Numerical Study on the Effect of Free Rotating Vaneless Diffuser of Exit Diameter to Inlet Diameter Ratio 1.3 with Speed Ratio 0.50 on Centrifugal Compressor Performance

Abstract

Innovative methods in the design of radial diffuser are necessary for reducing the energy losses associated with diffusion in order to design an efficient centrifugal compressor. Rotating vaneless diffusers is one such concept, in which a particular type, free rotating vaneless diffuser, the diffuser speed becomes a fraction of the rotating impeller speed and rotates independently. In this paper, an impeller with stationary vaneless diffuser alone of diffuser diameter ratio 1.40 and the same impeller with a freely rotating vaneless diffuser of diffuser diameter ratio 1.30 along with stationary vaneless diffuser at downstream for the remaining radius ratio are analyzed for flow diffusion and performance. Higher static pressure rise with reduced stagnation pressure losses and a marginally lesser efficiency by around 3.5% compared to SVD is achieved by the free rotating vaneless diffuser configuration (FRVD30SR0.5).