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Modeling and control of combustion instabilities

Feedback between unsteady heat release and the acoustic field in a confined environment often results in the excitation of high amplitude oscillations called thermoacoustic instability.This phenomenon has been a particularly plaguing problem in the gas turbine industry for the last 20 years. In the worst case, machine components may suffer structural failure induced by the strong pressure oscillations. However, even if this is not the case, combustion instabilities restrict the operating conditions so that the optimum efficiency and emission levels cannot be achieved.

 

We apply various feedback control schemes based on different actuators and control algorithms. Results for the application of an adaptive control scheme in one of our combustor test-rigs is shown to the right. The amplitude of the fluctuating combustor pressure is reduced by more than an order of magnitude by the controller.

 

In analogy to annular combustion chambers, we investigate the unstable azimuthal modes in an annular Rijke tube. In this set-up, 12 heater grids mimic premixed flames and are connected to an annular resonator.

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