CO ₂ Neutral Fuels in Series Engines - Demonstration of the Potential of OME with Regard to Efficiency and Ultra-Low Emissions 2021-24-0061

To meet the targets of the European Green Deal, CO₂ emissions in the transport sector must be eliminated by 2050. To achieve these goals, it is not enough just to increase the powertrain efficiency. Regeneratively produced synthetic fuels offer the opportunity to be part of the solution to these challenges, due to their high energy density and wide range of applications. One representative of synthetic diesel fuels is oxymethylene ether (OME), which, in addition to its potential regenerative production process, is characterized by an almost soot-free combustion. Previous studies have demonstrated the feasibility of OME operation in a series engine. However, due to the limited amount of fuel that can be injected into the combustion chamber by series components, the potential in terms of efficiency could not be exploited. Therefore, the aim of the presented investigations is to compare the efficiency and emissions of the reference injectors with those of injectors adapted to a higher nozzle flow rate in operation with OME. The tests show a deterioration in indicated efficiency of up to 2 % with the reference injectors. With the adapted injectors, it is possible to achieve indicated efficiencies, which are in the range of diesel. In addition, operation with OME has a higher EGR compatibility. The compatibility is characterized by low NO_x emissions and low particulate emissions. Due to the almost soot-free combustion, the efficiency of both systems can be increased by up to 1.5 % by reducing the injection pressure. Finally, the two injection systems are compared in the legislative test cycle WLTC. The study shows that transient load requirements can be achieved with both injection systems, as well as a significant reduction regarding to emissions compared to diesel. The findings show that OME as an energy carrier is a promising approach to contribute to future sustainable mobility.