Hydrogen aircraft

Abstract

The present invention is provided with: a machine body (10); a hydrogen tank (30) that stores liquid hydrogen; a propulsion device (40) that generates propulsion force of the machine body using hydrogen as fuel; a liquid hydrogen transfer device (50) that transfers the liquid hydrogen from the hydrogen tank (30) to the propulsion device (40); and a cooling device (70) that includes a heat exchanger (71) for exchanging heat between the liquid hydrogen and air inside the machine body (10) to cool the air, the cooling device (70) cooling the inner surface of an outer plate of the machine body (10) using the air cooled by the heat exchanger (71).

Description

Hydrogen aircraft

[0001] The present disclosure relates to hydrogen aircraft.

[0002] Patent Document 1 discloses an aircraft in which, in order to improve fuel efficiency, ducts for circulating fluid are formed inside the outer plates of the wings, and the outer plates of the wings are cooled by circulating low-temperature fuel through the ducts. Cooling the outer plates of the wing reduces air resistance on the surface of the outer plates, thereby improving the fuel efficiency of the aircraft.

[0003] In the above-described configuration of Patent Document 1, fuel flows inside the outer plate of the wing, which poses a problem of making the configuration complicated because it is necessary to prevent fuel leakage from the wing and unexpected reactions of the fuel on the wing.

[0004] U.S. Pat. No. 4,807,831

[0005] The present disclosure aims to provide a hydrogen aircraft that can improve fuel efficiency with a simple configuration.

[0006] A hydrogen aircraft according to one aspect of the present disclosure comprises an aircraft body, a hydrogen tank for storing liquid hydrogen, a propulsion device that generates thrust for the aircraft using hydrogen as fuel, a liquid hydrogen transfer device that transfers liquid hydrogen from the hydrogen tank to the propulsion device, and a cooling device that includes a heat exchanger that exchanges heat between the liquid hydrogen and air inside the aircraft to cool the air, and that uses the air cooled by the heat exchanger to cool the inner surface of the aircraft's outer panel.

[0007] According to the present disclosure, fuel efficiency can be improved with a simple configuration in a hydrogen aircraft.

[0008] Fig. 1 is a schematic bottom view of a hydrogen aircraft according to a first embodiment of the present disclosure. Fig. 2 is a schematic plan view showing the internal structure of a main wing. Fig. 3 is a schematic perspective view showing the structure of the tip of a main wing. Fig. 4 is a system diagram showing a propulsion system and a cooling device. Fig. 5 is a schematic perspective view showing the internal structure of a main wing in a hydrogen aircraft according to a second embodiment of the present disclosure. Fig. 6 is a schematic plan view showing the structure of the tip of a main wing in a hydrogen aircraft according to the second embodiment of the present disclosure.

[0009] 1 is a bottom view showing a schematic configuration of a hydrogen aircraft 1 according to a first embodiment of the present disclosure. The hydrogen aircraft 1 shown in this drawing includes an airframe 10, a hydrogen tank 30, a propulsion device 40, and a cooling device 70.

[0010] The hydrogen aircraft 1 is an aircraft that uses hydrogen as a propulsion energy source, and the propulsion device 40 uses hydrogen as fuel to generate thrust for the aircraft 10. Hereinafter, the propulsion direction of the hydrogen aircraft 1 will be referred to simply as the longitudinal direction, with the side ahead of the propulsion direction being referred to as the front and the opposite side being referred to as the rear. The vertical direction of a parked hydrogen aircraft 1 will also be referred to simply as the vertical direction, and the direction perpendicular to the longitudinal direction and the vertical direction will be referred to as the horizontal direction. The longitudinal direction coincides with the longitudinal direction of the fuselage 11, which will be described later.

[0011] The aircraft 10 includes a fuselage 11, a pair of left and right main wings 12, and a tail 13. The two main wings 12 have a symmetrical structure.

[0012] The fuselage 11 has a generally cylindrical shape extending in the longitudinal direction. The fuselage 11 includes structural members such as a circular frame and stringers, and fuselage panels assembled into a cylindrical shape. The fuselage panels are the outer plates of the fuselage 11. In other words, the fuselage panels are made of plate-like members and form the outer surfaces of the fuselage 11.

[0013] The pair of main wings 12 extend from the fuselage 11 to both outer sides in the left-right direction, i.e., to both outer sides in the width direction of the fuselage 11. Figure 2 is a schematic plan view showing the internal structure of the main wings 12. Figure 3 is a schematic perspective view showing the structure of the left-right end portions of the main wings 12.

[0014] The main wing 12 includes spars 21 extending in the left-right direction that define its exterior shape, and multiple ribs 22 arranged perpendicular to the spars 21. The main wing 12 also includes main wing panels 24 attached to the spars 21 and ribs 22. The main wing 12 also includes multiple stringers 23 extending in the left-right direction to connect the ribs 22 and reinforce the main wing 12. In the example shown in FIG. 2 , the main wing 12 includes two spars 21 aligned in the fore-and-aft direction, multiple stringers 23 aligned in the fore-and-aft direction along the upper inner surface of the main wing panel 24, and multiple stringers 23 aligned in the fore-and-aft direction along the lower inner surface of the main wing panel 24. The spars 21 are the main structure that bears the load during flight, and the stringers 23 are reinforcing members that support the main wing panel 24. The main wing panel 24 is the outer plate of the main wing 12. In other words, the main wing panel 24 is made of a plate-like member and forms the outer surface of the main wing 12. Flaps or ailerons may be further provided on the main wings 12. The position of the main wings 12 is not limited, but in the first embodiment, the main wings 12 are attached near the center of the fuselage 11 in the longitudinal direction.

