Regularities of influence of technological parameters and external factors on the temperature and composition of combustion products of pyrotechnical nitrate-metal mixtures

Methods for calculating the temperature and composition of combustion products of mixtures of magnesium and potassium nitrate powders, which are widely used in the equipment of various pyrotechnic articles (lighting, signaling, tracing, etc.), are currently absent. The aim of this work is to determine the use of thermodynamic methods to calculate the dependences of the temperature and composition of combustion products of pyrotechnic mixtures of magnesium and potassium nitrate powders on the ratio of components and external pressure. The results of thermodynamic calculations of the dependences of the temperature and composition of combustion products of pyrotechnic mixtures of magnesium and potassium nitrate powders on the coefficient of excess oxidant α = 0,1…3,0, the value of organic additive ε = 5…20 % and external pressure P = 10⁵… 3·10⁷ Pa, which determine the explosive modes of their combustion, are obtained. The research has been carried out using the methods of thermodynamic analysis of combustion processes of mixtures taking into account the phase imbalance of their combustion products. According to the thermodynamic calculation, the temperature of the combustion products significantly depends on the coefficient of excess oxidant in the mixture and pressure and has a maximum. From the data of thermodynamic calculations of the temperature of combustion products of mixtures of magnesium + potassium nitrate + paraffin, stearin, naphthalene, anthracene it follows that the introduction of additives of organic matter into the mixture of magnesium with sodium nitrate does not significantly change the overall temperature of combustion products, pressure for double mixture. The analysis of the results of calculations shows that regardless of the nature of the additive, the curve T_с(α), as in the case of a double mixture, at different pressures has a maximum. When adding paraffin, naphthalene and anthracene to the mixture, the value of T_с at α = 0,1, in contrast to the double mixture and the mixture with the addition of stearin, is greater than at α = 6,0. The introduction of the addition of stearin into the mixture, regardless of the coefficient of excess oxidant and pressure, leads to a significant reduction in T_с. The introduction of the same additives of paraffin, naphthalene and anthracene in the mixture leads to a significant decrease in T_с, regardless of α only in the region of low pressure, in the region of high pressure for large α (α > 5,0), on the contrary, increasing the addition of these substances leads to an increase in T_с. When adding stearin, naphthalene and anthracene additives to the mixture, the position of the maximum T_сmax is shifted towards the excess of oxidant, which is not observed when adding paraffin to the mixture

pyrotechnic mixtures; thermodynamic calculations; nitrate-containing oxidizer; metal fuel; combustion processes; fire safety