Abstract:
Gas turbine engine systems and related methods involving multiple gas turbine cores are provided. In this regard, a representative gas turbine engine includes: an inlet; a blade assembly mounted to receive intake air via the inlet; and multiple gas turbine cores located downstream of the blade assembly, each of the multiple gas turbine cores being independently operative in a first state, in which rotational energy is provided to rotate the blade assembly, and a second state, in which rotational energy is not provided to rotate the blade assembly.

Description:
[0001]    This application is a divisional of U.S. patent application Ser. No. 11/847,640 filed Aug. 30, 2007, which is hereby incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The disclosure generally relates to gas turbine engines. 
         [0004]    2. Description of the Related Art 
         [0005]    Gas turbine engines typically are designed to operate over a broad range of power settings in order to meet varying mission requirements. Unfortunately, various design tradeoffs typically are made in order to accommodate such a broad range of requirements. These tradeoffs oftentimes result in an engine that operates much of the time in a non-optimal manner 
       SUMMARY 
       [0006]    Gas turbine engine systems and related methods involving multiple gas turbine cores are provided. In this, regard, an exemplary embodiment of a gas turbine engine comprises: an inlet; a blade assembly mounted to receive intake air via the inlet; and multiple gas turbine cores located downstream of the blade assembly, each of the multiple gas turbine cores being independently operative in a first state, in which rotational energy is provided to rotate the blade assembly, and a second state, in which rotational energy is not provided to rotate the blade assembly. 
         [0007]    An exemplary embodiment of a gas turbine core assembly for mounting within a gas turbine engine that has a rotatable blade assembly comprises: a first gas turbine core comprising: a first compressor section; a first combustion section operative to receive compressed gas from the first compressor section; a first shaft; a first turbine section operative to impart rotational energy to the first compressor section via the first shaft; and a first drive segment coupled to the first shaft and operative to provide rotational energy from the first shaft to the blade assembly, the first drive segment being offset with respect to a centerline of the blade assembly. 
         [0008]    An exemplary embodiment of a method for operating a gas turbine engine comprises: selectively operating at least one of multiple gas turbine cores of the gas turbine engine; and imparting rotational energy from the at least one of the multiple gas turbine cores to a blade assembly, the blade assembly being rotatable to provide a flow of gas to the multiple gas turbine cores. 
         [0009]    Other systems, methods, features and/or advantages of this disclosure will be or may become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features and/or advantages be included within this description and be within the scope of the present disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    Many aspects of the disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
           [0011]      FIG. 1  is a schematic diagram depicting an exemplary embodiment of a gas turbine engine. 
           [0012]      FIG. 2  is a schematic cross-sectional view of the embodiment of  FIG. 1 . 
           [0013]      FIG. 3  is a flowchart depicting functionality of an embodiment of a gas turbine engine. 
           [0014]      FIG. 4  is a schematic diagram depicting another exemplary embodiment of a gas turbine engine. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    Gas turbine engine systems and related methods involving multiple gas turbine cores are provided, several representative embodiments of which will be described in detail. In this regard,  FIG. 1  is a schematic diagram depicting an exemplary embodiment of a gas turbine engine. 
         [0016]    As shown in  FIG. 1 , gas turbine engine  100  incorporates an inlet  102  that provides intake air to a blade assembly  104 . In this embodiment, engine  100  is a turbofan, with the blade assembly being configured as a fan incorporating multiple variable pitch blades, e.g., blade  106 . However, in other embodiments, the blade assembly could be a set of blades of a compressor of a turbojet, for example. Thus, the concepts described herein should not be construed as being limited to turbofans. 
         [0017]    Downstream of the blade assembly are located multiple gas turbine cores. Specifically, four such gas turbine cores are used in this embodiment although only cores  120 ,  130  are shown for ease of illustration in  FIG. 1 . Note that all four cores are depicted in  FIG. 2 . In other embodiments, various other numbers and arrangements of gas turbine cores can be used. 
         [0018]    Each of the gas turbine cores incorporates a casing, a compressor section, a combustion section, and a turbine section, with a shaft interconnecting the compressor section and the turbine section. Thus, gas turbine core  120  includes casing  121 , compressor section  122 , combustion section  124 , turbine section  126  and shaft  128 , whereas gas turbine core  130  includes casing  131 , compressor section  132 , combustion section  134 , turbine section  136  and shaft  138 . Each of the gas turbine cores is independently operable and can selectively provide rotational energy to the blade assembly. Notably, although depicted as single spool cores, various other configurations can be used in other embodiments. 
         [0019]    In the embodiment of  FIG. 1 , each gas turbine core is coupled to a corresponding clutch and gearbox that can provide rotational energy to the blade assembly via a main shaft  140 . Specifically, core  120  is able to apply torque to the blade assembly via a drive segment  129 , clutch  142  and gearbox  144 , and core  130  is able to apply torque to the blade assembly via drive segment  139 , clutch  146  and gearbox  148 . 
