Stall Warning and Adaptive Control Subjected to Rotating Inlet Distortion in Axial Flow Compressor

Abstract

Adaptive stability control is experimentally implemented in a single-stage axial flow compressor subjected to rotating inlet distortion. Stall margin variations are examined as a function of the distorted area and rotational speed. A critical minimum value is identified when the distorted sector rotates at 0.5 times the rotor speed (P0.5RS), which remains independent of the size of the distorted area and induced frequency. Unsteady pressure measurements indicate that with the rotating inlet distortion at P0.5RS, the circumferentially propagating speed of the stall cell-induced downstream of the distorted region closely matches the rotational speed of the distorted sector, which causes the stall cell to undergo repeated cycles of generation, circumferential propagation, decay, and re-generation, ultimately leading to premature deep stall as the disturbance energy accumulates. In addition, tip air injection can suppress the repeated periodic disturbance energy accumulation, thereby delaying stall. Based on successful verification of the early stall warning under rotating inlet distortion through cross-correlation analysis, an adaptive stability control strategy is devised to sense the stall warning signal in real time and feed back the signal to control the injected valve once the alarm line is triggering. Even under the rotating distorted inflow at P0.5RS, the stall margin can be improved online by more than 10% while reducing the injected energy by 80% compared with that corresponding to steady injection. It provides insights for mitigating the adverse effects of rotating distortion on the compressor performance in multispool aero-engines.