U.S. patent application number 09/758188 was filed with the patent office on 2001-08-23 for cooled blade for a gas turbine.
Invention is credited to Lutum, Ewald, Semmler, Klaus, Wolfersdorf, Jens.
Application Number | 20010016162 09/758188 |
Document ID | / |
Family ID | 7627366 |
Filed Date | 2001-08-23 |
United States Patent
Application |
20010016162 |
Kind Code |
A1 |
Lutum, Ewald ; et
al. |
August 23, 2001 |
Cooled blade for a gas turbine
Abstract
In a cooled blade for a gas turbine, in which blade a cooling
fluid, preferably cooling air, flows for convective cooling through
internal cooling passages (141-143) located close to the wall and
is subsequently deflected for external film cooling through
film-cooling holes (161-163) onto the blade surface, and the fluid
flow is directed in at least some of the internal cooling passages
(141-143) in counterflow to the hot-gas flow (18) flowing around
the blade, homogeneous cooling in the radial direction is achieved
owing to the fact that a plurality of internal cooling passages
(141-143) and film-cooling holes (161-163) are arranged one above
the other in the radial direction in the blade (10, 20, 30) in such
a way that the discharge openings of the film-cooling holes
(161-163) in each case lie so as to be offset from the internal
cooling passages (141-143), in particular lie between the internal
cooling passages (141-143).
Inventors: |
Lutum, Ewald; (Brugg,
CH) ; Semmler, Klaus; (Dachau, DE) ;
Wolfersdorf, Jens; (Untersiggenthal, CH) |
Correspondence
Address: |
Robert S. Swecker
BURNS, DOANE, SWECKER & MATHIS, L.L.P.
P.O. Box 1404
Alexandria
VA
22313-1404
US
|
Family ID: |
7627366 |
Appl. No.: |
09/758188 |
Filed: |
January 12, 2001 |
Current U.S.
Class: |
416/97R |
Current CPC
Class: |
F05D 2260/202 20130101;
F01D 5/186 20130101; F01D 5/187 20130101; F05D 2250/34 20130101;
F05D 2260/22141 20130101 |
Class at
Publication: |
416/97.00R |
International
Class: |
B63H 001/14 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 13, 2000 |
DE |
100 01 109.8 |
Claims
1. A cooled blade (10, 20, 30, 40) for a gas turbine, in which
blade (10, 20, 30, 40) a cooling fluid, preferably cooling air,
flows for convective cooling through internal cooling passages (14;
141-143) located close to the wall and is subsequently deflected
for external film cooling through first film-cooling holes (16;
161-163; 161', 162"; 162', 162") onto the blade surface (11), the
fluid flow being directed in at least some of the internal cooling
passages (14; 141-143) in counterflow to the hot-gas flow (18)
flowing around the blade (10, 20, 30, 40), characterized in that a
plurality of internal cooling passages (141-143) and film-cooling
holes (161-163) are arranged one above the other in the radial
direction in the blade (10, 20, 30) in such a way that the
discharge openings of the film-cooling holes (161-163) in each case
lie so as to be offset from the internal cooling passages
(141-143), in particular lie between the internal cooling passages
(141-143).
2. The blade as claimed in claim 1, characterized in that
turbulence-generating elements (19, 19') are arranged in the
internal cooling passages (14; 141-143).
3. The blade as claimed in either of claims 1 and 2, characterized
in that cavities (21) are arranged in the internal cooling passages
(14; 141-143) for setting the cooling-fluid pressure or the
cooling-fluid mass flow.
4. The blade as claimed in one of claims 1 to 3, characterized in
that first ribs (22, 23) are arranged in the internal cooling
passages (14; 141-143) for enlarging the heat-transfer area.
5. The blade as claimed in claim 4, characterized in that the first
ribs (22, 23) are designed so as to alternate in the flow direction
as outer ribs (22) and inner ribs (23), and in that the inner ribs
(23) preferably have a larger height and/or width than the outer
ribs (22).
