采用有限时间热力学深入研究了恒温热源一恒温冷源和变温热源一恒温冷源液氮发动机朗肯循环、布雷顿循环和斯特林循环的优化和对比；

• Based on the finite time thermodynamic theory, the thesis discusses the optimization of Rankine cycle, Brayton cycle and Stirling cycle between constant temperature heat source and constant temperature heat sink or between variable temperature heat source and constant temperature.