U.S. patent application number 14/877988 was filed with the patent office on 2017-04-13 for heating systems for rotor in-situ in turbomachines.
The applicant listed for this patent is General Electric Company. Invention is credited to Kristopher John Frutschy, Edward Leo Kudlacik, Carey Lorne Sykes, David Ernest Welch.
Application Number | 20170101897 14/877988 |
Document ID | / |
Family ID | 57189756 |
Filed Date | 2017-04-13 |
United States Patent
Application |
20170101897 |
Kind Code |
A1 |
Frutschy; Kristopher John ;
et al. |
April 13, 2017 |
HEATING SYSTEMS FOR ROTOR IN-SITU IN TURBOMACHINES
Abstract
Heating systems for a rotor in-situ in a turbomachine are
provided. In contrast to conventional systems that merely heat from
an external turbine casing, embodiments of the disclosure heat the
rotor. In one embodiment, a heating system includes a heating
element to heat a portion of an exterior surface of the rotor. In
another embodiment, the heating system may include a heating
element(s) at least partially positioned within the rotor, and the
rotor including the heating system. Each embodiment may include a
controller to control operation of the heating element(s).
Inventors: |
Frutschy; Kristopher John;
(Clifton Park, NY) ; Kudlacik; Edward Leo;
(Glenville, NY) ; Sykes; Carey Lorne; (Queensbury,
NY) ; Welch; David Ernest; (Amsterdam, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
General Electric Company |
Schenectady |
NY |
US |
|
|
Family ID: |
57189756 |
Appl. No.: |
14/877988 |
Filed: |
October 8, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01D 19/02 20130101;
F05D 2220/31 20130101; F22B 35/14 20130101; F01K 3/26 20130101;
F01K 3/186 20130101; F01D 25/10 20130101 |
International
Class: |
F01K 3/18 20060101
F01K003/18; F22B 35/14 20060101 F22B035/14; F01K 3/26 20060101
F01K003/26 |
Claims
1. A heating system for a rotor in-situ in a casing of a
turbomachine, the heating system comprising: a heating element for
heating at least a portion of the rotor in-situ in the casing of
the turbomachine.
2. The heating system of claim 1, wherein the heating element is
configured to heat at least a portion of an exterior surface of the
rotor.
3. The heating system of claim 2, further comprising a temperature
sensor configured to sense a temperature of the at least a portion
of the exterior surface of the rotor and a controller controlling
operation of the heating element based on the sensed
temperature.
4. The heating system of claim 2, wherein the heating element
includes an induction heating coil positioned adjacent the at least
a portion of the exterior surface of the rotor.
5. The heating system of claim 2, further comprising a susceptor
member surrounding the at least a portion of the exterior surface
of the rotor, the susceptor member having the heating element
therein.
6. The heating system of claim 5, wherein the heating element
includes at least one of: a resistance heater and an inductance
heater.
7. The heating system of claim 5, further comprising a temperature
sensor configured to sense a temperature of the rotor and a
controller controlling operation of the heating element based on
the sensed temperature.
8. The heating system of claim 7, wherein the temperature sensor is
in or on the susceptor member.
9. The heating system of claim 7, further comprising a seal pack
adjacent the rotor for sealing a portion of the casing with the
rotor, and wherein the temperature sensor is in or on the seal
pack.
10. The heating system of claim 1, wherein the heating element is
at least partially positioned within the rotor.
11. The heating system of claim 10, wherein the heating element
includes at least one calrod.
12. The heating system of claim 11, wherein each calrod extends
from an end of the rotor and into the rotor, and further comprising
at least one electrical contact to each calrod external to the
rotor to resistively heat a respective calrod.
13. The heating system of claim 11, wherein each calrod couples to
an induction transformer adjacent the induction heating coil for
powering the calrod.
14. The heating system of claim 10, further comprising a permanent
magnet generator operably coupled to the rotor for powering at
least one heating element.
15. The heating system of claim 10, wherein the heating element
includes a plurality of heating elements at least partially
positioned in the rotor, each heating element having a different
axial position of the rotor.
16. The heating system of claim 15, further comprising a controller
controlling operation of each heating element.
