Patent Description:
The use of alternative fuels, such as liquid hydrogen, are one of several approaches aimed at meeting future emissions targets. A difficulty in providing aircraft that are powered by fuels such as hydrogen is the need to store the fuel in pressurised fuel tanks. These pressurised fuel tanks typically require significant amounts of space and are therefore positioned away from the engines and other parts of the fuel system. The fuel lines may therefore extend significant distances across the aircraft.

This can present various challenges in the assembly of the aircraft, as well as present design considerations in terms of ensuring any leaks from the hydrogen fuel lines are contained. <CIT> describes a conduit protection system for a hydrogen fuel line connected between a hydrogen fuel tank and fuel cell. <CIT> describes an aircraft including a fuel line for connecting refueling cells. <CIT> describes a fuel pipe of an aircraft comprising an inner pipe defining a flow path through which fuel flows, and an outer pipe surrounding an outer periphery of the inner pipe to maintain temperature of fuel in the fuel pipe at an appropriate temperature.

A first aspect of the invention provides an aircraft assembly, comprising: an aircraft panel; a channel attached to the aircraft panel; a fuel line for carrying cryogenic fuel, the fuel line disposed in the channel; and a sealed containment space around the fuel line for containing cryogenic fuel leaked from the fuel line, the containment space defined between the channel, the fuel line, and the aircraft panel.

With this arrangement, any leakages or evacuations (e.g. emergency releases) of cryogenic fuels from the fuel line can be contained within the channel. The cryogenic fuel can be also be directed by the channel so that the cryogenic fuel is releasable at a designated location not necessarily co-located with the fuel line (e.g. an emergency exit line).

The aircraft assembly also provides advantages in its assembly, as the channel can be attached to the aircraft panel prior to integration of the aircraft panel (e.g. spar, cover, fairing) into the main aircraft assembly. This makes assembly of the aircraft easier and simpler, as there is no need for additional steps to be performed on the (e.g.) wing box that would ordinarily necessitate removing parts of the wing box in order to access the inner space of the wing box. The assembly process achievable as a result of this channel also means that the fuel line can also be assembled in larger sections within the wing box.

The channel may be rigidly attached to the aircraft panel, e.g. by fasteners or adhesive. The channel may be integral to the aircraft panel.

The fuel line may be configured to convey hydrogen fuel, and preferably liquid hydrogen fuel.

The channel may comprise fibre-reinforced composite materials.

The fibre-reinforced composite materials may comprise a metallic layer configured to decrease the permeability of the channel. The metallic layer may be between fibre reinforced layers of the channel.

The aircraft panel may comprise fibre-reinforced composite materials.

The aircraft assembly may comprise a vacuum or nitrogen in the containment space.

The channel may be spaced from the cryogenic fuel line.

The fuel line may be moveable axially relative to the channel.

The aircraft assembly may comprise a valve fluidically connected to the containment space.

The valve may be connected at a first end to the containment space and at a second end to atmosphere.

The aircraft panel may comprise an aircraft outer skin and/or a fairing.

The aircraft assembly may comprise two or more fuel lines for carrying cryogenic fuel, the fuel lines disposed in the channel.

The aircraft panel may comprise a spar of an aircraft wing.

The aircraft panel may comprise a cover of an aircraft wing.

The aircraft assembly may comprise an aircraft wing, wherein the channel extends along at least a portion of the aircraft wing.

The aircraft assembly may comprise an aircraft wing box, wherein the channel is within the wing box.

The aircraft assembly may comprise an aircraft fuselage, wherein the channel extends along at least a portion of the aircraft fuselage.

The channel may extend between a fuel tank for storing cryogenic fuel and an aircraft power plant.

The channel may extend between a fuel tank for storing cryogenic fuel and an aircraft refuelling port.

A second aspect of the invention provides an aircraft comprising the aircraft assembly of the first aspect.

A further aspect of the invention provides a method of assembling an aircraft wing box, comprising: the aircraft assembly of the first aspect wherein the aircraft panel comprises a spar and/or cover of an aircraft wing; the method comprising: attaching the aircraft assembly to one or more aircraft wing ribs.

<FIG> shows an aircraft <NUM> with port and starboard fixed wings <NUM>, <NUM>, engines <NUM>, a fuselage <NUM> with a nose end <NUM> and a tail end <NUM>, the tail end <NUM> including horizontal and vertical stabilising surfaces <NUM>, <NUM>. The aircraft <NUM> is 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 wing <NUM>, <NUM> of the aircraft <NUM> has a cantilevered structure with a length extending in a span-wise direction from a wing root <NUM> to a wing tip <NUM>, the root <NUM> being joined to the aircraft fuselage <NUM>.

