ARB Research Seminar

This page updated June 19, 2013

Issues Associated with Solid Particle Measurement

Heejung Jung, Ph.D., College of Engineering-Environmental Research and Technology (CE-CERT), University of California, Riverside

January 24, 2012
Cal EPA Headquarters, 1001 "I" Street, Sacramento, CA

Research Project


The European PMP (particle measurement protocol) aims to measure solid particle number emissions. As such the PMP specifies to measure only particles larger than 23 nm. However, during the Air Resources Board's previous studies on PMP, they found a significant number of appeared-to-be solid sub-23nm particles that can make it past the PMP volatile particle remover.

This study reports the nature of sub-23 nm particles found in the solid particle measurement and issues associated with them. The tests were conducted by comparing a PMP compliant system with a catalytic stripper using engine exhaust during chassis dynamometer testing and using model aerosol made of sulfuric acid and long chain hydrocarbon. The analysis suggests that sub-23nm particles are mainly re-nucleated particles downstream of the evaporation tube of the PMP system and they are present below 10 nm. This study raises issues on how to apply solid particle measurement method to more advanced engines (e.g., GDI and HCCI) with no particulate filter, which can have non-negligible number of solid particles below 23 nm. The first solution is to lower current cutoff diameter to 10 nm based on the results of this study. The second and more robust solution is to prevent re-nucleation of particles downstream of the PMP. The second solution is a subject for future study.

Speaker Biography

Heejung Jung, Ph.D., is an assistant professor at the University of California, Riverside (UCR). Dr. Jung is affiliated with department of mechanical engineering and CE-CERT (College of Engineering-Environmental Research and Technology). Professor Jung received his Ph.D. from the University of Minnesota, and received both his M.S. and B.S. degrees from Seoul National University in Mechanical Engineering. Upon completion of his masters, he joined Hyundai Motor Company as a research engineer. Dr. Jung later completed his postdoc research at the University of California, Davis before joining CE-CERT and UCR. Dr. Jung's current research focus areas are on vehicle emissions and air quality.

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