Factors Affecting the Control of Unstable Combustors

Active control systems for the attenuation of pressure oscillations in unstable combustors have been under development by a wide variety of investigators. Whereas many of these applications have been in simplified, bench-scale combustors, some significant efforts have been made in realistic systems...

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Bibliographic Details
Published in:Journal of propulsion and power 2003-09, Vol.19 (5), p.811-821
Main Authors: Cohen, Jeffrey M, Banaszuk, Andrzej
Format: Article
Language:English
Subjects:
Bandwidths
Combustion chambers
Control algorithms
Controllers
Design
Engineers
Gas turbine engines
Physics
Sensors
Signal processing
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Summary:Active control systems for the attenuation of pressure oscillations in unstable combustors have been under development by a wide variety of investigators. Whereas many of these applications have been in simplified, bench-scale combustors, some significant efforts have been made in realistic systems including full-scale gas turbine engines. Results from these efforts, although generally positive, have been varied. As the technology has matured, the understanding of the factors that currently limit its capability has improved. Some of these factors and how they may be quantified through experiments, models, or combined approaches are addressed. The application focus was lean, premixed combustors for industrial gas turbines. Both gas- and liquid-fueled systems were considered. In particular, the effects of actuation system time delay and actuated fuel mixing are examined, and the fundamental limits of control in systems with time delay are considered. The results indicate that the mixing of the actuated fuel with the remainder of the premixed reactants is significant in determining control authority. The effects of system time delays are shown to result in a peak splitting phenomenon, which limits the degree to which pressure oscillations can be reduced. A further examination of the fundamental limits of control demonstrates that it is not possible to arbitrarily decrease the level of pressure oscillations using linear controllers. The factors that limit the achievable reduction level are the time delay, the combustor damping, and the actuator bandwidth. (Author)
ISSN:0748-4658
1533-3876
DOI:10.2514/2.6196