Dynamics of an Acoustically Excited Swirl Flame
We present an experimental investigation of the dynamics of an acoustically excited swirl combustor. Simultaneous measurements were taken of the acoustic pressure, mean velocity, CH* and OH* radical chemiluminescence, and OH concentrations through planar laser induced fluorescence (PLIF) over a range of forcing frequencies, amplitudes and nozzle exit velocities. As the flame response grows linearly and monotonically with increasing forcing amplitude, the flame’s behavior becomes more complex at higher levels. The observed dynamics of the flame to some extent occur simultaneously, resulting from a combination of at least five flame/flow processes: (1) the oscillating velocity of the annular jet, oscillations in (2) position and (3) strength of the vortex breakdown bubble and separation bubble, (4) unsteady liftoff of the flame, and (5) an oscillating turbulent flame speed.
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