Uwe Gärtner

Impact of engine combustion on the reactivity of diesel soot from commercial vehicle engines

The regeneration behavior of diesel particulate filters is significantly influenced by the reactivity of the stored soot. However, there is still a lack of analyses which describe the effects that various engine operating parameters have on soot reactivity. A medium-duty OM936 single-cylinder engine with a common rail injection system was used to analyze the correlations between engine speed, swirl, combustion air–fuel ratio and soot reactivity. Diesel particulate samples were directly collected from the exhaust stream. The temperature programed oxidation was used to reveal the reactivity to oxygen of the soot samples. Diesel particulate filter regeneration experiments were additionally carried out on a medium-duty OM936 full engine test bench to analyze the influence of soot reactivity on the regeneration efficiency in particulate filters. The results give new insights into the relation between the diesel engine combustion process and soot reactivity and show how the active regeneration of diesel particulate filters is affected by soot reactivity.

Influence and potential of flexible injection rate shaping for medium and heavy duty diesel engine combustion processes

Modern fuel injection systems for medium and heavy duty diesel engines combine the potential of very high injection pressures and flexible injection rate shaping. Against this background, the Commercial Vehicle Division of DaimlerChrysler AG, in close collaboration with DaimlerChrysler Research, performed principle tests to assess the influence of a flexible injection process, focusing on the effects of injection rate shaping. Besides pressure indexing, optical diagnostic methods and simulation techniques provided valuable insights in this study. Within this project, four different injection systems with different potentials of flexibility were investigated. New insights, such as the influence of needle opening and closing behaviour on nitric oxide emissions and the influence of injection rate shaping on soot emissions have been elaborated.

Verdichtungsverhältnis und Zylinderspitzendruck

Moderne Einspritz- und Aufladesysteme liefern einen bedeutenden Beitrag zur entscheidenden Verbesserung des Wirkungsgrad-Emissions-Tradeoffs moderner Nutzfahrzeugmotoren. Angesichts weiter sinkender Emissionsgrenzwerte und einer verstarkten Kundenforderung nach niedrigstem Kraftstoffverbrauch wird die Bedeutung der Einspritz- und Aufladetechnik sicherlich auch weiterhin anhalten. Nichtsdestotrotz ist und bleibt der Einfluss der Brennraumgeometrie auf das Verbrennungs- und Emissionsverhalten vergleichbar wichtig wie der Einfluss der Einspritzausrustung und des Luftmanagements. Vor diesem Hintergrund wurde der Einfluss des Zylinderspitzendruckes und des Verdichtungsverhaltnisses von der Nutzfahrzeugmotoren-Vorentwicklung bei Daimler-Chrysler in sehr enger Zusammenarbeit mit der Konzernforschung unter Berucksichtigung der spezifischen Anforderungen analysiert und bewertet.

Compression ratio and peak cylinder pressure

Modern injection and charging systems provide an important contribution to the improvement of the efficiency/emissions trade-off of modern commercial vehicle components. In view of emission limits getting more and more stringent and stronger customer demands for lower fuel consumption, the significance of injection and charging technology is increasing. Nevertheless the influence of the combustion chamber on the combustion and emissions behavior remains as important as the influence of the injection equipment and air management. In this context, the influence of the cylinder peak pressure of commercial vehicle engine development and compression ratio has been analysed at Daimler-Chrysler and evaluated in close cooperation with DaimlerChrysler research in consideration of the requirements specified.