Analysis of a kinetic model describing the dynamic operation of a three-way catalyst

Abstract

Simulation models of three-way catalysts (TWC) are very useful for the design and tests of catalyst controllers. When applying such models to controller design, accurate descriptions of the emissions restricted by legislation and of the emissions driving the λ sensor (NOx, CO, HC, H2 and O2) are important. A kinetic one-channel model of a TWC, capable of calculating the demanded output, was recently published. That model was developed based on measurements from an engine test bench. Since, the dynamic behaviour of the catalyst is very complex and the variation of the exhaust gas composition is very limited on an engine test bench, various phenomena can hardly be analysed separately on an engine test bench. This fact led to the choice of the model-gas test bench, which allows the study of the individual phenomena under idealised conditions.This contribution now is to validate that model using measurement results obtained on a model-gas test bench. To analyse the performance of the TWC model, the response of the TWC to a defined input is measured under various conditions and compared with results of simulations. The main goals of this investigation include the analysis of dynamic effects, such as the deactivation of the catalyst under rich conditions, the role of water and hydrogen (water–gas shift reaction), and the storage of components other than oxygen.