U.S. patent application number 14/388411 was filed with the patent office on 2015-03-05 for turbine blade and associated method for producing a turbine blade.
This patent application is currently assigned to Siemens Aktiengesellschaft. The applicant listed for this patent is Siemens Aktiengesellschaft. Invention is credited to Fathi Ahmad, Hans-Thomas Bolms, Nihal Kurt.
Application Number | 20150064018 14/388411 |
Document ID | / |
Family ID | 48045493 |
Filed Date | 2015-03-05 |
United States Patent
Application |
20150064018 |
Kind Code |
A1 |
Ahmad; Fathi ; et
al. |
March 5, 2015 |
TURBINE BLADE AND ASSOCIATED METHOD FOR PRODUCING A TURBINE
BLADE
Abstract
A turbine blade is provided, having a fastening section, a
platform, and a blade, which follow one another along a
longitudinal axis of the turbine blade, wherein the platform, in
radial relation to the longitudinal axis, has an inner platform
part and an outer platform part, wherein the outer platform part is
designed as a closed platform frame that encloses the outer edge of
the inner platform part. An associated method for producing a
turbine blade is also provided.
Inventors: |
Ahmad; Fathi; (Kaarst,
DE) ; Bolms; Hans-Thomas; (Mulheim an der Ruhr,
DE) ; Kurt; Nihal; (Dusseldorf, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Siemens Aktiengesellschaft |
Munich |
|
DE |
|
|
Assignee: |
Siemens Aktiengesellschaft
Munich
DE
|
Family ID: |
48045493 |
Appl. No.: |
14/388411 |
Filed: |
March 27, 2013 |
PCT Filed: |
March 27, 2013 |
PCT NO: |
PCT/EP2013/056594 |
371 Date: |
September 26, 2014 |
Current U.S.
Class: |
416/90R ;
29/889.72 |
Current CPC
Class: |
Y10T 29/49339 20150115;
F01D 11/008 20130101; F05D 2240/80 20130101; F01D 5/147 20130101;
F01D 5/18 20130101; F01D 5/28 20130101 |
Class at
Publication: |
416/90.R ;
29/889.72 |
International
Class: |
F01D 5/18 20060101
F01D005/18; F01D 5/28 20060101 F01D005/28 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 29, 2012 |
EP |
12162103.1 |
Claims
1.-13. (canceled)
14. A turbine blade comprising: a fastening portion, with a
platform for delimiting a flow duct and with a blade airfoil, which
succeed one another along a longitudinal axis of the turbine blade,
wherein the platform comprises radially with respect to the
longitudinal axis an inner platform part and an outer platform
part, the outer platform part comprising a continuous one-piece
platform frame surrounding the outer margin of the inner platform
part.
15. The turbine blade as claimed in claim 14, wherein the platform
frame bears in a sheet-like manner against the inner platform part,
and the contact area forms at least partially with the longitudinal
axis an angle which is larger than 0.degree. and smaller than
90.degree..
16. The turbine blade as claimed in claim 15, wherein the angle has
a size of between 10.degree. and 35.degree..
17. The turbine blade as claimed in claim 14, wherein the inner
platform part and the fastening portion and/or the inner platform
part and the blade airfoil are monolithic.
18. The turbine blade as claimed in claim 14, wherein the platform
frame has, on at least one laterally outward-pointing surface, a
slot for the reception of a sealing element.
19. The turbine blade as claimed in claim 17, wherein the platform
frame has, on at least one laterally outwardly-pointing surface, a
slot for the reception of a sealing element.
20. The turbine blade as claimed in claim 14, wherein the platform
frame is shrunk on the inner platform part and/or is soldered
and/or welded to the latter.
21. The turbine blade as claimed in claim 17, wherein the platform
frame is shrunk on the inner platform part and/or is soldered
and/or welded to the latter.
22. The turbine blade as claimed in claim 18, wherein the platform
frame is shrunk on the inner platform part and/or is soldered
and/or welded to the latter.
23. The turbine blade as claimed in claim 14, designed as a guide
blade or as a moving blade.
24. The turbine blade as claimed in claim 17, designed as a guide
blade or as a moving blade.
25. The turbine blade as claimed in claim 18, designed as a guide
blade or as a moving blade.
26. The turbine blade as claimed in claim 20, designed as a guide
blade or as a moving blade.
27. The turbine blade as claimed in claim 14, wherein that surface
of the inner platform part over which the hot gas can flow is
substantially larger than that surface of the platform frame over
which the hot gas can flow.
