Catalyst-heating operation in compression-ignition engines: A comprehensive understanding using large eddy simulations
Catalyst-heating operation in compression-ignition engines is critical to ensure rapid light-off of exhaust catalysts during cold-start. This is typically achieved by using late post injections for increased exhaust enthalpy, where retardability is constrained mainly by emissions due to inactivity o...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
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Elsevier
2023-12-01
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| Series: | Applications in Energy and Combustion Science |
| Subjects: | |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S2666352X23000924 |
| _version_ | 1797676552544059392 |
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| author | Dario Lopez-Pintor Stephen Busch Angela Wu Tuan Nguyen Joonsik Hwang Seokwon Cho |
| author_facet | Dario Lopez-Pintor Stephen Busch Angela Wu Tuan Nguyen Joonsik Hwang Seokwon Cho |
| author_sort | Dario Lopez-Pintor |
| collection | DOAJ |
| description | Catalyst-heating operation in compression-ignition engines is critical to ensure rapid light-off of exhaust catalysts during cold-start. This is typically achieved by using late post injections for increased exhaust enthalpy, where retardability is constrained mainly by emissions due to inactivity of the oxidation catalyst at these conditions. Comprehensive understanding of formation mechanism of pollutant emissions is needed to optimize engine performance and minimize tailpipe harmful emissions. In this study, a computational fluid dynamics model of a medium-duty compression-ignition engine is developed and validated against with catalyst-heating operation experimental data using large eddy simulations. The engine is fueled with a full boiling-range diesel fuel and uses an optimized five-injections strategy that consists of two pilots, one main, and two post injections. Results show that, significant amounts of unburned hydrocarbons (UHCs) and oxygenated UHCs (OUHC) are formed by the pilot injections, which may persist until exhaust valve opening. UHCs accumulate mainly in the outer-upper part of the cylinder guided by the piston lip, in the inner-bowl due to the bowl geometry, near the injector nozzle by the fuel from the end-phase of injection, and in the space between spray plumes transported by the swirl motion. The main injection exhibits a short ignition delay and rapidly consumes most of UHC and OUHC, except for the central part of the chamber near the injector nozzle. The 1st post injection counteracts the expansion effect on temperature, plays a key role in increasing the exhaust enthalpy and reducing the harmful emissions by promoting combustion associated with the 2nd post injection. The fuel delivered by the 2nd post injection penetrates through the flame of the 1st post injection, creating cool flame clouds beyond the flame that eventually transition to a diffusion flame. Finally, a unique phenomenological model is proposed to better visualize the interactions of post injections. |
| first_indexed | 2024-03-11T22:30:51Z |
| format | Article |
| id | doaj.art-5d97d8c12c3c4386ad1b17c62e380ccb |
| institution | Directory Open Access Journal |
| issn | 2666-352X |
| language | English |
| last_indexed | 2024-03-11T22:30:51Z |
| publishDate | 2023-12-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Applications in Energy and Combustion Science |
| spelling | doaj.art-5d97d8c12c3c4386ad1b17c62e380ccb2023-09-23T05:12:42ZengElsevierApplications in Energy and Combustion Science2666-352X2023-12-0116100203Catalyst-heating operation in compression-ignition engines: A comprehensive understanding using large eddy simulationsDario Lopez-Pintor0Stephen Busch1Angela Wu2Tuan Nguyen3Joonsik Hwang4Seokwon Cho5Sandia National Laboratories, 7011 East Avenue, Livermore, CA 94550, USACummins, Inc., 1900 McKinley Ave, Columbus, IN 47201, USAConverget Science Inc., 6400 Enterprise Ln, Madison, WI 53705, USASandia National Laboratories, 7011 East Avenue, Livermore, CA 94550, USADepartment of Mechanical Engineering, Mississippi State University, Mississippi State, MS 39762, USA; Center for Advanced Vehicular Systems (CAVS), 200 Research Blvd., Starkville, MS 39759, USADepartment of Aerospace Engineering, Mississippi State University, Mississippi State, MS 39762, USA; Center for Advanced Vehicular Systems (CAVS), 200 Research Blvd., Starkville, MS 39759, USA; Corresponding author.Catalyst-heating operation in compression-ignition engines is critical to ensure rapid light-off of exhaust catalysts during cold-start. This is typically achieved by using late post injections for increased exhaust enthalpy, where retardability is constrained mainly by emissions due to inactivity of the oxidation catalyst at these conditions. Comprehensive understanding of formation mechanism of pollutant emissions is needed to optimize engine performance and minimize tailpipe harmful emissions. In this study, a computational fluid dynamics model of a medium-duty compression-ignition engine is developed and validated against with catalyst-heating operation experimental data using large eddy simulations. The engine is fueled with a full boiling-range diesel fuel and uses an optimized five-injections strategy that consists of two pilots, one main, and two post injections. Results show that, significant amounts of unburned hydrocarbons (UHCs) and oxygenated UHCs (OUHC) are formed by the pilot injections, which may persist until exhaust valve opening. UHCs accumulate mainly in the outer-upper part of the cylinder guided by the piston lip, in the inner-bowl due to the bowl geometry, near the injector nozzle by the fuel from the end-phase of injection, and in the space between spray plumes transported by the swirl motion. The main injection exhibits a short ignition delay and rapidly consumes most of UHC and OUHC, except for the central part of the chamber near the injector nozzle. The 1st post injection counteracts the expansion effect on temperature, plays a key role in increasing the exhaust enthalpy and reducing the harmful emissions by promoting combustion associated with the 2nd post injection. The fuel delivered by the 2nd post injection penetrates through the flame of the 1st post injection, creating cool flame clouds beyond the flame that eventually transition to a diffusion flame. Finally, a unique phenomenological model is proposed to better visualize the interactions of post injections.http://www.sciencedirect.com/science/article/pii/S2666352X23000924Catalyst-heating operationCFDLarge eddy simulationCompression-ignitionPollutant emissionsSpray interaction |
| spellingShingle | Dario Lopez-Pintor Stephen Busch Angela Wu Tuan Nguyen Joonsik Hwang Seokwon Cho Catalyst-heating operation in compression-ignition engines: A comprehensive understanding using large eddy simulations Applications in Energy and Combustion Science Catalyst-heating operation CFD Large eddy simulation Compression-ignition Pollutant emissions Spray interaction |
| title | Catalyst-heating operation in compression-ignition engines: A comprehensive understanding using large eddy simulations |
| title_full | Catalyst-heating operation in compression-ignition engines: A comprehensive understanding using large eddy simulations |
| title_fullStr | Catalyst-heating operation in compression-ignition engines: A comprehensive understanding using large eddy simulations |
| title_full_unstemmed | Catalyst-heating operation in compression-ignition engines: A comprehensive understanding using large eddy simulations |
| title_short | Catalyst-heating operation in compression-ignition engines: A comprehensive understanding using large eddy simulations |
| title_sort | catalyst heating operation in compression ignition engines a comprehensive understanding using large eddy simulations |
| topic | Catalyst-heating operation CFD Large eddy simulation Compression-ignition Pollutant emissions Spray interaction |
| url | http://www.sciencedirect.com/science/article/pii/S2666352X23000924 |
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