AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
The Effects of Aggressive Drive Cycles on the Characteristics and Measurement of GDI Vehicle PM Emissions
MATTI MARICQ, Joseph Szente, Amy Harwell, Michael Loos, Ford Motor Company
Abstract Number: 321 Working Group: Combustion
Abstract Changing emissions regulations are broadening the range of driving conditions subject to motor vehicle PM emissions standards. In the US, the EPA and CARB have introduced a 6 mg/mi PM standard for the US06 drive cycle. Europe and the remainder of the world are moving to the World Harmonized Light Vehicle Test Procedure, which includes an extra high speed portion. And solid particle number standards will apply to Real World Driving Emissions regulations.
This paper describes recent work which shows that PM emissions from GDI vehicles can change dramatically between moderate driving, such as on the Federal Test Procedure (FTP), and aggressive driving, such as the US06 cycle. These include changes to the size distribution as well as composition. Whereas PM emissions largely exhibit a lognormal accumulation mode of soot over the moderate FTP cycle, the distribution often becomes bimodal during the US06 cycle. The accumulation mode can also shift to a mean size of order 30 nm. This shift is accompanied by a decrease in the black carbon / elemental carbon ratio to 50% or less. These changes suggest that soot in aggressive driving is younger and less carbonized.
These changes also impact the ability of various aerosol instruments, such as the Engine Exhaust Particle Sizer, Dekati Mass Monitor, and AVL Micro Soot Sensor to accurately measure PM levels. The changes in size distribution alter the assumptions built in to PM mass determination from size distribution measurements, and the change in soot particles affect the ability to determine soot mass by light absorption.
Finally, the high exhaust temperatures encountered during aggressive driving lead to storage / release effects that interfere with PM emissions measurements. These can come from the vehicles exhaust system or the exhaust sampling system. Their impact on repeatable PM measurement is examined.