Vacuum insulated pipe assembly

Abstract

A vacuum insulated pipe assembly 100 comprises an outer pipe 120 and an inner pipe 111 within the outer pipe 120, the inner and outer pipes concentric along a common central axis 150, the inner pipe 1

Description

TECHNICAL FIELD

[0001] The present invention relates to vacuum-insulated pipe assemblies, hydrogen fuel systems, and aircraft. BACKGROUND

[0002] Hydrogen fuel systems for aircraft may comprise vacuum-insulated pipes for transporting cryogenic hydrogen fuel between components of the hydrogen fuel systems. Vacuum-insulated pipes employ a vacuum in a space between inner and outer pipes to thermally insulate the cryogenic hydrogen fuel flowing through the inner pipe. SUMMARY

[0003] A first aspect of the present invention provides a vacuum insulated pipe assembly comprising an outer pipe and an inner pipe within the outer pipe, the inner and outer pipes concentric along a common central axis, the inner pipe distanced from the outer pipe to define a space, the space evacuated to provide a vacuum. The outer pipe comprises a connector for connecting the vacuum insulated pipe assembly to a further fluid handling component. A portion of the inner pipe extends away from the common central axis, the portion engaged with the connector at an interface and defining a closed end of the space.

[0004] In this way, the connector provides a double-function of connecting the vacuum insulated pipe assembly to the further fluid handling component and connecting the inner pipe to the outer pipe. This may provide a pipe assembly that has fewer parts than an arrangement comprising separate parts for connecting the vacuum insulated pipe assembly to the further fluid handling component and for connecting the inner pipe to the outer pipe, thereby reducing weight and / or cost.

[0005] Optionally, the inner pipe comprises a tubular wall and the portion and the tubular wall are formed as a single unitary piece. Optionally, the tubular wall and the portion are made of a composite material, such as a Glass Fibre Reinforced Polymer (GFRP). Optionally, the tubular wall and the portion, when made of a composite material, are cocured or co-bonded together. Optionally, the portion is separately connected to the tubular wall, such as welded or adhered to the tubular wall.

[0006] Optionally, the portion of the inner pipe extends away from the common central axis, such as away from the tubular wall, in a direction substantially orthogonal to the common central axis. Optionally, the portion of the inner pipe defines an opening of the inner pipe. Optionally, the opening of the inner pipe has the same internal diameter as the tubular wall. Optionally, the portion forms an annular disc around the common central axis, the annular disc extending from the opening and / or the tubular wall to the connector. Optionally, the connector and the tubular wall define opposing surfaces of the space, and the portion is engaged with the connector to define the closed end of the space between the connector and the tubular wall.

[0007] Optionally, the inner pipe is configured to carry fluid therethrough, in use. Optionally, the pipe assembly is for handling cryogenic fluid, such as cryogenic hydrogen fuel. Optionally, the pipe assembly is for handling cryogenic nitrogen, cryogenic oxygen, or cryogenic helium. The vacuum may provide a thermally-insulating barrier between the inner pipe and the outer pipe, thereby limiting heat transfer between the fluid flowable through the inner pipe and an atmosphere external to the outer pipe, in use. This may be particularly advantageous when the pipe assembly is for handling cryogen fluid.

[0008] The further fluid handling component may be a further vacuum-insulated pipe assembly, for example so that plural vacuum-insulated pipe assemblies may be connected together along the common central axis to define a pipe system. Optionally, the further fluid handling component comprises a storage tank, a consumer unit (such as an engine), or a fluid control device, such as a pump or valve.

[0009] Optionally, the portion and the connector overlap when viewed along the common central axis, so that the connector restricts a relative movement of the inner and outer pipes in a direction along the common central axis. This may provide a convenient way to locate the inner pipe relative to the outer pipe during manufacture.

[0010] The vacuum, when provided, leads to a negative pressure inside the space relative to a pressure outside the space. This may cause a force to be exerted on the portion that urges the portion in a direction along the common central axis. The portion and the connector may be arranged such that the force urges the portion towards the connector. This may allow the portion to be held in place relative to the connector, without requiring a separate component for connecting the portion to the connector. This may, in turn, reduce a weight and / or cost of the pipe assembly.

[0011] Moreover, the force urging the portion towards the connector may improve a seal at the interface between the connector and the portion, particularly when the seal element is provided at the interface.

[0012] Optionally, the portion comprises a first side and a second side opposite to the first side in an axial direction along the common central axis, and the portion and the connector overlap such that the connector engages the first side of the portion. Optionally, the closed end of the second space is provided by the first side of the portion of the second inner pipe. Optionally, the portion of the second inner pipe, and in particular the first side, is substantially solid so that the closed end is defined by a continuous surface of the portion of the second inner pipe. Optionally, the portion is formed of a rigid material. This may reduce a likelihood of deformation of the portion due to the force urging the portion towards the connector, thereby limiting relative movement of the connector and the portion.

[0013] The portion and the connector may overlap by at least 20 mm, at least 30mm, at least 40mm or at least 50mm. The portion may be circular when viewed along the common central axis, and an outer 10% - 40%, such as 20% - 30% of the radius of the portion, as measured from the common central axis, may overlap the connector. A greater amount of overlap may provide a greater area of the portion in contact with the connector, which may better distribute stress over the first portion. A lower amount of overlap may reduce a size of the connector.

[0014] Optionally, the connector is configured to restrict a relative motion of the inner and outer pipes in a direction orthogonal to the common central axis. This may provide a convenient way to locate the inner pipe relative to the outer pipe during manufacture. Restricting the relative motion of the inner and outer pipes in the direction orthogonal to the common central axis may also ensure that the opening into the inner pipe remains coaxial with the common central axis.