[0015] The main wings 12 support nacelles 16, which are cylindrical housings extending in the longitudinal direction. Specifically, engine pylons 17 extending in the longitudinal direction are fixed to the undersides of the main wings 12. The nacelles 16 are connected to the engine pylons 17 and are supported by the main wings 12 via the engine pylons 17. The nacelles 16 are supported by the main wings 12 below the main wings 12 in the vertical direction, in a position that protrudes forward from the main wings 12 in a plan view. The nacelles 16 and engine pylons 17 are provided for each of the two main wings 12. In other words, the hydrogen aircraft 1 has a pair of left and right nacelles 16 and a pair of left and right engine pylons 17.

[0016] A fuselage fairing 14 is attached to the underside of the fuselage 11. The fuselage fairing is a member for eliminating the step between the fuselage 11 and the main wings 12, and covers from below the roots of the main wings 12 and the underside of the fuselage 11 connected to the roots of the main wings 12. In the first embodiment, the fuselage fairing 14 extends in the left-right direction between the two main wings 12.

[0017] The tail 13 is provided at the rear end of the fuselage 11. The tail 13 includes a vertical tail that extends upward from the upper surface of the rear end of the fuselage 11. The tail 13 includes a pair of horizontal tails 13A that extend left and right from the vertical tail.

[0018] The hydrogen tank 30 is a tank that stores hydrogen used as fuel. The hydrogen tank 30 is both thermally insulating and pressure resistant, and stores liquefied hydrogen, which is hydrogen that has been liquefied at an extremely low temperature of minus 253 degrees Celsius or below, while keeping the hydrogen cold and pressurized. The hydrogen tank 30 is mounted inside the fuselage 11. In the illustrated example, the hydrogen tank 30 is mounted at the front of the fuselage 11 in the fore-and-aft direction.

[0019] (Propulsion System) Figure 4 is a system diagram showing the general configuration of a propulsion system S1 including a propulsion unit 40 and a cooling unit 70, which will be described later. The hydrogen aircraft 1 of the first embodiment includes a pair of left and right propulsion systems S1, each including a propulsion unit 40, and a pair of left and right cooling units 70. Figure 4 shows one of the propulsion systems S1 and one of the cooling units 70. The two propulsion systems S1 are configured roughly symmetrically, and the following description will focus on one of the propulsion systems S1.

[0020] The propulsion system S1 includes a propulsion device 40 and a liquid hydrogen transfer device 50 that extracts liquid hydrogen from the hydrogen tank 30 and transfers it to the propulsion device 40. As described above, the hydrogen aircraft 1 has a pair of left and right propulsion systems S1, which include a pair of left and right propulsion devices 40 and a pair of left and right liquid hydrogen transfer devices 50.

[0021] The liquid hydrogen transfer device 50 includes a liquid hydrogen line 51, a downstream pump 52, and an upstream pump 53. The liquid hydrogen line 51 is a passage through which liquid hydrogen flows, and connects the hydrogen tank 30 and the propulsion device 40. The downstream pump 52 and the upstream pump 53 are provided midway along the liquid hydrogen line 51, and pump the liquid hydrogen stored in the hydrogen tank 30 toward the propulsion device 40. In terms of the flow direction of the liquid hydrogen, the downstream pump 52 is provided downstream of the upstream pump 53, i.e., closer to the propulsion device 40.

[0022] The propulsion device 40 includes a carburetor 41 and an engine 42. The engine 42 is housed inside the nacelle 16. The carburetor 41 is housed inside the engine pylon 17.

[0023] Vaporizer 41 is a device for vaporizing liquid hydrogen. Liquid hydrogen line 51 is connected to vaporizer 41 of propulsion device 40. Liquid hydrogen discharged from hydrogen tank 30 is introduced into vaporizer 41 and vaporized therein.

[0024] The engine 42 is a hydrogen gas turbofan engine including a combustor, a turbine, a compressor, and a fan. The carburetor 41 and the combustor are connected via an injector, and hydrogen gas vaporized by the carburetor 41 is injected into the combustor. Air compressed by the compressor is introduced into the combustor. The hydrogen gas and air react and burn in the combustor, generating combustion energy. The turbine receives the generated combustion energy and rotates to generate a jet stream, which also rotates the compressor and the fan. The engine 42 is disposed inside the nacelle 16 so that the jet stream generated by the turbine is ejected rearward and the fan blows air rearward. The jet stream and the rearward flow of air act on the aircraft 10 as propulsion, moving the aircraft 10 forward.

[0025] (Cooling Device) The two cooling devices 70 mounted on the hydrogen aircraft 1 are configured roughly symmetrically, and one of the cooling devices 70 will be described below.

[0026] The cooling system 70 includes a heat exchanger 71 and uses air cooled by the heat exchanger to cool the inner surface of the skin of the airframe 10. In the first embodiment, the cooling system 70 cools the skin of the main wing 12, i.e., the inner surface 24A of the main wing panel 24. In addition to the heat exchanger 71, the cooling system 70 includes a cooled air line 72C and a pre-cooled air line 72B. The cooling system 70 also includes a first branch line 73B and a second branch line 73C.

[0027] The heat exchanger 71 exchanges heat between liquid hydrogen and air. The heat exchanger 71 is an indirect heat exchanger that exchanges heat between two fluids without contact. Inside the heat exchanger 71, a first passage 72A and a second passage 73A are arranged, through which the two fluids flow independently. As will be described later, air from inside the aircraft body 10 is introduced into the first passage 72A, and liquid hydrogen is introduced into the second passage 73A. As described above, the liquid hydrogen is in an extremely low temperature state of minus 230 degrees or less, and the temperature of the liquid hydrogen is sufficiently lower than that of the air present inside the aircraft body 10. As a result, in the heat exchanger 71, the air is cooled by the liquid hydrogen.

