Variable guide vane assembly with bushing ring and biasing member

Abstract

A gas turbine engine has first and second components defining respective first and second gas path surfaces of an annular gas path, the first and second gas path surfaces being axially spaced apart from one another by an annular recess in the first component; a bushing ring disposed within the annular recess and defining a stem pocket therein; variable guide vanes pivotable about respective vane axes extending between first and second stems; and a biasing member housed within the annular recess and disposed axially between the bushing ring and one of the first and second components, the biasing member exerting a force on the bushing ring in an axial direction relative to the central axis and toward the other of the first and second components.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to gas turbine engines, and more particularly to a variable guide vane assembly as can be found in a compressor section of a gas turbine engine. BACKGROUND

[0002] In a gas turbine engine, air is pressurized by rotating blades within a compressor, mixed with fuel, and then ignited within a combustor for producing hot combustion gases that flow downstream through a turbine for extracting energy therefrom. Within the compressor of the engine, air is directed through circumferentially arranged rows of blades and vanes that pressurize the air in stages. Variable guide vanes (VGVs) are sometimes used in compressors and provide blades that are rotatable such that they can change the angle of attack defined by the incoming flow. Improvements to such variable guide vane assemblies are sought. SUMMARY

[0003] In one aspect, a gas turbine engine is provided, comprising: first and second components defining respective first and second gas path surfaces of an annular gas path extending circumferentially about a central axis, the first and second gas path surfaces being axially spaced apart from one another by an annular recess in the first component; a bushing ring disposed within the annular recess and defining stem pockets therein that are circumferentially distributed about the central axis; variable guide vanes circumferentially distributed about the central axis, the variable guide vanes having airfoils extending across the annular gas path, the variable guide vanes having first and second stems at first and second radial ends of the airfoils, the first stems rotatably engaged within the stem pockets in the bushing ring, the variable guide vanes being pivotable about respective vane axes extending between the first and second stems; and a biasing member housed within the annular recess and axially disposed between the bushing ring and one of the first and second components, the biasing member exerting a force on the bushing ring in an axial direction relative to the central axis and toward the other of the first and second components.

[0004] In some embodiments, the biasing member is a seal member.

[0005] In some embodiments, the seal member extends circumferentially about the central axis.

[0006] In some embodiments, the biasing member is a U-shaped seal.

[0007] In some embodiments, the biasing member is a W-shaped seal.

[0008] In some embodiments, the sealing member is made of an elastomeric material.

[0009] In some embodiments, the bushing ring has two body portions that are biased into abutting engagement with one another via a biasing member.

[0010] In some embodiments, the first and second gas path surfaces are disposed on a radially inner annular surface of the annular gas path.

[0011] In some embodiments, the first component is an inner casing of a gas turbine engine, and wherein the second component is a wall of a seal casing of the gas turbine engine.

[0012] In some embodiments, the annular recess is defined by a first section of the inner casing having a diameter that is less than a second section of the inner casing, a shoulder at an intersection between the first and second sections, and a bushing ring abutting against the shoulder.

[0013] In some embodiments, the biasing member is axially located between the bushing ring and a distal end of the wall of the seal casing.

[0014] In some embodiments, the wall of the seal casing axially overlaps the first section of the inner casing.

[0015] In some embodiments, a distal end of the wall of the seal casing defines a face extending about the central axis and facing the biasing member, the face being inclined away from the bushing ring in a radial direction away from the annular gas path.

[0016] In some embodiments, the variable guide vane is located within a compressor of the gas turbine engine.

[0017] In some embodiments, the variable guide vane is located at an inlet of the compressor.

[0018] In some embodiments, the biasing member is located downstream of the bushing ring relative to a flow direction in the annular gas path.

[0019] In some embodiments, the bushing ring defines a third gas path surface, the first, second, and third gas path surfaces collectively defining an annular surface of the annular gas path.

