Particulate emissions of a modern diesel passenger car under laboratory and real-world transient driving conditions

• Published in: Environmental pollution (1987) Vol. 265; p. 114948
• Main Authors: Wihersaari, Hugo, Pirjola, Liisa, Karjalainen, Panu, Saukko, Erkka, Kuuluvainen, Heino, Kulmala, Kari, Keskinen, Jorma, Rönkkö, Topi
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.10.2020
• Subjects: Diesel exhaust; Engine motoring; Lubricant; Nanoparticle emissions; Real-drive emissions; Nanoparticle emissions; Real-drive emissions; Engine motoring; Diesel exhaust; Lubricant
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2020.114948

Exhaust emissions from diesel vehicles are significant sources of air pollution. In this study, particle number emissions and size distributions of a modern Euro 5b -compliant diesel passenger car exhaust were measured under the NEDC and US06 standard cycles as well as during different transient driving cycles. The measurements were conducted on a chassis dynamometer; in addition, the transient cycles were repeated on-road by a chase method. Since the diesel particulate filter (DPF) removed practically all particles from the engine exhaust, it was by-passed during most of the measurements in order to determine effects of lubricant on the engine-out exhaust aerosol. Driving conditions and lubricant properties strongly affected exhaust emissions, especially the number emissions and volatility properties of particles. During acceleration and steady speeds particle emissions consisted of non-volatile soot particles mainly larger than ∼50 nm independently of the lubricant used. Instead, during engine motoring particle number size distribution was bimodal with the modes peaking at 10–20 nm and 100 nm. Thermal treatment indicated that the larger mode consisted of non-volatile particles, whereas the nanoparticles had a non-volatile core with volatile material condensed on the surfaces; approximately, 59–64% of the emitted nanoparticles evaporated. Since during engine braking the engine was not fueled, the origin of these particles is lubricant oil. The particle number emission factors over the different cycles varied from 1.0 × 1014 to 1.3 × 1015 #/km, and engine motoring related particle emissions contributed 12–65% of the total particle emissions. The results from the laboratory and on-road transient tests agreed well. According to authors’ knowledge, high particle formation during engine braking under real-world driving conditions has not been reported from diesel passenger cars. [Display omitted] •During acceleration and steady speeds engine emitted only non-volatile soot particles.•Under engine motoring conditions engine emitted particles even while not fueled.•Lubricants affected nanoparticles’ number emissions and volatility properties.•Engine-out particle number emission factors varied from 1.0 × 1014 to 1.3 × 1015 #/km.•Engine motoring related particle formation contributed 12–65% of total particles. Diesel passenger car engines emit bi-modal particle size distributions during engine motoring events, but these particles are efficiently filtered in exhaust lines equipped with particulate filters.