Abstract:
A concentric generator usable with a gas turbine engine having a shaft. Disclosed embodiments include a generator with a rotor integral with the gas turbine shaft and a stator mounted concentrically with respect to the rotor. The stator may be mounted inside the turbine engine housing, or outside the turbine housing. In some embodiments, both the rotor and stator are mounted outside the turbine housing and rotation of the turbine shaft is translated to the rotor via a transmission.

Description:
FIELD OF THE DISCLOSURE 
       [0001]    This disclosure relates to electric generators, and more particularly to concentric ring generators for advantageous use in aircraft having gas turbine engines. 
       BACKGROUND 
       [0002]    In general, military and commercial aircraft are increasingly relying on electrical systems to perform functions that were previously performed by mechanical or hydraulic systems. In general, some manufacturers are working to manufacture an “all electric” aircraft that has reduced weight and, thus, has increased fuel efficiency and/or range. 
         [0003]    Moreover, modern communication, navigation, avionics, weapons systems, etc., are consuming ever increasing amounts of electric power. As a result, power demands on the existing aircraft power plant are increasing and expected to continue increasing in the future. For example, some known aircraft generators currently in service are capable of generating approximately 100 kW of electric energy. While this quantity of energy is sufficient to meet today&#39;s typical aircraft energy requirements, it may not be sufficient to meet future energy requirements as discussed above. 
         [0004]    One solution to meeting additional power needs is to install a larger, higher output generator to meet the increased energy demands. However, installing a larger generator is often not feasible on modern aircraft. For example, the aircraft may not have enough “open space” to accommodate the physical size of a larger generator. For example, at least some known aircraft generators are driven by a single power take-off (“PTO”) shaft that also drives many other hydraulic and pneumatic pumps. As discussed above, as electrical power requirements increase, the torques and stresses on the PTO shaft due to a larger generator would also increase significantly. Additionally, it is often not practical to modify the aircraft to support a larger generator for cost and other reasons. Other drawbacks and disadvantages with current aircraft generators may also exist. 
       SUMMARY 
       [0005]    Accordingly, the disclosed systems and methods substantially address the above-noted drawbacks and disadvantages of existing systems. In general, the disclosed generator incorporates a concentric ring design that may be incorporated internally within a turbine engine, such as an aircraft engine, or externally around the outer surface of the engine, or in combinations of internal and external mounting. In so configuring the generator, it affords a relatively larger surface area for the stator coils of the generator and, in some embodiments, allows for the radial positioning of independent stator coils with respect to the rotor, which may be used to regulate output power and voltage as disclosed herein. 
         [0006]    In addition, the disclosed systems and methods allow for an efficient step down (buck) of the relatively high voltage created by embodiments of the disclosed generator, as compared to the step up (boost) required by conventional aircraft generators. Likewise, embodiments of the disclosed generator enable variable frequency output that may be advantageous in some applications. 
         [0007]    Embodiments of the disclosed generator also enable manufacturing of a generator with relatively less copper (in coils or windings) while allowing for higher voltages (with increased insulation). Furthermore, the concentric configuration enables a relatively simpler mechanical connection with the engine and may eliminate the need for PTO shafts or other transmissions. For embodiments that rely on planetary gearing, the loads and torques on the generator and engine can be distributed over numerous gears. Other advantages also exist. 
         [0008]    Accordingly, disclosed embodiments include a generator comprising a turbine engine comprising a shaft, a compressor, and a turbine, a rotor in mechanical communication with the shaft and configured to be rotated by motion of the shaft, a stator comprising at least one coil wherein the stator is disposed radially outward of the rotor and wherein rotation of the rotor within the stator causes the generation of electric power. In some embodiments, the rotor and the stator are concentric with the shaft of the turbine engine. In some embodiments, the rotor further comprises a permanent magnet rotor. 
         [0009]    In some embodiments the generator includes a housing substantially enclosing the turbine engine and the stator is mounted substantially inside the housing. In some embodiments, the stator is mounted substantially outside the housing. 
