US20120213634A1

US20120213634A1 - Gas turbine engine component

Info

Publication number: US20120213634A1
Application number: US13/504,487
Authority: US
Inventors: Rickard Samuelsson; Robert Reimers
Original assignee: Volvo Aero AB
Current assignee: GKN Aerospace Sweden AB
Priority date: 2009-10-27
Filing date: 2009-10-27
Publication date: 2012-08-23
Also published as: WO2011053198A1; EP2494155A1

Abstract

In a gas turbine engine at least one vanes is made of a composite material and an end part of the vane is fastened to the ring element by at least a first bracket member arranged in a corner region formed by the vane and a ring element. The first bracket member is fastened to the vane by a first fastening device arranged in association with a first hole extending through the vane. The first bracket member is fastened to the ring element by a second fastening device arranged in association with a second hole extending through the ring element. An opening is arranged in the ring element. A second bracket member at least partly has an angular cross section. The second, angled bracket member is arranged through the opening such as to be positioned on an opposite side of both the vane and the ring element in relation to the first bracket member. The second, angled bracket member is fastened to the first bracket member by the first and second fastening devices.

Description

BACKGROUND AND SUMMARY

This invention relates to a gas turbine engine component. In particular, the invention relates to fastening of load carrying composite vanes to a ring element. The invention also relates to a gas turbine engine comprising such a component.
Turbojet engines often comprise a fan part with a gas/air channel defined by an outer ring (outer casing) and an inner ring (inner mine) connected by a plurality of air-guiding vanes and structural, load-carrying vanes that extend in a radial direction between the two rings. An engine mount is usually also provided by means of which the engine can be suspended in a frame, such as a wing of an aircraft. The engine mount is commonly attached to the above-mentioned outer ring. A structure of the type described above will be subjected to large mechanical forces upon operation of the engine and must be designed to withstand such conditions.
Conventionally, the vanes and the ring elements have been made of metal and fastening of the vanes to the ring elements has been achieved by means of bolt or rivet friction joints. However, for the purpose of saving weight there is an increasing interest of making use of vanes and ring elements made of a composite material such as a fibre-reinforced polymer.
Fastening of composite components by bolts is generally more complex than fastening of metal components. One reason is that composite materials have a tendency to relax mechanically during its lifetime, which results in that an initially applied clamping friction force is likely to decrease with time. Another reason is that a fibre-reinforced composite material usually exhibits different mechanical properties in different directions, which requires certain considerations regarding the transmission of forces through the fastening arrangement. Conventional bolted friction joints are therefore normally not suitable for fastening e.g. a load-carrying composite vane to a ring element.
WO 2008/121047 discloses an arrangement for fastening a load carrying composite vane to a ring element using a ring element stiffening structure and an angled bracket member, wherein particular attention is paid to the subject of direction of forces.
There is still a need for improvements in this field, for instance regarding the problem related to the tendency of composite materials to relax mechanically during its lifetime.
It is desirable to provide a gas turbine engine component and gas turbine engine that exhibit improved properties concerning fastening of composite load-carrying vanes to a ring element compared to conventional gas turbine engines and components.
The invention concerns, according to an aspect thereof, a gas turbine engine component comprising a ring element and a plurality of circumferentially spaced load carrying vanes extending in a radial direction of the ring element, wherein at least one of said vanes is made of a composite material and wherein an end part of the at least one composite vane is fastened to the ring element by means of at least a first bracket member arranged in a corner region formed by the composite vane and the ring element, wherein the first bracket member is fastened to the composite vane by means of a first fastening device arranged in association with a first hole extending through the composite vane, and wherein the first bracket member is fastened to the ring element by means of a second fastening device arranged in association with a second hole extending through the ring element.
The invention, according to an aspect thereof, is characterized in that an opening is arranged in the ring element and that the component comprises a second bracket member that at least partly has an angular cross section, wherein the second, angled bracket member is arranged through said opening such as to be positioned on an opposite side of both the composite vane and the ring element in relation to the first bracket member, and wherein the second, angled bracket member is fastened to the first bracket member by means of said first and second fastening devices.
Thus, the inventive component according to an aspect of the present invention comprises a double-bracket arrangement where a conventional first, inner-corner bracket member, via first and second through holes, is connected to a second, angled outer-corner bracket member that extends through the first opening in the ring element. Such a double bracket arrangement for fastening the vane to the ring element provides for a rigid structure and makes it possible to transmit a load from the vane to the ring element by bearing stress which is advantageous for composite material. Further, by using metallic material in the bracket members and fastening devices it provides a possibility to clamp metal to metal when fastening the brackets, for instance by including a metallic bushing in the first and second holes. Thereby, the creeping problem of clamped composite material can be avoided, even in case also the ring element is made of a composite material.
An additional advantage of the inventive design according to an aspect of the present invention is, in case the ring element is an outer ring element that e.g. forms part of an outer casing, that the second bracket member provides an attachment point on the outer side of ring element for other devices, such as oil tanks. To provide such attachment points is normally a problem for composite ring elements.
In an advantageous embodiment of the invention a first insertion member is arranged in the first hole, wherein the relative dimensions of the first insertion member and the first hole are such as to provide a tight radial fit for the first insertion member in the first hole, and wherein the first insertion member is fixed in relation to both the first and the second bracket member.
Such a design provides for a tight fit between the vane and the bracket members and prevents sliding of one part in relation to the other. A load can thereby be transmitted from the vane to the bracket members by bearing stress. This is an advantage for a composite vane since no clamping force is needed for the purpose of establishing a rigid load path.
In a further embodiment of the invention is the first fastening device configured to press the first and second bracket members towards each other from opposite sides of the composite vane when tightened, wherein the component is arranged in such a way that each of the first and second bracket members exerts a pressure directly or indirectly onto its corresponding side of the composite vane when the first fastening device is tightened.
