Turbulent Flame Spread on Vertical Corner Walls.
Turbulent Flame Spread on Vertical Corner Walls.
(8531 K)
Qian, C.
NIST GCR 95-669; 161 p. April 1995.
Sponsor:
National Institute of Standards and Technology,
Gaithersburg, MD
Available from:
National Technical Information Service
Order number: PB96-114764
Keywords:
flame spread; turbulent flames; walls; corners; fire
research; experiments; fire science; fire spread; heat
transfer; polymethyl methacrylate; fire growth; flow
visualization
Abstract:
Fire science is a rapidly growing research area. The
motivation of fire research is to reduce fire loss and
the cost of fire protection. Fire research is devoted
to better understanding and prediction of fires. Flame
spread is one of the most important phenomena in fire
study because the spread rate is the measure of fire
growth. In reality, flames are nearly all turbulent due
to the large scale of building fires. Turbulent flame
spread along vertical corner walls has the fastest
spread rate among building fires. Because of the
complex geometrical configuration and strong unsteady
properties, the conventional instrumentations encounter
great limitations. Therefore, there is relatively
little data directly bearing on corner fire spreads. In
this study, attention is given to the corner fire spread
mechanism and the flame spread behavior. Infrared (IR)
radiometry and image analysis techniques have been
developed in this study to measure flame spread rate on
large areas with high resolution and frequency. In
addition to the flame spread measurement, the
fire-induced flow was studied by flow visualization, and
the total incident heat flux to the wall surface from
the flame was measured by Gardon-type heat flux meters.
Based on these experimental studies, a thermal model for
corner fire spread has been successfully developed. The
burning wall temperature measurement through flames
using an IR imaging technique has been studied both
theoretically and experimentally. For most materials,
the constant emissivity 1.0 can be used to determine the
pyrolysis front temperature due to soot deposition on
the surface. The flame effect consists of band
emissions mostly from excited CO2 and H2O and a
continuous emission from soot particles. The effects of
the band emissions can be eliminated by a bandpass
filter (10.6 + 0.5 mm), and the soot particle effects
can be neglected (epsilon < 0.03) for wall fires due to
the small optical depth. Two-dimensional flame spread
rate and the area of pyrolysis zone can be obtained by
the IR imaging technique.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899