Rotating nonuniformity induced by distortion inlet and its role on the compressor stall inception

This study conducts full-annulus, unsteady, three-dimensional computational fluid dynamics simulations, aiming to investigate the effect of distortion inlet and its role on the compressor stall inception. The results reveal that circumferential distortion induces both inherent and rotating nonuniformity. The unsteady flow structures affected by the nonuniformity within individual passages are recorded at each physical time step and analyzed using advanced post-processing techniques, including the vortex identification and quantification methods. The results highlight two primary vortex structures that play critical roles in stall initiation: the tip leakage vortex and the leading-edge vortex. Importantly, circumferential distortion does not merely introduce inherent nonuniformity; rather, it excites a rotating nonuniformity in which the first wavenumber is dominant, evident in the organized distribution of vortex structures across passages. Among these vortices, the leading-edge vortex—originating near mid-span suction surface—is identified as the dominant precursor to stall. Its initial spatial distribution pattern matches the inherent nonuniformity and subsequently begins to rotate circumferentially at a frequency of approximately 0.24 times the blade passing frequency. Then, the tip leakage vortex exhibits an upstream migration affected by the rotating nonuniformity and shedding leading-edge separation vortex, serving as a secondary contributor. The interaction between these two vortices eventually leads to the formation of a single rotating stall cell. These findings provide novel insights into how circumferential distortion can excite inherent and rotating nonuniformity within compressor systems and influence vortex interaction dynamics.