Acoustic damping: Analytical prediction with experimental validation of mixed porosity liners and analytical investigation of conical liners

摘要

Acoustic liners are widely used as passive damping devices to suppress acoustically driven combustion instabilities in jet engines. In this paper, analytical models for conical cavity-liner duct and liners with mixed porosity are developed by a control volume approach that account for acoustic coupling with the present mean flows. The developed analytical model has been generalised to any combination of liner and cavity section. Furthermore, the damping performance of liners of uniform and mixed porosity is investigated experimentally. In order to investigate the liner damping behavior experimentally, the two load method with convective wave numbers has been used. The performance of the mixed porosity cylindrical and conical liners is compared with that of a uniform porosity cylindrical liner. The troughs of absorption curves are observed to get shifted with the changing cone angles. The effects of changing cavity cone angles for the fixed liner cone angle and vice versa on the absorption have been also analyzed. (C) 2019 Elsevier Ltd. All rights reserved.