U.S. patent application number 13/245173 was filed with the patent office on 2013-03-28 for steam turbine single shell extraction lp casing.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. The applicant listed for this patent is Rajendra GONOOR, Erik Eduardo LOPEZ PARTIDA, Daniel Ross PREDMORE. Invention is credited to Rajendra GONOOR, Erik Eduardo LOPEZ PARTIDA, Daniel Ross PREDMORE.
Application Number | 20130078089 13/245173 |
Document ID | / |
Family ID | 47828052 |
Filed Date | 2013-03-28 |
United States Patent
Application |
20130078089 |
Kind Code |
A1 |
PREDMORE; Daniel Ross ; et
al. |
March 28, 2013 |
STEAM TURBINE SINGLE SHELL EXTRACTION LP CASING
Abstract
A single shell extraction casing includes a stepped shell which
is formed from a plurality of circumferentially shaped ledge rings
located along the axial length of the casing between turbine stages
and covered by a casing wrapper. The stepped shell has a simpler
construction than the double shell configuration of a conventional
turbine extraction casing. Pockets for supporting diaphragms
between the multiple stages in the stepped single shell extraction
casing are connected directly between ledge rings so they are away
from the casing wrapper. This decreases the amount of welding and
manufacturing complexity needed to install the diaphragm support
pockets.
Inventors: |
PREDMORE; Daniel Ross;
(Schenectady, NY) ; GONOOR; Rajendra; (Bangalore,
IN) ; LOPEZ PARTIDA; Erik Eduardo; (Queretaro,
MX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
PREDMORE; Daniel Ross
GONOOR; Rajendra
LOPEZ PARTIDA; Erik Eduardo |
Schenectady
Bangalore
Queretaro |
NY |
US
IN
MX |
|
|
Assignee: |
GENERAL ELECTRIC COMPANY
Schenectaady
NY
|
Family ID: |
47828052 |
Appl. No.: |
13/245173 |
Filed: |
September 26, 2011 |
Current U.S.
Class: |
415/213.1 |
Current CPC
Class: |
F05D 2220/31 20130101;
F01D 9/02 20130101 |
Class at
Publication: |
415/213.1 |
International
Class: |
F01D 25/28 20060101
F01D025/28 |
Claims
1. A single shell turbine casing with stepped structure, the
turbine casing comprising: a plurality of ledge rings positioned
along an axial length of the turbine casing so as to be located
between a plurality of stages located within the turbine casing,
and a casing wrapper covering the outer circumferences of the
plurality of ledge rings, the plurality of ledge rings have varying
diameters so as to form the stepped structure of the casing.
2. The turbine casing of claim 1 further comprising a plurality of
diaphragm support pockets extending along an axial length of the
turbine casing.
3. The turbine casing of claim 2, wherein the casing is formed from
first and second halves joined together along a joint extending
along the axial length of the turbine casing, and wherein the
plurality of diaphragm support pockets extending along the joint
between the first and second halves.
4. The turbine casing of claim 2, wherein each of the plurality of
diaphragm support pockets is connected between a corresponding pair
of the plurality of ledge rings.
5. The turbine casing of claim 2, wherein each of the plurality of
diaphragm support pockets is connected between a corresponding pair
of the plurality of ledge rings so as to be mounted away from the
casing wrapper.
6. The turbine casing of claim 2 further comprising a plurality of
steam extraction pipes to which the turbine casing is connected,
and through which steam is extracted from the turbine casing.
7. The turbine casing of claim 1, wherein the plurality of ledge
rings are each substantially circular in shape.
8. The turbine casing of claim 7, wherein the turbine casing has a
dual conical shape formed by the smallest diameters of the varying
diameter ledge rings being located substantially in the center of
the axial length of casing.
9. The turbine casing of claim 8, wherein the single shell turbine
casing is a steam extraction casing for a dual axial flow steam
turbine.
10. The turbine casing of claim 9 further comprising an inlet pipe
through which steam enters the center of the turbine casing and
flows in two opposite directions through the turbine casing.
11. The turbine casing of claim 10, wherein the inlet pipe is
conical shaped.
12. The turbine casing of claim 1, wherein the casing is formed
from first and second halves, and wherein the single shell turbine
casing, by reason of its stepped structure, requires a number of
bolts to join together the casing's first and second halves that is
less than a number of bolts required to join together a dual shell
turbine casing that is formed from first and second halves and that
is comparable in size to the single shell turbine casing.
13. The turbine casing of claim 6 further comprising a plurality of
steam extraction pockets through which steam is extracted from an
interior of the single shell turbine casing's stepped
structure.
14. The turbine casing of claim 13 further comprising a plurality
of conduit areas connecting the plurality of steam extraction
pockets to at least a portion of the plurality of steam extraction
pipes.
