U.S. patent application number 11/508170 was filed with the patent office on 2008-02-28 for singlet welded nozzle hybrid design for a turbine.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. Invention is credited to Steven Sebastian Burdgick, Thomas William Crall, Larry Duclos, Thomas Patrick Russo.
Application Number | 20080050222 11/508170 |
Document ID | / |
Family ID | 38457865 |
Filed Date | 2008-02-28 |
United States Patent
Application |
20080050222 |
Kind Code |
A1 |
Burdgick; Steven Sebastian ;
et al. |
February 28, 2008 |
Singlet welded nozzle hybrid design for a turbine
Abstract
A singlet welded nozzle hybrid design that includes a singlet,
that is, a single airfoil with respective inner and outer sidewall
components. The outer sidewall component is received in a radial
and circumferential groove of an outer carrier. The connection of
the inner sidewall can be achieved by mechanically fitting and
welded the inner sidewalls to either a seal carrier or a small
ring, or a small radial weld may be provided between the sidewall
endfaces of circumferentially adjacent singlets.
Inventors: |
Burdgick; Steven Sebastian;
(Schenectady, NY) ; Crall; Thomas William;
(Clifton Park, NY) ; Duclos; Larry; (Thorndike,
ME) ; Russo; Thomas Patrick; (Galway, NY) |
Correspondence
Address: |
NIXON & VANDERHYE P.C.
901 NORTH GLEBE ROAD, 11TH FLOOR
ARLINGTON
VA
22203
US
|
Assignee: |
GENERAL ELECTRIC COMPANY
Schenectady
NY
|
Family ID: |
38457865 |
Appl. No.: |
11/508170 |
Filed: |
August 23, 2006 |
Current U.S.
Class: |
415/170.1 |
Current CPC
Class: |
F01D 9/042 20130101;
F05D 2230/232 20130101; F01D 11/006 20130101; F01D 9/041 20130101;
F05D 2240/56 20130101 |
Class at
Publication: |
415/170.1 |
International
Class: |
F04D 29/08 20060101
F04D029/08 |
Claims
1. A turbine comprising: a turbine nozzle segment having at least
one stator airfoil, an inner sidewall at a radially inner end of
the stator airfoil, and an outer sidewall structure at the radially
outer end of said stator airfoil, a radially inner surface of the
inner sidewall having a circumferential groove defined therein, and
a complimentary ring component having a key portion for being
received in said circumferential groove, said ring component
extending at least part circumferentially of an axis of the turbine
to engage an inner sidewall of at least two respectively adjacent
nozzle inner sidewalls, wherein the ring component is mechanically
secured to the nozzle inner sidewalls.
2. A turbine as in claim 1, wherein the ring component is welded to
the nozzle inner sidewalls.
3. A turbine as in claim 1, wherein said ring component comprises a
seal carrier.
4. A turbine as in claim 3, wherein said seal carrier is a
brush-type seal carrier.
5. A turbine as in claim 3, wherein said seal carrier is a
laminated-type seal carrier.
6. A turbine as in claim 3, wherein said seal carrier is welded to
said nozzle inner sidewall.
7. A turbine as in claim 3, wherein a radial bolt is disposed to
extend through said seal carrier and into said nozzle inner
sidewall.
8. A turbine as in claim 1, wherein a radial bolt is disposed to
extend through said ring component and into said nozzle inner
sidewall.
9. A turbine as in claim 1, wherein said outer sidewall is slidably
disposed in a nozzle carrier of the turbine.
10. A turbine as in claim 9, wherein the outer sidewall is welded
to a solid ring disposed radially outwardly of said turbine nozzle
and extending circumferentially about a plurality of said nozzle
segments.
11. A turbine comprising: a turbine nozzle segment having at least
one stator airfoil and including an inner sidewall at a radially
inner end of the stator airfoil and an outer sidewall structure at
the radially outer end of said stator airfoil; and an outer ring
carrier having a radially inwardly open groove; wherein said outer
sidewall is configured to slideably engage said groove in a radial
direction while being restricted from moving in an axial direction
with respect thereto, and the inner sidewall is mechanically
coupled to circumferentally adjacent turbine nozzle segments.
12. A turbine as in claim 11, wherein said outer sidewall is welded
to an outer ring that is slideably received in said groove with
said outer sidewall.