6. The blade as claimed in one of claims 1 to 5, characterized in
that first impingement-cooling holes (13) are provided in order to
supply the internal cooling passages (14; 141-143), through which
impingement-cooling holes (13) the cooling fluid enters the
internal cooling passages (14; 141-143) in the form of impingement
jets.
7. The blade as claimed in one of claims 1 to 6, characterized in
that the cooling fluid is deflected in the direction of the hot-gas
flow (18) before discharge from the first film-cooling holes (16;
161-163; 161', 161"; 162', 162").
8. The blade as claimed in one of claims 1 to 7, characterized in
that, in addition to the internal cooling passages (14; 141-143), a
cooling passage (47) is arranged in the blade nose (43), to which
cooling passage (47)cooling fluid is admitted through second
impingement-cooling holes (49).
9. The blade as claimed in claim 8, characterized in that second
film-cooling holes (48) are directed from the cooling passage (47)
to the blade surface (11), in that the second impingement-cooling
holes (49) and the second film-cooling holes (48) are arranged
alternately, and in that second ribs or rib segments (51) are
arranged between the second impingement-cooling holes (49) and the
second film-cooling holes (48) for increasing the heat-transfer
area and for separating the zones of the cooling passage (47) which
belong to the second impingement-cooling holes (49) and the second
film-cooling holes (48).
10. The blade as claimed in one of claims 1 to 9, characterized in
that the internal cooling passages (141-143) run axially, and the
film-cooling holes (161-163) in each case branch off from an
associated internal cooling passage (141-143) at an angle in the
radial direction.
11. The blade as claimed in one of claims 1 to 9, characterized in
that the internal cooling passages (141-143) run axially, in that
the ends of the internal cooling passages (141-143) are connected
by radial passages (24), and in that the film-cooling holes
(161-163) are in each case arranged between the internal cooling
passages (141-143) and start from the radial passages (24).
12. The blade as claimed in one of claims 1 to 9, characterized in
that the internal cooling passages (141-143) run at an angle in the
radial direction, and the film-cooling holes (161-163) in each case
branch off from an associated internal cooling passage (141-143) in
the axial direction.
13. The blade as claimed in one of claims 1 to 9, characterized in
that the internal cooling passages (141-143) run at a first angle
in the radial direction, and the film-cooling holes (161-163) in
each case branch off from an associated internal cooling passage
(141-143) at a second angle in the radial direction.
14. The blade as claimed in one of claims 1 to 13, characterized in
that in each case a plurality of film-cooling holes (161-161";
162-162") branch off from an internal cooling passage (141, 142) in
such a way as to be distributed over the passage length.
15. The blade as claimed in one of claims 1 to 14, characterized in
that deflections (53, 54) are provided in the internal cooling
passages (141, 142) for producing the counterflow.
16. The blade as claimed in one of claims 1 to 14, characterized in
that the cooling medium is fed to the internal cooling passages
(142-143) at different axial positions for producing the
counterflow.
Description
[0001] The present invention relates to the field of gas-turbine
technology. It concerns a cooled blade for a gas turbine according
to the preamble of claim 1.
[0002] Such a blade has been disclosed, for example, by the
publication WO 99/06672.
[0003] To increase the output and the efficiency, ever increasing
turbine inlet temperatures are used in modern gas-turbine plants.
In order to protect the turbine blades from the increased hot-gas
temperatures, these blades have to be cooled more intensively than
hitherto. At correspondingly high turbine inlet temperatures, both
convective cooling and film-cooling elements are used. In order to
increase the effectiveness of these types of cooling, it is
desirable to reduce the wall-material thicknesses. Furthermore,
optimum distribution between convective heat absorption of the
cooling fluid and cooling-fluid temperature during the blow-out as
cooling film is to be aimed at.
[0004] Combinations of convective cooling and film cooling at
reduced wall thicknesses have been disclosed, for example, by U.S.
Pat. Nos. 5,562,409, 4,770,608 mentioned at the beginning, and U.S.
