Group contribution method for multicomponent evaporation with application to transportation fuels

Abstract

Transportation fuels consist of a large number of species that belong to different families of compounds. Predictions of physical and chemical properties of such multicomponent fuels require the accurate description of evaporation rates of all species initially contained in the liquid phase. Existing computational approaches are yet to do this without difficulty due to the lack of experimental data for physical properties of fuel components. In addition, a vast number of assumptions, which include idealized compositions and interpolation equations calibrated using experiments, are being introduced to make the problem tractable. By addressing this issue, an approach based solely on functional groups that are present in the components of the fuel is developed. This formulation is coupled to a multicomponent evaporation model to account for non-ideal behavior of mixtures and the consideration of pressure and temperature variations. This is done by using the fuel composition to evaluate the acentric factor and critical properties of each fuel component followed by the evaluation of certain physical properties using a group contribution method. This procedure thus allows the evaluation of evaporation rates of practical fuels based only on the intrinsic functional groups and their relative abundance. Studies of common fuel blends including those belonging to the Jet-A and JP-8 classes related to evaporation rates, distillation characteristics and speciation are presented. A discussion of the effect of polar species on evaporation properties utilizing the UNIFAC approach for non-ideal mixtures is presented. Due to the generalized nature of this approach, the proposed method provides an effective alternative to existing computational techniques dedicated to multicomponent droplet evaporation.