U.S. patent application number 12/346348 was filed with the patent office on 2010-07-01 for methods, systems and/or apparatus relating to steam turbine exhaust diffusers.
Invention is credited to Norman D. Lathrop, Raymond K. Overbaugh, JR., Edward J. Sharrow.
Application Number | 20100162705 12/346348 |
Document ID | / |
Family ID | 42221135 |
Filed Date | 2010-07-01 |
United States Patent
Application |
20100162705 |
Kind Code |
A1 |
Sharrow; Edward J. ; et
al. |
July 1, 2010 |
METHODS, SYSTEMS AND/OR APPARATUS RELATING TO STEAM TURBINE EXHAUST
DIFFUSERS
Abstract
An axial flow steam turbine flow path that includes a rotor and
a casing defining the axial steam flow path; and a toroidal
diffuser for diffusing the exhaust steam and turning the exhaust
steam from a generally axial flow direction to a generally
transverse or vertical and tangential direction; wherein the
toroidal diffuser comprises a diffuser that, at least in part,
incorporates the shape of a toroid or a section of a toroid; and
wherein a toroid comprises the shape generated by revolving a
circular or oval shape in three dimensional space about an axis
coplanar with the circular or oval shape, which does not touch the
circular or oval shape.
Inventors: |
Sharrow; Edward J.; (Scotia,
NY) ; Lathrop; Norman D.; (Ballston Lake, NY)
; Overbaugh, JR.; Raymond K.; (Berne, NY) |
Correspondence
Address: |
GE ENERGY GENERAL ELECTRIC;C/O ERNEST G. CUSICK
ONE RIVER ROAD, BLD. 43, ROOM 225
SCHENECTADY
NY
12345
US
|
Family ID: |
42221135 |
Appl. No.: |
12/346348 |
Filed: |
December 30, 2008 |
Current U.S.
Class: |
60/697 ;
415/207 |
Current CPC
Class: |
F01D 25/30 20130101;
F05D 2250/20 20130101; F05D 2250/70 20130101 |
Class at
Publication: |
60/697 ;
415/207 |
International
Class: |
F01D 25/30 20060101
F01D025/30 |
Claims
1. An axial flow steam turbine flow path comprising: a rotor and a
casing defining the axial steam flow path; and a toroidal diffuser
for diffusing the exhaust steam and turning the exhaust steam from
a generally axial flow direction to a generally transverse or
vertical and tangential direction.
2. The flow path according to claim 1, wherein the toroidal
diffuser comprises a diffuser that, at least in part, incorporates
the shape of a toroid or a section of a toroid.
3. The flow path according to claim 1, wherein a toroid comprises
the shape generated by revolving a circular or oval shape in three
dimensional space about an axis coplanar with the circular or oval
shape, which does not touch the circular or oval shape.
4. The flow path according to claim 3, wherein a toroid comprises
the shape generated by revolving a circle in three dimensional
space about an axis coplanar with the circle, which does not touch
the circle.
5. The flow path according to claim 1, wherein a toroidal diffuser
comprises: a conical guide, which functions as the initial guide
for the steam as it exits the last turbine section; a toroidal
section, which defines the upper half of the main chamber of the
toroidal diffuser; and a rectilinear section, which defines the
lower half of the main chamber of the diffuser and provides a flow
path to an outlet.
6. The flow path according to claim 5, wherein the toroidal section
comprises approximately one half of a toroid shape.
7. The flow path according to claim 5, wherein the toroidal section
engages the rectilinear section at a circumferential location that
is approximately horizontal with the rotor.
8. The flow path according to claim 5, wherein the axis of the
toroid that forms the toroidal section comprises the rotor of the
turbine.
9. The flow path according to claim 5, wherein the upstream end of
the conical guide is coupled to the casing by a flexible joint; and
wherein the conical guide comprise an outer radial boundary for
steam exiting a final stage of the turbine.
10. The flow path according to claim 5, wherein the conical guide
includes an expanding conical shape such that the cross-sectional
diameter of the conical guide increases as the distance downstream
from the flexible joint increases.
