Dynamic modeling of a three-way catalyst for SI engine exhaust emission control

Automotive emissions are severely regulated. Since 1980, a three-way catalyst (TWC) has been used to convert harmful emissions of hydrocarbons, carbon monoxide, and oxides of nitrogen into less harmful gases in order to meet these regulations. The TWC´s efficiency of conversion of these gases is primarily dependent on the mass ratio of air to fuel (A/F) in the mixture leaving the exhaust manifold and entering the catalyst, the velocity of the exhaust mass, and the temperature of the catalyst. The goal of the paper is to develop a dynamic control-oriented model of a TWC. First, the measurement capabilities are described. Then, a simplified, dynamic catalyst model that can be determined on the basis of medium bandwidth A/F measurements and low bandwidth temperature and emission measurements is developed and validated