[0028] In the first embodiment, the heat exchanger 71 is provided outside the hydrogen tank 30. Specifically, the heat exchanger 71 is mounted inside the main wing 12, in a position close to the engine pylon 17.

[0029] The first branch line 73B and the second branch line 73C are passages through which liquid hydrogen flows. The first branch line 73B and the second branch line 73C each branch off from the liquid hydrogen line 51. With respect to the flow direction of liquid hydrogen in the liquid hydrogen line 51, the branch point of the first branch line 73B to the liquid hydrogen line 51 is located upstream of the branch point of the second branch line 73C to the liquid hydrogen line 51. The first branch line 73B is connected to the heat exchanger 71 in communication with one end of the second passage 73A of the heat exchanger 71, connecting the liquid hydrogen line 51 to the second passage 73A. The second branch line 73C is connected to the heat exchanger 71 in communication with the other end of the second passage 73A of the heat exchanger 71, connecting the portion of the liquid hydrogen line 51 downstream of the branch point of the first branch line 73B to the second passage 73A.

[0030] With the above configuration, a portion of the liquid hydrogen flowing inside the liquid hydrogen line 51 and drawn out from the hydrogen tank 30 passes through the first branch line 73B and is introduced into the second passage 73A of the heat exchanger 71. After passing through the second passage 73A, i.e., the heat exchanger 71, this portion of the liquid hydrogen passes through the second branch line 73C and is returned to the liquid hydrogen line 51.

[0031] The first branch line 73B and the second branch line 73C branch off from a portion of the liquid hydrogen line 51 that is downstream of the downstream pump 52. In other words, one end of the first branch line 73B and the second branch line 73C, which is opposite the heat exchanger 71, connects the downstream pump 52, which is located furthest downstream in the direction of liquid hydrogen flow among the multiple pumps provided on the liquid hydrogen line 51, to the portion between the propulsion unit 40 and the propulsion unit 40. The downstream pump 52 corresponds to the pump in this disclosure.

[0032] In the first embodiment, an on-off valve 74 is provided midway along the first branch line 73B to open and close the first branch line 73B. When the on-off valve 74 is closed, the inflow of liquid hydrogen into the heat exchanger 71 is stopped. The on-off valve 74 is opened and closed in response to a signal from a control device mounted on the hydrogen aircraft 1. The on-off valve 74 is only opened while the hydrogen aircraft 1 is in flight. For example, the on-off valve 74 is opened when the altitude detected by an altimeter mounted on the hydrogen aircraft 1 is higher than a preset reference altitude, and closed when the detected altitude is equal to or lower than the reference altitude.

[0033] The cooling air line 72C and the pre-cooling air line 72B are passages through which air flows. The pre-cooling air line 72B is connected to the heat exchanger 71 in a state where it communicates with one end of the first passage 72A of the heat exchanger 71. The cooling air line 72C is connected to the heat exchanger 71 in a state where it communicates with the other end of the first passage 72A of the heat exchanger 71.

[0034] The cooling device 70 has an air intake 72E that opens to the outside of the airframe 10 and takes in air into the pre-cooling air line 72B from outside the airframe 10. In the first embodiment, the air intake 72E is formed in the fuselage fairing 14 and opens forward. As a result, headwind passing below the airframe 10, which flows rearward relative to the airframe 10 below the airframe 10, is mainly introduced into the pre-cooling air line 72B through the air intake 72E.

[0035] The air taken into the pre-cooling air line 72B from the air intake 72E is introduced into the first passage 72A of the heat exchanger 71. In the first embodiment, a portion of the pre-cooling air line 72B is arranged inside the fuselage 11, and the remaining portion is arranged inside the main wing 12. As a result, the air taken into the pre-cooling air line 72B through the air intake 72E passes through the inside of the fuselage 11 and the inside of the main wing 12 and is introduced into the first passage 72A of the heat exchanger 71.

[0036] The air introduced into the first passage 72A is cooled by heat exchange with liquid hydrogen in the heat exchanger 71. The air cooled in the heat exchanger 71 is then guided from the first passage 72A to the cooled air line 72C and circulates through the cooled air line 72C. In this manner, the air flows through the pre-cooled air line 72B, the first passage 72A (i.e., the heat exchanger 71), and the cooled air line 72C in this order. In other words, the pre-cooled air line 72B, the first passage 72A (i.e., the heat exchanger 71), and the cooled air line 72C are arranged in this order from upstream to downstream in the air flow direction. The air intake 72E is located at the upstream end of the line including the pre-cooled air line 72B, the first passage 72A (i.e., the heat exchanger 71), and the cooled air line 72C in the air flow direction.

[0037] The cooling air line 72C is provided inside the main wing 12. The cooling air line 72C extends from near the engine pylon 17 where the heat exchanger 71 is disposed to near the outer end of the main wing 12 in the left-right direction.

[0038] The cooling air line 72C branches into multiple air-side branch lines 72C2 midway. The cooling air line 72C is composed of multiple air-side branch lines 72C2, a pre-branch line 72C1, and a merging line 72C3. The pre-branch line 72C1 is the upstream portion from the branch point of the air-side branch line 72C2, i.e., the upstream portion from the upstream end of the air-side branch line 72C2 in the air flow direction. The merging line 72C3 is the downstream portion from the merging point of the multiple air-side branch lines 72C2, i.e., the downstream portion from their downstream ends. Each air-side branch line 72C2 extends in the left-right direction along the outer plate of the main wing 12, i.e., the inner surface 24A of the main wing panel 24.

