Identification of In-Cylinder Aerosol Flow Induced Emissions due to Piston Ring Design in a DISI Single Cylinder LV Engine Using Oxygenated Synthetic Fuels

In the near future, pollutant and GHG emission regulations in the transport sector will become increasingly stringent. For this reason, there are many studies in the field of internal combustion research that investigate alternative fuels, one example being oxygenated fuels. Additionally, the design of engine components needs to be optimized to improve the thresholds of clean combustion and thus reduce particulates. Simulations based on PRiME 3D® for dynamic behaviors inside the piston ring group provide a guideline for experimental investigation. Gas flows into the combustion chamber are controlled by adjusting the piston ring design. A direct comparison of regular and synthetic fuels enables to separate the emissions caused by oil and fuel. This study employed a mixture of dimethyl carbonate (DMC) and methyl formate (MeFo). These two components have no C-C bonds, and the mixture displayed extremely good performance in terms of the particle number (PN) emissions on an ambient level published in previous studies. This fuel property is employed in this study to identify oil induced, engine-out PN-emissions, while the combustion process remains almost identical to that of conventional gasoline. The PN-emissions are measured and subdivided into two ranges: larger than 10 nm and larger than 23 nm.

It was demonstrated that merely changing the piston ring design has an impact on raw PN engine emissions and gas flow behavior in the piston assembly. An increase in PN-emissions and lower blow-by level could only be detected by changing the piston ring design. With reduced, predicted fluid flows into the combustion chamber, lower VOC emissions could be observed during motored runs. The adaptations in the tested piston ring design demonstrate that it is possible to improve particulate emissions by modifying the piston ring group.