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) <NUM> may be located in any suitable location on the aircraft <NUM>, but are typically located in separate tanks below the wings <NUM>, <NUM> (e.g. in fuel pods), in the wings <NUM>, <NUM> or in one or more fuel tanks <NUM> located within or adjacent the fuselage <NUM>. <FIG> shows a hydrogen fuel tank <NUM> located towards the rear of the fuselage <NUM>, whilst <FIG> shows the tanks located in the wings <NUM>, <NUM>.

Hydrogen fuel lines 14a may extend from the fuel tank(s) <NUM> to the aircraft power plants (e.g. engines <NUM> and/or fuel cells <NUM>) so as to channel hydrogen fuel to the power plants (these fuel lines 14a may alternatively be referred to as hydrogen distribution lines 14a). Hydrogen fuel lines 14b may extend from refuelling ports <NUM> located on an outer surface of the aircraft <NUM> to the fuel tank(s) <NUM> (these fuel lines may be referred to as hydrogen refuelling lines 14b).

Dependent on the respective location of the fuel tank(s) <NUM>, power plants, and refuelling ports <NUM>, the hydrogen fuel lines 14a, 14b may extend significant distances through the wing box structure of the wings <NUM>, <NUM> and/or through the structure of the fuselage <NUM>. In the example shown in <FIG>, the hydrogen fuel lines 14a extend from the engines <NUM> on the wings <NUM>, <NUM> to a hydrogen fuel tank <NUM> located in the fuselage <NUM>, and hydrogen fuel lines 14b extend from the hydrogen fuel tank <NUM> to a refuelling port <NUM> located aft of the hydrogen fuel tank <NUM> in the fuselage <NUM>. In the example shown in <FIG>, the hydrogen fuel lines 14a extend from the engines <NUM> on the wings <NUM>, <NUM> to a hydrogen fuel tank <NUM> located on the wing <NUM>, <NUM>, and hydrogen fuel lines 14b extend from the hydrogen fuel tank <NUM> to a refuelling port <NUM> outboard of the hydrogen fuel tank <NUM>. It will be understood that there are many further permutations, but that at least some of the hydrogen fuel lines 14a, 14b are required to extend significant distances across the aircraft <NUM>.

Typical hydrogen fuel lines 14a, 14b (e.g. a refuel line, fuel supply line or return line) will be fixedly attached at connectors <NUM> at either end and include various pipes <NUM>, couplings <NUM>, bellows (e.g. axial compensators <NUM>), as well as valves and control sensors. For instance, <FIG> show a hydrogen line 14a, 14b in the port wing <NUM> and extending in the spanwise direction (x-direction) between a leading edge <NUM> and a trailing edge <NUM>, an upper cover <NUM> and a lower cover <NUM> of the wing <NUM>. The longitudinal direction of the aircraft <NUM> is indicated generally as the y-direction, and the vertical axis is indicated generally as the z-direction.

The fuel line 14a may include a connector <NUM> at each end, and several couplings <NUM> and axial compensators <NUM> along the length of the fuel line 14a, 14b. This can help to mitigate the effect of airframe deflections caused by aerodynamic and other external loads. The axial displacements of the fuel lines 14a, 14b need to be accounted for due to the exposure of the fuel lines 14a, 14b to 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 lines 14a, 14b in withstanding the axial and out-of-plane deflections often encountered by the hydrogen fuel lines 14a, 14b.

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

<FIG> shows an aircraft assembly <NUM>. The aircraft assembly includes an aircraft panel <NUM>, and a generally U-shaped channel <NUM> attached to the aircraft panel <NUM>.

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

The aircraft panel <NUM> and the channel <NUM> define a containment space <NUM> within. The hydrogen fuel line 14a, 14b extends through the containment space <NUM>. The containment space <NUM> is sealed such that any hydrogen fuel leaked/emitted from the hydrogen fuel line 14a, 14b is contained within the containment space <NUM>.

The hydrogen fuel line 14a, 14b may be spaced from the channel <NUM>, so as to reduce heat transfer between the hydrogen fuel line 14a, 14b and the channel <NUM>. The containment space <NUM> may be held at vacuum pressure to further reduce heat transfer between the hydrogen fuel line 14a, 14b and the channel <NUM>. Alternatively, the containment space <NUM> may contain a high concentration of an inert gas, such as nitrogen. The concentration of the insert gas may be greater than <NUM>%, or <NUM>%. The containment space <NUM> may comprise substantially no oxygen to prevent a reaction with the hydrogen fuel.

