Patent ID: 12240622

DETAILED DESCRIPTION OF EMBODIMENT(S)

FIG.1shows an aircraft1with port and starboard fixed wings2,3, engines9, a fuselage4with a nose end5and a tail end6, the tail end6including horizontal and vertical stabilising surfaces7,8. The aircraft1is a typical jet passenger transonic transport aircraft but the invention is applicable to a wide variety of fixed wing aircraft types, including commercial, military, passenger, cargo, jet, propeller, general aviation, etc. with any number of engines attached to the wings or fuselage.

Each wing2,3of the aircraft1has a cantilevered structure with a length extending in a span-wise direction from a wing root10to a wing tip11, the root10being joined to the aircraft fuselage4.

Endeavours to increase aircraft efficiency mean that improvements to existing aircraft are continuously being made, with one such solution being the use of cryogenic fuels such as liquid hydrogen.

Hydrogen may be utilised as an aviation fuel in a number of ways, such as hydrogen direct burn (e.g. a modified gas turbine engine may provide power by burning hydrogen in the turbojet combustion chambers) or converting the hydrogen to electricity by using fuel cell technology in which the electrochemical cell converts the chemical energy of the hydrogen fuel and an oxidising agent (e.g. oxygen) into electricity through redox reactions.

The hydrogen tank(s)12may be located in any suitable location on the aircraft1, but are typically located in separate tanks below the wings2,3(e.g. in fuel pods), in the wings2,3or in one or more fuel tanks12located within or adjacent the fuselage4.FIG.2shows a hydrogen fuel tank12located towards the rear of the fuselage4, whilstFIG.3shows the tanks located in the wings2,3.

Hydrogen fuel lines14amay extend from the fuel tank(s)12to the aircraft power plants (e.g. engines9and/or fuel cells90) so as to channel hydrogen fuel to the power plants (these fuel lines14amay alternatively be referred to as hydrogen distribution lines14a). Hydrogen fuel lines14bmay extend from refuelling ports16located on an outer surface of the aircraft1to the fuel tank(s)12(these fuel lines may be referred to as hydrogen refuelling lines14b).

Dependent on the respective location of the fuel tank(s)12, power plants, and refuelling ports16, the hydrogen fuel lines14a,14bmay extend significant distances through the wing box structure of the wings2,3and/or through the structure of the fuselage4. In the example shown inFIG.2, the hydrogen fuel lines14aextend from the engines9on the wings2,3to a hydrogen fuel tank12located in the fuselage4, and hydrogen fuel lines14bextend from the hydrogen fuel tank12to a refuelling port16located aft of the hydrogen fuel tank12in the fuselage4. In the example shown inFIG.3, the hydrogen fuel lines14aextend from the engines9on the wings2,3to a hydrogen fuel tank12located on the wing2,3, and hydrogen fuel lines14bextend from the hydrogen fuel tank12to a refuelling port16outboard of the hydrogen fuel tank12. It will be understood that there are many further permutations, but that at least some of the hydrogen fuel lines14a,14bare required to extend significant distances across the aircraft1.

Typical hydrogen fuel lines14a,14b(e.g. a refuel line, fuel supply line or return line) will be fixedly attached at connectors21at either end and include various pipes22, couplings23, bellows (e.g. axial compensators24), as well as valves and control sensors. For instance,FIGS.4&5show a hydrogen line14a,14bin the port wing2and extending in the spanwise direction (x-direction) between a leading edge25and a trailing edge26, an upper cover27and a lower cover28of the wing2. The longitudinal direction of the aircraft1is indicated generally as the y-direction, and the vertical axis is indicated generally as the z-direction.

The fuel line14amay include a connector21at each end, and several couplings23and axial compensators24along the length of the fuel line14a,14b. This can help to mitigate the effect of airframe deflections caused by aerodynamic and other external loads. The axial displacements of the fuel lines14a,14bneed to be accounted for due to the exposure of the fuel lines14a,14bto a wide range of operating temperatures ranging from the cryogenic temperatures of the liquid hydrogen to the potentially much higher temperatures of ambient, for which axial compensators or similar can be used. The connections between these various parts are a significant potential source of leaks and can increase thermal ingress. However, these various parts assist the hydrogen fuel lines14a,14bin withstanding the axial and out-of-plane deflections often encountered by the hydrogen fuel lines14a,14b.

Leak mitigation and leak prevention are therefore important factors when designing and implementing hydrogen fuel lines14a,14b.

