Effect of methane addition to ethylene on the morphology and size distribution of soot in a laminar co-flow diffusion flame

Abstract

The characteristics of soot in the diffusion flames of methane and ethylene under different oxygen concentrations and the influence of mixing methane in ethylene on soot generation were investigated using thermophoretic sampling and subsequent transmission electron microscopy image analysis. The process of soot particle nucleation, surface growth, coagulation, agglomeration and oxidation along the flame axis was analyzed. The variation of soot particle size distribution and aggregate characteristics at different heights along the centerline of the flame at different oxygen concentrations and methane doping ratios were obtained. Results show that the various stages of soot generation in methane flame obviously lags behind the ethylene flame at different oxygen concentrations, and increasing the oxygen concentration makes the various stages of soot formation in the flame advance. A 10% methane doping can promote soot generation at low flame locations. Increasing the doping amount to 30%, the generation of soot can be promoted at high flame locations. The synergistic effect of soot formation in fuel combustion occurs in the above two cases. However, the synergistic effect of the fuel will disappear under high blending ratio conditions. The effect of methane-ethylene at high blend ratios is more like a neutralization effect.