Patent Publication Number: US-2023138228-A1

Title: Module ensuring an attenuation of sound waves and a heat exchange

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims the benefit of the French patent application No. 2111740 filed on Nov. 4, 2021, the entire disclosures of which are incorporated herein by way of reference. 
     FIELD OF THE INVENTION 
     The present invention relates to a module ensuring an attenuation of sound waves generated by the flow of a first fluid and also allowing a heat exchange between this first fluid and a second fluid, to a method for producing such a module, to an aircraft nacelle comprising such modules, and also to an aircraft having such a module. 
     BACKGROUND OF THE INVENTION 
     A turbomachine of an aircraft, in particular a bypass turbomachine, has an air duct which opens at the front and through which fresh air enters the turbomachine. The air duct is delimited by walls which channel the air. A portion of the air is used to carry out a heat exchange with fluids of the aircraft. To this end, heat exchangers are fitted at the walls. 
     The inside of the duct is also lined with structures ensuring an attenuation of sound waves generated by the flow of air in the duct and thus allowing the noise of the turbomachine to be attenuated. Such structures generally comprise a perforated wall which is oriented towards the inside of the duct and at the rear of which a set of in particular honeycomb-shaped cavities is disposed. The cavities form quarter-wave resonators which attenuate a particular frequency. 
     An implementation of heat exchangers at the walls of the duct decreases the space assigned to the acoustic structures, this possibly leading to an increase in the noise of the turbomachine, and it is therefore necessary to fit a structure which ensures both an attenuation of sound waves and a heat exchange without limiting the attenuation surface. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to propose a module ensuring an attenuation of sound waves generated by the flow of a first fluid and a heat exchange between this first fluid and a second fluid. 
     To that end, there is proposed a module ensuring an acoustic attenuation of a flow of a first fluid and a heat exchange between the first fluid and a second fluid, the module comprising: 
     a first wall which is perforated, along which the first fluid flows and which has a cutout,   a second wall,   a cellular structure delimiting cells which extend from the second wall to the first wall, and having a first end secured to the second wall and a second end,   a recess provided in the cellular structure and delimited between a bottom and a top which are perforated, wherein the top closes off the cutout, wherein the bottom extends at a distance from the top, wherein, outside the recess, the second end of the cellular structure is secured to the first wall and wherein, at the recess, the second end of the cellular structure is secured to the bottom, and   a heat exchanger which is fixed inside the recess between the bottom and the top and in which the second fluid circulates.   

     Such a module ensures an attenuation of sound waves and a heat exchange without limiting the attenuation surface. 
     Advantageously, the heat exchanger comprises pipes which meander through the recess, a supply pipe which channels the second fluid from its zone of use as far as the pipes, and an extraction pipe which channels the second fluid from the pipes as far as its zone of use. 
     Advantageously, the supply pipe and the extraction pipe pass through the cellular structure, the bottom and the second wall through a bore. 
     Advantageously, the module comprises, for each supply pipe and extraction pipe, a seal which is positioned around the pipe and which closes off the bore at the bottom and at the second wall. 
     Advantageously, the module comprises an edge which is fixed around the bottom and which extends from the bottom as far as the top. 
     Advantageously, the module comprises foam between the edge and the cellular structure. 
     According to a particular embodiment, the module has, along the periphery of the top, a gap between the edge and the top, and a mastic is deposited so as to close off the gap. 
     According to a particular embodiment, the top overlaps the edge with formation of a joggle. 
     The invention also proposes a method for producing a module according to the preceding variant, the method comprising: 
     a first provision step during which the cellular structure is provided,   a shaping step during which the cellular structure thus provided is shaped so as to produce the recess,   a second provision step during which a shell comprising the perforated bottom is provided,   a first fixing step during which the shell is fixed in the recess,   a third provision step during which the first wall which is perforated and cut according to the cutout is provided,   a fourth provision step during which the second wall is provided,   a second fixing step during which the first wall and the second wall are fixed on either side of the cellular structure,   a fifth provision step during which the exchanger is provided,   a third fixing step during which the exchanger is fixed in the recess,   a sixth provision step during which the perforated top is provided, and   a fourth fixing step during which the top is fixed above the exchanger so as to close off the recess.   

     The invention also proposes a nacelle of an aircraft comprising an external wall and an internal wall delimiting an air duct and wherein the external wall and/or the internal wall bear at least one module according to one of the preceding variants and wherein the first wall is oriented towards the inside of the duct. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features of the invention mentioned above, along with others, will become more clearly apparent upon reading the following description of an exemplary embodiment, the description being given with reference to the appended drawings, in which: 
         FIG.  1    is a side view of an aircraft according to the invention, 
         FIG.  2    is a perspective view of a module according to the invention, and 
         FIG.  3    is a view in section at a pipe passing through a cellular structure of the module according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG.  1    shows an aircraft  10  which has a nacelle  20  inside which a turbomachine is disposed. Arranged inside the nacelle  20  is an air duct which passes through the nacelle and the turbomachine. The air duct is thus delimited by an external wall (also referred to as OFS, “outer fixed structure”) and an internal wall (also referred to as IFS, “internal fixed structure”) of the nacelle  20 . 
