GB2604141A

GB2604141A - Aircraft wing with tubular fuel tanks

Info

Publication number: GB2604141A
Application number: GB2102726.3A
Authority: GB
Inventors: Tulloch William
Original assignee: Airbus Operations Ltd
Current assignee: Airbus Operations Ltd
Priority date: 2021-02-25
Filing date: 2021-02-25
Publication date: 2022-08-31
Also published as: GB202102726D0

Abstract

An aircraft wing (fig.3,3) has a spanwise direction extending between a root (fig.3,16) and a tip end (fig.3,15), and a chordwise direction extending between a leading edge (fig.3,13) and a trailing edge (fig.3,14). A tubular fuel tank 12a-c is located between upper and lower wing covers 10,11, with a longitudinal axis extending in the spanwise direction. The fuel tank and each cover are integrally formed using composite material, such as carbon fibre reinforced or laminate materials. Preferably, pairs of fuel tanks are integrally formed, adjacent in the chordwise direction. Each tank may have a vertical wall extending between the covers forming a spar-like structure for the wing. Preferably, the tank cross-section is a rounded square or squircle, with a noodle or filler 78 used between rounded exterior corners of adjacent tanks. Each tank may have a port (fig.4a,81) for coupling to a fuel line, and be load bearing and safe-life for the aircraft wing. A method of manufacturing an aircraft wing by laying up composites and co-bonding the fuel tank to the covers is also claimed.

Description

AIRCRAFT WING WITH TUBULAR FUEL TANKS FIELD OF THE INVENTION

[0001] The present invention relates to an aircraft wing and to a method of manufacturing an aircraft wing.

BACKGROUND OF THE INVENTION

[0002] Recently, interested has grown in using Hydrogen as a fuel for powering aircraft. Current Hydrogen-based research aircraft design require the Hydrogen to be stored in the fuselage for simplicity, leaving the wing structures (typically used for fuel storage) empty and unused This would be highly inefficient for a commercial aircraft [0003] Current modern commercial aircraft which use liquid hydrocarbon based fuels have composite wings where a large part or even all of the wing structure comprises composite materials, typically carbon fibre reinforced polymer (CFRP).

[0004] In other industries, such as the automotive industry, hydrogen fuels are stored in pressurised tanks. These tanks may be made exclusively of metal, e.g. steel or aluminium, or may be metal tanks reinforced with a composite overwrap. Alternatively, the tanks may be made of composite materials, such as fibreglass/aramid or carbon fibre with a metal or polymer (thermoplastic) liner.

SUMMARY OF THE INVENTION

[0005] A first aspect of the invention provides an aircraft wing comprising a root end, a tip end, a leading edge, a trailing edge, a spanwise direction extending between the root end and the tip end, a chordwise direction extending between the leading edge and the trailing edge, an upper wing cover, a lower wing cover, and a generally tubular fuel tank between the upper wing cover and the lower wing cover with a longitudinal axis of the fuel tank extending generally in the spanwise direction, wherein the fuel tank and the upper wing cover and the lower wing cover each comprise composite material, and wherein the composite material of the fuel tank is integrally formed with the composite material of the upper wing cover and the composite material of the lower wing cover.

[0006] A further aspect of the invention provides a method of manufacturing an aircraft wing, comprising laying up a composite upper wing cover, laying up a composite lower wing cover, laying up a composite generally tubular fuel tank, and co-bonding the fuel tank to the upper wing cover and the lower wing cover.

[0007] The invention is advantageous in that the spanwise oriented fuel tanks integral with the upper and lower wing covers may form a complete wing box of the aircraft wing, which may eliminate the need for wing box ribs and may take all wing bending and brazier loads (i.e. the ovalisation of the wing structure due to bending) of the aircraft wing.

[0008] The composite material of the fuel tank may be bonded with the composite material of the upper wing cover and with the composite material of the lower wing cover.

