Modeling the Effects of EGR on a Heavy Duty DI Diesel Engine Using a new Quasi-Dimensional Combustion Model

The model has already been applied on an old technology, naturally aspirated HSDI Diesel engine and on a heavy-duty turbocharged DI one equipped with a high pressure PLN fuel injection system, and the results were satisfying as far as performance and pollutant emissions (Soot and NO) are concerned. Taking into account that the main scope of engine simulation models is to assist engineers and researchers to understand the complex mechanisms involved in diesel engine combustion and pollutants formation and that through the continues engine development, new techniques are implemented, it is obvious that engine simulation models must always be enhanced with new features in order to be kept up-to-date. In this study the model has been modified to take into account the effect of EGR, since the latter one is a measure that will be used more extensively in the future to control NO emissions from turbocharged HDDI Diesel engines. The model is validated using experimental data from a single cylinder test engine operating with various EGR percentages at two different engine loads (part and full load). Comparing calculated with experimental cylinder pressure traces a good agreement is observed and the trends of exhaust tailpipe emission values (Soot and NO) are quite well predicted, at all the operating conditions examined. Moreover taking into account what is already known about how EGR affects combustion and pollutant formation mechanisms, and considering the calculated in-cylinder spatial distribution of temperature and species concentrations, it is revealed that model's predictions are in the correct way. This is encouraging, since by using this new quasi-dimensional model it is possible to obtain a more fundamental understanding of the various processes taking place inside the combustion chamber compared to existing multi-zone models, in a fraction of the time required by the more detailed CFD models.