[0020] In another aspect, a gas turbine engine is provided, comprising: first and second components defining respective first and second gas path surfaces of an annular gas path extending circumferentially about a central axis, the first and second gas path surfaces being axially spaced apart from one another by an annular recess in the first component; a bushing ring disposed within the annular recess and defining a stem pocket in the bushing ring that is circumferentially distributed about the central axis; a variable guide vane circumferentially distributed about the central axis, the variable guide vane having an airfoil extending across the annular gas path, the variable guide vane having first and second stems at first and second radial ends of the airfoil, the first stem being rotatably engaged within the stem pocket in the bushing ring, the variable guide vane being pivotable about a respective vane axis extending between the first and second stems; and means for applying a force to the bushing ring in an axial direction relative to the central axis.

[0021] In some embodiments, the apparatus includes an elastomeric seal member housed within the annular recess, the elastomeric seal member being between the bushing ring and one of the first and second components.

[0022] In another aspect, a gas turbine engine is provided, comprising: an annular gas path extending circumferentially about a central axis, the annular gas path being radially defined between a first gas path surface and a second gas path surface; two walls defining a portion of the first gas path surface, the two walls being axially spaced apart from one another by a spacing; a stator having vanes circumferentially distributed about the central axis, the vanes having airfoils extending across the annular gas path, the vanes having first and second stems fixed to first and second radial ends of the airfoils, the vanes being pivotable about respective vane axes extending between the first and second stems, a bushing ring being radially supported by one or both of the two walls within the spacing between the two walls, the bushing ring defining a pocket housing the first stems of the vanes, the bushing ring rotatably supporting the first stems of the vanes; and a biasing member housed within a gap between the bushing ring and one of the two walls, the biasing member being axially compressed between the bushing ring and the one of the two walls.

[0023] In yet another aspect, a method of assembling a segment of a gas turbine engine is provided, comprising: obtaining two walls defining a gas path surface of an annular gas path of a gas turbine engine, a bushing ring, a biasing member, and a blade of a stator of the segment of the gas turbine engine, the two walls extending circumferentially about a central axis; mounting the bushing ring on a first of the two walls; mounting the biasing member on the first wall; joining a shank of the blade into a pocket defined by the bushing ring to allow the blade to rotate about a respective blade axis; and mounting a second of the two walls about a portion of the first wall and axially moving the two walls toward one another until the biasing member is compressed between the bushing ring and one of the two walls. BRIEF DESCRIPTION OF DRAWINGS

[0024] Reference will now be made to the drawings, wherein:

[0025] Figure 1 is a schematic cross-sectional view of a gas turbine engine;

[0026] Figure 2 is an enlarged view of a portion of Figure 1

[0027] Figure 3 is a three-dimensional cutaway view of a variable guide vane (VGV) assembly according to one embodiment, the VGV assembly being part of the engine of

[0028] Figure 4 is an enlarged plan view of a portion of Figure 3

[0029] Figure 5 is a three-dimensional view of a bushing ring of the VGV assembly of Figure 3

[0030] Figure 6 is a three-dimensional cutaway view of a VGV assembly according to another embodiment. DETAILED DESCRIPTION

[0031] The following disclosure relates generally to gas turbine engines, and more particularly to assemblies including one or more struts and variable orientation guide vanes, as can be found in a compressor section of a gas turbine engine. In some embodiments, the assemblies and methods disclosed herein can facilitate better performance of a gas turbine engine, such as by improving flow conditions in the compressor section under some operating conditions, improving the operable range of the compressor, reducing energy losses and aerodynamic loads on the rotor.

[0032] Figure 1 ​​​A gas turbine engine 10 (in this case, a turboprop engine) of the type that is preferably provided for subsonic flight, and that is drivingly engaged with a rotatable load described as a propeller 12, is shown. The gas turbine engine has a compressor section 14 for pressurized air in serial flow communication, a combustor 16 in which the compressed air is mixed with fuel and ignited for producing an annular flow of hot combustion gases, and a turbine section 18 for extracting energy from the combustion gases.

