Patent application title: TURBINE SHROUD ARRANGEMENT FOR A TURBINE SYSTEM AND METHOD OF CONTROLLING A TURBINE SHROUD ARRANGEMENT
Inventors:
Krishna Kishore Gumpina (Bangalore, IN)
Harish Bommanakatte (Bangalore, IN)
Harish Bommanakatte (Bangalore, IN)
Sheo Narain Giri (Bangalore, IN)
Sheo Narain Giri (Bangalore, IN)
Sanjeev Kumar Jha (Bangalore, IN)
Sanjeev Kumar Jha (Bangalore, IN)
Assignees:
GENERAL ELECTRIC COMPANY
IPC8 Class: AF01D2524FI
USPC Class:
415 1
Class name: Rotary kinetic fluid motors or pumps method of operation
Publication date: 2014-05-22
Patent application number: 20140140807
Abstract:
A turbine shroud arrangement for a turbine system includes a first region
of a tip shroud, the first region disposed in close proximity to an
adjacent tip shroud. Also included is a second region of the tip shroud,
the second region disposed in close proximity to the adjacent tip shroud,
the second region comprising a temperature sensitive material configured
to engage the second region and the adjacent tip shroud in contact over a
first operating condition of the turbine system and configured to provide
a second region gap over a second operating condition of the turbine
system.Claims:
1. A turbine shroud arrangement for a turbine system comprising: a first
region of a tip shroud, the first region disposed in close proximity to
an adjacent tip shroud; and a second region of the tip shroud, the second
region disposed in close proximity to the adjacent tip shroud, the second
region comprising a temperature sensitive material configured to engage
the second region and the adjacent tip shroud in contact over a first
operating condition of the turbine system and configured to provide a
second region gap over a second operating condition of the turbine
system.
2. The turbine shroud arrangement of claim 1, wherein the temperature sensitive material comprises a negative thermal expansion material.
3. The turbine shroud arrangement of claim 1, wherein the temperature sensitive material comprises a shape memory alloy.
4. The turbine shroud arrangement of claim 1, further comprising a first region gap disposed between the first region and the adjacent tip shroud during the first operating condition.
5. The turbine shroud arrangement of claim 4, wherein the first region and the adjacent tip shroud are in contact during the second operating condition.
6. The turbine shroud arrangement of claim 1, further comprising an adjacent second region of the adjacent tip shroud, the adjacent second region comprising the temperature sensitive material.
7. The turbine shroud arrangement of claim 1, wherein the first operating condition comprises a turbine operating speed range from about 0% to about 50% of a maximum speed of the turbine system.
8. The turbine shroud arrangement of claim 1, wherein the second operating condition comprises a turbine operating speed range from about 30% to about 100% of a maximum speed of the turbine system.
9. A turbine shroud arrangement for a turbine system comprising: a first region of a tip shroud, the first region disposed in close proximity to an adjacent first region of an adjacent tip shroud; a second region of the tip shroud, the second region disposed in close proximity to an adjacent second region of the adjacent tip shroud; and a temperature sensitive material disposed proximate the second region, the temperature sensitive material comprising a first volume during a first operating condition of the turbine system and a second volume during a second operating condition of the turbine system, wherein the second volume is less than the first volume.
10. The turbine shroud arrangement of claim 9, wherein the second region and the adjacent second region are in contact during the first operating condition and spaced to provide a second region gap during the second operating condition.
11. The turbine shroud arrangement of claim 9, wherein the temperature sensitive material comprises a negative thermal expansion material.
12. The turbine shroud arrangement of claim 9, wherein the temperature sensitive material comprises a shape memory alloy.
13. The turbine shroud arrangement of claim 9, further comprising a first region gap disposed between the first region and the adjacent first region during the first operating condition.
14. The turbine shroud arrangement of claim 13, wherein the first region and the adjacent first region are in contact during the second operating condition.
15. The turbine shroud arrangement of claim 9, wherein the adjacent second region comprises the temperature sensitive material.
