Abstract The off-design behavior of sCO2 recompression cycle caused by adjusting the CO2 flow to meet the production remains to be one of the most concerned problems. In this paper, a thermodynamic model of sCO2 recompression cycle based on sodium-cooled fast reactor was established. And the sensitivity analysis of inlet conditions at turbomachinery and cycle pressure ratio (PR) was conducted in combination with the flow split ratio (FSR). Based on the highest cycle efficiency, the performance analysis of the main compressor was performed by employing a similar method, which was extended to the system with the aim of investigating the off-design behavior. The sensitivity analysis results indicate that enlarging p1 can reduce the sensitivity of T1, and when the compressor inlet fluid approaches the critical state (304.12 K 7.38 MPa), the cycle efficiency reaches maximum at FSR = 0.31 and PR = 2.9. Then the off-design performance of the system in the case of flow adjustment is successfully predicted, during which excessive flow is found to reduce the output power of the system and lead to a maximum efficiency difference of about 13%. Also observe that the efficiency of the re-compressor in single-stage recompression mode is significantly lower than that of the main compressor and turbine. Finally, the mechanism of two-stage recompression to improve the compactness and off-design performance of the system is clarified and the applicability of the two-stage turbine without intermediate reheat is discussed.

中文翻译：

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核电超临界二氧化碳再压缩循环热力学设计与非设计研究

摘要 调整CO2流量以满足生产而导致sCO2再压缩循环的非设计行为仍然是最受关注的问题之一。本文建立了基于钠冷快堆的sCO2再压缩循环热力学模型。并且结合分流比（FSR）对涡轮机械和循环压力比（PR）的入口条件进行了敏感性分析。基于最高循环效率，采用类似的方法对主压缩机进行性能分析，并将其扩展到系统，目的是研究非设计行为。灵敏度分析结果表明，增大 p1 可以降低 T1 的灵敏度，当压气机入口流体接近临界状态（304.12 K 7.38 MPa）时，循环效率在 FSR = 0.31 和 PR = 2.9 时达到最大值。然后成功预测了系统在流量调整情况下的非设计性能，在此期间发现流量过大导致系统输出功率降低，导致最大效率差异约为13%。还观察到再压缩机在单级再压缩模式下的效率明显低于主压缩机和涡轮的效率。最后，阐明了两级再压缩提高系统紧凑性和非设计性能的机理，并讨论了无需中间再热的两级涡轮的适用性。在此期间发现流量过大会降低系统的输出功率，并导致最大约 13% 的效率差异。还观察到再压缩机在单级再压缩模式下的效率明显低于主压缩机和涡轮的效率。最后，阐明了两级再压缩提高系统紧凑性和非设计性能的机理，并讨论了无需中间再热的两级涡轮的适用性。在此期间发现流量过大会降低系统的输出功率，并导致最大约 13% 的效率差异。还观察到再压缩机在单级再压缩模式下的效率明显低于主压缩机和涡轮的效率。最后，阐明了两级再压缩提高系统紧凑性和非设计性能的机理，并讨论了无需中间再热的两级涡轮的适用性。