Abstract:
A gas turbine engine is disclosed that includes a spool having a compressor section. An inlet case is arranged axially upstream from the compressor section. A gearbox is secured to the inlet case. The gearbox couples the spool and a fan. A sealing assembly is arranged between the inlet case and the gearbox to provide a sealed bearing compartment. The inlet case, gearbox and seal assembly provide a module. A fastening element removably secures the module to the spool. The gas turbine engine can be serviced by disconnecting the fastening element from the engine core. The gearbox and inlet case can be removed as a module from the engine core without disassembling the gearbox.

Description:
BACKGROUND 
     This disclosure relates to a core housing and gearbox configuration for gas turbine engines. 
     Gas turbine engines for commercial aircraft applications typically include an engine core housed within a core nacelle. In one type of arrangement known as a turbofan engine, the core drives an upstream fan that provides airflow into the core. A fan case and nacelle surround the fan and at least a portion of the core. A compressor section within the core compresses the air from the fan and delivers it downstream into a combustion section. One type of compressor section includes low and high pressure compressors, each with one or more stages. The compressed air is mixed with fuel and combusted in the combustion section. The products of this combustion are then delivered downstream over turbine rotors, which are rotationally driven to provide power to the engine. 
     The core housing is typically constructed from multiple cases that support various portions of the core. The inlet case is arranged at the front of the core to receive airflow from the fan. Some gas turbine engines include a gearbox arranged at the front of the core between a spool and the fan. The spool supports one or more turbine stages that rotational drive the fan through the gearbox. One problem with geared fan engines is the lack of modularity at the front of the core. For example, when the gearbox needs to be removed from the engine. For example, to service the compressor section, it must be disassembled in order to remove it. In particular, in one type of arrangement, a gearbox bearing compartment seal is positioned such that it prevents the gearbox from being removed as a unit or module, which is time consuming and costly. Further, the gearbox cannot be removed along with the low pressure compressor inlet case. What is needed is a gas turbine engine front architecture configured to permit the gearbox and the inlet case to be removed as a single unit or module without disassembling the gearbox. 
     SUMMARY 
     A gas turbine engine is disclosed that includes a spool having a compressor section. An inlet case is arranged axially upstream from the compressor section. A gearbox is secured to the inlet case. The gearbox couples the spool and a fan. A seal assembly is arranged between the inlet case and the gearbox to provide a sealed bearing compartment. The inlet case, gearbox and seal assembly provide a module. A fastening element removably secures the module to the spool, in one example. 
     The gas turbine engine can be serviced by disconnecting the fastening element from the engine core. The gearbox and inlet case can be removed as a module from the engine core without disassembling the gearbox. The entire gearbox can be changed out quickly or easy access can be provided to the compressor section. 
     These and other features of the disclosure can be best understood from the following specification and drawings, the following of which is a brief description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a highly schematic cross-sectional view of a gas turbine engine with a geared architecture. 
         FIG. 2  illustrates a cross-sectional view of a case mounting and gearbox arrangement relative to the core housing. 
         FIG. 3  illustrates a cross-sectional view of an example case mounting arrangement according to the disclosure. 
         FIG. 4  illustrates an exploded view an engine front architecture, shown in  FIG. 3 , including an inlet case and gearbox module. 
         FIG. 5  illustrates an enlarged view of a portion of the module shown in  FIGS. 3 and 4  depicting seal assemblies. 
     
    
    
     DETAILED DESCRIPTION 
     A turbofan engine  10  with a geared architecture is shown in  FIG. 1 . A pylon  38  secures the engine  10  to an aircraft. The engine  10  includes a core nacelle  12  that surrounds a low spool  14  and high spool  24  rotatable about an axis A. The low spool  14  supports a low pressure compressor  16  and low pressure turbine  18 . In the example, the low spool  14  drives a fan  20  through a gearbox or gear train  22 . The high spool  24  supports a high pressure compressor  26  and high pressure turbine  28 . A combustor  30  is arranged between the high pressure compressor  26  and high pressure turbine  28 . Compressed air from compressors  16 ,  26  mixes with fuel from the combustor  30  and is expanded in turbines  18 ,  28 . 
