Turbomachine casing assembly

Abstract

A turbomachine casing assembly includes a first casing element locatable radially outward of one or more rotating aerofoil elements of a turbomachine, a second casing element located radially distal to the first casing element and one or more arcuate fence elements positioned between the first and second casing elements. Following impact of a detached fan blade, a radially outward movement of the first casing element causes the or each fence element to project into the air flow passing through the turbomachine.

Claims

1. A turbomachine casing assembly, comprising: a first casing element located radially outward of one or more rotating aerofoil elements of a turbomachine, and having a first end; a second casing element located radially distal to the first casing element, and having a first end; and an arcuate fence element, provided between a radially proximal face of the first casing element and a radially proximal face of the second casing element, at the first end of the first casing element, the fence element being arcuate in an axial plane of the turbomachine casing assembly, the fence element having a first end and a second end with the first end of the fence element located radially distal to the first casing element, the first end of the fence element being positioned radially between the first casing element and the second casing element, the fence element having a frangible spigot formed on a convex face of the fence element and positioned towards the second end of the fence element, the frangible spigot being arranged to locate against the first end of the second casing element; wherein the first end of the first casing element is aligned with the first end of the second casing element, and the first end of the first casing element is maintained in its radial position relative to the one or more rotating aerofoil elements by the fence element; and wherein upon failure of one of the rotating aerofoil elements, the first casing element urges the first end of the fence element in a radially outward direction causing the fence element to rotate and the second end of the fence element to project radially inwards of the radially proximal face of the first casing element, with the radially inward movement of second end of the fence element causing the frangible spigot to be sheared from the convex surface of the fence element.

2. The turbomachine casing assembly as claimed in claim 1, comprising a plurality of arcuate fence elements.

3. The turbomachine casing assembly as claimed in claim 2, wherein the second end of each fence element is positioned flush with the first end of the second casing element and the radially proximal face of the first casing element.

4. The turbomachine casing assembly as claimed in claim 2, wherein the plurality of fence elements is arranged as a circumferential array.

5. The turbomachine casing assembly as claimed in claim 1, wherein the fence element comprises a first portion and a second portion, with respective first and second portions being connected to one another.

6. The turbomachine casing assembly as claimed in claim 1, the first casing element further comprising a radially distal face having a fence portion, the fence portion extending from a first end of the first casing element and having a serpentine profile, the fence portion comprising the fence element.

7. The turbomachine casing assembly as claimed in claim 6, wherein the second end of the fence element is positioned flush with the first end of the second casing element and the radially proximal face of the first casing element.

8. A jet engine fan casing comprising the turbomachine casing assembly as claimed in claim 1.

9. A gas turbine comprising a turbomachine casing assembly as claimed in claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) There now follows a description of preferred embodiments of the invention, by way of non-limiting example, with reference being made to the accompanying drawings in which:

(2) FIG. 1 shows a partial, sectional view of a known fan casing assembly as used in a gas turbine engine casing;

(3) FIG. 2 shows a partial, sectional view of a fan casing assembly according to a first embodiment of the invention;

(4) FIG. 3 shows a partial, sectional view of the fan casing assembly of FIG. 2 showing the impact of a fan blade;

(5) FIG. 4 shows a partial, sectional view of a fan casing assembly according to a second embodiment of the invention; and

(6) FIG. 5 shows a partial, sectional view of the fan casing assembly of FIG. 4 showing the impact of a fan blade.

(7) It is noted that the drawings may not be to scale. The drawings are intended to depict only typical aspects of the invention, and therefore should not be considered as limiting the scope of the invention. In the drawings, like numbering represents like elements between the drawings.

DETAILED DESCRIPTION

(8) Referring to FIGS. 2 and 3, a fan casing assembly according to a first embodiment of the invention is designated generally by the reference numeral 100 and comprises a first casing element 110 and a second casing element 130.

(9) The first casing element 110 has a first end 112, a radially proximal face 114, and the second casing element 130 has a first end 132 and a radially proximal face 134.

(10) The first casing element 110 at least partially encloses one or more rotating aerofoil structures 150. These aerofoil structures 150 may comprise blades of a turbomachine, in particular the compressor fan blades of a gas turbine engine. The second casing element 130 is disposed radially distal to the first casing element 110.

(11) The turbomachine casing assembly 100 comprises a plurality of first casing elements 110 circumferentially disposed about a curve defined by the blade tip path of the one or more aerofoil structures 150 of the turbomachine.

(12) The first casing element 110 is typically formed as a filled Nomex honeycomb material, while the second casing element 130 may be metallic and may, for example, be formed of aluminium, titanium, steel or any other suitable metal.

(13) Each first casing element 110 comprises a radially proximal face 114 in the form of an abradable layer 118. An infill member 154 is positioned between the first and second casing elements 110,130 and is attached to the abradable layer 118. An exemplary material for the abradable layer 118 is an epoxy resin, which may be curable at room temperature. The abradable layer 118 provides a surface against which the fan blades 150 are able to rub and cut a path for itself. For example, the fan blades 150 may rub against the abradable layer 118 and form a seal during normal engine operation.

(14) The infill member 154 may be formed from a frangible or crushable structure, such as a foam or honeycomb material which provides structural reinforcement. The honeycomb material may be formed from a metal, such as aluminium, or from a non-metallic material, such as Nomex™ (a flame resistant aramid material).

(15) In an alternative embodiment of the invention, the infill member 154 may be formed separately from the first casing element 110, and positioned between the first and second casing elements 110,130.

(16) Optionally, a septum layer (not shown) may be provided as an interlayer between the abradable layer 118 and the infill member 154. The septum layer may be metallic or may be formed from a carbon fibre or glass fibre reinforced composite material.

