US20080063522A1

US20080063522A1 - Array of components

Info

Publication number: US20080063522A1
Application number: US11/822,108
Authority: US
Inventors: Duncan E. Ashley
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 2006-09-07
Filing date: 2007-07-02
Publication date: 2008-03-13
Also published as: GB2441543A; GB0617612D0; GB2441543B

Abstract

A support element 22 is fitted between adjacent vanes 8, 14 in a gas turbine engine, in order to suppress vibrations in the vanes 8, 14. The support element 22 comprises a body portion 24 and pad portions 38, 40 which contact the vanes 8, 14 over a wide area to restrain displacement of the vanes 8, 14 while minimising overstressing.

Description

This invention relates to an array of similar elongate components, and is particularly, although not exclusively, concerned with an array in which the components are vanes of a gas turbine engine.
A conventional gas turbine engine comprises an annular passage which is spanned by vanes which serve an aerodynamic function in that they direct working fluid of the engine to an appropriate angle of incidence for a downstream component, such as a bladed rotor. The vanes may also serve a structural function, by providing support for other components of the engine.
The vanes may have inner and/or outer shrouds at their radial ends, and these shrouds may be interconnected in groups to provide packs of two or more vanes. Such packs have a significantly increased stiffness compared to the individual vanes.
Each vane has various vibration modes. A vibrating vane may excite vibration also in adjacent vanes. Such vibrations may reduce the life of the vanes themselves and other components of the engine, and may also restrict the operating envelope of the engine. Damping of the vibrations by conventional means may be difficult, particularly for low strain vibration modes, such as torsional modes.
According to the present invention there is provided an array of vanes for a gas turbine engine, the array being an annular array disposed about a central axis, and the vanes being assembled in packs, wherein each pack comprises two rows of vanes, the vanes of each pack being supported at at least one end by a common support so as to be spaced apart from one another and which, in use, are subjected to excitation inputs which induce vibration in the vanes, a support element being disposed between two adjacent vanes in each row, the support element comprising respective body portions disposed between the adjacent vanes in each row and a pad portion which extends laterally from each body portion, the pad portion having a contact surface which contacts a surface of one of the adjacent components, characterised in that a bridge region is provided between the body portion regions.
The body portion may be provided with a said pad portion at each of two opposite sides of the body portion, the contact surface of each of the pad portions contacting a surface of a respective one of the adjacent vanes.
The body portion may comprise a central web, and the or each pad portion may be in the form of a flange which projects out of the plane of the web at an edge of the web. The web may be curved about an axis which is parallel to the gap direction.
The support element is preferably secured to at least one of the adjacent vanes. In one embodiment, securing of the support element may be achieved by bonding the pad portion, or at least one of the pad portions, to the respective vane at the contact surface. Alternatively or additionally, the support element may be secured by a mechanical fixing, such as a screw or bolt extending through the pad portion into the respective vane. Means may be provided for locating the support element with respect to the vanes. For example, the support element may be provided with a projection which is received in an aperture in one of the vanes.
The array may comprise an annular array of the vanes disposed about a central axis, with the vanes extending in a substantially radial direction from the axis. The vanes of the array may be assembled in packs, with the vanes of each pack being interconnected by a connecting element at at least one radial end of the vanes. The packs are subsequently assembled together to form the complete array. The support element may be disposed between adjacent vanes of the same pack, or it may be disposed between adjacent vanes of adjacent packs. In one particular embodiment, a plurality of the support elements are distributed around the array, with support elements being disposed between some, but not all, adjacent pairs of vanes in the array.
For some modes of vibration, it is desirable for the support element to be situated away from the radial ends of the vanes, for example at a position substantially midway along the lengths of the vanes. The body portion may be provided with an aerodynamic shape conforming to the flow of working fluid between the vanes in operation. The or each pad portion may also have an aerodynamic flow surface disposed opposite the contact surface.
If the vanes are assembled as vane packs, each vane pack may comprise two or more rows of vanes at different axial positions from each other. In such an array, the body portion of the support element may comprise respective body portion regions disposed between adjacent vanes of adjacent rows, and a bridge region interconnecting the body portion regions. Each body portion region preferably has at least one of the said pad regions. In order to fit between adjacent vanes of different rows, the body portion regions may be offset from each other in a tangential direction.

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:

FIG. 1 is a diagrammatic partial axial cross sectional view of a gas turbine engine;

FIG. 2 is a view in the direction of the arrow A in FIG. 1;

FIG. 3 shows a vane pack including a support element;

FIG. 4 shows a vane pack having an alternative embodiment of support elements;

FIGS. 5 to 8 show various views of the support element of FIG. 3.

