MODELING OF NEAR AND SUPERCRITICAL DROPLET VAPORIZATION

The objective of the work is to develop a theoretical model of the vaporization of a single fuel droplet in a high temperature, high pressure, convective gaseous environment. The model considers the case when a droplet, initially at ambient or elevated temperature, is suddently injected into a gaseous environment that is at a temperature that is well above, and at a pressure that is slightly below (near-critical), or well above (super-critical) those corresponding to the critical value of the liquid. The work is composed of three analyses that describe different aspects of the droplet vaporization process.;An analysis of the super-critical, convective, evaporation of a fuel droplet in a stagnant point flow is developed next. The present analysis describes the transient evaporation of a liquid fuel at its stagnation point in a high temperature, high pressure, environment. The transient conservation equations for both liquid and gas phases are solved simultaneously to determine the profiles of the vorticity, temperature and species distributions, and the regression velocity of the liquid-gas interface.;A third model is developed of the dispersion of a vapor fuel droplet that is suddenly set in motion in a gaseous environment that has a density similar to that of the fuel vapor. The initial droplet injection process is modeled by instantaneously creating a potential flow around a moving spherical gaseous droplet. In the analysis, the transient, axisymmetric, stream function-vorticity and species equations are solved to determine the evolution of the vorticity distribution, species mixing and the distortion of the initial interface. The results show that the initially spherical gaseous fuel droplet is extensively distorted, adopting a mushroom-like shape, and also the vapor mixing process is greatly enhanced around the vortex ring. (Abstract shortened with permission of author.).;First, an analysis is developed of the diffusionally controlled evaporation of a fuel droplet at near and super-critical conditions. The transient conservation equations for the gas and liquid phases are solved using an expansion solution in a power series in time. The series expansion solution provides an explicit expression for the interface regression, the transient heat diffusion in the liquid and gas phases, and the mass transfer in the gas phase.