15. The turbine casing of claim 14, wherein the plurality of
connecting conduit areas are located behind the plurality of
diaphragm support pockets and between the casing wrapper and an
inner wrapper extending between a portion of the plurality of ledge
rings.
16. The turbine casing of claim 15 further comprising a plurality
of openings in the casing wrapper through which steam passes from
the plurality of conduit areas into the steam extraction pipes.
17. The turbine casing of claim 16 further comprising a second
plurality of openings in the casing wrapper through which steam in
an interior of the turbine casing passes directly into the steam
extraction pipes.
18. A single shell turbine casing with stepped structure, the
turbine casing comprising: a plurality of ledge rings positioned
along an axial length of the turbine casing so as to be located
between a plurality of stages located within the turbine casing,
the plurality of ledge rings have varying diameters so as to form
the stepped structure of the casing, a casing wrapper covering the
outer circumferences of the plurality of ledge rings, a plurality
of diaphragm support pockets extending along an axial length of the
turbine casing, each of the plurality of diaphragm support pockets
being connected between a corresponding pair of the plurality of
ledge rings, and a plurality of steam extraction pockets through
which steam is extracted from an interior of the single shell
turbine casing's stepped structure, the plurality of steam
extraction pockets being connected to a plurality of steam
extraction pipes to which the turbine casing is connected by a
plurality of connecting conduit areas located behind the plurality
of diaphragm support pockets and between the casing wrapper and an
inner wrapper extending between a portion of the plurality of ledge
rings.
19. The turbine casing of claim 18, wherein the turbine casing is
formed from first and second halves, and wherein the single shell
turbine casing, by reason of its stepped structure, requires a
number of bolts to join together the casing's first and second
halves that is less than a number of bolts required to join
together a dual shell turbine casing that is formed from first and
second halves and that is comparable in size to the single shell
turbine casing.
20. A single shell turbine casing with stepped structure, the
turbine casing comprising: a plurality of ledge rings positioned
along an axial length of the turbine casing so as to be located
between a plurality of stages located within the turbine casing,
the plurality of ledge rings having varying diameters so as to form
the stepped structure of the casing, and a casing wrapper covering
the outer circumferences of the plurality of ledge rings, the
casing being formed from first and second halves joined together,
and wherein the single shell turbine casing, by reason of its
stepped structure, requires a number of bolts to join together the
casing's first and second halves that is less than a number of
bolts required to join together a dual shell turbine casing that is
formed from first and second halves and that is comparable in size
to the single shell turbine casing.
Description
[0001] The present invention relates to steam turbines, and more
particularly, to a turbine casing with a simpler structure
requiring less internal bolting to join together the casing's
halves.
BACKGROUND OF THE INVENTION
[0002] Steam turbines are machines that are used to generate
mechanical (rotational motion) power from the pressure energy of
steam. Steam turbines are typically comprised of a series of
different size stages. Each stage has a set of moving and fixed
blades. The moving blades are attached to the turbine's rotor,
while the stationary blades are called diaphragms. Each diaphragm
guides the steam to glide over the moving blades for the purpose of
producing rotary motion. To maximize turbine efficiency, the steam
is expanded as it flows through the turbine, generating work in the
multiple stages of the turbine.
[0003] In an extraction type turbine, steam is released from
various stages of the turbine, and used for industrial process
needs or sent to boiler feed water heaters to improve overall cycle
efficiency. Conventionally, an extraction turbine casing is
constructed in a double shell configuration due to the extractions.
To satisfy the extraction area the diaphragm pockets are supported
away from the turbine shell's major structure. However, several
problems with turbines of this type of construction are the weight
of the turbine casing, the amount of time needed to construct the
casing, and the complexity of the casing structure.
BRIEF DESCRIPTION OF THE INVENTION
[0004] The present invention is directed to constructing a turbine
extraction casing in a simpler manner using a single shell, instead
of a conventional double shell configuration. According to the
present invention, the inner casing of the turbine is a stepped
inner casing, instead of the conical and cylindrical casing used on
conventional extraction casings. Conventionally, extraction casings
are constructed using double shell configurations due to
extractions. To satisfy the extraction area, the diaphragm pockets
are supported away from the turbine's shell major structure.
According to the present invention, instead of building of one more
shells inside the casing, small diaphragm pockets are built, as
required, so as to build a simpler structure. The extraction casing
is simplified by eliminating the complexity of the conventional
structure through the use of a stepped inner casing. Use of the
stepped inner casing can also result in a significant reduction of
the amount of internal bolting needed to connect the two halves of
the casing together, which, in turn results in easier accessibility
to the internal components of the turbine. The shape and size of
the diaphragm support pockets and structure is also changed.
