U.S. patent application number 12/477959 was filed with the patent office on 2010-12-09 for clutched steam turbine low pressure sections and methods therefore.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. Invention is credited to Roy Paul Swintek.
Application Number | 20100310356 12/477959 |
Document ID | / |
Family ID | 42584631 |
Filed Date | 2010-12-09 |
United States Patent
Application |
20100310356 |
Kind Code |
A1 |
Swintek; Roy Paul |
December 9, 2010 |
CLUTCHED STEAM TURBINE LOW PRESSURE SECTIONS AND METHODS
THEREFORE
Abstract
Solutions for clutching steam turbine low pressure sections are
disclosed. In one embodiment, a system includes: a first low
pressure steam turbine including a first shaft; a second low
pressure steam turbine including a second shaft; a clutch for
coupling and uncoupling the first shaft and the second shaft; a
conduit for delivering a working fluid to the first low pressure
steam turbine and the second low pressure steam turbine; a valve
within the conduit, the valve having an open position and a closed
position, the closed position preventing flow of the working fluid
to the second low pressure steam turbine; and a controller for
operating the clutch and the valve, the controller uncoupling the
second shaft from the first shaft and closing the valve in response
to the first and second low pressure steam turbine attaining a
predetermined low part load.
Inventors: |
Swintek; Roy Paul;
(Altamont, NY) |
Correspondence
Address: |
Hoffman Warnick LLC
75 State Street, Floor 14
Albany
NY
12207
US
|
Assignee: |
GENERAL ELECTRIC COMPANY
Schenectady
NY
|
Family ID: |
42584631 |
Appl. No.: |
12/477959 |
Filed: |
June 4, 2009 |
Current U.S.
Class: |
415/18 ; 415/61;
60/39.182 |
Current CPC
Class: |
F02C 7/36 20130101; F05D
2220/31 20130101; Y02E 20/16 20130101; F02C 9/18 20130101 |
Class at
Publication: |
415/18 ; 415/61;
60/39.182 |
International
Class: |
F01D 21/00 20060101
F01D021/00; F01D 1/10 20060101 F01D001/10; F01K 23/02 20060101
F01K023/02 |
Claims
1. A steam turbine system comprising: a first low pressure steam
turbine including a first shaft; a second low pressure steam
turbine including a second shaft; a clutch for coupling and
uncoupling the first shaft and the second shaft; a conduit for
delivering a working fluid to the first low pressure steam turbine
and the second low pressure steam turbine; a valve within the
conduit, the valve having an open position and a closed position,
the closed position preventing flow of the working fluid to the
second low pressure steam turbine; and a controller for operating
the clutch and the valve, the controller uncoupling the second
shaft from the first shaft via the clutch and closing the valve in
response to the first and second low pressure steam turbine
attaining a predetermined low part load.
2. The steam turbine system of claim 1, further comprising a steam
turbine section coupled to the first low pressure steam turbine by
the first shaft.
3. The steam turbine system of claim 2, further comprising a
generator coupled to the first low pressure steam turbine and the
second low pressure steam turbine.
4. The steam turbine system of claim 3, further comprising a first
condenser operably connected to the first low pressure steam
turbine.
5. The steam turbine system of claim 4, further comprising a second
condenser operably connected to the second low pressure steam
turbine.
6. The steam turbine system of claim 1, wherein the controller
includes an electro-mechanical device.
7. A combined cycle power plant system comprising: a gas turbine
operably connected to a first generator; a heat exchanger operably
connected to the gas turbine; a steam turbine section operably
connected to the heat exchanger; and a steam turbine system
operably connected to the steam turbine section, the steam turbine
system including: a first low pressure steam turbine including a
first shaft; a second low pressure steam turbine including a second
shaft; a clutch for coupling and uncoupling the first shaft and the
second shaft; a conduit for delivering a working fluid to the first
low pressure steam turbine and the second low pressure steam
turbine; a valve within the conduit, the valve having an open
position and a closed position, the closed position preventing flow
of the working fluid to the second low pressure steam turbine; and
a controller for operating the clutch and the valve, the controller
uncoupling the second shaft from the first shaft via the clutch and
closing the valve in response to the first and second low pressure
steam turbine attaining a predetermined low part load.
8. The combined cycle power plant system of claim 7, further
comprising a second generator operably connected to the steam
turbine system.
9. The combined cycle power plant system of claim 8, wherein the
second generator is coupled to the first low pressure steam
turbine.
