US20170176004A1

US20170176004A1 - Combustor floating collar assembly

Info

Publication number: US20170176004A1
Application number: US14/974,555
Authority: US
Inventors: Douglas MacCAUL; Gaetan Girard
Original assignee: Pratt and Whitney Canada Corp
Current assignee: Pratt and Whitney Canada Corp
Priority date: 2015-12-18
Filing date: 2015-12-18
Publication date: 2017-06-22
Also published as: CA2936577A1; CA2936577C

Abstract

A combustor floating collar assembly having a floating collar disposed about an opening in an outer surface of a combustor liner. The floating collar is displaceable relative to the outer surface. A retention plate is attached to the outer surface of the combustor liner and traps the floating collar between the outer surface and the retention plate. At least a portion of the retention plate engages the floating collar and biases it toward the outer surface.

Description

TECHNICAL FIELD

The disclosure relates generally to gas turbine engine combustors and, more particularly, to a floating collar assembly for a combustor fuel nozzle or igniter.

BACKGROUND

Igniters of gas turbine engine combustors are typically retained on a boss of the gas generator case by being directly threaded into the boss or by being held in position with bolts. The igniters interface with the combustion chamber through a floating collar that is retained by a bracket. The bracket provides the collar with freedom of movement in the plane of its contact with the boss, and the collar is free to move normal to the bracket boss.
During engine operation, the collars may be exposed to aerodynamic loads generated by the upstream compressor which exert a force on the floating collar. When this force is greater than the inertial or gravitational loads on the collar, the collar is displaced. The dynamic nature of such aerodynamic loading, coupled with combustor dynamics, can create a fretting problem due to the intermittent displacement/impact of the collar against the igniter, or against the bracket or boss.

SUMMARY

There is provided a combustor floating collar assembly, comprising: a floating collar disposed about an opening in an outer surface of a combustor liner, the floating collar being displaceable relative to the outer surface; and a retention plate attached to the outer surface of the combustor liner, the retention plate trapping the floating collar between the outer surface and the retention plate, at least a portion of the retention plate engaging a portion of the floating collar and biasing the floating collar toward the outer surface.
There is also provided a gas turbine engine combustor, comprising: an annular combustion chamber defined by a combustor liner, the combustor liner having a plurality of openings therein extending between an inner surface and an outer surface of the combustor liner; a plurality of floating collars each disposed about one of the openings in the outer surface of the combustor liner, each floating collar being displaceable relative to the outer surface; and a plurality of retention plates attached to the outer surface, each retention plate trapping a corresponding one of the floating collars between the outer surface and the retention plate, at least a portion of each retention plate engaging a portion of the floating collar and biasing the floating collar toward the outer surface.
There is further provided a method for installing an annular floating collar about an opening in a liner of a gas turbine engine combustor, comprising: positioning the floating collar on an outer surface of the liner, the floating collar being displaceable with respect to the outer surface; attaching a retention plate to the outer surface to trap the floating collar between the outer surface and the retention plate; and biasing the floating collar toward the outer surface with at least a portion of the retention plate.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference is now made to the accompanying figures in which:

FIG. 1 is a schematic cross-sectional view of a gas turbine engine;

FIG. 2 is a side view of a combustor of the gas turbine engine of FIG. 1, the combustor having a floating collar assembly according to an embodiment of the present disclosure;

FIG. 3 is a perspective view of a floating collar assembly on the combustor of FIG. 2, according to an embodiment of the present disclosure;

FIG. 4A is an enlarged, partially-sectioned perspective view of the floating collar assembly of FIG. 3;

FIG. 4B is a side view of the enlarged, partially-sectioned view of the floating collar assembly of FIG. 4A, shown without a floating collar; and

FIG. 4C is another, enlarged partial side view of the floating collar assembly of FIGS. 3-4B.

