AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Accurate Measurement of Particle Size and Number Concentration for Meeting Regulatory Limits on Vehicle Emissions: Inter-comparison of Three Particle Sizing Instruments
NAOMI ZIMMERMAN, Krystal J. Godri-Pollitt, Cheol-Heon Jeong, Terry Jung, Josephine Cooper, James S. Wallace, Greg J. Evans, SOCAAR, University of Toronto
Abstract Number: 302 Working Group: Combustion
Abstract Upcoming Euro VI regulation limits diesel vehicle emissions by particle number concentration. Accurate characterization of particle number concentration requires sizing instruments capable of capturing transient events over a wide concentration range. The TSI Fast Mobility Particle Sizer (FMPS) and Engine Exhaust Particle Sizer (EEPS) are both able to provide these high-resolution size-distributed physical measurements. While these instruments share a common operation principle, differences exist between measurements. To understand these differences, we compared measurements of particulate matter (PM) with contrasting physicochemical characteristics (urban ambient, diesel exhaust, and laboratory-generated PM). The ambient PM was sampled at the intersection of two high-trafficked roads in downtown Toronto, Canada. Diesel PM was generated by a heavy-duty diesel engine under ISO8178 Mode 9 operation and diluted by a rotating disk thermodiluter (TSI 379020A). For a sub-25nm comparison, laboratory-generated measurements (TSI 3480 Electrospray Aerosol Generator) were conducted with two ionic solutions with particle diameter modes of 12.4 and 14.3nm, respectively. To determine the accuracy of the EEPS and FMPS, the diesel exhaust inter-comparison included a TSI Scanning Mobility Particle Sizer (SMPS).
In the diesel and ambient particle mixtures, EEPS number concentrations exceeded the FMPS in the sub-25nm (5-15% greater) and 93-220nm (11-32% greater) size ranges. For particles sized between 25-93nm, the measurements were within instrument error (<5%). The sub-25nm discrepancies were likely due to low total concentrations; comparisons using laboratory-generated PM reduced overestimation to <8%. From this we developed a new FMPS empirical correction for the EEPS when measuring diesel exhaust and ambient PM. Comparisons with the SMPS showed that for diesel exhaust PM a second empirical correction is required due to significant overestimation (25-38%) of particle concentrations by the EEPS and FMPS in the 29.4-107.5nm size range. The impact of particle morphology on the correction procedures required for the EEPS and FMPS will be discussed.