Post-induction processes in the case of thermal explosion in porous-medium-gaseous-reagent-solid-product systems

Шкадинский, К. Г.; Ozerkovskaya, N. I.; Мержанов, А. Г.

doi:10.1134/1.1433526

Cited by 3 publications

(3 citation statements)

References 2 publications

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“…The effective thermal conductivity of the condensed phase is assumed to be a power function of porosity: λ c = λ 0 (1 − m) n . As in [4], the chemical reaction rate is assumed to depend on the active gas pressure only weakly: f (p a ) = p a /(p a + p ε ) (p ε = const).…”

Section: Mathematical Formulationmentioning

confidence: 99%

Filtration combustion of porous metallic samples in a gas diluted by an inert component

Prokof’ev

Borodatov

Smolyakov

2008

Combust Explos Shock Waves

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Filtration combustion of a porous layer with natural filtration of the oxidizer diluted by an inert component is studied. The problem of ignition of a porous layer by a heated surface permeable for the gas is solved, and the time of ignition is determined as a function of pressure in the reactor and initial porosity of the sample. Formation of an inert gas "plug" preventing chemical interaction is examined. It is shown that the mean depth of conversion of the condensed reagent in the porous layer depends on the sample length, porosity, pressure of the gas mixture, and concentration of the inert component.

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Section: Mathematical Formulationmentioning

confidence: 99%

Filtration combustion of porous metallic samples in a gas diluted by an inert component

Prokof’ev

Borodatov

Smolyakov

2008

Combust Explos Shock Waves

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“…Shkadinskii et al [17][18][19][20] performed a cycle of theoretical studies of the thermal explosion regimes of gascondensed SHS synthesis. Unlike in gasless systems, in which thermal explosion results from noncompensation of volumetric chemical heat release and heat removal to the ambient medium, thermal explosion in gas-condensed systems involves mass-transfer processes in the condensed and gas phases.…”

mentioning

confidence: 99%

“…It is shown that the Semenov critical parameter decreases with increasing pore gas pressure. Ignition and postinduction processes in a distributed system in a one-temperature approximation have been studied [18][19][20] using boundary conditions of the second and third kinds for the skeleton temperature, depending on the gas permeability of the boundary and the direction of gas flow through the corresponding boundary of the porous layer. A double self-ignition regime, characterized by separation of the fronts and complete transformation at the front, occurs at a high gas content in the porous medium.…”

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confidence: 99%

Critical conditions of thermal explosion of a porous layer

Burkina

Prokof’ev

2008

Combust Explos Shock Waves

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The conditions and regimes of thermal ignition of a reactive porous layer are investigated under asymmetric conditions on its lateral surfaces and with an oxidizer supply to the layer by diffusion or filtration through the cold boundary. For a zero-order reaction, an analytical dependence of the critical value of the Frank-Kamenetskii parameter on the Zel'dovich parameter is obtained, which separates the regions of steady-state and unsteady regimes. A numerical analysis is made of the critical value of the Frank-Kamenetskii parameter on the Zel'dovich parameter, the Todes parameter, which determines the oxidizer consumption, and the parameter determining the oxidizer supply to the layer: the Lewis numbers or the filtration analog of the Peclet parameter.Key words: porous medium, natural filtration, critical conditions, thermal explosion, analytical and numerical solutions.The conditions of thermal self-ignition of reactive materials are one of the key issues of fire and explosion safety, and their investigation has therefore proceeded in parallel with the development of ignition and combustion theory, starting from the work of van't Hoff [1]. The critical conditions of thermal self-ignition of homogeneous reactive media with simple kinetics were determined and studied in the classical theories of Semenov [2] and Frank-Kamenetskii [3]. Subsequent investigation has shown that a chemical process or a thermal situation are capable, by virtue of complexity, of significantly changing the self-ignition limit [4]. The special features of chemical processes in porous materials, as was noted even by Zel'dovich [5], are related to the delivery of some reactants to the zone of localization of the chemical process and to the complex heat-transfer mechanism. The indicated specificity results in ignition regimes of porous systems qualitatively different from the ignition regimes of homogeneous media. The ignition limits and times of porous systems and the location of the ignition spot depend greatly on the conditions of the process and are determined by heat and mass transfer.Investigation of the initiation of chemical processes 1 Tomsk State University, Tomsk 634050; roza@ftf.tsu.ru.in porous media has been carried out in three directions: 1) self-ignition; 2) ignition of porous media by a hot body and radiative and convective heat flows; 3) hotspot ignition of porous media. The present paper is concerned with the processes related to the first direction. The effect of heat convection due to gas blowing through a reactive layer on the critical conditions of thermal explosion under symmetric conditions on the layer walls was studied by Eremin and Kolesnikov [6]. Steady-state temperature profiles and the dependence of the critical value of the Frank-Kamenetskii number Fk * on the Peclet parameter Pe were obtained numerically using a one-temperature model for a zero-order chemical process. The dependence for Pe < 4 was approximated by a polynomial with an accuracy of 4%. It was established that, for large values of the Peclet par...

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Analysis of the Thermal Explosion in Systems Porous Reagent–Active Gas–Solid Product

Шкадинский

Ozerkovskaya

Костин

2004

Combustion, Explosion, and Shock Waves

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Post-induction processes in the case of thermal explosion in porous-medium-gaseous-reagent-solid-product systems

Cited by 3 publications

References 2 publications

Filtration combustion of porous metallic samples in a gas diluted by an inert component

Filtration combustion of porous metallic samples in a gas diluted by an inert component

Critical conditions of thermal explosion of a porous layer

Analysis of the Thermal Explosion in Systems Porous Reagent–Active Gas–Solid Product

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