Nonideal regimes of deflagration and detonation of black powder

Russian Journal of Physical Chemistry B (Impact Factor: 0.36). 06/2010; 4(3):428-439. DOI: 10.1134/S1990793110030103


The explosive and deflagration properties of black powder differ significantly from those of modern propellants and compositions
based on ammonium nitrate or ammonium perchlorate. Possessing a high combustibility, black powder is capable of maintaining
stable combustion at high velocities in various shells, be it steel shells or thin-walled plastic tubes, without experiencing
deflagration-to-detonation transition. It is extremely difficult to detonate black powder, even using a powerful booster detonator.
The results of numerical simulations of a number of key experiments on the convective combustion and shock initiation of black
powder described in the literature are presented. The calculations were performed within the framework of a model developed
previously for describing the convective combustion of granulated pyroxylin powders, with small modifications being introduced
to allow for the specific properties of black powder. The thermophysical properties of the products of combustion and detonation
and the parameters of the equation of state of black powder were determined from thermodynamic calculations. The calculation
results were found to be in close agreement with the experimental data. The simulation results were used to analyze the regularities
of the wave processes in the system and their relation to the properties of black powder and the experimental conditions.
It was demonstrated that the effects observed could be explained by a weak dependence of the burning rate of black powder
on the pressure.

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Available from: Boris Ermolaev, Nov 26, 2014
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    ABSTRACT: Le Chatelier diagrams may be adopted for the definition of thermodynamic loci of explosion in terms of internal energy with respect to the temperature for either the primary explosion or for the deflagrative, post-combustion of the products of the first reaction with air, the afterburning reaction. In this paper, Le Chatelier diagrams are produced for TNT and black powder by using the CEA code. Pressure plots with respect to density or air/fuel ratio are also shown. These results are useful for the simulation of explosion (hydrodynamic codes), and more generally for the definition of safety of storage, transportation, and production of explosives and pyrotechnics. Furthermore, the method can be easily extended to any deflagrative pyrotechnic substances, for which information on explosion and afterburning effects are needed. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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