U.S. patent application number 14/405826 was filed with the patent office on 2015-05-07 for platform seal strip, turbine blade assembly and method for assembling it.
This patent application is currently assigned to Siemens Aktiengesellschaft. The applicant listed for this patent is Siemens Aktiengesellschaft. Invention is credited to Paul Headland.
Application Number | 20150125301 14/405826 |
Document ID | / |
Family ID | 48669897 |
Filed Date | 2015-05-07 |
United States Patent
Application |
20150125301 |
Kind Code |
A1 |
Headland; Paul |
May 7, 2015 |
PLATFORM SEAL STRIP, TURBINE BLADE ASSEMBLY AND METHOD FOR
ASSEMBLING IT
Abstract
A platform seal strip, in particular for use in a gas turbine
blade assembly, is provided. The platform seal strip includes an
upper side, a lower side, a first portion and a second portion. The
width of the first portion is smaller than the width of the second
portion. The first portion and the second portion are at least
partially bent downwards such that the upper side includes a convex
surface portion and the lower side includes a concave surface
portion.
Inventors: |
Headland; Paul; (Lincoln,
GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Siemens Aktiengesellschaft |
Munich |
|
DE |
|
|
Assignee: |
Siemens Aktiengesellschaft
Munich
DE
|
Family ID: |
48669897 |
Appl. No.: |
14/405826 |
Filed: |
June 12, 2013 |
PCT Filed: |
June 12, 2013 |
PCT NO: |
PCT/EP2013/062115 |
371 Date: |
December 5, 2014 |
Current U.S.
Class: |
416/174 ;
29/889.21 |
Current CPC
Class: |
F01D 11/006 20130101;
Y10T 29/49321 20150115; F01D 5/082 20130101; F01D 5/3015
20130101 |
Class at
Publication: |
416/174 ;
29/889.21 |
International
Class: |
F01D 11/00 20060101
F01D011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 26, 2012 |
EP |
12173650.8 |
Claims
1. A platform seal strip, comprising an upper side, a lower side, a
leading portion and a second portion, the width of the leading
portion being smaller than the width of the second portion, wherein
the leading portion and the second portion are at least partially
bent downwards such that the upper side comprises a convex surface
portion and the lower side comprises a concave surface portion.
2. The platform seal strip as claimed in claim 1, further
comprising a transition portion which is located between the
leading portion and the second portion, wherein the width of the
transition portion increases from the leading portion to the second
portion.
3. The platform seal strip as claimed in claim 1, wherein the strip
seal comprises a trailing portion extending downwards from the
second portion.
4. The platform seal strip as claimed in claim 1, further
comprising at least one nose located at the first portion or at the
second portion which is at least partially bent upwards such that
the upper side comprises a concave surface portion and the lower
side comprises a convex surface portion.
5. A turbine blade assembly comprising a number of platform seal
strips as claimed in claim 1, a disc and a number of blades, each
blade comprising a blade platform, wherein the blades are connected
to the disc and each platform seal strip is placed in a gap between
the blade platforms of adjacent blades.
6. The turbine assembly as claimed in claim 5, wherein the disc
comprises a rotation axis and the platform of each blade comprises
a side surface with a surface normal which includes a right angle
with the rotation axis, wherein the side surface comprises a slot
and part of the second portion of the platform seal strip engages
in the slot.
7. The turbine assembly as claimed in claim 6, wherein the platform
comprises a main platform part and a leading wall and the slot
extends along the main platform part and a leading wall.
8. The turbine assembly as claimed in claim 7, wherein the platform
comprises a trailing wall and the slot extends along the main
platform part and a trailing wall.
9. The turbine assembly as claimed in claim 5, wherein the disc
comprises a front face and a rear face and a first cover plate is
attached to the rear face and/or a second cover plate is attached
to the front face and the platform seal strip comprises a nose
which engages into a groove of the first cover plate or into a
groove of the second cover plate.
10. The turbine assembly as claimed in claim 5, wherein only one
platform seal strip is located between two adjacent blades.
11. A gas turbine comprising a turbine blade assembly as claimed in
claim 5.
12. A method for assembling a turbine blade assembly as claimed in
claim 5, comprising: loading the number of blades onto the disc
leaving a gap between the platforms of adjacent blades, inserting a
platform seal strip into the gap between the platforms of two
adjacent blades, and retaining the platform seal strips by
attaching a first cover plate to the disc.
