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Quantification of particulate and gaseous semi-volatiles in CFR-compliant dynamometer testing of GDI vehicles.
Citation:
Martin, J., I. George, M. Hays, R. Baldauf, AND J. Faircloth. Quantification of particulate and gaseous semi-volatiles in CFR-compliant dynamometer testing of GDI vehicles. CRC Real World Emissions Workshop, Long Beach, California, March 07 - 10, 2021.
Impact/Purpose:
Gas-Direct Injection (GDI) vehicles were introduced to the normal consumer market in 2007, and since then have rapidly gained a majority market share of the new vehicle market. Because emissions from internal combustion engines are highly dependent on engine type, previous emissions profiles gather on port-fuel injection (PFI) vehicles may not capture accurate emissions profiles of the current fleet. Continuing to optimize the effectiveness of models like CMAQ requires data which accurately characterizes emissions of the modern consumer vehicle fleet. to this end, in 2017 several GDI vehicles were tested in the RTP dynamometer facilities. Comprehensive emissions profiles were gathered, some of which have previously been reported on. This presentation is intended to present data regarding the emission of semi-volatile organic carbon (SVOC), captured in both gaseous and particulate phase. SVOCs have historically been ignored, until the past 15-20 years, when discussing vehicle emissions and formation of secondary-organic aerosol (SOA, a significant component of "smog"). However, in the past two decades, a considerable body of work in the scientific literature has demonstrated that SVOCs are responsible for a considerable, if not majority, contribution to secondary and primary organic aerosols from vehicle emissions. Including these data in CMAQ or other predictive air quality monitoring models will improve the sensitivity and utility of these models in informing regulators, scientists, and the general public. This presentation is intended principally to demonstrate that these data (i.e. gaseous and particulate SVOC concentrations in vehicle emissions) can be generated on CFR-compliant dynamometer studies. (The use of dynamometers for regulatory purposes is explicitly defined as a matter of law). By doing so, we hope to encourage the inclusion of SVOC analyses as a routine component of dynamometer studies of vehicle emissions. Ultimately, while the data from these three vehicles is directly useful, a comprehensive set of data from across the consumer and commercial market will be incredibly useful to emissions modeling and other efforts to explain and control particulate matter.
Description:
During 40 CFR 1066 compliant dynamometer studies, non-speciated emissions of intermediate and semi-volatile organic compounds (IVOC/SVOC) were quantified using the volatility basis set (VBS) paradigm. Three gas-direct injection vehicles (V1-3) were tested using the USEPA three-phase Federal Test Procedure (FTP1-3) simulating city driving, including a cold-start (FTP1). Vehicles were also tested using a supplementary FTP (US06) to simulate sustained higher speed driving. These tests were conducted at both 72 °F (22 °C) and 20 °F (-7 °C) using summer and winter gasoline blends, respectively. Because IVOC/SVOC are expected to be emitted in both gaseous and particulate phases, total IVOC/SVOC emissions were composited from direct thermal desorption of filter-captured particulate matter (PM) and thermal desorption of gaseous IVOC/SVOC captured in sample tubes using Carbotrap media. In all driving phases and temperatures, IVOC/SVOC emissions were predominantly collected in the gas phase, and for most drive phases and vehicles the collected gas phase compounds were at the extreme high-volatility end of the VBS range. In FTP2, V2 had large contributions from lower volatility SVOCs in the gas phase at both temperatures. Among IVOC/SVOC collected in the particulate phase, collected emissions were predominantly at the extreme low-volatility end of the VBS range. Total IVOC/SVOC emissions were highly dependent on vehicle, driving phase, and driving temperature. The emissions were greatest in FTP1 cold-start phase for all vehicles and temperatures, greatest in the 20 °F tests between phases and vehicles and were generally greater in V2 between phases and temperature.