Oscillation suppression of the duct thermoacoustic coupling system of a locally resonant membrane structure

Abstract

Thermoacoustic oscillation caused by the coupling of unstable heat release and acoustic field greatly influences the stability and vibration/noise level of a combustion system. Therefore, an effective strategy is proposed in this paper to control thermoacoustic oscillation. The coupling model of periodic resonant membrane structure-duct-flame is established based on the energy method and the sound pressure continuity condition. The suppression effect of the membrane structure on the thermal/acoustic modal stability of a duct thermoacoustic coupling system is studied. Further, the influence law of periodic structure acoustic bandgap on modal stability is revealed.Resultsshow that multimodal instability can be suppressed by introducing the membrane structure, especially for the acoustic mode. Additionally, the characteristic root distribution of the thermoacoustic coupling system is remarkably affected by the acoustic bandgap, and some modes show a sharp shift toward a low frequency. Modal stability can be improved for all modes within the scope of the frequency band presented herein in the presence of a periodic membrane. Therefore, the proposed periodic locally resonant membrane effectively suppresses the thermoacoustic coupling instability.