Title: Turbine engine sealing device
Abstract: A sealing system for reducing a gap between a tip of a turbine blade and a shroud of a turbine engine. As a turbine engine reaches steady state operating conditions, components of the sealing system reach their maximum expansion and reduce the size of the gap located between the blade tips and the engine shroud, thereby reducing the leakage of air past the turbine blades and increasing the efficiency of the turbine engine. The sealing system includes a ring segment having a sealing surface positioned proximate to a tip of a turbine blade. The ring segment may be coupled to a blade ring using a spindle having a coefficient of thermal expansion greater than the coefficient of thermal expansion for the blade ring.
Patent Number: 6,896,484 Issued on 05/24/2005 to Diakunchak
| Inventors:
|
Diakunchak; Ihor S. (Oviedo, FL)
|
| Assignee:
|
Siemens Westinghouse Power Corporation (Orlando, FL)
|
| Appl. No.:
|
661699 |
| Filed:
|
September 12, 2003 |
| Current U.S. Class: |
415/173.1; 416/189; 416/191 |
| Intern'l Class: |
F01D 011/08 |
| Field of Search: |
415/136,173.1
416/189,191
|
References Cited [Referenced By]
U.S. Patent Documents
| 3756738 | Sep., 1973 | Lee.
| |
| 3982850 | Sep., 1976 | Jenkinson.
| |
| 4050843 | Sep., 1977 | Needham et al.
| |
| 4527385 | Jul., 1985 | Jumelle et al.
| |
| 4557704 | Dec., 1985 | Ito et al.
| |
| 4578942 | Apr., 1986 | Weiler.
| |
| 5098257 | Mar., 1992 | Hultgren et al.
| |
| 5161908 | Nov., 1992 | Yoshida et al.
| |
| 5228828 | Jul., 1993 | Damlis et al.
| |
| 5333993 | Aug., 1994 | Stueber et al.
| |
| 6072661 | Jun., 2000 | Schirle.
| |
| 6206378 | Mar., 2001 | Sakata et al.
| |
| 6406256 | Jun., 2002 | Marx.
| |
| 6463729 | Oct., 2002 | Magoshi et al.
| |
| 6733235 | May., 2004 | Alford et al.
| |
| Foreign Patent Documents |
| 2381048 | Apr., 2003 | GB.
| |
Primary Examiner: Lopez; F. Daniel
Assistant Examiner: Kershteyn; Igor
Claims
1. A sealing system for reducing a gap between a tip of a turbine blade and a
shroud of a turbine engine, comprising:
a turbine blade assembly having at least one stage formed from a plurality of
turbine blades;
a blade ring radially surrounding the turbine blade assembly such that the blade
ring may radially expand and contract during operation as a result of thermal expansion
or contraction;
a ring segment having at least one ring segment sealing surface positioned in
close proximity to at least one tip of the plurality of turbine blades of the turbine
blade assembly such that the ring segment forms a gap between the at least one
ring segment sealing surface and the plurality of blades;
a spindle fixed to the blade ring at a first end of the spindle and coupled to
the ring segment at a second end of the spindle for supporting and positioning
the ring segment in close proximity with at least one tip of the plurality of blades; and
wherein the spindle is formed from a material having a coefficient of thermal
expansion that is greater than a coefficient of thermal expansion for a material
forming the blade ring.
2. The sealing system of claim 1, wherein the spindle is substantially parallel
to a radial axis extending from an axis of rotation of the turbine blade assembly.
3. The sealing system of claim 1, wherein the ring segment is supported solely
by a single spindle.
4. The sealing system of claim 3, wherein the ring segment is supported solely
by a single spindle coupled to the ring segment substantially at a center point
of the ring segment.
5. The sealing system of claim 1, further comprising an isolation ring positioned
between the ring segment and the blade ring and at least one web coupled to the
ring segment for sealing the ring segment to the isolation ring.