The hydrogen fuel line 14a, 14b may comprise a first fuel pipe 15a and a second fuel pipe 15b, the first fuel pipe 15a surrounding the second fuel pipe 15b. Such an arrangement may provide further insulation to hydrogen fuel in the second fuel pipe 15b.

<FIG> shows an example in which a hydrogen fuel line 14a is spaced from the channel <NUM> by a bracket <NUM>. The bracket <NUM> may include one or more clip portions <NUM> that attach to the walls of the channel <NUM>. A support portion <NUM> may extend across at least a portion of the hydrogen fuel line 14a, 14b to retain the hydrogen fuel line 14a, 14b in position relative to the channel <NUM>. The clip portions <NUM> may be integrally formed with the support portion <NUM> or, as shown for example in <FIG>, may be separately attach to the support portion <NUM> (e.g. by fasteners or other means known in the art).

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

The hydrogen fuel lines 14a, 14b may comprise one or more junctions at which three or more sections of the hydrogen fuel line 14a, 14b intersect. <FIG> shows an example in which the hydrogen fuel line 14a comprises at least one T-junction.

To account for this divergence in the hydrogen fuel lines 14a, 14b, the channel <NUM> may similarly comprise an intersection that encloses the hydrogen fuel lines 14a, 14b. <FIG> shows an example in which the U-shaped channel <NUM> encloses a T-junction of the hydrogen fuel line 14a with a corresponding T-junction of the U-shaped channel <NUM>. However, it will be appreciated that the intersection may be any suitable shape, e.g. a generally Y-shaped configuration such as shown in <FIG>.

The channel <NUM> extends substantially the entire length of the hydrogen fuel line 14a, 14b, so that a sealed containment space can be defined around the hydrogen fuel line 14a, 14b for containing any hydrogen fuel leaked from the hydrogen fuel line 14a, 14b.

A valve <NUM> may 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 valve <NUM> may be selectively operable to open and close, so that the contents of the containment space can be selectively evacuated.

The valve <NUM> may 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 valve <NUM> may 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 in <FIG>, in some examples, the hydrogen fuel line 14a, 14b may extend through the aircraft wing <NUM>,<NUM>, such that the channel <NUM> also extends through the aircraft wing <NUM>,<NUM>. Specifically, the channel <NUM> may extend from a fuel tank(s) <NUM> to one or more aircraft engines <NUM>. One end of the channel <NUM> may comprise a valve <NUM>.

In cases in which the channel <NUM> extends through the aircraft wing <NUM>,<NUM>, the aircraft panel <NUM> to which the channel <NUM> attaches may comprise a spar 61a, 61b or cover 62a, 62b of the wing box <NUM> of the aircraft <NUM>.

With this arrangement, the channel <NUM> may be pre-attached to the aircraft panel <NUM> (i.e. spar 61a, 61b or cover 62a, 62b) as a sub-assembly. In this way, at least a portion of the channel <NUM> and the hydrogen fuel line 14a, 14b may be attached to the aircraft panel <NUM> when the wing box <NUM> is initially assembled. Typically, fuel lines (such as the hydrogen fuel lines 14a, 14b discussed above) are inserted into the wing box <NUM> after the wing box <NUM> has been assembled, e.g. by removing the lower cover <NUM>. However, many of the assembled parts of the wing box <NUM> (e.g. the wing ribs <NUM>) disrupt the ability of adding the fuel lines 14a, 14b and thereby necessitate steps such as providing multiple shortened sections of fuel line 14a, 14b, or removing parts of wing box <NUM>. This adds unnecessary manufacturing steps and slows down assembly.

By attaching the channel <NUM> to the aircraft panel <NUM> as a sub-assembly, prior to assembly of the wing box <NUM>, it will be apparent that many of these difficulties are overcome. For example, the channel <NUM> may be attached to an aircraft panel <NUM>, and subsequently attached to a plurality of wing ribs <NUM>, thereby saving significant assembly time.

In some of the disclosed examples, the channel <NUM> may provide structural support. In the example shown in <FIG>, the channel <NUM> is one of a plurality of stiffeners <NUM> (only some of which are labelled) of the wing <NUM>,<NUM> extending along a portion of the wing <NUM>, <NUM> of the aircraft <NUM>.

In some examples, the hydrogen fuel lines 14a, 14b may extend, in addition, or alternatively, along and adjacent to the fuselage <NUM>. For example, the hydrogen fuel lines 14a, 14b may extend outside the pressure shell 4a of the fuselage <NUM>. By placing the hydrogen fuel lines 14a, 14b outside the pressure shell 4a of the fuselage <NUM>, any fuel leaks that might occur from the hydrogen fuel lines 14a, 14b are contained outside the pressure shell 4a.