16. The turbine shroud arrangement of claim 9, wherein the first operating condition comprises a turbine operating speed range from about 0% to about 50% of a maximum speed of the turbine system.
17. The turbine shroud arrangement of claim 9, wherein the second operating condition comprises a turbine operating speed range from about 30% to about 100% of a maximum speed of the turbine system.
18. A method of controlling a turbine shroud arrangement comprising: disposing a first region gap between a first region of a tip shroud and an adjacent tip shroud; reducing a second region gap disposed between a second region of the tip shroud and the adjacent tip shroud by depositing a temperature sensitive material proximate the second region; engaging the second region with the adjacent tip shroud during a first operating condition of a turbine system and providing the second region gap during a second operating condition of the turbine system; and providing the first region gap during the first operating condition and reducing the first region gap to engage the first region with the adjacent tip shroud during the second operating condition.
19. The method of claim 18, further comprising decreasing a volume of the temperature sensitive material during increased temperature operating conditions upon contraction of the temperature sensitive material.
20. The method of claim 18, further comprising depositing the temperature sensitive material on an adjacent second region of the adjacent tip shroud, the adjacent second region in close proximity with the second region of the tip shroud.
Description:
BACKGROUND OF THE INVENTION
[0001] The subject matter disclosed herein relates to turbine systems, and more particularly to turbine bucket tip shroud arrangements, as well as a method of controlling a turbine bucket tip shroud arrangement.
[0002] Turbine systems employ a number of rotating components or assemblies, such as compressor stages and turbine stages that rotate at high speed when the turbine is in operation, for example. In general, a stage includes a plurality of free-floating blades that extend radially outward from a central hub. Some blades include a tip shroud that limits vibration within a stage and provides sealing to increase efficiency of the overall system. The shroud is typically positioned at a tip portion of the blade, a mid-portion of the blade or at both the mid portion and the tip portion of the blade. The shrouds are designed such that the free-floating blades interlock to form an integral rotating member during operation.
[0003] Prior to rotation of the free-floating blades, a gap between contact surfaces of the shrouds is present. The distance of the gap determines how early an interlock of the shrouds occurs upon startup of the turbine system. Too large of a gap inefficiently delays the locking speed, thereby resulting in resonance, for example. Too small of a gap results in undesirable effects at high speed operation of the turbine system. Such effects include high stresses imposed on the turbine bucket due to increased transfer of forces between the contacting shrouds, for example. Therefore, current efforts to beneficially reduce the gap to provide an early interlock to address potential low speed aeromechanics issues are mitigated by the detrimental effects on tip shroud life that occur at steady state operating conditions.
BRIEF DESCRIPTION OF THE INVENTION
[0004] According to one aspect of the invention, a turbine shroud arrangement for a turbine system includes a first region of a tip shroud, the first region disposed in close proximity to an adjacent tip shroud. Also included is a second region of the tip shroud, the second region disposed in close proximity to the adjacent tip shroud, the second region comprising a temperature sensitive material configured to engage the second region and the adjacent tip shroud in contact over a first operating condition of the turbine system and configured to provide a second region gap over a second operating condition of the turbine system.
[0005] According to another aspect of the invention, a turbine shroud arrangement for a turbine system includes a first region of a tip shroud, the first region disposed in close proximity to an adjacent first region of an adjacent tip shroud. Also included is a second region of the tip shroud, the second region disposed in close proximity to an adjacent second region of the adjacent tip shroud. Further included is a temperature sensitive material disposed proximate the second region, the temperature sensitive material comprising a first volume during a first operating condition of the turbine system and a second volume during a second operating condition of the turbine system, wherein the second volume is less than the first volume.