10. The combined cycle power plant system of claim 7, further
comprising a first condenser operably connected to the first low
pressure steam turbine.
11. The steam turbine system of claim 10, further comprising a
second condenser operably connected to the second low pressure
steam turbine.
12. The steam turbine system of claim 7, wherein the controller
includes an electro-mechanical device.
13. A method of operating a steam turbine system, the method
comprising: uncoupling a second low pressure steam turbine from a
first low pressure steam turbine using a clutch, the uncoupling
being in response to the first and second low pressure steam
turbine attaining a predetermined low part load.
14. The method of claim 13, wherein the first low pressure steam
turbine includes a first shaft and the second low pressure turbine
includes a second shaft, and wherein the first shaft and the second
shaft are capable of coupling and uncoupling via a clutch.
15. The method of claim 13, further comprising: preventing flow of
a working fluid to the second low pressure steam turbine using a
valve, the preventing being in response to the first and second low
pressure steam turbine attaining a predetermined low part load.
16. The method of claim 15, further comprising performing the
preventing and the uncoupling substantially simultaneously.
17. The method of claim 15, further comprising controlling the
preventing and the uncoupling using a controller.
18. The method of claim 17, wherein the controller includes an
electromechanical device.
Description
BACKGROUND OF THE INVENTION
[0001] The subject matter disclosed herein relates to solutions for
clutching steam turbine low pressure sections. Specifically, the
subject matter disclosed herein relates to using a clutch-valve
mechanism to engage and disengage low pressure sections of a steam
turbine power generation system.
[0002] Steam turbine power systems are designed and built with
particular load conditions in mind. Often, these systems are built
to handle the peak or near-peak loads of their customers, which may
coincide with afternoon hours where the ambient temperature is high
(e.g., above 27 degrees Celsius). However, during periods of lower
demand, these systems must run at off-peak loads. For example, a
steam turbine power system may reduce its output to well below
fifty percent of its rated power during the evening hours (e.g.,
after 9:00 pm local time), when customers require very little
electricity. Reducing the output of the steam turbine power system
to such levels may cause, among other things, mechanical damage to
the steam turbine's components, resulting in more frequent parts
replacement and increased costs.
BRIEF DESCRIPTION OF THE INVENTION
[0003] Solutions for clutching steam turbine low pressure sections
are disclosed. In one embodiment, a system includes: a first low
pressure steam turbine including a first shaft; a second low
pressure steam turbine including a second shaft; a clutch for
coupling and uncoupling the first shaft and the second shaft; a
conduit for delivering a working fluid to the first low pressure
steam turbine and the second low pressure steam turbine; a valve
within the conduit, the valve having an open position and a closed
position, the closed position preventing flow of the working fluid
to the second low pressure steam turbine; and a controller for
operating the clutch and the valve, the controller uncoupling the
second shaft from the first shaft and closing the valve in response
to the first and second low pressure steam turbine attaining a
predetermined low part load.
[0004] A first aspect of the invention provides a steam turbine
system comprising: a first low pressure steam turbine including a
first shaft; a second low pressure steam turbine including a second
shaft; a clutch for coupling and uncoupling the first shaft and the
second shaft; a conduit for delivering a working fluid to the first
low pressure steam turbine and the second low pressure steam
turbine; a valve within the conduit, the valve having an open
position and a closed position, the closed position preventing flow
of the working fluid to the second low pressure steam turbine; and
a controller for operating the clutch and the valve, the controller
uncoupling the second shaft from the first shaft and closing the
valve in response to the first and second low pressure steam
turbine attaining a predetermined low part load.
[0005] A second aspect of the invention provides a combined cycle
power plant system comprising: a gas turbine operably connected to
a first generator; a steam turbine section operably connected to
the gas turbine; and a steam turbine system operably connected to
the steam turbine section, the steam turbine system including: a
first low pressure steam turbine including a first shaft; a second
low pressure steam turbine including a second shaft; a clutch for
coupling and uncoupling the first shaft and the second shaft; a
conduit for delivering a working fluid to the first low pressure
steam turbine and the second low pressure steam turbine; a valve
within the conduit, the valve having an open position and a closed
position, the closed position preventing flow of the working fluid
to the second low pressure steam turbine; and a controller for
operating the clutch and the valve, the controller uncoupling the
second shaft from the first shaft and closing the valve in response
to the first and second low pressure steam turbine attaining a
predetermined low part load.
