Effects of low ambient pressure on the flame characteristics of ethanol−gasoline blended pool fire

Abstract

The flame characteristics of Ethanol−Gasoline pool fire with different blend ratios were experimentally studied in a large−scale pressure−controlled compartment with ambient pressure of 40 kPa, 61 kPa, 80 kPa, and 101 kPa. The flame height, centerline temperature, and radiant heat flux were measured. The flame height increases notably with decreasing ambient pressure, but the flame temperature (intermittent and plume regions) slightly increases. With increasing ethanol ratio, the flame height and temperature decrease monotonously under large ambient pressure, but show a non−monotonic variation with a peak value at low ambient pressure and ethanol ratio of 10 %∼20 %. Heskestad’s flame height and temperature correlations were not suitable for blends pool fire under low ambient pressure. The new modified model for flame height correlation with ambient pressure and combustion heat of blends, and flame temperature correlation with flame height, fuel property parameter, and ambient pressure were developed with a better prediction. The addition of ethanol and decrease of ambient pressure led to the reduction of radiation loss from flame, and the non−monotonic variation with a peak value also occurs with increasing ethanol ratio at relatively large ambient pressure and ethanol ratio of 20 %. A new modified model based on the classical solid flame model was also developed to predict the radiative fraction, considering the ambient pressure, stoichiometric ratio, and the ratio of the combustion heat to the vaporization heat.