涡轮导叶吸力面簸箕型孔气膜冷却特性实验研究

Experimental Study of Film Cooling Characteristics for Dust-Pan Shaped Holes on Suction Side in Turbine Guide Vane

为了研究涡轮导叶吸力面的气膜冷却特性,在跨声速涡轮叶栅传热风洞中,采用瞬态方法实验测量了两个位置处的单排簸箕型气膜孔的冷却效率,分析了多个气动参数对其分布规律的影响。两排簸箕型孔分别位于相对弧长6.8%和21.7%处,叶栅通道基于叶片弦长的进口雷诺数为1.7×10^5-5.7×10^5,出口等熵马赫数为0.81-1.01,吹风比为0.6-2.1,涵盖了涡轮导叶典型工作状态。结果表明：对于簸箕型气膜孔,设计雷诺数条件下最佳吹风比在0.9-1.2附近,靠近前缘的孔排2的贴附性要好于孔排1;主流马赫数对孔后冷却效率的影响可以忽略,而低雷诺数下的冷却效率低于中高雷诺数工况;簸箕型气膜孔的冷却效率高于圆柱型孔,在BR〉1.5的中高吹风比时表现更明显;低吹风比时,凸面的冷却效率高于平板,尤其是s/d〈20距离内,而在高吹风比时,射流动量增加促进了气膜脱离凸面,从而降低了冷却效率。

In order to investigate the film cooling characteristics on suction side of a turbine guide vane, the film cooling effectiveness for two single rows of dust-pan holes was measured experimentally using transient method in a transonic cascade heat transfer wind tunnel, and the effects of several flow parameters on its distribution were analyzed. The two rows of holes are located at 6.8%, 21.7% relative arc, respectively. The range of in- let Reynolds number based on vane chord length is 1.7×10^5～5.7×10^5, the range of exit isentropic Mach number is 0.81 - 1.01 and the blowing ratio changes from 0.6 to 2.1, which cover the typical working states of turbine guide vane. The results show that, the optimum blowing ratio is around 0.9 - 1.2 for dust-pan shaped holes at the condition of designed Reynolds number, and the jet from Hole 2 near the leading edge attaches better than Hole 1. The effect of mainstream Mach number on cooling effectiveness after the hole can be neglected. The effectiveness of low Reynolds number cases is lower than that of moderate or high Reynolds number cases. The dust- pan shaped holes perform better than the cylinder holes, especially at moderate and high blowing ratio cases of BR〉1.5. At low blowing ratios, film cooling is more effective on the convex surface than on a flat surface especially with the distance of s/d〈20, while at high blowing ratios, the increased jet momentum promotes lift-off from the convex surface, thereby lowering the effectiveness.