17. The heating system of claim 16, further comprising a plurality
of temperature sensors, each temperature sensor configured to sense
a temperature of the rotor at a respective one of the different
axial positions, and wherein the controller controls operation of
each heater based on the sensed temperatures of the different axial
positions.
18. The heating system of claim 17, wherein the plurality of
temperature sensors are each part of a fiber optic temperature
sensor positioned within the rotor.
19. The heating system of claim 15, wherein each heating element
includes a calrod, each calrod extending a different length axially
into the rotor.
20. The heating system of claim 1, wherein the heating element
includes a plurality of heating elements, each heating element
configured to heat a different axial position of the rotor.
21. The heating system of claim 1, wherein the heating element
includes at least one first heating element at least partially
positioned in the rotor and at least one second heating element
configured to heat at least a portion of an exterior surface of the
rotor.
22. The heating system of claim 1, further comprising a heating
blanket configured to heat an exterior of the casing.
23. The heating system of claim 1, further comprising a turning
gear for rotating the rotor during the heating.
24. The heating system of claim 1, further comprising a temperature
sensor configured to sense a temperature of the rotor and a
controller controlling operation of the heating element based on
the sensed temperature.
25. The heating system of claim 24, wherein the controller further
controls flow of a working fluid into the turbomachine.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The application is related to U.S. application Nos. ______
and ______, docket numbers 282941A and 282941B, respectively, filed
concurrently, and currently pending.
BACKGROUND OF THE INVENTION
[0002] The disclosure relates generally to heating systems, and
more particularly, to heating systems for a rotor in-situ in a
turbomachine, and a related rotor.
[0003] In order to start up certain turbomachines, such as steam
turbines, it is typically necessary to ensure that parts of the
turbomachine are at appropriate temperatures. Start-up temperature
control is desirable regardless of whether the turbomachine is
starting from a cold start, warm start or from a hot start, i.e.,
after power generation has temporarily stopped. Start-up
temperature control is necessary to, for example, ensure and
optimize proper tolerances and clearances between parts, prevent
slow start-up caused by having to heat parts with a working fluid,
and control low cycle fatigue that can shorten part life.
[0004] Conventionally, heat blankets are applied to a casing (or
shell) of a turbomachine to apply heat, e.g., to the outside of a
steam turbine high pressure or intermediate pressure casing. The
heat from the blankets is conducted through the casing into various
parts of the turbine including the buckets and ideally into and
through the rotor. Heat blankets work adequately for single
casings, but pose challenges where double-casing units are
employed. In particular, as shown in the schematic cross-section of
FIG. 1, for a double casing turbine 6, heat transmission 8 from
heat blanket 10 is more difficult because the heat needs to be
conducted through a separation 12 between outer casing 14 and inner
casing 16 before it reaches the internal parts. In addition, the
thermal conductivity of different materials/parts present in the
turbomachine may create a series of thermal resistances between
junctions 20 (dots) having an insulative effect which can be
detrimental to the desired heat transmission. For example, a
thermal resistance for outer casing 14 may be higher than that of
inner casing 16, or the thermal resistance of inner casing 16 may
be higher than that of rotor 24, causing temperature drops between
each junction set. A heat blanket arrangement also allows heat,
which should be conducted to and through rotor 24 to be
detrimentally sapped through the working fluid 18 flow path.
BRIEF DESCRIPTION OF THE INVENTION
[0005] A first aspect of the disclosure provides a heating system
for a rotor in-situ in a casing of a turbomachine, the heating
system comprising: a heating element for heating at least a portion
of the rotor in-situ in the casing of the turbomachine.
[0006] A second aspect of the disclosure provides a heating system
for a rotor in-situ in a casing of a turbomachine, the heating
system comprising: a first heating element configured to heat at
least a portion of an external surface of the rotor in-situ in the
casing of the turbomachine; and a controller for controlling
operation of the first heating element.
[0007] A third aspect of the disclosure provides a rotor for a
turbomachine, the rotor comprising: an elongated body; and a
heating element at least partially positioned in the elongated body
for heating at least a portion of the rotor in-situ in the
turbomachine.
