A numerical investigation of the performance of oxymethylene ethers blended with fossil diesel to reduce soot emissions in compression ignition engines

Abstract

The reduction of the carbon footprint of internal combustion engines and the pollutant emissions is mandatory for the survival of this technology. In this sense, e-fuels are considered as a potential pathway to achieve this reduction and even remarkable carbon footprint mitigation in compression ignition engines. Among numerous e-fuels, oxymethylene ethers stand out because of their low soot formation characteristics. However, the complexity of their physical and chemical properties makes it a challenge to be used in conventional engines. The aim of the current study is to investigate the effects of the stoichiometry of oxymethylene ether on the in-cylinder combustion behaviour and the pollutant formation when blended with fossil diesel. For this purpose, numerical simulations of a medium duty optical engine fuelled with these blends were carried out using CONVERGE CFD, which were validated with experimental data. Different reaction mechanisms that can be found in the literature were evaluated, using n-heptane as to the fossil diesel surrogate and OME3 as the oxymethylene ether surrogate. Results highlight the differences in terms of equivalence ratio fields achieved when varying the e-fuel content in the blend. As a consequence, the combustion process is faster and the soot formation is drastically reduced when the oxymethylene ethers content is above 30%. This makes these blends interesting to reduce the well-known soot-NOx trade off of compression ignition engines.