       FIG.  2    shows a module  100  according to the invention which ensures, on the one hand, an acoustic attenuation of noises generated by a first fluid flowing along this module  100 , and, on the other hand, a heat exchange between the first fluid and a second fluid circulating inside this module  100 . 
     Such a module  100  can be fitted at the external wall and/or at the internal wall of the nacelle  20  or in another environment as long as it is necessary to attenuate the noise generated by the flow of a first fluid and to carry out a heat exchange between the first fluid and a second fluid. Such a module  100  lines the surface of the wall to which it is fixed and there may be several of these modules  100  borne by the wall. In the embodiment of the invention shown in  FIG.  2   , the module is in the shape of a block, but it may have a different shape so as to be adapted to the geometry of the wall to which it is fixed. 
     The module  100  comprises a first wall  102  (cut on the left) which is perforated and therefore passed through by holes  103   a , and a second wall  104  at a distance from and, in this case, parallel to the first wall  102 . 
     The first wall  102  is in contact with the first fluid, in particular a gas, which flows in the duct along the first wall  102  and which is represented in this case by the arrow F. 
     The second wall  104  is solid and fixed to the wall which delimits the duct. 
     The module  100  also comprises a plurality of intermediate walls  106  which extend from the second wall  104  to the first wall  102 . In the embodiment of the invention shown here, the intermediate walls  106  extend perpendicularly with respect to the first wall  102  and to the second wall  104 . 
     The intermediate walls  106  are disposed, and secured, relative to one another so as to form cells  108 , which in this case have a hexagonal section and extend from the second wall  104  to the first wall  102 . Each cell  108  has a first end secured to the second wall  104  and a second end. 
     The intermediate walls  106  thus together define a cellular structure  109  which has a first end secured to the second wall  104  and a second end. 
     The first wall  102  has a cutout  152 , which in this case has a rectangular shape. 
     The module  100  comprises a recess  150  provided in the cellular structure  109  and delimited between a bottom  154  and a top  156 . 
     The top  156  (cut in this case on the left) closes off the cutout  152  and is also perforated and therefore passed through by holes  103   b . In order to limit the aerodynamic impacts, the top  156  and the first wall  102  are overall aligned. 
     The bottom  154  extends at a distance from the top  156 , and in this case parallel thereto, and it is recessed inside the module  100  towards the second wall  104 . In this case, the bottom  154  covers the same surface area as the top  156  overall. The bottom  154  is also perforated and therefore passed through by holes  103   c . 
     Outside the recess  150 , the second end of each cell  108  and therefore the second end of the cellular structure  109  are secured to the first wall  102  and, at the recess  150 , the second end of each cell  108  and therefore the second end of the cellular structure  109  are secured to the bottom  154 . The intermediate walls  106  are therefore shorter at the recess  150  than outside the recess  150 . 
     In the case of a flow of the first fluid, preferably a gas, in the duct, the first wall  102  is oriented towards the inside of the duct. The first fluid, which is air in this case, flows along the first wall  102 , and the holes 103a-c ensure that a portion of the air enters the cells  108  and therefore sound waves generated by the flow of air are attenuated. Depending on the position, the air passes through the first wall  102  or the top  156  and the bottom  154  before reaching a cell  108 . 
     The fact that the cells  108  are secured relative to one another even under the recess  150  makes it possible to ensure that the module  100  constitutes a structural element. 
     The module  100  also comprises a heat exchanger  180  which is fixed inside the recess  150  between the bottom  154  and the top  156  and in which a second fluid, which may be, for example, oil of the turbomachine and which is cooled by heat exchange with the first fluid through the heat exchanger  180 , circulates. The heat exchanger  180  is fixed, for example, with the aid of inserts which are implanted in the cellular structure  109  and clamping screws which cooperate with these inserts. 
     The heat exchanger  180  in this case comprises pipes  182  which meander through the recess  150 . 
     In order to ensure the circulation of the second fluid in the pipes  182 , the heat exchanger  180  comprises a supply pipe  184  which channels the second fluid from its zone of use as far as the pipes  182 , and an extraction pipe  186  which channels the second fluid from the pipes  182  as far as its zone of use. 
     In the embodiment of the invention shown in  FIG.  2   , the supply pipe  184  and the extraction pipe  186  pass through the cellular structure  109 , the second wall  104  and the bottom  154  through bores which are provided for that purpose. 
     The heat exchanger  180  is thus integrated into the module  100  without reducing the surface area associated with the acoustic attenuation, while still ensuring the rigidity of the module due to the presence of the cells  108  over the entire surface of the module  100 . 
     In the embodiment of the invention shown in  FIG.  2   , there is a single recess  150  and a single heat exchanger  180 , but it is possible to have several recesses  150  provided inside the same module  100  and to have one heat exchanger  180  per recess  150 . 
