WO2014022358A1

WO2014022358A1 - Buckle joint for split fairing of a gas turbine engine

Info

Publication number: WO2014022358A1
Application number: PCT/US2013/052672
Authority: WO
Inventors: Derek Thomas DREISCHARF; Scott Patrick RYCZEK
Original assignee: General Electric Company
Priority date: 2012-08-01
Filing date: 2013-07-30
Publication date: 2014-02-06
Also published as: CN104508250A; CN104508250B; CA2880516A1; JP6002325B2; CA2880516C; BR112015002084A2; JP2015524533A; EP2893154A1

Abstract

A gas turbine engine strut fairing (10, 110) includes: inner and outer bands; a hollow, airfoil-shaped vane (12, 112) extending between the bands; wherein the fairing (10, 110) is split along a transverse plane passing through the bands and vane (12, 112), defining a nose piece (24, 124) and a tail piece (26, 126); wherein the vane (12, 112) is defined by a spaced-apart sidewalls (18) extending between a leading edge and a trailing edge, each the sidewalls (18) being split into forward and aft portions by the transverse plane; wherein each of the sidewall portions carries a radially-inwardly extending post (32, 34, 132, 134), having a mating face (40, 46, 140, 146), the posts (32, 34, 132, 134) positioned with pairs of the posts (32, 34, 132, 134) lie adjacent to each other, with their respective mating faces (40, 46, 140, 146) contacting each other; and a pair of slotted buckles (38, 138), each buckle (38, 138) surrounding and clamping together a pair of the posts (32, 34, 132, 134); wherein a mechanical element (76, 143) engages the mating faces (40, 46, 140, 146) of the paired posts (32, 34, 132, 134), so as to block relative radial movement of the paired posts (32, 34, 132, 134).

Description

BUCKLE JOINT FOR SPLIT FAIRING OF A GAS TURBINE ENGINE

BACKGROUND OF THE INVENTION

[0001] This invention relates generally to gas turbine engine turbines and more particularly to fairings for stationary structural members of such engines.

[0002] Gas turbine engines frequently include a stationary turbine frame, also referred to as an inter-turbine frame or turbine center frame ("TCF"), which provides a structural load path from bearings which support the rotating shafts of the engine to an outer casing, which forms a backbone structure of the engine. Turbine frames commonly include an annular, centrally- located hub surrounded by an annular outer ring, which are interconnected by a plurality of radially-extending struts. The turbine frame crosses the combustion gas flowpath of the turbine and is thus exposed to high temperatures in operation. Such frames are often referred to as "hot frames", in contrast to other structural members which are not exposed to the combustion gas flowpath.

[0003] To protect them from high temperatures, turbine frames are typically lined with high temperature resistant materials that isolate the frame structure from hot flow path gasses. The liner must provide total flow path coverage including the frame outer ring or case, hub structure, and struts.

[0004] One known configuration to protect the struts is an interlocking split fairing arrangement in which forward and aft sections of individual fairing/nozzle components are sandwiched around the struts. This arrangement uses a tab-and-buckle (or post-and- buckle) coupling assembly having a buckle with a rectangular opening that receives generally rectangular tabs to keep the fairing halves together after assembly to the frame. An example of this tab-and-buckle arrangement is described in U.S. Patent 8,152,451 to Manteiga et al.

[0005] While effective to secure the fairing halves together, the prior art rectangular post/buckle configuration, however, requires tight tolerance match machining of the post and buckle to ensure alignment and fit of the members and relies on clearance gaps in the buckle joint to accommodate assembly. This can lead to gaps at assembly and in operation, creating potential "forward facing steps" or "aft facing steps" and air leakage into the flowpath.

[0006] Accordingly, there is a need for a post-and-buckle joint for a turbine strut fairing which is positively locked to avoid flowpath steps.

BRIEF SUMMARY OF THE INVENTION

[0007] This need is addressed by the present invention, which provides a split fairing assembly for a turbine frame incorporating a post-and-buckle coupling arrangement with a shear member to prevent misalignment.