DETAILED DESCRIPTION

FIG. 1 illustrates a gas turbine engine 10 of a type preferably provided for use in subsonic flight, generally comprising in serial flow communication a fan 12 through which ambient air is propelled, a compressor section 14 for pressurizing the air, a combustor 16 in which the compressed air is mixed with fuel and ignited for generating an annular stream of hot combustion gases, and a turbine section 18 for extracting energy from the combustion gases. The combustor 16 includes a combustion chamber 17 defined by a combustor liner 19 which contains and conveys the hot combustion gases. The combustor 16 is housed within a gas generator case 3.
Referring to FIG. 2, the shape of the combustor 16 is typically defined by the combustor liner 19 which may include one or more relatively thin sheet metal walls supported within a plenum filled with compressed air. The compressed air typically enters the combustor 16 through various openings 15 in the combustor liner 19 and/or via fuel nozzles, to mix with the fuel sprayed within the combustor 16. Fuel nozzles or igniters are inserted into the combustor 16 through some of the openings 15.
Many of the openings 15 are circumscribed by bosses 13, which can be annular or another shape and protrude from an outer surface 9 of the combustor liner 19 about the openings 15 and coaxial therewith. The “outer surface 9” of the combustor liner 19 is the surface of the combustor liner 19 which does not face inwardly into the combustor 16 toward the hot combustion gases. The bosses 13 facilitate attachment or insertion of fuel nozzles or igniters into the combustor liner 19 and allow for the mounting of collars to improve sealing between the combustor liner 19 and the gas generator case. The bosses 13 can be formed during the manufacturing of the combustor liner 19, or can be attached thereto. If attached, the bosses 13 are welded to the outer surface 9 of the combustor liner 19. Whether integral with, or attached to, the combustor liner 19, the bosses 13 are fixedly attached to the combustor liner 19 and are not displaced relative thereto.
Referring to FIGS. 2 and 3, a floating collar assembly 20 is mounted to the outer surface 9 of the combustor liner 19 about one of the openings 15. Each floating collar assembly 20, and in particular, its floating collar, helps to seal the fuel nozzles or igniters in the openings 15. The floating collar assemblies 20 also help to accommodate the relative movement between the fuel nozzles or igniters and the combustor 16, which results from thermal expansion and contraction. The floating collar assemblies 20 can also be used to control the flow of air from the plenum or gas generator case into the combustion chamber enclosed by the combustor liner 19 of the combustor 16.
FIG. 3 shows the floating collar assembly 20, according to an embodiment of the present disclosure. The floating collar assembly 20 (or simply “assembly 20”) is mounted to the outer surface 9 of the combustor liner 19. More particularly, and as shown in this embodiment, the assembly 20 is mounted to one of the bosses 13 of the outer surface 9. It will be appreciated that the assembly 20 may be mounted directly to the outer surface 9 about an opening therein.
The assembly 20 includes a floating collar 30, having an annular or other shape, which engages the boss 13 and can be displaced relative thereto. The assembly 20 also includes a retention plate 40 which confines the floating collar 30 to the outer surface 9 and biases the floating collar 30 toward the outer surface 9. When a fuel nozzle or igniter 7 is inserted into the floating collar 30, it is then radially located through a small tolerance loose fit with the floating collar 30, allowing radial growth and in plane play from the loose fit.
Referring to FIGS. 4A to 4C, the annular floating collar 30 has a combustor-facing first surface 32 that engages the outer surface 9, which is represented in this embodiment by the boss 13, and an outward-facing second surface 34. A central collar aperture 36 extends through the floating collar 30 between the first and second surfaces 32,34, and is generally co-axial with the opening in the combustor liner. The central collar aperture 36 is adapted for axial engagement with the cylindrical body of the fuel nozzle or igniter, in order to effectively seal the combustor liner from uncontrolled entry of compressed air from the plenum. More particularly, a pressure differential across the floating collar 30 seals the first surface 32 to the boss 13. The first surface 32 is disposed on the boss 13 such that the floating collar 30 can be displaced relative to the boss 13, as will be described in greater detail below. The displacement of the floating collar 30 may be caused, for example, by aerodynamic loads from the compressor or from vibration of the whole assembly.
