Abstract:
A gas turbine engine includes a gearbox. The gearbox includes a housing at a forward part of a core compartment of a gas turbine engine. A plurality of accessory drives are each configured to rotatably couple the gas turbine engine accessory gearbox to one of a plurality of accessory components.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Application No. 61/703446, which was filed on 20 Sep. 2012 and is incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    This disclosure relates generally to an accessory gearbox and, more particularly, to mounting and placing an accessory gearbox within a gas turbine engine. 
         [0003]    Gas turbine engines, such as gas turbine engines, typically include a fan section, a compression section, a combustion section, and a turbine section. Gas turbine engines may employ a geared architecture connecting portions of the compression section to the fan section. 
         [0004]    Gas turbine engines often include an accessory gearbox that is utilized to rotatably drive various accessories. Packaging the accessory gearbox and the accessories is difficult. It is especially difficult to package the accessory gearbox and accessories within gas turbine engines having geared fan-drive architectures as these gas turbine engines typically have a shorter overall axial length than other types of gas turbine engines. Some conventional accessory gearboxes are located near the aft of the engine and require a relatively long driveshaft from the compressor. Placing the accessory gearbox in this area exposes the accessory gearbox to relatively high temperatures. Some conventional accessory gearboxes are mounted to a fan case of the engine. 
       SUMMARY 
       [0005]    A gas turbine engine according to an exemplary aspect of the present disclosure includes a gearbox. The gearbox includes a housing at a forward part of a core compartment of a gas turbine engine. A plurality of accessory drives are each configured to rotatably couple the gearbox to one of a plurality of accessory components. 
         [0006]    In a further non-limiting embodiment of the foregoing gas turbine engine, the gas turbine engine includes a generator rotatably coupled to the one of the plurality of accessory drives at the lowest elevation relative to the other of the plurality of accessory drives. 
         [0007]    In a further non-limiting embodiment of either of the foregoing gas turbine engines, the plurality of accessory drives are exclusively on an aft side of the housing relative to a direction of flow through the gas turbine engine. 
         [0008]    In a further non-limiting embodiment of any of the foregoing gas turbine engines, the housing abuts an intermediate case of the gas turbine engine. 
         [0009]    In a further non-limiting embodiment of any of the foregoing gas turbine engines, the gas turbine engine includes a high pressure compressor and a low pressure compressor. The intermediate case is positioned axially between the high-pressure compressor and the low-pressure compressor. 
         [0010]    In a further non-limiting embodiment of any of the foregoing gas turbine engines, the housing is directly attached to a core section of the gas turbine engine. 
         [0011]    In a further non-limiting embodiment of any of the foregoing gas turbine engines, the housing comprises a first housing portion and a second housing portion located on an opposing lateral side of the gas turbine engine from the first housing portion. 
         [0012]    In a further non-limiting embodiment of any of the foregoing gas turbine engines, the first portion includes accessory drives on exclusively the aft side of the housing. 
         [0013]    In a further non-limiting embodiment of any of the foregoing gas turbine engines, the first portion includes accessory drives on both a forward and an aft side of the housing. 
         [0014]    In a further non-limiting embodiment of any of the foregoing gas turbine engines, the first portion and the second portion are at the same axial location. 
         [0015]    A gas turbine engine according to another exemplary aspect of the present disclosure includes a geared architecture configured to be driven by a shaft that is rotating at a first speed. The geared architecture is configured to rotate a fan at a second speed different than the first speed. An accessory gearbox housing abuts an intermediate case of the gas turbine engine. 
         [0016]    In a further non-limiting embodiment of the foregoing gas turbine engine, the accessory gearbox is configured to drive an aircraft generator that is secured to an aft side of the accessory gearbox, the aircraft generator at a low elevation relative other accessories driven by the accessory gearbox. 
         [0017]    In a further non-limiting embodiment of either of the foregoing gas turbine engines, the accessory gearbox is a first accessory gearbox portion and a second accessory gearbox portion is secured to the intermediate case opposite the first accessory gearbox portion. 
         [0018]    In a further non-limiting embodiment of any of the foregoing gas turbine engines, the second accessory gearbox includes accessory drives on both a forward and an aft side. 
         [0019]    In a further non-limiting embodiment of any of the foregoing gas turbine engines, the accessory gearbox is configured to attach to a core of a gas turbine engine. 
         [0020]    A method of positioning an accessory gearbox according to another exemplary aspect of the present disclosure includes, placing an accessory gearbox in a forward portion of a core compartment of a gas turbine engine, and securing the accessory gearbox to a core of the gas turbine engine. 
         [0021]    In a further non-limiting embodiment of the foregoing method of positioning an accessory gearbox, the method includes driving an aircraft generator accessory from a drive location of the accessory gearbox, the drive location at a relatively low elevation compared with other drive location of the accessory gearbox. 
