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