Flammability characteristics of the rod-stabilized laminar premixed flame

A premixed flame can be stabilized by an axially mounted rod introduced into the gas flow, creating an inverted, partially inverted, or regular (Bunsen) flame. Such a setup has been used in the present study to obtain experimentally the characteristic regions of flame stability for low Reynolds numbers (3600) of a butane/air flame. The results confirm three different shapes of the stable flame: a regular (Bunsen) type for very fuel-rich mixtures and inverted and partially inverted types for stoichiometric and fuel-lean mixtures, respectively. At specific regions, either inverted or partially inverted flames can exist, primarily in dependence on axial distance and radial direction of the ignition source. The blow-off limits show that the convex shape of the inverted flame represents less interaction with the surrounding air, thus enabling the burner to operate at very fuel-lean mixtures. The flashback region has an elongated unstable area, where the flame slowly travels upstream due to reduced quenching effect, which is caused by heat conduction to the rod from the flame.Department of Mechanical Engineerin