Suppression of High Speed Flames and Quasi-Detonations.
Suppression of High Speed Flames and Quasi-Detonations.
(3475 K)
Gmurczyk, G. W.; Grosshandler, W. L.
NIST SP 890; Volume 1; Section 2; November 1995.
Fire Suppression System Performance of Alternative
Agents in Aircraft Engine and Dry Bay Laboratory
Simulations. Volume 1. Section 2, Gann, R. G.,
Editor(s), 9-75 pp, 1995.
Available from:
National Technical Information Service
Order number: PB96-117775
Keywords:
fire suppression; aircraft engines; nacelle fires;
simulation; detonation; effectiveness; deflagration;
experiments; combustion; ethane; propane; fuel/air
mixtures; halon 1301; halon alternatives
Abstract:
A dry bay is a normally confined space adjacent to a
fuel tank in which a combustible mixture and an ignition
source could co-exist following penetration by an
anti-aircraft projectile. They vary considerably in
volume, typically being in the range of 0.2 to 3.0 m3.
They are located in the wings and fuselage, and their
shape is most often irregular. Aspect ratios up to 10:1
are not uncommon. The bays may or may not be
ventilated, and are usually cluttered with electronic,
hydraulic and mechanical components. Compared to the
events leading to engine nacelle fire suppression, the
required timing is two orders-of-magnitude faster for
dry bay protection. The previous study using a
deflagration/detonation tube was concerned with
establishing a comprehensive experimental program to
screen the performance of over a dozen agents. The
experiments were designed to cover the range of
conditions that might occur in a dry bay. Although
actual measurements of fuel concentrations in a dry bay
during live-fire testing have never been made, one could
envision a worst-case situation in which the fuel is
vaporized and partially premixed with the air just prior
to ignition, producing a rapidly moving turbulent flame.
If the suppressing agent were not well mixed and the dry
bay geometry were conductive, the turbulent flame could
accelerate, generating a shock wave ahead of it and
transitioning to a detonation before encountering the
agent. Ethene was chosen as the fuel in the previous
study because it was known to detonate easier than many
other hydrocarbons. This provided the most severe test
for all the agents under conditions that were not
duplicated in any of the other bench-scale studies. The
specific objectives of the current research project are
the following: (a) To determine the effectiveness of
HFC-125, relative to FC-218, in suppressing high speed
turbulent propane/air flames using the
detonation/deflagration tube apparatus; (b) To determine
the conditions in the detonation/deflagration tube
(equivalence ratio, tube geomtery) which lead to
excessive pressure build-up during suppression by
HFC-125 of propane/air mixtures initially at room
temperature and pressure; (c) To determine the
effectiveness of CF3I, relative to FC-218, in
suppressing high speed turbulent propane/air flames
using the detonation/deflagration tube apparatus; (d) To
recommend a ranking of the three agents for full-scale
dry bay applications based upon the current and previous
suppression experiments.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899