[0039] In this first embodiment, the air side branch line 72C2 is formed by a portion of the stringer 23 provided on the main wing 12 and the main wing panel 24. In other words, in this first embodiment, the portion of the multiple stringers 23 provided on the main wing 12 and the main wing panel 24 are structural materials for the main wing 12 and are also members that define the air side branch line 72C2.

[0040] 3 is a diagram schematically illustrating the cross-sectional structure of the main wing 12. Hereinafter, the stringers 23 provided on the main wing 12 and defining the air-side branch line 72C2 are referred to as cooling-line stringers 123. In the illustrated example, four stringers 23 provided between the two spars 21, 21 of the main wing 12 and running along the upper inner surface 24A of the main wing panel 24 are each a cooling-line stringer 123.

[0041] The multiple cooling-line stringers 123 have the same structure. The cooling-line stringers 123 are hollow members. Specifically, as shown in FIG. 3 , a cross section of the cooling-line stringer 123 perpendicular to the left-right direction has a shape that bulges downward and opens upward. That is, the cooling-line stringer 123 is curved or bent so as to protrude downward, and the upper end portion of the cooling-line stringer 123 itself is open. In the example of FIG. 3 , the cooling-line stringer 123 is approximately U-shaped. That is, the cooling-line stringer 123 has a bottom wall that extends in the left-right direction along a plane that intersects the up-down direction, and side walls that extend upward from the front and rear edges of the bottom wall. The cooling line stringer 123 is disposed so that its upper end contacts the upper inner surface 24A of the main wing panel 24, and the inner surface 24A of the main wing panel 24 closes the upper opening of the cooling line stringer 123. As a result, a space extending in the left-right direction is defined between the cooling line stringer 123 and the inner surface 24A of the main wing panel 24, and an air-side branch line 72C2 through which air flows is defined. The cooling line stringer 123 corresponds to the reinforcing member in this disclosure.

[0042] The cooling device 70 has an air discharge section 72F that opens to the outside of the airframe 10 and discharges air inside the cooling air line 72C to the outside of the airframe 10. In the first embodiment, the air discharge section 72F opens to the outside of the main wing 12 at the outer lateral end of the main wing panel 24. The air discharge section 72F is connected to the downstream end of the cooling air line 72C. Specifically, the junction line 72C3 is provided at the outer lateral end of the main wing panel 24, and the downstream end of the junction line 72C3 located at the outer lateral end of the main wing panel 24 is connected to the air discharge section 72F.

[0043] In the first embodiment, the air release section 72F is provided on the upper surface of the main wing panel 24. During flight of the hydrogen aircraft 1, the pressure on the upper surface of the main wing panel 24 decreases. Specifically, the pressure on the upper surface of the main wing panel 24 is lower than the pressure at least at the opening of the air intake section 72E, which is subjected to the headwind as described above. Thus, in the first embodiment, the air release section 72F is provided at a position where the pressure at the opening of the air release section 72F is lower than the pressure at the opening of the air intake section 72E during flight. This configuration in the first embodiment promotes the introduction of air into the path through which air flows from the air intake section 72E to the air release section 72F, i.e., the path consisting of the pre-cooled air line 72B, the first passage 72A, and the cooled air line 72C.

[0044] In the first embodiment, the air discharge section 72F is provided at the rear of the upper surface of the main wing panel 24, rearward of the center in the longitudinal direction of the main wing panel 24. As a result, the air in the cooling air line 72C is discharged from the rear of the upper surface of the outer end of the main wing panel 24 in the lateral direction to the outside of the main wing 12 and the airframe 10.

[0045] As described above, by discharging air from the rear of the main wing panel 24 to the outside of the airframe 10, in the first embodiment, separation of an air layer at the leading edge of the main wing panel 24, etc., due to this discharged air, is prevented. If an air layer were to separate at the leading edge of the main wing panel 24, there is a risk of a decrease in the efficiency of the aircraft due to a decrease in lift and an increase in air resistance. Therefore, according to the first embodiment, by preventing separation of an air layer at the leading edge of the main wing panel 24, etc., as described above, the efficiency of the aircraft is maintained while the air in the cooling air line 72C can be discharged to the outside of the main wing 12 and the airframe 10. As shown in Figure 5 and other figures, in the first embodiment, the rear of the main wing panel 24 has an inclined portion extending diagonally downward and rearward, and an air discharge portion 72F is provided on this inclined portion.

[0046] As described above, air cooled in the heat exchanger 71 is introduced into the cooling air line 72C. The air-side branch line 72C2 of the cooling air line 72C extends in the left-right direction from near the engine pylon 17 to near the outer left-right end of the main wing 12. As a result, the air cooled in the heat exchanger 71 moves along the inner surface 24A of the main wing panel 24 from near the engine pylon 17 to near the outer left-right end of the main wing 12 while cooling the inner surface 24A, and then is discharged outside the main wing 12 from the air discharge section 72F.

[0047] (Operations, etc.) As described above, in the hydrogen aircraft 1 according to the first embodiment, liquid hydrogen stored as fuel in the hydrogen tank 30 and carried inside the aircraft 10 is cooled by heat exchange in the heat exchanger 71 with air taken into the interior of the aircraft 10. The cooled air then flows along the inner surface 24A of the main wing panel 24 through the cooling air line 72C provided inside the main wing 12. Therefore, the inner surface 24A of the main wing panel 24 can be cooled by the air.

