Passive Suppression of Self-Excited Combustion Instabilities in Liquid Spray Flame Using Microperforated Plate

Abstract

This paper presents an experimental investigation of using a microperforated plate (MPP) backed by an adjustable cavity to mitigate the combustion instabilities of liquid fuel swirl flame. The acoustic properties of MPPs with different porosities and aperture diameters were first tested in an impedance tube. At low bias flow rates, the sound reflection coefficients of MPPs with large holes commensurate well with the Luong model, and at high bias flow rates, the results of MPPs with small holes agree well with the predictions. The maximum sound absorption coefficient of each panel at the target frequency exceeded 95%. The perforated panels were then selected and integrated into a spray combustor individually. It was shown that the maximum reduction of pressure and heat release fluctuations inside the chamber was 14.91 dB and 13.40 dB, respectively. After noise elimination, the main frequencies of pressure and CH* signals were slightly shifted toward low frequencies. When the combustion conditions change, the MPPs operating near the optimal bias flow rates still have good sound absorption characteristics. After noise suppression, the synchronization between pressure and heat release signals was reduced, and the flame shapes were relatively stable. More generally, this study can promote the application of MPPs under bias flow in stabilizing the liquid spray combustion.