Detailed Characterization of Solid and Volatile Particle Emissions of Two Euro 6 Diesel Vehicles

Featured Application The particle number emissions of two Diesel vehicles, weighted with one Diesel particulate filter (DPF) active regeneration, were around 2 x 10(11) #/km for solid particles but 20-300 x 10(11) #/km for volatile particles. The solid particle number emissions of Diesel vehicles are very low due to the particulate filters as exhaust aftertreatment devices. However, periodically, the trapped particles are oxidized (i.e., active regeneration) in order to keep the backpressure at low levels. The solid particle number emissions during regenerations are only partly covered by the regulations. Many studies have examined the emissions during regenerations, but their contribution to the overall emissions has not been addressed adequately. Furthermore, the number concentration of volatile particles, which is not included in the regulations, can be many of orders of magnitude higher. In this study, the particulate emissions of two light-duty Euro 6 vehicles were measured simultaneously at the tailpipe and the dilution tunnel. The results showed that the weighted (i.e., considering the emissions during regeneration) solid particle number emissions remained well below the applicable limit of 6 x 10(11) #/km (solid particles > 23 nm). This was true even when considering solid sub-23 nm particles. However, the weighted volatile particle number emissions were many orders of magnitude higher, reaching up to 3 x 10(13) #/km. The results also confirmed the equivalency of the solid particle number results between tailpipe and dilution tunnel locations. This was not the case for the volatile particles which were strongly affected by desorption phenomena. The high number of volatiles during regenerations even interfered with the 10 nm solid particle number measurements at the dilution tunnel, even though a catalytic stripper equipped instrument was also used in the dilution tunnel.

Automated summary

This study investigates the particulate emissions of two light-duty Euro 6 vehicles by measuring them simultaneously at the tailpipe and the dilution tunnel. The results show that while the solid particle number emissions remain within the applicable limit, the number emissions of volatile particles, taking into account the emissions during regeneration, are significantly higher.