[0048] Here, when a fluid flows along a given wall surface, the lower the wall surface temperature, the larger the range of the laminar boundary layer formed on the wall surface (more specifically, the distance in the fluid flow direction), and the smaller the range of the turbulent boundary layer. Furthermore, the frictional resistance of the fluid in the laminar boundary layer is smaller than the frictional resistance of the fluid in the turbulent boundary layer. Therefore, in the hydrogen aircraft 1 according to the first embodiment, the cooling of the main wing panels 24 reduces the frictional resistance, i.e., air resistance, of the main wing 12 during flight, thereby improving fuel efficiency. In particular, in the hydrogen aircraft 1 according to the first embodiment, the cooling of the main wing panels 24 of the outer skin of the airframe 10 reduces the air resistance on the main wing 12. Therefore, in the hydrogen aircraft 1 according to the first embodiment, the thrust generated by the engine can be reduced by the reduced air resistance, thereby reliably improving fuel efficiency.

[0049] Furthermore, in the hydrogen aircraft 1 according to the first embodiment, air cooled by liquid hydrogen, rather than liquid hydrogen itself, flows through the cooling air line 72C. Therefore, there is no need to configure the cooling air line 72C to accommodate liquid hydrogen. For example, there is no need to increase the airtightness of the passage to prevent liquid hydrogen leakage, and there is no need to manage the temperature inside the passage to prevent unexpected reactions of liquid hydrogen. Therefore, with the hydrogen aircraft 1 according to the first embodiment, the fuel efficiency of the hydrogen aircraft 1 can be improved with a simple configuration.

[0050] Furthermore, in the hydrogen aircraft 1 according to the first embodiment, the heat exchanger 71 is provided outside the hydrogen tank 30, and the liquid hydrogen discharged from the hydrogen tank 30 exchanges heat with the air in the heat exchanger 71. Therefore, in the hydrogen aircraft 1 according to the first embodiment, fluctuations in the temperature and hence the pressure of the liquid hydrogen in the hydrogen tank 30, i.e., fluctuations in the pressure of the hydrogen tank 30, can be suppressed compared to when the heat exchanger 71 is provided inside the hydrogen tank 30 and heat is exchanged between the liquid hydrogen and air within the hydrogen tank 30.

[0051] Furthermore, in the hydrogen aircraft 1 according to the first embodiment, the first branch line 73B branches off from a portion of the liquid hydrogen line 51 downstream of the downstream pump 52. Liquid hydrogen flowing through the liquid hydrogen line 51 downstream of the downstream pump 52 is introduced into the heat exchanger 71 and exchanges heat with air. In other words, the liquid hydrogen flowing through the portion of the liquid hydrogen line 51 close to the vaporizer 41 of the propulsion unit 40 exchanges heat with air. Therefore, in the hydrogen aircraft 1 according to the first embodiment, the liquid hydrogen heated by heat exchange with air can be introduced into the vaporizer 41 at an early stage, preventing the liquid hydrogen from unexpectedly vaporizing before it is introduced into the vaporizer 41.

[0052] Furthermore, in the hydrogen aircraft 1 according to the first embodiment, an air discharge section 72F is provided on the main wing panel 24. The air discharge section 72F opens to the outside of the main wing 12 and discharges the air flowing inside the cooling air line 72C to the outside of the main wing 12. The air flowing inside the cooling air line 72C is air for cooling the inner surface 24A of the main wing panel 24. Therefore, there is no need to provide the hydrogen aircraft 1 with passages, pumps, etc. for returning the air after cooling the main wing 12 back into the airframe 10. Therefore, the hydrogen aircraft 1 according to the first embodiment can achieve the above-mentioned effects while avoiding an increase in the weight of the hydrogen aircraft 1.

[0053] Furthermore, in the hydrogen aircraft 1 according to the first embodiment, the air release section 72F provided on the main wing 12 is provided at the rear of the main wing panel 24, so that air can be released rearward from the air release section 72F, as described above. This prevents the air released from the air release section 72F from separating from the air layer formed around the leading edge of the main wing panel 24 during flight. Therefore, in the hydrogen aircraft 1 according to the first embodiment, the main wing panel 24 can be cooled while ensuring the lift generated by the main wing panel 24 and preventing an increase in air resistance.

[0054] Furthermore, in the hydrogen aircraft 1 according to the first embodiment, the air discharge section 72F provided on the main wing 12 is provided on the upper surface of the main wing panel 24. Therefore, during flight, the pressure at the opening of the air intake 72E is higher than the pressure at the opening of the air discharge section 72F. In other words, the pressure at the upstream end of the line formed by the pre-cooling air line 72B, the first passage 72A, and the cooling air line 72C is higher than the pressure at the downstream end of the line. Therefore, in the hydrogen aircraft 1 according to the first embodiment, air can be reliably introduced and circulated through the line formed by the pre-cooling air line 72B, the first passage 72A, and the cooling air line 72C, and the main wing 12 can be reliably cooled by the air. Furthermore, in the hydrogen aircraft 1 according to the first embodiment, it is possible to omit pumps and other devices for introducing and circulating air through the above-mentioned lines, thereby achieving the above-mentioned effects while avoiding an increase in the weight of the hydrogen aircraft 1.

[0055] Furthermore, in the hydrogen aircraft 1 according to the first embodiment, the air-side branch line 72C2 and thus a portion of the cooling air line 72C are defined by the inner surface 24A of the main wing panel 24. Furthermore, a portion of the cooling air line 72C is in contact with the inner surface 24A of the main wing panel 24 and extends along this inner surface 24A. Therefore, in the hydrogen aircraft 1 according to the first embodiment, the main wing panel 24 can be directly cooled by the air flowing inside the cooling air line 72C, and the temperature of the main wing panel 24 can be reliably lowered.

