Gas Generator Induced Flow and Its Effect on Fire Flame Extinction.
Gas Generator Induced Flow and Its Effect on Fire Flame
Joulain, P.; Torero, J. L.
NIST GCR 98-745; 48 p. April 1998.
Sponsor:National Institute of Standards and Technology,
Available from: National Technical Information Service
Order number: PB98-146129
gas generators; flame extinguishment; fire suppression;
test methods; solid propellants; flow fields; heat
transfer; ignition; velocity measurement; walls
A limiting factor to the development of new suppression
technology is the lack of appropriate screening methods.
Among the new technologies that are intended to replace
Halon 1301 are Solid Propellant Gas Generators (SPGG's),
or flame suppressing gas generators. SPGG's are a
spin-off from airbag technology and have demonstrated
their ability to suppress certain types of fire,
particularly aircraft engine nacelle and dry bay fires.
To date there is no adequate screening method for
SPGG's. The flow originating from burning a solid
propellant reduces the Damkohler number by decreasing
the residence time (high velocity flow of products) and
increasing the chemical time (by directly altering the
reactant concentrations, oxygen displacement effect).
If the Damkohler number decreases below a critical value
sudden extinction of the flame occurs. A facility that
will serve to assess the performance of SPGG's has to be
able to evaluate the combined effects of the gas
discharge. Several alternatives have been proposed for
an adequate flame and enclosure that will represent a
"worst case" scenario for extinction and subsequent
re-ignition. Among these alternatives is the
recirculation zone induced by either a bluff body, a
baffle, a backward facing step or a trench inside a wind
tunnel. These configurations provide a controlled
increase in the residence time, thus an increase in the
Damkohler number. This report describes a preliminary
evaluation of these configurations by means of a
literature search and some preliminary computations
using Large Eddy Simulation (LES) code developed at