GB2504969A

GB2504969A - Pivoted fan outlet guide vane

Info

Publication number: GB2504969A
Application number: GB1214549.6A
Authority: GB
Inventors: Matthew Ashley Charles Hoyland
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 2012-08-15
Filing date: 2012-08-15
Publication date: 2014-02-19
Also published as: GB201214549D0

Abstract

A gas turbine engine comprising a core, a fan case and a plurality of fan outlet vanes situated between the core and the fan case, at least one of the vanes has first and second pivots 82, 84 to enable rotation about a first and second axiss parallel to a rotational axis of the core. Preferably the guide vanes are aligned on a vector offset from the radial axis of the core (figure 4). Also described is a method of manufacturing fan outlet guide vanes comprising wrapping one or more lengths of material around two fixed position rigid members to form with a matrix material a fixed length composite vane with first and second pivots. In one arrangement the rigid members are removed and a sheath inserted in the apertures, in another version the rigid members are hollow and retained in the vane.

Description

Fan Outlet Guide Vane

FIELD OF THE INVENTION

Embodiments of the present invention relate to fan outlet guide vanes.

In particular, they relate to fan outlet guide vanes in gas turbine engines.

Embodiments of the present invention also relate to a method of manufacture of fan outlet guide vanes.

BACKGROUND TO THE INVENTION

Gas turbine engines comprise a core and a fan case, the fan case surrounding the core. Fan outlet guide vane arrangements comprising a plurality of vanes are positioned between the core and the fan case of a gas turbine engine to remove the rotation component of the flow introduced by the fan. The fan outlet guide vane arrangement is a critical structural component in a gas turbine engine. They transfer load between the core and the fan case and are typically formed of titanium.

BRIEF DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION

According to various, but not necessarily all, embodiments of the invention there is provided a gas turbine engine comprising a core, a fan case, a plurality of vanes situated between the core and the fan case, a first pivot configured to enable rotation of at least one vane of the plurality of vanes about a first axis parallel to a rotational axis of the core and passing through the first pivot and a second pivot configured to enable rotation of the at least one vane of the plurality of vanes about a second axis parallel to the rotational axis of the core and passing through the second pivot.

In use, the at least one vane may be aligned on a vector, offset from a radial axis of the core.

The gas turbine engine may further comprise a retainer configured to maintain a tensile force through the vane.

Tensioning may be facilitated by stretching of the vane between the first pivot and the second pivot and the retainer may be configured to control and maintain the tensile force through the vane in the stretched condition.

The plurality of vanes may provide a single plane structure forming a primary structural connection between the core and fan case, the single plane structure being capable of withstanding fan blade off loads.

The pivots may be configured to allow at least one vane to be removable while the core is in situ relative to the fan case.

The gas turbine engine may be an aero engine with bypass The at least one vane may have a length, a width and a depth and may be formed of an anisotropic material such that the tensile strength of the material along the length is greater than the tensile strength of the material along the width and the depth, the at least one vane extending lengthwise, in use, between the core and the fan case.

According to various, but not necessarily all, embodiments of the invention there is provided a fan outlet guide vane comprising: a vane body; a first pivot configured to interconnect the vane body to a gas turbine engine core; and a second pivot configured to interconnect the vane body to a gas turbine engine fan case, the first pivot being configured to enable relative rotation between the fan outlet guide vane and the gas turbine engine core about a first axis parallel to a rotational axis of the core and passing through the first pivot and the second pivot being configured to enable relative rotation between the fan outlet guide vane and the gas turbine engine fan case about a second axis parallel to the rotational axis of the core and passing through the second pivot.

The vane body may have a length, a width and a depth, the vane body may comprise a first end and a second end separated lengthwise, the first pivot may be positioned towards the first end of the vane body, and the second pivot may be positioned towards the second end of the vane body.

The first pivot may comprise a single aperture and the second pivot may comprise a single aperture.

The fan outlet guide vane may be formed of a material selected from: an anisotropic material; a composite material; a fibre reinforced composite material; an organic matrix composite material; and a metal matrix composite material.

