Adaptive Combustion Instability Control with Saturation: Theory and Validation

The control of a class of combustion systems, susceptible to damage from self-excited combustion oscillations, is considered. The controller injects some fuel unsteadily into the burning region, thereby altering the heat release, in response to an input signal detecting the oscillation. An adaptive control design, called self-tuning regulator (STR), has recently been developed, which attempts to meet the apparently contradictory requirements of relying as little as possible on a particular combustion model while providing some guarantee that the controller will cause no harm. This paper focuses on an extension of the STR design, when, as a result of stringent emission requirements and to the danger of flame extension, the amount of fuel used for control is limited in amplitude. A Lyapunov stability analysis is used to prove the stability of the modified STR when the saturation constraint is imposed. Simulation and experimental results show that in the presence of a saturation constraint the self-excited oscillations are damped more rapidly with the modified STR than with the original STR.