13. The method as claimed in claim 12, further comprising attaching
a second cover plate to the disc before loading the blades onto the
disc.
14. The method as claimed in claim 12, further comprising using a
platform seal strip having at least one nose located at the first
portion or at the second portion which is at least partially bent
upwards such that the upper side comprises a concave surface
portion and the lower side comprises a convex surface portion and
inserting the at least one nose into a groove in the first or
second cover plate.
15. The method as claimed in claim 12, further comprising
positioning a seal means between the first cover plate and the disc
and/or positioning a seal means between the second cover plate and
the disc.
16. The platform seal strip of claim 1 adapted for use in a gas
turbine blade assembly.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is the US National Stage of International
Application No. PCT/EP2013/062115 filed Jun. 12, 2013, and claims
the benefit thereof. The International Application claims the
benefit of European Application No. EP12173650 filed Jun. 26, 2012.
All of the applications are incorporated by reference herein in
their entirety.
FIELD OF INVENTION
[0002] The present invention relates to a platform seal strip, a
turbine blade assembly and a gas turbine. It further relates to a
method for assembling a turbine blade assembly, for example a gas
turbine blade assembly.
BACKGROUND ART
[0003] The documents EP 2 053 285 A1 and EP 2 053 286 A1 describe a
seal strip with varying width that is bent at a downstream end and
trapped between a blade platform and the locking plate in the
assembly.
[0004] In the document U.S. Pat. No. 3,918,842 a sealing member
such as a wire is mounted in a groove between blade platforms of a
gas turbine engine to seal between the adjacent platforms.
[0005] U.S. Pat. No. 6,561,764 B1 describes a gas turbine rotor
comprising blade platforms with recesses into which insert strips
are inserted. The recess reaches as far as the disc-side base of
the blade platform and the insert strip to have a form fit to the
disc, which protects against axial displacement in a direction of
inserting of the gas turbine blade.
[0006] Moreover, turbine seals are described in EP 0 816 638 A2, EP
1 635 037 A2 and U.S. Pat. No. 5,281,097.
[0007] U.S. Pat. No. 3,834,831 disclosures gas turbine engine,
wherein cooling fluid may escape through radially directed
passageways within the turbine blade or through a space between the
adjacent blade platforms.
[0008] It has been accepted that a leakage flow will occur between
the adjacent blade platforms of gas turbine blades. The air is used
to cool the underside of the platforms before it leaks into the gas
path. Excessive cooling air leakage wastes valuable cooling air and
has an impact on the engine efficiency. Currently the sealing of a
blade root can have up to 3 small seals to cover the two vertical
joints and the one horizontal joint making them difficult to
assemble and prone to leaking when all components are hot.
SUMMARY OF INVENTION
[0009] It is a first objective of the present invention to provide
an advantageous seals strip, in particular for use in a gas turbine
blade assembly. A second objective of the present invention is to
provide an advantageous turbine blade assembly and an advantageous
gas turbine. A third objective of the present invention is to
provide an advantageous method for assembling a turbine blade
assembly, for example a gas turbine blade assembly.
[0010] The first objective is solved by a platform seals strip as
claimed. The second objective is solved by a turbine blade assembly
as claimed and by a gas turbine as claimed. The third objective is
solved by a method for assembling a turbine blade assembly as
claimed. The depending claims define further developments of the
present invention.
[0011] The inventive platform seals strip, in particular for use in
a gas turbine blade assembly, comprises an upper side and a lower
side. It further comprises a first portion and a second portion.
The first portion may be a leading portion. The second portion may
be a main platform part. The width of the first portion is smaller
than the width of the second portion, which means that the width of
the first portion has a smaller value than the width of the second
portion. The first portion and the second portion are at least
partially bent downwards such that the upper side comprises a
convex surface portion and the lower side comprises a concave
surface portion. In other words, the first portion and the second
portion are bent towards the lower side.
[0012] "Downward" may mean, once the seal strip is installed, in
direction of an axis of rotation of the machine. "Downward" also
defines the orientation of the bend in respect of the upper side
and the lower side, meaning that "downward" is a motion in
direction of the lower side.
[0013] "Upper" and "lower" may merely define two opposite sides of
the seal platform strip. Particularly "upper" may also mean, once
the seal strip is installed, a direction away from of the axis of
rotation of the machine. "Lower" may mean, once the seal strip is
installed, a direction directed to the axis of rotation of the
machine.
