Abstract:
A ring seal apparatus for high temperature sealing includes a first ring including a pair of radial faces and a second ring including a second pair of radial faces, the second ring adapted to coact with the first ring. The first and second rings together define a pair of coacting mating faces. The mating faces are obliquely angled relative to the radial faces, such that each of the coacting mating faces is adapted to seal an interface of the two rings at an angle relative to their substantially parallel radial faces. The pair of coacting rings is adapted to seal a circumferential gap between a pair of components.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is 35 U.S.C. §371 U.S. National Stage filing of International Patent Application No. PCT/US13/32605 filed on Mar. 15, 2013, claiming priority to U.S. provisional Patent Application No. 61/707,514 filed on Sep. 28, 2012. 
    
    
     BACKGROUND OF THE DISCLOSURE 
     The present disclosure generally relates to sealing between cylindrical components having large radial and axial displacements Turbine engine seals are subject to relatively high and cyclic temperature conditions, ranging from atmospheric to 1600° F. The cyclic temperature variation results in expansions and contractions of parts, including radial and axial displacements of seals within their seats. Within the turbine engine environment, the temperature variation issue is compounded by a need to effectively seal between parts subject to high pressure differentials. 
     Within a combustion section of a commercial jet engine, a further sealing challenge as related to mid-turbine vanes is in sealing between surfaces that may not be symmetrically oriented relative to one another. For example, in sealing between a conical and a cylindrical surface, particularly where large radial and axial displacements occur, one current approach has been to use a piston ring for accommodating large axial deflections. However, such a ring may require a relatively thick section to provide fairly tall and robust rails in at least one of the relatively movable components in order to provide a groove for capturing the ring and to provide an axial seal face about a full circumference in view of very high and dynamically undulating axial loads and displacements encountered. Such a thick full-hoop section may be subjected to extremely high stresses under the large thermal gradients common to the internal environment of a gas turbine engine. 
     SUMMARY OF THE DISCLOSURE 
     In accordance with one aspect of the disclosure, a ring seal apparatus for high temperature sealing includes a first ring including a pair of radial faces, and a second ring including a second pair of radial faces substantially parallel to the first pair of radial faces, and the second ring is adapted to coact with the first ring. The first and second rings together define a pair of coacting mating faces obliquely angled relative to their radial faces, so that each of the mating faces is adapted to slide at an angle relative to the radial faces to seal an interface of the two rings at an angle relative to the radial faces. The pair of coacting rings is adapted to seal a circumferential gap between a pair of components. 
     In accordance with another aspect of the disclosure, a ring seal apparatus and axial support structure for high temperature sealing of a circumferential gap between a pair of components includes a first ring including a pair of radial faces, a second ring including a second pair of radial faces substantially parallel to the first pair of radial faces, the second ring adapted to coact with the first ring. The support structure is formed of a pair of axially spaced abutments adapted to axially retain the first and second rings. Together, the first and second rings define a pair of coacting mating faces. The mating faces are obliquely angled relative to the radial faces so that each of the mating faces is adapted to slide at an angle relative to the radial faces. The pair of coacting rings is adapted to seal a circumferential gap between a pair of components and the abutments are fixed to one of the aligned components. 
     In an additional and/or alternative embodiment of any of the foregoing embodiments, the first and second rings are axially positioned side-by-side so that the coacting mating faces slide relative to each other at an angle to the radial faces of the rings when the ring seal apparatus is subject to thermal expansion and vibration. 
     In an additional and/or alternative embodiment of any of the foregoing embodiments, the obliquely angled mating faces form a separate sealing interface between the first and second rings, in addition to the seal of the circumferential gap provided by the ring seal apparatus. 
     In an additional and/or alternative embodiment of any of the foregoing embodiments, the sealing interface between the first and second rings functions as a wedge to enhance radial sealing of the ring seal apparatus. 
     In an additional and/or alternative embodiment of any of the foregoing embodiments, the radial sealing of the ring seal apparatus is enhanced as a direct function of axial pressure between the coacting mating faces of the first and second rings. 
     In an additional and/or alternative embodiment of any of the foregoing embodiments, each of the first and second rings is a component sealing surface. 
     In an additional and/or alternative embodiment of any of the foregoing embodiments, each component sealing surface is defined by a rounded corner. 
     In an additional and/or alternative embodiment of any of the foregoing embodiments, at least three sealing contacts are established between the ring seal and the component surfaces when the seals are applied to asymmetrically oriented component surfaces. 