     In the example shown, the engine  10  is a high bypass turbofan arrangement. In one example, the bypass ratio is greater than 10, and the turbofan diameter is substantially larger than the diameter of the low pressure compressor  16 . The low pressure turbine  18  has a pressure ratio that is greater than 5:1, in one example. The gear train  22  is an epicyclic gear train, for example, a star gear train, providing a gear reduction ratio of greater than 2.2:1. It should be understood, however, that the above parameters are only exemplary of a contemplated turbofan engine with a geared architecture. That is, the invention is applicable to other engines including direct drive turbofans. 
     Airflow enters a fan nacelle  34 , which surrounds the core nacelle  12  and fan  20 . The fan  20  directs air into the core nacelle  12 , which is used to drive the turbines  18 ,  28 , as is known in the art. Turbine exhaust E exits the core nacelle  12  once it has been expanded in the turbines  18 ,  28 , in a passage provided between the core nacelle  12  and a tail cone  32 . 
     Referring to  FIG. 2 , a core  13  is arranged within the core nacelle  12  and is supported within the fan nacelle  34  by structure  36 , such as flow exit guide vanes, extending radially inwardly from a fan case  46 . A generally annular bypass flow path  39  is arranged between the core and fan nacelles  12 ,  34 . The examples illustrated in the Figures depict a high bypass flow arrangement in which approximately eighty percent of the airflow entering the fan nacelle  34  bypasses the core nacelle  12 . The bypass flow B within the bypass flow path  39  exits the fan nacelle  34  through a fan nozzle exit area at the aft of the fan nacelle  34 . 
     The core  13  generally includes at least an inlet case  64 , a low pressure compressor case  66 , and an intermediate case  76 . The inlet case  64  guides airflow from the fan  20  to the low pressure compressor case  66 . As shown in  FIG. 2 , the low pressure compressor case  66  in an example gas turbine engine  80  supports a plurality of compressor stator vanes  68 . A rotor  70  rotates about the axis A, and, with the compressor stator vanes  68 , help compress air moving through the low pressure compressor case  66 . 
     The guide vanes  36  are axially aligned with the intermediate case  76  in one example. The guide vanes  36  secure the intermediate case  76  to the fan case  46 . The guide vanes  36  each include at least a rearward attachment  74  and a forward attachment  78 , which are arranged on a forward side  89  of the guide vanes  36 . The rearward attachment  74  connects to the intermediate case  76  while the forward attachment  78  connects to the inlet case  64 . An aft attachment  90  extends from an aft side  91  of the guide vanes  36  and intersects with the rearward attachment  74  at the front of the intermediate case  76 . The lower pressure compressor case  66  is supported through the intermediate case  76  and the inlet case  64  in the arrangement shown in  FIG. 2 . 
     In one type of example gas turbine engine configuration shown in  FIG. 2 , a rear bearing compartment seal assembly for the gearbox  22  includes a seal plate  123  and a carbon seal  125 . Removing the gearbox  22  as a module is not possible since the carbon seal  125  cannot move axially past the seal plate  123 , which is affixed to the low pressure compressor rotor  121  and is not removed. As a result, the components of the gearbox  22  must be disassembled in order to remove it from the engine  80 . 
     Returning now to an example of the disclosed arrangement shown in  FIG. 3 , the forward attachment  78  attaches to a front portion of the low pressure compressor case  66 . In this example, the forward attachment  78  extends from the guide vanes  36  to support the low pressure compressor case  66 . Together, the forward attachment  78  and guide vanes  36  act as a support member for the low pressure compressor case  66 . A plumbing connection area  82  is positioned upstream of the forward attachment  78  facilitating access to the plumbing connection area  82 . In this example, an operator may directly access the plumbing connection area  82  after removing the fan stream splitter  86 . The plumbing connection area  82  typically provides access to a lubrication system  82   a , a compressed air system  82   b , or both. The lubrication system  82   a  and compressed air system  82   b  are typically in fluid communication with the gear train  22 . 