[0008] A fourth aspect may include a heating system for a rotor
in-situ in a casing of a turbomachine, the heating system
comprising: a heating element configured to be at least partially
positioned within the rotor for heating an internal portion of the
rotor in-situ in the casing of the turbomachine; and a controller a
controller controlling operation of the heating element.
[0009] The illustrative aspects of the present disclosure are
designed to solve the problems herein described and/or other
problems not discussed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] These and other features of this disclosure will be more
readily understood from the following detailed description of the
various aspects of the disclosure taken in conjunction with the
accompanying drawings that depict various embodiments of the
disclosure, in which:
[0011] FIG. 1 shows a schematic cross-sectional view of a
conventional turbomachine employing a heat blanket.
[0012] FIG. 2 shows a perspective, partial cut away view of an
illustrative turbomachine in the form of a steam turbine employing
a heating system according to embodiments of the disclosure.
[0013] FIG. 3 shows a schematic cross-sectional view of a
turbomachine employing a heating system according to embodiments of
the disclosure.
[0014] FIG. 4 shows a detailed cross-sectional view of a heating
system for an external surface of a rotor according to embodiments
of the disclosure.
[0015] FIG. 5 shows a detailed cross-sectional view of a heating
system for an external surface of a rotor according to another
embodiment of the disclosure.
[0016] FIG. 6 shows a detailed cross-sectional view of a heating
system for an external surface of a rotor according to another
embodiment of the disclosure.
[0017] FIG. 7 shows a detailed cross-sectional view of a heating
system for an internal portion of a rotor according to embodiments
of the disclosure.
[0018] FIG. 8 shows a detailed cross-sectional view of a heating
system for an internal portion of a rotor according to another
embodiment of the disclosure.
[0019] FIG. 9 shows a detailed cross-sectional view of a heating
system for an internal portion of a rotor employing a permanent
magnet generator according to embodiments of the disclosure.
[0020] FIG. 10 shows a detailed cross-sectional view of a heating
system for different internal axial positions of a rotor according
to embodiments of the disclosure.
[0021] FIG. 11 shows a detailed cross-sectional view of the heating
system of FIG. 10 employing various alternative structures
according to embodiments of the disclosure.
[0022] It is noted that the drawings of the disclosure are not to
scale. The drawings are intended to depict only typical aspects of
the disclosure, and therefore should not be considered as limiting
the scope of the disclosure. In the drawings, like numbering
represents like elements between the drawings.
DETAILED DESCRIPTION OF THE INVENTION
[0023] As indicated above, the disclosure provides heating systems
for a rotor in-situ in a turbomachine. In contrast to conventional
systems that merely conduct heat from an external casing,
embodiments of the disclosure heat the rotor directly. The heating
systems may take form in a variety of embodiments. In one
embodiment, a heating system includes a heating element to heat a
portion of an exterior surface of the rotor in-situ in the
turbomachine. In another embodiment, the heating system may include
a heating element at least partially positioned within the rotor to
heat the rotor in-situ in the turbomachine. Each embodiment may
include a controller to control operation of the heating
element(s). Heating systems as described herein may provide
advantages such as but not limited to: closed loop temperature
control to supplement and/or counteract internal heat flow from the
heat blankets to maintain a desired component temperature, control
temperature ramp rates, control pre-startup and in startup process
temperature rates, create component temperatures commensurate with
a desired start up profile, and coordination of casing and rotor
temperatures to manage and optimize clearances, rotor stress,
casing stress and differential cycle fatigue during startup.
Additional advantages include recovery of a rotor "bow" condition
prior to startup (using rotor heat and turning gear), and reducing
startup vibration and startup time from a rotor bowed condition.
Embodiments of the disclosure may also be used to reduce rotor to
rotor rabbit fit interface temperature differentials during startup
(that may, if excessive differential temperature occurs, result in
loss of coupled or rabbit fit and turbomachine excessive
vibration).