Pat. No. 5,720,431. In this case, the convective cooling is carried
out via impingement cooling, only a small part of the surface being
cooled by the respective cooling-fluid jet, which is subsequently
used for the film cooling. The convective cooling capacity of the
fluid is therefore only partly utilized.
[0005] U.S. Pat. Nos. 5,370,499 and 5,419,039 describe a method of
avoiding this disadvantage. In this case, the cooling fluid is
first of all used for convective cooling in passages close to the
wall before it is blown out as a film. At the same time, the
convective cooling passages may be provided with
turbulence-increasing devices (ribs, cylinders or crossed
passages). However, the cooling fluid is always directed in these
devices in parallel with the main-gas flow, which does not
constitute the best solution for optimum cooling.
[0006] In the publication WO-A1-99/06672 mentioned at the
beginning, it has now been proposed to direct the cooling fluid in
the convective part in an antiparallel manner, i.e. in counterflow
to the main-gas flow (and thus to the film-cooling flow). This
certainly results in cooling which is more homogeneous in the axial
direction or in the direction of the hot-gas flow. However, it is
still open to question as to how homogeneous cooling or temperature
distribution in the longitudinal direction of the blade, that is in
radial extent, can be achieved.
[0007] The object of the invention, then, is to provide a cooled
gas-turbine blade which also ensures a homogeneous distribution of
the material temperature at the blade in the radial direction.
[0008] The object is achieved by all the features of claim 1
together.
[0009] The essence of the invention consists in arranging a
plurality of internal cooling passages and film-cooling holes one
above the other in the radial direction in the blade in such a way
that the discharge openings of the film-cooling holes in each case
lie so as to be offset from the internal cooling passages, and in
particular lie between the internal cooling passages. Since the
cooling effect of the film cooling between the holes is less than
in the axial direction downstream of the holes, the cooling effect
of the internal cooling is utilized in these intermediate regions
by the arrangement according to the invention.
[0010] The cooling fluid is first of all directed in counterflow to
the hot-gas flow in convective passages close to the wall, which
are integrated in the overall structure and can be provided with
turbulence-generating devices, before the cooling fluid is used for
film cooling. As a result, very uniform temperature distributions
are produced, which is very important for the small wall
thicknesses desired and the low wall thermal resistance associated
therewith, since the temperature balance is impaired by heat
conduction in the wall at small wall thicknesses. Furthermore, due
to the deflection of the cooling fluid, which automatically occurs,
an impulse can be applied, and this impulse is advantageous for the
cooling effect of the cooling film, as has been described, for
example, in U.S. Pat. No. 4,384,823, or a swirl can also be
produced in the "prechamber" of the film-cooling hole, as described
in U.S. Pat. No. 4,669,957.
[0011] A first preferred embodiment of the blade according to the
invention is distinguished by the fact that turbulence-generating
elements are arranged in the internal cooling passages. In this
way, the contact between cooling fluid and passage wall and thus
the internal cooling can be further improved.
[0012] Specific setting of the cooling can be achieved if, in a
second preferred embodiment of the invention, cavities are arranged
in the internal cooling passages for setting the cooling-fluid
pressure or the cooling-fluid mass flow.
[0013] The internal cooling can also be improved if, in another
preferred embodiment, first ribs are arranged in the internal
cooling passages for enlarging the heat-transfer area, in which
case, in particular, the first ribs are designed so as to alternate
in the flow direction as outer ribs and inner ribs, and in the
inner ribs have a larger height and/or width than the outer
ribs.
[0014] A further increase in the cooling effect in the interior is
achieved if, in a further preferred embodiment of the invention,
first impingement-cooling holes are provided in order to supply the
internal cooling passages, through which impingement-cooling holes
the cooling fluid enters the internal cooling passages in the form
of impingement jets.
