Abstract:
The present disclosure provides, in one embodiment, a unique gas turbine engine. Other embodiments include unique gas turbine engines, and unique active balancing systems; as well as apparatuses, systems, devices, hardware, methods, and combinations for gas turbine engines and active balancing systems. Further embodiments, forms, features, aspects, benefits, and advantages of the present application will become apparent from the description and figures provided herewith.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to and the benefit of U.S. Provisional Patent Application No. 61/777,976, filed 12 Mar. 2013, the disclosure of which is now expressly incorporated herein by reference. 
    
    
     FIELD OF THE DISCLOSURE 
     The present disclosure relates to gas turbine engines. More particularly, the present disclosure relates to active balancing systems and gas turbine engines having active balancing systems. 
     BACKGROUND 
     Balancing systems for gas turbine engines remain an area of interest. Some existing systems have various shortcomings, drawbacks, and disadvantages relative to certain applications. Accordingly, there remains a need for further contributions in this area of technology. 
     SUMMARY 
     One embodiment of the present disclosure is a unique gas turbine engine. Other embodiments include unique gas turbine engines, and unique active balancing systems; as well as apparatuses, systems, devices, hardware, methods, and combinations for gas turbine engines and active balancing systems. Further embodiments, forms, features, aspects, benefits, and advantages of the present application will become apparent from the description and figures provided herewith. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein: 
         FIG. 1  schematically illustrates some aspects of a non-limiting example of a gas turbine engine in accordance with an embodiment of the present disclosure; 
         FIG. 2  schematically illustrates some aspects of a non-limiting example of a balancing system in accordance with an embodiment of the present disclosure, wherein the balancing system is employed in conjunction with a turbine rotor disk; 
         FIG. 3  schematically illustrates some aspects of a non-limiting example of a balancing system in accordance with an embodiment of the present disclosure, and illustrates an example of a plurality of magnetic elements that may be activated to reduce or eliminate vibration in a rotor system and/or rotor system component; and 
         FIG. 4  schematically illustrates some aspects of a non-limiting example of a balancing system in accordance with an embodiment of the present disclosure, and illustrates an example of magnetic elements interacting to reduce an unbalance in a particular direction. 
     
    
    
     DETAILED DESCRIPTION 
     For purposes of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. It will nonetheless be understood that no limitation of the scope of the disclosure is intended by the illustration and description of certain embodiments of the disclosure. In addition, any alterations and/or modifications of the illustrated and/or described embodiment(s) are contemplated as being within the scope of the present disclosure. Further, any other applications of the principles of the disclosure, as illustrated and/or described herein, as would normally occur to one skilled in the art to which the disclosure pertains, are contemplated as being within the scope of the present disclosure. 
     Referring to the drawings, and in particular  FIG. 1 , there are illustrated some aspects of a non-limiting example of a gas turbine engine  20  in accordance with an embodiment of the present disclosure. In one form, engine  20  is a propulsion engine, e.g., an aircraft propulsion engine. In other embodiments, engine  20  may be any other type of gas turbine engine, e.g., a marine gas turbine engine, an industrial or power generation gas turbine engine, or any aero, aero-derivative or non-aero derivative gas turbine engine. In one form, engine  20  is a two spool engine having a high pressure (HP) spool  24  and a low pressure (LP) spool  26 . In other embodiments, engine  20  may include only a single spool, or may include three or more spools, e.g., may include an intermediate pressure (IP) spool and/or other spools and/or partial spools, e.g., on-axis or off-axis compressor and/or turbine stages (i.e., stages that rotate about an axis that is the same or different than that of the primary spool(s)). In one form, engine  20  is a turbofan engine. In other embodiments, engine  20  may be any other type of gas turbine engine, such as a turboprop engine, a turboshaft engine, a propfan engine, a turbojet engine or a hybrid or combined cycle engine. As a turbofan engine, LP spool  26  is operative to drive a propulsor  28  in the form of a turbofan (fan) system, which may be referred to as a turbofan, a fan, or a fan system. As a turboprop engine, LP spool  26  powers a propulsor  28  in the form of a propeller system (not shown), e.g., via a reduction gearbox (not shown). As a propfan engine, LP spool  26  powers a propulsor  28  in the form of a propfan. In other embodiments, propulsor  28  may take other forms, such as one or more helicopter rotors or tilt-wing aircraft rotors, for example, powered by one or more engines  20  in the form of one or more turboshaft engines. 