According to various, but not necessarily all, embodiments of the invention there is provided a method of manufacture of a fan outlet guide vane comprising wrapping one or more lengths of material around two fixed position rigid members to form, with a matrix material, a fixed length composite vane body with a first pivot located at the first rigid member and a second pivot located at the second rigid member, the first and second pivots being located on a lengthwise axis of the vane.

One or more of the rigid members may be a solid member, which may be subsequently removed to provide a cylindrical aperture with a cylindrical axis substantially perpendicular to the lengthwise axis of the vane.

One or more of the rigid members may be a retained hollow member, comprising a cylindrical aperture with a cylindrical axis substantially perpendicular to the lengthwise axis of the vane.

A sheath may be inserted into one or more of the apertures.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of various examples of embodiments of the present invention reference will now be made by way of example only to the accompanying drawings in which: Fig. 1 is a cross sectional view of an example of a gas turbine engine; Fig. 2 is a cross sectional view of a fan outlet guide vane arrangement of a gas turbine engine; Fig. 3 is a different cross sectional view of the outlet guide vane arrangement of a gas turbine engine, illustrated in Fig. 2; Fig. 4 is a diagrammatic representation of the positioning of a vane, in use, relative to the core and fan case; Fig. 5 is a cross sectional view of an example of a mounted vane and pivot; Fig. 6 is a cross section of the mounted vane illustrated in Fig. 5; Fig. 7 is a cross sectional view of another example of a mounted vane; Fig. 8 is a cross sectional view of a further example of a mounted vane; Fig. 9 is a diagrammatic view of the manufacture of a vane.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS OF THE

INVENTION

The figures illustrate a gas turbine engine 10 comprising a core 22, a fan case 24, a plurality of vanes 20 situated between the core 22 and the fan case 24, a first pivot 40 configured to enable rotation of at least one vane 20 of the plurality of vanes 20 about a first axis 44 parallel to a rotational axis 48 of the core 22 and passing through the first pivot 40 and a second pivot 42 configured to enable rotation of the at least one vane 20 of the plurality of vanes 20 about a second axis 46 parallel to the rotational axis 48 of the core 22 and passing through the second pivot 42.

Referring to Fig. 1, a gas turbine engine is generally indicated at 10 and comprises a core 22, a fan case 24 and a plurality of vanes 20 situated between the core 22 and the fan case 24. The gas turbine engine comprises, in axial flow series, an air intake 11, a propulsive fan 12, an intermediate pressure compressor 13, a high pressure compressor 14, a combustor 15, a turbine arrangement comprising a high pressure turbine 16, an intermediate pressure turbine 17 and a low pressure turbine 18, and an exhaust nozzle 19.

The gas turbine engine 10 operates in a conventional manner so that air entering the intake 11 is accelerated by the fan 12 which produces two air flows: a first air flow into the intermediate pressure compressor 13 and a second air flow which provides propulsive thrust. The intermediate pressure compressor 13 compresses the air flow directed into it before delivering that air to the high pressure compressor 14 where further compression takes place.

The compressed air exhausted from the high pressure compressor 14 is directed into the combustor 15 where it is mixed with fuel and the mixture combusted. The resultant hot combustion products then expand through, and thereby drive, the high, intermediate and low pressure turbines 16, 17 and 18 before being exhausted through the nozzle 19 to provide additional propulsive thrust. The high, intermediate and low pressure turbines 16, 17 and 18 respectively drive the high and intermediate pressure compressors 14 and 13 and the fan 12 by suitable interconnecting shafts 26, 28, 30 aligned with a rotational axis 48.

The second air flow of the gas turbine engine 10 provides propulsive thrust through a bypass 25 located between the core 22 and the fan case 24.

In some implementations the gas turbine engine 10 may be an aero engine.

In an example, shown in Figs. 2 and 3, a plurality of vanes 20 is arranged in relation to the core 22 and the fan case 24, within the bypass 25.

The plurality of vanes 20 forms at least part of a fan outlet guide vane arrangement 21. In the illustrated example, the plurality of vanes 20 provides a single plane structure 62 forming a primary structural connection between the core 22 and fan case 24. The single plane structure 62 is orthogonal to a rotational axis 48 of the core 22. The single plane structure 62, formed at least in part by the plurality of vanes 20, is capable of taking 100% of the load generated by the core in normal operation. Further, the single plane structure 62 is capable of withstanding fan blade off loads.

