GB2461503A

GB2461503A - A sliding joint for a gas turbine engine fuel manifold

Info

Publication number: GB2461503A
Application number: GB0811830A
Authority: GB
Inventors: Christopher David Williams
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 2008-06-30
Filing date: 2008-06-30
Publication date: 2010-01-06
Also published as: GB0811830D0

Abstract

A fluid supply line sliding joint comprises an annular diaphragm seal 13 coupling the end of the fluid supply line 12 to the end of the fluid receiving part 11, the diaphragm / membrane seal 13 having radially inner and outer flange portions 13a, 13b which are respectively attached to the fluid supply line 12 and the fluid receiving part 11, the diaphragm seal being accommodated in an annular space between the two ends and permitting axial telescopic movement. Ideally the sliding joint connects the fuel line to the fuel spray nozzle connectors (or to another fuel line) in the fuel manifold of a gas turbine engine of an aircraft, and accommodates effects of thermal expansion by serving as a rolling seal. A threaded collar may be used to secure the flanges of the seal. A back-up O-ring seal 14 may be located in the annular space in between.

Description

SLIDING JOINT

The present invention relates to a sliding joint for joining a fluid supply line to a fluid receiving part. The joint may be used in the fuel manifold of a gas turbine engine.

In aero gas turbine engines, compliant joints are often used in fuel pipe networks where relative movement is required to accommodate thermal growth. One application of such joints is in the connecting pipes that feed fuel to and from fuel spray nozzles, i.e. the fuel manifold.

Double 0-ring sliding joints are shown, for example, in Figure 1(a), which is a view of part of the fuel manifold of an aero gas turbine engine, and Figure 1(b), which is an exploded detailed view of the joint between a fuel spray nozzle head 1 and a connecting pipe 2 of the manifold. Further detail is shown in Figure 2, which is a cross-section of the part of the fuel manifold of Figure 1 (a) . Each sliding joint is formed by the connection between end portion la of the respective fuel spray nozzle head, and an end 2a of the corresponding connecting pipe.

End portion la contains a sealing bore 3, and two axially spaced 0-rings 4 located on the end 2a seal to the inner surface of the sealing bore to prevent fuel leaking from the joint. At the same time, however, the joint allows a degree of axial sliding movement of the connecting pipe relative to the fuel spray nozzle head. Retaining clip 5 prevents excessive axial sliding movement.

Compared to pipe networks having rigid joints, such sliding joints can greatly reduce stresses resulting from differential thermal mismatch. Assemblies based on such sliding joints may also have fewer resonance frequencies within, e.g. first engine order frequency ranges, which can lead to improved high cycle fatigue resistance.

The double 0-ring arrangement provides redundancy, so that if one 0-ring fails or leaks, the other may still function correctly.

However, fretting and wear at the sealing surfaces can lead to surface deterioration and loss of sealing integrity. The fretting damage is generally caused by small magnitude, high frequency relative displacement of the 0-ring seal against the sealing bore.

Further, double 0-ring seals require good alignment between the two mating parts to ensure correct seal compression. Alignment features (e.g. dowels, bushing and fixtures) and the tolerances they impose can add cost, weight and complexity to the joint.

Where there are leakage concerns, an additional outer pipe (or skin) or manifold ring is sometimes can be incorporated to capture fuel leaks and direct the leakage to a drain. However, such drainage hardware adds cost, weight and complexity. US patent no. 4708371 proposes an outer drainage pipe, and US patent no. 5031407 proposes a drainage manifold.

In general terms, the present invention provides a sliding joint for joining a fluid supply line to a fluid receiving part, in which an annular diaphragm seal joins an end of the fluid supply line to an end of the fluid receiving part.

More particularly, a first aspect of the invention provides a sliding joint for joining a fluid supply line to a fluid receiving part, the joint including: respective ends of the fluid supply line and the fluid receiving part; and an annular seal which sealingly joins the end of the fluid supply line to the end of the fluid receiving part to allow transmission of fluid therebetween while also allowing axial sliding motion of the fluid supply line relative to the fluid receiving part; wherein the annular seal has radially inner and outer flange portions and a flexible annular diaphragm portion therebetween, the flange portions being sealingly engaged to respective engagement portions of the fluid supply line and the fluid receiving part, and the annular diaphragm portion being located in an annular space which accommodates changes to the configuration of the annular diaphragm portion when the axial sliding motion alters the relative axial positions of the inner and outer flange portions.

The flange portions of the diaphragm seal, being sealingly engaged to respective engagement portions, are not subject to the same fretting and wear as the sealing surfaces of an 0-ring. In particular, relative axial movement is accommodated by changes to the configuration of the annular diaphragm portion, which does not need to be in sealing contact with other parts of the joint, whereas the flange portions can remain in a fixed relative positions relative to their respective engagement portions. Thus fretting and wear at the flange portions can be reduced or eliminated, increasing the reliability and life of the seal.

