A thermal characterization of the flame quenching behavior of different fuels

Abstract

The study of flame quenching for different fuels is of great scientific importance to estimate the efficiency of a combustion process inside an enclosed environment. Therefore, laminar head-on flame quenching was studied in a closed vessel for several fuels via heat flux measurements. The investigated fuels were methane, propane, propene, ethanol, ethene, n-butane, and 2-butanone at different pressures (0.94–3.59 bar). First, a literature formulation for the derivation of the quenching distance by the maximum heat flux was reviewed for its applicability to methane and propane. It was found that the formulation showed an incorrect trend between methane and propane compared to previous optical investigations. Subsequently, an alternative method was developed that could correctly reflect the quenching trends of methane and propane. This method is based on characteristic points of the flame temperature profile of a freely propagating flame and the measured wall heat flux. The theoretical considerations of this method were based on a transient 1-D CFD simulation with the KICK solver. Afterward, the method was applied to the measured heat flux data. The results indicated that most of the investigated fuels have a fairly similar quenching behavior, whereas methane has exceptionally large and ethene particularly small quenching distances. In addition, it was shown that lean combustion has the most drastic impact on the quenching distance, e.g. an increase of 79% at 3.1 bar for propane at an equivalence ratio of 0.7 compared to the stoichiometric case. Finally, a linear correlation between the reciprocal flame power and the quenching distance was found, which can be used to estimate the quenching behavior of fuels.