Effects of dimethoxymethane and isopropanol blending on soot formation in ethylene and propane counterflow diffusion flames

Introducing low-carbon oxygenated fuels into the current transport sector provides an effective pathway for mitigating the emissions of greenhouse gases and harmful pollutants such as soot. Previous studies have revealed that oxygenated fuels can reduce soot formation, but the soot-reduction potential is closely related to the chemical interaction between the oxygenates and the baseline hydrocarbons. This work is devoted to study the effects of blending dimethoxymethane (DMM) and isopropanol (IPA) on soot formation in ethylene-based and propane-based counterflow diffusion flames. Soot formation in the target flames was experimentally characterized using a planar light extinction technique, accompanied by numerical analysis to provide complementary insights. The results confirmed that the effects of blending oxygenates on soot formation are sensitive to the fuel-specific molecular structure of the oxygenates and hydrocarbons. For the C₂H₄-based flames, blending DMM and IPA could lead to a synergistic effect on soot formation due to chemical fuel interaction, with stronger synergy observed with IPA blending. In contrast, no evident synergistic effects on soot formation were observed in the C₃H₈-based flames, for which a notable soot reduction was observed with DMM blending. Reaction pathway analysis suggested that the occurrence of soot synergy in the C₂H₄-based flames is mainly due to the chemical interaction between the methyl radicals generated from DMM/IPA and the C₂ species from C₂H₄. This study is expected to deepen our understanding of the soot formation behavior of DMM- and IPA-blended flames, thus contributing to their successful usage as clean alternative fuels.