[0014] The invention seal strip may for example have an U-shape or
a shape like an U. Convex surface portion or concave surface
portion means that at least part of the surface has a curvature or
bending which is convex if seen from the upper side or upper
surface and which is concave if seen from the lower side or lower
surface of the first portion or of the second portion. As a result
of the bending the first portion may comprise an upper surface
portion with a surface normal and the second portion may comprise
an upper surface portion with a surface normal which includes an
angle a with the surface normal of the first portion between
0.degree. and 180.degree., which means
0.degree.<a.ltoreq.180.degree., advantageously between
90.degree. and 180.degree..
[0015] The inventive seal strip has the advantage that inter seal
leakage, for example between two adjacent blade platforms can be
overcome by using a single piece seals strip.
[0016] Advantageously the inventive seal strip comprises a
transition portion which is located between the first portion and
the second portion. The width of the transition portion increases
from the first portion to the second portion. In an advantageous
embodiment, the width of the transition portion continuously
increases from the first portion to the second portion.
[0017] The strip seal may comprise a trailing portion extending
downwards from the second portion.
[0018] The width of the first portion may be constant and/or the
width of the second portion may be constant. Constant width means
that the width has the same value at each position of the mentioned
portion. In an advantageous embodiment, the width of the first
portion has a value w.sub.1, which is constant at each position
along length of the first portion, and the width of the second
portion has a value w.sub.2, which is constant at each position
along length of the second portion and which is higher than the
width w.sub.1 of the first portion (w.sub.1<w.sub.2). In an
advantageous embodiment, a transition portion with a width, which
continuously increases from the first portion to the second
portion, is located between the first and the second portion.
[0019] Moreover, the second portion may comprise or may define the
widest section of the seal strip. The second portion can
advantageously have only one width changing section, for example
only at one of its end. Alternatively, second portion can have only
a width changing section at each end of the second portion. The
width of the width changing section may change continuously, for
instance only increase continuously or only decrease continuously.
One advantage of the present seal strip is its very simple design
compared with the solutions known from the state of the art. This
reduces the manufacturing costs.
[0020] Generally the platform seal strip may comprise metal or may
consist of metal.
[0021] In an advantageous embodiment, the inventive seal strip
comprises at least one nose. The nose may be located at the first
portion or at the second portion. Advantageously one nose is
located the first portion and an additional nose is located at the
second portion. The nose is at least partially bent upwards such
that the upper side of the seals strip with the nose comprises a
concave surface portion and the lower side of the seal strip with
the nose comprises a convex surface portion.
[0022] In the context of the present invention the term nose
describes a portion of the seal strip which is bent with respect to
the adjacent first or second portion. For example, the nose may
have a surface portion with a surface normal. The first portion or
the second portion may comprise a surface adjacent to the nose.
This surface may have a surface normal which may include an angle
.beta. with the surface normal of the nose portion between
0.degree. and 180.degree., which means
0.degree.<.beta.<180.degree., and in an advantageous
embodiment between 60.degree. and 90.degree..
[0023] The inventive turbine blades assembly comprises a number of
platform seal strip, as previously described, a disc and a number
of blades. Each blade comprises a blade platform. The blades are
connected to the disc, for example loaded onto the disc. Each seal
strip is placed in a gap between the blade platforms of adjacent
blades.
[0024] The disc may comprise a rotation axis. The platform of each
blade may comprise a side surface with a surface normal which
includes a right angle with the rotation axis, especially when the
blade is loaded onto a disc. The side surface of the platform may
comprise a slot and part of the second portion of the seal strip
engages in the slot.
[0025] The turbine blade may comprise a main platform part and a
leading wall and the slot may extend along the main platform part
and the leading wall. The turbine blade may comprise the platform
having a trailing wall and the slot extends along the main platform
part and the trailing wall. The slot may be continuous along a side
surface defined by the main platform part and/or the leading wall
and/or the trailing wall.
[0026] Furthermore, the platform may comprise a leading edge side
or upstream side and a trailing edge side or downstream side. The
slot may extend up to the trailing edge side or downstream side.
Generally the leading edge side of the platform is defined such
that it corresponds to the leading edge of the aerofoil portion of
the blade and the trailing edge side of the platform is defined
such that it corresponds to the trailing edge of the aerofoil
portion of the blade.
