Abstract
Particle emissions and secondary aerosol formation from internal combustion engines deteriorate air quality and significantly affect human wellbeing and health. Both the direct particle emissions and the emissions of compounds contributing to secondary aerosol formation depend on choices made in selecting fuels, engine technologies, and exhaust aftertreatment (EAT). Here we study how catalytic EATs, particle filtration, and fuel choices affect these emissions concerning heavy-duty diesel engine. We observed that the most advanced EAT decreased the emissions of fresh exhaust particle mass as much as 98% (from 44.7 to 0.73 mg/kWh) and the formation of aged exhaust particle mass ∼100% (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 contained more sulfates and organics. The fuel choices had minor effects on the secondary aerosol formation, implicating 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 indicate that the utilization of EAT in diesel engines would produce benefits with respect to exhaust burden on air quality, and thus their utilization should be promoted especially in geographical areas suffering from poor air quality.
Highlights
Health studies have revealed the association of untreated diesel exhaust with short-term and long-term adverse health effects in humans.[1]
The study of Timonen et al.,[21] made with gasoline direct injection (GDI) passenger car, indicates that the aromatic content of fuel may even determine the emissions of SOA precursors from gasoline-fueled internal combustion engines
We think that this can indicate a higher role of lubricant oil in SOA precursor formation for diesel engine when compared to GDI passenger cars
Summary
Health studies have revealed the association of untreated diesel exhaust with short-term and long-term adverse health effects in humans.[1]. Fitting the DPF between the DOC and the SCR (Figure 1d) removed most of the soot mode of tailpipe and fresh aerosol but left traces of particles in the nucleation mode size range This nucleation mode substantially grew in both concentration and size in the PAM reactor, again a possible result of new particle formation or growth from sizes not detected by EEPS. The photochemical aging of exhaust sample in the PAM chamber increased the fractions of sulfates, nitrates, and ammonium in the aged PM so that they reached clearly elevated and detectable concentrations (Figure 3) This was observed with both low sulfur fuels, indicating that the lubricant oil may contribute to secondary sulfate. It can be seen that the ammonium concentration was not remarkable, even when measured downstream the SCR, indicating low levels of ammonia slip in the SCR
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