Suppression of Thermoacoustic Instabilities using an Electric Field and Feedback Control

The suppression of a thermoacoustic instability using an electric field and feedback control is reported here. The experimental setup consists of a 3.4 kW methane-air flame mounted in a Rijke tube configuration, creating a thermoacoustic instability at 141 Hz and 134 dBA. The electric field acts through the well-known ionic wind effect to modulate the flame heat-release and is shown to be key to interacting with the thermoacoustic instability. A phase-shift feedback controller is used to apply the electric field to the thermoacoustic instability and the closed-loop system suppresses the instability in less than 60 msec and reduces the peak pressure amplitude by 27 dB. Once stabilized, the electric field requires only 36 mW of electrical power to maintain stabilization. This successful demonstration to the classic thermoacoustic instability problem combined with the low electrical power use shows the promising potential of electric fields as actuators in combustion.