EXPERIMENTAL INVESTIGATION ON THE SUPPRESSION OF THERMOACOUSTIC OSCILLATIONS USING ACOUSTIC LINER IN A RIJKE TUBE

Thermoacoustic oscillations, prevalent in combustion power devices such as boilers, gas turbines, aeroengines, and rocket engines, are introduced by the coupling between the unsteady heat release and the acoustic waves. This phenomenon leads to increased pressure pulsations, resulting in elevated noise levels and thermal loads. In severe cases, it can cause combustion chamber erosion and even engine failure. Extensive research has been conducted to suppress thermoacoustic oscillations in engines, with passive control methods widely adopted in practice. Acoustic liners are common noise reduction devices, and while theoretical studies have explored their impact on thermoacoustic oscillations, there is still a lack of corresponding experimental research. This study investigates the nature of thermoacoustic oscillations and the inhibitory effects of acoustic liners using the Rijke tube as an experimental model. In the experiment, the Rijke tube, a vertically oriented aluminum tube, features a spring-like nickel-chromium alloy wire as the electrically heated heat source, generating flow through thermal convection. Experimental results demonstrate that thermal convection is established within the tube upon energizing the alloy wire, leading to thermoacoustic oscillations. The amplitude of the sound pressure increases rapidly in an exponential fashion, followed by a gradual decrease in growth rate, eventually reaching a stable limit cycle. Downstream installation of an acoustic liner segment increases the voltage required to initiate thermoacoustic oscillations. Additionally, a significant reduction in the amplitude of the limit cycle is observed, with a decrease of over 5 dB in the fundamental frequency sound pressure level. When the acoustic liner parameters are appropriate, complete suppression of thermoacoustic oscillations is achieved.