Modeling the self-propagation reaction in heterogeneous and dense media: Application to Al/CuO thermite

This article provides a computational analysis of the reaction of fully-dense layered aluminum and copper oxide systems. After the detailed presentation of the 2D nonstationary model implementing both oxygen and aluminum diffusion, the propagation of the reaction front in an Al/CuO thin film was studied. The model qualitatively reproduces the dependency of the reaction front progression rate spatially as a function of the fuel concentration. Calculations also evidence the inverse evolution of flame front width with respect to the reaction front velocity. A procedure to estimate the heat loss generated by the fact that the reactants and products may vaporize prior to reaction completion was proposed by imposing a flame temperature limit close to Cu vaporization point. This work also shows that microscopic fluctuations in the instantaneous reaction front velocity can be observed for reactant diffusion activation energy ( E-a ) of 125 kJ/mol, before quenching for greater E-a . Finally, we demonstrate the potential of this new 2D nonstationary model to investigate the thermal effect of additives such as metallic impurities in the Al/CuO thin film that can lead to the flame front corrugation at the microscale. The simulations show that a metallic particle acts first to boost the reaction velocity as its high thermal conductivity helps the upfront heating. Then, the particle being also a heat sink, a local slowing down of the front velocity is observed. (c) 2021 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Automated summary

This study provides a computational analysis of the reaction between fully-dense layered aluminum and copper oxide systems, incorporating a 2D nonstationary model with oxygen and aluminum diffusion. The model successfully reproduces the spatial dependency of reaction front progression rate on fuel concentration, as well as the inverse evolution of flame front width with reaction front velocity. Additionally, a method to estimate heat loss due to vaporization of reactants and products was proposed, and microscopic fluctuations in reaction front velocity were observed for different activation energies before quenching.