基于瞬态液晶测量技术的收缩-张形孔气膜冷却特性

 采用一种进行全表面测量的瞬态液晶测量技术测量了新型气膜孔（收缩-张形孔）的气膜冷却特性，研究了动量比对冷却效率和换热系数的影响，并与传统的圆柱形孔气膜冷却特性进行了对比，结果表明：收缩-扩张形孔中心线附近区域的冷却效率相对较低，而两孔之间区域的冷却效率相对较高，与圆形孔分布规律相反；在上游区域，两孔中间区域的换热系数比相对孔中心线附近区域较高，而在下游区域，两孔中间区域的换热系数比相对孔中心线附近又较低，与圆形孔相比也有较大不同。相对于圆柱形孔，收缩缝形孔的平均换热系数比在上游较高，在下游较低；收缩-扩张形孔喷出气膜对下游壁面区域的有效覆盖率远大于圆柱形孔，其展向平均冷却效率明显高于圆柱形孔；收缩-扩张形孔在动量比为2时的平均冷却效率最高。

Film Cooling Characteristics of Converging-xpanding Hole with Transient Liquid Crystal Measurement Technique

Film cooling characteristics of a converging-expanding hole were measured using a transient liquid crystal measurement technique which could process nonuniform initial temperatures. The impact of momentum flux ratio was tested, and comparison was carried out between the converging slot-hole and cylindrical hole. The results show that the film cooling characteristic distributions of a converging-expanding hole are quite different from those of cylindrical holes because of their different flow structures. Jets from the converging-expanding hole cover the entire downstream surface. And the cooling effectiveness in the hole centerline region is greater than that in the region between adjacent holes for a converging-expanding hole. In the upstream region, interaction of adjacent jets enhances heat transfer in the region between adjacent holes for a converging-expanding hole. However, in the downstream region the couple vortices make heat transfer lower than that in the centerline region. Under the same momentum ratios, the average normalized heat transfer coefficient of the converging-expanding hole is larger than that of a cylindrical hole in the upstream, but lower in the downstream. The laterally averaged effectiveness of the converging-expanding hole is much larger than that of the cylindrical hole, and it reaches its highest value when momentum flux ratio I=2.