Information
-
Patent Grant
-
6742783
-
Patent Number
6,742,783
-
Date Filed
Wednesday, November 14, 200122 years ago
-
Date Issued
Tuesday, June 1, 200420 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Knight; Anthony
- Boswell; Christopher J.
Agents
- Taltavull; W. Warren
- Manelli, Denison & Selter PLLC
-
CPC
-
US Classifications
Field of Search
US
- 277 628
- 277 630
- 277 632
- 277 637
- 277 641
- 277 644
- 277 650
- 277 651
- 277 652
- 277 653
- 277 654
- 415 1734
- 415 1735
- 415 180
-
International Classifications
-
Abstract
A seal segment (66) as described for a seal segment ring (64) of a turbine (16) in a gas turbine engine (10). The seal segment (66) has an inner surface (70) adapted to face the turbine blades (36) in use. Path means (72) is defined in the seal segment (66). The path means (72) is adapted to extend, in use, generally parallel to the principal axis of the turbine and has downstream inlet means (74) through which a cooling fluid to cool the seal segment can enter the path means (72) and upstream outlet means (76) from which the cooling fluid can be exhausted from the path means (72). The cooling fluid can flow along the path means (72) in a generally upstream direction opposite to the flow of gas through the turbine.
Description
FIELD OF THE INVENTION
This invention relates to seal segments for gas turbine engines. More particularly, but not exclusively, the invention relates to seal segments for high pressure turbines of gas turbine engines. The invention also relates to wall structures for turbines formed of a plurality of seal segments.
BACKGROUND OF THE INVENTION
In gas turbine engines seal segments form a seal segment ring around the turbine blades of the engine. These seal segments can overheat because of leakage of hot gases flowing through the turbine around the tips of the turbine blades. This is a particular problem in high pressure turbines.
SUMMARY OF THE INVENTION
According to one aspect of this invention there is provided a seal segment for a seal segment ring of a gas turbine engine, the seal segment comprising a main body having an inner surface adapted to face the turbine blades in use, wherein path means for a cooling fluid is defined in the main body, the path means extending, in use, between upstream and downstream regions of the seal segment.
The main body may be formed as a one piece element.
According to another aspect of this invention there is provided a seal segment for a seal segment ring of a gas turbine engine, the seal segment having an inner surface adapted to face the turbine blades in use, wherein path means is defined in the seal segment, the path means being adapted to extend, in use, between upstream and downstream regions of the seal segment, and having downstream inlet means through which a cooling fluid to cool the segment can enter the path means and upstream outlet means from which the cooling fluid can be exhausted from the path means, whereby cooling fluid can flow along the path means in a generally upstream direction opposite to the flow of gas through the turbine.
The outlet means is preferably arranged, in use, upstream of the turbine blades. In one embodiment, the outlet means for the cooling fluid is arranged to open in a downstream direction. In another embodiment, the outlet means is directed generally radially inwardly. Thus, in these embodiments, cooling fluid exhausted from the path means may pass over said inner surface of the segment in a downstream direction. The outlet means may be directed, in use, at an angle to the principal axis of the turbine, such that cooling fluid exits from the path means in substantially the identical direction to the flow of gas through the turbine at said outlet means.
The path means preferably extends, in use, generally parallel to the principal axis of the turbine. A preferred embodiment of this invention has the advantage that improved heat transfer is achieved by the provision of path means in which the flow of cooling fluid is from a downstream region of the seal segment to an upstream region. The flow of the cooling fluid in the path means in this preferred embodiment is counter to the main flow of gas through the engine, having the advantage of increasing heat transfer. The inlet means may be angled, in use, relative to the principal axis of the turbine such that the flow of the cooling fluid through the path means is substantially directly opposite to the flow of gas through the engine.
The path means preferably extends to one or more regions of the main body adjacent the inner surface to provide cooling at the, or each, of said regions in use.