     In one form, engine  20  includes, in addition to fan  28 , a bypass duct  30 , a compressor  32 , a diffuser  34 , a combustor  36 , a high pressure (HP) turbine  38 , a low pressure (LP) turbine  40 , a nozzle  42 A, a nozzle  42 B, and a tailcone  46 , which are generally disposed about and/or rotate about an engine centerline  49 . In other embodiments, there may be, for example, an intermediate pressure spool having an intermediate pressure turbine or other turbomachinery components, such as those mentioned above. In one form, engine centerline  49  is the axis of rotation of fan  28 , compressor  32 , turbine  38 , and turbine  40 . In other embodiments, one or more of fan  28 , compressor  32 , turbine  38 , and turbine  40  may rotate about a different axis of rotation. 
     In the depicted embodiment, engine  20  core flow is discharged through nozzle  42 A, and the bypass flow from fan  28  is discharged through nozzle  42 B. In other embodiments, other nozzle arrangements may be employed, e.g., a common nozzle for core and bypass flow; a nozzle for core flow, but no nozzle for bypass flow; or another nozzle arrangement. Bypass duct  30  and compressor  32  are in fluid communication with fan  28 . Nozzle  42 B is in fluid communication with bypass duct  30 . Diffuser  34  is in fluid communication with compressor  32 . Combustor  36  is fluidly disposed between compressor  32  and turbine  38 . Turbine  40  is fluidly disposed between turbine  38  and nozzle  42 A. In one form, combustor  36  includes a combustion liner (not shown) that contains a continuous combustion process. In other embodiments, combustor  36  may take other forms, and may be, for example, a wave rotor combustion system, a rotary valve combustion system, a pulse detonation combustion system, a continuous detonation combustion system, and/or a slinger combustion system, and may employ deflagration and/or detonation combustion processes. 
     Fan system  28  includes a fan rotor system  48  driven by LP spool  26 . In various embodiments, fan rotor system  48  may include one or more rotors (not shown) that are powered by turbine  40 . In various embodiments, fan  28  may include one or more fan vane stages (not shown in  FIG. 1 ) that cooperate with fan blades (not shown) of fan rotor system  48  to compress air and to generate a thrust-producing flow. Bypass duct  30  is operative to transmit a bypass flow generated by fan  28  around the core of engine  20 . Compressor  32  includes a compressor rotor system  50 . In various embodiments, compressor rotor system  50  includes one or more rotors (not shown) that are powered by turbine  38 . Compressor  32  also includes a plurality of compressor vane stages (not shown in  FIG. 1 ) that cooperate with compressor blades (not shown) of compressor rotor system  50  to compress air. In various embodiments, the compressor vane stages may include a compressor discharge vane stage and/or one or more diffuser vane stages. In one form, the compressor vane stages are stationary. In other embodiments, one or more vane stages may be replaced with one or more counter-rotating blade stages. 
