Performance analysis of centrifugal compressors in supercritical CO₂ Brayton cycles considering non-equilibrium condensation

Energy storage technologies play a critical role in balancing energy supply and demand, as well as facilitating large-scale integration of renewable energy sources. The supercritical carbon dioxide (sCO₂) Brayton cycle, known for its high efficiency and compact design, is widely regarded as an ideal solution for large-scale energy storage. However, the dramatic variation in sCO₂ thermodynamic properties near the critical point can induce condensation within compressors, adversely affecting system performance and stability. To address this challenge, this paper presents a novel condensation flow model that integrates the entropy transport equation with real gas thermodynamics, enabling precise prediction of condensation behavior and its impact on compressor performance. The results show that when the inlet temperature decreases from 320 K to 310 K, condensation is significantly intensified, with phase-change entropy generation increasing by 9.16 times and heat transfer entropy generation increasing by 47.2 %, resulting in greater exergy destruction and reduced efficiency. Compared to conventional dry gas models, the proposed model provides a more accurate assessment of compressor efficiency, avoiding overestimation errors of up to 11.6 %. This theoretical tool offers the scientific community a new approach for in-depth analysis of condensation phenomena within compressors, supporting the optimization of sCO₂ energy storage system design, enhancing system stability and efficiency, and addressing engineering challenges such as blade corrosion. • Systematic analysis of performance in small-scales CO₂ centrifugal compressors. • Distribution of condensation on the leading-edge suction side of blades. • Qualitative and quantitative analysis of condensation impact on entropy generation. • As T in decreases from 320 K to 310 K, S gen , L increases by a factor of 9.16. • The dry gas model overestimates the energy efficiency by up to 11.6 %.