Evaluation of Active Suppression in Simulated Post-Collision Vehicle Fires.
Evaluation of Active Suppression in Simulated
Post-Collision Vehicle Fires.
NISTIR 6379; 175 p. November 2000.
Available from: National Technical Information Service
(NTIS), Technology Administration, U.S. Department of
Commerce, Springfield, VA 22161.
1-800-553-6847 or 703-605-6000;
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Order number: PB2001-102011
passenger vehicles; automobile fires; compartment fires;
experiments; postcrash fires; nozzles; fire suppression;
An investigation of the effectiveness of fire
suppressants in simulated post-collision vehicle fires
is presented. Two distinct fire scenarios were
considered. The first configuration was a simulated
engine compartment fire. The second configuration was a
simulated underbody fire. The configurations were
defined based on geometric and fire-related pammeters.
Experiments were performed using both laboratory test
devices and a mid-size passenger vehicle. A set of
criteria was constructed for selection of suppressants
for use in the suppression tests. The criteria were
based on information from the fire literature and
engineering judgement. Commercially available fire
suppressants and several emerging suppressants were
evaluated in terms of the criteria and a number of
representative suppressants were selected for testing.
Both traditional and emerging active fire suppressants
were tested. These included dry powders, inert
suppressants, compressed liquefied halogenated
compounds, and a number of unique devices. The
suppressants tested in the engine compartment
suppression experiments were HFC-125 (C2HF5), HFC-227ea
(C3HF7), ABC powder (NH4H2PO4, mono-ammonium phosphate),
BC powder (NaHCO3, sodium bicarbonate), a tubular
suppression system, solid propellant generators, and
aerosol generators. The suppressants tested in the
underbody fire suppression experiments were HFC-125, ABC
powder, BC powder, solid propellant generators, and
aerosol generators. A number of experimental protocols
were developed to appraise the feasibility of fire
suppression using the representative suppressants. The
apparatus in each of the experimental configurations
included a fire zone and a suppressant delivery system.
The experimental procedure in each of the four
configurations was essentially the same. A fire was
established and after a specified duration, a controlled
mass of suppressant was delivered to the fire zone.
Suppressant distribution was optimized through careful
nozzle selection, placement, and discharge duration.
After suppressant delivery, observation determined
whether the fire was suppressed or not suppressed. A
number of experiments were conducted to test the
importance of operating conditions on suppressant
effectiveness in the simulated vehicle fires. These
included geometrical factors and suppressant delivery
parameters. Long fuel trails extending beyond the
confines of the vehicle and environmental factors such
as wind were considered. The results showed that it is
highly improbable that an on-board fire suppression
system will be able to extinguish all engine compartment
and underbody fires. Many suppressant types were found
to be impractical for post-collision engine compartment
applications. The experiments have shown, however, that
under certain conditions, fire suppression is feasible.
A unique pyrotechnic device, the solid propellant
generator, was the most effective suppressant tested in
the full-scale engine compartment scenario. These
devices rapidly deliver a gas/particulate effluent.
Full-scale suppression experiments in the engine
compartment of an uncrashed stationary vehicle in the
absence of forced ventilation (radiator fan off) showed
that suppression of a 200 mL/min gasoline fire was
achievable with less than 500 g of the solid propellant
generator. Full-scale underbody experiments showed that
suppression of a (333 mL volume) gasoline pool fire was
achieved with less than 300 g of ABC and BC powder
suppressants when the fuel was located under the vehicle
footprint for low wind conditions. If a fuel puddle in
an underbody fire extended beyond the vehicle footprint
and if moderate to high winds were present, then the
powder suppression system failed to reliably extinguish