Radiative Energy Blockage in Large Pool Fires

Abstract

During the combustion process, a thin, cool, fuel-rich core region is established near the fuel surface. In large-scale fires, where radiation is the dominant mechanism for energy feedback to the fuel surface, the attenuation of the radiant flux by the core gases significantly affects the mass consumption rate. A simple flame-radiation model is proposed to account for this blockage effect. It consists of two discrete, homogeneous, isothermal regions: a high temperature, luminous flame, and a cool, fuel-rich core. The thin core layer (about 7 percent of the flame height) has a surprisingly significant impact on the radiant feedback, as it attenuates the radiant flux to the surface by 25 to 35 percent. The simplified model is able to predict, with great accuracy, the mass consumption rate and total radiative power output of PMMA pool fires without rigorous specification of the temperature and concentration distributions within the flame.