28. The turbine blade as claimed in claim 17, wherein that surface
of the inner platform part over which the hot gas can flow is
substantially larger than that surface of the platform frame over
which the hot gas can flow.
29. The turbine blade as claimed in claim 18, wherein that surface
of the inner platform part over which the hot gas can flow is
substantially larger than that surface of the platform frame over
which the hot gas can flow.
30. The turbine blade as claimed in claim 20, wherein that surface
of the inner platform part over which the hot gas can flow is
substantially larger than that surface of the platform frame over
which the hot gas can flow.
31. The turbine blade as claimed in claim 27, wherein that surface
of the inner platform part over which the hot gas can flow is
substantially larger than that surface of the platform frame over
which the hot gas can flow.
32. A method for producing a turbine blade, comprising: producing a
monolithic trunk blade, comprising a blade airfoil, a platform as
an inner platform part for delimiting a flow duct, and a fastening
portion, producing a continuous one-piece platform frame, and
mounting of the continuous one-piece platform frame on the margin
of the platform.
33. The method as claimed in claim 32, wherein, to produce the
trunk blade, the platform margin of an operationally stressed
turbine blade is set back along its entire periphery in order to
produce a bearing surface for a continuous platform frame and in
order to convert the platform into the inner platform part.
34. The method as claimed in claim 32, wherein the trunk blade,
comprising a fastening portion, a platform and a blade airfoil, is
produced by a casting method, and the platform margin is configured
as a bearing surface for a continuous platform frame.
35. The method as claimed in claim 32, further comprising the
platform frame being shrunk on the inner platform part and/or
soldered and/or welded to the trunk blade.
36. The method as claimed in claim 32, further comprising the inner
platform part and the platform frame being coated in a coating
operation.
37. The method as claimed in claim 35, further comprising the inner
platform part and the platform frame being coated in a coating
operation.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is the US National Stage of International
Application No. PCT/EP2013/056594 filed Mar. 27, 2013, and claims
the benefit thereof. The International Application claims the
benefit of European Application No. EP12162103 filed Mar. 29, 2012.
All of the applications are incorporated by reference herein in
their entirety.
FIELD OF INVENTION
[0002] The invention relates to a turbine blade with a fastening
portion, with a platform for delimiting a flow duct and with a
blade airfoil, which succeed one another along a longitudinal axis
of the turbine blade. The invention relates, furthermore, to a
method for producing a turbine blade, comprising the step:
production of a monolithic trunk blade comprising a blade airfoil,
a platform for delimiting a flow duct and a fastening portion.
BACKGROUND OF INVENTION
[0003] Turbine blades and methods for producing turbine blades are
known in many different forms from the abundant prior art. For
example, turbine blades for gas turbines are often produced by a
casting method. During casting, the blade foot, platform and blade
airfoil are formed simultaneously from the casting material, and
therefore turbine blades of this type are in one piece. The
surfaces, that it to say the platform and blade airfoil, which are
exposed to the hot gas of the turbine are subsequently also
provided with a corrosion protection layer and with a heat
protection layer, in order to increase the service life of the
turbine blade. The cast turbine blades are mostly also of hollow
form, so that a means for cooling the blade material can flow
inside. Turbine blades of steam engines are mostly milled from
solid or forged.
[0004] The turbine blades used in stationary turbomachines are
subjected, when the turbomachine is in operation, to a multiplicity
of loads which cause the turbine blades to age and to become worn
both in a predictable and in an unpredictable way.
[0005] In detail, both low-cyclic and higher-cyclic fatigue loads
and also thermal mechanical loads occur. Turbine blades must also
be protected against oxidation and against creep. The
abovementioned loads relate particularly to those surfaces and
components of the turbine blades which are exposed directly to the
hot gas or hot steam. Moreover, turbine blades are also exposed on
the fastening side to what are known as "bearing loads" and
"frictional loads". In view of these different loads and
requirements, the material of one-piece turbine blades has to be
selected such that, as far as possible, a multiplicity, if not even
all, of the loads are absorbed by the material, without premature
aging or a premature end of the service life of the turbine blade
being reached. With regard to the thermal load and to the corrosion
load, it is known, for example, to equip turbine blades of gas
turbines with a layer system which protects their material both
against corrosion and against an excessive introduction of
heat.
[0006] Nevertheless, in various regions of the turbine blades, wear
phenomena, such as cracks, may occur, which put the operation of
the turbomachine at risk. For this reason, it is known to check
turbine blades for defects of this kind after a predetermined
period of use and, if one of these is discovered, to exchange the
affected turbine blades or treat them again.
