REGULARITIES OF THE INFLUENCE OF DIFFERENT FACTORS ON THE RATE OF DEVELOPMENT OF THE COMBUSTION PROCESS OF PYROTECHNIC MIXTURES BASED ON OXYGEN-CONTAINING OXIDIZERS AND METALLIC FUELS

Abstract

Of great practical importance in preventing possible destruction of pyrotechnic products based on mixtures of powders of oxygen-containing oxidants and metal fuels in conditions of external thermal effects is the ability to regulate the speed of development of the combustion process of mixtures, first of all, with the help of technological parameters (ratio and dispersion of components, compaction coefficient, amount and nature of additives of organic and inorganic substances, etc.). Currently, the influence of the above-mentioned technological parameters on the burning rate is sufficiently well studied. In addition to the main parameters listed above, there are a number of other unstudied factors that also have a significant impact on the burning rate of mixtures (for example, heat exchange with the environment, which depends on the diameter of the charge and the material of the shell that isolates it, as well as the humidity of the oxidizer, composition and humidity of environment in which mixture charges are stored and fired, external pressures, etc.). The purpose of the work is to establish the regularities of the influence of heat exchange with the environment, its composition, humidity and pressure, as well as the humidity of the oxidizer on the speed and stability of the combustion process of compacted mixtures of oxygen-containing oxidizer powders and metal fuels. Replacement of more heat-conductive shell of a sample of Mg + NaNO₃, Mg + Sr(NO₃)₂, Al + NaNO₃, PAM + NaNO₃ mixtures with a less heat-conductive one (for example, metal with paper one) leads to a decrease in the burning rate by more than 2...3 times and a noticeable stabilization of the combustion process. The strongest influence of the coefficient of shell thermal conductivity is manifested with an increase in the size of the particles of metal fuel and oxidizer. The regulation of technological parameters (ratio and dispersion of components, compaction coefficient) also leads to an increase in the stability of the combustion process of mixtures. The reduction of the degree of hydration of the oxidizing agent (for example, NaNO₃ or Sr(NO₃)₂ by encapsulating its particles (for example, with aluminum)) also leads to a decrease in the burning rate of the mixture and its stabilization. The encapsulation of particles of oxidizing powders leads to weakening of the u(Р) dependence and an increase in the resistance of the mixture combustion process to external thermal influences. The burning rate of mixtures of Mg + NaNO₃, Mg + Sr(NO₃)₂, Al + NaNO₃, PAM + NaNO₃ increases more than 3…4 times with the increase in thermal conductivity of the shell, and the burning process becomes unstable and explosive. The transition from a sample of the mixture in a shell (for example, a paper one) to a sample without a shell leads to an increase in the burning rate and to a change in the nature of the u(α) dependence: the maximum on the curve shifts to the side of the oxidant excess. A decrease in the humidity of the external environment (for example, air) leads to an increase in the rate of combustion of mixtures, shift of the position of the maximum on the curve u(α) towards an excess of metallic fuel and, in general, to a destabilization of the combustion process of mixtures.