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Field measurements of gasoline direct injection emission factors: spatial and seasonal variability Naomi Zimmerman, Jonathan M Wang, Cheol-Heon Jeong, Manuel Ramos, Nathan Hilker, Robert M. Healy, Kelly Sabaliauskas, James S Wallace, and Greg Evans Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.5b04444 • Publication Date (Web): 21 Jan 2016 Downloaded from http://pubs.acs.org on January 25, 2016
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Environmental Science & Technology
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Field measurements of gasoline direct injection
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emission factors: spatial and seasonal variability
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Naomi Zimmerman,† Jonathan M. Wang, † Cheol-Heon Jeong, † Manuel Ramos, ‡
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Nathan Hilker, † Robert M. Healy, † Kelly Sabaliauskas, † James S. Wallace, ‡ Greg J. Evans†,*
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†
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Ontario M5S3E5 Canada
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‡
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M5S3G8 Canada
Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto,
Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario
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Corresponding author: Dr. Greg J. Evans Dept. of Chemical Engineering and Applied Chemistry University of Toronto 200 College Street, Room 127, Toronto, Canada, M5S 3E5 Email.
[email protected] Tel. 416-978-1821 Fax. 416-978-8605
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KEYWORDS
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Gasoline direct injection, real-world, fuel-based, vehicle, emission factors, ultrafine particles,
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black carbon, volatility, size distribution
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TOC/Abstract Art:
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ABSTRACT
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Four field campaigns were conducted between February 2014 and January 2015 to measure
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emissions from light-duty gasoline direct injection (GDI) vehicles (2013 Ford Focus) in an urban
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near-road environment in Toronto, Canada. Measurements of CO2, CO, NOx, black carbon (BC),
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benzene, toluene, ethylbenzene-xylenes (BTEX), and size-resolved particle number (PN) were
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recorded 15 m from the roadway and converted to fuel-based emission factors (EFs). Other than
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for NOx and CO, the GDI engine had elevated emissions compared to the Toronto fleet, with BC
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and BTEX EFs in the 80-90th percentile, and PN EFs in the 75th percentile during wintertime
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measurements. Additionally, for three campaigns, a second platform for measuring PN and CO2
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was placed 1.5-3 m from the roadway to quantify changes in PN with distance from point of
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emission. GDI vehicle PN EFs were found to increase by up to 240% with increasing distance
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from the roadway, predominantly due to an increasing fraction of sub-40 nm particles. PN and
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BC EFs from the same engine technology were also measured in the laboratory. BC EFs agreed
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within 20% between the laboratory and real-world measurements; however, laboratory PN EFs
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were an order of magnitude lower due to exhaust conditioning.
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1.
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In the United States, the Corporate Average Fuel Economy (CAFE) standards have specified a
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minimum fuel economy of 37.8 mpg by 20161,2, with similar fuel economy regulations set in
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Canada and Europe. The CAFE standard will continue to increase by 5% per year until 2025,
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when minimum fuel economy must exceed 55 mpg. In response to these stringent regulatory
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requirements on passenger vehicle fuel economy, automobile manufacturers have been
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increasingly turning to gasoline direct injection (GDI) engines, which offer up to a 25%
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improvement in fuel economy compared to port fuel injection (PFI) engines3. Market share of
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GDI vehicles is increasing rapidly; between model years 2009 and 2014 there was a ten-fold
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increase in GDI engine sales4, and it is projected that in 2016 the market share of new light-duty
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vehicles with this technology will exceed 50%5.
INTRODUCTION
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Compared to PFI-equipped vehicles, GDI-equipped vehicles emit substantially more particulate
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matter (PM)6–9 due to incomplete fuel volatilization causing fuel impingement on cylinder and
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piston surfaces and incomplete fuel mixing with air resulting in pockets of fuel rich combustion.
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Particle size distributions from GDI engine exhaust have generally been observed to be either
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bimodal10–13, unimodal9,14–16, or vary7,17 depending on factors such as engine operation, ethanol
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fuel content, and fuel injection system. Of the observed bimodal size distributions, the smaller
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mode is typically