         [0022]    Although the different examples have the specific components shown in the illustrations, embodiments of this disclosure 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. 
     
    
     
       DESCRIPTION OF THE FIGURES 
         [0023]    The various features and advantages of the disclosed examples will become apparent to those skilled in the art from the detailed description. The figures that accompany the detailed description can be briefly described as follows: 
           [0024]      FIG. 1  shows a cross-section view of an example turbine engine gas turbine engine. 
           [0025]      FIG. 2  shows a variation of the  FIG. 1  gas turbine engine. 
           [0026]      FIG. 3  shows a partial section view of a side of the gas turbine engine of  FIG. 2 . 
           [0027]      FIG. 4  shows a section view of the gearbox in  FIG. 3  at line  4 - 4  with the accessories removed. 
           [0028]      FIG. 5  shows a partial section view of an opposing side of the gas turbine engine of  FIG. 3 . 
           [0029]      FIG. 6  shows a partial section and perspective view from a rear of another example gas turbine engine gas turbine engine. 
           [0030]      FIG. 7  shows a partial section and perspective view from a front of the gas turbine engine of  FIG. 6 . 
           [0031]      FIG. 8  shows a partial section and perspective view from the rear and on an opposite side of the gas turbine engine of  FIG. 6 . 
       
    
    
     DETAILED DESCRIPTION 
       [0032]      FIG. 1  schematically illustrates an example gas turbine engine  20  that includes a fan section  22 , a compressor section  24 , a combustor section  26 , and a turbine section  28 . Alternative engines might include an augmenter section (not shown) among other systems or features. The fan section  22  drives air along a bypass flow path B while the compressor section  24  draws air in along a core flow path C where air is compressed and communicated to a combustor section  26 . In the combustor section  26 , air is mixed with fuel and ignited to generate a high pressure exhaust gas stream that expands through the turbine section  28  where energy is extracted and utilized to drive the fan section  22  and the compressor section  24 . 
         [0033]    Although the disclosed non-limiting embodiment depicts a turbofan gas turbine engine, 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; for example a turbine engine including a three-spool architecture in which three spools concentrically rotate about a common axis and where a low spool enables a low pressure turbine to drive a fan via a gearbox, an intermediate spool that enables an intermediate pressure turbine to drive a first compressor of the compressor section, and a high spool that enables a high pressure turbine to drive a high pressure compressor of the compressor section. 
         [0034]    The example engine  20  generally includes a low speed spool  30  and a 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 . It should be understood that various bearing systems  38  at various locations may alternatively or additionally be provided. 
         [0035]    The low speed spool  30  generally includes an inner shaft  40  that connects a fan  42  and a low pressure (or first) compressor section  44  to a low pressure (or first) turbine section  46 . The inner shaft  40  drives the fan  42  through a speed change device, such as 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 (or second) compressor section  52  and a high pressure (or second) turbine section  54 . The inner shaft  40  and the outer shaft  50  are concentric and rotate via the bearing systems  38  about the engine central longitudinal axis A. 
         [0036]    A combustor  56  is arranged between the high pressure compressor  52  and the high pressure turbine  54 . In one example, the high pressure turbine  54  includes at least two stages to provide a double stage high pressure turbine  54 . In another example, the high pressure turbine  54  includes only a single stage. As used herein, a “high pressure” compressor or turbine experiences a higher pressure than a corresponding “low pressure” compressor or turbine. 
         [0037]    The example low pressure turbine  46  has a pressure ratio that is greater than about  5 . The pressure ratio of the example low pressure turbine  46  is measured prior to an inlet of the low pressure turbine  46  as related to the pressure measured at the outlet of the low pressure turbine  46  prior to an exhaust nozzle. 
         [0038]    A mid-turbine frame  58  of the engine static structure  36  is arranged generally between the high pressure turbine  54  and the low pressure turbine  46 . The mid-turbine frame  58  further supports bearing systems  38  in the turbine section  28  as well as setting airflow entering the low pressure turbine  46 . 
         [0039]    The core airflow C is compressed by the low pressure compressor  44  then by the high pressure compressor  52  mixed with fuel and ignited in the combustor  56  to produce high speed exhaust gases that are then expanded through the high pressure turbine  54  and low pressure turbine  46 . The mid-turbine frame  58  includes vanes  60 , which are in the core airflow path and function as an inlet guide vane for the low pressure turbine  46 . Utilizing the vane  60  of the mid-turbine frame  58  as the inlet guide vane for low pressure turbine  46  decreases the length of the low pressure turbine  46  without increasing the axial length of the mid-turbine frame  58 . Reducing or eliminating the number of vanes in the low pressure turbine  46  shortens the axial length of the turbine section  28 . Thus, the compactness of the gas turbine engine  20  is increased and a higher power density may be achieved. 
