ABSTRACT
Recent years have seen an increased interest in the study and control of sub-23 nm particle emissions from internal combustion engines. However, the nature of sub-23 nm particles has not been thoroughly studied in much depth up to this point. Decarbonized propulsion systems have been suggested as sensible solutions for heavy-duty vehicles and maritime transportation. However, they are likely to amplify emissions of nanoparticles at these tiny sizes, as there is also growing evidence of increased sub-23 nm particles emissions from different types of lubricating oils.
This paper investigates how the appropriate selection of lubricant oils can support cleaner internal combustion engines. In this study, differential mobility spectrometer measurements with and without the catalytic stripper are analysed. Measurements are taken from the exhaust stream of a 1.0L gasoline direct injection engine. Three oil formulations are evaluated: 0W-16 Low volatility- Low Ash (LoLo), 0W-16, High Volatility-High Ash (HiHi) and 0W-20 Mid-Ash as Baseline. The engine is operated at 1750 rpm with 20 Nm brake torque; the fuel used for all testing is gasoline with an anti-fouling additive designed to keep injectors clean and lessen the effect of injector fouling on particulate emissions. Results show that particulate emissions can be significantly impacted by the type of oil and its composition. HiHi presents the highest TPN, followed by Baseline and LoLo. From Baseline to HiHi TPN increases from 2.81e + 05 to 3.45e + 05 (+32%) without catalytic stripper and SPN from 2.10E + 05 to 2.47e + 05 (+23%) with. On the other hand, from Baseline to LoLo TPN drops from 2.81e + 05 to 2.47E + 05 without catalytic stripper (−28%) and SPN from 2.10e + 05 to 1.52e + 05 (−12%) with. All oils exhibit a nucleation peak at 10 nm with catalytic stripper and at 13 nm without. In addition, for all oils 80%–90% of the TPN is in the sub-23 nm region. Transmission electron microscopy was then used to qualitatively analyse soot collected for the LoLo and the HiHi case. This has confirmed very small particles in the sub-23/sub-10 nm region.
