RESEARCH OF THE MECHANISM AND DEVELOPMENT OF MODELS FOR THE DEVELOPMENT OF THE COMBUSTION PROCESS OF TWO-COMPONENT PYROTECHNIC MIXTURES OF METAL FUELS WITH FLUOROPLASTS UNDER CONDITIONS OF EXTERNAL THERMAL INFLUENCES

Purpose. Establishing the combustion mechanism of two-component metal-compacted fuels and fluoroplastics, developing a model of their combustion to determine the critical ranges of changes in the burning rate of mixtures under the influence of external thermal effects. Methods. For the research, well-known methods of physicochemical analysis were used, in particular contact and non-contact methods of temperature measurement, as well as high-speed microfilming of combustion processes. Methods of mathematical modeling, numerical analytical methods for solving heat and mass transfer equations, chemical kinetics, as well as methods of mathematical statistics were also used, using standard software for modern numerical methods. The relative error of measurements of the main characteristics of combustion of mixtures (temperatures of combustion products of mixtures, burning rate, etc.) under the specified conditions did not exceed 6…8%. Results. External thermal effects on the surfaces of the bodies of products with charges of the studied mixtures during storage, transportation, firing and flight can lead to significant heating of their bodies. This heating causes the development of an explosive combustion process of the mixture charge at elevated temperatures and pressures of the external environment. This is the main reason for the acceleration of the combustion process, premature operation of the product and its fire-hazardous destruction. Therefore, at the design stage and bench tests that simulate these external thermal effects, it is important to determine the critical ranges of changes in the burning rate of the mixture charges, exceeding which leads to fire-explosive destruction of products in extreme operating conditions. Scientific novelty. The combustion mechanism of two-component mixtures of metal fuel and fluoroplastic powders has been established, according to which the process of converting the initial mixture into combustion products is stationary, one-dimensional and occurs in three spatially separated zones: a heated layer in the condensed phase of the mixture; a reaction zone of the condensed phase of the mixture; a flame zone (heat release zone of the gas phase). A model of combustion of mixtures has been developed that takes into account the kinetic characteristics of thermal decomposition of fluoroplastics and high-temperature oxidation, ignition and combustion of metal particles in the decomposition products, which allows more accurately (relative error reduced to 6…8% instead of 10…12% in existing models) to determininge critical ranges of changes in the burning rate of mixtures under conditions of external thermal effects, the excess of which leads to an acceleration of the combustion process of mixtures and fire-explosive destruction of pyrotechnic products based on them. Practical significance. The results of theoretical and experimental research, obtained in the form of mathematical models and an experimental database, allow optimizing technological parameters (ratio of components, dispersion of metal fuel, nature of metal and oxidizer) at the stage of manufacturing products, increasing their ignition temperature and reducing the probability of fire and explosive destruction during storage and transportation. When launching products, optimizing the speeds and angles at which they are fired, it is possible to reduce the heating temperature of metal shells of mixture charges and reduce the number of premature explosive destructions during firing and flight.