The examples illustrated in Figs. 2, 3 and 4 may be described with reference to a coordinate system, as shown in Fig. 3. The origin of the coordinate system may be taken to be at the rotational axis 48 of the core 22.

The rotational axis 48 is the axis around which various components of the gas turbine engine 10, such as the propulsive fan 12, high pressure turbine 16, intermediate pressure turbine 17 and low pressure turbine 18, rotate. The coordinate system has an axis z, parallel with the rotational axis 48 of the core 22, and a radial axis r that is orthogonal to the axis z. The axis z is along the page in Fig. 3, in line with the rotational axis 48.

Fig. 2 is a cross sectional view of an example of the fan outlet guide vane arrangement 21 of a gas turbine engine 10 in a plane orthogonal to the rotational axis 48 of the core 22, through the line 1-1 of Fig. 1. Only three vanes 20-1, 20-2, 20-3 of the plurality of vanes 20 are shown in Fig. 2 for clarity. It will be appreciated that the plurality of vanes 20 may comprise any number of vanes which may be arranged between the core 22 and the fan case 24. Typically between 40 and 60 vanes are arranged in the fan outlet guide vane arrangement 21 though less or more vanes could be used.

Fig. 3 shows a cross sectional view of an example of the fan outlet guide vane arrangement 21, through the line 2-2 of Fig. 2. The view of Fig. 3 is therefore orthogonal to the view of Fig. 2. For simplicity the following description considers the structure and the operation of a single vane of the fan outlet guide vane arrangement 21.

Referring to the orthogonal views of Figs. 2 and 3, the vane 20-1 has a vane body 34 with a length 54, a width 56 and a depth 58. The vane body 34 has a first inner end 36 and a second outer end 38 separated lengthwise.

The vane 20-1 is situated between the core 22 and the fan case 24.

The vane 20-1 may be formed of one or more of an anisotropic material, a composite material, a fibre reinforced composite material, an organic matrix composite material or a metal matrix composite material.

Organic matrix composites include using a high strength fibre such as carbon with a polymer matrix material such as epoxy The vane 20-1 may be formed of an anisotropic material such that the tensile strength of the material along the length 54 of the vane 20-1 is greater than the tensile strength of the material along the width 56 of the vane 20-1 and the depth 58 of the vane 20- 1. In an example of a vane 20-1, anisotropic composite material may be used where the fibres of the composite material are aligned along the length 54 of the vane 20-1, the length 54 being the primary loading direction in which a load is applied, in use.

A first pivot 40 is positioned towards the first end 36 of the vane body 34. The first pivot 40 is configured to interconnect the vane body 34 to the core 22. The interconnection may include no intermediate components, or may include any number of intermediate components. The first pivot 40 is configured to enable rotation of the vane 20-1 relative to the core 22.

A second pivot 42 is positioned towards the second end 38 of the vane body 34. The second pivot 42 is configured to interconnect the vane body 34 to the fan case 24. The interconnection may include no intermediate components, or may include any number of intermediate components. The second pivot 42 is configured to enable rotation of the vane 20-1 relative to the fan case 24.

In particular the rotation of the vane 20-1 may be, as illustrated in Fig. 4, a rotation of the vane 20-1 at the first pivot 40 relative to the core 22 and a rotation of the vane 20-1 at the second pivot 42 relative to the fan case 24.

Fig. 4 is a diagrammatic representation of the positioning of a vane 20- 1, rotated, in use, relative to the core 22 and fan case 24. Fig. 4 shows a vane 20-1 that has been rotated by an angle B from the radial axis 50. The rotation of the vane 20-1, to a position offset by an angle B from the radial axis 50, may be carried out as part of a pre-tensioning process and/or applied when a torque load is applied to the core 22 of the gas turbine engine 10, in use The vane 20-1 is mounted through the first pivot 40 for rotation about a first axis 44 which is parallel to the rotational axis 48 of the core 22. The first axis 44 passes through the first pivot 40.

