%0 Journal Article %A Moore, Jeffrey D. %A Risha, Grant %A Zhang, Baoqi %A Kuo, Kenneth K. %D 2007 %I Begell House %N 6 %P 691-712 %R 10.1615/IntJEnergeticMaterialsChemProp.v6.i6.30 %T ACOUSTIC EMISSION MEASUREMENTS FOR CHARACTERIZING HYDROCARBON/OXYGEN DIFFUSION FLAME BEHAVIOR %U https://www.dl.begellhouse.com/journals/17bbb47e377ce023,46ae61aa3e0cddf4,77f8586633c5aeba.html %V 6 %X An investigation was performed to characterize the behavior of a hydrocarbon/oxygen diffusion flame by acoustic emission measurements. Experiments were performed in a horizontally mounted, 2-D axisymmetric stainless steel chamber with a single shear coaxial injector and an adjustable graphite nozzle at the chamber exit for maintaining a constant chamber pressure. Methane gas flowed through the annular injector port while oxygen exited the center port. Ignition of the diffusion flame was achieved by a C2H6/O2 torch. Four acoustic transducers placed circumferentially around the diffusion flame at various locations were used in combination with a Pyrex viewing window to observe and classify the diffusion flame as either an anchored flame to the injector, a detached flame with small amplitudes of oscillation, or a near-blowout flame with large amplitudes of oscillation. Results showed that there was a noticeable difference in diffusion flame acoustic emission spectra based on flame stability behavior. Anchored diffusion flames showed no significant trace of acoustic emission at fuel flow rates below 0.65 g/s. Stable, small oscillating detached flames showed minimal amplitude acoustic levels, whereas near-blowout diffusion flames covered a wide range of acoustic frequencies. As the diffusion flame exhibited greater instability behavior, more frequency hits (a measure of the number of times an acoustic signal exceeded a preset threshold) at higher amplitudes were generated until eventual flame blowout occurred. Any increase in the (O/F)mass resulted in an increase in acoustic frequency amplitude and absolute energy. Narrower frequency ranges at higher amplitude values also accompanied this increase in (O/F)mass. %8 2007-11-01