13. A turbine as in claim 12, wherein said outer sidewall has a
flat radially outer face that engages a flat radially inner face of
said outer ring.
14. A turbine as in claim 12, wherein outer ring extends part
circumferentially and is welded to a plurality of said outer
sidewalls.
15. A turbine as in claim 11, respectively adjacent nozzle inner
sidewall endfaces of said circumferentally adjacent turbine nozzle
segments are welded or braised together.
16. A turbine as in claim 11, wherein said inner sidewall has a
circumferential groove defined therein and a complimentary ring
component having a key portion for being received in said
circumferential groove, said ring component extending at least part
circumferentially of an axis of the turbine to engage an inner
sidewall of at least two respectively adjacent turbine nozzle
segments, and wherein the ring component is mechanically secured to
the nozzle inner sidewalls.
17. A turbine as in claim 16, wherein the ring component is welded
to the nozzle inner sidewalls.
18. A turbine comprising: a turbine nozzle segment having at least
one stator airfoil and including an inner sidewall at a radially
inner end of the stator airfoil and an outer sidewall structure at
the radially outer end of said stator airfoil, wherein respectively
adjacent nozzle inner sidewall endfaces are welded or braised
together.
19. A turbine as in claim 18, wherein said outer sidewall is
slidably disposed in a circumferential groove defined in a nozzle
carrier of the turbine.
20. A turbine as in claim 19, wherein said outer sidewall is welded
to an outer ring that is slideably received in said circumberential
groove with said outer sidewall.
Description
BACKGROUND OF THE INVENTION
[0001] Steam turbine designs consist of static nozzle segments that
direct the steam flow into rotating buckets that are connected to a
rotor. In steam turbines, the nozzle construction is typically
called a diaphragm stage. Typical diaphragm stages are constructed
using one of two methods. The first method is a "band/ring" method
that uses an assembly comprised of a plurality of airfoils
contained in inner and outer bands and then that banded airfoil
assembly is welded into inner (web) and outer rings. The second
method involves welding airfoils directly to inner and outer rings
using a fillet weld at the interface. The second method is
typically used for larger airfoils, where access for creating the
weld is possible. However, there are also limitations to using the
band construction on smaller stages. One drawback is the inherent
weld distortion of both the flow path and the steam path sidewalls.
In this regard, the weld used for the assembly is of considerable
size and heat input. This material and heat input causes the flow
path to distort and the airfoils often need to be adjusted after
welding and stress relief. The result of the distortion is reduced
stage efficiency.
[0002] In turbines, thermally induced stresses have always led to
cracking in turbine nozzles. Due to the harsh environment, previous
field history has shown cracking along the engine axial (chordwise)
direction of nozzle airfoils. Should a crack propagate through the
entire length of an airfoil, such that the airfoil fails
catastrophically, large pieces of the nozzle might dislodge and
move downstream into a turbine's rotating hardware. The subsequent
damage to the turbine's hardware (both rotating and static) can be
both extreme and costly.
[0003] In doublet or triplet nozzle designs (2 or 3 airfoils per
nozzle segment, respectively), the increased number of airfoils
provides a certain amount of insurance against catastrophic failure
through the redundancy of multiple load paths. However, with a
singlet design (one airfoil per nozzle segment), if not retained at
both platforms, a large section of nozzle (airfoil and/or platform)
could be lost into the flowpath if the airfoil were to crack
completely in two.
BRIEF DESCRIPTION OF THE INVENTION
[0004] The invention provides a singlet welded nozzle hybrid design
which inter alia addresses the distortion problem noted above. More
particularly, in an example embodiment of the invention a
construction is provided wherein a singlet (single airfoil with
sidewalls) is seated directly in a radial and circumferential
groove of an outer carrier or welded to an outer ring and seated
with in a groove of an outer carrier. The inner connection is
effected with a unique inner sidewall construction. In one example
embodiment, the inner sidewalls are mechanically fit and welded to
a circumferentially extending ring, or to one another via a small
radial weld between inner sidewall endfaces (slashfaces).
