Soot growth mechanism in C2H2 combustion with H2 addition: A reactive molecular dynamics study

Abstract

A numerical investigation of the effect of H2 addition on soot formation was conducted in C2H2 combustion process from the molecular level. The results showed that the chemical effect of H2 (CE-H2) inhibited the soot formation of C2H2 combustion. With the gradual increase of H2 doping ratio, the soot morphology became sparser and the soot particle size decreased. The CE-H2 significantly inhibited the surface growth and coalescence of soot. Addition of H2 led to an increase in the H2 concentration in the combustion process, which inhibited the dehydrogenation reaction of the primary soot particle with C2H2, free radicals, and polycyclic aromatic hydrocarbons (PAHs). The CE-H2 increased the consumption rate of C2H2 and the formation rate of H2O, and it decreased the formation rate of CO. Moreover, the addition reaction of free radicals and PAHs played an important role in the soot growth process, which effectively promoted the soot surface growth process. And the coalescence process significantly increased the soot mass and affected the soot size and morphology although its frequency was relatively low.