C_2H_2 and PAH as Soot Growth Reactants in premixed C_2H_4-Air Flames

摘要

The assumption that all of the soot mass growth in flames occurs by C-2H_2 reaction with the soot particles is widely used in soot modeling, thereby taking no explicit account of published evidence that polycyclic aromatic hydrocarbons (PAHs) are imortant contributors to soot growth. In one of the most influential flame stuides leading to the simple C_2H_2-soot mechanism. PAH concentrations were not measured but were assumed to be too low for these species to be significant in soot growth. The original basis for the C_2H_2-soot mechanism has been reasessed in the present study by measuring PAH concentraitons in premixed C_2H_4-air flat flames used in the original study and by using the data to evaluate the contributions of both PAH-soot and C_2H_2-soot reactions in these flames. Polycyclic aromatic hydrocarbons were found in sufficient concentrations for their contribution to soot growth to be important. The observed mass growth rates of the total PAHs and soot are consistent with a simple mechanism in which both C_2H_2 and PAHs react with soot and C_2H_2 reacts with PAHs. The PAH-soot reaction occurs with a collision effiiency of order 5000 times larger than that of the C_2H_2-soot reaction and contributes 95