[0007] It is also known for turbine blades to have a modular
configuration and for the corresponding modules to be produced from
those materials which are tailored to their local requirements.
However, a permanent and reliable connection is often absent
here.
[0008] In this respect, for example, U.S. Pat. No. 4,650,399 A1
discloses a moving blade with two platform halves which are
arranged on both sides of a blade airfoil. In order to prevent the
platform halves from being displaced along the blade airfoil, a
positive connection is provided, the two platform halves being
pinned to one another. However, the fastening of the platforms is
classed as unsafe. EP 1 905 950 A1 and US 4,019,832 A1 disclose
likewise dividing platforms into two halves.
[0009] Instead of the platform halves of U.S. Pat. No. 4,650,399
A1, WO 2000/057032 A1 discloses a single platform element between
two directly adjacent moving blades of a moving blade ring. The
mounting of the components on the rotor seems to be a disadvantage
here.
[0010] Further variants of built-up turbine blades are shown in
U.S. Pat. No. 3,451,654 A1 and U.S. Pat. No. 7,762,781 B1. In both
publications, it is proposed to use a one-piece platform for
turbine blades which has a recess conforming to the profile of the
blade airfoil. To complete the turbine blades, in each case the
platform-free blade airfoil is inserted through the platform and is
fastened by means of intermediate pieces.
SUMMARY OF INVENTION
[0011] An object of the invention is to provide a turbine blade
with a fastening portion, with a platform for delimiting a flow
duct and with a blade airfoil, which succeed one another along a
longitudinal axis of the turbine blade, which turbine blade can be
regenerated at especially low outlay. A further object of the
invention is to provide a method for producing turbine blades.
[0012] The object aimed at the turbine blade is achieved by means
of a turbine blade according to the features of the claims. The
object aimed at the method for producing a turbine blade is
achieved by means of the method steps according to the claims.
Advantageous refinements are specified in the respective subclaims.
In this case, the features of the respective subclaims can be
readily combined with the features of other subclaims.
[0013] Aspects of the invention are based on the recognition that,
particularly in the case of operationally stressed turbine blades,
defects caused by oxidation may occur even at the outer margin of
the platform. These oxidation problems arise, in particular, when
the heat insulation layer often also provided there flakes off
locally. Such consequences may lead in the turbine blade to an
increased operating risk, and therefore turbine blades of this type
are exchanged or treated. The retreatment of the turbine blade has
hitherto been comparatively complicated. At the same time, the
regeneration rate, that is to say the fraction of retreated blades
which, after retreatment, actually still qualify for use in the
turbomachine, may be rather small. In order to counteract these
effects, it is proposed by the invention that the platform
comprises radially with respect to a central longitudinal axis an
inner platform part and an outer platform part, the outer platform
part being designed as a continuous platform frame surrounding the
outer margin of the inner platform part. The platform frame is thus
continuously peripheral and in one piece and could also be
designated as closed.
[0014] In this case, the invention does not attempt to provide a
design for modular turbine blades, and therefore that surface of
the inner platform part over which the hot gas can flow is
preferably substantially larger than that surface of the platform
frame over which the hot gas can flow.
[0015] Insofar as an operationally stressed turbine blade is to be
regenerated in the region of the platform margin, the defects
specified further above in the vicinity of the platform margin must
be removed by the margin of the platform being set back, for
example, by milling or grinding. According to aspects of the
invention, there is in this case provision whereby not only the
local defect is removed when the platform margin is set back.
[0016] On the contrary, the platform margin is set back along the
entire periphery in order thereby to produce a monolithic trunk
blade, the platform of which, as an inner platform part of the
turbine blade to be produced, provides a bearing surface for a
platform frame. After a continuous platform frame has been attached
to the inner platform part, the turbine blade thus produced then
has a platform, the dimensions of which correspond to the original
turbine blade.
[0017] Admittedly, in this method, unimpaired or undamaged blade
material is also removed. However, this has the advantage that
retreatment does not have to be carried out individually, that is
to say as a function of the defect, but can take place in an
automated way. This reduces the outlay for retreatment and the
reject rate.
