Abstract

This study investigates the influence of dimethyl ether (DME) substitution for propane on soot formation, oxidation, and chemical pathways in coflow diffusion flames under iso-carbon conditions. Detailed numerical simulations, validated against experimental measurements, were performed for a series of fuel mixtures in which propane was progressively replaced by DME while maintaining constant carbon content. The results reveal a pronounced decrease in soot volume fraction and primary particle size as propane is progressively replaced by DME, accompanied by a clear shrinking of the region within the flame where soot is produced and a significant reduction in carbon-to-soot conversion efficiency. Mechanistic analysis shows that DME substitution suppresses the formation of key aromatic precursors and heavy polycyclic aromatic hydrocarbons (PAHs), while enhancing oxidation processes through increased local oxygen availability and modified flame structure. Integrated reaction rate analysis demonstrates that both soot formation and oxidation rates diminish in DME-rich flames, with the balance between these processes shifting toward lower overall soot yields. Notably, nitrogen oxide emissions decrease with increasing DME content despite higher flame temperatures, reflecting changes in radical soot composition and flame residence times. These findings highlight the effectiveness of fuel oxygenation in mitigating soot and pollutant emissions and provide insight into the underlying chemical and physical mechanisms responsible for soot suppression in oxygenated fuel flames. © 2025 The Energy Institute