Abstract
Lean gasoline engine operation provides clear efficiency benefits relative to conventional stoichiometric combustion approaches. One of the key hurdles to the widespread, practical implementation of lean gasoline combustion remains the challenge of lean NOx control. One of the potential approaches for controlling NOx emission from lean gasoline engines is the so-called passive selective catalytic reduction (SCR) system. In such systems, periods of rich operation generate ammonia over a three-way catalyst (TWC), which is then adsorbed on the downstream SCR and consumed during lean operation. Brief periods of rich operation must occur in response to the depletion of stored ammonia on the SCR, which requires reliable measurements of the SCR ammonia inventory. Presently, lean exhaust system controls rely on a variety of gas sensors mounted up- and downstream of the catalysts, and which only provide an indirect inference of the operation state. In this study, a radio frequency (RF) sensor was used to provide a direction measurement of the amount of ammonia adsorbed on the SCR in real-time. The RF sensor was calibrated and deployed on a BMW N43B20 4-cylinder lean gasoline engine equipped with a passive SCR system. Brief periods of rich operation performed at lambda values between 0.98 and 0.99 generated the ammonia, subsequently stored on the SCR for consumption during periods of lean operation. The experiments compared real-time measurements of SCR ammonia inventory from the RF sensor with estimates of ammonia coverage derived from exhaust gas composition measurements upstream and downstream of the catalyst. The results showed a high degree of correlation between the RF measurements and SCR ammonia storage inventory, and demonstrated NOx conversion efficiencies above 98%, confirming the feasibility of the concept. Relative to stoichiometric operation, lean-gasoline operation resulted in fuel efficiency gains of up to 10%, which may be further improved through direct feedback control from the RF sensor to optimize lean - rich cycling based on actual, measured SCR ammonia levels.
| Original language | English |
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| Title of host publication | ASME 2019 Internal Combustion Engine Division Fall Technical Conference, ICEF 2019 |
| Publisher | American Society of Mechanical Engineers (ASME) |
| ISBN (Electronic) | 9780791859346 |
| DOIs | |
| State | Published - 2020 |
| Event | ASME 2019 Internal Combustion Engine Division Fall Technical Conference, ICEF 2019 - Chicago, United States Duration: Oct 20 2019 → Oct 23 2019 |
Publication series
| Name | ASME 2019 Internal Combustion Engine Division Fall Technical Conference, ICEF 2019 |
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Conference
| Conference | ASME 2019 Internal Combustion Engine Division Fall Technical Conference, ICEF 2019 |
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| Country/Territory | United States |
| City | Chicago |
| Period | 10/20/19 → 10/23/19 |
Funding
This material is based upon work supported by the Department of Energy under contract DE-EE0007214. The authors would like to thank Roland Gravel from the DOE and Jason Conley from DOE NETL for their support and engaging discussions. The authors would also like to thank the support from Commercial and National Laboratory Project Partners: Corning Incorporated, Oak Ridge National Laboratory, Daimler Trucks NA / Detroit Diesel, Cummins, FCA and DSNY. This material is based upon work supported by the Department of Energy under contract DE-EE0007214. The authors would like to thank Roland Gravel from the DOE and Jason Conley from DOE NETL for their support and engaging discussions. The authors would also like to thank the support from Commercial and National Laboratory Project Partners: Corning Incorporated, Oak Ridge National Laboratory, Daimler Trucks NA / Detroit Diesel, Cummins, FCA and DSNY. Disclaimer: This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.
Keywords
- Ammonia Storage
- Lean Gasoline
- NOx Reduction
- Passive SCR
- RF Sensing
- SCR