Droplet ignition of approximately continuous liquid mixtures of n-paraffins and n-alkyl aromatics

This paper presents experiments on the auto ignition of single droplets of liquid mixtures which have a composition such that their distillation behaviour approximates a “continuous” mixture, i.e. one which can be described by a continuous distribution function. A number of such mixtures of both n-paraffins and n-alkyl aromatics were designed by matching their distillation curves to those of equivalent continuous distributions, and single droplet ignition experiments were then performed on them. To correlate the results and gain insight into the mixture ignition process, a continuous mixture droplet ignition model was devised by adding a continuous formulation for a global reaction rate expression to an existing droplet evaporation model. Expressions for rate parameters as functions of the distribution variable (molecular mass) were developed from experiments on pure hydrocarbons. The resulting ignition model was found to reproduce experimental mixture ignition delay times well. The mixtures tested here behave similarly to pure compounds of the same average molecular mass.