Noise reduction assembly for aircraft turbojet

Abstract

A noise reduction assembly located at a junction plane between an air intake structure and a fan casing of an aircraft turbojet has improved acoustic properties since the alternation of acoustic and non-acoustic zones is displaced or eliminated. In particular, the inner wall of the air intake structure includes a projecting part that extends towards the aft direction beyond the junction plane, in other words the flange of the fan casing. The projecting part may be sufficiently long so that its inner skin is continuous as far as the limit between the acoustic zone and the non-acoustic zone of the nacelle.

1 . Noise reduction assembly for a turbojet comprising an air intake structure fitted with an inner wall with a sound wave attenuation structure, and an annular connection part fitted with a first connection part that will be fixed to an engine casing flange and a second tubular connection part that will be fixed on the inner wall, in which, when the annular connection part is fixed to the inner wall, the inner wall comprises a projecting part that extends towards the aft direction from the projection on the inner wall of the first connection part to an aft end of the projecting part.  
     
     
         2 . Noise reduction assembly according to  claim 1  in which the inner wall includes an inner skin permeable to air, an outer skin impermeable to air, and a cellular core, that form the sound wave attenuation structure.  
     
     
         3 . Noise reduction assembly according to  claim 2  in which the cellular core of the inner wall has a constant thickness.  
     
     
         4 . Noise reduction assembly according to  claim 2  in which the cellular core of the inner wall extends towards the aft end of the projecting part.  
     
     
         5 . Noise reduction assembly according to  claim 1  in which the aft end of the projecting part includes a reinforced acoustic structure.  
     
     
         6 . Noise reduction assembly according to  claim 1  in which the aft end of the projecting part comprises a non-acoustic stiffener part.  
     
     
         7 . Noise reduction assembly according to  claim 1  in which a portion of the projecting part is reinforced.  
     
     
         8 . Noise reduction assembly according to  claim 1  in which the second portion of the annular part is fixed by attachment means on the projecting part, between the aft end of the projecting part and the projection of the first part.  
     
     
         9 . Noise reduction assembly according to  claim 8  in which the aft end of the projecting part comprises a recess such that at least part of the attachment means opens up in the recess.  
     
     
         10 . Noise reduction assembly according to  claim 9  in which the longitudinal section of the annular connection part is in an L shape such that its first part is substantially perpendicular to its second part.  
     
     
         11 . Noise reduction assembly according to  claim 1  in which the second portion of the annular part is fixed on the inner wall on the side opposite the projecting part with respect to the first portion.  
     
     
         12 . Noise reduction assembly according to  claim 11  in which the longitudinal section of the annular connection part is in an L shape such that its first portion is substantially perpendicular to its second portion.  
     
     
         13 . Noise reduction assembly according to  claim 12  in which the second portion of the annular part forms an integral part of the inner wall.  
     
     
         14 . Noise reduction assembly according to  claim 1  in which the annular connection part also comprises at least one centring part.  
     
     
         15 . Noise reduction assembly according to  claim 1  also comprising a fan casing fitted with an annular outer flange at its forward end and fixed to the first portion of the annular part through said flange.  
     
     
         16 . Noise reduction assembly for a turbojet comprising an air intake structure fitted with an inner wall with a sound wave attenuation structure, and an annular connection part with an L-shaped longitudinal section, with a first connection part that will be fixed to an engine casing flange, that is substantially perpendicular to a second tubular connection part that will be fixed to the inner wall, and in which, when the annular connection part is fixed on the inner wall, the inner wall comprises a projecting part that extends towards the aft direction from the projection on the inner wall of the first connection part to an aft end of the projecting part.  
     
     
         17 . Noise reduction assembly according to  claim 16  in which the projecting part is fitted with a stiffener structure.  
     
     
         18 . Noise reduction assembly according to  claim 17  in which the inner wall comprises a cellular core that extends in the projecting part.  
     
     
         19 . Fan casing for a turbojet, comprising: 
 an annular outer flange at the forward end of the fan casing,    an air intake structure fitted with an inner wall comprising an inner skin permeable to air, an outer skin impermeable to air and a cellular core,    a noise reduction assembly fitted with a first connection part fixed to the engine casing fan and a second tubular connection part fixed to the inner wall,    in which, the inner wall comprises a projecting part that extends towards the aft direction from the projection on the inner wall of the first connection part to an aft end of the projecting part, the cellular core of the inner wall extending in the projecting part.    
     
     
         20 . Casing according to  claim 19  also comprising a centring part at the flange.