Abstract:
Disclosed is a seal for a turbomachine including at least one fixed component located proximate to a rotating component of the turbomachine defining a clearance therebetween. At least one magnet is located at the at least one fixed component. The at least one magnet is, when activated, capable of moving the at least one fixed component thereby adjusting the clearance between the fixed component and the rotating component. Further disclosed is a turbomachine utilizing the seal and a method for adjusting a position of at least one fixed component of a turbomachine.

Description:
BACKGROUND 
       [0001]    The subject invention relates generally to turbomachinery. More particularly, the subject invention relates to adjustment of turbomachinery components via magnetic forces. 
         [0002]    Turbomachinery typically includes seals which are utilized to control clearances between rotating components and nonrotating components of the turbomachine. Examples of turbomachine seals include tip shrouds outboard of rotating bucket rows, and single or multi-tooth seals typically utilized between rows of fixed blades and a rotating shaft. During certain operating conditions, such as startup or shutdown and during transients, vibration and/or thermal growth of components may cause excessive wear to the seals and/or damage to other turbomachine components. Excessive wear of the seals shortens their useful life and also causes an increase in leakage of flow in the turbomachine which decreases the turbomachine&#39;s efficiency. 
         [0003]    Control of clearance between the seals and rotating components is typically achieved through the use of radial and/or tangential springs to bias a seal&#39;s location. Seal position is sometimes controlled through the use of hydraulic or pneumatic actuators. The actuators, though, located outside of the casing of the turbomachine, require penetration through the casing of the turbomachine, which increases cost and potentially increases leakage through the casing. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0004]    According to one aspect of the invention, a seal for a turbomachine includes at least one fixed component located proximate to a rotating component of the turbomachine defining a clearance therebetween. At least one magnet is located at the at least one fixed component. The at least one magnet is, when activated, capable of moving the at least one fixed component thereby adjusting the clearance between the fixed component and the rotating component. 
         [0005]    According to another aspect of the invention, a turbomachine includes a casing and at least one rotating component located in the casing and rotatable about a central axis of the turbomachine. At least one fixed component is located in the casing to define a clearance between the at least one rotating component and the at least one fixed component, and at least one magnet located such that when the at least one magnet is activated, the clearance between the at least one rotating component and the at least one fixed component is adjusted. 
         [0006]    According to yet another aspect of the invention, a method for adjusting a position of at least one fixed component of a turbomachine includes locating at least one magnet proximate to the at least one fixed component and activating the at least one magnet thereby creating a magnetic field in magnetic communication with the at least one fixed component. The at least one fixed component is moved via the magnetic field. 
         [0007]    These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0009]      FIG. 1  is a cross-sectional view of an embodiment of a turbomachine; 
           [0010]      FIG. 2  is a cross-sectional view of an embodiment of a single or multi-tooth seal with magnetic adjustment; 
           [0011]      FIG. 3  is a cross-sectional view of another embodiment of a single or multi-tooth seal with magnetic adjustment; 
           [0012]      FIG. 4  is a cross-sectional view of an embodiment of a tip shroud with magnetic adjustment; and 
           [0013]      FIG. 5  is a cross-sectional view of another embodiment of a tip shroud with magnetic adjustment. 
           [0014]      FIG. 6  is a cross-sectional view of another embodiment of a tip shroud with magnetic adjustment; 
           [0015]      FIG. 7  is another cross-sectional view of the tip shroud of  FIG. 6 ; 
           [0016]      FIG. 8  is a view of a magnetically adjustable variable vane; and 
           [0017]      FIG. 9  is a partially exploded view of the variable vane of  FIG. 8 . 
