Refined flow organization in squealer tip gap and its impact on turbine aerodynamic performance

Squealer tips are widely used in high-pressure axial turbines to control tip leakage loss. A well-designed squealer tip is essential for improving the turbine aerodynamic performance. This paper aims to obtain some guidelines for the flow organization in the squealer tip gap. Firstly, to investigate the effects of tip flow organization on the turbine aerodynamic performance, four different squealer tips are constructed by analyzing the flow and loss characteristics of the conventional squealer tip. Then, the refined flow organization results are detailedly analyzed. Finally, the effects of tip flow organization on the turbine aerodynamic performance are investigated. Results show that the key to the refined flow organization in the squealer gap is to manage the vortices inside the cavity, especially the scraping vortex. The primary object in the refined flow organization is to enlarge the extent of the effective control region, enhance its intensity, and place it within the high-leakage region in the meantime. The characteristics of the effective control region are primarily determined by the characteristics of the scraping vortex, such as the streamwise range, cross-location, size and intensity. Organizing the scraping vortex carefully through a refined design for the squealer geometry can control the leakage flow and hence the leakage loss effectively, which provides an effective means for the design of the high-performance squealer tip.