Tip region vortices control based on cutback squealers in a high-loading axial turbine

The evolution of tip region vortices has a significant influence on the aerodynamic performance of the turbine. Most studies on squealer tip optimization focused on enhancing the blockage effect of the vortices inside the clearance but had limited effect on controlling the vortices outside the clearance. In this paper, both the vortices inside and outside the clearance are controlled based on the trailing edge suction side cutback in a non-cooled turbine. The results indicate that inside the clearance, the scraping vortex plays a crucial role in reducing leakage. The cutback enhances the strength of the scraping vortex, thereby expanding the effective blockage range. While outside the clearance, the tip leakage vortex breakdown exacerbates its dissipation effects, leading to a significant loss downstream of the blade. The cutback injects greater fluid momentum into the tip leakage vortex, leading to increased mixing loss between leakage jet and mainstream. Concurrently, this also inhibits the tip leakage vortex breakdown, resulting in a notable reduction in its dissipation loss. The combined impact effectively controls the total leakage loss. It has been demonstrated that there exists an optimal cutback length for the suction side squealer rim at the trailing edge, which can be determined by setting the cutback opening at the initiation of the tip leakage vortex breakdown. The aforementioned effects of the cutbacks are prominently observed under different operating conditions, which indicates that the cutbacks possess good applicability in a certain range. This offers valuable guidance for tip region vortices control and squealer tip optimization.