[0018] Of course, new components, that is to say turbine blades
which are not operationally stressed, can also be produced
according to the method, in that, first, what is known as a trunk
blade comprising a blade airfoil, a platform and a fastening
portion is provided in a monolithic embodiment. The monolithic
trunk blade can be produced conventionally by the casting method
and, for example, can also be solidified in a monocrystalline or
directional manner. After the production of the trunk blade, the
platform margin of the trunk blade has to be brought to the
predetermined exact dimension, if appropriate, also along the
entire periphery, by minor grinding or milling, in order to provide
the inner platform part of the turbine blade with a dimensionally
accurate bearing surface for the platform frame. Before, during or
after this, the platform frame must be produced as a mostly
rectangular structure. After the attachment or mounting of the
platform frame on the dimensionally accurate margin of the inner
platform part, the turbine blade is then produced as a new
component. The platform frame may have various forms in cross
section. However, those forms are preferred which bring about a
positive connection to the margin of the inner platform part. For
example, the cost-sectional form may be diamond-shaped or C-shaped.
The margin of the inner platform part is in this case always
designed to match with the cross-sectional form.
[0019] A particular advantage of the turbine blade according to
aspects of the invention and also of the method is that, in
particular, even two different materials can be used for the trunk
blade and for the platform frame. Thus, the various local loads can
additionally be taken into account, thereby leading, where
appropriate, to a prolonged service life of the turbine blade.
[0020] A further advantage of the turbine blade according to
aspects of the invention is the higher precision in terms of the
outer dimensions of the platform, since these can be implemented
more simply during the production of the platform frame than when a
purely monolithic turbine blade is being cast.
[0021] Various methods can be employed for connecting the platform
frame permanently to the trunk blade. Since the platform frame is
configured as a continuous frame, it is preferably appropriate to
shrink the platform frame onto the peripheral margin of the inner
platform part. Before shrinking on, the platform frame can be
heated and/or the trunk blade cooled. After the assembling of the
platform frame and trunk blade and subsequent temperature
equalization, the platform frame is then seated firmly on the
peripheral margin of the inner platform part. Even soldering and
welding, in spot form and also along the connecting line of the
margin of the inner platform part and platform frame, are
possible.
[0022] According to a first advantageous development, the platform
frame bears against the inner platform part in a sheet-like manner,
the contact area forming at least partially with the longitudinal
axis at an angle which is larger than 0.degree. and smaller than
90.degree.. Such an arrangement prevents a parallel displacement of
the platform frame along the longitudinal axis, at least in one
direction, this being advantageous particularly when the invention
is used on turbine moving blades. In this case, the centrifugal
force acting upon the platform frame during the operation of the
turbomachine is also transferred by positive connection into the
platform part because the contact area is inclined with respect to
the longitudinal axis. This reliably prevents the loss of the
platform frame due to the centrifugal force.
[0023] Preferably, the angle amounts to a size of between
15.degree. and 35.degree., for example the angle lies at
20.degree..
[0024] According to a second advantageous development, the platform
frame has, on at least one surface pointing laterally outward, a
slot for the reception of a sealing element. Such a refinement
affords the advantage that, in the event of wear of slots present
in the platform margin, because of the sheet-like sealing elements
seated in them, the invention which is in this case provided offers
a simple and reliable possibility of regenerating even
operationally stressed turbine blades of this type. Moreover, such
slots can be produced most cost-effectively than in the case of
purely monolithic turbine blades.
[0025] The turbine blade may expediently be designed both as a
guide blade or as a moving blade.
[0026] So that the turbine blade, with the inner platform part and
the outer platform part in the form of the continuous platform
frame surrounding the inner platform part, can be used even in
high-temperature applications, it is advantageous if the inner
platform part and the platform frame are coated in a coating
operation. A seamless protective layer can thus be applied to both
platform parts.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Further advantages of features of the invention are
specified in the description of the figures in which:
[0028] FIG. 1 shows, in a perspective illustration, the side view
of a turbine blade according to an embodiment of the invention,
[0029] FIG. 2 shows, in a perspective illustration, the top view of
a platform frame,
[0030] FIG. 3 shows the cross section through a turbine blade
according to FIG. 1, and
[0031] FIG. 4 shows a detail of the corner of a platform of the
turbine blade according to FIG. 1 during the assembly of the trunk
blade and platform frame.
DETAILED DESCRIPTION OF INVENTION
[0032] Identical features are given identical reference numerals in
all the figures.
[0033] FIG. 1 shows a perspective illustration of a turbine blade
10. The turbine blade 10 is designed as a moving blade. However, it
may also be designed as a guide blade. The turbine blade 10
comprises, succeeding one another directly along its longitudinal
axis 12, a fastening portion 14, a platform 16 and a blade airfoil
18. The fastening portion 14 is contoured in a manner of a pine
tree profile in a way typical of a moving blade. Guide blades for
turbines mostly have, instead of the pine tree-shaped fastening
portion 14, a plurality of hooks which are pushed into a guide
blade carrier, not illustrated in any more detail, of the
turbomachine.