FIG.6shows an aircraft assembly40. The aircraft assembly includes an aircraft panel41, and a generally U-shaped channel42attached to the aircraft panel41.

Whilst the channel42is described as generally U-shaped channel, it will be appreciated that the channel42may be any suitable shape for housing a hydrogen fuel line14a,14b. For example, the channel42may be V-shaped, omega-shaped or any other suitable variation of shape that defines a containment space.

The aircraft panel41and the channel42define a containment space48within. The hydrogen fuel line14a,14bextends through the containment space48. The containment space48is sealed such that any hydrogen fuel leaked/emitted from the hydrogen fuel line14a,14bis contained within the containment space48.

The hydrogen fuel line14a,14bmay be spaced from the channel42, so as to reduce heat transfer between the hydrogen fuel line14a,14band the channel42. The containment space48may be held at vacuum pressure to further reduce heat transfer between the hydrogen fuel line14a,14band the channel42. Alternatively, the containment space48may contain a high concentration of an inert gas, such as nitrogen. The concentration of the insert gas may be greater than 98%, or 99%. The containment space48may comprise substantially no oxygen to prevent a reaction with the hydrogen fuel.

The hydrogen fuel line14a,14bmay comprise a first fuel pipe15aand a second fuel pipe15b, the first fuel pipe15asurrounding the second fuel pipe15b. Such an arrangement may provide further insulation to hydrogen fuel in the second fuel pipe15b.

FIG.7shows an example in which a hydrogen fuel line14ais spaced from the channel42by a bracket50. The bracket50may include one or more clip portions51that attach to the walls of the channel42. A support portion52may extend across at least a portion of the hydrogen fuel line14a,14bto retain the hydrogen fuel line14a,14bin position relative to the channel42. The clip portions51may be integrally formed with the support portion52or, as shown for example inFIG.7, may be separately attach to the support portion52(e.g. by fasteners or other means known in the art).

It will be appreciated that in some examples, two or more hydrogen fuel lines14a,14bmay extend in a common direction for at least a portion of their length. The two or more hydrogen fuel lines14a,14bmay perform separate functions (e.g. a refuel line, a return line, or a safety vent line), and/or further hydrogen fuel lines14a,14bmay be provided for redundancy, for example in the event that one or more of the hydrogen fuel lines14a,14bis inoperable or otherwise inadequate. In some examples, the two or more hydrogen fuel lines14a,14bmay be located in a common channel42.FIG.8shows an example in which two hydrogen fuel lines14aextend through a common U-shaped channel42.

The hydrogen fuel lines14a,14bmay comprise one or more junctions at which three or more sections of the hydrogen fuel line14a,14bintersect.FIG.3shows an example in which the hydrogen fuel line14acomprises at least one T-junction.

To account for this divergence in the hydrogen fuel lines14a,14b, the channel42may similarly comprise an intersection that encloses the hydrogen fuel lines14a,14b.FIG.9Ashows an example in which the U-shaped channel42encloses a T-junction of the hydrogen fuel line14awith a corresponding T-junction of the U-shaped channel42. However, it will be appreciated that the intersection may be any suitable shape, e.g. a generally Y-shaped configuration such as shown inFIG.9B.

The channel42extends substantially the entire length of the hydrogen fuel line14a,14b, so that a sealed containment space can be defined around the hydrogen fuel line14a,14bfor containing any hydrogen fuel leaked from the hydrogen fuel line14a,14b.

A valve55may be fluidically connected to the sealed containment space so that any hydrogen gas, or other contaminants in the sealed containment space, can be selectively evacuated from the containment space. The valve55may be selectively operable to open and close, so that the contents of the containment space can be selectively evacuated.

The valve55may be connected at a first end to the containment space and at a second end to atmosphere, such that the contents within the containment space can be emptied to atmosphere. In some examples, the valve55may comprise a rupture disc configured to release gaseous pressure within the containment space when the pressure in the containment space exceeds a set pressure.

As shown inFIG.10, in some examples, the hydrogen fuel line14a,14bmay extend through the aircraft wing2,3, such that the channel42also extends through the aircraft wing2,3. Specifically, the channel42may extend from a fuel tank(s)12to one or more aircraft engines9. One end of the channel42may comprise a valve55.

In cases in which the channel42extends through the aircraft wing2,3, the aircraft panel41to which the channel42attaches may comprise a spar61a,61bor cover62a,62bof the wing box60of the aircraft1.

