SCREWED CONNECTION FOR ROCKET ENGINE

Description

Technical Field

[0001] This disclosure relates to a rocket engine threaded connection configured to connect a fluid line to another element of the rocket engine. Prior art

[0002] The use of screwed connections in a rocket engine is common. These screwed connections must meet demanding specifications and must in particular: a. Provide a seal at temperatures ranging from cryogenic to above ambient temperatures. b. Withstand significant vibration conditions. c. Maintain their seal when the pipe and / or screwed connection becomes deformed.

[0003] Furthermore, the screw connection must maintain its performance during transient conditions of the rocket engine, conditions in which temperature and vibration conditions change.

[0004] Some known screwed connections can at least partially meet these specifications, including the screwed connection commonly referred to by the acronym "RLSEP" and the screwed connection with seals commonly referred to by the acronym "VSEP". These two types of connections are particularly expensive.

[0005] On the other hand, other screwed connections comprising flat gaskets are known, but do not meet the specifications set out above. In particular, flat gaskets have the disadvantage of creeping at room temperature. Their use requires prior maintenance each time the engine containing them is used, which is prohibitive.

[0006] There is therefore a need for cost reduction and improvement of known devices. DE 1015650 B discloses a cap with a deformable collar. US 3971566 discloses a hydraulic seal. Statement of the invention

[0007] The present disclosure relates to a threaded connection of a fluid pipe to a support, comprising a seal secured to the support, a joining portion configured to cooperate with the seal by clamping, and an arm extending around the pipe outside the pipe, connecting the pipe to the joining portion, wherein the joining portion has a stiffness greater than that of the arm and the seal.

[0008] In this disclosure, it is understood that the term "stiffness" refers to a structural stiffness. In this disclosure, it is understood that the stiffness of the arm in bending is lower than the stiffness of the joint portion in compression. It is then understood that when a stress is applied to the screwed connection, the arm is deformed before the joint portion.

[0009] Thus, such a screw connection has an arm that is capable of flexing to reduce the stresses imposed by expansions and compressions undergone by the connection under the effect of temperature. Consequently, this screw connection can be used over a wide temperature range. In particular, such a screw connection can be used over a wider temperature range than known screw connections.

[0010] Furthermore, this configuration is able to withstand the vibration stresses that can be experienced in a rocket engine. Generally speaking, this screwed connection is compatible with the transient operating regimes of the rocket engine and is able to withstand rapid temperature variations.

[0011] Also, the screwed connection described above is simple to manufacture, and in particular simpler to manufacture than the known RLSEP and VSEP connections. It is therefore less expensive. In general, the screwed connection of this presentation is inexpensive.

[0012] The conduit may extend along an axis, and the arm may comprise an axial thickness, in the direction of the axis, less than the axial thickness of the joining portion. In one example, the axial thickness of the arm is at least two times less than the axial thickness of the joining portion. In one example, the axial thickness of the arm is at least three times less than the axial thickness of the joining portion. In one example, the axial thickness of the arm is at least three or four times less than the axial thickness of the joining portion.

[0013] In certain configurations, the axial stiffness of the assembly consisting of the arm, the joint portion and the seal is lower than the axial stiffness of a portion of the pipe of an axial length equal to the axial length of the assembly consisting of the arm, the joint portion and the seal. Preferably, the axial stiffness of the assembly consisting of the arm, the joint portion and the seal is at least three times lower than the axial stiffness of the pipe portion of corresponding length.

[0014] In the present disclosure, the screwed connection comprises a first threaded portion and the support comprises a second threaded portion, the first threaded portion and the second threaded portion being configured to cooperate to assemble the connection to the support by screwing.

[0015] In some configurations, a portion of the seal portion is configured to plasticize when fluid passes through the conduit.

[0016] In this configuration, the tightness of the screwed connection is improved. Plasticization occurs during the passage of the cryogenic fluid, and results in the creation of a plasticized zone which improves the tightness.

[0017] In this presentation, the joint has a stiffness greater than that of the arm. It is understood that the compressive stiffness of the joint is greater than the bending stiffness of the arm.

[0018] In this configuration, the arm is the first element to flex when a stress is applied to the screwed connection. Since the arm is the most flexible part of the connection, the connection is then able to more easily absorb the stresses it is subjected to.

[0019] In some embodiments, the support is another conduit.

[0020] In this configuration, the screw connection can be used in a greater number of situations, and thus be included in a greater number of lines, thereby reducing the manufacturing cost of the rocket engine.

[0021] In some embodiments, the gasket is made of copper.

[0022] Copper has properties that ensure rigidity of the joint part compatible with the rigidity of the joint and the support during steady state and transient conditions.

[0023] This configuration is also advantageous because copper does not creep at room temperature. Thus, a screwed connection that is assembled and then stored does not lose its tightness due to creep of the joint, since the latter does not creep. En In particular, the ratio between the assembly and storage temperature and the melting temperature of copper is less than 0.25, a value from which creep phenomena can appear. In this case, this same ratio is 0.31 for aluminum joints, which makes creep of an aluminum joint possible and requires regular tightening.

