Effects of the Ribbed-Squealer Tip on the Blade Tip Aerothermal Performance in a High Pressure Gas Turbine Cascade

In modern gas turbines, High-temperature gas gives rise to the heat load dramatically to the tip region, inducing the leakage flow through the blade tip gap by the lateral pressure difference. Squealer tip, as an efficient technique, has been widely utilized to reduce the tip leakage flow and the heat load. In order to enhance efficiency of squealer tip, the present research proposed kinds of ribbed-squealer tip. Ribs along the axial direction and the circumferential direction are inserted inside the conventional squealer tip. The effects of different squealer tips on the blade tip leakage flow and heat transfer characteristic were numerically investigated. Three-dimensional (3D) Reynolds-Averaged Navier-Stokes (RANS) equations and standard k-ω turbulence model were solved to conduct the simulations. The numerical results indicated that the ribs significantly alter the full development of various vortices inside the tip cavity, thus improving the aerothermal performance in the ribbed-squealer tip. In all simulated cases, the case with the staggered rib within 0-40% chord region obtains the smallest heat transfer coefficient, and achieve the best performance in minimizing the tip leakage mass flux within the 0-10% stream-wise region.