[0024] Referring to the drawings, FIG. 2 shows a perspective
partial cut-away of a turbomachine 90 in the exemplary form of a
steam turbine 100. Steam turbine 100 includes a rotor 114 and a
plurality of axially spaced rotor wheels 118. A plurality of
rotating blades 120 are mechanically coupled to each rotor wheel
118. More specifically, blades 120 are arranged in rows that extend
circumferentially around each rotor wheel 118. A plurality of
stationary vanes 122 extends circumferentially around rotor 114,
and the vanes are axially positioned between adjacent rows of
blades 120. Stationary vanes 122 cooperate with blades 120 to form
a stage and to define a portion of a steam flow path through
turbine 100. In operation, steam 124 enters an inlet 126 of turbine
100 and is channeled through stationary vanes 122. Vanes 122 direct
steam 124 downstream against blades 120. Steam 124 passes through
the remaining stages imparting a force on blades 120 causing rotor
114 to rotate. At least one end of rotor 114 may be attached to a
load or machinery (not shown) such as, but not limited to, a
generator, and/or another turbine. In one embodiment of the present
disclosure as shown in FIG. 2, turbine 100 comprises five stages.
The five stages are referred to as L0, L1, L2, L3 and L4. Stage L4
is the first stage and is the smallest (in a radial direction) of
the five stages. Stage L3 is the second stage and is the next stage
in an axial direction. Stage L2 is the third stage and is shown in
the middle of the five stages. Stage L1 is the fourth and
next-to-last stage. Stage L0 is the last stage and is the largest
(in a radial direction). It is to be understood that five stages
are shown as one example only, and each turbine may have more or
less than five stages. Also, as will be described herein, the
teachings of the invention do not require a multiple stage turbine.
Furthermore, it is emphasized that while the teachings of the
invention will be described relative to a steam turbine,
turbomachine 90 can include any form of turbomachine requiring
heating of internal parts, for example during startup thereof,
including but not limited to: gas turbines, steam turbines and
compressors.
[0025] FIG. 3 shows a schematic cross-sectional view of an
illustrative turbomachine 190, e.g., a steam turbine, employing a
heating system 200 according to embodiments of the disclosure.
Turbomachine 190 may include any section of a larger turbomachine
system, e.g., a gas turbine, a high, intermediate or low pressure
section of a steam turbine system, a compressor, etc. Illustrative
turbomachine 190 is shown including an outer casing 204 and an
inner casing 206. It is emphasized, however, that the teachings of
the invention are not limited to a double shell turbomachine and
can be equally applied to a single shell machine. A rotor 210 is
shown positioned in-situ in turbomachine 190, i.e., in an operative
position in casings 204, 206. Turbine 212 is coupled to rotor 210
and may include blade/vane stages of turbomachine 190 (collectively
indicated by a trapezoid), as described relative to turbomachine 90
of FIG. 2. A working fluid 214 (e.g., steam, air, combusted fuel,
etc.) is shown moving through and/or about turbine 212. Heat
transmission paths according to embodiments of the disclosure are
illustrated with curved arrows 220, and thermal resistance
junctions 222, e.g., discrete temperature positions in the
turbomachine, are shown in the form of dots. A number of bearings
224 may be employed along an axial length of rotor 210 in a
conventional fashion.
[0026] In the embodiment shown in FIG. 3, a heating system 200 is
illustrated according to embodiments of the disclosure for heating
rotor 210 in-situ in casing 204 and/or 206 of turbomachine 190. In
general, heating system 200 may include any form of heating element
230 for heating at least a portion of rotor 210 in-situ in the
casing of the turbomachine--illustrative embodiments of which will
be further described herein. As illustrated, in contrast to
conventional systems, heat is created within rotor 210 and is
transmitted axially therethrough and into internal parts such as
casings 204, 206 such that it travels radially outward as indicated
by arrows 220. As will be described herein, where a heat blanket
232 is also employed, heating system 200 may act to balance heat
transmission and/or improve heat transmission through turbomachine
190, e.g., through thermal resistance junctions 222.
[0027] Referring to FIGS. 4-11, illustrative embodiments of heating
systems 200 according to the disclosure are provided. FIGS. 4-6
show enlarged detailed cross-sectional views of rotor 210 where a
heating element 330, 430 is configured to heat at least a portion
of an exterior surface 240 of the rotor; and FIGS. 7-11 show
enlarged detailed cross-sectional views of rotor 210 where a
heating element 530 is configured to heat at least a portion of an
interior of the rotor.
