Effect of aromatic fuels on aromatic species and soot distributions in laminar, co-flow, non-premixed flames at atmospheric pressure

Aromatic hydrocarbons form a considerable fraction of the total volume of hydrocarbons present in the jet fuels. During combustion, the aromatic fuel components drive substantially higher levels of particulate formation as compared to the aliphatic fuel components. The aim of the present study is to aid in understanding the effects of four different aromatic fuels on the aromatic species and the soot volume fraction in laminar, co-flow, non-premixed flames at atmospheric pressure. The four fuels consist of binary mixture of n-dodecane with toluene, m-xylene, 1,3,5 trimethylbenzene and n-propylbenzene. The total carbon and carbon fraction from each component is kept constant to facilitate comparison between the four fuels. The laser induced incandescence and laser extinction are used to obtain two-dimensional soot volume fraction in the flames. The laser induced fluorescence is used to obtain the two-dimensional aromatic species distribution in the flames. The experimental results indicate that the 1,3,5 trimethylbenzene/n-dodecane and n-propylbenzene/n-dodecane flames have the highest and the lowest peak soot volume fraction, respectively, amongst the four fuels; the peak soot volume fraction in m-xylene/n-dodecane and toluene/n-dodecane flames fall between these two extremes. Furthermore, for all the four binary fuel mixtures, the addition of aromatic component to the n-dodecane flame results in significant differences in the aromatic species and soot volume fraction spatial distribution in the flames. The combined 2D LIF-LII result provides a unique dataset to validate soot and chemical numerical models for the four fuels: toluene, m-xylene, 1,3,5 trimethylbenzene and n-propylbenzene.