Investigation into the Evolution Mechanism of Secondary Vortices in the Endwall Region of Cantilevered Stator in an Axial Compressor Stage

Unsteady numerical simulations were conducted on a single-stage compressor with a cantilevered stator to investigate the evolution mechanism and unsteady characteristics of complex vortical structures in the stator endwall region, thereby providing a theoretical foundation for subsequent flow control strategies. Initially, vortices associated with tip leakage flow and corner separation were visualized using the Q-criterion. On the hub side, multiple vortical structures exhibit periodic evolution due to interference from upstream wake. Specifically, at the peak efficiency condition, the leakage vortex develops periodic branches, whereas near the stall condition, a vortex pair formed following vortex breakdown demonstrates periodic variation. On the casing side, as the flow deteriorates, a ring-shaped vortex emerges, indicating a transition from open-type to closed-type corner separation. This transition weakens the regulatory effect of the upstream wake on boundary layer separation along the blade suction surface. The influence of the upstream wake on the stator flowfield was also quantitatively assessed. Periodic fluctuations in the reverse flow region were observed as a result of the wake's indirect effect. On the hub side, with decreasing mass flow rate, the unsteady flow caused by leakage vortex breakdown interacts with the upstream wake, leading to a significant increase in both the mean volume and fluctuation amplitude of the reverse flow region. In contrast, the volume increment on the casing side is two orders of magnitude greater than that on the hub side, indicating that the casing-side corner separation is a primary factor constraining compressor performance and stability.