[0028] Referring to FIG. 4, in one embodiment, heating element 330
for heating a portion of exterior surface 340 of rotor 210 may
include an induction heating coil 332 positioned adjacent the at
least a portion of exterior surface 240 of rotor 210. (Heating coil
332 extends into and out of the page as it surrounds rotor 210).
Heating coil 332 may encompass as much of rotor 210 as is necessary
to provide the desired heating, e.g., 90.degree., 180.degree.,
350.degree., 360.degree.. Induction heating is a well-known
technique in which an electronic oscillator passes a high frequency
current (AC) through a metal induction heat coil 332. This current
causes an electromagnetic flux within the volume encompassed by the
coil. If an object with low electrical resistance (e.g., metal) is
placed within this volume, an eddy current will be generated on the
outer surface of the object to oppose the incoming coil flux. The
eddy current then heats the object due to Joule heating. A
controller 340 may be coupled to heating element 330 to control
operation thereof. One or more temperature sensors 334 may be
provided and configured to sense a temperature of the at least a
portion of the exterior surface of rotor 210. Temperature sensors
334 as described throughout the disclosure may include any now
known or later developed temperature sensors such as thermocouples,
infrared sensors, fiber optic sensors, etc. As will be described
relative to a later embodiment, temperature sensors 334 may also be
provided in the form of a fiber optic temperature sensor.
[0029] In another embodiment shown in FIG. 5, a susceptor member
432 may be provided surrounding at least a portion of exterior
surface 240 of rotor 210, e.g., 90.degree., 180.degree.,
350.degree., 360.degree., etc. Susceptor member 432 may include any
material capable of absorbing energy from induction heating coil
334A and/or electrical resistance heater 434 and transmitting heat
therefrom and/or converting energy to heat, e.g., a metal. In the
FIG. 5 embodiment, a seal pack 338 is also provided to seal outer
casing 204 and rotor 210. Seal pack 338 may include any now known
or later developed seal pack structure. Use of susceptor member 432
with seal pack 338 applies heat to both rotor 210 and outer casing
204, providing additional heat loss blocking compared to the FIG. 4
embodiment. Further, because heat enters susceptor member 432 first
and then enters rotor 210, use of susceptor member 432 may act to
spread heat better compared to the FIG. 4 embodiment and thus may
reduce overheating of rotor 210 and/or bearing 224. In the FIG. 5
embodiment, susceptor member 432 may include a heating element 430
therein. As shown in FIG. 5, in one embodiment, heating element 430
may include a resistance heater 434, i.e., any element capable of
creating heat by passing an electric current therethrough.
Alternatively, as shown in FIG. 6, heating element 430 may include
resistance heater 434 and an inductance heater 436 (similar to
inducting heating coil 332 (FIG. 4)). In any event, each heater 434
and/or 436 may be coupled to a controller 340 for controlling
operation of the heater(s). As shown in FIGS. 4-6, one or more
temperature sensors 334 may be configured to sense a temperature of
rotor 210 or other parts. Controller 340 can control operation of
the heating element(s) 434 and/or 436 based on the sensed
temperature(s).
[0030] Temperature sensor(s) 334 can be positioned in any number of
locations where temperature monitoring is desired. In one
embodiment, as shown in FIGS. 5-6, a temperature sensor(s) 334A is
in or on the susceptor member 432. In addition thereto or as an
alternative, where a seal pack 338 is positioned adjacent rotor 210
for sealing a portion of outer casing 204 with rotor 210, a
temperature sensor 334B may be positioned in or on the seal pack.
Although not shown in the cross-sectional views, it is understood
that temperature sensors 334 may be positioned anywhere about rotor
210.
[0031] With further regard to the FIGS. 4-6 embodiments, while one
axial position is shown being heated at one end of casing 204, it
is emphasized that any number of axial positions of rotor 210 may
be heated using a heating element(s) 230, 330, 430, as described
herein. For example, as shown in FIG. 3, rotor 210 may be heated at
each end of casing 204. Alternatively, as shown in FIG. 4, more
than one axial position on one end of casing 204 may be heated,
e.g., using heating elements 330 and 330' (in phantom). Similar,
multiple axial positions heating can be applied with the FIGS. 5
and 6 embodiments.