[0008] According to one aspect of the invention, a fairing for a strut in a gas turbine engine includes: an inner band; an outer band; a hollow, airfoil-shaped vane extending between the inner and outer bands; wherein the fairing is split along a generally transverse plane passing through the inner band, outer band and vane, so as to define a nose piece and a tail piece; wherein the vane is defined by a pair of spaced-apart sidewalls extending between a leading edge and a trailing edge, each of the sidewalls being split into forward and aft portions by the transverse plane; wherein each of the sidewall portions carries a radially-inwardly extending post, each post including a mating face, the posts positioned such that pairs of the posts lie adjacent to each other, with their respective mating faces contacting each other; and a pair of slotted buckles, wherein each slotted buckle surrounds and clamps together a pair of the posts; wherein a mechanical element engages the mating faces of the paired posts, so as to block relative radial movement of the paired posts.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The invention may be best understood by reference to the following description taken in conjunction with the accompanying drawing figures in which:

[0010] FIG. 1 is a perspective view of a strut fairing constructed according to an aspect of the present invention; [0011] FIG. 2 is an exploded perspective view of the strut fairing of FIG. 1;

[0012] FIG. 3 is a schematic plan view of a portion of the buckle and posts of the strut fairing of FIG. 1;

[0013] FIG. 4 is a partially-cut-away side view of the buckle and post of FIG. 3;

[0014] FIG. 5 is a perspective view of an alternative strut fairing constructed according to an aspect of the present invention;

[0015] FIG. 6 is an exploded perspective view of the strut fairing of FIG. 5;

[0016] FIG. 7 is a schematic plan view of a portion of the buckle and posts of the strut fairing of FIG. 6; and

[0017] FIG. 8 is a rear elevation view of a portion of a post of the strut fairing of FIG. 5. DETAILED DESCRIPTION OF THE INVENTION

[0018] Referring to the drawings wherein identical reference numerals denote the same elements throughout the various views, FIG. 1 depicts a strut fairing 10 suitable for use in a gas turbine engine, for example to surround and protect a structural strut or a service tube of a structural frame. The strut fairing 10 includes an airfoil-shaped vane 12 that is supported between an arcuate outer band 14 and an arcuate inner band 16. The inner and outer bands 16 and 14 are axially elongated and shaped so that they define a portion of the flowpath through the turbine frame.

[0019] The vane 12 is axially elongated and includes spaced-apart sidewalls 18 extending between a leading edge 20 and a trailing edge 22. The sidewalls 18 are shaped so as to form an aerodynamic fairing for the a gas turbine engine frame strut or other similar structure of a known type (not shown) The components of the strut fairing 10, including the inner band 16, outer band 14, and vane 12 are split, generally along a common transverse plane, so that the strut fairing 10 has a nose piece 24 and a tail piece 26 (see FIG. 2). Each of the sidewalls 18 is divided into forward and aft portions.

[0020] The nose pieces 24 and tail pieces 26 are cast from a metal alloy suitable for high- temperature operation, such as a cobalt- or nickel-based "superalloy", and may be cast with a specific crystal structure, such as directionally-solidified (DS) or single-crystal (SX), in a known manner. An example of one suitable material is a nickel-based alloy commercially known as RENE N4.

[0021 ] The interior lateral spacing between the sidewalls 18 is selected such that the nose piece 24 can slide axially over the strut or other structure from forward to aft, and the tail piece 26 can slide axially over the strut or other structure from aft to forward. This permits installation or removal of the nose piece 24 or tail piece 26 without disassembly of the turbine frame or removal of the strut. The inner lateral interior surfaces of the sidewalls 18 are substantially free of any protuberances, hooks, bosses, or other features that would interfere with the free axial sliding.

[0022] Optionally, the mating faces 28 and 30 of the nose piece 24 and the tail piece 26 may have a shape that is at least partially non-planar as a means of blocking leakage of cooling air or ingestion of hot flowpath gases.

[0023] Means are provided for securing the nose piece and the tail piece 24 and 26 to each other. In the illustrated example, the nose piece 24 includes posts 32 which extend in a generally radially inward direction adjacent its aft face 28, and the tail piece 26 includes posts 34 which extend in a generally radially inward directly adjacent its forward face 30. When assembled, the posts 32 and 34 are received in a slot 36 of a metallic buckle 38. (It is noted that to permit assembly, the posts 32 and 34 may be oriented in a direction that is not strictly radial to the engine centerline, but rather perpendicular to a waterline cut through the engine; that is, the posts 32 and 34 would be generally parallel to each other).

