Design and development of a stable supercritical CO2 centrifugal compressor

Introducing supercritical carbon dioxide (s-CO2) as a working fluid can enhance the power generation of Brayton cycles. However, various challenges are involved in designing, and developing a stable s-CO2 centrifugal compressor on a reasonably sized s-CO2 Brayton cycle. This article presents a 1-D design and development procedure for s-CO2 centrifugal compressors suitable for Brayton power cycles. The 1-D compressor design approach employs the Widom region, AMC, and internal and external loss models to optimize the compressor design. The 1-D design code is validated with CFD simulation and experimental data from Sandia. Further, a new stable compressor for a 10 MWe s-CO2 Brayton cycle is designed, proposed, and discussed in this paper. Based on the 1-D design code and the CFD results, the newly designed compressor exhibits an improved operational range. Additionally, a loss analysis of the designed s-CO2 compressor revealed that internal losses accounted for 75.8% of the total enthalpy loss. The compressor's internal flow behavior at choke is investigated by utilizing a novel analogy between the impeller at choke and a converging-diverging nozzle. The CFD results showed that condensation is inevitable in an s-CO2 centrifugal compressor operation; however, condensation does not significantly affect compressor performance near the design point.