U.S. patent application number 12/961659 was filed with the patent office on 2011-09-29 for blade for a gas turbine and casting technique method for producing same.
This patent application is currently assigned to ALSTOM TECHNOLOGY LTD. Invention is credited to Roland DUCKERSHOFF, Jorg KRUCKELS, Jose Anguisola MCFEAT, Brian Kenneth WARDLE.
Application Number | 20110236222 12/961659 |
Document ID | / |
Family ID | 39698763 |
Filed Date | 2011-09-29 |
United States Patent
Application |
20110236222 |
Kind Code |
A1 |
MCFEAT; Jose Anguisola ; et
al. |
September 29, 2011 |
BLADE FOR A GAS TURBINE AND CASTING TECHNIQUE METHOD FOR PRODUCING
SAME
Abstract
A blade for a gas turbine has a leading edge and a trailing
edge, and an interior cavity, which is delimited by internal
surfaces, for guiding cooling air therethrough. A multiplicity of
turbulators or pins, which are formed on the wall, are arranged in
a distributed manner in the region of the trailing edge and project
from the internal surfaces into the cavity, to improve the transfer
of heat between the wall of the blade and the cooling air. An
improvement of the internal cooling is achieved by the turbulators
or pins extending into the cavity in a direction which can be
freely selected within an angular range.
Inventors: |
MCFEAT; Jose Anguisola;
(Lauchringen, DE) ; KRUCKELS; Jorg; (Birmenstorf,
CH) ; DUCKERSHOFF; Roland; (Hohr Grenhausen, DE)
; WARDLE; Brian Kenneth; (Brugg-Lauffohr, CH) |
Assignee: |
ALSTOM TECHNOLOGY LTD
Baden
CH
|
Family ID: |
39698763 |
Appl. No.: |
12/961659 |
Filed: |
December 7, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/EP2009/056150 |
May 20, 2009 |
|
|
|
12961659 |
|
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Current U.S.
Class: |
416/97R ;
164/6 |
Current CPC
Class: |
B22C 7/06 20130101; F01D
5/147 20130101; B22D 25/02 20130101; F05D 2230/211 20130101; B22C
9/10 20130101 |
Class at
Publication: |
416/97.R ;
164/6 |
International
Class: |
F01D 5/18 20060101
F01D005/18; B22C 9/00 20060101 B22C009/00; B22D 25/02 20060101
B22D025/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 12, 2008 |
CH |
00898/08 |
Claims
1. A blade (10) for a gas turbine, said blade (10) having a leading
edge (11) and a trailing edge (12), and an interior cavity (16),
which is delimited by internal surfaces (19, 20), for guiding
cooling air therethrough, wherein for improving the transfer of
heat between a wall (15) of the blade and the cooling air, a
multiplicity of members (18), which are formed on the wall (15) to
improve cooling, are arranged in a distributed manner in the region
of the trailing edge (12) and project from the internal surfaces
(19, 20) into the cavity (16), the members (18) extend into the
cavity (16) in a direction which can be freely selected within an
angular range.
2. The blade as claimed in claim 1, wherein the members are
turbulators or pins (18) which extend into the cavity (16) in a
direction which is essentially perpendicular to the associated
internal surface.
3. A method for producing a blade (10) for a gas turbine by a
casting technique, said blade (10) having a leading edge (11) and a
trailing edge (12), and an interior cavity (16), which is delimited
by internal surfaces (19, 20), for guiding cooling air
therethrough, wherein for improving the transfer of heat between
the wall (15) of the blade and the cooling air, a multiplicity of
members (18), which are formed on the wall (15) to improve cooling,
are arranged in a distributed manner in the region of the trailing
edge (12) and project from the internal surfaces (19, 20) into the
cavity (16), the members (18) extend into the cavity (16) in a
direction which can be freely selected within an angular range, the
method comprising the following steps: providing a core mold (23;
23a, b) for forming a casting core (21) which keeps the cavity (16)
of the blade (10) free, producing the casting core (21) is by means
of the core mold (23; 23a, b); removing the casting core (21) from
the core mold (23; 23a, b); and casting the blade (10) by the
casting core (21), wherein the core mold (23; 23a, b) which is
provided in the first step comprises two mold halves (23a, b),
which during demolding are drawn apart in a first direction,
wherein at least one mold insert (27, 28), which is provided for
forming the members (18), is arranged in the mold halves (23a, b)
in the trailing edge region, and in the third step, after the
parting of the mold halves (23a, b) in the first direction, the at
least one mold insert (27, 28) is withdrawn from the formed casting
core (21) in a second direction which differs from the first
direction.