[0032] Controllers as used in the various embodiments described
herein, e.g., controller 340 in FIGS. 4-6, may include any now
known or later developed industrial machine control processor
capable of controlling the heating element(s) based on a feedback
from one or more temperature sensors used. Controller 340 can be a
stand-alone controller, or can be integrated with other
turbomachine 190 controls. For example, with the FIGS. 4-6
embodiments, controller 340 may automatically control operation of
heating element 330, 430 and/or 330' (FIG. 4) based on the sensed
temperature(s) to generate the desired heat and prevent
overheating, e.g., of bearing(s) 224. Controller 340 can operate
the heating element(s) to achieve any of a wide variety of goals
such as but not limited to: provide closed loop temperature control
to supplement and/or counteract internal heat flow from the heat
blankets 232 (FIG. 3) (where provided) to maintain a desired
temperature, control temperature ramp rates, control pre-startup
and in startup process temperature rates, create a temperature
commensurate with a desired start up temperature, coordination of
casing and/or rotor temperatures to manage and optimize clearances
during startup, manage rotor temperature to eliminate rotor bow. In
another example, controller 340 may control rotor temperature
during startup early stages to optimize clearances and to minimize
cooling effect of first entry steam. While a particular number of
wires/lines from controller to various other components have been
illustrated herein, it is emphasized that the number of wires may
vary depending on the embodiment(s) used. For example, where a
rotor is grounded, the number of calrod rotating electrical
connections could be reduced, e.g., from 2 to 1 per calrod, as the
rotor body could be used for the electrical current return
path.
[0033] The non-contact nature of the FIGS. 4-6 embodiments provides
a number of advantages. For example, heating element 330, 430
and/or 330' can be easily installed in a new turbomachine or
retrofit to a rotor already in the field where space allows.
Further, heat can be applied to a rotating member such as rotor 210
without any changes to rotor 210.
[0034] Referring to FIGS. 7-11, in another embodiment, a heating
element 530 may be at least partially positioned within rotor 210.
As used herein, "positioned within" indicates the heating element
is at least partially inside an elongated body of rotor 210 in such
a manner that heat from the heating element may be transmitted into
the rotor; the heating element need not necessarily be completely
in contact or encompassed by the material of the rotor. That is, an
opening or bore 532 in rotor 210 in which heating element 530 is
positioned may be in close proximity or in contact with heating
element 530, as shown in FIG. 7, or may simply surround heating
element 530 as shown in FIG. 8, or some combination thereof.
[0035] In FIGS. 7-11, heating element 530 may include at least one
calrod 540. A "calrod" can be any variety of well-known wire
heating elements in the form of tubes, coils or other
configurations in which heat is resistively (Joule heating)
produced by an electric current. Calrods 540 may be employed in a
number of ways such as, but not limited to, cartridge heaters
available from, for example, Watlow Electric Manufacturing Co.
under the FIREROD.RTM. brand. Cartridge heaters typically include a
casing that encloses calrod and any necessary electrical
connections thereto. In the embodiments illustrated, each calrod
540 extends from an end of rotor 210 and into the rotor (bore 532).
Each calrod 540 may include at least one electrical contact 542
external to rotor 210 to provide power to the calrod as rotor 210
rotates. In one embodiment, as shown in FIG. 7, where a single
calrod 540 is employed, electrical contact 542 may include a brush
electrical connection 544 that electrically contacts an exterior of
a respective calrod 540 as it rotates with rotor 210. Brush
electrical connection 544 is operatively coupled to controller 340,
which may include an alternating current (AC) power supply sized to
power calrod 540. In another embodiment, as shown in FIG. 8,
electrical contact 542 may include an induction transformer 550
operatively coupled to calrod 540 for powering the calrod.
Induction transformer 550 may include any now known or later
developed device for electromagnetically inducting power between a
stationary part and a rotating part on rotor 210. Induction
transformer 550 is also operatively coupled to controller 340,
which may include an alternating current (AC) power supply sized to
power calrod(s) 540. Each calrod 540 may have its own coupling to
induction transformer 550, or calrods may share couplings.
