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Study of Entrainment and Flow Patterns in Pool Fires Using Particle Imaging Velocimetry. Final Report.


pdf icon Study of Entrainment and Flow Patterns in Pool Fires Using Particle Imaging Velocimetry. Final Report. (11896 K)
Zhou, X. C.; Gore, J. P.

NIST GCR 97-706; Final Report; 229 p. March 1996.

Sponsor:

National Institute of Standards and Technology, Gaithersburg, MD

Available from:

National Technical Information Service
Order number: PB97-165070

Keywords:

pool fires; entrainment; flow fields; laser doppler velocimetry; methanol; toluene; heptane; flame velocity; equations; heat release rate; air entrainment

Abstract:

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.