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Optimizing the On Board Diagnostic System (OBD) to Monitor for Reduction of the SCR Catalyst Conversion Efficiency using the NOx Sensor
ISSN: 0148-7191, e-ISSN: 2688-3627
Published October 06, 2010 by SAE International in United States
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Due to the independent operation of the aftertreatment system from the engine, the aim of the OBD system (On Board Diagnostic) is to guarantee the powertrain emissions stay within the emissions standards during all the vehicle useful life. In the case of heavy-duty diesel vehicles, that uses the SCR system (Selective Catalytic Reduction) as the aftertreatment technology to meet the stringent emissions levels, the use of a NOx sensor in the exhaust pipe will be indispensable for a reliable monitoring of the emissions.
Analyzing the European directives that are legislating the OBD system, the NOx sensor must be monitored by the emissions control system, guaranteeing faults detection in the aftertreatment system that could increase the emissions. According to the annex 4 of the directive 2005/78/EC item 22.214.171.124 (requirements for the OBD system Stage 2), it is needed to monitor the catalyst efficiency as an isolated component of the system.
In case of efficiency reduction of the aftertreatment system, due to the low quality of the SCR reagent liquid, physical damage or catalyst aged, the current softwares are ready to detect the faults, but providing a generic and inaccurate diagnostic.
The SCR catalyst aging, due to the high level of sulfur in the diesel, to the lubricant oil burning or to the high exhaust gas temperature, will be verified in real applications when the SCR system is implemented. When it is aged, the main feature of the catalyst (the ammonia storage capacity) is reduced, which can cause ammonia emissions (slip) in the ambient. The treatment of this particular feature can also be found in sophisticated software strategies, but applying a theoric factor to the catalyst aging based on the system operating conditions to be applied as a correction factor in the closed-loop dosing control strategy.
This work consists in the development of a software algorithm to be integrated to the OBD system that allows diagnosing, through a dynamic functional test, a NOx conversion efficiency reduction in the SCR catalyst as an isolated component of the complete system. With this diagnostic, applied within the strategies for catalyst aging detection, the dosing controller can correct the reagent liquid injection, preventing ammonia emissions in the ambient, and getting a faster and easier fault resolution.
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Citationde Oliveira Costa, L. and Rossin, F., "Optimizing the On Board Diagnostic System (OBD) to Monitor for Reduction of the SCR Catalyst Conversion Efficiency using the NOx Sensor," SAE Technical Paper 2010-36-0198, 2010, https://doi.org/10.4271/2010-36-0198.
- Costa, L. O., “OBD for SCR Systems using NOx Sensor”, presented at 2° Colloquium SAE Electro-Electronic, Brazil, November 13, 2009.
- Predelli, O., Jungblut, T., and Habekost, M., “Development Strategies for Heavy-Duty On-Board Diagnosis”, ATZ Elektronik: 2-4, March 2006.
- Bunting, B., and Toops, T., “The Development of Rapid Aging and Poisoning Protocols for Diesel Aftertreatment Devices”, presented at DEER 2006, USA, August 24, 2006.
- Official Journal of the European Union, “Requirements for the Emission Control Monitoring System for use in Vehicles and exemptions for Gas Engines”, Directive 2005/55/EC, Rev. Sep. 28, 2005.
- Official Journal of the European Union, “Requirements for the Emission Control Monitoring System for use in Vehicles and exemptions for Gas Engines”, Directive 2005/78/EC, Rev. Nov. 14, 2005.
- Official Journal of the European Union, “Requirements for the Emission Control Monitoring System for use in Vehicles and exemptions for Gas Engines”, Directive 2006/51/EC, Rev. Jun. 6, 2006.
- Häberer, R., “SCR Systems for NOx Reduction”, presented at 1° MinNOx Conference, Germany, February 1-2, 2007.
- Bartels, O., “Lambdasonde und NOx-Sensor”, presented at IAV GmbH Freitagsvortrag, Germany, October 31, 2008.
- Palombo, F., “Oportunidades para Eficiência de Combustíveis”, presented at Workshop Petrobrás 2004, Brazil, December 2-3, 2004.