[0024] The posts 32 and 34 and the buckle 38 may be collectively configured to define a "tripod" contact configuration which is self-aligning and which does not require precise match-machining of the component parts.

[0025] Each of the posts 32 includes a mating face 40 facing the nose piece/tail piece split line, a pressure face 42 opposite the mating face 40, and a pair of spaced-apart side faces 44. The pressure face 42 is disposed at an acute angle "A" to an engine radial direction "R" (which is also parallel to the nosepiece/tailpiece split line). The mating face 40 includes a transverse groove 41 formed therein (in the illustrated example the groove has a semicircular cross-sectional shape). The axis of the groove 41 extends parallel to a waterline cut through the engine. The groove 41 is formed during a drilling operation which is described in more detail below.

[0026] Each of the posts 34 includes a mating face 46 facing the nose piece/tail piece split line, and a pair of spaced-apart side flank faces 48. The flank faces 48 are oriented to form a "V" shape, and in conjunction with the mating face 46 they form a generally triangular shape in plan view. The flank faces 48 extend generally parallel to the radial direction "R". The mating face 46 includes a transverse groove 43 formed therein (in the illustrated example the groove has a semicircular cross-sectional shape). The axis of the groove 43 extends parallel to a waterline cut through the engine. The groove 43 is formed during a drilling operation which is described in more detail below.

[0027] The buckle 38 is a monolithic structure with a forward and aft ends 50 and 52, inner and outer surfaces 54 and 56, and side surfaces 58 and 60. A slot 62 is formed in the buckle 38 extending from the inner surface 54 to the outer surface 56. The slot 62 includes a forward wall 64 adjacent the forward end 50, and a pair of flanking walls 66 adjacent the aft end 52. The forward wall 64 is generally planar and is inclined at an acute angle to the outer surface 56. The forward wall 64 is angled to as to lie generally parallel to the pressure face 42 of the post 32 when installed. Each of the flanking walls 66 is generally planar. The flanking walls 66 are oriented so as to lie generally parallel to the flank faces 48 of the post 34 when installed. The flanking walls 66 are oriented to form a "V" shape, and in conjunction with the forward wall 64 they form a generally triangular shape in plan view from the outer surface 56. Transition walls 68 may interconnect the flanking walls 66 and the forward wall 64. The slot 62 is sized and shaped such that there will be essentially no contact between the side faces 44 of the post 32 and the slot 62 when assembled.

[0028] Referring to FIG. 3, When the nose piece 24 and the tail piece 26 are assembled to each other, the mating face 40 of each post 32 contacts the mating face 46 of the corresponding post 34. The slot 62 of the buckle 38 receives the posts 32 and 34. The flanking walls 66 of the slot 62 bear against the corresponding flank faces 48 of the post 34, and the forward wall 64 of the slot 62 bears against the pressure face 42 of the post 32. As the buckle 38 is moved in a generally radial direction towards the nose piece 24 and tailpiece 26, interaction of the pressure face 42 forces the buckle 38 against the flank faces 48, removing substantially all of the clearance between the two posts 32 and 34, and between the buckle 38 and the posts 32 and 34. To the extent that the posts 32 and 34 and the slot 62 do not match their nominally-specified dimensions, the buckle 38 is simply forced on to the posts 32 and 34 to a greater or lesser degree.

[0029] Once the buckle 38 has been dry- fitted and all assembly clearance removed, the buckle 38 is temporarily secured to the post 34. For example, the buckle 38 could be tack- welded to the post 34. Alternatively, holes can be line-drilled through the buckle 38 and the post 34, and a press-fit buckle pin 70 installed. The nose piece 24 can then be removed, and the buckle 38 is rigidly secured to the post 34, for example by a known brazing process.

[0030] Once the buckle 38 has been secured to the post 34, the nose piece 24 and the tail piece 26 are reassembled. The forward portion of the buckle 38 and the split line between the posts 32 and 34 are then line-drilled, resulting in holes 72 and 74 in the forward portion of the buckle 38 (see FIG. 3). The line-drilling operation forms the grooves 41 and 43 described above. A press-fit shear pin 76 is then installed engaging the holes 72 but not the grooves 41 or 43. Optionally, the holes 74 can be staked or swaged. The shear pin 76 is a representative example of a shear member. Other types of machine elements such as a square key could be used as a shear member in place of the circular-cross- section shear pin 76.