[0015] Optionally, the connector comprises a rim that engages with the portion to restrict the relative motion of the inner and outer pipes in the direction orthogonal to the common central axis. Optionally, the portion comprises an outer rim, such as when the portion defines an annular disc around the opening and / or tubular wall. Optionally, the rim of the connector engages the outer rim of the portion to restrict the relative motion of the inner and outer pipes in the direction orthogonal to the common central axis.

[0016] Optionally, the vacuum insulated pipe assembly comprises a seal element at the interface between the portion and the connector. The seal element may inhibit an exchange of fluid between the space and an atmosphere external to the outer pipe. This may, for example, reduce a likelihood of a fluid, which has leaked into the space from the inner pipe, passing to the external atmosphere along the interface. This may be particularly advantageous when the inner pipe is for carrying hydrogen fuel. The seal element may similarly reduce a likelihood of the external atmosphere passing into the evacuated space, in use. This may maintain the thermal insulation properties provided by the vacuum.

[0017] Optionally, the connector comprises a groove in which the seal element is located. This may improve an ease of manufacture of the vacuum insulated pipe assembly, such as by allowing the seal element to be held in place in the groove whilst the portion of the inner pipe is offered up to the connector.

[0018] A second aspect of the present invention provides a pipe system comprising the vacuum insulated pipe assembly of the first aspect of the present invention, wherein the vacuum insulated pipe assembly is a first vacuum insulated pipe assembly, the outer pipe is a first outer pipe, the inner pipe is a first inner pipe, the space is a first space, the connector is a first connector, and the interface is a first interface. The pipe system comprises a second vacuum insulated pipe assembly comprising: a second outer pipe and a second inner pipe within the second outer pipe, the second inner and outer pipes concentric along the common central axis, the second inner pipe distanced from the second outer pipe to define a second space, the second space evacuated to provide a vacuum. The second outer pipe comprises a second connector connected to the first connector. A portion of the second inner pipe extends away from the common central axis, the portion of the second inner pipe engaged with the second connector at a second interface and defining a closed end of the second space.

[0019] The first and second vacuum insulated pipe assemblies may be manufactured as sub-assemblies and connected together to form the pipe system. For instance, the first and second spaces may be evacuated prior to connection of the respective first and second pipe assemblies to form the pipe system. This may reduce the time to manufacture the pipe system compared to a pipe system where the first and second pipe assemblies are connected together before evacuating the respective first and second spaces. This is because it may take a substantial amount of time, such as hours or days, to evacuate the first and second spaces. By performing such evacuation separately, the first and second vacuum insulated pipe assemblies can be provided as individual sub-assemblies and connected together comparatively quickly, without the need to evacuate the first and second spaces after connection.

[0020] Optionally, the first and second inner pipes define a flow path along which a fluid is flowable, in use. Optionally, the first portion defines an opening into the first inner pipe and the second portion defines an opening into the second inner pipe. Optionally, the first and second portions are located so that the openings of the first and second inner pipes are fluidically connected and aligned along the common central axis.

[0021] Optionally, the second pipe assembly and / or the pipe system is for handling cryogenic fluid, such as cryogenic hydrogen fuel. Optionally, the pipe assembly is for handling cryogenic nitrogen, cryogenic oxygen, or cryogenic helium. The second vacuum may provide a thermally-insulating barrier between the second inner pipe and the second outer pipe, thereby limiting heat transfer between the fluid flowable through the second inner pipe and an atmosphere external to the second outer pipe, in use. This may be particularly advantageous when the second pipe assembly and / or the pipe system is for handling cryogen fluid.

[0022] Optionally, the first and second portions are in contact with each other at a portion interface. Optionally, the first and second portions are urged together by the connection between the first and second connectors. By providing the first and second portions in contact with each other, and optionally urged together, a likelihood of fluid passing between the first and second portions may be reduced compared to an arrangement where there is a space between the first and second portions. This may reduce a likelihood of fluid from the inner pipe contacting the first and / or second connector after passing between the first and second portions, which may, in turn, limit a conduction of heat across the first and / or second connector between the fluid and an atmosphere external to the first and / or second connector.

[0023] Optionally, the tubular wall of the first inner pipe is a first tubular wall, and the second inner pipe comprises a second tubular wall, wherein the portion of the second inner pipe and the second tubular wall are formed as a single unitary piece. Optionally, the second tubular wall and the portion of the second inner pipe are made of a composite material, such as a Glass Fibre Reinforced Polymer (GFRP). Optionally, the second tubular wall and the portion of the second inner pipe, when made of a composite material, are co-cured or co-bonded together. Optionally, the portion of the second inner pipe is separately connected to the second tubular wall, such as welded or adhered to the second tubular wall.

[0024] Optionally, the portion of the second inner pipe extends away from the common central axis, such as away from the second tubular wall, in a direction substantially orthogonal to the common central axis. Optionally, the portion of the second inner pipe defines an opening of the second inner pipe. Optionally, the opening of the second inner pipe has the same internal diameter as the second tubular wall. Optionally, the portion of the second inner pipe forms an annular disc around the common central axis, the annular disc extending from the opening and / or the tubular wall of the second inner pipe to the second connector. Optionally, the second connector and the second tubular wall define opposing surfaces of the second space, and the portion of the second inner pipe is engaged with the second connector to define the closed end of the second space between the second connector and the second tubular wall.

