Numerical study of particle dynamics in laminar diffusion flames of gasoline blended with different alcohols

Abstract

Alcohols have been considered as promising clean alternative fuels for IC engines. At present, the difference and mechanism of particle dynamics for different alcohols is unclear. In this work, numerical simulation of laminar diffusion flame of gasoline blended with different alcohols was carried out by coupling a gas-phase chemical kinetic model and fixed sectional particle model, then the micro-processes of particle nucleation, growth and oxidation were analyzed. The results show that the dilution effect of different alcohol blending on the reduction of soot is quantitatively similar under the same blending ratio, while the chemical effect increases with the increase of alcohol carbon chain length. The molecular structure of alcohols increases the chemical action during the formation of soot particles. At the same blending ratio, the difference of temperature field caused by adding different alcohols has little effect on the growth of particles. The proportion of PAHs condensation in surface growth increases with the increase of carbon chain length of alcohols. PAHs condensation rate together with HACA rate determines the inhibiting ability of different alcohols on soot particle growth, but PAHs condensation plays a dominant role. With the addition of alcohols, the oxidation rate of O2 decreases, but the oxidation rate of OH increases. However, as the particles formed in laminar diffusion flames of alcohol/gasoline is mainly oxidized by O2, the increase of OH oxidation rate has little effect on particle reduction. From the oxidation region, the particles are oxidized first by OH, then by the co-oxidation of O2 and OH.