[0009] The fuel tank may have a lower wall portion and an upper wall portion, and the fuel tank lower wall portion has an exterior surface generally corresponding to an interior surface of the lower wing cover, and the fuel tank upper wall portion has an exterior surface generally corresponding to an interior surface of the upper wing cover. The lower wall portion and the upper wall portion may be flattened as compared with a circular cylindrical tube but may not be flat as the upper and lower wing covers may have curvature of the aerofoil profile and/or wing dihedral curvature [0010] The aircraft wing may further comprise a plurality of the generally tubular fuel tanks between the upper wing cover and the lower wing cover, wherein each of the plurality of fuel tanks comprises composite material.

[0011] A pair of fuel tanks of the plurality of fuel tanks may be adjacent in the chordwise direction, and one of the pair of fuel tanks may be integrally formed with the other of the pair of fuel tanks.

[0012] The composite material of one of the pair of fuel tanks may be bonded to the composite material of the other of the pair of fuel tanks.

[0013] Each fuel tank of the pair of fuel tanks may have a generally vertical tank wall portion extending between the upper wing cover and the lower wing cover, and the adjacent generally vertical tank wall portions may have corresponding exterior surfaces.

[0014] The adjacent generally vertical tank wall portions may be integrally formed to provide a spar-like structure for the aircraft wing Where the aircraft has three or more fuel tanks, a multi-spar aircraft wing structure may result.

[0015] A section of the generally tubular fuel tank approximates a rounded square or a squircle.

[0016] The aircraft wing may further comprise a noodle or filler between rounded exterior comers of adjacent fuel tanks.

[0017] The generally tubular fuel tank may have a closed end and a ported end for coupling to a fuel line. The ends of the fuel tank may be formed as pressure boundaries and may be generally dome shaped with corner radii to the tubular section of the tank.

[0018] The fuel tank integral with the upper and lower wing covers may be load bearing and safe-life for the aircraft wing. Here, a load bearing fuel tank integrated with the wing structure means that the fuel tank forms part of the primary load bearing structure of the aircraft wing. Safe-life means that the fuel tank structure is not designed to be removed or inspected or repaired through the design life of the aircraft wing but is considered to be structurally safe throughout the design life of the aircraft. The safe-life philosophy may not extend to the ported end of the fuel tank for connection to a fuel line but otherwise covers the entire structure of the fuel tank.

[0019] The fael tank may comprise carbon fibre reinforced composite material [0020] The upper and lower wing covers may each comprise carbon fibre reinforced composite material. The upper and lower wing covers may be laid up as pre-preg fibre layers.

[0021] The fuel tank may be configured to contain a pressurised fuel, preferably hydrogen fuel. Alternative fuels may include any liquid or gaseous fuels, which may be pressurised or unpressurised.

[0022] The fuel tank may comprises laminate composite material. The fuel tank structure (i.e. the fuel tank walls) may be seamless throughout, with no joins or discontinuities in the laminate composite material.

[0023] A further aspect of the invention provides an aircraft comprising an aircraft wing according to the first aspect of the invention [0024] Laying up the generally tubular fuel tank may comprise forming the fuel tank by winding fibre layers around a mandrel.

[0025] The method may further comprise laying up a plurality of the composite generally tubular fuel tanks, and co-bonding adjacent fuel tanks together during co-bonding the fuel tanks to the upper wing cover and the lower wing cover.

[0026] Where a section of each of the generally tubular fuel tanks may approximate a rounded square or a squircle, the method may further comprise inserting a noodle or filler between rounded exterior corners of adjacent fuel tanks before co-bonding the plurality of fuel tanks to the upper and lower wing covers

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Embodiments of the invention will now be described with reference to the accompanying drawings, in which: [0028] Figure us a plan view of an aircraft; [0029] Figure 2 is a front view of the aircraft of Figure 1; [0030] Figure 3 is a schematic plan view of the port wing showing the fuel system and propulsion system with the upper cover removed; [0031] Figure 4 a) is a schematic spanwise section through one of the fuel tanks, and b) is a schematic chordwise section through a plurality of the fuel tanks; [0032] Figure 5 is a schematic section view through one of the fuel tanks, [0033] Figures 6 to 9 show assembly steps for manufacturing an aircraft wing with fuel tanks integral with the upper and lower wing covers; [0034] Figure 10 is a schematic section view of winding fibre layers onto a mandrel to form the fuel tank, and [0035] Figure 11 is another schematic plan view of the port wing showing an alternative arrangement of the fuel tanks.