11. The flow path according to claim 5, wherein at a downstream end
the conical guide comprises a flared lip.
12. The flow path according to claim 5, wherein the conical guide
extends into the toroidal section and the rectilinear section.
13. The flow path according to claim 12, wherein the conical guide
extends across approximately half the axial width of the toroidal
section and the rectilinear section.
14. The flow path according to claim 5, wherein an inner boundary
for the steam moving through the conical guide comprises a
cylindrical rotor plate that is disposed around the rotor of the
turbine, the cylindrical rotor plate comprising a smooth
cylindrical shape that substantially encloses the rotor and extends
axially from the last stage of the turbine to a downstream wall of
the toroidal diffuser.
15. The flow path according to claim 1, wherein the casing and the
toroidal diffuser are independently mounted relative to one another
on a foundation.
16. The flow path according to claim 1, wherein a flexible
connection connects the casing and the toroidal diffuser.
17. The flow path according to claim 16, wherein the flexible
connection comprises expansion bellows that are configured to allow
for differential thermal expansion.
18. The flow path according to claim 1, wherein bearings for the
rotor are supported on one or more stanchions that are directly
supported by the foundation of the turbine.
19. An axial flow steam turbine flow path comprising: a rotor and a
casing defining the axial steam flow path; and a toroidal diffuser
for diffusing the exhaust steam and turning the exhaust steam from
a generally axial flow direction to a generally transverse or
vertical and tangential direction; wherein the toroidal diffuser
comprises a diffuser that, at least in part, incorporates the shape
of a toroid or a section of a toroid; and wherein a toroid
comprises the shape generated by revolving a circular or oval shape
in three dimensional space about an axis coplanar with the circular
or oval shape, which does not touch the circular or oval shape.
20. The flow path according to claim 19, wherein a toroidal
diffuser comprises: a conical guide, which functions as the initial
guide for the steam as it exits the last turbine section; a
toroidal section, which defines the upper half of the main chamber
of the toroidal diffuser; and a rectilinear section, which defines
the lower half of the main chamber of the diffuser and provides a
flow path to an outlet.
Description
BACKGROUND OF THE INVENTION
[0001] This present application relates generally to methods,
systems, and/or apparatus for improving the efficiency and/or
operation of turbine engines. More specifically, but not by way of
limitation, the present application relates to methods, systems,
and/or apparatus pertaining to improved steam turbine diffusers and
related components.
[0002] In conventional steam turbine design, the inner case of the
steam turbine, which, for example, may be a double flow down
exhaust unit, has an encompassing exhaust hood split vertically and
extending along opposite sides and ends of the turbine. This large
box-like structure houses the entire low pressure section of the
turbine. The exhaust steam from the turbine flows downstream in a
general axial direction. Then, the steam exhaust is redirected from
an axial flow direction to a flow direction 90.degree. relative to
the axial flow direction. This 90.degree. flow direction may be in
any plane, downwardly, upwardly or transversely.
[0003] Generally, conventional exhaust hoods for steam turbines
constitute large rectilinear structures at the exit end of the
conical section for turning and diffusing the steam flow at right
angles. The steam flow path was thus somewhat tortuous, which
resulted in losses and adverse pressure drop. It will also be
appreciated that access to various parts of the turbine, for
example, the bearing for maintenance purposes was difficult in that
it could necessitate the removal of the upper half of the exhaust
hood. Further, it will be appreciated that the exhaust hood in
conventional steam turbines typically supports the inner casing of
the turbine and the associated steam path parts such as diaphragms
and the like. Accordingly, there has been found a need to provide a
new geometry to improve exhaust steam pressure recovery and overall
performance of the turbine.
