Active combustion control in a coaxial dump combustor

Abstract Suppression of combustion instability in a dump combustor was demonstrated with open-loop and closed-loop active control systems. Pressure oscillations and CH-emission sensors were used to monitor the combustion process. Acoustic drivers were used to modulate the fuel and modify the shear layer at the dump. The open-loop active-control system applied high frequency acoustic forcing to break down the coherence of the large-scale vortical structures, thus reducing the periodic heat release which excites the instability. The closed-loop controller used the CH-emission signal or the pressure fluctuations, after filtration, to lock the acoustic excitation at various relative phase angles. The pressure locking was more effective in suppressing the oscillations at a relative phase angle range of 250-330°. The reduced oscillations were observed by both CH and pressure sensors. The CH locking was significantly less effective relative to the pressure locking, but had a similar range of phase angles in whic...