The effects of swirling purge leakage on aerothermal performance of flat and non-axisymmetric endwalls

Abstract

The relative rotation of turbine rotor determines the velocity triangle of the purge flow, which significantly influences the aerothermal performance of turbine endwalls. In this paper, a turbine cascade model is constructed to simulate the relative motion effect between the rotor endwall and the purge leakage. The effects of the swirl ratio of the purge leakage on the aerothermal performance of two endwall schemes (flat endwall and non-axisymmetric endwall) are investigated and compared. The results show that due to the relative motion, the purge leakage's flow direction and migration trajectory shift towards the blade suction side. The cooling jets tend to push the boundary layer towards the suction side, thus enhancing the lateral secondary flows. At a low MFR, with the decrease of swirl ratio, both endwalls' film cooling effectiveness is gradually reduced, with the aerodynamic performance and heat transfer coefficient changing very little. At a high MFR, with the decrease of swirl ratio, the aerodynamic loss and heat transfer coefficient of both endwalls are gradually increased, while the endwall film cooling effectiveness is gradually decreased. Globally, compared to the flat endwall, the non-axisymmetric endwall can dramatically enhance the film cooling effectiveness while effectively reducing the aerodynamic loss and heat transfer levels for all swirl ratios and MFRs investigated.