混合工质对sCO₂布雷顿循环热效率与高点压力的协同提升机制

Synergistic Enhancement Mechanism of Mixed Working Fluids on Thermal Efficiency and Peak Pressure in sCO₂ Brayton Cycles

摘要: 超临界二氧化碳(sCO₂)布雷顿循环因高热效率和紧凑性被广泛关注，但其依赖纯CO₂工质需在高温高压(临界点304.13 K/7.39 MPa)下运行，导致设备成本高且热源适配性受限。针对此问题，本研究通过热力学建模与数值模拟，系统研究了乙烷、丙烷、R116等低浓度(0~10 mol%)混合工质对sCO₂循环热效率与系统高点压力的协同调控作用，明确了工质临界参数对循环性能的调控规律。结果表明，丙烷在800 K工况下既能使热效率提升2.5%，又能降低系统高点压力15.2%，在效率–压力权衡中表现最优；R116和R125则分别适用于效率优先与压力敏感场景。该研究为sCO₂循环在核能、太阳能热发电等领域的高效低碳运行提供了明确的工质选型策略，拓展了混合工质调控技术的应用边界。

Abstract: The supercritical carbon dioxide (sCO₂) Brayton cycle has attracted extensive attention due to its high thermal efficiency and compactness. However, its reliance on pure CO₂ as working fluid requires operation under high temperature and pressure conditions (critical point: 304.13 K/7.39 MPa), leading to elevated equipment costs and restricted thermal source compatibility. To address these challenges, this study systematically investigates the synergistic regulation effects of low-concentration (0~10 mol%) mixed working fluids (ethane, propane, R116) on thermal efficiency and peak system pressure of sCO₂ cycles through thermodynamic modeling and numerical simulations. The regulatory mechanisms of working fluid critical parameters on cycle performance are elucidated. Results demonstrate that propane achieves optimal trade-off performance under 800 K operating conditions, simultaneously improving thermal efficiency by 2.5% and reducing peak system pressure by 15.2%. R116 and R125 are respectively recommended for efficiency-prioritized and pressure-sensitive scenarios. This research provides clear working fluid selection strategies for efficient and low-carbon operation of sCO₂ cycles in nuclear energy and solar thermal power generation applications, thereby expanding the application boundaries of mixed working fluid regulation technology.