带肋横流对凹槽孔气膜冷却特性影响的机理研究

Mechanism Investigation on Effects of Ribbed Crossflow on Film Cooling Characteristics of Trenched Holes

关键词:  带肋横流  气膜冷却  凹槽孔  气膜冷却效率  换热系数比

Key words:  Ribbed crossflow  Film cooling  Trenched holes  Film cooling effectiveness  Heat transfer ratio

摘要:

为了探究带肋横流对凹槽孔气膜冷却特性的影响，运用Realizable k-ε湍流模型，对光滑通道、45°肋通道和135°肋通道进气的凹槽孔进行了数值研究，吹风比为0.5、1.0和2.0，主流和横流的进口雷诺数分别为1×10⁴和1×10⁵。结果表明：45°肋通道与光滑通道在气膜孔内具有相似的螺旋流动，但其流量系数相比光滑通道降低了9.2%~43.6%，而135°肋通道气膜孔内的流动以直线流动为主，其流量系数最高。受横流影响，三种通道的气膜冷却效率分布都不均。在吹风比为0.5和1.0时，45°肋通道的气膜冷却效率要比光滑通道的分别低11.2%和3.6%，135°肋通道的则要比光滑通道的高65%和44.6%。吹风比为2.0时，三种通道的气膜冷却效率相差不大。此外，45°肋通道的换热系数要比光滑通道的高1.5%~8%，而135°肋通道的换热系数要比光滑通道的低0.9%~3%。

Abstract:

In order to investigate the effects of ribbed crossflow on film cooling characteristics of trenched holes， the trenched holes fed coolant by smooth channel， 45° ribbed channel and 135° ribbed channel are numerically investigated using realizable k-ε turbulence model. The blowing ratio is fixed at 0.5， 1.0 and 2.0. The inlet Reynold number of mainstream and crossflow is 1×10⁴ and 1×10⁵ ， respectively . The results show that the 45° rib case has a similar helical motion to the smooth case in film hole， but the discharge coefficient of the 45° rib case is lower 9.2%~43.6% than that of the smooth case. For the 135° rib case， the flow structure in film hole is mainly straight motion and the discharge coefficient is the highest. Because of the crossflow， the distributions of film cooling effectiveness are asymmetrical for the three cases. When the blowing ratio is 0.5 and 1.0， the film cooling effectiveness of the 45° rib case is lower 11.2% and 3.6% and that of the 135° rib case is higher 65% and 44.6% than the smooth case. When the blowing ratio is 2.0， the film cooling effectiveness of the three cases has little difference. In addition， the heat transfer ratio of the 45° rib case is higher 1.5%~8% and that of the 135° rib case is lower 0.9%~3% than the smooth case.