Numerical study of the effect of the cavity depth on the leakage control in a cooled honeycomb-tip turbine cascade

Highlights: • The effect of the cavity depth is studied in a honeycomb-tip turbine cascade. • The honeycomb tip is cooled by the injection from the bottom center. • The cavity depth affects the leakage flow and the total pressure loss. • The internal flow in the gap and cavities varies with increasing the depth. • The heat transfer condition is better improved in relatively deep cavities. The effect of the cavity depth on the leakage flow and tip cooling has been numerically investigated in a honeycomb-tip turbine cascade with cooling injection. Coolant is ejected through the center holes on the honeycomb cavity bottoms. Three dimensional flow fields were simulated using the Reynolds-averaged Navier-Stokes (RANS) method and the k-ω turbulence model. Then the tip configurations are evaluated according to several performance parameters, such as leakage mass flow rate, total pressure loss and film cooling effectiveness, in the upper passage, the gap and the honeycomb cavities. Furthermore, the secondary velocity streamlines are plotted at the cascade exit to characterize the upper passage vortices. The isothermal surface and contours of dimensional temperature are presented to explore the mixing between the coolant and the cavity vortices. The numerical results show that the aerodynamic and thermodynamic performance differs significantly with the cavity depth.