Determination of the spread rate in opposed-flow flame spread over thick solid fuels in the thermal regime

Bhattacharjee, Subrata; West, Jeff; Altenkirch, Robert A.

doi:10.1016/s0082-0784(96)80369-9

Cited by 41 publications

(22 citation statements)

References 12 publications

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“…In agreement with [27], transport coefficients for the gas phase as well as the gas density value have been evaluated at the reference temperature (T f + T ∞ )/2, where T f is the flame temperature that here follows the adiabatic flame expression [12] …”

Section: Results and Comparison To Experimentsmentioning

confidence: 99%

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Analytical expressions for the flame front speed in the downward combustion of thin solid fuels and comparison to experiments

Pujol

Comas

2011

Phys. Rev. E

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We derive analytical expressions for the propagation speed of downward combustion fronts of thin solid fuels with a background flow initially at rest. The classical combustion model for thin solid fuels that consists of five coupled reaction-convection-diffusion equations is here reduced into a single equation with the gas temperature as the single variable. For doing so we apply a two-zone combustion model that divides the system into a preheating region and a pyrolyzing region. The speed of the combustion front is obtained after matching the temperature and its derivative at the location that separates both regions. We also derive a simplified version of this analytical expression expected to be valid for a wide range of cases. Flame front velocities predicted by our analytical expressions agree well with experimental data found in the literature for a large variety of cases and substantially improve the results obtained from a previous well-known analytical expression.

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Section: Results and Comparison To Experimentsmentioning

confidence: 99%

“…(25) into (26) we obtain Section IV includes a discussion on the implications of using a = 1 in Eq. (27).…”

Section: Combustion Modelmentioning

confidence: 99%

Analytical expressions for the flame front speed in the downward combustion of thin solid fuels and comparison to experiments

Pujol

Comas

2011

Phys. Rev. E

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“…Based on these results, Fernán-dez-Pello and Williams [3] developed a theory relaxing some of the assumptions made by De Ris. Wichman et al [4] and Wichman and Williams [5] considered a given uniform shear flow; their results, as those obtained by numerical analysis by Bhattacharje et al [6], showed the importance of the fluid flow in the determination of the flame propagation velocity.…”

Section: Introductionmentioning

confidence: 85%

Flame spread over solid fuels in opposite natural convection

Fernández-Tarrazo

Liñán

2002

Proceedings of the Combustion Institute

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The downward spread of a flame along the surface of a thermally thick solid fuel inclined at an angle to the vertical is investigated. The flow and the heat transfer in the flame front region that controls the spread rate are described numerically using a single-step Arrhenius model for the gas-phase reaction. The effect of the finite rate kinetics is discussed in terms of a Damkö hler number defined as the square of the ratio of the speed of the planar stoichiometric flame of the fuel vapor to the characteristic speed induced by buoyancy in the flame front region. The computed spread rate is lower when the burning surface faces downward than when it faces upward due to the influence of the pressure gradient parallel to the surface.

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“…Note that the effect of the sample width on flame spread rate measurements has been extensively observed for thin fuels (Altenkirch et al 1980;Shih and T'ien 2003;Zhang and Yu 2011). For opposed flame spread, attempts have been made to correlate the spread rate with the Damköhler number, and a Damköhler number correlation has been successful for both moderate-velocity flow (thermal) regime and high-velocity (kinetic) regime (Fernandez-Pello et al 1981;Bhattacharjee et al 1996). In Fig.…”

Section: Flame Spread Ratesmentioning

confidence: 97%

“…Flame spread over a thermally-thick solid fuel in oxidizer flow has been studied extensively during the past decades (e.g., de Ris 1969;Fernandez-Pello et al 1981;Bhattacharjee et al 1996). The phenomena result from the inherently complex interaction of heat and mass transport processes, and the chemical reaction in both gas and condensed phases.…”

Section: Introductionmentioning

confidence: 99%

Flame Spread and Extinction Over a Thick Solid Fuel in Low-Velocity Opposed and Concurrent Flows

Zhu

Wang

2015

Microgravity Sci. Technol.

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Flame spread and extinction phenomena over a thick PMMA in purely opposed and concurrent flows are investigated by conducting systematical experiments in a narrow channel apparatus. The present tests focus on lowvelocity flow regime and hence complement experimental data previously reported for high and moderate velocity regimes. In the flow velocity range tested, the opposed flame is found to spread much faster than the concurrent flame at a given flow velocity. The measured spread rates for opposed and concurrent flames can be correlated by corresponding theoretical models of flame spread, indicating that existing models capture the main mechanisms controlling the flame spread. In low-velocity gas flows, however, the experimental results are observed to deviate from theoretical predictions. This may be attributed to the neglect of radiative heat loss in the theoretical models, whereas radiation becomes important for low-intensity flame spread. Flammability limits using oxygen concentration and flow velocity as coordinates are presented for both opposed and concurrent flame spread configurations. It is found that concurrent spread has a wider flammable range than opposed case. Beyond the flammability boundary of opposed spread, there is an additional flammable area for concurrent spread, where the spreading flame is sustainable in concurrent mode

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Determination of the spread rate in opposed-flow flame spread over thick solid fuels in the thermal regime

Cited by 41 publications

References 12 publications

Analytical expressions for the flame front speed in the downward combustion of thin solid fuels and comparison to experiments

Analytical expressions for the flame front speed in the downward combustion of thin solid fuels and comparison to experiments

Flame spread over solid fuels in opposite natural convection

Flame Spread and Extinction Over a Thick Solid Fuel in Low-Velocity Opposed and Concurrent Flows

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