Optimization of automotive catalytic converter by numerical modeling and simulation with detailed mechanism

• We couple the 2-D flow model of catalytic converter with the reaction model.
• The detailed surface reaction mechanism over Rh is employed instead of the global one.
• Increasing substrate length ratio of dual-substrate converter improves flow uniformity.
• Light-off process is accelerated as the content of precious metal increases.

Based on a detailed surface reaction mechanism of CO–O2 reaction over rhodium, a computational fluid dynamics package coupled with CHEMKIN code was employed to analyze the flow field and catalytic reaction of full-size automotive catalytic converters. The effect of geometrical factors on flow uniformity inside a dual-substrate catalytic converter was investigated. Results indicated that with the gap width and total substrate length fixed, increasing the substrate length ratio (front substrate/rear substrate) promotes flow uniformity. The influences of substrate length ratio and precious metal loading on its light-off performance were also discussed. It was found that the converter with high substrate length ratio achieved a good flow uniformity performance, as well as possessed a low light-off temperature. The effect of precious metal loading was analyzed and a significant improvement in CO conversion was obtained at a typical low temperature for all the three substrates with different cell density when the content of precious metal loading was doubled. Furthermore, the light-off temperature of the 400 cpsi/6.5 mil substrate was lowered with increasing precious metal loading. The predicted results reveal that the coupling approach of detailed kinetic model and flow field can be a proper method in optimization of converter design.

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