08PFL-534 Parametric Study Based on a Phenomenological Model to Investigate the Effect of Post Fuel Injection on HDDI Diesel Engine Performance and Emissions–Model Validation Using Experimental Data D.T. Hountalas, V.T. Lamaris, and E.G. Pariotis School of Mechanical Engineering, National Technical University of Athens H. Ofner AVL List GmbH, Fuel and Engine Management Systems, Commercial Powertrain Systems, Graz A-8020, Austria Copyright © 2008 SAE International ABSTRACT 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. Using the proposed model a parametric study has been conducted varying both post fuel injection quantity and dwell angle and maintaining model’s constants the same when switching from normal to post injection. From this analysis it is revealed that post fuel injection enhances soot oxidation due to the increase of in-cylinder temperature at the late phase of combustion cycle, and mainly due to the improved air- fuel mixing as a result of the post injection mechanism. To validate the model various performance parameters and exhaust tailpipe values are compared with experimental data obtained from measurements performed on a heavy duty turbocharged DI Diesel engine, equipped with a common rail fuel injection system with and without post injection. As observed the model manages in general to capture the effect of both post injection parameters examined on engine performance and emissions despite differences observed in absolute values for some cases. Furthermore, information is provided for soot formation and oxidation rates and the actual effect of post injection upon them. INTRODUCTION The DI diesel engine is widely used in the transportation sector due to its high efficiency. Despite the accomplishments achieved towards diesel engine emission reduction there is still a great deal to be done until we reach values that will satisfy future emission limits [1]. The required reduction of both gaseous and particulate emissions to meet future emission limits is still considerable. The main effort focuses on the reduction of both NOx and particulate emissions. Towards this direction two are the most promising solutions: reduction of both pollutants inside the combustion chamber (internal measures) and reduction at the diesel engine exhaust using external measures (aftertreatment). The control of both NOx and particulate emissions using internal measures is difficult because the two pollutants are affected differently from the parameters that control combustion inside the combustion chamber. However the reduction of pollutant emissions inside the combustion chamber is of significant importance even if external measures are used to reduce tailpipe exhaust emissions, because the required conversion efficiency is lower and minimizes the resulting fuel penalty. The mechanism which mostly affects pollutants formation is in-cylinder air fuel mixing which is affected mainly by fuel spray injection and the in-cylinder flow field. For this reason, during the last years serious efforts have been conducted to improve these mechanisms using elevated injection pressures, injection rate shaping and improved combustion chamber geometry [2-6]. As a result, a significant reduction of both NOx and particulate emissions has