4. The method as claimed in claim 3, wherein the second direction
is perpendicular to the internal surface (19, 20) which is
associated with the members (18).
5. The method as claimed in claim 3, wherein a plurality of mold
inserts (27, 28) are arranged in the mold halves (23a, b) and
during demolding are withdrawn from the formed casting core (21) in
different directions which differ from the first direction.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of International
Application No. PCT/EP2009/056150, filed May 20, 2009, which claims
priority to Swiss Patent Application No. 00898/08, filed Jun. 12,
2008, the entire contents of all of which are incorporated by
reference as if fully set forth.
FIELD OF INVENTION
[0002] The present invention relates to the field of gas turbine
technology. It refers to a blade for a gas turbine and a method for
producing such a blade by a casting technique.
BACKGROUND
[0003] Blades of gas turbines, which are fastened either as rotor
blades on the rotor or fastened as stator blades on the casing
which encloses the rotor, are subjected to impingement by hot gas
which comes from the combustor and are exposed to thermal loads in
the process. These blades, in the course of improving the thermal
efficiency, are increasingly exposed to circumferential flow at
still higher turbine inlet temperatures. It is not to be ignored,
therefore, that these blades have to be cooled internally and/or
externally by a cooling medium, especially cooling air, being
introduced preferably via the blade root into the hollow interior
of the blade airfoil, cooling the blade internally there via
convectively applied cooling methods or selectively by means of
impingement cooling, and then being blown out into the hot gas
flow, in order to carry out a so-called film cooling there if
necessary on the external side of the blade. The cooling medium
flows through the interior of the blade mostly in a plurality of
cooling passages which are connected in a serpentine-like manner
and extend through the blade airfoil in the radial direction.
[0004] When producing such a blade by a casting technique, a
casting core, which forms and keeps the internal hollow cavity of
the blade with the cooling passages free and further details during
the casting of the blades, has to be created. For producing the
casting core, use is made of a core mold assembled from two halves
which during demolding of the finished casting core are drawn apart
in a specified direction (see U.S. Pat. No. 5,716,192, for
example). Contingent upon the direction in which the two mold
halves have to be drawn apart, limitations ensue in the design of
the casting core and therefore in the design of the cavity of the
subsequent blade. These limitations play a role particularly in the
case of complex shapes of the cavity, as are described in
WO-A1-03/042503, for example. In order to create the cavity of the
blade there, which cavity consists of various cooling circuits and
a multiplicity of pins and turbulators, a plurality of casting
cores are produced and combined with each other, which leads to a
very costly production process.
SUMMARY
[0005] In a first aspect, the present disclosure is directed to a
blade for a gas turbine. The blade includes a leading edge and a
trailing edge, and an interior cavity, which is delimited by
internal surfaces, for guiding cooling air therethrough. To improve
the transfer of heat between the wall of the blade and the cooling
air, a multiplicity of members, which are formed on the wall to
improve cooling. The members are arranged in a distributed manner
in the region of the trailing edge and project from the internal
surfaces into the cavity. The members extend into the cavity in a
direction which can be freely selected within an angular range.