DETAILED DESCRIPTION OF EMBODIMENT(S)

[0036] An aircraft 1 shown in Figures 1 and 2 comprises a fuselage 2 and a pair of wings 3, 4. Each wing comprises a wingbox 5, comprising an upper cover 10, a lower cover 11, and integral, closed, generally tubular fuel tanks 12. The wing has a leading edge 13, a trailing edge 14, a tip end 15 and a root end 16. The wing spanwise direction extends between the root end 16 and the tip end 15. The wing chordwise direction extends between the leading edge 13 and the trailing edge 14.

[0037] The upper cover 10 is shown in Figure 1, and part of the wingbox 5 is shown in Figure 3 with the upper cover 10 removed to make the internal parts visible. Figure 3 is a plan view of the port wing with various internal parts shown. In Figure 3, the tubular fuel tanks 12 are shown in the outboard portion of the wing 3 and the mid and inboard portions of the wing may have a different wingbox construction and/or may have a different fuel storage solution. In the following, the wingbox 5 of the outboard wing portion will be discussed in detail.

[0038] The fuel tanks 12 are elongate and are oriented with their longitudinal axes oriented generally in the spanwise direction. Spanwise tapering of the wing may promote a tapered shape of the fuel tank 12, with the fuel tank having a greater section at its inboard end compared to its outboard end in the wing spanwise direction. Alternatively, the fuel tank 12 may have a substantially constant section between its ends. The fuel tank 12 may be a pressure vessel.

[0039] In this example, a plurality of tubular hydrogen fuel tanks 12 form part of the structure of the wingbox 5 of the wing 3, but in an alternative example only a single fuel tank 12 may be provided.

[0040] A fuel cell system 30 is also located inside the wingbox 5, in a bay between a pair of ribs 17 shown in Figure 3. The fuel cell system 30 comprises a fuel cell 32 and a battery 33. A first fuel line 40 is configured to deliver hydrogen fuel from the fuel tanks 12 to the fuel cell system 30. The fuel cell 32 is an electrochemical cell (or stack of cells) which converts chemical energy of the hydrogen fuel into electrical energy which is stored in the battery 33.

[0041] A propulsion system 50 is carried by the wing 3. As shown in Figure 3, the propulsion system 50 is located outside the wing 3. The propulsion system 50 comprises a power control unit 51, a motor 52 and a shrouded propeller 53. In this example the propulsion system 50 is suspended under the wing 3. In an alternative example the propulsion system 50 may be located over the wing 3, or carried by the wing or fuselage 2 in another configuration. An electrical power line 60 is configured to deliver electrical power from the fuel cell system 30 to the propulsion system 50.

[0042] It will be appreciated that in other examples the fuel tanks may be used to store fuels other than hydrogen, in liquid or gaseous form. The manner of conversion of energy stored in the fuel tanks to propulsive force to power the aircraft 1 will depend on the fuel used and so the conversion of chemical energy and the type of propulsion system may change from the above example depending on the fuel stored in the fuel tanks 12.

[0043] Figure 4 shows schematic section views of the wingbox 5 with figure 4a) showing a schematic spanwise section through one of the fuel tanks 12, and figure 4b showing a schematic chordwise section through the plurality of fuel tanks 12. The fuel tanks 12, the upper wing cover 10 and the lower wing cover 11 may each comprise a laminate carbon fibre reinforced polymer composite construction [0044] The composite material of the fuel tanks 12 is integrally formed with the composite material of the upper wing cover 10 and the composite material of the lower wing cover 11. In particular, the composite material of the fuel tank 12 is bonded with the composite material of the upper wing cover 10 and with the composite material of the lower wing cover 11 by co-bonding during manufacture of the wingbox 5.

