Patent Publication Number: US-2022231311-A1

Title: Aircraft with a fuel cell and a structure having a tank containing a heat-transfer fluid ensuring the cooling of the fuel cell

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims the benefit of the French patent application No. 2100433 filed on Jan. 18, 2021, the entire disclosures of which are incorporated herein by way of reference. 
     FIELD OF THE INVENTION 
     The present invention relates to an aircraft comprising at least one fuel cell and a structure having a tank allowing the storage of a two-phase heat-transfer fluid ensuring the cooling of said fuel cell. 
     BACKGROUND OF THE INVENTION 
     In order to reduce the fuel consumption of an aircraft, it is known practice to use fuel cells, in which each generates an electrical current used to power an electric motor turning one or more propellers. 
     The fuel cell makes it possible to convert chemical energy deriving from an oxidoreduction reaction of dihydrogen and of dioxygen into electrical energy, into heat and into water. 
     In order to control the temperature of the fuel cell, such an installation comprises a cooling system. 
       FIG. 4  is a schematic representation of such an installation  400  in an aircraft, which comprises a fuel cell  402 , and a cooling system  404  which comprises a line  406  which takes a heat-transfer fluid at an output of the fuel cell  402  and which introduces this heat-transfer fluid at an input of the fuel cell  402 . 
     The cooling system  404  also comprises a pumping system comprising at least one pump  408  which is arranged on the line  406  to drive the heat-transfer fluid in the line  406  between the output and the input of the fuel cell  402 . 
     The cooling system  404  also comprises a heat exchanger  410  which is arranged on the line  406  and which ensures the transfer of calories from the heat-transfer fluid to a cold fluid, conventionally the air outside the aircraft. Thus, the outside air passes through the heat exchanger  410  then is rejected outside. At the same time, the heat-transfer fluid passes through the heat exchanger  410  and the calories of the heat-transfer fluid are transferred to the outside air. 
     Because of the large quantity of calories to be discharged, the heat exchanger  410  has a relatively large size, which is detrimental in terms of weight and of drag. 
     It is therefore desirable to find an installation which makes it possible to discharge the calories while having smaller dimensions. 
     SUMMARY OF THE INVENTION 
     One object of the present invention is to propose an aircraft comprising at least one fuel cell and a structure having a tank allowing the storage of a two-phase heat-transfer fluid ensuring the cooling of said fuel cell. 
     To this end, an aircraft is proposed comprising:
         a structure comprising a leakproof tank delimited by walls, of which at least one is in contact with the air outside the aircraft, and filled partly with a first, two-phase heat-transfer fluid,   a fuel cell that is passed through by a second heat-transfer fluid, and   at least one line which takes the second heat-transfer fluid at an output of the fuel cell, and which reintroduces this second heat-transfer fluid at an input of the fuel cell,       