[0006] In a second aspect, the present disclosure is directed to
method for producing the above blade. The method includes, in a
first step, providing a core mold for forming a casting core which
keeps the cavity of the blade free. The method also includes, in a
second step, producing the casting core by means of the core mold,
in a third step, removing the casting core from the core mold and,
in a fourth step, casting the blade by the casting core. The core
mold which is provided in the first step comprises two mold halves,
which during demolding are drawn apart in a first direction. At
least one mold insert, which is provided for forming the members,
is arranged in the mold halves in the trailing edge region. In the
third step, after the parting of the mold halves in the first
direction, the at least one mold insert is withdrawn from the
formed casting core in a second direction which differs from the
first direction.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The invention shall subsequently be explained in more detail
based on exemplary embodiments in conjunction with the drawing. All
elements which are not essential for the direct understanding of
the invention have been omitted. Like elements are provided with
the same designations in the various figures. In the drawings:
[0008] FIG. 1 shows in cross section in a greatly simplified view
an exemplary embodiment of a blade according to the invention with
turbulators or pins which project into the cavity perpendicularly
to the wall surface in the region of the trailing edge;
[0009] FIG. 2 shows in section the simplified casting core for
producing the blade from FIG. 1 by a casting technique;
[0010] FIG. 3 shows the problems which are associated with the mold
halves of the core mold when producing the casting core from FIG.
2;
[0011] FIG. 4 shows in a view which is comparable to FIG. 3 a core
mold, which is modified within the scope of the invention, with
mold inserts for overcoming the limitations which are associated
with the core mold according to FIG. 3, and
[0012] FIG. 5 shows one of the mold inserts from FIG. 4.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Introduction to the Embodiments
[0013] The invention should provide a remedy here. It is therefore
an object of the invention to propose a blade which is improved
with regard to internal cooling, overcoming certain limitations
created by the casting core, and which at the same time can be
produced with little additional cost. It is furthermore an object
of the invention to disclose a method for producing such a
blade.
[0014] The object is achieved by means of the entirety of the
features of the independent claims. It is a feature of the
invention that the turbulators or pins which are formed on the wall
in the region of the trailing edge for improving the heat transfer
between the wall of the blade and the cooling air extend into the
cavity in a direction which can be freely selected within an
angular range.
[0015] With regard to the cooling, it is particularly advantageous
if, according to one development of the invention, the turbulators
or pins extend into the cavity in a direction which is essentially
perpendicular to the associated internal surface.
[0016] The method according to the invention for producing the
blade by a casting technique, in which, in a first step, a core
mold is provided for forming a casting core which keeps the cavity
of the blade free, in a second step, the casting core is produced
by means of the core mold, in a third step, the casting core is
removed from the core mold, and in a fourth step, the blade is cast
by means of the casting core. The core mold, which is provided in
the first step, comprises two mold halves which during demolding
are drawn apart in a first direction, wherein at least one mold
insert, which is provided for forming the turbulators or pins, is
arranged in the mold halves in the trailing edge region, and in the
third step, after the parting of the mold halves in the first
direction, the at least one mold insert is withdrawn from the
formed casting core in a second direction which differs from the
first direction.
[0017] In one development of the method according to the invention,
the second direction is perpendicular to the internal surface which
is associated with the turbulators or pins.
[0018] According to another development of the method, a plurality
of mold inserts are arranged in the mold halves and during
demolding of the formed casting core are withdrawn in different
directions which differ from the first direction.
DETAILED DESCRIPTION
[0019] FIG. 1 shows, in cross section in a greatly simplified view,
an exemplary embodiment of a gas turbine blade according to the
invention. The blade 10 has an airfoil profile with a leading edge
11, a trailing edge 12 and also a (convex) suction side 13 and a
(concave) pressure side 14. The blade 10 has a wall 15 which
encloses a hollow cavity 16 which is used for the guiding of
cooling air which inter alia can discharge into the outside space
from cooling air outlets 17 which are provided at the trailing edge
12. The cavity 16 can be divided into a plurality of sub-chambers
by means of one or more ribs 29.
