Measurement of extinction limits and OH radicals for trimethybenzene and n-propylbenzene diffusion flames

Kinetic effects of aromatic molecular structure on the extinction limits of diffusion flames have been investigated with toluene, n-propylbenzene, 124- and 135- trimethylbenzenes in the counterflow configuration. To validate the present kinetic models of these aromatic fuels, OH PLIF measurements have been conducted for each fuels and revealed that the present toluene and n-propylbenzene models reproduce reasonably OH concentration whereas 124-trimethylbenzene model fails to predict the extinction limits of diffusion flames as well as OH concentration. The production and consumption pathways of OH radical were analyzed with toluene diffusion flames and found that the initial fuel fragmentation pathway significantly contributes to determine the OH concentration, which is the most important radical to produce the heat as well as to progress the chain propagation/branching reactions in order to sustain the diffusion flames for the given strain rate.