Patent Publication Number: US-11655760-B2

Title: Air intake of an aircraft turbojet engine nacelle comprising ventilation orifices for a de-icing flow of hot air

Description:
TECHNICAL FIELD 
     The present invention relates to the field of aircraft turbojet engines and is more particularly directed to an air intake of an aircraft turbojet engine nacelle comprising a de-icing device. 
     In a known manner, an aircraft comprises one or more turbojet engines to allow its propulsion by acceleration of an air stream that circulates from upstream to downstream in the turbojet engine. 
     With reference to  FIG.  1   , a turbojet engine  100  extending along an axis X and comprising a fan  101  rotatably mounted about axis X in a nacelle comprising an external shell  102  in order to accelerate an air stream F from upstream to downstream is represented. Hereinafter, the terms upstream and downstream are defined with respect to the circulation of the air stream F. The nacelle comprises at its upstream end an air intake  200  comprising an internal wall  201  pointing to axis X and an external wall  202  which is opposite to the internal wall  201 , the walls  201 ,  202  are connected through a leading edge  203  also known as “air intake lip”. Thus, the air intake  200  allows the incoming air stream F to be separated into an internal air stream INT guided by the internal wall  201  and an external air stream EXT guided by the external wall  202 . The walls  201 ,  202  are connected through the leading edge  203  and an internal partition wall  205  so as to delimit an annular cavity  204  known to the person skilled in the art as “D-DUCT”. Hereinafter, the terms internal and external are defined radially with respect to axis X of the turbojet engine  100 . 
     In a known manner, during the flight of an aircraft, due to temperature and pressure conditions, ice is likely to accumulate at the leading edge  203  and the internal wall  201  of the air intake  200  and form blocks of ice that are likely to be ingested by the turbojet engine  100 . Such ingestions have to be avoided in order to improve the life of the turbojet engine  100  and reduce malfunctions. 
     To eliminate ice accumulation, with reference to  FIG.  1   , it is known to provide a de-icing device comprising an injector  206  of a hot air stream FAC into the internal cavity  204 . The circulation of such a hot air stream FAC allows, by heat exchange, the internal wall  201 , external wall  202  and lip  203  to be heated and thus ice accumulation which melts or evaporates as it accumulates to be avoided. In a known manner, with reference to  FIGS.  2  and  3   , the internal cavity  204  comprises ventilation openings  103  formed in the external wall  202  of the air intake  200  so as to allow discharge of the hot air stream FAC after heating of the internal cavity  204 . As an example, with reference to  FIG.  3   , each ventilation opening  103  has an elongated, preferably oblong, shape along the engine axis X. 
     In practice, acoustic nuisance appears during the circulation of the external air stream EXT over the ventilation openings  103 , in particular, hissing and/or resonances. Such acoustic nuisance is increased when the de-icing device is inactive. 
     An immediate solution to eliminate this drawback is to provide a ventilation duct connecting the internal cavity  204  to ventilation openings offset from the exterior wall of the air intake. Preferably, such a ventilation duct allows the ventilation openings to be positioned in a zone in which the velocity of the outside air stream EXT is lower, thereby limiting acoustic disturbances. In practice, the addition of a ventilation duct increases the overall size and mass of the turbojet engine, which is not desired. In addition, a ventilation duct has the drawback of ejecting a hot FAC air stream in proximity to heat-sensitive downstream zones, for example, of composite material. 
     One of the objects of the present invention is to provide an air intake comprising ventilation openings formed in the external wall of the air intake and not inducing acoustic nuisance. 
     Incidentally, a curved guide grille for the hot air stream when exhausted is known from patent application U.S. Pat. No. 5,257,498, but it has no impact on acoustic nuisance. 
     SUMMARY 
     The invention relates to an air intake of an aircraft turbojet engine nacelle extending along an axis X in which an air stream circulates from upstream to downstream, the air intake extending circumferentially about axis X and comprising an internal wall pointing to axis X to guide an internal air stream INT and an external wall, which is opposite to the internal wall for guiding an external air stream EXT, the walls being connected through a leading edge and an internal partition wall so as to delimit an annular cavity, the air intake comprising means for injecting at least one hot air stream FAC into the internal cavity and at least one ventilation opening formed in the external wall to allow exhaust of the hot air stream FAC after heating the internal cavity. 
     The invention is remarkable in that it comprises at least one member for disturbing the external air stream EXT, positioned upstream of the ventilation opening, which extends projecting outwardly from the external wall. Advantageously, such a disturbance member allows formation of sound pressure fluctuations to be avoided in the vicinity of the ventilation opening. 
     Preferably, the disturbance member has a width at least equal to half the width of the ventilation opening, more preferably to the width of the ventilation opening. 