     Turbine  38  includes a turbine rotor system  52 . In various embodiments, turbine rotor system  52  includes one or more rotors having turbine blades (not shown) operative to extract power from the hot gases flowing through turbine  38  (not shown), to drive compressor rotor system  50 . Turbine  38  also includes a plurality of turbine vane stages (not shown) that cooperate with the turbine blades of turbine rotor system  52  to extract power from the hot gases discharged by combustor  36 . In one form, the turbine vane stages are stationary. In other embodiments, one or more vane stages may be replaced with one or more counter-rotating blade stages. Turbine rotor system  52  is drivingly coupled to compressor rotor system  50  via a shafting system  54 . Turbine  40  includes a turbine rotor system  56 . In various embodiments, turbine rotor system  56  includes one or more rotors having turbine blades (not shown) operative to drive fan rotor system  48 . Turbine  40  also includes a plurality of turbine vane stages (not shown in  FIG. 1 ) that cooperate with the turbine blades of turbine rotor system  56  to extract power from the hot gases discharged by turbine  38 . In one form, the turbine vane stages are stationary. In other embodiments, one or more vane stages may be replaced with one or more counter-rotating blade stages. Turbine rotor system  56  is drivingly coupled to fan rotor system  48  via a shafting system  58 . In various embodiments, shafting systems  54  and  58  include a plurality of shafts that may rotate at the same or different speeds and directions for driving fan rotor system  48  rotor(s) and compressor rotor system  50  rotor(s). In some embodiments, only a single shaft may be employed in one or both of shafting systems  54  and  58 . Turbine  40  is operative to discharge the engine  20  core flow to nozzle  42 A. 
     During normal operation of gas turbine engine  20 , air is drawn into the inlet of fan  28  and pressurized. Some of the air pressurized by fan  28  is directed into compressor  32  as core flow, and some of the pressurized air is directed into bypass duct  30  as bypass flow. Compressor  32  further pressurizes the portion of the air received therein from fan  28 , which is then discharged into diffuser  34 . Diffuser  34  reduces the velocity of the pressurized air, and directs the diffused core airflow into combustor  36 . Fuel is mixed with the pressurized air in combustor  36 , which is then combusted. The hot gases exiting combustor  36  are directed into turbines  38  and  40 , which extract energy in the form of mechanical shaft power to drive compressor  32  and fan  28  via respective shafting systems  54  and  58 . The hot gases exiting turbine  40  are discharged through nozzle system  42 A, and provide a component of the thrust output by engine  20 . 
     During operation, engine  20  may experience vibration resulting from one or more causes, such as rotor component imbalance, rotor assembly imbalance, uneven wear of one or more components, material deposition on one or more components, operation in a bend mode or other vibratory mode, induced vibration from other sources, e.g., other rotors, and other causes. In many circumstances, the vibration may be reduced by balancing all or a portion of the rotating components, e.g., rotors, or engine  20 . It is desirable to operate engine  20  with as little vibration as practicable. Accordingly, embodiments of the present disclosure include means for balancing a rotating machine, such as all or a portion of engine  20  or any other machine having one or more rotating components. In some embodiments, the means for balancing operates on the fly, that is, performing balancing of engine  20  or components thereof during the operation of engine  20 , including in-service operation such as in-flight and/or ground operation of normal commercial passenger and/or cargo transport aircraft, fighter aircraft, helicopter, and/or other aircraft-type operations. In some embodiments, the means for balancing may also be employed to generate electrical power. 
     Referring to  FIGS. 2, 3, and 4 , some aspects of a balancing system  70  configured to balance at least a portion of a rotating machine (i.e., a machine having one or more rotating components), such as all or a portion of engine  20 , which may include all or a portion of fan rotor system  48  (for engines so equipped), compressor rotor system  50 , and/or turbine rotor system  52  in accordance with an embodiment of the present disclosure are schematically illustrated. In one form, balancing system  70  is considered a part of engine  20 . In other embodiments, balancing system  70  may be considered a part of another rotating machine, for example, another turbomachinery device or system, or other another type of rotating machine. Balancing system  70  is an active balancing system that is configured to balance at least a portion or component of the rotating machine, e.g., engine  20 , during operation of the rotating machine, e.g., normal operation. Balancing system  70  includes a plurality of magnetic elements  72  affixed to a static engine component  74 ; a plurality of magnetic elements  76  affixed to a rotor component  78 , for example, but not limited to an arm  80  extending from a turbine rotor disk  82  to which a plurality of turbine blades  83  are coupled; a vibration sensor  84 ; a controller  86 ; and a power supply  88 . 
