Design and assessment of a distributed active acoustic liner concept for application to aircraft engine noise reduction
Résumé
Acoustic liners are a widespread solution for noise mitigation at aircraft engine level, due to lightweight and relatively small dimensions for integration within nacelles. Although conventional liners might be designed so as to target multiple tonal frequencies, their passive principle prevents the adaptation to varying engine speeds and therefore lowers their performance during flight, especially in the take-off and landing phases. This paper presents the design of a novel concept of active acoustic liner, based on an architectured distribution of electromechanical resonators, aiming at absorbing noise over a broad frequency bandwidth. Integration issues have been taken into account so as to fit to the targeted application to aircraft engines, yielding thickness and weight minimization, with a view to challenging existing passive, frequency-limited, liners. The sound absorption performance of the proposed active lining concept is evaluated, through commercially available finite-element software, in a configuration mimicking an aeronautical insertion-loss measurement setup, and then tested in the corresponding experimental facility in the presence of flow. The results show that such a concept is readily surpassing conventional passive liners, both in terms of insertion loss value and frequency bandwidth.