Conventional floating collars can fret at the contact points with the fuel nozzle or igniter, or at the contact point with the boss, because of the intermittent displacement or “chattering” caused by the aerodynamic or vibration loads encouraging the displacement of the floating collar 30 against the fuel nozzle or igniter in a highly dynamic environment. The retention plate 40 disclosed herein helps to reduce such fretting by biasing the floating collar 30 toward the boss 13 to frictionally reduce at least some of this chattering movement.
More particularly, the retention plate 40 is attached to the outer surface 9 and/or its boss 13 such that relative displacement is eliminated between the retention plate 40 and the boss 13. The retention plate 40 can be welded to the boss 13 to form weld lines 42 between the retention plate 40 and the boss 13. The retention plate can also be attached to outer surface 9 using any other technique. When installed, the retention plate 40 overlies both the boss 13 and the floating collar 30 such that at least some portion of the floating collar 30 is positioned between the boss 13 and the retention plate 40. The dimensional interference of the retention plate 40 with the floating collar 30 frictionally limits displacement of the floating collar 30 relative to the boss 13, thereby confining the floating collar 30 to the boss 13. It can thus be appreciated that the retention plate 40 “retains” the floating collar 30 in sealing engagement with the fuel nozzle or igniter, and traps the floating collar 30 between itself and the outer surface 9.
Referring specifically to FIG. 4C, and in addition to this retaining functionality, the retention plate 40 also provides a “loading” functionality. More particularly, at least a portion of the retention plate 40 engages at least a portion of the floating collar 30 and biases it toward the boss 13 with a biasing force F. The engagement of the retention plate 40 with the floating collar 30 provides a compressive load, acting substantially radially inward on the second surface 34 of the floating collar 30, which pushes the (inner) first surface 32 of the floating collar 30 toward and/or against the boss 13. When the first surface 32 abuts against and engages the boss 13, friction between the two surfaces creates a shear force or restraint of the floating collar 30 in a plane of the boss 13. The shear restraint in the plane of the boss 13 can be greater than the aerodynamic loads which impact the floating collar 30.
The retention plate 40 of the assembly 20 disclosed herein therefore maintains its “retention” functionality while also helping to reduce or eliminate the fretting associated with conventional floating collars. This may be achieved, for example, because the biasing engagement of the retention plate 40 limits the displacement of the floating collar 30 relative to the boss 13. For example, the biasing force F applied by the retention plate 40 may allow the floating collar 30 to displace only in a plane that is parallel to the plane of the boss 13. The biasing engagement of the retention plate 40 may thus reduce or prevent displacement of the floating collar 30 in a direction parallel to a center axis of the opening in the combustor liner. In such instances, the retention plate 40 is used to radially (i.e. a direction along the center axis of the opening) secure the floating collar 30 to the boss 13, while still permitting relative movement between the floating collar 30 and the boss 13 only in the plane of the boss 13, or directly along the outer surface 9. Allowing the floating collar 30 to be displaced relative to the boss 30 or outer surface 9 helps accommodate the radial growth of the components of the assembly 20, and the in-plane play from the loose fit between the fuel nozzle or igniter and the floating collar 30.
Various embodiments of the retention plate 40 can achieve such functionality, all of which are within the scope of the present disclosure. FIGS. 4A-4C show one such embodiment of the retention plate 40. The retention plate 40 includes a substantially planar middle portion 44 extending between two attachment portions 46 which are attached to the outer surface 9 and which extend radially outwardly from the middle portion 44. The attachment portions 46 may be curved at their ends toward the outer surface 9. A free extremity 48 of each attachment portion 46 is fixedly attached to the boss 13 or outer surface 9. In one embodiment, each free extremity 48 can be welded to the boss 13 to form weld lines 42 between the retention plate 40 and the boss 13, or the outer surface 9 of the combustor liner. The distance between the free extremities 48 in this embodiment is greater than a diameter of the floating collar 30, such that the retention plate 40 overlies a greater extent of the outer surface 9 than the floating collar 30.
