Effect of Methanol Blending on Soot Formation in Laminar Diffusion Flames of Gasoline

In a coflow diffusion burner, the soot concentration distributions in laminar diffusion flames of gasoline blending with methanol were measured using TC-LII technique. This study was carried out under both the same fuel flow and the same carbon flow conditions. The results show that compared with the gasoline, the peak and average soot concentration in the M20, M40, M60 and M80 flames decrease by 50.7%, 74.8%, 91.0%, 97.8% and 53.4%, 85.6%, 97.3%, 99.8% respectively under the same fuel flow condition, while they appears only a slight reduction under the same carbon flow condition. Therefore, the reduction in mass flow of carbon due to methanol blending has little contribution to soot reduction under the same fuel flow rate. The soot reduction by methanol blending under the same fuel flow condition is mainly caused by the dilution of aromatics in gasoline and the influence of chemical reaction kinetics. In the whole flame, the initial height of soot formation increases with methanol ratio increasing. In flame center line, the initial height of soot formation decreases with methanol ratio increasing under the same fuel flow condition, while it increases under the same carbon flow condition. In addition, it is also found that the soot concentration along the flame center line presents three variation stages with the flame height. The radial peak soot concentration of the flame moves from outside to inside gradually with flame height increasing, and the peak value increases first and then decreases.