[0045] Integrally forming the fuel tanks 12 with the upper and lower wing covers 10, 11 may eliminate the need for wing box ribs in the wing box 5 which may take all wing bending and brazier loads (i.e. the ovalisation of the wing structure due to bending) of the aircraft wing.

[0046] Each fuel tank 12 is generally tubular with a closed pressure boundary at one end 70 and a closed pressure boundary at its opposite end 80with a ported opening 81. The ported opening 81 is configured for coupling to the fuel line 40 and may include a valve (not shown) The ends 70, 80 of the fuel tank are formed as pressure boundaries and are generally dome shaped with corner radii to the tubular section of the tank 12 between the ends 70, 80.

[0047] As shown in figure 4b the section of each of the generally tubular fuel tanks 12 may approximate a rounded square or a squircle.

[0048] A rounded square is generated by separating four quarters of a circle and connecting their loose ends with straight lines. A squircle is a type of superellipse. The tubular fuel tanks 12 may only approximate a rounded square or squircle and need not be mathematically identical. What is important is that the corners are rounded and the sides are flattened as compared with a circle or ellipse, which shapes are commonly used as pressure vessel sections due to their optimised ability to manage hoop stresses. By flattening the sides, the fuel tanks 12 are slightly compromised in term of their ability to handle hoop stresses but offer significant advantages in terms of integration to form the wing box 5, as will be described below.

[0049] Each fuel tank 12 has a lower wall portion 71 and an upper wall portion 72 as best shown in figure 5. The lower wall portion 71 has an exterior surface 73 generally corresponding to an interior surface 74 of the lower wing cover 11. The upper wall portion 72 has an exterior surface 75 generally corresponding to an interior surface 76 of the upper wing cover 10. The lower wall portion 71 and the upper wall portion 72 may be flattened as compared with a circular cylindrical tube but may not be flat as the upper and lower wing covers may have curvature of the aerofoil profile of the wing and/or dihedral curvature of the wing 3.

[0050] The fuel tank 12 further comprises generally vertical tank wall portions 77 extending between the lower wall portion 71 and the upper wall portion 72. The generally vertical tank wall portions 77 have outer surfaces 79. The tank wall portions 71, 72 and 77 are joined by radiused corners.

[0051] Figure 6 -9 show assembly steps for manufacturing the aircraft wing 3 with fitel tanks 12 integral with the upper and lower wing covers 10, 11. In figure 6 a first fitel tank 12a is positioned on a stack of pre-preg fibre composite layers of the lower wing cover II A noodle 78 or filler is placed between the outer radiused corner of the fuel tank 12a and the interior surface 74 of the lower wing cover 11.

[0052] As shown in figure 7 this process is repeated by the introduction of a second fuel tank 12b positioned on the stack of pre-preg fibre layers of the lower wing cover 11 such that the outer surfaces 79 of the generally vertical tank wall portions 77 of the first and second fuel tanks 12a, 12b are in contact. Additional noodles 78 or fillers are introduced in the interstitial spaces between rounded exterior corners of adjacent fuel tanks 12 [0053] This process can be repeated by the introduction of a third fuel tank 12c and any number of subsequent fuel tanks 12 as desired. Finally, as shown in figure 8 the prepreg fibre layers of the upper wing cover 10 are laid upon the upper wall portions 72 of the fuel tanks 12a, 12b, 12c and the entire wingbox 5 is consolidated and co-cured.

[0054] The resultant structure is shown in figure 9 in which one or a plurality of composite fuel tanks 12 are integrally formed with a composite material of the upper wing cover 10 and the composite material of the lower wing cover 11. As can be seen, since the generally vertical tank wall portion 77 of the adjacent fuel tanks 12 have corresponding exterior surfaces 79, the adjacent generally vertical tank wall portions 77 become integrally formed to provide a spar-like structure 82 (shown in broken lines in figure 9) for the wingbox 5 when the wingbox is co-cured.

[0055] Where the number of fuel tanks 12 is three or more a plurality of these spar-like structures 82 is formed creating a multi-spar wingbox.

