关键词: 热机;卡诺循环;布雷顿循环;最优方案

Abstract: The performances of steady flow in Brayton and Carnot thermal engine cycles are studied for infinite thermal capacitance rates of heat reservoirs. The fundamental relations between power output and efficiency, the maximum power outputs and the corresponding efficiency bounds of the cycles are derived. A comparison of the characteristics of the two cycles under same boundary conditions (same heat source/sink temperatures and heat exchanger conductances) is presented.Theoritical analysis shows that the power output for Brayton cycle approaches as value as that for Carnot cycle when the factor (ratio of thermal capacitance rate of the working fluid to the total heat exchanger inventory) approaches infinity. Numerical calculation indicates that the power output for Brayton reaches higher than 99% of that for Carnot as the factor equals to 1. 5.

Key words: Heat engine;Carnot cycle;Brayton cycle;Optimal plan