[0025] Optionally, the portion of the second inner pipe and the second connector overlap when viewed along the common central axis, so that the second connector restricts a relative movement of the second inner and outer pipes in a direction along the common central axis. This may provide a convenient way to locate the second inner pipe relative to the second outer pipe during manufacture.

[0026] The vacuum, when provided, leads to a negative pressure inside the second space relative to a pressure outside the second space. This may cause a force to be exerted on the portion of the second inner pipe that urges the portion in a direction along the common central axis. The portion of the second inner pipe and the second connector may be arranged such that the force urges the portion of the second inner pipe towards the second connector. This may allow the portion of the second inner pipe to be held in place relative to the second connector, without requiring a separate component for connecting the portion of the second inner pipe to the second connector. This may, in turn, reduce a weight and / or cost of the vacuum insulated pipe assembly and / or the pipe system.

[0027] Moreover, the force urging the portion of the second inner pipe towards the second connector may improve a seal at the interface between the second connector and the portion of the second inner pipe, particularly when the seal element is provided at the interface between the second connector and the portion of the second inner pipe.

[0028] Optionally, the portion of the second inner pipe comprises a first side and a second side opposite to the first side in an axial direction along the common central axis, and the portion of the second inner pipe and the second connector overlap such that the second connector engages the first side of the portion of the second inner pipe. Optionally, the closed end of the second space is provided by the first side of the portion of the second inner pipe. Optionally, the portion of the second inner pipe, and in particular the first side, is substantially solid so that the closed end is defined by a continuous surface of the portion of the second inner pipe. Optionally, the portion of the second inner pipe is formed of a rigid material. This may reduce a likelihood of deformation of the portion of the second inner pipe due to the force urging the portion of the second inner pipe towards the second connector, thereby limiting relative movement of the second connector and the portion of the second inner pipe.

[0029] The portion of the second inner pipe and the second connector may overlap by at least 20 mm, at least 30 mm, at least 40mm, or at least 50mm. The second portion may be circular when viewed along the common central axis, and an outer 10% - 40%, such as 20%-30% of the radius of the portion, as measured from the common central axis, may overlap the second connector. A greater amount of overlap may provide a greater area of the second portion in contact with the second connector, which may better distribute stress over the first portion. A lower amount of overlap may reduce a size of the second connector.

[0030] Optionally, the second connector is configured to restrict a relative motion of the second inner and outer pipes in a direction orthogonal to the common central axis. This may provide a convenient way to locate the second inner pipe relative to the second outer pipe during manufacture of the second vacuum insulated pipe assembly and / or the pipe system. Restricting the relative motion of the second inner and outer pipes in the direction orthogonal to the common central axis may also ensure that the opening into the second inner pipe remains coaxial with the common central axis (and / or with the opening into the first inner pipe).

[0031] Optionally, the connector comprises a rim that engages with the portion to restrict the relative motion of the inner and outer pipes in the direction orthogonal to the common central axis. Optionally, the portion comprises an outer rim, such as when the portion defines an annular disc around the opening and / or tubular wall. Optionally, the rim of the connector engages the outer rim of the portion to restrict the relative motion of the inner and outer pipes in the direction orthogonal to the common central axis.

[0032] Optionally, the first connector comprises a first flange, the second connector comprises a second flange, and the vacuum insulated pipe assembly comprises an outer seal element clamped between the first and second connectors. The outer seal element restricts the passage of fluid along an interface between the first and second connectors. For example, the outer seal element may restrict an exchange of fluid between the atmosphere external to the first and / or the second connector and the first space, the second space, the first inner pipe, and / or the second inner pipe. In this way, the outer seal element may provide redundancy, such as in the event of a leak of fluid across the first and / or second seal elements.

[0033] Optionally, the outer seal element comprises a metallic gasket. Optionally, at least one of the first and second flanges comprises a protrusion. Optionally, the protrusion is a knife-edge protrusion. Optionally, the protrusion is engaged with the metallic gasket such that the metallic gasket is plastically deformed in the region of the protrusion. During connection of the first and second flanges to each other, the metallic gasket is clamped between the first and second flanges. A force provided by the clamping effect causes the protrusion to engage the metallic gasket and cause plastic deformation of the metallic gasket in the region of the protrusion.

[0034] The plastically-deformed metallic gasket fills in machining marks and surface defects in the first and second flanges, providing a hermetic seal. Furthermore, the metallic gasket is work-hardened by the plastic deformation. This provides a strong and resilient metallic gasket that is resilient to movement of the first and / or second flanges, such as due to expansion or contraction of the first and / or second flanges in the event of a change in temperature of the first and / or second flanges. This may, in turn, provide a seal that is more resilient to changes in temperature than, for example, an elastomeric seal elastically deformed between the first and second flanges, which may experience greater expansion and / or contraction on exposure to changing temperatures than the metallic gasket, such as in the event of a leak of cryogenic fluid from the first and / or second inner pipes. Thus, the plastically deformed metallic gasket may be more resilient and / or more reliable than an elastomeric seal, particularly when the first and second inner pipes are configured to carry cryogenic fluid, such as cryogenic hydrogen fuel, cryogenic nitrogen, cryogenic oxygen, or cryogenic helium.

[0035] Optionally, the first and second flanges comprise co-axial bolt holes, and the vacuum-insulated pipe assembly comprises bolts that extend through the co-axial bolt holes to connect the first and second flanges to each other. The bolts urge the first and second flanges towards each other, and thereby compress the metallic gasket between the first and second flanges to maintain the hermetic seal.

