An Integrated Approach for the Design of Diesel Engine Exhaust Systems to meet Euro 4 and beyond Emissions Legislations

Abstract

CO₂ emissions can be significantly reduced through increased deployment of the modern high-efficient Diesel engines in the transportation sector, provided that engine manufacturers meet increasingly tightened particulate and NO_x emission levels (EURO 4 and beyond). In order to achieve such emission levels, considerable progress concerning the control of the combustion process using “second generation” common rail systems, characterised by higher fuel injection pressures and better electronic control of the injection process, has been made (Bernard et al. 1998). Nevertheless, for vehicle classes of inertia test weight higher than 1.600 kg the feasibility of engines meeting Euro 4 NO_x and particulate emission regulations appears to be strongly connected to the parallel application of catalysts and Diesel particulate filter systems (Bernard et al. 1998; Waish 1999; Konstandopolous and Kostoglou 1999).

Engine development work so far has proven that the envisaged emission standards do not allow optimising the behaviour of the individual exhaust gas aftertreatment devices. Therefore it is highly desirable to have tools available for the systematic layout of optimal Diesel engine exhaust. This will be possible by applying predictive computer models permitting the analysis of entire Diesel engine exhaust systems. Further to use these models in such a way that various options in the early design phase can be assessed rapidly to determine the most suitable layout for a particular engine prototype or vehicle.

Hence the objective of the present work conducted within an European joint research project “SYLOC-DEXA” was the development of a generally applicable toolkit, consisting of sub-modules representing the behaviour of individual exhaust gas aftertreatment components and their interaction, by accurate simulation of the physical and chemical processes occurring in Diesel engine exhaust gas aftertreatment devices.

The results achieved so far concerning the design of a state-of-the-art 1.9 l HSDI engine exhaust system have been very promising and are in good agreement with the available experimental data.