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A method for determining the contribution of lubricating oil and fuel to particulates emitted from diesel engines is described. Methylene chloride extracts of the particulates were separated by silica gel fractionation using hexane, methylene chloride, acetone and methanol. The molecular weight distribution of each fraction was determined using size exclusion chromatography. The speciation of diesel particles into unoxidized oil, oxidized oil, unoxidized fuel and oxidized fuel was determined systematically for a diesel engine modified over a period of more than a year. These modifications significantly affected the total extractable material (12.6 -72.3%) and distribution of oil and fuel components. Engine oil was consistently found to be the major contributor to the extractable material, varying from 10 to 60% of the total particulates emitted.

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A model of the combustion and emission formation processes was formulated to identify modifications to combustion process parameters with potential for reducing NOx and particulate emissions in a diesel engine. The model was calibrated using data from an experimental, single-cylinder, direct injection diesel engine. Several combustion system modifications were made to the engine that reduced NOx and particulate emissions. The model was used to estimate the changes in the combustion process parameters responsible for the reductions observed. After calibration, the model was used to evaluate the effects of a wide range of modifications to the combustion process parameters on NOx and particulate emissions. These results were used to estimate changes in the combustion process parameters required to approach the objectives assumed for the 1991 Federal emission regulations for heavy-duty diesel engines. A reduction in the lubricating oil contribution to the particulate emissions was also projected to be required to approach the 1991 objectives.