Response of Triple Flame to Acoustic Oscillations

Abstract

The flame curvature and the lift-off height of a triple flame under acoustic oscillations are investigated. The multi-slot burner, which can make uniform streamwise flow velocity and stabilize the triple flame two-dimensionally is employed. The triple flame is formed at the anti-node of velocity oscillations. The flame curvature and the lift-off height of the triple flame are measured from images that are taken by a high speed camera. The fuel concentration gradient of the mixing layer which flows into the flame surface with acoustic oscillations is calculated by using the model of the meandering mixing layer. As a result, the flame curvature changes periodically and its period of change corresponds with that of acoustic oscillations approximately. When the triple flame moves in the direction of the air flow, the flame curvature increases. When the triple flame moves in the direction of the mixture flow, the flame curvature decreases. It is estimated that the fuel concentration gradient changes in the half-period of acoustic oscillations. However, the flame curvature changes in the same period of acoustic oscillations.