LAUSR

This study experimentally and numerically examines the influence of localized, disk-side suction applied within the vaneless diffuser of the National Aeronautics and Space Administration (NASA) Low-Speed Centrifugal Compressor (LSCC) on the inception and spatial evolution of rotating stall. The stall is triggered by a large-scale reverse-flow zone that occupies 60% of the diffuser passage height. This region is driven by an adverse pressure gradient along the disk end wall and disrupts the jet-wake structure, ultimately forming a circumferentially propagating helical stall cell. Motivated by this mechanism, an active bleed strategy is proposed: rectangular suction ports are positioned at 55% of the diffuser inlet radius. The bleed removes the low-momentum fluid beneath the stall vortex, truncates the reverse-flow core, and suppresses its radial–circumferential coupling instability. In addition, the extracted bleed flow increases the radial momentum flux of the remaining mainstream, enhancing its resistance to the adverse gradient, while inducing a beneficial interaction between the passage vortex and the wake that promotes re-energization and re-mixing of the low-energy fluid. As a result, the near-stall operating point is shifted toward 15.86% lower mass flow with only a 0.4% penalty in peak isentropic efficiency. Simultaneously, both the total pressure ratio and isentropic efficiency are improved under reduced flow conditions.