Computational Study of Rotating-Stall Inception in Axial Compressors

Abstract

Rotating-stall inception in axial-e ow compressors has been studied computationally using a quasi-threedimensional time-marching Navier ‐ Stokes method with a mixing-length turbulence model. Of particular interest was the effect of external circumferential disturbances corresponding to inlet stagnation pressure distortions and rotor/stator blade interactions. The present results show that rotating stall onset patterns in terms of number of stall cells and rotating speeds were ine uenced by small external circumferential stationary or rotational disturbances. First mode circumferential disturbances had the most destabilizing effect, resulting in a single-cell pattern rotating in the absolute frame at about 50% rotor speed, as is observed in most experiments. Short-scale multiple-cell patterns rotating at a higher absolute speed could also be excited by a disturbance with the same circumferential length scale. Short-scale multiple-cell patterns tended to be more persistent in an isolated blade row than in a stage. In the latter case, a shortscale pattern initiated by a rotor ‐ stator interaction would quickly change into a long-scale single-cell pattern, associated with a distinct change of the rotating speed.