     In one form, magnetic elements  72  are electromagnets. In other embodiments, magnetic elements  72  may be permanent magnets, or may be formed of a magnetic material, such as a ferromagnetic material, but without being electromagnets or permanent magnets. Although the present embodiments include a plurality of magnetic elements  72 , some embodiments may employ only a single magnetic element  72 . 
     Static engine component  74  may be any stationary component of engine  20 , for example, a static seal component, an engine case structure and/or a static component dedicated for use in balancing system  70 , or any other static component of a gas turbine engine or other machine having one or more rotating components. Magnetic elements  72  are distributed along a 360 degrees arc  90  on static engine component  74 . In one form, magnetic elements  72  are evenly spaced circumferentially along arc  90 . In other embodiments, other spacing distributions may be employed. In  FIG. 3 , only two magnetic elements  72  and two magnetic elements  76  are illustrated for purposes of clarity, although it will be understood that any number of magnetic elements  72  and magnetic elements  76  may be employed. Some embodiments may employ the same number of magnetic elements  72  as the number of magnetic elements  76 . Other embodiments may employ a different number of magnetic elements  72  than the number of magnetic elements  76 . 
     In one form, magnetic elements  76  are permanent magnets. In other embodiments, magnetic elements  76  may be electromagnets, or may be formed of a magnetic material, such as a ferromagnetic material, but without being electromagnets or permanent magnets. Although the present embodiments include a plurality of magnetic elements  76 , some embodiments may employ only a single magnetic element  76 . In one form, magnetic elements  76  are evenly spaced circumferentially along 360 degrees arc  92 . In other embodiments, other spacing distributions may be employed. Magnetic elements  72  and  76  are disposed to be positioned opposite each other for at least one point during the rotation of rotor component  78 . In one form, magnetic elements  72  are disposed radially inward of magnetic elements  76 . In other embodiments, magnetic elements  72  may be disposed radially outward of magnetic elements  76  in addition to or in place of being disposed radially inward of magnetic elements  76 , and/or may be disposed axially opposite magnetic elements  72 , e.g., at the same or similar radial position. In still other embodiments, any relative positional arrangement between magnetic elements  72  and magnetic elements  76  may be employed. 
     Rotor component  78  is configured to rotate about an axis  94 . In one form, rotor component  78  is a component of a turbine rotor  96 , which may be all or a portion of turbine rotor system  52 . In other embodiments, rotor component  78  may be all or a portion of fan rotor system  48  (for engines so equipped), compressor rotor system  50 , and/or another rotor system in engine  20 . In still other embodiments, rotor component  78  may be a rotor component of another type of turbomachine or other rotary machine. In one form, rotor component  78  includes arm  80  and turbine rotor disk  82 . In other embodiments, rotor component  78  may not be or include an arm or rotor disk such as arm  80  and turbine rotor disk  82 . 
     Vibration sensor  84  is configured to sense vibration in engine  20 . In particular, vibration sensor  84  is configured to sense rotational vibration in engine  20 , i.e., vibration stemming from imbalance in one or more rotating components of engine  20 . In one form, vibration sensor  84  is an accelerometer. In other embodiments, other types of vibration sensors may be employed, for example and without limitation, any piezoelectric sensor, an optical sensor and/or other sensor types. In one form, vibration sensor  84  is configured to sense vibration in a plurality of directions. In other embodiments, vibration sensor  84  may be configured to sense vibration in only a single direction. In one form, vibration sensor  84  is a discreet device, e.g., located at a particular position on a static component of engine  20 . In other embodiments, sensor  84  may be located on a rotating component or system. In still other embodiments, sensor  84  may be formed of more than one discreet component, e.g., discreet or other sensor components located at one or more positions on a static and/or rotating component or system of engine  20 . 