[0020] For forming the cavity 16 and the details and elements which
are arranged therein, a casting core 21 (FIG. 2), which has to be
produced in advance, is required when producing the blade 10 by a
casting technique. For producing the casting core 21, use is made
as a rule of a core mold 23 according to the type shown in FIG. 3,
which is assembled from two mold halves 23a and 23b which can
separated along a parting plane 25 and which during demolding are
drawn apart in the direction which is indicated by the arrows in
FIG. 3. As a result of the specified direction, in which the two
mold halves 23a and 23b have to be drawn apart during demolding
(demolding direction), the orientation of specific elements in the
cavity 16 of the blade is also indirectly determined via the
casting core 21. Thus, the rib 29 in the cavity 16 of the blade
extends inevitably in the demolding direction because the mold
halves 23a and 23b with their corresponding rib elements 30 can
only be withdrawn from the finished casting core in this way.
[0021] According to the invention, additional elements 18 in the
cavity, which can be formed as (round) pins or (rib-like)
turbulators and improve the transfer of heat between the cooling
air which flows in the cavity 16 and the wall 15, are now arranged
or formed in the trailing edge region of the blade 10. The
direction in which the elements 18 project from the wall 15 into
the cavity 16 should now be able to be selected within an angular
range independently of the demolding direction of FIG. 3, i.e. the
orientation of the elements 18 can differ from the orientation of
the rib 29. In particular, the elements 18, for fluidic reasons,
are intended to be perpendicular to the internal surface 19 or 20
of the wall from which they extend, as is indicated by the right
angle in FIG. 1.
[0022] In order to be able to realize the elements 18 from FIG. 1
with the orientation which is shown there, the casting core 21
would have to have correspondingly formed and oriented recesses 22
(FIG. 2). In the case of the two-part core mold 23 of FIG. 3,
corresponding mold elements 26 would have to be arranged on the
mold halves 23a and 23b for forming the recesses 22. However, it is
immediately apparent in the view of FIG. 3 that in the case of mold
elements 26 which are differently orientated in such a way the two
mold halves 23a and 23b during demolding can no longer be drawn
apart in the demolding direction without the formed recesses 22
being damaged or being destroyed, or the mold elements 26 being
sheared off.
[0023] In order to be able to create such differently oriented
elements 18 in a simple manner and without the risk of damage
within the production process for the casting core 21, however,
according to FIGS. 4 and 5 provision is made for separate mold
inserts 27, 28 for the region in which the elements 18 are to be
arranged, which mold inserts are responsible for forming the
recesses 22 and can be withdrawn separately from the mold halves
23a and 23b.
[0024] During the production of the casting core 21 with a core
mold configuration according to FIG. 4, the mold halves 23a and
23b, during demolding, are first of all drawn apart in the
demolding direction (vertically upwards and downwards in FIG. 4).
The mold inserts 27 and 28 remain on the casting core 21 in this
phase. If the mold halves 23a and 23b are removed, the mold inserts
27 and 28 can be withdrawn from the casting core in those
directions which correspond to the orientation of the elements 18
(inclined arrows in FIG. 4). In this way, it is possible within the
scope of the customary casting process to create in a simple way
elements 18 in the cavity 16 of the blade 10 which are optimized
for cooling and the orientation of which differs from the (main)
demolding direction of the core mold.
LIST OF DESIGNATIONS
[0025] 10 Blade (gas turbine) [0026] 11 Leading edge [0027] 12
Trailing edge [0028] 13 Suction side [0029] 14 Pressure side [0030]
15 Wall [0031] 16 Cavity [0032] 17 Cooling air outlet [0033] 18
Turbulator (pin) [0034] 19, 20 Internal surface [0035] 21 Casting
core [0036] 22 Recess [0037] 23 Core mold [0038] 23a, b Mold halves
[0039] 24 Cavity [0040] 25 Parting plane [0041] 26 Mold element
[0042] 27, 28 Mold insert [0043] 29 Rib [0044] 30 Rib element
* * * * *