6. The sealing system of claim 1, wherein the at least one web coupled to the
ring segment extends away from the at least one ring segment sealing surface, is
substantially parallel to the spindle, and has a sealing portion at a first end
of the at least one web, which is opposite to a second end of the at least one
web coupled to the ring segment, that is generally parallel with the at least one
ring segment sealing surface.
7. The sealing system of claim 1, wherein the at least one ring segment sealing
surface is substantially parallel with at least one tip of at least one blade of
the plurality of blades forming the blade assembly.
8. A sealing system for reducing a gap between a tip of a turbine blade and a
shroud of a turbine engine, comprising:
a turbine blade assembly having at least one stage formed from a plurality of
turbine blades;
a blade ring radially surrounding the turbine blade assembly such that the blade
ring may radially expand and contract during operation as a result of thermal expansion
or contraction;
a ring segment having at least one ring segment sealing surface positioned in
close proximity to at least one tip of the plurality of turbine blades of the turbine
blade assembly such that the ring segment forms a gap between the at least one
ring segment sealing surface and the plurality of blades;
a spindle fixed to the blade ring at a first end of the spindle and coupled to
the ring segment at a second end of the spindle for supporting and positioning
the ring segment in close proximity with at least one tip of the plurality of blades;
wherein the spindle is substantially parallel to a radial axis extending from
an axis of rotation of the turbine blade assembly; and
wherein the spindle is formed from a material having a coefficient of thermal
expansion that is greater than a coefficient of thermal expansion for a material
forming the blade ring.
9. The sealing system of claim 8, wherein the ring segment is supported solely
by a single spindle.
10. The sealing system of claim 9, wherein the ring segment is supported solely
by a single spindle coupled to the ring segment substantially at a center point
of the ring segment.
11. The sealing system of claim 8, further comprising an isolation ring positioned
between the ring segment and the blade ring and at least one web coupled to the
ring segment for sealing the ring segment to the isolation ring.
12. The sealing system of claim 8, wherein the at least one web coupled to the
ring segment extends away from the at least one ring segment sealing surface, is
substantially parallel to the spindle, and has a sealing portion at a first end
of the at least one web, which is opposite to a second end of the at least one
web coupled to the ring segment, that is generally parallel with the at least one
ring segment sealing surface.
13. The sealing system of claim 8, wherein the at least one ring segment sealing
surface is substantially parallel with at least one tip of at least one blade of
the plurality of blades forming the blade assembly.
14. A method for reducing a gap between a tip of a turbine blade in a turbine
engine and a ring segment forming a portion of a shroud surrounding the turbine
blade, comprising:
coupling a blade ring to a turbine casing such that the blade ring may radially
expand and contract during operation as a result of thermal expansion or contraction
and surrounds the plurality of turbine blades of the turbine blade assembly;
coupling a ring segment to the blade ring using a spindle, wherein the spindle
is coupled to the blade ring at a first end of the spindle and is coupled to the
ring segment at a second end of the spindle for supporting the ring segment and
positioning at least one ring segment sealing surface of the ring segment in close
proximity with at least one tip of the turbine blade to form a gap, wherein the
spindle is formed from a material having a coefficient of thermal expansion that
is greater than a coefficient of thermal expansion for a material forming the blade
ring; and
heating at least the ring segment and the spindle, which causes the spindle to
lengthen at a greater rate than the blade ring and move the at least one ring segment
sealing surface.
15. The method of claim 14, wherein coupling the ring segment to the blade ring
using a spindle further comprises using a spindle positioned substantially parallel
to a radial axis extending from an axis of rotation of the turbine blade assembly.
16. The method of claim 14, wherein coupling the ring segment to the blade ring
using a spindle further comprises attaching the spindle to the center of the ring segment.
Description
FIELD OF THE INVENTION
This invention is directed generally to turbine engines, and more particularly
to systems for sealing gaps between blade tips and shrouds in turbine engines.