[0056] Furthermore, in the hydrogen aircraft 1 according to the above embodiment, the air-side branch line 72C2, i.e., a part of the cooling air line 72C, is partitioned by a cooling line / stringer 123 that reinforces the main wing panel 24. As a result, in the hydrogen aircraft 1 according to the first embodiment described above, the air-side branch line 72C2 can be provided on the main wing 12 while avoiding an increase in the weight of the hydrogen aircraft 1, compared to when a member for partitioning the air-side branch line 72C2 is provided separately from the stringer 23.

[0057] Second Embodiment Fig. 5 is a schematic perspective view showing the internal structure of the main wing 12 of a hydrogen aircraft 1 according to a second embodiment of the present disclosure. Fig. 6 is a schematic plan view showing the structure of the end of the main wing 12 of a hydrogen aircraft 1 according to the second embodiment of the present disclosure.

[0058] The hydrogen aircraft 1 according to the second embodiment differs from the hydrogen aircraft 1 according to the first embodiment only in the structure of the cooling air line 72C. Therefore, only the cooling air line 72C of the hydrogen aircraft 1 according to the second embodiment will be described below. Note that in the following description of the hydrogen aircraft 1 according to the second embodiment and in Figures 5 and 6, the same reference numerals will be used for the same elements as those in the first embodiment.

[0059] In the second embodiment, as in the first embodiment, the cooling air line 72C is defined by the cooling line stringer 223 and the upper inner surface 24A of the main wing panel 24. Specifically, the cooling line stringer 223 has a shape that bulges downward and opens upward. The cooling line stringer 223 is disposed so that its upper end contacts the upper inner surface 24A of the main wing panel 24, and the inner surface 24A of the main wing panel 24 closes the upper opening of the cooling line stringer 223. As a result, in the second embodiment, as in the first embodiment, a space extending in the left-right direction and allowing air to circulate is defined between the cooling line stringer 223 and the main wing panel 24.

[0060] On the other hand, in the second embodiment, the cooling air line 72C does not branch midway, and only one of the stringers 23 of the main wing 12 functions as both the cooling line stringer 223 and the cooling air line 72C. Also, in the second embodiment, the longitudinal dimension of the cooling line stringer 223 is set to be longer than the other stringers 23. For example, the longitudinal dimension of the cooling line stringer 223 is set to be three or more times the dimension of the other stringers 23.

[0061] In the second embodiment, the flow path area of ​​the cooling air line 72C decreases toward the downstream side. Specifically, the height dimension of the cooling line / stringer 223 is substantially constant in the left-right direction, i.e., in the air flow direction. Meanwhile, the front-rear direction dimension of the cooling line / stringer 223 decreases toward the outside in the left-right direction, i.e., toward the downstream side in the air flow direction. As a result, the cross-sectional area of ​​the flow path of the cooling air line 72C decreases toward the downstream side.

[0062] (Operation, etc.) In the second embodiment, the cooling air line 72C does not branch midway, which simplifies the configuration of the cooling air line 72C.

[0063] Furthermore, the temperature of the air flowing downstream of the cooling air line 72C in the air flow direction is higher than the temperature of the air flowing upstream due to heat received from the main wing panel 24. In contrast, in the second embodiment, the flow path area of ​​the cooling air line 72C is smaller toward the downstream side, so the flow velocity of the air flowing through the cooling air line 72C can be increased toward the downstream side. Therefore, even in the portion of the main wing panel 24 cooled by the air flowing downstream of the cooling air line 72C, the temperature can be reliably reduced by the air flowing through the cooling air line 72C. Specifically, as described above, in a configuration in which the cooling air line 72C extends from near the engine pylon 17 toward the outer ends of the main wing panel 24 in the lateral direction, the temperature of the outer portions of the main wing panel 24 in the lateral direction can also be reliably reduced.

[0064] As described above, the configurations other than the cooling air line 72C are the same between the first and second embodiments, and the second embodiment can also provide the same effects as the first embodiment.

[0065] (Other Modifications) In the first embodiment described above, the number of air-side branch lines 72C2 is four, but the number of air-side branch lines 72C2 is not limited to this. Furthermore, the specific shape of the air-side branch line 72C2 is not limited to the above. Furthermore, the air-side branch line 72C2 may be omitted. In other words, the cooling air line 72C may be a single line. Furthermore, the air-side branch line 72C2 according to the first embodiment may be configured so that the flow path area decreases toward the downstream side, as in the second embodiment.

[0066] Furthermore, in the above first and second embodiments, the case where the air side branch line 72C2 is defined by the stringer 23 and the main wing panel 24 has been described, but the air side branch line 72C2 may be defined only by the stringer 23. Furthermore, the air side branch line 72C2 may be defined by a member separate from the stringer 23.

[0067] Furthermore, the positions of the air intake portion 72E and the air discharge portion 72F are not limited to those described above.

[0068] Furthermore, the location of the heat exchanger 71 is not limited to the above. For example, the heat exchanger 71 may be disposed inside the engine pylon 17 or inside the nacelle 16.

[0069] The location of the carburetor 41 is not limited to the above. However, the carburetor 41 is preferably disposed near the engine 42. Therefore, the carburetor 41 is preferably disposed inside the engine pylon 17 or inside the nacelle 16, as described above.

[0070] Furthermore, the number of hydrogen tanks 30 is not limited to one, and multiple hydrogen tanks 30 may be mounted on the aircraft 10. Furthermore, the location of the hydrogen tank 30 is not limited to inside the fuselage 11, and it may be located outside the fuselage 11 or the main wing 12.