[0056] Since the fuel tanks 12 are integrally formed with the upper wing cover 10 and the lower wing cover 11 the fuel tanks 12 are designed to be load bearing in the sense that they form part of the primary load bearing structure of the aircraft wing, and are also 'safe life'. Safe life means that the fuel tank's structure is not designed to be removed or inspected or repaired through the design life of the aircraft wing but is considered to be structurally safe throughout the design life of the aircraft The safe life philosophy may not extend to the ported aperture 81 in the end 80 of the fuel tank for connection to the fuel line 40 but otherwise the safe life philosophy covers the entire structure of the fuel tank 12.

[0057] The fuel tank structure (i.e. the fuel tank walls) may be seamless throughout, with no joins or discontinuities in the laminate composite material. The fuel tank 12 is designed to accommodate pressure loads so that the fuel tank 12 may carry pressurised fuel, such as hydrogen fuel.

[0058] The tubular fuel tank 12 may be constructed on a mandrel 90 which may be collapsible so that it can be removed from inside the fuel tank 12 after manufacturing the fuel tank. Layers of carbon fibre material 91, or fibre composite material in the case of pre-preg, may be unwound from a spool 92 as the mandrel 90 is rotated. The ends of the mandrel 90 may be rounded and shaped so as to form the pressure boundaries at the ends 70, 80 of the fuel tank 12.

[0059] The orientation of the fibres in the fibre material 91 may take any desired orientation, e.g. +1-45 degrees with respect to the longitudinal axis of the fuel tank 12. Additional zero degree fibres may be included in the layup such that the spanwise orientation of the fuel tanks 12 in the wingbox 5 may accommodate the wing bending loads efficiently. These, and other fibre orientations and layups may be tailored as desired. Whilst in the illustrated example the fuel tank 12 is formed by winding fibre material, it will be appreciated that techniques other than winding may alternatively be used.

[0060] When pre-preg material is used to create the fuel tank 12, the fuel tank 12 may be cured or partially cured prior to incorporating with any other fuel tanks 12 and the upper and lower wing covers 10, 11. When dry fibre material is used to create the fuel tank 12, the fibre material may be infused with resin and cured prior to incorporating with the upper and lower wing covers 10, 11. Similarly, the upper and lower wing covers 10, 11 may be laid up as either pre-preg or dry fibre which is subsequently infused with resin.

[0061] The step of curing the resin of the upper and lower wing covers 10, 11 whilst in contact with the fuel tanks 12 ensure the fuel tanks 12 become co-bonded and integrally formed with the upper and lower wing covers 10, 11. Similarly, the step of curing the resin of adjacent fuel tanks 12 whilst their vertical walls 77 are in contact ensures ensure the fuel tanks 12 become co-bonded and integrally formed together.

[0062] In a composite aircraft wing lightning strike protection measures may be required and so a metal film or mesh may be included in the fibre layup during manufacture of the fuel tanks 12 and/or the upper or lower wing covers 10, 11. In addition to lighting strike protection, equipotential bonding static discharge measures may also be included.

[0063] Inside the fuel tanks 12 one or more baffles may be included to alleviate the effects of 'fuel slosh'. These baffles may be oriented in the spanwise and/or chordwise directions.

[0064] Figure 11 is another schematic plan view of the port wing 3 showing an alternative arrangement of the fuel tanks 12. The arrangement of the wing structure is similar in many respects to that shown in figure 3, but in figure 11 both the outboard portion, the mid and inboard portions of the wing all comprise a wingbox 5 having fuel tanks 12 integrally formed with the composite material of the upper wing cover and the composite material of the lower wing cover. Accordingly, whilst in the examples shown in figure 3 inboard and mid-span wing portions may have a different fuel tank design to that of this invention, in figure 11 substantially all of the wing 3 comprises the spanwi se oriented integral fuel tanks 12. Rib boundaries 17 may be included between the fuel tanks 12. It will also be appreciated that the invention may be employed only on inboard or mid-span wing portions.

[0065] Where the word 'or' appears this is to be construed to mean 'and/or' such that items referred to are not necessarily mutually exclusive and may be used in any appropriate combination.