With this arrangement, the channel42may be pre-attached to the aircraft panel41(i.e. spar61a,61bor cover62a,62b) as a sub-assembly. In this way, at least a portion of the channel42and the hydrogen fuel line14a,14bmay be attached to the aircraft panel41when the wing box60is initially assembled. Typically, fuel lines (such as the hydrogen fuel lines14a,14bdiscussed above) are inserted into the wing box60after the wing box60has been assembled, e.g. by removing the lower cover28. However, many of the assembled parts of the wing box60(e.g. the wing ribs63) disrupt the ability of adding the fuel lines14a,14band thereby necessitate steps such as providing multiple shortened sections of fuel line14a,14b, or removing parts of wing box60. This adds unnecessary manufacturing steps and slows down assembly.

By attaching the channel42to the aircraft panel41as a sub-assembly, prior to assembly of the wing box60, it will be apparent that many of these difficulties are overcome. For example, the channel42may be attached to an aircraft panel42, and subsequently attached to a plurality of wing ribs63, thereby saving significant assembly time.

In some of the disclosed examples, the channel42may provide structural support. In the example shown inFIG.11, the channel42is one of a plurality of stiffeners46(only some of which are labelled) of the wing2,3extending along a portion of the wing2,3of the aircraft1.

In some examples, the hydrogen fuel lines14a,14bmay extend, in addition, or alternatively, along and adjacent to the fuselage4. For example, the hydrogen fuel lines14a,14bmay extend outside the pressure shell4aof the fuselage4. By placing the hydrogen fuel lines14a,14boutside the pressure shell4aof the fuselage4, any fuel leaks that might occur from the hydrogen fuel lines14a,14bare contained outside the pressure shell4a.

To ensure the hydrogen fuel lines14a,14bare not exposed to the outside airflow, the hydrogen fuel lines14a,14bmay be covered by a fairing75. The fairing has an outer aerodynamic surface exposed to the external airflow over the aircraft1. The fairing75defines an unpressurised space between the pressure shell4aand the fairing75.

FIG.12shows an example in which the hydrogen fuel line14ais located between the fairing75and the pressure shell4aof the fuselage4, so that the hydrogen fuel line14ais outside the pressure shell4aof the fuselage4. A channel42attaches to the fairing75, so that a sealed containment space is defined around the hydrogen fuel line14a.

It will be appreciated that, in some examples, the channel42may be pre-attached to the fairing75as a sub-assembly. A fuel line14a,14bmay be located in the channel42. As with the sub-assembly of the wing box60described above, this may help to speed up the assembly of the aircraft1.

It will be appreciated that access to the containment space within the channel42may be provided by any suitable means.

FIG.13Ashows an example in which an upper portion42aof the u-shaped channel42is removeable so as to provide access to the containment space.

FIG.13Bshows an alternative example in which a portion41aof the aircraft panel, such as example the upper cover62a, is removeable so as to provide access to the containment space.

In some examples, the channel42may be integrally formed with the aircraft panel41.

FIG.13Cshows an example in which the aircraft panel41and the channel42comprise fibre-reinforced composite materials. Similarly, the aircraft panel41may comprise fibre-reinforced composite materials. The aircraft panel41and the channel42may be integrally formed, e.g. by co-curing or co-bonding.

It will be appreciated that the fuel line14ashown inFIG.13Ccontacts the aircraft panel41and the channel42, however in alternative examples the fuel line14a,14bmay be spaced from the aircraft panel41and/or channel42.

In order to decrease the permeability of the channel42(e.g. the permeability to liquid or gaseous hydrogen), the U-shaped channel42may comprise a metallic layer44, such as shown inFIG.13C.

In such examples, the fuel line14a,14bmay be accessible via the wing tip11. For example, the fuel line14a,14bmay be inserted or removed from the channel42by removing at least part of the wing tip11.

As previously discussed in relation toFIG.7, the hydrogen fuel line14a,14bmay be spaced from the channel42by any suitable means, such as a bracket50or similar device.

The bracket50may be formed of metal. As shown inFIG.14A, an elastomer seal53may be provided between the bracket50and the hydrogen fuel line14a,14bthat reduces heat transfer between the hydrogen fuel line14a,14band the channel42.

In an alternative example, such as shown inFIG.14B, a foam spacer54may be formed that separates the hydrogen fuel line14a,14bfrom the channel42and reduces heat transfer therebetween. The foam spacer54may be shaped, or otherwise cut, to provide a containment space for containing any hydrogen fuel emitted from the hydrogen fuel lines14a,14b.