[0006] A third aspect of the invention provides a method of
operating a steam turbine system, the method comprising: uncoupling
a second low pressure steam turbine from a first low pressure steam
turbine using a clutch, the uncoupling being in response to the
first and second low pressure steam turbine attaining a
predetermined low part load.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] These and other features of this invention will be more
readily understood from the following detailed description of the
various aspects of the invention taken in conjunction with the
accompanying drawings that depict various embodiments of the
invention, in which:
[0008] FIG. 1 shows a schematic block diagram illustrating a steam
turbine system including clutched steam turbine low pressure
sections according to embodiments of the invention.
[0009] FIG. 2 shows a schematic block diagram illustrating portions
of a combined cycle power plant system according to embodiments of
the invention.
[0010] FIG. 3 shows a steam turbine exhaust loss curve illustrating
performance characteristics of clutched steam turbine low pressure
sections according to embodiments of the invention.
[0011] It is noted that the drawings of the invention are not to
scale. The drawings are intended to depict only typical aspects of
the invention, and therefore should not be considered as limiting
the scope of the invention. In the drawings, like numbering
represents like elements between the drawings.
DETAILED DESCRIPTION OF THE INVENTION
[0012] As indicated above, aspects of the invention provide for
clutched steam turbine low pressure sections. As used herein,
unless otherwise noted, the term "set" means one or more (i.e., at
least one) and the phrase "any solution" means any now known or
later developed solution.
[0013] As is known in the art of steam turbine power systems, the
terms "rated power" and "rated mass flow" refer to the total power
output and total mass flow, respectively, of one or more devices
under certain predefined conditions. Typically, the rated
power/mass flow of a steam turbine system is designed for a
particular set of conditions, and these designed conditions are set
as the 100 percent rated power/mass flow marks. When operating at
conditions other than design conditions, the power and mass flow of
a steam turbine system may deviate from the 100 percent rated
power/mass flow mark. Operating conditions below the 100 percent
rated power/mass flow mark may fall into a few categories. One such
category, known as "low part load," is characterized by running a
steam turbine at or under approximately 25% of its rated power/mass
flow. Low part load is a distinct subset of the broad category
known as "part load," which is characterized by running a steam
turbine at less than 100% of its rated power/mass flow. As used
herein, "low part load" refers to a range of loads that may be
approximately 5-25% of a rated power/mass flow of a steam turbine
system. Low part load conditions may occur at different percentages
of rated power/mass flow depending upon a plurality of steam
turbine conditions. For example, these conditions may include: the
low pressure turbine geometry (e.g., last-stage bucket length),
operating conditions (e.g., condenser pressure, temperatures,
etc.), operation planning/history (e.g., planned duration of low
part loading, previous frequency/duration of low part loading) and
maintenance schedules.
[0014] Operating a steam turbine system at its low part load may
cause accelerated mechanical damage to either or both of a first
low pressure steam turbine and a second low pressure steam turbine.
In particular, operating low pressure steam turbines at low part
loads can cause complications such as windage overheating,
aerodynamic flow separation, flow instability, etc. These
complications may result in accelerated mechanical damage to low
pressure section buckets, shafts, rotors, seals, etc. These
complications and the mechanical damages they cause may result in
costly steam turbine maintenance, stoppages, catastrophic damage,
reduced steam turbine reliability and availability, etc.
[0015] While one alternative to running a steam turbine system at
low part load is to completely shut down the system, this may cause
a variety of other problems. For example, every time a steam
turbine power system is shut down, it may not restart as planned,
resulting in additional maintenance costs and/or missed power
generation opportunities. Even further, the cycle of shutting down
and restarting the steam turbine power system causes wear on plant
components such as boilers, heat recovery steam generators (HRSGs),
conduits/pipes, etc. and system components such as shafts, last
stage buckets, rotors, etc. In order to avoid the aforementioned
undesirable consequences, clutched steam turbine low pressure
sections are disclosed.
[0016] While clutched steam turbine sections have been used in the
past, they have aimed at improving the efficiency of steam turbine
power generation systems by reducing the exhaust loss of each
individual steam turbine. These prior clutched steam turbine
sections have attempted to improve efficiency by disengaging one
low pressure steam turbine from the system when the steam turbine
system runs at approximately 50 percent of its rated power
(operating at "part load"). While this approach produces decreased
exhaust losses and an increased annulus velocity, it does not
address the problems associated with running a steam turbine system
at low part load. In particular, the prior approach does not
attempt to reduce the mechanical damage inflicted on steam turbine
components due to running at low part loads. Further, the prior
approach does not attempt to reduce the need for a shut-down and
subsequent restart of the steam turbine system during times of low
part load.
