A numerical study on soot formation in methane-ethanol diffusion flames

•Soot volume fraction and particle number density increase with ethanol blending ratio.•The degree of soot enhancement decreases with further increase in ethanol blending ratio.•Effect of ethanol on soot concentration follows the order: chemical > dilution > thermal.•Thermal effect has a dominant influence on the flame temperature, but not on soot.•Ethanol addition promotes the HACA pathway and surface growth mechanism.