A propulsion assembly includes a fan and a fan case system disposed about the fan. The fan case system includes at least one perforated portion including a plurality of holes. The propulsion assembly further includes at least one acoustic panel mounted to the exterior surface of the fan case system coincident with the at least one perforated portion. The at least one acoustic panel includes a core including a plurality of cells extending between a first side of the core and a second side of the core. The at least one acoustic panel further includes a back skin attached to the second side of the core. The first side of the core is in contact with the exterior surface of the fan case system to form a plurality of resonant cavities defined by the plurality of holes, the plurality of cells, and the back skin.

The invention relates to an air intake lip of an aircraft turbomachine nacelle extending along an axis X, in which an air flow circulates from upstream to downstream, the lip extending annularly about the X-axis and having an inner wall facing the X-axis and an outer wall which is opposite the inner wall, the inner wall and the outer wall being connected by an upstream wall so as to delimit an annular cavity, the lip comprising an annular acoustic device mounted in the annular cavity. The lip has a first module, comprising the outer wall, the wall and a front wall forming an upstream portion of the inner wall, and a second module, comprising the acoustic device and a front skin forming a downstream portion of the inner wall, the first module and the second module being secured together so that the front wall and the front skin together form the inner wall of the lip.

An active device for attenuating the acoustic emissions of an aircraft turbojet engine includes circulation conduits for a pressurized air flow rate supplying rotary elements each having a pulsation system for the delivered air. The rotary elements are controlled in amplitude and phase and deliver, to outlet diffusers, a pulsed air flow rate with a pulsation at the frequency of the noise to be attenuated having an amplitude and a phase adjusted according to a local feedback law with microphones to attenuate the radiated acoustic power.

An air intake structure for a nacelle of an aircraft is disclosed having an air intake lip with a U-shaped section open towards the rear, an acoustic panel that extends the air intake lip towards the rear and on an inner side, an outer panel extending the air intake lip towards the rear and on an outer side, and a rear strengthening frame fixed between the outer panel and the acoustic panel, where the rear strengthening frame partly defines an inner volume that is immediately in front of the rear strengthening frame. The air intake structure comprises an impact absorber element positioned in the inner volume and the impact absorber element assumes the form of a structure that is deformable during an impact and that is at least partially filled with a fluid. The impact absorber element is a flexible shroud filled with a pressurized gas.

An active laminar flow control arrangement may comprise an outer skin having an inner surface, an outer surface, and a perforated area, and a panel coupled to the inner surface. The panel may comprise a longitudinal wall, a sidewall extending from the longitudinal wall, a ridge intersecting the sidewall, a cavity disposed in the panel and at least partially defined by the sidewall and the longitudinal wall, and a division wall disposed in the cavity and extending from the longitudinal wall, wherein the division wall divides the cavity into a first plenum and a second plenum. The longitudinal wall, the sidewall, the ridge, and the division wall may comprise a single, monolithic piece.

An air inlet for an aircraft nacelle, including a lip and a front frame, which together form a duct with D-shaped section receiving hot air. The front frame is arranged in an advanced position inside the lip. The lip has de-icing grooves, which communicate with the duct and extend essentially downstream of the front frame. Downstream of the front frame, outside of the de-icing grooves, the lip has perforated zones provided with sound absorption holes. The air inlet includes a foil, which hermetically seals the de-icing grooves and is provided with sound absorption holes facing the perforated zones. The air inlet comprises acoustic panels inside the lip downstream of the front frame. The advanced position of the front frame, due to the de-icing grooves which ensure the de-icing of the lip downstream of the front frame, allows the acoustic treatment surface of the air inlet to be increased.

According to one embodiment, a system for reducing interference noise of rotor and stator blades includes rotor blades, stator blades, loudspeakers, one or more reference microphones, and a controller. The rotor blades rotate about a central axis. The loudspeakers are discretely arranged on a circle that has a center positioned on the central axis. Each loudspeaker generates a control sound. The controller causes the loudspeakers to generate control sounds of a same phase and a same amplitude. The control sounds correspond to the loudspeakers. The r is selected based on a preset attenuation level concerning the interference noise, and the k, where a is a length of the rotor blades, b is a radius of the circle, r=a/b, k is an upper limit wavenumber.

A nacelle assembly includes a fixed inlet segment and a translating inlet segment. The translating inlet segment includes a slider beam laterally between a pair of tracks of the fixed inlet segment. The slider beam is mated with and slidable longitudinally along the pair of tracks. The translating inlet segment is configured to translate longitudinally between a retracted position and an extended position. An aft end of the translating inlet segment is abutted against a forward end of the fixed inlet segment when the translating inlet segment is in the retracted position. An airflow inlet into an inlet passage of the nacelle assembly is opened longitudinally between the aft end of the translating inlet segment and the forward end of the fixed inlet segment when the translating inlet segment is in the extended position.

An acoustic absorption structure includes: a porous layer in contact with a medium through which the sound waves travel, a cellular layer including a plurality of cells, which has at least one exterior annular canal open towards the porous layer, and a reflective layer. An aircraft propulsion system having at least one such acoustic absorption structure is also described.

Variably porous panels and panel assemblies incorporating shape memory alloy components along with methods for actuating the shape memory alloys are disclosed to predictably alter the porosity of a substrate surface, with the shape memory alloy maintained in an orientation relative to the panel that is in-plane with a mold-line of the panel outer surface.