Preferably, the path means comprises at least one passage which is preferably elongate, and the passage may extend laterally across the seal segment, preferably in a generally circumferential direction, in use. Preferably each seal segment defines two or more of said passages, which may be defined side-by-side, and each may extend laterally across the segment part way, preferably substantially half way. The path means may comprise a plurality of such passages each passage preferably extending generally parallel to the principal axis of the turbine in use. Preferably, the path means is configured to conform substantially to the profile of said inner surface.
The seal segment may include a plurality of heat removal members in the path means. The heat removal members may be in the form of pedestals, which may extend from a radially inner wall of the path means to a radially outer wall of the path means.
The path means may comprise one or more steps. In one embodiment, the path means comprises first and second axial sections, the first section extending from the inlet means to a region upstream thereof, and the second section extending from said region to the outlet means. The first and second sections may axially overlap and a conduit may extend between the first and second sections in said region. The configuration of said conduit is preferably arranged to produce impingement cooling of said seal segment by the cooling fluid as it enters the second section from said conduit. Alternatively, or in addition, the configuration of the conduit may be arranged to produce cooling of the seal segment by other enhanced heat transfer mechanisms. In another embodiment the path means comprises a single axial section which may include one or more steps.
In one embodiment, the path means extends to one or more regions of the seal segment adjacent the inner surface of the seal segment.
According to another aspect of this invention, there is provided a seal segment ring for a turbine of a gas turbine engine, the seal segment ring being formed from a plurality of seal segments as described above, the segments being arranged, in use, circumferentially around the turbine.
Preferably, the path means of successive segments defines a plurality of axially extending passages arranged side-by-side circumferentially around the seal ring to define an annulus of said cooling passages.
According to another aspect of this invention there is provided a core for use in a method of making a seal segment, the core comprising a main portion to form path means in the seal segment and projection means extending therefrom. In the preferred embodiment, the projection means is so arranged on the main portion and so configured to minimise the amount of material used in the method.
Preferably, the projection means is arranged generally centrally of the core conveniently on a substantially central axis. The projection means may comprise a first projection extending from a first surface of the main portion, and a second projection extending from a second surface of the main portion. The first surface is preferably a longitudinally and laterally extending surface. The second surface is preferably an edge surface, conveniently a laterally extending edge surface.
The first projection may have a generally cylindrical region, and the second projection may have a generally conical main region. The first projection may include a connecting region to connect the main region to the surface, the connecting region tapering outwardly from the main region.
BRIEF DESCRIPTION OF THE DRAWINGS
An embodiment of the invention will now be described by way of example only with reference to the accompanying drawings, in which:
FIG. 1
is a sectional side view of the upper half of a gas turbine engine;
FIG. 2
is a perspective view of part of a high pressure turbine of an example of the engine shown in
FIG. 1
; and
FIG. 3
is a vertical cross-section through part of the turbine arrangement shown in
FIG. 2
showing one embodiment;
FIG. 4
is a view similar to
FIG. 3
showing another embodiment of a seal segment;
FIG. 5
is a side view of a core for use in forming path means in a seal segment;
FIG. 6
is a perspective view of the core shown in
FIG. 5
; and
FIG. 7
is a side view of a seal segment during a process of forming the seal segment.
DETAILED DESCRIPTION OF THE INVENTION
Referring to
FIG. 1
, a gas turbine engine is generally indicated at
10
and comprises, in axial flow series, an air intake
11
, a propulsive fan
12
, an intermediate pressure compressor
13
, a high pressure compressor
14
, combustion equipment
15
, a turbine arrangement comprising a high pressure turbine
16
, an intermediate pressure turbine
17
and a low pressure turbine
18
, and an exhaust nozzle
19
.
The gas turbine engine
10
operates in a conventional manner so that air entering the intake
11
is accelerated by the fan
12
which produce two air flows: a first air flow into the intermediate pressure compressor
13
and a second air flow which provides propulsive thrust. The intermediate pressure compressor compresses the air flow directed into it before delivering that air to the high pressure compressor
14
where further compression takes place.