The vane 20-1 is also mounted through the second pivot 42 for rotation about a second axis 46 which is parallel to the rotational axis 48 of the core 22. The second axis 46 passes through the second pivot 42.

When a torque load is applied to the gas turbine engine 10, the force exerted on the core 22 results in relative rotational movement between the core 22 and the fan case 24 about the rotational axis 48 of the core 22. This relative rotational movement results in a circumferential displacement of the core 22 relative to the fan case 24.

As the core 22 is circumferentially displaced from the fan case 24, the vane 20-1 is rotated in a first sense, which may be a clockwise or an anticlockwise sense, at the first pivot 40 and in a second sense, which may be an anticlockwise or a clockwise sense, at the second pivot 42. The rotation of the vane 20-1 at the first pivot 40 is in an opposite rotational sense to the rotation at the second pivot 42. The relative circumferential displacement of the core 22 and the fan case 24 may be in a clockwise or an anticlockwise sense. The relative circumferential displacement of the core 22 and fan case 24, which are interconnected by the vane 20-1, leads to an increase in the tensile force applied along the lengthwise direction of the vane 20-1 as the vane 20-1 is stretched between the first pivot 40 and second pivot 42.

The first axis 44 and second axis 46, as shown in Fig. 3, are parallel to each other in order to provide free rotation of the vane 20-1 as the core 22 is circumferentially displaced relative to the fan case 24.

When the vane 20-1 is rotated at the at the first pivot 40 and the second pivot 42, the vane is displaced from the radial axis 50, to be aligned on a vector 52, angularly offset from the radial axis 50 and intercepting the radial axis 50 at a position offset from the rotational axis 48 of the core 22.

In one example of a pre-tensioning process, a relative rotational movement is provided between the core 22 and the fan case 24 about the rotational axis 48 of the core 22. This relative rotational movement results in a circumferential displacement of the core 22 relative to the fan case 24. As the core 22 is circumferentially displaced from the fan case 24, the vane 20-1 is rotated in a first sense, which may be a clockwise or an anticlockwise sense, at the first pivot 40 and in a second sense, which may be an anticlockwise or a clockwise sense, at the second pivot 42. The relative circumferential displacement of the core 22 and fan case 24, which are interconnected by the vane 20-1, requires the rotation of the vane 20-1 at the first pivot 40 and the rotation at the second pivot 42 to be in opposite rotational sense. The relative circumferential displacement of the core 22 and the fan case 24 may be in a clockwise or an anticlockwise sense. The benefit of pre-tensioning is to reduce circumferential displacement between the core 22 and the fan case 24. Pre-tensioning may also increase vibration frequencies out of the running range when aerodynamic loading is applied to the vane 20-1.

The amount of relative rotation, in a first sense, between the core 22 and the fan case 24, is selected to define a rotation threshold, such that the vane 20-1 is tensioned along its length 54, by a selected amount of tension, at the rotation threshold. A retainer 60 is configured to allow further relative rotation, in the first sense, between the core 22 and the fan case 24, beyond the rotation threshold. The retainer is configured to stop relative rotation between the core 22 and the fan case 24, beyond the rotation threshold in a second sense, opposite to the first sense.

Fig. 6 illustrates a cross section through the length 54 of the vane 20-1 at a first end 36 and a second end 38. Referring to Fig. 6, the first end 36 of the vane 20-1 has only a single aperture 70. The aperture 70 at the first end 36 of the vane 20-1 extends perpendicularly or substantially perpendicularly to the length 54 and width 56 of the vane 20-1. In use, the aperture 70 extends orthogonally to the rotational axis 48 of the core 22 and is aligned with the axis of rotation 44 as illustrated in fig. 3.

A first pin 76 may be positioned through the aperture 70 at the first end 36 of the vane 20-1 in line with the first axis 44 about which the vane 20-1 rotates. The first pin 76 may be fixed in position relative to the core 22 and is a cylinder with a circular cross section to facilitate rotational movement of the vane 20-1 about the first axis 44.

In relation to the first end 36 of the vane 20-1, the first pin 76 may be formed of metal, such as titanium, or of another durable material. The first pin 76 may be removed from the aperture 70 for replacement.