[0036] A third aspect of the present invention provides a hydrogen fuel system comprising the vacuum-insulated pipe assembly of the first aspect of the present invention or the pipe system of the second aspect of the present invention. Optionally, the hydrogen fuel system comprises a hydrogen fuel tank and the pipe system is configured to pass fuel from the hydrogen fuel tank to an engine via the first and second inner pipes. Optionally, the hydrogen fuel system is an aircraft hydrogen fuel system, and the engine is an aircraft engine. Optionally, the engine comprises a combustion engine and / or a fuel cell.

[0037] A fourth aspect of the present invention provides an aircraft comprising the vacuum insulated pipe assembly of the first aspect of the present invention, the pipe system of the second aspect of the present invention, or the hydrogen fuel system of the third aspect of the present invention.

[0038] A fifth aspect of the present invention provides a method of manufacturing a vacuum insulated pipe assembly, the method comprising inserting an inner pipe into an outer pipe so that the inner pipe is concentric with the outer pipe along a common central axis, and is distanced from the outer pipe to define a space. The outer pipe comprises a connector for connecting the outer pipe to a further fluid handling component, and the inner pipe comprises a portion extending away from the common central axis. The method comprises inserting the inner pipe into the outer pipe until the portion engages the connector at an interface and defines a closed end of the space.

[0039] The connector provides a double-function of connecting the vacuum insulated pipe assembly to the further fluid handling component and connecting the inner pipe to the outer pipe. This may provide a pipe assembly that has fewer parts than an arrangement comprising separate parts for connecting the vacuum insulated pipe assembly to the further fluid handling component and for connecting the inner pipe to the outer pipe, thereby reducing weight and / or cost.

[0040] Optionally, the method comprises providing a sealing element at the interface between the portion and the connector. The seal element may inhibit an exchange of fluid between the space and an atmosphere external to the outer pipe. This may, for example, reduce a likelihood of a fluid, which has leaked into the space from the inner pipe, passing to the external atmosphere along the interface. This may be particularly advantageous when the inner pipe is for carrying hydrogen fuel. The seal element may similarly reduce a likelihood of the external atmosphere passing into the evacuated space, in use. This may maintain the thermal insulation properties provided by the vacuum.

[0041] Optionally, the method comprises evacuating the space after engaging the first inner flange with the first connector to provide a vacuum in the space. A negative pressure in the space due to the vacuum may provide a force on the portion that pulls the portion towards the space, in a direction into the outer pipe, and thus towards the connector. In this way, the vacuum may provide a force holding the portion in engagement with the connector. This may provide a simple method of manufacturing the pipe assembly, such as by not requiring a further step for fixing the portion to the connector.

[0042] The vacuum insulated pipe assembly may be the vacuum insulated pipe assembly of the first aspect of the present invention. It will be appreciated that the vacuum insulated pipe assembly may comprise and / or benefit from any of the optional features and / or advantages ascribed to the vacuum insulated pipe assembly of the first aspect of the present invention.

[0043] A sixth aspect of the present invention provides a method of manufacturing a pipe system, the method comprising manufacturing the pipe assembly according to the fifth aspect of the present invention, wherein the pipe assembly is a first pipe assembly, the outer pipe is a first outer pipe, the inner pipe is a first inner pipe, the space is a first space, the connector is a first connector, the interface is a first interface, and the common central axis is a first common central axis. The method comprises inserting a second inner pipe into a second outer pipe so that the second inner pipe is concentric with the second outer pipe along the common central axis, and is distanced from the second outer pipe to define a second space. The second outer pipe comprises a second connector, and the second inner pipe comprises a portion extending away from the second common central axis. The method comprises: inserting the second inner pipe into the second outer pipe so that the portion of the second inner pipe engages the second connector at a second interface and defines a closed end of the space; and connecting the second connector to the first connector to fluidically couple the first and second inner pipes.

[0044] In this way, the first and second pipe assemblies may be manufactured as separate sub-assemblies and connected together to form the pipe assembly. This may provide a convenient way to manufacture the pipe assembly.

[0045] Optionally, the method comprises evacuating the second space after engaging the portion of the second inner pipe with the second connector, but before connecting the second connector to the first connector, to provide a vacuum in the second space. Optionally, the method comprises evacuating the first space after engaging the portion of the first inner pipe with the first connector, but before connecting the second connector to the first connector, to provide a vacuum in the first space.

[0046] Evacuating the first and / or second spaces before connecting the first connector to the second connector may improve an efficiency in manufacturing the pipe system compared to evacuating the spaces after connecting the second connector to the first connector. This is because evacuating the space may take hours, or days. The first and / or second spaces may therefore be evacuated during manufacture of the respective first and / or second vacuum insulated pipe assemblies. The first and / or second vacuum-insulated pipe assemblies may then be provided as sub-assemblies that can be comparatively quickly assembled together, without the need to subsequently evacuate the first and / or second spaces.