     According to one aspect, the distance between the disturbance member and the ventilation opening is between 0.5 and 3 times the length of the disturbance member. 
     According to another aspect, the distance between the disturbance member and the ventilation opening is less than 2 times the length of the ventilation opening. 
     According to another aspect, the disturbance member has a height between 0.2 and 1 time the length of the disturbance member. 
     Preferably, the disturbance member is mounted as an insert to the external wall. 
     According to one aspect, the external wall comprises a through opening for mounting that is positioned upstream of the ventilation opening. The disturbance member extends through the through opening for mounting, preferably from within the internal cavity. 
     According to one aspect, the disturbance member is a deflection member that comprises a domed external surface, preferably, with a profile having an elliptical portion. This advantageously allows external air to be deflected not to interact at high velocity with the ventilation opening. 
     According to another aspect, the disturbance member is a vortex generating member. The formation of vortices, that is, turbulent aerodynamic structures, allows formation of acoustic waves to be avoided. In particular, the acoustic nuisance is low when the dimensions of the turbulent aerodynamic structures are far from those of a ventilation opening. 
     Preferably, the vortex generating member is polyhedral, preferably tetrahedral or pyramidal. 
     Preferably, the vortex generating member has a convex shape. 
     Preferably, the vortex generating member comprises a plurality of projecting ridges. 
     The invention relates to an air intake of an aircraft turbojet engine nacelle extending along an axis X in which an air stream circulates from upstream to downstream, the air intake extending circumferentially about axis X and comprising an internal wall pointing to axis X to guide an internal air stream INT and an external wall, which is opposite to the internal wall to guide an external air stream EXT, the walls being connected through a leading edge and an internal partition wall so as to delimit an annular cavity, the air intake comprising means for injecting at least one hot air stream FAC into the internal cavity and at least one ventilation opening formed in the external wall to allow exhaust of the hot air stream FAC after heating the internal cavity. 
     The invention is remarkable in that the ventilation opening comprises an upstream edge whose circumferential profile is discontinuous to generate turbulence and/or a downstream edge whose radial profile is aerodynamic to limit formation of pressure fluctuations. 
     Advantageously, the turbulent aerodynamic structures formed by the upstream edge make it possible not to interact with the ventilation opening so as not to generate acoustic waves. Advantageously, the aerodynamic radial profile of the downstream edge allows the flow of the external air stream to be modified in order to avoid any hissing phenomenon. 
     According to one aspect, the circumferential profile of the upstream edge has at least one point of curvature discontinuity in the vicinity of which the direction of the tangent of the profile is modified by an angle greater than 60°, preferably less than 180°. 
     Preferably, the upstream edge comprises between 1 and 8 points of curvature discontinuity for turbulence generation. 
     Preferably, the upstream edge comprises at least two turbulence generation patterns, preferably at least four. 
     Preferably, the turbulence generation pattern has a scallop or chevron shape. 
     According to one aspect, the upstream edge is inscribed within the aerodynamic lines of the external wall. 
     According to another aspect, the upstream edge comprises an outwardly projecting portion. 
     Preferably, the projecting portion forms an angle with the overall plane of the ventilation opening that is less than 45°. 
     Preferably, the downstream edge has a rounded, preferably domed, radial profile. 
     According to one aspect, the ventilation opening defines an aerodynamic line as an extension of the external surface of the external wall of the air intake. The downstream edge is positioned internally to the aerodynamic line. 
     According to one aspect, the external wall comprising a through opening for assembling, the ventilation opening is formed in a ventilation member mounted in the through opening for assembling, preferably from inside. 
     The invention relates to an air intake of an aircraft turbojet engine nacelle extending along an axis X in which an air stream circulates from upstream to downstream, the air intake extending circumferentially about axis X and comprising an internal wall pointing to axis X to guide an internal air stream INT and an external wall, which is opposite to the internal wall, to guide an external air stream EXT, the walls being connected through a leading edge and an internal partition wall so as to delimit an annular cavity, the air intake comprising means for injecting at least one hot air stream FAC into the internal cavity and at least one ventilation opening formed in the external wall to allow exhaust of the hot air stream FAC after heating the internal cavity. 
     The invention is remarkable in that it comprises at least one acoustic member positioned in the internal cavity facing the ventilation opening so as to modify acoustic resonance frequencies and/or attenuate acoustic waves formed in the internal cavity via the ventilation opening. 
     Such an acoustic member makes it possible to modify resonance frequencies or attenuate acoustic waves so as to limit acoustic nuisance likely to bother local residents. The effects of acoustic nuisance are thus reduced. 
