Abstract:
A gas turbine engine has a fan inlet and a fan configured to deliver air to an exhaust nozzle. A core gas turbine engine. including in serial order extending further into the engine, a core turbine section, a combustor and a core compressor section. A core engine inlet duct is spaced from the fan inlet. A method is also described.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    This application claims priority to U.S. Provisional Application No. 61/725,172, filed Nov. 12, 2012. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]    This application relates to a reverse core gas turbine engine which is to be mounted above an aircraft wing. 
         [0003]    Gas turbine engines are known and, when utilized in aircraft applications, include a fan delivering air into a compressor section. The air is compressed and passed downstream into a combustor where it is mixed with fuel and ignited. Products of this combustion pass downstream over turbine rotors, driving them to rotate. 
         [0004]    Historically, the engines have had the fan, then the compressor, then the combustor and, finally, the turbine section serially aligned in an axial direction extending into the engine and all centered on a common axis. More recently, so called reverse core engines have been proposed wherein the components are the fan, then the turbine, then the combustor, then the compressor as one moves serially along an axial direction into the engine. The reverse core engine allows a more compact arrangement. In addition, it is known that the reverse core engine can be centered on a center axis which is not aligned with a center drive axis for the fan. 
         [0005]    The use of a reverse core engine has not been proposed for mounting at a location above an aircraft wing. 
       SUMMARY OF THE INVENTION  
       [0006]    In a featured embodiment, a gas turbine engine has a fan inlet and a fan configured to deliver air to an exhaust nozzle. A core gas turbine engine includes, in serial order extending further into the engine relative to the fan inlet, a core turbine section, a combustor and a core compressor section. A core engine inlet duct is spaced from the fan inlet relative to a fan radial center. 
         [0007]    In another embodiment according to the previous embodiment, the core gas turbine engine is centered along a first axis. The fan rotates about a second axis. The first and second axes are non-parallel. 
         [0008]    In another embodiment according to any of the previous embodiments, a core engine inlet duct extends to a turning section where the air is turned to communicate with the core compressor section. 
         [0009]    In another embodiment according to any of the previous embodiments, a particle separator is positioned to allow removal of impurities from the air prior to it turning into the core compressor section. 
         [0010]    In another embodiment according to any of the previous embodiments, the outlet nozzle is not centered about an axis of the fan, but rather is positioned to be larger on one side of the axis of the fan. 
         [0011]    In another embodiment according to any of the previous embodiments, a free turbine is positioned downstream of the core engine turbine. The free turbine receives products of combustion from the core engine turbine, and drive the fan. 
         [0012]    In another embodiment according to any of the previous embodiments, the free turbine drives the fan rotor through a gear reduction. 
         [0013]    In another featured embodiment, an aircraft has a wing mounting an engine. The engine includes a fan inlet and a fan configured to deliver air to an exhaust nozzle. A core gas turbine engine includes in serial order extending further into the engine, a core turbine section, a combustor and a core compressor section, a core engine intake duct. The exhaust nozzle is vertically above a leading edge of the wing. The inlet duct is vertically below a leading edge of the wing. 
         [0014]    In another embodiment according to the previous embodiment, the core gas turbine engine is centered along a first axis. The fan rotates about a second axis. The first and second axes are non-parallel. 
         [0015]    In another embodiment according to any of the previous embodiments, a core engine inlet duct extends to a turning section where the air is turned to communicate with the core compressor section. 
         [0016]    In another embodiment according to any of the previous embodiments, a particle separator is positioned to allow removal of impurities from the air prior to it turning into the core compressor section. 
         [0017]    In another embodiment according to any of the previous embodiments, an outlet nozzle is not centered about the second axis but rather is positioned to be larger on a vertically upper side of the second axis. 
         [0018]    In another embodiment according to any of the previous embodiments, a free turbine is positioned downstream of the core engine turbine. The free turbine receives products of combustion from the core engine turbine, and drive the fan. 
         [0019]    In another embodiment according to any of the previous embodiments, the free turbine drives the fan rotor through a gear reduction. 
         [0020]    In another featured embodiment, a method of operating an engine includes the steps of passing air in an inlet of a fan along a first direction, and passing core air into a core duct inlet at a location radially offset from a fan center axis of the fan. The core air is then turned along an acute angle in a direction having at least a component in a reverse direction relative to the fan center axis, and in a direction radially toward the fan center axis. The core air then enters a core engine to sequentially travel through a compressor section, a combustor, and a turbine section. 