FIG. 1 shows, by way of example, part of a compressor section of a gas turbine engine. The compressor section comprises a bladed rotor 2 which is rotatable about an axis disposed below FIG. 1. The rotor 2 is rotatable within a casing 4, which supports circumferential arrays of stator vanes 6 and 8. In operation, gas flow through the compressor section takes place in the direction of the arrow X. The downstream array of stator vanes 8 is shown partially in FIG. 2. The array is made up of a plurality of vane packs 10. The vanes 8 in each pack 10 are connected together by straps 12 (see FIG. 3). In the embodiment shown in FIG. 2, each vane pack comprises three vanes 8.
FIG. 3 shows a vane pack in more detail. In this instance, the vane pack comprises two circumferentially disposed vane elements, each vane element comprising two axially spaced vanes 8, 14 extending between shroud portions 16, 18. Thus, an assembled array made up of vane packs 10 as shown in FIG. 3 would comprise two rows of vanes 8, 14 disposed with one axially downstream of the other.
The strap 12 extends across the shroud portions 16 to secure the vane elements together to form the pack 10. A similar strap 20 is provided at the radially inner end of the vane pack, interconnecting the inner shroud portions 18.
The flow direction X is indicated in FIG. 3, from which it will be appreciated that the leading edges of the vanes 8, 14 face into the page.
A support element 22 is provided in the vane pack 10. The support element 22 extends across both rows of vanes 8 and 14, and extends between adjacent blades 8, 14 of each row. The support element 22 is positioned away from the ends of the vanes 8, 14, and is generally midway between the ends. As shown in FIG. 3, the support element 22 is situated slightly radially outwardly beyond the precise midpoint between the ends of the vanes.
The support element 22 is shown in more detail in FIGS. 5 to 8. It comprises a body portion 24, generally in the form of a central web which extends the full length of the support element in the axial direction (ie the direction of gas flow X in FIG. 3). The body portion comprises first and second body portion regions 26, 28, for positioning between the respective pairs of vanes 14, 8. The body portion regions 26 and 28 are interconnected by a bridge region 30 which, in use, extends between the two rows of vanes 8, 14. As can be appreciated from FIG. 8, the body portion 24 is slightly curved about an axis which extends generally parallel to the direction of the gap between adjacent vanes 8, 14, as indicated by an arrow G in FIGS. 3 and 4 (referred to for convenience as the “gap direction”). The body portion 22 is also curved, about an axis extending generally radially of the vane pack, as shown most clearly in FIGS. 6 and 7, in order to conform to the shape of the path between the vanes.
Each body portion region 26, 28 is provided at opposite side edges with laterally extending pad portions 32, 36 respectively, in the form of flanges projecting from the central web of the body portion 24. Each pad portion has a vane contact surface 38, 40 which conforms to the shape of the surface of the vane 8, 14 against which the respective contact surfaces 38, 40 lie in the assembled condition, as shown in FIG. 3.
It will be appreciated that the body portion regions 26, 28 are offset from each other, as shown in FIGS. 5 to 7, in the gap direction G, reflecting the relative positions of the vanes 8 and 14 of the vane pack 10.
The support element 22 may be made of any suitable material which can withstand the temperatures to which it will be exposed in use, which is sufficiently stiff to resists loads imposed upon it by vibration of the vanes 8, 14. Suitable materials are glass or carbon reinforced plastics materials, or aerospace alloys of aluminium and/or titanium.
It will be appreciated that the support element 22 fits intimately between the adjacent vanes 8, 14 with the contact surfaces 38, 40 of the pad portions 32, 36 in face-to-face contact with the oppositely facing surfaces of the vanes 8 and 14. The support element may be configured so that it locks in position between the vanes 8, 14, or it may be secured, for example by bonding at the contact surfaces 38, 40 or by mechanical fixings. In an alternative embodiment shown FIG. 4, the support element 22 has projections 42 and 44 extending respectively from the body portion 24 and one of the pad portions 32, 36. These projections 42 and 44 extend into appropriately shaped holes in the vanes 8 to lock the support element 22 in position. It will be appreciated that, in the embodiment shown in FIG. 4, the support element 22 must be fitted as the vanes 8 of the vane pack 10 are assembled together or as the vane packs 10 are assembled into a complete annular array. However, in other embodiments, it is possible for the support element 22 to be introduced between the vanes 8, 14 after the vane pack 10 has been assembled, and possibly after the entire array of vanes has been installed in an engine. Thus, in some embodiments, the support elements 22 are retrofitable to an engine without major dismantling of the engine.
The configuration of the body portion 24 and the shapes of surfaces 46, 48 on the sides of the pad portions 32, 36 opposite the contact faces 38, 40 are designed to minimise the obstruction to the flow of working fluid through the vane packs 10. Thus, the curved configuration of the body portion 24 is designed to follow the path taken by the working fluid between the vanes 8, 14 so as to minimise any pressure drop caused by the support element 22 and to avoid any instability in the flow.
The purpose of the support element 22 is to suppress vibration of the vanes 8, 14 in operation of the engine. Such vibrations may be excited by aerodynamic effects in the engine, and one vibrating vane can excite vibrations in adjacent vanes. For example, antiphase first torsional mode vibration may be excited between adjacent vanes 8 or 14 but suitable positioning of the support element 22 can significantly restrain, or even eliminate, these vibrations. Because the pad portions 32, 36 extend over the full chordal width of the vanes 8, 14, displacements arising from torsional vibration can be adequately resisted in a manner which would not be possible by connecting elements engaging the vanes over only a small part of the chordal width. Thus, it will be appreciated that the pad portions 32, 36 should preferably extend over at least 50%, and more preferably at least 75%, of the chordal width of the vanes 8, 14. Furthermore, because the amplitude of displacements generated by first torsional mode vibration will be at a maximum towards the midpoint between the ends of the vanes 8, 14, it is desirable, if adequate suppression of the vibration is to be achieved, for the support element 22 to be positioned at, or close to, the midpoint. However, if suppression of higher order harmonics is to be achieved, different positioning of the support element 22, or use of multiple support elements 22, may be desirable.
In the embodiment shown in FIG. 3, the vane pack includes two rows of vanes 8, 14. Because the support element 22 extends between the rows, a vane row, for example the vanes 14, which are subject to little or no vibration can assist in stabilising vanes in a different row, for example the vanes 8, which would otherwise be subject to vibration.
Because the pad portions 32, 36 have substantial contact surfaces 38, 40, any load on the vanes 8, 14 imposed by the support elements 22 is spread over a significant area of the vane surfaces. Consequently, local overstressing of the vane 8, 14 or of the support element 22 can be avoided.
As shown in FIGS. 3 and 4, the support element 22 is disposed between adjacent vanes 8, 14 in the same vane pack 10. However, it is also possible for the support element 22 to be disposed between adjacent vane packs 10, contacting a vane or vanes of one pack 10 on one side, and of the other vane pack 10 on the other side.
The support element 22 may be one of several support elements distributed around the array of vanes. A support element 22 need not be provided in each gap between adjacent vanes 8, 14, although in most circumstances each vane 8, 14 would be connected by a support element 22 to at least one other vane in the same row. The support elements 22 may all be at the same radial distance along the vanes 8, 14, at least in each row of vanes. However, since different vane rows experience different exciting inputs, the radial position of the support elements 22 may be different in different rows.
Because the support element 22 can be retrofitted, it is possible to remedy vibrations which occur in the vanes of an engine in operation, after analysing the causes and nature of the vibrations that occur.
Although the present invention has been described with reference to vanes in a gas turbine engine, it will be appreciated that the underlying principles of the invention may be applicable also in other types of vaneed machinery, or in other circumstances where vibrations may be excited in the components of an array. For example, support elements as described above may also be positioned between adjacent components of aerial arrays, acoustic equipment, or panels formed from thin skinned components.

