Thermal flame propagation into a quiescent combustible mixture consisting of liquid fuel droplets, fuel vapor and air is modelled using the heat release from (i) combustion of single droplets after ignition, and (ii) homogeneous reaction of the fuel vapor in the ambient gas. The purpose of the model is to show how it is possible to calculate a burning velocity acceleration effect due to the presence of liquid droplets in the mixture, in support of a limited number of previous experimental observations. The calculated results for a variety of fuels are in agreement with available experimental data which, however, is mostly outside the range of droplet diameters for which the burning velocity attains a maximum value.