[0006] According to yet another aspect of the invention, a method of controlling a turbine shroud arrangement is provided. The method includes disposing a first region gap between a first region of a tip shroud and an adjacent tip shroud. Also included is reducing a second region gap disposed between a second region of the tip shroud and the adjacent tip shroud by depositing a temperature sensitive material proximate the second region. Further included is engaging the second region with the adjacent tip shroud during a first operating condition of a turbine system and providing the second region gap during a second operating condition of the turbine system. Yet further included is providing the first region gap during the first operating condition and reducing the first region gap to engage the first region with the adjacent tip shroud during the second operating condition.
[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 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 schematic view of a turbine system;
[0010] FIG. 2 is a partial perspective view of a turbine stage of the turbine system;
[0011] FIG. 3 is a top plan view of a turbine bucket tip shroud arrangement having a first region and a second region;
[0012] FIG. 4 is a schematic view of the first region and the second region in a first operating condition;
[0013] FIG. 5 is a schematic view of the first region and the second region in a second operating condition; and
[0014] FIG. 6 is a flow diagram illustrating a method of controlling the turbine bucket tip shroud arrangement.
[0015] 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
[0016] Referring to FIG. 1, a turbine system, shown in the form of a gas turbine engine, constructed in accordance with an exemplary embodiment of the present invention, is indicated generally at 10. The turbine system 10 includes a compressor 12 and a plurality of combustor assemblies arranged in a can annular array, one of which is indicated at 14. As shown, the combustor assembly 14 includes an endcover assembly 16 that seals, and at least partially defines, a combustion chamber 18. A plurality of nozzles 20-22 are supported by the endcover assembly 16 and extend into the combustion chamber 18. The nozzles 20-22 receive fuel through a common fuel inlet (not shown) and compressed air from the compressor 12. The fuel and compressed air are passed into the combustion chamber 18 and ignited to form a high temperature, high pressure combustion product or air stream that is used to drive a turbine 24. The turbine 24 includes a plurality of stages 26-28 that are operationally connected to the compressor 12 through a compressor/turbine shaft 30 (also referred to as a rotor).
[0017] In operation, air flows into the compressor 12 and is compressed into a high pressure gas. The high pressure gas is supplied to the combustor assembly 14 and mixed with fuel, for example process gas and/or synthetic gas (syngas), in the combustion chamber 18. The fuel/air or combustible mixture ignites to form a high pressure, high temperature combustion gas stream. Alternatively, the combustor assembly 14 can combust fuels that include, but are not limited to, natural gas and/or fuel oil. In any event, the combustor assembly 14 channels the combustion gas stream to the turbine 24 which converts thermal energy to mechanical, rotational energy.
[0018] At this point, it should be understood that each of the plurality of stages 26-28 is similarly formed, thus reference will be made to FIG. 2 in describing stage 26 constructed in accordance with an exemplary embodiment of the present invention with an understanding that the remaining stages, i.e., stages 27 and 28, have corresponding structure. Also, it should be understood that the present invention could be employed in stages in the compressor 12 or other rotating assemblies that require wear and/or impact resistant surfaces. In any event, the stage 26 is shown to include a plurality of rotating members, such as an airfoil 32, which each extend radially outward from a central hub 34 having an axial centerline 35. The airfoil 32 is rotatable about the axial centerline 35 of the central hub 34 and includes a base portion 36 and a tip portion 38.
[0019] A tip shroud 50 covers the tip portion 38 of the airfoil 32. The tip shroud 50 is designed to receive, or nest with, tip shrouds on adjacent rotating members in order to form a continuous ring that extends circumferentially about the stage 26. The continuous ring creates an outer flow path boundary that reduces gas path air leakage over top portions (not separately labeled) of the stage 26, so as to increase stage efficiency and overall turbine performance. In the exemplary embodiment shown, during high or operational speeds, adjacent airfoils interlock through the tip shroud 50 of each respective airfoil by virtue of centrifugal forces created by the operation of the turbine 24.