Claims

1. An array of vanes for a gas turbine engine, the array being an annular array disposed about a central axis, and the vanes being assembled in packs, wherein each pack comprises two rows of vanes, the vanes of each pack being supported at at least one end by a common end support so as to be spaced apart from one another and which, in use, are subjected to excitation inputs which induce vibration in the vanes, a support element being disposed between two adjacent vanes in each row, the support element comprising respective body portions disposed between the adjacent vanes in each row and a pad portion which extends laterally from each body portion, the pad portion having a contact surface which contacts a surface of one of the adjacent components, characterised in that a bridge region is provided between the body portion regions.

2. An array as claimed in claim 1, characterised in that the body portion regions are offset with respect to each other in a direction (G) extending between the adjacent vanes.

3. An array as claimed in claim 1, characterised in that the pad portion is one of two pad portions disposed at opposite sides of the body portion, the contact surface of each pad portion contacting a respective one of the adjacent vanes.

4. An array as claimed in claim 1, characterised in that the body portion comprises a central web, the or each pad portion comprising a flange extending from an edge of the web.

5. An array as claimed in claim 4, characterised in that the central web is curved about an axis extending parallel to the direction (G) extending between the adjacent vanes.

6. An array as claimed in claim 1, characterised in that the support element is secured to at least one of the adjacent vanes.

7. An array as claimed in claim 6, characterised in that the support element is secured to the adjacent vane by bonding at the contact surface.

8. An array as claimed in claim 6, characterised in that the support element is secured to the adjacent vane by means of a projection on the support element which engages an aperture in the vane.

9. An array as claimed in claim 1, characterised in that the vanes extend substantially radially with respect to the axis.

10. An array as claimed in claim 1, characterised in that the vanes of each pack are interconnected by a connecting element at at least one radial end.

11. An array as claimed in claim 10, characterised in that the support element is disposed between adjacent vanes of a common pack.

12. An array as claimed in claim 1, characterised in that the support element is disposed between adjacent vanes of adjacent packs.

13. An array as claimed in claim 1, characterised in that the support element is disposed substantially midway between the ends of the vanes.

14. An array as claimed in claim 1, characterised in that the body portion has an aerodynamic profile conforming to fluid flow in use between the vanes.

15. An array as claimed in claim 1, characterised in that each pad portion has an aerodynamic flow surface on a side of the pad portion opposite the contact surface.

16. An array as claimed in claim 1 characterised in that the array has a plurality of support elements, and the support elements are disposed between some only of the vanes of the array.

17. A support element for use in an array of vanes for a gas turbine engine in accordance with claim 1.