Patent Grant
8186945
The subject matter disclosed herein relates to clearance control techniques, and more particularly to a system for adjusting the clearance between a stationary component and a rotary component of a rotary machine.
In certain applications, a clearance may exist between components that move relative to one another. For example, a clearance may exist between rotary and stationary components in a rotary machine, such as a compressor, turbine, or the like. The clearance may increase or decrease during operation of the rotary machine due to temperature changes or other factors. In turbine engines, it is desirable to provide greater clearance during transient conditions, such as start-up (e.g., to mitigate the occurrence of a rub between a turbine blade and a shroud), while providing lesser clearance during steady-state conditions (e.g., to increase power output and operational efficiency).
Certain embodiments commensurate in scope with the originally claimed invention are summarized below. These embodiments are not intended to limit the scope of the claimed invention, but rather these embodiments are intended only to provide a brief summary of possible forms of the invention. Indeed, the invention may encompass a variety of forms that may be similar to or different from the embodiments set forth below.
In one embodiment, a system includes a turbine engine. The turbine engine includes a shaft having an axis of rotation. The turbine engine further includes a plurality of blades coupled to the shaft. Additionally, the turbine engine includes a shroud having a plurality of segments disposed circumferentially about the plurality of blades. Each of the segments includes a fixed shroud portion having a first magnet and a movable shroud portion having a second magnet opposite from the first magnet. In each segment, at least one of the first or second magnets includes an electromagnet, wherein the movable shroud portion is magnetically actuated by the first and second magnets to move in a radial direction relative to the rotational axis of the shaft to vary a clearance between the plurality of blades and the movable shroud portion.
In another embodiment, a system includes an annular shroud. The annular shroud is configured to extend around a plurality of blades of a compressor or a turbine. The annular shroud includes a fixed shroud portion having a first electromagnet and a movable shroud portion having a second electromagnet. The movable shroud portion is magnetically actuated by the first and second electromagnets to move in a radial direction relative to a rotational axis of the blades to vary a clearance between the plurality of blades and the movable shroud portion.
In yet a further embodiment, a system includes a turbine clearance controller. The turbine clearance controller is configured to independently adjust clearances of a plurality of shroud segments about a plurality of blades via first and second magnets opposite from one another in fixed and movable portions of each shroud segment.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
One or more specific embodiments of the present invention will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.
When introducing elements of various embodiments of the present invention, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Any examples of operating parameters and/or environmental conditions are not exclusive of other parameters/conditions of the disclosed embodiments. Additionally, it should be understood that references to “one embodiment” or “an embodiment” of the present invention are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.
As discussed in detail below, the present disclosure generally relates to magnetically controlled clearance techniques that may be implemented in a system, such as a turbine engine-based system (e.g., aircraft, locomotive, power generator, etc.). As used herein, the term “clearance” or the like shall be understood to refer to a spacing or gap that may exist between two or more components of the system that move relative to one another during operation. The clearance may correspond to an annular gap, a linear gap, a rectangular gap, or any other geometry depending on the system, type of movement, and other various factors, as will be appreciated by those skilled in the art. In one application, the clearance may refer to the radial gap or space between housing components surrounding one or more rotating blades of a compressor, a turbine, or the like. By controlling the clearance using the presently disclosed techniques, the amount of leakage between the rotating blades and the housing may be reduced to increase operational efficiency, while simultaneously minimizing the possibility of a rub (e.g., contact between housing components and the rotating blades). As will be appreciated, the leakage may correspond to any fluid, such as air, steam, combustion gases, and so forth.
In accordance with embodiments of the invention, a turbine engine utilizing the magnetic clearance control techniques disclosed herein may include a housing component having a stationary shroud portion and one or more movable shroud portions positioned circumferentially about a rotational axis of the turbine engine to define an inner surface of the housing. Each of one or more magnetic actuating elements may provide radial movement of a respective one of the movable shroud portions in response to control signals provided by a clearance controller. In one embodiment, each movable shroud portion (by way of its corresponding magnetic actuating element) may be actuated independently to provide for varying radial displacements for each movable shroud portion. In this manner, a substantially consistent clearance with respect to rotating turbine blades (or compressor blades) may be maintained about the inner surface of the housing, even if the turbine housing itself is out-of-round, or becomes out-of-round during operation (e.g., due to deformation caused by uneven thermal expansion, etc.). Further, in some embodiments, the radial positions of the movable shroud portions may be adjusted in real-time depending on one or more operating conditions of the turbine engine. Such operating conditions may be measured by sensors, such as temperature sensors, vibration sensors, position sensors, etc. By providing real-time adjustment of the moveable shroud portions, the clearance between the turbine housing and the turbine blades (or compressor blades) may be finely adjusted to balance the turbine efficiency against the possibility of contact (e.g., a rub) between the turbine blades and the turbine housing. In some embodiments, the adjustment of the moveable shroud portions may be determined based at least partially upon a current operating condition of the turbine, i.e., start-up, steady-state, full-speed full-load, turndown, etc.
With the foregoing in mind,
In operation, air enters the turbine system 10 through the air intake section 14 (indicated by the arrows) and may be pressurized in the compressor 16. The compressor 16 may include compressor blades 26 coupled to the shaft 24. The compressor blades 26 may span the radial gap between the shaft 24 and an inner wall or surface 28 of a compressor housing 30 in which the compressor blades 26 are disposed. By way of example, the inner wall 28 may be generally annular or conical in shape. The rotation of the shaft 24 causes rotation of the compressor blades 26, thereby drawing air into the compressor 16 and compressing the air prior to entry into the combustor section 18. As such, it is generally desirable to maintain a small radial gap between the compressor blades 26 and the inner wall 28 of the compressor housing 30 in order to prevent contact between the compressor blades 26 and the inside surface 28 of the compressor housing 30. For instance, contact between the compressor blade 26 and the compressor housing 30 may result in an undesirable condition generally referred to “rubbing” and may cause damage to one or more components of the turbine engine 12.