A sheath 74 may be inserted into the aperture 70 at the first end 36 of the vane 20-1, and can be fixed, for example by being bonded, in the aperture to prevent wear on the vane 20-1. The sheath 74 has a circular inner aperture. The first pin 76 has an outer diameter equal to or smaller than the inner diameter of the sheath 74. Lubrication can be applied between the sheath 74 and the first pin 76 to aid in the free rotation of the vane 20-1 at the first pivot 40. Where a sheath 74 is used, it may have a circular inner aperture but the aperture 70 of the vane 20-1 may be non-circular but conforming to exterior dimensions of the sheath 74.

It will be appreciated that a similar arrangement may be formed at the second end 38 of the vane 20-1.

The second end 38 of the vane 20-1 has only a single aperture 71.

The aperture 71 at the second end 38 of the vane 20-1 extends perpendicularly or substantially perpendicularly to the length 54 and width 56 of the vane 20-1. In use, the aperture 71 extends orthogonally to the rotational axis 48 of the core 22 and defines the axis of rotation 46 as illustrated in fig. 3.

A second pin 77 may be positioned through the aperture 71 at the second end 38 of the vane 20-1 in line with the second axis 46 about which the vane 20-1 rotates. The second pin 77 may be fixed in position relative to the fan case 24 and is a cylinder with a circular cross section to facilitate rotational movement of the vane 20-1 about the second axis 46.

In relation to the second end 38 of the vane 20-1, the second pin 77 may be formed of metal, such as titanium, or of another durable material. The second pin 77 may be removed from the aperture 71 for replacement.

A sheath 74 may be inserted into the aperture 71 at the second end 38 of the vane 20-1, and can be fixed, for example by being bonded, in the aperture 71 to prevent wear on the vane 20-1. The sheath 74 has a circular inner aperture. The second pin 77 has an outer diameter equal to or smaller than the inner diameter of the sheath 74. Lubrication can be applied between the sheath 74 and the second pin 77 to aid in the free rotation of the vane 20- 1 at the second pivot 42. Where a sheath 74 is used, it may have a circular inner aperture but the aperture 70 of the vane 20-1 may be non-circular but conforming to exterior dimensions of the sheath 74.

The first pivot 40 and the second pivot 42 may be configured to allow the vane to be removable while the core 22 is in situ relative to the fan case 24.

Examples of different pivots 40, 42 are described below in relation to Figs. 5, 7 and 8. The examples shown in Figs. 5, 7 and 8 are described in relation to the first pivot 40 at the first end 36 of the vane 20-1. It will be appreciated that each of these examples may be applied in relation to the second pivot 42 at the second end 38 of the vane 20-1.

Fig. 5 illustrates a cross sectional view of a first example vane 20-1 comprising a first pivot 40. The first pin 76 is configured to be positioned in the aperture 70 of the vane 20-1. In this first example, the first pin 76 comprises a first internally threaded axial section 98 at one end of the first pin 76 and a second internally threaded axial section 99 at the opposite end of the first pin 76, to facilitate the insertion of transverse bolts 90 into the first pin 76. The internally threaded axial sections 98, 99 provide, via engagement, a secure fixing of the inserted bolts 90 to the first pin 76. The bolts 90 comprise an enlarged head 94 and an externally threaded shaft 96.

A mounting structure 92 comprises a first section 100 and a second section 102. The first section 100 has a first bolt clearance aperture 104 through which the externally threaded shaft 96 of a bolt 90 is inserted to be engaged with the first internally threaded axial section 98 of the first pin 76.

The second section 102 has a second bolt clearance aperture 106 through which the externally threaded shaft 96 of a bolt 90 is inserted to be engaged with the second internally threaded axial section 99 of the first pin 76. By inserting the bolts 90 in the first internally threaded axial section 98 and second internally threaded axial section 99 of the first pin 76, through the first bolt clearance aperture 104 of the first section 100 of the mounting structure 92 and the second bolt clearance aperture 106 of the second section 102 of the mounting structure 92, the first pin 76 is fixed relative to the mounting structure 92 and aligned with the rotational axis 44 for rotation of the vane 20-1.

