Characterization of particles from a current technology heavy-duty diesel engine

Abstract

The physical properties, chemical properties, and morphology of particles from a current technology diesel engine run under steady-state conditions were determined during five campaigns across three calendar years. Concentrations of particulate matter, NO(x), HC, CO, and CO2 measured at a fixed sampling position were found to be repeatable between different campaigns. However, particle size distributions and number concentrations were significantly affected by dilution conditions. Particle density, estimated using a volume size distribution estimated from an ELPI together with measured mass, was found to be below 1 g/cm3 at nonzero loads, but this is explained by an overestimation of volume by the ELPI due to particle fractal properties. Particle phase SO42-, NO3-, PAH, organic carbon, and elemental carbon were found to vary with engine operating modes. Particles emitted from a modern diesel engine had similar cluster structures to those from old engines but consisted of smaller basic particles when analyzed with a TEM. A semivolatile liquid fraction was not normally visible in the TEM but was seen when trapped within a folded carbon film. Very fine (<10 nm) single particles were observed in diluted exhaust by TEM and confirmed by SMPS.