Effects of inclined squealer rims on tip leakage vortex and loss in a transonic axial turbine

Abstract

In this paper, to investigate the effects of inclined squealer rims on tip leakage flow and loss, numerical simulations have been performed on a transonic high-pressure turbine. Based on the geometry of prototype with conventional cavity tip, six modifications with different inclined rims are constructed. The effects of inclined suction side squealer rim (SSSR) on tip leakage flow (TLF) is analyzed emphatically. The results show that it is advantageous to control the TLF and loss if the internal and external surface of SSSR are inclined in a proper direction. When the internal surface of SSSR is inclined toward the cavity, the scraping vortex and its pneumatic labyrinth sealing effect are enhanced, which is beneficial to blocking the TLF and reducing the mixing loss. As the external surface of SSSR is inclined toward the passage, the pressure gradient near the tip changes and the intensity of adverse pressure gradient decreases, which is conducive to suppressing the breakdown of tip leakage vortex (TLV). In addition, the inclined external surface could make the TLV away from the blade and reduce the viscous dissipation. Regarding the aerodynamic performance of the turbine, the inclined pressure side squealer rim (PSSR) could improve the stage efficiency of the turbine by 0.08% relative to the prototype, while the proper inclined SSSR could further improve that by 0.18%.