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Oxygenated synthetic fuels such as oxymethylene ether (OME) are a promising approach to reduce the emissions of diesel engines and to improve sustainability of mobility. The soot-free combustion of OME allows an optimization of the combustion process to minimize remaining pollutants. Considering the injection system, one strategy is to decrease the rail pressure, which has a positive impact on the reduction of nitrogen oxides without increasing the particle formation. Furthermore, due to the reduced lower heating value of OME compared to diesel fuel, an adaptation of the injector nozzle is recommended. This work describes a method for analyzing the injection process for OME, using the Mie scattering effect in an optically accessible heavy-duty diesel engine. The design of the 1.75 l single cylinder engine allows operation up to 300 bar peak cylinder pressure, providing optical access through the piston bowl and through a second window lateral below the cylinder head.

Polyoxymethylene dimethyl ethers (OME) are synthetic fuels, which offer the property of sustainability because the reactants of production base on hydrogen and carbon dioxide on the one hand, and the air pollution control in consequence of a soot-free combustion in a diesel engine on the other hand. High exhaust gas recirculation (EGR) rates are a promising measure for nitrogen oxide (NOx) reduction without increasing particle emissions because of the resolved soot-NOx trade-off. However, EGR rates towards stoichiometric combustion in OME operation reveals other trade-offs such as methane and formaldehyde emissions. To avoid these, a lean mixture with a combination of EGR and exhaust after-treatment with selective catalytic reduction (SCR) is useful. The limitation of urea dosing due to the light-off temperature of SCR systems requires heating measures.