title: Effect of vorticity flip-over on the premixed flame structure: Experimental observation of type-I inflection flames.
abstract: Premixed flames propagating in horizontal tubes are observed to take on a convex shape towards the fresh mixture, which is commonly explained as a buoyancy effect. A recent rigorous analysis has shown, on the contrary, that this process is driven by the balance of vorticity generated by a curved flame front with the baroclinic vorticity, and predicted existence of a regime in which the leading edge of the flame front is concave. We report experimental realization of this regime. Our experiments on ethane and n-butane mixtures with air show that flames with an inflection point on the front are regularly produced in lean mixtures, provided that a sufficiently weak ignition is used. The observed flame shape perfectly agrees with that theoretically predicted.
authors.affiliation: Institute Pprime, CNRS - UPR 3346, Poitiers, France.
authors.forename: Hazem
authors.initials: H
authors.lastname: El-Rabii
authors.affiliation: Moscow State University, Moscow, Russian Federation.
authors.forename: Kirill A
authors.initials: KA
authors.lastname: Kazakov