[0071] In the first and second embodiments described above, the inner surface 24A of the main wing panel 24 is cooled by air cooled by liquid hydrogen in the heat exchanger 71. However, the object to be cooled may be any inner surface of the outer panel of the airframe 10, and is not limited to the inner surface 24A of the main wing panel 24. For example, the inner surface of a fuselage panel, which is an outer panel of the fuselage 11, may also be cooled by air. In this case, too, the air resistance generated on the fuselage panel can be reduced, and fuel efficiency can be improved.

[0072] In the first and second embodiments, the propulsion device includes the carburetor 41 and the engine 42, and the engine 42 is a hydrogen gas turbofan engine that uses hydrogen as fuel and includes a combustor, a turbine, a compressor, and a fan. However, the propulsion device that generates thrust for the airframe 10 using hydrogen as fuel is not limited to this. For example, the airframe 10 may be equipped with a propulsion device that includes a carburetor, an engine that generates combustion energy by burning hydrogen as in the above embodiments but does not include a turbine, unlike the above embodiments, and an electric motor driven by the engine. In this case, thrust for the airframe 10 is generated by rotating the turbine using the electric motor.

[0073] (Summary) The above-described embodiment and its modifications include the following disclosures.

[0074] A hydrogen aircraft according to a first aspect of the present disclosure comprises an aircraft body, a hydrogen tank for storing liquid hydrogen, a propulsion device that generates thrust for the aircraft using hydrogen as fuel, a liquid hydrogen transfer device that transfers liquid hydrogen from the hydrogen tank to the propulsion device, and a cooling device that includes a heat exchanger that exchanges heat between the liquid hydrogen and air inside the aircraft to cool the air, and that uses the air cooled by the heat exchanger to cool the inner surface of the aircraft's outer plate.

[0075] According to the first aspect, the inner surface of the aircraft's skin can be cooled by air cooled by liquid hydrogen. This reduces the frictional resistance, or air resistance, that occurs on the aircraft's skin during flight, improving fuel efficiency. Moreover, in the first aspect, air cooled by liquid hydrogen, rather than liquid hydrogen itself, flows through the cooling air line to cool the skin. This eliminates the need to configure the cooling air line to accommodate liquid hydrogen, and the fuel efficiency of a hydrogen aircraft can be improved with a simple configuration.

[0076] A hydrogen aircraft according to a second aspect is the hydrogen aircraft of the first aspect, wherein the heat exchanger exchanges heat between the liquid hydrogen drawn out from the hydrogen tank by the liquid hydrogen transfer device and air.

[0077] According to the second aspect, the air can be cooled by the liquid hydrogen while suppressing pressure fluctuations in the hydrogen tank.

[0078] A third aspect of the hydrogen aircraft is the same as the second aspect, wherein the propulsion device includes a vaporizer that vaporizes liquid hydrogen, the liquid hydrogen transfer device includes a liquid hydrogen line that connects the hydrogen tank and the vaporizer and through which liquid hydrogen flows, and a pump provided midway along the liquid hydrogen line, and the heat exchanger exchanges heat between the liquid hydrogen flowing through the liquid hydrogen line downstream of the pump and air.

[0079] According to the third aspect, the liquid hydrogen heated by heat exchange with air can be introduced into the vaporizer at an early stage, thereby preventing the liquid hydrogen from unexpectedly vaporizing before it is introduced into the vaporizer.

[0080] A hydrogen aircraft according to a fourth aspect is any one of the first to third aspects, wherein the cooling device includes a cooling air line through which air flows to cool the inner surface of the outer skin of the aircraft, and an air discharge section that opens to the outside of the aircraft and discharges the air that has passed through the cooling air line to the outside of the aircraft.

[0081] According to the fourth aspect, the air that has passed through the cooling air line is discharged to the outside of the aircraft via the air discharge section. This eliminates the need for a passage or pump to return the air that has cooled the aircraft back inside. This makes it possible to avoid an increase in the weight of the hydrogen aircraft and improve fuel efficiency with a simple configuration.

[0082] A hydrogen aircraft according to a fifth aspect is the fourth aspect, wherein the cooling device includes a pre-cooled air line through which air flowing into the heat exchanger flows, and an air intake section that opens to the outside of the aircraft and takes in air from outside the aircraft into the pre-cooled air line, and the air intake section is located at a position where the pressure at the opening of the air intake section is higher than the pressure at the opening of the air discharge section while the aircraft is in flight.

[0083] According to the fifth aspect, air can be introduced into and circulated through a line that is made up of a pre-cooling air line, a heat exchanger, and a cooling air line, by utilizing the differential pressure between an air intake provided at the upstream end of the line and an air discharge provided at the downstream end of the line. This eliminates the need for a pump or the like for introducing and circulating air through the line, thereby achieving the above-mentioned effects while avoiding an increase in the weight of the hydrogen aircraft.

[0084] A hydrogen aircraft according to a sixth aspect is the fifth aspect, wherein the aircraft comprises a fuselage and main wings extending from the fuselage outward in the width direction of the fuselage, the cooling air lines are provided along the inner surfaces of the outer plates of the main wings, and the air discharge section is provided at the rear of the outer plates of the main wings.

[0085] According to the sixth aspect, the cooling air lines are provided along the inner surface of the outer plate of the wing, allowing the wing to be cooled by air. Furthermore, the air discharge section is provided at the rear of the outer plate of the wing, preventing the air discharged from the air discharge section from interfering with the rearward airflow formed around the wing during flight. In other words, it is possible to prevent the air layer formed around the leading edge of the wing panel 24 during flight from separating due to the air discharged from the air discharge section. Therefore, the wing panel 24 can be cooled while ensuring lift generated around the wing panel 24 and its surroundings and preventing an increase in air resistance.

