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Fuel Property Effects on Polyaromatic Hydrocarbon Emissions From Modern Heavy-Duty Engines
Published June 24, 1996 by Institution of Mechanical Engineers in United Kingdom
Event: International Seminar on Application of Powertrain and Fuel Technologies to Meet Emissions Standards
Recent years have seen an increasing concern over the levels of polyaromatic hydrocarbons (PAH) emitted to the environment. Exhaust emissions from diesel vehicles are one such source of atmospheric PAH and the influence of changes in engine design, engine maintenance practices, exhaust aftertreatment technologies and fuel properties are all of interest.
This work addresses the influence of diesel fuel properties, specifically fuel PAH content, on the levels of the PAH associated with the exhaust particulate matter (PM), for a modern heavy-duty engine running over the European legislated R49 cycle. It shows that the exhaust particulate matter includes significant PAH, both for fuels which themselves contain virtually zero PAH, as well as for fuels which meet the current European EN 590 specification. It is shown that, in the above tests, the majority of the PAH associated with the PM do not originate from the fuel PAH, but may be attributed to material pyro-synthesized in the combustion process. The lubricating oil was shown to make a negligible net contribution to exhaust PAH over the duration of the regulated cycle.
These findings are in line with increasing evidence in the recent literature that, for modern heavy-duty diesel engines, running on fuel meeting current specifications, surviving fuel PAH molecules are playing a diminishing role as a source of exhaust PAH. This evidence is in contrast to previous beliefs and will contribute to an informed assessment of exhaust PAH emissions from diesel engines allowing the contribution of fuels to be put in context with other factors, such as engine design and aftertreatment technologies.