REMOVABLE FITTING FOR VACUUM INSULATED CRYOGENIC TUBES AND CORRESPONDING CONNECTION METHOD.

Abstract

Detachable fitting (10) for vacuum-insulated cryogenic tubes (13, 14), said tubes (13, 14) each comprising an external female part (22, 24) and an internal male part (21, 23) having an external male part (38, 39) projecting axially relative to the external female part (22, 24), characterized in that it comprises connection means (20) for the removable connection of an external male part (38) of a first tube (13) coaxially to an external male part (39) of a second tube (14), a casing (25) surrounding the connection means (20) between the first tube (13) and the second tube (14), the casing (25) being removably coupled between a first connecting flange (18) and a second connecting flange (19) so as to ensure a thermally sealed connection between the first tube (13) and the second tube (14). Figure for the summary: Fig 3

Description

Title of the invention: REMOVABLE FITTING FOR CRYOGENIC TUBES WITH VACUUM INSULATION AND CORRESPONDING CONNECTION METHOD. technical field

[0001] The invention relates to the connection of vacuum-insulated pipes intended, in particular, for distributing a supercooled or cryogenic fluid. In a particularly interesting application, the invention relates to a fitting for vacuum-insulated cryogenic tubes installed on board aircraft, especially aircraft powered by hydrogen or methane. The invention also applies to the connection of aircraft components, such as pumps or heat exchangers. Previous techniques

[0002] The Applicant is constantly working to reduce its negative climate impact by using methods and operating virtuous development and manufacturing processes that minimize greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

[0003] Technological research efforts have already led to very significant improvements in the environmental performance of aircraft. The Applicant takes into account the factors impacting all phases of design and development in order to obtain aeronautical components and products that are less energy-intensive, more environmentally friendly, and whose integration and use in civil aviation have moderate environmental consequences, with the aim of improving the energy efficiency of aircraft.

[0004] This sustained research and development work focuses on both new generations of hydrogen or methane aircraft, the lightening of aircraft, in particular through the materials used and lighter and more compact on-board equipment, and the development of the use of hydrogen or methane technologies to provide propulsion.

[0005] To this end, the invention is the result of technological research aimed at significantly improving aircraft performance and, in this sense, contributes to reducing the environmental impact of aircraft.

[0006] Cryogenic fuels such as hydrogen are generally stored on board aircraft in cryogenic tanks and transported using thermally insulated pipes with vacuum insulation. Such pipes conventionally have a double wall with vacuum insulation between them.

[0007] By way of example, hydrogen fuel is stored at a temperature of around 20 to 22 Kelvins (-253°C to -251°C) in a cryogenic tank of the aircraft.

[0008] The difference between the ambient temperature (20°C) and the hydrogen storage temperature is relatively high (-253°C), which causes oxygen condensation on the surface of uninsulated pipes and fittings. This oxygen condensation is undesirable for hydrogen transport because it increases the risk of fire. Therefore, proper insulation of cryogenic pipes is necessary to keep liquid hydrogen in designated areas, such as the tank, pipes, and aircraft pumps.

[0009] In the prior art, the presence of hydrogen vapor in cryogenic zones can create flow instabilities in cryogenic pipes due to large density variations caused by the presence of hydrogen bubbles. Hydrogen vapor can also destabilize the operation of cryogenic pumps.

[0010] It is therefore important to isolate the transport lines for such cryogenic liquids.

[0011] The problem of insulation is more acute in connection areas cryogenic tubes.

[0012] Vacuum-insulated cryogenic tubes are, for example, connected by means of bayonet fittings, also known as Johnston fittings. In this way, icing at the coupling point of the two cryogenic lines and thermal ingress from the outside into the cryogenic fluid are limited.

[0013] As illustrated in [Fig. 1], which shows a system for connecting two vacuum-insulated cryogenic tubes 1 and 2 in a Johnston fitting 3, the two double-walled cryogenic tubes 4 and 5, separated by a volume 6 of vacuum insulation, are connected one inside the other. The male part of the connection system, formed by the inner wall of one of the double-walled cryogenic tubes, is inserted into the female part formed by the outer tube of the other cryogenic tube. In this way, the outer surfaces of the cryogenic tubes are thermally insulated from the inner tube in a very effective manner. However, the two double-walled cryogenic tubes must be inserted one inside the other to a predetermined length.Depending on the material and the desired thermal insulation, typical lengths of the male part of the cryogenic pipe connected to the female part are between 200 mm and 600 mm, with thermal insulation being better the longer the removable fitting is designed to be.

