Abstract:
A turbofan engine includes a core engine section including a compressor section feeding air to a combustor to generate high speed exhaust gases that drive a turbine section all disposed about an engine axis, a geartrain driven by the core engine section, a fan section driven by the geartrain about a fan axis spaced apart from the engine axis, and an accessory gearbox driven by the geartrain and mounted apart from the core engine section and the fan section.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to U.S. Provisional Application No. 61/775,875 filed on Mar. 11, 2013. 
     
    
     BACKGROUND 
       [0002]    Commercial aircraft typically utilize a gas turbofan engine mounted under wing or in a tail structure. The gas turbine engine typically includes a fan section, and a core section including a compressor section, a combustor section and a turbine section all rotating about a common axis. Air entering the compressor section is compressed and delivered into the combustion section where it is mixed with fuel and ignited to generate a high-speed exhaust gas flow. The high-speed exhaust gas flow expands through the turbine section to drive the compressor and the fan section. 
         [0003]    The fan section drives air through a bypass passage to develop a majority of thrust produced by the engine. Larger fan diameters increase engine efficiencies. Increased diameters require correspondingly large cases and nacelle structures that are currently mounted under an aircraft wing. Accommodations such as longer landing gear, cantilevered engine mounting structures and/or complex wing structures required due to the larger fan sections increase weight and counteract the engine efficiency gains. 
         [0004]    Accordingly, engine and aircraft manufactures continue to seek further improvements to aircraft design to take advantage of advances in engine performance including improvements to thermal, transfer and propulsive efficiencies. 
       SUMMARY 
       [0005]    A turbofan engine according to an exemplary embodiment of this disclosure, among other possible things includes a core engine section including a compressor section feeding air to a combustor to generate high speed exhaust gases that drive a turbine section all disposed about an engine axis, a geartrain driven by the core engine section, a fan section driven by the geartrain about a fan axis spaced apart from the engine axis, and an accessory gearbox driven by the geartrain and mounted apart from the core engine section and the fan section. 
         [0006]    In a further embodiment of the foregoing turbofan engine, includes an input shaft driven by the core engine section and a first output shaft driven by the geartrain for driving the fan section. The input shaft and first output shaft rotate about different axes. 
         [0007]    In a further embodiment of any of the foregoing turbofan engines, the input shaft extends axially forward of the core engine section. 
         [0008]    In a further embodiment of any of the foregoing turbofan engines, includes a second output shaft driven by the geartrain driving the accessory gearbox. 
         [0009]    In a further embodiment of any of the foregoing turbofan engines, the fan axis is spaced horizontally apart from the engine axis. 
         [0010]    In a further embodiment of any of the foregoing turbofan engines, the fan axis and the engine axis are substantially parallel. 
         [0011]    In a further embodiment of any of the foregoing turbofan engines, the fan section includes a bypass ratio greater than about 10. 
         [0012]    An aircraft propulsion system according to an exemplary embodiment of this disclosure, among other possible things includes a core engine section mounted within an aft portion of an aircraft fuselage. The core engine section includes a compressor section feeding air to a combustor to generate high speed exhaust gases that drive a turbine section all disposed about an engine axis. A geartrain is mounted within the aircraft fuselage and driven by the core engine section. A fan section is externally mounted to the aircraft fuselage and driven by the geartrain about a fan axis spaced apart from the engine axis. An accessory gearbox is supported within the aircraft fuselage and driven by the geartrain and mounted apart from the core engine section and the fan section. 
         [0013]    In a further embodiment of the foregoing aircraft propulsion system, includes an inlet for supplying air to the core engine section mounted to the aircraft fuselage. 
         [0014]    In a further embodiment of any of the foregoing aircraft propulsion systems, includes a fan case surrounding the fan section. The fan case includes a first thrust reverser movable to a position directing thrust from the fan section in a direction to slow the aircraft. 
         [0015]    In a further embodiment of any of the foregoing aircraft propulsion systems, includes an exhaust nozzle disposed about the engine axis. The exhaust nozzle includes a second thrust reverser for directing exhaust gases from the core engine section in a direction to slow the aircraft. 
         [0016]    In a further embodiment of any of the foregoing aircraft propulsion systems, includes an input shaft driven by the core engine section for driving the geartrain, a first output shaft from the geartrain driving the fan section, and a second output shaft from the geartrain driving the accessory gearbox. 