[0066] Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.

Claims

CLAIMSI. An aircraft wing comprising a root end, a tip end, a leading edge, a trailing edge, a spanwise direction extending between the root end and the tip end, a chordwise direction extending between the leading edge and the trailing edge, an upper wing cover, a lower wing cover, and a generally tubular fuel tank between the upper wing cover and the lower wing cover with a longitudinal axis of the fuel tank extending generally in the spanwise direction, wherein the fuel tank and the upper wing cover and the lower wing cover each comprise composite material, and wherein the composite material of the fuel tank is integrally formed with the composite material of the upper wing cover and the composite material of the lower wing cover.
2. An aircraft wing according to claim 1, wherein the composite material of the fuel tank is bonded with the composite material of the upper wing cover and with the composite material of the lower wing cover.
3. An aircraft wing according to claim 1 or claim 2, wherein the fuel tank has a lower wall portion and an upper wall portion, and the fuel tank lower wall portion has an exterior surface generally corresponding to an interior surface of the lower wing cover, and the fuel tank upper wall portion has an exterior surface generally corresponding to an interior surface of the upper wing cover.
4. An aircraft wing according to any preceding claim, further comprising a plurality of the generally tubular fuel tanks between the upper wing cover and the lower wing cover, wherein each of the plurality of fuel tanks comprises composite material An aircraft wing according to claim 4, wherein a pair of fuel tanks of the plurality of fuel tanks are adjacent in the chordwi se direction, and one of the pair of fuel tanks is integrally formed with the other of the pair of fuel tanks.6. An aircraft wing according to claim 5, wherein the composite material of one of the pair of fuel tanks is bonded to the composite material of the other of the pair of fuel tanks.7 An aircraft wing according to claim 5 or claim 6, wherein each fuel tank of the pair of fuel tanks has a generally vertical tank wall portion extending between the upper wing cover and the lower wing cover, and the adjacent generally vertical tank wall portions have corresponding exterior surfaces.8 An aircraft wing according to claim 7, wherein the adjacent generally vertical tank wall portions are integrally formed to provide a spar-like structure for the aircraft wing 9 An aircraft wing according to any preceding claim, wherein a section of the generally tubular fuel tank approximates a rounded square or a squircle.10. An aircraft wing according to claim 9 when dependent on claim 4, further comprising a noodle or filler between rounded exterior corners of adjacent fuel tanks.11. An aircraft wing according to any preceding claim, wherein the generally tubular fuel tank has closed end and a ported end for coupling to a fuel line.12. An aircraft wing according to any preceding claim, wherein the fuel tank integral with the upper and lower wing covers is load bearing and safe-life for the aircraft wing.13 An aircraft wing according to any preceding claim, wherein the fuel tank comprises carbon fibre reinforced composite material.14 An aircraft wing according to any preceding claim, wherein the upper and lower wing covers each comprises carbon fibre reinforced composite material.15. An aircraft wing according to any preceding claim, wherein the fuel tank is configured to contain a pressurised fuel, preferably hydrogen fuel.16. An aircraft wing according to any preceding claim, wherein the fuel tank comprises laminate composite material.17. A method of manufacturing an aircraft wing, comprising: laying up a composite upper wing cover; laying up a composite lower wing cover; laying up a composite generally tubular fuel tank; and co-bonding the fuel tank to the upper wing cover and the lower wing cover.18. A method according to claim 17, wherein laying up the generally tubular fuel tank comprises forming the fuel tank by winding fibre layers around a mandrel.19. A method according to claim 17 or claim 18, further comprising: laying up a plurality of the composite generally tubular fuel tanks; and co-bonding adjacent fuel tanks together during co-bonding the fuel tanks to the upper wing cover and the lower wing cover.20. A method according to claim 19, wherein a section of each of the generally tubular fuel tanks approximates a rounded square or a squircle, and the method further comprising: inserting a noodle or filler between rounded exterior corners of adjacent fuel tanks before co-bonding the plurality of fuel tanks to the upper and lower wing covers.