[0014] However, in embedded systems, for example in a hydrogen-powered aircraft, these Johnston fittings present a significant drawback. Indeed, the connection lengths required with these fittings are not compatible with the highly constrained environments of aircraft. Furthermore, with the increase in the As the length of the removable fitting increases, its handling becomes more and more difficult. This difficulty is compounded when such fittings are handled in the already congested environment of an aircraft.

[0015] However, the level of sealing is essential to avoid uncontrolled evaporation and therefore thermo-hydraulic instabilities.

[0016] There is therefore a need for a detachable fitting, particularly for applications in the constrained field of aircraft. Description of the invention

[0017] In view of the foregoing, the invention aims to eliminate at least some of the aforementioned disadvantages by proposing a detachable fitting for connecting cryogenic tubes which is simple and compact and which allows a high level of thermal insulation to be maintained.

[0018] The invention therefore relates to a detachable fitting for cryogenic tubes with vacuum insulation, said tubes each comprising an external female part and an internal male part having an external male part in axial projection relative to the external female part.

[0019] This fitting includes:

[0020] connection means for the removable connection of a male external part of a first tube coaxially to a male external part of a second tube,

[0021] an enclosure surrounding the means of connection between the first tube and the second tube, the enclosure being removably coupled between a first connecting flange and a second connecting flange so as to ensure a thermally sealed connection between the first tube and the second tube.

[0022] Such a fitting allows two double-walled cryogenic tubes to be connected without requiring relatively long push-fit sections, thus shortening the overall length of the fittings and consequently improving their integration and maneuverability. This is particularly advantageous on board aircraft where space for installing such a fitting is limited.

[0023] The detachable fitting is advantageous in that it can be disassembled when necessary to repair or replace one of the cryogenic tubes or one of the components to which the cryogenic tube is connected. The detachable fitting can also connect two aircraft components, such as a pump or a heat exchanger.

[0024] In one embodiment, the envelope comprises at least two envelope sectors in the shape of a portion of a cylinder and connected by removable connecting means.

[0025] Preferably, the shape of the casing corresponds to the shape of a hollow cylinder. In this way, the installation and handling of such a fitting does not present any problems due to the thickness or shape of the connection.

[0026] Advantageously, the envelope comprises a tubular body including at least one deformable envelope portion intended to be deformed to thermally seal the envelope between the first connecting flange and the second connecting flange.

[0027] The deformable envelope part allows the envelope to close perfectly on the connection and ensures a very good level of thermal insulation.

[0028] According to another feature, the connecting flanges each include a sealing gasket, for example an O-ring sealing gasket intended to be fitted onto the connecting flanges by elastic deformation under the pressure of the casing.

[0029] In one embodiment, the first male internal part and the first female external part are held relative to each other by at least one first joining element, and the second male internal part and the second female external part are held relative to each other by at least one second joining element.

[0030] The connecting elements also allow for the alignment of the two male external parts and maintain the same distance between the male internal part and the female external part of the tubes. By centering the male internal parts and the female external parts inside the cryogenic tubes, the central positioning of these two tubes is ensured during their assembly.

[0031] Preferably, the first joining element and the second joining element include a spacer intended to limit the distance between the first male internal part and the first female external part and between the second male internal part and the second female external part respectively.

[0032] The invention also relates to a method for connecting cryogenic vacuum-insulated tubes, said tubes each comprising an external female part and an internal male part having an external male part projecting axially relative to the external female part, characterized in that it comprises the steps of: - removable connection of a male external part of a first tube coaxially to a male external part of a second tube, - assembly of a casing around the means of connection between the first tube and the second tube, the casing being removably coupled between a first connecting flange and a second connecting flange so as to ensure a thermally sealed connection between the first tube and the second tube. Brief description of the drawings

[0033] Other objects, features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example and made with reference to the accompanying drawings in which:

[0034] - Fig. 1, which has already been mentioned, is a schematic cross-sectional view longitudinal of a Johnston type fitting according to the prior art;

[0035] - Figures [Fig. 2] and [Fig. 3] represent a fitting for cryogenic tubes according to the invention, respectively during assembly and after assembly;

[0036] - [Fig. 4] is a perspective view of a fitting according to the invention, showing the connection of the male internal parts and the casing, during assembly;

[0037] - [Fig.5] is a perspective view of one of the cryogenic tubes and the fitting;

[0038] - Figures [Fig. 6A] and [Fig. 6B] represent a schematic cross-sectional view of a tube cryogenic in which an internal male part and an external female part are held together by junction elements. Detailed description

[0039] Reference will be made to Figures 2 and 3, which illustrate an embodiment of a detachable fitting 10 according to the invention. The fitting 10 is intended to connect a first cryogenic tube 13 and a second cryogenic tube 14, for example, cryogenic tubes supplying an aircraft with cryogenic fuel. This cryogenic fuel can be, for example, hydrogen or methane stored at a cryogenic temperature ranging from -150°C to -273°C. Preferably, hydrogen cooled to a temperature of approximately 20 to 22 Kelvin (-253°C to -251°C) is used.

