Active control of reheat buzz

Reheat buzz is a low-frequency combustion instability involving the propagation of longitudinal pressure waves inside a duct in which a flame is anchored. Active control has been successfully applied to this instability. The controller alters the upstream acoustic boundary condition and thereby changes the energy balance in the duct. Control is found to reduce the peak in the pressure spectrum resulting from combustion instability by 20 dB. The acoustic energy in the whole 0-800-Hz bandwidth is reduced to about 10% of its uncontrolled value. A comparison with numerical calculations is presented.