Regularities of the influence of technological parameters and external factors on the speed and explosively unsafe combustion modes of pyrotechnic nitrate-metallized mixtures with additives of organic substances
Abstract
Prevention of possible fire-explosive destruction of products in the conditions of external thermal actions is of significant practical importance. For this, it is necessary to have a controlled database on the rate of development of combustion of mixtures under conditions of elevated heating temperatures and external pressures, with the help of which it is possible to quickly determine the conditions for the occurrence of explosive modes of combustion of mixtures during their forced activation. There are no studies on the effect of a number of practically important additives of organic substances (for example, urotropin, paraffin, stearin, metaldehyde, rosin, iditol) on the rate of development of the combustion process of mixtures under conditions of elevated heating temperatures and external pressures inherent in thermal effects. The purpose of the work is to obtain a database for determining the regularities of the influence of additives of organic substances used in pyrotechnic production in the composition of two-component pyrotechnic mixtures of metal fuel powders (magnesium, aluminum) and a nitrate-containing oxidizer (sodium nitrate) on the rate of development of the process of their combustion under conditions of increased heating temperatures (up to 800 K) and external pressures (up to 107 Pa). Experimental studies have been conducted to determine the regularities of influence of technological parameters (ratio and dispersion of components) and external conditions (elevated heating temperatures and external pressures) on the speed and explosive modes of combustion of compacted mixtures of metal fuel powders (magnesium, aluminum), nitrate-containing oxidizer (sodium nitrate) and additives of organic substances used in pyrotechnic production (paraffin, stearin, naphthalene, anthracene, urotropine, metaldehyde, rosin, iditol). As a result of experimental studies of the influence of the main parameters of external thermal actions (heating temperatures, external pressures) for the ranges of changes in technological parameters used in practice (coefficient of excess oxidant, relative content of organic matter additive, dispersion of metallic fuel) on the rate and modes of combustion of mixtures, concentration limits of combustion are established. The conducted experimental studies make it possible to establish that an increase in T0 from 293 K to 800 K leads to an increase in the burning rate of mixtures by 1,5...3,8 times and a strengthening of the u(T0) dependence by 1,3...1,6 times; an increase in the oxidant content from α = 0,5 to α = 2,5 leads to a decrease in the burning rate by 1,7...4,2 times and a weakening of the u(T0) dependence by 1,7...2,3 times; a decrease in the average size of metal fuel particles leads to an increase in the burning rate by 1,9...2,8 times and a strengthening of the u(T0) dependence by 1,7...2,5 times; an increase in external pressure leads to an increase in the burning rate by 1,8...3,1 times and a strengthening of the u(Т0) dependence by 1,8...2,3 times. According to the degree of reduction in the speed and stabilization of the combustion process of mixtures under conditions of external thermal effects (increased heating temperatures and external pressures), additives of organic substances can be arranged in the following series: iditol > rosin > anthracene > urotropin > stearin > metaldehyde > naphthalene > paraffin. In practice, the obtained research results can be used at the stage of manufacturing of mixture charges by adjusting the nature and amount of organic substance additives to reduce their sensitivity to possible thermal effects
Keywords
fire safety; pyrotechnic mixtures; combustion processes; burning speed; organic substances; metallic fuels
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