Vaneless Diffuser Flow With Extremely Distorted Inlet Profile

Abstract

The exit flow distribution of 90-deg centrifugal compressor impellers is distorted in peripheral direction as well as over the diffuser depth. First, there are the rotating jet-and-wake regions behind each impeller channel. Second, the flow has a completely distorted inlet profile from the front to the back wall of the diffuser. Measurements of static and total pressure, total temperature, and flow angle profiles along the whole diffuser length have been carried out in a high specific speed compressor. The results show great angle and total pressure differences in the first part of the diffuser and a backflow zone near the front wall. At the end of the diffuser, a separation zone was located. It is shown that by means of a one-dimensional calculation method, using a dissipation factor, the measured representative mean values of the diffuser flow can be determined very well in the regions where no separation occurs.