Study of Reynolds stresses and loss generation at the inlet to a centrifugal vaneless diffuser

Abstract

Detailed flow measurements at the inlet to a centrifugal compressor vaneless diffuser are presented. The mean velocities and six component stress tensor are used to determine the turbulence production terms which lead to total pressure loss. Four regions in the flow are identified as potential sources of loss - the blade wake, the shear layers between passage wake and jet, the thickened hub boundary layer and the interaction region between the secondary flow within the blade wake and the passage vortex. The blade wakes generate most turbulence, with smaller contributions from the hub boundary layer and secondary flows, but no significant contribution is apparent from the passage wake shear layers.