Numerical simulation of rotating stall in a centrifugal compressor with vaned diffuser

This paper reports a numerical study on the process from normal operating conditions to rotating stall in a cen- trifugal compressor with vaned diffuser.The purpose is to better understand the flow characteristics near stall point under the interactions between centrifugal impeller and vaned diffuser.Numerical results show that under certain conditions just preceding stall point the tip leakage vortex begins to fluctuate at roughly half of the blade passing frequency.This phenomenon is similar to rotating instability in axial compressors.With the flow rate re- duced further the impeller stalls and five stall cells propagating at a frequency of 85 percent of impeller rotation speed are found.