     Preferably, with the ventilation opening comprising a normal axis, the acoustic member comprises at least one acoustic surface extending substantially orthogonal to the normal of the ventilation opening. 
     Preferably, the projection of the acoustic surface onto the plane of the ventilation opening along the normal axis is larger than the ventilation opening. 
     According to one aspect, with the ventilation opening comprising a normal axis, the acoustic surface being spaced from the ventilation opening along the normal axis by a spacing distance, the spacing distance is greater than the length of the ventilation opening. 
     According to another aspect, with the ventilation opening comprising a normal axis, the acoustic surface being spaced from the ventilation opening along the normal axis by a spacing distance, the spacing distance is less than twice the length of the ventilation opening. 
     According to one aspect, the acoustic member comprises at least one absorption material to form an acoustic absorption surface. 
     According to one aspect, the acoustic member is in the form of a corner piece comprising an acoustic treatment surface and a mounting surface. 
     According to one aspect, the acoustic member is attached to the internal surface of the external wall. 
     According to one aspect, the acoustic member is attached to the internal wall of the internal cavity. 
     According to one aspect, the internal partition wall comprises a convex upstream face pointing to the ventilation opening. 
     According to one aspect, the internal partition wall comprises a concave portion extending substantially orthogonal to the normal of the ventilation opening. 
     By virtue of the invention, sources and effects of the acoustic nuisance relating to the ventilation openings are treated alternatively or simultaneously in order to improve the comfort to the users located in the aircraft but also that of the local residents. Advantageously, the invention makes it possible to integrate into a high-temperature thermal environment (circulation of the hot flow) without impacting the discharge flow rate and/or increasing the aerodynamic drag. 
     The invention can be implemented in a practical manner to act on the acoustic frequencies desired to be modified. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood upon reading the following description, which is given only by way of example, and referring to the appended drawings given as non-limiting examples, in which identical references are given to similar objects and in which: 
         FIG.  1    is a schematic representation of an axial cross-section view of a turbojet engine according to prior art; 
         FIG.  2    is a schematic representation of a cross-section view of an air intake according to prior art in which a hot air stream for de-icing circulates; 
         FIG.  3    is a schematic perspective representation of a plurality of ventilation openings according to prior art; 
         FIG.  4    is a schematic representation of an axial cross-section view of a turbojet engine according to prior art; 
         FIG.  5    is a schematic representation in an axial cross-section view of an air intake comprising an upstream disturbance member; 
         FIG.  6    is a top schematic representation of an upstream disturbance member associated with a ventilation opening; 
         FIG.  7    is a close-up schematic representation of a first type of mounting of a deflection member; 
         FIG.  8    is a close-up schematic representation of a second type of mounting of a deflection member; 
         FIG.  9    is a schematic representation in an axial cross-section view of an air intake comprising an upstream vortex generating member; 
         FIG.  10    is a schematic perspective representation of a first embodiment of an upstream vortex generating member; 
         FIG.  11    is a schematic perspective representation of a second embodiment of an upstream vortex generating member; 
         FIG.  12    is a top schematic representation of the perimeter of a ventilation opening according to prior art; 
         FIG.  13 A ,  FIG.  13 B , and  FIG.  14    are top schematic representations of a ventilation opening having an upstream edge with scallops; 
         FIG.  15 A ,  FIG.  15 B , and  FIG.  16    are schematic top views of a ventilation opening having an upstream edge with chevrons; 
         FIG.  17    and  FIG.  18    are top schematic representations of a ventilation opening having a raised upstream portion; 
         FIG.  19    is a schematic longitudinal representation in a cross-section view of a ventilation opening according to prior art; 
         FIGS.  20 - 23    are schematic representations in a longitudinal cross-section view of ventilation openings according to the invention with a downstream edge having an aerodynamic radial profile; 
         FIG.  24    is a schematic longitudinal representation in a partial cross-section view of a ventilation member mounted as an insert in a through opening for assembling; 
         FIG.  25    and  FIG.  26    are schematic representations of an acoustic member mounted in the internal cavity to the internal partition wall; 
         FIG.  27    is a schematic representation of an acoustic member mounted in the internal cavity to the external wall; 
         FIG.  28    is a schematic representation of an acoustic member integrated to the internal partition wall; 
         FIGS.  29 - 31    are schematic representations of an acoustic member comprising an absorption material. 
     
    
    
     It should be noted that the figures set out the invention in detail for implementing the invention, said figures of course being able to serve to better define the invention if necessary. 
