Reducing noise emissions is one of the main design targets driving the development of new aircraft engines, and is therefore a key priority for the competitiveness of the aerospace sector. Ultra-high bypass ratios (UHBR) turbofan engines are expected to equip the next generation of aircraft to maximize efficiency. The noise generated by these engines will concern lower frequencies compared to existing engine technologies. Also, with a thinner nacelle, absorption performances are expected to drop at low frequencies. And with a shorter nacelle, less surface area will be available for acoustic treatments. UHBR engine technologies then represent significant challenges for the design of next-generation acoustic treatments.
The SALUTE project has tackled these challenges by developing a new acoustic liner technology based on arrays of small loudspeakers or passive membranes. This innovative approach is proved to be able to deliver excellent sound absorption at low frequencies while remaining sufficiently small to fit into thin nacelle geometries. This development has been carried out on three different concepts, which has been compared and down-selected in the course of the project.
According to the project flow, these acoustic treatments were first tested using 2D (i.e. flat) prototypes at TRL 3, which constituted the baseline configuration of the project. The SALUTE project went further by testing 3D prototypes with a geometry corresponding to a small-scale fan at the PHARE test facility. This allows us to validate TRL4 of the proposed system and the associated manufacturing processing. Secondly, gaining more insight into the physical interaction between the transducers, the control system and the high-speed flow has been studied and results published for future developments. This has been achieved through multi-physics simulations coupling the adaptive liner and aero-acoustic flow validated by experimental confrontation.
The SALUTE project belongs to the Clean Sky 2 program.
