PREVENTION OF PREMATELY FIRE EXPLOSION AND UNSAFE USE OF PYROTECHNIC MIXTURES IN THE CONDITIONS OF SHOT AND FLIGHT

Abstract

The regularities of the effect of external thermal shock effects of supersonic blowing with an air stream on metal hemispherical shells of charges of nitrate-metallized mixtures with additives of organic and inorganic substances, which are used to equip pyrotechnic products (pyrotechnic IR emitters, elements of rocket and space technology, etc.) have been established. Temperature distributions along the outer and inner shells and along their thickness were studied. The critical values of air blowing speeds and times of its thermal shock effect were determined, exceeding which leads to premature ignition of mixture charges, a sharp acceleration of their combustion under the shells and, ultimately, to fire-explosive destruction of the products.

For the first time, the existence of the maximum permissible ranges of changes in the main parameters of the external shock thermodynamics of the supersonic air flow on the surface of the hemispherical metal shells of mixture charges (blowing speed, time of its influence (j = 1, 2,...)), exceeding which leads to premature self-heating of the mixture charges as a result the process of exothermic oxidation of metal fuel particles in gaseous products of thermal decomposition of the oxidizer and additives of organic and inorganic substances, which leads to their ignition, the occurrence of combustion in closed volumes with its further acceleration and, ultimately, to premature activation and fire-hazardous destruction of pyrotechnic products with the release of high-temperature combustion products into the environment.

A comparison of the results of calculations of temperature fields in metal cases of products (hemispherical shells) during shock thermodynamics of an external supersonic air flow with the obtained experimental data showed that the developed mathematical models can be used in practice as more accurate methods (the relative error is reduced to 7...9% instead of 10...15% - in existing methods) for predicting dangerous areas on the surface of products with maximum thermal effects, where they are subjected to the most intensive heating; temperature levels on the inner surface of the product bodies, which is in contact with the charges of pyrotechnic mixtures, and the permissible values of both the parameters of external thermodynamics and the technological parameters of the mixtures by applying the necessary data on the ignition temperatures of metal particles in the gaseous decomposition products of the oxidizer and additives of organic and inorganic substances.