     DETAILED DESCRIPTION 
     The invention will be set out with reference to  FIG.  4    showing a turbojet engine  1  extending along an axis X and comprising a fan  11  mounted rotatably about axis X in a nacelle  2  comprising an external shell  12  in order to accelerate an air stream F from upstream to downstream. Hereinafter, the terms upstream and downstream are defined with respect to the circulation of the air stream F. The nacelle  2  comprises at its upstream end an air intake  2  comprising an internal wall  21  pointing to axis X and an external wall  22  which is opposite to the internal wall  21 , the walls  21 ,  22  are connected through a leading edge  23  also referred to as “air intake lip”. Thus, the air intake  2  allows the incoming air stream F to be separated into an internal air stream INT guided by the internal wall  21  and an external air stream EXT guided by the external wall  22 . The walls  21 ,  22  are connected through the leading edge  23  and an internal partition wall  25  so as to delimit an annular cavity  24  known to the skilled person as “D-DUCT”. Hereinafter, the terms internal and external are defined radially with respect to axis X of the turbojet engine  1 . 
     The air intake  2  comprises a de-icing device comprising means for injecting  26  a hot air stream FAC into the internal cavity  24 , for example, an injector. The circulation of such a hot air stream FAC allows, by heat exchange, the internal wall  201 , external wall  202  and lip  203  to be heated and thus ice accumulation which melts or evaporates as it accumulates to be avoided. As illustrated in  FIG.  4   , the internal cavity  24  comprises one or more ventilation openings  3  formed in the external wall  22  of the air intake  2  so as to allow the hot air stream FAC to be discharged after heating the internal cavity  24 . In practice, the ventilation openings  3  are positioned upstream of the injector  26  relative to the point of injection of the hot air stream FAC into the air intake  2 , where upstream is defined in this sentence with respect to the circumferential circulation of the hot air stream from upstream to downstream in the circumferential air intake  2 . 
     According to one aspect of the invention, with reference to  FIGS.  5  and  6   , the air intake  2  comprises at least one disturbance member  4  for the external air stream EXT, positioned upstream of a ventilation opening  3 , which extends projecting outwardly from the external wall  22 . In other words, the disturbance member  4  makes it possible to act on the excitation causing the acoustic nuisance by reducing its influence. 
     Hereinafter, the invention is set forth in an orthogonal reference frame P, Q, N in which axis P extends along the external wall from upstream to downstream, axis N extends normally to the ventilation opening  3  from inside to outside and axis Q extends tangentially. 
     The ventilation opening  3  is defined in the orthogonal reference frame P, Q, N. To this end, the ventilation opening  3  comprises a length P 3  defined along axis P and a width Q 3  defined along axis Q as illustrated in  FIG.  6   . 
     In order to be able to optimally influence the upstream external air stream EXT, that is the acoustic excitation, the disturbance member  4  has a width Q 4  at least equal to half the width Q 3  of the ventilation opening  3 , preferably to the width Q 3  of the ventilation opening  3  as illustrated in  FIG.  6   . Preferably, the widths Q 3 , Q 4  are of the same order of magnitude to limit aerodynamic disturbances. Also, the distance ΔP, defined along axis P, between the disturbance member  4  and the ventilation opening  3  is between 0.5 and 3 times the length P 4  of the disturbance member  4 . Preferably, the distance ΔP is less than 2 times the length P 3  of the ventilation opening  3 . This advantageously allows the external air stream EXT to be disturbed prior to its interaction with the ventilation opening  3  while limiting drag.
 
0.5 *P 4 ≤ΔP≤ 3 *P 4  [Math. 1]
 
Δ P ≤2 *P 3  [Math. 2]
 
     Even more preferably, as illustrated in  FIG.  7   , the disturbance member  4  has a height N 4 , defined along axis N, between 0.2 and 1 time the length P 4  of the disturbance member  4 . Such a restricted height allows an acoustic interaction of the external air stream EXT with the ventilation opening  3  to be avoided while limiting aerodynamic disturbances. 
     According to one aspect of the invention, with reference to  FIG.  7   , the disturbance member  4  is of the same material as the external wall  22  or attached as an insert to its external surface  22   a , for example, by bonding, welding or the like. According to another aspect of the invention, with reference to  FIG.  8   , the external wall  22  comprises a through opening  400  for mounting, positioned upstream of the ventilation opening  3 . The disturbance member  4  extends through the through opening  400  for mounting so as to extend projecting outwardly from the external wall  22 . In the example shown in  FIG.  8   , the disturbance member  4  comprises a mounting base  41  configured to be attached to the internal surface  22   b  of the external wall  22 , in particular, by bonding welding, riveting or the like. In other words, the disturbance member  4  can be mounted from outside ( FIG.  7   ) but also from inside ( FIG.  8   ) depending on mounting and overall size restrictions. 
     Two embodiments of a disturbance member  4  will now be set forth in detail. 
