The Optimal Thermodynamic Analysis Of Brayton Heat Engine

On the basis of understanding and summarizing the current developments of Brayton thermodynamic cycles,this paper focuses on the studies of thermodynamic optimal performance of irreversible Brayton cycle and the Brayton combined cycles using the method of theoretical analysis and numerical calculation.It consists of the following three main parts:The first part concentrates on the exergy optimization of the Joule-Brayton cogeneration cycle.Considering the difference in the quality of energy,chapter 2 carries out exergy optimization for an irreversible Joule-Brayton cogeneration cycle using the theory of thermodynamic optimization.Objective functions of the total produced exergy rate have been defined as function of the design parameters of the system.An equivalent temperature is used to model the exergy rate of heat transfer from the heat recovery generator.The analytical expressions of maximum dimensionless total exergy and the corresponding exergy efficiency are derived. Considering the irreversibility in the non-isentropic compression and expansion processes,the optimum values of the design parameters of the irreversible cogeneration cycle at maximum dimensionless total exergy are determined and the effects of these parameters on exergrtic performance are investigated by numerical analysis.The second part concentrates on the performance optimization of the solar reheated Brayton cycle.Chapter 3 builds up the models of solar collector and irreversible reheated Brayton cycle.The overall efficiency of the system is adopted to be an objective function.The optimum operating temperature of the solar collector is carried out;the effects of the reheated temperature rate and the irreversibility on optimum operating temperature of the solar collector and the performance of the system are evaluated by detailed numerical examples under the linear heat-loss model and the radiative heat-loss model of solar collectors respectively.The third part concentrates on the performance optimization of the combined Brayton-Rankine cycle.Chapter 4 uses the exergy-based ecological function as an objective function,building up the model of combined Brayton-Rankine cycle model with finite-rate heat transfer,heat leak,supplemental combustion and internal irreversibility.The effects of the above factors on the ecological performance of the system are evaluated by detailed numerical examples,and the results will compare with the power and efficiency performance.