         [0010]    In some embodiments, the generator includes a transmission to transfer motion of the shaft to the rotor, and the rotor and stator are concentrically mounted substantially outside the housing. In some embodiments, the transmission further comprises at least one gear in mechanical communication with the rotor and imparting rotational motion to the rotor in response to motion of the shaft. In some embodiments, the at least one gear is a planetary gear. 
         [0011]    In some embodiments, the generator further includes positioning means for moving the at least one coil. In some embodiments, the positioning means enables the at least one coil to move radially with respect to the rotor. 
         [0012]    Also disclosed is a method of manufacturing a generator comprising connecting a rotor in mechanical communication with a shaft of a turbine engine so that the rotor is rotated by motion of the shaft, positioning a stator comprising at least one coil radially outward of the rotor, concentric with the rotor and the shaft of the turbine engine, and wherein rotation of the rotor within the stator causes the generation of electric power. 
         [0013]    In some embodiments, the method further comprises mounting the stator substantially inside a housing of the turbine engine. In some embodiments, the method further comprises mounting the stator substantially outside a housing of the turbine engine. 
         [0014]    In some embodiments, the method of manufacturing further comprises concentrically mounting the rotor and stator substantially outside a housing of the turbine engine, connecting a transmission to transfer motion of the shaft to the rotor, and providing positioning means for moving the at least one coil. 
         [0015]    Also disclosed is a concentric generator comprising a turbine engine comprising a shaft, a compressor, and a turbine, a rotor, mounted concentrically with the shaft, and in mechanical communication with the shaft wherein the rotation of the shaft causes rotation of the rotor, a stator comprising at least one movable coil positioned concentrically and radially outward of the rotor and wherein rotation of the rotor within the stator causes the generation of electric power. 
         [0016]    In some embodiments, the turbine engine further comprises a housing and the stator is mounted substantially outside the housing. In some embodiments, the stator is mounted substantially inside the housing. 
         [0017]    In some embodiments the generator is manufactured such that the rotor is formed integrally with at least one of the compressor and turbine. In some embodiments, the rotor and compressor are both in mechanical communication with the shaft. In some embodiments, the rotor and turbine are both in mechanical communication with the shaft. Other advantages and characteristics of the disclosed embodiments will be apparent from the following detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is a schematic side view of an internal concentric ring generator in accordance with some disclosed embodiments. 
           [0019]      FIG. 2  is a schematic side view of a concentric ring generator with an external stator in accordance with some disclosed embodiments. 
           [0020]      FIG. 3  is a schematic side view of an internal concentric ring generator in accordance with some disclosed embodiments. 
           [0021]      FIG. 4  is a schematic front view of an external concentric ring generator in accordance with some disclosed embodiments. 
           [0022]      FIG. 5  is a schematic illustration of a movable stator coil in accordance with some disclosed embodiments. 
           [0023]      FIG. 6  is a schematic representation of electrically reconfigurable embodiments of the concentric ring generator. 
           [0024]      FIG. 7  is a schematic representation of a bypass mechanism in accordance with some disclosed embodiments. 
           [0025]      FIG. 8  is a schematic representation of a switching matrix in accordance with disclosed embodiments. 
       
    
    
       [0026]    While the disclosure is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. However, it should be understood that the disclosure is not intended to be limited to the particular forms disclosed. Rather, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
       DETAILED DESCRIPTION 
       [0027]    In general, a concentric ring generator  100  is disclosed. In some embodiments, the generator  100  is used in conjunction with a turbine engine  110 , such as a gas turbine engine commonly used on jet aircraft. The generator  100  may be driven by the turbine  110  on-board an aircraft. The generator  100  includes a rotor  160  and a stator  170  generally arranged in a concentric fashion. In some embodiments, the rotor  160  is ring shaped with an inner diameter that is sized to be located radially outward from the turbine engine  110 . In some embodiments, the generator  100  is configured to be placed around the turbine engine  110 . In other embodiments, the generator  100  may be integral with the turbine engine  110 . For embodiments where the generator  100  encircles the turbine engine  110 , appropriate gearing may be used (e.g., planetary gears  180  shown in  FIG. 4 ) to enable the turbine engine  110  to drive the rotor  160 . 
