Patent Publication Number: US-9410483-B2

Title: Gas turbine engine forward bearing compartment architecture

Description:
RELATED APPLICATIONS 
     This application is a continuation of prior U.S. application Ser. No. 13/346,832, filed Jan. 10, 2012, the entirety of which is herein incorporated by reference. 
    
    
     BACKGROUND 
     The present disclosure relates to a gas turbine engine, and in particular, to a case structure therefor. 
     Geared turbofan architectures may utilize epicyclic reduction gearboxes with planetary or star gear trains for their compact design and efficient high gear reduction capabilities. The geared turbofan architecture de-couples a fan rotor from a low spool through the reduction gearbox which results in isolation of the forwardmost bearing compartment. 
     SUMMARY 
     A gas turbine engine according to an exemplary aspect of the present disclosure includes a geared architecture at least partially supported by a front center body case structure. A bearing structure mounted to the front center body case structure to rotationally support a shaft driven by the geared architecture. A bearing compartment passage structure in communication with the bearing structure through the front center body case structure. 
     A method of communicating a buffer supply air for a gas turbine engine according to an exemplary aspect of the present disclosure includes communicating a buffer supply air across an annular core flow path. 
    
    
     
       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 schematic cross-section of a sectional of the gas turbine engine; 
         FIG. 3  is a schematic view of a gas turbine engine with a bearing compartment passage structure which bypasses around a geared architecture; and 
         FIG. 4  is an enlarged schematic cross-section of a sectional of the gas turbine engine, which illustrates the bearing compartment passage structure. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  schematically illustrates a gas turbine engine  20 . The gas turbine engine  20  is disclosed herein as a 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  26  then expansion through the turbine section  28 . 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 such as a three-spool (plus fan) engine wherein an intermediate spool includes an intermediate pressure compressor (IPC) between the LPC and HPC and an intermediate pressure turbine (IPT) between the HPT and LPT. 
     The engine  20  generally includes a low spool  30  and a high spool  32  mounted for rotation about an engine central longitudinal axis A relative to an engine static structure  36  via several bearing structures  38 . The low spool  30  generally includes an inner shaft  40  that interconnects a fan  42 , a low pressure compressor  44  (“LPC”) and a low pressure turbine  46  (“LPT”). The inner shaft  40  drives the fan  42  through a geared architecture  48  to drive the fan  42  at a lower speed than the low spool  30 . An exemplary reduction transmission is an epicyclic transmission, namely a planetary or star gear system. 
     The high spool  32  includes an outer shaft  50  that interconnects a high pressure compressor  52  (“HPC”) and high pressure turbine  54  (“HPT”). 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 and burned 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 spool  30  and high spool  32  in response to the expansion. 
     The engine shafts  40 ,  50  are supported at a plurality of points by bearing structures  38  within the engine static structure  36 . In one non-limiting embodiment, bearing structures  38  includes a #1 bearing structure  38 - 1  forward of the gearbox  72  and a #2 bearing structure  38 - 2  located aft of the gearbox  72 . 
     With reference to  FIG. 2 , the engine static structure  36  proximate the compressor section  24  generally includes a front center body case structure  60  and an intermediate case structure  62  which mounts aft of the front center body case structure  60 . It should be appreciated that various case structures may alternatively or additionally be provided, yet benefit from the architecture described herein. 
     The front center body case structure  60  generally defines an annular core flow path  64 A for the core airflow into the low pressure compressor  44 . The intermediate case structure  62  defines the core flow path  64 B aft of the core flow path  64 A into the high pressure compressor  52  core flow path  64 C. The core flow path  64 B is generally radially inward of the core flow path  64 A to transition into the radially smaller diameter core flow path  64 C. That is, the core flow path  64 B generally defines a “wasp waist” gas turbine engine architecture. 
     The #2 bearing structure  38 - 2  at least partially supports the inner shaft  40  relative to the front center body case structure  60 . A #3 bearing structure  38 - 3  generally supports the outer shaft  50  relative the intermediate case structure  62 . That is, the #2 bearing structure  38 - 2  at least partially supports the low spool  30  and the #3 bearing structure  38 - 3  at least partially supports the high spool  32 . It should be appreciated that various bearing systems such as thrust bearing structures and mount arrangements will benefit herefrom. 
     A flex support  68  provides a flexible attachment of the geared architecture  48  within the front center body case structure  60 . The flex support  68  reacts the torsional loads from the geared architecture  48  and facilitates vibration absorption as well as other support functions. A centering spring  70 , which is a generally cylindrical cage-like structural component with a multiple of beams that extend between flange end structures, resiliently positions the #2 bearing structure  38 - 2  with respect to the low spool  30 . In one embodiment, the beams are double-tapered beams arrayed circumferentially to control a radial spring rate that may be selected based on a plurality of considerations including, but not limited to, bearing loading, bearing life, rotor dynamics, and rotor deflection considerations. 