[0027] The disc can comprise a front face or upstream side and a
rear face or downstream side, which are defined with respect to a
hot gas flow through the turbine. A first cover plate or cover disc
may be attached to the rear face of the turbine disc and/or a
second cover plate may be attached to the front face of the turbine
disc. Adding cover plates or cover discs to the front and/or rear
face of the turbine disc assembly allows for making more efficient
use of the cooling air. The cover plates or discs contain and
direct cooling air in a more efficient manner than previously used,
since they may comprise fluid channels for guiding cooling air.
[0028] By means of the describe seal strip the sealing at the plate
platform is improved. For example, the seal strip may comprise a
nose which engages into a groove of the first cover plate or into a
groove the second cover plate. Advantageously the seal strip
comprises a first nose at the first portion and a second nose at
the second portion. The first nose can engage into a groove of the
cover plate at the front face and the second nose can engage into a
groove of the cover plate at the rear face.
[0029] In an advantageous embodiment only one seal strip is located
between two adjacent blades. This reduces the number of necessary
components to be assembled and reduces the time for assembling.
[0030] The cover discs, especially the second cover discs or
forward cover disc which is attached to the front face, may
comprise a seal means, for example a C-seal or O-ring or rope seal
as appropriate. The seal means my comprise metal or may consist of
metal. The seal means may be located such that it faces the leading
edge side or the trailing edge side of the platform of the blade or
the blade root.
[0031] The inventive gas turbine comprises a turbine blade assembly
as previously described. It generally has the same properties and
advantages as described in conjunction with the inventive seal
strip and the inventive turbine blade assembly.
[0032] The inventive method for assembling a turbine blade assembly
is related to a turbine blade assembly as previously described. The
method comprises the steps of loading the number of blades onto the
disc leaving a gap between the platforms of adjacent blades,
inserting a seal strip into the gap between the platforms of two
adjacent blades, and retaining the seal strips by attaching a first
cover plate to the disc.
[0033] Advantageously a second cover plate, for example a forward
cover disc, may be attached to the disc before loading the blades
onto the turbine disc. If the second cover plate is identical with
a forward cover disc, than the first cover plate is identical with
an aft cover disc. The forward cover disc may be connected to the
front face of the disc and the aft cover disc may be connected to
the rear face of the disc.
[0034] In an advantageous embodiment, a seal strip with at least
one nose is used and the at least one nose is inserted into a
groove in the first or in the second cover plate. Advantageously
the seal strip comprises two noses and a first nose is inserted
into a groove in the forward cover disc and the second nose is
inserted into a groove in the aft cover disc.
[0035] Moreover, a seal means can be positioned between the first
cover plate, for example the aft cover disc, and the turbine disc.
Additionally or alternatively a seal means can be positioned
between the second cover plate, for example a forward cover disc,
and the turbine disc. A C-seal or an O-ring or a rope seal can be
used as seal means. The used seal means may comprise metal or may
consist of metal.
[0036] The present invention improves the sealing of turbine hot
blade components. The improved sealing includes improved retention
of the cooling fluid supplied to the blade under platform cavity to
prevent the coolant escaping the cavity via the gap.
Advantageously, more of the cooling fluid is used for better
cooling the blade. The improved sealing includes preventing hot
working gases ingressing the blade under platform cavity and mixing
with and reducing the effectiveness of the cooling fluid. By
improving the sealing also the cooling of a turbine blade can be
improved. Furthermore, the amount of cooling air consumed by the
turbine blades can be reduced. Moreover, the lifetime of the
components is increased, leakages are reduced and the cooling air
efficiency is improved. Furthermore, the part count and assembly
time is reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] Further features, properties and advantages of the present
invention will become clear from the following description of
embodiments in conjunction with the accompanying drawings. The
embodiments do not limit the scope of the present invention which
is determined by the appended claims. All described features are
advantageous as separate features or in any combination with each
other.
[0038] It has to be noted that embodiments of the invention have
been described with reference to different subject matters. In
particular, some embodiments have been described with reference to
apparatus type claims whereas other embodiments have been described
with reference to method type claims. However, a person skilled in
the art will gather from the above and the following description
that, unless other notified, in addition to any combination of
features belonging to one type of subject matter also any
combination between features relating to different subject matters,
in particular between features of the apparatus type claims and
features of the method type claims is considered as to be disclosed
with this document.
