Influence of exhaust aftertreatment devices on heavy-duty diesel engine's particulate emissions

This paper describes the impact of two exhaust after treatment devices, an oxidation catalytic converter and a diesel particulate filter, on the parti culate emissions of a heavy-duty diesel engine, the emphasis being on diese l particulate composition and size distribution. The analysis showed that t he catalytic converter did not alter the size distribution significantly, e xcept for an increased production of nanosized particles below 30 n miles i n mean diameter. On the other hand, the ceramic monolith wall flow filter r educed the emitted particle number up to 100 times. The results again indic ated that a diesel particulate filter can also increase the number of nanos ized particles. Further investigations, however, revealed that the formatio n of nanosized particles downstream of the oxidation catalytic converters a nd diesel particulate filters, respectively, is biased by inadequate sampli ng conditions. As long as realistic sampling conditions are applied, both c atalyst and filter reduce particle emissions over the entire size range.