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Measurements and Predictions of the Velocity Field Induced by Pool Fires.


pdf icon Measurements and Predictions of the Velocity Field Induced by Pool Fires. (450 K)
Zhou, X. C.; Gore, J. P.; Baum, H. R.

NISTIR 6030;

Combustion Institute/Central and Western States (USA) and Combustion Institute/Mexican National Section and American Flame Research Committee. Combustion Fundamentals and Applications. Joint Technical Meeting. Proceedings. April 23-26, 1995, San Antonio, TX, Gore, J. P., Editor, 578-583 pp, 1995 AND U.S./Japan Government Cooperative Program on Natural Resources (UJNR). Fire Research and Safety. 13th Joint Panel Meeting. Volume 1. March 13-20, 1996, Gaithersburg, MD, Beall, K. A., Editor, 201-207 pp, 1997, 1995.

Available from:

National Technical Information Service (NTIS), Technology Administration, U.S. Department of Commerce, Springfield, VA 22161.
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Order number: PB97-184204

Keywords:

combustion; pool fires; velocity; entrainment; fluid flow; equations; flow fields; axial flow

Abstract:

Due to the importance of the air entrainment rate in determining fire size, radiation properties, and soot production, various techniques have been applied to its measurement. The measurement techniques can be roughly classified into four categories. The first category involves monitoring of the air flow rate needed to meet the entrainment requirement of the fire while maintaining ambient pressure. The second category is to sample combustion products and solve a set of global mass balance equations to obtain equivalence ratio and hence the entrainment rate. The third category involves measurement of the velocity and the temperature profiles inside the flame and subsequent calculation of the axial flow rate by either direct radial integration or integrations of resulting curve fits. One common disadvantage of the above three experimental methods is that information about the details of the entrainment flow field itself is not obtained. The fourth measurement category addresses the problem by obtaining detailed measurements of the flow induced by the fire. The mean and the fluctuating velocity field around a 7.1 cm tolune pool fire was mapped with a Laser Doppler Velocimeter (LDV). It was found that the value of the entrainment rate depends strongly on its definition implied by the first three measurement categories. In addition to the experimental work, a few studies involving analyses and computations of the entrainment flow field have also been reported. Taylor calculated the air flow outside a thermal jet originating from a point source with the assumption that the entrainment rate is proportional to the jet velocity. Utilizing published experimental data, Baum and McCaffrey applied a kinematic approach to predict the flow pattern induced by unconfined fires. The present paper reports application and extension of their methodology to the prediction of the entrainment flow field around 7.1 cm and 15 cm pool fires burning heptane and toluene.