Effects of Reynolds Number on Performance Characteristics of a Centrifugal Compressor, With Special Reference to Configurations of Impellers

The influences of Reynolds number on performance characteristics of centrifugal compressor were examined for various impeller configurations, that is, a double shrouded impeller with straight radial blades, a single shrouded impeller with straight radial blades, a single shrouded impeller with forward curved blades and a single shrouded impeller with backward curved blades. As a test equipment, a closed circuit of duct was employed, and the Reynolds number was varied by changing air pressure in a plenum chamber located upstream of the compressor. From the results, it was found that: (1) Among losses generated within a compressor stage, rates of losses independent of the Reynolds number became minimum at a certain flow coefficient. (2) As to the critical Reynolds number, the relation between relative surface roughness and critical Reynolds number for a stationary circular pipe is roughly applicable. (3) The secondary flow losses within impeller channels may be related to ζ_s = 51/Re_wl^0.5. In addition, the amount of each loss generated within a compressor stage was estimated.