[0047] The pipe system may be the pipe system of the second aspect of the present invention. It will be appreciated that the pipe system may comprise and / or benefit from any of the optional features and / or advantages ascribed to the pipe system of the second aspect of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0049] Figure 1 shows a schematic view of an example aircraft;

[0050] Figure 2 shows a schematic view of an example hydrogen fuel system;

[0051] Figure 3 shows a schematic view of an example vacuum-insulated pipe assembly;

[0052] Figure 4A shows a schematic view of a connector of the vacuum-insulated pipe assembly of Figure 3, when viewed along a common central axis;

[0053] Figure 4B shows a schematic view of an example metallic gasket for use with the connector of Figure 4B,

[0054] Figure 5 shows an example exploded view of the vacuum-insulated pipe assembly; and

[0055] Figure 6 shows an example method of assembling the vacuum-insulated pipe assembly. DETAILED DESCRIPTION

[0056] Figure 1 shows an example aircraft 1 comprising a fuselage 2, a wing 3 and an engine 4 mounted on the wing 3. The aircraft 1 comprises a hydrogen fuel system 10 comprising a hydrogen fuel tank 11 storing cryogenic hydrogen fuel. The hydrogen fuel system 10 comprises a vacuum-insulated pipe assembly 100 fluidically connected between the fuel tank 10 and the engine 4 (here shown as a single line, for ease of comprehension). The vacuum-insulated pipe assembly 100 is configured to provide hydrogen fuel to the engine 4. The fuel tank is located in the fuselage 2, and the vacuum-insulated pipe assembly 100 extends from the fuselage 2 along the wing 3 of the aircraft 1. The engine 4 comprises a combustion engine, but in other examples, the engine 4 may comprise a hydrogen fuel cell, which may generate electricity for powering a propulsor of the aircraft 1.

[0057] The hydrogen fuel system 10 is shown in more detail in Figure 2. The hydrogen fuel system 10 comprises the fuel tank 1 storing the cryogenic hydrogen fuel for the engine 4. The hydrogen fuel system 10 also comprises a valve 12, a pump 13, first vacuum-insulated pipe 14 fluidically connecting the valve 12 to the fuel tank 10, and a second vacuum-insulated pipe 15 fluidically connecting the pump 13 to the valve 14. The first and second vacuum-insulated pipes 14, 15 are shown as single lines for ease of comprehension.

[0058] The hydrogen fuel system 10 also comprises a controller 50 configured to operate the pump 13 and the valve 12 to selectively cause hydrogen fuel to flow through from the hydrogen fuel tank 10 to the engine 4 via the vacuum-insulated pipe assembly 100. It will be appreciated that the arrangement shown in Figure 2 is exemplary only, and that in other examples the hydrogen fuel system 10 may comprise any other suitable arrangement of pumps, valves, vacuum-insulated pipe assemblies and / or other components for distributing fuel in the hydrogen fuel system 10.

[0059] The vacuum-insulated pipe assembly 100 comprises first and second outer pipes 111, 112, first and second inner pipes 121, 122, first and second annular walls 112a, 112b of the first and second inner pipes 121, 122, first and second spaces 130a, 130b, a first closed end 131a of the first space 130a, and a second closed end 131b of the second space 130b.

[0060] The first and second inner and outer pipes 110, 120 are concentric about a common central axis 150. The first inner pipe 111 is spaced from the first outer pipe 121 to define the first space 130a. The second inner pipe 112 is spaced from the first outer pipe 122 to define the second space 130b. The first outer pipe 121 comprises a first flange 122a connected to a second flange 122b of the second outer pipe 122 to fluidically connect the first outer pipe 121 to the second outer pipe 122. The first annular wall 112a extends radially away from the common central axis 150 and is connected to the first flange 122a, such that the first annular wall 112a defines the first closed end 131a of the first space. The second annular wall 112b extends radially away from the common central axis 150 and is connected to the second flange 122b, such that the second annular wall 112b defines the second closed end of the second space 130b. The first inner and outer pipes 111, 121 are connected to the pump 13 by a pump connector 16, and the second inner and outer pipes 112, 122 are connected to the engine 4 by an engine connector 17. The pump connector 16 defines a further closed end of the first space 130, opposite to the first closed end 131a defined by the first annular wall 112a, and the engine connector 17 define a further closed end of the second space 130b, opposite to the second closed end 131b defined by the second annular wall 112b.

[0061] Turning now to Figures 3, 4A and 4B, features of the vacuum-insulated pipe assembly 100 are shown and described in more detail. Components which are also shown in Figure 2 are labelled with the same reference numerals in Figures 3, 4, 5A and 5B.

[0062] The first inner pipe 110a comprises a first tubular wall Illa, and the second inner pipe comprises a second tubular wall 111b. The first and second flanges 122a, 122b are annular and define respective first and second inner walls, which are axially aligned with the respective first and second outer pipes 110, 120. The first annular wall 112a extends radially away from the first tubular wall 11 la to the first flange 122a, and a face of the first annular wall 112a contacts a corresponding face of the first flange 122a. The face of the first flange 122a is provided by a first recess 143a in the first flange 122a, which extends radially outwardly from the first inner wall defined by the first flange 122a. A solid surface of the first annular wall 112a therefore extends between the first tubular wall Illa and the first flange 122a to define the first closed end 13 la of the first space 130a. The second annular wall 112b similarly extends radially away from the second tubular wall 11 lb, and a face of the second annular wall 112b contacts a corresponding face of the second flange 122b. The face of the second flange 122b is provided by a second recess 143b in the second flange 122b, which extends radially outwardly from the second inner wall defined by the second flange 122b. A solid surface of the second annular wall 112b therefore extends between the second tubular wall 111b and the second flange 122b to define the second closed end 13 lb of the second space 130b second annular wall 112b.

[0063] The first annular wall 112a defines a first opening 132a of the first inner pipe 110a, and the second annular wall 112b defines a second opening 132b of the second inner pipe 110b. The first annular wall 112a engages the second annular wall 112b so that the first and second openings are fluidically connected and aligned along the common central axis 150.

