Kyrychenko Y. Increasing the Fire Safety of Pyrotechnic Products Based on Mixtures of Metal Fuel Powders and Metal Oxides

The prevention of forced premature fire-hazardous destruction of products in case of exposure to external thermal actions is of great practical importance. At the same time, they should be based on scientifically based methods of determining the critical values of parameters of thermal effects on products and technological parameters of charges of mixtures, the excess of which leads to premature fire-hazardous destruction of products. To develop such methods, it is necessary to have the results of theoretical and experimental studies of the processes of heating product bodies for different values of external heat flows and their action times, as well as the processes of ignition and development of combustion of mixture charges under different external conditions (elevated heating temperatures, external pressures). The idea of the work is determined by the solution of an actual scientific and applied problem, which consists in the development of the scientific foundations of increasing the fire safety of pyrotechnic products based on compacted mixtures of magnesium, aluminum powders and metal oxides by establishing the basic regularities of their heating, ignition and development of combustion as a basis for preventing fires in case of external thermal actions. The scientific novelty of the obtained results is as follows. For the first time: the regularities of influence of technological parameters of mixtures (ratio of components, dispersion of Mg and Al powders, nature of metal oxide) on critical values of parameters of external thermal actions (external heat flow, time of its exposure) were established, the control of which allows preventing premature ignition of mixtures and fire-hazardous destruction of products; regularities of influence of technological parameters of mixtures have been established (of powder particles Mg and Al of medium size, of the relative content of oxygen in the decomposition products of the metal oxide, of coefficient of excess oxidant) and external factors (heating temperature, external pressure) on the main characteristics of the processes of ignition and the development of the combustion of mixtures (of ignition temperature and time of burning of metal fuel particles in metal oxide decomposition products, combustion rates of mixtures). Further development was clarified and received: mathematical models of external thermal influence on samples of mixtures, which take into account the temperature dependence of the thermophysical properties of mixtures, as well as the material of their shells (steel, copper, cardboard, etc.), which allows to more accurately determine the critical parameters of external thermal actions, and thereby prevent the development of a fire hazard state of products; a mathematical model of the combustion process of compacted two-component mixtures of Mg, Al powders and metal oxides, which takes into account: temperature dependence of the thermophysical properties of the mixtures; kinetic characteristics of thermal decomposition of metal oxides and high-temperature oxidation of Mg and Al powders, which allows to more accurately determine the influence of technological parameters on the rate of development of the combustion process of mixtures and prevent its unstable and explosive development. The practical significance of the obtained results lies in the development and implementation in the activities of State Emergency Service of Ukraine and enterprises and organizations of Ukraine: the method of determining the critical values of parameters of external thermal actions and technological parameters of mixtures, the excess of which leads to their premature ignition and fire-hazardous destruction of products; means of control and technological recommendations used in organizations and enterprises of Ukraine to reduce the probability of fire-hazardous destruction of products based on the considered mixtures during their circulation, taking into account the influence of external heating, as well as reducing the number of premature explosive destruction of products in conditions of thermal shock effects during their launches; in the educational process of Cherkasy Institute of Fire Safety named after Chornobyl Heroes of the National University of Civil Protection of Ukraine.