利用上游斜坡改善气膜冷却效率的数值研究

Numerical investigation on improving film cooling effectiveness with an upstream ramp

关键词:  航空、航天推进系统  薄膜冷却  斜坡  流动传热  数值计算

Key words:  Aerospace propulsion system  Film cooling  Ramp  Flow and heat transfer  Numerical calculation

摘要:

为了获得气膜孔上游放置斜坡对气膜冷却效率的影响规律,采用数值模拟方法研究了斜坡的台阶高度分别为0.3D,0.5D,0.75D,1.0D和1.5D时不同吹风比下的流动过程和冷却效率分布情况,并与常规气膜孔冷却结构形式进行对比,以揭示斜坡对气膜冷却效率改善作用的影响机理。研究表明,在气膜孔上游设置斜坡,延缓了主流通过反向涡对对冷却气流的掺混作用,反向涡对强度减弱,冷却气流出流后的贴壁效果更好,提高了气膜冷却效率,随着吹风比的增加,斜坡高度较高时无论是在气膜孔中心线处还是在两气膜孔之间区域的冷却效率值都得到大幅度的提高。

Abstract:

To investigate the effects of an upstream ramp on film cooling effectiveness,a numerical study of the distributions of the flow fields and cooling effectiveness was performed with different heights of upstream ramps in several ratios.Their distributions were compared with the distributions of baseline holes to reveal the effects of the upstream ramps on the film cooling performance.The results show that the upstream ramp delays the entrainment of hot gases by the counter-rotating vortex pairs(CRVP) in the film-cooling jets and reduces the effect of this CRVP,so the film effectiveness is higher with better coverage on the hot side.Both the improvement of the centerline adiabatic effectiveness and the improvement of the laterally averaged adiabatic effectiveness are significant at higher blowing ratio with higher upstream ramp.