Nanoscale characteristics and reactivity of nascent soot from n-Heptane/2,5-dimethylfuran inverse diffusion flames with/without magnetic fields

Abstract

In this study, the differences of nanostructure and oxidation reactivity of the nascent soot formed in n-heptane/2,5-dimethylfuran (DMF) inverse diffusion flames (IDF) with/without influence of magnetic fields were studied, and the effects of DMF-doped and magnetic fields were discussed. Morphology and nanostructures of the soot samples were investigated using high-resolution transmission electron spectroscopy and X-ray diffraction, and the oxidation reactivity characteristics were analyzed by thermogravimetric analyzer. Results demonstrated that both additions of DMF-doped and magnetic fields could promote soot production and modify the soot nanostructure and oxidation reactivity in IDF. Soot production increased along with the increase of DMF-doped. With DMF blends, more clustered soot particles and typical core-shell structures with well-organized fringes were exhibited compared with that formed from the pure n-heptane IDF. With effects of magnetic fields, the precursor formation and the oxidization of soot were promoted, soot production was enhanced. Soot particles became relatively more mature with typical core-shell structure, thicker shell, longer fringe lengths, smaller fringe tortuosity, higher graphitization degree and lower oxidation reactivity. With magnetic force pointed to the central line and the inner direction of IDF under the conditions of N pole and S pole of the magnet facing the flame, oxygen was trapped, having an increased residence time to get more chance to react with the fuel molecules to cause more soot to be yielded and oxidized. That resulted in the soot precursor promotion, soot production enhancement, and soot part-oxidization and graphitization.