That the bracket members exert a pressure/force onto opposite sides of vane has the effect that they become fixed to the vane as seen in axial direction of the first hole. In practice this normally means that the composite vane becomes at least slightly compressed, which enhances the bearing strength. It also means that any insertion member does not prevent this fixation, e.g. by bearing against the two bracket members and preventing them from exerting a pressure onto the sides of the vane
In a further embodiment of the invention the component is arranged in such a way that each of the first and second bracket members exerts a pressure directly or indirectly onto opposite sides of the first insertion member, as seen in an axial direction of the first, hole, when the first fastening device is tightened.
Thus, the insertion member has a position, shape and axial length that allow the insertion member to bear directly or indirectly against the first and second bracket members when the first fastening device is tightened, but that at the same time still allow the bracket members to exert a pressure/force onto opposite sides of vane as explained above. Thus, the insertion member is exposed to a clamping force between the bracket members, which preferably results in a slight axial compression and radial expansion of the insertion member. This has in turn the effect that the already tight fitting of the insertion member in the first hole becomes even tighter.
A further effect is that the first insertion member forms a bridge between the first and second bracket members through the composite material in the vane. By using brackets, insertion member etc. made of metallic material it is possible to clamp metal to metal when fastening the brackets to the vane. This way creeping problem of clamped composite material (vane) is avoided.
In a further embodiment of the invention the first insertion member extends in the first hole along an axial direction thereof. Preferably, the first insertion member is a bushing member. Preferably, the first fastening device comprises a first fastening member that extends in an axial direction through the first hole and that the bushing member extends at least partly around and along the fastening member. The fastening member is preferably a bolt or a rivet or another type of elongated fastening member.
In a further embodiment of the invention a second insertion member is arranged in the second hole, wherein the relative dimensions of the second insertion member and the second hole are such as to provide a tight radial fit for the second insertion member in the second hole, and wherein the second insertion member is fixed in relation to both the first and the second bracket member.
In similarity with what is described above in relation to the vane, this provides a tight fit with no sliding and allows a load to be transmitted between the bracket members and the ring element by bearing stress. No application of clamping force on the ring element is thereby required for the purpose of establishing a rigid load path. Thus, this design allows also the ring element to be made of composite material or at least to comprise composite material in an area where the vane is fastened.
In a further embodiment of the invention the second fastening device is configured to press the first and second bracket members towards each other from opposite sides of the ring element when tightened, wherein the component is arranged in such a way that each of the first and second bracket members exerts a pressure directly or indirectly onto its corresponding side of the ring element when the second fastening device is tightened.
The advantageous effects of these features with regard to a composite ring element are similar to what is described above with regard to the composite vane.
In a further embodiment of the invention the component is arranged in such a way that each of the first and second bracket members exerts a pressure directly or indirectly onto opposite sides of the second insertion member, as seen in an axial direction of the second hole, when the second fastening device is tightened.
Again, the advantageous effects of these features with regard to a composite ring element are similar to what is described above with regard to the composite vane.
In a further embodiment of the invention the second insertion member extends in the second hole along an axial direction thereof. Preferably, the second insertion member is a bushing member. Preferably, the second fastening device comprises a second fastening member that extends in an axial direction through the second hole and that the bushing member extends at least partly around and along the fastening member.
In a further embodiment of the invention the second insertion member forms an integrated part of the first bracket member.
In a further embodiment of the invention the first bracket member has a third hole and a fourth hole and is arranged such that the third and fourth holes coincide with said first and second holes, respectively.
In a further embodiment of the invention the third hole is arranged in a first part of the first bracket member, which first part extends in a plane that is substantially in parallel with a radial direction of the ring element, and that the fourth hole is arranged in a second part of the first bracket member, which second part extends in a plane that is substantially in parallel with a circumferential direction of the ring element.
In a further embodiment of the invention the second, angled bracket member is provided with a fifth hole and a sixth hole, wherein the fifth hole coincides with the first hole and the sixth hole coincides with the second hole.
In a further embodiment of the invention the fifth hole is arranged in a radially directed part of the second, angled bracket member, which radial part extends in a plane that is substantially in parallel with a radial direction of the ring element, and that the sixth hole is arranged in a circumferentially directed part of the second, angled bracket member, which circumferentially part extends in a plane that is substantially in parallel with a circumferential direction of the ring element.
In a further embodiment of the invention the first and second bracket members are made of a metallic material.
In a further embodiment of the invention the first insertion member is made of a metallic material.
In a further embodiment of the invention the second insertion member is made of a metallic material.
In a further embodiment of the invention the tight radial fit corresponds to a radial play of <0.1 mm.
In a further embodiment of the invention the component comprises an inner ring element and an outer ring element connected by said plurality of circumferentially spaced load carrying vanes.
In a further embodiment of the invention the component is configured to define a gas flow in a gas turbine engine, such as a turbo jet engine.
In a further embodiment of the invention the component comprises a further set of bracket members, fastening devices, holes and opening for fastening the end part of the at least one composite vane to the ring element, wherein said further set is positioned at a distance from the set as seen in an axial direction of the ring element.
In a further embodiment of the invention a further bracket member of said further set, which further bracket member corresponds to the first bracket member, is arranged on an opposite side of the composite vane in relation to the first bracket member.
The invention also concerns a gas turbine engine comprising a component of the above type.

