A Study on the Rotating Stall of Centrifugal Compressors (2nd Report, Effect of Vaneless Diffuser Inlet Shape on Rotating Stall)

Abstract

Rotating stall induced in a vaneless diffuser is examined. Combination of several low specific speed impellers and three types of diffusers with different inlet shape are tested. In the lower specific speed stages, the critical inlet flow angle for rotating stall depends not only on diffuser width ratio b/γ2, and contraction ratio b/b2, but also on the inlet shape of the diffuser. As the inlet shape parameter Δγ/γ2 becomes smaller than value of 0.1, the critical inlet flow angle becomes larger than the predicted value by the Senoo method. The empirical prediction formula of critical inlet flow angle in the first report is corrected by considering the influence of inlet shape. Influence of inlet shape on rotating stall phenomenon is also shown. © 1990, The Japan Society of Mechanical Engineers. All rights reserved.