CFD Analysis of Inlet Flow Region in a Centrifugal Compressor

Abstract The inlet region of a typical multi-stage centrifugal compressor for oil and gas applications consists of an inlet flange/nozzle, splitter vanes, and inlet guide vanes (IGVs). Recent findings of an existing legacy multi-stage centrifugal compressor, which had been recently revamped, indicated a lower flow capacity than what is expected. Further testing of the compressor revealed a potential scope for improvement in flow capacity. After performing stage-by-stage analysis, it was determined that an improvement in the design of the inlet region could enhance the performance. The inlet region plays a crucial role in guiding the flow towards the impeller, ideally distributing the flow uniformly with minimal loss. Flow distortions may occur in any inlet, the extent of which may differ depending on its design and can further lead to poor performance characteristics of the compressor. This paper will describe the work completed to reduce the flow losses and distortions in the inlet region by performing Computational Fluid Dynamics (CFD) analysis with the help of a simulation software. A parametric study was carried out to optimize the flow characteristics in the inlet region, where it was observed that rotating the IGV angles by a certain amount, loss coefficient and pressure distortions are reduced. The results obtained and lessons learned can be used for enhancing the performance and improving existing correlations when designing future compressors.