A Study of Performance Improvement for High Specific Speed Centrifugal Compressors by Using Diffusers With Half Guide Vanes

Abstract

The experimental results from eighteen different centrifugal compressor stages showed that the pressure recovery of vaneless diffusers for high specific speed compressors was extremely low compared with the value expected by an ideal two-dimensional analysis. Consequently a new type of diffuser with half guide vanes on the shroud side wall was proposed. The pressure recovery of this diffuser at distorted inlet flow was considerably improved by the half guide vanes. The optimum height of the vanes was a little less than one half of the diffuser width. Measurements of the velocity distribution in the diffusers using Pitot tubes and a laser-two-focus velocimeter, clearly showed that the small height guide vanes gave a uniform flow in the axial direction and improved the pressure recovery of the diffuser.