Analysis of morphology, nanostructure, and oxidation reaction of soot particulates from CI engines with dimethoxymethane-diesel blends under different loads and speeds

Dimethoxymethane (DMM)-diesel blended fuels can simultaneously reduce exhaust emissions of soot and nitrogen oxide (NOX); several studies have been conducted in this regard. However, the influence of additive DMM on the production of inception and precursors of particulates, especially the relation between oxidation, morphology, and the nanostructure of soot particles has not been extensively investigated. In this study, a transmission electron microscope (TEM) and a thermogravimetric analyzer are introduced to acquire TEM images and conduct temperature-programmed-oxidation experiments. Aiming to study the influence of DMM addition on soot oxidation, morphology, and nanostructure, tests are conducted at different rotational speeds (1400 rpm and 2200 rpm), two engine loads (0.6 MPa and 1.2 MPa), and three fuels (D100, DMM6.4, and DMM13). The results show that the diameter distributions of all samples display a similar distribution, with the range of sample diameters being from 10 to 45 nm, and the addition of DMM reduces the dp (primary particle diameters) and the Df (fractal dimension), indicating a decreased structural compactness of aggregates, compared with diesel. Moreover, with increasing load and speed, La (the length of the fringe) increases and d (the distance between adjacent layer planes) decreases. Furthermore, with the addition of DMM, a more regular and higher degree of graphitization within soot particles can be observed in comparison to D100. The nanostructure influences the oxidation reaction of graphene segments with a line relation, leading to a difference in soot oxidation property.