Study of Entrainment and Flow Patterns in Pool Fires Using Particle Imaging Velocimetry. Final Report.
Study of Entrainment and Flow Patterns in Pool Fires
Using Particle Imaging Velocimetry. Final Report.
Zhou, X. C.; Gore, J. P.
NIST GCR 97-706; Final Report; 229 p. March 1996.
Sponsor:National Institute of Standards and Technology,
Available from: National Technical Information Service
Order number: PB97-165070
pool fires; entrainment; flow fields; laser doppler
velocimetry; methanol; toluene; heptane; flame velocity;
equations; heat release rate; air entrainment
An experimental and theoretical study of the flow fields
induced by pool fires was completed. Pool burners of
three diameters, namely 7.1 cm, 15 cm and 30 cm, were
used. For the two smaller pool burners, the effects of
a 51 cm sheet metal floor around the pool at the surface
were also studied. Three fuels (methanol, toluene and
heptane) were burned as representatives of alcohols,
paraffins and aromatics. The velocity field induced by
the 7.1 cm toluene pool fire with the metal floor was
mapped with a Laser Doppler Velocimetry (LDV) system.
The transient characteristics of the velocities were
studied by analyzing their discrete Probability Density
Functions (PDFs) and their Power Spectral Densities
(PSDs). The instantaneous fire induced flow fields
around all the pool fires were studied using Particle
Imaging Velocimetry (PIV). The PIV data for the 7.1 cm
toluene pool fire were confirmed using the LDV data.
Following a favorable comparison, PIV, which is a faster
technique, was used for the remaining fires. The mean
flow patterns were obtained by averaging 100
instantaneous velocity vector plots. Air entrainment
rates were calculated based on the mean velocity fields
and normalized using the fire Froude number, which was
shown to be the appropriate nondimensional number using
the governing equations for the buoyant diffusion
flames. A theoretical model was utilized to predict the
entrainment flow field with the volumetric heat release
rate distribution and vorticity distribution assumed to
be known a priori.