[0031] To subsequently assemble the strut fairing 10 in an engine, the tail piece 26 is slipped axially forward over the strut (not shown). Next, the nose piece 24 is slipped axially rearward over the strut and pivoted so the posts 32 engage the slots 62.

[0032] The shear pins 76 are then driven fully into place so that they engage the grooves 41 and 43 as well as the holes 72 and 74. The swaged holes 74 act as a secondary retention feature for the shear pins 76. Alternatively, the shear pins 76 could be staked or swaged after being driven into place.

[0033] Finally, the radially outer ends of the nose and tail pieces 24 and 26 are secured together with shear bolts 78 or other similar fasteners installed through mating flanges 80 (see FIG. 2). Even without the shear pins 76 in place, interaction between the pressure face 42 and the forward wall 64 of the slot 62 resists movement of the nose piece 24. If the nose piece 24 should move in operation, it can only move to a position which creates an aft-facing step relative to the combustion gas flowpath, not an undesirable forward- facing step.

[0034] When the nose piece 24 and tail piece 26 are assembled with the shear pins 76 in place, interaction between the shear pins 76 and the grooves 41 and 43 resists or blocks relative radial movement of the nose piece 24 and the tail piece 26. (see FIG. 4) This configuration prevents the nose piece from moving in operation, and therefore avoids both forward- facing steps and aft-facing steps relative to the combustion gas flowpath. It is noted that the shear pin feature and the taper feature may be incorporated individually or in combination.

[0035] The buckle-to-post joint can be disassembled by pressing the shear pins 76 out of engagement with the posts 32 and 34. A simple manual or powered pin-press type tool, similar to a conventional chain pin tool (not shown) may be used for this purpose.

[0036] FIGS. 5 and 6 depict an alternative strut fairing 110. Its construction, including material selection, is substantially identical to the strut fairing 10 described above except for the configuration of the posts. Elements of the strut fairing 110 not specifically described in detail may be taken to be identical to the corresponding elements of the strut fairing 10. The strut fairing 110 includes an airfoil-shaped vane 112, outer and inner bands 114 and 116, and is split, generally along a common transverse plane, to define a nose piece 124 and a tail piece 126.

[0037] The nose piece 124 includes posts 132 which extend in a generally radially inward direction adjacent its aft face 128, and the tail piece 126 includes posts 134 which extend in a generally radially inward directly adjacent its forward face 130. When assembled, the posts 132 and 134 are received in a slot of a metallic buckle 138. (It is noted that to permit assembly, the posts 132 and 134 may be oriented in a direction that is not strictly radial to the engine centerline, but rather perpendicular to a waterline cut through the engine; that is, the posts 132 and 134 would be generally parallel to each other).

[0038] The posts 132 and 134 and the buckle 138 may be collectively configured to define a "tripod" contact configuration as described above.

[0039] Each of the posts 132 includes a mating face 140 facing the nose piece/tail piece split line, The mating face 140 incorporates an alignment element 141 defining at least one element that is protruding or recessed in the axial direction relative to the remainder of the otherwise planar mating face 140. In the illustrated example the alignment element 141 is an "S-cut" or S-shaped profile or other similar shape (see FIG. 7). The axis of the S-cut extends perpendicular to a waterline cut through the engine, and may be formed during the same cut procedure used to split the nose piece 124 from the tail piece 126.

[0040] Each of the posts 134 includes a mating face 146 facing the nose piece/tail piece split line, The mating face 146 incorporates an alignment element 143 defining at least one element that is protruding or recessed in the axial direction relative to the remainder of the otherwise planar mating face 146. In the illustrated example the alignment element 143 is an "S-cut" or S-shaped profile or other similar shape (see FIG. 7). The axis of the S-cut extends perpendicular to a waterline cut through the engine, and may be formed during the same cut procedure used to split the nose piece 124 from the tail piece 126. The alignment element 143 is complementary to the alignment element 141 of the post 132.

