交叉扭转椭圆前缘冲击腔抑制横流及强化换热机理研究

Study on the Mechanism of Cross Flow Suppression and Heat Transfer Enhancement of Alternating Elliptical Leading Edge Impingement Chamber

为强化高温叶片前缘内部冲击冷却,提高换热系数,从抑制前缘冲击冷却横流、减小横流对下游冲击射流的阻挡作用出发,基于交叉扭转椭圆冷却通道内的多纵向涡涡系结构,提出了一种交叉扭转椭圆前缘冲击腔,将横流转换为中心方向与冲击射流方向相同的纵向涡。采用三维定常数值分析方法,对比研究了半椭圆柱形前缘冲击腔和交叉扭转椭圆冲击腔的流动结构和换热特性。结果表明:半椭圆柱形前缘冲击腔内冲击冷却效果受横流影响严重,下游换热效果恶化;交叉扭转椭圆冲击腔对横流有较好的抑制作用,强化了冲击冷却换热效果。随横流比增大,交叉扭转椭圆冲击腔抑制横流和强化换热效果增强。

This paper proposed a kind of alternating elliptical impingement chamber in the leading edge of gas turbine blade,to restran the cross flow and enhance the heat transfer of impingment cooling.According to the multi-longitudinal vortex in the alternating elliptical channel,this kind of impingement chamber could transfer the cross flow to a pair of longitudinal vortices,and the flow direction at the centre of the cross section is parallel to the impingement jet.Numerical simulations are performed by solving 3D steady Reynolds-averaged Navier-Stokes equations(RANS)with the SST k–ωturbulence model.The influence of alternating of the cross section on impingement flow and heat transfer of the chamber at different cross flow velocity ratios(CR)is studied by comparing with the smooth semi-elliptical impingement chamber.The results show that in the semi-elliptical impingement chamber,the impingement jet is deflected by the initial cross flow,and the heat transfer performance is degraded.However,in the alternating elliptical chamber,the cross flow is transformed to a pair of longitudinal vortices,and the flow direction at the centre of the cross section is parallel to the impingement jet,thus improving the jet penetration ability and enhancing the impingement heat transfer significantly.In addition,with the increase of the cross flow velocity ratio,the heat transfer enhancement is very obvious.