AN ADAPTIVE OPTIMAL COMBUSTION CONTROL STRATEGY

A strategy for optimizing the performance of a laboratory-scale combus tor with respect to volumetric heat release (maximize) and pressure fl uctuations (minimize) has been developed. This strategy utilized (1) a ctuation techniques that simultaneously control volumetric heat releas e and pressure fluctuations; (2) sensing techniques that measure combu stor performance; and (3) an adaptive optimal control strategy. Actuat ion techniques were chosen for their ability to alter the unsteady flo w associated with the shear layer and recirculating flow regions of th e combustor. Periodic spanwise forcing of the inlet boundary layer is used to reduce combustion-induced pressure fluctuations. Crossflow jet s upstream of the inlet are used to control volumetric heat release. S ensing techniques were selected to measure or estimate the two perform ance parameters to be controlled. A fast-response piezoelectric pressu re transducer measure the magnitude of the pressure fluctuations. A st reamwise array of photodiodes measures light emission from the flame a nd enables estimation of volumetric heat release. Combustor performanc e is explicitly defined in terms of a cost function that is a weighted combination of rms pressure fluctuations and mean volumetric heat rel ease. The control strategy performs an on-line minimization of the cos t function by continuously seeking the optimal combination of actuator settings and subsequently maintaining the cost at a minimum when the combustor is subject to unknown inlet condition changes, such as flow disturbances. The strategy has been tested with large flow disturbance s and found capable of indirectly sensing a change in combustor inlet conditions and finding the new optimal actuator settings.