Modeling ignition and extinction in condensed phase combustion

The characteristics of ignition and extinction in thermites and intermetallics are a subject of interest in developing the latest generation of energetic materials. An experimental “striker confinement” shock compression experiment was developed in the Prof. Glumac’s research group at the University of Illinois to study ignition and reaction in composite reactive materials. These include thermitic and intermetallic reactive powders. We discuss our model for the ignition of copper oxide-aluminum thermite in the context of the striker experiment and how a Gibbs formulation model, that includes multi-components for liquid and solid phases of aluminum, copper oxide, copper and aluminum oxide, can predict the events observed at the particle scale in the experiments. Furthermore, the characteristics of a steady diffusion flame that arises at the interfaces of two condensed phase reactant (titanium-boron) and gas reactant (methane-air) streams that form an opposed counterflow are discussed. In the the gas flow scenario, the asymptotic analysis is carried on both constant and variable density formulations and compared the solutions to those obtained numerically. In the case of condensed phase reactants, several types of analyses are carried out at increasing levels of complexities: an asymptotic analysis valid in the limit of low strain rates (high residence time in the reaction zone), a constant mixture density assumption that simplifies the flow description, diffusion models with equal and unequal molecular weights for the various species, and a full numerical study for finite rate chemistry, composition-dependent density and strain rates extending from low to moderate values