涡轮导叶压力面气膜孔排位置对气膜冷却特性的影响

Effects of Film Hole Row Location on Film Cooling Characteristic for Pressure Side of a Turbine Vane

为了研究气膜孔排位置对气膜冷却特性的影响,在涡轮导叶压力面布置了4排单排扩张型气膜孔(分别用PS1~PS4表示)并在跨声速风洞中进行了实验,通过气膜孔排下游的热电偶获得了气膜冷却效率和换热系数。叶栅进口雷诺数Re为3.0×10^5~9.0×10^5,PS1~PS4的吹风比BR为0.5~2.0,叶栅出口马赫数为0.8。实验结果表明:PS1位置的顺压梯度较大导致下游冷却效率随吹风比增大而升高,PS2下游小于30D(D为气膜孔直径)的区域最佳吹风比为BR=1.2,而大于30D的区域BR=2.0时气膜冷却效率最高。吹风比相同时,PS1由于孔的倾角较大导致其冷却效率低于PS2,而具有相同倾角的PS2,PS3,PS4冷却效率逐渐减小。除了PS2在BR=0.5时的工况,其它工况下冷气射流与主流的掺混导致PS1~PS4下游的换热系数比都大于1,PS2和PS3下游的换热系数比随吹风比增大而增大,PS1和PS4下游的换热系数比受吹风比影响较小。综合考虑气膜冷却效率和换热系数,在相同冷气量时PS2的冷却效果是最好的。

An experiment was conducted in the transonic wind tunnel to study the effect of film hole row position on the film cooling characteristic,four rows of single-row diffused film hole(represented by PS1~PS4)were arranged on the turbine vane pressure side.The film cooling effectiveness and heat transfer coefficient were achieved by the thermocouples downstream of the film cooling hole rows.The inlet Reynolds numbers of the cascade ranged from 3.0×10^5 to 9.0×10^5,the blowing ratios of PS1~PS4 ranged from 0.5 to 2.0 and the exit Mach number of the cascade was 0.8.The experimental results show that the film cooling effectiveness downstream of PS1 increases with the increase of blow ratio because of strong favorable pressure gradient.For PS2,the optimal blowing ratio in the region of less than 30 D downstream of the hole row is BR=1.2(D represents the diameter of film hole),whereas the highest film cooling effectiveness is obtained at BR=2.0 in the region of lager than 30 D.At the same blowing ratio conditions,the film cooling effectiveness downstream of PS1 is lower than that of PS2 because the inclination angle of PS1 is larger,while the film cooling effectiveness downstream of PS1,PS2 and PS3 with the same inclination angle gradually decreases.The heat transfer coefficient ratio downstream of PS1~PS4 is greater than 1.0 due to the mixing of the coolant and mainstream,except for PS2 at BR=0.5.Higher blowing ratio produces higher heat transfer coefficient ratio for PS2 and PS3,while the effect of blowing ratio on heat transfer coefficient ratio is not pronounced for PS1 and PS4.Taking the film cooling effectiveness and heat transfer coefficient into consideration,the cooling performance of PS2 is the best with the same amount of coolant for PS1~PS4.