[0033] It should be noted that the terms "upstream" and "downstream" as used herein refer to the direction of air / gas flow through the annular gas path 20 of the gas turbine engine 10. It should also be noted that the terms "axial", "radial", "angular" and "circumferential" are used with respect to a central axis 11 of the gas path 20, which can also be a central axis of the gas turbine engine 10. The gas turbine engine 10 is depicted as a counterflow engine, in which air flows in the annular gas path 20 from a rear of the engine 10 to a front of the engine 10 relative to a direction of travel T of the engine 10. This is in contrast to a throughflow engine in which air flows within the gas path 20 in a direction opposite the direction of travel T from a front of the engine toward a rear of the engine 10. The principles of the present disclosure are applicable to both counterflow and throughflow engines, as well as any other turbomachinery engine, such as turbofan and turboprop engines.

[0034] Reference is now made to Figure 2 , which shows an enlarged view of a portion of the compressor section 14. The compressor section 14 includes a plurality of stages, in this illustrated embodiment three stages, but more or fewer stages are also contemplated, each stage including a stator 22 and a rotor 24. The rotors 24 are rotatable relative to the stators 22 about the central axis 11. Each stator 22 includes a plurality of vanes 23 distributed circumferentially about the central axis 11 and extending into the gas path 20. Each rotor 24 also includes a plurality of vanes 25 distributed circumferentially about the central axis 11 and extending into the gas path 20, the rotors 24, and thus their vanes 25, rotating about the central axis 11. As will be seen in further detail below, at least one of the stators 22 includes vanes 23 that are variable guide vanes (VGVs), and thus includes a variable guide vane assembly 40 as will be described.

[0035] In the depicted embodiment, the gas path 20 is defined radially between an outer wall or casing 26 and an inner wall or casing 28. The vanes 23 and the buckets 25 extend radially between the outer casing 26 and the inner casing 28 relative to the central axis 11. As used herein, “radially extending” does not necessarily imply extending entirely radially along a ray that is entirely perpendicular to the central axis 11, but is intended to encompass directions of extension that have a radial component relative to the central axis 11. The vanes 23 can be fixedly oriented or variably oriented guide vanes (hereinafter referred to as VGVs). Examples of rotors include fans, compressor rotors (e.g., impellers), and turbine rotors (e.g., those downstream of a combustion chamber).

[0036] Referring to Figure 3 , an example of a variable guide vane (VGV) assembly of the stator 22 of the engine 10 is shown at 40. Figure 2 Any of the stators 22 of the compressor section 14 depicted in FIG. 1 can be implemented as the variable guide vane of the VGV assembly 40. It will be appreciated that in some cases, the VGV assembly 40 can be used as a stator of the turbine section 18 of the engine 10 without departing from the scope of the present disclosure. The VGV assembly 40 can be located at an uppermost upstream location LI of the compressor section 14. Figure 2 That is, the VGV assembly 40 can be a variable inlet guide vane assembly located at an inlet of the compressor section 14.

[0037] The VGV assembly 40 includes a plurality of variable guide vanes 42 that are circumferentially distributed about the central axis 11 and radially extend between the inner casing 28 and the outer casing 26. In the present embodiment, the vanes 42 are rotatably supported at their two ends by the inner casing 28 and the outer casing 26. In particular, each vane 42 has an airfoil 42a having a leading edge 42b and a trailing edge 42c, both of which extend along a span of the airfoil 42a. Each vane 42 has an inner shank 42d, also referred to as an inner shaft portion, that is fixed to an inner end 42e of the airfoil 42a, and an outer shank 42f, also referred to as an outer shaft portion, that is fixed to an outer end 42g of the airfoil 42a.

[0038] In the illustrated embodiment, the inner gas path surface 22a that defines a radially inner boundary of the annular gas path 20 is defined by a plurality of components that are axially disposed along the central axis 11 and extend circumferentially about the central axis 11. In particular, in the illustrated embodiment, the plurality of components that define the inner gas path surface 22a include the inner casing 28 and the seal housing 32 of the gas turbine engine 10. Each of these components has a wall that defines a respective one of first and second gas path surface portions of the inner gas path surface 22a.