     Controller  86  is communicatively coupled to vibration sensor  84 , and is operative to receive vibration data from vibration sensor  84 . In one form, controller  86  is configured to execute program instructions to selectively activate one or more magnetic element(s)  72  selectively attract and/or repel the magnetic element(s)  72  to and/or from one or more magnetic elements  76  in order to shift the position of all or a portion of the rotor, e.g., rotor component  78 , by a small amount, locally (e.g., at one or more desired locations on the rotor or rotor component), and thereby reduce the vibration in engine  20 . In various embodiments, controller  86  may be configured to execute program instructions to activate one or more of magnetic element(s)  72  and/or one or more of magnetic element(s)  76  to selectively attract one to the other or both to each other, and/or to selectively repel one from the other or both from each other, to reduce the vibration that stems from rotation of the rotor. 
     In one form, controller  86  is microprocessor based and the program instructions are in the form of software stored in a memory (not shown). However, it is alternatively contemplated that the controller and program instructions may be in the form of any combination of software, firmware, and hardware, including state machines, and may reflect the output of discreet devices and/or integrated circuits, which may be co-located at a particular location or distributed across more than one location, including any digital and/or analog devices configured to achieve the same or similar results as a processor-based controller executing software or firmware based instructions. 
     Power supply  88  is electrically coupled to both controller  86  and to magnetic elements  72 . Power supply  88  is configured to selectively supply electrical power to one or more individual magnetic elements  72  and/or one or more groups of magnetic elements  72  under the direction of controller  86 , i.e., to selectively supply or not supply electrical power to any one or more magnetic elements  72  under the direction of controller  86 . In some embodiments, power may be likewise supplied to one or more magnetic elements in addition to or in place of magnetic elements  72 , e.g., via a built-in rotor alternator and/or generator, controller and vibration sensor. In some embodiments, magnetic elements  72  and  76  may also or alternatively be configured to generate electrical power upon the rotation of rotor component  78 . In one form, magnetic elements  72  and  76  are configured to form a permanent magnet alternator. In other embodiments, magnetic elements  72  and  76  may be configured to form one or more other types of alternators and/or generators. In embodiments where magnetic elements  72  and  76  are configured to generate electrical power, power supply  88  may include one or more power conditioning devices for conditioning the power received via magnetic elements  72  (and/or magnetic elements  76 ) for use by another engine  20  components or non-engine  20  component). 
     During operation, magnetic elements  76  rotate through arc  92  in close proximity to magnetic elements  72  disposed about arc  90 . In this regard, “close proximity” is the proximity that is sufficient for interaction between magnetic elements  72  and magnetic elements  76  to a degree that allows a reduction in vibration, and in some embodiments, the generation of electrical power. The proximity requirement will vary in accordance with one or more parameters, such as the magnetic field strength of the magnetic elements, the stiffness and/or mass of the rotor, and other potential factors not mentioned herein. The proximity requirement is readily determined via manual calculations, two and/or three dimensional electronic modeling, and/or simple experimentation by those of ordinary skill in the art. During the rotation of rotor  96 , its vibration, e.g., absolute or above a desired threshold, is sensed by sensor  84 . Sensor  84  provides a signal, e.g., proportional to the vibration or otherwise representative of the vibration, to controller  86 . Controller  86  is configured to resolve the sensor  84  vibration data into one or more vibration magnitude and one or more vibration directions, e.g., such as imbalance loads stemming, such as a simple mass imbalance load having a direction that rotates with the rotor  96  and rotor component  78 . In other embodiments, controller  86  may be configured to resolve data from imbalance such as an imbalance stemming from an orbital displacement of rotor  96 , an imbalance resulting from a bend mode or other vibratory mode of rotor  96  and/or another rotor, and/or other sources of vibration. The resolution performed by controller  86  may