Oxymethylene ether-n -dodecane blend spray combustion: Experimental study and large-eddy simulations

E-fuels, made from renewable electricity and a CO 2 source, have been proposed as a renewable alternative for the mobility sector. In this work, the ignition process and soot formation of the e-fuel oxymethylene ether 1 (OME 1 ) and its blends with n -dodecane are investigated. Experiments of the spray ignition of both neat fuels and a promising fuel blend are conducted under the Engine Combustion Network Spray A conditions in a high-pressure spray chamber and it is found that the fuel blend ignites very similar to n -dodecane. To investigate this behavior in more detail, first a kinetic reaction mechanism for blends of OME 1 and n -dodecane is developed and validated using new shock tube measurements. Large-eddy simulations are then performed for the experimental conditions, and spray characteristics as well as ignition delay and flame structure agree well with the experimental results. A super-linear reduction in common soot precursors in the gas phase is found for the fuel blend, which is mainly attributed to a shift of soot precursor production towards higher mixture fractions due to the oxygen content in the fuel. The ignition behavior of OME 1 and the fuel blend is investigated in mixture fraction space using one-dimensional unsteady flamelets. It is found that the slow ignition behavior of OME 1 is rooted in its high stoichiometric mixture fraction, shifting the most reactive mixture for second stage ignition to very fuel-rich regions, which have a low temperature in a spray case with a cold fuel side. The ignition process of the fuel blend is dominated by its n -dodecane fraction up to 60 mol% OME 1 in the blend, and the low increase of ignition delay in this range can be explained by dilution of n -dodecane with OME 1 . (c) 2020 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Automated summary

This study investigates the ignition process and soot formation of e-fuels, finding that the fuel blend ignites similarly to n-dodecane and the oxygen content in the fuel leads to a reduction in common soot precursors in the gas phase. The ignition behavior of OME 1 is rooted in its high stoichiometric mixture fraction, while the fuel blend ignition process is dominated by its n-dodecane fraction up to 60 mol%.