主流湍流度对涡轮导叶压力面扩张型气膜孔冷却特性的影响

Effects of Mainstream Turbulence Intensity on Film Cooling Characteristics of Diffused Holes on Turbine Vane Pressure Side

为了研究主流湍流度对涡轮导叶压力面扩张型气膜孔冷却特性的影响,在高亚声速风洞中进行了实验,通过热电偶测得了气膜孔排下游的气膜冷却效率和换热系数,叶栅进口雷诺数的范围为3.0×105~9.0×105,出口马赫数为0.8。两排单排扩张型气膜孔分别位于压力面25%和70%的相对弧长处,高低湍流度分别为14.7%和1.3%。实验结果表明:对于孔排1,随着吹风比的增大,气膜冷却效率在低湍流度时呈现先增后减的特征,而在高湍流度时单调提升;在相同吹风比时,主流湍流度升高增强了主流和冷气的掺混,加快了冷气的耗散从而降低了气膜冷却效率。对于孔排2,主流湍流度升高在小吹风比时使气膜冷却效率降低,而在大吹风比时抑制了冷气脱离壁面从而提高了气膜冷却效率。吹风比增大显著增强了孔排1下游的换热,而对孔排2影响较小;主流湍流度升高显著提高了孔排1和孔排2下游的换热系数比。整体来看,主流湍流度升高降低了孔排1和孔排2下游的气膜冷却效果。

To investigate the influence of mainstream turbulence intensity on the film cooling characteristics of diffused film cooling holes on turbine vane pressure side,an experiment was carried out in the high subsonic wind tunnel,and the film cooling effectiveness and heat transfer coefficient downstream of the film hole row were measured by thermocouples.The inlet Reynolds number of the cascade ranged from 3.0×105 to 9.0×105,and the exit Mach number was 0.8.Two rows of single-row diffused film holes were located at the relative arc lengths of 25% and70% on the pressure side.The high and low turbulence intensities were 14.7% and 1.3%,respectively.The experimental results show that for the row A,with the increase of the blowing ratio,the film cooling effectiveness increases first and then decreases in low turbulence intensity condition,while increases monotonously in high turbulence intensity condition.For the same blowing ratio condition,increased mainstream turbulence intensity strengthens the mixing of mainstream and coolant and enhances the dissipation of coolant,thus decreases the film cooling effectiveness.For the row B,elevated mainstream turbulence intensity decreases film cooling effectiveness at small blowing ratios,however suppresses the lift-off of coolant at large blowing ratios and increases film cooling effectiveness.The increase of blowing ratio significantly strengthens the heat transfer downstream of the row A,however has less effect on the row B.The increase of the mainstream turbulence intensity obviously raises the heat transfer coefficient ratio downstream of the row A and B.Overall,elevated mainstream turbulence intensity deteriorates the film cooling performance of the row A and B.