Active Stabilization of Thermoacoustic Oscillation
Combustion processes serve as important sources of energy for both power generation and for transport, ranging from large scale power stations to micro turbines and aeroplane engines. Lean premixed combustion offers a potential to reduce the emission levels, but suffers from instability problems which can be overcome by the use of active control. This thesis addresses the problem of actively controlling thermoacoustic instabilities in a laboratory test com- bustion chamber. Different strategies for actuation are discussed and evaluated experimentally. Relations to industrial relevance are taken into consideration, and a fuel actuator is developed and implemented. Experiments confirm the general view within the combustion control community that actuator design is a significant challenge and limitation for the success of active combustion control. The dynamics of the different configurations of the combustion chambers is modeled using both analytical methods and system identification methods. System identification shows the best potential to be transfered to more sophisticated combustion chambers. Successful damping of the combustion oscillations is shown with different control design methods. The most convincing results are obtained with a Kalman filter based LQR control design.
Control Engineering, subspace–based identification, fuel actuation, thermoacoustic instability, LQR, Active control
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Department of Automatic Control, Lund Institute of Technology, Lund University