Progress in the research on non-equilibrium condensation of the compressor in the supercritical CO2 closed Brayton cycle system

The supercritical carbon dioxide (S-CO2) closed Brayton cycle holds significant promise for revolutionizing the future of efficient and comprehensive new energy utilization. However, the compressor operation in this cycle is characterized by rapid pressurization, which induces substantial fluctuations in temperature and pressure, potentially triggering non-equilibrium condensation of S-CO2. This phenomenon disrupts the flow field within the compressor, thereby decreasing the overall performance of the cycle system. Therefore, exploring this mechanism is of great significance for improving the performance of the cycle system. This work summarizes various improvement types of S-CO2 closed Brayton systems and engineering applications across various fields. Subsequently, it reviews the development of non-equilibrium condensation theories within S-CO2 compressors, focusing on the nucleation and growth models. In addition, the current research status of condensation characteristics of S-CO2 under high-speed and high-pressure conditions is summarized, based on convergent-divergent nozzle experiments and simulations. This work systematically reviews the progress in non-equilibrium condensation research within S-CO2 closed Brayton cycle system compressors, from various perspectives, such as the origin of the technological bottleneck, the nature of the scientific problem, and the current state of research. By reviewing the current status of the compressor blade humidity control method under non-equilibrium condensation, it is proposed that the technology of active blade humidity control based on multi-objective coordination should be the direction of further research. The findings of this analysis can provide a reference for the design and further research on compressor blades in the S-CO2 closed Brayton cycle system.