yield one or more imbalance loads at one or more rotating directions and at one or more speeds of rotation. Controller  86  is configured to direct power supply  88  to supply power to selected magnetic elements  72  (based on the unbalance load magnitude, direction and speed) in order to selectively attract and repel magnetic elements  76  to and from selected magnetic elements  72  so as to reduce the vibration by deflecting rotor component  78  in a direction opposite to the unbalance load. For example, in the depiction of  FIG. 3 , an unbalance load direction  100  is detected, which represents the direction of the unbalance load in rotor component  78  at an instantaneous point in time during the rotation of rotor  96  and rotor component  78 . Controller  86  is configured to execute program instructions to direct power supply  88  to supply power in one direction or polarity, e.g., a positive voltage, to magnetic element  72 A, to attract magnetic element  72 A to magnetic element  76 A in order to reduce the vibration. Controller  86  is also configured to execute program instructions to direct power supply  88  to supply power in the opposite direction or polarity, e.g., a negative voltage, to magnetic element  72 B to repel magnetic element  72 B from magnetic element  76 B. By doing so, the center of mass of rotor  96 , e.g., of rotor component  78 , is shifted in the opposite direction of the unbalance load, thereby reducing the unbalance load. As rotor  96  continues to rotate, the direction of the unbalance load rotates with it. In one form, controller  86  is configured to execute program instructions to power other magnetic elements  72  e.g., circumferentially subsequent to magnetic elements  72 A and  72 B and/or other magnetic elements that are disposed in the direction of the unbalance load. For example, in the depiction of  FIG. 4 , assuming a direction of rotation indicated by arrow  102 , controller  86  would execute program instructions to direct power supply  88  to power magnetic element  72 C, then magnetic element  72 D, then magnetic element  72 E, then magnetic element  72 F, then magnetic element  72 G and so on, to generate attraction and/or repulsion with corresponding magnetic elements  76 A- 76 G and so on, depending on the unbalance load direction, to yield a rotational speed of the actuation of the magnetic elements  72  that matches the rotational speed of rotor  96  and/or the rotational speed(s) of the imbalance(s) if different than the rotational speed of rotor  96 , thereby reacting against the unbalance load as the unbalance load rotates with rotor  96 . In other embodiments, controller  86  may be configured to direct power supply  88  to activate magnetic elements  72  at a different rate and/or in a different direction to cause magnetic attraction and/or repulsion in the imbalance direction or in more than one imbalance direction, e.g., in the event rotor  96  is exhibiting an orbital vibration mode or is experiencing a rotating unbalance load that rotates at a different speed than the rotation speed of rotor  96 , or is experiencing multiple imbalance loads that have one or more different directions. 
     In one form, controller  86  includes feedback loop control algorithms configured to achieve and maintain a desired vibration level, e.g., below a selected value. In various embodiments, control algorithms may include proportional, integral, and/or derivative control and/or other feedback loop control functions and/or non-feedback control algorithms configured to achieve and maintain a desired vibration level. Although the embodiment described herein employs both magnetic attraction and magnetic repulsion as between magnetic elements  72  and magnetic elements  76  in order to reduce vibration, other embodiments may employ only magnetic attraction or magnetic repulsion. By attracting and/or repelling magnetic elements  72  and  76 , e.g., when opposite each other in the direction of the unbalance load, the relative position of rotor component  78  can be adjusted during the rotation rotor  96  in order to balance the rotor and reduce or eliminate the vibration. 
     In some embodiments, the relative rotation between magnetic elements  72  and magnetic elements  76  may be employed to generate electrical power in magnetic elements  72 , e.g., in the form of a permanent magnet alternator or an inductive generator or other type of alternator or generator. In some embodiments, electrical power generated in magnetic elements  72  may be controlled by controller  86  and power supply  88 , which may also include power conditioning electronics (not shown) or which may direct the generated power to power conditioning electronics for subsequent use by engine  20 , an airframe, or any electrical device or system. 
