Droplet Combustion of Chlorinated Benzenes,Alkanes,and Their Mixtures in a Dry Atmosphere

Abstract

Combustion of three chlorobenzenes (monochlorobenzene, dichlorobenzene, trichlorobenzene) and five alkanes (octane, decane, dodecane, tetradecane, and hexadecane) were investigated. Using high-speed video photography, the size and velocity of the burning drops at various points during their lifetime were measured. From such data, the time-variation of a droplet's burning rate was deduced. It was found that the variations of the burning rates for the mixtures were qualitatively similar when viewed as functions of the chlorine to hydrogen atom ratio. Starting from a pure alkane, as Cl/H increased, the burning rate first decreased, then slightly increased, and then fell sharply near Cl/H = 0.5 to approximately the vaporization rate of the pure chlorobenzene. It was also found that prior droplet combustion studies (performed in the H₂O-rich atmosphere of combustion-heated reactors) exhibited burning rates of the same liquid blends that were nearly twice the present dry atmosphere results. We have demonstrated that when the hydrogen in the surrounding atmospheric H₂O is included in the ratio Cl/H, these previous results yield curves of burning rate vs. Cl/H that are similar to those of the present study. This implies that the enhanced burning rate observed when an alkane is blended into a pure chlorobenzene is partly due to the hydrogen provided by the alkane, and that a similar effect appears achievable by adding water vapor to the gas phase.