Experimental Investigation to Determine the Effect of Fuel Aromatic Content on Gaseous and Particulate Emissions of IDI Diesel Engines

The diesel engine is a thermal machine with very high efficiency when compared to other similar engines. But up to now its application for automotive purposes is limited due to the existing limits in power concentration, speed and noise. Up to now most diesel engines used for automotive applications are of the Indirect Injection type due to their ability to operate at relatively high rotational speeds and at low Air Fuel Ratios when compared to direct injection diesel engines. Currently the research is mainly concentrated to DI diesel engines due to their lower specific fuel consumption. Nevertheless it is not entirely clear that IDI diesel engines will be completely replaced. But if we consider in general the diesel engine regardless of its type, it is widely recognized that one of the major problems with their application on automobiles is the emission of particulates (smoke etc.). Beyond the various technologies available for the reduction of soot due to the very strict limits that are to be applied in the near future a great deal of research is taking place to examine the effect of fuel formulation on particulate emissions. The present research group has in the past presented the results from an experimental investigation concerning the effect of the type of Aromatics on particulate and gaseous emissions from diesel engines. From the results it was revealed that no strong relation exists between type of aromatics contained in the diesel fuel and particulate emissions. For this reason it was decided to examine the effect of the total amount of aromatics on engine performance and emissions. In the present work are given the results from an extended experimental investigation conducted on an IDI high speed single cylinder test engine using fuels of various total aromatic contents ranging from almost 0% up to 12% by volume. The fuels were produced synthetically in a refinery and special effort was given to maintain their physical properties (viscosity, density etc.) at a narrow range. Measurements of engine performance and emissions were taken at various engine speeds and loads covering the entire operating range of the engine. From the analysis of experimental data it is revealed that some type of relation exists between total aromatics and particulate emissions but which is not strong. For this reason a more extensive investigation is required to verify this initial observations using gravimetric measurements for the estimation of particulate emissions. On the other hand it results that the effect on gaseous pollutants and engine performance is relatively low. Taking into account the rather complicated nature of the IDI diesel engine due to the continuous mass and energy exchange between the two chambers we have decided to make an investigation on direct injection diesel engine as well. In any case more extensive investigation is required before general conclusions can be made.