BRIEF DESCRIPTION OF DRAWINGS

In the description of the invention given below reference is made to the following figure, in which:

FIG. 1 shows, in a schematic view, a turbo-jet engine provided with a component according to the invention,

FIG. 2 shows, in a perspective view, an embodiment of the inventive component,

FIGS. 3-6 show an enlarged view of a fastening arrangement that forms part of the component shown in FIG. 2.

DETAILED DESCRIPTION

FIG. 1 shows a turbojet engine. The turbojet engine comprises a central body 1, an annular outer casing 2 (fan casing), an annular inner casing 3 (engine casing), a fan or blower 4, a low pressure compressor 5, a high pressure compressor 6, a combustion chamber 7, a high pressure turbine 8 and a low pressure turbine 9. It further comprises a set of arms 10 extending in a radial direction from the inner casing 3 to an outer ring element 14 forming part of the outer casing 2. The arms 10 comprise aerodynamic vanes 11 primarily provided to act as guide vanes for air passing through the annular channel between the inner casing 3 and the outer casing 2 in an axial direction, i.e. a longitudinal direction, of the engine. The arms 10 further comprise structural arms or load carrying vanes 12 primarily provided to guarantee a certain mechanical strength of the construction. Here, the aerodynamic vanes 11 and the load carrying vanes 12 are arranged in axially separated sets of arms. However, they could as well be arranged in an interleaving relation in one and the same set of arms. Further, a single arm may have both an aerodynamic function and a load carrying function.
The flow through the turbojet engine is divided into two major streams, a first one of which passes through an annular channel between the central body 1 and the inner casing 3, and passes the compressors 5, 6, the combustion chamber 7 and the turbines 8, 9. A second stream passes through the annular channel between the inner casing 3 and the outer casing 2. A temperature of the second stream is in operation lower than a temperature of the first stream, but the second stream substantially increases the thrust of the turbojet engine. An engine mount (not shown) is arranged onto the outer ring element 14 by means of which the turbojet engine is attached to and held in position in relation to an aircraft.
FIGS. 2-6 show an embodiment of a gas turbine engine component 15 according to the invention. As shown in FIG. 2, the component 15 comprises an outer ring element 14 that forms part of the outer casing 2, an inner ring element 27 that forms part of the inner casing 3, and a plurality of circumferentially spaced load carrying vanes 12 that extend in a radial direction of the outer and inner ring elements 14, 27 and that connects the two ring elements 14, 27. The outer ring 14 comprises a wall structure in the form of a sheet with main surfaces facing in a radial direction.
In the embodiment shown the extension direction of the load carrying vanes 12 coincides with a radial direction of the component 15. However, according to an alternative, the load carrying vanes may be arranged with an inclination (preferably <30° in relation to the radial direction of the component.
The load carrying vanes 12 are made of a fibre-reinforced light weight polymer material, i.e. a composite material, with a density below that of, for example, light weight metals such as aluminum and titanium. Vanes of this type are, as such, well known to a person skilled in the art. Further, the load carrying vanes 12 have an aerodynamically adapted cross-section, with a leading upstream edge and a trailing downstream edge as seen in the axial direction, i.e. the flow direction through the channel between the outer ring 14 and the inner casing 3. It is not necessary for the invention that all vanes are made of a composite material; some vanes may be made of metal. Neither is it necessary that the load carrying vanes 12 have an aerodynamically adapted cross-section.
Also the outer ring element 14 is in this embodiment made of a composite material, i.e. a material made of a fibre-reinforced light weight polymer material.
FIGS. 3-6 show, in an enlarged view of a part of the component shown in FIG. 2, a fastening arrangement configured to fasten the composite vane 12 to the outer ring element 14. The fastening arrangement comprises two separate double- bracket arrangements 30, 50 that are positioned at a distance from each other as seen in an axial direction of the ring element 14, wherein one is nearer and the other farther in the figures (see FIG. 3). The two bracket arrangements 30, 50 are similar in structure but are facing in different directions. FIG. 3 shows a perspective view of the fastening arrangement, FIG. 4 shows a perspective view with the ring element 14 made transparent, FIG. 5 is similar to FIG. 4 but with the farther bracket arrangement 50 shown in an exploded view; and FIG. 6 shows a sectional view of the nearer bracket arrangement 30. That the two bracket arrangements 30, 50 are arranged in different directions is clearly shown in e.g. FIG. 4. Since the structures of the two bracket arrangements 30, 50 are similar some details of the bracket arrangements 30, 50 are shown more clearly for the first bracket arrangement 30, whereas some details are shown more clearly for the second bracket arrangement 50. In general, the description below refers to a single bracket arrangement but with figure references to both bracket arrangements 30, 50.
As shown in FIGS. 3-6, each bracket arrangement 30, 50 comprises a first bracket member 31, 51 arranged in a corner region formed by the composite vane 12 and the ring element 14. Such a corner region is formed on both sides of the vane 12 when arranged with an end part thereof in the vicinity of the ring element 14. In this example the first bracket member 31, 51 is angled and has a first part that extends in a plane that is substantially in parallel with a radial direction of the ring element 14 and a second part that extends in a plane that is substantially in parallel with a circumferential direction of the ring element 14 (see FIG. 6).
