A NOx trap study using fast response emission analysers for model validation

Lean-burn aftertreatment systems using NOX traps for reducing emissions from diesel exhausts require periodic regeneration after each storage stage. Optimizing these events is a challenging problem and a model capable of simulating these processes would be highly desirable. This study describes an experimental investigation, which has been designed for the purpose of validating a NOX trapping and regenerating model. A commercial computational fluid dynamics (CFD) package is used, to model NOX trapping and regeneration, using the porous medium approach. This approach has proved successful for three-way catalysis modelling. To validate the model a one-dimensional NOX trap system has been tested on a turbocharged, EGR-cooled, direct injection diesel engine controlled with an engine management system via DSPACE. Fast response emission analyzers have been used to provide high resolution data across the after-treatment system for model validation. Measurements show CO is the primary reductant. After the trap NO and NO₂ spikes (NOX slippage) were observed both at the beginning and end of the regeneration period. The former is believed to be due to insufficient reductant. Whilst the model can qualitatively describe the main storage and regeneration phases it failed to predict NOX slippage. Publisher statement: Copyright © 2006 SAE International. This paper is posted on this site with permission from SAE International and is for viewing only. It may not be stored on any additional repositories or retrieval systems. Further use or distribution is not permitted without permission from SAE.