BACKGROUND
Typically, gas turbine engines are formed from a combustor positioned
upstream from a turbine blade assembly. The turbine blade assembly is formed from
a plurality of turbine blade stages coupled to discs that are capable of rotating
about a longitudinal axis. Each turbine blade stage is formed from a plurality
of blades extending radially about the circumference of the disc. Each stage is
spaced apart from each other a sufficient distance to allow turbine vanes to be
positioned between each stage. The turbine vanes are typically coupled to the shroud
and remain stationary during operation of the turbine engine.
The tips of the turbine blades are located in close proximity to an inner surface
of the shroud of the turbine engine. There typically exists a gap between the blade
tips and the shroud of the turbine engine so that the blades may rotate without
striking the shroud. During operation, high temperature and high pressure gases
pass the turbine blades and cause the blades and disc to rotate. These gases also
heat the shroud and blades and discs to which they are attached causing each to
expand due to thermal expansion. After the turbine engine has been operating at
full load conditions for a period of time, the components reach a maximum operating
condition at which maximum thermal expansion occurs. In this state, it is desirable
that the gap between the blade tips and the shroud of the turbine engine be as
small as possible to limit leakage past the blade tips.
However, reducing the gap cannot be accomplished by simply positioning the
components so that the gap is minimal under full load conditions because the configuration
of the components forming the gap must account for emergency shutdown conditions
in which the shroud, having less mass than the turbine blade and disc assembly,
cools faster than the turbine blade assembly. In emergency shutdown conditions,
the diameter of the shroud reduces at a faster rate than the length of the turbine
blades. Therefore, unless the components have been positioned so that a sufficient
gap has been established between the turbine blades and the turbine shroud under
operating conditions, the turbine blades strike the shroud because the diameter
of the shroud is reduced at a faster rate than the turbine blades. Collision of
the turbine blades and the shroud often causes catastrophic results. Thus, a need
exists for a system for reducing gaps between turbine blade tips and a surrounding
shroud under full load operating conditions while accounting for necessary clearance
under emergency shutdown conditions.
SUMMARY OF THE INVENTION
This invention relates to a sealing system for reducing a gap between a tip
of a turbine blade and a shroud of a turbine engine. As a turbine engine reaches
steady state operation, components of the sealing system reach their maximum expansion
and reduce the size of the gap located between the blade tips and the engine shroud,
thereby reducing the leakage of air past the turbine blades and increasing the
efficiency of the turbine engine. In at least one embodiment, the sealing system
includes a turbine blade assembly having at least one stage formed from a plurality
of turbine blades. The sealing system also includes a blade ring radially surrounding
the turbine blade assembly such that the blade ring may radially expand and contract
during operation as a result of thermal expansion or contraction. A ring segment
having at least one surface positioned in close proximity to at least one tip of
the turbine blade assembly may be positioned such that the ring segment forms a
gap between the at least one surface of the ring segment and the plurality of blades.
A spindle may be fixed to the blade ring at a first end of the spindle and coupled
to the ring segment at a second end of the spindle for supporting and positioning
the ring segment in close proximity with at least one tip of the plurality of blades.
The spindle may be formed from a material having a coefficient of thermal expansion
that is greater than a coefficient of thermal expansion for a material forming
the ring segment.
While the turbine engine is at rest, there exists a gap between the blade tips
and the ring segments. During operation, the ring segments reach maximum operating
temperature before the turbine blade assembly. As the ring segments are heated,
the spindle lengthens a greater amount than the blade ring. In other words, the
length of the spindle increases a greater distance than the diameter of the blade
ring increases. As a result, the ring segment attached to the end of the spindle
undergoes a net radial displacement towards the tips of the blades. As the turbine
blade assembly reaches its maximum operating temperature, the blades lengthen to
their steady state operating positions. Operating a turbine engine using this sealing
system reduces the gap between the tips of the turbine blades and the ring segments
by about 0.04 inches to about 0.05 inches, depending on the difference in thermal
expansion coefficients between the spindle and the blade ring. The larger the difference
in coefficients of the spindle and the blade ring, the larger the reduction in
gap spacing. Upon shutdown, even in emergency conditions, the ring segment undergoes
a net radial displacement away from the blade tips, thereby preventing the blade
tips from contacting the ring segments.