The first bracket member 31, 51 is fastened to the composite vane 12 by means of a first fastening device 33, 53 arranged in association with a first hole 16, 17 (see FIGS. 5 and 6) extending through the composite vane 12. The first fastening device 33, 53 is a clamping device and comprises a first bolt member 41, 61 and a first screw member 42, 62. Further, the first bracket member 31, 51 is fastened to the ring element 14 by means of a second fastening device 34, 54 arranged in association with a second hole 18, 19 (see FIGS. 5 and 6) that extends through the ring element 14. Also the second fastening device 34, 54 is a clamping device and comprises a second bolt member 43, 63 and a second screw member 44, 64.
The first bracket member 31, 51 is provided with a third hole 46, 66 extending through the first part thereof and a fourth hole 47, 67 extending through the second part thereof. The first bracket member 31, 51 is arranged such that the third and fourth holes 46, 66, 47, 67 coincide with said first and second holes 16-19, respectively.
The component 15, and also the fastening arrangement and each of the bracket arrangements 30, 50, further comprises a second bracket member 32, 52 that at least in a portion thereof has an angular cross section. This second, angular bracket member 32, 52 is arranged through an opening 40, 60 arranged through the ring element 14 such as to be positioned on an opposite side of both the composite vane 12 and the ring element 14 in relation to the first bracket member 31, 51. Further, the second, angled bracket member 32, 52 is fastened to the first bracket member 31, 51 by means of said first and second fastening devices 33, 53, 34, 54.
The second, angled bracket member 32, 52 has a radially directed part that extends in a plane that is substantially in parallel with a radial direction of the ring element 14 and a circumferentially directed part that extends in a plane that is substantially in parallel with a circumferential direction of the ring element 14. The radial part is the part inserted through the opening 40, 60, which opening 40, 60 is arranged to provide a clearance for the radial part so that positioning of the second, angled bracket member 32, 52 becomes easy.
The second bracket member 32, 52 is provided with a fifth hole 48, 68 extending through the radial part thereof and a sixth hole 49, 69 extending through the circumferential part thereof. The second bracket member 32, 52 is arranged such that the fifth and sixth holes 48, 68, 49, 69 coincide with said first and second holes 16-19, respectively.
All bracket members 31, 51, 32, 52 and fastening devices 33, 53, 34, 54 are made of metallic material.
The first bolt member 41, 61 extends through the third hole 46, 66, the first hole 16, 17 (in the vane 12) and the fifth hole 48, 68. The first screw member 42, 62 is screwed onto the first bolt member 41, 61 as to tighten and clamp the first and second bracket member 31, 51, 32, 52 together around the vane 12 and to lock the first fastening device 33, 53. Similarly, the second bolt member 43, 63 extends through the sixth hole 49, 69, the second hole 18, 19 (in the ring element 14) and the fourth hole 47, 67. The second screw member 44, 64 is screwed onto the second bolt member 43, 63 as to tighten and clamp the first and second bracket member 31, 51, 32, 52 together around the ring element 14 and to lock the second fastening device 34, 54.
Thus, each of the first and second fastening devices is configured to press the first and second bracket members towards each other from opposite sides of the composite vane 12 and the ring element 14, respectively, when tightened. Further, the component 15 is arranged in such a way that each of the first and second bracket members exerts a pressure directly or indirectly onto its corresponding side of the composite vane 12 and the ring element 14, respectively, when the first and second fastening device, respectively, is tightened. In practice this means that the vane 12 and the ring element 14 will be at least slightly compressed when the first and second fastening devices 33, 53, 34, 54 are tightened.
A first insertion member in the form of a first tubular bushing member 35, 55 made of a metallic material is arranged in the first hole 16, 17 as to extend along an axial direction of the first hole 16, 17. The relative dimensions of the first bushing member 35, 55 and the first hole 16, 17 are such as to provide a tight radial fit for the first insertion member 35, 55 in the first hole 16, 17. The first bushing member 35, 55, which in this example is a separate part, extends in an axial direction through the third hole 46, 66 and has a flange positioned on an outer side of the first bracket member 31, 51. The first bushing member 35, 55 extends around and partly along the first bolt member 41, 61. When the first fastening device 33, 53 is tightened the first bushing member 35, 55 becomes fixed in relation to both the first and the second bracket member 31, 51, 32, 52.
The relative dimensions of the first bushing member 35, 55 and the third hole 46, 66 are such as to provide a fit that can take up tolerances. The magnitude of the tolerances to take up depends e.g. on the tolerances of the first bracket member 31, 51. With close tolerances of the first bracket member 31, 51 (around ±0.05 mm) a suitable radial play between the first bushing member 35, 55 and the third hole 46, 66 is around 0.2 mm. The smaller the radial play, the more rigid the structure. A larger radial play between the first bushing member 35, 55 and the third hole 46, 66 may be used to reduce or eliminate fitting problems during assemblage.
The position of the first bushing member 35, 55 in the axial direction is such that, before tightening of the first fastening device 33, 53, it will not extend through the entire length of the first hole 16, 17 but instead end a small distance from the surface of the side of the vane 12 where the second bracket member 32, 52 is (to be) positioned. That is, a small annular gap is created between the first bushing member 35, 55 and the second bracket member 32, 52 when the first bushing member 35, 55 and the second bracket member 32, 52 are placed in position but before tightening of the first fastening device 33, 53.
