AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
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Secondary Organic Aerosol Forming Potential from Emerging Light-Duty Gasoline Direct Injection Vehicles
PATRICK ROTH, Diep Vu, Jiacheng Yang, Tyler Berte, Thomas D. Durbin, Georgios Karavalakis, Akua Asa-Awuku, University of California, Riverside
Abstract Number: 196 Working Group: Combustion
Abstract Vehicle emissions are an important source of VOCs, NOx, CO, and PM, which can contribute to SOA and ozone formation. Previous work has characterized the physical and chemical properties of aged emissions from vehicles operating over realistic driving conditions. However, these studies focused on older technology vehicles, such as Port Fuel Injection (PFI) vehicles, with less attention on newer technology gasoline direct injection (GDI) vehicles.
GDI technology has become the preferred standard to PFI engines in the US and European markets due to its increased specific output and improved fuel economy. However, GDI vehicles will have difficulty meeting the 3 mg/mile LEVIII PM Standard (2017) due to increased PM emissions; whereas PFI vehicles generally emit below 1 mg/mile. As a result, manufacturers may begin electing to utilize gasoline particulate filters (GPF) to meet the LEVIII PM Standard.
For this study, the SOA forming potential from the emissions generated from five GDI vehicles (one with GPF filter) were investigated over the LA-92 driving cycle in triplicate. The exhaust was collected in CE-CERT’s 30m3 Mobile Atmospheric Chamber (MACh). The emissions were then photochemically aged and real-time particle and gaseous phase measurements were analyzed.
As the gaseous emissions aged and condensed, the fractal, primary particles (BC) quickly transitioned to more dense, spherical particles. The change in composition and morphology impacts 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 vehicle equipped with the GPF filter displayed a considerable decrease in primary PM along with differences in the physical and chemical compositions of aged aerosols. The data generated from this work will aid manufacturers and regulatory agencies understand the impacts of the increasing market share of GDI engines.