Potential of long-chain oxymethylene ether and oxymethylene ether-diesel blends for ultra-low emission engines.

Highlights • Long-chain oxymethylene ether show a soot-free combustion. • Oxymethylene ether suppress the nitrous oxide - soot trade-off in diesel engines. • Solubility of long chain oxymethylene ether in diesel fuel is limited. • Oxymethylene ether is a promising diesel substitute for dedicated engines. Abstract Oxymethylene ether (OME n) has recently drawn high attention due to its high pollutant emission reduction potential and the sustainable synthesis pathways involving carbon capture and renewable hydrogen. In this work, five blends of OME n in diesel fuel in addition to pure OME 3-5 and diesel fuel as reference were investigated in a single cylinder engine. Each OME n -Diesel blend was prepared with a different chain length, ranging from OME 1 to OME 5. The blending ratio of OME n in fossil diesel fuel was set to 35 vol%, corresponding to a ∼23.5% diesel fuel substitution on a heating value basis. We find that OME n contributes to improved oxidation conditions, resulting in a more complete combustion compared to conventional diesel fuel operation. This is reflected by reduced emissions of unburned hydrocarbons and carbon monoxide (up to 90%), higher burned mass fractions after the main combustion phase, higher indicated efficiencies (up to +3%) and lower exhaust gas temperatures (up to −70 °C). Furthermore, while pure OME n burns soot-free, a significant soot reduction was measured for the OME n -Diesel blends. Based on the findings of this work, it is concluded that from a combustion and emission point of view, the OME n chain length is of minor importance for applications where OME n is blended with diesel fuel up to a ratio of 35 vol%. Thus, the main considerations for an optimal OME n chain length range should focus on aspects like fuel properties and OME n synthesis. In this regard, a simple and efficient synthesis process (e.g. synthesis of OME 1) must be weighed up against favorable fuel properties of the synthesis product (e.g. OME 3-5). Hence, bearing in mind that OME n is not a drop-in fuel and will always demand a dedicated engine, the preference of long chain OME n over OME 1 is not straight forward and strongly depends on the application. [ABSTRACT FROM AUTHOR]