The structure and radiation of an ethanol pool fire

Abstract

The structure of the flame above a burning 0.5 m diameter pool of ethanol has been examined. The average concentration of CO 2, CO, H 2O, and hydrocarbons, the mean and standard deviation of temperature, and the mean velocity are reported from the surface up to 1.5 diameters downstream. The local soot absorption coefficient has been found to be less than 0.7 m −1 everywhere in the fire using a fiber optic laser attenuation probe. Instantaneous temperatures measured simultaneously at 11 positions along the diameter show no correlation between fluctuations on the centerline and at the edge of the fire, and moderate correlation between thermocouple pairs located at similar radial positions across the fire. In all cases the cross-correlation is maximum where the time delay is zero for any given height. The temperature probability distribution and a measured dominant flickering frequency of 1.96 Hz are consistent with observations made in other moderate sized pool fires of various fuels. The radiative loss in the first 0.75 m is 19% of the 72.8 kW thermal input. Measurements of radiant intensity distributions from the fire are compared to values predicted from nonisothermal radiation models. When account is taken of the low frequency, large scale fluctuations in temperature, concentration, and soot absorption coefficient, predictions of intensity are in closer agreement with experiment than predictions from models based only upon time mean temperature and composition. The data reported here provide a comprehensive basis for evaluation of other fire and radiation models as well.