         [0040]    The disclosed gas turbine engine  20  in one example is a high-bypass geared aircraft engine. In a further example, the gas turbine engine  20  includes a bypass ratio greater than about six (6), with an example embodiment being greater than about ten (10). The example geared architecture  48  is an epicyclical gear train, such as a planetary gear system, star gear system or other known gear system, with a gear reduction ratio of greater than about 2.3. 
         [0041]    In one disclosed embodiment, the gas turbine engine  20  includes a bypass ratio greater than about ten (10:1) and the fan diameter is significantly larger than an outer diameter of the low pressure compressor  44 . It should be understood, however, that the above parameters are only exemplary of one embodiment of a gas turbine engine including a geared architecture and that the present disclosure is applicable to other gas turbine engines. 
         [0042]    A significant amount of thrust is provided by the bypass flow B due to the high bypass ratio. The fan section  22  of the engine  20  is designed for a particular flight condition—typically cruise at about 0.8 Mach and about 35,000 feet. The flight condition of 0.8 Mach and 35,000 ft., with the engine at its best fuel consumption—also known as “bucket cruise Thrust Specific Fuel Consumption (‘TSFC’)”—is the industry standard parameter of pound-mass (lbm) of fuel per hour being burned divided by pound-force (lbf) of thrust the engine produces at that minimum point. 
         [0043]    “Low fan pressure ratio” is the pressure ratio across the fan blade alone, without a Fan Exit Guide Vane (“FEGV”) system. The low fan pressure ratio as disclosed herein according to one non-limiting embodiment is less than about 1.50. In another non-limiting embodiment the low fan pressure ratio is less than about 1.45. 
         [0044]    “Low corrected fan tip speed” is the actual fan tip speed in ft/sec divided by an industry standard temperature correction of [(Tram° R)/(518.7° R)] 0.5 . The “Low corrected fan tip speed,” as disclosed herein according to one non-limiting embodiment, is less than about 1150 ft/second. 
         [0045]    The example gas turbine engine includes the fan  42  that comprises in one non-limiting embodiment less than about 26 fan blades. In another non-limiting embodiment, the fan section  22  includes less than about 20 fan blades. Moreover, in one disclosed embodiment the low pressure turbine  46  includes no more than about 6 turbine rotors schematically indicated at  34 . In another non-limiting example embodiment the low pressure turbine  46  includes about 3 turbine rotors. A ratio between the number of fan blades and the number of low pressure turbine rotors is between about 3.3 and about 8.6. The example low pressure turbine  46  provides the driving power to rotate the fan section  22  and therefore the relationship between the number of turbine rotors  34  in the low pressure turbine  46  and the number of blades in the fan section  22  disclose an example gas turbine engine  20  with increased power transfer efficiency. 
         [0046]    Referring now to  FIGS. 2 to 5  with continuing reference to  FIG. 1 , an engine  62  is a variation of the engine  20 . The engine  62  includes an accessory gearbox  66  that is utilized to rotatably drive various accessories. In this example, these accessories include at least a starter  64 , an aircraft generator  68 , a Permanent Magnet Alternator/Permanent Magnet Generator (PMA/PMG)  72 , a hydraulic pump  76 , and a lubricant scavenge pump  78 . A tower shaft (not shown) may rotatably couple the accessory gearbox  66  to the high speed spool  32 . During operation, rotation of the high speed spool  32  rotatably drives the accessory gearbox  66 . 
         [0047]    In this example, the starter  64 , the generator  68 , and the PMA/PMG  72 , are rotatably coupled to of a plurality of accessory drives, such as, for example, three drives D 1 , D 2 , D 3 , respectively. These three drives D 1 -D 3  are located on an aft side  80  of the accessory gearbox  66 . The hydraulic pump  76  and lubricant scavenge pump  78 , by contrast, are rotatably coupled to fourth and fifth accessory drives D 4  and D 5  on a forward side  84  of the accessory gearbox  66 . Aft and forward are determined with reference to the general direction of flow through the engine  62 . The five accessory drives D 1 -D 5  represent the location where the accessories rotatably engage the accessory gear box  60 . 
         [0048]    Of the accessories rotatably coupled to the accessory gearbox  66 , the generator  68  is located at the vertically lowest position. That is, the generator  68  is rotatably coupled to the third accessory drive D 3  that is at a first elevation, and the starter  64 , the PMA/PMG  72 , the hydraulic pump  76  and the lubricant scavenge pump  78  are coupled to all but the third accessory drive, that is, the four other accessory drives D 1 , D 2 , D 4 , and D 5  at elevations that are higher than the first elevation. Elevation, in this disclosure, refers generally to a distance or height when a system is in an orientation representative of the engine  62  or an associated aircraft being on level ground or in straight or level flight. 