[0039] Referring to Figures 3-4The inner shell 28 has first and second sections 28b, 28c of different diameters and a shoulder 28a at the intersection between these first and second sections 28b, 28c. The second section 28c has a smaller diameter than the diameter of the first section 28b. The first section 28b of the inner shell 28 defines a first gas path surface portion of the inner gas path surface 22a. The shoulder 28a defines an abutment surface that extends around the central axis 11 and towards a direction having an axial component relative to the central axis 11. The seal housing 32 has a wall 32a that axially overlaps a portion of the second section 28c of the inner shell 28. The wall 32a of the seal housing 32 defines a second gas path surface portion of the inner gas path surface 22a. In the illustrated embodiment, the first and second gas path surface portions are spaced apart from each other by an annular recess 28d defined by the inner shell 28.

[0040] In the illustrated embodiment, the inner stems 42d of the vanes 42 are rotatably engaged within a bushing ring 44. The bushing ring 44 extends circumferentially around the central axis 11 and defines a third portion of the inner gas path surface 22a of the annular gas path 20. The bushing ring 44 is axially located between the shoulder 28a defined by the inner shell 28 and the wall 32a of the seal housing 32 that is fixed to the inner shell 28. The inner gas path surface 22a of the annular gas path 20 is collectively defined by the inner shell 28, the bushing ring 44, and the wall 32a of the seal housing 32. Similar bushing rings can be used to rotatably support the outer stems 42f of the vanes 42.

[0041] The outer stems 42f of the vanes 42 can be engaged by a unison ring, and the unison ring can be engaged by an actuator, such that powering the actuator causes each of the vanes 42 to rotate about its respective pivot axis A to change the angle of attack defined between the vane 42 and the flow F in the annular gas path 20. An example of a system for rotating the vanes 42 is described in, for example, U.S. Patent Application Publication US-2020-0072243-A1.

[0042] Reference is now made to Figure 5 The bushing ring 44 is shown in more detail. The primary function of the bushing ring 44 is to secure the inner stems 42d, also referred to as stems, of the vanes 42 in place. In some embodiments of the engine, assembly constraints require that the bushing ring 44 be made in two separate components and be engaged together in the engine.

[0043] In the illustrated embodiment, the bushing ring 44 includes a first ring body portion 45 and a second ring body portion 47 that is securable to the first ring body portion 45. In the illustrated embodiment, the first and second ring body portions 45, 47 are sized and fitted to accommodate the inner stems 42d of the vanes 42. It will be appreciated that the bushing ring 44 can be located in any suitable location and can be used to accommodate the outer stems 42f.

[0044] In the depicted embodiment, the bushing ring 44 includes a first axial face 44a defined by the first ring body portion 45, a second axial face 44b opposite the first axial face 44a and defined by the second ring body portion 47, a radially inner surface 44c defined by both the first and second ring body portions 45, 47 and oriented toward the central axis 11, and a radially outer surface 44d defined by both the first and second ring body portions 45, 47 and oriented away from the central axis 11. Both the radially inner and outer surfaces 44c, 44d of the bushing ring 44 extend axially from the first axial face 44a to the second axial face 44b.

[0045] Still referring to Figure 5 , the bushing ring 44 defines a plurality of stem pockets 44e distributed circumferentially about the central axis 11 of the engine 10. Each of these pockets 44e includes a first pocket portion 44f having a first diameter Dl and extending from the radially outer surface 44d toward the radially inner surface 44c, and a second pocket portion 44g having a second diameter D2 that is less than the first diameter Dl and extending from the first pocket portion 44f to the radially inner surface 44c. Each of the first and second pocket portions 44f, 44g is sized to accommodate a respective portion of the inner stem 42d of a vane 42. In the present embodiment, the peripheral surface 42h of the inner stem 42d of a vane is in direct contact with the peripheral surface 44h of the ring 44 defining the pocket 44e. Each of these peripheral surfaces 44h of the pocket 44e extends circumferentially about a respective vane pivot axis A Figure 3 ) of the vane 42. Use of the disclosed bushing ring 44 can allow for omission of a separate bushing disposed about each stem 42d of a vane 42, which can reduce part count and weight.

