COMBUSTION OSCILLATION CONTROL BY CYCLIC FUEL-INJECTION

A number of recent articles have demonstrated the use of active contro l to mitigate the effects of combustion instability in afterburner and dump combustor applications. In these applications, cyclic injection of small quantities of control fuel has been proposed to counteract th e periodic heat release that contributes to undesired pressure oscilla tions. This same technique may also be useful to mitigate oscillations in gas turbine combustors, especially in test rig combustors characte rized by acoustic modes that do not exist in the final engine configur ation To address this issue, the present paper reports on active contr ol of a subscale, atmospheric pressure nozzle/combustor arrangement. T he fuel is natural gas. Cyclic injection of 14 percent control fuel in a premix fuel nozzle is shown to reduce oscillating pressure amplitud e by a factor of 0.30 (i.e., -10 dB) at 300 HZ. Measurement of the osc illating heat release is also reported.