Feedback Control of Rijke-Type Thermo-Acoustic Instability

Abstract

Thermo-acoustic instabilities are characterized by large-amplitude pressure oscillations, which are detrimental to land-based gas turbine and aero-engines. In this work, a real-time monitoring and feedback control strategy is developed, which involves two algorithms. One is an identification algorithm, which is used to 'sense' the condition of a combustion system and to conduct system identification. The algorithm performs somewhat similar to short-time Fourier transform, but is suitable for real-time computation and is able to more accurately estimate frequency using a shorter sample length. Furthermore it can output a reconstructed signal whose frequency is twice of the input signal, which has great potential to be used for system identification. The other algorithm is a revised infinite impulse response (IIR) filter; its efficiency is optimized by using LMS (least mean square). Finally, the control strategy is then experimentally implemented on a Rijke tube. It is found that approximately 50 dB sound reduction is achieved by actuating a loudspeaker. In addition, the control strategy is demonstrated to be able to track and prevent the onset of new limit cycle results from changes of fuel flow rate.

Experimental study on sliding mode variable structure control of active vibration isolation system of floating raft under multiple excitations

“…Substitute formula (7) into formula (6) to obtain the discrete control input voltage based on index reaching law uðkÞ ¼ ðCeBÞ À1 ðCe Á rðk þ 1Þ þ sðkÞ þ TsðÀeq à sgnðsðkÞÞ À qsðkÞÞ À CeAxðkÞÞ (8) To control buffeting of controller and the limit of input voltage, saturation function sat(s(k)) is adopted to substitute sgn(s(k)) in formula (8) satðsÞ ¼…”

“…6 studied the application of LMS algorithm in practice and achieved good results. 7,8 With regard to floating raft vibration isolation system, Chen 9 studied feedforward control by using Fx-LMS algorithm and pointed out the impact of sound feedback on reference signal in Fx-LMS algorithm. However, the self-adaptive feedforward control method based on LMS algorithm requires reference signal to be stable and known.…”

Experimental Investigation of Feedback Control of Thermoacoustic Oscillations Using Least Mean Square-Based Algorithms

“…Neglecting the phase delay can result in control failure. The path information can be obtained by 'offline' identification [10] or with 'online secondary path identification' procedure [43]. In this work, off-line identification is performed to estimate the path information between the loudspeaker output and the microphone, as shown in Fig.…”