Active control of combustion oscillations in a lean premixed gas-turbine combustor

Active control of combustion oscillations occurring in a methane-air lean premixed model combustor is accomplished by the method of secondary fuel injection. The main flame is sustained by an axial vane swirler. The central part of the swirler is endowed a function as the secondary fuel injector. The fuel jets from the injector enhance the flame stability by producing rich stable flames in the region of the flame base. Open-loop controls by secondary fuel injection with constant flow rates have been conducted on a naturally unstable condition. The results show sensitivity to the injection amount. It indicates that the flame base is very sensitive to the additional fuel distribution. A similar discussion is made on NOx emission also. Finally, a closed-loop control has been performed by implementing the mixed H2/H∞ controller. An obvious effect of the closed-loop control on the suppression of pressure oscillations is found without loosing an advantage for low NOx emissions.