For example, the annular diaphragm portion may adopt a doubled up configuration in the annular space. In such a configuration, opposing portions of the diaphragm portion can move passed each other when the relative axial positions of the inner and outer flange portions are altered.

The sliding joint may include a second annular seal which sealingly joins the end of the fluid supply line to the end of the fluid receiving part to allow transmission of fluid therebetween while also allowing axial sliding motion of the fluid supply line relative to the fluid receiving part, the second seal being a backup seal to the first seal, and being of non-annular diaphragm type. For example, the second annular seal may an 0-ring.

A possible problem with conventional double 0-ring seals, as illustrated in Figures 1 and 2, is that the 0-rings, being of identical or similar type, can be susceptible to the same failure mechanism, leading to simultaneous breech of both seals. However, by adopting two seals of different type, e.g. a diaphragm seal and an 0-ring seal, the risk of simultaneous breeches is reduced.

The fluid supply line and the fluid receiving part may be elements of a fuel manifold, e.g. the fuel manifold of a gas turbine engine.

The fluid receiving part may be a second fluid supply line. When the fluid supply line and the fluid receiving part are elements of a fuel manifold, the fluid receiving part may be a fuel spray nozzle head.

Preferably, one of the fluid supply line and the fluid receiving part includes an annular retaining member for sealingly retaining the respective flange portion at the engagement portion of that one of the fluid supply line and the fluid receiving part. The annular retaining member can help to ensure that the respective flange portion remains in a fixed relative position relative to the engagement portion, thereby reducing fretting and wear. When the respective flange portion is the radially outer flange portion, the annular space in which the annular diaphragm portion is located may conveniently be formed between an axial extension of the annular retaining member and the other of the fluid supply line and the fluid receiving part.

Preferably, the other of the fluid supply line and the fluid receiving part also includes an annular retaining member for sealingly retaining the other flange portion at the engagement portion of that other of the fluid supply line and the fluid receiving part.

Conveniently, the or each annular retaining members can be replaced should, e.g. the surface of the member that seals to the respective flange portion become damaged.

Further aspects of the invention provide a fuel manifold having a sliding joint of the first aspect, and a gas turbine engine having a sliding joint of the first aspect.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1(a) is a view of part of the fuel manifold for an aero gas turbine engine, and Figure 1(b) is an exploded detailed view of the joint between a fuel spray nozzle head and a connecting pipe of the manifold; Figure 2 is a cross-section of the part of the fuel manifold of Figure 1(a); and Figure 3 shows a schematic longitudinal cross-section through a sliding joint of an embodiment of the present invention.

Figure 3 shows a schematic longitudinal cross-section through a sliding joint of an embodiment of the present invention. The joint is formed between respective ends of a fuel spray nozzle head 11 and a connecting pipe 12 of a fuel manifold of an aero gas turbine engine.

The sliding joint has two seals axially spaced on the end of the connecting pipe 12. The primary seal 13 is an annular diaphragm seal, having a radially outer flange portion 13a, a radially inner flange portion 13b, and an annular diaphragm portion 13c between the two flange portions. The secondary seal 14, which serves as a backup to the primary seal, is an 0-ring 14 sited in a recess 12a formed in the outer surface of the connecting pipe.

An inner retaining clamp 15, screwed into the end of connecting pipe 12, sealingly clamps the inner flange portion 13b to the end face engagement portion 12c of the connecting pipe. Likewise, an outer retaining clamp 16 sealingly clamps the outer flange portion 13a into a recess engagement portion ha formed in the end face of the fuel spray nozzle head 11. The clamp 16 is urged against the outer flange portion 13a by a collar 17 that threads onto the end of fuel spray nozzle head to apply the appropriate clamping force without shearing the flange portion. The collar is sized to be able to freely rotate about the outer retaining clamp 16.

The outer retaining clamp 16 has an axial extension sleeve 16a which surrounds and is spaced from an outer surface 12b of the end of the connecting pipe to form an annular space 18. The annular diaphragm portion 13c, which is formed of flexible material, is located in this space in a doubled-up configuration. The annular diaphragm seal 13 may be formed from a reinforced elastomeric material, or other suitable material, and constructed to resist pressure, fuel, other fluids, and contaminants.

On axial movement of the connecting pipe 12 relative to the spray nozzle head 11, the flexible annular diaphragm portion 13c rolls in and out of the annular space 18 as opposing parts of the diaphragm portion move passed each other. The annular diaphragm portion is urged by fluid pressure against the inner surface of the outer retaining clamp 16 and the outer surface 12b of the end of the connecting pipe. These surfaces, which support the flexible annular diaphragm portion, are smooth and free from sharp corners. The relatively tight radius of curvature adopted by the doubled-up flexible annular diaphragm portion in the annular space, allows the diaphragm portion to withstand high fluid pressures.

