A numerical study of the effects of n-propylbenzene addition to n-dodecane on soot formation and aggregate structure in a laminar coflow diffusion flame

摘要

A numerical study is performed to investigate the effects of n-propylbenzene addition to n-dodecane on soot formation and aggregate structure in a laminar coflow diffusion flame. The numerical model employed uses a gas phase chemical kinetic mechanism which describes the pyrolysis and oxidation of the fuel, and the formation of PAHs as a whole. The mechanism is coupled to a detailed sectional soot particle dynamics model to solve the combustion chemistry and soot formation. The model is able to accurately predict the trends observed experimentally with increasing mole fraction of n-propylbenzene in the liquid fuel mixture without any tuning or modification of the model parameters for different cases. The simulation results show that mixing n-propylbenzene into the liquid fuel mixture would increase soot inception, and surface growth per unit surface area by PAH condensation, while surface growth per unit surface area by HACA is shown to decrease modestly with n-propylbenzene addition. Regarding the overall effects of n-propylbenzene addition on each of the two surface growth mechanisms combined with inception, the contribution of PAH condensation per unit volume increases with n-propylbenzene addition, while the contribution of HACA growth per unit volume almost does not change.