ARB Research Seminar
This page updated June 19, 2013
Characteristics and Measurement of Nanoparticles from Engines
Professor David B. Kittelson, Center for Diesel Research and Particle Technology Laboratory, Department of Mechanical Engineering, University of Minnesota
March 18, 2002
Cal EPA Headquarters, 1001 "I" Street, Sacramento, CA
Also presented in El Monte on March 19, 2002
Ultrafine and nanoparticles are found in high concentrations on and near urban roadways. These particles are emitted by both diesel and spark ignition engines. Recent on-road measurements made in Minnesota using a mobile aerosol laboratory and related engine laboratory measurements will be described. The main focus of this presentation will be on measurement and properties of particles emitted by diesel engines, which are much better understood than particles from spark ignition engines. The diesel engine generated fraction of roadway particles mainly consists of submicron diameter particles in two distinct but overlapping size modes, a nuclei mode in roughly the 3 to 30 nm diameter range and an accumulation mode in roughly the 30 to 500 nm range. These two modes are formed by different mechanisms and at different times. The accumulation mode is formed early in the combustion process inside the engine. It consists mainly of carbonaceous agglomerates that eventually adsorb hydrocarbons and sulfates as the exhaust cools and dilutes. Most of the particle mass is found in the accumulation mode. The nuclei mode is not usually formed within the engine but instead forms from volatile precursors as the exhaust dilutes and cools. These particles are formed from volatiles and thus are volatile. Most of the particle number is found in the nuclei mode.
The formation of the nuclei mode and the sensitivity of nuclei mode formation to dilution conditions will be described. Recent measurements of the characteristics of both the nuclei and accumulation modes formed by modern diesel engines and the instruments used to characterize them will be described.
Professor Kittelson received his Ph.D. in Chemical Engineering at the University of Cambridge, England. He joined the Department of Mechanical Engineering at the University of Minnesota in 1970. He currently heads the Power and Propulsion Division and the Center for Diesel Research. His research interests lie in the areas of energy conversion and particle technology with a focus on the formation of pollutants and contaminants, especially particulate matter, by energy conversion and manufacturing processes. Recent activities include: measurement of nanoparticle emissions from diesel and SI engines, dynamics of particle formation during engine exhaust dilution, in situ measurements of the formation of NOX and particulate matter in diesel engines, combustion processes in very small scale engines, development of timing and air-fuel ratio control systems for natural gas fueled engines, studies of the particle removal mechanisms in ultrasonic and megasonic cleaning baths, and particle measurement in vacuum systems.
The work described has involved many investigators including Professor Peter McMurry, Dr. Hiromu Sakarai, Dr. Win Watts, Mr. Jason Johnson and Mr. Kihong Park of the University of Minnesota and Professor Paul Ziemann of the University of California, Riverside.