Effects of cetane number and fuel properties on diesel-exhaust emissions

The effects of cetane number and fuel properties on diesel emissions, especially particulate matter (PM) emission and poly-nuclear aromatic hydrocarbon (PAH) emission, were investigated in a single-cylinder DI diesel engine. Normal paraffin fuel and isoparaffin fuel were used to prepare the base fuel. Various test fuels were prepared, by adding cetane number improver, aromatic compounds and heavy fraction to base fuel, to investigate the effects of cetane number, aromatic compounds, and heavy fractions on emissions. PAHs in the soluble organic fraction (SOF) were measured using the HPLC/UV method. Increased cetane number or aromatic compound content of the fuel caused greater soot emissions. Addition of heavy fraction to the fuel caused a higher soluble organic fraction (SOF) in the PM emissions. The PAHs were probably produced mainly from PAHs from unburned fuel. Experimental results using commercialized gas oil support this idea. Aromatic compounds have little effect on the in-cylinder formation of PAHs. This result suggests that PAHs and soot are produced by different pathways. Measurements of unburned hydrocarbon (THC) emissions, carbon mono-oxide (CO) emissions and oxides of nitrogen (NO.) emissions corresponded to previous studies.