     In a first embodiment, with reference to  FIGS.  5  to  8   , the disturbance member is a deflection member configured to deflect the external air stream EXT in order to prevent it from having a grazing incidence during its interaction with the ventilation opening  3 . The formation of acoustic pressure fluctuations in the vicinity of the ventilation opening  3  is avoided, thereby reducing acoustic nuisance. 
     Preferably, the deflection member comprises an external surface  40  that is domed. Advantageously, this prevents too high a deviation of the flow of the modified external air stream EXTm. Preferably, the external surface  40  has a portion of elliptical profile, that is, inscribed within an elliptical perimeter along an axial cross-sectional plane (N, P) as illustrated in  FIGS.  5 ,  7  and  8   . Such an external surface  40  allows to modify stream lines without generating a significant increase in drag. The dynamic flow remains minimally disturbed and is simply deflected. 
     In a second embodiment, with reference to  FIGS.  9  to  11   , the disturbance member is a vortex generating member  4 ′ in order to create aerodynamic disturbances. Vortices are aerodynamic structures with a turbulent character, which prevents the generation of acoustic pressure fluctuations due to the interaction between the external stream EXT and the ventilation opening  3 . 
     The geometrical dimensions previously set out for the disturbance member apply to the deflection member and the vortex generating member. They will not be detailed again. 
     As illustrated in  FIGS.  9  to  11   , the vortex generating member  4 ′ is polyhedral, preferably tetrahedral (triangle base) or pyramidal (square base). The presence of faces and/or ridges allows generation of vortices EXTv as illustrated in  FIG.  9    in the external air stream EXT along a plurality of different directions in order to generate an external air stream with aerodynamic disturbances. 
     According to a first aspect, with reference to  FIG.  10   , the vortex generating member  4 ′ has a convex, preferably solid, shape so as to define a plurality of deflection faces  41 ′ which are connected through projecting ridges  42 ′. According to a second aspect, with reference to  FIG.  11   , the vortex generating member  4 ′ comprises a plurality of projecting ridges  42 ′ that are connected through concave portions  43 ′ so as to significantly disturb the external air stream EXT. 
     A reduction in acoustic nuisance has been set out for a single ventilation opening  3 , but it goes without saying that some or all of the ventilation openings  3  could be associated with members  4 ,  4 ′ for disturbing the external air stream having identical or different natures. 
     When several disturbance elements  4 ,  4 ′ are used together, they can be independent or connected together, for example, in a continuous manner between two adjacent ventilation openings  3 . 
     Advantageously, such disturbance members  4 ,  4 ′ make it possible to act on the cause of the acoustic nuisance, that is, on the external air stream EXT located upstream of the ventilation opening  3  so as to reduce generation of acoustic pressure fluctuations. 
     In a conventional manner, with reference to  FIG.  12    representing a ventilation opening  3  according to prior art, the ventilation opening  3  has an oblong shape whose length is defined along axis P extending from upstream to downstream. The upstream edge  31  and the downstream edge  32  have a curvilinear shape so as to limit mechanical fatigue. 
     According to one aspect of the invention, with reference to  FIGS.  12  to  18   , the ventilation opening  3  comprises an upstream edge  31  whose circumferential profile is discontinuous to generate turbulence and/or a downstream edge  32  whose radial profile is aerodynamic to limit formation of pressure fluctuations. In other words, the profile of the edge of the ventilation opening  3  is modified so as to limit acoustic disturbances. An irregular upstream edge  31  allows relaxing of small turbulent aerodynamic structures that do not generate acoustic nuisance with the ventilation opening  3 . 
     On the one hand, as will be set forth later, the upstream edge  31  can comprise a discontinuous circumferential profile to generate turbulence and thus disturb the upstream external air stream in the manner of an upstream disturbance member as set forth previously. In other words, the upstream edge forms a disturbance member integrated to the ventilation opening  3 . Thus, the interaction with the ventilation opening  3  is controlled. 
     On the other hand, as will be set forth later, the downstream edge  32  can comprise an aerodynamic profile along the radial direction to limit formation of pressure fluctuations. Advantageously, this prevents the occurrence of hissing. Thus, antagonistic treatments of opposite edges  31 ,  32  of a ventilation opening  3 , alternatively or cumulatively, allows the generation of acoustic nuisance to be counteracted. 
     Preferably, the ventilation opening  3  has a ratio of length, defined along axis P, to width, defined along axis Q, that is between 2 and 5. 