When the first fastening device 33, 53 is tightened the vane 12 will compress so that the small annular gap disappears. At this point the first bushing member 35, 55 bears against the second bracket member 32, 52 at one end and against a head of the first bolt member 41, 61 at its other, flanged end. By tightening the first fastening device 33, 53 further, preferably a predetermined further tightening verified by a torque indicator, the first bushing member 35, 55 becomes clamped between the second bracket member 32, 52 and the head of the first bolt member 41, 61. This results in a slight compression and radial expansion of the first bushing member 35, 55 which is useful for reducing or eliminating any radial play between the first bushing member 35, 55 and the first hole 16, 17. Another result of this is that the first bushing member 35, 55 forms a metallic bridge between the first and second (metallic) bracket members 31, 51, 32, 52 through the composite vane 12. This is useful since metal can be clamped to metal when fastening the bracket members 31, 51, 32, 52 to the composite vane 12, which means that the creeping problem associated with clamped composite material is avoided.
Accordingly, the component 15 is arranged in such a way that each of the first and second bracket members 31, 51, 32, 52 exerts a pressure directly or indirectly onto opposite sides of the first insertion member 35, 55, as seen in an axial direction of the first hole 16, 17, when the first fastening device 33, 53 is tightened.
If the first bushing member 35, 55 has an end part positioned too close to the second bracket member 32, 52 before tightening of the first fastening device 33, 53, for instance because it is too long in its axial direction, it is likely that the first bushing member 35, 55 will interfere when the first and second bracket member 31, 51, 32, 52 are to be pressed together around the vane 12 during tightening of the first fastening device 33, 53. As a result of this, the first and second bracket members 31, 51, 32, 52 will not be properly fixed to the vane 12 in the axial direction of the first hole 16, 17.
If the first bushing member 35, 55 has an end part positioned too far away from the second bracket member 32, 52 before tightening of the first fastening device 33, 53, for instance because it is too short in its axial direction, it may be that the first bushing member 35, 55 will not be compressed and not form any metallic bridge as described above. In some occasions this may anyway be acceptable because the load can still be transmitted between the vane 12 and the bracket members 31, 51, 32, 52 by means of bearing stress due to the tight fit between the first bushing member 35, 55 and the first hole 16, 17.
The optimum axial position of the first bushing member 35, 55 that provides an optimum size of the annular gap, i.e. the position of the first bushing member 35, 55 that provides both a proper axial fixation and a proper metallic bridge, depends on a number of factors, such as the dimensions of the vane, the bracket members, the holes etc, as well as which materials that are used. An optimum position can be achieved by using close tolerances of the parts involved. It is also possible to adjust the axial position of the first bushing member 35, 55 before tightening of the first fastening device 33, 53, for instance by using shims placed under the flange of the first bushing member 35, 55.
A second insertion member in the form of a second tubular bushing member 36, 56 is arranged in the second hole 18, 19 as to extend along an axial direction of the first hole 18, 19. The second bushing member 36, 56 has in principal the same function with regard to the ring element 14 as the first bushing member 35, 55 with regard to the vane 12.
The second bushing member 36, 56 forms an integrated, metallic part of the first bracket member 31, 51. The relative dimensions of the second bushing member 36, 56 and the second hole 18, 19 are such as to provide a tight radial fit in the second hole 18, 19. The second bushing member 36, 56 protrudes from the first bracket member 31, 51 as to form an elongation of the fourth hole 47, 67. The second bushing member 36, 56 extends around and partly along the second bolt member 43, 63. When the second fastening device 34, 54 is tightened the second bushing member 36, 56 becomes fixed in relation to both the first and the second bracket member 31, 51, 32, 52.
The length of the second bushing member 36, 56 in the axial direction is such that, before tightening of the second fastening device 34, 54, it will not extend through the entire length of the second hole 18, 19 but instead end a small distance from an outer surface of the ring element 14 where the second bracket member 32, 52 is (to be) positioned. That is, a small annular gap is created between the second bushing member 36, 56 and the second bracket member 32, 52 when the first bracket member 31, 51 (including the integrated second bushing member 36, 56) and the second bracket member 32, 52 are placed in position but before tightening of the second fastening device 34, 54.
When the second fastening device 34, 54 is tightened the composite ring element 14 will compress so that the small annular gap disappears. At this point the second bushing member 36, 56 bears against the second bracket member 32, 52. By tightening the second fastening device 34, 54 further, preferably a predetermined further tightening verified by a torque indicator, the second bushing member 36, 56 becomes clamped between the first an second bracket members 31, 51, 32, 52. This results in a slight compression and radial expansion of the second bushing member 36, 56 which is useful for reducing or eliminating any radial play between the second bushing member 36, 56 and the second hole 18, 19. Another result of this is that the second bushing member 36, 56 forms a metallic bridge between the first and second (metallic) bracket members 31, 51, 32, 52 through the composite ring element 14. This is useful since metal can be clamped to metal when fastening the bracket members 31, 51, 32, 52 to the composite ring element 14, which means that the creeping problem associated with clamped composite material is avoided.
Accordingly, the component 15 is arranged in such a way that each of the first and second bracket members 31, 51, 32, 52 exerts a pressure directly or indirectly onto opposite sides of the second insertion member 36, 56, as seen in an axial direction of the second hole 18, 19, when the second fastening device 34, 54 is tightened.
