Comparative Study on Soot Reduction, Soot Nanostructure and Oxidation Reactivity of n-heptane/DMC and Isooctane/DMC Inverse Diffusion Flames

Abstract

Dimethyl carbonate (DMC) is an environmentally oxygenated compound which can be used efficiently for soot reduction. This paper compared the soot reduction, soot nanostructure and oxidation reactivity from inverse diffusion flames (IDFs) of the hydrocarbon fuels, namely n-heptane and isooctane doped with DMC. Effects of DMC additions on soot reduction were discussed. DMC addition is more effective for the soot reduction of n-heptane/DMC IDF than isooctane/DMC IDF. The morphology and nanostructures of soot particles were investigated by Transmission Electron Microscopy (TEM) and High Resolution TEM (HRTEM), and the soot graphitization and oxidation reactivity were analyzed by X-ray Diffraction (XRD) and Thermogravimetric Analyzer (TGA), respectively. The results of HRTEM images showed that many larger aggregates were observed for the structures of soot particles from IDFs with DMC additions. The soot particles exhibited more liquid-like material, more amorphous, higher disorganized layers, and less graphitic than that of IDFs without DMC additions. With increasing of DMC blending rate, soot particles changed younger to have shorter fringe length, higher tortuosity, and greater fringe separation. Based on the XRD and TGA results, the degree of the soot graphitization level decreased; the soot mass lost significantly faster, and the soot become more reactive.