[0015] In addition to the internal cooling passages, a cooling
passage may also be arranged in the blade nose, to which cooling
passage cooling fluid is admitted through second
impingement-cooling holes, in which case second film-cooling holes
are preferably directed from the cooling passage to the blade
surface, the second impingement-cooling holes and the second
film-cooling holes are arranged alternately, and second ribs are
arranged between the second impingement-cooling holes and the
second film-cooling holes for increasing the heat-transfer area and
for separating the zones of the cooling passage which belong to the
second impingement-cooling holes and the second film-cooling
holes.
[0016] The internal cooling passages may run axially, and the
film-cooling holes may in each case branch off from an associated
internal cooling passage at an angle in the radial direction.
However, it is also conceivable for the internal cooling passages
to run axially, for the ends of the internal cooling passages to be
connected by radial passages, and for the film-cooling holes to in
each case be arranged between the internal cooling passages and
start from the radial passages. Furthermore, it is conceivable in
this connection for the internal cooling passages to run at an
angle in the radial direction, and for the film-cooling holes to in
each case branch off from an associated internal cooling passage in
the axial direction, or for the internal cooling passages to run at
a first angle in the radial direction, and for the film-cooling
holes to in each case branch off from an associated internal
cooling passage at a second angle in the radial direction. In all
cases, the film-discharge surfaces are arranged so as to be offset
from the convective internal cooling passages, so that the internal
cooling takes place precisely where the film cooling is less
effective.
[0017] Further embodiments follow from the dependent claims.
[0018] The invention is to be explained in more detail below with
reference to exemplary embodiments in connection with the drawing,
in which:
[0019] FIG. 1 shows, in a cross section of the marginal region, a
first preferred exemplary embodiment for an individual internal
cooling passage with cooling fluid directed in counterflow to the
hot-gas flow, without and with additional turbulence-generating
means, in a blade according to the invention;
[0020] FIG. 2 shows an exemplary embodiment comparable with FIG. 1
having cavities in the internal cooling passages for setting the
cooling-fluid mass flow;
[0021] FIG. 3 shows an exemplary embodiment comparable with FIG. 1
having additional ribs in the internal cooling passage for
enlarging the heat-transfer area;
[0022] FIG. 4 shows, in a cross section, the leading-edge region of
a cooled blade in another exemplary embodiment of the invention
having an additional cooling passage in the blade nose;
[0023] FIG. 5 shows, in an enlarged detail from FIG. 4, the blade
nose with additional subdividing ribs in the cooling passage close
to the edge;
[0024] FIGS. 6-9 show various exemplary embodiments for the
(offset) arrangement according to the invention of internal cooling
passages and film-cooling holes in the radial direction of the
blade in a blade according to the invention;
[0025] FIG. 10 shows two preferred exemplary embodiments for the
arrangement of a plurality of film-cooling holes for each internal
cooling passage in a blade according to the invention;
[0026] FIG. 11 shows an exemplary embodiment of the blade according
to the invention having a deflection of the fluid flow into the
counterflow by specific directing of the internal cooling passages;
and
[0027] FIG. 12 shows another exemplary embodiment of the blade
according to the invention having a deflection of the fluid flow by
the positioning of the feeds (impingement-cooling holes) for the
cooling fluid to the internal cooling passages.
[0028] For a blade according to the invention, a first preferred
exemplary embodiment of an individual internal cooling passage
having cooling fluid directed in counterflow to the hot-gas flow,
without and with additional turbulence-generating means, is shown
in FIG. 1 in a cross section of the marginal region. The blade 10
is exposed with its blade surface 11 to a hot-gas flow 18 (long
arrow pointing from right to left). Arranged below the blade
surface 11 are internal cooling passages 14, which are separated
from the blade surface 11 only by a thin wall 12 of thickness D and
run parallel to the blade surface 11. A cooling fluid-- preferably
cooling air--is fed at one end to the internal cooling passages 14,
preferably via impingement-cooling holes 13. The cooling fluid then
passes through the internal cooling passages 14 in counterflow to
the (external) hot-gas flow 18. It is deflected in a deflection
space 15 located at the other end of the internal cooling passages
14 and leaves the blade 10 as a film flow 17 through film-cooling
holes 16, which start from the deflection space 15 in the direction
of the hot-gas flow 18, in order to form a cooling film on the
blade surface 11. In this case, the internal cooling passages 14
may have smooth walls, but may also be provided with
turbulence-generating elements 19, 19' known per se, as can be seen
on the right in FIG. 1.