If the second bushing member 36, 56 has an end part positioned too close to the second bracket member 32, 52 before tightening of the second fastening device 34, 54, for instance because it is too long in its axial direction, it is likely that the second bushing member 36, 56 will interfere when the first and second bracket member 31, 51, 32, 52 are to be pressed together around the ring element 14 during tightening of the second fastening device 34, 54. As a result of this, the first and second bracket members 31, 51, 32, 52 will not be properly fixed to the ring element 14 in the axial direction of the second hole If the second bushing member 36, 56 has an end part positioned too far away from the second bracket member 32, 52 before tightening of the second fastening device 34, 54, for instance because it is too short in its axial direction, it may be that the second bushing member 36, 56 will not be compressed and not form any metallic bridge as described above. In some occasions this may anyway be acceptable because the load can still be transmitted between the ring element 14 and the bracket members 31, 51, 32, 52 by means of bearing stress due to the tight fit between the second bushing member 36, 56 and the second hole 18, 19.
The optimum axial position of the second bushing member 36, 56 that provides an optimum size of the annular gap, i.e. the position of the second bushing member 36, 56 that provides both a proper axial fixation and a proper metallic bridge, depends on a number of factors, such as the dimensions of the ring element, the bracket members, the holes etc, as well as which materials that are used. An optimum position can be achieved by using close tolerances of the parts involved. It is also possible to adjust the position of the circumferential part of the second bracket member 32, 52 before tightening of the second fastening device 34, 54, for instance by using shims placed between the second bracket member 32, 52 and the second bushing member 36, 56.
That the fit is tight means in principle that the diameter of the hole is as small as possible without making it (too) difficult to insert the corresponding insertion member, i.e. in this case the corresponding bushing member. A small radial play will normally be present in a tight fit. A typical tight fit radial play is in this application <0.1 mm, typically within the interval 0.015-0.1 mm. The radial play may be further reduced by cooling/shrinking the insertion member before insertion.
The tight fittings provide in this case a fixed position of the vane 12 in relation to the bracket members 31, 51, 32, 52 and further to the ring element 14. This provides for a rigid load path between the vane 12 and the ring element 14. Since the parts that are clamped together are made of metallic material there is no problem related to the tendency of composite materials to relax mechanically during its lifetime.
The outer ring 14 may comprise metallic material in addition to the fibre-reinforced composite light weight material. The outer ring 14 may, as in the shown embodiment, be of annular shape and may have a length in the longitudinal, i.e. axial direction of the engine corresponding to the extension of each of the arms 12 in said axial direction. The ring 14 may further be configured for transferring axial loads between upstream and downstream gas turbine components.
The invention has above been described for a static application in a gas turbine engine. However, the invention may also be applied in a rotational component, such as a fan and wherein there are provided aerodynamic guide vanes for the guiding of gases in a by pass channel of the engine. The invention may be used for any assembled/fabricated metal/composite structure.
In a broad sense, the invention relates to all kinds of structures in turbojet engines wherein there is a plurality of arms, typically vanes or load carrying vanes, connected to a ring element. For example, such structural vanes may be arranged in an engine core gas channel, but also in a fan section of an engine type where the fan section is arranged in a common gas channel upstream of a division into a core gas channel and a bypass gas channel.
The term “ring element”, as referred to herein, may comprise only a part, i.e. a sector, of a ring, or a continuous full ring. Further, the ring element may form part of a housing, casing, or other similar component.
The first hole 16, 17 extends through the composite vane 12 from a suction side to a pressure side thereof. The second hole 18, 19 extends through the ring element 14 from an outer side to an inner side thereof.
The invention is not limited by the embodiments described above but can be modified in various ways within the scope of the claims. For instance, either of the first and second insertion members 35, 55, 36, 56 can be an integrated part of one of the bracket members. Further, both insertion members can be separate parts. In principle both bushings can form integrated parts of any of the bracket members, but this likely leads to fitting problems during assemblage of the component.
Moreover, the first bracket member 31, 51 does not necessarily have to be angled; it can e.g. have a rectangular cross section. The second, angled bracket member 32, 52 can have a number of different shapes; it can e.g. extend in an axial and/or circumferential direction of the ring element 14 and provide attachment points for auxiliary equipment that is to be mounted to the ring element 14. With regard to the present invention it is only required that a portion thereof is angled and adapted to be inserted through the opening in the ring element for attachment to the first bracket member 31, 51.
In the embodiment described the inventive fastening arrangement has been used to fasten load carrying vanes 12 to the outer ring element 14 of the gas turbine component 5. However, the invention is applicable also for fastening the load carrying vanes 12 to the inner ring element 27, i.e. it can be used on the inner and/or the outer ring element.
It is not required that the component 15 comprises two double- bracket arrangements 30, 50. If more than one point of attachment is needed for fastening the vane 12 to the ring element 14 a single inventive double-bracket arrangement can be complemented with a further inventive double-bracket arrangement or with another type of attachment point.