[0086] A hydrogen aircraft according to a seventh aspect is the same as the sixth aspect, except that the aircraft comprises a fuselage and main wings extending from the fuselage outward in the width direction of the fuselage, the cooling air lines are provided along the inner surfaces of the outer plates of the main wings, and the air discharge sections are provided on the upper surfaces of the outer plates of the main wings.

[0087] The pressure generated on the upper surface of the main wing during flight is kept relatively low. Thus, according to the seventh aspect, the pressure at the air intake section can be reliably made higher than the pressure at the air discharge section during flight.

[0088] In the hydrogen aircraft of the eighth aspect, in any one of the first to seventh aspects, the cooling device includes a cooling air line that extends along the inner surface of the skin of the aircraft while being in contact with the inner surface of the skin of the aircraft, and through which air that cools the inner surface of the skin of the aircraft flows.

[0089] According to the eighth aspect, heat can be efficiently exchanged between the air flowing inside the cooling air line and the inner surface of the skin of the airframe, thereby efficiently cooling the skin.

[0090] A ninth aspect of the hydrogen aircraft is any one of the first to eighth aspects, wherein the cooling device includes a cooling air line through which air flows to cool the inner surface of the skin of the aircraft, and the aircraft includes a hollow reinforcing member that reinforces the skin of the aircraft and defines at least a portion of the cooling air line.

[0091] According to the ninth aspect, the weight of the hydrogen aircraft can be reduced compared to when a member for partitioning the cooling air line through which air for cooling the inner surface of the aircraft's skin flows is provided separately from a member for reinforcing the aircraft's skin.

[0092] A hydrogen aircraft according to a tenth aspect is any one of the first to ninth aspects, wherein the cooling device includes a cooling air line through which air flows to cool the inner surface of the outer panel of the aircraft, and the cooling air line has a shape in which the flow path area becomes smaller toward the downstream side.

[0093] According to the tenth aspect, in a cooling air line through which air flows to cool the inner surface of the skin of an airframe, the flow velocity of the air can be increased toward the downstream side of the cooling air line, so that the skin of the airframe can be reliably cooled even by air at a higher temperature downstream of the cooling air line than upstream.

Claims

1. A hydrogen aircraft comprising: an aircraft; a hydrogen tank for storing liquid hydrogen; a propulsion unit that generates thrust for the aircraft using hydrogen as fuel; a liquid hydrogen transfer unit that transfers liquid hydrogen from the hydrogen tank to the propulsion unit; and a cooling unit that includes a heat exchanger that exchanges heat between the liquid hydrogen and the air inside the aircraft to cool the air, and that uses the air cooled by the heat exchanger to cool the inner surface of the exterior panel of the aircraft.

2. A hydrogen aircraft as claimed in claim 1, wherein the heat exchanger exchanges heat between the liquid hydrogen drawn out from the hydrogen tank by the liquid hydrogen transfer device and air.

3. A hydrogen aircraft as described in claim 2, wherein the propulsion device includes a vaporizer that vaporizes liquid hydrogen, the liquid hydrogen transfer device includes a liquid hydrogen line that connects the hydrogen tank and the vaporizer and through which liquid hydrogen flows, and a pump provided midway along the liquid hydrogen line, and the heat exchanger exchanges heat between the liquid hydrogen flowing through the liquid hydrogen line downstream of the pump and air.

4. A hydrogen aircraft as described in claim 1, wherein the cooling device includes a cooling air line through which air flows to cool the inner surface of the skin of the aircraft, and an air discharge section that opens to the outside of the aircraft and discharges air that has passed through the cooling air line to the outside of the aircraft.

5. A hydrogen aircraft as described in claim 4, wherein the cooling device includes a pre-cooled air line through which air flowing into the heat exchanger flows, and an air intake section that opens to the outside of the aircraft and takes in air from outside the aircraft into the pre-cooled air line, and the air intake section is located at a position where the pressure at the opening of the air intake section is higher than the pressure at the opening of the air discharge section while the aircraft is in flight.

6. A hydrogen aircraft as described in claim 5, wherein the aircraft comprises a fuselage and a main wing extending from the fuselage outward in the width direction of the fuselage, the cooling air line is provided along the inner surface of the outer plate of the main wing, and the air discharge section is provided at the rear of the outer plate of the main wing.

7. A hydrogen aircraft as described in claim 5, wherein the aircraft comprises a fuselage and a main wing extending from the fuselage outward in the width direction of the fuselage, the cooling air line is provided along the inner surface of the outer plate of the main wing, and the air discharge section is provided on the upper surface of the outer plate of the main wing.

8. A hydrogen aircraft as described in claim 1, wherein the cooling device includes a cooling air line extending along the inner surface of the skin of the aircraft while being in contact with the inner surface of the skin of the aircraft, and through which air for cooling the inner surface of the skin of the aircraft flows.

9. A hydrogen aircraft as claimed in any one of claims 1 to 8, wherein the cooling device includes a cooling air line through which air flows to cool the inner surface of the skin of the aircraft, and the aircraft includes a hollow reinforcing member that reinforces the skin of the aircraft and defines at least a portion of the cooling air line.

10. A hydrogen aircraft as described in claim 1, wherein the cooling device includes a cooling air line through which air flows to cool the inner surface of the outer plate of the aircraft, and the cooling air line has a shape in which the flow path area becomes smaller toward the downstream side.

Images