     In accordance with yet another aspect of the disclosure, a method of forming a ring seal apparatus includes providing a first ring having a pair of radial faces; forming a second ring having a second pair of radial faces substantially parallel to the first pair of radial faces, and providing that the second ring is adapted to coact with the first ring. The method further includes forming an obliquely angled face in each of the first and second rings to define a pair of coacting mating faces relative to the radial faces of each ring, such that each of the mating faces is adapted to slide at an angle relative to the radial faces. The method further includes juxtaposing the first and second rings axially side-by-side so that their coacting mating faces are adapted to seal a circumferential gap between asymmetrically aligned components. 
     In an additional and/or alternative embodiment of any of the foregoing embodiments, a method of forming a ring seal apparatus further includes providing a pair of abutments on one of the components to axially retain the first and second rings. 
     In an additional and/or alternative embodiment of any of the foregoing embodiments, a method of forming a ring seal apparatus further includes providing the pair of abutments such that they define a peripheral slot adapted to axially retain the rings. 
     In an additional and/or alternative embodiment of any of the foregoing embodiments, a method of forming a ring seal apparatus further includes forming rounded corners on each ring to define enhanced component sealing surfaces. 
     These and other aspects and features of the present disclosure will be better understood in light of the following detailed description when read in light of the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of a turbofan gas turbine engine. 
         FIG. 2  is a cross-sectional view of a portion of the view of  FIG. 1 . 
         FIG. 3  is a cross-sectional view of a prior art component. 
         FIG. 4  is a cross-sectional view of the disclosed radially coacting ring seal. 
     
    
    
     It should be understood that the drawings are not necessarily to scale and that the disclosed embodiments are sometimes illustrated diagrammatically and in partial views. It should be further understood that this disclosure is not limited to the particular embodiments illustrated herein. 
     DETAILED DESCRIPTION 
     Referring now to the drawings and with initial reference to  FIG. 1 , a cross-section of a turbofan gas turbine engine  10  is depicted. Intake air  12  (indicated by arrows) consists of an atmospheric airflow as may be required to support the successful operation of the gas turbine engine  10 . The intake air  12  is pulled into the gas turbine engine  10  by fan blades  14 , adapted to rotate within a fan case  16  on a multistage turbine shaft  15 . The intake air  12  may be split into two paths; a first path may be provided via a bypass duct  18 , which longitudinally and circumferentially encases the internal working components of the gas turbine engine  10 . The so-called bypass air flowing through the bypass duct  18  may be employed for producing additional thrust in modern turbofan jet engines, and as those skilled in the art may appreciate. 
     The second air path may be directed to and through an axial flow compressor  20 , commonly called a low-pressure stage compressor. From the low-pressure stage compressor  20 , the second air path may enter a high-pressure centrifugal compressor  22 , where the air may be further compressed and then pushed out through a diffuser  24  into a high-pressure air plenum  26 . 
     A plurality of combustors  30  may surround the multistage turbine shaft  15 ; the combustors  30  may be situated just radially inwardly of the bypass duct  18 . Each of the combustors  30  may be supplied fuel via fuel supply tubes  32 . The combustors  30  may be perforated with a plurality of apertures  36  to permit entry of high-pressure air into the combustors  30 . Ignition of the fuel takes place in the combustors  30 , and the products of combustion in the form of highly expansive gases pass through nozzle guide vanes  40  and then through turbines  42  to develop flight-sustaining thrust. 
     Referring now to  FIG. 2 , within the environment of high-pressure and high temperature gas flows, it may be necessary to seal between a turbine support case housing  44  and an outer shroud  52 , as shown. As shown in this prior art depiction, a single piece resilient sealing ring  48  may provide sealing between the inner surface  50  of the case housing  44  and the outer shroud  52 . For this purpose, a peripheral groove  46  has been employed for retention of the sealing ring  48 . 
     The single piece resilient sealing ring  48  has an outer extremity  54  which directly engages an inner surface  50  of the case housing  44 , as well as radial faces  56  adapted to engage mating faces of a pair of axial retention abutments  58 ,  60 . As will be appreciated, the axial retention abutments  58 ,  60  form the slot or peripheral groove  46  in which the seal  48  may be axially retained. 
     Referring now to  FIG. 3 , an enlarged view of such a prior art seal is depicted as seal  48 ′ along with its associated mating components, including retention abutments  58 ′ and  60 ′ within which the seal  48 ′ may be adapted to provide sealing between a turbine support case housing  44 ′ and an outer shroud  52 ′, as earlier described. It may be appreciated that any significant vibratory movements of the sealed components  44 ′ and  52 ′ may produce shifting and/or cocking of those components, which may at least occasionally challenge the capability of the seal  48 ′ to effectively maintain a full sealing effect. 
     Moreover, the overall sealing structure of the prior art seal  48 ′ has required a thickened full hoop region  55 ,  60  in either of the components  44 ′,  52 ′ (in this case component  44 ′) which may potentially give rise to problems due to the stress prone nature of significant thermal expansions and cyclic pressure fluctuations. Moreover, the full hoop region  55 ,  60  may be relatively expensive to manufacture. 