The axial extension sleeve 16a also provides the outer sealing surface for 0-ring 14, the inner sealing surface being provided by recess 12a. Axial movement of the connecting pipe 12 relative to the spray nozzle head 11 results in the axial extension 16a sliding over 0-ring 14.

Thus the joint embodies two distinct and separate sealing methods, which helps to eliminate common failure risks and modes. The annular diaphragm seal 13 provides a physical barrier to pressurised fuel in the manifold, in contrast to the 0-ring seal 14 which relies on dynamic sealing contact to two opposing surfaces. The joint is therefore more reliable than one based on e.g. two 0-ring seals, and can avoid a need for a separate drainage manifold or outer pipe.

The rolling in and out of the diaphragm portion 13c under relative axial movement is fundamentally different to the rubbing and sliding experienced by the 0-ring seal.

The diaphragm seal may therefore experience less wear, which in turn can lead to an increased service life.

The inner 15 and outer 16 retaining clamps and collar 17, which will typically be metal, can be replaceable, low cost items.

Some concentricity and angularity differences between the connecting pipe 12 and the fuel spray nozzle head 11 can be accommodated by the diaphragm seal 13. In particular, the compliance of the diaphragm portion 13c allows the connecting pipe 12 to rotate quite freely about any axis which coincides with a diameter of the 0-ring seal. The angular limit of such rotation is reached when a part of the structure of the connecting pipe 12 and the inner retaining clamp 15 interferes with a part of the structure of the fuel spray nozzle head 11 and the outer retaining clamp 16. Such rotation can reduce the need for high tolerances and alignment fixtures like those used on double 0-ring sliding joints.

Although the secondary seal 14 is shown in the above embodiment as a circular cross-section 0-ring, it could take the form of any type of circumferential seal. For example, the circular cross-section 0-ring, could be replaced with a D or star cross-section circular seal, or with a PTFE energised seal etc. While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. For example, the joint can be applied to oil or air lines, as well as fuel lines. For high temperature applications, the annular diaphragm seal may be formed with a flexible metallic diaphragm portion. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

Claims

CLAIMS1. A sliding joint for joining a fluid supply line to a fluid receiving part, the joint including: respective ends of the fluid supply line and the fluid receiving part; and an annular seal which sealingly joins the end of the fluid supply line to the end of the fluid receiving part to allow transmission of fluid therebetween while also allowing axial sliding motion of the fluid supply line relative to the fluid receiving part; wherein the annular seal has radially inner and outer flange portions and a flexible annular diaphragm portion therebetween, the flange portions being sealingly engaged to respective engagement portions of the fluid supply line and the fluid receiving part, and the annular diaphragm portion being located in an annular space which accommodates changes to the configuration of the annular diaphragm portion when the axial sliding motion alters the relative axial positions of the inner and outer flange portions.
2. A sliding joint according to claim 1, further including a second annular seal which sealingly joins the end of the fluid supply line to the end of the fluid receiving part to allow transmission of fluid therebetween while also allowing axial sliding motion of the fluid supply line relative to the fluid receiving part, the second seal being a backup seal to the first seal, and being of non-annular diaphragm type.
3. A sliding joint according to claim 2, wherein the second seal is an 0-ring.
4. A sliding joint according to any one of the previous claims, wherein the fluid supply line and the fluid receiving part are elements of a fuel manifold.
5. A sliding joint according to claim 4, wherein the fuel manifold is a gas turbine engine fuel manifold.
6. A sliding joint according to any one of the previous claims, wherein the fluid receiving part is a second fluid supply line.
7. A sliding joint according to claim 5, wherein the fluid receiving part is a fuel spray nozzle head.
8. A sliding joint according to any one of the previous claims, wherein one of the fluid supply line and the fluid receiving part includes an annular retaining member for sealingly retaining the respective flange portion at the engagement portion of that one of the fluid supply line and the fluid receiving part.
9. A sliding joint according to claim 8, wherein the respective flange portion is the radially outer flange portion, and the annular space is formed between an axial extension of the annular retaining member and the other of the fluid supply line and the fluid receiving part.
10. A sliding joint according to claim 8 or 9, wherein the other of the fluid supply line and the fluid receiving part also includes an annular retaining member for sealingly retaining the other flange portion at the engagement portion of that other of the fluid supply line and the fluid receiving part.
11. A fuel manifold having the sliding joint of claim 4.
12. A gas turbine engine having the sliding joint of claim 5.
13. A sliding joint as any one herein described with reference to and/or as shown in Figure 3.