Conventional perforate acoustic liners are presently used in hot areas of aero-engines. However, current liner technology regarding linear liners for engine intakes (“cold stream”) does not meet the thermal and other functional requirements valid for engine exhaust areas (“hot stream”).
It has, however, been shown that a liner top sheet assembly, consisting of a layer of metallic foam in combination with perforate, shows acoustic characteristics that are nearly independent of both flow and temperature.
The objective of this proposal was to integrate such an acoustic absorber into the TEC structure to demonstrate the performance in a relevant environment. This technology enabled the extension of the acoustically treated area to strongly reduce the noise radiation from the core duct ("hot stream").
The objective of this project was to define and tune a hybrid acoustic liner to the Blade Passing Frequencies (BPF) of the SAGE4 Geared Turbofan (GTF) Demonstrator low pressure turbine (LPT). In this specific application, the liner has to be integrated into the TEC structure. As the main purpose of the demonstrator test is the verification of the liner’s integration aspects and the demonstration of structural integrity under realistic engine conditions, the acoustic design of the liner panels did not have to be fully optimized. However, the acoustic performance of the selected design has been demonstrated and validated by simulations and sample testing in a relevant aerodynamic and acoustic environment.