Study of Emission and Fuel Consumption Trade-offs of a Diesel Engine System Equipped with Electrically Heated Catalysts

Wen  Wang, Gamma Technologies

Wen Wang, Jon Brown, Dominik Artukovic, Syed Wahiduzzaman
Gamma technologies Incorporated, Westmont, Illinois, USA

In order to meet the more stringent emissions requirements including EPA Tier 4 standard and the emerging SULEV regulations in California, it is crucial to reduce the light off time required on a catalyst especially during the cold-start and extended engine off periods in a hybrid application. One of the strategies that are being considered to shorten light off time is to electrically heat the catalyst monolith. In this regard, a model for an electrically heated monolith converter has been developed. The model solves a quasi-steady (QS) system with a highly efficient adaptive mesh and timestep scheme under the assumption that the spatial changes are much greater than the temporal ones in the gas conservation equations. On the other hand, the substrate temperature and surface coverages are solved in time and space coordinates in a fully coupled manner. The model has been validated using literature data for vehicle emissions tests and catalyst substrate temperatures during cold start. The numerical scheme is shown to be robust and efficient in handling initial transients and high gradients at the moving light-off front. This methodology is then applied to an AT system model consisting an electrically heated DOC at the upstream of an SCR to investigate the effect of overall AT system efficiency during an FTP cycle. Finally, the AT system model is integrated with an engine model in order to study the trade-offs of tailpipe emissions and BSFC.

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