Exhaust aftertreatment was observed to diminish the particulate emissions of a diesel engine
The study indicates that for the diesel engine the most advanced exhaust aftertreatment (EAT) decreases the emissions of fresh exhaust particle mass as much as 98% (from 44.7 to 0.73 mg/kWh). The formation of aged exhaust particle mass decreases nearly completely (from 106.2 to ~0 mg/kWh).
The composition of emitted particles depended significantly on the EAT and oxidative aging. While black carbon typically dominated the composition of fresh exhaust particles, aged particles were observed to contain more sulfates and organics. The fuel choices were observed to have a minor effect on the secondary aerosol formation. This implies that, in diesel engines, either the lubricant is a significant source of secondary aerosol precursors, or the precursors are formed in the combustion process.
Results clearly indicate that the utilization of EAT in diesel engines can diministh the particulate emissions and would produce benefits with respect to exhaust burden on air quality. Thus, utilization of EATs should be promoted especially in geographical areas suffering from poor air quality.
Particle emissions and secondary aerosol formation from internal combustion engines deteriorate air quality and significantly affect human wellbeing and health in urban areas. Both the direct particle emissions and the emissions of compounds contributing to secondary aerosol formation in the atmosphere depend on choices made in selecting fuels, engine technologies and exhaust aftertreatment (EAT).
The measurements were conducted with a test engine that was a prototype high-speed 4.4 L turbo-charged intercooled nonroad diesel engine prototype producing at maximum 100 kW. To compare different vehicle technologies, particle emissions were studied for four different EAT combinations and two fuels under laboratory conditions. The studied EAT combinations were: no exhaust aftertreatment (No EAT), a diesel oxidation catalyst (DOC), a combination of diesel oxidation catalyst and an SCR system (DOC+SCR), and a combination of a diesel oxidation catalyst, a diesel particulate filter and an SCR system (DOC+DPF+SCR).
The study was conducted in collaboration by Tampere University, Finnish Meteorological Institute and Turku University of Applied Sciences. It was supported by the Health relevant and energy efficient regulation of exhaust particle emissions (HERE) project, funded by Business Finland (Tekes), AGCO Power Oy, Dinex Finland Oy, Dekati Oy, Neste Oyj, Pegasor Oy and Wärtsilä Finland Oy.
Further information:
Senior researcher Hilkka Timonen, Finnish Meteorological Institute, tel. +358 50 380 2864, hilkka.timonen@fmi.fi
Reference: Strategies To Diminish the Emissions of Particles and Secondary Aerosol Formation from Diesel Engines, Environ Sci Technol, 53, 10408-10416, 10.1021/acs.est.9b04073, 2019.
