Theoretical shell formation model for single droplet of heavy fuel oil

Abstract

Combustion of heavy fuel oil (HFO) involves the complete combustion of volatile components and the emission of pollutants and solid particles. In most cases, solid particles are seen in the form of the cenosphere. Cenosphere is a hollow particle with a thin, brittle porous shell composed of solids leftover from the HFO. Controlling and reducing these polluting particles requires knowing their nature. Therefore, in this article, an innovative numerical model of how the cenosphere is formed has been developed, in which it is possible to accurately measure the mass, diameter, and thickness of the cenosphere, as well as the effect of changes in fuel concentration and temperature on each of the parameters. In this model, it was assumed that due to heat, the fuel turns into two parts, lighter or volatile and heavier. The lighter component evaporates and the heavy component remains as a solid and causes the formation of the cenosphere. The equations used in this approach include the following: the energy conservation and the evaporation equation for the liquid droplet, the kinetic reaction equations to replace the fuel thermal decomposition and calculate the mass of the coke, and the expansion and compression pressure balance equations for obtaining cenosphere diameter. The expansion pressure caused by the fluid flow through the porous shell, and the compression pressure due to the intermolecular force of the Carbon layers, is dissolved. In modeling fuel properties varying with temperature, an ordinary local HFO has been calculated by assuming a transient single-component droplet and using the distillation curve. The results of the model are in acceptable agreement with the experimental data available in the literature. The difference between the experimental and calculated results of the model for a wide range of results was less than 10%.