[0024] In some embodiments, a sealing volume is provided between the pipe on the one hand and the seal and the joining portion on the other hand, the sealing volume being configured to collect the fluid escaping from the junction between the first threaded portion and the second threaded portion, said threaded portions typically not having the function of ensuring a sealed connection.

[0025] In this configuration, the sealing volume allows the fluid escaping from the permeable thread to be contained in the sealing volume.

[0026] In some embodiments, the seal and the joining portion are annular.

[0027] In some embodiments, the seal portion includes an annular sealing projection extending from a face of the seal portion configured to contact the gasket, and configured to penetrate the gasket upon tightening of the seal portion onto the gasket.

[0028] This configuration provides an additional element to ensure the tightness of the connection. The tightness is then ensured by the projection and by the tightening of the joining part against the gasket.

[0029] The disclosure further relates to a rocket engine comprising one of the screw connections described above.

[0030] Thus, the rocket engine includes the advantages mentioned above, namely lower cost and increased reliability.

[0031] In some embodiments, the rocket engine comprising said screwed connection has this connection disposed in a cryogenic conduit.

[0032] The disclosure further relates to a spacecraft comprising a rocket engine as described above. Brief description of the drawings

[0033] The invention and its advantages will be better understood upon reading the detailed description given below of different embodiments of the invention given as non-limiting examples. This description refers to the appended pages of figures, in which: [ Fig. 1 ] There figure 1 represents a spacecraft comprising a screw connection according to one embodiment. Fig. 2 ] There figure 2 represents a sectional view of a screwed connection according to a first embodiment. Fig. 3A-3D ] There figure 3A represents a partial sectional view of an unassembled screwed connection according to the first embodiment, the figure 3B represents a partial sectional view of a screwed connection assembled according to the first embodiment of a pipe in which no fluid has passed, the figure 3C represents a partial sectional view of a screwed connection according to the first embodiment when the rocket engine is in transient mode and when a cold fluid passes through the pipe, the figure 3D represents a partial sectional view of a screwed connection according to the first embodiment when the rocket engine is in transient mode and when a hot fluid passes through the pipe. Fig. 4A-4B ] There figure 4A represents a partial sectional view of an unassembled fitting according to a second embodiment, the figure 4B represents a partial sectional view of a fitting assembled according to the second embodiment. Description of the embodiments

[0034] There figure 1 schematically represents a spacecraft 500 comprising a rocket engine 80, itself comprising a screwed connection 10. The screwed connection 10 is arranged within a pipe 50 partially shown in the figures 2à 3 .

[0035] There figure 2 represents a screwed connection 10 according to a first embodiment. This screwed connection (or connection) 10 comprises a first threaded part 11, a joining part 12, a seal 14 and an arm 16. The connection 10 is secured to the pipe 50, and the latter extends along an axis X. The present description takes the non-limiting example of a cryogenic pipe 50, but the pipe is capable of conveying other types of fluid. In the present example, the arm 16 has an axial thickness, in the direction of the axis X, smaller than the axial thickness of the joining part 12. In particular, the axial thickness of the arm 16 is at least three times smaller than the axial thickness of the joining part 12.

[0036] The arm 16 is secured to the pipe 50 while the seal 14 is secured to a support 20. The arm 16 extends from the outer periphery of the pipe 50, and has a generally annular shape. The arm 16 is configured to deform elastically under the intended conditions of use of the screwed connection 10.

[0037] The support 20 comprises a second threaded portion 21 and the first threaded portion 11 of the connector 10 is configured to cooperate with the second threaded portion 21 of the support 20. The support 20 may furthermore be another fluid conduit or an element of the rocket engine. In the example of the first embodiment, the support 20 is a part of the rocket engine secured to the conduit 50 through the cooperation of the first threaded portion 11 and the second threaded portion 21.

[0038] A sealing volume 18 is provided between the pipe 50 on the one hand and the seal 14 and the joint part 12 on the other hand. In the example of the first embodiment, the sealing volume 18 is covered by the arm 16 from above and by the support 20 from below.

[0039] The arm 16 and the joining portion 12 of the connector 10 may be supplied in one piece with the pipe 50.

[0040] When assembling the connector 10 with the support 20 by cooperation of their respective threaded part 11, 21, the joining part 12 is tightened against the seal 14, which ensures sealing.

[0041] The seal 14 is typically an annular element with an inner radius greater than 5 mm and less than 15 mm, preferably less than 10 mm, and an outer radius greater than 16 mm and less than 25 mm, preferably greater than 20 mm. The seal 14 is, for example, made of copper or a copper-based alloy, i.e. an alloy whose largest mass fraction is copper.

[0042] The joint part 12 is for example annular, made of stainless steel and has dimensions compatible with its tightening on the joint 14.

