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Earlier work [1] shows that kinetics of Diesel soot oxidation is different from that of ethylene diffusion flame soot oxidation [2], possibly due to metals from lube oil. This study investigates the influence of metals on soot oxidation and the exhaust particle emissions using lube oil dosed fuel (2 % by volume). This method does not simulate normal lube oil consumption, but is used as a means of adding metals to particles for oxidation studies. This study also provides insight into the effect of systems that mix lube oil with fuel to minimize oil change service. The HTO-TDMA (High Temperature Oxidation-Tandem Differential Mobility Analyzer) technique [1] was used to measure the surface specific oxidation rate of Diesel particles over the temperature range 500-750 °C. Diesel particles sampled from the exhaust stream of a Diesel engine were size segregated by differential mobility and oxidized in situ in air in a heated flow tube of known residence time and temperature profile.

A study of factors affecting hydrocarbon oxidation in a diesel oxidation catalyst was undertaken. The objective was to determine whether interactions between particulate-adsorbed hydrocarbons and the catalyst significantly influenced hydrocarbon oxidation. Theoretical modeling supported by experimental data obtained at the U.S. Bureau of Mines' Diesel Emissions Research Laboratory indicated that the mass of particles interacting with the ceramic support was negligible. Additionally, a model of hydrocarbon adsorption onto diesel particulate predicted that over 98% by mass of exhaust hydrocarbons would be gas-phase, rather than particulate-adsorbed, at converter operating temperatures. A second physical process, the diffusion of gas phase hydrocarbons to the catalytic surface, was subsequently investigated. Theoretical and experimental results for the unburnt fuel hydrocarbons indicated that hydrocarbon oxidation was diffusion limited under high temperature operating conditions.