Forced cocurrent smoldering combustion

Dosanjh, Sudip S.; Pagni, Patrick J.; Fernandez‐Pello, A. C.

doi:10.1016/0010-2180(87)90052-6

Cited by 101 publications

(64 citation statements)

References 7 publications

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“…The heat released by the smolder reaction is in turn partially transferred ahead of the reaction and partially lost to the surrounding environment. Under these conditions, the smolder propagation is determined by a balance between the heat released by the reaction, the energy required to heat the virgin foam and incoming air to the smolder temperature and the heat losses to the environment (Dosanjh et al 1987). The application of such an energy balance provides the following expression for the opposed smolder propagation-velocity:…”

Section: Analysis Of the Resultsmentioning

confidence: 99%

“…Smolder temperatures are obtained from thermocouple measurements, and the permeability of the char is obtained from the UIS. Theoretically, it is predicted that smolder propagation velocity depends linearly on the oxidizermass flux to the smolder front (Dosanjh et al 1987). Linear optimization to the experimental data thus provides the value of constant C 0 (Table 2).…”

Section: Oxidizer Mass Fluxmentioning

confidence: 99%

“…It is well established that smolder propagation is strongly dependent on the mass flux of oxidizer to the smolder front (Ohlemiller 1985, Dosanjh 1987. Gravity can induce complex buoyant flows through the porous material and as a result affect smolder propagation through a buoyantly induced oxidizer-mass flux .…”

Section: Introductionmentioning

confidence: 99%

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The Effect of Buoyancy on Opposed Smoldering

Bar-Ilan

Rein

Walther

et al. 2004

Combustion Science and Technology

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An experimental investigation on the effects of buoyancy on opposed flow smolder is presented. Tests were conducted on cylindrical samples of open-cell, unretarded polyurethane foams at a range of ambient pressures using the Microgravity Smoldering Combustion (MSC) experimental apparatus. The samples were tested in the opposed configuration, in which the flow of oxidizer is induced in the opposite direction as the propagation of the smolder front. These data were compared with opposed forced-flow tests conducted aboard STS-69, STS-77, and STS-105 and their ground based simulations. Thermal measurements were made of the smolder reaction to obtain peak reaction temperatures and smolder velocities as a function of the ambient pressure in the MSC chamber. The smolder reaction was also observed using high-frequency ultrasound pulses as part of the Ultrasound Imaging System (UIS). The UIS measurements were used as a second means of providing smolder propagation velocities as well as to obtain permeabilities of the reacting samples. Results of forced flow testing in normal gravity were compared to results in microgravity at a range of ambient pressures and forced flows. Results indicate that a critical oxidizer mass flux of roughly 0.5 to 0.8 g/m 2 s is required in normal gravity for a self-sustaining propagation in this configuration. In microgravity tests, self-sustained smolder propagation was observed at a significantly lower oxidizer mass flux of 0.30 g/m 2 s. Analysis suggests that the removal of buoyancyinduced heat losses in microgravity allows for self-sustained propagation at an oxidizer mass flux below the critical value observed in normal-gravity testing. Normal-gravity tests also show that the smolder propagation velocity is linearly dependent on the total oxidizer mass flux in an oxidizer-limited regime. Pressure effects on the chemical kinetics of a smolder reaction are inferred by comparison of normalgravity and microgravity tests and believed to be only weakly dependent on pressure (~P 1/3 ).

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Section: Analysis Of the Resultsmentioning

confidence: 99%

Section: Oxidizer Mass Fluxmentioning

confidence: 99%

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The Effect of Buoyancy on Opposed Smoldering

Bar-Ilan

Rein

Walther

et al. 2004

Combustion Science and Technology

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“…A one-dimensional model of smolder propagation is used to obtain an explicit expression for the smolder velocity and to correlate the experimental results. The model used in this study is based on the analysis of Dosanjh et al [7] but extended to include the radial heat losses to the environment.…”

Section: Simplified Theoretical Analysismentioning

confidence: 99%

Forced forward smoldering experiments in microgravity

Bar-Ilan

Rein

Fernandez‐Pello

et al. 2004

Experimental Thermal and Fluid Science

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Results from two forward forced-flow smolder tests on polyurethane foam using air as oxidizer conducted aboard the NASA Space Shuttle (STS-105 and STS-108 missions) are presented in this work. The two tests provide the only presently available forward smolder data in microgravity. A complimentary series of ground-based tests were also conducted to determine, by comparison with the microgravity data, the effect of gravity on the forward smolder propagation. The objective of the study is to provide a better understanding of the controlling mechanisms of smolder for the purpose of control and prevention, both in normaland microgravity. The data consists of temperature histories from thermocouples placed at various axial locations along the fuel sample centerline, and of permeability histories obtained from ultrasonic transducer pairs also located at various axial positions in the fuel sample. A comparison of t he tests conducted in normal-and microgravity indicates that smolder propagation velocities are higher in microgravity than in normal gravity, and that there is a greater tendency for a transition to flame in microgravity than in normal gravity. This is due primarily to the reduced heat losses in the microgravity environment, leading to increased char oxidation. This observation is confirmed through a simplified one-dimensional model of the forward smolder propagation. This finding has important implications from the point of view of fire safety in a space-based environment, since smolder can often occur in the forward mode and potentially lead to a smolder-initiated fire.

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“…This is due to a negligible role of diffusive transfer on distances of the order of the reaction zone width. More recent applications of the method in the field of packed bed combustion are given by Dosanjh et al [8], Fateni and Kaviany [9], and Escobedo and Viljoen [10]. A packed bed can be considered as a combination of the diffusion governed and the convection governed case.…”

Section: Introductionmentioning

confidence: 99%

Theoretical analysis of the propagation of a reaction front in a packed bed

Gort

Brouwers

2001

Combustion and Flame

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The propagation of a reaction front through a packed bed is analyzed theoretically. The chemical reaction rate is represented by Arrhenius temperature kinetics with external transfer limitation and general power law dependency on both gaseous and solid reactant concentrations. Analogous to so-called "Activation Energy Asymptotics" developed for premixed laminar flames, the largeness of the activation energy of the chemical reaction is exploited to derive asymptotic solutions from the three governing differential equations pertaining to transport of heat, of solid reactant, and of gaseous reactant, making use of the method of matched asymptotic expansions. Two regions are distinguished, i.e., an outer region or preheat zone and an inner region or reaction zone. In the preheat zone, the reaction terms can be neglected as compared to the convective and diffusive terms. In the reaction zone, the diffusion of heat is dominating over the convective heat transport mechanism and balances the heat of reaction. In accordance with the magnitudes taken for the Lewis numbers, for solid and gaseous reactants convective transports are dominating and submitting diffusive transports in the reaction zone, respectively. Solutions in closed form are presented for governing variables including reaction front velocity whereby previously published results appear as special cases. The solutions provide direct insight into underlying physical processes and enable the effects of important parameters to be quantified analytically. © 2001 by The Combustion Institute

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Forced cocurrent smoldering combustion

Cited by 101 publications

References 7 publications

The Effect of Buoyancy on Opposed Smoldering

The Effect of Buoyancy on Opposed Smoldering

Forced forward smoldering experiments in microgravity

Theoretical analysis of the propagation of a reaction front in a packed bed

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