[0046] The first and second ring body portions 45, 47 can be made from any suitable material, including but not limited to a compression molded composite such as, for example, a polyamide with carbon filler (e.g., 40% carbon filler). The first and second ring body portions 45, 47 can then be machined in groups to form the surfaces of the vane pockets 44e and a portion of the gas path surfaces 22a defining the gas path 20. Manufacturing the bushing ring 44 in this order can ensure that each group of parts has acceptable tolerances.

[0047] As shown in Figure 5 , each of the first and second ring body portions 45, 47 defines a portion (e.g., one half) of the circumferential portion of the pocket 44e. That is, the peripheral surface 44h extending about the pocket 44e is defined jointly by the first ring body portion 45 and the second ring body portion 47. Each of the first and second pocket portions 44f, 44g is defined by both the first ring body portion 45 and the second ring body portion 47.

[0048] Referring to Figure 4 The bushing ring 44 is received within the annular recess 28d and is sized to fit axially between the shoulder 28a of the inner casing 28 and the wall 32a of the seal casing 32. In the disclosed embodiment, the bushing ring 44 is received axially between the inter-compressor casing portion of the inner casing 28 and the seal casing 32. The radially outer surface 44d has a shape configured to bridge the gap between the shoulder 28a of the inner casing 28 and the wall 32a of the seal casing 32. In other words, the radially outer surface 44d defines a third portion of the inner gas path surface 22a of the gas path 20 of the engine 10.

[0049] The plurality of components of the gas turbine engine 10 are axially stacked along the central axis 11. Each of these components is manufactured with a particular tolerance. In some cases, tight tolerances are required to ensure that the bushing ring 44 fits tightly between the inter-compressor casing portion of the inner casing 28 and the seal casing 32. Obtaining these tolerances can be challenging in some cases. These tight tolerances can ensure that no axial movement occurs between the bushing ring 44 and the cavity in which it is located.

[0050] In the embodiment shown in Figure 3 , the biasing member 50 is received within the annular recess 28d and is used to fill the gap G between the shoulder 28a defined by the inner casing 28 and the bushing ring 44, or as shown in Figure 4 , the gap G between the wall 32a of the seal casing 32 and the bushing ring 44. In the embodiment shown, the biasing member 50 is disposed axially between the second axial face 44b of the bushing ring 44 and the wall 32a of the seal casing 32. In the current case, the biasing member 50 is located downstream of the bushing ring 44 relative to the direction of the gas flow F within the annular gas path 20. In the present embodiment, the biasing member 50 is a sealing member, in the current case, a U-shaped seal. The biasing member 50 can be made of an elastomeric material. The biasing member 50 can be made of a metal seal shape. In operation, the load on the blades pushes them forward. Having the biasing member 50 located downstream of the bushing ring 44 can allow for a fixed wall at the front to hold the blade assembly fixed. The biasing member 50 can absorb tolerance slack and can seal against leakage and can ensure that the shroud does not move backwards when the engine is shut down.

[0051] The biasing member 50 serves to secure the bushing ring 44 in place by limiting axial movement of the bushing ring 44 relative to the central axis 11. A pin or other device can be used to limit rotation of the bushing ring 44. The use of the biasing member 50 can have the additional benefit of acting as a damper to account for the range of stack-up in the area between the inner housing 28 and the seal housing 32. The biasing member 50 is compressed in the gap G between the wall 32a of the seal housing 32 and the bushing ring 44. In other words, the biasing member 50 has a rest, uncompressed state in which the thickness of the biasing member 50 along the central axis 11 is greater than the axial width of the gap G relative to the central axis 11.

