“Rumble” is a self-excited combustion instability, usually occurring at the start-up of aero-engines with fuel-spray atomizers at sub-idle and idle conditions, and exhibiting low limit frequencies in the range of . Entropy waves at the (nearly) choked combustor outlet are supposed to be the key feedback mechanism for the observed self-excited pressure oscillations. The experimental study presented here aims at clarifying the role of entropy waves in the occurrence of rumble. A generic air-blast atomizer with a design prone to self-excitation has been incorporated into a thermoacoustic combustor test rig with variable outlet conditions. The thermoacoustic response of the flame was characterized by recording the chemiluminescence, the dynamic pressures, the dynamic temperatures, and by applying PIV. The measurements have shown the occurrence of periodic hot spots traveling with the mean flow with considerable dispersion. Measurements have been conducted with an open-ended resonance tube in order to eliminate the impact of entropy waves on the mechanism of self-excitation. The oscillation obtained, comparable in amplitude and frequency, proved that self-excitation primarily depends on convective time delays of the droplets in the primary zone and thus on the atomization characteristics of the nozzle.
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April 2006
Technical Papers
Experimental Study on the Role of Entropy Waves in Low-Frequency Oscillations in a RQL Combustor
J. Eckstein,
J. Eckstein
Lehrstuhl für Thermodynamik,
Technische Universität München
, 85747 Garching, Germany
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E. Freitag,
E. Freitag
Lehrstuhl für Thermodynamik,
Technische Universität München
, 85747 Garching, Germany
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C. Hirsch,
C. Hirsch
Lehrstuhl für Thermodynamik,
Technische Universität München
, 85747 Garching, Germany
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T. Sattelmayer
T. Sattelmayer
Lehrstuhl für Thermodynamik,
Technische Universität München
, 85747 Garching, Germany
Search for other works by this author on:
J. Eckstein
Lehrstuhl für Thermodynamik,
Technische Universität München
, 85747 Garching, Germany
E. Freitag
Lehrstuhl für Thermodynamik,
Technische Universität München
, 85747 Garching, Germany
C. Hirsch
Lehrstuhl für Thermodynamik,
Technische Universität München
, 85747 Garching, Germany
T. Sattelmayer
Lehrstuhl für Thermodynamik,
Technische Universität München
, 85747 Garching, GermanyJ. Eng. Gas Turbines Power. Apr 2006, 128(2): 264-270 (7 pages)
Published Online: March 1, 2004
Article history
Received:
October 1, 2003
Revised:
March 1, 2004
Citation
Eckstein, J., Freitag, E., Hirsch, C., and Sattelmayer, T. (March 1, 2004). "Experimental Study on the Role of Entropy Waves in Low-Frequency Oscillations in a RQL Combustor." ASME. J. Eng. Gas Turbines Power. April 2006; 128(2): 264–270. https://doi.org/10.1115/1.2132379
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