关于气膜冷却均匀度评价指标的探讨

Discuss on Evaluation of Film Cooling Uniformity

在对文献进行充分回顾的基础之上,以气膜冷却效果的评判为出发点,指出现有的反映气膜冷却均匀程度的指标CUC的不合理性,进而提出新的反映气膜冷却均匀程度的评价指标。应用Fluent软件对带有不同复合角的平板气膜冷却流场进行计算,并用新的指标评判不同工况下的气膜冷却效果和均匀程度。发现:基于均方差的思想所提出的un指标能够很合理地反映带有复合角射流的气膜冷却效果的均匀程度,克服了传统的CUC指标的局限性;un指标能够和传统的横向平均冷却效率指标保持较好的一致性,复合角可以改善气膜冷却效果的均匀性,同时也增大了整体的气膜冷却效率;虽然30°复合角比0°复合角的横向平均冷却效率要高,但30°复合角的均匀性最差,所以,在考虑均匀性后,小复合角射流并没有明显的冷却优势,90°复合角在高吹风比时有最佳的均匀性和最大的气膜冷却效率。

First,the literature review is conducted based on the evaluation of film cooling effect. The unreasonableness of the existed film cooling uniformity index CUC is pointed out and the new index is put forward. Then, FLUENT software was used to calculate the flow field of fiat plate film cooling with different compound angle holes, and the new index was used to evaluate the film cooling uniformity. It can be found that：the new index un based on the mean square deviation can reflect reasonably the uniformity of the film cooling with compound angel hole, which overcome the limitation of the traditional index CUC,and can keep good consistency with the conventional lateral average film cooling effectiveness. Compound angle can improve the film cooling uniformity, but also increases the overall film cooling effectiveness; although the 30° compound angle hole have higher effectiveness than that of the 0° hole, but the uniformity of 30° compound angle hole is the worst. After taken the uniformity in consideration, small compound angle holes have no obvious advantage, and 90° compound angle hole at high blowing ratio has the best uniformity and the largest film cooling effectiveness.