[0034] The fastening portion 14 merges into the platform 16.
According to the illustration chosen in FIG. 1, the platform 16 has
an upwardly pointing platform surface 20 on which the blade airfoil
18 is seated. In the exemplary embodiment illustrated, the platform
16 comprises radially with respect to the longitudinal axis 12 an
inner platform part 22 and an outer platform part 24, the outer
platform part 24 being designed as a continuous platform frame 28
surrounding the outer margin 26 of the inner platform part 22.
According to the exemplary embodiment illustrated, both the
fastening portion 14, the inner platform part 22 and the blade
airfoil 18 are formed monolithically, that is to say in one piece.
This monolithic unit is also designated as a trunk blade 19. The
surfaces 20 of the inner platform part 22 and of the outer platform
part 24 which point toward the blade airfoil 18 according to this
illustration are offset-free with respect to one another, so that,
when the turbine blade 10 is used in a turbomachine, they provide
an edge-free and step-free boundary wall for the working medium
flowing in the turbomachine.
[0035] In this case, that surface of the inner platform part 22
over which the hot gas can flow is substantially larger than that
surface of the platform frame 28 over which the hot gas can
flow.
[0036] The turbine blade 10 may be designed to be internally cooled
with the aid of a cooling medium in any way. Even film cooling
ports and trailing edge ports for coolant may be provided. The
turbine blade may, of course, also be uncooled.
[0037] FIG. 2 shows a perspective illustration of the platform
frame 28. The platform frame 28 comprises two longitudinal struts
30 parallel to one another and two transverse struts 32 parallel to
one another. The platform frame 28 may be produced from a material
other than that of the trunk blade 19 illustrated in FIG. 1.
However, the platform frame 28 may also be produced from the same
material. The platform frame may also be produced by welding the
longitudinal struts 30 to the transverse struts 32. It may also be
cast or be milled from solid. FIG. 3 shows a section through the
turbine blade 10 along the longitudinal axis 12. In contrast to the
turbine blade illustrated in FIG. 1, the fastening portion
according to FIG. 3 is not of pine tree-shaped form, but instead is
dovetail-shaped. Moreover, FIG. 3 shows the platform frame 28
during mounting on the trunk blade 19, shortly before the platform
frame 28 reaches its ultimate mounting position. According to the
exemplary embodiment illustrated, the platform frame 28 is
diamond-shaped in cross section. Other forms are also possible.
[0038] Each strut 30, 32 of the platform frame 28 has an inwardly
directed first bearing surface 34 and a second bearing surface 36.
The outer margin 26 of the inner platform part 22 likewise has a
laterally outward-pointing first bearing surface 38 and a second
bearing surface 40. After the mounting of the platform frame 28,
its first bearing surface 34 bears in a sheet-like manner against
the first bearing surface 38 of the inner platform part 22 and its
second bearing surface 36 bears in a sheet-like manner against the
second bearing surface of the inner platform part 22. The first
contact areas and second contact areas thus formed are inclined
differently with respect to the longitudinal axis 12. The first
contact area is oriented parallel to the longitudinal axis 12 in
cross section. However, the second contact area is inclined in
cross section at an acute angle .alpha. to the longitudinal axis
12. This embodiment also prevents, by positive connection, the
release of the platform frame 28 from the trunk blade 19 under
centrifugal forces acting upon the turbine blade 10.
[0039] FIG. 4 shows a perspective illustration of a corner of the
inner platform part 22 and of the platform frame 28 during
mounting. In addition to the features already described, FIG. 4
also shows, on a laterally outward-pointing surface 42 of the
platform frame 28, a slot 44 for the reception of a sheet-like
sealing element.
[0040] Thus, overall, the invention relates to a turbine blade 10
with a fastening portion 14, with a platform 16 and with a blade
airfoil 18, which directly succeed one another along a longitudinal
axis 12 of the turbine blade. In order to provide a turbine blade
10 having an especially long service life, it is proposed that the
platform 16 comprises radially with respect to the longitudinal
axis 12 an inner platform part 22 and an outer platform part 24,
the outer platform part 24 being designed as a continuous platform
frame 28 surrounding the outer margin 26 of the inner platform part
22. In terms of the method, it is proposed to use a monolithically
produced trunk blade 19 or to adapt or set back an already
operationally stressed turbine blade 10 along the entire periphery
of the platform margin and to produce a continuous platform frame
28 which can subsequently be mounted on the platform margin 26, in
order thereby to produce the original or planned dimensions of the
turbine blade 10.
* * * * *