Claims

1. Gas turbine engine component, comprising

a ring element and a plurality of circumferentially spaced load carrying vanes extending in a radial direction of the ring element,

wherein at least one of the vanes is made of a composite material and wherein an end part of the at least one composite vane is fastened to the ring element by means of at least a first bracket member arranged in a corner region formed by the composite vane and the ring element,

wherein the first bracket member is fastened to the composite vane by means of a first fastening device arranged in association with a first hole extending through the composite vane, and wherein the first bracket member is fastened to the ring element by means of a second fastening device arranged in association with a second hole extending through the ring element, wherein an opening is arranged in the ring element and that the component comprises a second bracket member that at least partly has an angular cross section,

wherein the second, angled bracket member is arranged through the opening such as to be positioned on an opposite side of both the composite vane and the ring element in relation to the first bracket member, and

wherein the second, angled bracket member is fastened to the first bracket member by means of the first and second fastening devices.

2. Gas turbine engine component according to claim 1, wherein a first insertion member is arranged in the first hole, wherein the relative dimensions of the first insertion member and the first hole are such as to provide a tight radial fit for the first insertion member in the first hole, and wherein the first insertion member is fixed in relation to both the first and the second bracket member.

3. Gas turbine engine component according to claim 1, wherein the first fastening device is configured to press the first and second bracket members towards each other from opposite sides of the composite vane when tightened, wherein the component is arranged in such a way that each of the first and second bracket members exerts a pressure directly or indirectly onto its corresponding side of the composite vane when the first fastening device is tightened.