       
    
    
       [0018]    The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    Shown in  FIG. 1  is a cross-sectional view of an embodiment of a turbine  10  of, for example, a gas turbine or steam turbine. The turbine  10  includes a turbine rotor  12  having one or more rows of turbine buckets  14  arrayed circumferentially around a rotor disc  60 . The rotor  12  is rotatable about a central axis  18  and is disposed in a casing  20 . The turbine  10  includes one or more blade rows  22  which are disposed axially between rows of the turbine buckets  14 . At least one tip shroud  24  is disposed radially outboard of each row of the one or more rows of turbine buckets  14 . Each tip shroud  24  may be comprised of a plurality of shroud segments (not shown). The tip shroud  24  and the turbine buckets  14  define a tip clearance  28  therebetween, as best shown in  FIG. 4 . Referring again to  FIG. 1 , a ring of seals, for example, single or multi-tooth seals  30  may be disposed radially between each blade row  22  and rotating structure, for example, a rotating seal  16 . The rotating seal  16  and the seals  30  define a rotor clearance  32  therebetween, as best shown in  FIG. 2 . 
         [0020]    During operation of the turbine  10 , it may be advantageous to change a position of the seals  30  to adjust the rotor clearance  32  during, for example, start up or shutdown of the turbine  10 , or during transients. In these operating conditions, vibration and/or thermal growth of the components could lead to excessive wear of the seals  30 . As shown in  FIG. 2 , at least one magnetic actuator  34  is disposed at the seal  30 , in some embodiments fixed to a seal housing  36 . The at least one magnetic actuator  34  is configured and disposed such that when an electric current is introduced to the magnetic actuator  34 , a magnetic field is generated which causes the seal  30  to move away from the rotating seal  16  thus increasing the rotor clearance  32 . Alternatively, the magnetic actuator  34  may be configured to move the seal  30  toward the rotating seal  16  when electrical current is introduced to the at least one magnetic actuator  34 . It is to be appreciated that, while the electromagnetic actuator  34  of the embodiment of  FIG. 2  is configured to move the seal  30  in a radial direction, it is to be appreciated that the electromagnetic actuator  34  may be configured to move the seal  30  in other directions, for example, an axial direction. 
         [0021]    In some embodiments, at least one feedback device, for example at least one proximity sensor  38  is disposed at the seal  30 . The proximity sensor  38  is disposed to measure and provide feedback on clearance between the seal  30  and the rotating seal  16 . In some embodiments, the proximity sensor  38  is in operable communication with the at least one magnetic actuator  34  such that the magnetic actuator  34  moves the seal  30  based on feedback from the proximity sensor  38 . Further, in some embodiments, one or more springs  40  may be disposed at a radially outward portion of the seal  30  to bias the position of the seal  30 . The springs  40  may be configured to bias the position of the seal  30  in a direction to assist the magnetic actuator  34  in moving the seal  30 , or to counter the magnetic actuator  34  in moving the seal  30 . 
         [0022]    In some embodiments, as shown in  FIG. 3 , a magnetic field may be utilized to move the seal  30  via at least one magnet  42  disposed outside of the casing  20 . In some embodiments, the at least one magnet  42  is an electromagnet secured outside of the casing  20 , such that when a magnetic field is generated by introducing electrical current to the magnet  42 , the seal  30  is moved away from the magnet  42  by the magnetic field. In some embodiments, the magnet  42  moves the seal  30  by moving the blade row  22  associated with the desired seal  30  away from the magnet  42 . It is to be appreciated that, in some embodiments, the magnet  42  may be configured to attract, rather than repel the blade row  22  and/or the seal  30  thus moving the seal  30  toward the magnet  42  when the magnetic field is generated. In the embodiment shown in  FIG. 3 , since the magnet  42  is disposed outside of the casing  20 , there is no need to penetrate the casing  20  thereby reducing the potential for leakage from the casing  20 , and simplifying fabrication of and reducing cost of the casing  20 . 
