冲角和孔排间距对端壁气膜冷却效率的影响

The Influence of Incidence and Hole Spacing on Endwall Film Cooling Efficiency

燃气轮机在变工况运转时透平叶栅和级的特性对燃机总体性能影响极大,而叶栅端壁气膜冷却效率是关键因素。为了提高端壁气膜冷却效率,通过优化气膜孔间距排列的方法,在叶栅端壁20%、50%、90%轴向弦长处和距前缘-10%轴向弦长端壁处布置单排带复合角度的圆柱形气膜冷却孔,运用CFD(计算流体动力学)方法对冲角(10°、0°、-10°)在不同吹风比(1、1.5、2)条件下端壁气膜冷却效率进行对比分析。结果表明:采用气膜孔非等距排列方式能有效缓解因横向压力梯度变化引起的马蹄涡在压力侧的阻隔作用,压力侧冷却效率较高;高吹风比的冷却射流会出现抛射冷却,能有效抑制冷却射流脱离壁面,壁面平均冷却效率提高;主流正冲角有利于提高端壁吸力侧气膜冷却效率,压力侧变化不大。

Influence of turbine cascade and characteristics of stage on gas turbine performance is great in the variable corditions of operation,while,the cascade endwall film cooling efficiency is the key factor. In order to improve the endwall film cooling efficiency,by optimizing the gas film hole spacing arrangement,a single row of cylindrical gas film cooling hole with compound angle were configured on cascade endwall 20%,50%,and 90% axial chord length and10% axial chord length from the leading edge. CFD method was used to compare the endwall film cooling efficiency with attack angles of 10°,0° and-10°,and different blowing ratios of 1,1. 5,and 2. Result showed that film holes with unenven arrangement can effectively alleviate the barrier of horseshoe vortex in pressure side which is caused by horizontal pressure gradient changes,and pressure side cooling efficiency is relatively high. The cooling blast with high blowing ratio results in mass ejection cooling,which can effectively inhibit cooling blast out of the wall,so the average wall cooling efficiency is improved. The mainstream incidence improves the film cooling efficiency on the suction side of the endwall,while it has little effect on the pressure side.