         [0028]    In some embodiments, generator  100  may include a stator  170  that is capable of moving with respect to the rotor  160  and thereby, among other things, being able to control the amount of generated output current. For example, in some embodiments, at least portions of stator  170  may be movable radially outward with respect to the rotor  160  to control the amount of current generated by generator  100 . Other embodiments may also move the coils out of the field in directions other than radially. 
         [0029]      FIG. 1  is a schematic side view of an internal concentric ring generator in accordance with some disclosed embodiments. As shown generator  100  may be integrated into a turbine engine  110 . As schematically indicated turbine engine  110  will have an intake portion  112  and an exhaust portion  114 . An engine shaft  120  will rotate a compressor  130  to draw in air from intake portion  112  and direct it into a combustion chamber  140  and out through turbine  150  and exhaust portion  114 . 
         [0030]    As shown in  FIG. 1 , embodiments of generator  100  may comprise a rotor  160  that is integrally formed in any of the compressor  130 , turbine  150 , or both. For example, rotor  160  may comprise an outer portion of compressor  130 , or rotor  160  may comprise a separate structure, such as a magnetized ring, or segments of permanent magnets that is mounted on an outer portion of compressor  130  and enabled to rotate therewith. Similar configurations may also be located at the turbine  150 , or both compressor  130  and turbine  150  may include a rotor  160 . 
         [0031]    As shown in  FIG. 1 , embodiments of generator  100  may also comprise a stator  170 . For the embodiment shown in  FIG. 1  the stator  170  is mounted internally in engine  110  and encircles rotor  160 . For the embodiment shown in  FIG. 2 , stator  170  is mounted externally to engine  110  and encircles rotor  160  internal to engine  110 . In addition, other combinations of internal and external mounting may be used. 
         [0032]    Rotor  160  and stator  170  may comprise any suitable components of an electrical machine and will further comprise coils, windings, magnets, ferrous materials, or the like to enable the generation of electrical current. As is also typical, rotor  160  will rotate under the influence of the forces generated by the engine  110  and stator  170  will remain generally stationary. Furthermore, either rotor  160  or stator  170  may comprise one or the other of the field producing component and the current producing component (i.e., armature). 
         [0033]      FIG. 3  is a schematic side view of an internal concentric ring generator in accordance with some disclosed embodiments. In the embodiments shown in  FIG. 3 , rotor  160  may comprise a discrete component separate from either compressor  130  or turbine  150 . Rotor  160  may be connected to shaft  120  and will still rotate under the influence of engine  110 . In addition, while rotor  160  is shown as being mounted “downstream” of compressor  130  and “upstream” of turbine  150 , the generator  100  is not so limited and other mounting locations of rotor  160  may be used. 
         [0034]      FIG. 4  is a schematic front view of an external concentric ring generator  100  in accordance with some disclosed embodiments. For this embodiment, both the rotor  160  and stator  170  are externally mounted, concentrically, on the engine  110  and one or more gears  180  may be used to impart the motion of the engine shaft  120  to the rotor  160 . As indicated, gears  180  may be part of planetary gearing system selected to rotate rotor  160  at any desired rotations per minute (“RPM”). Of course, other gearing, or transmission systems, may also be implemented. 
         [0035]    As also illustrated in  FIG. 4 , embodiments of the generator  100  may also include discrete stator coils  190  that may further comprise moveable portions that enable the movement of the coils  190  to change the field strength, the current, or the voltage produced by the generator  100 . 
