Abstract:
A runner assembly for a circumferential seal assembly includes a runner defined about an axis. The runner has an inwardly extending runner mounting flange. A radially flexible clamp is engaged with the inwardly extending mounting flange. An axial spring is trapped between an axial retainer and the runner. The runner, the radially flexible clamp, the axial spring, and the axial retainer are co-rotatable about the axis. The axial retainer is radially inline with the runner and spaced from a radially inner surface of the runner such that there is a radial gap between the axial retainer and the radially inner surface of the runner permitting radial movement of the runner.

Description:
BACKGROUND 
     The present disclosure relates to circumferential seals, and in particular, to a circumferential seal having a ceramic runner for gas turbine engines. 
     Seal systems with ceramic circumferential runners are often used in the high temperature environment of gas turbine engines where rotational structure extends through stationary structures, for example, to seal mainshaft bearing compartments. The runner is mounted to the rotational structure such as the engine shaft through a flexible mount structure and ride upon a rotationally stationary carbon seal. 
     A primary challenge to utilization of ceramic runners within a circumferential seal is the flexible mount structure. 
     SUMMARY 
     A runner assembly for a circumferential seal assembly according to an exemplary aspect of the present disclosure includes a runner defined about an axis of rotation, the runner having an inwardly extending runner mounting flange adjacent to a distal end of the runner. A radially flexible clamp is engaged with the inwardly extending mounting flange. An axial retainer which traps an axial spring between the axial retainer and the runner. 
     A runner assembly for a circumferential seal assembly according to an exemplary aspect of the present disclosure includes a runner defined about an axis of rotation, the runner having an inwardly extending runner mounting flange adjacent to a distal end of the runner. An axially flexible clamp engaged with the distal end of the runner and a radially flexible clamp engaged with the inwardly extending mounting flange. 
     A runner assembly for a circumferential seal assembly according to an exemplary aspect of the present disclosure includes a runner defined about an axis of rotation, the runner having an inwardly extending runner mounting flange adjacent to a distal end of the runner. A radially flexible clamp includes a radially inwardly extending flange at one end section and an axially extending lip at an opposite end section connected by a radial flex arm, the axially extending lip engaged with the distal end of said runner. An axial retainer engaged with said inwardly extending runner mounting flange. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various features will become apparent to those skilled in the art from the following detailed description of the disclosed non-limiting embodiment. The drawings that accompany the detailed description can be briefly described as follows: 
         FIG. 1  is a schematic cross-section of a gas turbine engine; 
         FIG. 2  is an enlarged sectional view of a section of the gas turbine engine which illustrates a circumferential seal assembly; 
         FIG. 3  is an enlarged sectional view of a circumferential seal assembly according to one non-limiting embodiment of the present disclosure; 
         FIG. 4  is an enlarged sectional view of a circumferential seal assembly according to another non-limiting embodiment of the present disclosure; 
         FIG. 5  is an enlarged sectional view of a circumferential seal assembly according to another non-limiting embodiment of the present disclosure; 
         FIG. 6  is an enlarged sectional view of a circumferential seal assembly according to another non-limiting embodiment of the present disclosure; and 
         FIG. 7  is an enlarged sectional view of a circumferential seal assembly according to another non-limiting embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  schematically illustrates a gas turbine engine  20 . The gas turbine engine  20  is disclosed herein as two-spool turbofan that generally incorporates a fan section  22 , a compressor section  24 , a combustor section  26  and a turbine section  28 . Alternative engines might include an augmentor section (not shown) among other systems or features. The fan section  22  drives air along a bypass flowpath while the compressor section  24  drives air along a core flowpath for compression and communication into the combustor section. Although depicted as a turbofan gas turbine engine in the disclosed non-limiting embodiment, it should be understood that the concepts described herein are not limited to use with turbofans as the teachings may be applied to other types of turbine engines. 
     The engine  20  generally includes a low speed spool  30  and high speed spool  32  mounted for rotation about an engine central longitudinal axis A relative to an engine static structure  36  via several bearing systems  38 . The low speed spool  30  generally includes an inner shaft  40  that interconnects a fan  42 , a low pressure compressor  44  and a low pressure turbine  46 . The inner shaft  40  may drive the fan  42  either directly or through a geared architecture  48  to drive the fan  42  at a lower speed than the low speed spool  30 . The high speed spool  32  includes an outer shaft  50  that interconnects a high pressure compressor  52  and high pressure turbine  54 . A combustor  56  is arranged between the high pressure compressor  52  and the high pressure turbine  54 . The inner shaft  40  and the outer shaft  50  are concentric and rotate about the engine central longitudinal axis A which is collinear with their longitudinal axes. 