[0039] FIG. 1 schematically shows a gas turbine.
[0040] FIG. 2 schematically shows part of an inventive turbine
blade assembly in a sectional and perspective view.
[0041] FIG. 3 schematically shows the cooling fluid flow part of an
inventive turbine blade assembly a sectional and perspective
view.
[0042] FIG. 4 schematically shows an inventive platform seal strip
1 in a perspective view.
[0043] FIGS. 5 and 6 schematically show part of an inventive
turbine blade assembly in a perspective view during the insertion
of the platform seal strip.
[0044] FIG. 7 schematically shows part of an inventive turbine
blade assembly in a sectional and perspective view when the
assembling process is finished.
DETAILED DESCRIPTION OF INVENTION
[0045] FIG. 1 schematically shows a gas turbine. A gas turbine
comprises a rotation axis with a rotor. The rotor comprises a shaft
107. Along the rotor a suction portion with a casing 109, a
compressor 101, a combustion portion 151, a turbine 105 and an
exhaust portion with a casing 190 are located.
[0046] The combustion portion 151 communicates with a hot gas flow
channel which may have a circular cross section, for example. The
turbine 105 comprises a number of turbine stages. Each turbine
stage comprises rings of turbine blades. In flow direction 103 of
the hot gas in the hot gas flow channel a ring of turbine guide
vanes 117 is followed by a ring of turbine rotor blades 115. The
turbine guide vanes 117 are connected to an inner casing of a
stator. The turbine rotor blades 115 are connected to the rotor.
The rotor is connected to a generator, for example.
[0047] During operation of the gas turbine air is sucked and
compressed by means of the compressor 101. The compressed air is
led to the combustion portion 151 and is mixed with fuel. The
mixture of air and fuel is then combusted. The resulting hot
combustion gas flows through a hot gas flow channel to the turbine
guide vanes 117 and the turbine rotor blades 115 and actuates the
rotor.
[0048] FIG. 2 schematically shows part of an inventive turbine
blade assembly in a sectional and perspective view. The turbine
blade assembly comprises a disc 12, a number of rotor blades 151, a
first cover plate or aft cover disc 7 and a second cover plate or
forward cover disc 6. The rotor blades 151 are mounted onto the
disc 12.
[0049] The disc 12 comprises a front face or upstream side 26 and a
rear face or downstream side 27, which are defined with respect to
the hot gas flow direction 103. Before loading the blades 151 onto
the disc 12, the forward cover disc 6 is connected to the front
face 26. The aft cover disc 7 is connected to the rear face 27. The
aft cover disc 7 is fitted after the blades 151 and seal strips 1
are loaded to the disc 12.
[0050] A seal means 8 is placed between the forward cover disc 6
and the blades 151, for example part of the platforms 3 of the
blades, especially for preventing a hot gas flow into the blade
root cavity 15. A further seal means 16 is placed between the
forward cover disc 6 and the front face 26 of the disc 12. The seal
means 8 and/or the seal means 16 may comprise metal or may consist
of metal. The seal means 8 and/or seal means 16 may be a C-seal or
an O-ring or a rope seal. Moreover, between the aft cover disc 7
and the blades 151, for example part of the platform 3 of the
blades 151, a seal means 9 is positioned, for example to prevent a
hot gas flow into the blade root cavity 15. The seal means 9 may
have the same properties as the previously described seal means 8
or seal means 16.
[0051] The blades 151 comprise an aerofoil portion 2, a blade
platform 3 and a blade root 19, which is not shown in FIG. 2. The
blade platform 3 is located between the aerofoil portion 2 and the
blade root 19. The blade aerofoil portion 2 comprises a leading
edge 4 and a trailing edge 5.
[0052] When loaded onto the disc 12, a small gap occurs between the
platforms 3 of the adjacent blades 151. To seal this gap an
inventive platform seal strip 1 is inserted between the adjacent
platforms 3. In an advantageous embodiment, only one platform seal
strip 1 is inserted between each two adjacent platforms 3.
[0053] FIG. 3 schematically shows the cooling fluid flow in part of
an inventive turbine blade assembly in a sectional and perspective
view. The blades 151 comprise a blade under platform cavity 15,
which is located inside the blade 151 below the platform 3 towards
the blade root 19. Through this blade under platform cavity 15
cooling fluid, for example cooling air, can be guided into the
aerofoil portion 2.
