Effect of film cooling on flow and heat transfer of flat tip in transonic turbine cascade

Computational fluid dynamics (CFD) was used to investigate the aerothermal performance of tip leakage flow of a flat tip in a transonic high pressure turbine cascade. The effects of tip film cooling were considered. For the flat tip without tip cooling, shock waves were reflected between the endwall and the blade tip within the tip gap. As a result, the surface heat transfer coefficient is distributed as stripe pattern on the tip surface from blade midchord to the trailing edge. The injection of the coolant has a significant effect on the flow patterns within the tip gap. The coolant reduces the velocity of the flow within the tip gap. As a result, oblique shock waves are no longer obviously observed. The coolant covers the areas downstream the cooling holes. When increasing the inlet stagnation total pressure ratio of the coolant to the main flow from 0.7 to 1.0, the average film cooling effectiveness on the tip varies from 18.7% to 11.5%. Compared to the uncooled flat tip, at the inlet stagnation total pressure ratio of 0.9, the average surface heat transfer coefficient on the cooled flat tip increases by 16.9%, and the heat flux of the tip reduces by 8.7%.