Hot-spot modelling of thermite mixtures

Oxidizer and fuel particles are the ingredients of classical pyrotechnics. Beside the concentration and resulting heat of reaction the burning behavior of such systems are controlled by particle size, melting, evaporation and decomposition of the particles, the heat and mass transfer and the reaction kinetics. Also the distribution and location of the single particles play an important role in the progression and temperature of overall reaction. In further works a hot-spot approach modeled the reaction progress in three dimensions taking into consideration the particulate nature of pyrotechnic compositions and the kinetic of oxidizer decomposition as the rate-determining step. In the next step of development the model was expanded by a more complex kinetic regime which also takes into account the oxidation of the fuel. The influences of the different parameters on the progression-rate and conversion of educts, which are taken into account by the model, were investigated by different parameter variations. The model is applied to different particle concentrations of regular and randomized assemblies. The results were compared and validated with progression rates and temperatures measured from various Al/CuO-thermite mixtures with aluminum contents from 8% to 70%.