DEVELOPMENT OF A REALISTIC MULTICOMPONENT FUEL EVAPORATION MODEL

An evaporation model far realistic multicomponent fuels is described. In the model a new approach, named the discrete/continuous multicomponent (DCMC) model, is used to describe the properties and composition of realistic multicomponent gasoline fuels. With this approach gasoline is assumed to consist of five discrete families of hydrocarbons: n-paraffins, i-paraffins, naphthenes, aromatics, and olefins. Each family of hydrocarbons is composed of an infinite number of continuous components, which are modeled as a probability density function (PDF), and the mass fraction of each family of hydrocarbons is represented by a PDF, and the mean and variance of each PDF are tracked. Compared with the discrete multicomponent model, which must model hundreds of components for gasoline, the DCMC model saves computer time. Compared with the continuous multicomponent model, the DCMC model has much higher accuracy. Unsteady evaporation of multicomponent fuel can be described for both normal and flash-boiling evaporation conditions. An unsteady internal heat flux model and a model for the determination of the droplet surface temperature were formulated. An approximate solution to the quasi-steady energy equation was used to derive an explicit expression for the heat flux from the surrounding gas to the droplet gas interface, with interdiffusion of fuel vapor and the surrounding gas taken into account. The present DCMC evaporation model was implemented into a multidimensional computational fluid dynamics code and applied to calculate the evaporation processes of single- and multicomponent fuel droplets.