         [0049]    The generator  68  is one of the heaviest accessories driven by the accessory gearbox  66 . Placing the generator  68  at a lower elevation positions the generator  68  in a location convenient for maintenance and repair. 
         [0050]    An outer housing  70  of the example accessory gearbox  66  is mounted directly to a casing  88  of a core of the engine  62 . Mechanical fasteners can be used to secure the outer housing  70 . 
         [0051]    The casing  88  generally provides the outer boundary of a core flowpath C through the engine  62 . The core flowpath extends through the low-pressure compressor  44 , the high-pressure compressor  52 , the combustor  56 , the high-pressure turbine  54 , and the low pressure turbine  46 . At a given axial location, the core is generally the portions of the engine  62  radially inside the bypass flowpath. 
         [0052]    Another casing  90  of the core may be positioned radially outside the accessory gearbox  66 . The casing  90  has been removed in  FIGS. 3 to 5  to show the accessory gearbox  66 . This casing  90  generally provides the inner boundary of a bypass flowpath B through the engine  62 . 
         [0053]    The engine  62  includes a core compartment  92  bounded by the casing  88  and the casing  90 . The example accessory gearbox  66  is positioned within the core compartment  92 . 
         [0054]    In this example, a forward boundary of the core compartment  92  is established by an intermediate case  94  of the engine  62 . The intermediate case  94  is a structural case positioned between the high-pressure compressor  52  and the low-pressure compressor  44 . 
         [0055]    The example accessory gearbox  66  is mounted at a forward position within core compartment  92  of the engine  62 . Due to the hydraulic pump  76  and the lubricant scavenge pump  78 , which are coupled at drive positions on the forward side  84  of the accessory gearbox  66 , the accessory gearbox  66  is spaced axially a distance d from the intermediate case  94 . 
         [0056]    The example accessory gearbox  66  extends laterally across the rotational axis A of the engine  62  such that portions of the accessory gearbox  66  are on either side of the rotational axis A. 
         [0057]    Referring now to  FIGS. 6 to 8  with reference to  FIG. 2 , another example engine  120  includes an accessory gearbox  160  directly connected to an intermediate case  194 . Due to the direct connection, there is substantially no axial space between the accessory gearbox  160  and the intermediate case  194 . The accessory gearbox  160  is located in the forwardmost position within a core compartment  192  of the engine  120 . A casing  188  and a casing  190  radially bound the core compartment  192  of the engine  120 . 
         [0058]    The example accessory gearbox  160  includes a first portion  96  and a second portion  98 . The first portion  96  is separate from the second portion  98 . The first portion  96  and the second portion  98  are essentially separate gearboxes used to rotatably drive different accessories. The first portion  96  and the second portion  98  of the gearbox  160  can be driven by a separate power takeoff from the engine  120 , such as by separate tower shafts, or by a common takeoff through a linking drive mechanism. 
         [0059]    The first portion  96  and the second portion  98  are located on opposite laterally sides of the rotational axis A of the engine  120 . In this example, the first portion  96  and the second portion  98  include areas that axially overlap and are thus considered axially to be at the same axial location within the gas turbine engine  120 . Using a rotatable input from, for example, the high speed spool  32  the first portion  96  rotatably drives at least a PMA/PMG  172 , a generator  168 , and a hydraulic pump  178 . All of the accessories driven by the first portion  96  engage sixth through eighth accessory drives D 6 -D 8 , on an aft side  180  of the first portion  96 . The PMA/PMG  172 , the generator  168 , and the hydraulic pump  178  are all rotatably coupled to the first portion  96  at different ones of the sixth through eighth accessory drives D 6 -D 8 . The first portion  96  includes at least a housing  97  holding gearing suitable for transferring the rotatable input to the sixth through eighth accessory drives D 6 -D 8  of the first portion  96 . 
         [0060]    Using a rotatable input from, for example, the high speed spool  32  the second portion  98  of the accessory gearbox  160  rotatably drives at least the starter  164 . The starter  164  and any other accessories driven by the second portion  98  are rotatably coupled to the second portion  98  at different accessory drives, such as a ninth drive D 9 . All of the accessories driven by the second portion  98  engage accessory drives, such as the ninth drive D 9 , on the aft side  180 ′ of the second portion  98 . The second portion  98  includes at least a housing  99  holding gearing suitable for transferring the rotatable input to the accessory drives of the second portion  98 . 
         [0061]    Features of the disclosed examples include an accessory gearbox mounted in a location facilitating nacelle aero line performance and in a location providing favorably thermal energy levels. 
         [0062]    The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. Thus, the scope of legal protection given to this disclosure can only be determined by studying the following claims.