Simultaneous high repetition rate measurement of flame surface and flow field in an acoustically excited swirling flame with time-resolved two-dimensional temperature field measurement

In this study, a simple swirling flame burner with a loudspeaker to provide upstream external forcing is constructed. Time-resolved sequence of simultaneous PIV/PLIF measurement showing the development of acoustic-flame interaction. The time-resolved flame temperature was measured using a two-dimensional phase-locked direct absorption technique. Two type of flame configurations were studied. For the anchored V-shape swirling flame, the combined temperature field, flow-field and flame front variation shows that the periodic flame temperature variations can be roughly divided into an inception stage and a mixing stage. The temperature fluctuations are mainly produced near the nozzle exit and dissipates downstream of the flame at the flow speed of the burnt gas. For the lifted U-shape swirling flame, we studied the effect of equivalence ratio and external acoustic modulation on the transition from V-shape flames to U-shape flames. The time-resolved lift-off and reattachment dynamics of the swirling flame during intermittent transitions between U-shape state and the V-shape state are captured, which mark the onset of IRZ detachment and PVC formation. The detailed understanding of flow-flame interaction in swirling flame configurations reported here is important for the study of unsteady turbulent swirling flames and turbine engines combustion.