     Embodiments of the present disclosure include a gas turbine engine comprising a compressor, a combustor in fluid communication with the compressor; a turbine in fluid communication with the combustor; and an active balancing system configured to balance at least a portion of the gas turbine engine during operation of the gas turbine engine. The active balancing system includes a static engine component having a first magnetic element, a rotor component operative to rotate about an axis, a vibration sensor, and a controller. The rotor component has a second magnetic element. The second magnetic element and the first magnetic element are disposed to be positioned opposite each other at one point during a rotation of the rotor component. The vibration sensor is configured to sense a vibration in the gas turbine engine. The controller is configured to execute program instructions to activate one or both of the first magnetic element and the second magnetic to selectively attract one to the other and/or to selectively repel one from the other element based on an output of the vibration sensor to reduce the vibration. 
     In a refinement, the controller is configured to execute program instructions to activate one or both of the first magnetic element and the second magnetic element to selectively attract one to the other and to selectively repel one from the other. In another refinement, one or both of the first magnetic element and the second magnetic element is an electromagnet. 
     In yet another refinement, the first magnetic element or the second magnetic element is a permanent magnet. In still another refinement, one or both of the first magnetic element and the second magnetic element is formed of a ferromagnetic material, but is not an electromagnet or a permanent magnet. 
     In yet still another refinement, the gas turbine engine further comprises a plurality of first magnetic elements and a plurality of second magnetic elements. In a further refinement, the first magnetic element and the second magnetic element are configured to generate electrical power upon rotation of the rotor component. 
     In a yet further refinement, the first magnetic element and the second magnetic element are configured to form a permanent magnet alternator. In a still further refinement, the vibration sensor is an accelerometer. 
     Embodiments of the present disclosure include an active balancing system for a rotating machine comprising a static engine component including a first magnetic element, a rotor having a rotor component operative to rotate about an axis, a vibration sensor, and a controller. The rotor component includes a second magnetic element. The second magnetic element and the first magnetic element are disposed to be positioned opposite each other at one point during rotation of the rotor component. The vibration sensor is configured to sense a vibration associated with the rotor. The controller is configured to execute program instructions to activate one or both of the first magnetic element and the second magnetic element to selectively attract one to the other and/or selectively repel one from the other element based on an output of the vibration sensor to reduce the vibration. 
     In a refinement, the controller is configured to execute program instructions to activate one or both of the first magnetic element and the second magnetic element to selectively attract one to the other and to selectively repel one from the other. In another refinement, one or both of the first magnetic element and the second magnetic element is an electromagnet. 
     In yet another refinement, the first magnetic element or the second magnetic element is a permanent magnet. In still another refinement, one or both of the first magnetic element and the second magnetic element is formed of a ferromagnetic material, but is not an electromagnet or a permanent magnet. 
     In yet still another refinement, the active balancing system further comprises a plurality of first magnetic elements and a plurality of second magnetic elements. In a further refinement, the first magnetic element and the second magnetic element are configured to generate electrical power upon rotation of the rotor component. 
     In a yet further refinement, the first magnetic element and the second magnetic element are configured to form a permanent magnet alternator. In a still further refinement, the vibration sensor is an accelerometer. 
     Embodiments of the present disclosure include a gas turbine engine, comprising a compressor, a combustor in fluid communication with the compressor, a turbine in fluid communication with the combustor, and means for actively balancing at least a portion of the gas turbine engine during operation of the gas turbine engine. In a refinement, the means for actively balancing includes a controller configured to execute program instructions to activate at least one magnetic element. 
     While the disclosure has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the disclosure is not to be limited to the disclosed embodiment(s), but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as permitted under the law. Furthermore it should be understood that while the use of the word preferable, preferably, or preferred in the description above indicates that feature so described may be more desirable, it nonetheless may not be necessary and any embodiment lacking the same may be contemplated as within the scope of the disclosure, that scope being defined by the claims that follow. In reading the claims it is intended that when words such as “a,” “an,” “at least one” and “at least a portion” are used, there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. Further, when the language “at least a portion” and/or “a portion” is used the item may include a portion and/or the entire item unless specifically stated to the contrary.