[0020] Referring now to FIGS. 3-5, the tip shroud 50 is illustrated in greater detail and is in close proximity with an adjacent tip shroud 52. The tip shroud 50 includes a first region 54 and a second region 56, each configured to engage the adjacent tip shroud 52 at various operating conditions of the turbine system 10. Specifically, the first region 54 engages an adjacent first region 58 of the adjacent tip shroud 52, while the second region 56 engages an adjacent second region 60 of the adjacent tip shroud 52. At various operating conditions of the turbine system 10, which will be described in detail below, a first region gap 62 is present between the tip shroud 50 and the adjacent tip shroud 52, and more particularly between the first region 54 and the adjacent first region 58. Similarly, at various operating conditions, a second region gap 64 is present between the tip shroud 50 and the adjacent tip shroud 52, and more particularly between the second region 56 and the adjacent second region 60.
[0021] To achieve an early interlock of the tip shroud 50 and the adjacent tip shroud 52, at least one of the second region 56 and the adjacent second region 60, but typically both the second region 56 and the adjacent second region 60, include a thermally sensitive material 70. The thermally sensitive material 70 is configured to dimensionally adjust in response to temperature variation. In one embodiment, the thermally sensitive material 70 is a negative thermal expansion material defined by having a negative coefficient of thermal expansion, such that the material contracts in response to increased temperature exposure, rather than expanding. It is to be appreciated that any material having a negative coefficient of thermal expansion may be suitable for inclusion with the second region 56 and the adjacent second region 60. Examples of such materials include zircon, zirconium tungstate and A2(MO4).sub.3 compounds. In another embodiment, the thermally sensitive material 70 comprises a shape memory alloy configured to be manipulated in response to thermal changes. Examples of suitable shape memory alloys includes materials comprising a titanium nickel (TiNi) alloy, palladium (Pd), gold (Au) and zirconium (Zr), among others. Although the second region 56 has been described as a single region, it is to be appreciated that a plurality of regions may include the thermally sensitive material 70 for establishing contact during operating conditions similar to the second region 56 and the adjacent second region 60. One such illustrative region is shown as a third region 68 and an adjacent third region 69, for example. For clarity of description, the second region 56 and the adjacent second region 60 will be described herein, with the understanding that additional similarly constructed and positioned regions may be present.
[0022] Forming at least a portion of the second region 56 and the adjacent second region 60 with the thermally sensitive material 70 advantageously allows for an early interlock between the tip shroud 50 and the adjacent tip shroud 52 during a first operating condition (FIG. 4) corresponding to a first turbine speed range. The first turbine speed range may vary depending on the application, but in one embodiment the first turbine speed range is from about 0% to about 50% of a maximum turbine operating speed. Operation over this range corresponds to a cooler operating environment for the tip shroud 50 relative to a second operating condition (FIG. 5) corresponding to a second turbine speed range. Similar to the first turbine speed range, the second turbine speed range may vary depending on the application, but in one embodiment the second turbine speed range is from about 30% to about 100% of the maximum turbine operating speed. The maximum turbine operating speed will vary based on the particular application as well. It can be appreciated that during the first operating condition, the thermally sensitive material 70, and therefore the second region 56, is disposed at a first position and is of a first dimension, such as a volume. As the operating environment increases in temperature, the position and/or the dimensions of the second region 56 changes. Specifically, the thermally sensitive material 70 contracts and/or retracts from the adjacent second region 60, thereby forming the second region gap 64 at the transition to the second operating condition. As noted above, the adjacent second region 60 may include the thermally sensitive material 70, such that it may similarly contract or retract from the second region 56. In other words, the second region 56 and the adjacent second region 60 may contract from a first volume to a smaller, second volume or may simply retract from one another as the temperature increases.
