| A quasi-dimensional multi-zone combustion model and a radiation heat transfer model are developed for the study of turbocharged diesel engine performance and energy and availability balance. The quasi-dimensional multi-zone combustion model is based on the air and fuel mixing process with a temperature and concentration dependent fuel burning rate. In order to study the combustion process, several submodels, such as the fuel evaporation and air entrainment, are developed based on critical phenomena. The model shows that predicted cylinder pressure and heat release shape are in good agreement with experimental data under rated speed and load conditions. In the radiation heat transfer model, a modified two flux model is used to analyze penetration of radiation through translucent materials. The model, in addition to transient heat conduction through combustion chamber walls, is especially important to the design of ceramic-insulated engines. Based on the combustion and radiation heat transfer models, the energy is balanced by both the first law and the second law of thermodynamics. The results provide insight into the sources of availability destruction and their relative contributions. In particular, combustion loss due to the entropy generated when reactants are transformed into products can account for over 20% of the fuel availability, and less than 60% of the energy contained in the exhaust gases can be recovered using ideal thermodynamic devices. It is also shown that the model produces expected trends under different engine operating conditions. |