[0029] This type of cooling is based on the idea of directing the
cooling fluid first of all in counterflow to the hot-gas flow 18 in
convective passages located close to the wall, which are integrated
in the overall structure and can be provided with
turbulence-generating devices, before the cooling fluid is used for
the film cooling. As a result, very uniform temperature
distributions are produced, which is very important for the small
wall thicknesses D desired and the low wall thermal resistance
associated therewith, since the temperature balance is impaired by
heat conduction in the wall 12 at small wall thicknesses.
Furthermore, due to the deflection of the cooling fluid, which
automatically occurs, an impulse can be applied, and this impulse,
as already mentioned at the beginning, is advantageous for the
cooling effect of the cooling film forming on the surface.
[0030] Furthermore, according to FIG. 2, the convectively cooled
internal cooling passages 14 may be provided with larger cavities
21 which enable the fluid pressure to be set in order to improve
the film-cooling effectiveness and set the desired cooling-fluid
mass flow.
[0031] FIG. 3 shows a further variant, by means of which the fluid
pressure can be set and the surface necessary for the heat
dissipation can be enlarged and the turbulence and thus the heat
transfer can be increased. In this case, the integral convective
internal cooling passages 14 are directed serpentine-like around
inner and outer ribs 23 and 22 respectively. The internal cooling
passage is again fed with cooling fluid by one (or more)
impingement-cooling hole(s) 13. The cooling fluid is then passed as
a cooling film (through film-cooling holes 16 which are angled in
the flow direction and/or in the lateral direction and may be
provided with diffuser extensions) in counterflow onto the outer
blade surface 11. On account of the different temperature
conditions, the inner ribs 23 should preferably be designed to be
larger in height and/or width than the outer ribs 22.
[0032] Especially effective cooling can be achieved with this
cooling geometry according to FIG. 4 in the leading-edge region of
a gas-turbine blade, in which case a combination with an
impingement-cooled (and possibly film-cooled) blade nose 43, as
described in Patent EP-A1-0 892 151, is possible. Accommodated in
this case in the walls of the blade 40 are a plurality of the
cooling arrangements 44-46 already described, which in each case
comprise internal bores 14, which are supplied with cooling fluid
in counterflow on the inlet side from a (radial) main passage 50
via impingement-cooling holes 13 and allow the cooling fluid to
discharge as a cooling film on the outlet side via deflection
spaces 15 and film-cooling holes 16 onto the blade surface
(pressure surface 41 or suction surface 42). Provided for cooling
in the blade nose 43 is a cooling passage 47, which is supplied
from the main passage 50 through impingement-cooling holes 49 and
delivers the cooling film to the outside via film-cooling holes
48.
[0033] At the same time, the configuration specified, according to
FIG. 5, may be advantageously extended with the outer ribs 51
described above. These ribs 51, which may also be interrupted in
the radial direction and then constitute rib segments (or pins),
increase the heat-dissipating surface and separate those surfaces
which are struck by the impingement jets from the
impingement-cooling holes 49 from the cavities from which the
film-cooling holes 48 start. In this case, the film-cooling holes
48 may be arranged at an angle in the radial direction
(perpendicular to the drawing plane of FIG. 5). This achieves the
effect that the cooling fluid sweeps over the entire
heat-dissipating surface available and high cooling effectiveness
is achieved.
