Computational analysis of the performance characteristics of a supercritical CO2 centrifugal compressor

Abstract

A centrifugal compressor working with supercritical CO2 (S-CO2) has several advantages over other supercritical and conventional compressors. S-CO2 is as dense as the liquid CO2 and becomes difficult to compress. Thus, during the operation, the S-CO2 centrifugal compressor requires lesser compression work than the gaseous CO2. The performance of S-CO2 compressors is highly varying with tip clearance and vanes in the diffuser. To improve the performance of the S-CO2 centrifugal compressor, knowledge about the influence of individual components on the performance characteristics is necessary. This present study considers an S-CO2 compressor designed with traditional engineering design tools based on ideal gas behaviour and tested by SANDIA national laboratory. Three-dimensional, steady, viscous flow through the S-CO2 compressor was analysed with computational fluid dynamics solver based on the finite volume method. Navier-Stokes equations are solved with K-ω (SST) turbulence model at operating conditions in the supercritical regime. Performance of the impeller, the main component of the centrifugal compressor is compared with the impeller with vaneless diffuser and vaned diffuser configurations. The flow characteristics of the shrouded impeller are also studied to analyse the tip-leakage effect.