The Performance Optimization Of Generalized Irreversible Miller And Otto Heat Engine Cycle

Finite time thermodynamics is an extension and promotion of classical thermodynamics, as a significant branch of the modern thermodynamics, is mainly aimed to investigate the regulation of energy and entropy flows of non-equilibrium systems in finite time. Finite time thermodynamics can deal with the change processes of the time and rate, such as output power, the entropy production rate, et al. After introducing the heat leak loss, friction loss, internal irreversibility and temperature-variable heat capacities, the new optimal criterions for the actual process are provided.The generalized irreversible Miller heat engine and generalized irreversible Otto heat engine cycle performance characteristics are studied in this thesis. By theoretical analysis and numerical calculation, the following works are made.1. The generalized irreversible air-standard Miller heat engine cycle model is established after considering the working substance with temperature-variable heat capacities, heat leak through the cylinder wall, finite-rate heat transfer, friction loss and the internal irreversibility of non-isentropic adiabatic processes. The detail expressions for the power output and efficiency are derived. By numerical calculation, the maximum output power, maximum efficiency and the corresponding parameter values are obtained. The graphs between these parameters to reflect their changes are plotted. Moreover, the influences of the heat leak, internal irreversibility, temperature-variable heat capacities and friction loss on the performance parameters of the Miller heat engine are discussed and the optimal operating regions of the important parameters are determined.2. The generalized irreversible air-standard Otto heat engine cycle model is set up, in which contains finite-rate heat transfer, heat leak loss through the cylinder wall, temperature-variable heat capacities, friction loss and the internal irreversibility. The analytic expressions for the power output and efficiency are derived. The curves of the power output versus the efficiency are plotted, and their optimal operating regions are found. Moreover, the influences of the heat leak, temperature-variable heat capacities, internal irreversibility and friction loss on the performance parameters of the Otto heat engine are discussed.