To ensure the hydrogen fuel lines 14a, 14b are not exposed to the outside airflow, the hydrogen fuel lines 14a, 14b may be covered by a fairing <NUM>. The fairing <NUM> has an outer aerodynamic surface exposed to the external airflow over the aircraft <NUM>. The fairing <NUM> defines an unpressurised space between the pressure shell 4a and the fairing <NUM>.

<FIG> shows an example in which the hydrogen fuel line 14a is located between the fairing <NUM> and the pressure shell 4a of the fuselage <NUM>, so that the hydrogen fuel line 14a is outside the pressure shell 4a of the fuselage <NUM>. A channel <NUM> attaches to the fairing <NUM>, so that a sealed containment space is defined around the hydrogen fuel line 14a.

It will be appreciated that, in some examples, the channel <NUM> may be pre-attached to the fairing <NUM> as a sub-assembly. A fuel line 14a, 14b may be located in the channel <NUM>. As with the sub-assembly of the wing box <NUM> described above, this may help to speed up the assembly of the aircraft <NUM>.

It will be appreciated that access to the containment space within the channel <NUM> may be provided by any suitable means.

<FIG> shows an example in which an upper portion 42a of the u-shaped channel <NUM> is removeable so as to provide access to the containment space.

<FIG> shows an alternative example in which a portion 41a of the aircraft panel, such as example the upper cover 62a, is removeable so as to provide access to the containment space.

In some examples, the channel <NUM> may be integrally formed with the aircraft panel <NUM>.

<FIG> shows an example in which the aircraft panel <NUM> and the channel <NUM> comprise fibre-reinforced composite materials. Similarly, the aircraft panel <NUM> may comprise fibre-reinforced composite materials. The aircraft panel <NUM> and the channel <NUM> may be integrally formed, e.g. by co-curing or co-bonding.

It will be appreciated that the fuel line 14a shown in <FIG> contacts the aircraft panel <NUM> and the channel <NUM>, however in alternative examples the fuel line 14a, 14b may be spaced from the aircraft panel <NUM> and/or channel <NUM>.

In order to decrease the permeability of the channel <NUM> (e.g. the permeability to liquid or gaseous hydrogen), the U-shaped channel <NUM> may comprise a metallic layer <NUM>, such as shown in <FIG>.

In such examples, the fuel line 14a, 14b may be accessible via the wing tip <NUM>. For example, the fuel line 14a, 14b may be inserted or removed from the channel <NUM> by removing at least part of the wing tip <NUM>.

As previously discussed in relation to <FIG>, the hydrogen fuel line 14a, 14b may be spaced from the channel <NUM> by any suitable means, such as a bracket <NUM> or similar device.

The bracket <NUM> may be formed of metal. As shown in <FIG>, an elastomer seal <NUM> may be provided between the bracket <NUM> and the hydrogen fuel line 14a, 14b that reduces heat transfer between the hydrogen fuel line 14a, 14b and the channel <NUM>.

In an alternative example, such as shown in <FIG>, a foam spacer <NUM> may be formed that separates the hydrogen fuel line 14a, 14b from the channel <NUM> and reduces heat transfer therebetween. The foam spacer <NUM> may be shaped, or otherwise cut, to provide a containment space for containing any hydrogen fuel emitted from the hydrogen fuel lines 14a, 14b.

In some examples, the hydrogen fuel line 14a, 14b may be substantially unconstrained along its axial direction between a first end <NUM> and a second end <NUM>, with at least one end <NUM>, <NUM> of the hydrogen fuel line 14a, 14b moveable in the axial direction of the hydrogen fuel line 14a, 14b.

<FIG> shows an example in which two hydrogen fuel lines 14b extend from a respective hydrogen fuel tank <NUM> at a first end to a common aircraft refuelling port <NUM>. The hydrogen fuel lines 14a, 14b are substantially unconstrained at the first end <NUM>, located at each fuel tank <NUM>, and attach to a common coupling <NUM> at the second end <NUM>, located at the aircraft refuelling port <NUM> of the aircraft <NUM> (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 lines 14a, 14b (e.g. loads imposed by wing bending, thermal expansion, thermal contraction, or other loads), as an end <NUM>, <NUM> of the hydrogen fuel 14a, 14b is able to move to compensate for any axial forces applied to the hydrogen fuel lines 14a, 14b.