[0036] In another embodiment, shown in FIG. 9, as an option, a
permanent magnet generator 560 may be operatively coupled to rotor
210 to power, e.g., heating element(s) 530 and/or controller 340.
Generator 560 interacts with rotor 210 to generate power for
controller 340 and/or heating element 530 in a known fashion.
Controller 340 may control power generated by generator 560 and
delivered to heating element(s) 530. While FIG. 9 shows heating
system 200 including an induction transformer 550, it is emphasized
that generator 560 may be employed with any of the embodiments
described herein.
[0037] Referring to FIG. 10, in another embodiment, heating element
530 may include a plurality of heating sub-elements 570, e.g.,
calrods 540 in the form of cartridge heaters, at least partially
positioned in rotor 210. In this case, each heating sub-element 570
heats a different axial position of rotor 210. That is, each
heating sub-element 570 may extend a different distance into rotor
210 to heat a different axial position of rotor 210. In this
fashion, rotor 210 can be very precisely heated. A controller 340
may control operation of each heating sub-element 570. Multiple
calrods also increase rotor heating system reliability, because the
rotor can still be heated as long as one calrod is operational.
[0038] A plurality of temperature sensors 334 may be employed with
each temperature sensor 334 configured to sense a temperature of
rotor 210 at a respective one of the different axial positions.
Controller 340 may control operation of each heating sub-element
570 based on the sensed temperatures of the different axial
positions, e.g., its respective temperature and/or those around it.
Temperature sensors 334 may be implemented in a number of fashions,
e.g., thermocouples on rotor 210, light-based sensors focused on
different exterior axial positions for rotor 210. In one
embodiment, shown in FIG. 10, plurality of temperature sensors 334
such as thermocouples or fiber optic temperature sensors are
positioned within rotor 210. As understood in the art, fiber optic
temperature sensor 580 may include one or a number of fiber optic
strands 582 (see FIG. 11), the ends of which are positionable at
selected axial positions of rotor 210 to measure a temperature
thereat. Fiber optic temperature sensor 580 can provide rotor
temperature monitoring along the rotor axis internal to rotor
opening 532 at multiple locations with single fiber optic cable.
Although shown only with the FIGS. 10 and 11 embodiments, fiber
optic temperature sensor 580 may be applied to any embodiment
described herein.
[0039] Referring to FIG. 11, in another embodiment, variations of
heating system 200 described herein may be combined, which may be
advantageous, for example, to reduce capacity of internal heating
element(s) 530 or as a backup system to provide supplemental heat
during turbine 212 (FIG. 3) startup. Combined systems may be
particularly beneficial for a forward end of a steam turbine rotor.
FIG. 11 shows one example of a combined heating element, which may
include at least one first heating sub-element 570 positioned in
rotor 210, as in FIGS. 7-10, and at least one second heating
element 330 (e.g., induction heating coil) configured to heat at
least a portion of an exterior surface 240 of rotor 210, as in
FIGS. 4-6. Although particular embodiments of the internal and
external heating elements are shown in FIG. 11, it is emphasized
that any of the embodiments can be used together. As also shown in
FIG. 11, any of the above-described embodiments may also be
employed with a heating blanket 583 configured to heat an exterior
of outer casing 204.
[0040] Controller 340 may also be operatively coupled to control a
turning gear 584, part of turbomachine 190, for rotating rotor 210
during the heating, which may assist in more evenly heating the
rotor and preventing hot spots. Controller 340 may also be
operatively coupled to control flow of a working fluid into
turbomachine 190, e.g., through controlling flow valves directly or
through an overall turbomachine controller, thus allowing it to
further control heating of the turbomachine by controlling working
fluid flow.
[0041] Embodiments of the disclosure, as shown in FIGS. 7-11, may
also include rotor 210 for turbomachine 190. Rotor 210 may include
an elongated body 218 (FIG. 10), and a heating element 530, as
described herein, positioned at least partially in the elongated
body for heating at least a portion of the rotor. A heating system
200 for rotor 210 in-situ in casing 204 of turbomachine 190 is also
provided in which heating element 530 is configured to be
positioned at least partially within the rotor for heating an
internal portion of the rotor. Controller 340 controls operation of
heating element 530.
