Abstract:

Based on the first law of thermodynamics, a thermodynamic analysis of the recompression Brayton cycle with supercritical CO₂ mixed working medium is carried out. The effects of the gas type and proportion, turbine inlet temperature, turbine inlet pressure, split ratio and main compressor inlet temperature on the thermodynamic performance of the cycle are mainly discussed under the medium and low temperature heat source (200—400℃). The results show that the addition of 0—10% propane, neopentane, isobutane, and n-butane can all increase the cycle efficiency and improve the thermodynamic performance of the cycle system. When the turbine inlet temperature is lower than 260℃, the cyclic thermal efficiency of adding ethane is lower than that of CO₂. With the increase of mixing ratio, turbine inlet temperature and pressure, and shunt ratio, the system circulation efficiency also increases. As the inlet temperature of the main compressor increases, the circulation efficiency decreases.

Key words: medium and low temperature, supercritical CO₂, mixed working medium, recompression Brayton cycle, thermodynamic properties

摘要：

基于热力学第一定律对超临界CO₂混合工质再压缩布雷顿循环进行了热力学分析，重点讨论了在中低温热源下(200~400℃)加入气体种类及比例、透平入口温度、透平入口压力、分流比、主压缩机入口温度对循环热力学性能的影响。结果表明：加入0~10%的丙烷、新戊烷、异丁烷、正丁烷均能够提高循环效率，改善循环系统的热力学性能。在透平入口温度低于260℃时，加入乙烷的循环热效率低于单一工质CO₂。随着混合比例、透平入口温度和压力、分流比的增加，系统循环效率也随之提高。主压缩机入口温度增加，循环效率反而下降。

关键词: 中低温, 超临界二氧化碳, 混合工质, 再压缩布雷顿循环, 热力学性质