[0040] The tubes 13 and 14 are double-walled tubes and each have an inner wall 15, an outer wall 16 and an interstitial cylindrical void volume 17 between the inner and outer walls 15, 16. In the connection zone of the cryogenic tube portions 13, 14, the inner wall 15 extends axially relative to the outer wall 16 and forms a male outer part 38, 39 which extends protruding from the female outer part 22, 24.

[0041] In the assembly position, the external male parts 38, 39 protruding from the tubes 13 and 14 are arranged end to end coaxially to be fixed to each other by connecting means 20.

[0042] The connecting means 20 may include, for example, screwing threaded portions, bolting flanges, a clamp collar, a hose clamp, crimping, blind rivets, clipping, or any other connecting means known to those skilled in the art. The connecting means 20 are removable and therefore allow tubes 13, 14 to be disassembled for maintenance reasons, for example.

[0043] The connection between the male external parts 38, 39 has a very good level of sealing to prevent leakage of the cryogenic liquid to the outside of the tubes 13, 14. With reference to [Fig.3], each male external part 38, 39 includes an internal sealing gasket 33, 34, for example an O-ring sealing gasket.

[0044] For example, the internal sealing gasket 33, 34 is suitable for use in cryogenic conditions and can be, for example, a compact indium gasket, a compressible hermetic gasket, a compression gasket, a detachable cryogenic gasket, an indium O-ring flange gasket, an indium wire O-ring, a low profile indium gasket, a rotary gasket, a D-profile gasket, a flat metal gasket, a helicoflex type gasket.

[0045] Referring also to figures 3 to 5, the fitting 10 further comprises a casing 25 surrounding the connecting means 20 and extending between the external walls 16 of the first tube 13 and the second tube 14.

[0046] This enclosure 25 comprises at least one enclosure sector 26, 27 capable of adopting an open configuration allowing access to the connection means 20 and a closed position in which the connection means 20 are confined within a closed and sealed volume. The enclosure 25 ensures the continuity of the interstitial cylindrical vacuum volume 17 between the cryogenic tubes 13, 14 and consequently the thermally sealed connection between the cryogenic tubes 13, 14.

[0047] For example, as shown, the casing 25 comprises two semi-cylindrical sectors 26, 27 designed to cooperate with each other. Of course, this does not depart from the scope of the invention if the casing 25 comprises any number of sectors.

[0048] As seen in [Fig.4], the longitudinal edge of each envelope sector 26, 27 has a longitudinal flange intended to cooperate with a complementary flange carried by the complementary longitudinal edge of another envelope sector 26, 27 so as to be assembled by connecting means 28, for example by bolting.

[0049] The means for connecting the envelope sectors 28 may be, in another example, threaded portions, a clamp collar, a hose clamp, a crimp, blind rivets, a clip, or any other means of connection known to those skilled in the art. The first tube 13 also includes a first connecting flange 18, and the second tube 14 includes a second connecting flange 19.

[0050] The casing 25 is connected to the connecting flanges 18, 19 by known connection means – threaded flange, flange with collar, screw flange, clamp flange, sliding flange, swivel flange, pivot flange, threaded flange, push-fit flange, overlap flange, blind flange. The casing sectors 26, 27 comprise means for contacting the connecting flanges 18, 19 for connection.

[0051] The external sealing gasket 31, 32 located on each connecting flange 18, 19 is then elastically deformed under the pressure of the casing 25 to ensure a seal of the connection between the casing sectors 26, 27 and the connecting flanges 18, 19. The external sealing gasket 31, 32 is intended for use under cryogenic conditions and can be one of the internal sealing gaskets 33, 34 described previously.

[0052] In one embodiment, the casing 25 comprises a deformable casing portion 29, illustrated in [Fig. 3], which is designed to be deformed to create a thermally sealed seal between the casing 25 and the second connecting flange 19. This facilitates the insertion of the casing 25 between the connecting flanges 18 and 19. The deformable casing portion 29 can be corrugated, curved, or concave, but this is not a limiting example, and any other shape is also possible. This deformable envelope portion 29 is preferably located in the part adjacent to the connection between the connecting flanges 18, 19 and the envelope 25. The deformable envelope portion 29 can also be formed on a circumferential part of the envelope 25, thus facilitating the airtight closure of the envelope 25 on the connecting flanges 18, 19.

