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The use of catalyzed diesel particulate filter (CDPF) systems in light duty diesel (LDD) vehicles is becoming increasingly common. The primary functions of the system are to remove carbon monoxide (CO) and hydrocarbons (HC) from the vehicle exhaust stream, while simultaneously reducing the level of particulate matter (PM) emissions to ambient background levels. These systems can comprise either a separate diesel oxidation catalyst (DOC) and a downstream CDPF, or a single unit CDPF with the DOC functions incorporated within the CDPF. The single CDPF unit provides higher regeneration efficiency as it is located nearer to the engine and also cost benefits, as only a single unit is required compared to the alternative separate DOC and CDPF arrangement. A model describing the performance of the single unit CDPF for emissions control has been developed, with particular emphasis on achieving predictions of the CO and HC emissions over transient vehicle drive cycles.

The Diesel Oxidation Catalyst (DOC) is an important technology for the removal of CO and hydrocarbons (HC) from the exhaust of diesel engines, as well as for generating exotherms for active regeneration, and for producing NO₂ used by downstream components. This paper describes the development of a one-dimensional numerical model for a Pt-Pd DOC for use in designing aftertreatment systems. The model is based on kinetics developed from laboratory microreactor data. The model is a significant advance over previous DOC models we have developed. A much larger experimental matrix was used enabling the kinetics and inhibition effects to be much better defined. The experiments included rich conditions enabling the model to be used in NOX trap systems, where the exhaust becomes rich during regeneration. Reduction of NO₂ to NO by CO and HC has been included in the model.