Patent Application
20150345792
1. Field of the Invention
The invention relates to gas turbine engine combustor top hat cover attachment systems. More particularly, embodiments of the invention incorporate lugged backing plates that interlock with mating recesses formed in the corresponding midframe combustor portal. The top hat cover is in turn fastened to the combustor portal by top hat cover fasteners that engage the corresponding threaded apertures formed in the backing plate.
2. Description of the Prior Art
Referring to
A typical known engine 10 has sixteen combustors 20. Each typical known combustor top hat cover 24 is affixed to the combustor midframe with twenty-four threaded fasteners. Thus, a typical known gas turbine engine 10 requires formation of approximately 384 threaded apertures 27 during its midframe manufacture. The aperture holes 27 must be drilled with relatively precise coaxial and circumferential alignment, on a large and relatively complex three dimensional midframe 22 fabrication. Each of those drilled holes is then hand threaded. Damage repair of any of the threaded apertures 27 formed in the midframe 22—whether damage is incurred during initial fabrication or discovered during subsequent service inspection of the engine 10—is labor intensive, complex and time consuming. Lost time during service outages potentially delays resumption of the turbine engine 10 power generation operation.
Accordingly, a suggested object of the invention is to reduce or eliminate the turbine engine manufacturing step of forming threaded apertures in the combustor mid frame that have been necessary for combustor top hat cover attachment to a corresponding combustor portal.
Another suggested object of the invention is to eliminate the need to repair damaged threaded apertures in the combustor midframe, such as in the combustor portal mating surface, that retain combustor top hat cover fasteners.
These and other objects are achieved in one or more embodiments of the invention by attaching combustor top hat covers to midframe combustor portals with a lugged backing plate that interlocks with mating recesses formed in the corresponding midframe combustor portal. Exemplary embodiments utilize twist lock engagement of backing plate ring lugs under projecting tabs formed over a lug raceway recess in the combustor portal mating surface. The top hat cover is in turn fastened to the combustor portal by fasteners that engage corresponding threaded apertures formed in the backing plate. In exemplary embodiments of the invention he threaded aperture backing plate reduces or eliminates the need to form threaded apertures directly in the combustor midframe. Furthermore, the backing plate is replaceable during engine service outages in the event that a damaged threaded aperture is discovered during engine service. The damaged backing plate can be scrapped or alternatively repaired more easily than attempting to repair a damaged aperture in situ within a combustor midframe.
Exemplary embodiments of the invention feature a backing plate for affixing a combustor top hat cover to a midframe combustor portal of a gas turbine engine. The backing plate comprises a ring, including a plurality of projecting ring lugs, which is adapted for locking mating insertion into corresponding recesses formed within a gas turbine engine midframe combustor port. The backing plate defines an array pattern of threaded holes that correspond to an array pattern of top hat cover fastener apertures, which are adapted for capture of top hat cover fasteners.
Other exemplary embodiments of the invention feature a gas turbine engine combustor top hat cover attachment system. The attachment system includes a combustor section midframe defining a combustor portal. A combustor portal mating surface circumscribes an outwardly exposed periphery of the combustor portal. The mating surface defines an array of projecting tabs that are separated by lug recesses. A lug raceway is defined within the combustor portal mating surface beneath the projecting tabs, which is in communication with the lug recesses. A first array pattern of through hole apertures is defined in the combustor portal mating surface that correspond to an array pattern of combustor top hat cover fastener apertures. A backing plate having a ring, including a plurality of projecting ring lugs, is adapted for interlocking engagement with the combustor portal mating surface by insertion of the ring lugs into the lug recesses and rotation of the ring lugs in the lug raceway under the projecting tabs in a twist lock fashion. The backing plate defines a second array pattern of threaded apertures that correspond to an array pattern of top hat cover fastener apertures. The second array of threaded apertures is adapted for coaxial alignment with the first array corresponding through hole apertures and capture of top hat cover fasteners.
Additional exemplary embodiments of the invention feature a method for attaching a gas turbine engine combustor top hat cover to a combustor section midframe combustor portal. The method is practiced by providing a combustor section midframe defining a combustor portal with a combustor portal mating surface circumscribing an outwardly exposed periphery of the combustor portal. The provided mating surface defines an array of projecting tabs that are separated by lug recesses. A lug raceway is defined within the combustor portal mating surface beneath the projecting tabs that is in communication with the lug recesses. A first array pattern of through hole apertures is defined in the combustor portal mating surface that correspond to an array pattern of combustor top hat cover fastener apertures. In the method a backing plate is provided, having a ring, including a plurality of projecting ring lugs, that is adapted for interlocking engagement with the combustor portal mating surface by insertion of the ring lugs into the lug recesses and rotation of the ring lugs in the lug raceway under the projecting tabs. The provided the backing plate defines a second array pattern of threaded apertures that correspond to an array pattern of top hat cover fastener apertures. The second array of threaded apertures is adapted for coaxial alignment with the first array corresponding through hole apertures and capture of top hat cover fasteners. The provided backing plate is inserted into the combustor portal mating surface, so that the ring lugs pass through the lug recesses. The inserted backing plate is rotated so that the lugs are oriented under the projecting tabs. The first and second aperture arrays are coaxially aligned. A top hat cover having a third array pattern of apertures corresponding to the first and second array patterns of apertures is provided and the third array pattern of apertures is coaxially aligned with the first and second aperture arrays. Top hat cover fasteners are passed through the third and second array pattern of apertures and they engage the corresponding threaded apertures of the first array pattern of apertures.
The respective objects and features of the invention may be applied jointly or severally in any combination or sub-combination by those skilled in the art.
The teachings of the invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawings, in which:
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures.
After considering the following description, those skilled in the art will realize that exemplary embodiments of the present invention can be readily utilized in attachment of combustor top hat covers to combustor portal mating surfaces with top hat cover fasteners but without the need to form threaded fastener apertures in the combustor midframe (such as in the portal mating surface) that have been previously needed to engage and anchor those fasteners. The invention interposes a backing plate between the top hat cover flange and the combustor portal mating surface that incorporates the threaded apertures needed for anchoring the top hat cover fasteners. The backing plate has ring lugs that are inserted in a lug raceway and that are engaged under projecting tabs formed in combustor portal mating surface, such as by a “twist lock” motion analogous to a bolt action rifle bolt engagement in a corresponding lug raceway formed in the rifle receiver. It is easier to drill and tap threaded fastening apertures in the backing plate than in the combustor midframe during their initial fabrication. If at any time any of the backing plate threaded apertures are damaged, the entire backing plate can be disengaged from the combustor midframe mating surface by reverse unlocking twist and replaced with an undamaged backing plate.
Referring to
As shown in
Referring generally to
The backing plate 60 and top hat cover 24 are installed on the combustor midframe 40 over the combustor portal 23 by inserting the backing plate into the combustor portal mating surface 42, so that the ring lugs 62 pass through the corresponding lug recesses 46 and into the lug raceway 47 (see the arrow I insertion direction). Next, the inserted backing plate 60 is rotated so that the ring lugs 62 are oriented under the projecting tabs 44, so that the paired aperture arrays 48 and 64 are coaxially aligned. The top hat cover 24 is placed over the interlocked portal mating surface 42 and backing plate 60, so that its array of top hat flange through holes 29 are coaxially aligned with the paired aperture arrays 48 and 64. As shown in
Although various embodiments that incorporate the teachings of the present invention have been shown and described in detail herein, those skilled in the art can readily devise many other varied embodiments that still incorporate these teachings. The invention is not limited in its application to the exemplary embodiment details of construction and the arrangement of components set forth in the description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.
