Atmospheric Environment 37 (2003) 5227–5236 Potential of IC-engines as minimum emission propulsion system Helmut Eichlseder*, Andreas Wimmer Institute for IC Engines and Thermodynamics, Graz University of Technology, Austria Received 13 December 2002; received in revised form 12 May 2003; accepted 14 May 2003 Abstract Forced by the increasing mobility and the greenhouse effect a further reduction of emissions of pollutants and CO 2 is required. The main demand for improvement will be reduction of NO x and particulate emissions from diesel engines and fuel consumption/CO 2 -emission from spark ignition (SI)-engines. New technologies for combustion and exhaust gas aftertreatment being under development are introduced and discussed. These technologies with increased complexity show significant potential for minimum emission and are able to fulfil future demands. r 2003 Elsevier Ltd. All rights reserved. Keywords: Internal combustion engine; Diesel; SI-engine; Emission; Exhaust gas aftertreatment; Alternative fuels 1. Introduction The IC-engine is the favoured propulsion system for passenger and freight traffic. Due to this wide range of use the entire emission, which required important developmental processes for its reduction in the past, and will also demand even greater ones in the future, is considerable. Nowadays the legally permissible max- imum emissions differ in a wide range, even in whole orders of magnitude, depending on the means of transport and on special national regulations. Supposing the further increase in mobilization, one question with special emphasis is the further develop- ment of traffic-caused emissions. Especially, the one referring to the potential of IC-engines, looking back to more than 100 years of developmental history, its technical realization and alternatives. Basically, very low emissions of IC-engines can be achieved either with exhaust gas after treatment or optimized combustion processes. Further considerations have to combine both means, as these two measures do not lead to success when regarded isolated. 2. Legal emission standards 2.1. Pollutant emissions In the course of the last 30 years legal egulations demanded and also gained (see Fig. 1) distinct emission reductions. From the year 2005 onwards, passenger cars with spark ignition (SI)-engines, for instance, have to fulfil EU-4 limits with HC and NO x emissions being only 3% of the values of 1970. This development with the considerable reduction of the emissions of new passenger cars was the reason that at the same time the emission quota of vehicles with a bad servicing state, faulty exhaust gas aftertreatment system or high run performance has risen considerably. Estimations of the American Environmental Protection Agency EPA showed that in 1990 about 60% of the unburned hydrocarbon emissions from vehicles were caused by gasoline vehicles with a faulty exhaust gas aftertreatment system. ARTICLE IN PRESS *Corresponding author. E-mail address: helmut.eichlseder@vkma.tu-graz.ac.at (H. Eichlseder). 1352-2310/$-see front matter r 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2003.05.001