Actively passive control of thermoacoustic instability

Abstract

In this work, experimental studies of actively passive control of perforated liner with a bias flow on mitigating thermoacoustic instability are performed. For this, a well-designed Rijke-type thermoacoustic combustor with a perforated liner implemented is designed. A premixed propane-fueled flame is confined in the bottom half. A mean cooling flow (known as bias flow) generated from a centrifugal pump is forced to pass through the lined section. To maximize the damping capacity of the perforated liners, the bias flow rate is optimized by implementing a real-time tuning algorithm. The algorithm determines the optimum actuation signal to drive the centrifugal pump. On implementing the tuning algorithm, the unstable thermoacoustic combustor is successfully stabilized by reducing sound pressure level over 64 dB. To evaluate the off-design performance of the developed control approach, an extension tube is added/removed to the Rijke-type thermoacoustic combustor to give rise to the dominant unstable mode frequency being changed by approximately 17\%. It is found that the present actively passive control approach is able to mitigate the new limit cycle. And sound pressure level is reduced by about 41 dB. This confirms that the developed actively passive control scheme is sufficiently robust for use in real combustion systems.