Abstract:
A resilient ring for sealing between an inner housing surface of revolution and a coaxial outer housing surface of revolution, one of the housing surfaces being a sloped surface with a sloped profile intersecting an axially extending plane and the other housing surface being an axial abutment surface in a substantially radially extending plane. The ring has a circumferential sealing surface for sealing engagement of the ring with the sloped housing surface, and a planar abutment surface for sealing engagement of the ring with the axial abutment housing surface.

Description:
TECHNICAL FIELD 
   The invention relates to use of a single diametrically energized ring to seal between an axially sloped housing surface and an axial abutment housing surface, particularly in the assembly of a gas turbine engine. 
   BACKGROUND OF THE ART 
   A piston ring assembly is used in assembling together components of the gas turbine engine usually where there is a pressure differential between the sealed components or the pressure differential alternates. 
   It will be understood that the invention relates to sealing of any housing components with a pressure differential while accommodating relative axial movement and simultaneous radial movement between the two components. 
   For example, in gas turbine engines that are assembled of numerous coaxial housings and components that require sealing between them, axial and radial motion occurs due to thermal expansion and contraction and due to resilient movement under pressure differential. An example is the conventional sealing between a turbine support case and a vane ring outer shroud. Conventionally, (as shown in FIG.  2  and discussed further below) a sealing ring has a generally triangular cross-section and is used to seal against two orthogonal surfaces sealing both axially and radially. A second inner ring acts as a resilient energizer to apply a resilient biasing force exerted against the triangular sealing ring to maintain the seal. The tension or compression in the energizing ring expands or contracts to wedge between the vane ring and the conical surface of the triangular ring thereby forcing the triangular ring against the axial mating surface and the radial surface in a sealing engagement. The turbine support case generally has a cylindrical sealing surface and the vane ring includes a circumferential groove with axial sealing surface and an axial abutment face against which the energizing ring reacts. 
   A disadvantage of this conventional arrangement is the requirement to manufacture and assemble two rings in order to accommodate the assembly tolerances, thermal expansion and contraction, as well as displacements caused by any pressure differential. Sealing rings of this type are often replaced during engine overhauls and since the rings are often made from castings to provide better creep properties, the cost of replacing such rings is significant. 
   It is an object of the invention to provide a low cost piston ring sealing arrangement that can be utilized for newly constructed engines or as a retrofit during regular engine maintenance. 
   Further objects of the invention will be apparent from review of the disclosure, drawings and description of the invention below. 
   DISCLOSURE OF THE INVENTION 
   The invention provides a resilient ring and method for sealing between an inner housing surface of revolution and a coaxial outer housing surface of revolution, one of the housing surfaces being a sloped surface with a sloped profile intersecting an axially extending plane and the other housing surface being an axial abutment surface in a substantially radially extending plane. The ring has a circumferential sealing surface for sealing engagement of the ring with the sloped housing surface, and a planar abutment surface for sealing engagement of the ring with the axial abutment housing surface. 

   
     DESCRIPTION OF THE DRAWINGS 
     In order that the invention may be readily understood, embodiments of the invention are illustrated by way of example in the accompanying drawings. 
       FIG. 1  is an axial cross-section view through a turbofan gas turbine engine showing general layout of the conventional components and in particular showing a vane ring  10  adjacent to the combustor  8  to which the example provided herein is directed. 
       FIG. 2  shows a detailed axial cross-sectional view through the vane ring showing conventional prior art triangular shaped ring with axial and radial sealing surfaces and an energizing ring disposed in a peripheral groove in the vane ring. 
       FIG. 3  shows a first embodiment of the sealing ring according to the invention with a sloped profile diametrically energized radially outwardly against a sloped surface of the outer housing and retained within the axially abutting surfaces of a groove in the vane ring. 
       FIG. 4  shows a second embodiment of the sealing ring according to the invention with a cusped or peaked profile diametrically energized radially outwardly against the sloped surface of the outer housing. 
       FIG. 5  is an axial cross-sectional view showing a third embodiment of the invention with a sloped conical sealing profile energized diametrically radially inwardly to seal against a sloped conical surface of the housing and an axial surface simultaneously. 
       FIG. 6  is an isometric view of the ring of  FIG. 4  showing details of the circumferential lap joint. 
     FIGS.  7 ( a )-( f ) show alternative profiles for the ring in sectional views along line  7 — 7  of FIG.  6 . 
     Further details of the invention and its advantages will be apparent from the detailed description included below. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1  shows an axial cross-section through a typical turbofan gas turbine engine. It will be understood however that the invention is equally applicable to any type of engine with a combustor and turbine section such as a turbo shaft, a turboprop, auxiliary power unit, gas turbine engine or industrial gas turbine engine. Air intake into the engine passes over fan blades  1  in a fan case  2  and is then split into an outer annular flow through the bypass duct  3  and an inner flow through the low-pressure axial compressor  4  and high-pressure centrifugal compressor  5 . Compressed air exits the compressor  5  through a diffuser  6  and is contained within a plenum  7  that surrounds the combustor  8 . Fuel is supplied to the combustor  8  through fuel tubes  9  which is mixed with air from the plenum  7  when sprayed through nozzles into the combustor  8  as a fuel air mixture that is ignited. A portion of the compressed air within the plenum  7  is admitted into the combustor  8  through orifices in the side walls to create a cooling air curtain along the combustor walls or is used for cooling to eventually mix with the hot gases from the combustor and pass over the nozzle guide vane  10  and turbines  11  before exiting the tail of the engine as exhaust. It will be understood that the foregoing description is intended to be exemplary of only one of many possible configurations of an environment or application suitable for incorporation of the present invention. 
