Chemical effect of ethanol on the aromatics formation in methane-ethanol coflow diffusion flame at pressures from 1 to 6 bar: A numerical study

A numerical study of laminar coflow diffusion flame was performed to investigate the effect of ethanol on the aromatics formation of methane diffusion flame at elevated pressure conditions. The amount of ethanol in methane was 10% based on the carbon contribution to the total fuel stream, and the pressure condition ranged from 1 to 6 bar. A decoupling method was proposed to numerically isolate the dilution, thermal, and chemical effects of ethanol by introducing two different types of fictitious species for ethanol. The results showed that the addition of ethanol increased the aromatics concentration of methane diffusion flame, whereby the chemical effect was dominant, followed by the dilution effect, while the thermal effect being the least. Detailed chemical kinetic analysis revealed that the pyrolysis of ethanol increased the concentrations of C₂ and C₃ precursors. Besides that, the enhanced ability of ethanol on aromatics concentration decreased as the pressure increased. The increase in pressure was found to accelerate the aromatics production significantly. The reason was associated with the narrowing of the flames at elevated pressures, which improved the air entrainment and resulted in significant acceleration of the overall reactivity.