The effect of aromatic hydrocarbons and oxygenates on diesel engine emissions

Tests were conducted in a Cooperative Fuel Research (CFR) diesel engine aim ed at discerning the effects of fuel aromatic and oxygenate compounds on ex haust emissions. The base fuel was heptane to which were added increasing a mounts of monoaromatic toluene and diaromatic methylnaphthalene. Blends of heptane and toluene containing oxygenated compounds (methanol, ethanol, hep tanol and diglyme) were also tested. The results indicate that both toluene and methyl-naphthalene increase smoke, oxides of nitrogen (NOx) and unburn ed hydrocarbon (UHC) emissions substantially. The results also showed that increases in ignition delay could account for some of these rises in exhaus t emissions. The oxygenated fuel blends tested caused reductions in NOx and smoke emissions. The exception was heptanol, which Showed no reduction in smoke emission. This may be associated with the fact that heptanol had the lowest amount of molecular-bound oxygen.