1998-02-23

The Influence of Speciated Diesel Fuel Composition on Speciated Particulate SOF Emissions 980527

A base diesel fuel with 37% 1-3 ring aromatics and 12.9% PAH was passed through a dearomatising process that removed the two and three ring aromatics and reduced the single ring aromatics to 14%. These two fuels plus a combination of 60% of the original fuel with 40% of the low aromatic fuel were tested on a Perkins Phaser TCIC diesel engine of US 1991 emissions standards over the EC 13 mode cycle. The fuels and particulate SOF were analysed for all the n-alkanes and all of the PAH of significant concentration. The high speed maximum power particulate SOF were analysed in detail for all three fuels and mass emissions of 15 n-alkanes and 15 PAH determined and 15 other non-fuel PAH searched for. Most of the results showed that the composition of the SOF in terms of n-alkane and PAH was predominantly unburnt fuel compounds, the fuel with negligible PAH had very low PAH emissions compared with the parent fuel with a high PAH content. The specific search for pyrosynthesised compounds showed that Chrysene, Carbozole, Benzo(a)pyrene, Benzo(c) pyrene, Anthracene and Dibenzothiophene were all formed in the engine at this high temperature condition as the fuel contained none of these compounds. Six nitro-PAH were searched for on a GC-MS but no evidence of pyrosynthesis of these compounds could be found. The fuel with very low two and three ring compounds also produced the lowest PAH emissions, indicating that a high fuel PAH content would result in high PAH emissions. In addition a Perkins 4-236 engine with a VCO fuel injector was investigated for two fuels with only a 3% PAH content. Full speciation of the fuel and the particulate SOF was undertaken at the high speed maximum power condition. No PAH pyrosynthesis was found, except de-alkylation of unburnt fuel alkyl-PAH. The PAH and n-alkane emissions were very low due to the use of the VCO nozzle, which eliminated the main source of the unburnt fuel.

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