Abstract:
A bearing assembly for a gas turbine engine rotor includes a damper bearing configured to support the rotor, a bearing centering sub-assembly configured to position the damper bearing relative to the rotor, and a retainer. The damper bearing includes a frame that defines a bearing bore, an inner race, and an outer race, said inner and outer races within said bearing bore. The bearing centering apparatus sub-assembly includes a plurality of first springs and a plurality of second springs. The retainer is coupled to the bearing housing and is configured to maintain an axial position of the bearing outer race with respect to the support structure.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This application relates generally to gas turbine engine rotor assemblies and, more particularly, to bearing assemblies for gas turbine engine rotor assemblies.  
           [0002]    Gas turbine engines typically includes a fan rotor assembly, a compressor, and a turbine. The fan rotor assembly includes a fan including an array of fan blades extending radially outward from a rotor shaft. The rotor shaft transfers power and rotary motion from the turbine to the compressor and the fan, and is supported longitudinally with a plurality of bearing assemblies. Bearing assemblies support the rotor shaft and typically include rolling elements located within an inner race and an outer race.  
           [0003]    Additionally, at least some known damper bearing assemblies include a plurality of springs attached between the bearing outer race and a mounting flange. The springs support the bearing and act as an antirotation device that substantially prevents the bearing outer race from rotating with respect to a bearing support. Because the strength and effectiveness of the antirotation device is limited by the stiffness requirement of the bearing support, at least some known bearing supports include a catcher device that is coupled to the bearing assembly to substantially limit aft movement of the bearing outer race with respect to the bearing support if high dynamic loading is induced into the bearing assembly.  
           [0004]    At least some known damper bearing assemblies are positioned within sumps, and space limitations within the sump do not enable a catcher device to be coupled to the bearing assembly without expensive design modifications. Furthermore, because such bearing assemblies are positioned in the sumps, such assemblies may be exposed to high operating temperatures and soakback conditions, and thus may require costly seal assemblies to facilitate preventing sump oil leakage.  
         BRIEF DESCRIPTION OF THE INVENTION  
         [0005]    In one aspect a method for assembling a gas turbine engine rotor assembly is provided. The engine includes a rotor shaft and a bearing assembly that includes an annular damper bearing and an annular spring. The method comprises forming at least one groove that is defined within and extends partially circumferentially around at least one of the annular damper and the annular spring, supporting the rotor shaft with the annular spring, and coupling the annular damper bearing to the annular spring using the at least one groove such that the spring extends circumferentially between the damper bearing and the rotor shaft.  
           [0006]    In another aspect of the invention, a bearing assembly for a gas turbine engine rotor is provided. The bearing assembly includes an annular spring and an annular damper bearing. The annular spring is configured to support the gas turbine engine rotor. The annular damper bearing is concentrically aligned with the annular spring, and is radially outward from said annular spring, such that the damper bearing supports the spring. At least one of the damper bearing and the spring includes at least one groove defined therein. At least one of the damper bearing and the spring includes a retainer extending therefrom. The at least one groove is sized to receive the retainer therein for coupling the damper bearing to the spring.  
           [0007]    In yet a further aspect, a rotor assembly is provided. The rotor assembly includes a rotor shaft and a bearing assembly. The bearing assembly supports the rotor shaft, and includes an annular damper bearing and an annular spring. The damper bearing extends circumferentially around the spring such that the spring is between the damper bearing and the rotor shaft. At least one of the damper bearing and the spring includes at least one groove defined therein for slidably coupling the damper bearing to the spring.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is schematic illustration of a gas turbine engine;  
         [0009]    [0009]FIG. 2 is a cross-sectional view of a rotor assembly that may be used in the gas turbine engine shown in FIG. 1;  
         [0010]    [0010]FIG. 3 is a partial perspective view of an exemplary unassembled bearing assembly used with the rotor assembly shown in FIG. 2; and  
         [0011]    [0011]FIG. 4 is a partial perspective view of the bearing assembly shown in FIG. 3 in an assembled configuration. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0012]    [0012]FIG. 1 is a schematic illustration of a gas turbine engine  10  including a fan assembly  12 , a high pressure compressor  14 , and a combustor  16 . Engine  10  also includes a high pressure turbine  18 , a low pressure turbine  20 , and a booster  22 . Fan assembly  12  includes an array of fan blades  24  extending radially outward from a rotor disc  26 . Engine  10  has an intake side  28  and an exhaust side  30 .  
