Experimental and Computational Study of DOC on CSF for Heavy Duty Applications 2019-01-0586
For diesel exhaust aftertreatment applications with space limitations, as well as to move the selective catalytic reduction system (SCR) to a warmer location closer to the engine, DOC on CSF technology can be used. This technology combines the diesel oxidation catalyst (DOC) and catalyzed soot filter (CSF) functionalities on one component, thereby enabling volume reduction while maintaining the abatement of hydrocarbon (HC), carbon monoxide (CO), and particulate matter (PM), in addition to the oxidation of nitric oxide (NO) to nitrogen dioxide (NO2) for passive soot oxidation and fast SCR reaction of NOx on a downstream SCR catalyst. In this study, the performance of DOC on CSF was compared to a DOC + bare diesel particulate filter (DPF) and to a DOC + CSF, to understand the performance benefits and challenges.
Experimental data and simulations were used to understand the underlying mechanisms in the DOC on CSF technology. HC oxidation for a DOC on CSF at high temperatures was superior compared to DOC + bare DPF due to better diffusion characteristics in a wall flow monolith. The soot oxidation characteristics of the DOC on CSF were evaluated in comparison to a DPF or CSF downstream of a DOC under passive and active soot oxidation conditions. In addition, the contribution of back diffusion on the soot oxidation was assessed. The passive soot oxidation characteristics of a DOC on CSF were found to be similar, or better, compared to DOC + bare DPF under certain conditions. The active regeneration efficiency was lower for the DOC on CSF due to the gradual increase in temperature along the length of the part during fuel injection. Possible techniques to improve the efficiency of soot are considered. This work demonstrates the differences between the DOC on CSF and DOC + bare/coated DPF systems, thus enabling a better understanding of the performance of DOC on CSF to current applications.