考虑有限温差传热、不可逆压缩过程和不可逆膨胀过程等不可逆因素,应用有限时间热力学理论建立了变温热源条件下的回热型超临界二氧化碳布雷顿循环模型。首先，分析了工质质量流率、压比、透平效率和压缩机效率对循环净输出功率、热效率和循环最高温度的影响；然后,在总热导率一定的条件下分别以输出功率最大和热效率最大为目标，对加热器、冷却器和回热器热导率分配比进行优化。结果表明：回热型SCO2布雷顿循环功率-效率特性曲线呈过原点的扭叶型，存在相应的压比使得输出净功率与热效率分别达到最大；相比于初始设计参数计算的循环性能，优化后循环净输出功率可提高27.3%，最大比功可提高46.9%，最大热效率可提高17.78%。

In view of the irreversible factors such as finite temperature difference heat transfer,irreversible compression process and irreversible expansion process,the theory of finitetime thermodynamics was used to establish a regenerative SCO2 Brayton cycle model under the condition of variable temperature heat source.Firstly,the influences of the mass flow rate of the working fluid,pressure ratio,turbine efficiency and compressor efficiency on the net power output of the cycle,the thermal efficiency and the maximum temperature of the cycle were analyzed.Then,the maximum net power output and heat efficiency were chosen as optimization objectives respectively,and the heat conductivity distribution ratios of the heater,cooler and regenerator were further optimized at the fixed total heat conductivity.The results show that the power vs.efficiency characteristic curve of the regenerative SCO2 Brayton cycle is a loopshaped curve through the origin,there is a corresponding pressure ratio to maximize the net power output and thermal efficiency respectively; compared with the cycle performance calculated by the initial design parameters,the optimized net power output of the cycle can be increased by 27.3%,the maximum specific work can be increased by 46.9%,and the maximum thermal efficiency can be increased by 17.78%.

TK123

国家自然科学基金（51976235，51606218，51576207）；湖北省自然科学基金(2018CFB708)