[0054] Between the disc 12 and the forward cover disc 6 a flow
channel 17 is formed, through which cooling fluid can be guided
into the blade under platform cavity 15. The direction of the
cooling fluid flow is indicated by arrows 18.
[0055] The platform portion 3 of the blade 151 comprises a leading
edge side 21, corresponding to the leading edge of the aerofoil
portion 4, a trailing edge side 22, corresponding to the trailing
edge 5 of the aerofoil portion 2, and a side surface 23. The side
surfaces 23 of adjacent blades 151 are facing towards each other.
The side surface 23 comprises a surface normal 25. The surface
normal 25 includes a right angle with a rotation axis 102 of the
disc 12. The rotation axis 102 of the disc 12 may correspond to the
rotation axis 102 of a gas turbine.
[0056] The blade 151 further comprises a leading wall 80 and a
trailing wall 82 as seen in FIG. 3. It can also be said that the
leading wall 80 and the trailing wall 82 form extensions of the
platform 3. The platform 3 has a main platform part 3A that extends
both generally axially and circumferentially and along with a
neighbouring platform, defines a gas-wash surface at least between
adjacent blades. The main platform part 3A extends generally
between the leading edge side 21 and the trailing edge side 22.
[0057] The leading wall 80 is located at the forward or upstream
part of the blade 151 and the trailing wall 82 is located at the
rearward or downstream part of the blade 151. The leading wall 80
and trailing wall 82 are located radially inwardly of the main
platform part 3A. The leading wall 80 extends from the main
platform part 3A, in this example from about the leading edge side
21, and in a generally radially inward direction and towards the
disc 12. The trailing wall 82 extends from the main platform part
3A, in this example from a downstream or rearward part of the
platform, and in a generally radially inward direction and towards
the disc 12. The main platform part 3A, the leading wall 80 and the
trailing wall 82 at least partly define the blade under platform
cavity 15.
[0058] When loaded onto the disc 12, a small gap occurs between the
respective platforms 3, the leading walls 80 and the trailing walls
82 of the adjacent blades 151. This small gap is referred to as a
circumferential gap. A second gap 84 occurs between a radially
inner part of the leading wall 80 and the disc 12. During engine
operation cooling fluid flow 18 enters the blade under platform
cavity 15 via the second gap. A third gap 86 occurs between a
radially inner part of the trailing wall 80 and the disc 12. During
engine operation cooling fluid flow 18 can exit the blade under
platform cavity 15 via the third gap 86 to cool the downstream face
27 of the disc. The second and third gaps may be referred to as
radial gaps 84, 86.
[0059] The side surface 23 of the platform 3, including the main
platform part 3A, the leading walls 80 and the trailing walls 82
comprise a slot 24. The slot runs nearly parallel to the rotation
axis 102 along the main platform part 3A and extends up to the
trailing edge side 22. Part of the platform seal strip 1 engages
into the slot 24.
[0060] The platform seal strip 1 comprises a first nose or rebate
13 and a second nose or rebate 14. The first nose 13 engages into a
corresponding groove 10 in the forward cover disc 6. The second
nose 14 engages into a corresponding groove 11 in the aft cover
disc 7. This provides a very effective seal between the forward
cover disc 6, the platform 3 and the aft cover disc 7, as well as
between adjacent blade platforms 3.
[0061] The inventive platform seal strip will now be described with
reference to FIG. 4. FIG. 4 schematically shows an inventive
platform seal strip 1 in a perspective view. The seal strip 1
comprises a first portion 31 and a second portion 32. The first
portion 31 has a width 33, advantageously a constant width. The
second portion 32 has a width 34, preferably a constant width,
which is larger than the width 33 of the first portion 31. Between
the first portion 31 and the second portion 32 a transition portion
35 is located. The width of the transition portion 35 decreases
continuously from the second portion 32 towards the first portion
31.
