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International Journal of Rotating Machinery
Volume 2006, Article ID 56420, 11 pages

Two-Dimensional Rotating Stall Analysis in a Wide Vaneless Diffuser

1Section of Energy Technology, Division Thermo Fluids Engineering, Department of Mechanical Engineering, Eindhoven University of Technology, Den Dolech 2, Eindhoven, MB 5600, The Netherlands
2Department of Flow and Structural Dynamics, TNO Science and Industry, P.O. Box 155, Delft, AD 2600, The Netherlands

Received 26 August 2005; Accepted 7 September 2005

Copyright © 2006 S. Ljevar et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


We report a numerical study on the vaneless diffuser core flow instability in centrifugal compressors. The analysis is performed for the purpose of better understanding of the rotating stall flow mechanism in radial vaneless diffusers. Since the analysis is restricted to the two-dimensional core flow, the effect of the wall boundary layers is neglected. A commercial code with the standard incompressible viscous flow solver is applied to model the vaneless diffuser core flow in the plane parallel to the diffuser walls. At the diffuser inlet, rotating jet-wake velocity pattern is prescribed and at the diffuser outlet constant static pressure is assumed. Under these circumstances, two-dimensional rotating flow instability similar to rotating stall is found to exist. Performed parameter analysis reveals that this instability is strongly influenced by the diffuser geometry and the inlet and outlet flow conditions.