     According to one aspect of the invention, the profile of the upstream edge  31  in the circumferential direction has at least one point of curvature discontinuity  34  in the vicinity of which the tangent is modified by an angle ΔT greater than 60°, preferably less than 180°. Preferably, the upstream edge  31  comprises at least two, preferably, at least four turbulence generating patterns  33 . Preferably, the turbulence generating patterns  33  are adjacent to each other. The circumferential profile is defined in the plane (P, Q). 
     As illustrated in  FIGS.  13 A and  13 B , there is represented an upstream edge  31  comprising two scallop-shaped turbulence generating patterns  33  so as to define at their interface a point of curvature discontinuity  34  that extends projecting to the center of the ventilation opening  3 .  FIG.  13 B  illustrates the tangent T 1  of the first turbulence generating pattern  33  and the tangent T 2  of the second turbulence generating pattern  33  which are separated by an angle ΔT of between 160° and 180°. Such a point of discontinuity  34  allows the flow of the external air stream EXT to be disturbed before it interacts with the downstream edge  32 . 
     According to another embodiment illustrated in  FIG.  14   , the upstream edge  31  comprises four scallop-shaped turbulence generating patterns  33  and three points of curvature discontinuity  34  that extend projecting to the center of the ventilation opening  3  in order to generate a large number of aerodynamic disturbances. 
     Similarly, according to another embodiment illustrated in  FIGS.  15 A and  15 B , there is represented an upstream edge  31  comprising two chevron-shaped turbulence generation patterns  33 ′ so as to define an inner point of curvature discontinuity  34 ′ and a point of curvature discontinuity  34 ′ at the interface with another generation pattern  33 ′. Also, in this example, the upstream edge  31  comprises 3 points of curvature discontinuity  34 ′, 1 of which extends projecting to the center of the ventilation opening  3  and 2 of which extend projecting oppositely to generate a large number of aerodynamic disturbances. Similarly to  FIG.  13 B ,  FIG.  15 B  illustrates the tangent T 1 ′ of the first turbulence generating pattern  33 ′ and the tangent T 2 ′ of the second turbulence generating pattern  33 ′ being spaced apart by an angle ΔT′ between 90° and 110°. 
     With reference to  FIG.  16   , the upstream edge  31  comprises four chevron-shaped turbulence generation patterns  33 ′ and 7 points of curvature discontinuity  34 ′, 3 of which project toward the center of the ventilation aperture  3  and 4 of which extend projecting oppositely in order to generate a large number of aerodynamic disturbances. 
     It goes without saying that the number and shape of turbulence generating patterns  33 ,  33 ′ as well as the number, shape and position of the points of curvature discontinuity  34 ,  34 ′ can vary as required. Preferably, the upstream edge  31  comprises between 1 and 8 points of curvature discontinuity  34 ,  34 ′ for vortex generation depending on the desired acoustic effect. 
     According to one aspect of the invention, the upstream edge  31  is inscribed in the aerodynamic lines and belongs to the plane (P, Q), that is, along an aerodynamic line. Such an upstream edge  31  is simple to make. According to another aspect, the upstream edge  31  comprises an outwardly projecting portion  35 ′. As an example, as illustrated in  FIGS.  17  and  18    representing an upstream edge  31  comprising chevron-shaped turbulence generating patterns  33 ′, a point of curvature discontinuity  34 ′ extends projecting to the center of the ventilation opening  3  and extends projecting outwardly, that is, above the plane (P, Q) in which the ventilation opening  3  extends. In other words, the point of curvature discontinuity  34 ′ makes it possible to generate turbulence in the manner of an upstream disturbance member  4 ,  4 ′ as set forth previously by modifying the incidence of the external air stream EXT upstream of the ventilation opening  3 . Preferably, the projecting portion  35 ′ forms an angle θ with the overall plane (P, Q) of the ventilation opening  3  that is less than 45°. 
     Advantageously, the profile of the upstream edge  31  is produced by mechanical cutting, water jet, laser or punching. 
     In a conventional manner, with reference to  FIG.  19    representing a ventilation opening  3  according to prior art, the ventilation opening  3  comprises a downstream edge  32  having a projecting ridge  320  in the plane (P, Q) of the ventilation opening  3 , that is, at the interface with the external air stream EXT that sweeps the external wall  22 . This interface line, hereinafter referred to as the “aerodynamic line LA”, interacts with the projecting ridge  320  of the downstream edge  32  and generates hissing and other acoustic nuisance. 
     According to one aspect of the invention, as illustrated in  FIGS.  20 - 24   , the downstream edge  32  has an aerodynamic profile in the radial direction to limit formation of pressure fluctuations, that is, to avoid any shearing in the aerodynamic line LA by a projecting ridge. The radial profile is defined in the plane (P, N). 
