Analysis of diesel particulate: influence of air-fuel ratio and fuel composition on polycyclic aromatic hydrocarbon content

Polycyclic aromatic hydrocarbons (PAH) are pollutants produced during the combustion process and are considered as soot precursors. PAH emissions are not presently regulated although they may have dangerous effects on human health. A comparison is presented here of the influence of engine parameters (air-fuel ratio and brake mean effective pressure) on the composition of par-ticulates. The effects of a water-fuel emulsion on PAH (commonly examined in large engines) are also studied in a 1.9 L commonrail diesel engine: 13 per cent of water added to the fuel decreases the PAH concentration in diesel soot by half. The PAH emissions during cold-start of an automotive diesel engine are also presented.