Experimental Investigation on the Oxidation Characteristics of Diesel Particulates

Hwansoo  Chong, University of Illinois, Chicago

Diesel engines generally require diesel particulate filter (DPF) systems to meet increasingly stringent emissions regulations. While significant advances have been reported in DPF technology, major efforts are still needed to develop optimum DPF regeneration methodologies for efficient removal of particulate matter (PM). It is essential to investigate the effects of SOF concentration, thermal aging, and oxygen mass transfer on the oxidation behavior of diesel PM relevant to DPF regeneration. To investigate these effects, we obtained experimental data using a thermogravimetric analyzer (TGA). Diesel PM samples were collected from a bench-scaled DPF test system, connected to the exhaust stream of a 1.9-L, 4-cylinder light-duty diesel engine. The experiment data for diesel PM revealed significant differences in the oxidation behavior with respect to the period of thermal aging, while there is no significant effect of the SOF concentration. The isothermal oxidation of diesel PM was characterized by two distinct zones, where the rate of mass loss was nearly constant (zone1), or decreased rapidly with oxidation (zone 2). In the oxidation temperature range of 500 and 600°C, zone 1 turned out to be controlled kinetically, while the limitation of oxygen diffusion was found in zone 2, which thereby lowered the oxidation rate. In addition, the differences in the oxidation behavior of diesel PM and surrogate soot have been investigated. For surrogate soot, small amount of volatile component were found, and the oxidation behavior of surrogate soot is independent of thermal aging. In addition, the experiment of surrogate soot indicates kinetically-controlled oxidation in that temperature range.

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