The interaction mechanism between sealing flow and endwall secondary flow in the low-pressure vane of counter-rotating turbine

Counter-rotating turbine technology, widely utilized in modern advanced aero-engines, requires substantial cooling and sealing air to ensure safe turbine operation. However, the introduction of sealing flow interacts with the main flow within the turbine passage. As secondary flow losses in the end wall region of the low-pressure guide vane in the counter-rotating turbine continue to increase, turbine performance is notably affected. Therefore, this study investigates the influence of sealing flow on the development of secondary flow in the hub end wall region of the low-pressure guide vane cascade in a counter-rotating turbine. First, the characteristics of the sealing flow were adjusted the flow rate and temperature. Subsequently, numerical simulations were conducted to analyze how the sealing flow affects the primary and secondary flow structures. The results demonstrate that increasing the sealing flow rate and temperature enhances the passage vortex and elevates associated losses. As the sealing flow rate increases from 2% to 9%, the circumferential distance of the vortex core decreases from 34.6% to 4.2%. Similarly, increasing the sealing temperature from 500 to 950 K expands the circumferential distance of the vortex core from 10.1% to 15.2%. This study explores the interaction between sealing flow and the mainstream, clarifying the underlying mechanisms governing low-pressure turbine sealing flow and end wall secondary flow. The findings quantitatively establish the dual effects of sealing flow parameters on vortex migration and loss generation, providing actionable strategies to balance aerodynamic performance and thermal characteristics in the design of low-pressure guide vanes for counter-rotating turbines.