[0005] Thus, the invention may be embodied in a turbine comprising:
a turbine nozzle segment having at least one stator airfoil, an
inner sidewall at a radially inner end of the stator airfoil, and
an outer sidewall structure at the radially outer end of said
stator airfoil, a radially inner surface of the inner sidewall
having a circumferential groove defined therein, and a
complimentary ring component having a key portion for being
received in said circumferential groove, said ring component
extending at least part circumferentially of an axis of the turbine
to engage an inner sidewall of at least two respectively adjacent
nozzle inner sidewalls, wherein the ring component is mechanically
secured to the nozzle inner sidewalls.
[0006] The invention may also be embodied in a turbine comprising:
a turbine nozzle segment having at least one stator airfoil and
including an inner sidewall at a radially inner end of the stator
airfoil and an outer sidewall structure at the radially outer end
of said stator airfoil; and an outer ring carrier having a radially
inwardly open groove; wherein said outer sidewall is configured to
slideably engage said groove in a radial direction while being
restricted from moving in an axial direction with respect thereto,
and the inner sidewall is mechanically coupled to circumferentally
adjacent turbine nozzle segments.
[0007] The invention may also be embodied in a turbine comprising:
a turbine nozzle segment having at least one stator airfoil and
including an inner sidewall at a radially inner end of the stator
airfoil and an outer sidewall structure at the radially outer end
of said stator airfoil, wherein respectively adjacent nozzle inner
sidewall endfaces are welded or braised together.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a schematic elevational view of a conventional
stage having a nozzle diaphragm formed using the band/ring
method;
[0009] FIG. 2 is a schematic elevational view of a singlet
construction according to an example embodiment of the
invention;
[0010] FIG. 3 is a schematic elevational view of the radially inner
end of a singlet construction having a brush-type seal according to
an example embodiment of the invention;
[0011] FIG. 4 is a schematic elevational view of the radially inner
end of a singlet construction having a laminated-type seal
according to another example embodiment of the invention;
[0012] FIG. 5 is a schematic elevational view of the radially inner
end of a singlet construction having a brush type seal according to
yet another example embodiment of the invention;
[0013] FIG. 6 is a schematic elevational view of the radially inner
end of a singlet construction according to a further example
embodiment of the invention;
[0014] FIG. 7 is a schematic elevational view of a singlet
construction according to another example embodiment of the
invention;
[0015] FIG. 8 is a schematic elevational view of a singlet
construction according to yet another example embodiment of the
invention; and
[0016] FIG. 9 is an axial view illustrating adjacent singlet
nozzles welded at inner sidewall endfaces according to a further
example embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0017] FIG. 1 shows the traditional construction of an impulse type
turbine stage that uses partition, bands and rings welded into an
assembly. More specifically, this traditional construction uses a
diaphragm assembly 10 comprised of a plurality of airfoils 12
contained in inner and outer bands 14, 16 that is welded as at 18,
20, 22, 24 into an inner ring (web) 26 and an outer ring 28.
[0018] As noted above, current methods of construction
incorporating single nozzle constructions into rings do not have
determinant weld depth, lack assembly alignment features, and also
lack retainment features in the event of weld failure.
Additionally, one major issue with current methods of diaphragm
construction is that they can cause significant flow path
distortion. Indeed, traditional singlet nozzle assemblies may use
high heat input weld methods that cause undesired flow path
distortion.
[0019] The present invention improves the steam path flow path of
the stator nozzle (diaphragm) components. This is done with a
simplified, determinant, low heat input singlet welded assembly
using novel approaches at the inner sidewall connection such as,
for example, welded endwalls, low heat input seal welds with
mechanical lock, or small ring key welded to inner sidewalls, as
described hereinbelow. The invention also improves the production
cost and cycle by adding features that assist in assembly
procedures and that assist in machining fixturing. Further, the
invention adds features that reduce the risk of unintended turbine
shut down due to hardware weld failure.
[0020] The singlet welded nozzle hybrid design provided according
to example embodiments of the invention creates a construction that
includes a singlet, that is, a single airfoil with respective inner
and outer sidewall components. The outer sidewall component
mechanically fit and then welded to an outer ring carrier.
[0021] The connection of the inner sidewall can be achieved in
several ways. As described in various embodiments hereinbelow, the
inner sidewalls of the singlets of the diaphragm can be
mechanically fit and welded to either a seal carrier or a small
ring, or a small radial weld may be provided between the sidewall
endfaces (slashfaces) of circumferentially adjacent singlets. This
construction is suited primarily to nozzle constructions that are
considered reaction-type turbines or "drum" construction turbine
sections, characterized by much smaller axial spacing of the stages
and a typically increased number of stages.