The compressed air exhausted from the high pressure compressor
14
is directed into the combustion equipment
15
where it is mixed with fuel and the mixture combusted. The resultant hot combustion products then expand through, and thereby drive, the high, intermediate and low pressure turbines
16
,
17
and
18
before being exhausted through the nozzle
19
to provide additional propulsive thrust. The high, intermediate and low pressure turbine
16
,
17
and
18
respectively drive the high and intermediate pressure compressors
14
and
13
, and the fan
12
by suitable interconnecting shafts.
Referring to
FIG. 2
, there is shown part of a high pressure turbine
16
which is a single stage turbine and is connected to, and drives, the high pressure compressor
14
via a shaft
26
. It will be appreciated that the turbine could be a multiple stage turbine, for example a two stage turbine. A casing
24
extends around the high pressure turbine
16
and also extends around the intermediate and low pressure turbines
17
and
18
.
The high pressure turbine
16
comprises a stator assembly
31
in the form of an annular array of fixed guide vanes
32
arranged upstream of a rotor assembly
35
comprising an annular array of turbine blades
36
rotatably mounted on the shaft
26
(see FIG.
1
). A support structure
34
for the guide vanes
32
extends circumferentially around the array of guide vanes
32
which are fixedly mounted on the support structure
34
.
A wall structure or seal segment ring
64
is shown schematically in FIG.
2
and extends circumferentially around the array of turbine blades
36
. The seal segment ring
64
comprises a plurality of seal segments
66
together defining the annular seal segment ring
64
. In the embodiment shown, the blades
36
are provided with shrouds
37
, but it will be appreciated that the blades
36
can be shroudless. The shrouds
37
comprise ribs or other projections
37
A.
The intermediate and low pressure turbines
17
and
18
also comprise arrangements of guide vanes and rotor blades. The intermediate pressure turbine
17
receives air from the high pressure turbine
16
and is connected to and drives the intermediate pressure compressor
13
via a shaft
28
(see FIG.
1
). Similarly, the low pressure turbine
18
receives air from the intermediate pressure turbine
17
and is connected to, and drives, the fan
12
via a shaft
30
(see FIG.
1
).
Referring to
FIG. 3
, there is shown diagrammatically a sectional view of part of the high pressure turbine
16
shown in FIG.
2
.
FIG. 3
shows in detail the support structure
34
for the nozzle guide vanes
32
. The support structure
34
supports the guide vanes in a known manner through first mounting means
62
at the downstream end region of the array of guide vanes
32
and further mounting means (not shown) at the upstream end region.
In the embodiment shown, the support structure
34
also supports a seal segment ring
64
extending circumferentially around the array of high pressure turbine blades
36
. The seal segment ring
64
comprises a plurality of seal segments
66
, only one of which is shown in FIG.
3
.
The seal segment ring
64
is disposed in substantial radial alignment with the turbine blades
36
and a gap
68
is defined between the shrouds
37
of the blades
36
and the seal segment ring
64
. Each seal segment
66
has an inner surface
70
facing the blades
36
. The inner surface
70
has a profile which corresponds generally to the shape of the shrouds
37
of the turbine blades
36
.
The seal segment
66
shown in the drawings includes a main body
71
which defines therein path means in the form of a plurality of passages
72
in the seal segment
66
to allow the flow therethrough of cooling fluid in the form of cooling air. The main body
71
may define one or more passages
72
, each of which, in the embodiment shown, extends generally parallel to the principal axis Y—Y of the turbine arrangement, the line Z—Z in
FIG. 3
being parallel to the axis Y—Y. Each passage
72
also extends laterally of the seal segment
66
substantially half way across.
In the embodiment shown, the main body
71
of each seal segment
66
defines two passages
72
arranged side-by-side and separated from each other by a wall. It will be appreciated that in other embodiments the main body
71
may define more than two of the passages
72
, e.g. four passages
72
. The plurality of passages
72
are defined by the main bodies
71
of the respective seal segments
66
arranged side-by-side circumferentially around the seal segment ring
64
, and together form an annular array of passages around the turbine blades
36
. Each passage
72
is provided with heat removal members in the form of pedestals
73
extending between the radial inner and outer walls of the passages
72
. The heat removal members could take other forms, for example ribs or other features to cause turbulent flow.