[0064] The first annular wall 112a and the first tubular wall 11 la form a single unitary piece. Similarly, the second annular wall 112b and the second tubular wall 111b form a single unitary piece. The first annular wall 112a and the first tubular wall Illa comprise a glass-fibre reinforced polymer material (GFRP), the first annular wall 112a and the first tubular wall Illa co-cured to form the first inner pipe 110a. The second annular wall 112b and the second tubular wall 11 lb similarly comprise a GFRP material, the second annular wall 112b and the second tubular wall 111b co-cured to form the second inner pipe 110b. It will be appreciated that the first and second tubular walls Illa, 111b and the first and second annular walls 112a, 112b may be formed of any other suitable material in other examples.

[0065] The first annular wall 112a extends away from the common central axis 125 to such an extent that an outer 25% of the radius of the first annular wall 112a, as measured from the common central axis 150, overlaps the first flange 122a when viewed along the common central axis 150. Specifically, the outer 25% of the radius of the first annular wall 112a is received in, and overlaps, the first recess 143a, and the first recess 143a is sized to accommodate this overlapping portion of the first annular wall 112a.

[0066] The overlapping portion of the first annular wall 112a contacts the face of the first recess 143a and inhibits a movement of the first inner pipe 110a in an axial direction along the common central axis 150 into the first outer pipe 120a, i.e., to the left in Figure 3. The evacuated first space 130a exerts a negative pressure on the first closed end 13 la, thereby generating a force that urges the first annular wall 112a towards the first flange 122a. This holds the first annular wall 112a in place on the first flange 122a, and thereby fixes the first inner pipe 110a to the first outer pipe 120a.

[0067] Similarly, the second annular wall 112b extends away from the common central axis 125 to such an extent that an outer 25% of the radius of the second annular wall 112b, as measured from the common central axis 150, overlaps the second flange 122b when viewed along the common central axis 150. Specifically, the outer 25% of the radius of the second annular wall 112b is received in, and overlaps, the second recess 143b, and the second recess 143b is sized to accommodate this overlapping portion of the second annular wall 112b. The overlapping portion of the first annular wall 112a contacts the face of the second recess 143b and inhibits a movement of the second inner pipe 110b in the axial direction along the common central axis 150 into the second outer pipe 120b, i.e., to the right in Figure 3. The evacuated second space 130b exerts a negative pressure on the second closed end 131b, thereby generating a force that urges the second annular wall 112b towards the second flange 122b. This holds the second annular wall 112b in place on the second flange 122b, and thereby fixes the second inner pipe 110b to the second outer pipe 120b.

[0068] The first and second annular walls 112a, 112b overlap the respective first and second recesses 143a, 143b by 30 mm. In some examples, the first and second annular walls 112a, 112b may overlap the respective first and second recesses 143a, 143b by up to 20 mm, up to 30 mm, up to 40 mm, up to 50 mm, or greater than 50 mm. It will be appreciated that the first and second recesses 143a, 143b and the first and second annular walls 112a, 112b are sized to provide space for a sealing element (as will be described below) between the first and second annular walls 112a, 112b and the respective first and second recesses 143a, 143b. In some examples, the overlap between the first and second recesses 143a, 143b and the respective first and second annular walls 112a, 112b can be increased to provide a greater contact area, although this would also increase a size of the first and second flanges 122a, 122b.

[0069] The first and second annular walls 112a, 112b comprise respective first and second outer rims 134a, 134b. The first and second recesses 143a, 143b define respective first and second rim portions 133a, 133b, which engage with the respective first and second outer rims 134a, 134b to inhibit a movement of the first and second annular walls 112a, 112b in a radial direction relative to the common central axis 150. In this way, the first and second inner pipes 110a, 110b are in a fixed location relative to the first and second outer pipes 120a, 120b.

[0070] The vacuum-insulated pipe assembly 100 comprises a first elastomeric O-ring 124a located between the first flange 122a and the first annular wall 112a in a first groove 123a of the first flange 122a. The first groove 123a is located in the first recess 143a. The vacuum-insulated pipe assembly 100 also comprises a second elastomeric O-ring 124b located between the second flange 122b and the second annular wall 112b in a second groove 123b of the second flange 122b. The second groove 123b is located in the second recess 143b. The first and second elastomeric O-rings 124a, 124b provide a fluid-tight seal between the first and second flanges 122a, 122b and the respective first and second annular walls 112a, 112b to facilitate evacuation of the respective first and second spaces 130a, 130b.

[0071] As best shown in Figure 4A, the first and second flanges 122a, 122b comprise, respectively, first and second outer faces 141a, 141b, which each extend radially inwardly from an outer periphery of the respective first and second outer flanges 122a, 122b. The first and second outer faces 141a, 141b of the first and second flanges 122a, 122b are releasably connected to each other at a connection interface 125 by bolts 126 connected through respective bolt holes 127 equally spaced around each of the first and second flanges 122a, 122b.