The retention plate 40 also has one or more inner biasing portions 49 of the retention plate 40 which engage the floating collar 30, and which extend radially inwardly from the middle portion 44. The inner biasing portion 49 can be curved, bent, or otherwise protrude toward the boss 13. Such a curved inner biasing portion 49 provides a curved line of contact with the second (outer) surface 34 of the floating collar 30 which helps to reduce stress concentrations. In the embodiment shown in FIGS. 4A-4C, the retention plate 40 can engage the floating collar 30 via one or more dimples or depressions 49A in the retention plate 40. Each depression 49A extends from the planar portion 44 toward the boss 13 and contacts the second surface 34 of the floating collar 30. Other shapes for the inner biasing portion 49 of the retention plate 40 engaging the floating collar 30 are also possible, including “U”-shaped depressions.
The depression or engagement can be formed during installation of the assembly 20. For example, while welding the free extremities 48 of the attachment portion 46 to the boss 13, it is possible to also manipulate the retention plate 40 to engage the floating collar. The biasing load can be therefore be pre-loaded, and created by bending the retention plate 40 so that it interferes with the floating collar 30 at assembly of the retention plate 40 to the boss 13. In some instances, the retention plate 40 will be secured to the boss 13 before positioning the floating collar 30 on the boss 13. This would allow the floating collar 30 to be a replaceable item with no need to remanufacture the collar assembly 20.
Still referring to FIGS. 4A to 4C, there is also disclosed a method for installing the annular floating collar 30 about the opening in the combustor liner. The method includes positioning the floating collar 30 on the outer surface 9 such that the floating collar 30 is displaceable with respect to the outer surface 9. The retention plate 40 is attached to the outer surface 9 to trap the floating collar 30 between the retention plate 40 and the outer surface 9. The retention plate 40 is manipulated to bias the floating collar 30 toward the boss 13. The biased floating collar 30 may be prevented from being displaced in a direction normal to the outer surface 9, and may be allowed to displace along the outer surface 9.
In an embodiment, the method includes applying a heat treatment to the welded or attached retention plate 40. This can permit control/normalization of the load applied on the floating collar 30 by the biasing retention plate 40.
There is also disclosed a method for dampening displacement of an annular floating collar 30 that is already installed. More particularly, the method helps to dampen or reduce unwanted radial displacement of the floating collar 30 relative to the annular boss 13 in assemblies where the floating collar 30 is confined to the boss 13 with the retention plate 40 disposed over the floating collar 30 and fixed to the boss 13. Such a method can be used to adapt an existing floating collar assembly to reduce displacement of the floating collar, such as during after-market maintenance. The method includes biasing the floating collar 30, by bending or another mechanical manipulation of a portion of the retention plate 40, toward the boss 13 with at least a portion of the retention plate 40. Alternatively, an existing retention plate can be replaced with a pre-formed retention plate 40 having a biasing element 49 as described above.
In light of the preceding, it can thus be appreciated that a fuel nozzle or igniter can be inserted through the opening 15 and remove therefrom without any part of the floating collar assembly 20 being disturbed or removed from the combustor liner. This ability of the retention plate 40 to retain itself and the floating collar 40 in place, even when the fuel nozzle or igniter is positioned within the opening 15 of the combustor liner 19, prevents these components repositioning themselves relative to the retention plate 40 during installation. This can be problematic during installation of a collar assembly. Such functionality also improves maintenance of the features of the assembly 20 because complete disassembly of the assembly 20 and its components is not required. Furthermore, easier access can be provided to the internal components of the gas generator assembly, e.g. for boroscope inspection. These possibilities can be achieved by enhancing the components of a conventional floating collar assembly, and does not require adding additional parts.
In contrast to some conventional floating collar assemblies, the assembly 20 disclosed herein does not require other components (e.g. the fuel nozzle, the igniter, or features of these) to maintain the floating collar 30 in place, or to apply the biasing force F with the retention plate 40. Instead, the assembly 20 disclosed herein presents a self-contained “one-piece” solution, wherein the retention plate 40 both retains the floating collar in place, and applies compressive loading thereto.
The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to the embodiments described without departing from the scope of the invention disclosed. Still other modifications which fall within the scope of the present invention will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the appended claims.