[0017] Turning to the drawings, FIG. 1 shows a schematic block
diagram of a steam turbine system 100 according to one embodiment
of the invention. Arrows are shown depicting the flow of a working
fluid between components of steam turbine system 100. The term
"working fluid" may refer to any fluid capable of performing the
functions described herein.
[0018] Steam turbine system 100 may include a first low pressure
steam turbine 120 including a first shaft 175, along with a second
low pressure steam turbine 130 including a second shaft 185. Steam
turbine system 100 may also include a clutch 140 for coupling and
uncoupling first shaft 175 and second shaft 185. Clutch 140 may
function as a mechanical linkage between first shaft 175 and second
shaft 185 during operation of steam turbine system 100. This
linkage may allow first shaft 175 and second shaft 185 to rotate at
approximately the same rate of speed. However, under certain
operating conditions, clutch 140 may uncouple second low pressure
steam turbine 130 from first low pressure steam turbine 120 by
disengaging second shaft 185 from first shaft 175. Steam turbine
system 100 may further include a conduit 160 for delivering a
working fluid (numbering omitted) to first low pressure steam
turbine 120 and second low pressure steam turbine 130. Conduit 160
may be, for example, a duct or a pipe made in part from metal,
composite, or a polymer. Also included in steam turbine system 100
may be a valve 150 located within conduit 160. Valve 150 may have
an open position and a closed position, where the closed position
prevents flow of the working fluid to second low pressure steam
turbine 130. Valve 150 may be, for example, a two-way valve. As is
known in the art of fluid mechanics, a two-way valve either
prevents a portion of the flow of a working fluid through a
pathway, or it allows a portion of that flow to pass. Valve 150 may
primarily function either in a closed position (total obstruction)
or open position (no obstruction), however, valve 150 may also
function in a partially open position (partial obstruction). Valve
150, may, for example, be a gate valve, a butterfly valve, a globe
valve, etc.
[0019] Steam turbine system 100 may further include a controller
145 for operating clutch 140 and valve 150. Controller 145 may be
mechanically and/or electrically connected to clutch 140 and valve
150 such that controller 145 may actuate clutch 140 and/or valve
150. Controller 145 may instruct clutch 140 to uncouple second
shaft 185 from first shaft 175 and/or may instruct valve 150 to
close in response to the first low pressure steam turbine 120 and
second low pressure steam turbine 130 attaining a predetermined low
part load. Controller 145 may be a computerized, mechanical, or
electromechanical device capable of actuating valve 150 and
engaging/disengaging clutch 140. In one embodiment, controller 145
may be a computerized device capable of providing operating
instructions to valve 150 and/or clutch 140. In this case,
controller 145 may monitor the load of steam turbine system 100
(via monitoring flow rates, temperature, pressure, and working
fluid parameters), and provide operating instructions to valve 150
and/or clutch 140. For example, controller 145 may send operating
instructions to close valve 150 and disengage clutch 140 under
certain operating conditions (e.g., low part load). In this
embodiment, valve 150 and clutch 140 may each include
electromechanical components, capable of receiving operating
instructions (electrical signals) from controller 145 and producing
mechanical motion (e.g., closing of valve, uncoupling of shafts).
In another embodiment, controller 145 may be a mechanical device,
capable of use by an operator. In this case, the operator may
physically manipulate controller 145 (e.g., by pulling a lever),
which may actuate valve 150 and/or clutch 140. For example, the
lever of controller 145 may be mechanically linked to valve 150 and
clutch 140, such that pulling the lever causes valve 150 and/or
clutch 140 to fully actuate (e.g., by sealing off conduit 160
between first and second low pressure steam turbines 120, 130
and/or disengaging second shaft 185). In another embodiment,
controller 145 may be an electromechanical device, capable of
electrically monitoring (e.g., with sensors) parameters indicating
that steam turbine system 100 is running at a low part load, and
mechanically actuating valve 150 and/or clutch 140. While described
in several embodiments herein, controller 145 may operate valve 150
and/or clutch 140 through any conventional means.
