主流湍流度对涡轮导叶吸力面W型气膜孔冷却效率影响的实验研究

Experimental Investigation for Effects of Mainstream Turbulence on Film Cooling Effectiveness of W-Shaped Film Hole on Suction Side of a Turbine Guide Vane

关键词:  W型气膜孔  气膜冷却  吸力面  湍流度  吹风比

Key words:  W-shaped hole  Film cooling  Suction side  Turbulence intensity  Blowing ratio

摘要:

为了获得亚声速涡轮导叶吸力面不同位置处单排W型气膜孔的气膜冷却特性，在短周期跨声速风洞中实验研究了吹风比、主流湍流度对W型气膜孔冷却效率的影响。两列单排气膜孔分别布置在吸力面16%和21%相对弧长处，实验进口雷诺数范围为3.0×10⁵~9.0×10⁵，吹风比范围是0.5~2.0，叶栅出口等熵马赫数为0.8，高低湍流度分别为14.7% 和1.3%。实验结果表明：低湍流度时孔排1和孔排2下游的气膜冷却效率都随吹风比的增大先增大后减小，最佳吹风比分别为BR=1.2和BR=0.8。由于孔排1和孔排2所处位置的主流边界层状态不同，导致湍流度对于气膜冷却效率有不同的影响。对于孔排1，大吹风比时高湍流度使冷气核心向壁面移动，提高了气膜冷却效率；而小吹风比时，湍流度对冷却效率的影响随雷诺数升高而减弱。对于孔排2，大吹风比时高湍流度提高了孔附近区域的冷却效率，同时加快了冷却效率沿流向下降的速度，而在小吹风比时高湍流度显著降低了孔排下游气膜冷却效率。

Abstract:

In order to achieve the film cooling characteristic of W-shaped film holes at different positions on the suction side of a subsonic turbine vane, an experiment was conducted in the short-duration transonic wind tunnel to investigate the effect of blowing ratio and mainstream turbulence intensity on the film cooling effectiveness. Two single row of film cooling holes （SS1 and SS2）， are respectively located at 16% and 21% relative arc length on the suction side. The range of inlet Reynolds numbers was 3.0×10⁵~9.0×10⁵ and the range of blowing ratios was 0.5~2.0. The isentropic exit Mach number of the cascade was 0.8. The high and low turbulence intensity was 14.7% and 1.3%, respectively. The experimental results show that: at low turbulence intensity, the film cooling effectiveness downstream of SS1 and SS2 increases first and then decreases with the increase of blowing ratio, and the optimal blowing ratio is BR=1.2 and BR=0.8, respectively. The turbulence intensity has different effects on the film cooling effectiveness of SS1 and SS2, because the states of mainstream boundary layer is different. For SS1, high turbulence intensity makes the core of coolant to move towards the wall surface and improves the film cooling effectiveness at large blowing ratio, however, reduces the cooling effectiveness at small blowing ratio. The influence is weaker as the Reynolds number increases. For SS2, high turbulence intensity increases the cooling effectiveness in the vicinity of the film holes and increases the rate of decay along the flow direction at large blowing ratio, however, significantly reduces the film cooling effectiveness downstream of film cooling holes at small blowing ratio.