A Simulation Study On The Characteristics Of NO_x Emission In Di Diesel Engine

In this paper, NOX formation model of direct injection diesel engines was established, which combines the quasi-dimensional spray combustion model based on Hiroyuki Hiroyasu's model with the detailed chemical kinetics mechanism of NOX formation. The experimental study proves that the model has good precision, so it can be applied to explain the main factors which affect NOX formation during the combustion of direct injection diesel engines.After a detailed analysis of the characteristics of zero-, quasi-, and multi-dimensional models of direct injection diesel engines, we make proper simplifications on the quasi-dimensional combustion model. At the same time, the minute chemical kinetics mechanism of NOX formation, during the combustion of direct injection diesel engines, has been detailedly investigated. In the model, the mechanism of NOX formation is the synthetic of the extended Zeldovich mechanism and Fenimore mechanism of NO formation as well as NO2 formation mechanism.On the basis of the model the author wrote the programs with the scientific calculating programming language-MATLAB. The simulation results have been compared with experimental data on a single-cylinder direct injection diesel engine. Predicted cylinder pressure diagram and the characteristics of NOX emission show acceptable quantitative agreement with the experimental data. A parametric study of the effect of variation in injection timing is then carried out. Both the simulation results and experimental data show that deferred injection timing leads to decreases in combustion pressure and NOX concentration.