         [0013]    In operation, air flows through fan assembly  12  and compressed air is supplied to high pressure compressor  14 . The highly compressed air is delivered to combustor  16 . Airflow (not shown in FIG. 1) from combustor  16  drives turbines  18  and  20 , and turbine  20  drives fan assembly  12 .  
         [0014]    [0014]FIG. 2 is a cross-sectional view of an exemplary embodiment of a rotor assembly  40  that may be used with a gas turbine engine, such as engine  10  shown in FIG. 1. FIG. 3 is a partial perspective view of an exemplary unassembled bearing assembly  42  that may be used with rotor assembly  40 , and FIG. 4 is a partial perspective view of bearing assembly  42  shown in an assembled configuration. In one embodiment, the gas turbine engine is an LMX 7000 available from General Electric Company, Cincinnati, Ohio. Rotor and bearing assembly  40  includes a rotor shaft  44  which supports an array of fan blades  24  (shown in FIG. 1) that extend radially outward from rotor disc  26 . Rotor shaft  44  is rotatably secured to a structural support frame  46  with a plurality of bearing assemblies  42  that support rotor shaft  44 . In the exemplary embodiment, bearing assembly  42  is a damper bearing assembly, and support frame  46  is a sump housing.  
         [0015]    Bearing assembly  42  includes a paired race  50  and a rolling element  52 , positioned within a sump  53  radially bounded by shaft  44  and housing  46 . Paired race  50  includes an outer race  54  and an inner race  56  that is radially inward from outer race  54 . Rolling element  52  is located between inner race  56  and outer race  54 . Outer race  54  is formed integrally with a plurality of spring fingers  58 , such that a face  60  of outer race  54  is positioned in rollable contact with rolling element  52 . Spring fingers  58  are spaced circumferentially around shaft  44 . In an alternative embodiment, fingers  58  are coupled to outer race  54 .  
         [0016]    Outer race  54  includes a pair of annular grooves  70  and  72  that are defined in a radially outer surface  74  of outer race  54 . More specifically, grooves  70  and  72  extend radially inwardly from spring finger member outer surface  74  and are positioned respectively upstream and downstream from an upstream side  76  and a downstream side  78  of outer race  54 .  
         [0017]    Outer race  54  also includes at least one retainer groove  80  that extends radially inwardly from outer surface  74 , such that retainer groove  80  is aligned substantially perpendicularly to an axis of rotation of rotor assembly  40 . In one embodiment, groove  80  is formed by machining. Retainer groove  80  is arcuate and extends only partially circumferentially around spring finger member  58 . More specifically, retainer groove  80  is positioned between groove  70  and an upstream edge  84  of outer race  54 , such that retainer groove  70  is a distance  86  from member edge  84 . In the exemplary embodiment, outer race  54  includes a pair of identical grooves  80  that are oppositely positioned and are offset from each other by approximately 180°. In an alternative embodiment, race  54  includes more than two grooves  80 .  
         [0018]    Each groove  80  has a width  88 , and an arcuate length  90  that is measured between a stop edge  92  and an entrance slot  94 . Entrance slot  94  extends partially circumferentially from groove  80 , and is radially aligned with respect to groove  80 . In one embodiment, slot  94  is formed by machining. More specifically, entrance slot  94  is aligned substantially perpendicularly to the axis of rotation of rotor assembly  40 , and has an arcuate length  96  measured between groove  80  and a stop edge  98 . Entrance slot  94  extends aftward from member upstream edge  84  to an aft wall  112  that defines an aft wall of both groove  80  and slot  94 . Accordingly, a width  114  of entrance slot  94  is larger than groove width  88 .  
         [0019]    An annular damper bearing  120  is positioned radially outwardly from outer race  54  such that a gap  122  is defined between a radially inner surface  124  of damper bearing  120  and outer race surface  74 . Damper bearing  120  includes an upstream side  126  and a downstream side  128 . In the exemplary embodiment, edge  128  includes a plurality of openings  130  extending therethrough for receiving fasteners (not shown) for coupling damper bearing  120  to housing  44 . Damper bearing  120  also includes a seal member  132  that is integrally formed with damper bearing  120  and mates with seal teeth  134  extending from a rotating air/oil seal.  