     Preferably, the thickness of the downstream edge  32  is different from that of the upstream edge  31 . Preferably, the thickness of the downstream edge  32  is enlarged relative to the upstream edge so as to form an aerodynamic radial profile. Advantageously, the aerodynamic radial profile has a continuous curvature, devoid of discontinuities, in particular, with respect to the aerodynamic line LA. Advantageously, the aerodynamic radial profile allows for a progressive deflection. 
     As illustrated in  FIG.  20   , the downstream edge  32  has an upper aerodynamic, in particular rounded or domed, profile  321  at aerodynamic line LA. In this embodiment, only the upper portion of the downstream edge  32  is modified. 
     With reference to  FIG.  21   , it is suggested to form a fully rounded or domed downstream edge  32  so as to guide the aerodynamic line LA without turbulence both internally or externally thereto. As illustrated in  FIGS.  22  and  23   , the downstream edge  32  is sloped inwardly of the internal cavity  24  so as to avoid contact between the external air stream EXT and a projecting ridge. With reference to  FIG.  22   , the downstream edge  32  is deformed, in particular, with an inwardly directed protrusion. With reference to  FIG.  23   , the downstream edge  32  is deformed inwardly so as to lie below the aerodynamic line LA. Preferably, the radial profile of the downstream edge  32  can be made by local deformation of the material. 
     According to one aspect of the invention, with reference to  FIG.  24   , the external wall  22  comprises a through opening  305  for mounting and the ventilation opening  3  is formed in a ventilation member  300  mounted in the through opening  305  for assembling, preferably from inside. Such an embodiment is advantageous insofar as it allows a through opening  305  for assembling to be formed in a simple shape, without any particular aerodynamic restrictions in the external wall  22 . Each ventilation member  300  can be manufactured independently and advantageously comprise upstream  31  and downstream  32  edges that are worked to reduce acoustic disturbances. Each ventilation member  300  can then be attached as an insert to a through opening  305  for assembling, in particular, at its upstream end  301  and downstream end  302  as illustrated in  FIG.  24   . Such an embodiment combines improved acoustic performance and ease of industrialization. 
     Modification of an upstream edge  31  and/or a downstream edge  32  of a ventilation opening  3  allows for the formation of a ventilation opening  3  with reduced acoustic impact. 
     A reduction in acoustic impact for a single ventilation opening  3  has been set forth, but it is understood that some or all of the ventilation openings  3  could comprise an upstream edge  31  and/or downstream edge  32  modified according to the invention. 
     According to one aspect of the invention, with reference to  FIGS.  25 - 31   , the air intake  2  comprises at least one acoustic member  5  mounted in the internal cavity  24  facing the ventilation opening  3 . By facing the ventilation opening, it is meant that the acoustic member  5  is distant from the ventilation opening  3  so as not to disturb exhaust of the hot air stream FAC but aligned with the latter to allow treatment of the acoustic waves coming from said ventilation opening  3 . 
     Thus, unlike a treatment of the acoustic excitation as taught in the first part, it is suggested here to treat the acoustic resonance as such by shifting frequencies off the resonant zones or even by attenuating acoustic waves. The sound amplification of acoustic nuisance is advantageously reduced. 
     As illustrated in  FIGS.  25  and  26   , according to a first embodiment, the acoustic member  5  comprises an acoustic surface  50  extending in front of the ventilation opening  3 . Here, the acoustic surface  50  is substantially planar to improve its efficiency but it could also be curved. Advantageously, the acoustic surface  50  is acoustically reflective so as to modify acoustic wavelengths and thus reduce resonances. Preferably, the treatment surface  50  is made of a metal or ceramic material in order to have good high temperature resistance. 
     As illustrated in  FIG.  25   , the ventilation opening  3  comprises a normal axis N and the projection of the acoustic member  5 , the acoustic surface  50 , onto the plane (P, Q) of the ventilation opening  3  along the normal axis N is larger than the ventilation opening  3  in order to allow containing all of the acoustic waves entering through the ventilation opening  3 . Preferably, the acoustic surface  50  is substantially parallel to the plane (P, Q) of the ventilation opening  3 . In other words, the acoustic surface  50  extends substantially orthogonal to the normal N of the ventilation opening  3 . According to a preferred aspect, as illustrated in  FIG.  26   , the acoustic surface  50  comprises at its circumferential end a curved edge  53  so as to further allow guiding exhaust of the hot air stream FAC towards the ventilation opening  3 . 
     In order to achieve optimal acoustic performance, with reference to  FIG.  25   , the acoustic member  5  is spaced from the ventilation opening  3  along the normal axis by a spacing distance N 5  which is preferably less than 20 mm. This ensures optimal hot air exhaust as well as a shift of the acoustic frequencies into a frequency range that is less disturbing to the human ear. 
