The results of thermodynamic calculations of temperature dependences of combustion products of pyrotechnic mixtures based on magnesium, aluminum and metal oxides and their content of high-temperature condensate on the relevant technological parameters and relevant external conditions are presented. The ratio of the components of the mixture, the type of metal fuel, the type of oxidant are considered as technological parameters of pyrotechnic mixtures. The influence of temperature and external pressure is determined as external conditions. It is determined that high values of combustion products and high content of condensed combustion products of pyrotechnic oxide-containing mixtures pose a fire hazard to the surrounding objects when the products are forced to operate under external thermal conditions. As a result of the calculations, it was found that the value of the combustion temperature of oxide-containing mixtures has a maximum value of 3870 K at a maximum value of the relative fuel content of 0.35 and the corresponding external pressures of 105...3107 Pa. It is determined that with increasing external pressure in the ranges from 105 tо 3107 Pa there is a significant increase in the temperature of combustion products: for oxide-containing mixtures based on metallic fuel magnesium - up to 3650 K; for oxide-containing mixtures based on metallic aluminum fuel - up to 3870 K. It is determined that in oxide-containing mixtures with metallic fuel content from 0.06 to 0.49, regardless of the type of metallic fuel and oxidant with increasing external pressure increases the temperature to 1.8 times.
Mathematical models of external heating of charges of pyrotechnic products based on compacted mixtures of aluminum-magnesium alloy powders and nitrate-containing oxidizers (sodium, potassium, strontium, and barium nitrates) were refined by taking into account the temperature dependence of their thermophysical properties (volumetric heat capacity and coefficient of thermal conductivity), which allowed to more accurately determine the critical values of heat flows and durations of their influence.
New data were obtained to determine the critical ranges of the change in the burning rate of mixtures under conditions of elevated heating temperatures and external pressures for various values of technological parameters (the coefficient of excess oxidizer α; the average particle size of metal fuel powders dм microns and oxidizer dN), exceeding the ranges of which leads to premature ignition mixtures under conditions of external thermal effects and leads to unstable explosive development of their combustion process and fire-hazardous destruction of pyrotechnic products.
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