AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Two Sources of Errors in Determination of the Particle Concentration Reduction Factor of the Volatile Particle Remover Used in Legislated Vehicle Emission Measurement
Abstract Number: 718 Working Group: Instrumentation and Methods
Abstract We investigated sources of errors in determination of the particle concentration reduction factor (fr) of the volatile particle remover (VPR) used in legislated vehicle emission measurement. Sodium chloride and soot are two of the most frequently used materials of particles used in the fr evaluation. We identified two sources of errors that are associated with the use of these materials: One is the variation of the detection efficiency of condensation particle counters (CPCs) against sodium chloride particles, which was found to depend on the preheated temperature of the particles. The other is the size shrinkage of soot particles generated with a propane flame burner that are not thermally pre-treated, when the particles were heated at temperatures typically set at the evaporation tube of VPRs. These two sources of errors have presumably caused disagreement of fr values obtained with particles of the two materials. We found that, by selecting appropriate CPCs and also by sufficiently pre-heating the particles, disagreement due to these errors could be eliminated. As a result, consistent fr values were obtained between measurements with the two different particle materials, i.e., sodium chloride and soot.