Analysis of the Piston Group Friction in a Single-Cylinder Gasoline Engine When Operated with Synthetic Fuel DMC/MeFo 2022-01-0485

Synthetic fuels for internal combustion engines offer CO₂-neutral mobility if produced in a closed carbon cycle using renewable energies. C1-based synthetic fuels can offer high knock resistance as well as soot free combustion due to their molecular structure containing oxygen and no direct C-C bonds. Such fuels as, for example, dimethyl carbonate (DMC) and methyl formate (MeFo) have great potential to replace gasoline in spark-ignition (SI) engines. In this study, a mixture of 65% DMC and 35% MeFo (C65F35) was used in a single-cylinder research engine to determine friction losses in the piston group using the floating-liner method. The results were benchmarked against gasoline (G100). Compared to gasoline, the density of C65F35 is almost 40% higher, but its mass-based lower heating value (LHV) is 2.8 times lower. Hence, more fuel must be injected to reach the same engine load as in a conventional gasoline engine, leading to an increased cooling effect. To determine this effect, the temperatures of the cylinder liner and piston of the research engine were measured. Depending on the load point, friction losses were reduced by up to 12.6% compared to gasoline operation. Although the floating-liner engine is operated with port fuel injection (PFI), the temperatures of the cylinder liner dropped by up to 4°C and those of the piston by up to 8°C. C65F35 therefore not only shows decreased emissions, but also leads to a reduction in friction losses, mainly due to the lower temperatures in the combustion chamber.