US20100290889A1

US20100290889A1 - Turbine wheelspace temperature control

Info

Publication number: US20100290889A1
Application number: US12/467,378
Authority: US
Inventors: Michael James Fedor
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 2009-05-18
Filing date: 2009-05-18
Publication date: 2010-11-18
Also published as: JP2010265901A; CN101892867A; DE102010016828A1; CH701139A2

Abstract

Apparatus for controlling an amount of cooling air provided to a wheelspace of a turbine section of a gas turbine includes a sensor that senses a temperature of the wheelspace and provides a sensed temperature signal. The apparatus also includes a processor, responsive to the sensed temperature signal, that determines if the temperature of the wheelspace exceeds a desired value. If the temperature of the wheelspace exceeds the desired value, the processor activates an actuator control signal to control movement of a cooling air control valve to allow a greater amount of cooling air sourced from a compressor section of the gas turbine or from a cooling air cooler which receives air from the compressor section of the gas turbine to flow to the wheelspace, thereby cooling the temperature of the wheelspace.

Description

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates to gas turbines and, in particular, to control of the temperature of the wheelspaces of a turbine section of a gas turbine through control of the cooling airflow provided to the wheelspaces.
Turbine wheelspaces are those cavities or areas in the turbine section of a gas turbine located between the turbine rotor discs or wheels that support corresponding rows of turbine blades. The wheelspaces are located radially inward of the mainstream flow of gas through the adjacent turbine stages. Typically, the radially inward discs are heated by various effects, including conduction through the rotor blades, ingress of mainstream flow into the wheelspace cavities, and windage heating within the wheelspaces.
The actual turbine wheelspace temperatures are in general a function of turbine output, ambient temperature and unit degradation or condition. Wheelspace temperatures are typically sensed or monitored and alarms may be used to signal higher than acceptable temperature readings. Gas turbine operators may reduce power to prevent such alarms from occurring due to unacceptably high wheelspace temperatures. However, this practice causes a loss of revenue and potentially limits total plant output on relatively hot days.
Another method for achieving reductions in wheelspace temperatures includes shutting the gas turbine down, changing orifice plates in the cooling supply circuit, and then restarting the gas turbine. This procedure, however, causes shutdown and startup delays, and requires frequent adjustment as a function of the outside ambient temperature.
A further method for adjusting wheelspace temperatures includes a reduction in cooling flow, thereby having the effect of increasing wheelspace temperatures. Setting relatively higher wheelspace temperatures results in increased performance; however, it may also reduce the life cycle of the gas turbine.
It is also known to provide cooling airflow to the wheelspaces simultaneously in series or in parallel with cooling airflows provided to other components of the gas turbine. However, a problem with some embodiments of this practice, even with variable cooling airflows, is that if adequate cooling airflow is provided to the wheelspaces then typically the cooling airflow provided to other gas turbine components (e.g., turbine nozzles, diaphragms, shrouds) may be insufficient for adequate cooling of those other components.

BRIEF DESCRIPTION OF THE INVENTION

According to one aspect of the invention, apparatus for controlling an amount of cooling air provided to a wheelspace of a turbine section of a gas turbine includes a sensor that senses a temperature of the wheelspace and provides a sensed temperature signal. The apparatus also includes a processor, responsive to the sensed temperature signal, that determines if the temperature of the wheelspace exceeds a desired value. If the temperature of the wheelspace exceeds the desired value, the processor activates an actuator control signal to control movement of a cooling air control valve to allow a greater amount of cooling air sourced from a compressor section of the gas turbine or from a cooling air cooler which receives air from the compressor section of the gas turbine to flow to the wheelspace, thereby cooling the temperature of the wheelspace.
According to another aspect of the invention, apparatus for controlling an amount of cooling air provided to a wheelspace of a turbine section of a gas turbine includes a sensor that senses a temperature of the wheelspace and provides a sensed temperature signal. The apparatus also includes a processor, responsive to the sensed temperature signal, that determines if the temperature of the wheelspace is below a desired value. If the temperature of the wheelspace is below the desired value, the processor activates an actuator control signal to control movement of a cooling air control valve to allow a lesser amount of cooling air sourced from a compressor section of the gas turbine or from a cooling air cooler which receives air from the compressor section of the gas turbine to flow to the wheelspace, thereby allowing the temperature of the wheelspace to increase.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWING

The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is block diagram of a gas turbine having embodiments of the invention located therein;

FIG. 2 is cross section of a portion of a turbine section of a gas turbine that includes an embodiment of the invention; and

FIG. 3 is a cross section of a portion of a turbine section of a gas turbine that includes another embodiment of the invention.

