The physical and chemical action of fire suppressants

Sheinson, Ronald S.; Penner‐Hahn, James E.; Indritz, Doren

doi:10.1016/0379-7112(89)90015-5

Cited by 127 publications

(67 citation statements)

References 7 publications

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“…For propane in a cup burner, Trees et al [5] found the value of X* to be 0.32 for N 2 , 0.41 for Ar, and 0.039 for CF 3 Br. Others have found similar results [29]. effectiveness of the SPGG hybrid significantly exceeds the model predictions.…”

Section: Data Correlationsupporting

confidence: 69%

Transient application, recirculating pool fire, agent effectiveness screen:

Grosshandler¹,

Hamins²,

McGrattan³

et al. 2001

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NISTIR 6733ii EXECUTIVE SUMMARY * Because of its many positive attributes, halon 1301, or trifluorobromomethane (CF 3 Br), has been used as a fire extinguishing agent in many applications including aircraft, ships, and specialized structures. Due to its high ozone depletion potential, however, world-wide production was halted in 1994. In the search for a long-range replacement, novel types of extinguishing agents and delivery mechanisms are under development. To gauge the suitability of a replacement agent, methods are needed to evaluate the material's suppression effectiveness under conditions that relate to field applications.In this study, a laboratory-scale facility has been developed to screen the suppression effectiveness of agents that are delivered in a transient fashion such as solid propellant gas generators. The transient application, recirculating pool fire (TARPF) agent effectiveness screen features a propane fire stabilized behind an obstruction, which is known to be a highly challenging suppression configuration. The character of the flame and the impact of the air flow, fuel flow, obstruction geometry, and rate of agent addition on the amount of material needed for suppression are evaluated for N 2 , CF 3 Br, and a solid propellant gas generator (SPGG). The importance of the injection process on the flow field and the transport of the agent downstream is examined, and a simple mixing model is used to explain the observed trend of decreasing suppressant mole fraction with increasing injection duration, even for agents as different as CF 3 Br and N 2 . Direct numerical simulation of the suppression event is shown to successfully predict the quantity and rate of N 2 required to extinguish the flame based upon a published global reaction rate for premixed propane/air flame propagation. Important Findings:• The minimum mole fraction of agent for suppression, normalized by the cup burner value, correlates with [1 -exp(-∆ t/ τ )] -1 , where ∆ t is the injection time interval and τ characterizes the mixing time behind the obstacle in the flow.• The general character of the flame and its extinction by a thermal gaseous agent is captured by a direct numerical simulation of the flow based upon single -step chemistry, and numerical experiments have corroborated the simple correlation of the experimental data for N 2 .• The measured difference between the decrease in agent storage bottle pressure and the arrival of the agent at the fire highlight the importance of determining the agent concentration locally and the difficulty in relating changes in bottle pressure to actual mixing conditions. • For the first time, both compressed and solid-propellant generated gases can be compared side by side, and the effect on performance of different formulations, particle loadings and burning rates for various SPGG designs can be unambiguously discriminated.• When the temperature of a hot surface downstream of the pool is above 800 o C, the flame, following suppression, will reignite and stabilize on the hot surface. At ...

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Section: Data Correlationsupporting

confidence: 69%

Transient application, recirculating pool fire, agent effectiveness screen:

Grosshandler¹,

Hamins²,

McGrattan³

et al. 2001

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“…Due to the practical importance of HFP in fire protection, as well as its somewhat lower suppression efficiency than Halon 1301 [2,3], it is desirable to understand this compound's chemical behavior in flame environments. Of particular importance is the origin and magnitude of suppression due to fluorine chemistry, as opposed to physical effects of the agent's addition to the flame.…”

Section: Introductionmentioning

confidence: 99%

Intermediate species profiles in low-pressure methane/oxygen flames inhibited by 2-H heptafluoropropane: comparison of experimental data with kinetic modeling

Williams

espÉrance

Fleming

2000

Combustion and Flame

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Experimental profiles of the intermediate species H, OH, CH, CF, CF 2 , and CHF are obtained in a 10 torr premixed flat flame of methane/oxygen in a 1:2 molar ratio, inhibited by a 4% mole fraction of 2-H heptafluoropropane (HFP, CF 3 CHFCF 3 ). These data are compared to calculations using a recently published kinetic mechanism describing the consumption of this fire suppression agent. The profiles in the flame inhibited by HFP are compared to previously published data for flames containing CHF 3 and CH 2 F 2 under the same conditions of stoichiometry and flux of fluorine atoms. The species profiles relative to the flames containing the fluoromethanes are accurately predicted and atmospheric pressure flame speeds are fairly well predicted by the kinetic mechanism. Under equal fluorine loadings, profiles of temperature and of H and OH mole fraction are virtually identical between the flames containing HFP and CHF 3 . The flame inhibited by HFP, however, has approximately twice as much CH* emission as the flame containing CHF 3 . The kinetic model predicts that thermal decomposition, rather than H atom abstraction, is the primary destruction mechanism for HFP under the conditions studied.

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“…Their experiments show that the extinction concentration is insensitive to the air flow velocity. Sheinson et al [36] performed cup-burner experiments on the extinction of diffusion flames formed over n-heptane liquid pool by different diluents, including nitrogen, introduced into the air co-flow of about 4 cm/sec. They reported 29.4 mass % (within 3% accuracy) nitrogen in the air feed is needed to extinguish both n-heptane and 2-propanol liquid pool flames.…”

Section: Resultsmentioning

confidence: 99%

Extinction Dynamics of a Co-flow Diffusion Flame by Very Small Water Droplets Injected into the Air Stream

Ananth¹,

Mowrey²

2008

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Standard Form 298 (Rev. 8-98)Prescribed by ANSI Std. Z39.18Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Computations are performed to examine the effectiveness of mono-disperse water droplets in extinguishing a co-flow, propane diffusion flame by injecting the droplets into the air stream. The calculations show that the droplets entrained into the reaction kernel at the flame base are crucial for extinction. The reaction kernel detaches from the burner rim and blows-off when the droplet concentration is increased to a critical value (extinction concentration). At the critical value, the maximum chain-branching reaction (H2+O=OH+H) rate in the reaction kernel was found to be reduced by a factor of 5 in our computations. A large decrease in the reaction rate indicates that the maximum heat generations rate and Damkholer number are too low to sustain the flame, and cause the flame blow-off. Large drops are more effective than small drops, and the extinction concentration of water increases from 10.5% to 15% by mass as the size is reduced from 32 to 4 micro m. As the droplet size is increased further (>32 micro m), the trend will reverse as the evaporation rates get too small despite increased penetration of flame core by the drops. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) SPONSOR / MONITOR'S ACRONYM(S) 9. SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) SPONSOR / MONITOR'S REPORT NUMBER(S) 28-07-2008Memorandum Report

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The physical and chemical action of fire suppressants

Cited by 127 publications

References 7 publications

Transient application, recirculating pool fire, agent effectiveness screen:

Transient application, recirculating pool fire, agent effectiveness screen:

Intermediate species profiles in low-pressure methane/oxygen flames inhibited by 2-H heptafluoropropane: comparison of experimental data with kinetic modeling

Extinction Dynamics of a Co-flow Diffusion Flame by Very Small Water Droplets Injected into the Air Stream

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