A review of physics and correlations of pool fire behaviour in wind and future challenges

A series of measurements designed to investigate the heat feedback in pool fires burning liquid fuels are reported. Such measurements are essential for the development and validation of detailed models which predict the burning rate of liquid hydrocarbons and solid polymers. The radial variation of the local radiative and local net heat flux incident on the surface of 0.30 m diameter pool fires were measured. A water-cooled, nitrogen purged, narrow view-angle gauge was developed to measure the radiative flux incident on the fuel surface. Measurements of the mass burning rate in a burner composed of annular rings was used to estimate the local heat feedback. A number of different fuels were studied, yielding flames with a wide range of heat release rates and luminosities. Consideration of the heat balance for a control volume enclosing the liquid PPOI indicated that radiation was an important component of the heat feedback for non-luminous fires and a dominant component in luminous fires.

Heat Feedback to the Fuel Surface in Pool Fires

A mathematical model of a turbulent diffusion buoyant flame based on a number of simplifying assumptions is presented. The model predicts the general characteristics of a free-burning fire in both the region where combustion is occurring and the hot gas plume formed above the combustion section. The solution yields the mass-flow rate as a function of height which can be directly related to the excess air. It was found that the height at which 400% excess air has been entrained corresponds to the visible flame height according to data taken in our laboratory as well as that presented by a number of other workers.

Prediction of the Height of Turbulent Diffusion Buoyant Flames

Pool fires – An empirical correlation

Average centreline temperatures of a buoyant pool fire obtained by image processing of video recordings

The rates of diffusive burning of liquid methanol, chosen as a fuel which produces a nonluminous flame, were measured in special concentric vessels having three compartments as well as in the usual single laboratory vessels The experimental results obtained include the interesting observation that the burning rate is much greater at the vessel rime (next to the flame base) than near the vessel center, and that the total burning rate in the compartments of a concentric vessel is equal to that in a single vessel of the same size These data are discussed in the light of burning-rate theories presented independently by Spalding and by Hottel, and an attempt has been made to extend the latter's theory by introducing empirical local heat-transfer coefficients The equation proposed by the authors explains successfully all the results of the present study Thus, it appears that Hottel's theory can be applied not only to the turbulent luminous combustion of liquid fuels, but also to nonluminous combustion under condistions of laminar flow

K. Akita

Papers

Heat transfer in small pools and rates of burning of liquid methanol