[0062] The platform seals strip 1 further comprises an upper side
36 and a lower side 37. The first portion 31 comprises a bending
towards the lower side 37. As result the bending forms a convex
surface portion 41 of the upper side 36 and a concave surface
portion 43 of the lower side 37. The second portion 32 also
comprises a bending towards the lower side 37. The bending forms a
convex surface portion 42 of the upper side 36 and a concave
surface portion 44 of the lower side 37. As a result of the two
bending or curvatures of the platform seal strip 1 the first
portion 31 comprises an upper side surface portion with an surface
normal 71 and the second portion 32 comprises an upper side surface
portion with a surface normal 72, which includes an angel a having
a value between 0.degree. and 180.degree.
(0.degree.<a.ltoreq.180.degree.). In FIG. 4 the angle a has a
value between 160.degree. and 180.degree.. Because of the bending
of the first portion 31 and the second portion 32 the platform seal
strip 1 has a shape of a U in a side view, as for example shown in
FIG. 3.
[0063] The first portion 31 further comprises a nose 13. The nose
13 is bent such that the upper side 36 comprises a concave surface
portion 53 and the lower side 37 comprises a convex surface portion
51. The second portion 32 also comprises a nose 14, which is at
least partially bent towards the upper side 36. The bending of the
nose 14 forms a concave surface portion 54 at the upper side 36 and
a convex surface portion 52 at a lower side 37.
[0064] For example, the noses 13 and 14 may have a surface portion
with a surface normal. In FIG. 4 the surface normal 73 of the nose
14 is shown as example. The first portion or the second portion may
comprise a surface adjacent to the nose. This surface may have a
surface normal, for example the surface normal 72 of the second
portion, which includes an angle .beta. with the surface normal 73
of the nose portion 14 between 0.degree. and 180.degree., which
means 0.degree.<.beta.<180.degree., and in an advantageous
embodiment between 60.degree. and 90.degree..
[0065] The first portion 31 of the seal strip 1 may be referred to
as a leading portion 31 and which engages into the part of the slot
24 defined by the leading wall 80. Thus when assembled and in use
in a blade assembly, the leading portion 31 extends in a generally
radially inward or downward direction from the second portion 32.
The nose 13 extends from a radially inward part of the leading
portion 31 and in use extends under or radially inwardly of the
leading wall 80 to engage the corresponding groove 10 in the
forward cover disc 6. The nose 13 extends into or through the
second gap 84. Alternatively the nose 13 may extend through the
leading wall 80 to engage the forward cover disc 6.
[0066] The second portion 32 may be referred to as a main portion
32 and the portion of the seal strip 1 that engages the slot 24
defined in the trailing wall 82 may be referred to as a third
portion 38. The third portion 38 may be referred to as a trailing
portion 38 of the seal strip. The third portion 38 comprises the
nose 14 at its radially inward end. A third portion 31 may be
referred to as a trailing portion 31 and which engages into the
part of the slot 24 defined by the trailing wall 82.
[0067] Thus when assembled and in use in a blade assembly, the
leading portion 31 extends in a generally radially inward or
downward direction from the second portion 32. The nose 14 extends
from a radially inward part of the trailing portion 38 and in use
extends to engage the corresponding groove 11 in the rear cover
disc 7. The slot 24 runs out of the trailing wall 82 and creates an
opening positioned radially outwardly of the radially inward end of
the trailing wall 82. The seal strip 1 can therefore extend
rearward out of the downstream face of the trailing wall 82 and
engage the groove 11. Alternatively, the slot 24 may extend to the
radially inward end of the trailing wall 82 where the nose 14 may
extend into or through the third gap.
[0068] The leading and trailing portions 31, 38 are shown as
extending from the second portion 32 in a generally radially inward
direction and it should be appreciated that this direction is not
limited to perpendicular to the axis 102 and may typically be
angled relative to a radial line from the axis 102.
[0069] The slot 24 is continuous across the circumferentially
facing side surface 23 of the main platform part 3A and the leading
wall 80. The slot 24 may also be continuous across the
circumferentially facing side surface 23 of the main platform part
3A and the trailing walls 82.
[0070] The trailing portion 38 of the seal strip is shown reducing
in width between the main platform part 3A and the nose 14. The
reduction in width may be a regular or irregular taper. The noses
13 and 14 are also shown tapering to their free ends; however, the
noses 13, 14 may have a constant width. The noses 13, 14 may have a
width equal to or less than the leading or trailing portions 31, 38
respectively. In particular, the noses 13, 14 may have a width
equal to or less than the leading or trailing portions 31, 38
respectively at their radially inward most part.
