Investigation of Extinguishment by Thermal Agents Using Detailed Chemical Kinetic Modeling of Opposed Jet Diffusion Flames.
Investigation of Extinguishment by Thermal Agents Using
Detailed Chemical Kinetic Modeling of Opposed Jet
Diffusion Flames.
(948 K)
Pitts, W. M.; Blevins, L. G.
NISTIR 6588; November 2000.
U.S./Japan Government Cooperative Program on Natural
Resources (UJNR). Fire Research and Safety. 15th Joint
Panel Meeting. Volume 1. Proceedings. March 1-7, 2000,
San Antonio, TX, Bryner, S. L., Editor(s), 242-249 pp,
2000.
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Order number: PB2001-101517
Keywords:
fire safety; fire research; jet flames; diffusion
flames; extinguishment; thermal agents; reaction
kinetics
Abstract:
Thermal fire-fighting agents are being investigated as
potential replacements for halons which can no longer be
manufactured due to their deleterious effects on
stratospheric ozone. This work describes a detailed
chemical kinetic modeling study of methane planar
opposed jet laminar diffusion flames burning in air
diluted with various thermal agents. Extinction
conditions are characterized as a timction of agent
concentration. Comparison of the calculated results for
burning in nitrogen-diluted air with literature values
for the extinguishing concentration allows the
corresponding maximum flame temperature at
extinguishment to be estimated as 1550 K. By applying
this criterion, extinguishing concentrations are
calculated for argon, helium, carbon dioxide, and water
vapor. Calculated values are shown to be in good
agreement with measurements in cup burners using heptane
fuel. Surrogate agents having non physical behaviors
have been used to characterize particular aspects of
flame extinguishment by thermal agents. It is shown that
dilution effects result from passage of oxygen through
the flame front and that these effects should be
accounted for when estimating the amount of a particular
thermal agent required to extinguish a flame. By the use
of a surrogate agent which absorbs heat by unimolecular
reaction, it is demonstrated that the physical location
of the heat extraction relative to the flame front does
not modify the effectiveness of a thermal agent as long
as the agent is subsequently convected into the flame
zone.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899