The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1 is a gas turbine 10 that includes a compressor section 12, which provides compressed air. The compressor 12 may be axially aligned with a turbine section 14 of the gas turbine 10 on a single shaft represented by a longitudinal centerline 16. Most of the compressed air may be supplied to the turbine combustors (not shown), but some of the compressed air may be extracted for other uses. For example, cooling air may be extracted from the compressor 12 at extraction ports 18, and supplied via lines (e.g., pipes, ducts, etc.) 22, 24 to selected areas of the turbine section 14 and ultimately to the wheelspaces (FIGS. 2-3) within the turbine section 14 via inlet ports 26, 28, 30, 32, (e.g., holes in the turbine casing) in accordance with embodiments of the invention, as described in more detail hereinafter and illustrated in FIGS. 2-3. In an alternative embodiment, a cooling air cooler 33 may be provided in one of the lines 24 and located external to the gas turbine 10. Cooling air sourced from the compressor section 12 on the line 24 may be provided to the cooling air cooler 33, which further cools the compressed air that is then provided to the corresponding input ports 26, 28. In a similar manner, cooling air may be extracted from compressor ports 34, 36 and supplied via lines 38, 40 (e.g., pipes, ducts, etc.) and ultimately to the wheelspaces within the turbine section 14 via inlet ports 42, 44, 46, 48, (e.g., holes in the turbine casing) also in accordance with embodiments of the invention, as described in more detail hereinafter and illustrated in FIGS. 2-3.
Embodiments of the invention may include a feedback control loop to control the wheelspace temperature to above or below desired lower and upper limits or values, respectively (e.g., within an acceptable range of values). Thus, embodiments of the invention may include a microprocessor 50 or other suitable type of processor, computing or logic circuit. The microprocessor 50 is responsive to one or more signals on corresponding signal paths 52, such as at least one of wired or wireless lines or the like that establish each of the paths 52, or combinations thereof. Each signal on the corresponding signal path 52 is directly or indirectly indicative of the temperature of a corresponding wheelspace as provided by a suitable temperature sensor located in the wheelspace (FIGS. 2-3). However, other suitable sensed signals may be used that directly or indirectly indicate the temperature of the wheelspace. As described in more detail hereinafter with respect to FIGS. 2-3, the microprocessor 50 is responsive to the wheelspace temperature signals to provide one or more actuator control signals on corresponding signal paths 54, such as at least one of wired or wireless lines or the like that establish each of the paths 54, or combinations thereof. The actuator control signals are utilized to control the amount of cooling airflow from the compressor for control of the temperature of each of the various wheelspaces to desired or acceptable values.
In FIG. 2 is an embodiment of the invention in which a hole is formed through the solid (e.g., cast iron) turbine casing 60 and into an inner cavity or plenum 62. Disposed through the hole is one of the lines (pipes, ducts, etc) 22, 24, 38, 40, which provides the compressed air from the compressor 12 (FIG. 1) into the open area plenum 62. The compressed air in the plenum 62 flows unrestricted downward in FIG. 2 into a hollow nozzle 64, which may be airfoil shaped, as is known. That same compressed air may also flow unrestricted down into an open area diaphragm 66. As described in detail hereinafter, the compressed air that enters the plenum 62 is utilized to control the temperature of a corresponding wheelspace 68 illustrated in FIG. 2 within the turbine section 14 (FIG. 1), in accordance with an embodiment of the invention.
One or more temperature sensors 70 may be located within each one of the wheelspaces 68. Each wheelspace 68 may be an uninterrupted 360-degree circumferential cavity in the turbine section 14 of the gas turbine 10 (FIG. 1). Since the turbine section 14 (FIG. 1) typically has multiple rows of turbine blades, there exists a multiple number of wheelspaces 68 between the rows of blades. The sensor 70 may be any suitable type of sensor that senses the temperature of the wheelspace 68 either directly or indirectly and provides the wheelspace temperature signal on the signal path 52 to the microprocessor 50. In accordance with an embodiment of the invention, when the microprocessor 50 determines that the then-current temperature of any one or more particular wheelspaces 68 is greater than a desired or acceptable upper value (for example, by comparing the sensed wheelspace temperature to a desired one or more values, e.g., stored in a memory associated with the microprocessor 50), the microprocessor 50 activates the actuator control signal on the signal path 54 to ultimately reduce the temperature of that particular wheelspace 68 to a desired value.
