Laminar Burning Velocity under Quenching Conditions for Propane-Air and Ethylene-Air Flames

摘要

The aim of this study was to examine the influence of walls on laminar burning velocity for flames propagating in propane-air and ethylene-air mixtures near the quenching limit. Experiments were carried out in a narrow wedge-shaped channel and recorded by a camera. Results of measurements of laminar burning velocity under quenching conditions were compared with laminar burning velocity obtained for adiabatic and unstretched flames. It was found that the measured laminar burning velocity is lower than adiabatic laminar burning velocity for lean mixtures. For flames propagating in rich mixtures its value can equal the adiabatic laminar burning velocity. This phenomenon can be explained by the Lewis number effect (Le < 1). Additionally, quenching distance for flames propagating in ethylene-air mixtures was determined. These results were used to determine the critical Peclet number. Values of the number for ethylene-air flames are between Pe = 30.2÷ 36.2.