Ignition of porous materials by gas filtration (unsteady downstream filtration)

Seplyarskii, B. S.; Gordopolova, I. S.

doi:10.1007/bf02674385

Cited by 1 publication

(3 citation statements)

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“…(2) We assume a single temperature for both gas and solid, i.e., local temperature equilibrium between the two phases. Although this assumption is widely used, see for example [3,4,10,[12][13][14][15][16][17][18] and references therein, we stress that one must generally allow for finite rates of inter-phase heat transfer. For this reason we shall drop this assumption in Sect.…”

Section: Model and Equations For A Single Temperaturementioning

confidence: 99%

“…The results of that section will allow us to draw conclusions about the effectiveness of the PH model. (3) As in [3,4,[10][11][12][13][14][15][16][17][18] we neglect structural defects of the porous solid in our model. This allows us to focus on the effects of the gas movement, gas production and inter-phase heat transfer that leads up to the ignition event, after which structural deformation could occur.…”

Section: Model and Equations For A Single Temperaturementioning

confidence: 99%

“…Other related applications of FC include important processes such as smouldering and self-propagating high-temperature synthesis (see [10] and [11] for a review). Although much of the literature is concerned with the propagation of such waves, initiation problems have also received attention, [12][13][14]. In FC, gas is assumed to be forced through the material, effectively leading to a constant temperature at one end.…”

Section: Introductionmentioning

confidence: 99%

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Gas-phase and heat-exchange effects on the ignition of high- and low-exothermicity porous solids subject to constant heating

Shah

Brindley

McIntosh³

et al. 2006

J Eng Math

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This article investigates the ignition of low-exothermicity reactive porous solids exposed to a maintained source of heat (hotspot), without oxygen limitation. The gas flow within the solid, particularly in response to pressure gradients (Darcy's law), is accounted for. Numerical experiments related to the ignition of low-exothermicity porous materials are presented. Gas and solid products of reaction are included. The first stage of the paper examines the (pseudo-homogeneous) assumption of a single temperature for both phases, amounting to an infinite rate of heat exchange between the two. Isolating the effect of gas production and flow in this manner, the effect of each on the ignition time is studied. In such cases, ignition is conveniently defined by the birth of a self-sustained combustion wave. It is found that gas production decreases the ignition time, compared to equivalent systems in which the gas-dynamic problem is effectively neglected. The reason for this is quite simple; the smaller heat capacity of the gas allows the overall temperature to attain a higher value in a similar time, and so speeds up the ignition process. Next, numerical results using a two-temperature (heterogeneous) model, allowing for local heat exchange between the phases, are presented. The pseudo-homogeneous results are recovered in the limit of infinite heat exchange. For a finite value of heat exchange, the ignition time is lower when compared to the single-temperature limit, decreasing as the rate of heat exchange decreases. However, the decrease is only mild, of the order of a few percent, indicating that the pseudo-homogeneous model is in fact a rather good approximation, at least for a constant heat-exchange rate. The relationships between the ignition time and a number of physico-chemical parameters of the system are also investigated.

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