Flame Growth Around a Spherical Solid Fuel in Low Speed Forced Flow in Microgravity

To further our understanding of flammability and quenching limit of thick solid fuels, a microgravity experiment Growth and Extinction Limits is to be conducted aboard the International Space Station with the emphasis to quantify the effect of the flame heat loss to the thermally thick solid interio...

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Bibliographic Details
Published in:Fire technology 2020, Vol.56 (1), p.5-32
Main Authors: Endo, Makoto, T’ien, James S., Ferkul, Paul V., Olson, Sandra L., Johnston, Michael C.
Format: Article
Language:English
Subjects:
Burning
Characterization and Evaluation of Materials
Civil Engineering
Classical Mechanics
Combustion
Convective flow
Engineering
Fire protection
Flammability
Flammability limits
Heat
Heat flux
Heat loss
International Space Station
Low speed
Mathematical models
Microgravity
Physics
Polymethylmethacrylate
Quenching
Solid fuels
Spacecraft
Surface temperature
Temperature gradients
Vapor phases
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Summary:To further our understanding of flammability and quenching limit of thick solid fuels, a microgravity experiment Growth and Extinction Limits is to be conducted aboard the International Space Station with the emphasis to quantify the effect of the flame heat loss to the thermally thick solid interior by directly measuring the sub-surface temperature gradient. A precursor microgravity combustion experiment in the Burning and Suppression of Solids (BASS) project was used to assess the experimental operation and validate the accompanied numerical model. The present paper reports the development of the flame model over a solid sphere in low-speed pure convective flow (less than 100 cm/s). Computed time sequence result of one of the BASS conditions is presented. The combination of gas phase reaction rate, solid internal temperature and surface heat flux distribution reveals the effect of solid in-depth heat-up on flame growth. The experimental observations agree with the trend predicted by the model. For thick solids, flame quenching limit in low speed flow is not only a function of flow speed but also the degree of solid interior heat-up. Flammability limit can have profound implication to the current spacecraft fire protection protocol that requires turning-off of circulation flow in case of detected fire. The present and the follow-up studies will provide more quantitative estimate of the low velocity-quenching limit with heated samples. For the Polymethylmethacrylate spheres investigated, the limit is lower than 2 cm/s in air.
ISSN:0015-2684
1572-8099
DOI:10.1007/s10694-019-00848-2