Abstract:
A turbomachine includes a compressor portion, a turbine portion operatively connected to the compressor portion, a combustor assembly fluidly connected to each of the compressor portion and the turbine portion, a blade element including a base portion, an airfoil portion, and a natural frequency generated during rotation of the blade element. The blade element is rotatably mounted within one of the compressor portion and the turbine portion, and a blade tuning member rotatably mounted in the one of the compressor portion and the turbine portion. The blade tuning member is configured for engagement with the blade element to alter the natural frequency.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The subject matter disclosed herein relates to the art of turbomachines and, more particularly, to a turbomachine including a blade tuning system. 
         [0002]    Many turbomachines include a compressor portion linked to a turbine portion through a common compressor/turbine shaft or rotor and a combustor assembly. The compressor portion guides a compressed air flow through a number of sequential stages toward the combustor assembly. In the combustor assembly, the compressed air flow mixes with a fuel to form a combustible mixture. The combustible mixture is combusted in the combustor assembly to form hot gases. The hot gases are guided to the turbine portion through a transition piece. The hot gases expand through the turbine portion along a hot gas path and impart a force to a series of buckets or blades mounted to rotors that, in turn, are coupled to a shaft. 
         [0003]    The force causes the blade to rotate creating work that is output through the shaft to, for example, power a generator, a pump, or to provide power to a vehicle. In addition to providing compressed air for combustion, a portion of the compressed airflow is passed through the turbine portion for cooling purposes. The hot gases flowing over the blades create a sound footprint. That is, the blades possess a natural frequency property that is triggered by the hot gas flow. Occasionally, the natural frequency of the blades may match combustor frequency tone ranges. In such cases, the turbomachine may vibrate excessively. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0004]    According to one aspect of the exemplary embodiment, a turbomachine includes a compressor portion, a turbine portion operatively connected to the compressor portion, a combustor assembly fluidly connected to each of the compressor portion and the turbine portion, a blade element including a base portion, an airfoil portion, and a natural frequency generated during rotation of the blade element. The blade element is rotatably mounted within one of the compressor portion and the turbine portion, and a blade tuning member rotatably mounted in the one of the compressor portion and the turbine portion. The blade tuning member is configured for engagement with the blade element to alter the natural frequency. 
         [0005]    According to another aspect of the exemplary embodiment, a method for adjusting a natural frequency of a blade element in a turbomachine during operation includes rotating a blade element within the turbomachine, positioning a blade tuning member having a predetermined stiffness to contact the blade element, and adjusting a natural frequency of the blade element through contact between the blade element and the blade tuning member. 
         [0006]    These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0007]    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 features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0008]      FIG. 1  is a schematic view of a turbomachine including a blade tuning system in accordance with an exemplary embodiment; 
           [0009]      FIG. 2  is a partial cross-sectional view of a turbine portion of the turbomachine of  FIG. 1 ; 
           [0010]      FIG. 3  is a detail view of a blade tuning member having a blade tuning element contacting a blade tuning component formed on a blade of the turbine portion of  FIG. 2 ; 
           [0011]      FIG. 4  is a detail view of the blade tuning element of  FIG. 3  contacting a blade tuning component in accordance with another aspect of the exemplary embodiment; and 
           [0012]      FIG. 5  is a detail view of first and second blade tuning members contacting corresponding blade tuning components formed on an upstream side and a downstream side of the blade of  FIG. 3 . 
       
    
    
       [0013]    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 
       [0014]    With reference to  FIGS. 1 and 2 , a turbomachine constructed in accordance with an exemplary embodiment is indicated generally at  2 . Turbomachine  2  includes a compressor portion  4  operatively connected to a turbine portion  6 . A combustor assembly  8  is fluidly connected to compressor portion  4  and turbine portion  6 . Combustor assembly  8  is formed from a plurality of circumferentially spaced combustors, one of which is indicated at  10 . Of course it should be understood that combustor assembly  8  could include other arrangements of combustors. Compressor portion  4  is also linked to turbine portion  6  through a common compressor/turbine shaft  12 . With this arrangement, compressor portion  4  delivers compressed air to combustor assembly  8 . The compressed air mixes with a combustible fluid or fuel to form a combustible mixture. The combustible mixture is combusted in combustor  10  to form products of combustion or hot gases that are delivered to turbine portion  6  through a transition piece (not shown). The hot gases expand through turbine portion  6  along a gas path  18  to power, for example, a generator, a pump, a vehicle or the like (also not shown). 
