Patent Application
20070048131
This application relates generally to turbine engines and, more particularly, to methods and apparatus for controlling contact within turbine engine stator assemblies.
At least some known rotor assemblies include at least one row of circumferentially-spaced rotor blades. Each row of rotor blades is positioned between a pair of axially-spaced rows of circumferentially-spaced stator vanes or blades. At least some known stator vanes are fabricated with a base and an integrally-formed airfoil that extends radially outward from the base. Each base is configured to couple the stator vanes within the engine such that the stator vanes extend radially through a flow path defined within the rotor assembly.
Within at least some known stator assemblies, the base of each stator vanes is substantially wedge-shaped or square based such that a radially outer surface of the base may have an arcuate length that is longer than a corresponding length of a radially inner surface of the base. The wedge shape facilitates coupling the stator vanes circumferentially within the stator assembly. However, within such stator vanes the geometry of the base also makes control of contact between adjacent stator vanes, known as circumferential contact, and between each stator vanes and the casing, known as axial contact, difficult to accurately predict. As a result, during rotor operation excitation responses generated by such stator vanes often do not match predicted experimental frequencies. Over time, the increased excitation responses may result in shortening the useful life of the stator vanes.
In one aspect, a method for assembling a stator assembly for a turbine engine is provided. The method comprises forming a recess within a portion of each base, and coupling the stator vanes within the turbine engine in a circumferentially-spaced arrangement such that the recessed portion of each base facilitates reducing excitation responses of each of the plurality of stator vanes during engine operation.
In another aspect, a stator vane for a turbine engine is provided. The stator vane includes a base and an airfoil. The base is configured to couple the stator vane within the turbine engine. The airfoil extends radially outward from the base. The base includes a pair of circumferentially-spaced sides coupled together by an upstream side and a downstream side, wherein at least a portion of the base is recessed to facilitate reducing excitation responses of the vane during engine operation.
In a further aspect, a rotor assembly including a rotor shaft and a plurality of stator vanes circumferentially-spaced around the rotor shaft is provided. Each stator vane includes a base and an integrally-formed airfoil extending radially outward from the base. Each base includes a pair of circumferentially-spaced sides coupled together by an upstream side and a downstream side, wherein at least a portion of each base is recessed to facilitate reducing excitation responses of each of the plurality of stator vanes during rotor operation.
In operation, air flows through compressor 12 and compressed air is supplied to combustor 20. Combustion gases 28 from combustor 20 propels turbines 14. Turbine 14 rotates shaft 18, compressor 12, and electric generator 16 about a longitudinal axis 30.
When assembled within the stator assembly, each stator vane 40 is coupled to an engine casing (not shown) that extends circumferentially around a rotor shaft, such as shaft 18 (shown in
Each airfoil 60 includes a first sidewall 70 and a second sidewall 72. First sidewall 70 is convex and defines a suction side of airfoil 60, and second sidewall 72 is concave and defines a pressure side of airfoil 60. Sidewalls 70 and 72 are joined together at a leading edge 74 and at an axially-spaced trailing edge 76 of airfoil 60. More specifically, airfoil trailing edge 76 is spaced chord-wise and downstream from airfoil leading edge 74. First and second sidewalls 70 and 72, respectively, extend longitudinally or radially outward in span from its root positioned adjacent base 62 to an airfoil tip 80.
Base 62 facilitates securing stator vanes 40 to the casing. In the exemplary embodiment, base 62 is known as a “square-faced” base and includes a pair of circumferentially-spaced sides 90 and 91 that are connected together by an upstream face 92 and a downstream face 94. Alternatively, base 62 could include an arcuate surface. In the exemplary embodiment, sides 90 and 91 are identical and are substantially parallel to each other. In an alternative embodiment sides 90 and 91 are not parallel. Moreover, in the exemplary embodiment, upstream face 92 and downstream face 94 are substantially parallel to each other.
A pair of integrally-formed hangers 100 and 102 extend from each respective face 92 and 94. Hangers 100 and 102, as is known in the art, engage the casing to facilitate securing stator vane 40 within the stator assembly. In the exemplary embodiment, each hanger 100 and 102 extends outwardly from each respective face 92 and 94 adjacent a radially outer surface 104 of base 62.
To facilitate controlling contact between circumferentially-adjacent stator vanes 40 during rotor operation, in the exemplary embodiment, at least one of circumferential sides 90 and 91 includes a recessed or scalloped portion 110 that extends partially between radially outer surface 104 and a radially inner surface 112 of base 62. Recessed portion 110 is sized and oriented to facilitate controlling an amount of contact between adjacent stator vanes 40 during rotor operation. More specifically, in the exemplary embodiment, recessed portion 110 extends from radially outer surface 104 towards radially inner surface 112 such that a hinge 116 is created adjacent radially inner surface 112. Accordingly, when adjacent stator vanes are coupled within the stator assembly, a gap 118 is defined between adjacent stator vanes 40 and contact between the stator vanes is limited being only along hinge 116. As a result, line contact between adjacent stators 40 is driven along the rotor assembly flow path. Alternatively, line contact may be anywhere between hinge 116 and side 91.
In addition, to facilitate controlling contact between each respective stator vane 40 and the engine casing during rotor operation, in the exemplary embodiment, upstream face 92 includes a recessed portion 120 that extends across face 92 between sides 90 and 91. Recessed portion 120 is sized and oriented to facilitate controlling an amount of contact between stator vane 40, along face 92, and the engine casing. More specifically, in the exemplary embodiment, recessed portion 120 extends from hanger 100 to a hinge 117. As a result, line contact between each stator vane 40 and the engine casing is controlled. Alternatively, line contact may be anywhere along portion 120.
The combination of recessed portions 120 and 110 facilitates controlling stator-to-stator contact and stator-to-casing contact. The enhanced control of the contact facilitates each stator base 62 being defined more accurately such that the stator vanes natural frequencies can be optimized more accurately to match predicted expermimental frequencies. Moreover, excitation responses induced within each stator vane 40 are facilitated to be reduced, thus resulting in fewer component failures and extending a useful life of the stator vanes.
The above-described stator vanes provide a cost-effective and reliable method for optimizing performance of a rotor assembly. More specifically, each stator vane includes recessed portions that facilitate controlling circumferential and axial contact with each stator vane such that excitation responses induced within each stator vane during engine operation are facilitated to be reduced. As a result, the redefined base geometry facilitates extending a useful life of the stator assembly and improving the operating efficiency of the gas turbine engine in a cost-effective and reliable manner.
Exemplary embodiments of stator vanes and stator assemblies are described above in detail. The stator vanes are not limited to the specific embodiments described herein, but rather, components of each stator vane may be utilized independently and separately from other components described herein. For example, each stator vane recessed portion can also be defined in, or used in combination with, other stator vanes or with other stator or rotor assemblies, and is not limited to practice with only stator vane 40 as described herein. Rather, the present invention can be implemented and utilized in connection with many other vane, stator, and rotor configurations.
While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.
