壁厚对气膜冷却效率影响数值模拟

Effect of wall thickness on film cooling effectiveness: numerical simulation

为了探讨薄壁尺寸对气膜冷却效率影响,对壁厚为1倍、2倍和3倍孔径结构下游流场、温度场及气膜冷却效率进行了数值模拟研究。结果表明:壁厚为1倍孔径时气膜孔出口截面处出现高速区,使气膜孔出口垂直主流方向射流动量大,促进冷气被抬离壁面,气膜孔出口展向速度指向孔中心线,减弱气膜展向扩散性;在吹风比为1.0、1.5和2.0时,壁厚为1倍孔径结构的展向平均气膜冷却效率比壁厚为3倍孔径结构分别低9%~45%、21%~43%和9%~62%;壁厚为2倍和3倍孔径结构的展向平均气膜冷却效率相差较小。

To explore the influence of thin wall size on film cooling performance, numerical simulation was carried out to investigate the flow field, temperature field and cooling effectiveness under conditions with wall thickness of one time, two times and three times of diameter of the film-cooling hole. The results show that, high-speed region appears at the hole exit with the wall thickness of one time of the hole diameter, resulting in an increase in the jet momentum and promoting the coolant being lifted offthe wall. The lateral velocity of the coolant is towards to the center line of the hole, which weakens the spanwise diffusion. Compared with the wall thickness of three times of the hole diameter, the values of spanwise averaged film cooling effectiveness for one times of the hole diameter are about 9%--45%, 21%-43% and 9%-62% lower at blowing ratios of 1.0, 1.5 and 2.0, respectively. There is little difference in spanwise averaged film cooling effectiveness between the wall thickness of two times and three times of the hole diameter.