构的冷却核心主要是由下游气膜孔出流的冷气构成,上游气膜孔出流促使下游气膜孔出流贴近壁面,主射流作用形成的反肾型涡对可以促进冷气横向发展。在掺混损失方面,随着Ma_(m)增大,主射流速度、温度差异增大,气膜冷却造成的熵增不断增大,且主射流速度差异引起的熵增主要发生下游气膜孔出口附近,主射流温度差异引起的熵增主要发生在主射流掺混交界面附近。

Film cooling characteristics and mixing loss mechanism changed by the mainstream Mach number(Ma_(m))were numerically simulated for double-jet hole and contracted double-jet hole.The results showed that the lateral average cooling effectiveness near the air film hole area is promoted and the film is closer to the wall when Ma_(m) increases.The core of coolant of the two structures are mainly composed of the coolant of the downstream film hole.The coolant from the upstream hole makes the coolant from the downstream hole closer to the wall,and the anti-kidney vortex pair formed by mixing between the mainstream and coolant can prevents the film lift-off.In terms of mixing loss,the velocity and temperature difference between mainstream and coolant increases with the increase of Ma_(m),and the entropy caused by the film cooling increases.The entropy caused by velocity difference mainly occurs near the outlet of the downstream film hole;the entropy caused by the temperature difference occurs near the mixing interface between the main and film.