Book Description

For mixtures containing many components, as in the case of commercial fuels and polymer solutions for example, it is practically impossible to have a complete listing of all the components. A method known as continuous thermodynamics has recently been developed for use when dealing with such mixtures. Continuous thermodynamics describes the composition of the mixture by a probability density function with respect to one or more variable, such as molecular mass, boiling point or any other physical property. This method is used here to study the vaporization of multicomponent fuel droplets. Liquid droplet vaporization plays an important role in the formation of the fuel/air mixture necessary for combustion, and the fuel composition has an effect on the performance of combustion equipment such as Diesel engines. Transport equations are developed, which describe species diffusion in terms of the parameters of the distribution function. These equations are developed for "fuel" vapour as a whole and for the mean and second moment of the distribution. A continuous thermodynamics form of the energy equation is also developed. These general equations are then applied to the vaporizing droplet problem. A gamma distribution function, with molecular mass as the characterizing variable has been chosen. The transport equations in continuous form have been incorporated into a finite difference model of droplet vaporization. Physical property correlations have also been developed in terms of the characterizing variable chosen and integrated in the model. The numerical solution of these equations and the equations of conservation of mass and species at the droplet surface gives the droplet vaporization rate, the mixture composition field in the vapour phase surrounding the droplet and the change of the liquid composition with time.