An advantage of this invention is that the size of the gap between blade tips
and shrouds of turbine engines may be reduced without introducing the possibility
that the blade tips may contact the shroud, thereby damaging the turbine engine.
These and other embodiments are described in more detail below.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and form a part of the specification,
illustrate embodiments of the presently disclosed invention and, together with
the description, disclose the principles of the invention.
FIG. 1 is a perspective view of an embodiment of this invention.
FIG. 2 is a side view of the embodiment of this invention taken at 2—2
in FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
As shown in FIGS. 1–2, this invention is directed to a sealing system
10
for a turbine engine. In particular, the sealing system
10 is operable to
reduce a gap
12 between one or more tips
14 of a turbine blade
16
in a turbine engine
18 and a surrounding shroud
20 while the turbine
engine
18 is operating. The gap
12 exists in the turbine engine
18
so that the tips
14 do not contact the shroud
20. In at least one
embodiment, the turbine engine
18 includes a turbine blade assembly
22
formed at least in part from a plurality of turbine blades
16 coupled to
a disc
24. The blades
16 may be coupled to the disc
24 at
various points along the disc
24 and may be assembled into rows, which are
commonly referred to as stages
23, having adequate spacing to accommodate
stationary vanes between adjacent stages of the blades
16. The stationary
vanes are typically mounted to a casing of the turbine engine
18. The disc
24 may be rotatably coupled to the turbine engine
18.
The turbine engine
18 may also include a plurality of blade rings
26.
The blade rings
26 may be positioned radially surrounding the turbine blade
assembly
22 such that the blade ring
26 may radially expand and contract
during operation as a result of thermal expansion or contraction. The size and
configuration of the blade rings
26 depend on the size and configuration
of the turbine engine
18.
A ring segment
28 may be coupled to a blade ring
26 using a spindle
30. The ring segment
28 may have at least one sealing surface
32
positioned in close proximity to at least one tip
14 of the plurality of
turbine blades
16 of the turbine blade assembly
22. The ring segment
28 may be positioned so that a gap
12 is formed between the tips
14 of the turbine blades
16 and the ring segment
28.
In at least one embodiment, the ring segment
28 may be supported by a
single
spindle
30. The spindle
30 may be attached to the ring segment
28
substantially at a center point
34 of the ring segment
28. The spindle
30 may be fixed to the blade ring
26 at a first end
36 and
coupled to the ring segment
28 at a second end
38 for supporting
and positioning the ring segment
28 in close proximity with at least one
tip
14 of the plurality of turbine blades
16. The spindle
30
may be fixed to the blade ring
26 at the first end
36 using one or
more bolts, welds, interference fits, or other appropriate mechanical connectors.
The spindle
30 may be fixed so that as the temperature of the spindle
30
increases, and the length of the spindle
30 thereby increases. As a result,
the second end
38 of the spindle
30 extends from the blade ring
26.
In at least one embodiment, the turbine blades
16 are substantially of equal
lengths and the ring segment
28 is positioned in close proximity to all
of the tips
14 of the turbine blades
16. In at least one embodiment,
the spindle
30 may be positioned substantially parallel to a radial axis
39 extending from an axis of rotation
40 of the turbine blade assembly
22. Spindle
30 may be formed from a material having a coefficient
of thermal expansion greater than a coefficient of thermal expansion for the material
forming the blade ring
26. For instance and not by way of limitation, the
spindle
30 may be formed from A286 disc alloy having a coefficient of thermal
expansion of about 9.7 inch per inch per degree Fahrenheit, and the blade ring
26 may be formed from IN909 having a coefficient of thermal expansion of
about 4.5 inch per inch per degree Fahrenheit.
