布雷顿和卡诺热机循环性能比较(Ⅱ)定常态流变温热源循环

COMPARISON IN PERFORMANCE OF BRAYTON AND CARNOT THERMAL ENGINE CYCLES(Ⅱ)STEADY FLOW CYCLES WITH FINITE RESERVOIRS

研究定常态变温热源热机循环性能，导出内可逆卡诺热机和布雷顿热机的最佳功率、效率关系和最大功率及相应的效率界限，并对这两种热机循环的最优性能进行了比较。理论分析表明，在相同的边界条件和热效率下，布雷顿循环的功率可以高于卡诺循环的功率，极限情况下前者是后者的两倍。对于变温热源条件，布雷顿循环主要受益于其工质与热源间有较佳的匹配。所得结果对热机工作参数和工质的最优选择有一定指导意义。

The performance of steady flow Brayton and Carnot engine cycles is studied for finitethermal capacitance of heat reservoirs. The optimal power output cycle efficiency and their limit arederived. A comparison between the performance characteristics of the two cycles is performed.Theoritical analysis shows that the optimal power output of the Brayton cycle is higher than that ofthe Carnot cycle under the same specified boundary conditions. The former can be twice as high as thelatter in the limit case. The Brayton cycle is benefited from the matching between working fluids andthe variable-temperature heat reservoivs. The results given in this paper provides a guidance forpracticing engines in selecting operating parameters and working fluids.