Ignition and combustion of energetic materials

Melius, C. F. Thermochemical Modeling II. Application to Ignition and Combustion of Energetic Materials. In Chemistry and Physics of... 

The ability to model the detailed chemistry of ignition and combustion of energetic materials requires the simultaneous treatment of the chemical kinetics behavior of large chemical reaction systems combined with convective and diffusive transport of mass, momentum, and energy. Such models require the evaluation of equations of state, thermodynamic properties, chemical rate expressions, and transport properties. The computer software used to evaluate these quantities is referred to as the Chemkin package.33-35 includes an interpreter for the chemical reactions, a thermochemical data base, a linking file, and gas-phase subroutine libraries. The interpreter reads in the list of elementary chemical reactions. The forward reaction rates are given in the form of the Arrhenius rate expression... 

External heating is needed for ignition, and successive heating is needed from the high-temperature burned portion to the low-temperature unbumed portion for combustion. The ignition and combustion of reactive gases and energetic solid materials are fundamentally the same. However, additional physicochemical pro-... 

Some of the aforementioned comments on the application of fast thermolysis to explosives extend to the ignition and combustion processes of propellants and vice versa. Because a considerable amount of our effort has been directed at understanding the sub-surface and near super-surface processes of energetic materials, this article will conclude with some further generalities that can be drawn about fast heated materials in relation to their pre-ignition, ignition, and combustion-like state. 

Brill, T.B. and Subramanian, R. Thermal Decomposition of Energetic Materials 35. A Mechanism Study of Decomposition and the Transition to the Ignition-Like State in Trinitromethyl Alkyl Compounds Combustion and Flame, in press. 

The ignition of energetic materials unlike the steady-state combustion is a transient process. It is affected by thermal conductivity of the pyrolant, k density, p specific heat, Cp) surface area. A ignition temperature, T Ta = ambient temperature and heat flow into the material, q. The time to ignition as derived by McLain [1] reads... 

A flat material of thickness is placed on a hot plate of controlled temperature Tb. The material is energetic and exothermic with a heat of combustion of Ahc and its reaction is governed by zeroth-order kinetics, Ae E RT the mass loss rate per unit volume. Notation is as used in the text. The differential equation governing the process to ignition is given as... 

Lewis, B. und Elbe, G. von Combustion, Flames and Explosives of Gases, 3. Aufl., Academic Press, Orlando, Florida 1987 Energetic Materials New Synthesis Routes, Ignition, Propagation and Stability of Detonation, Hrsg. Field, J.E. und Gray, R, The Royal Society, London 1992... 

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