Acoustic damping characterization of a double-perforated liner in an aero-engine combustor

Double-perforated liners are widely used in gas turbine combustors because of their improved thermal load characteristics and broader acoustic damping compared with single-layer perforations. The present study examines the absorption of normal-incidence acoustic waves by double perforated liner, and provides quantitative analysis results on the effects of key liner parameters on the acoustic damping characteristics using the electro-acoustic analogy method. The developed impedance model is successfully validated against the measured data in the literature. Then, the impedance model is applied to the design of a double-perforated liner in the aero-engine combustor under development and the optimal liner design results are shown in terms of acoustic damping. It is found that the dome plate porosity and the plate gap, which is the space between the dome and splash plate, have a major impact on acoustic absorption for a given combustor geometry and flow condition. In contrasts, the splash porosity and plate thickness have minor significance over frequency range of interest. Thus, the optimized liner configurations are proposed from the viewpoint of acoustic damping.