Effects of biodiesel, engine load and diesel particulate filter on nonvolatile particle number size distributions in heavy-duty diesel engine exhaust

Highlights: ► The effects of waste cooking oil biodiesel, engine load and DOC + DPF on nonvolatile particle size distributions in HDDE exhaust. ► Increasing biodiesel blends cause slight decreases in the total particle number concentrations and negligible changes in size distributions. ► Increasing load results in modest increases in both the total particle number concentrations and sizes. ► The effects of semivolatile materials are strongest at idle, during which nonvolatile cores <16 nm were observed. ► The DOC + DPF shows remarkable filtration efficiency for both the core and soot particles, irrespective of biodiesel blend and load. - Abstract: Diesel engine exhaust contains large numbers of submicrometer particles that degrade air quality and human health. This study examines the number emission characteristics of 10–1000 nm nonvolatile particles from a heavy-duty diesel engine, operating with various waste cooking oil biodiesel blends (B2, B10 and B20), engine loads (0%, 25%, 50% and 75%) and a diesel oxidation catalyst plus diesel particulate filter (DOC + DPF) under steady modes. For a given load, the total particle number concentrations (NTOT) decrease slightly, while the mode diameters show negligible changes with increasing biodiesel blends. For a given biodiesel blend, both the NTOT and mode diameters increase modestly with increasing load of above 25%. The NTOT at idle are highest and their size distributions are strongly affected by condensation and possible nucleation of semivolatile materials. Nonvolatile cores of diameters less than 16 nm are only observed at idle mode. The DOC + DPF shows remarkable filtration efficiency for both the core and soot particles, irrespective of the biodiesel blend and engine load under study. The NTOT post the DOC + DPF are comparable to typical ambient levels of ∼104 cm−3. This implies that, without concurrent reductions of semivolatile materials, the formation of semivolatile nucleation mode particles post the aftertreatment is highly favored.