M.S Thesis abstract

Abstract

Mathematical modeling of combustion synthesis phenomena has been the interest to many researchers for the last several decades. This area of research has proven to be very challenging due to the complexity of combustion processes, especially those involving condensed phases. One example of such class of reactions is a numerical simulation of temperature and conversion profiles in the self-propagation high-temperature synthesis (SHS), also known as combustion synthesis. Despite the significant progress, the mathematical modeling has not been thoroughly conducted, especially when partial vaporization or combustion-induced gas flow take place. The main objective of this research, of which this work is only one facet, was to simulate the combustion wave propagation in a condensed reacting system, both with and without the presence of uniaxial gas pressure gradient. The modeling studies were divided into two parts. The first one focused on modeling studies of the dynamic profiles of temperature and conversion in the Ti-Mo-Si reacting system without the presence of uniaxial gas pressure gradient. The second part was focused on simulation of dynamic profiles of temperature, pressure, velocity, density, and conversion in the same reacting system with the presence of uniaxial gas pressure gradient. In addition, effects of gas pressure gradient and change in porosity due to the reaction on the propagation velocity were also studied.

It was found that an increase in gas pressure increases the propagation velocity due to additional preheating of reactants. It was also observed that an increase in porosity due to vaporization also increases the combustion front propagation. It has been also shown that the maximum propagation front velocity corresponds to stoichiometric mixture of 5Ti + 3Si whereas for the same system diluted with 30% of Ti₅Si₃ the combustion front velocity reduces by 75%. It was determined that the increase of effective thermal conductivity results in faster propagation.