4. Gas turbine engine component according to claim 2, wherein the first fastening device is configured to press the first and second bracket members towards each other from opposite sides of the composite vane when tightened, wherein the component is arranged in such a way that each of the first and second bracket members exerts pressure directly or indirectly onto its corresponding side of the composite vane when the first fastening device is tightened, and the component is arranged in such a way that each of the first and second bracket members exerts a pressure directly or indirectly onto opposite sides of the first insertion member, as seen in an axial direction of the first hole, when the first fastening device is tightened.

5. Gas turbine engine component according to claim 2, wherein the first insertion member extends in the first hole along an axial direction thereof.

6. Gas turbine engine component according to claim 2, wherein the first insertion member is a bushing member.

7. Gas turbine engine component according to claim 6, wherein the first fastening device comprises a first fastening member that extends in an axial direction through the first hole and that the bushing member extends at least partly around and along the fastening member.

8. Gas turbine engine component according to claim 1, wherein a second insertion member is arranged in the second hole,

wherein the relative dimensions of the second insertion member and the second hole are such as to provide a tight radial fit for the second insertion member in the second hole, and

wherein the second insertion member is fixed in relation to both the first and the second bracket member.

9. Gas turbine engine component according to claim 1, wherein the second fastening device is configured to press the first and second bracket members towards each other from opposite sides of the ring element when tightened, wherein the component is arranged in such a way that each of the first and second bracket members exerts a pressure directly or indirectly onto its corresponding side of the ring element when the second fastening device is tightened.

10. Gas turbine engine component according to claim 8, wherein the second fastening device is configured to press the first and second bracket members towards each other from opposite sides of the ring element when tightened, wherein the component is arranged in such a way that each of the first and second bracket members exerts a pressure directly or indirectly onto its corresponding side of the ring element when the second fastening device is tightened, and the component is arranged in such a way that each of the first and second bracket members exerts a pressure directly or indirectly onto opposite sides of the second insertion member, as seen in an axial direction of the second hole, when the second fastening device is tightened.

11. Gas turbine engine component according to claim 8, wherein the second insertion member extends in the second hole along an axial direction thereof.

12. Gas turbine engine component according to claim 8, wherein the second insertion member is a bushing member.

13. Gas turbine engine component according to claim 12, wherein the second fastening device comprises a second fastening member that extends in an axial direction through the second hole and that the second bushing member extends at least partly around and along the fastening member.

14. Gas turbine engine component according to claim 8, wherein the second insertion member forms an integrated part of the first bracket member.

15. Gas turbine engine component according to claim 1, wherein the first bracket member has a third hole and a fourth hole and is arranged such that the third and fourth holes coincide with the first and second holes, respectively.

16. Gas turbine engine component according to claim 15, wherein the third hole is arranged in a first part of the first bracket member, which first part extends in a plane that is substantially in parallel with a radial direction of the ring element, and that the fourth hole is arranged in a second part of the first bracket member, which second part extends in a plane that is substantially in parallel with a circumferential direction of the ring element.

17. Gas turbine engine component according to claim 1, wherein the second, angled bracket member is provided with a fifth hole and a sixth hole, wherein the fifth hole coincides with the first hole and the sixth hole coincides with the second hole.

18. Gas turbine engine component according to claim 17, wherein the fifth hole is arranged in a radially directed part of the second, angled bracket member, which radial part extends in a plane that is substantially in parallel with a radial direction of the ring element, and that the sixth hole is arranged in a circumferentially directed part of the second, angled bracket member, which circumferentially part extends in a plane that is substantially in parallel with a circumferential direction of the ring element.

19. Gas turbine engine component according to claim 1, wherein the first and second bracket members are made of a metallic material.

20. Gas turbine engine component according to claim 2, wherein the first insertion member is made of a metallic material.

21. Gas turbine engine component according to claim 8, wherein the second insertion member is made of a metallic material.

22. Gas turbine engine component according to claim 2, wherein the tight radial fit corresponds to a radial play of <0.1 mm.

23. Gas turbine engine component according to claim 1, wherein the component comprises an inner ring element and an outer ring element connected by the plurality of circumferentially spaced load carrying vanes.

24. Gas turbine engine component according to claim 1, wherein the component is configured to define a gas flow in a gas turbine engine, such as a turbo-jet engine.

25. Gas turbine engine component according to claim 1, wherein the component comprises a further set of bracket members, fastening devices, holes and opening according to claim 1 for fastening the end part of the at least one composite vane to the ring element, wherein the further set is positioned at a distance from the set according to claim 1 as seen in an axial direction of the ring element.

26. Gas turbine engine component according to claim 24, wherein a further bracket member (51) of the further set, which further bracket member corresponds to the first bracket member, is arranged on an opposite side of the composite vane in relation to the first bracket member.

27. Gas turbine engine, wherein it comprises a component according to claim 1.