         [0021]    In another embodiment according to the previous embodiment, the core air downstream of the turbine section passes over a free turbine, driving the free turbine to rotate. The free turbine in turn drives the fan. 
         [0022]    In another embodiment according to any of the previous embodiments, the free turbine drives the fan through a gear reduction. 
         [0023]    In another embodiment according to any of the previous embodiments, the fan inlet is positioned vertically above an aircraft wing. The core inlet duct is positioned vertically below the aircraft wing. 
         [0024]    In another embodiment according to any of the previous embodiments, the fan inlet is positioned vertically above an aircraft wing, and the core inlet duct is positioned vertically below the aircraft wing. 
         [0025]    In another embodiment according to any of the previous embodiments, a particle separator is positioned in the core air flow downstream from the core inlet duct, and removes impurities prior to the core air entering the core engine. 
         [0026]    These and other features may be best understood from the following drawings and specification. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0027]      FIG. 1  shows an aircraft wing. 
           [0028]      FIG. 2A  shows mount details of an engine. 
           [0029]      FIG. 2B  shows flow details of the  FIG. 2A  engine. 
           [0030]      FIG. 3  is a cross-sectional view through the engine. 
       
    
    
     DETAILED DESCRIPTION  
       [0031]    As shown in  FIG. 1 , an aircraft  20  includes a wing  22 , with an engine  24  mounted to be vertically above the wing. A fan  26  is positioned inwardly of a fan inlet duct  27 . 
         [0032]    A core inlet duct  28  is positioned vertically below the fan inlet  27  and leads to a duct body  30 . 
         [0033]    As can be seen, an engine outlet  44  is vertically above a wing leading edge  99 , while core inlet duct  28  is below it. 
         [0034]    As shown in  FIG. 2A , vanes  129  are positioned at a rear end adjacent outlet  44 . A core engine  130  is positioned inwardly from the vanes  129 , and the core inlet duct  28  and the duct  30  communicates with the core engine  130 . Pylons  41  mount the engine within a central space in the wing  22 . 
         [0035]    As shown in  FIG. 2B , an outlet  110  serves as a particle ejector, as will be explained below. Further, a duct  111  separates the core engine components from the remainder of the engine  24 . An outlet nozzle  44  serves as a main outlet for the engine. 
         [0036]      FIG. 3  is a cross-sectional view through the engine  24 . 
         [0037]    As shown, air driven by the fan  26  moves through a bypass duct as propulsion air and outwardly of the outlet  44 . Air enters the core inlet duct  28  formed in a duct body  30 . Dirt or other impurities may be ejected outwardly of outlet or particle separator  110 . Turning vanes  112  assist in turning the air flow into a compressor section  114 . A combustor  116  is positioned downstream of the compressor  114  and a turbine section  118  is downstream of the combustor  116 . The core engine  130  is mounted on a centerline C which is offset relative to a centerline A about which the fan  26  rotates. 
         [0038]    A free turbine  120  receives the products of combustion downstream of the turbine section  118  and is driven to rotate to, in turn, drive a shaft  128  and then drive the fan rotor  26  through a gear reduction  131 . 
         [0039]    As illustrated, moving further into the aircraft engine along the axis A, the first rotating element is the fan  26 , then the free turbine  120 , then the core engine turbine  118  and core engine compressor  114 . The non-rotating combustor  116  is between the rotating core turbine  118  and compressor  114 . 
         [0040]    As can be appreciated from  FIG. 3 , the core exhaust nozzle  44  is not centered on axis A but instead is largely on a vertically upper side of axis A. 
         [0041]    In addition, core engine components, including core turbine and core compressor sections and the combustor, are oft referenced as a gas generator portion of the engine. In the illustrated configuration, a propulsor portion of the engine would include the free turbine  120  and fan  26 . However, other component groupings and descriptors may be utilized without limiting the nature or scope of the disclosed embodiments. 
         [0042]    In this arrangement, the engine exhaust  44  is above the wing  22 , whereas the core inlet duct  28  is below the wing. This provides improved lift for the engine. Further, the disclosed arrangement results in a very compact engine and one which is well integrated into the aircraft wing. 
         [0043]    In a method, air enters an inlet of a fan  26  along a first direction, and air enters a core duct inlet  28  at a location radially offset from a center axis A of the fan, with a free stream of airflow entering the core inlet duct, and then being turned along an acute angle in a direction C having at least a component in a reverse direction relative to the center axis A, and having a component in a direction radially toward the center axis A. The air then passes through a core engine  130 , to sequentially travel through a compressor section  114 , a combustor  116 , and a turbine section  118 . 
         [0044]    Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.