     Core airflow is compressed by the low pressure compressor  44  then the high pressure compressor  52 , mixed with the fuel in the combustor  56 , then expanded over the high pressure turbine  54  and low pressure turbine  46 . The turbines  54 ,  46  rotationally drive the respective low speed spool  30  and high speed spool  32  in response to the expansion. 
     With reference to  FIG. 2 , the main engine shafts  40 ,  50  extend through several engine compartments B, C and are supported at a plurality of points by the bearing system  38  and the static structure  36 . Various types of bearing systems  38  are known for such a purpose. 
     A circumferential seal assembly  60  ensures that the shafts  40 ,  50  are sealed at several points to prevent unwanted fluid leakage between, for example, engine compartments B, C. Circumferential seals are widely used in gas turbine engines for sealing of mainshaft bearing compartments where, for example, bearing lubrication oil in the bearing compartment must be separated from cooling compartments. The category of circumferential seals includes, but not limited to, mechanical sealing technologies commonly referred to as segmented circumferential contacting seals, archbound circumferential seals, and controlled-gap seals. 
     The circumferential seal assembly  60  generally includes a stator seal assembly  62  mounted to the static structure  36  and a runner assembly  64  mounted to a rotating component such as the main engine shafts  40 ,  50 . This disclosure is directed to the runner assembly  64  such that the stator seal assembly  62  is not within the scope of the disclosure and may be of various forms. 
     The stator seal assembly  62  typically supports a carbon sealing ring  66 . The carbon sealing ring  66  has a radially inwardly facing curved surface  68  upon which a runner  70  of the runner assembly  64  runs. The runner  70  defines a radially outward facing curved sealing surface  72  which engages the radially inwardly facing curved surface  68  to control fluid leakage therebetween. 
     With reference to  FIG. 3 , the runner  70  is supported upon a retainer assembly  74 . The runner  70  is manufactured of a structural ceramic material while the retainer assembly  74  may be manufactured of metallic material such as a steel alloy. The thermal growth of the ceramic material is low due to its low coefficient of thermal expansion. The mechanical radial growth due to centrifugal forces is also low due to the high stiffness-to-weight ratio of the ceramic material. Thus, the runner  70  closely tracks the carbon sealing ring  66  to provide a more constant gap therebetween throughout the entire operating envelope of the engine  20 . The retainer assembly  74  provides a relatively simple and cost effective resilient mount for the ceramic runner  70 . 
     At one axial end section, the runner  70  may include an optional radially outward extending flange  76  which operates as an oil slinger. At this same axial end section, the runner  70  has a radially inwardly extending mounting flange  78  adapted to receive a clamping load. 
     In one non-limiting embodiment, the retainer assembly  74  generally includes a radially flexible clamp  80 , an axial retainer  82  and an axial spring  84  which provides the clamping load. In this non-limiting embodiment, the radially inwardly extending mounting flange  78  is located at a distal end  70 D of the runner  70 . 
     The radially flexible clamp  80  includes a cylindrical portion  80 A having a radially inwardly extending flange  80 F at one end section, and a radially outwardly extending lip  80 L at an opposite end section. The length and thickness of the cylindrical portion  80 A may be selected to impart a desired radial flexibility to the radially flexible clamp  80 . That is, the cylindrical portion  80 A operates as a cantilevered beam rigidly fixed at the flange  80 F by, for example, a spacer  86  or other axial stop, which interfaces with other structures (not shown). 
     The axial retainer  82  traps the axial spring  84  between the axial retainer  82  and the distal end  70 D of the runner  70 . The axial spring  84  may be an annular member, such as a wave spring, a belville washer, or other element that imparts an axial bias to the runner  70  such that axial loads thereon are absorbed with minimal impact loads to the runner  70 . That is, the axial retainer  82  traps the axial spring  84  to accommodate axial movement and provide a clamping load while the axial retainer  82  is essentially a stop to retain the axial spring  84 . 
     With reference to  FIG. 4 , another non-limiting embodiment of a retainer assembly  174  generally includes a radially flexible clamp  180 , an axial retainer  182  and an axial spring  184  which provides the clamping load to the inwardly extending mounting flange  178 . In this non-limiting embodiment, the radially inwardly extending mounting flange  178  is located axially inboard of a distal end  170 D of the runner  170 . 
