Characteristics of flame tip oscillation of a bunsen type premixed flame with burner rotation

Flame tip oscillation of a Bunsen type premixed flame with burner rotation is experimentally investigated. Methane/air mixture and Propane/air mixture are used to take into account the effect of Lewis number. Cross sectional images of unburnt mixture are visualized by a laser tomographic technique. Time variations of flame tip location, flame curvature and thermodiffusive zone thickness are measured from visualized images. As the flame tip is oscillated, the flame curvature and the preheat zone thickness along the centerline are varied periodically. Furthermore, it is shown that values of the flame curvature at the same location of the flame tip are different whether the flame tip moves upward or downward. In other words, the flame tip oscillates with a hysteresis. This suggests that the instantaneous burning intensity at the flame tip varies periodically with the hysteresis, which results in the periodical oscillation.