[0052] In the illustrated embodiment, the biasing member 50 abuts against an end face 32c defined by a distal end 32b of the wall 32a of the seal housing 32. The end face 32c extends around the central axis 11 and is inclined such that the gap G widens in a radial direction relative to the central axis and towards the central axis 11 and away from the annular gas path 20. In other words, the end face 32c is inclined away from the bushing ring 44 in a radial direction away from the annular gas path 20. The gap G expands in a direction extending radially away from the inner gas path surface 22a. This can help to retain the biasing member 50 in the gap G as it is compressed.

[0053] The biasing member 50 exerts a force on the bushing ring 44 in an axial direction relative to the central axis 11 and towards the shoulder 28a of the inner housing 28. In other words, the biasing member 50 pushes the bushing ring 44 away from the wall 32a of the seal housing 32. In other words, the biasing member 50 can exert a counter force when compressed between a range of displacements. The biasing member 50 can be used to accommodate the entire stack-up of the spacing between the inner housing 28 (more specifically the shoulder 28a of the inner housing 28) and the seal housing 32 (more specifically the wall 32a of the seal housing 32 defining a portion of the gas path surface 22a). In the illustrated embodiment, the axial length of the biasing member 50 relative to the central axis 11 is greater than the maximum gap between the shoulder 28a and the distal end of the wall 32a of the seal housing 32 such that, under worst-case tolerance conditions, the biasing member 50 remains compressed and thus exerts a force on the components, axially compressing it. The force exerted by the biasing member 50 when compressed can also serve to squeeze the two body portions 45, 47 of the bushing ring 44 together and axially against the compressor intercase.

[0054] The disclosed embodiments using the biasing member 50 can require less control over the tolerances of the surrounding components, but rather accommodate any axial gaps that exist through the use of the expansion characteristics of the biasing member 50. Figure 5 As a result of using those less stringent tolerances, cost can be saved at the manufacturing stage.

[0055] Reference is now made toFigure 6 The biasing member 50 is shown here as a W-seal. The W-seal is axially located between the distal end 32b of the wall 32a of the seal housing 32 and the bushing ring 44. Other locations for the biasing member 50 are contemplated. For example, it can be located between the shoulder 28a defined by the inner housing 28 and the bushing ring 44.

[0056] The biasing member 50 can be used to dampen vibrations of the engine 10. That is, the airflow F can flow in the annular gas path 20 and be redirected by changing the angle of attack of the vanes 42. These changes in flow direction can cause turbulence and vibrations. Thus, the biasing member 50 can deform to allow axial movement between the inner housing 28 and the seal housing 32, thereby dampening some of these vibrations.

[0057] It will be appreciated that any device capable of applying an axial force to the bushing ring 44 as described above can be used without departing from the scope of the present disclosure. For example, the biasing member can be a spring, such as a wave spring, elastomer, or the like. The biasing member can include a plurality of springs distributed within the gap G and spaced circumferentially about the central axis 11. Any suitable biasing member can be used. Expanded polypropylene (EPS) material can be used for the biasing member.

[0058] The embodiments described in this document provide non-limiting examples of possible implementations of the present technology. Upon reviewing this disclosure, one of ordinary skill in the art will recognize that changes can be made to the embodiments described herein without departing from the scope of the present technology. For example, other applications of the present disclosure can include using an axial seal as a method of fastening a multi-piece VGV inner ring together. This can be particularly useful for environments where space is limited, and can make assembly easier by using a multi-piece inner ring that is to be assembled in the engine rather than on a workbench. Furthermore, the disclosed bushing ring and biasing member can be located radially outward of the annular gas path relative to the central axis of the gas turbine engine. Further modifications can be made by one of ordinary skill in the art in light of this disclosure, which will be within the scope of the present technology.