     In the embodiment of in  FIGS.  25  and  26   , the acoustic member  5  is in the form of a corner piece defining an acoustic surface  50  and a mounting surface  51 . Preferably, the corner piece has an L-shaped cross-section. Such a simple structure allows for acoustic efficiency without significantly increasing mass. As illustrated in  FIG.  25   , the acoustic member  5  can be attached via its mounting surface  51  to the internal partition wall  25  of the internal cavity  24  ( FIG.  25   ) or to the internal surface  22   b  of the external wall  22  ( FIG.  27   ) so that the acoustic surface  50  extends into the immediate vicinity of the ventilation opening  3 . 
     According to another aspect of the invention, with reference to  FIG.  28   , the internal partition wall  25 ′ forms the acoustic member  5 , this advantageously avoids the addition of an insert member. Preferably, the upstream face of the internal partition wall  25 ′ comprises a concave portion  50 ′ or flat part extending substantially orthogonal to the normal N of the ventilation opening  3  so as to form an acoustic surface reflecting the waves entering through the ventilation opening  3 . In this way, advantage is taken of the internal partition wall  25 ′ to treat acoustic waves without increasing mass of the air intake  20 . Preferably, the upstream face of the internal partition wall  25 ′ is overall convex and is locally deformed to form the concave portion  50 ′ with acoustic surface. 
     With reference to  FIGS.  29  to  31   , according to one aspect of the invention, the acoustic member  5  comprises at least one absorption material  52  so as to form an acoustic absorbing surface. Preferably, the absorbing material  52  is resistant to high temperatures, for example in the order of 350° C., which corresponds to the order of magnitude of the temperature of the hot air stream FAC used for de-icing. 
     By way of example, the absorption material  52  is of the porous, in particular, metallic, type with or without honeycomb. Of course, other materials could be suitable, for example, a metal foam, ceramic material with a perforated skin and the like. 
     As illustrated in  FIGS.  29  and  30   , an absorption material  52  is positioned on the acoustic surface  50  of the embodiments of  FIGS.  25  and  27    in order to significantly reduce acoustic nuisance. In such a case, the surface  50  is common and has only a support function, with the absorption material  52  performing the acoustic treatment by absorption. 
     In this embodiment, the absorption material  52  is spaced from the ventilation opening  3  along the normal axis by a spacing distance N 52  which is greater than the length P 3  of the ventilation opening  3 . Even more preferably, the spacing distance N 52  is less than twice the length P 3  of the ventilation opening  3 . Such a compromise ensures optimal hot air exhaust as well as an optimal acoustic absorption. 
     With reference to  FIG.  31   , the internal partition wall  25  comprises a convex upstream face pointing to the ventilation opening  3  and the absorption material  52  is directly attached to the internal partition wall  25  facing the ventilation opening  3 . In other words, the acoustic member  5  is formed by the partition wall  25  to which the absorption material  52  is attached. 
     By virtue of the invention, acoustic waves are treated in a manner internal to the internal cavity  24 , which makes it possible not to impact the overall size of the air intake  2  as well as the external wall  22 . The acoustic member makes it possible to keep the acoustic frequencies away from the ranges of sensitivity of the human ear likely to cause acoustic nuisance. 
     A reduction in acoustic pollution has been set forth for a single ventilation opening  3 , but it goes without saying that some or all of the ventilation openings  3  could be associated with acoustic elements  5 . When several acoustic members  5  are used together, these can be independent or connected together, for example, continuously between two adjacent ventilation openings  3 . 
     Advantageously, the various aspects of the invention can be combined with each other for a same ventilation opening or for different ventilation openings. 
     Also, a disturbance, deflection or vortex generating member can advantageously be associated with a ventilation opening  3  having an upstream edge  31  whose circumferential profile is discontinuous to generate turbulence and/or a downstream edge  32  whose radial profile is aerodynamic to limit pressure fluctuation. 
     Similarly, a disturbance, deflection or vortex generating member can advantageously be associated with an acoustic member, with or without absorption material. 
     Similarly, an acoustic member, with or without absorption material can advantageously be associated with a ventilation opening  3  having an upstream edge  31  whose circumferential profile is discontinuous to generate turbulence and/or a downstream edge  32  whose radial profile is aerodynamic to limit formation of pressure fluctuations. 
     According to one aspect of the invention, an acoustic member, with or without absorption material, can advantageously be associated, in a cumulative manner, with a ventilation opening  3  having an upstream edge  31  whose circumferential profile is discontinuous to generate turbulence and/or a downstream edge  32  whose radial profile is aerodynamic to limit formation of pressure fluctuations, as well as with a disturbance, deflection or vortex generating member.