Buoyant plumes of large-scale pool fires

Abstract

A series of large-scale pool fire tests were conducted to investigate the variation of plume gas temperature and velocity. Three pool diameters: 1.219 m, 1.737 m and 2.438 m, were selected; four fuels with drastically different heat release rates were employed. In each test, measurements were made of plume gas temperatures and velocities and weight loss of the fuel pool. The measured plume temperature profiles at several elevations were fitted with Gaussian distributions in order to determine plume centerline position and centerline values of gas temperatures and velocities. The plume convective heat flux was then determined from the fitted profiles of plume temperatures and velocities. The plume centerline temperature followed the 2/3 power of the convective heat flux, Q c , and the −5/3 power of the pulme height with respect to the virtual source location, z-z o , down to the level where intermittent flames were found; the centerline gas velocity varied as the 1/3 power of Q c and −1/3 power of z-z o . The virtual source locations were found to be related to the flame heights. For large values of the ratio of flame height versus pool diameter, the distance from the flame tip to the virtual source is proportional to the 2/5 power of the convective heat flux and the virtual source location correlates well with a parameter 10 sed for flame correlation. For small flame-height to pool-diameter ratios, in several tests, the virtual source locations were below the pool surface; however, the virtual source moved upward as the pool diameter increased or the convective heat flux per unit pool surface increased.