(17) The first end 112 of the first casing element 110 is aligned with the first end 132 of the second casing element 120 and is maintained in its radial position relative to the fan blades 150 by a plurality of arcuate fence elements 160.

(18) Each of the fence elements 160 comprise a first portion 166 and a second portion 168, with respective first and second portions 166,168 being connected to one another. Each fence element 160 further comprises a first end 162 corresponding to the first portion 166, and a second end 164 corresponding to the second portion 168.

(19) Each fence element 160 is positioned between the first and second casing elements 110,130, with its first and second ends 162,164 facing towards the first casing element 110. The first end 162 abuts against the radially proximal face 114 of the first casing element 110. The second end 164 is positioned between the first end 112 of the first casing element 110, and the first end 132 of the second casing element 130.

(20) Each fence element 160 has a frangible spigot 170 formed on the convex face of the fence element 160 and positioned towards the second end 164. The frangible spigot 170 locates against the second end 132 of the second casing element 130, such that the respective first ends 112,132, second end 164 of each of the first casing element 110, second casing element 130 and fence element 160 align to form a smooth, uninterrupted surface.

(21) In this embodiment, the frangible spigot 170 is attached to the second end 132 of the second casing element 130 with radially positioned fasteners (not shown) to simplify removal of individual first casing elements, for example for maintenance purposes.

(22) In use, when a fan blade 150 becomes detached, it travels in a generally radially outward direction as indicated by the arrow A in FIG. 3. The detached blade first strikes the proximal face 114 of the forward portion of the first casing element 110. The energy associated with this impact event is then transferred to the first ends 162 of the fence elements 160, which each move radially outwards. This causes each of the fence elements 160 to rotate (about a common “annular” axis of rotation) and results in the second ends 164 of the fence elements 160 being forced in a radially inward direction, as indicated by the arrow B in FIG. 3. In doing so, the frangible spigot 170 is sheared from the convex surface of each fence element 160. As the second ends 164 of the fence elements 160 move radially inwards, they protrude into the path of the air flow passing through the rotating aerofoil structure 150. As the detached blade 150 continues to travel radially outwards, the blade tip engages with the protruding second end 164 of the fence element 160 and subsequently becomes trapped in the casing assembly 100.

(23) Referring to FIGS. 4 and 5, a fan casing assembly according to a second embodiment of the invention is designated generally by the reference numeral 200. Features of the fan casing assembly 200 which correspond to those of fan casing assembly 100 have been given corresponding reference numerals for ease of reference.

(24) The fan casing assembly 200 has a first casing element 210 and a second casing element 130.

(25) In this embodiment, the first casing element 210 has a first end 212, a radially proximal face 214 and a radially distal face 216. The radially proximal face 214 comprises an abradable layer 118. The radially distal face 216 of the first casing element 210 corresponds generally to a radially proximal face 134 of the second casing element 130.

(26) The radially proximal and distal faces 214,216 of the first casing element 210 are spaced radially apart from one another with an infill member 254 positioned therebetween.

(27) The radially distal face 216 of the first casing element 210 extending from the first end 212 of the first casing element 210 has a serpentine profile and is formed as a fence element 260. The fence element 260 comprises a first portion 266 and a second portion 268, formed contiguously with one another. The fence element further comprises a first end 262 corresponding to the first portion 266, and a second end 264 corresponding to the second portion 268.

(28) The fence element 260 is formed such that each of the first and second ends 262,264 faces towards the radially proximal face of the first casing element 210. The first end 262 abuts against the radially proximal face 214 of the first casing element 210. The second end 264 is positioned between the first end 212 of the first casing element 210, and the first end 132 of the second casing element 130.

(29) The fence element 260 has a frangible spigot 270 formed on the convex face of the fence element 260 towards the second end 264. The frangible spigot 270 locates against the first end 132 of the second casing element 130, such that the first ends 212,132, second end 264 of each of the first casing element 210, second casing element 130 and fence element 260 align to form a smooth, uninterrupted surface. As described above in relation to the first embodiment, the frangible spigot 270 can be fastened to the first end 132 of the second casing element 130 to allow for the removal of individual first casing elements 210 for maintenance or repair.

(30) In use, when a fan blade 150 becomes detached, it travels in a generally radially outward direction as indicated by the arrow A in FIG. 5. The detached blade first strikes the proximal face 214 of the forward portion of the first casing element 210. The energy associated with this impact event is then transferred to the distal face 216 of the first casing element 210, via the first end 264 of the fence element 260, which moves radially outwards. This causes the serpentine portion of the distal face 216 of the first casing element 210 to straighten out. This, in turn, results in the second end 264 of the fence element 260 being forced in a radially inward direction, as indicated by the arrow B in FIG. 5. In doing so, the frangible spigot 270 is sheared from the convex face of the fence element 260.

(31) As the second end 264 of the fence element 260 moves radially inward, it protrudes into the path of the air flow passing through the rotating aerofoil structure 150. As the detached blade 150 continues to travel radially outwards, the blade tip engages with the protruding second end 264 of the fence element 260 and subsequently becomes trapped in the casing assembly 200.

(32) The casing assemblies disclosed herein are equally applicable to solid and hollow fan blades and may be used with light-weight (hollow line-core or solid composite) fan blades. The casing assemblies may also be used with aerofoil structures, e.g. fan blades, comprising a foreign object damage resistant member at the front of the aerofoil structure, such as a picture frame or metallic sheath. The present disclosure may also be applied to swept or unswept aerofoil structures.

(33) The foregoing description of various aspects of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously, many modifications and variations are possible. Such modifications and variations that may be apparent to a person of skill in the art are included within the scope of the invention as defined by the accompanying claims.