Thermoacoustic oscillations present a challenge to the advancement of aircraft engines, spurring intensive research to mitigate their adverse effects. This study conducts experiments in a Rijke tube and employs a three-dimensional method to investigate the acoustic liners' suppression effect on their thermoacoustic oscillations. The findings reveal that acoustic liners exhibit a substantial suppression effect on thermoacoustic oscillations, with the suppression efficiency improving as the liner length increases. Notably, the impact of the liner's position on oscillation suppression is contingent upon its length. For the shorter liner, the position exerts minimal influence, whereas for the longer, the position plays a critical role, with optimal suppression observed when the liner is positioned closer to the outlet. The experimental results are well-supported by theoretical predictions, thus validating the theoretical approach. An in-depth analysis of acoustic energy reveals that the suppression occurs through a reduction in the coupling strength between the unsteady heat release rate and acoustic waves, coupled with enhanced dissipation. The proximity of the acoustic liner to the outlet further amplifies the suppression, as it increases the acoustic pressure difference across the perforated plate, thereby improving the overall suppression of thermoacoustic oscillations.
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