The temperature dependence of the laminar burning velocity of ethanol flames

Abstract

The Heat Flux method was extended for the first time towards liquid fuels and used to determine burning velocities under conditions when the net heat loss from the flame to the burner is zero. Non-stretched flames were stabilized on a perforated plate burner at 1atm. Uncertainties of the measurements were analyzed and assessed experimentally. The overall accuracy of the burning velocities was estimated to be better than ±1cm/s. Excellent reproducibility of the experiments over an extended period of time was demonstrated. Measurements of the adiabatic burning velocity of ethanol+air flames in the range of initial mixture temperatures from 298 to 358K are presented. Experimental results are in a good agreement with the recent literature data obtained in constant volume bombs. Both the ethanol combustion mechanism of Saxena and Williams and the Konnov mechanism significantly over-predict ethanol laminar burning velocities in lean and near-stoichiometric mixtures. The effects of initial temperature on the adiabatic laminar burning velocities of ethanol were interpreted using the correlation SL=SL0 (T/T0)α. Particular attention was paid to the variation of the power exponent α with equivalence ratio at atmospheric pressure. Experimental data and proposed empirical expressions for α as a function of equivalence ratio were summarized. They were compared with the predictions of detailed kinetic models. The existence of a minimum in α in the slightly rich mixtures is demonstrated experimentally and confirmed computationally.