Thermal Response of Monolithic Catalytic Converters During Sustained Engine Misfiring: A Computational Study

The thermal response characteristics of automobile monolithic converters during sustained engine misfiring have been studied using a mathematical model which accounts for the simultaneous processes of heat transfer, mass transfer, and catalytic reaction. Particular attention was given to the effects of converter properties and inlet exhaust conditions on the location and magnitude of the temperature peak developed during the transient. Our simulation results show that the temperature excursions in typical monolith converters during engine misfiring are generally characterized by an ignition zone (where a steep exothermic temperature rise occurs as a result of rapid reaction) preceded by a relatively short, unreactive region near the inlet. Also, the predicted maximum wall temperature correlates well with the adiabatic reaction temperature, and the melting point of the monolith substrate would not be exceeded unless the extent of engine misfiring is 40% or higher.