A Numerical Analysis of the Effects of Liquid Carryover on the Performance of a Two-Stage Centrifugal Compressor

To extend the current understanding of the effects of liquid carryover on compressor performance, a detailed analysis including the aerothermodynamics of the compression process and the flow field within the compressor is required. This paper presents a CFD analysis of a two-stage, in-line centrifugal compressor, operating in a two-phase flow environment of a single constituent, refrigerant R134a. The computational method implemented in this analysis accounts for the real gas behavior, and also incorporates the effects of interphase heat, mass and momentum transfer, as well as the droplet dynamics. The investigations revealed that liquid carryover altered the flow field within the compressor, causing both stages to operate at off-design conditions. This effect was observed to be more pronounced for the second stage. The overall effects of liquid carryover were shown to be detrimental to the compressor performance. Increasing the amount of liquid carryover resulted in further lowering of the performance. On the other hand, the effects of the size of the ingested droplets were seen to be negligible.