BRIEF DESCRIPTION OF THE INVENTION
[0004] The present application thus describes an axial flow steam
turbine flow path that includes a rotor and a casing defining the
axial steam flow path; and a toroidal diffuser for diffusing the
exhaust steam and turning the exhaust steam from a generally axial
flow direction to a generally transverse or vertical and tangential
direction; wherein the toroidal diffuser comprises a diffuser that,
at least in part, incorporates the shape of a toroid or a section
of a toroid; and wherein a toroid comprises the shape generated by
revolving a circular or oval shape in three dimensional space about
an axis coplanar with the circular or oval shape, which does not
touch the circular or oval shape.
[0005] These and other features of the present application will
become apparent upon review of the following detailed description
of the preferred embodiments when taken in con junction with the
drawings and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] These and other objects and advantages of this invention
will be more completely understood and appreciated by careful study
of the following more detailed description of exemplary embodiments
of the invention taken in conjunction with the accompanying
drawings, in which:
[0007] FIG. 1 is a schematic cross-sectional illustration of
approximately half of a double flow down exhaust steam turbine
according to conventional design;
[0008] FIG. 2 is a schematic side cross-sectional view of
approximately half of a steam turbine illustrating an exhaust
diffuser having a toroidal configuration according to an exemplary
embodiment of the present application;
[0009] FIG. 3 is a schematic cross-sectional view from a downstream
perspective of an exhaust diffuser having a toroidal configuration
according to an exemplary embodiment of the present application;
and
[0010] FIG. 4 is an exemplary toroid shape from which diffusers
according to the present application may the formed.
DETAILED DESCRIPTION OF THE INVENTION
[0011] Referring now to the drawings, particularly to FIG. 1 there
is illustrated a portion of a steam turbine, generally designated
10, that includes a rotor 12 that mounts a plurality of turbine
buckets 14. An inner casing 16 is also illustrated mounting a
plurality of diaphragms or stator blades 18. A centrally disposed
generally radial steam inlet 20 applies steam to each of the
turbine buckets 14 and stator blades 18 on opposite axial sides of
the turbine to drive the rotor 12. The stator vanes of the
diaphragms 18 and the axially adjacent buckets 14 form the various
stages of the turbine 10 and a flow path therethrough. It will be
appreciated that the steam is exhausted from the final stage of the
turbine for flow through a diffuser and into a condenser not
shown.
[0012] Also illustrated in FIG. 1 is an outer exhaust hood 22 that
surrounds and supports the inner casing 16 of the turbine 10 as
well as other parts such as the bearings. In the illustration of
FIG. 1, the turbine 10 includes steam guides 24 for directing the
steam exhausting from the turbine 10 into an outlet 26 for flow to
one or more condensers (not shown). With the use of an exhaust hood
22 supporting the turbine 10, bearings and ancillary parts, the
exhaust steam path, as illustrated, is tortuous and subject to
pressure losses. As one of ordinary skill in the art will
appreciate, this results in a reduction in performance and
efficiency.
[0013] Referring now to FIGS. 2 and 3, there is illustrated an
aspect of the present invention wherein like reference numerals as
in FIG. 1 are applied to like parts preceded by the numeral "1". As
illustrated, the exhaust hood 22 of the prior art is completely
eliminated in favor of an exemplary toroidal diffuser 40 according
to the present invention. As used herein and as discussed in more
detail below, a toroidal diffuser is a diffuser that, at least in
part, incorporates the shape of a toroid or a section of a toroid.
An exemplary toroid, a toroid 41, is illustrated in FIG. 4. As
shown, a toroid is the shape generated by revolving a circle in
three dimensional space about an axis coplanar with the circle,
which does not touch the circle. Typically, a toroid includes a
circular shape that is revolved; however, as used herein, a toroid
may include approximate circular shapes, such as an oval.
[0014] According to a preferred embodiment, the toroidal diffuser
40 generally includes a conical guide 45, which functions as the
initial guide for the steam as it exits the last turbine section, a
toroidal section 42, which, as illustrated, defines the upper half
of the main body or chamber of the diffuser, and a rectilinear
section 43, which defines the lower half of the main body or
chamber of the diffuser and provides the flow path to an outlet 46.
