Modeling of multi-component fuel vaporization for spray simulations using continuous thermodynamics

Practical fuels are multi-component with many species. The composition distributions of fuel vapor in a combustion chamber affect the ignition behavior, combustion quality, and emissions formation directly. Understanding multi-component fuel vaporization and air-fuel mixing processes in the chamber is needed.; A new, computationally efficient approach to modeling the multi-component nature of practical fuels is proposed for multi-dimensional vaporization and spray computations. Continuous thermodynamics is used to describe the composition with a continuous distribution function, and to capture reasonably well the entire range of composition in practical fuels by tracking the mean and variance rather than the large number of species. Using this approach, we have developed vaporization models for complex practical fuels. The nonuniformity in the liquid phase is taken into account for both droplet and wall-film vaporization models. The vapor-liquid equilibrium relations for high-pressure conditions, and the effects of high-pressure gas absorption in the liquid phase on droplet vaporization and breakup are discussed. Practical fuel film boiling also shows quite different characteristics from those of a single-component fuel; therefore the vaporization behavior of practical fuels may not be approximated with a single-component substitute. The models are first validated against experimental data or detailed numerical solutions by the finite-difference method, and good agreement is found; then the models are applied in simulations of gasoline and diesel sprays. The computations show that the developed models have adequate accuracy with low computational cost.; A preliminary study on drop-bubble dynamics and instability with Marangoni effects is also given. This issue is motivated by its potential application for improving air-fuel mixing and understanding the possible drop-bubble breakup mechanism.