Search Results

Even though the 3-way catalyst chemistry has been studied extensively in the literature, some performance aspects of practical relevance have not been fully explained. It is believed that the Oxygen Storage Capacity function of 3-way catalytic components dominates the behavior during stoichiometry transitions from lean to rich mode and vice versa whereas a number of mathematical models have been proposed to describe the dynamics of pollutant conversion. Previous studies have suggested a strong impact of Sulfur on the pollutant conversion after a lean to rich transition, which has not been adequately explained and modelled. Lean to rich transitions are highly relevant to catalyst ‘purging’ needed after exposure to high O2 levels (e.g. after fuel cut-offs). This work presents engine test measurements with an engine-aged catalyst that highlight the negative impact of Sulfur on pollutant conversion after a lean to rich transition.

Hydrocarbon traps for gasoline engines are promising candidates for cold start emission control, provided that their design is based on a “systems approach”. In this paper, an existing CAE methodology for exhaust after-treatment is expanded to include HC trap technology. The flow, heat transfer and chemical kinetics in a typical complex system, comprising a “barrel type” adsorber and two conventional catalysts are studied. A mathematical model is developed and applied for the computation of the flow and pressure distribution, as well as transient heat transfer in the barrel type adsorber. A physically relevant model is used to simulate HC adsorption desorption on the adsorbing material. The model is used in combination with an existing 2-d 3-way catalyst model to simulate different HC trap concepts. The aim is to understand and quantify the particular thermal response and HC retention behavior of hydrocarbon adsorber systems.