U.S. patent application number 13/680974 was filed with the patent office on 2014-05-22 for turbine bucket shroud arrangement and method of controlling turbine bucket interaction with an adjacent turbine bucket.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. The applicant listed for this patent is GENERAL ELECTRIC COMPANY. Invention is credited to Sheo Narain Giri, Krishna Kishore Gumpina, Sanjeev Kumar Jha, Mahesh Pasupuleti.
Application Number | 20140140841 13/680974 |
Document ID | / |
Family ID | 50625738 |
Filed Date | 2014-05-22 |
United States Patent
Application |
20140140841 |
Kind Code |
A1 |
Gumpina; Krishna Kishore ;
et al. |
May 22, 2014 |
TURBINE BUCKET SHROUD ARRANGEMENT AND METHOD OF CONTROLLING TURBINE
BUCKET INTERACTION WITH AN ADJACENT TURBINE BUCKET
Abstract
A turbine bucket shroud arrangement for a turbine system
includes a contact region of a tip shroud, wherein the contact
region is in close proximity to an adjacent tip shroud. Also
included is a negative thermal expansion material disposed
proximate the contact region, the contact region comprising a first
volume during a startup condition and a shutdown condition of the
turbine system and a second volume during a steady state condition
of the turbine system, wherein the second volume is less than the
first volume.
Inventors: |
Gumpina; Krishna Kishore;
(Bangalore, IN) ; Giri; Sheo Narain; (Bangalore,
IN) ; Jha; Sanjeev Kumar; (Bangalore, IN) ;
Pasupuleti; Mahesh; (Bangalore, IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GENERAL ELECTRIC COMPANY |
Schenectady |
NY |
US |
|
|
Assignee: |
GENERAL ELECTRIC COMPANY
Schenectady
NY
|
Family ID: |
50625738 |
Appl. No.: |
13/680974 |
Filed: |
November 19, 2012 |
Current U.S.
Class: |
416/1 ;
416/179 |
Current CPC
Class: |
F01D 5/225 20130101 |
Class at
Publication: |
416/1 ;
416/179 |
International
Class: |
F01D 5/22 20060101
F01D005/22 |
Claims
1. A turbine bucket shroud arrangement for a turbine system
comprising: a contact region of a tip shroud, wherein the contact
region is in close proximity to an adjacent tip shroud; and a
negative thermal expansion material disposed proximate the contact
region, the contact region comprising a first volume during a
startup condition and a shutdown condition of the turbine system
and a second volume during a steady state condition of the turbine
system, wherein the second volume is less than the first
volume.
2. The turbine bucket shroud arrangement of claim 1, wherein the
negative thermal expansion material comprises at least one of
zircon, zirconium tungstate and an A.sub.2(MO.sub.4).sub.3
compound.
3. The turbine bucket shroud arrangement of claim 1, further
comprising an adjacent contact region of the adjacent tip
shroud.
4. The turbine bucket shroud arrangement of claim 3, wherein the
adjacent contact region comprises a negative thermal expansion
material.
5. The turbine bucket shroud arrangement of claim 1, wherein the
contact region comprises a composition of the negative thermal
expansion material and a wear resistant material.
6. The turbine bucket shroud arrangement of claim 5, wherein the
composition comprises a layer disposed on a base metal of the tip
shroud.
7. The turbine bucket shroud arrangement of claim 5, wherein the
composition comprises a plurality of layers disposed on a base
metal of the tip shroud.
8. The turbine bucket shroud arrangement of claim 7, wherein each
of the plurality of layers comprise a distinct volume fraction of
the negative thermal expansion material.
9. The turbine bucket shroud arrangement of claim 5, wherein the
composition is brazed to the tip shroud.
10. The turbine bucket shroud arrangement of claim 5, wherein the
composition is welded to the tip shroud.
11. A method of controlling turbine bucket interaction with an
adjacent turbine bucket comprising: reducing a gap disposed between
a contact region of a tip shroud and an adjacent tip shroud by
depositing a negative thermal expansion material proximate the
contact region; engaging the contact region of the tip shroud with
the adjacent tip shroud during a startup operating condition and a
shutdown operating condition; and decreasing a volume of the
contact region during increased temperature operating conditions
upon contraction of the negative thermal expansion material,
wherein decreasing the volume reduces turbine bucket tip shroud
contact forces and stresses during a steady state operating
condition.
12. The method of claim 11, further comprising depositing the
negative thermal expansion material proximate an adjacent contact
region of the adjacent tip shroud.
13. The method of claim 11, further comprising forming a
composition proximate the contact region, wherein the composition
comprises the negative thermal expansion material and a wear
resistant material.
14. The method of claim 13, further comprising forming a plurality
of layers of the composition proximate the contact region.
15. The method of claim 14, wherein each of the plurality of layers
comprises a distinct volume fraction of the negative thermal
expansion material.
16. The method of claim 13, wherein the composition is brazed to
the tip shroud.
17. The method of claim 13, wherein the composition is welded to
the tip shroud.
18. The method of claim 13, wherein the composition is laser
cladded to the tip shroud.
19. The method of claim 13, wherein the composition is cold sprayed
onto the tip shroud.
20. The method of claim 13, wherein the composition is deposited
during a plasma transferred arc process.
Description
BACKGROUND OF THE INVENTION
[0001] The subject matter disclosed herein relates to turbine
systems, and more particularly to turbine bucket shroud
arrangements, as well as a method of controlling turbine bucket
interaction with an adjacent turbine bucket.
