直肋对扩张型尾缘半劈缝气膜冷却特性影响的实验研究

Experimental Investigation of Effects of Straight Ribs on Film Cooling Performance of Expanded Cutback Surface for Trailing-Edge

关键词:  涡轮叶片尾缘  扰流半劈缝结构  直肋  压力敏感漆  瞬态热色液晶  气膜冷却

Key words:  Turbine blade trailing-edge  Turbulated cutback structure  Straight rib  Pressure sensitive paint  Transient thermochromic liquid-crystal  Film cooling

摘要:

为探究布置直肋扰流结构的尾缘半劈缝冷却结构的气膜冷却特性，分别采用压力敏感漆技术和瞬态热色液晶技术研究了直肋对扩张型尾缘半劈缝表面的绝热气膜效率和对流换热系数的影响，详细对比分析了吹风比及直肋宽度对三种不同扩张型半劈缝表面的气膜冷却特性。实验结果表明：直肋的加入对小扩张型半劈缝表面的气膜覆盖产生了不利影响，但仅限在小吹风比工况；而直肋对大扩张型半劈缝表面的气膜覆盖有略小的促进作用，但其绝热气膜效率始终低于小扩张型半劈缝表面。肋宽对半劈缝表面的换热增强大小受半劈缝表面形状影响，随着半劈缝表面扩张程度的增大，宽直肋结构的高换热优势逐渐超越窄直肋结构。直肋型尾缘半劈缝冷却结构可有效提升1.45~2倍的壁面热流密度，小吹风比工况时宜选用带有窄直肋的扩张程度较小的半劈缝表面结构，而大吹风比时宜选用带有宽直肋的扩张程度较大的半劈缝表面结构。

Abstract:

To explore the film cooling performance of the cutback trailing-edge with straight-rib turbulence structures, the effects of the straight ribs on the adiabatic film effectiveness and heat transfer coefficient of the expanded cutback surface were studied using the pressure-sensitive paint technology and transient thermochromic liquid-crystal technology, respectively. The effects of the blowing ratio and the rib width on the film cooling performance of the three different expanded cutback surfaces were analyzed and compared in detail. The experimental results show that the addition of straight ribs has an adverse effect on the film coverage on the small expanded cutback surface, but only in the case at low blowing ratio. The straight ribs have a slightly promotion effect on the adiabatic film effectiveness for the large expanded cutback surface, while its adiabatic film effectiveness is always lower than that for the small expanded cutback surface. The heat transfer enhancement of the cutback surface by different rib widths is mainly affected by the shape of the expanded cutback surface. As the expansion of the cutback surface increases, the high heat transfer advantages of the case with wide-ribs gradually surpass the case with narrow-ribs. Compared with the primeval cutback trailing-edge, the wall heat flux of the cutback trailing-edge with straight ribs can significantly improve by a factor of 45%～100%. At the low blowing ratio, it is advisable to choose the case of the small expanded cutback surface with narrow-ribs, while the case of the large expanded cutback surface with wide-ribs should be selected at the high blowing ratio.