Response and stall mechanism for axial compressor under rotating inlet distortion

For multi-shaft aero-engines, the downstream compressor inlet will be exposed to rotating inlet distortion once rotating stall occurs in the upstream fan or low-pressure compressor. In this paper, an experimental study is carried out on six axial compressors under rotating inlet distortion, aiming to clarify the effects of rotating inlet distortion and reveal the stall mechanism. The result under rotating inlet distortion shows that the rotational speed of distortion strongly affects the stability of the compressor. Within a certain band of distortion speeds, i.e., in the dangerous distortion speed band, the stability margin of the compressor decreases extremely severely. Comparing the results from the six compressors, it is discovered that the left boundary of the dangerous distortion speed bond coincides with the propagation speed of rotating stall, whereas the right boundary is associated with the distortion angle. When introduced rotating inlet distortion, flow separation is prone to occur in the high-load region, which consequently induces stall disturbance. The reason for the varying stability margin with the distortion speed is that the distortion zone at different speeds affects the spatiotemporal evolution of the stall disturbance. Within the dangerous distortion speed bond, the intensified effect of the distortion zone accelerates the evolution of stall disturbance into rotating stall. At the end of this paper, a model is proposed to explain the impact of distortion speed and distortion angle on compressor stall.