Simon J. Illingworth

Adaptive Feedback Control of Combustion Instability in Annular Combustors

An adaptive feedback control strategy for axisymmetric annular combustors is developed. The controller uses the pressure perturbation at a fixed axial location downstream of the flame—provided by multiple pressure measurements around the combustor circumference—as the control input. Control is achieved via modulation of the fuel flow rate at multiple fuel valve locations. The controller is implemented in a computational low-order thermoacoustic network model of an annular combustor. Time domain simulations show that the controller stabilizes both longitudinal and circumferential unstable modes (including the simultaneous control of multiple unstable modes), even from within the limit cycle. By changing the flame transfer function with time, it is shown that control is retained following a large change in the combustor operating conditions.

Advances in feedback control of the Rijke tube thermoacoustic instability

This paper considers methods for the feedback control of thermoacoustic oscillations. Two distinct approaches to the problem are considered. The first is robust model-based control, which involves two stages: finding a model of the system, and designing a controller based on that model. The focus is on using model reduction techniques to find a low-order, balanced model of the Rijke tube which, despite having few degrees of freedom, is useful for feedback control design purposes. The second approach uses adaptive (or self-tuning) control, which does not require a model of the system, but instead requires that it meets some general properties. The focus here is on reducing how much must be known a priori about the plant. Specifically, an adaptive controller is considered which does not require knowledge of the sign of the plants high-frequency gain, and this is done by employing a Nussbaum gain. The controllers are successfully applied in experiments on a Rijke tube. Both controllers completely eliminate ...

Adaptive Control of Combustion Instabilities in Annular Combustors

An adaptive control algorithm based on Lyapunov’s direct method has been implemented in a low-order thermoacoustic network model of an axisymmetric annular combustor. The pressure perturbation at a fixed axial location downstream of the flame — provided by multiple pressure measurements around the combustor circumference — acts as the control input. Control is achieved via modulation of the fuel flow rate at multiple fuel valve locations. New expressions for the controller’s adaptation rates are derived by specifying the desired control settling time: these adaptation rates are functions of known parameters only. Time domain simulations show that the controller successfully stabilises both longitudinal and circumferential modes (including the simultaneous control of multiple unstable modes), even from within the limit cycle. The adaptive controller successfully retains control following a large change in the combustor operating conditions.© 2008 ASME