In some examples, the hydrogen fuel line14a,14bmay be substantially unconstrained along its axial direction between a first end31and a second end32, with at least one end31,32of the hydrogen fuel line14a,14bmoveable in the axial direction of the hydrogen fuel line14a,14b.

FIG.15shows an example in which two hydrogen fuel lines14bextend from a respective hydrogen fuel tank12at a first end to a common aircraft refuelling port16. The hydrogen fuel lines14a,14bare substantially unconstrained at the first end31, located at each fuel tank12, and attach to a common coupling21at the second end32, located at the aircraft refuelling port16of the aircraft1(it will be appreciated the second may alternatively or in addition by unconstrained).

Such an arrangement can help to mitigate the effects of various loads imparted on the hydrogen fuel lines14a,14b(e.g. loads imposed by wing bending, thermal expansion, thermal contraction, or other loads), as an end31,32of the hydrogen fuel14a,14bis able to move to compensate for any axial forces applied to the hydrogen fuel lines14a,14b.

In this context, substantially unconstrained refers to the end of the hydrogen fuel line14bnot being fixedly attached, although it may still be attached at the end31,32in some manner, if the constraint allows at least some relative axial movement to compensate for the loads acting on the hydrogen fuel lines14a,14b.

By providing a hydrogen fuel line14a,14bthat is moveable in its axial direction, the number of pipes, couplings, bellows and other components of the hydrogen fuel line14a,14bmay be reduced or eliminated.

As in the examples described above, and shown inFIG.16, the hydrogen fuel line(s)14a,14bis disposed in a channel42. In order to accommodate the axial movement of the hydrogen fuel line14a,14b, the hydrogen fuel line14a,14binside the channel42may be configured to be moveable relative to the channel42.

It will be appreciated that the examples are described above are applicable to a hydrogen fuel line14a,14bextending between any suitable components of the aircraft1, and may extend through any sections of the aircraft (e.g. the wings2,3, fuselage4, or therebetween).

FIG.17shows an example in which a hydrogen fuel tank12is located in the fuselage4, with a plurality of channels42(housing hydrogen fuel lines14a) extending between the hydrogen fuel tank12and respective aircraft engines9located on the wings2,3.

In addition, a channel42(housing a hydrogen fuel line14b) extends from the hydrogen fuel tank12to an aircraft refuelling port16located on the fuselage4, although it will be understood that the aircraft refuelling port16may be located elsewhere on the aircraft1.

Whilst the examples above show an aircraft1that includes hydrogen fuel lines14a,14bthat are part of a fuel system which directly burns the liquid hydrogen, it will be understood that the fuel system is equally applicable to hydrogen fuel lines14a,14bforming part of any aircraft power plant system that includes fuel cells90.

FIG.18shows an example in which an aircraft1includes fuel cells90configured to power an electromotor92, that drive one or more propellers91. A channel42(housing a hydrogen fuel line14a) extends from the hydrogen fuel tank12to each of the fuel cells90, with the hydrogen converted to electricity by the fuel cells90to power (e.g.) the electromotor92.

The examples described above reference an aircraft1including one fuel tank12, although it will be appreciated that the aircraft1may include any suitable number of fuel tanks12(e.g. two, three, or more). One or more of the fuel tanks12may be co-located, so as to be located directly next to one another, and/or one or more of the fuel tanks12may be located in different locations on the aircraft1. For example, one or more fuel tanks12may be located in the wings2,3, and one or more fuel tanks12may be located in the fuselage4. The fuel tanks12may be located in separate parts of the wings2,3, such as towards a wing tip and towards a wing root, and may be located in separate parts of the fuselage4, such as towards a nose end5and towards a tail end6of the fuselage4. The one or more fuel tanks12may be mounted to an outer surface of the aircraft1, such as mounted to a wing2,3in a fuel pod.

The examples described above refer to the engines9and/or fuel cells90as being located on the wings2,3, although it will be appreciated that the engines9and/or fuel cells90may be located on any suitable part of the aircraft, such as the fuselage4.

It will be appreciated that reference to a hydrogen fuel line14a,14bmay refer to any suitable hydrogen fuel line14a,14barrangement, including e.g. two or three pipes arranged concentrically, and one or more sections of pipe between various connectors21, couplings23, bellows (e.g. axial compensators24), and valves55.

The examples described above refer to the fuel as hydrogen fuel, however it will be appreciated that the examples, and many of the advantages described, are equally applicable to a fuel line14a,14bsuitable for carrying any cryogenic fuel.

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.

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.