Open-loop control methodologies were used to suppress symmetric and helical thermoacoustic instabilities in an experimental low-emission swirl-stabilized gas-turbine combustor. The controllers were based on fuel (or equivalence ratio) modulations in the main premixed combustion (premixed fuel injection (PMI)) or, alternatively, in the secondary pilot fuel. PMI included symmetric and asymmetric fuel injection. The symmetric instability mode responded to symmetric excitation only when the two frequencies matched. The helical fuel injection affected the symmetric mode only at frequencies that were much higher than that of the instability mode. The asymmetric excitation required more power to obtain the same amount of reduction as that required by symmetric excitation. Unlike the symmetric excitation, which destabilized the combustion when the modulation amplitude was excessive, the asymmetric excitation yielded additional suppression as the modulation level increased. The emissions were reduced to a greater extent by the asymmetric modulation. The second part of the investigation dealt with the control of low frequency symmetric instability and high frequency helical instability by the secondary fuel injection in a pilot flame. Adding a continuous flow of fuel into the pilot flame controlled both instabilities. However, modulating the fuel injection significantly decreased the amount of necessary fuel. The reduced secondary fuel resulted in a reduced heat generation by the pilot diffusion flame and therefore yielded lower emissions. The secondary fuel pulsation frequency was chosen to match the time scales typical to the central flow recirculation zone, which stabilizes the flame in the burner. Suppression of the symmetric mode pressure oscillations by up to was recorded. High frequency instabilities were suppressed by , and CO emissions reduced by using low frequency modulations with 10% duty cycle.
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e-mail: oliver.paschereit@tu-berlin.de
e-mail: ephraim.gutmark@uc.edu
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January 2008
Research Papers
Combustion Instability and Emission Control by Pulsating Fuel Injection
Christian Oliver Paschereit,
Christian Oliver Paschereit
Chair of Fluid Dynamics
Hermann-Föttinger-Institute,
e-mail: oliver.paschereit@tu-berlin.de
Technical University Berlin
, 10623 Berlin, Germany
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Ephraim Gutmark
Ephraim Gutmark
Aerospace Engineering and Engineering Mechanics Department,
e-mail: ephraim.gutmark@uc.edu
University of Cincinnati
, Cincinnati, OH 45221-0070
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Christian Oliver Paschereit
Chair of Fluid Dynamics
Hermann-Föttinger-Institute,
Technical University Berlin
, 10623 Berlin, Germanye-mail: oliver.paschereit@tu-berlin.de
Ephraim Gutmark
Aerospace Engineering and Engineering Mechanics Department,
University of Cincinnati
, Cincinnati, OH 45221-0070e-mail: ephraim.gutmark@uc.edu
J. Turbomach. Jan 2008, 130(1): 011012 (8 pages)
Published Online: January 25, 2008
Article history
Received:
July 21, 2005
Revised:
January 28, 2007
Published:
January 25, 2008
Citation
Paschereit, C. O., and Gutmark, E. (January 25, 2008). "Combustion Instability and Emission Control by Pulsating Fuel Injection." ASME. J. Turbomach. January 2008; 130(1): 011012. https://doi.org/10.1115/1.2749292
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