Kinetic effects of methanol addition on benzene formation in methyl decanoate/air counterflow nonpremixed flames

Abstract

In this study, counterflow nonpremixed flame modeling was conducted to examine the effects of methanol addition on benzene (A1) formation in methyl decanoate (MD) /air flames. Methanol was added to either the fuel side or oxidant side of the counterflow flames, to explore the chemistry difference in A1 formation when different methanol addition strategies were adopted. The formation routes of A1 were emphatically analyzed, and some important polycyclic aromatic hydrocarbons (PAHs), such as naphthalene (A2) and phenanthrene (A3) were also evaluated in terms of emission index. Results show that most of A1 is produced at the downstream of MD pyrolysis zone, through the recombination reactions of C3 radicals, while methanol is primarily to produce methyl groups within a relatively higher temperature zone. Both the air-side and fuel-side additions of methanol can decrease A1 concentration, but the former shows a more significant inhibiting effect. Methanol addition featured both dilution and chemical inhibitory effects on the formation of A1 precursors, and the dilution effect was superior to the chemical effects. The chemical inhibition on A1 formation was mainly achieved through the enhancement in the generation trend of active groups and the H-addition reaction of methyl groups. The air-side addition of methanol featured a minimal effect on A1 formation, and the reduced A1 concentration within the flames was mainly attributed to the increased radial leakages of reactive species. Besides, both addition strategies of methanol show the inhibitory effect on A2 and A3 formation, but the change in flames with the air-side addition is relatively weaker than that of the fuel-side addition flames.