Comparison of Experimental and Numerical Results Concerning the Damping of Perforated Liners With Bias Flow

Abstract

Perforated liners with bias flow are integrated in the wall of gas turbine combustors to suppress thermoacoustic instabilities. The suppression of these unstable pressure oscillations is a requirement for the safe and stable operation of a gas turbine while applying new combustion concepts concerning more efficiency and cleanliness. Previous experiments have shown the high potential of perforated liners absorbing sound energy and therefore minimize combustion instabilities. In this collaborative work, the absorption properties of a liner are determined from both experimental measurements and numerical simulations. In both cases the analysis is based on acoustic pressure data recorded at several axial positions upstream and downstream of the liner. In the experiments this data is acquired by microphone measurements and in the simulation it is numerically calculated applying a three dimensional compressible URANS approach. The dissipation coefficient of the liner is identified for plane wave propagation at ambient conditions while a grazing flow is present in the duct. Parameters are the bias flow velocity and the amplitude of the incident sound wave. Comparing the results of the highly accurate experiments and the simulation reveals the abilities and limits of the numerical approach to model the absorption effect. The results are in very good agreement for the case without bias flow. However, the discrepancy between the experimental and numerical results is increasing while a bias flow is present.