[0022] FIG. 2 illustrates an example embodiment of the invention
wherein a singlet nozzle is slid into a carrier. The singlet is
comprised of an airfoil 30 and inner and outer sidewalls 32, 34. In
the embodiment of FIG. 2, an outer ring carrier 40 configured to
slideably engage and radially and axially mechanically lock to
outer sidewall 34. To that end, in the illustrated embodiment the
outer sidewall 34 is formed to extend radially for being received
in a circumferentially extending groove 42 of the outer ring
carrier 40. In the illustrated example embodiment, the axial end
faces of the outer sidewall 34 define first and second grooves 44,
46 that extend in a circumferential direction for receiving
corresponding axial protrusions 48, 50 in the ring carrier groove
42. There is no weld between the singlet 34 outer platform and the
carrier 40. These nozzles would be slid into the carrier in a
circumferential manner and welded only at the inner sidewall to the
inner ring, as described in greater detail below. These nozzles can
be singlets, doublets, or any other count slid into the groove 42.
If they are doublets or greater, then one could weld the singlet to
a partial outer ring (to form a doublet or greater count
sub-assembly) that has the carrier interface grooves in it (hybrid
design).
[0023] According to example embodiments, the radially inner
sidewalls 32 of circumferentially adjacent singlets are coupled.
According to certain example embodiments, an inner ring 52 may be
keyed and welded 54, 56 to the construction. The keyed inner ring
may define a seal carrier. According to another, alternative
example embodiment, the singlet inner sidewalls 32 are welded to
each other at their abutting endfaces. Examples the above mentioned
assemblies are described in greater detail below with reference to
FIGS. 3-6 and 9. These example embodiments are described using some
of the same reference numbers (used with reference to FIG. 2) and
with some corresponding reference numbers, but incremented by
multiples of 100, as appropriate.
[0024] FIG. 3 shows an example inner ring 152 disposed to extend at
least part circumferentially of the rotor, thereby to couple
circumferentially adjacent singlets. To define an
alignment/failsafe interface with the inner sidewalls 132, the
inner ring 152 includes a keyed protrusion 158 to engage a
corresponding cutout 160 of the inner sidewall 132. More
specifically, the singlets are retained axially by the inner ring
interfacing with the keyed cutout 160 of the inner sidewall. As
illustrated, a low heat ring weld (seal weld) 154, 156 is provided
between [each] nozzle inner sidewall and the seal carrier. This
weld is not necessarily meant to be a significant structural weld
as the mechanical interlock at the radially outer end (FIG. 2) will
hold the nozzle ends from moving downstream. In this regard, a
mechanical design as described allows welds that are very low heat
input to cause minimal distortion of the airfoil and steampath
surfaces.
[0025] In this example embodiment, the inner ring 152 is configured
to also comprise a seal carrier. The seal carrier is very small in
design such that it can fit in the small axial and radial spacing
typical of drum construction turbine types. This is generally
different from the significant real estate required to hold the
traditional packing segments at the rotor interface. Thus, the
proposed carrier would facilitate the more advanced seals, i.e.,
brush seals, shingle type seals or abradable seals. This carrier
could also be coated with abradable spray prior to assembly and the
small seal welds could be machined away for ring removal when a
repair (re-coat) is required. In the example embodiment of FIG. 3,
the inner seal carrier ring 152 carries a brush-type seal structure
162.
[0026] FIG. 4 shows an alternate inner seal carrier ring 252,
having a laminated-type seal 262. Again, a keyed interface 258/260
is provided between the seal carrier ring 252 and the inner
sidewalls 232. Also, low heat ring welds (seal welds) 254, 256 are
provided upstream and downstream, as illustrated, to fix the inner
seal carrier ring 252 to the inner sidewalls 232 of the respective
series of singlet nozzles.
