Objective In recent years, CO₂ power generation systems have garnered significant attention from researchers worldwide. Adding other working fluids to CO₂ can alter its thermal properties, thereby modifying the performance of thermal systems. Building upon the recompression cycle, this paper proposes a power generation system featuring two-stage compression and reheating processes, aiming to provide insights for the development of CO₂ mixed-working-fluid power generation systems.

Method Energy analysis and exergy analysis models were established. Binary working fluids composed of CO₂ and working fluids such as propane, ethane, pentane, n-butane, and isobutane were employed as working fluids, calibrated according to their molar fraction ratios. The study investigated how key parameters, including high-pressure turbine inlet pressure, minimum cycle temperature, minimum cycle pressure, reheat pressure, and intermediate pressure, influenced system performance.

Result Analysis of all operating conditions indicates optimal system performance occurs at a minimum cycle pressure of 7 MPa with a CO₂/isobutane mixed working fluid (0.93/0.07). This configuration constitutes a transcritical cycle, achieving a maximum thermal efficiency of 50.610%. This represents a 5.743% improvement over pure CO₂ systems, The exergy efficiency reaches 74.753%, representing an 8.482% improvement over pure CO₂ systems.

Conclusion The system performance under different operating conditions is significantly influenced by the proportion of mixed working fluids. The cycle process is either supercritical or transcritical. Furthermore, when identical operating conditions vary within a certain range, the optimal thermal efficiency and exergy efficiency exhibit fixed patterns of change. Propane, ethane, butane, and isobutane, at specific proportions and operating conditions, enable the system to achieve the highest thermal efficiency and exergy efficiency. Pentane generally yields inferior system performance compared to other mixed working fluids under most operating conditions.