关键词: 航空发动机;涡轮;涡轮效率;二次流;流动特性

Abstract: This paper presents a numerical investigation of a novel method for tip desensitization based on casing air injection.The detailed three-dimensional flow structure was revealed inside the tip clearance.The effects of different injection position on turbine performance were compared with the baseline case without injection.The results show that casing air injection can reduce tip clearance massflow effectively,and delay the inception of tip clearance vortex axially.Moreover,sizes of both tip clearance vortex and tip passage vortex decrease.Thus turbine isotropic efficiency can be improved with appropriate injection position.The 30% axial chord injection case yields the largest reduction of loss in regions occupied by the tip passage vortex,but injection at the 60% axial chord has more effect on the tip leakage vortex.In the current study,the optimum isotropic efficiency occurs when 1% passage massflow is injected at 30% axial chord,which is improved by 0.3341 percent points.

Key words: Aircraft engine;Turbine;Turbine effectiveness;Secondary flow;Flow characteristic