低稠度涡轮导向叶片端壁高效气膜冷却特性研究

Study on Efficient Film Cooling Characteristics of Low Consistency Turbine Guide Blade End Wall

采用低稠度涡轮导向叶片设计方案,可减少导向叶片的用量,减轻涡轮重量,降低发动机冷气用量及耗油率,但同时也带来导向叶片端壁冷却负荷增大等问题。依据低稠度涡轮导向叶片端壁的结构与流动换热特点,制定了槽缝和气膜孔共同冷却的方案。通过数值模拟和分析,重点研究了低稠度涡轮导向叶片端壁前缘气膜孔在不同方向角、孔数、孔径以及叶栅通道中气膜孔布置等条件下的流动及冷却特性。研究结果表明:对低稠度涡轮导向叶片端壁前缘气膜孔进行优化设计,可以有效克服导向叶片端壁前缘高强度马蹄涡对于气膜冷却效果的不良影响;在叶栅通道内合理设置气膜孔,可以改善通道内复杂涡旋对端壁气膜的卷吸作用,提高气膜冷却效果;当槽缝和气膜孔中的冷气流量比分别为3%和2%、气膜孔方向角为45°、气膜孔直径为1.25 mm、叶片前缘和叶栅通道气膜孔数分别为8和1时,叶片端壁表面被冷气膜全部覆盖,此时端壁面平均气膜冷却效率相对最高,达到53.7%。

Adopting a low consistency turbine guide blade design scheme can reduce the number of guide blades,reduce the weight of the turbine and reduce the amount of cold air and fuel consumption rate of the engine,but at the same time,it also brings about problems such as increased cooling load on the end wall of the guide blade.Based on the structure and flow heat transfer characteristics of the end wall of low consistency turbine guide blades,it was proposed a scheme for joint cooling of slot and film holes.Through numerical simulation and analysis,the flow and cooling characteristics of the leading edge film holes on the end wall of low consistency turbine guide blades were studied under different conditions such as direction angle,number and bore diameter of the film holes,and arrangement of film holes in the cascade channel.The research results indicate that optimizing the design of the leading edge film holes on the end wall of low consistency turbine guide blades can effectively overcome the adverse effect of highstrength horseshoe vortices on the film cooling effect of the leading edge of the guide blade end wall;reasonably setting film holes in the cascade channel can improve the suction effect of complex vortices on the end wall film in the channel and improve the film cooling effect;when the cold air flow ratios in the slot and film holes are 3%and 2%respectively,the direction angle of film holes is 45°,the bore diameter is 1.25 mm,and the number of film holes on the leading edge of the blade and the cascade channel is 8 and 1 respectively,the blade end wall surface is fully covered by the cold air film,and in this case the average film cooling efficiency of the end wall is relatively highest,reaching 53.7%.