Unsteady CFD simulation for high speed centrifugal compressor operating near surge

Abstract

Centrifugal compressor surge and stall are an instabilities flow and system phenomenon, which can lead to a loss of engine power, large pressure transients and, in some cases, failure of the compressor and bearing system. Three-dimensional, compressible, unsteady Navier-Stokes equations are solved, using the sliding mesh at the interface between the moving and stationary parts. The investigated computational domain is composed of inlet pipe, inlet bell, impeller followed by a diffuser. The impeller side cavities are included in the computational domain, to make the simulation more close to the actual case. The present article focuses on the unsteady pressure and velocity results within the impeller and diffuser, at an operating condition close to the surge of the compressor. The computational data compares favorably with the measured data, from literature, for the same compressor and operational point. The pressure fluctuation results are analyzed for the surge and design operating conditions. Through the acquisition of both velocity and transient pressure data, the time evaluation of the unsteady flow during surge is revealed.