Fig. 7 illustrates a cross sectional view of a second example vane 20-1 comprising a first pivot 40. The first pin 76 is configured to be positioned in the aperture 70 of the vane 20-1. In this second example, the first pin 76 comprises an internally threaded axial section 98 at only one end of the first pin 76, to facilitate the insertion of a transverse bolt 90 into the first pin 76.

The opposite end of the first pin 76 comprises an enlarged section 110 of larger diameter than the aperture 70. The internally threaded axial section 98 provides, via engagement, a secure fixing of the inserted bolt 90 to the first pin76. The bolt 90 comprises an enlarged head 94 and an externally threaded shaft 96.

The second section 102 has a pin clearance aperture 108 through which the first pin 76 is inserted such that the enlarged section 110 is retained at the pin clearance aperture 108 without being able to pass through it. By inserting the bolt 90 in the first internally threaded axial section 98 of the first pin 76, through the first bolt clearance aperture 104 of the first section 100 of the mounting structure 92, the first pin 76 is fixed relative to the mounting structure 92 and aligned with the rotational axis 44 for rotation of the vane 20-1.

Fig. 8 illustrates a cross sectional view of a third example vane 20-1 comprising a first pivot 40. The first pin 76 is configured to be positioned in the aperture 70 of the vane 20-1. In this third example, the first pin 76 comprises a first radial aperture 120 at one end of the first pin 76 and a second radial aperture 122 at the opposite end of the first pin 76, to facilitate the insertion of radial bolts 90 into and through the first pin 76. The first radial aperture 120 and the second radial aperture 122 may be internally threaded to receive corresponding externally threaded shafts 96 of the bolts 90.

Alternatively the first radial aperture 120 and second radial aperture 122 may be clearance holes, not engaging with the externally threaded shafts 96 of the bolts 90. The bolts 90 further comprise enlarged heads 94 which are larger than the first radial aperture 120 and second radial aperture 122.

A mounting structure 124 comprises a first section 126 and a second section 128. The first section 126 has a first internally threaded aperture 130, disposed in the radial axis 50, into which the externally threaded shaft 96 of a bolt 90 is inserted to secure, via engagement, the first pin 76 to the mounting structure 124. The second section 128 has a second internally threaded aperture 132, disposed in the radial axis 50, into which the externally threaded shaft 96 of a bolt 90 is inserted to secure, via engagement, the first pin 76 to the mounting structure 124. By inserting the bolts 90 in the first internally threaded aperture 130 of the mounting structure 124 and in the second internally threaded aperture 132 of the mounting structure 124, through the first radial aperture 120 of the first pin 76 and the second radial aperture 122 of the first pin 76, the first pin 76 is fixed relative to the mounting structure 124 and aligned with the rotational axis 44 for rotation of the vane 20-1.

In an example of the arrangement of Fig. 8, retainers, such as shims 134 may be configured to maintain a tensile force through the vane 20-1. The shims 134 may be positioned between the first pin 76 and the first section 126 of the mounting structure 124 and between the first pin 76 and the second section 128 of the mounting structure 124. By varying the thickness or the number of shims 134 disposed in the arrangement, the amount of stretching of the vane 20-1 between the first pin 76 and the second pin 77 may be varied, the shims 134 being configured to control and maintain the pre-tension in the stretched condition, therefore the tension applied to the vane 20-1 upon securing the first pin 76 to the mounting structure 124 via the bolts 90 can be varied. Thus by using thinner, or less, shims 134 in the arrangement, a greater pre-tension can be applied to the vane 20-1 along its length 54 between the first pivot 40 and the second pivot 42. It will be appreciated that shims 134 may be omitted altogether from the example arrangement described above.

In example embodiments, including those of Figs. 5, 6, 7 and 8, a sheath 74 may be located between the first pin 76 and the aperture 70 of the vane 20-1 to provide wear protection for the vane 20-1 and/or lubrication for the rotation of the vane 20-1 relative to the first pin 76. The sheath 74 shown as an example in Fig. 6 is cylindrical, however it will be appreciated that the aperture 70 in the vane 20-1 may be of a non-circular cross section and the outer perimeter of the sheath 74 may be of non-circular cross section.

