Detailed Characterization of Criteria Pollutant Emissions from Dedicated EGR Light Duty Vehicle

Cary  Henry, Southwest Research Institute

Recent legislation has been enacted requiring unprecedented reductions in greenhouse gas emissions, and thus improved fuel efficiency, from internal combustion engines. For light duty automotive applications, this mandated reduction in greenhouse gas emissions directly coincides with a required 80% reduction in gaseous criteria pollutant emissions, and a 90% reduction in particulate emissions. The dedicated EGR combustion strategy, developed by Southwest Research Institute, has been shown to provide reductions in fuel economy of up to 15% when compared with conventional non-EGR type strategies [1,2]. In addition to these observed improvements in fuel consumption, the use of cooled EGR has been shown to reduce certain criteria pollutants, including PM and PN emissions [2,3]. In this study, the criteria pollutant emissions from a D-EGR light duty vehicle were compared with emissions from an identical production GDI vehicle without externally cooled EGR. In addition to the comparison of criteria pollutant mass emissions, an analysis of the gaseous and particulate chemistry was conducted to understand how the change in combustion system affects the optimal aftertreatment control system. Hydrocarbon emissions from the vehicle were analyzed using a variety of methods to quantify over 200 compounds raging in HC chain length from C1 to C12. The particulate emissions were also characterized to quantify physical properties such as: mass, number, and size distribution; as well as chemical properties such as: the ratio of solid to volatile fraction, the source (lube oil vs. fuel) of volatile particulate emissions, and the ratio of elemental to organic carbon. Gaseous and particulate emissions were sampled and analyzed from both vehicles operating on the FTP-75, HWFET, US06, and WLTP drive cycles at the engine outlet location. The information gathered from this study provides insights into the impact of advanced combustion regimes on emissions chemistry, and will enable the optimization of catalytic components to reduce tailpipe emission of criteria pollutant species allowing these novel combustion concepts to achieve their maximum improvement in fuel consumption.

1. Alger, T., Mangold, B., Dedicated EGR: A New Concept in High Efficiency Engines, SAE Technical Paper 2009-01-0694, 2009
2. Chadwell, C., Alger, T., Zuehl, J., and Gukelberger, R., Demonstration of D-EGR on a 2.0 L GDI Engine, SAE Technical Paper 2014-01-1190, 2014
3. Hedge, M., Weber, P., Gingrich, J., Alger, and Khalek, I., Effect of EGR on Particle Emissions from a GDI Engine, SAE Technical Paper 2011-01-0636, 2011

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