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A major challenge for researchers and engineers in the field of diesel engine development is the simultaneous reduction of both NOx and soot emissions from diesel engines to comply with strict future emission legislation. One of the promising internal measures that focus on the reduction of soot emissions is post fuel injection which does not have a serious effect on NOx emissions. The main parameters involved when using this technique are post fuel quantity and dwell angle between the main and the post fuel injection events. In the present work a detailed computational investigation has been conducted to determine the effect of post fuel injection on engine performance and pollutant emissions (NOx and soot). To this scope, a phenomenological multi-zone combustion model has been used, properly modified to take into account the interaction of post and main injected fuel amounts.

The past decade significant research effort has concentrated on the DI diesel engine due to stringent future emission legislation which requires drastic reduction of engine tail pipe pollutant emissions, mainly PM and NOx, without significant deterioration of specific fuel consumption. Towards this effort, the important role of modeling to investigate and understand the impact of various internal measures on combustion and emissions has been widely recognized. Phenomenological models can significantly contribute towards this direction because they have acceptable prediction capability and the advantage of low computational time. This enables the production of results, on a cycle basis, that indicate the effect of various parameters on both engine performance and emissions. Therefore their use can significantly reduce engine development time (i.e. reduction of experimental effort) and cost.

The direct injection heavy-duty diesel engine is the main propulsion unit for trucks, lories and other heavy-duty vehicles mainly due to its superior efficiency when compared to other existing reciprocating engines. However, this engine suffers from relatively high particulate and nitric oxide emission levels. Considering current legislation for emissions and especially future limits, it seems that a great deal of research is required to satisfy these limits and maintain efficiency at a high level. As widely recognized, the fuel injection mechanism plays an important role for both engine performance and pollutant emissions. The major problem is to seek solutions that enable the control of major pollutants, nitric oxide and particulate matter. For this reason, various injection rate shapes have been proposed which require sophisticated fuel injection equipment and extremely high fuel injection pressures. Now two main categories are considered, common rail fuel injection system and PLN.