[0053] Advantageously, the fitting 10 includes an insulation layer 35 surrounding the inner wall 15 of each tube 13, 14. This insulation layer 35 is located within the cylindrical void space 17 and advantageously provides multilayer insulation (MLI). Examples include rigid polyisocyanurate foam, cellular glass, mineral wool, a primary or secondary vapor barrier, self-adhesive tape, a metallic coating, steel strapping, a shrink gasket, a vapor barrier coating, a cryogenic sealant, or any other known type of insulation. The insulation layer 35 improves thermal insulation between the male internal parts 21, 23 and the female external parts 23, 24. The casing 25 surrounds the insulation layer 35 without damaging it and provides an additional level of thermal insulation.

[0054] The insulation layer 35 is installed overlapping the existing insulation between each male internal part 21, 23 and each female internal part 22, 24 and between the male external parts 38, 39, the connection means 20 and the casing 25, ensuring continuity of thermal insulation in the removable connection 10.

[0055] In one embodiment, [Fig.6A] and [Fig.6B] represent a schematic cross-sectional view of the cryogenic tube 13, 14 in which the male internal part 21, 23 and the female external part 22, 24 are held together by a first connecting element 36. In another embodiment illustrated in [Fig.6B], the male internal part 21, 23 and the female external part 22, 24 are held together by a second connecting element 37, such as a thin wall for example.

[0056] The connecting elements 36, 37 maintain the same radial distance between the inner wall 15 and the outer wall 16 of the tubes 13, 14, respectively. By centering the male external parts 38, 39 and the female external parts 22, 24 within the two cryogenic tubes 13, 14, the central positioning of these two tubes 13, 14 is ensured during assembly. Thus, thermal sealing is further improved. The connecting elements 36, 37 can be a spacer, a thin wall, or any other means known in the prior art for optimally centering the two tubular bodies 13, 14, while minimizing induced thermal conduction through the choice of insulating materials, a thin part, or a labyrinthine part, for example.

Claims

Demands

1. A detachable fitting (10) for vacuum-insulated cryogenic tubes (13, 14), said tubes (13, 14) each comprising a female external portion (22, 24) and a male internal portion (21, 23) having a male external portion (38, 39) projecting axially relative to the female external portion (22, 24), characterized in that it comprises connection means (20) for the removable connection of a male external portion (38) of a first tube (13) coaxially to a male external portion (39) of a second tube (14), a casing (25) surrounding the connection means (20) between the first tube (13) and the second tube (14), the casing (25) being removably coupled between a first connecting flange (18) and a second connecting flange (19) so as to ensure a thermally sealed connection between the first tube (13) and the second tube (14).

2. Fitting according to claim 1, wherein the envelope (25) comprises at least two envelope sectors (26, 27) in the form of a portion of a cylinder and connected by removable connecting means (28).

3. Fitting according to claim 1, wherein the casing (25) comprises a tubular body including at least one deformable casing portion (29) intended to be deformed to thermally seal the casing (25) between the first connecting flange (18) and the second connecting flange (19).

4. Fitting according to claim 1 or 2, wherein the connecting flanges (18, 19) each include a sealing gasket (31, 32) intended to be fitted onto the connecting flanges (18, 19) by elastic deformation under the pressure of the casing (25).

5. Fitting according to any one of the preceding claims, wherein the first male inner part (21) and the first female outer part (22) are held together with respect to each other by at least one joining element (36, 37), and the second male inner part (23) and the second female outer part (24) are held together with respect to each other by at least one joining element (36, 37).

6. Fitting according to claim 5, wherein the joining elements (36, 37) comprise a spacer for limiting the space between the first male inner part (21) and the first female outer part (22) and between the second male inner part (23) and the second female outer part (24) respectively.

7. Method for connecting vacuum-insulated cryogenic tubes (13, 14), said tubes (13, 14) each comprising a female external part (22, 24) and a male internal part (21, 23) having a male external part (38, 39) projecting axially relative to the female external part (22, 24), characterized in that it comprises: removably connecting a male external part (38) of a first tube (13) coaxially to a male external part (39) of a second tube (14), assembling a sheath (25) around the connecting means (20) between the first tube (13) and the second tube (14), the sheath (25) being removably coupled between a first connecting flange (18) and a second connecting flange (19) so as to ensure a thermally sealed connection between the first tube (13) and the second tube (14).

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