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ISSN Imprimir: 2150-766X
ISSN On-line: 2150-7678
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MODELING OF TRANSIENT COMBUSTION REGIMES OF ENERGETIC MATERIALS WITH SURFACE EVAPORATION
RESUMO
A one-dimensional transient model of the combustion of energetic material (EM) with surface evaporation is formulated. The model considers heat propagation and EM condensed phase decomposition via a 1st order reaction. In the gas phase, it considers heat propagation, species diffusion, exothermic decomposition of vapor via a 1st order reaction and exothermic conversion of gas components via a 2nd order reaction. The matching condition at the surface corresponds to equilibrium evaporation in the form of the Clausius-Clapeyron equation. An external radiant flux is assumed to be absorbed in the bulk of EM and not to be absorbed in the gas phase. When simulating radiative ignition, it has been revealed that it can occur in one-, two- or three-stages. First, under irradiation, the evaporation and exothermic reaction in the condensed phase is initiated with a gas flame being formed far from the burning surface. The conductive heat flux from the gas to the EM surface is vanishingly small and the low rate gasification regime is realized. If the radiant flux gradually decreases up to zero, the flame approaches the EM surface and the heat feedback from the gas phase increases several times. A sustaining combustion is governed by heat feedback from the gas flame with burning rate several times higher than the gasification rate. Numerical experiments performed with the combustion model under study have revealed the intrinsic instability of steady-state combustion in case of EM with the rate controlling zone in the condensed phase.