Suppression of Premixed Flames by Water Mist in Microgravity: Findings From the MIST Experiment on STS-107.
Suppression of Premixed Flames by Water Mist in
Microgravity: Findings From the MIST Experiment on
STS-107.
(435 K)
Abbud-Madrid, A.; McKinnon, J. T.; Amon, F. K.; Gokoglu,
S.
Halon Options Technical Working Conference, 14th.
Proceedings. HOTWC 2004. Sponsored by: 3M Specialty
Materials, Boeing, Chemical Development Studies, Inc.,
DuPont Fire Extinguishants, Halon Alternative Research
Corp., Hughes Associates, Inc., Kidde-Fenwal, Inc.,
Sandia National Laboratories, SEVO Systems, Next
Generation Fire Suppression Technology Program. May
4-6, 2004, Albuquerque, NM, 1-14 pp, 2004.
Keywords:
halon alternatives; halons; fire suppression; water
mist; premixed flames; microgravity; space shuttle;
flame fronts; burning velocity; flame propagation
Abstract:
A preliminary analysis of the results obtained from the
Water-Mist Fire Suppression experiment (Mist) that flew
on the STS-107 mission of the Space Shuttle is
presented. The objective of Mist is to study the
effects of droplet size distribution and water
concentration on the burning velocity of a propagating
premixed propane-air flame. Changes of the laminar
flame speed and shape are used as the measure of flame
suppression efficacy. Thirty-two tests were conducted
with four different fuel-air equivalence ratios (0.6,
0.7, 1.0, and 1.3), two droplet size distributions
(count median diameters of 20 and 30 mm), and water
loadings (measured in water mass fraction) ranging from
0.0 to 0.1. The injection of water mist in microgravity
resulted in a uniformly distributed and quiescent
droplet cloud. Lean flames with a parabolic flame front
monotonically slowed down to a steady-state velocity
through the mist cloud. Small droplet size
distributions are consistently more effective than
larger ones in suppressing the propagation of lean
flames with the effect of droplet size diminishing at
the lowest burning velocities. Increased water loading
always results in slower flames, with lean flames more
easily suppressed than richer ones. Flame extinction
was obtained for lean flames with water mass fractions
under 0.05.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899