Influence of the MeFo and DMC Content in the Fuel on the Gasoline DI Spray Characteristics with the Focus on Droplet Speed and Size 2021-01-1191

E-fuels are proven to be a major contributing factor to reduce CO₂ emissions in internal combustion engines. In gasoline engines, C1 oxygenate are seen as critical to reach CO₂ and emission reduction goals. Their properties affect the fuel injection characteristics and thus the fuel mixture formation and combustion emissions. To exploit the full potential of e-fuels, the detailed knowledge of their spray characteristic is necessary. The correlation between the fuel content of C1 oxygenates and particulate emissions do not appear to be linear. To understand this correlation, the spray characteristics have to be investigated in detail. The reduced stoichiometric air requirement leads to an increase of the injected fuel mass, which has to evaporate. This can lead to a changed fuel film interaction within the combustion chamber walls and therefore a change of particle formation. On the other hand, the oxygen content in the fuel can suppress soot formation, support soot oxidation and reduce particle emissions. The fuel components which are investigated in this paper are dimethylcarbonate (DMC) and methylformiat (MeFo). Both are added to the base fuel RON95 different concentrations. This paper focuses on the spray properties droplet speed, size and spatial distribution. The influence of MeFo- and DMC-content on the spray droplets is characterized with a phase doppler anemometry. Several experiments are performed with varying fuel compositions, temperatures and pressures. The spray is characterized in multiple distances to the nozzle and in a grid of 2mm inside the spray jacket. Both fuels change the spray characteristics similarly, although the influence by MeFo is usually more pronounced. Above all, it can be observed that fuel evaporation is improved by blending DMC/MeFo. However, droplet decomposition is slower and thus leads to larger SMD. The droplet velocity increases significantly with increasing DMC/MeFo content.