Effects of Ribbed-Cavity Tip on the Blade Tip Aerothermal Performance in a High Pressure Turbine Stage

For unshrouded blade tip, the high-temperature gas flows through the tip clearance by force of the lateral pressure difference. Thereby, the blade tip endures increasing thermal load. Furthermore, the conventional blade tip treatment cannot continuously provide protection for the deteriorating service environment. In the present study, aerothermal characteristics of the squealer blade tip with staggered ribs, partial squealer rim and different partial squealer rim thickness were investigated to explore the influences of ribbed-cavity tip on the tip heat transfer, leakage flow and turbine stage efficiency. The numerical results indicate that the ribbed-cavity tips are beneficial for the reduction of the blade tip thermal load and leakage flow. Among the present six blade tip designs, the minimal area-averaged heat transfer coefficient is obtained by the case with the staggered ribs and a deeper squealer rim, which is reduced by 31.41% relative to the squealer tip. Plus, the blade tip modification closer to leading edge or tip mid-chord region performs better than trailing edge in reducing the tip leakage flow.