基于瞬态液晶全表面测量技术的圆柱形孔气膜冷却特性研究

采用瞬态液晶测量技术测量了圆柱形孔的冷却特性分布,研究了动量比的影响.结果表明:大动量比下,射流脱离壁面后重新贴回壁面,冷却效率沿流向率逐渐升高,且下游孔间区域的冷却效率较高;小动量比的冷却效率分布规律与此相反.动量比越大,换热增强效果越显著;在上游区域,大动量比射流诱导出的回流涡形成了一个局部强换热区;在下游区域,各个动量比的传热系数比分布比较相似,两孔中间区域的换热强于孔中心线附近区域.

Experimental research on film cooling characteristics of cylindrical hole with transient liquid crystal measurement technique

Film cooling characteristics of cylindrical hole were measured using a transient liquid crystal measurement technique which can process nonuniform initial temperature. The influence of momentum flux ratio was tested. The results show that jets of large momentum ratio lift off the wall after ejecting out and the cooling effectiveness in the upstream is very low. However, the area covered by jet and the effectiveness increase along streamwise direction because the jets reattach the wall after lifting off, and moreover the cooling effectiveness in the region between adjacent holes is higher than that in the hole centerline region in the downstream. The cooling effectiveness distribution of small momentum ratio is just opposite to that of large momentum ratio. The normalized heat transfer coefficient distributions are similar for all momentum ratios in the downstream region. Heat transfer in the region between jets is stronger than the heat transfer in the hole centerline region because of the couple vortices. In the upstream region, a large and strong vortex is induced by the lifting off jet. And a local region with high normalized heat transfer coefficient is formed due to this vortex.