Fire Propagation in Concurrent Flows. Annual Progress Report. September 1, 1991-August 31, 1992.
Fire Propagation in Concurrent Flows. Annual Progress
Report. September 1, 1991-August 31, 1992.
Fernandez-Pello, A. C.
Annual Progress Report; 17 p. 1993.
Sponsor:National Institute of Standards and Technology,
fire spread; gas flow; oxygen concentration;
experiments; turbulent flow; laminar flow
A research program is being conducted to study the
mechanisms controlling the spread of fire in oxidizing
gas flows moving in the direction of flame propagation.
During this reporting period research has been conducted
to study concurrent flame spread under varied oxygen
concentrations, with emphasis on vitiated conditions.
Experiments have been completed with laminar flow, and
are currently underway in turbulent flow. The
parameters varied in the experiments are the oxidizer
flow velocity, turbulence intensity and oxygen
concentration, and the geometrical orientation (floor
and ceiling). Their effect on the flame spread process
is studied by measuring the rate of flame spread, flame
length, surface heat flux, products of combustion and
soot. Experiments are conducted with thick PMMA sheets
as fuel and mixtures of oxygen nitrogen as oxidizer.
The results of the experiments show that at low oxygen
concentrations, the flame spread rate increases almost
linearly as the flow velocity or oxygen concentration is
increased. For high oxygen concentrations, the
dependence of the spread rate on the oxygen
concentration follows a second power law. By comparing
the floor and ceiling results it is found that buoyancy
has two opposite effects, one is enhancing the heat
transfer to the surface by reducing the flame stand-off
distance and the other reducing the chemical reaction
completeness by intensifying the flame quenching at the
wall. The overall buoyancy effect on the flame spread
and mass burning processes depends on the flow