Downward Smolder Of Polyurethane Foam

Torero, José L.; Fernandez‐Pello, A. C.; Kitano, Michio

doi:10.3801/iafss.fss.4-409

Cited by 8 publications

(5 citation statements)

References 19 publications

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“…Consistent with the findings of Torero et al [32,33], thermally assisted opposed flow smolder (downward) has a larger spread rate (0.08 mm/s) than forward (upward) smolder (0.07 mm/s). This indicates that the major effect of buoyancy on quiescent thermally supported smolder is to introduce oxidizer, hence larger heat release, to the reaction zone.…”

Section: Quiescent Testssupporting

confidence: 80%

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Space shuttle based microgravity smoldering combustion experiments

Walther

Fernandez‐Pello

Urban

1999

Combustion and Flame

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Results from four microgravity smoldering combustion experiments conducted aboard the NASA Space Shuttle are presented in this work. The experiments are part of the NASA funded Microgravity Smoldering Combustion (MSC) research program, aimed to study the smolder characteristics of porous combustible materials in a microgravity environment. 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 normal-and microgravity. The microgravity smolder experiments reported here have been conducted to investigate the propagation of smolder through a polyurethane foam sample under both diffusion driven and opposed forced flow driven smoldering. The present experiments, although limited, are unique in that they provide the only available information about smolder combustion in microgravity in sample sizes large enough to allow the self-propagation of the smolder reaction throughout the sample length. Two quiescent tests at ambient oxygen concentrations of 35% and 40% and two opposed forced flow tests with air as oxidizer, were conducted aboard the NASA Space Shuttle (STS-69 and STS-77 missions).The MSC data are compared with normal-gravity data to determine the effect of gravity on smolder, and are used to verify present theoretical models of smolder combustion. It is found that for the present test conditions, the microgravity opposed flow smolder reaction temperatures, propagation velocities, toxic compound production and reaction extent lie between those of normal-gravity upward and downward tests. Thermogravimetric analysis shows little effect of gravity on the kinetics of the smolder process in these cases. Neither of the two quiescent, microgravity cases resulted in self-sustained smolder propagation, while the normal-gravity downward cases propagated vigorously. The difference in these results shows that gravity has a significant effect on smolder combustion, at least for the sample size tested. Correlation of the forced flow smolder velocity data with a heat transfer based model, indicates that simplified heat transfer models of smolder propagation can effectively describe vigorous smolder, away from limiting conditions such as extinction and flaming.

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Section: Quiescent Testssupporting

confidence: 80%

“…These results are due to the different characteristics of the smolder process for downward (opposed) and upward (forward) propagation [32,33]. Temperature profiles along the foam centerline for the 40% O 2 case are presented in Fig.…”

Section: Quiescent Testsmentioning

confidence: 99%

Space shuttle based microgravity smoldering combustion experiments

Walther

Fernandez‐Pello

Urban

1999

Combustion and Flame

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“…Oxidizer is forced into the test section through a diffuser section to provide uniformity of the flow throughout the test section. Flow rate and oxygen concentration are During the ignition phase of the tests, the oxidizer flow velocity (0.1 mm/s) is chosen to simulate the conditions observed during natural convection smolder ignition [23,24]. For forward flow smolder, the forced oxidizer velocity (3.0 mm/s) during the propagation phase of the test is chosen to be high enough such that the smolder reaction had the characteristics of forward smolder [23].…”

Section: Methodsmentioning

confidence: 99%

Smolder ignition of polyurethane foam: effect of oxygen concentration

Walther¹,

Anthenien²,

Fernandez‐Pello³

2000

Fire Safety Journal

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Experiments have been conducted to study the ignition of both forward and opposed smolder of a high void fraction, flexible, polyurethane foam in a forced oxidizer flow. Tests are conducted in a small scale, vertically oriented, combustion chamber with supporting instrumentation. An electrically heated Nichrome wire heater placed between two porous ceramic disks, one of which is in complete contact with the foam surface, is used to supply the necessary power to ignite and sustain a smolder reaction. The gaseous oxidizer, metered via mass flow controllers, is forced through the foam and heater. A constant power is applied to the igniter for a given period of time and the resulting smolder is monitored to determine if smolder is sustained without the assistance of the heater, in which case smolder ignition is considered achieved. Reaction zone temperature and smolder propagation velocities are obtained from the temperature histories of thermocouples embedded at predetermined positions in the foam with junctions placed along the fuel centerline. Tests are conducted with oxygen mass fractions ranging from 0.109 to 1.0 at a velocity of 0.1 mm/s during the ignition period, and 0.7 or 3.0 mm/s during the self-sustained propagation period. The results show a well defined smolder ignition regime primarily determined by two parameters: igniter heat flux, and the time the igniter is powered. These two parameters determine a minimum igniter/foam temperature, and a minimum depth of smolder propagation (char), which are conditions required for ignition to occur. The former is needed to establish a strong smolder reaction, and the latter to reduce heat losses from the incipient smolder reaction to the surrounding environment. The ignition regime is shifted to shorter times for a given igniter heat flux with increasing oxygen mass fraction. A model based on concepts similar to those developed to describe the ignition of solid fuels has been developed that describes well the experimental ignition results.3

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“…2(b) is similar to the opposed flame spread in Fig. 4(d) [28,98], which will be explored in this section.…”

Section: Smoldering Spread Inside Porous Mediamentioning

confidence: 63%