An improved two-zone model for the design of supercritical CO2 centrifugal compressors and verification

The supercritical carbon dioxide (SCO₂) Brayton cycle is a promising power cycle characterized by its high efficiency and compact turbomachinery. As a key component, the centrifugal compressor significantly impacts the cycle performance. However, drastic changes in CO₂’s physical properties near the critical point pose significant challenges to compressor aerodynamic design. To enhance the accuracy of SCO₂ centrifugal compressor design and alleviate the design workload, an improved two-zone model has been proposed and implemented through computer programming for one-dimensional aerodynamic design. The aerodynamic performance and flow characteristics of the compressor designed with this model were then examined by solving the steady Reynolds-averaged Navier-Stokes (RANS) equations. The results indicate that, under design conditions, the compressor designed using the improved two-zone model exhibits relative errors of less than 1.5% for both the total-to-total pressure ratio and total-to-total isentropic efficiency. Additionally, the design process time has been reduced to one-third of its original duration. Notably, the impeller blade tip clearance significantly affects compressor performance, and the flow impacts the leading edge of the vaned diffuser, which leads to an increase in the Mach number and heightens the risk of cavitation for SCO₂. Three-dimensional numerical calculations have verified the validity of the improved two-zone model in designing SCO₂ centrifugal compressors. This finding is of significant importance for advancing the application of SCO₂ centrifugal compressors in the field of power engineering.