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Extinguishment of Combustible Porous Solids by Water Droplets. Annual Progress Report.


pdf icon Extinguishment of Combustible Porous Solids by Water Droplets. Annual Progress Report. (2195 K)
Atreya, A.

NIST GCR 93-621; Annual Progress Report; 28 p. April 1993.

Sponsor:

National Institute of Standards and Technology, Gaithersburg, MD

Available from:

National Technical Information Service
Order number: PB93-198893

Keywords:

porous solids; extinguishment; diffusion flames; fire extinguishing; fire suppression; flame spread; droplets; water; infrared photography; polymethyl methacrylate

Abstract:

This report presents a brief summary of the previous research on fire suppression with the objective to provide guidance for the present work. Reasons for the adopted methodology are summarized and the apparatus developed for the study is described. Finally, some results for PMMA are presented along with conclusions and future work. Two experimental configurations are chosen for this study: (1) Stagnation-point flow apparatus: which allows studying both the gas-phase and the condensed-phase suppression actions and enables transient chemical measurements in the exhaust gas. These measurements are used to study the suppression mechanisms and quantify the suppression effectiveness. (2) Counterflow diffusion flame apparatus: which allows detailed flame structure measurements but is limited to studying gas-phase suppression mechanisms (chemical and/or physical). Initally, the work is done using the stagnation-point flow apparatus with water as the extinguishing agent and PMMA as the burning solid to establish a standard for comparison of suppression effectiveness of various agents. Our experimental results for PMMA show that there are two simultaneous effects as a result of water application: (1) chemical enhancement of the burning rate (which is important only when the flames are sooty; Note: most fires are sooty), and (2) physical cooling of the solid via water evaporation. The chemical effect has not been previously noted because water is usually applied in much greater quantities than needed and in this domain the physical cooling effect dominates. Thus, future work is directed toward better understanding the suppression mechanisms.