[0072] The vacuum-insulated pipe assembly 100 comprises a metallic gasket 128, shown in Figure 3 and in isolation in Figure 5B, which is annular and concentric with the common central axis 150. The outer metallic gasket 128 is clamped between the first and second flanges 122a, 122b. Specifically, the first and second flanges 122a, 122b comprise respective first and second gasket recesses 142a, 142b located between the first and second outer faces 141a, 141b and the first and second recesses 143a, 143b. The first and second gasket recesses 142a, 142b define respective faces which are stepped away from the first and second outer faces 141a, 141b in the axial direction along the common central axis 150. The faces of the first and second recesses 143a, 143b are stepped away from the respective first and second gasket recesses 142a, 142b in the same axial direction. The first and second ridges 133a, 133b thereby extend between the respective first and second recesses 143 a, 143b and the respective first and second gasket recesses 142a, 142b. The first and second flanges 122a, 122b comprise respective first and second knife-edge protrusions 129a, 129b which extend around the common central axis 150 and are engaged with the outer metallic gasket 128. The first and second knife-edge protrusions 129a, 129b are located respectively on the respective first and second gasket recesses 142a, 142b. The outer metallic gasket 128 is plastically deformed in the region of the first and second knife-edge protrusions 129a, 129b due to the clamping force between the first and second flanges 122a, 122b. In this way, the outer metallic gasket 128 is work hardened by the plastic deformation, providing a hermetic seal at the outer connection interface 125 that is resilient to movement of the first and / or second flanges 122a, 122b.

[0073] It will be appreciated that the metallic gasket 128 hinders a flow of cryogenic hydrogen from the first and / or second inner pipes 110a, 110b to an external atmosphere external to the first and second flanges 122a, 122b, in use. This is particularly advantageous where the external atmosphere comprises oxygen, which is highly reactive with hydrogen. The metallic gasket 128 also hinders a flow of fluid from the external atmosphere into the first and second spaces 130a, 130b, thereby maintaining the vacuum in the first and second spaces 130a, 130b and the thermal insulation properties the vacuums provide.

[0074] With reference now to Figure 5, the first inner pipe 110a and the first outer pipe 120a are assembled as a first vacuum-insulated pipe sub-assembly 200a, with the first inner pipe 110a held in place due to the vacuum in the first space 130a as described above. Similarly, the second inner pipe 110b and the second outer pipe 120b is formed as a second vacuum-insulated sub-assembly 200b, which is connected to the first vacuum-insulated sub-assembly to form the vacuum-insulated pipe assembly.

[0075] To assemble the first vacuum-insulated sub-assembly, the first elastomeric O-ring 124a is inserted into the first groove 123a, and the first inner pipe 110a is inserted into the first outer pipe 120a in an axial direction along the common central axis 125 until the first annular wall 112a engages the first flange 122a and the first elastomeric O-ring 124a. The first space 130a is closed at an opposite end to the first closed end 13 la by the pump connector 16 (although in other examples the first space 130a could be closed in any other suitable way). The first space 130a is then evacuated, such as using a vacuum pump, to provide the vacuum in the first space 130b.

[0076] The second vacuum-insulated sub-assembly 200b is assembled in a similar way to the first vacuum-insulated sum-assembly 200a. The second elastomeric O-ring 124b is inserted into the second groove 123b, and the second inner pipe 110b is inserted into the second outer pipe 120b in the axial direction until the second annular wall 112b engages the second flange 122b and the second elastomeric O-ring 124b. The second space 130b is closed at an opposite end to the second closed end 131b by the engine connector 17 (although in other examples the second space 130b could be closed in any other suitable way). The second space 130b is then evacuated, such as using a vacuum pump, to provide the vacuum in the second space 130b.

[0077] The first and second vacuum-insulated pipe subassemblies 200a, 200b are aligned along the common general axis 125, and the metallic gasket 128 is positioned between the first and second flanges 122a, 122b. The first and second flanges 122a, 122b are brought together, in the direction shown by the arrows labelled 201a and 201b in Figure 5, so that the first and second knife-edge protrusions 129a, 129b engage the metallic gasket 128. The bolts 126 are inserted and connected through the respective holes 127 to connect the first and second flanges 122a, 122b, and thus the first and second vacuum-insulated pipe subassemblies 200a, 200b, together. The bolts 126 are tightened to cause the knife-edge protrusions 129a, 129b to penetrate and plastically deform the metallic gasket 128 and provide a fluid tight seal between the first and second flanges 122a, 122b.

[0078] It will be appreciated that, in other examples, the components of the vacuum-insulated pipe assembly 100 may be assembled together before evacuating the first and second spaces 130a, 130b. In such examples, the first and second spaces 130a, 130b may be evacuated before the vacuum-insulated pipe assembly 100 is to be installed in the hydrogen fuel system 10, or after the vacuum-insulated pipe assembly 100 is installed in the hydrogen fuel system 10.

[0079] Shown in Figure 6 is an example method 400 of manufacturing the vacuum-insulated pipe assembly 100. The method 400 comprises: locating 410 the first elastomeric O-ring 124a between the first annular wall 112a and the first flange 122a; and inserting 420 the first inner pipe 110a into the first outer pipe 120a until the first annular wall 112a engages the first flange 122a. The first inner pipe 110a is inserted into the first outer pipe 120a so that the first inner pipe 110a is concentric with the first outer pipe 120a and distanced from the first outer pipe 120a to define the first space 130a. The method comprises evacuating 430 the first space 130a.

[0080] The method 400 also comprises: locating 440 the second elastomeric O-ring 124b between the second annular wall 112b and the second flange 122b; and inserting 450 the second inner pipe 110b into the first outer pipe 120a until the second annular wall 112b engages the second flange 122b. The second inner pipe 110b is inserted into the second outer pipe 120b so that the second inner pipe 110b is concentric with the second outer pipe 120b and distanced from the second outer pipe 120b to define the second space 130b. The method comprises evacuating 460 the second space 130b.

[0081] The method comprises: locating 470 the metallic gasket 128 between the first and second flanges 122a, 122b; and connecting 480 the first and second flanges 122a, 122b to fluidically couple the first and second inner pipes 110a, 110b.