     Maintenance and repair of the gear train  22  may require removing the gear train  22  from the engine  10 . Positioning the plumbing connection area  82  ahead of the forward attachment  78  simplifies maintenance and removal of the gear train  22  from other portions of the engine  10 . Draining oil from the gear train  22  prior to removal may take place through the plumbing connection area  82  for example. The plumbing connection area  82  is typically removed with the gear train  22 . Thus, the arrangement may permit removing the gear train  22  on wing or removing the inlet case  64  from the gas turbine engine  10  separately from the low pressure compressor case  66 . This reduces the amount of time needed to prepare an engine for continued revenue service, saving an operator both time and money. 
     Connecting the forward attachment  78  to the low pressure compressor case  66  helps maintain the position of the rotor  70  relative to the interior of the low pressure compressor case  66  during fan rotation. In this example, the intermediate case  76  supports a rear portion of the low pressure compressor case  66  near a compressed air bleed valve  75 . 
     Referring to  FIGS. 4 and 5 , enlarged views are depicted of the example gas turbine configuration shown in  FIG. 3 , which permits removal of the gearbox  22  and inlet case  64  as a single unit. This enables replacement of the entire gearbox  22  on-wing or easy access to the compressor section. Stator vanes  68  extend radially between outer and inner walls of the inlet housing  64 . A housing portion  94  extends from the inner wall of the inlet housing  64  toward an input shaft  102  of the gearbox  22 . 
     The gearbox  22  includes the input shaft  102 , which is connected to a central input gear  104 . Intermediate gears  106  are arranged about and mesh with the input gear  104  and a ring gear  108 . In the example shown, the ring gear  108  is coupled to an output shaft  110 , which drives the fan  20 . Blades of the fan  20  are mounted to a fan support  112  provided on the output shaft  110 . A seal housing  136  provides a first seal assembly  126  that seals the bearing compartment  114 . The seal housing  136  also carries a portion (honeycomb seal  132 ) of a second seal assembly  130  that provides a seal between the gearbox and inlet case module  100  relative to a low pressure compressor module  98 . 
     To remove the gearbox and inlet case module  100 , spinner portions  118   a ,  118   b  are removed from the fan support  112 . The individual fan blades are disconnected from the fan support  112 . The fan stream splitter  86  is removed from the inlet case  64 , if desired. A shaft cover  116  is detached from the gearbox  22  to expose a low shaft nut  120 . The low shaft nut  120  is removed to decouple the input shaft  102  from the low spool  14 . The forward attachment  78  is disconnected from the flow exit guide vanes  36 . The gearbox and inlet case module  100  can then be removed axially as a unit. 
     As can be appreciated from  FIG. 5 , the second seal assembly  130  is arranged radially inboard from the low pressure compressor rotor  92 , which is mounted on hub  96 , such that the gearbox and inlet case module  100  can be axially removed. The second seal assembly  130  includes a honeycomb seal  132  and knife edges  134  that permit axial movement of the gearbox and inlet case module  100 . In the example shown, the first seal assembly  126  is removed with the module  100 , which enables the bearing compartment  114  to remain intact preventing contamination. Only the shaft cover  116  is detached for removal of the gearbox and inlet case module  100  as a unit. The first seal assembly  126  includes a seal plate  122  that is supported by the input shaft  102  and a carbon seal  124  that is carried by the seal housing  136 . The seal plate  122  can be serviced by removing the seal housing  136  from the housing portion  94 , and removing a retainer  128  from the input shaft  102 . 
     As can be appreciated by the example embodiment, the gearbox  22  does not need to be disassembled to gain access to the front of the core, for example, to the low pressure compressor rotor  92 . Moreover, the bearing compartment  114  does not need to be compromised during removal of the module  100 . 
     Although an example embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of the claims. For that reason, the following claims should be studied to determine their true scope and content.