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.
Highlights
The soot particle is one important part of the common pollution emissions of combustion systems such as furnaces, internal combustion engines and gas turbine engines [1,2]
It is universally accepted that the soot particles produced in hydrocarbon flames involve complex physical-chemical processes taking place by steps including fuel pyrolysis, polycyclic aromatic hydrocarbons (PAHs) formation, particle inception, Energies 2018, 11, 1698; doi:10.3390/en11071698
Combustion experiments on the nanostructure and oxidation reactivity of soot in n-heptane inverse diffusion flames (IDF) with additions of DMF were carried out
Summary
The soot particle is one important part of the common pollution emissions of combustion systems such as furnaces, internal combustion engines and gas turbine engines [1,2]. Soot particles pollute the air [3] but harm the human respiratory system as well [4,5,6]. The formation and variation tendency are important for understanding the growth processes of soot particles. More interests and attention of researchers have been focused on the studies of soot particles, especially on the formations and variation tendency of growth processes. The soot formation process has been studied widely [7,8,9,10,11,12,13]. It is universally accepted that the soot particles produced in hydrocarbon flames involve complex physical-chemical processes taking place by steps including fuel pyrolysis, polycyclic aromatic hydrocarbons (PAHs) formation, particle inception, Energies 2018, 11, 1698; doi:10.3390/en11071698 www.mdpi.com/journal/energies
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