[0082] It will be appreciated that, in other examples, any of the actions of locating 410 the first sealing O-ring 124a, inserting 420 the first inner pipe 110a into the first outer pipe 120a, and evacuating 430 the first space 130a may be performed before, after, or in tandem with any of the actions of locating 440 the second elastomeric O-ring 124b, inserting 450 the second inner pipe 110b into the second outer pipe 120b, and evacuating 460 the second space 130b. It will also be appreciated that, in other examples, the evacuating 430, 460 the first and second spaces 130a, 130b may be performed after the connecting 480 the first and second flanges.

[0083] Various modifications may be made to the examples described above within the scope of the invention as defined in the appended claims. For instance, whilst the first annular wall 112a, the first tubular wall Illa, the second annular wall 112b, and the second tubular wall 11 lb comprise GFRP material, other materials may be used in other examples. For instance, the first annular wall 112a, the first tubular wall 11 la, the second annular wall 112b, and the second tubular wall 111b may comprise any other suitable polymeric material, such as a thermoplastic. In some such examples, the first annular wall 112a may be welded to the first tubular wall 11 la, and the second annular wall 112b may be welded to the second tubular wall 11 lb.

[0084] It is to be noted that the term “or” as used herein is to be interpreted to mean “and / or”, unless expressly stated otherwise.

Claims

1. A vacuum insulated pipe assembly comprising an outer pipe and an inner pipe within the outer pipe, the inner and outer pipes concentric along a common central axis, the inner pipe distanced from the outer pipe to define a space, the space evacuated to provide a vacuum, wherein:the outer pipe comprises a connector for connecting the vacuum insulated pipe assembly to a further fluid handling component; anda portion of the inner pipe extends away from the common central axis, the portion engaged with the connector at an interface and defining a closed end of the space.

2. The vacuum insulated pipe assembly of claim 1, wherein the portion and the connector overlap when viewed along the common central axis, so that the connector restricts a relative movement of the inner and outer pipes in a direction along the common central axis.

3. The vacuum insulated pipe assembly of any one of claims 1 to 2, wherein the connector is configured to restrict a relative motion of the inner and outer pipes in a direction orthogonal to the common central axis.

4. The vacuum insulated pipe assembly of any one of claims 1 to 3, comprising a seal element at the interface between the portion and the connector.

5. A pipe system comprising the vacuum insulated pipe assembly of any one of claims 1 to 4, wherein the vacuum insulated pipe assembly is a first vacuum insulated pipe assembly, the outer pipe is a first outer pipe, the inner pipe is a first inner pipe, the space is a first space, the connector is a first connector, and the interface is a first interface, wherein the pipe system comprises a second vacuum insulated pipe assembly comprising:a second outer pipe and a second inner pipe within the second outer pipe, the second inner and outer pipes concentric along the common central axis, thesecond inner pipe distanced from the second outer pipe to define a second space, the second space evacuated to provide a vacuum, wherein:the second outer pipe comprises a second connector connected to the first connector; anda portion of the second inner pipe extends away from the common central axis, the portion of the second inner pipe engaged with the second connector at a second interface and defining a closed end of the second space.

6. The pipe system of claim 5, wherein the first connector comprises a first flange, the second connector comprises a second flange, and the vacuum insulated pipe assembly comprises an outer seal element clamped between the first and second connectors.

7. The pipe system of claim 6, wherein:the outer seal element comprises a metallic gasket, at least one of the first and second flanges comprises a protrusion, and the protrusion is engaged with the metallic gasket such that the metallic gasket is plastically deformed in the region of the protrusion.

8. A hydrogen fuel system comprising the vacuum-insulated pipe assembly of any one of claims 1 to 4 or the pipe system of any one of claims 5 to 7.

9. An aircraft comprising the vacuum insulated pipe assembly of any one of claims 1 to 5, the pipe system of any one of claims 6 to 8, or the hydrogen fuel system of claim 8.

10. A method of manufacturing a vacuum insulated pipe assembly, the method comprising inserting an inner pipe into an outer pipe so that the inner pipe is concentric with the outer pipe along a common central axis, and is distanced from the outer pipe to define a space, wherein:the outer pipe comprises a connector for connecting the outer pipe to a further fluid handling component, and the inner pipe comprises a portion extending away from the common central axis; andthe method comprises inserting the inner pipe into the outer pipe until the portion engages the connector at an interface and defines a closed end of the space.

11. The method of claim 10, comprising providing a sealing element at the interface between the portion and the connector.

12. The method of claim 10 or claim 11, comprising evacuating the space after engaging the first inner flange with the first connector to provide a vacuum in the space.

13. A method of manufacturing a pipe system, the method comprising manufacturing the pipe assembly according to any one of claims 10 to 12, wherein the pipe assembly is a first pipe assembly, the outer pipe is a first outer pipe, the inner pipe is a first inner pipe, the space is a first space, the connector is a first connector, the interface is a first interface, and the common central axis is a first common central axis andthe method comprises inserting a second inner pipe into a second outer pipe so that the second inner pipe is concentric with the second outer pipe along the common central axis, and is distanced from the second outer pipe to define a second space, wherein the second outer pipe comprises a second connector, and the second inner pipe comprises a portion extending away from the second common central axis;inserting the second inner pipe into the second outer pipe so that the portion of the second inner pipe engages the second connector at a second interface and defines a closed end of the space; andconnecting the second connector to the first connector to fluidically couple the first and second inner pipes.

14. The method of claim 14, comprising evacuating the second space after engaging the portion of the second inner pipe with the second connector, but before connecting the second connector to the first connector, to provide a vacuum in the second space.

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