[0023] In the first operating condition, the first region 54 and the adjacent first region 58 are spaced from one another, thereby defining the first region gap 62. To alleviate stresses imposed on the tip shroud 50, the adjacent tip shroud 52 and the airfoil 32, the first region 54 and the adjacent first region 58 are not engaged into contact until the second operating condition is satisfied. Stress reduction is achieved by avoiding early and continuous contact that otherwise may be employed to meet rapid interlock goals. Rather, early interlock during the first operating condition is achieved by engagement of the second region 56 and the adjacent second region 60 and subsequent engagement of the first region 54 and the adjacent first region 58 during the second operating condition. During the second operating condition, the first region 54 and the adjacent first region 58 may thermally expand and shift due to temperature increase and increased centrifugal forces, respectively. Such responses increase the stresses noted above, however, these stresses are mitigated by the delayed engagement of the first region 54 and the adjacent first region 58. As described above, the second region 56 and the adjacent second region 60 are thermally manipulated to establish the second region gap 64 during the second operating condition, thereby reducing any stresses that may otherwise be imposed during increased temperature and centrifugal force application during the second operating condition.
[0024] The first region gap 62 and the second region gap 64 both may vary in dimension depending on the application, but in one embodiment the first region gap 62 may range from about 5 mils (about 0.005'' or about 0.127 mm) to about 50 mils (about 0.050'' or about 1.27 mm) In yet another embodiment, the first region gap 62 is about 20 mils (about 0.020'' or about 0.508 mm) The second region gap 64 may range from about 5 mils (about 0.005'' or about 0.127 mm) to about 75 mils (about 0.075'' or about 1.905 mm) In yet another embodiment, the second region gap 64 ranges from about 20 mils (about 0.020'' or about 0.508 mm) to about 50 mils (about 0.05'' to about 1.27 mm) The preceding description of dimensions of the first gap region 62 and the second gap region 64 is merely exemplary and is not intended to be limiting of various other suitable dimensions. The first region gap 62 and the second region gap 64 are dimensionally selected based on a desirable early interlock of the tip shroud 50 and the adjacent tip shroud 52 upon operation of the turbine system 10 and rotation of the airfoil 32.
[0025] It is contemplated that the second region 56 and the adjacent second region 60 are coated or integrally formed with the tip shroud 50 and the adjacent tip shroud 52, respectively. The second region 56 and the adjacent second region 60 may be formed of one or more composition layers that typically include a fraction of the thermally sensitive material 70 and a fraction of a wear resistant material. In an embodiment having a plurality of composition layers, it is to be appreciated that distinct volume and/or weight fractions of the thermally sensitive material 70 may be present in the plurality of composition layers. In one embodiment, the fraction of the thermally sensitive material 70 progressively increases in each layer, relative to moving away from a base metal of the tip shroud 50 and the adjacent tip shroud 52. It is to be appreciated that each of the plurality of composition layers may vary in thickness from one another and may comprise the thermally sensitive material 70 in a fraction ranging from about 0% to about 100%.
[0026] The second region 56 and/or the adjacent second region 60, whether a single layer or a plurality of composition layers, may be deposited or integrated with the tip shroud 50 and the adjacent tip shroud 52 in a number of application processes. Examples of such processes include brazing, welding, laser cladding, cold spraying and a plasma transferred arc (PTA) process. The preceding list is merely illustrative and is not intended to be limiting of numerous other suitable application procedures.
[0027] As illustrated in the flow diagram of FIG. 6, and with reference to FIGS. 1-5, a method of controlling a turbine shroud arrangement 100 is also provided. The turbine system 10, as well as the tip shroud 50 and the second region 56, have been previously described and specific structural components need not be described in further detail. The method of controlling a turbine shroud arrangement 100 includes disposing a first region gap between a first region of a tip shroud and an adjacent tip shroud 102. A second region gap disposed between a second region of the tip shroud and the adjacent tip shroud is reduced by depositing a temperature sensitive material proximate the second region 104. The second region is engaged with the adjacent tip shroud during a first operating condition of the turbine system 106, thereby providing the second region gap during a second operating condition of the turbine system. The first region gap is provided during the first operating condition 108, thereby reducing the first region gap to engage the first region with the adjacent tip shroud during the second operating condition.
[0028] 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.
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