[0043] In the present example, the axial stiffness of the assembly consisting of the arm 16, the joining part 12 and the seal 14 is at least three times lower than the axial stiffness of a portion of the pipe 50 of an axial length equal to the axial length of the assembly consisting of the arm 16, the joining part 12 and the seal 14. This difference in axial stiffness is obtained, at least in part, by the small axial thickness of the arm 16 compared to the axial thickness of the joining part 12.

[0044] THE figures 3A-D represent connection 10 in different states.

[0045] There figure 3A represents a connection 10 before screwing the first threaded part 11 into the second threaded part 21. It can be seen that the arm 16 is not bent.

[0046] There figure 3B represents a connection 10 in which the first threaded part 11 is screwed into the second threaded part 21, as could be obtained immediately after screwing or after storage. No fluid flows into the pipe 50. It can be seen that the arm 16 is slightly bent, so that the seal 14 is more tightly tightened. This bending of the arm 16 is elastic. En In particular, the seal 14 is slightly plasticized. Thus, a screwed and then stored connection 10 retains its tightness.

[0047] There figure 3C represents a screwed connection 10 of a pipe 50 crossed by cold fluid, while the connection 10 is in transient thermal regime. It can be seen that the arm 16 flexes more significantly compared to its flexion under the conditions of the figure 3B . This bending of the arm 16 remains elastic. Consequently, the joint 14 is more tightly tightened.

[0048] There figure 3D represents a screwed connection 10 of a pipe 50 crossed by a hot fluid, while the connection 10 is in a transient thermal regime. In this situation, the pipe 50 expands, which lowers the flexion of the arm 16: that is to say that it tends to return to a position in which it is not constrained, compared to its flexion under the conditions of the figure 3B , while remaining flexed. This deflection of the arm 16 remains elastic. However, the connector 10 retains its seal and the joint portion 12 remains tight against the seal 14. Indeed, the deflection of the arm 16 is less than its flexion at rest, when no fluid passes through the pipe 50. The arm 16 therefore remains flexed even when the pipe is crossed by a hot fluid. Thus, the joint portion 12 remains in contact with the seal 14.

[0049] THE figures 4A et 4Brepresent a connector 10 according to a second embodiment, respectively disassembled and assembled. This connector 10 comprises a joint portion 12, a seal 14 and an arm 16. The connector 10 of the second embodiment comprises an annular projection 13 arranged on the joint portion 12. This projection 13 is arranged on a face of the joint portion 12 configured to be in contact with the seal 14 and penetrate it in the screwing direction of the connector 10. Thus, the projection 13 improves the sealing of the screwed connector 10.

[0050] Although the present invention has been described with reference to specific exemplary embodiments, it is obvious that modifications and changes may be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various illustrated / mentioned embodiments may be combined in additional embodiments. Therefore, the description, dimensions and drawings should be considered in an illustrative rather than restrictive sense.

[0051] It is also obvious that all the characteristics described with reference to a method are transposable, alone or in combination, to a device, and conversely, all the characteristics described with reference to a device are transposable, alone or in combination, to a method.

Claims

1. A screw connector (10) for connecting a fluid pipe (50) to a support (20), the screw connector comprising the pipe (50), a seal (14) intended to be secured to the support (20), a joining part (12) configured to cooperate with the seal (14) by clamping, and an arm (16) extending around the pipe (50) outside the pipe (50) and connecting the pipe (50) to the joining part (12), wherein the joining part (12) has a greater stiffness than the arm (16) and the seal (14), that is, the flexural stiffness of the arm (16) is less than the compressive stiffness of the joining part (12), and the screw connector (10) comprises a first threaded part (11) and the support (20) comprises a second threaded part (21), the first threaded part (11) and the second threaded part (21) being configured to cooperate to assemble the connector to the support by screwing, characterized in that: the seal (14) has a stiffness greater than that of the arm (16), that is, the compressive stiffness of the seal (14) is greater than the flexural stiffness of the arm (16).

2. The screw connector (10) according to claim 1, wherein the support (20) is another pipe (50).

3. The screw connector (10) according to one of claims 1 or 2, wherein the seal (14) is made of copper.

4. The screw connector (10) according to one of claims 1 to 3, wherein a sealing volume (18) is provided between the pipe (50) on the one hand and the seal (14) and the joining part (12) on the other hand, the sealing volume (18) being configured to collect fluid having leaked from the pipe (50).

5. The screw connector (10) according to one of claims 1 to 4, wherein the joining part (12) and the seal (14) are annular.

6. The screw connector (10) according to one of claims 1 to 5, wherein the joining part (12) comprises an annular sealing projection (13) extending from a face of the joining part (12) configured to enter into contact with the seal (14), and configured to penetrate the seal (14) when tightening the joining part (12) on the seal (14).

7. A rocket engine (80) comprising a screw connector (10) according to any one of claims 1 to 6.

8. The rocket engine (80) according to claim 7, wherein the screw connector (10) is disposed in a cryogenic line.

9. A spacecraft (500) comprising a rocket engine (80) according to claim 8.