Pockets for supporting diaphragms between the multiple stages in
the stepped single shell extraction casing are connected directly
between ledge rings so they are away from the casing wrapper. This
decreases the amount of welding and manufacturing complexity needed
to install the diaphragm support pockets.
[0005] In an exemplary embodiment of the invention, a single shell
turbine casing with stepped structure comprises a plurality of
ledge rings positioned along an axial length of the turbine casing
so as to be located between a plurality of stages located within
the turbine casing, and a casing wrapper covering the outer
circumferences of the plurality of ledge rings, the plurality of
ledge rings have varying diameters so as to form the stepped
structure of the casing.
[0006] In another exemplary embodiment of the invention, a single
shell turbine casing with stepped structure comprises a plurality
of ledge rings positioned along an axial length of the turbine
casing so as to be located between a plurality of stages located
within the turbine casing, the plurality of ledge rings have
varying diameters so as to form the stepped structure of the
casing, a casing wrapper covering the outer circumferences of the
plurality of ledge rings, a plurality of diaphragm support pockets
extending along an axial length of the turbine casing, each of the
plurality of diaphragm support pockets being connected between a
corresponding pair of the plurality of ledge rings, and a plurality
of steam extraction pockets through which steam is extracted from
an interior of the single shell turbine casing's stepped structure,
the plurality of steam extraction pockets being connected to a
plurality of steam extraction pipes to which the turbine casing is
connected by a plurality of connecting conduit areas located behind
the plurality of diaphragm support pockets and between the casing
wrapper and an inner wrapper extending between a portion of the
plurality of ledge rings.
[0007] In a further exemplary embodiment of the invention, a single
shell turbine casing with stepped structure comprises a plurality
of ledge rings positioned along an axial length of the turbine
casing so as to be located between a plurality of stages located
within the turbine casing, the plurality of ledge rings having
varying diameters so as to form the stepped structure of the
casing, and a casing wrapper covering the outer circumferences of
the plurality of ledge rings, the casing being formed from first
and second halves joined together, and wherein the single shell
turbine casing, by reason of its stepped structure, requires a
number of bolts to join together the casing's first and second
halves that is less than a number of bolts required to join
together a dual shell turbine casing that is formed from first and
second halves and that is comparable in size to the single shell
turbine casing.
[0008] All together, the foregoing features result in a significant
impact on extraction inner casing design, manufacturing and cost,
resulting in a decrease in weight, manufacturing time and simpler
structure for the extraction casing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1A is a cross sectional elevational view of a
conventional double shell continuous cylindrical extraction casing
for a dual axial flow low pressure steam turbine.
[0010] FIG. 1B is a cross sectional perspective view of the bottom
half of the conventional cylindrical extraction casing shown in
FIG. 1A.
[0011] FIG. 2A is a cross sectional elevational view of a single
shell stepped extraction casing for a dual axial flow low pressure
steam turbine constructed according to the present invention.
[0012] FIG. 2B is a cross sectional perspective view of the bottom
half of the single shell stepped extraction casing shown in FIG.
2A.
DETAILED DESCRIPTION OF THE INVENTION
[0013] A low pressure (LP) turbine can be either single or dual
axial flow machine. An LP turbine is typically located next to a
high pressure (HP) turbine. In dual axial flow LP turbines, steam
enters the center of the turbine from a cross over pipe and flows
across the reaction blading in two opposite directions. The steam
flows parallel to the turbine's rotor and exhausts into a main
condenser.
[0014] FIG. 1A is a cross sectional, elevational view of a
conventional double shell continuous cylindrical extraction casing
10 for a dual axial flow LP steam turbine. FIG. 1B is a cross
sectional, perspective view of the bottom half of the conventional
cylindrical extraction casing 10 shown in FIG. 1A.
[0015] Extraction casing 10 has an upper half 11 and a lower half
13, which are bolted together along a horizontal joint 17 by a
plurality of bolts (not shown), so as to create a metal to metal
fit that is sealed. Extending along horizontal joint 17 are a
plurality of diaphragm support pockets 19 for supporting the
diaphragms (not shown) between the multiple stages 15 in casing
10.
[0016] The casing 10 includes a conical shaped inlet pipe 22
through which steam from a crossover pipe (not shown) enters the
center of the turbine casing 10 and flows across the reaction
blading in two opposite directions. This crossover pipe is
connected to inlet pipe 22 at an inlet crossover ring 21.
[0017] In an extraction type turbine, steam is released from
various stages of the turbine, and used for industrial process
needs or sent to boiler feedwater heaters to improve overall cycle
efficiency. Conventionally, an extraction casing is constructed in
a double shell configuration due to the extractions. Thus, casing
10 includes a continuous cylindrically shaped outer shell 12 with a
plurality of circumferentially shaped ledge rings 16 and a stepped
inner shell 14 with a plurality of circumferentially shaped ledge
rings 20. To satisfy the area needed for the extractions, the
diaphragm support pockets 19 are supported away from the major
structure of shell 12. The casing 10 is also connected to a
plurality of steam extraction pipes 24 through which steam is
extracted from casing 10.