In this context, substantially unconstrained refers to the end of the hydrogen fuel line 14b not being fixedly attached, although it may still be attached at the end <NUM>, <NUM> in some manner, if the constraint allows at least some relative axial movement to compensate for the loads acting on the hydrogen fuel lines 14a, 14b.

By providing a hydrogen fuel line 14a, 14b that is moveable in its axial direction, the number of pipes, couplings, bellows and other components of the hydrogen fuel line 14a, 14b may be reduced or eliminated.

As in the examples described above, and shown in <FIG>, the hydrogen fuel line(s) 14a, 14b is disposed in a channel <NUM>. In order to accommodate the axial movement of the hydrogen fuel line 14a, 14b, the hydrogen fuel line 14a, 14b inside the channel <NUM> may be configured to be moveable relative to the channel <NUM>.

It will be appreciated that the examples are described above are applicable to a hydrogen fuel line 14a, 14b extending between any suitable components of the aircraft <NUM>, and may extend through any sections of the aircraft (e.g. the wings <NUM>, <NUM>, fuselage <NUM>, or therebetween).

<FIG> shows an example in which a hydrogen fuel tank <NUM> is located in the fuselage <NUM>, with a plurality of channels <NUM> (housing hydrogen fuel lines 14a) extending between the hydrogen fuel tank <NUM> and respective aircraft engines <NUM> located on the wings <NUM>, <NUM>.

In addition, a channel <NUM> (housing a hydrogen fuel line 14b) extends from the hydrogen fuel tank <NUM> to an aircraft refuelling port <NUM> located on the fuselage <NUM>, although it will be understood that the aircraft refuelling port <NUM> may be located elsewhere on the aircraft <NUM>.

Whilst the examples above show an aircraft <NUM> that includes hydrogen fuel lines 14a, 14b that 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 lines 14a, 14b forming part of any aircraft power plant system that includes fuel cells <NUM>.

<FIG> shows an example in which an aircraft <NUM> includes fuel cells <NUM> configured to power an electromotor <NUM>, that drive one or more propellers <NUM>. A channel <NUM> (housing a hydrogen fuel line 14a) extends from the hydrogen fuel tank <NUM> to each of the fuel cells <NUM>, with the hydrogen converted to electricity by the fuel cells <NUM> to power (e.g.) the electromotor <NUM>.

The examples described above reference an aircraft <NUM> including one fuel tank <NUM>, although it will be appreciated that the aircraft <NUM> may include any suitable number of fuel tanks <NUM> (e.g. two, three, or more). One or more of the fuel tanks <NUM> may be co-located, so as to be located directly next to one another, and/or one or more of the fuel tanks <NUM> may be located in different locations on the aircraft <NUM>. For example, one or more fuel tanks <NUM> may be located in the wings <NUM>, <NUM>, and one or more fuel tanks <NUM> may be located in the fuselage <NUM>. The fuel tanks <NUM> may be located in separate parts of the wings <NUM>, <NUM>, such as towards a wing tip and towards a wing root, and may be located in separate parts of the fuselage <NUM>, such as towards a nose end <NUM> and towards a tail end <NUM> of the fuselage <NUM>. The one or more fuel tanks <NUM> may be mounted to an outer surface of the aircraft <NUM>, such as mounted to a wing <NUM>, <NUM> in a fuel pod.

The examples described above refer to the engines <NUM> and/or fuel cells <NUM> as being located on the wings <NUM>,<NUM>, although it will be appreciated that the engines <NUM> and/or fuel cells <NUM> may be located on any suitable part of the aircraft, such as the fuselage <NUM>.

It will be appreciated that reference to a hydrogen fuel line 14a, 14b may refer to any suitable hydrogen fuel line 14a, 14b arrangement, including e.g. two or three pipes arranged concentrically, and one or more sections of pipe between various connectors <NUM>, couplings <NUM>, bellows (e.g. axial compensators <NUM>), and valves <NUM>.

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 line 14a, 14b suitable for carrying any cryogenic fuel.

Claim 1:
An aircraft assembly (<NUM>), comprising:
an aircraft panel (<NUM>);
a channel (<NUM>) attached to the aircraft panel (<NUM>);
a fuel line (14a, 14b) for carrying cryogenic fuel, the fuel line (14a, 14b) disposed in the channel (<NUM>); and
a sealed containment space around the fuel line (14a, 14b) for containing cryogenic fuel leaked from the fuel line (14a, 14b), the containment space defined between the channel (<NUM>), the fuel line (14a, 14b), and the aircraft panel (<NUM>).