Soot particles formed by n-heptane and n-heptane/oxymethylene ether-3 in an inverse diffusion flame: A comparative analysis of chemical features

Abstract

Oxymethylene ether-3 (OME3) is a promising synthetic e-fuel and alternative fuel for diesel engines. In contrast to diesel fuel, the use of OME3 leads to a distinct combustion process in which soot particles are generated, which leads to changes in the chemical properties of these particles. These chemical properties are intricately connected to both the concentration and availability of potential radical sites, which, in turn, exert a substantial influence on soot oxidation during diesel particulate filter (DPF) regeneration. Hence, it is crucial to investigate the chemical features of soot samples. Nevertheless, a thorough investigation into the chemical features of n-heptane/OME3 soot samples has not been fully understood. Here, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), elemental analyser, and thermogravimetric analysis (TGA) were used to examine the impact of blending OME3 on chemical features of soot particles at various flame heights of an inverse n-heptane-OME3 flame. XPS results from C1s and O1s peaks showed that OME3 incorporation enhanced the concentrations of C = O, C–O, and O = C–O groups, especially C = O groups, with the percentage increase ranging from 11.93 % to 49.74 %. Similarly, the content of aliphatic C − H groups, along with O and H, increased with higher levels of OME3 blending. Moreover, it was discovered that blending OME3 altered the spatial distribution of hybridisation orbitals of carbon atoms, leading to a decrease in the sp2/sp3 ratio by as much as 40 % with the increase in the OME3 blending ratio. The alteration in these chemical properties due to the addition of OME3 enhanced the oxidative reactivity of soot particles, as manifested by up to a 15 % reduction in the measured activation energy. These findings are useful to optimise control strategies of DPF regeneration with the more widespread use of e-fuel.