         [0020]    Application of torque to the blade assembly can be accomplished in a variety of manners. For instance, a clutch can be configured to disengage a corresponding core from the blade assembly responsive to available torque of that core dropping below a threshold level. Thus, in such an embodiment, shutdown of the core can initiate the disengagement. In other embodiments, an operating core with fully available torque can be disengaged from the blade assembly by a clutch. 
         [0021]    In some embodiments, a gas turbine core can be used to provide electricity. In this regard, engine  100  incorporates a generator  149  that is driven by a core; in this case, core  120 . Depending on the mode of operation, the generator can be driven whether or not core  120  is providing torque to the blade assembly. Thus, such a generator can be coupled to a core in various locations, such as between the core and the clutch or between the core and the gearbox, for example. 
         [0022]    In operation, one or more of the cores can be shutdown based on the overall power requirements of the gas turbine engine  100 . For instance, if power requirements are high, all of the cores can be operating, whereas, if power requirements are low as few as one of the cores could be operating. This tends to improve thermodynamic efficiency of the engine as the operating core(s) can be operated within a high efficiency range of operating parameters. 
         [0023]    Notably, efficiency of the engine can be further increased by altering one or more of various gas flow parameters. By way of example, in a high speed mode, in which all of the cores may be operating, fan pressure ratio of the engine can be increased, such as by reducing bypass flow and increasing blade angle of the variable pitch blades of the blade assembly. In contrast, in a reduced speed mode, in which less than all of the cores typically are operating, bypass ratio of the engine can be increased while decreasing the blade angle of the variable pitch blades of the blade assembly. 
         [0024]      FIG. 2  is a schematic cross-sectional view of the embodiment of  FIG. 1 . In particular,  FIG. 2  depicts the four gas turbine cores ( 120 ,  130 ,  150  and  160 ) positioned annularly about the centerline of the gas turbine engine. In this embodiment, each gas turbine core shaft is oriented parallel and offset with respect to the main shaft. Additionally, each opposing pair of gas turbine cores exhibits axial symmetry about the centerline of the main shaft. 
         [0025]      FIG. 3  is a flowchart depicting functionality of an embodiment of a gas turbine engine that includes multiple gas turbine cores. In this regard, the functionality (or method) may be construed as beginning at block  302 , in which at least one of multiple gas turbine cores of the gas turbine engine is selectively operated. In block  304 , rotational energy from the at least one of the multiple gas turbine cores is imparted to a blade assembly. Notably, the blade assembly is rotatable to provide a flow of gas to the multiple gas turbine cores. 
         [0026]    Another embodiment of a gas turbine engine is depicted schematically in  FIG. 4 . As shown in  FIG. 4 , gas turbine engine  400  incorporates an inlet  402  that provides intake air to a blade assembly  404 . 
         [0027]    Downstream of the blade assembly are located multiple gas turbine cores. Specifically, four such gas turbine cores are used in this embodiment although only cores  420 ,  430  are shown for ease of illustration. 
         [0028]    Each of the gas turbine cores incorporates a casing, a compressor section, a combustion section, and a turbine section, with a shaft interconnecting the compressor section and the turbine section. Thus, gas turbine core  420  includes casing  421 , compressor section  422 , combustion section  424 , turbine section  426  and shaft  428 , whereas gas turbine core  430  includes casing  431 , compressor section  432 , combustion section  434 , turbine section  436  and shaft  438 . Each of the gas turbine cores is independently operable and can selectively provide rotational energy to the blade assembly. 
         [0029]    In the embodiment of  FIG. 4 , each gas turbine core is coupled to a corresponding clutch and gearbox that can provide rotational energy to the blade assembly via a main shaft  440 . Specifically, core  420  is able to apply torque to the blade assembly via a drive segment  429 , clutch  442  and gearbox  444 , and core  430  is able to apply torque to the blade assembly via drive segment  439 , clutch  446  and gearbox  448 . 
         [0030]    Notably, the blade assembly  404  of this embodiment is a compound fan incorporating a main (inner) fan  460  and a tip rotator  462 . In operation, main fan  460  provides a flow of air to the cores, as well as a flow of bypass air (via primary bypass inlets  464 ), during operation of the gas turbine engine. The tip rotor  462  selectively provides thrust based on the position of secondary bypass inlets  466 . Specifically, in the open position (depicted in the upper portion of  FIG. 4 ), air is provided to the tip rotor for providing thrust, whereas, in the closed position (depicted in the lower portion of the figure), additional air is not provided to the tip rotor. 
         [0031]    It should be emphasized that the above-described embodiments are merely possible examples of implementations set forth for a clear understanding of the principles of this disclosure. Many variations and modifications may be made to the above-described embodiments without departing substantially from the spirit and principles of the disclosure. By way of example, although the exemplary embodiments described herein involve the use of single stage fans, multiple stage fans could also be used. As another example, while multiple gearboxes also have been described (i.e., each turbine core uses a corresponding gearbox), other embodiments multiple turbine cores could share one or more gearboxes. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the accompanying claims