In at least one embodiment, as shown in FIG. 2, a web
44 may be coupled
to the ring segment
28 and extend away from the sealing surface
32.
As shown in FIG. 1, the web
44 may extend circumferentially around the axis
of rotation
40 of the turbine blade assembly
22. As shown in FIG.
2, the web
44 may extend from the ring segment
28 such that the web
44 may be substantially parallel to the spindle
30. The web
44
may also include a sealing portion
46 that may be generally parallel to
the sealing surface
32 of the ring segment
28 and a hook
47
at a first end
48 that is opposite to the second end
50 coupled to
the ring segment
28. The spindle
30 may be coupled to the ring segment
28 using one or more bolts
61, or other suitable releasable mechanical
connections. In particular, a mechanical connector (not shown) may be passed through
an orifice
51 in the hook
47 and an orifice
53 in a flange
49 of the spindle
30 and coupled to the ring segment
28 to
attach the ring segment
28 to the spindle
30. In alternative embodiments,
the hook
47 may be discontinuous and may be present at intermittent locations
along the length of the web
44.
Under steady state operating conditions, the web
44 may thermally expand
toward an isolation ring
42 and seal the ring segment
28 to the isolation
ring
42 using a seal
45. The seal
45 may be, but is not limited
to, a spring seal, or other seal capable of withstanding the high temperatures
present in the turbine engine
18. The isolation ring
42 may extend
circumferentially around the axis of rotation
40 of the turbine blade assembly
22. The isolation ring
42 may be used to seal the ring segment
28
to the supporting turbine components. The isolation ring
42 may include
one or more channels
43 for positioning the seal
45 between the ring
segment
28 and the isolation ring
42.
During operation, the temperature of the turbine engine
18 increases,
which causes the blade ring
26, the ring segment
28, and the turbine
blades
16 forming the turbine blade assembly
22 to heat up. Each
of the blade ring
26, the ring segment
28, and the turbine blades
16 expand as the temperature of each component increases. In particular,
as the temperature of the turbine engine
18 increases, the length of each
turbine blade
16, the diameter of the blade ring
26, and the length
of the spindle
30 increase. Because the coefficient of thermal expansion
of the spindle
30 is greater than the coefficient of thermal expansion of
the blade ring
26, the ring segment
28 coupled to the spindle
30
undergoes a net positive radial displacement towards the tips
14 of the
turbine blades
16 even though the diameter of the blade ring
26 is
increasing. In other words, as the tip of the blades
16 lengthen towards
the ring segment
28, the sealing surface
32 of the ring segment
28
extends towards the tip of the turbine blades
16. This configuration results
in a steady state, hot running blade tip clearance reduction of between about 0.04
inches and about 0.05 inches, depending on the difference in coefficients of thermal
expansion between the spindle
30 and the blade ring
26.
In the event the turbine engine
18 is shutdown quickly, such as during
emergency shutdown, the spindle
30 cools more quickly than the turbine blade
assembly
22 because the spindle
30 has less mass than the turbine
blade assembly
22. As the spindle
30 cools, the ring segments
28
may be withdrawn toward the blade ring
26 so that the sealing surface
32
of the ring segment
28 does not contact the tips
14 of the turbine
blades
16. Because the coefficient of thermal expansion of the spindle
30
is greater than the coefficient of thermal expansion of the blade ring
26,
the spindle
30 is retracted a greater distance than the distance that the
blade ring
26 is reduced as the blade ring
26 cools. Thus, the gap
12 between the tips
14 of the turbine blades
16 and the sealing
surface
32 of the ring segment
28 is increased as the temperature
of the turbine engine
18 is reduced.
The foregoing is provided for purposes of illustrating, explaining, and describing
embodiments of this invention. Modifications and adaptations to these embodiments
will be apparent to those skilled in the art and may be made without departing
from the scope or spirit of this invention.
*