[0034] The arrangements specified permit a homogeneous material
temperature distribution in the flow direction of the hot-gas flow
18, i.e. in the axial direction of the gas turbine. However, it is
essential for the invention to also achieve a homogeneous
distribution in radial extent (perpendicular to the drawing plane
in FIGS. 1 to 5) in order to increase the service life of a
gas-turbine blade. This is ensured by the special arrangement
according to the invention of internal cooling passages and
film-cooling holes. It is essential in this case to have
arrangements in which the film-discharge surfaces (discharge
openings of the film-cooling holes) are arranged so as to be offset
from the convective internal cooling passages. Since the cooling
effect of the film cooling between the holes is less than in the
axial direction downstream of the holes, the cooling effect of the
internal cooling can be utilized in these intermediate regions.
[0035] FIGS. 6-9 show possible basic arrangements which follow this
idea. In FIG. 6, a plurality of internal cooling bores 141-143 are
arranged in the radial direction 52 of the blade one above the
other and so as to run parallel to one another at a uniform
distance apart in the axial direction (parallel to the hot-gas flow
18). Film-cooling holes 161-163 go from the outlet-side ends of the
internal-cooling passages 141-143 to the blade surface, which lies
in the drawing plane. The film-cooling holes 161-163 are made at an
angle in the radial direction, so that their (oval) film-discharge
openings are in each case arranged between the internal cooling
passages 141-143 lying in the wall.
[0036] Shown in FIG. 7 is an arrangement in which the ends of
internal cooling passages 141-143 running axially in the wall are
connected by radial passages 24. The film-cooling holes 161-163 are
made between the internal cooling passages 141-143 so as to start
from the radial passages 24 and run parallel to the internal
cooling passages 141-143.
[0037] FIG. 8 shows a further possibility. The internal cooling
passages 141-143 are in this case made in the blade wall at an
angle in the radial direction, whereas the film-cooling holes
161-163 branching off from them run axially. Combinations of these
arrangements are conceivable, as shown in FIG. 9 for example. In
this case, both the internal cooling passages 141-143 and the
film-cooling holes 161-163 are made at an associated angle in the
radial direction. The matrix structure produced is especially
effective for homogenization of the material temperature in the
radial direction. In all cases, a plurality of film-cooling holes
161-161" and 162-162" for each internal cooling passage 141 and 142
respectively are also conceivable, as shown in FIG. 10 for angled
passages and axial holes (part A of figure; comparable with FIG. 8)
and respectively for angled passages and angled holes (part B of
figure; comparable with FIG. 9). This is of course also possible
for the other arrangements described.
[0038] The counterflow principle according to the invention for the
homogenization of the wall temperature in the axial and radial
directions may also be realized by the convective internal cooling
passages 141-143 themselves, as indicated in FIGS. 11 and 12. In
this case, for the internal cooling air, the counterflow is
achieved either by deflections 53, 54 (FIG. 11) or by feeding and
discharging the cooling medium (e.g. via impingement-cooling holes
and the film-cooling holes, as described above) at different axial
positions (FIG. 12).
List of Designations
[0039] 10, 20, 30 Blade (gas turbine)
[0040] 11 Blade surface
[0041] 12 Wall
[0042] 13 Impingement-cooling hole
[0043] 14 Internal cooling passage
[0044] 15 Deflection space
[0045] 16 Film-cooling hole
[0046] 17 Film flow
[0047] 18 Hot-gas flow
[0048] 19, 19' Turbulence-generating element
[0049] 21 Cavity
[0050] 22, 23 Rib
[0051] 24 Radial passage
[0052] 40 Blade (gas turbine)
[0053] 41 Pressure surface
[0054] 42 Suction surface
[0055] 43 Blade nose
[0056] 44-46 Cooling arrangement
[0057] 47 Cooling passage
[0058] 48 Film-cooling hole
[0059] 49 Impingement-cooling hole
[0060] 50 Main passage
[0061] 51 Rib or rib segment
[0062] 52 Radial direction (blade)
[0063] 53, 54 Deflection
[0064] 141-143 Internal cooling passage
[0065] 161-163 Film-cooling hole
[0066] 161', 161" Film-cooling hole
[0067] 162', 162" Film-cooling hole
[0068] D Thickness (wall)
* * * * *