A Study of the Effect of Light-Off Temperatures and Light-Off Curve Shape on the Cumulative Emissions Performance of 3-Way Catalytic Converters

Liam Mc Grane; Roy Douglas; Kurtis Irwin; Jonathan Stewart; Andrew Woods; Fabian Muehlstaedt

doi:10.4271/2021-01-0594

The results of this paper will show the reader how to quantify a minimum light-off temperature to meet the required emissions standards with the use of a 3-way catalytic converter. The method can be applied to both motorcycle and larger automotive catalysts to help meet their respective emissions standards (Euro 5/Euro 7). The ability to predict a light-off temperature for any catalyst at the beginning of the project saves both time and resource.

With an emphasis on how the shape of the light-off curve affects the cumulative tailpipe emissions and how shape of the light-off curves change with the ageing process. Changes in the light-off curves will be reviewed to understand how the chemical reactions and pore diffusion mechanisms within the catalyst deplete to negatively affect performance over its life time.

Using the total cumulative emissions target to achieve the OBD (On Board diagnostic) requirement along with WMTC data, light-off curves were modelled using predicted catalyst specifications with the CATAGEN combined global and micro kinetic model to predict T50 light-off temperatures to achieve the required tailpipe emissions. The original simulations assumed the catalyst achieved 100% conversion of all gases.

The catalysts were aged using RAT (Rapid Ageing Test) on a CATAGEN Omega test reactor. Throughout ageing light-off check points were used to assess the level of degradation of the catalyst’s performance. During the ageing process the maximum light-off conversion dropped below 100%. The kinetic model was utilised to understand the effects this would have on the cumulative tailpipe emissions. This data was used to understand a potential trade-off between maximum conversion percentage and light-off temperature. The catalysts were finally tested on an engine test bench to confirm model predictions.

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A Study of the Effect of Light-Off Temperatures and Light-Off Curve Shape on the Cumulative Emissions Performance of 3-Way Catalytic Converters 2021-01-0594

SAE MOBILUS