Study On The Multicomponent Vaporization Simulation Of Complex Fuel Drops

The vaporization process of liquid fuel drops can have a significant impact on the combustion and exhaust emission in internal combustion engines.Petroleum fuels,such as diesel fuel and gasoline,are usually composed of 200~300 hydrocarbon species.Focusing on the multicomponent feature of petroleum fuels,a hybrid multicomponent(HMC)drop vaporization model was proposed in this study,having the characters of both discrete component approach and continuous thermodynamics approach.In the present HMC model,petroleum fuels are assumed to be the mixture of species from five hydrocarbon groups,including n-alkane,i-alkane,olefin,cycloalkane,and aromatic.Using this model,each group of species has a composition described by a single Gamma distribution about the molecular weight,and the thermo-physical properties of each group are finally functions of mean molecular weight,pressure,and temperature.The vaporphase transport equations,variation rate of liquid-phase composition,vapor-liquid phase equilibrium,heat and mass transfer model,and methods for the thermo-physical properties of each group were also derived to constitute the HMC model.The HMC model was firstly used to simulate the vaporization of a stagnant n-heptane drop,and it was found that the predicted histories of drop size agreed with the experimental data especially in the mass vaporization rate and drop lifetime.Comparing the fuel compositions and thermo-physical properties predicted by the HMC model with those by a simple model and experiments,it was found that the present HMC model improved the traditional continuous thermodynamics models in the prediction of fuel composition and physical properties.An improved prediction of the distillation curve of gasoline was also obtained using the HMC model.The HMC model was finally used to simulate the vaporization of a single diesel fuel and gasoline drop.A more comprehensive variation of liquid-phase composition was observed during the drop vaporization process.For both fuel drops,lighter species in the same species group vaporized earlier.The olefin and aromatic species groups were found to vaporize earlier than other groups for the diesel fuel drop.For the gasoline drop,the aromatic species group was found to be more sluggish to vaporize than other species groups,and the n-paraffin group and olefin group showed similar vaporization characteristics.