Claims

1. A gas turbine engine, comprising: a first component and a second component defining respective first and second gas path surfaces of an annular gas path extending circumferentially about a central axis, the first and second gas path surfaces being axially spaced apart from one another by an annular recess in the first component; a bushing ring disposed within the annular recess and defining a stem pocket therein that is circumferentially distributed about the central axis; a variable guide vane circumferentially distributed about the central axis, the variable guide vane having an airfoil extending across the annular gas path, the variable guide vane having first and second stems at first and second radial ends of the airfoil, the first stem being rotatably engaged within the stem pocket in the bushing ring, the variable guide vane being pivotable about a respective vane axis extending between the first and second stems; and a biasing member housed within the annular recess and axially disposed between the bushing ring and one of the first and second components, the biasing member exerting a force on the bushing ring in an axial direction relative to the central axis and toward the other of the first and second components, the biasing member having an uncompressed state and a compressed state, a thickness of the biasing member in the uncompressed state being greater than an axial width of the annular recess.

2. The gas turbine engine of claim 1, wherein the biasing member is a sealing member.

3. The gas turbine engine of claim 2, wherein the sealing member extends circumferentially about the central axis.

4. The gas turbine engine of claim 2, wherein the biasing member is a U-shaped seal.

5. The gas turbine engine of claim 2, wherein the biasing member is a W-shaped seal.

6. The gas turbine engine of claim 2, wherein the sealing member is made of an elastomeric material.

7. The gas turbine engine of claim 1, wherein the bushing ring has two body portions that are biased against one another via the biasing member.

8. The gas turbine engine of claim 1, wherein the first and second gas path surfaces are disposed on a radially inner annular surface of the annular gas path.

9. The gas turbine engine of claim 8, wherein the first component is an inner casing of the gas turbine engine, and wherein the second component is a wall of a seal casing of the gas turbine engine.

10. The gas turbine engine of claim 9, wherein the annular recess is defined by a first section of the inner casing having a diameter that is less than a diameter of a second section of the inner casing, a shoulder at an intersection between the first and second sections, and the bushing ring abutting against the shoulder.

11. The gas turbine engine of claim 10, wherein the biasing member is positioned axially between the bushing ring and a distal end of the wall of the seal case.

12. The gas turbine engine of claim 10, wherein the wall of the seal case axially overlaps the first segment of the inner casing.

13. The gas turbine engine of claim 11, wherein the distal end of the wall of the seal case defines a face extending about the central axis and facing the biasing member, the face being angled away from the bushing ring in a radial direction away from the annular gas path.

14. The gas turbine engine of claim 1, wherein the variable guide vane is located within a compressor of the gas turbine engine.

15. The gas turbine engine of claim 14, wherein the variable guide vane is located at an inlet of the compressor.

16. The gas turbine engine of claim 1, wherein the biasing member is located downstream of the bushing ring relative to a flow direction in the annular gas path.

17. The gas turbine engine of claim 1, wherein the bushing ring defines a third gas path surface, the first gas path surface, the second gas path surface, and the third gas path surface collectively defining an annular surface of the annular gas path.

18. A gas turbine engine, comprising: an annular gas path extending circumferentially about a central axis, the annular gas path being radially defined between a first gas path surface and a second gas path surface; two walls defining a portion of the first gas path surface, the two walls being axially spaced apart from one another by a spacing; a stator having vanes circumferentially distributed about the central axis, the vanes having airfoils extending across the annular gas path, the vanes having first and second shanks fixed to first and second radial ends of the airfoils, the vanes being pivotable about respective vane axes extending between the first and second shanks, a bushing ring radially supported between the two walls by one or both of the two walls within the spacing between the two walls, the bushing ring defining a pocket accommodating the first shanks of the vanes, the bushing ring rotatably supporting the first shanks of the vanes; and a biasing member accommodated within a gap between the bushing ring and one of the two walls, the biasing member being axially compressed between the bushing ring and the one of the two walls, the biasing member having an uncompressed state and a compressed state, a thickness of the biasing member in the uncompressed state being greater than an axial width of the gap. ​

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