渐扩后倾肩臂孔平板气膜冷却特性数值模拟

Numerical simulation on cooling characteristics of plate film from backward-expanding shoulder arm hole

为进一步改善气膜冷却效果,提出了渐扩后倾肩臂孔的构型。对圆形孔、扩张孔、原肩臂孔和渐扩后倾肩臂孔的平板气膜冷却特性进行数值计算研究,主要分析了各孔型在吹风比0.5~2.0情况下的展向平均气膜冷却效率。研究表明:采用渐扩后倾肩臂孔的平板模型可提高展向平均气膜冷却效率,在各吹风比方案下气膜冷却性能均优于其它三种孔型,扩张孔方案气膜冷却性能次之,原肩臂孔方案略优于圆形孔方案。对吹风比2.0情况下各孔型方案的流场和被冷却壁面气膜冷却效率分布对比得知,渐扩后倾肩臂孔与扩张孔出流口下游截面中心处的流场及温度场相似,但渐扩后倾肩臂孔两侧的出流小孔对中心的肾形涡有一定的抑制作用,从而使渐扩后倾肩臂孔中心线附近的绝热气膜冷却效率也比渐扩孔还要高。圆形孔数值计算结果与试验数据对比的一致性验证了计算模型的可靠性。

In order to improve the cooling eefect of a film, the configuration of backward-expanding shoulder arm hole was presented. The cooling characteristics were compared by CFD method for a flat plate with circular hole, expanding hole, original shoulder arm hole, and backward-expanding shoulder arm hole. The spanwise averaged film cooling efficiency wasmainly analyzed for all the configurations at 0. 5？2. 0blowing ratio . The results showthat the flat plate with the backward-expanding shoulder arm hole can improve the spancooling efficiency. This configuration has better film cooling performance than the other three ones. The performance of the expanding hole configuration is better than that of the original shoulder arm hole one and the circular hole one, and the shoulder arm hole provides slightly better behavior than the circular hole. Based on the comparison between these configurations for the flow field and the film cooling efficiency of cooledwall at 2. 0 blowing ratio,the flow field and temperature field of the backward-expanding shoulder arm hole are similar with those of the expanding hole at the center of outlet section downstream. The small holes on both sides of thebackward-expanding shoulder arm suppress the kidney-shape vortex at the center of the flowfield. This suppression leads to that the adiabatic film cooling efficiency near the center line of thebackward-expanding shoulder arm hole is higher than that of the expanding hole. The reliabilityof the present calculation model was validated by the good agreement between the numerical and the experimental results for the circular hole configuration.