The toroidal section 42 may comprise approximately one half of a
toroid shape, though other configurations are also possible. The
toroidal section 42 engages and transitions to the rectilinear
section 43 at a circumferential location that is approximately
horizontal with the rotor 112. The axis of the toroid that forms
the toroidal section 42 generally is the rotor 112.
[0015] The toroidal diffuser 40 may include other components that
allow it to function in a more efficient and cost-effective manner.
In some preferred embodiments, as already described, the toroidal
diffuser 40 may include the conical guide 45. The upstream end of
the conical guide 45, as illustrated, may be coupled to the inner
casing 116 by a flexible joint 44. The conical guide 45 generally
provides the outer radial boundary for steam exiting the final
stage of the turbine. As illustrated, the conical guide 45
generally includes an expanding conical shape that has an axis
along the rotor 112. Accordingly, the conical guide 45 has an
increasing cross-sectional area, which allows the exiting steam to
expand and, thereby, reduce its pressure. Particularly, the conical
guide 45 has a cross-sectional diameter that increases as the
distance from the flexible joint 44 increases. The conical guide 45
extends downstream and terminates at a flared lip 47. The flared
lip 47 helps to smooth the flow and lessen the pressure of the
steam into the toroidal section 42. As illustrated, the conical
guide 45 may extend into the toroidal section 42 and/or rectilinear
section 43. More specifically, the conical guide 45 may extend
across approximately half the axial width of the toroidal section
42 and/or the rectilinear section 43. According to preferred
embodiments, the inner boundary for the steam moving through the
conical guide 45 may be provided by a cylindrical formed rotor
plate 49. The cylindrical rotor plate 49 generally forms a smooth
cylindrical shape that encloses the rotor and extends axially from
the last stage of the turbine to the downstream wall of the
toroidal diffuser 40. The axis of the rotor plate 49 also may be
the rotor 112.
[0016] It has been discovered that the geometry of the toroidal
section 42, according to the present invention, is effective at
allowing the exiting steam to expand and reduce its pressure. These
benefits are further enhanced by the combination of the toroidal
section 42 and the conical guide 45. The toroidal diffuser 40, with
the toroidal section 42 and/or the conical guide 45, is also
effective at guiding the diffused steam to the outlet 46 with a
minimum pressure loss. It will be appreciated that the outlet 46
need not be a down exhaust but can be a side or upwardly directed
exhaust.
[0017] Apart from the increased performance due to the diffusion of
the steam in a toroid on the steam exhaust side of the turbine,
there are additional advantages. For example, the exhaust hood in
prior conventional steam turbines is eliminated and there is no
longer a need to support the inner casing and associated steam path
parts, such as diaphragms from the exhaust hood. Cost reduction is
also realized because an exhaust hood is no longer used to enclose
the inner casing. Steam guides previously necessary are also
entirely eliminated. Importantly, the inner casing and the toroidal
diffuser of the turbine are each supported directly from the
foundation of the turbine. To facilitate this, a flexible
connection 44 (FIG. 2) is provided between the inner casing and the
toroidal diffuser 40. The flexible connection may be of many
different types such as an expansion bellows to allow for
differential thermal expansion. Further, the previously utilized
exhaust hood is no longer necessary for the support of the turbine
bearings. As illustrated in FIG. 2, the bearings 54 may be
supported on stanchions 56 in turn directly supported by the
foundation of the turbine. Thus, the stanchions provide a rigid
support for the bearings with improved turbine reliability as a
result. The toroid diffuser 40 may be formed of a composite
material, steel plate or pipe, structural steel, fiber-reinforced
plastic or any combination of these materials to obtain the
required structural integrity and desired steam flow diffusion
characteristics.
[0018] From the above description of preferred embodiments of the
invention, those skilled in the art will perceive improvements,
changes and modifications. Such improvements, changes and
modifications within the skill of the art are intended to be
covered by the appended claims. Further, it should be apparent that
the foregoing relates only to the described embodiments of the
present application and that numerous changes and modifications may
be made herein without departing from the spirit and scope of the
application as defined by the following claims and the equivalents
thereof.
* * * * *