Abstract:
A gas turbine engine is disclosed that includes at least first and second gearboxes rotationally coupled to at least one spool. Accessory drive components are mounted on and driven by the gearboxes. The accessory drive components include, for example, a fuel pump, a hydraulic pump, a generator, a lubrication pump, or a starter. The accessory drive components are split between the two gearboxes to reduce the diameter of the nacelle adjacent to each gearbox.

Description:
BACKGROUND 
       [0001]    This disclosure relates to a gas turbine gearbox arrangement that is used to support and rotationally drive accessory drive components, such as a fuel pump, hydraulic pump, generator, lubrication pump and/or starter. 
         [0002]    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 a large fan upstream from the core that provides airflow into the core. One or more spools are arranged within the core, and a gear train may be provided between one of the spools and the fan. A fan case and nacelle surround the fan and at least a portion of the core. 
         [0003]    An inlet of the fan nacelle is designed to avoid flow separation. At cruise conditions, a thinner inlet lip is desired to minimize drag and increase fuel economy. The nacelles are sized to accommodate the widest section of engine, which is often dictated by the size of a single accessory drive gearbox. The accessory drive gearbox, which is driven by a spool through a radial tower shaft and angle gearbox, is typically contained within either the fan nacelle or the core nacelle. A fuel pump, hydraulic pump, generator, lubrication pump, starter and numerous other components are typically mounted to the same accessory drive gearbox, which takes up significant space. As a result, the diameter of the nacelle housing the accessory drive gearbox and accessory components must be increased beyond a desired size. The larger diameter nacelle results in a thicker inlet lip thereby increasing drag at cruise conditions. Increased nacelle diameter also increases weight and fuel consumption. What is needed is a gas turbine engine design with a reduced diameter nacelle. 
       SUMMARY 
       [0004]    A gas turbine engine is disclosed that includes first and second gearboxes rotationally coupled to at least one spool. Accessory drive components are mounted on and driven by the gearboxes. The accessory drive components include, for example, a fuel pump, a hydraulic pump, a generator, a lubrication pump, or a starter. The accessory drive components are split between the two gearboxes to reduce the diameter of the nacelle adjacent to each gearbox, enabling the design of slimmer nacelles and more efficient engines. Each gearbox may be housed within a different nacelle, or the gearbox may be housed within the same nacelle. 
         [0005]    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 
         [0006]      FIG. 1  is a highly schematic view of a turbofan gas turbine engine. 
           [0007]      FIG. 2   a  is a schematic view of a first accessory drive gearbox associated with the engine shown in  FIG. 1 . 
           [0008]      FIG. 2   b  is a schematic view of a second accessory drive gearbox associated with the engine shown in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    An engine  10  with geared architecture is shown in  FIG. 1 . A pylon 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  that are rotatable about a common 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 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 . 
         [0010]    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 epicycle gear train, for example, a star gear train, providing a gear reduction ratio of greater than 2.5:1. It should be understood, however, that the above parameters are only exemplary of a contemplated geared architecture engine. That is, the invention is applicable to other engines including direct drive turbofans. 
         [0011]    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 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 . 
         [0012]    A core housing  11  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  35 . A generally annular bypass flow path  38  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 within the bypass flow path  38  exits the fan nacelle  34  through a fan nozzle exit area at the aft of the fan nacelle  34 . 
         [0013]    In the example shown in  FIG. 1 , at least two accessory drive gearboxes  40 ,  140  are used to drive accessory components at different location within the engine. Instead of the single accessory drive gearbox typically used, the work can be split between the gearboxes  40 ,  140  to reduce the size of each gearbox and, thus, the size of the associated nacelle. Example accessory drive components are: a fuel pump  42 , hydraulic pump  44 , generator  46 , lubrication pump  48  and other accessory drive components  53 . 
         [0014]    In one example, one accessory drive gearbox  40  is arranged in a radial space between the fan case  35  and an exterior surface  33  of the fan nacelle  34 . The other accessory drive gearbox  140  is arranged in a radial space between the core housing  11  and an exterior surface  13  of the core nacelle  12 . Both accessory drive gearboxes  40 ,  140  can be housed within the same nacelle, if desired. The accessory drive gearboxes are axially and radially spaced from one another, which enables desired packaging of the gearboxes. 
         [0015]    Referring to  FIGS. 1 and 2   a , the accessory drive gearbox  40  is driven by the low spool  14 . The low spool  14  is coupled to a tower shaft  62  with bevel gears, as is known. The tower shaft  62  drives an input shaft  52  through an angle gearbox  64 , which is mounted to the fan case  35 , for example. The accessory drive gearbox  40  is supported by the fan case  35 , and receives rotational drive from the input shaft  52 . The accessory components shown mounted on the accessory drive gearboxes  40 ,  140  are exemplary only and may be different than depicted in the Figures. The accessory components for each gearbox are selected, for example, based upon packaging considerations and the desired rotational speed of the accessory component. In the example shown in  FIG. 1 , the accessory drive gearboxes  40 ,  140  are respectively driven by the low and high spools  14 ,  24  to provide the desired rotational speed to accessory drive components associated with the gearboxes. 
         [0016]    Referring to  FIG. 2   b , the accessory drive gearbox  140  is driven by the high spool  24 . The high spool  24  is coupled to a tower shaft  162  with bevel gears. The tower shaft  162  drives an input shaft  152  through an angle gearbox  164 , which is mounted to the core housing  11 , for example. The accessory drive gearbox  140  is supported by the core housing  11 , and receives rotational drive from the input shaft  152 . 
         [0017]    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.