Concurrent Flow Flame Spread Study.
Concurrent Flow Flame Spread Study.
(3753 K)
Loh, H. T.
NIST GCR 92-603; 161 p. March 1992.
Sponsor:
National Institute of Standards and Technology,
Gaithersburg, MD
Available from:
National Technical Information Service
(NTIS), Technology Administration, U.S. Department of
Commerce, Springfield, VA 22161.
Telephone:
1-800-553-6847 or 703-605-6000;
Fax: 703-605-6900; Rush
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Website:
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Order number: PB94-156866
Keywords:
flame spread; oxygen concentration; paper; plastics;
polymethyl methacrylate
Abstract:
An experimental study has been performed of the spread
of flames over the surface of thick PMMA and thin filter
paper sheets in a forced gaseous flow of varied oxygen
concentration moving in the direction of flame spread.
It is found that the rate of spread of the PMMA
pyrolysis front is time independent, linearly dependent
on the gas flow velocity and approximately square power
dependent on the oxygen concentration of the gas. The
experimental data with thin filter paper sheets shows
that the flame spread rate is independent of the flow
velocity for forced flow conditions and linearly
dependent on the oxygen concentration of the flow. In
both experiments, it was found that the flame spread
rate data can be correlated in terms of parameters
deduced from heat transfer considerations only. This
indicates that heat transfer from the flame to the
condensed fuel is the primary mechanism controlling the
spread of flame. Finite rate chemical kinetic effects
have apparently a small influence on the flame spread
process itself. Analytical and numerical methods were
also employed to study theoretically the flame spread
process over thermally thick fuel and the influence on
the flow field behavior in the presence of a flame. It
is found that an analytical model based on a
quasi-steady analysis and the flame sheet approximation
predicts a square power law dependence of the flame
spread rate on the flow oxygen concentration and a
linerar dependence on the flow velocity. The correct
and encouraging qualitative descriptions of the flow
structure and surface fluxes in the region downstream
from the pyrolysis front.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899