The Optimal Thermodynamic Analysis Of Brayton And Its Combined Cycle

On the basis of understanding and summarizing the current development of Brayton thermodynamic cycles, By theoretical analysis and numerical calculations, this paper focus on the studies of thermodynamic optimal performance of three types of Brayton's combined cycle with the constant-temperature heat-reservoirs and the consideration of the heat resistance of exchanger,irreversible losses in the compressors and turbine.It consists of the following three main parts:The first part concentrates on the exergy optimization of the Joule-Brayton cogeneration cycle. Considering the work and the heat is difference in quality. At first, chapter 2 analyze the irreversible intercooled model, non-dimensionless total output of the exergy as the objective function, The influence of some specific parameters of the cogeneration system on its total output of non-dimensional exergy and exergy efficiency is discussed. Within the rational range of compressors efficiency and turbine efficiency, simple model add to the intercooled process will improve the exergy efficiency of the original system. Through optimizing the distribution of thermal conductivity of the heat exchanger, the maximum non-dimensional exergy and the corresponding exergy efficiency are determined. Then analyze the reheated model, exergy efficiency as the objective function, the optimal distribution of thermal conductivity of the heat exchanger,the corresponding parameters and the maximum exergy efficiency are determined.The second part concentrates on the thermal efficiency optimization of the solar-driven Brayton heat engine. At first, chapter 3 builds up the models of solar collectors and an irreversible regenerated Brayton heat engine, overall efficiency as the objective function with the consideration of the linear heat loss and the radiated heat loss model of solar collectors. By optimizing the operating temperature of the solar collectors and the distribution of thermal conductivity, the optimum operating temperature of the solar collectors,the optimum distribution of thermal conductivity values and the maximum overall efficiency are determined. Then the models of solar collectors and an endo-reversible intercooled regenerated Brayton heat engine is built up. Analyzing the overall efficiency under the linear heat loss model of solar collectors, the optimal operating temperature and pressure ratio are determined.The third part concentrates on the ecological optimization of the combined Brayton and inverse Brayton cycles. Chapter 4 uses the exergy-based ecological coefficient as an objective function, at first, analyzing the endo-reversible model. The optimal ecological performance is determined through optimizing the total pressure ratio when the first level compression ratio at a given. Then analyzing the irreversible model, the maximum ecological coefficient is determined when the first level expansion ratio equal the second level. And on this basis, the double optimal ecological performance is determined by optimizing the total pressure ratio. The effects of the above factors on the ecological performance of the system are discussed, and the results compare with the power,the efficiency and the entropy performance.