     A method for producing such a module  100  comprises, for example, a first provision step during which the cellular structure  109  is provided. The production method continues with a shaping step during which the cellular structure  109  thus provided is shaped so as to produce the recess  150  and the potential bores which are provided in the bottom  154  for the passage of the supply pipe  184  and the extraction pipe  186  and inserts for fixation of the heat exchanger  180 . The cellular structure  109  is for example made of metal (aluminum and its alloys, titanium and its alloys) or of synthetic fibers (Nomex®, Kevlar®). Before the provision of the bores, a resin may be injected in the cells in which the bores will be provided, in order to facilitate the machining. 
     The method comprises a second provision step during which a shell is provided. The shell comprises the perforated bottom  154  pierced with the potential bores for the passage of the supply pipe  184  and the extraction pipe  186  and inserts for fixation of the heat exchanger  180 . The shell may also comprise guides for the subsequent fitting of the heat exchanger  180 . 
     In the embodiment of the invention shown in  FIG.  2   , the shell also comprises an edge  158  which is fixed around the bottom  154  and which extends from the bottom  154  as far as the top  156  so as to laterally delimit the recess  150 . 
     The shell is for example made of metal (aluminum and its alloys, titanium and its alloys) or of composite materials. 
     The method then comprises a first fixing step during which the shell is fixed in the recess  150 . The shell is fixed, for example, by adhesive bonding of the bottom  154  to the cellular structure  109  using a crosslinked adhesive. The crosslinking of the adhesive may be effected directly on the shell or on the cellular structure  109 . 
     In order to absorb the dimensional tolerances and the expansions between the shell and the cellular structure  109 , intumescent adhesive which expands during polymerization is injected between the edge  158  and the cellular structure  109 . 
     Optionally, a perforated sheet  160  constituting thermal protection is fixed between the cellular structure  109  and the bottom  154 . The perforated sheet  160  is, for example, a carbon sheet. 
     The method comprises a third provision step during which the first wall  102  which is perforated and cut according to the cutout  152  is provided. The first wall  102  is for example made of metal (aluminum and its alloys, titanium and its alloys) or of composite materials. 
     The method comprises a fourth provision step during which the second wall  104  is provided. The second wall  104  is for example made of metal (aluminum and its alloys, titanium and its alloys, steel and its alloys) or of composite materials. 
     The method then comprises a second fixing step during which the first wall  102  and the second wall  104  are fixed, for example by adhesive bonding, on either side of the cellular structure  109 . The first wall  102  is fixed on the side of the recess  150  by aligning the cutout  152  with the recess  150 , and the second wall  104  is fixed on the side opposite to the recess  150 . 
     The method comprises a fifth provision step during which the exchanger  180  is provided, and a third fixing step during which the exchanger  180  is fixed in the recess  150 , potentially by making the supply pipe  184  and the extraction pipe  186  pass through the cellular structure  109 . 
     The method comprises a sixth provision step during which the perforated top  156  is provided, and a fourth fixing step during which the top  156  is fixed above the exchanger  180  so as to close off the recess  150 . 
     Thermal protection may potentially be fixed against the second wall  104 . 
       FIG.  3    shows an exemplary arrangement at the supply pipe  184 , but a similar arrangement can be produced for the extraction pipe  186 . 
     A bore  302  is produced through the cellular structure  109 , and also the bottom  154  and the second wall  104 , and the supply pipe  184  is accommodated in the bore  302 . 
     If thermal protection is fixed against the second wall  104 , the bore  302  also passes through the thermal protection. 
     In order to ensure tightness at the bottom  154  and at the second wall  104 , the module comprises a seal  304   a - b  which is positioned around the supply pipe  184  and which closes off the bore  302  at the bottom  154  and respectively at the second wall  104 . 
     Each seal  304   a - b  is for example made of silicone which is reinforced, if required, with ceramic materials and glass fibers. 
     According to a particular embodiment, the extent of the top  156  is smaller than the extent of the edge  158  of the shell. The module  100  then has, along the periphery of the top  156 , a gap between the edge  158  and the top  156 . In order to close off this gap, a mastic is deposited so as to close off and seal the gap. This mastic also makes it possible to absorb geometric variations due to thermal expansions. 
     According to another particular embodiment, the extent of the top  156  is greater than the extent of the edge  158  of the shell and the top  156  then overlaps the edge  158  with formation of a joggle in order to limit the aerodynamic impact. The joggle formation consists in bridging the vertical gap between the top  156  and the edge  158  with a doubly bent surface which is flush with the top  156  and the edge  158  and which is realized, for example, with a mastic. 
     Any other shapes that make it possible to reduce the aerodynamic disruption can be used, such as a chamfer. 
     The top  156  is fixed, for example, with the aid of clamping screws which screw through the top  156  into holes which are provided for that purpose. The holes are advantageously oblong holes oriented in different orientations in order to absorb geometric variations of the top  156  due to thermal expansions. 
     While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a” or “one” do not exclude a plural number, and the term “or” means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.