A downstream inlet
74
A extends through the seal segment
66
from a radially outer surface to the passage
72
at the downstream end region of the seal segment
66
, to allow air to enter the passage
72
from an annular space
75
. Air is supplied to the space
75
via a conduit
75
A in the support structure
34
. On entering each passage
72
, air flows from the inlet
74
A to an outlet
77
in the upstream direction, as indicated by the arrows A. The flow of air along the passage
72
extracts heat from the surrounding material thereby cooling the material.
Further inlets
74
B and
74
C may be provided upstream of the inlet
74
A and may allow air to enter the passage
72
at various locations upstream from the inlet
74
A. The number and position of the inlets can be varied as desired to provide localised cooling of pre-selected areas of the seal segment
66
. For example, the inlet
74
B may be provided to cool a region
66
A of the seal segment
66
, which may have been found on testing to be prone to overheating. Similarly, other regions which are prone to overheating may be provided with inlets opposite to direct incoming cooling air directly onto such regions.
Since the air flowing through the turbine
17
may be swirled, i.e. it flows at an angle to the principal axis of the turbine, the outlets can be angled such that air exhausted from the passages
72
is directed in the substantially identical direction to the main flow of air through the turbine
17
.
As can be seen in
FIG. 3
, each passage
72
of each of the seal segments
66
is configured to conform generally to the profile of the inner surface
70
of the seal segment ring
64
. Each passage
72
comprises a first section
76
extending from the downstream inlet
74
A to a central region
78
of the seal segment
66
. A second section
80
extends from the region
78
to the outlet
77
. The first and second sections overlap and a connecting conduit
82
, of narrower diameter than the sections
76
,
80
extends from the first section
76
to the second section
80
in the central region
78
. Thus, as the cooling air enters the second section
80
from the connecting conduit
82
, it impinges upon the walls of the second section
80
of the passage
72
to effect impingement cooling of the walls. Along the rest of the passage
72
cooling is effected by transpiration cooling or other types of cooling, for example convection and conduction.
The outlet
77
may open in the downstream direction and directs air, as shown by the arrows B along the inner surface
70
of the seal segment ring
64
. This has a two-fold effect. First, it provides cooling of the surface
70
and/or the blade
36
. Second, it ensures that it is the air flow from the passages
72
which passes through the gap
68
in preference to the air which is swirled from the guide vanes
32
, which is better used in driving the blades
36
thereby improving work output and efficiency. Alternatively, the outlet
77
A may be arranged to extend radially inwardly, as shown by the dashed lines. With this alternative arrangement, the air exiting from the passages
72
via the outlet
77
A may be directed in the same direction as air exiting from outlets
77
by the pressure thereon.
In another embodiment, as shown in
FIG. 4
, the passage
72
is a single passage extending in a stepwise configuration from the upstream end region to the downstream end region. In
FIG. 4
, all the features have been allocated the same reference numeral as in FIG.
3
.
FIG. 4
differs from
FIG. 3
in that the conduit
82
is omitted.
As with the embodiment shown in FIG.
3
and described above, the number and position of the inlets can be varied as described to cool regions of the seal segment
66
which are prone to overheating.
An advantage of the above described embodiments is that it allows cooling passages
72
to be formed as close as possible to the radially inner surface
70
of each seal segment
66
. For example, in each of the embodiments the channel
72
defines a region
72
A adjacent the outlet
77
. The material of the seal segment surrounding the region
72
A is prone to overheating and the regions
72
A provides cooling fluid to prevent such overheating.