[0020] In any case, when controller 145 uncouples second shaft 185
from first shaft 175 and closes valve 150 (preventing working fluid
flow), second low pressure steam turbine 130 is effectively taken
"off-line." This allows substantially all of the working fluid to
flow through first low pressure steam turbine 120, causing
increased efficiency in first low pressure steam turbine 120 (shown
and described with reference to FIG. 3). This further allows for
reduced mechanical damage to both second low pressure steam turbine
130 and first low pressure steam turbine 120. Additionally, first
low pressure steam turbine 120 may continue operating even during
low loading conditions. This may provide the additional benefit of
allowing steam turbine system 100 to operate continuously without a
shut-down and restart.
[0021] Also shown in FIG. 1 is a steam turbine section 110, which
is coupled to first low pressure steam turbine 120 by first shaft
175, and operably connected to first low pressure steam turbine 120
and second low pressure steam turbine 130 via conduit 160. Steam
turbine section 110 may, for example, be an intermediate pressure
steam turbine, a high pressure steam turbine, or may include both
high pressure and intermediate pressure sections. In any case,
steam turbine section 110 may provide working fluid (steam exhaust)
to one or both of first low pressure steam turbine 120 and second
low pressure steam turbine 130. Further shown in FIG. 1 is a
generator 210, coupled to first low pressure steam turbine 120 and
steam turbine section 110. In one embodiment, generator 210 may be
coupled to first low pressure steam turbine 120 by first shaft 175.
Generator 210 may be any standard generator capable of converting
mechanical energy (rotation of first shaft 175) into electrical
energy. It is understood that while generator 210 and steam turbine
section 110 are shown as coupled to first low pressure steam
turbine 120 by first shaft 175, generator 210 and steam turbine
section 110 may be coupled to second shaft 185 when clutch 140 is
engaged. However, in conditions of low part load, second low
pressure steam turbine 130 does not provide mechanical energy to
generator 210.
[0022] FIG. 1 further shows a first condenser 170 operably
connected to first low pressure steam turbine 120, and a second
condenser 180 operably connected to second low pressure steam
turbine 130. First condenser 170 and second condenser 180 may be
conventional condensers which cool the working fluid exiting first
low pressure steam turbine 120 and second low pressure steam
turbine 130, respectively.
[0023] FIG. 2 shows portions of a combined cycle power plant system
200 according to embodiments of the invention. FIG. 2 includes many
components shown and described with reference to steam turbine
system 100 of FIG. 1. However, combined cycle power plant system
200 may additionally include a gas turbine 300, a first generator
310, and a heat exchanger 400 (additional items shown in dashed box
"A"). Gas turbine 300 may be operably connected to first generator
310. Gas turbine 300 may be a conventional gas turbine that
generates mechanical energy via the flow of combustion gas through
a turbine (components not shown). First generator 310 may be a
conventional generator, capable of converting the mechanical energy
of gas turbine 300 into electrical energy. First generator 310 may
be coupled to gas turbine 300 via a third shaft 275. Further shown
in FIG. 2 is heat exchanger 400 operably connected to gas turbine
300 and steam turbine section 110. While heat exchanger 400 is
shown as being operably connected to gas turbine 300 and steam
turbine section 110, it is understood that heat exchanger 400 may
further be operably connected to one or more of conduit 160, first
low pressure steam turbine 120 and second low pressure steam
turbine 130.
[0024] Heat exchanger 400 may supply steam to steam turbine section
110, first low pressure steam turbine 120, and/or second low
pressure steam turbine 130, via a conventional conduit, such as
those described herein (numbering omitted). Heat exchanger 400 may
be a conventional heat recovery steam generator (HRSG), such as
those used in a conventional combined-cycle power station. As is
known in the art of power generation, heat recovery steam
generators may use hot exhaust from gas turbine 300, combined with
a water supply, to create steam. This steam may then flow to steam
turbine section 110, first low pressure steam turbine 120, and/or
second low pressure steam turbine 130 via a conduit (e.g., conduit
160).
[0025] It is understood that while steam turbine system 100 and
combined cycle power plant system 200 are shown and described
herein as including two low pressure steam turbines (first 120 and
second 130), additional low pressure steam turbines may be included
as well. For example, in nuclear or fossil power plants, a third
low pressure steam turbine may be coupled to second low pressure
steam turbine 130 via shaft 185 or an additional shaft (not shown).
