Unsteady Passing Wake Effect On Turbine Blade Tip Aerodynamic And Aerothermal Performance

The inlet of the turbine is certainly non-uniform due to the existence of the guide vane unsteady passing wake and the turbine design and optimization method based on the steady uniform flow condition will arouse a certain difference between the predicted characteristics and real performance.Therefore,the influence of non-uniform inlet conditions caused by guide vane unsteady passing wake is numerically investigated in detail.The blade profiles and operating conditions of the GE-E~3 first-stage high-pressure turbine that is a typical modern aeroengine,were selected to conduct the 3D steady and unsteady numerical simulations respectively under different blade tips.The first stage high-pressure turbine of GE-E~3 has46 guide vanes and 76 rotor blades,and the number of the vane to the blade was reduced to 38:76 in order to compromise the computational resources and accuracy.Each computational domain consists of one guide vane pass-age and two rotor blade passages,and the boundary conditions of the computational domain are consistent with the GE-E~3annular cascade test operating conditions.In the present study,the aerodynamic and aerothermal characteristics of the flat tip,squealer tip as well as the air-cooled squealer tip were calculated and analyzed.The emphasis is on the difference between steady and unsteady characteristics,and the relative variation of unsteady instantaneous performance in one cycle,which can clearly identify the relative magnitude of unsteady wake effect.The instantaneous deviations of unsteady heat transfer coefficient within the tip region will exceed 20%and30%for squealer tip and air-cooled squealer tip.The aerodynamic performance variation caused by the unsteady wake could make a balance in one cycle,and the time-averaged leakage flow and pressure loss are very close to the steady value.Therefore,according to the present research results,it is necessary to consider the unsteady characteristics caused by the passing wake in turbine blade design and optimization,which is of great significance for the blade structural strength and fatigue prediction.