The seal segments
66
are manufactured by an investment casting process, which typically involves forming a master die from an original pattern and casting from that master die a working pattern in wax (or a similar material). After the wax working pattern has been formed, it is coated in a ceramic shell to form a final mould. The final mould is then fired in an oven until it is set. The heat of firing melts the wax, enabling it to run out. After firing, molten metal alloy is poured into the mould to form the segment. When the metal has solidified, the mould is destroyed to remove the seal segment.
The formation of the seal segments
66
of the preferred embodiment are cast using generally the above method, but after the master die has been formed, cores
110
(see
FIGS. 5 and 6
) are arranged in the die. The cores are formed of a ceramic material and will eventually form the passages
72
. The molten wax is injected in the die and forms around the cores
110
. After firing the final mould, and melting out the wax working pattern, the cores remain in place. When the molten metal has been poured into the final mould and allowed to solidify, the cores
110
are dissolved away by pouring in a suitable solution, for example an acidic solution to form the passages
72
.
An example of a core
110
is shown in
FIGS. 5 and 6
. The core
110
comprises a main portion
112
which, as can be seen, has a configuration which corresponds to the passages
72
shown in
FIGS. 3 and 4
. The core
110
also extends laterally and has a width which is substantially equal to half the circumferential length of the seal segment
66
which is to be formed around it. The main portion
112
defines a plurality of cylindrical through bores
114
which will form the pedestals
73
, and a plurality of through slots of elongate configuration which will form stiffening ribs
82
in the seal segment
66
formed using the core
110
.
First and second projections
118
,
120
extend outwardly from the main portion
112
. These are provided to assist in the casting of the passages
72
in the seal segments
66
. If reference is made to
FIG. 5
, the first projection
118
extends from surface
122
of the core
110
and the second projection
120
extends from an edge
124
of the core
110
. For ease of reference, in
FIG. 5
, the surface
122
is referred to as upper surface and the edge
124
is referred to as the left hand edge of the core
110
. However, it will be appreciated that the surfaces and the edge do not need to be upper or left hand.
The first projection
118
comprises a main region
126
of a generally cylindrical configuration, and a connecting region
128
which tapers outwardly from the main region
126
to connect the main region
126
to the surface
122
. The second projection
120
comprises a substantially conical main region
130
which tapers outwardly from the edge
124
.
Referring to
FIG. 7
, there is shown a seal segment
66
just after the ceramic core
110
has been dissolved away. Extending from the channel
72
is a first aperture
88
in a radially outward direction, and a second aperture
90
in an upstream direction. The first and second apertures
88
,
90
are formed respectively from the first and second projections
118
,
122
after the core
110
has been dissolved away. In order to complete the manufacture of the seal segment
66
the apertures
88
,
90
are plugged with an appropriate material, for example a welding material. Inlets and outlets can be drilled in desired positions before or after the apertures
88
,
90
have been plugged. The drilling can be carried out by any suitable technique, for example by the use of lasers or by EDM (Electro Discharge Machining).
The position, size and shape of the first and second projections
118
,
120
is carefully selected in the embodiment described to allow the core
110
to be held securely by the master die when the wax working pattern is formed and also by the final mould during the pouring of the metal alloy and its subsequent cooling and solidifying. Further, the first and second projections also minimise the amount of material required to form the core
110
and to form the plugs in the first and second apertures
88
,
90
.
Various modifications can be made without departing from the scope of the invention. For example, the passages
72
could be formed of several sections, with connecting conduits extending between adjacent sections. Moreover while the invention has particular application in relation to high pressure turbines, similar arrangements may be used in association with low or intermediate pressure turbines if desired. Further, the passages
72
need not extend precisely parallel to the principal axis of the turbine. The passages
72
could instead be arranged to allow circumferential swirl of the cooling air passing therethrough.
There is thus described a seal segment, the preferred embodiment of which allows inlets and/or outlets to be drilled in desired numbers and in desired positions to provide the most appropriate cooling in the segment. This provides the advantage that the cooling can be tuned to a fine degree without any changes in casting or in the core, as may be the case for the different requirements for different engines or in response to engines or components tested or run under different conditions, for example different altitude or different temperature.
Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.
Claims
- 1. A seal segment for a seal segment ring of a gas turbine engine, the seal segment comprising a main body having an inner surface adapted to face blades in use, wherein path means for a cooling fluid is defined in the main body, the path means extending, in use, between upstream and downstream regions of the seal segment.
- 2. A seal segment according to claim 1 wherein the main body is formed as a one piece element.
- 3. A seal segment according to claim 1 wherein the path means has upstream inlet means through which a cooling fluid to cool the segment can enter the path means, and downstream outlet means from which the cooling fluid can be exhausted from the path means.
- 4. A seal segment for a seal segment ring of a gas turbine engine, said seal segment having upstream and downstream regions, the seal segment comprising a main body having an inner surface adapted to face blades in use, wherein path means for a cooling fluid is defined in the main body, the path means extending, in use, between said upstream and downstream regions of the seal segment wherein the path means has downstream inlet means through which a cooling fluid to cool the segment can enter the path means, and upstream outlet means from which the cooling fluid can be exhausted from the path means, whereby cooling fluid can flow along the path means in a generally upstream direction opposite to the flow of gas through the engine.
- 5. A seal segment according to claim 4, wherein the outlet means for the cooling fluid is arranged to open in a downstream direction, whereby cooling fluid exhausted from the path means may pass over said inner surface of the segment in a downstream direction.
- 6. A seal segment according to claim 5 wherein the outlet means is directed at an angle to the principal axis of the turbine such that cooling fluid can exit from the path means in substantially the same direction as the flow of gas through the turbine at said outlet means.
- 7. A seal segment according to claim 4 wherein the outlet means for the cooling fluid is directed generally radially inwardly.
- 8. A seal segment according to claim 1, wherein the path means extends to one or more regions of the main body adjacent the inner surface to provide cooling at the, or each, said region in use.
- 9. A seal segment according to claim 1, wherein the path means comprises at least one elongate passage which extends laterally across the seal segment.
- 10. A seal segment according to claim 9 wherein the path means comprises at least two of said passages defined side-by-side in the segment, each extending laterally across the segment substantially half-way.
- 11. A seal segment according to claim 1, wherein the path means is configured to conform substantially to the profile of said inner surface.
- 12. A seal segment according to claim 11, wherein the path means comprises first and second axial sections, the first axial section extending from the inlet means to a region upstream thereof, and the second axial section extending from said region to the outlet means.
- 13. A seal segment according to claim 12, wherein the first and second axial sections overlap each other and a conduit extends between the first and second axial sections in said region, said second axial section including a wall structure, the configuration of said conduit being arranged to produce impingement cooling of said wall structure by the cooling fluid as it enters the second axial section from said conduit.
- 14. A seal segment according to claim 11 wherein the path means comprises a single axial section.
- 15. A seal segment according to claim 1 wherein the path means includes a plurality of heat removal members.
- 16. A seal segment according to claim 15 wherein the heat removal members extend from a radially inner wall of the path means to a radially outer wall of the path means.
- 17. A seal segment ring for a turbine of a gas turbine engine, the seal segment ring being formed from a plurality of seal segments as claimed in claim 1.
- 18. A seal segment ring according to claim 17, wherein the path means of successive segments defines a plurality of axially extending cooling passages arranged side-by-side circumferentially around the seal ring to define an annulus of said cooling passages.
- 19. A turbine for a gas turbine engine incorporating a seal segment ring as claimed in claim 17.
- 20. A gas turbine engine incorporating a turbine as claimed in claim 19.
Priority Claims (1)
Number |
Date |
Country |
Kind |
0029337 |
Dec 2000 |
GB |
|
US Referenced Citations (12)
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Number |
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Country |
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Sep 1979 |
GB |
2168110 |
Jun 1986 |
GB |
2242710 |
Oct 1991 |
GB |
2245316 |
Jan 1992 |
GB |
WO 9412775 |
Jun 1994 |
WO |