[0027] FIG. 5 depicts yet another embodiment of the inner carrier
ring 352 that is retained axially as in the embodiments of FIGS. 3
and 4 by the interface of the inner seal carrier ring 352 with a
keyed cutout 360 of the inner sidewall 332. As illustrated, in this
embodiment, rather than provided ring welds 54, 56 as described
with reference to the embodiments of FIGS. 2, 3, and 4, the seal
carrier ring 352 has radial bolts 364 into the inner sidewall 332
and airfoil 330 to hold the carrier ring 352 in place with respect
to the singlet nozzles. In this example, the seal carrier ring 352
incorporates a brush-type seal 362, although the illustrated radial
fastening could be incorporated in other inner ring structures
without departing from this invention.
[0028] FIG. 6 illustrates yet a further alternate embodiment of the
invention wherein a key ring 452 is provided but the seal carrier
aspect is omitted in its entirety. Thus, in this embodiment, the
nozzle inner sidewalls each have a key notch or groove 460 defined
circumferentially therethrough and the key ring 452 is seated in
the circumferential groove 460 and welded in place with a low heat
ring welds (seal welds) 454, 456. The welded key ring thus
circumferentially integrates the nozzle singlets with both a welded
and mechanical interlock.
[0029] As mentioned above with reference to FIG. 3, in a first
example embodiment, the nozzles, or more specifically, the nozzle
outer sidewalls are respectively slid into a carrier thereby
providing a radial and axial lock at the outer end of the nozzles.
FIG. 7 shows a further alternate embodiment wherein the singlet
nozzle outer sidewall 534 is welded to a solid outer ring 538 is
using small axial welds forward and aft 566, 568. The assembly of
the singlet nozzle and outer ring is then seated in a corresponding
groove 542 of the nozzle carrier 540. The nozzle assembly (outer
ring 538 and nozzle(s) welded thereto) are not welded to the
carrier; the nozzle assembly can move radially in the carrier
groove 542. Thus, in this embodiment, the carrier 540 does not have
circumferential grooves as is typical in a reaction turbine design
that uses slid-in nozzles.
[0030] The mechanical features of the interface between the singlet
and the outer ring 538 are used as an assembly and alignment
feature and allow for improved reliability and risk abatement. In
this regard, the mechanical lock between the ring and nozzle(s)
means that, in the even of failure of an airfoil, the rings and
nozzles cannot go downstream as there is a mechanical interference
preventing the assembly from failing due to the pressure.
Additionally, the mechanical lock serves the purpose of a
pre-determined and repeatable weld stop. In this regard, the weld
beam (assuming an EB weld) would stop when it hits the radial
interlock interface. A further advantage of the FIG. 7 embodiment
is that the radially outer face of the nozzle outer sidewall is
configured as a flat end instead of a more costly circumferentially
cut end as in the embodiment of FIG. 2.
[0031] The example embodiment of FIG. 7 has an inner ring 552 that
is mechanically locked and braised or welded to the nozzle inner
sidewall 532, as in the embodiments of FIGS. 2-4 and 6, or just
mechanically locked to the nozzle, as in the embodiment of FIG.
5.
[0032] FIGS. 8 and 9 depict yet a further example embodiment of the
invention. More particularly, FIG. 8 shows a side view of the
singlet nozzle welded as in the FIG. 7 embodiment to an outer ring
538 at the radially outer sidewall 534. On the radially inner end,
however, rather than providing a ring seal 552 as in the FIG. 7
embodiment, the inner sidewall 632 endfaces 670 are welded to each
other. Thus, FIG. 9 shows in an axial view the inner sidewall
endwalls/slashfaces respectively welded together. It is envisioned
that this weld would be a low heat input weld similar to a butt
weld done with a Laser weld or Electron Beam weld (EBW). This
interface could also be considered for a braise joint should it be
considered more economical. The goal of this radial weld is to
create the continuous coupling of the inner sidewall. This weld
does not necessarily need to be a structural weld but more to cause
zero gap between the nozzle segment inner sidewalls (endfaces).
[0033] While as mentioned above the typical singlet nozzle outer
wall interface is a circumferentially cut end, it is to be
understood that as an alternative the singlet nozzle outer sidewall
interface may be machined as a flat end which is less costly than a
circumferential cut end.
[0034] While the invention has been described in connection with
what is presently considered to be the most practical and preferred
embodiment, it is to be understood that the invention is not to be
limited to the disclosed embodiment, but on the contrary, is
intended to cover various modifications and equivalent arrangements
included within the spirit and scope of the appended claims.
* * * * *