[0041] The buckle 138 is a monolithic structure including a slot 162 formed therein. When the nose piece 124 and the tail piece 126 are assembled to each other, the mating face 140 of each post 132 contacts the mating face 146 of the corresponding post 134. The slot 162 of the buckle 138 receives the posts 132 and 134. [0042] Once the buckle 138 has been dry- fitted and all assembly clearance removed, the buckle 138 is temporarily secured to the post 134. For example, the buckle 138 could be tack- welded to the post 134. Alternatively, holes can be line-drilled through the buckle 138 and the post 134, and a press-fit buckle pin 170 installed. The nose piece 124 can then be removed, and the buckle 138 is rigidly secured to the post 134, for example by a known brazing process.

[0043] To subsequently assemble the strut fairing 110 in an engine, the tail piece 126 is slipped axially forward over the strut. Next, the nose piece 124 is slipped axially rearward over the strut and pivoted so the posts 132 engage the slots 162.

[0044] Finally, the radially outer ends of the nose and tail pieces 124 and 126 are secured together with shear bolts 178 or other similar fasteners installed through mating flanges 180 (see FIG. 6). When the nose piece 124 and tail piece 126 are assembled, interaction between the alignment elements 141 and 143 resists radial movement of the nose piece 124 relative to the tail piece 126. More specifically, as shown in FIG. 8, there is a nonzero angle Θ between the long axis "L" of the alignment element 141 and a radial direction R. This relationship creates an interference condition which prevents or blocks relative movement of the nose piece 124 and the tail piece 126 in the radial direction, and therefore avoids both forward- facing steps and aft- facing steps relative to the combustion gas flowpath.

[0045] It is noted that the buckle-and-post configurations described herein may be employed at the inboard end of a split fairing, at its outboard end, or at both ends.

[0046] The split fairing configuration described herein has several advantages over prior art designs, including: 1) Manufacturing tolerance relief, reducing cost. 2) Assembly ease through guided engagement, reducing cost. 3) Self-alignment of the joint, resulting in a zero-clearance fit. 4) Minimized flowpath gaps, abating wear. 5) Reduced leakage through flowpath gaps, improving engine performance. 6) Avoidance of forward facing steps into the flowpath, improving engine performance.

[0047] The present invention precludes the traditional tight tolerances required on the post and buckle that are necessary to achieve a matched fit to facilitate producibility, assembly and limited leakage loss at the split line. The proposed invention provides the added benefits of preventing aerodynamically undesirable steps into the flowpath at the split line while further reducing buckle-to-post assembly gaps, leading to a reduction in backside pressurization air leaking into the flowpath.

[0048] Cost is reduced due to relaxed tolerances and simplified assembly. The present invention allows utilization of an "as-cast" buckle, as opposed to a precision match machined detail part.

[0049] The foregoing has described a split fairing buckle joint for a gas turbine engine. While specific embodiments of the present invention have been described, it will be apparent to those skilled in the art that various modifications thereto can be made without departing from the spirit and scope of the invention. Accordingly, the foregoing description of the preferred embodiment of the invention and the best mode for practicing the invention are provided for the purpose of illustration only and not for the purpose of limitation.

Claims

WHAT IS CLAIMED IS:

1. A fairing (10, 1 10) for a strut in a gas turbine engine, comprising:

an inner band (16, 116);

an outer band (14, 114);

a hollow, airfoil-shaped vane (12, 112) extending between the inner and outer bands;

wherein the fairing (10, 110) is split along a generally transverse plane passing throughthe inner band (16, 116), outer band (14, 114) and vane (12, 112), so as to define a nose piece (24, 124) and a tail piece (26, 126);

wherein the vane (12, 112) is defined by a pair of spaced-apart sidewalls (18) extending between a leading edge and a trailing edge, each of the sidewalls (18) being split into forward and aft portions by the transverse plane;

wherein each of the sidewall portions carries a radially-inwardly extending post (32, 34, 132, 134), each post (32, 34, 132, 134) including a mating face (40, 46, 140, 146), the posts (32, 34, 132, 134) positioned such that pairs of the posts (32, 34, 132, 134) lie adjacent to each other, with their respective mating faces (40, 46, 140, 146) contacting each other; and

a pair of slotted buckles (38, 138), wherein each slotted buckle (38, 138) surrounds and clamps together a pair of the posts (32, 34, 132, 134);

wherein a mechanical element (76, 143) engages the mating faces (40, 46, 140, 146) of the paired posts (32, 34, 132, 134), so as to block relative radial movement of the paired posts (32, 34, 132, 134).