   The embodiments of the invention described herein are in respect of a sealing ring  19  applied to seal the nozzle guide vane  10  with its outer shroud to the surrounding turbine support case. It will be understood however that the invention may be applied to many other areas of the gas turbine engine or any combination of a sloped and an axial abutment surface requiring sealing against a pressure differential, while accommodating thermal expansion and contraction, with simultaneous axial and radial displacements. 
     FIG. 2  shows the prior art arrangement including the nozzle guide vane  10  which is immediately downstream of the combustor  8 . The nozzle guide vane  10  includes an outer shroud  12  and an inner shroud  13  between which the air foil vanes extend to create the vane ring. The outer shroud  12  engages the turbine support case housing  14 , which as can be seen in  FIG. 1  performs the function of supporting the downstream components. 
   The outer shroud  12  includes a peripheral groove  15  having an upstream and a downstream axial abutment surfaces between which the sealing ring  16  and the energizing ring  17  are resiliently housed. The conventional sealing ring  16  and the energizing ring  17  seal simultaneously against the upstream axial abutment face of the peripheral groove  15  and the cylindrical inner face  18  of the turbine support case housing  14 . The sealing ring  16  simultaneously acts to seal the surface of the peripheral groove  15  and the cylindrical face  18  sealing both axially and radially against pressure differentials while accommodating relative thermal expansion and contraction and any flexural displacement due to the pressure differential. The prior art energizing ring  17  illustrated is resiliently biased radially outwardly causing it to expand and wedge between the downstream radially extending axial abutment face of the groove  15  and push against the conical or hypotenuse inner surface of the sealing ring  16  forcing the sealing ring  16  against the adjacent axial and radially extending mating surfaces. 
   As well known to those skilled in the art, the area immediately adjacent the combustor  8  and nozzle guide vane  10  experiences dramatic thermal fluctuations, vibration and relative movement between components. During engine overhauls the rings  16  and  17  are often replaced. Since these rings  16  and  17  are often formed by casting in order to provide improved creep properties, the cost of these rings  16  and  17  can be significant. 
     FIG. 3  shows a first embodiment of the invention which provides a radially energized resilient ring  19  for sealing between a sloped conical inner housing surface of revolution  20  of the turbine support case housing  14  and the coaxial axial abutment housing surface  21  within the peripheral groove  15 . The outwardly energized resilient ring  19  has a sloped ring surface  24  that is adapted for sealing engagement with the sloped housing surface  20  and also has an axial abutment ring surface  23  adapted for sealing engagement against the axial abutment housing surface  21 .  FIG. 6  shows the ring  19  in an isometric view to illustrate details of the lap joint  22  and further shows details of the radially extending axial abutment ring surface  23  and the sloped ring surface  24 . 
   As illustrated in  FIG. 6 , the circumferential expansion lap joint  22  has overlapping surfaces that provide sufficient sealing for resisting pressure differentials while providing the ring  19  with an outwardly directed radially energized resilience that is sufficient to exert pressure against the sloped housing surface  20 . Due to the sloped inclined surface  20 , interacting with the sloped ring surface  24 , an axially directed forward force also develops to exert axial pressure against the radially extending axial abutment housing surface  21 . The rings  19  may be constructed as cast or forged metal rings of nickel, for example. Any suitable material and manufacturing method may be used. As shown in  FIG. 4 , in a second embodiment a cusped sealing surface  25  may be adopted such that a single point of contact along the cusp is provided for sealing. FIGS.  7 ( a )-( d ) also shows variations in the shape of the sloped sealing surface including a conical surface  24 , a cusped surface  25 , a curved surface  26  and an arcuate surface  27 . 
     FIG. 5  shows an alternate third embodiment where the resilient ring  19  is radially energized to exert a radially inward force against the sloped housing surface  20  with the sloped ring surface  24 . As a result of the interaction between the sloped surfaces  20  and  24  an axially directed force is developed and the radially extending axial abutment ring surface  23  exerts an axially rearward pressure against the axial abutment housing surface  21 . 
     FIG. 6  shows a circumferentially sliding lap joint  22 . However other expansion joints are equally applicable such as a circumferentially sliding beveled joint (not shown). 
   Therefore, the invention provides the advantage of a single diametrically energized piston ring  19  that can be used to replace the relatively complex sealing ring  16  and energizing ring  17  of the prior art shown in FIG.  2 . Further, the rings  19  of the invention can be used to seal any static component provided one has a sloped surface and the other has a radially extending axial abutment face as illustrated in the example shown in  FIGS. 3-5 . The single ring  19  can accommodate axial and radial movement between the components and maintain a seal between two adjacent cavities or plenums across a pressure differential. 
   Although the above description relates to specific preferred embodiments as presently contemplated by the inventor, it will be understood that the invention in its broad aspect includes mechanical and functional equivalents of the elements described herein.