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The new generation of Ultra-High-By-Pass-Ratio (UHBR) turbofan engine while considerably reducing fuel consumption, threatens higher noise levels at low frequencies because of its larger diameter, lower number of blades and rotational speed. This is accompanied by a shorter nacelle, leaving less available space for acoustic treatments. Therefore, alternative solutions to classic liners are required. The SALUTE H2020 project has taken up this challenge, proposing electro-active acoustic liners, made up of loudspeakers (actuators) and microphones (sensors). The electro-active means allow to program the surface impedance on the electroacoustic liner, but also to conceive alternative boundary laws. Test-rigs of gradually increasing complexities have allowed to raise the Technology Readiness Level (TRL) up to 3-4. In this paper, we illustrate the control strategies and the experimental results achieved on the Phare2 test-bench. Phare2 is a reproduction of a real turbofan (scale 1:3), available in the Laboratory of Fluid Mechanics and Acoustics in the Ecole Centrale of Lyon. The noise attenuation accomplished by the electroacoustic liner is assessed by an antenna of microphones surrounding the turbofan inlet, and two rings of microphones placed upstream and downstream the liner in the nacelle. Both broadband and tonal noise are targeted with very promising results.
Bono et al. (Fri,) studied this question.