Soot particles generated by n-heptane and n-heptane/OME3 in an inverse diffusion flame: A comparative analysis of physical properties and oxidative reactivity

Abstract

The widespread adoption of E-fuel, oxymethylene ether-3 (OME₃), is a promising solution to accelerate the decarbonisation of the transport sector. However, the application of OME₃ inevitably alters the combustion characteristics, affecting the soot generation process and consequently changing the physical properties of these soot particles. These alterations, in turn, influence not only associated health and climate concerns but also the control strategies of diesel particulate filter (DPF) regeneration. Here, high-resolution transmission electron microscopy (HRTEM) and thermogravimetric analysis (TGA) were employed to explore the effects of blending OME₃ on soot primary particle size, fractal dimension, nanostructure, and oxidative characteristics. The results show that the addition of OME₃ form smaller soot precursors and accelerates the oxidation of soot particles, which subsequently reduces the size of primary particles. The smaller size of soot particles favours oxidation, but they are likely to pose more severe health risks. The smaller primary particles exhibit more pronounced Brownian motion and weaker van der Waals forces, leading to the formation of a looser agglomerate structure and smaller fractal dimensions (D_f). Furthermore, the addition of OME₃ results in a reduction of long-range order in C atoms network and an increase of odd-number carbon rings during the generation of soot particles, which in turn leads to a reduction in fringe length (L_f) and an increase in fringe tortuosity (T_f) and separation distance (S_f) of soot particles. These nanostructural changes induced by OME₃ enhance the oxidative reactivity of soot particles, as evidenced by the lower oxidative characteristic temperatures and reduced activation energy.