         [0017]    In a further embodiment of any of the foregoing aircraft propulsion systems, the fan axis is parallel to the engine axis. 
         [0018]    In a further embodiment of any of the foregoing aircraft propulsion systems, the core engine section includes a first core engine section and a second core engine section mounted side-by-side within the aft portion of the aircraft fuselage and the fan section includes first and second fan sections driven by a corresponding one of the first and second core engine sections. 
         [0019]    In a further embodiment of any of the foregoing aircraft propulsion systems, geartrain includes first and second geartrains and the accessory gearbox includes first and second accessory gearboxes driven by a corresponding one of the first and second geartrains. 
         [0020]    An aircraft system according to an exemplary embodiment of this disclosure, among other possible things includes an elongated fuselage. A wing structure extends from opposing sides of the fuselage. A vertical stabilizer includes a horizontal stabilizer surface mounted to an upper portion of the vertical stabilizer. A core engine section is mounted within an aft portion of an aircraft fuselage. The core section includes a compressor section feeding air to a combustor to generate high speed exhaust gases that drive a turbine section all disposed about an engine axis. A geartrain is mounted within the aircraft fuselage and driven by the core section. A fan section is externally mounted to the aircraft fuselage and driven by the geartrain about a fan axis spaced apart from the engine axis. An accessory gearbox is supported within the aircraft fuselage and driven by the geartrain and mounted apart from the core section and the fan section. 
         [0021]    In a further embodiment of the foregoing aircraft system, the core section includes first and second core sections and the fan section includes first and second fan sections driven by corresponding ones of the first and second core engine sections. 
         [0022]    In a further embodiment of any of the foregoing aircraft systems, includes an air inlet supplying air to each of the first and second core engine sections. 
         [0023]    In a further embodiment of any of the foregoing aircraft systems, the fan section is mounted above the wing structure. 
         [0024]    In a further embodiment of any of the foregoing aircraft systems, the fan section includes a bypass ratio greater than about 10. 
         [0025]    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. 
         [0026]    These and other features disclosed herein can be best understood from the following specification and drawings, the following of which is a brief description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]      FIG. 1  is a schematic view of an example aircraft including ultra-high bypass turbofan engines. 
           [0028]      FIG. 2  is an aft perspective view of the example aircraft and propulsion system. 
           [0029]      FIG. 3  is an enlarged view of a portion of the example propulsion system. 
           [0030]      FIG. 4  is a side view of the aft portion of the aircraft including the example propulsion system. 
           [0031]      FIG. 5  is an aft view of the example propulsion system. 
           [0032]      FIG. 6  is another perspective view of the example propulsion system. 
           [0033]      FIG. 7  is an example view of a thrust reverser of the example propulsion system. 
       
    
    
     DETAILED DESCRIPTION 
       [0034]    Referring to  FIGS. 1 and 2 , an example aircraft  10  is shown that includes wings  14  that extend from a fuselage  12 . The aircraft  10  includes landing gear  16  are provided on each of the wings  14  and at a front of the fuselage  12 . The example aircraft  10  includes a T-tail  18 . The T-tail  18  includes a vertical stabilizer  20  and a horizontal stabilizer  22  disposed at an upper end of the vertical stabilizer  20 . 
         [0035]    The fuselage  12  includes an aft portion  24  that supports a propulsion system  25 . The example propulsion system  25  includes core engine sections  26   a,    26   b  that drive corresponding fan sections  28   a  and  28   b.  The core engine sections  26   a  and  26   b  are disposed about respective axes A that are spaced apart from respective axes B of the fan sections  28   a  and  28   b.  An inlet  30  defined within the fuselage  12  provides airflow to feed the core engine sections  26   a  and  26   b.    
         [0036]    Referring to  FIGS. 2 and 3  with continued reference to  FIG. 1 , the example propulsion system  25  includes two core engine sections  26   a  and  26   b  that are mounted side-by-side at the aft portion  24  of the fuselage  12 . Each of the core engine sections  26   a,    26   b  include a compressor section  48 , a combustor section  50  and a turbine section  52  disposed about respective axes A. An auxiliary power unit  34  is also mounted in the aft portion  14  of the fuselage  12 . 