The mounting structure 92, 124, when located at the first end 36 of the vane 20-1, may be comprised in or on the core 22. Alternatively the mounting structure 92, 124 may be an inner ring to which each of the vanes in the plurality of vanes 20 is interconnected. The inner ring may be interconnected to the core 22 via one or more brackets, flanges or by other securing means.

The mounting structure 92, 124, when located at the second end 38 of the vane 20-1, may be comprised in or on the tan case 24. Alternatively the mounting structure 92,124 may be an outer ring to which each of the vanes in the plurality of vanes 20 is interconnected. The outer ring may be interconnected to the fan case 24 via one or more brackets, flanges or by other securing means.

In one example, each of the vanes of the plurality of vanes 20 is interconnected to an inner ring, via first pivots 40, and to an outer ring, via second pivots 42.

The second pivot 42 may be configured to be the same as the first pivot 40 or configured to be different from the first pivot 40.

In a further example arrangement, some of the vanes in the plurality of vanes 20 are interconnected to the core 22 and/or fan case 24 via the arrangements described above in relation to Figs. 5, 6, 7 and 8 while other vanes in the plurality of vanes 20 may be fixedly interconnected to the core 22 and/or fan case 24 without being configured to rotate.

One method of manufacture of a vane 20-1 for a fan outlet guide vane arrangement 21 as described above, is shown diagrammatically in Fig. 9.

The manufacture of a vane 20-1 for a fan outlet guide vane arrangement 21 may be facilitated by wrapping one or more lengths of material 80 around two fixed position rigid members 82, 84 to form, with a matrix material, a fixed length composite vane body 34, as previously described. A single length of material 80 can be used to alternatively wrap around the first fixed position rigid member 82 and the second fixed position rigid member 84. Alternatively a first length 86 of material 80 can be looped around the first fixed position rigid member 82 and a second length 88 of material 80 can be looped around the second fixed position rigid member 84 to overlap or partially overlap the first length 86 of material 80. This process may be repeated at alternate fixed position rigid members 82, 84, to provide an interleaved arrangement of layers of material 80 as shown in Fig. 9. The benefit of this manufacture process is that a large shear area is produced such that the vane 20-1 has high tensile strength in the length 54 direction. Further structural reinforcement can be applied, such as by z-pinning or stitching the overlapping lengths of material 80 together with structural fibres, through the thickness of the overlapped layers. Such reinforcement may help prevent layers of the composite material from delaminating.

The fixed length composite vane body 34 has a first pivot 40 located at the first rigid member 82 and a second pivot 42 located at the second rigid member 84, the first and second pivots 40, 42 being located on a lengthwise axis of the vane 20-1 as previously described.

One or more of the rigid members 82, 84 may be a solid member. The or each solid member may be subsequently removed or partially removed to provide an aperture 70, 71 which may be cylindrical and have an axis extending perpendicularly or substantially perpendicularly to the length 54 of the vane 20-1, as described above. The removal of the solid member may be facilitated by drilling the aperture 70 in the solid member, or the solid member may be coated in a releasing agent, prior to application of the material 80, to facilitate removal of the rigid members 82, 84 from the vane 20-1 once the composite vane 20-1 has been produced, to leave a corresponding aperture 70, 71 in the vane 20-1.

Alternatively, one or more of the rigid members 82, 84 may be a hollow member. The hollow member may be retained in situ in the vane 20-1, and may provide an aperture 70. The hollow member may alternatively act as a sheath 74 to protect the vane 20-1 from wear. The hollow member may comprise an aperture 70 which may be cylindrical and have an axis extending perpendicularly or substantially perpendicularly to the length 54 of the vane 20-1, as described above. The hollow member may alternatively be removed by drilling or via a similar operation, or may be coated in a releasing agent, prior to application of the material 80, to facilitate removal of the rigid members 82, 84 from the vane 20-1 once the composite vane 20-1 has been produced, to leave a corresponding aperture 70, 71 in the vane 20-1.

In the examples described above, a sheath 74 may be inserted into the aperture 70 of the vane 20-1 to provide wear protection for the vane 20-1 and/or lubrication for the rotation of the vane 20-1 relative to any subsequently introduced pin.

Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed.

Features described in the preceding description may be used in combinations other than the combinations explicitly described.

Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not.

Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not.

Whilst endeavoring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

CLAIMS1. A gas turbine engine comprising a core, a fan case, a plurality of vanes situated between the core and the tan case, a first pivot configured to enable rotation of at least one vane of the plurality of vanes about a first axis parallel to a rotational axis of the core and passing through the first pivot and a second pivot configured to enable rotation of the at least one vane of the plurality of vanes about a second axis parallel to the rotational axis of the core and passing through the second pivot.
2. A gas turbine engine according to claim 1, wherein, in use, the at least one vane is aligned on a vector, offset from a radial axis of the core.
3. A gas turbine engine according to any preceding claim, further comprising a retainer configured to maintain a tensile force through the vane.
4. A gas turbine engine according to claim 3, wherein tensioning is facilitated by stretching of the vane between the first pivot and second pivot and the retainer is configured to control and maintain the tensile force through the vane in the stretched condition.
5. A gas turbine engine according to any preceding claim, wherein the plurality of vanes provides a single plane structure forming a primary structural connection between the core and fan case, the single plane structure being capable of withstanding fan blade off loads.
6. A gas turbine engine according to any preceding claim, wherein the pivots are configured to allow at least one vane to be removable while the core is in situ relative to the fan case.
7. A gas turbine engine according to any preceding claim, wherein the gas turbine engine is an aero engine with bypass.
8. A gas turbine engine according to any preceding claim, wherein the at least one vane has a length, a width and a depth and is formed of an anisotropic material such that the tensile strength of the material along the length is greater than the tensile strength of the material along the width and the depth, the at least one vane extending lengthwise, in use, between the core and the fan case.
9. A fan outlet guide vane comprising: avanebody; a first pivot configured to interconnect the vane body to a gas turbine engine core; and a second pivot configured to interconnect the vane body to a gas turbine engine fan case, the first pivot being configured to enable relative rotation between the fan outlet guide vane and the gas turbine engine core about a first axis parallel to a rotational axis of the core and passing through the first pivot and the second pivot being configured to enable relative rotation between the fan outlet guide vane and the gas turbine engine fan case about a second axis parallel to the rotational axis of the core and passing through the second pivot.
10. A fan outlet guide vane according to claim 9, the vane body having a length, a width and a depth, the vane body comprising a first end and a second end separated lengthwise, the first pivot being positioned towards the first end of the vane body, and the second pivot being positioned towards the second end of the vane body.
11. A fan outlet guide vane according to claim 9 or claim 10, wherein the first pivot comprises a single aperture and the second pivot comprises a single aperture.
12. A tan outlet guide vane according to any of claims 9 to 11, wherein the fan outlet guide vane is formed of a material selected from: an anisotropic material; a composite material; a fibre reinforced composite material; an organic matrix composite material; and a metal matrix composite material.
13. A method of manufacture of a fan outlet guide vane comprising wrapping one or more lengths of material around two fixed position rigid members to form, with a matrix material, a fixed length composite vane body with a first pivot located at the first rigid member and a second pivot located at the second rigid member, the first and second pivots being located on a lengthwise axis of the vane.
14. A method of manufacture of a fan outlet guide vane according to claim 13, wherein one or more of the rigid members is a solid member, which is subsequently removed to provide a cylindrical aperture with a cylindrical axis substantially perpendicular to the lengthwise axis of the vane
15. A method of manufacture of a fan outlet guide vane according to claim 13 or claim 14, wherein one or more of the rigid members is a retained hollow member, comprising a cylindrical aperture with a cylindrical axis substantially perpendicular to the lengthwise axis of the vane.
16. A method of manufacture of a fan outlet guide vane according to claim 14 or claim 15, wherein a sheath is inserted into one or more of the apertures.
17. A gas turbine engine substantially as hereinbefore described with reference to Figures 2 to 9.
18. A fan outlet guide vane substantially as hereinbefore described with reference to Figures 2 to 9.
19. A method of manufacture substantially as hereinbefore described with reference to Figures 2 to 9.