     in which the line passes through the leakproof tank immersed in the first heat-transfer fluid in liquid phase. 
     Thus, the use of a first, two-phase heat-transfer fluid allows for a better transfer of the calories from the second heat-transfer fluid to the first heat-transfer fluid and the storage of the first heat-transfer fluid in a tank of the structure of the aircraft in contact with the outside air ensures the cooling of the first heat-transfer fluid at lower cost in terms of bulk and drag. 
     Advantageously, the structure comprises a fuselage with an inner wall and an outer wall, and the leakproof tank is delimited between the inner wall and the outer wall. 
     Advantageously, the structure comprises at least one wing with a lower surface wall and an upper surface wall, and the leakproof tank is delimited between the lower surface wall and the upper surface wall. 
     Advantageously, the first heat-transfer fluid is water. 
     Advantageously, the line is divided into a plurality of sublines in the leakproof tank. 
     Advantageously, the aircraft comprises a heat exchanger arranged on the line and ensuring the transfer of calories from the second heat-transfer fluid to the outside air. 
     Advantageously, the aircraft comprises an overpressure system arranged at the leakproof tank. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features of the invention mentioned above, and others, will become more clearly apparent on reading the following description of an exemplary embodiment, said description being given in relation to the attached drawings, in which: 
         FIG. 1  is a schematic representation of an installation implemented in an aircraft according to the invention, 
         FIG. 2  is a schematic representation in cross section through a front-end plane of an aircraft according to the invention, 
         FIG. 3  is a side and cross-sectional view of a wing of an aircraft according to the invention, and 
         FIG. 4  is a schematic representation of an installation of the state of the art. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  is a schematic representation of an installation  100  implemented in an aircraft according to the invention and represented schematically in  FIG. 2 . 
     The installation  100  comprises a fuel cell  102  which converts the chemical energy deriving from an oxidoreduction of dihydrogen and of dioxygen into electrical energy, into heat and into water. To this end, the aircraft  200  comprises a tank of dihydrogen and a line circuit ensuring that the fuel cell  102  is supplied with the dihydrogen. Likewise, the fuel cell  102  is supplied with dioxygen, either from a tank of dioxygen of the aircraft  200 , or by the outside air. Such an architecture is conventional and is not described further. 
       FIG. 2  is a schematic representation of the aircraft  200  which comprises a structure  202  and engines  204 . 
     The structure  202  conventionally comprises a fuselage  206  and a wing  208  on either side of the fuselage  206 . The aircraft  200  here comprises two engines  204  under each wing  208 . Obviously, the aircraft can comprise just one or more than two engines  204  under each wing  208 . The fuel cells  102  electrically power the engines  204  which are, for example, propeller engines. 
     In order to control the temperature of the fuel cell  102 , the latter is passed through by a heat-transfer fluid, called second heat-transfer fluid. The second heat-transfer fluid is generally in liquid phase. The second heat-transfer fluid can also be a two-phase heat-transfer fluid having a gaseous phase and a liquid phase. The second heat-transfer fluid can be water, or a mixture of water and additives, such as glycol water. The installation  100  also comprises a cooling system  104  which ensures the cooling of the second heat-transfer fluid. 
     The cooling system  104  comprises at least one line  106  which takes the second heat-transfer fluid at an output of the fuel cell  102  and which reintroduces this second heat-transfer fluid at an input of the fuel cell  102 . The line  106  and the fuel cell  102  thus form a closed loop of circulation of the second heat-transfer fluid. 
     The cooling system  104  also comprises a pumping system comprising at least one pump  108  which is arranged on the line  106  to drive the second heat-transfer fluid in the line  106  between the output and the input of the fuel cell  102 . 
     The structure  202  comprises at least one leakproof tank  210 . 
     The leakproof tank  210  can be a part of the wing  208  and/or a part of the fuselage  206 . For example, if the fuel cell  102  is in the engine  204  on the wing  208 , it is preferable to provide the leakproof tank  210  in the wing  208 , and if the fuel cell  102  is in the fuselage  206 , it is preferable to provide the leakproof tank  210  in the fuselage  206  to reduce the length of the line  106 . However, other layouts are possible. 
     The leakproof tank  210  is delimited by walls of the aircraft  200  of which at least one is in contact with the air outside the aircraft  200 . In the case where the leakproof tank  210  is in the wing  208 , the leakproof tank  210  is delimited between the lower surface wall and the upper surface wall of the wing  208 , and the two walls are in contact with the outside air. In the case where the leakproof tank  210  is in the fuselage  206  which has an inner wall and an outer wall, the leakproof tank  210  is delimited between the inner wall and the outer wall which is the wall in contact with the outside air. 
     The leakproof tank  210  is filled partly with a heat-transfer fluid, called first heat-transfer fluid, which has two phases, namely a liquid phase  50  and a gaseous phase  52 , within the temperature ranges considered, that is to say, according to the temperature of the heat-transfer fluid coming from the fuel cell  102 . The leakproof tank  210  forms a closed loop of circulation of the first heat-transfer fluid. 
     The first heat-transfer fluid is distinct from the second heat-transfer fluid. 
     According to a preferred embodiment, the first heat-transfer fluid is water which all evaporates at approximately 100° C. at ground level (in conventional atmospheric conditions) and at approximately 75° C. at an altitude of 25,000 feet. Because of this, it is possible to cool this first heat-transfer fluid to a lower temperature at altitude than at ground level. The first heat-transfer fluid can also be a mixture of water and of additives, such as glycol water. 
     The line  106  passes through the leakproof tank  210  at a height where the line  106  is immersed in the first heat-transfer fluid in liquid phase  50 , that is to say more in the lower part of the leakproof tank  210 . 
     Thus, when the second heat-transfer fluid coming from the output of the fuel cell  102  passes through the leakproof tank  210 , the first heat-transfer fluid which surrounds the line  106  picks up the calories from the second heat-transfer fluid and evaporates, then, in contact with the wall in contact with the outside air, the vapor thus given off condenses to drop back into the liquid phase  50 . The outside air (arrows  54  along the lower surface and the upper surface) cools the wall of the leakproof tank  210  and thus makes it possible to lower the temperature of the first heat-transfer fluid and condense it. Since the first heat-transfer fluid reverts to its liquid state, and the first heat-transfer fluid considered has a significant latent heat, there is no need to install a very significant volume and mass of said first heat-transfer fluid. 
     The second heat-transfer fluid can be in liquid phase and/or in gaseous phase in the line  106  between the output of the fuel cell  102  and the leakproof tank  210 , and in liquid phase in the line  106  between the leakproof tank  210  and the input of the fuel cell  102 . 
     The quantity of calories thus discharged is then relatively great without it being necessary to put in place one or more imposing heat exchangers in terms of weight and drag. 
     To enhance the transfer of calories, the line  106  can be divided into a plurality of sublines in the leakproof tank  210  as is represented in  FIG. 2 . 
       FIG. 3  shows the wing  208  with the plurality of sublines immersed in the first heat-transfer fluid in liquid phase  50 . 
     In the case where the discharge of the calories by the first heat-transfer fluid would not be sufficient, it is possible to arrange one or more heat exchangers  110  on the line  106 . Depending on the surface of the tank in contact with the outside air, this heat exchanger  110  can be of very much smaller size than that of the state of the art, because it serves only to discharge a small part of the calories. This heat exchanger  110  ensures the transfer of calories from the heat-transfer fluid to a cold fluid, for example the air outside the aircraft  200 . Thus, the outside air passes through the heat exchanger  110  then is rejected outside. At the same time, the second heat-transfer fluid passes through the heat exchanger  110  and the calories from the second heat-transfer fluid are transferred to the outside air. This heat exchanger  110  is preferentially installed downstream of the leakproof tank  210  with respect to the direction of flow of the second heat-transfer fluid. Obviously, this heat exchanger  110  can be installed upstream of the leakproof tank  210  with respect to the direction of flow of the heat-transfer fluid. 
     An overpressure system comprising at least one valve  212  can be provided at the leakproof tank  210  in order to release the pressure if the latter becomes too great. 
     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.