Modeling evaporation of Jet A , JP - 7 and RP - 1 drops at 1 to 15 bars

A model describing the evaporation of an isolated drop of a multicomponent fuel containing hundreds of species has been developed. The model is based on Continuous Thermodynamics concepts wherein the composition of a fuel is statistically described using a Probability Distribution Function (PDF). Following previous studies, this PDF is parametrized on the species molar weight. However, unlike in previous studies, a unified formulation is developed wherein the same PDF holds for three major homologous hydrocarbon classes. The new PDF is a double-GammaPDF that is parametrized on the square root of the molar weight. The additional advantage of the formulation is that it is valid in the subcritical region from 1 to 15 bars. Discrete species distributions for Jet A, JP-7 and RP-1 are fitted using this novel PDF and extensive calculations for isolated drops of these kerosenes are performed. The results show that under the quasi-steady gas phase assumption, the D2 law is recovered after an initial tansient. The evaporation constant is (1) Preprint submitted to Elsevier Science 28 May 2003 ~JI increasing function of of the far field temperature and pressure, (2) a complex function of far field composition according to the values of the far field temperature and pressure, and (3) a strong function of the far field pressure but a weak function of the difference between the surface and far field vapor molar fraction. The composition of the vapor at the drop surface is kerosene-fuel specific. A comparison between results obtained with a model assuming the drop interior to be well mixed and a model wherein the drop may evaporate either in a well-mixed mode or at unchanging composition shows that the percentage difference between the evaporation constant predicted by the two models is within the range of uncertainty in the transport properties.