Modeling Ablation in Al/CuO Nanothermite Pellet Combustion

Abstract

Nanothermites are reactive materials composed of metal and metal oxide nanoparticles, engineered to produce rapid exothermic reactions with high energy density. Aluminum and copper oxide (Al/CuO) are widely used due to their strong reactivity and ability to achieve efficient combustion, making them ideal for applications in energetic materials. This thesis investigates the combustion of Al/CuO nanothermite pellets, with a particular focus on ablation—mass loss due to thermal degradation and chemical reactions. A numerical model is developed to capture key combustion characteristics, including flame speed, pressure distribution, and temperature response, while accounting for both thermal and mechanical effects across varying packing densities. Leveraging the Porous-material Analysis Toolbox based on OpenFOAM (PATO), this model simulates complex reactions, heat flux, and ablation dynamics, thereby addressing existing gaps in understanding ablation effects on nanothermite combustion and enhancing predictive capabilities for these materials. In its simulation methodology, this study adapts PATO to model multiphase reactive materials, formulating governing equations for mass, momentum, and energy conservation. A two-dimensional axisymmetric model was selected to represent the cylindrical pellet structure. Key parameters, including material porosity, permeability, specific heat, and thermal conductivity, were tailored to the properties of nanothermite materials, while distinct boundary conditions were applied to simulate ignition and ablation phases. Simulations were conducted across various packing densities, with some models incorporating ablation-specific boundary conditions to capture changes in flame speed, peak pressure, and pellet stability under different conditions. Results indicate that ablation intensity significantly influences the combustion dynamics, with higher intensities leading to reduced flame speeds and peak pressures. The study's findings highlight the potential for controlled nanothermite combustion by optimizing pellet packing density and ablation characteristics, offering applications in propulsion and micro-energetics.