Embodiments of the invention may also have the microprocessor 50 determine if the then-current temperature of any one or more particular wheelspaces 68 is less than a desired or acceptable lower value using, e.g., a similar comparison method. If the sensed temperature is less than the desired value, the microprocessor may activate the actuator control signal on the signal path 54 to ultimately increase the temperature of that particular wheelspace 68 to a desired value.
The actuator control signal on the signal path 54 may connect to a device 72, such as an electromechanical device (e.g., a motor), a hydraulic actuator or other suitable device. The output 74 of the device 72 may connect to an optional synch ring 76, which may be contiguous and encircle the entire circumference of the turbine section 14 of the gas turbine 10 (FIG. 1). The synch ring 76, if utilized, connects to each one of a plurality of actuators 78 located outside of the turbine casing 60. One such actuator 78 is shown in FIG. 2. The output shaft of the actuator 78, which may be rotatable or movable is some other suitable manner, connects to a shaft 80 that may also be rotatable or movable in some other suitable manner. The shaft 80 connects at its bottom end (as viewed in FIG. 2) located within the plenum 62 to a cooling air control valve 82 having one or more oblong (or other suitable) shaped openings 84. The valve 82, which may be located within the plenum 62, may be rotatable or movable in some other suitable manner. The cooling air control valve 82 may also comprise other suitable types of valves, such as a butterfly valve, a gate valve, or a ball valve. Seals and/or bushings 86 are provided to properly seal the shaft 80 at its connection with the output of the actuator 78. A bushing 86 is also placed through a hole formed (e.g., drilled) in the turbine casing 60 to provide a seal around the shaft 80. The seals and/or bushings 86 reduce leakage of compressed air gasses from the inside of the turbine casing 60 to the outside of the casing 60.
A tube 90 is located within the hollow nozzle 64 and in the diaphragm 66. The top or upper portion of the tube 90 (as viewed in FIG. 2) also has one or more oblong (or other suitable) shaped holes 92 in the same general vertical location as the holes 84 in the bottom portion of the shaft 80. The bottom portion of the tube 90 has a narrower diameter portion that is in fluid communication with the wheelspace 68.
In operation, when the microprocessor 50 determines that the then-current temperature of a particular wheelspace 68 is greater than a desired or acceptable upper value, the microprocessor activates the actuator control signal on the signal path 54, which ultimately causes the holes 84 in the cooling air control valve 82 to line up (either fully or partially) with the holes 92 in the upper portion of the tube 90. When lined up as such, this allows an amount of the compressed air in the plenum 62 to flow into and down through the tube 90 and ultimately into the wheelspace 68. This compressed air is typically cooler than the sensed hotter air in the wheelspace 68 that exceeded an upper value and caused the flow of the cooling compressed air to the wheelspace 68 to occur, thereby reducing the temperature of the wheelspace 68. Once the microprocessor 50 determines that the wheelspace temperature is equal to or below an upper value and, thus, is at an acceptable value, the microprocessor then activates the actuator control signal on the signal path 54 to cause the cooling air control valve 82 to move and, thus, cause the holes 84 in the valve 82 to not align, or only partially align, with the holes 92 in the upper portion of the tube 90. This stops or reduces the flow of the cooling compressed air to the wheelspace 68 through the tube 90.
Similarly, when the microprocessor 50 determines that the then-current temperature of a particular wheelspace 68 is less than a desired or acceptable lower value, the microprocessor activates the actuator control signal on the signal path 54, which ultimately causes the holes 84 in the valve 82 to line up (either partially or not at all) with the holes 92 in the upper portion of the tube 90. When lined up as such, this allows no compressed air or only a small amount of compressed air in the plenum 62 to flow into and down through the tube 90 and ultimately into the wheelspace 68. This reduction in the amount of cooling air provided to the wheelspace 68 allows the temperature of the wheelspace 68 to increase by way of the causes previously mentioned.