2. The fairing (10, 110) of claim 1 wherein:

Each of the mating faces (40, 46, 140, 146) has a transverse groove (41, 43) formed therein; and

a shear member passes laterally through each buckle (38, 138) and engages the transverse grooves (41 , 43) in the mating faces (40, 46, 140, 146) of the paired posts (32, 34, 132, 134), so as to block relative radial movement of the paired posts (32, 34, 132, 134).

3. The fairing (10, 110) of claim 2 wherein the shear member is a circular cross- section pin (76).

4. The fairing (10, 110) of claim 1 wherein each of the mating faces (40, 46, 140, 146) includes at least one alignment element (143) that is protruding or recessed in the axial direction relative to the remainder of the otherwise planar mating face (40, 46, 140, 146), the posts (32, 34, 132, 134) positioned such that pairs of the posts (32, 34, 132, 134) lie adjacent to each other, with their respective mating faces (40, 46, 140, 146) contacting each other such that the respective alignment element (143)s engage each other.

5. The fairing (10, 110) of claim 4 wherein the alignment feature is an S-shaped profile.

6. The fairing (10, 110) of claim 4 wherein there is a there is a nonzero angle between a long axis of the alignment element (143) and a radial direction, defining an interference condition which prevents relative radial movement.

7. The fairing (10, 110) of claim 1 wherein:

each pair of adjacent posts (32, 34, 132, 134) includes at least two non-parallel faces; and

wherein each pair of adjacent posts (32, 34, 132, 134) contacts a slot of the corresponding buckle (38, 138) in a tripod contact configuration

8. The fairing (10, 110) of claim 1 wherein the post (34, 134) of each sidewall portion of the tail piece (26, 126) includes a mating face (46, 146) and a pair of flank faces (48) opposite the mating face (46, 146), the flank faces (48) oriented to form a "V" shape.

9. The fairing (10, 110) of claim 1 wherein the post (32, 132,) of each sidewall portion of the nose piece (24, 124) includes a mating face (40, 140), a pressure face (42) opposite the mating face (40, 46, 140, 146), and a pair of spaced-apart side faces (44) flanking the pressure face (42), wherein the pressure face (42) is disposed at an acute angle to the transverse plane.

10. The fairing (10, 110) of claim 9 wherein the slot (62, 162) is sized and shaped such that there will be substantially no contact between the side faces (44) of the post (32, 132), and the slot (62, 162) when assembled.

11. The fairing (10, 110) of claim 1 wherein:

the buckle (38, 138) is a monolithic structure with a forward and aft ends, inner and outer surfaces, and side surfaces;

a slot (62, 162) is formed in the buckle (38, 138) extending from the inner surface to the outer surface, the slot (62, 162) including a forward wall adjacent the forward end, and a pair of flanking walls adjacent the aft end;

the flanking walls are oriented to form a "V" shape; and

in conjunction with the forward wall, the flanking walls form a generally triangular shape in plan view from the outer surface.

12. The fairing (10, 110) of claim 11 wherein:

the forward wall of the buckle (38, 138) is generally planar and is inclined at an acute angle to the outer surface, so as to lie generally parallel to the pressure face of the post (32, 34, 132, 134) when installed; and

each of the flanking walls of the buckle (38, 138) is generally planar, and the flanking walls are oriented so as to lie generally parallel to the flank faces of the post (32, 34, 132, 134) when installed.

13. The fairing (10, 110) of claim 1 wherein a pin (70) passes through the buckle (38, 138) and at least one of the posts (32, 34, 132, 134).

14. The fairing (10, 110) of claim 1 wherein mating surfaces ofthe sidewalls (18) have a non-planar shape.

15. the fairing (10, 110) of claim 1 wherein the slotted buckles (38, 138) are secured to the posts (32, 34, 132, 134) of the tail piece (26, 126) by brazing.