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The direct injection diesel engine is one of the most efficient thermal engines known to man. For this reason DI diesel engines are widely used for heavy-duty applications and especially for the propulsion of trucks. Even though the efficiency of these engines is currently at a high level there still exist possibilities for further improvement. One way to accomplish this is by increasing the injection timing which usually improves, depending on the operating conditions, the indicated efficiency of the engine. On the other hand advanced injection timing has a negative effect on peak pressure causing a serious increase of its value, a negative effect on NO emissions which are also seriously increased and a positive effect on Soot emissions which are reduced. In the present work a theoretical and experimental investigation is presented to determine the effect of more advanced injection timing on engine performance and pollutant emissions.

Pollutant emissions and specifically NO and soot are one of the most important problems that engineers have to face when developing heavy duty DI diesel engines. Two main strategies exist as options for their control, reduction inside the engine cylinder using advanced combustion and fuel injection technologies and use of after-treatment systems. In the present work it is examined the use of EGR to control the formation of NO inside the cylinder of an engine with extremely high peak pressure. The work is applied on a single cylinder truck test engine developed under a project funded by the European Community focusing on the improvement of heavy duty DI diesel engine efficiency using increased injection timing. Use is made of a simulation model to predict the effect of more advanced injection timing on engine performance and emissions. The model has been modified to include the effect of EGR used to c ontrol the formation of NO which is considerably increased at high injection timings.