Claims

1. A combustor floating collar assembly, comprising:

a floating collar disposed about an opening in an outer surface of a combustor liner, the floating collar being displaceable relative to the outer surface; and

a retention plate attached to the outer surface of the combustor liner, the retention plate trapping the floating collar between the outer surface and the retention plate, at least a portion of the retention plate engaging a portion of the floating collar and biasing the floating collar toward the outer surface.

2. The floating collar assembly of claim 1, wherein the retention plate includes a substantially planar middle portion extending radially outwardly to an attachment portion being attached to the outer surface.

3. The floating collar assembly of claim 2, wherein retention plate includes an inner biasing portion extending radially inwardly from the substantially planar middle portion, the inner biasing portion extending toward the outer surface and contacting the floating collar.

4. The floating collar assembly of claim 3, wherein said inner biasing portion of the retention plate contacting the floating collar is curved toward the outer surface.

5. The floating collar assembly of claim 2, wherein the attachment portion is curved toward the outer surface.

6. The floating collar assembly of claim 2, wherein the attachment portion of the retention plate is fixedly attached to the outer surface.

7. The floating collar assembly of claim 6, wherein the attachment portion of the retention plate is welded to the outer surface.

8. The floating collar assembly of claim 1, wherein the floating collar is positioned on an annular boss of the outer surface, the retention plate including a substantially planar middle portion extending radially outward to an attachment portion being attached to the boss.

9. The floating collar assembly of claim 1, wherein said portion of the retention plate which engages the portion of the floating collar prevents displacement of the floating collar in a direction normal to the outer surface.

10. A gas turbine engine combustor, comprising:

an annular combustion chamber defined by a combustor liner, the combustor liner having a plurality of openings therein extending between an inner surface and an outer surface of the combustor liner;

a plurality of floating collars each disposed about one of the openings in the outer surface of the combustor liner, each floating collar being displaceable relative to the outer surface; and

a plurality of retention plates attached to the outer surface, each retention plate trapping a corresponding one of the floating collars between the outer surface and the retention plate, at least a portion of each retention plate engaging a portion of the floating collar and biasing the floating collar toward the outer surface.

11. The combustor of claim 10, wherein each retention plate includes a substantially planar portion middle extending radially outwardly to an attachment portion being fixedly attached to the outer surface.

12. The combustor of claim 11, wherein the retention plate includes an inner biasing portion extending radially inwardly from the substantially planar middle portion, the substantially planar middle portion and the inner biasing portion overlaying the floating collar, the inner biasing portion extending toward the outer surface and contacting the floating collar.

13. The combustor of claim 12, wherein the inner biasing portion of the retention plate contacting the floating collar is curved toward the outer surface.

14. The combustor of claim 10, wherein each floating collar is positioned on an annular boss of the outer surface, the corresponding retention plate including a substantially planar middle portion extending radially outwardly to an attachment portion being fixedly attached to the boss.

15. The combustor of claim 10, further comprising at least one igniter or at least one fuel nozzle, said nozzle or fuel nozzle being inserted through a corresponding one of the openings, and engaging a corresponding floating collar.

16. A method for installing an annular floating collar about an opening in a liner of a gas turbine engine combustor, comprising:

positioning the floating collar on an outer surface of the liner, the floating collar being displaceable with respect to the outer surface;

attaching a retention plate to the outer surface to trap the floating collar between the outer surface and the retention plate; and

biasing the floating collar toward the outer surface with at least a portion of the retention plate.

17. The method of claim 16, wherein biasing the floating collar toward the outer surface includes compressive loading the floating collar with said portion of the retention plate.

18. The method of claim 17, wherein compressive loading the floating collar includes increasing a shear restraint of the floating collar in a plane of the outer surface.

19. The method of claim 16, wherein biasing the floating collar includes welding the retention plate to the outer surface to engage the floating collar with said portion of the retention plate.

20. The method of claim 16, further comprising inserting a fuel nozzle or an igniter through the opening in the liner to engage the floating collar, and removing the fuel nozzle or the igniter from the opening while maintaining in place the floating collar and retention plate.