Development and application range of mathematical models for 3-way catalytic converters

The need for reliable 3-way catalytic converter modeling in the design of demanding exhaust systems for low-emitting vehicles has been widely recognised. Although a number of related models have been presented in the literature, the efficient performance in actual 3-way applications requires further development and validation. The major difficulties posed in such modeling efforts arise from the complexities in the reaction schemes and the respective rate expressions for the multitude of currently used catalytic formulations. This paper presents a two-dimensional catalytic converter model, featuring a number of innovations regarding the catalyst transient behaviour, the reaction kinetics and the solution procedure. The oxygen storage submodel presented is capable of accounting for the redox and temperature dependence of the oxygen availability under transient operation. The redox sensitivity of the reaction scheme gives a clearer insight in the 'lambda-window' behavior of 3-way catalysts. The application range of the model and the expected accuracy levels in the most common engineering problems are discussed. It is concluded, that although the task of predicting emissions over random driving scenarios is quite demanding in both chemical kinetics and inlet conditions data, most optimization applications may be sufficiently handled with existing kinetic expression information.