Abstract View
Nanoparticles from Engines: Then and Now
DAVID KITTELSON, University of Minnesota
Abstract Number: 125
Working Group: Invited by Conference Chair
Abstract
The earliest measurements of engine exhaust size distributions involved manual collection and counting or weighing. Frey and Corn (1967) characterized particles collected from a small diesel engine with an electron microscope. They found them to be very small aggregates with geometric mean diameters ranging from 21 to 62 nm depending on engine load. Vuk et al. (1976) reviewed manual sizing methods focusing mainly on cascade impactors that had poor size resolution in the submicron size range, lumping all particles smaller than 600 nm into a single size bin. Such manual methods were associated with long collection and analysis times.
Whitby and Clark (1966) described the first automated, near real-time, instrument for sizing submicron particles. It sized particles by electrical mobility diameter in 12 size bins between 10 nm and 1 μm. Whitby et al., (1975) describe size distributions measured upwind and downwind of a California freeway in 1972. They found that nearly all the particles added by the roadway, weighted by surface area, were in the ultrafine range, This early on-road work laid the foundation for measurements of engine exhaust size distributions in controlled laboratory settings at the University of Minnesota. For many years the work focused on improving our understanding the influence engine design, operating conditions, and fuels on particle emissions. However, in the mid-1990s new interest in particle size emerged as a result of a study by the Health Effects Institute (Bagley et al., 1996). This work showed that some new diesel engine technologies reduced mass emissions, which were regulated, but increased number emissions, which were not. This focused attention on measurement of particles in the nucleation mode where most of the particle number, mainly nanoparticles smaller than 50 nm diameter, is found. Since then work all over the world has focused on measurement and regulation of engine generated nanoparticles, diesel, spark, and even aircraft gas turbine.
Critical issues associated with such measurements will be reviewed.