Effects of air-side dimethyl ether premixing on combustion characteristics of nonpremixed biodiesel/air counterflow flames

•Air-side premixed reaction zone enhanced flame reaction.•Thermal interaction between multiple reaction zones enhanced the radial leakage at SP.•Air-side DME premixing can exert chemical effects on benzene formation. Counterflow flame modeling was conducted to investigate the effects of air-side dimethyl ether premixing on the combustion of biodiesel/air non-premixed flames, using the detailed kinetic mechanisms of bio-diesel and dimethyl ether. Methyl decanoate was adopted as the bio-diesel surrogate component. Comparative analyses focused on heat release, methyl decanoate oxidation, and the soot precursor, i.e. benzene production in the flames. The complex triple-flame structures were observed in the flames with air-side addition of dimethyl ether. Due to the interactions in the hybrid reaction zones, the flames with air-side premixing had higher peak temperatures, broadened flame thickness, and greater production of the integrated OH radical, consequently resulting in more robust flame power. The reactions related to self-pyrolysis and H-abstraction are the top main routes for methyl decanoate oxidation. The thermal effect induced by the higher flame temperature enhanced the radial leakage of MD and other intermediates and lowered the benzene production rate. The non-premixed reaction zone was the most active region for benzene production. The air-side premixing could exert its chemical effect on benzene formation within this zone by changing propargyl and phenyl chemistry.