     Referring now to  FIG. 4 , a modified turbine support case housing  44 ″ may be employed to, among other benefits, avoid need for inclusion of the thickened full hoop region  55 ,  60  of the case housing  44 ′ of  FIG. 3 . More specifically, a radially coacting sealing ring  70  may incorporate an outer or upper sealing ring portion  72 , adapted to coact with a lower or inner sealing ring portion  74 . Each of the sealing ring portions  72 ,  74  may include an oblique sealing face, such as oblique sealing face  80  situated on portion  72 , and oblique sealing face  82  situated on portion  74 . The oblique sealing faces  80 ,  82  may be adapted to matingly coact, and to seal more effectively over a wider range of thermal displacements that include relatively wide vertical cyclic separations between the case housing  44 ″ and outer shroud  52 ″. 
     Region  66  (depicted as an arrow) is part of a high temperature combustion flow path. Region  68  (also depicted as an arrow) is a high-pressure cooler side of the case housing  44 ″. It may be appreciated that the high-pressure region  68  will tend to force the radially coacting sealing ring  70  to the right in the view shown, and that appropriate sizing of the outer diameter  76  of outer ring portion  72  relative to the case housing  44 ″ may be effective to create at least two circumferential sealing contact lines at all times i.e. between the ring portion  72  and between the inner diameter  64  of the case housing  44 ″ and the outer diameter  76  of the sealing ring portion  72 . Those skilled in the art will appreciate that a line sealing contact may be more effectively achieved via the rounded corner  86  which defines one edge of the outside diameter  76  of the sealing ring portion  72 . Such corner  86  may thus provide an enhanced component sealing surface. 
     In addition, the inner diameter  78  of the inner or lower sealing ring portion  74  may be sized to sealingly engage the outside diameter  62  of the outer shroud  52 ″. As in the case of the outer diameter of ring portion  72 , the inner diameter  78  of the ring portion  74  may also include rounded corners  88  to accommodate cocking and other asymmetric movements of the case housing  44 ″ and outer shroud  52 ″ components relative to one another. Such movements between components may be associated with extreme thermal variations, as well as actual temperature gradients, across the parts/components, as well as other factors including extreme turbulence, for example. 
     The coacting mating oblique sealing faces  80 ,  82 , combined with a sealing design adapted to more effectively accommodate larger vertical separations between the housing and shroud components  44 ″ and  52 ″, in environments of considerable vibration and temperature fluctuations that may result in expansion of parts, including that of the radially coacting sealing ring  70 , may promote an inherently better sealing arrangement, particularly since sealing contacts are established between the ring seal and the component surfaces when the seals are applied to asymmetrically oriented component surfaces. 
     In the disclosed embodiment, the sealing ring  70  may have each of its respective portions  72  and  74  formed of high temperature alloys, such as, but not limited to, Nickel, Inconel, e.g. Inconel 718 and Inconel 750, for example, and/or other metallurgical structures that exhibit great durability and strength at temperatures that may reach or its exceed 1600° F. 
     INDUSTRIAL APPLICABILITY 
     From the foregoing, it may be appreciated that the technology disclosed herein has industrial applicability in a variety of settings such as, but not limited to sealing vertical gaps or radial separation spaces between shrouds and case housing environments within a jet engine. However, from the foregoing, it may also be noted that the teachings of this disclosure may find industrial application in any number of different situations, including but not limited to, turbine engines. Such engines may be used, for example, on aircraft for generating thrust, or in land, marine, or aircraft applications for generating power. 
     The disclosure provides an effective and reliable radially coacting sealing ring structure for a turbine engine that may be used to seal a circumferential space between a turbine support case housing and an outer shroud as described herein. To the extent that each of the seal portions may be adapted to be positioned in relatively axial side-by-side positions with respect to the other for both radial and axial interaction via their obliquely angled mating surfaces, each of the rings may be sized and adapted to more closely engage the respective components to be sealed. As such, one of the ring portions may be adapted to seal radially on its outside diameter more closely with one of the cylindrical and/or conical components, while the other of the ring seals may be adapted to seal radially on its inside diameter more closely with the other component. Finally, to the extent that a high-pressure region may exist on one side of the pair of sealing portions, the obliquely angled mating surfaces of the sealing portions may provide a sealing interface between the rings to function as a wedge for enhancement of radial sealing as a function of axial pressure between the rings seal portions. 
     While the foregoing detailed description has been provided with respect to certain specific embodiments, it is to be understood that the scope of the disclosure should not be limited to such embodiments, but that the same are provided simply for enablement and best mode purposes. The breadth and spirit of the present disclosure is broader than the embodiments specifically disclosed and encompassed within the claims appended hereto.