         [0037]    As appreciated each of the core engine sections  26   a  and  26   b  include similar structure for powering respective fan sections  28   a  and  28   b.  One of the example core engine sections  26   a  is described with the understanding that identical structure (not shown) is duplicated for the core engine section  26   b.    
         [0038]    The core engine section  26   a  drives an input shaft  42  that in turn drives a geartrain  38 . The geartrain  38  includes a first output shaft  44  that drives the corresponding fan section  28   a.  The fan section  28   a  includes a plurality of fan blades disposed within corresponding fan cases  32   a  that rotate about the axis B. The axis B is spaced apart and parallel to the axis A of the core engine section  26   a.    
         [0039]    The geartrain  38  also includes a second output shaft  46  that drives an accessory gearbox  36 . The accessory gearbox  36  drives systems required to support operation of the corresponding core engine  26   a  along with systems utilized for aircraft operation. Moreover, although the disclosed embodiment includes an accessory gearbox  36  for each core engine  26   a,    26   b,  it is within the contemplation of this disclosure that a single accessory gearbox  36  could be utilized for both core engine sections  26   a,    26   b.    
         [0040]    Referring to  FIGS. 4 ,  5  and  6 , the example fan sections  28   a  and  28   b  are mounted to a side of the fuselage  12  and above the wings  14 . Gas turbine engines that are mounted below the wing  14  are limited as to the size of the fan due to restrictions and minimum clearance requirements for the aircraft  10 . Large fan sections that are mounted under the wing  14  require longer aircraft landing gear  16  that in turn add weight that can eliminate or reduce the effectiveness and efficiencies provided by the larger fan sections  28   a  and  28   b.    
         [0041]    In this example, the aircraft  10  includes the fan sections  28   a  and  28   b  that are mounted to the aft portion  24  of the fuselage  12  in a position above the wing  14  and therefore can provide ultra-high bypass ratios greater than about 10. Moreover, by separating the core engine sections  26   a,    26   b  from the fan sections  28   a,    28   b,  the mounting structures supporting the fan sections  28   a  and  28   b  can be lighter to further increase engine efficiency. 
         [0042]    The T-tail section  18  includes the vertical stabilizer  20  and the horizontal stabilizer  22 . The horizontal stabilizer  22  is mounted substantially on an upper tip of the vertical stabilizer  20  such that airflow over the control surfaces of the horizontal stabilizer  22  is not detrimentally affected by airflow output from the fan sections  28   a  and  28   b.    
         [0043]    Referring to  FIG. 7 , the example propulsion system  25  includes thrust reversing features. In this example, both the fan sections  28   a  and  28   b  include a thrust reverser  56   a,    56   b  along with thrust reverser  58  mounted to the core engine sections  26   a  and  26   b.  In operation, the fan sections  28   a  and  28   b  both include the corresponding thrust reversers  56   a,    56   b  that include doors that open radially outward to direct thrust outwardly to slow the aircraft  10 . 
         [0044]    The propulsion system  25  also includes thrust reversing doors on a nozzle  40  corresponding to the core engines  26   a  and  26   b.  The thrust reversing portion  58  includes doors that close along a center line of each of the core engines  26   a  and  26   b.  Thrust generated by the core engines  26   a  and  26   b  is thereby directed in a manner to slow the aircraft once it has landed. 
         [0045]    The aft fuselage mounting of the core engine sections  26   a  and  26   b  eliminates requirements for heavier and more robust engine mounting structures that would be required for traditional wing and fuselage mounted turbofan engines. Moreover, the coupling of the core engine sections  26   a  and  26   b  from the corresponding fan sections  28   a  and  28   b  allows for a more efficient and smaller fan support structures. Furthermore, a fuselage mounting of the fan sections  28   a  and  28   b  along with the core engine sections  26   a  and  26   b  does not require extending or raising the aircraft  10  by providing longer landing gear structures. 
         [0046]    Accordingly, the example aircraft and propulsion system disclosed for the example aircraft provides for the use of an ultra-high bypass fan section in commercial aircraft without limit to the fan diameter or without the requirement for heavy mounting structures to support core engine and fan components. 
         [0047]    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 this disclosure. For that reason, the following claims should be studied to determine the scope and content of this disclosure.