Coupling effect of radial non-uniform temperature at cascade inlet and blade tip leakage vortex on film cooling characteristics in the near-tip region

Local thermal ablation and material spallation commonly occur in the near-tip region of turbine blades, severely compromising the operational safety and reliability of aeroengines. The coupling effect between the radial non-uniform temperature at the cascade inlet and the blade tip leakage vortex gives rise to complex film cooling characteristics in this region. The impacts of the tip leakage vortex and cascade inlet radial temperature distribution factor ( D T = 0, 0.1, 0.2) on the gas recovery temperature were numerically investigated. Furthermore, systematic analyses were conducted on the adiabatic wall temperature and film cooling effectiveness distributions at blowing ratios of 0.5, 1.0, and 1.5. The results show that the tip leakage vortex contributes to the rise of gas recovery temperature in the near-tip region and deflects the gas and the coolant from the near-tip region toward the tip-transition region, while the coolant deflects more significantly than the gas. Increasing both the blowing ratio and D T reduces the adiabatic wall temperatures in the NTR. The lowest adiabatic wall temperatures occur at h/H = 0.65 for studied D T = 0, D T = 0.1, D T = 0.2 cases and respectively show the reduction of 8.4%, 11.6%, and 16.9%, compared with the inlet radial temperature at the corresponding heights. Raising blowing ratios can enhance the capacity of the coolant to resist deflection by the tip leakage vortex; the improvement in spanwise-averaged film cooling effectiveness of the near-tip region is more pronounced compared with that of the tip-transition region and mid-span region when blowing ratio increases from 0.5 to 1.5. This study provides theoretical support for the optimization of turbine blade cooling structures and thermal protection design.