[0018] Ledge rings 20 are connected together by axially extending
continuous internal ribs 18. Internal ribs 18 are circumferentially
shaped. The axially extending continuous internal ribs 18
connecting together the ledge rings 20 in the turbine's casing
serve to control axial deflections and mechanical stresses that may
occur in the casing 10. However, several problems with turbines of
the type of construction shown in FIGS. 1A and 1B are the weight of
the turbine casing, the amount of time needed to construct the
casing, and the complexity of the casing structure. For example, a
turbine casing of the type shown in FIGS. 1A and 1B requires a
large amount of internal bolting to join together the casing's
halves 11 and 13.
[0019] FIG. 2A is a cross sectional, elevational view of a single
shell stepped extraction casing 30 for a dual axial flow steam
turbine, such as an LP steam turbine.
[0020] Casing 30 has an upper half 31 and a lower half 33, which
are bolted together at a horizontal joint 35 by a plurality of
bolts (not shown) so as to create a metal to metal fit that is
sealed. FIG. 2B is a cross sectional, perspective view of the
bottom half 33 of casing 30 shown in FIG. 2A. The single shell
stepped extraction casing 30 shown in FIGS. 2A and 2B excludes the
axially extending continuous internal ribs 18 used with the casing
10 shown in FIGS. 1A and 1B.
[0021] The number of bolts needed to join together upper half 31
and a lower half 33 of casing 30 and seal horizontal joint 35 is
reduced due to the stepped structure of casing 30. This reduction
in the number of bolts needed is best seen by comparing the cross
sectional perspective view of the bottom half of the single shell
stepped extraction casing 30 shown in FIG. 2B with the cross
sectional perspective view of the bottom half of the conventional
cylindrical extraction casing shown in FIG. 1B.
[0022] The single shell extraction casing 30 includes a stepped
shell 34 which is formed from a plurality of circumferentially
shaped ledge rings 36 positioned between the turbine stages 44
located along the axial length of casing 30. The plurality of
circumferentially shaped ledge rings 36 have varying diameters so
as to form a stepped shell 34 having a dual conical shape with the
smallest circumferences being in the center of the axial length of
casing 30. Covering the outer circumferences of ledge rings 36 is a
casing wrapper 32. The stepped shell 34 is designed to have a
simpler construction than the double shell configuration of the
conventional turbine casing 10 shown in FIGS. 1A and 1B, which
includes the continuous cylindrically shaped outer shell 12 and the
stepped inner shell 14.
[0023] Casing 30 includes a conical shaped inlet pipe 39 through
which steam from a crossover pipe (not shown) enters the center of
the turbine casing 30 and flows across the reaction blading in two
opposite directions. The crossover pipe is connected to inlet pipe
39 at an inlet crossover ring 38. Surrounding inlet pipe 39 is an
inlet flange 49. In the center of inlet pipe 39 is a stiffening
plate 41.
[0024] Turbine extraction casings are conventionally done in double
shell configurations because of the steam extraction function they
perform. However, rather than building one or more shells inside a
turbine casing, in casing 30 shown in FIGS. 2A and 2B, small
diaphragm pockets 37 for supporting the diaphragms (not shown)
between the multiple stages 44 in casing 30 are built, as required,
with simpler structure along casing 30. As can be seen in FIGS. 2A
and 2B, a plurality of diaphragm support pockets 37 extend along
horizontal joint 35 of casing 30, and thus along the axial length
of casing 30. To satisfy the steam extraction area that may be
needed for a particular application or customer, the diaphragm
pockets 37 are supported away from the major structure of shell 34.
Stated differently, diaphragm support pockets 37 are connected
directly between the ledge rings 36 so that they are away from the
casing wrapper 32. This arrangement decreases the amount of welding
and manufacturing complexity needed to install the diaphragm
support pockets 37.
[0025] As can be seen in FIGS. 2A and 2B, casing 30 is also
connected to a plurality of steam extraction pipes 40. Steam is
extracted from stepped shell 34 through extraction pockets 43,
after which it passes through conduit areas 45 behind diaphragm
support pockets and between outer casing wrapper 32 and an inner
wrapper 42 extending between some of the ledge rings 36. The steam
in conduit areas 45 passes out of casing 30 through openings 46 in
casing wrapper 32 and into steam extraction pipes 40. Steam is also
extracted through additional openings 47 in casing wrapper 32.
[0026] 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.
* * * * *