涡轮叶片端壁槽缝气与离散气膜孔冷却特性实验研究

真实发动机涡轮叶片端壁为曲面造型,并且其冷却受槽缝气、泄漏流和离散气膜冷却多种冷却气叠加影响,同时又受到主流二次流影响,因此呈现复杂冷却特性。为研究接近真实发动机涡轮叶片端壁构型和工况下的气膜冷却特性,本文采用高速风洞(主流雷诺数为37万)及压敏漆(PSP)技术,研究了槽缝气、泄漏流以及离散气膜对曲面端壁的气膜冷却效率的影响,并针对不同冷气流量比对端壁气膜冷效的影响规律进行了对比分析。结果表明:端壁表面气膜冷效随着槽缝气流量比增大而增大,当流量比增大到1.71%时,槽缝气膜几乎可以覆盖整个端壁表面;与槽缝气相比,端壁表面的离散气膜冷气覆盖范围较为有限,端壁压力面侧下游区域气膜覆盖较差;在喉部之前,随着流量比增大,离散气膜冷效呈现下降趋势;在喉部之后,随着流量比从1.3%增大到1.9%,离散气膜冷效呈现上升趋势;与仅有离散气膜相比,包含槽缝气、泄漏流、离散气膜的全气膜覆盖更为均匀,全气膜冷效的叠加使得端壁冷效相比仅有离散气膜时整体提高了93.4%。

Experimental Study of the Slot Film and Discrete Film Cooling Characteristics for the Endwall of Turbine Vane

The turbine endwall of a real engine is curved shape,and its cooling type is a superposition of the slot flow,leakage flow and discrete film cooling flow.Meanwhile the endwall cooling is influenced by the secondary flow of the gas flow.The reasons above make complex cooling characteristics on the endwall.In order to investigate the film cooling characteristics close to the configuration and working condition of the endwall of a real engine,the effects of the slot flow,leakage flow and discrete film cooling effectiveness on the curved endwall are studied using the high-speed wind tunnel(Reynolds number of the gas flow is 370000)and pressure-sensitive paint(PSP)technology.Meanwhile the influence of the cooling mass flow ratios on the endwall film cooling effectiveness is obtained.The results show that the slot film effectiveness on the endwall increases with the rise of slot cooling flow ratio.The slot cooling film covers the whole endwall by the flow ratio of 1.71%.The discrete film cooling has limited coverage on the endwall compared to the slot.The film coverage on the downstream area of the suction side is poor.The discrete film cooling effectiveness before throat becomes lower with the increase of the film cooling flow ratios.However after the throat,the discrete film cooling effectiveness becomes higher with the increase of the film cooling flow ratio from 1.3%to 1.9%.The total film cooling effectiveness involved in the slot flow,leakage flow and discrete cooling flow is 93.4%higher than the discrete cooling only owing to the superposition of the cooling film.The total film cooling has more uniform coverage on the endwall.