     The axial retainer  182  is offset from a radially inwardly facing curved surface  1701  of the runner  170  by a radial gap to permit an envelope for radial movement of the runner  170  through the radially flexible clamp  180 . The location of the radially inwardly extending mounting flange  178  facilitates an axial displacement of the retainer assembly  174  inboard of the distal end  170 D to reduce axial packaging space. 
     With reference to  FIG. 5 , another non-limiting embodiment of a retainer assembly  274  generally includes a radially flexible clamp  280 , and an axially flexible clamp  282  which provides the clamping load to the runner  70 . 
     The radially flexible clamp  280  is generally similar to that described in the  FIG. 4  embodiment, while the axially flexible clamp  282  integrates the axial spring function therein. The axially flexible clamp  282  includes a conical cylindrical portion  282 A having a radially inwardly extending flange  282 F at one end section, and a radially outwardly extending lip  282 L at the opposite end section. The cone angle, wall thickness, and length of the conical cylindrical portion  282 A may be selected to impart a desired axial force to the runner  70 . 
     With reference to  FIG. 6 , another non-limiting embodiment of a retainer assembly  374  generally includes a radially flexible clamp  380 , and an axially flexible clamp  382  which provides a clamping load on runner  70 . 
     The axially flexible clamp  382  is generally similar to that described in the  FIG. 5  embodiment. The radially flexible clamp  380  is in an opposed position relative to the spacer  392 . The radially flexible clamp  380  is on one side of the spacer  392  while the axially flexible clamp  382  is on the other side to trap the spacer  392  therebetween. 
     The radially flexible clamp  380  includes a conical cylindrical portion  380 A having a radially inwardly extending flange  380 F at one end section, and a radially outwardly extending lip  380 L at the opposite end section. An axially extending shelf  380 S extends toward the axially flexible clamp  382  to support the inwardly extending mounting flange  78  and provide a cantilevered beam to radially support the runner  70 . The cone angle, length, and thickness of the conical cylindrical portion  380 A may be selected to impart radial flexibility while the radially outwardly extending lip  380 L operates as stop to react the force applied by the axially flexible clamp  382 . 
     The axially flexible clamp  382  includes a conical cylindrical portion  382 A having a radially inwardly extending flange  382 F at one end section, and a radially outwardly extending lip  382 L at the opposite end section. The cone angle and the wall thickness of the conical cylindrical portion  382 A may be selected to impart a desired axial force to the runner  70 . 
     With reference to  FIG. 7 , another non-limiting embodiment of a retainer assembly  474  generally includes a flexible clamp  480  and an axial retainer  482 . The flexible clamp  480  and the axial retainer  482  are in an opposed position relative to a spacer  492  generally similar to that describe above in the  FIG. 6  embodiment. 
     The axial retainer  482  in one non-limiting embodiment is a cylindrical ring which axially supports the runner  70  through interaction with the inwardly extending mounting flange  78 . That is, the axial retainer  482  operates as a stop. 
     The flexible clamp  480  includes a radially inwardly extending flange  480 F at one end section and an axially extending lip  480 L at the opposite end section connected by a radial flex arm  480 A. That is, the radially inwardly extending flange  480 F and the flex arm  480 A essentially define a cylindrical plate with a relatively thicker inner diameter which defines the radially inwardly extending flange  480 F and a relatively thinner outer diameter which defines the flex arm  480 A. The length, thickness and cone angle of the flex arm  480 A may be selected to impart the desired axial flexibility and operates as an integral axial spring through the axially extending lip  480 L which abuts a distal end  70 D of the runner  70 . 
     An axially extending shelf  480 S axially extends toward the axial retainer  482  to support the inwardly extending mounting flange  78  and operates as a cantilevered beam to radially support the runner  70 . The axially extending shelf  480 S may extend from the interface between the radially inwardly extending flange  480 F and the flex arm  480 A generally parallel to the axially extending lip  480 L. The length and thickness of the axially extending shelf  480 S may be selected to impart the desired radial flexibility. 
     It should be understood that like reference numerals identify corresponding or similar elements throughout the several drawings. It should also be understood that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit herefrom. 
     Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present invention. 
     The foregoing description is exemplary rather than defined by the limitations within. Various non-limiting embodiments are disclosed herein, however, one of ordinary skill in the art would recognize that various modifications and variations in light of the above teachings will fall within the scope of the appended claims. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced other than as specifically described. For that reason the appended claims should be studied to determine true scope and content.