Size-Dependent Volatility of Diesel Nanoparticles:  Chassis Dynamometer Experiments

Abstract

We analyzed the size-dependent volatility of nanoparticles in a diameter range of 30-70 nm in diesel exhaust emissions. The test system included a medium-duty diesel truck on a chassis dynamometer, a single-stage dilution tunnel, a tandem differential mobility analyzer (TDMA) equipped with an electric furnace, and a condensation particle counter. The size shifts of monodispersed diesel nanoparticles under changing furnace temperatures were measured by TDMA in the gas phase. Together with the reduction of average particle size and volume, we observed the development of bimodal size distributions resulting from the separation between semivolatile and nonvolatile species as the furnace temperature was increased. While 91-98% of the particles were found to be semivolatile species by total volume during the idling engine condition, only 6-9% were semivolatile during the one-half engine load condition. We also found that smaller particles contained a larger fraction of semivolatile species.

Analysis of model-based PM2.5 emission factors for on-road mobile sources in Mexico

“…In general, PM2.5 emission factors were higher for higher average vehicle speeds, consistent with studies indicating higher PM emission rates observed under high engine load conditions (i.e., vehicle Table 1. speeds) (Kean et al, 2003;Cadle et al, 2007;Zavala et al, 2009b). Similarly, recent studies are consistent with the observation that fine PM emissions increase with engine load for diesel-powered engines and that volatile fraction of fine PM decreases with increasing load (Ziemmann et al, 2002;Kwon et al, 2003). This can be explained by the high fraction of unburned lubricating oil observed in the PM exhausts with respect to combustion oxidation products and unburned fuel.…”

Current Understanding of Ultrafine Particulate Matter Emitted from Mobile Sources

“…Kwon et al 27 used a medium-size diesel truck on a chassis dynamometer to study the volatility of UFPM. Particle size distributions were measured with a TDMA, where an electric furnace was connected to the exhaust to vary the temperature of the sampled UFPM, thereby influencing the volatilization of the UFPM compounds.…”

Physical and Chemical Characteristics and Volatility of PM in the Proximity of a Light-Duty Vehicle Freeway

“…Measurements of particle emissions from motor vehicles have been accomplished via dynamometer source testing (Chase et al 2000;Kwon et al 2003;Sakurai et al 2003aSakurai et al , 2003bSchauer et al 1999Schauer et al , 2002Suess and Prather 2002), roadway tunnel sampling (Allen et al 2001;Fraser et al 1998;Laschober et al 2004;McGaughey et al 2004), on-road chase experiments (Shah et al 2004;Vogt et al 2003), and roadside measurements Sturm et al 2003;Zhu et al 2002aZhu et al , 2002bZhu et al , 2004. In general, particles directly emitted from motor vehicles are in the size range from 20 to 130 nm in aerodynamic diameter for diesel engines and from 20 to 60 nm for gasoline engines (Ristovski et al 1998).…”