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Modeling and Simulation of Automotive Catalytic Converters Tariq Shamirn Deppartment of’Mechmical Engineering, Universfy of Michigan, Dearborn, M 481 28, USA [email protected] Abstract This paper describes the development o LI comprehensive ma fhema ical and numerical model for simulating the performunce o f automotive three-way catalytic convertem, which are employed to reduce enigine exhaust emisfions. The model simulates the emissiori sysrem behavior by using an exhaust system heat consen~ahm nd catalvsf chemical kinetic sub- model. The resitlting governing equations are solved nzunericolly. Good agreements were found between the nrtmerical predictiotzs and e,qxrimental nwu~iti~ements nder both steaaIy state and transient conditions. The developed model i s employed to invesligule the converter dynumic wsponse during tr-onseni driving conditions. The transient conditions are simiilaied by considering modulutions in the air fidel ratio. Nomenclature gas phase concentration of speciesj, 1noiim’ surface concentration of specie sj, mo1i1n3 specific heat of gas, J/kgK specific heat of substrate, J/kg.K empirical constant for oxygen storage eaction rates activation energy, ~a -m~/g-mol empirica cons tant for reaction rates geometric surface area, m2/m3 heat of reaction of species k, Jimol heat transfer coefficient between flow and substrate, J/mZ.s.K heat transfer coefficient between substrate and atmosphere, J/m2.s.K empirical constant for oxygen storage reaction rates mass transfer coefficient for species , m/s reaction rate ofkth eaction, mol/m2,s external surface to volume area ratio, in2/m3 time, s ambient temperature, K gas temperature, K substrate temperature, K gas flow velocity, m/s mole fraction of species in substrate coordinate along catalyst axis, m hydrogen-to-carbon ratio in the fuel void volume fraction [value ranging from zero (for no void) to one] thermal conductivity o f substrate, J/m.s.K gas density, kgim3 substrate density, kgim’ I. Tntroduction Emissions from engines are major sources of urban air pollution. The engine exhaust gases contain oxidcs of nitrogen (NO,)? carbon monoxide (CO), and partially burned or unburned hydrocarbons (HC). These pollutants have hazardous effects on environmcnt and living beings. They may cause acid rain, smog, and several respiratory diseases. Accordingly, they are being subjected to stringent regulations worldwide. I gasoline engine applications, thcse pollutants can be removed from the exhaust gases by employing catalytic converters. Catalytic converters have been used in automobiles for several years and various types of them are available. They can reduce engine emissions by more than 90 . However, due to progressively stricter emission regulations, the catalytic converter design and performance need to be continuously improved. The design improvement efforts require broadening of fundamental understanding of various physiochemical processes that occur in a catalytic converter. In the past, much of the design and engineering process to optimize various components of engine emission systems has involved the prototype testing. The complexity of modern systems and the resulting flow dynamics and thermal and chemical mechanisms havc increased the difficulty in assessing and optimizing system operation. Due to overall complexity and increased costs associated with these factors, modeling continues to be pursued as a method of obtaining valuable information supporting the 0-7803-8680-9/04/ 20.00 02004 IEEE. INMIC 2004

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