Event Details
Catalytic Converter Study at Cold-Start Regime
Presenter: Figen Lacin - Department of Mechanical Engineering, Michigan State University
Supervisor:
Date: Fri, March 8, 2002
Time: 11:00:00 - 12:00:00
Place: EOW 430
ABSTRACT
Abstract:
The monolith-catalytic converter is one of the most important and commonly used parts of the exhaust system to control exhaust emissions. Many interesting physical processes occur at the same time in catalytic converters: heat transfer with convection, conduction and radiation; chemical reactions in the gas phase; surface chemical reactions; the effect of flow oscillation; condensation of water vapor at the cold start regime; diffusion mechanisms, etc. It is almost impossible to take into account all these effects in a single model. In the present study, a one-dimensional, mathematical model that physically represents a single channel of the honeycomb structure is developed. The result of the computations is compared with the related literature. The effects of the geometrical parameters are investigated for the cold start regime. The importance of the surface temperature distribution is noticed. This model is modified to two dimensions to be able to study the further effects of the surrounding insulation.
Moreover, from our model calculations, we observed that the monolith's temperature and therefore the light-off time are greatly affected by the noble-metal distribution over the honeycomb walls of the monolith. We have demonstrated that the light-off time is significantly shortened by approximately 35% by using a simple, step-function for noble-metal distribution. Therefore, the emissions of the exhaust gas are reduced without increasing the cost of noble-metal materials used in the converter. For a given converter geometry and an amount of noble-metal distribution, an optimum noble-metal distribution is being investigated with the understanding that the optimum noble-metal distribution proposed has to be practical in the area of manufacturing. Since the main source of the exhaust emissions is during the warm-up period of converters from a cold start, the reduction of emissions shown in our model calculations is quite substantial.