         [0015]    In the exemplary embodiment shown, turbine portion  6  includes first and second stages  20  and  21  that define gas path  18 . Of course it should be understood that the number of stages in turbine portion  6  could vary. First stage  20  includes a plurality of first stage stators or nozzles, one of which is indicated at  30 , and a plurality of first stage buckets or blade elements, one of which is indicated at  32 , mounted to a first stage rotor wheel  34 . Second stage  21  includes a plurality of second stage stators or nozzles, one of which is indicated at  37 , and a plurality of second stage buckets or blade elements, one of which is indicated at  39 , mounted to a second stage rotor wheel  41 . Blade elements  32  include a base portion  60  and an airfoil portion  61 . Likewise, blade elements  39  include a base portion  63  and an airfoil portion  64 . Blade elements  32  and  39  also include a natural frequency property that is associated with blade element geometry and blade element material. 
         [0016]    In accordance with an exemplary embodiment, turbomachine  2  includes a blade tuning member  70  arranged between first and second turbine stages  20  and  21 . As will become more fully evident below, blade tuning member  70  is configured to adjust the natural frequency of blade elements  32  and  39 . In the exemplary embodiment shown, blade tuning member  70  takes the form of near flow path seal  78 . However, it should be understood that blade tuning member  70  may be a separate structure provided in turbine portion  6 . In the exemplary embodiment shown, blade tuning member  70  includes a first blade tuning element  86  and a second blade tuning element  87 . First blade tuning element  86  is cantilevered from blade tuning member  70  and extends toward base portion  60  of blade elements  32 . Second blade tuning element  87  is cantilevered from blade tuning member  70  and that extends toward base portion  63  of blade elements  39 . At this point it should be understood that blade tuning member  72  and  74  include generally similar structure. 
         [0017]    As best shown in  FIG. 3 , blade tuning element  87  includes a first end  90  that extends to a second end  91 . Second end  91  includes a crown element  93  that contacts and exerts pressure upon base portion  63  of blade elements  39 . More specifically, blade elements  39  include a blade tuning component  96  having a projection  99  that extends axially upstream from base portion  63 . Blade tuning element  87  has a stiffness property that is selectively chosen to tune the natural frequency property of blade elements  39  to a predetermined value. With this arrangement, the natural frequency property of blade elements  39  can be adjusted to reduce vibratory response. At this point it should be understood that blade tuning element  86  acts upon base portions  60  of blade elements  32  in a similar manner.  FIG. 4  illustrates a blade tuning component  102  having a projection  103  provided with a radially projecting appendage  104 . Crown member  93  contacts and applies pressure to radially extending appendage  104  to alter the natural frequency property of blade element  39 . The particular length of radially projecting appendage  104  may be varied to achieve a desired natural frequency property for blade elements  39 . 
         [0018]      FIG. 5  illustrates an upstream side  111  and a downstream side  112  of base portion  63 . Blade tuning component  96  is arranged on upstream side  111  and another blade tuning component  113  having a projection  114  is arranged on downstream side  112 . Blade tuning element  87  acts upon blade tuning component  96  and blade tuning member  72  acts upon blade tuning component  113 . More specifically blade tuning member  72  includes a blade tuning element  115  that acts upon blade tuning component  113 . Blade tuning element  115  includes a first end  116  that extends from blade tuning member  72  to a second, cantilevered end  117 . Second end  117  includes a crown element  119  that acts upon projection  114 . With this arrangement, blade tuning member  70  acts upon base portion  63  to tune the natural frequency property of blade element  39 . 
         [0019]    At this point it should be understood that the exemplary embodiments describe a system for adjusting a natural frequency property of rotating turbomachine blade elements. Blade tuning members act upon base portions of the rotating blade element to alter blade element stiffness. In this manner, blade element stifthess can be adjusted to tune the natural frequency property of each blade element to a desired value. Stiffness can be adjusted by adding elements to the base portion of the buckets, increasing or decreasing a length of the blade tuning elements, altering a thickness of the blade tuning elements, adjusting a height of the crown elements, or altering a volume of the blade tuning elements, e.g., forming hollow regions in the blade tuning element. Selectively altering or tuning the natural frequency property of each blade element row will separate natural frequency property of one stage from a natural frequency of another stage to improve frequency margin requirements. 
         [0020]    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.