Effects of Coriolis force on the aero-thermal performance of stator-rotor purge flow

Abstract

The hot-end components of gas turbines necessitate efficient cooling strategies to enhance performance and durability. This research focuses on how the Coriolis force affects the purge flow’s cooling effectiveness on the turbine endwall. Utilizing both experimental and numerical methods, the study examines various rotational speeds and Mach numbers to understand the Coriolis force’s impact on aerodynamic losses and cooling effectiveness. This study’s methodological innovations are demonstrated in the following aspects: The implementation of a deflector plate within the rim seal ensures that the circumferential velocity of the purge flow relative to the rotor remains constant at any cascade speed, thereby guaranteeing that the focus of this research is on the “Coriolis effect” rather than the “rotational effect.” The development of a dual-coordinate analysis method allows for a clear presentation of the mechanism by which the Coriolis force influences the vortex’s motion characteristics. Increasing the rotational speed of the cascade enhances the adiabatic cooling effectiveness of the endwall. Similarly, increasing the Mach number of both the main flow and the purge flow under the same blowing ratio also enhances the endwall’s adiabatic cooling effectiveness. This study demonstrates that the underlying mechanisms of these effects are essentially the same, as both alter the Coriolis forces acting on the fluid. Coriolis forces expand the pressure leg of the horseshoe vortex and the passage vortex while reducing the suction leg of the horseshoe vortex. Given that vortex cores are low-pressure regions, the purge flow is entrained into the cores of the pressure leg of the horseshoe vortex and the passage vortex. The increase in rotational speed and Mach number results in greater Coriolis forces, inducing a movement away from the vortex core that expels the denser cooling air from the core. The conclusions of this study can provide insights for the design of gas turbines. Furthermore, the research methodology employed here can serve as a reference for studies on the interaction between purge flow and main flow.