Loss mechanisms of leakage flow in a cantilevered stator with/without moving end wall

Secondary flow loss is one of the main loss sources in cantilevered stators and has a significant influence on compressor efficiency. However, under more complex inflow and end wall conditions, the combined effects of corner separation and hub leakage flow (HLF) are becoming increasingly complex and difficult to understand. In this paper, the interaction mechanism between corner separation and HLF in a cantilevered stator fore-loading airfoil is investigated using Reynolds-averaged Navier–Stokes simulations, which are validated by experimental measurements. Numerical simulations are performed for six different clearances (from 0.1 τ to 2 τ) under moving and static end walls. The results show that at 0° and 4° incidence, there exists an optimal clearance 0.5 τ with the static end wall. At this clearance, HLF and corner separation achieve dynamic equilibrium, resulting in the lowest entropy loss. The moving end wall eliminates the optimal clearance effect, with its entropy loss increasing as the clearance enlarges. Moreover, by causing the boundary layer to skew and enhancing the circumferential momentum of HLF, the moving end wall significantly alters the flow field structure, thereby significantly suppressing corner separation. Under the −10° incidence condition, the sensitivity of entropy loss to clearance is significantly reduced in large clearances (above 0.5 τ) with both static and moving end walls. This is because the high entropy generated at the leading edge of the pressure side of the blade dominates the flow loss in the cascade channel, while the loss caused by leakage flow occurs near the trailing edge of the blade, or even downstream of the blade.