In accordance with embodiments of the invention, each wheelspace 68 may utilize a plurality of the actuator 78 and valve 82 combinations as shown in FIG. 2 and described hereinabove. As such, the synch ring 76, if utilized, may be used to cause the simultaneous activation of the plurality of actuator 78 and valve 82 combinations that encircle the entire circumference of the turbine section 14 (FIG. 1) and correspond to a single wheelspace 68, to thereby properly control the temperature of that wheelspace 68 to a desired value. Each wheelspace 68 may have its own dedicated synch ring 76.
In FIG. 3 is another embodiment of the invention that is somewhat similar to the embodiment of FIG. 2. Thus, as between FIGS. 2 and 3, like reference numbers refer to like elements. In FIG. 3 in place of the tube 90 the shaft 80 extends downward (as viewed in FIG. 3) through the entire height of the hollow nozzle 64 and into the diaphragm 66. At the bottom of the shaft 80 is a movable (e.g., rotatable) linkage 100 that connects to a cooling air control valve 102 in the form of a rotating valve ring with one or more spaced apart openings 104 formed therein. Similar to the embodiment of FIG. 2, the cooling air control valve 102 may comprise other suitable types of valves, such as a butterfly valve, a gate valve, or a ball valve. The rotating valve ring may encircle the entire circumference of the turbine section 14 of the gas turbine 10 (FIG. 1). Each opening 104 is in fluid communication with the wheelspace 68 through a corresponding hole 106 formed (e.g., drilled) in a solid metal portion of the diaphragm 66.
In operation, when the microprocessor 50 determines that the then-current temperature of a particular wheelspace 68 is greater than a desired or acceptable upper value, the microprocessor activates the actuator control signal on the signal path 54, which ultimately causes the shaft 80 to move (e.g., rotate) and causes the linkage 100 to move (e.g., rotate) until each of the openings 104 in the rotating valve ring 102 lines up (either fully or partially) with the corresponding one of the holes 106. When the openings 104 are lined up as such, this allows an amount of the cooling compressed air in the diaphragm 66 to flow through the lined up openings 104 and into and down through the holes 106 (as viewed in FIG. 3) and ultimately into the wheelspace 68, thereby reducing the temperature of the wheelspace 68 to an acceptable value. Similar to the embodiment of FIG. 2, once the microprocessor 50 determines that the wheelspace temperature is below an upper value, the microprocessor activates the actuator control signal on the signal path 54 to cause the cooling air control valve 102 to move (e.g., rotate) and, thus, cause the openings 104 in the rotating valve ring 102 to not align, or only partially align, with the corresponding holes 106. This stops or reduces the flow of cooling compressed air to the wheelspace 68.
Also, when the microprocessor 50 determines that the then-current temperature of a particular wheelspace 68 is less than a desired or acceptable lower value, the microprocessor activates the actuator control signal on the signal path 54, which ultimately causes the shaft 80 to move (e.g., rotate) and causes the linkage 100 to move (e.g., rotate) until each of the openings 104 in the rotating valve ring 102 does not line up (either fully or partially) with the corresponding one of the holes 106. When the openings 104 are lined up as such, this allows no cooling compressed air or only a small amount of cooling compressed air into the diaphragm 66 to flow through the lined up openings 104 and into and down through the holes 106 (as viewed in FIG. 3) and ultimately into the wheelspace 68. This allows the temperature of the wheelspace 68 to increase to a desired or acceptable value by way of the causes previously mentioned.
Embodiments of the invention provide for improved control of turbine wheelspace temperature through control of the cooling compressed airflow provided to the wheelspace 68 largely separate and apart from the cooling airflows delivered to other gas turbine components. Thus, embodiments of the invention have no negative impact on, and are not influenced by, the cooling airflow provided separately to these other gas turbine components and any leakages associated therewith. Embodiments of the invention may be applied to the wheelspaces of gas turbines either as a modification (retrofit) or as part of an original design.
Embodiments of the invention also provide for reduction in the use of parasitic secondary airflows, thereby increasing gas turbine efficiency and power output. By using compressor extraction flow modulation coupled with the microprocessor 50 as part of a feedback control system, a reduced amount of compressed airflow can be delivered to the wheelspaces 68 regardless of variations in ambient conditions, load, and machine-to-machine variations in leakage flows.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.

