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Simulation of catalytic exhaust gas aftertreatment systems is a cost and time saving method in the early development design stage to meet current and upcoming emission standards. Three-way catalytic (TWC) converter systems which target for 99% HC and NOx conversion need to be optimized for catalyst light-off as well as high conversion efficiency in the hot phase of the driving cycles. A mathematical model of the three-way catalytic converter which contains all phenomena relevant for the simulation of the transient emission performance is described. Special attention is given to oxygen storage and release since a proper description of this mechanism turns out to be crucial. The 1D simulation model balances the enthalpy in the gas and in the solid phase, the species H2, CO, C3H6, C3H8, O2 and NO in the gas bulk phase and close to the catalytic surface. Furthermore, the oxidation extent of the oxygen storage is accounted for.

Strict legislation standards for automotive emission limits (e.g. ULEV, SULEV), which target for HC conversion rates beyond 99 %, impose the necessity to dramatically shorten catalyst Light-Off time and increase catalytic efficiency through improved catalytic converter heat-up. Especially, in early design stages, modeling thermal energy management is crucial to predict wether emissions standards can be met. The CAE method (Computer Aided Engineering) presented in this study gives the flexibility composing the frontal exhaust system from modular numerical models, which describe heat transfer in single exhaust components, as e.g. takedown-pipes, flexible coupling element (FCE), flanges and conversion characteristics in catalytic converter. Each module upstream of the converter internally couples the energy equations of 1Dgas to 1D/2D-solid-structure, including heat transfer mechanism as radiation, natural and forced convection.

Future requirements of the legislative body in the USA and Europe, towards the reduction of exhaust emissions of motor vehicles, forces the automobile industry to improve its technology continually. An electrically heated catalyst, abbreviated EHC, offers a very high potential for exhaust gas reduction in the cold start phase of the engine. A team of German automobile manufacturers is therefore developing a complete EHC System and laying down specifications which will enable the supply industry to undertake goal-orientated development of following components. The complete system comprises the components: heated catalyst, electricity supplier, electronic control, cables, plug and socket connections, secondary air system and their respective functions. In the following, the possible variations of the EHC system are explained and the components presented.