[0042] Embodiments of the disclosure that provide internal heating
to rotor 210, FIGS. 7-11, provide a number of additional advantages
compared to the external heaters of FIGS. 4-6. For example,
internal heating provides heat directly to a core of turbine 212
(FIG. 3), where it is most effectively applied via a centralized
bore (opening) 532 (FIG. 10) along an axis of rotor 210. Internal
heating may also be safer because heating element(s) 530 are
positioned in low-stress region of rotor 210. Internal heating
elements 530 also allow for easy heating element addition, removal
and replacement, e.g., during routine maintenance. Internal heating
elements 530 may also improve "rotor bow" recovery time and reduce
rotor vibration due to rotor bow during slow roll and/or turning
gear operation. Further, internal heating provides internal turbine
or compressor casing temperature (indirect or radiated) heating
from rotor 210, thereby reducing thermal gradients during startup,
allowing for reduced startup rates and time. It also allows
management of rotor-to-casing thermal growths, and optimization of
rotor, casing, seal pack and related component clearances, thus
reducing thermal growth transient clearance extremes and improving
startup thermal performance. Consequently, it also improves
rotating bucket, blade, airfoil and nozzle/diaphragm airfoil life
cycle through reduced thermal gradients and shocking during steam
turbine startup thereby improving low cycle fatigue (LCF) concerns
and component life cycles.
[0043] Use of multiple heating elements 530 internal to rotor 210,
as described relative to FIGS. 10-11, also provides a number of
additional advantages. For example, multiple heating elements
minimizes bearing 224 heating by allowing selecting of heating
positions by choosing appropriate heating element lengths, i.e., to
optimize heat transmission away from bearing(s) 224. Heating power
can also be readily customized for rotor axial position with
multiple heating elements. Varied heating element lengths also
allows for "zone rotor temperature control" along an axis of rotor
210 to provide variable heating of rotor 210 along its length, if
desired, or increased temperature for turbine startup optimization.
Multiple heating elements 530 also provide some level of redundancy
for reliability over turbomachine 190 life.
[0044] As noted, embodiments of the disclosure are applicable in
any turbomachine setting, e.g., steam turbines, gas turbines, and
compressors. Consequently, embodiments of the disclosure can
significantly reduce or eliminate rotor cycle stresses including
low cycle fatigue and increase rotor life-cycle by eliminating
temperature cycles associated with cold startups for a wide variety
of turbomachines. Teachings of the disclosure can further be
applied to: monitor and control temperatures and temperature rate
of change, control temperature transients and maintain desired
temperatures, control cooldown rates, and match rotor and casing
temperatures. Teachings of the disclosure can be applied to various
turbomachine sections to allow for variable heat input to different
sections requiring different temperatures, e.g., high, low and
intermediate pressures rotors in steam turbine applications.
[0045] While the teachings of the disclosure have been described
herein relative to a number of embodiments, it is emphasized that
heating can be provided to rotor in a number of alternative ways
considered within the scope of the disclosure. For example, a rotor
may be heated with other mediums such as pressurized hot water or
steam via channels in the rotor.
[0046] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the disclosure. As used herein, the singular forms "a", "an" and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise. It will be further understood
that the terms "comprises" and/or "comprising," when used in this
specification, specify the presence of stated features, integers,
steps, operations, elements, and/or components, but do not preclude
the presence or addition of one or more other features, integers,
steps, operations, elements, components, and/or groups thereof.
[0047] The corresponding structures, materials, acts, and
equivalents of all means or step plus function elements in the
claims below are intended to include any structure, material, or
act for performing the function in combination with other claimed
elements as specifically claimed. The description of the present
disclosure has been presented for purposes of illustration and
description, but is not intended to be exhaustive or limited to the
disclosure in the form disclosed. Many modifications and variations
will be apparent to those of ordinary skill in the art without
departing from the scope and spirit of the disclosure. The
embodiment was chosen and described in order to best explain the
principles of the disclosure and the practical application, and to
enable others of ordinary skill in the art to understand the
disclosure for various embodiments with various modifications as
are suited to the particular use contemplated.
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