A Model of Hydrocarbon Fuel Droplet Combustion in Supercritical Pressure Environments

Hydrocarbon fuel as a class of petroleum derived fuels is an essential component of energy resources, and its main application is releasing energy through spray combustion. The evaporation and combustion of fuel droplet serve as the basis for spray combustion. The evaporation and combustion of the fuel spray inside the combustion chamber of direct injection diesel and gasoline engine, gas turbine and liquid-propellant rocket take place at supercritical pressure (ambient pressure is larger than the critical pressure of fuel). Accordingly, the study on the combustion of hydrocarbon fuel droplets is extremely necessary. The objectives of this paper are to theoretically provide a novelty explanation for the physical scenario that the combustion of fuel droplets in supercritical pressure environment result in the evaporation of the droplets instantly, and establish theoretical foundation for the study on the fuel droplet evaporation and combustion that take place after the transition of droplet surface respectively. This study used the equations of mass conservation, component conservation, and energy conservation to describe the physical process of gas phase and liquid phase in droplet combustion, which can be applied to establish the uniform description of the physical process of transition between gas and liquid within large density range. This paper introduces the concept of vapor-liquid equilibrium, mixture critical point and evaporation enthalpy for the heat and mass exchange of droplet surface. In our study the physical process around the transition of droplet surface is thoroughly analyzed as well. This study focuses on developing a numerical model and program for the combustion and evaporation of hydrocarbon fuel droplets. The model was validated by comparison with the data from experiment.