Fluid Mechanical Instabilities of an Acoustically Excited, Turbulent Jet Flame
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This paper describes investigations and analysis of the evolution of the flame brush thickness of acoustically excited, lean, turbulent premixed flames. Two sets of experiments were conducted with a piloted, conical Bunsen flame and a swirl stabilized, annular flame. Phased locked particle image velocimetry (PIV) and OH planar laser induced fluorescence (PLIF) were used to measure flow velocities, track the evolution of the flame, and visualize the flow and flame dynamics over a frequency and amplitude sweep. The results show that the flame brush thickness grew in a monotonic style for the unforced case, while the flame brush thickness grew in a step-like function under acoustic excitation. The velocity field revealed the locations of the peak vorticity was not at the same locations as the peak velocities. The results imply that acoustic excitation to a turbulent flame plays a significant role in the flame's global heat release response and that flame stretch may play a significant role in the evolution of the flame brush thickness.