气膜抽吸与叶片前缘内部壁面射流的作用机制

Mechanism of Action Between Film Suction and Wall Jet in Leading Edge of Blades

为揭示气膜抽吸对壁面射流流动与换热的干涉效应,获得壁面射流冷却通道内的流动特性与换热特性,建立了涡轮叶片前缘带气膜抽吸的单通道壁面射流冷却计算模型。采用RANS方法,结合SSTk-ω湍流模型,研究了气膜抽吸、射流雷诺数、气膜孔位置和数量等因素对壁面射流内部冷却特性的影响机制。结果表明:气膜抽吸会大幅提高流动结构的稳定性,气膜孔入口的分离涡则会显著提高孔口附近的换热系数;气膜抽吸引起壁面射流流量的降低不利于靶面下游的冷却,但滞止区和通道内的流动损失降低幅度大于气膜孔内的掺混损失,从而使整体流动损失系数降低了4.5%;射流雷诺数的增加会提高换热强度,但对流动结构几乎没有影响;单孔结构中,在前缘滞止线处开孔能够提供最高的气膜流量比,且对前缘内部靶面的冷却效果良好;多孔结构中,双气膜孔结构的流动损失最大,三气膜孔结构的流动损失和换热强度最为均衡。研究结果可为壁面射流冷却结构的气膜孔布置提供依据,为进一步提高壁面射流冷却结构的冷却效果提供参考。

The computational models of single-channel wall jet cooling with film suction are established at the leading edge of turbine blades in this paper to reveal the interference effect of film suction on the flow and heat transfer of wall jet and obtain the flow and heat transfer characteristics in the wall jet cooling channel.The RANS method with SST k-ωturbulence model is adopted to research the effects of film suction,jet Reynolds number,film hole position,number and other factors on the internal cooling characteristics of wall jet.The results show that film suction can significantly improve the stability of flow structures.The heat transfer coefficient near the inlet of film hole can be raised notably by the separation vortex.The decreased mass flow rate of the wall jet brought from the film suction is not conductive to the cooling of the downstream target.However,the decreasing level of flow loss at the stagnation area and channel is larger than the mixing loss in film hole,thereby reducing the overall flow loss coefficient by 4.5%.With the increase of the Reynolds number,the heat transfer intensity will improve,which,however,has little effect on the flow structure.Among the structures with a single film hole,the opening at the position of the leading edge stagnation line can provide the highest film flow ratio and has a good cooling effect on the target surface inside the leading edge.Among the structures with multiple holes,the structure with double film holes has the largest flow loss,and the structure with three film holes has the most balanced flow loss and heat transfer intensity.The research results provide a basis for the arrangement of film holes for the wall jet cooling structure,and provide a reference for further improvement of the cooling effect.