Rotating stall in a two-dimensional vaneless diffuser flow

This paper reports a numerical investigation aimed at understanding the rotating stall mechanism in radial vaneless diffuser. The study of vaneless diffuser flow instability is restricted to a two-dimensional flow analysis, where the influence of wall boundary layers is neglected. A commercial code with the standard laminar viscous flow solver is applied to model the incompressible vaneless diffuser flow in the plane parallel to the diffuser walls. At diffuser inlet rotating jet-wake velocity profile is prescribed and at diffuser outlet constant pressure. Current study reveals that a two-dimensional rotating instability in the vaneless radial diffuser occurs when the critical flow angle is reached. The diffuser flow stability limit is determined for different diffuser radius ratios, which reveals that the core flow stability in the vaneless radial diffuser improves as the diffuser radius ratio decreases.