Background: Today, the overwhelming majority of vehicles is equipped with internal combustion engines that use fossil derived fuels. This on-road traffic represents the main source of pollutant emissions of carbon monoxide, volatile organic compounds (VOC, unburned hydrocarbons), and nitrogen oxides. Today, three-way catalytic converters (3WCC) are used extensively to reduce the pollutant emissions of internal combustion engines. The role of the 3WCC is the complete oxidation of carbon monoxide, formed in the combustion process, and unburned hydrocarbons to harmless water and carbon dioxide, and the reduction of nitrogen oxides to molecular nitrogen. The simultaneous conversion of all these harmful species can only be ensured if the exhaust gas composition is very close to the stoichiometric ratio. This requirement is technically controlled by the lambda-sensor and accompanying electronics for engine control. Meanwhile, the performance of 3WCC is almost perfect after the catalytic reaction is ignited. However, at low operating temperatures, below 570 K, almost no conversion of the pollutant emissions occurs. Therefore, current research and development focuses on the reduction of this start-up period.

Picture courtesy of J. Eberspächer GmbH & Co

Project: In this project, we develop models and computational tools for the numerical simulation of the transient behavior of a typical 3WCC as commonly used in passenger cars. The goal is to numerically simulate a driving test cycle for the converter based on detailed physical and chemical models, which included detailed heterogeneous reaction mechanism, the impact of the washcoat, two-dimensional description of the flow field in the single channels and the heat transfer in the solid structure of the converter. The computational tools assist in catalytic converter design and optimization.

    

click on the picture

A maldistribution of the velocity field at the converter inlet (left) leads to an unsymmetrical temperature field (2nd left) compared to the ideal one (3rd left) sacrifying overall conversion of the pollutants (right); simulation (J. Windmann et al.) with DETCHEM^MONOLITH

CO₂-Concentration

C₃-H₈-Concentration

Temperature

Transient behavior of a single channel of a three-way catalytic converter during the start-up period. To see the movie click on the picture

Co-workers: Luba Maier, Steffen Tischer, Daniel Chatterjee (now DaimlerChrysler), Chrys Correa (now BASF)

Collaboration/Funding: Eberspächer GmbH & Co, DaimlerChrysler AG

Further information:

J. Windmann, J. Braun, P. Zacke, D. Chatterjee, O. Deutschmann, J. Warnatz. Impact of the Inlet Flow Distribution on the Light-Off Behavior of a 3-Way Catalytic Converter. SAE Technical paper 2003-01-0937 (2003)

J. Braun, T. Hauber, H. Többen, J. Windmann, P. Zacke, D. Chatterjee, C. Correa, O. Deutschmann, L. Maier, S. Tischer, J. Warnatz. Three-Dimensional Simulation of the Transient Behavior of a Three-Way Catalytic Converter. SAE Technical paper 2002-01-0065 (2002)

D. Chatterjee, O. Deutschmann, J. Warnatz. Detailed surface reaction mechanism in a three-way catalyst. Faraday Discussions 119 (2001) 371-384.

J. Braun, T. Hauber, H. Többen, P. Zacke, D. Chatterjee, O. Deutschmann, J. Warnatz. Influence of Physical and Chemical Parameters on the Conversion Rate of a Catalytic Converter: A Numerical Simulation Study. SAE paper 2000-01-0211(2000).