A Novel Low-Cost Diffuser for High-Performance Centrifugal Compressors

Abstract

A novel, low-cost diffuser based upon discrete pipe drillings has been developed for high-performance centrifugal compressors. These discrete drillings are arranged in symmetrical array to mutually intersect in a radial plane so that a gradual transition from the open vaneless space at rotor tip to the individual throats of each pipe is implicitly defined. To draw a comparison, alternate cambered-vane and flat-plate diffusers were defined using the best available yet practical thinking. With a nominal 5:1 stage pressure ratio, rotor, 81.8 percent efficiency was obtained with the “pipe” diffuser at 5.42 pressure ratio. This efficiency level exceeded the best cambered-vane and flat-plate performance by 6.8 and 8.8 percent, respectively. Further testing with a second rotor yielded 81.3 percent efficiency at 6:1 pressure ratio for the pipe diffuser and 73 percent efficiency at 6:1 for the cambered-vane diffuser.