Evaluation of Polycyclic Aromatic Hydrocarbon Formation in Counterflow Diffusion Flames

Polycyclic aromatic hydrocarbons (PAHs) have been heralded as mutagenic and carcinogenic substances and currently,
their emissions are subject to regulatory control due to recently imposed stricter environmental regulations.
Hence, it has become necessary to have a detailed understanding of their chemistry. In this work, a short review of the
available PAH relevant counterflow diffusion flame datasets is presented. Following that, the reliability of four widely
used PAH mechanisms and the revised PAH mechanism, within the scope of this work, is assessed by validating them
against these collected experimental datasets. The formation of the first aromatic ring is investigated based on the
performed reaction path analyses. The results show that the dominant reaction pathways for the formation of benzene
are “even carbon atom” pathways (H-abstraction acetylene addition) and “odd carbon atom” pathways (recombination
of propargyl radicals). The dominance of one pathway over the other was found to be strongly dependent on the fuel
structure and its doping with other components.