The disclosure relates generally to gas turbine engine combustors and, more particularly, to a floating collar assembly for a combustor fuel nozzle or igniter.
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.
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.
Reference is now made to the accompanying figures in which:
Referring to
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
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
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
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.
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
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
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.