Prediction of HF Formation During Suppression.
Prediction of HF Formation During Suppression.
(5704 K)
Linteris, G. T.; Gmurczyk, G. W.
NIST SP 890; Volume 2; Section 10; November 1995.
Fire Suppression System Performance of Alternative
Agents in Aircraft Engine and Dry Bay Laboratory
Simulations. Volume 2, Gann, R. G., Editor(s), 201-318
pp, 1995.
Available from:
National Technical Information Service
Order number: PB96-117783
Keywords:
fire suppression; aircraft engines; nacelle fires;
simulation; halon 1301; halon alternatives; fire
suppression; premixed flames; flame structure; burning
velocity; experiments; large scale fire tests
Abstract:
The acid gases hydrogen fluoride, hydrogen chloride, and
hydrogen bromide (HX, where X denotes a halogen), are
thought to be the most damaging and dangerous of the
potential decomposition products, and much study has
been devoted to determining the amounts of these
chemicals formed during fire suppression by CF3Br and
halon alternatives. While CF3Br is known to readily
decompose to form HF, HBr, and COF2 in laboratory
premixed and diffusion flames and in larger scale fires,
the amounts were not considered to be a major threat
compared to that of the fire itself. The alternative
agents have been found to produce significantly more
acid gas than CF3Br, and consequently, there exists a
need to understand and predict the mechanisms of
formation of acid gases in laboratory flames, and
ultimately, suppressed fires. The goal of this project
is to develop an ability to predict the quantity of HF
formed during suppression of aircraft fires. In order
to understand the formation rates of acid gases in dry
bay and engine nacelle fires it is necessary to examine
the thermodynamics and chemical kinetics relevant to the
formation of the acid gases as well as the effects of
the flow field and mixing on the chemistry. An engine
nacelle fire may be similar to a steady turbulent spray
diffusion flame, whereas a dry bay fire may resemble a
rapidly advancing turbulent premixed flame. Because
suppression of the dry bay fires occurs in a time of
about 100 ms, it is also necessary to consider transient
effects on the acid gas formation. The formation of
toxic and corrosive by-products in flames/fires
inhibited by halogenated hydrocarbons is controlled by
transport rates of the agent into the flame, chemical
kinetic rates, or equilibrium thermodynamics. These
factors are affected by the fuel type, local mixture
composition, inhibitor type and concentration, and the
characteristics of the flow field such as mixing rate,
strain rate, and stabilization mechanism in the case of
laboratory burner flames. The approach taken in the
present work is to examine the HF production in the
fire, for a range of conditions.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899