         [0036]      FIG. 5  is a schematic illustration of a movable stator coil  190  in accordance with some disclosed embodiments. As illustrated schematically in  FIG. 5 , stator coils  190  may be mounted on a positioning means  200  so that coil  190  may be moved “closer” or “farther” from the rotor  160 . Positioning means  200  may comprise a mechanical positioner such as a screw jack, a rack and pinion gear system, levers, hinged arms, or the like that enable the motion of the coil  190  back-and-forth radially with respect to rotor  160 , and, generally will comprise an actuator  210  and a reciprocal biasing member  220 . For example, actuator  210  may comprise the screw portion of a screw jack and the reciprocal biasing member may comprise the reversible motor that drives the screw in the forward or reverse direction that moves the coil  190  back-and-forth. 
         [0037]    Positioning means  200  may also comprise a pneumatic, hydraulic, or other pressure-based position changer. As indicated schematically in  FIG. 5 , for embodiments when positioning means  200  comprises a pressure-based system it may include an actuator  210  at a first pressure and reciprocal biasing side  220  that is at a different pressure and can be used to bias the stator coil  190  in the opposite direction as the actuator  210 . 
         [0038]    In addition, embodiments of positioning means  200  may also comprise piezo-electric or other electrical transducer that can be used to position the coils  190  by changing the current or voltage to the transducer. 
         [0039]    In general, positioning means  200  may be used as a safety mechanism by enabling a stator coil  190  to be “dumped” or removed from the system if it shorts or otherwise fails by moving the coil  190  out of range of the rotor  160 . 
         [0040]    In addition, the movement of stator coils  190  can function as a voltage regulator as follows. In general, the closer the stator coil  190  is to the rotor  160  the greater the voltage and power it will generate. Further, for embodiments of the generator  100  that are operated under a variable source of mechanical power (e.g., when turbine engine  110  is part of an aircraft that experiences different speeds during flight) the voltage of the generator  100  will increase as the RPM of the engine  110  turns the rotor  160  faster. Therefore, by using positioning means  200  to “back out” the stator coils  190  as the R.P.M. of the rotor  160  (and engine  110 ) increase, the voltage of the generator  100  can be substantially kept at the desired level. 
         [0041]      FIG. 6  is a schematic representation of electrically reconfigurable embodiments of the generator  100 . Use of the independent stator coils  190  allows for independent and individualized wiring of the coils  190  so that different loads may be accommodated by generator  100 . This is particularly useful in the aircraft environment where the electrical needs of aircraft sub-systems (e.g., navigation, radar, weapons systems) can vary and cause interference with each other, in particular when powered by a common generator. As shown in  FIG. 6 , one set of coils  190 A may be wired to power a first load  230  while a different set of coils  190 B may be wired to power a second load  240 . As represented schematically, an increased set of coils  190 B may be used to power higher electrical power loads and a lesser set  190 A may be used for lower electrical power loads. In addition, other coils  190 C may be used for other loads, may remain out of use, be used as a backup, or the like. 
         [0042]      FIG. 7  is a schematic representation of a bypass mechanism in accordance with some disclosed embodiments. This may be implemented with the independent stator coils  190  as follows. Coil  190  may short or otherwise fail and this failure condition may be indicated by an appropriate sensor (not shown) such as a temperature sensor, current sensor, voltage sensor, or the like. If such a condition is sensed, switch  250  may open to remove the coil  190  from the power generation circuit and switch  260  may close to enable another coil (not shown) to replace coil  190  in the circuit. Of course, this sensing and switching may be automated by appropriate control logic, or the like. 
         [0043]      FIG. 8  is a schematic representation of a switching matrix in accordance with disclosed embodiments. In such embodiments, each stator coil  190  is connected to a switch matrix  270  which enables the selective switching of one or more of the stator coils  190  to one or more of the loads (e.g.,  230 ,  240 ,  280 ,  290 ). In this manner, the number of coils  190  can be matched to the size or need of the loads (e.g.,  230 ,  240 ,  280 ,  290 ). 
         [0044]    Although various embodiments have been shown and described, the present disclosure is not so limited and will be understood to include all such modifications and variations are would be apparent to one skilled in the art.