         [0020]    Damper bearing  120  is coupled to spring finger member  58  by a pair of identical retainers  140  that each extend radially inwardly from damper bearing  120 , such that each retainer  140  defines a portion of gap  122 . In the exemplary embodiment, retainers  140  are formed integrally with damper bearing  120 . In an alternative embodiment, retainers  140  are coupled to damper bearing  120 . More specifically, each retainer  140  extends radially inwardly from damper bearing upstream edge  126  such that an inner edge  142  of each retainer  140  is a distance  144  from damper bearing radially inner surface  124 . In the exemplary embodiment, retainers  140  are offset from each other by approximately 180°.  
         [0021]    Each retainer  140  has an arcuate length  146  that is smaller than groove arcuate length  90  and slot arcutate length  96 . Additionally, each retainer  140  has a thickness  150  that is slightly smaller than groove width  88 . In an alternative embodiment, damper bearing  120  includes more than two retainers  140 .  
         [0022]    A sleeve damper  160  is positioned between damper bearing  120  and outer race  54 . Specifically, sleeve damper  160  is annular and extends aftward from retainers  140  through gap  122  between spring finger member  58  and damper bearing  120 . Sleeve damper  160  includes an annular alignment lip  162  that extends radially outwardly from damper downstream side  128 .  
         [0023]    During assembly of rotor assembly  40 , outer race  54  is positioned circumferentially around shaft  44  such that shaft  44  is rotatably coupled to outer race  54 . Sleeve damper  160  is then positioned circumferentially around outer race  54 . Damper bearing  120  is then positioned upstream from outer race  54  such that retainers  140  are aligned substantially circumferentially with respect to outer race entrance slots  94 , as shown in FIG. 3. Damper bearing  120  is then guided aftward and coupled to sump housing  44  such that retainers  140  are received within entrance slots  94 . Outer race  54  is then rotated such that retainers  140  are circumferentially guided into grooves  80  and secured using fasteners that extend through openings  130 . When retainers  140  are fully received within grooves  80 , as shown in FIG. 4, because a tight tolerance is defined between grooves  80  and retainers  140 , grooves  80  facilitate retaining damper bearing  120  being coupled to outer race  54 .  
         [0024]    During engine operation, springs  58  facilitate supporting bearing assembly  42  such that shaft  46  is substantially centered within outer race  54  with a desired radial stiffness. However, due to damper radial clearance, an engine unbalance may cause outer race  54  to orbit within housing  46 . The orbiting produces a torque through springs  58  called harmonic drive. Retainers  140  facilitate preventing springs  58  and outer race  54  from deflecting above a yield limit of the material used in fabricating springs  58  and outer race  54 . More specifically, retainers  140  facilitate limiting circumferential motion of outer race  54 , as well as maintaining an axial position of outer race  54  such that radial loading from rotor assembly  40  is transmitted into frame  46 . Accordingly, because axial movement of outer race  54  is facilitated to be reduced, inadvertent contact between rotor shaft  44  and frame  46  is facilitated to be prevented post spring failure. As a result, retainers  140  facilitate extending a useful life of bearing assembly  40  in a cost-effective and reliable manner.  
         [0025]    The above-described rotor assembly is cost-effective and highly reliable. The rotor assembly includes a pair of retainers that extend radially inwardly from the damper bearing and into calibrated slots defined on the spring finger member. The retainers facilitate maintaining an axial position of the outer race relative to the support frame. Accordingly, radial loading induced to the bearing assembly is transmitted into the frame, and inadvertent contact between the rotor shaft and the frame is prevented. As a result, the retainers facilitate extending a useful life of the bearing assembly when the engine is operating.  
         [0026]    Exemplary embodiments of rotor assemblies are described above in detail. The rotor assemblies are not limited to the specific embodiments described herein, but rather, components of each assembly may be utilized independently and separately from other components described herein. Each rotor assembly component can also be used in combination with other rotor assembly components.  
         [0027]    While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.