Second-by-Second On-Board Real-World Particle Number Emissions for Comparable Conventional and Hybrid-Electric Gasoline Vehicles in a City Driving Environment

MITCHELL K. ROBINSON (1), Britt A. Holmén (1)

(1) University of Vermont

     Abstract Number: 228
     Last modified: April 30, 2010

Abstract
Many recent studies indicate a strong correlation between airborne particulate number (PN) and a variety of cardiovascular and pulmonary diseases. Motor vehicles have been shown to emit high numbers of particle number. This study investigates particle number emissions using The Total On-Board Tailpipe Emissions Measurement System (TOTEMS) to sample directly from the tailpipe of two 2010 Toyota Camry gasoline vehicles with different drivetrains; conventional and hybrid-electric. TOTEMS instruments collect data with a minimum resolution of 1-second while the test vehicle was driving a 5.1 mile route under real-world conditions in the City of Burlington, VT. Data were collected in February and March of 2010 with average temperatures between -5 degrees C and 9 degrees C. Road grade ranged from -12.8% to +10.3% and 40 traffic devices exist; 22 stop lights and 18 stop signs.
Two particle instruments measure exhaust particle number in TOTEMS: a TSI Model 3090 Engine Exhaust Particle Sizer (EEPS) and a TSI Model 3025A Ultrafine Condensation Particle Counter (UCPC). The EEPS counts and sizes particles (5.6 – 560 nm) in 32 size channels, while the UCPC counts total particle number (3 – 3000 nm). Exhaust is diluted in two stages to a total dilution ratio of 1:108. Particle number emissions from the hybrid vehicle were typically higher than the conventional vehicle in the city environment. PN hybrid emissions were characterized by frequent sharp peaks, which occurred at engine-on events, up to magnitudes of 2.32 x10^7 #/cc (corrected for dilution). These peaks are typically followed by smaller peaks reaching 4.12 x10^6 #/cc (corrected for dilution) that occurred as the vehicle accelerated away from complete stops. The conventional vehicle had total particle number reaching 6.24 x 10^6 #/cc (corrected for dilution). Mean distributions are similar between vehicles with nearly all sizes from the hybrid being larger in concentration than the conventional vehicle.