Adaptive control of combustion instability with on-line system identification

In this study, an adaptive control system is developed for suppressing pres sure oscillations in a generic combustor, where the unsteady flowfield asso ciated with the combustion instability is described by a nonlinear inhomoge neous wave equation, Control action is achieved by injecting auxiliary liqu id fuel, and is modeled as an array of time-delayed combustion sources. The adaptive controller employs on-line system identification (SID) for robust ness with respect to transient operating states, modeling uncertainties, ex ternal disturbances, and additional modes of instability that may arise in the course of control. Comparisons are made between the adaptive controller and a previously developed proportional-plus-integral (PI) controller, in terms of performance (degree of oscillation suppression, and speed with whi ch oscillations are damped), robustness against plant parameter changes (pa rticularly unknown factors of the auxiliary characteristics), and control-f uel mass expenditure. The adaptive controller exhibits good performance wit h a clear advantage over the PI controller in robustness. Also, the adaptiv e controller with on-line SID stabilizes the pressure oscillations without exciting additional mode(s).