In the case where the third low pressure steam turbine shares shaft
185 with second low pressure steam turbine 130, both second (130)
and third low pressure steam turbine may be taken "off-line" from
first low pressure steam turbine 120. Where an additional shaft is
used, the third low pressure steam turbine may be taken "off-line"
from second low pressure steam turbine 130. In this case, a second
clutch and second valve may couple and operably connect the third
low pressure steam turbine to second low pressure steam turbine
130, respectively. Controller 145 may control the second clutch and
second valve similarly to clutch 140 and valve 150. However, a
second controller may be used to control the second clutch and the
second valve. This second controller may function substantially
similarly to first controller, and may take any form of controller
described herein.
[0026] It is further understood that while combined cycle power
plant system 200 depicts gas turbine 300 on a different shaft
(second shaft 275) than steam turbine section 110 and first low
pressure steam turbine 120, these components may all be located on
the same shaft (first shaft 175). This configuration is known in
the art as a "single-shaft" system. In contrast, FIG. 2 depicts
combined cycle power plant system 200 as a "multi-shaft" system. It
is understood that clutched steam turbine sections described herein
may be used in either a single-shaft system or a multi-shaft
system. In a single-shaft configuration, it is understood that gas
turbine 400, steam turbine section 110, and first low pressure
steam turbine 120 may all be operably connected to first shaft 175.
In this case, generator 210 may be the only generator operably
connected to first shaft 175. In any case, the locations of
generator 210, steam turbine section 110 and first low pressure
steam turbine 120 on first shaft 175 may be interchanged. For
example, in one embodiment, generator 210 may be located between
gas turbine 300 and steam turbine section 110 on first shaft
175.
[0027] While FIG. 2 depicts combined cycle power plant system 200
including a single gas turbine 300 and a single heat exchanger 400,
it is understood that additional gas turbines, heat exchangers, and
generators may be employed. For example, additional sets of
components shown in phantom box A may be operably connected to, for
example, steam turbine section 110. In this case, steam turbine
section 110 may receive steam inputs from a plurality of heat
exchangers, resulting in a greater mass flow through steam turbine
section 110. Accordingly, steam turbine section 110 must be large
enough to process the increased mass flow. This also means that
first low pressure steam turbine 120 and second low pressure steam
turbine 130 must be large enough to process their respective shares
of the increased mass flow. However, where first low pressure steam
turbine 120 and second low pressure steam turbine 130 are large
enough to process increased mass flow, even greater mechanical
damage may occur during times of low part load. For example, during
operation of combined cycle power plant system 200 using a
plurality of gas turbines, a decrease in demand for power may cause
an operator to shut down one or more of the gas turbines. Where
this shutdown causes combined cycle power plant system 200 to run
at low part load, it may result in mechanical damage to components
of first low pressure steam turbine 120 and/or second low pressure
steam turbine 130. In such a case, clutched steam turbine sections
may provide even greater assistance in reducing mechanical damage
within components of combined cycle power plant system 200 than in
steam turbine system 100.
[0028] Turning to FIG. 3, a steam turbine exhaust loss curve
illustrating reduced mechanical damage to steam turbine system 100
is shown. This exhaust curve is well known in the art of steam
turbine power systems, and illustrates the thermodynamic optimum
point (characterized by minimal dry exhaust loss), at which a steam
turbine system is most efficient. Point "A" depicts the performance
of steam turbine system 100 at low part load before uncoupling of
second shaft 185 (second low pressure steam turbine 130) from first
shaft 175 (first low pressure steam turbine 120). As shown, steam
turbine system 100 is far from running at its thermodynamic optimum
at point A. However, as explained herein, clutched steam turbine
sections may reduce mechanical damage to components of steam
turbine system 100 by increasing mass flow of the working fluid
through first low pressure steam turbine 120. Point "B" depicts
steam turbine system 100 after uncoupling of second shaft 185 from
first shaft 175. While steam turbine system 100 is still running at
low part load at both point A and point B, the mechanical damage to
its components may be reduced by taking second low pressure steam
turbine 130 "off-line" (uncoupling second shaft 185 and first shaft
175).
[0029] This written description uses examples to disclose the
invention, including the best mode, and also to enable any person
skilled in the art to practice the invention, including making and
using any devices or systems and performing any incorporated
methods. The patentable scope of the invention is defined by the
claims, and may include other examples that occur to those skilled
in the art. Such other examples are intended to be within the scope
of the claims if they have structural elements that do not differ
from the literal language of the claims, or if they include
equivalent structural elements with insubstantial differences from
the literal languages of the claims.
* * * * *