         [0023]    While the embodiments described to this point have utilized magnetic fields to move seals  30 , magnetic fields may be utilized to move other components, for example, the at least one tip shroud  24 . As shown in  FIG. 4 , at least one magnetic actuator  34  is disposed at the casing  20  and is configured to move the tip shroud  24  when the magnetic actuator  34  is activated to adjust the tip clearance  28 . The magnetic actuator  34  may be configured to attract or repel the tip shroud  24  when activated, depending on the requirements of the particular turbine  10 . In some embodiments, at least one proximity sensor  38  is disposed at the tip shroud  24  to measure the tip clearance  28 . The magnetic actuator  34  may move the tip shroud  24  based on feedback from the proximity sensor  38 . 
         [0024]    Further, as shown in  FIG. 5 , at least one magnet  42  disposed outside the casing  20  may be utilized to move the tip shroud  24  via the magnetic field created by the magnet  42 . In the embodiment of  FIG. 5 , since the magnet  42  is disposed outside of the casing  20  there is no need to penetrate the casing  20  to allow access for components which move the ring of the tip shroud  24 . This reduces leakage through the casing  20 , and also simplifies and reduces cost of fabrication of the casing  20 . 
         [0025]    As shown in  FIG. 6 , at least one magnet  42  may be utilized to move a tapered seal  44  in an axial direction to adjust the tip clearance  28 . The tapered seal  44  is positioned between the turbine buckets  14  and the casing  20 . In the embodiment of  FIG. 6 , two magnets  42  are disposed at the casing  20 . When an electrical current is provided to magnet  42   a , a magnetic field is created which moves the tapered seal  44  in an axial direction toward magnet  42   a , thus adjusting the tip clearance  28  from a closed condition as shown in  FIG. 6  to an opened condition as shown in  FIG. 7 . With the tip clearance  28  in the opened condition, the electrical current to magnet  42   a  may be turned off, and an electrical current provided to magnet  42   b  to create a magnetic field which moves the tapered seal  44  toward magnet  42   b  thus adjusting the tip clearance from the opened condition to the closed condition shown in  FIG. 6 . Further, in some embodiments, the magnets  42   a  and  42   b  may be configured with switchable, opposing polarity. For example, magnet  42   a  may initially have a positive polarity and magnet  42   b  may have a negative polarity. To move the tapered seal  44  toward magnet  42   a , both magnets  42   a  and  42   b  are energized, with magnet  42   a  attracting the tapered seal  44  and magnet  42   b  repelling the tapered seal  44  thus providing additional force to move the tapered seal  44  toward magnet  42   a . To move the tapered seal toward magnet  42   b , the polarities are reversed such that magnet  42   b  attracts the tapered seal  44  and magnet  42   a  repels tapered seal  44 . 
         [0026]    As shown in another embodiment shown in  FIGS. 8 and 9 , an electromagnetic actuator  34  may be utilized to adjust positions of gas path components such as rotating variable vanes  46 . In the embodiment of  FIG. 8 , the electromagnetic actuator  34  is disposed outside of the casing  20 , and is in magnetic communication with a target  48  disposed inside of the casing  20 . The target  48  is connected to a slider-follower cam  50 , which in this embodiment includes an internal spline  52 , as best shown in  FIG. 9 . A slide connector  54  with a corresponding external spline  56  is inserted into the cam  50  and is connected to the variable vane  46 . When the electromagnetic actuator  34  is activated, the target  48  is either attracted to or repelled from the electromagnetic actuator  34  along a slider axis  58 . The movement of the target  48  along the slider axis  58  is translated into rotational motion of the variable vane  46  about the slider axis  58  via the cam  50 . Although a slider-follower cam  50  is utilized in the embodiments of  FIGS. 8 and 9 , other means for translating linear motion to rotational motion, for example, a helical spline connection may be utilized. Some embodiments may include one or more springs (not shown) to return the variable vane  46  to a home position when the electromagnetic actuator  34  is deactivated. Further, reversing a polarity of the electromagnetic actuator  34  may also accomplish this function. 
         [0027]    While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.