Claims

1. Apparatus for controlling an amount of cooling air provided to a wheelspace of a turbine section of a gas turbine, the apparatus comprising:

a sensor that senses a temperature of the wheelspace and provides a sensed temperature signal;

a processor, responsive to the sensed temperature signal, that determines if the temperature of the wheelspace exceeds a desired value; and

if the temperature of the wheelspace exceeds the desired value, the processor activates an actuator control signal to control movement of a cooling air control valve to allow a greater amount of cooling air sourced from a compressor section of the gas turbine or from a cooling air cooler which receives air from the compressor section of the gas turbine to flow to the wheelspace, thereby cooling the temperature of the wheelspace.

2. The apparatus of claim 1, the cooling air being provided to a plenum in which the cooling air control valve is located.

3. The apparatus of claim 1, the actuator control signal provided to a first actuator that controls movement of an output shaft of the first actuator in response to the actuator control signal, the output shaft of the first actuator being connected with the cooling air control valve, the movement of the first actuator output shaft controlling the movement of the cooling air control valve to allow the cooling air to flow to the wheelspace.

4. The apparatus of claim 3, the cooling air control valve being connected with a tube having one or more openings that align with one or more openings in the cooling air control valve to allow the cooling air to flow to the wheelspace when the temperature of the wheelspace exceeds the desired value.

5. The apparatus of claim 3, the first actuator output shaft and the cooling air control valve being rotatable.

6. The apparatus of claim 1, a second actuator being connected to the actuator control signal, the second actuator having an output connected to the first actuator that controls movement of an output shaft of the second actuator in response to the actuator control signal, the output shaft of the first actuator being connected with the cooling air control valve, the movement of the first actuator output shaft controlling the movement of the cooling air control valve to allow the cooling air to flow to the wheelspace.

7. The apparatus of claim 6, the second actuator comprising one of a motor or hydraulic actuator.

8. The apparatus of claim 1, the cooling air being provided by a pipe, duct or hole to a plenum in which the cooling air control valve is located.

9. The apparatus of claim 1, a plurality of first actuators being connected to the actuator control signal, each of the plurality of first actuators having an output connected to a synch ring that simultaneously controls movement of an output shaft of each of the plurality of first actuators in response to the actuator control signal, the output shaft of each of the plurality of first actuators being connected to a corresponding one of a plurality of the cooling air control valves, the movement of each one of the first actuator output shafts controlling the movement of the corresponding cooling air control valve to allow the cooling air to flow to the wheelspace.

10. The apparatus of claim 1, the cooling air control valve comprising a rotating valve ring located within a diaphragm, the cooling air being provided to the diaphragm in which the rotating valve ring is located.

11. Apparatus for controlling an amount of cooling air provided to a wheelspace of a turbine section of a gas turbine, the apparatus comprising:

a processor, responsive to the sensed temperature signal, that determines if the temperature of the wheelspace is below a desired value; and

if the temperature of the wheelspace is below the desired value, the processor activates an actuator control signal to control movement of a cooling air control valve to allow a lesser amount of cooling air sourced from a compressor section of the gas turbine or from a cooling air cooler which receives air from a compressor section of the gas turbine to flow to the wheelspace, thereby allowing the temperature of the wheelspace to increase.

12. The apparatus of claim 11, the cooling air being provided to a plenum in which the cooling air control valve is located.

13. The apparatus of claim 11, the actuator control signal provided to a first actuator that controls movement of an output shaft of the first actuator in response to the actuator control signal, the output shaft of the first actuator being connected with the cooling air control valve, the movement of the first actuator output shaft controlling the movement of the cooling air control valve to allow the cooling air to flow to the wheelspace.

14. The apparatus of claim 13, the cooling air control valve being connected with a tube having one or more openings that align with one or more openings in the cooling air control valve to allow the cooling air to flow to the wheelspace when the temperature of the wheelspace is below the desired value.

15. The apparatus of claim 13, the first actuator output shaft and the cooling air control valve being rotatable.

16. The apparatus of claim 11, a second actuator being connected to the actuator control signal, the second actuator having an output connected to the first actuator that controls movement of an output shaft of the second actuator in response to the actuator control signal, the output shaft of the first actuator being connected with the cooling air control valve, the movement of the first actuator output shaft controlling the movement of the cooling air control valve to allow the cooling air to flow to the wheelspace.

17. The apparatus of claim 16, the second actuator comprising one of a motor or hydraulic actuator.

18. The apparatus of claim 11, the cooling air being provided by a pipe, duct or hole to a plenum in which the cooling air control valve is located.

19. The apparatus of claim 11, a plurality of first actuators being connected to the actuator control signal, each of the plurality of first actuators having an output connected to a synch ring that simultaneously controls movement of an output shaft of each of the plurality of first actuators in response to the actuator control signal, the output shaft of each of the plurality of first actuators being connected to a corresponding one of a plurality of the cooling air control valves, the movement of each one of the first actuator output shafts controlling the movement of the corresponding cooling air control valve to allow the cooling air to flow to the wheelspace.

20. The apparatus of claim 11, the cooling air control valve comprising a rotating valve ring located within a diaphragm, the cooling air being provided to the diaphragm in which the rotating valve ring is located.