Numerical modeling of the processes of heating, evaporation and combustion of emulsified fuel

Abstract

The issue of mixing fuel oil with water, i. e. emulsification, is considered. Emulsified fuel of the “water-fuel oil” type is a promising alternative fuel, as it causes water to boil at high temperatures, which can improve the atomization of the fuel spray. The process of heating and evaporation of a droplet of emulsified fuel depends on the diffusion and coalescence of the smallest water particles in the fuel oil, which occur during heating. The article presents a model that accounts for the process of water diffusion in droplets of emulsified fuels, as well as the physical properties of the entire medium. The model incorporates these important physical phenomena and offers an effective method for calculating the ratio of emulsion components. It is designed to describe the heating and evaporation of droplets of emulsified fuel, such as “water-fuel oil”. The process of water coalescence is simplified by the fact that dispersed water droplets instantly combine into a single water subdroplet in the center of the fuel oil droplet. During the calculations, the proportions of each component are taken into account; in addition to the combustion of the carbon content of the fuel oil, it is necessary to consider the heat release of water vapor, the release of hydrogen, the dissociation of water and the thermal effect of hydrogen combustion. These processes occur in the same proportions as in the water-fuel oil emulsion. To address the tasks at hand, the ANSYS CFX module was selected, which allows for the simulation of chemical reactions and combustion processes associated with liquid flow. This will enable a detailed study of the phenomena occurring and help determine the optimal parameters of the water-fuel oil emulsion, thereby increasing operational efficiency. Based on the proposed model, the combustion process in the furnace volume as a function from the water content in the emulsified fuel was analyzed.