Combustion Control of Thermo-Acoustics Instability on Methane / Air Premixed Swirl-Type Flames

Abstract

Control technique of the oscillatory combustion in a swirl-type combustor was investigated to suppress the pressure perturbation and the combustion noise. In this study, development of an active combustion control (ACC) on oscillatory flame was carried out with feedback system using loudspeaker and microphone as an actuator and a sensor, respectively. Modern H² control algorithm based on experimental modal analysis for system identification was applied to control the oscillatory flame. Furthermore, for the future development of closed loop feedback system using the secondary injection method, optimization of the injection method was carried out. To examine the exothermic fluctuation, LIF measurement was carried out. OH radical distribution near the region of flame holder was visualized. As the results, two types of oscillatory flames were observed in this investigation. One of them was characterized by low-frequency mode. On the other hand, oscillatory flame with high-frequency mode was produced with a remarkable frequency near the resonance of the combustor. As for the performance of the developed ACC system, pressure fluctuation was suppressed with an efficiency of about 30% decrease. Furthermore, as for the secondary injection, it was found that jet interaction near the flame holder was an effective way to control the oscillatory flame.