水平喷流对叶顶气膜冷却效率影响的数值研究

为进一步提高燃气轮机叶顶区域的气膜冷却效率,在叶顶模型结构上对4种叶顶冷却结构的流动和传热进行了数值模拟,结果显示带有盖板的水平喷流结构能够有效地提高叶顶区域的气膜冷却效率,对于圆孔,可以将气膜冷却效率提高至原来的2倍以上.通过流场的分析发现:水平喷流结构可以调整冷却工质的流动,使得冷却工质的贴壁性更好、分布更加均匀,进而提高气膜冷却效率.此外还研究了间隙宽度、盖板尾缘厚度、盖度和整流栅对水平喷流结构气膜冷却效率的影响.结果表明:增加盖度和减小间隙宽度可以提高气膜冷却效率,但是盖度和间隙宽度的选取受到了强度、工艺和冷却工质入口压力等因素的限制.水平盖板结构的冷却效果比倾斜盖板结构的好.整流栅足够长时可以调整流动、提高气膜冷却效率. 

Numerical study on the effect of parallel injection on film-cooling effectiveness at turbine blade tip

For the purpose of improving the film-cooling effectiveness on blade tip region of gas turbine, numerical simulation was carried out on the blade tip model to investigate the flow and heat transfer for four kinds of cooling holes. It was found that the covered structure can double the film-cooling effectiveness compared to the uncovered structure for aclinic injection structure.The physics was revealed by analysis of the flow filed, and results showed that the aclinic injection can improve flow distribution, obtain better film-coverage and more uniform flow distribution, consequently increasing the film-cooling effectiveness.The effect of gap width, cover degree, cover thickness and fence on film-cooling effectiveness was studied, and the results showed that the increase of the cover degree and decrease of the gap width can get a higher film-cooling effectiveness, but the cover degree and gap width were restricted by structural strength, technological level and secondary flow inlet pressure.Aclinic cover can obtain a better film-cooling effectiveness than the inclined one and there is a best cover thickness enabling to obtain the highest film-cooling effectiveness for the aclinic one.Sufficiently long fence can improve the flow distribution and increase the film-cooling effectiveness.