New: Defense of M.Sc. thesis:
The thesis defense by Mr. Seyed Ahmad Reza Salehi, a M.Sc. student in aerospace, entitled "Modeling of Liquid Fuel Droplet Combustion under Near-Critical Conditions", will be held on 2025-06-11 at 14:00 (Tehran time) at the School of Mechanical Engineering of Iranian University of Science and Technology (IUST). The members of the Space Propulsion Research Laboratory (SPRL) invite all interested parties in this field and the other relevant areas to participate in this defense.
 
Abstract
The combustion of liquid fuel droplets represents one of the fundamental yet complex phenomena in the field of engineering, playing a pivotal role in the operation of thermal and propulsion systems, including combustion engines, turbines, reactors, and jet engines. In this context, the present study aims to numerically model the transient process of evaporation and combustion of a single-component fuel droplet under high-temperature conditions, atmospheric pressure, a quiescent environment, and zero gravity. To this end, the species, momentum, and energy conservation equations in the gas phase, as well as the energy conservation equation in the liquid phase, are numerically solved using a finite volume approach and a fully implicit method. Thermophysical properties are defined as temperature-dependent functions and vary with both time and space. Furthermore, the chemical reaction of the fuel is incorporated into the model using a global reaction mechanism. For validation purposes, the results obtained for heptane fuel are compared with experimental data in the temperature range of 470 to 740K for the pure evaporation process and with numerical data in the range of 1200 to 1600K for the combustion process. The effects of ambient temperature, initial droplet diameter, and the composition of the surrounding gas on the evaporation or combustion process have been examined. Consequently, variations in droplet diameter, average evaporation or burning rate, temperature, and flame position have been determined.
The results indicate that the impact of increasing temperature on the burning rate is approximately 3% greater than that of increasing the initial droplet diameter. On the other hand, increasing the initial surface temperature of the droplet leads to a reduction in droplet lifetime due to a shorter heating period, yet has no significant effect on flame temperature or location. Additionally, a threefold increase in oxygen concentration in the ambient air raises the flame temperature by over 1000K and causes the flame to form at radii very close to the droplet surface. In contrast, an increase in the initial carbon dioxide concentration exhibits an opposing effect to that of oxygen, weakening the flame formation.

Keywords: Evaporation, ignition, droplet combustion, liquid fuel, heptane, flame, modeling.