[0071] Further, the width of the first portion is constant and/or
the width of the second portion is constant. Alternatively, the
first portion may change in width between the main platform part 3A
and the nose 13. This change in width may be a regular or irregular
taper. The taper may be towards the nose 13.
[0072] The inventive method for assembling a turbine blade assembly
will now be described with reference to FIGS. 5, 6 and 7. FIGS. 5
and 6 schematically show part of an inventive turbine blade
assembly in a perspective view during the insertion of the platform
seal strip. FIG. 7 schematically shows part of an inventive turbine
blade assembly in a sectional and perspective view when the
assembling process is finished.
[0073] At first the forward cover disc 6 was attached to the disc
12. Then, the blades 151 were loaded onto the disc 12, for example
by inserting at least part of the blade root 19 into corresponding
grooves 20 in the disc 12. Between adjacent platforms 151 a gap is
left. After loading the blades 151 onto the disc 12 the seal strips
1 are inserted into the gap between the platforms 3 of adjacent
blades 151. This is schematically shown in FIGS. 5 and 6. In FIG. 5
the first portion 31 is inserted into the blade root cavity 15 via
an opening between two adjacent blades 151 close to the slot 24 in
the platforms 3. In doing so the seal strip 1 is canted over or
turned. In FIG. 6 the seal strip 1 is turned back into a correct
position. The second portion 32 and part of the transition portion
35 slide into the slot 24.
[0074] The finished insertion is shown in FIG. 7. Part of the
second portion 32 and part of the transition portion 35 of the
seals strip 1 engages into the slots 24 of the adjacent blades 151.
The nose 13 of the first portion 31 is inserted into the
corresponding groove 10 in the forward cover disc 6. For retaining
the seal strips 1 and the blades 151 a first cover plate, in FIG. 7
the aft cover disc 7, is attached to the disc 12. The nose 14 of
the second portion 32 of the seal strip 1 is inserted or engages
into the corresponding groove 11 of the aft cover disc 7.
[0075] Generally the present invention uses a single piece seal
strip 1 to overcome inter seal leakage in order to make more
efficient use of the cooling air. Cover discs 6 and 7 have been
added to the front face 26 and the rear face 27 of the, for example
CT, disc assembly. The cover discs 6 and 7 can contain and direct
cooling air in a more efficient manner then in previously known
solutions. The present layout gives the opportunity to improve the
sealing at the blade platform as shown in FIGS. 3 and 5 to 7.
[0076] The benefit of the invention is that the seal strip 1 is a
single piece, for example of metal, eliminating leaks and joint
inter faces and making assembly easier. The assembly of the single
piece strip is allowed due to profile of the strip as shown in FIG.
4. The narrow nose 13 allows it to be inserted into the gap between
adjacent blades 151. The wider portion 32 of the strip then engages
in the seal groove 24 machined into the side 23 of each blade 151,
directly beneath the platform 3. The seal strip 1 is then pushed
fully into the gap as shown in FIGS. 5 to 7. Following the
insertion of seal strips 1 the aft cover plate 7 is attached to
retain the strip 1.
[0077] To summarise, an embodiment of the invention is related to a
platform seal strip 1, in particular for use in a gas turbine blade
assembly, the platform seal strip 1 having sections that are
substantially planar and sections that are curved. The platform
seal strip 1 comprises an upper side 36 and a lower side 37. The
platform seal strip 1 particularly being a sheet of metal that is
three-dimensionally formed. The platform seal strip 1 comprises a
first portion 31--the first portion 31 being substantially
planar--and a second portion 32--the second portion 32 being
substantially planar--, the width 33 of the first portion 31 being
smaller than the width 34 of the second portion 32. The first
portion 31 and the second portion 32 are connected via bent or
curved sections, such that the upper side 36 comprises a convex
surface portion 41, 42 and the lower side 37 comprises a concave
surface portion 43, 44. The convex surface portion 41 and the
concave surface portion 43 are opposite surfaces of the platform
seal strip 1. The convex surface portion 42 and the concave surface
portion 44 are also opposite surfaces of the platform seal strip 1.
A first bend defined by the convex surface portion 42 and the
concave surface portion 44 may be sharper than a second bend
defined by the convex surface portion 41 and the concave surface
portion 43. The first bend may have a substantially sharp edge
whereas the second bend defines a smooth transition between the
first portion 31 and the second portion 32.
* * * * *