Numerical research on performance of new structure centrifugal compressor for supercritical CO2 power systems

The supercritical carbon dioxide (sCO2) power cycle system is a potential thermoelectric conversion system with the advantages of high efficiency and compactness, which can be used in the fields of solar thermal power, nuclear power, and other thermal power systems. The compressor is one of the important machines in sCO2 power systems. To improve the performance and reduce the condensation risk of sCO2 centrifugal compressors, a new structure sCO2 centrifugal compressor is proposed in this paper, which has a partial-cover impeller and self-circulation-channel casing (PISC). The internal flow of the compressor with the new structure is analyzed by the CFD method. The flow and condensation in sCO2 centrifugal compressors with the PISC structure and that with the semi-open impeller and traditional casing (SITC) are compared. The results show that the PISC sCO2 compressor has an inhibiting effect on the condensation at the compressor inlet location, reducing the condensation volume to approximately 82% of that of the original structure under design conditions. The total pressure ratio and isentropic efficiency of compressors are simulated, and the result shows that the minimum stable mass flow rate is reduced by about 13% by introducing the new PISC structure into the sCO2 centrifugal compressor, and the maximum isentropic efficiency is increased from 83.5% to 84.4% compared to that of the SITC compressor. A new design idea for the impeller and sCO2 compressor structure is provided in this paper. The research results can be applied to sCO2 compressors and improve the performance and stability of sCO2 power cycle systems.