[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 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, which may result in resonance, for
example. Too small of a gap results in undesirable effects at high
speed operation of the turbine system. Such effects include lower
damping effectiveness and flutter margin, as well as 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 bucket
shroud arrangement for a turbine system includes a contact region
of a tip shroud, wherein the contact region is in close proximity
to an adjacent tip shroud. Also included is a negative thermal
expansion material disposed proximate the contact region, the
contact region comprising a first volume during a startup condition
and a shutdown condition of the turbine system and a second volume
during a steady state condition of the turbine system, wherein the
second volume is less than the first volume.
[0005] According to another aspect of the invention, a method of
controlling turbine bucket interaction with an adjacent turbine
bucket is provided. The method includes reducing a gap disposed
between a contact region of a tip shroud and an adjacent tip shroud
by depositing a negative thermal expansion material proximate the
contact region. Also included is engaging the contact region of the
tip shroud with the adjacent tip shroud during a startup operating
condition and a shutdown operating condition. Further included is
decreasing a volume of the contact region during increased
temperature operating conditions upon contraction of the negative
thermal expansion material, wherein decreasing the volume reduces
tip shroud contact forces and stresses during a steady state
operating condition.
[0006] 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
[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 turbine system;
[0009] FIG. 2 is a partial perspective view of a turbine stage of
the turbine system;
[0010] FIG. 3 is a top plan view of a turbine bucket shroud
arrangement having a contact region;
[0011] FIG. 4 is an enlarged top plan view of the contact region of
FIG. 3;
[0012] FIG. 5 is a schematic view of the contact region comprising
a composition;
[0013] FIG. 6 is a schematic view of a plurality of layers of the
composition; and
[0014] FIG. 7 is a flow diagram illustrating a method of
controlling turbine bucket interaction with an adjacent turbine
bucket.
[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 and thermal
loads created by the operation of the turbine 24.
[0020] Referring now to FIGS. 3 and 4, 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 contact region
54 configured to engage the adjacent tip shroud 52 during operation
of the turbine system 10. Specifically, the contact region 54
engages an adjacent contact region 56 of the adjacent tip shroud
52. A gap 58 is present between the tip shroud 50 and the adjacent
tip shroud 52, and more particularly between the contact region 54
and the adjacent contact region 56. The gap 58 is present prior to
startup of the turbine system 10. The gap 58 is 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. Subsequent to interlock of the
tip shroud 50 and the adjacent tip shroud 52, the operating
environment increases in temperature, thereby resulting in thermal
expansion of most components within the turbine 24.
[0021] To alleviate the stresses imposed by potential expansion of
already contacted components, at least one of the contact region 54
and the adjacent contact region 56, but typically both the contact
region 54 and the adjacent contact region 56, include a negative
thermal expansion material 60. The negative thermal expansion
material 60 is 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 contact
region 54 and the adjacent contact region 56. Examples of such
materials include zircon, zirconium tungstate and
A.sub.2(MO.sub.4).sub.3 compounds. Forming at least a portion of
the contact region 54 and the adjacent contact region 56 with the
negative thermal expansion material 60 advantageously allows for
the gap 58 to be dimensionally reduced to facilitate an early
interlock between the tip shroud 50 and the adjacent tip shroud 52,
while also reducing the contact forces associated with interaction
between the tip shroud 50 and the adjacent tip shroud 52, thereby
reducing stresses imposed on various portions of the tip shroud 50,
the adjacent tip shroud 52 and the airfoil 32 attached thereto. The
stress reduction is achieved by maintaining an interlock, but
contracting the negative thermal expansion material 60. In other
words, the contact region 54 comprises a first volume during a
startup condition of the turbine system 10 and a smaller, second
volume during a steady state operating condition of the turbine
system 10.
[0022] Referring now to FIGS. 5 and 6, the contact region 54 is
schematically illustrated in greater detail. The tip shroud 50
includes a base metal region 62 that is coated or integrally formed
with the contact region 54. The contact region 54 is formed of one
or more composition layers that typically include a fraction of the
negative thermal expansion material 60 and a fraction of a wear
resistant material. As noted above, the contact region 54 may
include a single composition layer (FIG. 5) or a plurality of
composition layers (FIG. 6). In an embodiment having a plurality of
composition layers 72, it is to be appreciated that distinct volume
and/or weight fractions of the negative thermal expansion material
60 may be present in the plurality of composition layers 72, such
as a first layer 64, a second layer 68 and a third layer 70, as
shown. In one embodiment, the fraction of the negative thermal
expansion material 60 progressively increases in each layer,
relative to moving away from the base metal region 62.
Specifically, the first layer 64 may include a lower fraction of
the negative thermal expansion material 60 than the second layer
68, with the second layer 68 having a lower fraction than the third
layer 70. Gradually transitioning the inclusion of the negative
thermal expansion material 60 from the base metal region 62 reduces
thermal fight at the interface between the contact region 54 and
the base metal region 62 of the tip shroud 50. It is to be
appreciated that each of the plurality of composition layers 72 may
vary in thickness from one another and may comprise the negative
thermal expansion material 60 in a fraction ranging from about 0%
to about 100%.
[0023] The contact region 54, whether a single layer or the
plurality of composition layers 72, may be deposited or integrated
with the tip shroud 50 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.
[0024] As illustrated in the flow diagram of FIG. 7, and with
reference to FIGS. 1-6, a method of controlling turbine bucket
interaction with an adjacent turbine bucket 100 is also provided.
The turbine system 10, as well as the tip shroud 50 and the contact
region 54, have been previously described and specific structural
components need not be described in further detail. The method of
controlling turbine bucket interaction with an adjacent turbine
bucket 100 includes reducing a gap between a contact region of a
tip shroud and an adjacent tip shroud by depositing a negative
thermal expansion material proximate the contact region 102. The
contact region is engaged with the adjacent tip shroud during a
startup operating condition 104. A volume of the contact region is
decreased during increased temperature operating conditions upon
contraction of the negative thermal expansion material 106.
[0025] 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.
* * * * *