AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Secondary Aerosol Forming Potential of Gasoline Direct Injection Vehicles with Varying After-Treatment Technologies
PATRICK ROTH, Jiacheng Yang, Diep Vu, Thomas D. Durbin, Georgios Karavalakis, Akua Asa-Awuku, University of California, Riverside
Abstract Number: 112 Working Group: Combustion
Abstract Gasoline Direct Injection (GDI) technology has become the preferred standard to Port Fuel Injection (PFI) engines in the US and European markets due to its improved fuel economy. However, GDI vehicles may have difficulty meeting the new two phase LEV III PM Standard set at 3 mg/mile by 2017, and 1 mg/mile by 2025. The use of gasoline particulate filters (GPF), as seen in Europe, can help GDI vehicles meet future PM emissions standards.
In addition to PM, vehicle emissions are an important source of VOCs, NOx, NH3 and CO which through a variety of complex oxidation reactions, can contribute to secondary aerosol and ozone formation in the atmosphere. The focus of this work was to evaluate how the addition of PM emission control systems affects the secondary aerosol formation potential of new technology GDI vehicles over realistic driving cycles.
For this study, the SOA and ozone forming potential from two GDI vehicles (with and without a GPF filter, both in triplicate) were generated over a cold start, LA-92 driving cycle. The exhaust was measured to certification standards, and subsequently collected in CE-CERT’s 30m3 Mobile Atmospheric Chamber (MACh). The emissions were then photochemically aged for 8-10 hours, and real-time particle and gaseous phase measurements were analyzed.
As expected, the GPF equipped vehicles displayed a considerable decrease in primary PM (~95%) compared to the stock configurations. The composition of the primary aerosol varied with only ~25% of PM mass attributable to BC in the GPF configurations compared to 85% BC in stock configurations. As the gaseous emissions aged and condensed, primary fractal particles (ρ=0.6 g/cm3) quickly transitioned to more dense (ρ=1.4-1.7 g/cm3), spherical particles, composed of ammonium nitrate and organic species. The change in composition and morphology impacted both volatility and hygroscopicity measurements. Aged emission masses were found to exceed the primary masses with varying ratios of inorganic ammonium nitrate and secondary organic material (HR-TOF AMS). The data generated from this work will aid manufacturers and regulatory agencies understand the atmospheric impacts of the increasing market share of GDI equipped vehicles with varying after-treatment technologies.