Development of a Mixing and Combustion Zero-Dimensional Model for Diesel Engines 2006-01-1382
The aim of this work is to develop a combustion and emissions (NOx and soot) predictive tool that allows rapid parametric explorations of operating conditions and geometric configurations in diesel engines. This paper will present the mixing and combustion models used.
All the models are constructed around a spray-mixing model. This mixing model is based on the gaseous steady jets theory. The transient behavior description of the initial and final phases of the injection-combustion process is obtained from CFD studies. The mixing model allows the determination of the instantaneous local conditions of temperature and species mass fraction, used by the ignition, premixed and diffusion combustion models. The ignition and premixed combustion models are based on a simplification and parameterization of a complete n-heptane chemical kinetics description.
Some constants of the models are adjusted by a genetic algorithm with experimental information from different engines. The adjusted models are valid for a wide range of tested engines and operating conditions. Only one constant of the mixing model, mainly related to the nozzle characteristics, has to be adapted when the engine configuration changes (this is also applicable to any CFD model).
The result of the work is a practical tool that predicts with sufficient accuracy several engine operating parameters such as: combustion law, in-cylinder pressure evolution and gradient, available energy at the exhaust, etc. It also forms a good basis for the prediction of NOx and soot emissions. These predictions will be analyzed in future studies.