Comparison of Promising Sustainable C1-Fuels Methanol, Dimethyl Carbonate, and Methyl Formate in a DISI Single-Cylinder Light Vehicle Gasoline Engine

On the way to a climate-neutral mobility, synthetic fuels with their potential of CO₂-neutral production are currently in the focus of internal combustion research. In this study, the C1-fuels methanol (MeOH), dimethyl carbonate (DMC), and methyl formate (MeFo) are tested as pure fuel mixtures and as blend components for gasoline. The study was performed on a single-cylinder engine in two configurations, thermodynamic and optical. As pure C1-fuels, the previously investigated DMC/MeFo mixture is compared with a mixture of MeOH/MeFo. DMC is replaced by MeOH because of its benefits regarding laminar flame speed, ignition limits and production costs. MeOH/MeFo offers favorable particle number (PN) emissions at a cooling water temperature of 40 °C and in high load operating points. However, a slight increase of NO_x emissions related to DMC/MeFo was observed. Both mixtures show no sensitivity in PN emissions for rich combustions. This was also verified with help of the optical engine. DMC was also used as a blend component for gasoline. Advantages in PN emissions, knock resistance and injector tip coking were observed. Furthermore, to evaluate resistance against abnormal combustions of pure C1-fuels, two knock resistant fuels, toluene and pure MeOH were used as reference. Resistance against abnormal combustions was investigated at the operating point at 1500 rpm / 17 bar IMEP / ε = 14.91 with the T_intake increased until initial abnormal combustions were detected. Finally, DMC/MeFo was used in a scavenged pre-chamber to determine the potential of the ultra-low soot combustion inside the pre-chamber. Therefore, the lean limit of DMC/MeFo was extended to λ = 2.2 and an indicated efficiency of more than 41 % was achieved at 7 bar IMEP.