     The gearbox  72  of the geared architecture  48  is driven by the low spool  30  in the disclosed non-limiting embodiment through a coupling shaft  74 . The coupling shaft  74  transfers torque through the #2 bearing structure  38 - 2  to the gearbox  72  as well as facilitates the segregation of vibrations and other transients. The coupling shaft  74  in the disclosed non-limiting embodiment includes a forward coupling shaft section  76  and an aft coupling shaft section  78 . The forward coupling shaft section  76  includes an interface spline  80  which mates with the gearbox  72 . An interface spline  82  of the aft coupling shaft section  78  connects the coupling shaft  74  to the low spool  30  through, in this non limiting embodiment, a low pressure compressor hub  84  of the low pressure compressor  44 . 
     A fan rotor bearing support structure  86  aft of the fan  42  extends radially inward from the front center body case structure  60 . The fan rotor bearing support structure  86  and the front center body case structure  60  defines a bearing compartment B- 2 . It should be appreciated that various bearing structures  38  and seals  88  may be supported by the fan rotor bearing support structure  86  to contain oil and support rotation of an output shaft  100  which connects with the geared architecture  48  to drive the fan  42 . 
     The low pressure compressor hub  84  of the low pressure compressor  44  includes a tubular hub  90  and a frustro-conical web  92 . The tubular hub  90  mounts to the inner shaft  40  through, for example, a splined interface adjacent to the #2 bearing structure  38 - 2 . The frustro-conical web  92  extends in a forwardly direction from the tubular hub  90  axially between the #2 bearing structure  38 - 2  and the #3 bearing structure  38 - 3 . That is, the frustro-conical web  92  is axially located between the bearing structures  38 - 2 ,  38 - 3 . 
     The #1 bearing structure  38 - 1  supports the output shaft  100  which connects the geared architecture  48  to the fan  42 . The #1 bearing structure  38 - 1  is located within a bearing compartment B- 1  that is isolated by the geared architecture  48  from bearing compartment B- 2 . That is, the #1 bearing compartment B- 1  is isolated from the engine core aft of the geared architecture  48  and receives its buffer pressurization supply of buffer supply air through a #1 bearing compartment passage structure  110  that crosses the annular core flow path  64 A for the core airflow into the low pressure compressor  44  ( FIG. 3 ). 
     With reference to  FIG. 4 , the #1 bearing compartment passage structure  110  is in communication with the core engine such as with the high pressure compressor  52  to supply a higher pressure bleed air flow of buffer supply air into the #1 bearing compartment B- 1  such as the seal  88 - 1  to, for example, pressurize the seal  88 - 1  and seal lubricating fluid with respect to the #1 bearing structure  38 - 1 . The buffer supply air may be communicated from various other sources and may pass through, for example, a conditioning device  112  such as a buffer heat exchanger. The conditioning device  112  may further condition bleed flow C 1 , C 2  from the high pressure compressor It should be appreciated the various bleed sources from the high pressure compressor  52  may be selected through a valve  116 . 
     The #1 bearing compartment passage structure  110  may be at least partially defined by a hollow front center body strut  60 S of the front center body case structure  60  to permit the buffer supply air to cross the annular core flow path  64 A without flow interference. That is, the buffer supply air is communicated through the hollow front center body strut  60 S and the core airflow passes around the hollow front center body strut  60 S. 
     From the hollow front center body strut  60 S, the buffer supply air is communicated through a passage  114  in the fan rotor bearing support structure  86  to, for example, the seal  88 - 1 . It should be appreciated that various passages may alternatively or additionally be provided. 
     The passage of buffer supply air through the fan rotor bearing support structure  86  advantageously promotes heat transfer between the buffer supply air and the #1 bearing compartment B- 1  to reduce buffer supply air maximum temperate at high power condition and increases buffer supply air minimum temperatures at lower power settings. As the #1 bearing structure  38 - 1  operates at a generally constant temperature, the #1 bearing compartment B- 1  operates as a thermal ground with respect to the buffer supply air. 
     Downstream of the #1 bearing compartment B- 1 , the buffer supply air may be communicated in various manners for various usages such as toward the spinner  120  to facilitate spinner die-icing. The buffer supply air may alternatively or additionally be ejected outward aft of the fan  42  to recirculate into the annular core flow path  64 A to minimize any effect upon engine efficiency. 
     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. 
     Although the different examples have specific components shown in the illustrations, embodiments of this invention are not limited to those particular combinations. It is possible to use some of the components or features from one of the examples in combination with features or components from another one of the examples. 
     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.