Effects of swirling combustion on soot characteristics in 2,5-dimethylfuran/n-heptane diffusion flames

Soot particles emitted from the combustion of engines and furnaces threaten human health gravely. The present work focuses on the nanostructure and oxidation reactivity of soot particles formed from 2,5-dimethylfuran (DMF)/n-heptane non-swirling and swirling flames. Effects of swirling and collection time on the nanostructure and oxidation reactivity of soot particles under the conditions of different 2,5-dimethylfuran (DMF)/n-heptane blending ratios were investigated in details using the high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Results demonstrated that soot from 50% n-heptane/50% DMF flame presented a typical core-shell structure with larger planar lamellae, while partly graphitic and partly amorphous structures were found in soot from pure n-heptane and 80% n-heptane/20% DMF flames. Swirling combustion could strengthen the mixability of the oxidizer stream and fuel stream, decreasing the existence of reactive soot particles from the flames doped with 20% and 50% DMF. More reactive soot particles were collected by pure n-heptane swirling flame due to the reduction of residence time. The effect of collection time was non-significant on soot particles from pure n-heptane and 80% n-heptane/20% DMF flames. However, for soot particles from the 50% n-heptane/50% DMF flames, the graphitization degree was increased obviously with the increase of collection time due to the oxidizing atmosphere provided during the collecting process.