The combustor section 18 includes a combustor housing 32 disposed concentrically or annularly about the shaft 24 and axially between the compressor section 16 and the turbine 20. Within combustor housing 32, the combustor section 20 may include a plurality of combustors 34 disposed at multiple circumferential positions in a generally circular or annular configuration about the shaft 24. As compressed air exits the compressor 16 and enters each of the combustors 34, the compressed air may be mixed with fuel for combustion within each respective combustor 34. For example, each combustor 34 may include one or more fuel nozzles that may inject a fuel-air mixture into the combustor 34 in a suitable ratio for optimal combustion, emissions, fuel consumption, and power output. The combustion of the air and fuel may generate hot pressurized exhaust gases, which may then be utilized to drive one or more turbine blades 36 within the turbine 20.
The turbine 20 may include the above-mentioned turbine blades 36, and a turbine housing 40. The turbine blades 36 may be coupled to the shaft 24 and span the radial gap between the shaft 24 and the inside or inner wall 38 of turbine housing 40. By way of example, the inner wall 38 may be generally annular or conical in shape. The turbine blades 36 are generally separated from the inner wall 38 of the turbine housing 40 by a small radial gap to prevent the occurrence of contact (or a rub) between the turbine blades 36 and the inner wall 38 of the turbine housing 40. As will be appreciated, contact between the turbine blade 36 and the turbine housing 40 may result in rubbing, as discussed above, which may cause damage to one or more components of the turbine engine 12.
The turbine 20 may include a rotor element that couples each of the turbine blades 36 to the shaft 24. Additionally, the turbine 20 depicted in the present embodiment includes three stages, each stage being represented by a respective one of the illustrated turbine blades 36. It should be appreciated, however, that other configurations may include more or fewer turbine stages. In operation, the combustion gases flowing into and through the turbine 20 flow against and between the turbine blades 36, thereby driving the turbine blades 36 and, thus, the shaft 24 into rotation to drive a load. The rotation of the shaft 24 also causes the blades 26 within the compressor 16 to draw in and pressurize the air received by the intake 14. Further, in some embodiments, the exhaust exiting the exhaust section 22 may be used as a source of thrust for a vehicle such as a jet plane, for example.
As further shown in
The clearance control techniques described herein may be better understood with reference to
To provide a suitable balance between increasing the efficiency of the turbine 20 and decreasing the possibility of contact or rubbing between the turbine blades 36 and the turbine housing 40, the magnetic actuating elements 44 may be utilized for moving the movable shroud portion 54 in a radial direction towards or away from the rotational axis (e.g., axis along shaft 24) of the turbine 20 to increase or decrease the size of radial gap 56. In the presently illustrated embodiment, the movable shroud portion 54 is shown as being coupled directly to the turbine housing 40. In other embodiments, an intermediate shroud segment may be intermediately coupled between the housing 40 and the movable shroud portion 54. In other words, the movable shroud portion 54 may be coupled to an intermediate shroud segment, and the intermediate shroud segment may be coupled to the turbine housing 40. Thus, depending on the particular configuration of the turbine section 20, a generally annular-shaped shroud structure that surrounds the turbine blades 36 may include the movable shroud portions 54 and the turbine housing 40, or may include the movable shroud portions 54, intermediate shroud portions, and the turbine housing 40.
As will be more clearly illustrated in
Referring now to
In the illustrated embodiment, the polarity of the magnets 70 and 72 may be aligned to provide a repelling force between the stationary magnet 70 and the movable magnet 72. In some embodiments, one or both of the stationary magnet 70 and the movable magnet 72 may be electromagnets. For instance, as shown in
In some embodiments, heat from the combustion gases flowing through the turbine 20 may result in a high temperature within the cavity 68. For instance, during operation of the turbine engine 12, the temperature within the cavity 68 may reach approximately 800 to 1700 degrees Fahrenheit or more. Accordingly, the coil 74 and the core 76 corresponding to each of the stationary magnet 70 and the movable magnet 72 may include materials that are stable and exhibit suitable electrical properties at high temperatures. By way of example only, in some embodiments, the coil 74 may include nickel, and the core 76 may include an iron/cobalt/vanadium alloy, such as Vacoflux50® (approximately 49.0% cobalt, 1.9% vanadium, and 49.1% iron), available from Vacuumschmelze GmbH of Hanau, Hesse, Germany, or Hiperco50® (approximately 48.75% cobalt, 1.9% vanadium, 0.01% carbon, 0.05% silicon, 0.05% columbium/niobium, 0.05% manganese, and 49.19% iron), available from Carpenter Technology Corporation of Wyomissing, Pa., USA. Additionally, to reduce temperatures within the cavity 68, the housing 40 may include vents 80 and 82 that provide a flow path for a cooling fluid to circulate through the cavity 68, as indicated by the flow arrows 84 and 86. In one embodiment, the cooling fluid may be a portion of air siphoned from the compressor 16.
As further shown in
In the illustrated embodiment, the movable shroud portion 54 may further be coupled to the housing 40 by one or more biasing members, depicted here as springs and referred to by reference number 100. The springs 100 may normally bias the movable shroud portion 54 radially away, i.e., in the direction 98, from the rotational axis 62 of the turbine 20. In this manner, a failsafe mechanism is provided, wherein the movable shroud portion 54 will be moved radially away from the rotational axis 62, thereby increasing the clearance (e.g., the gap distance 56) between the inner wall 38 of the turbine housing 40 and the turbine blades 36, if the magnets 70 and 72 become inoperative (e.g., due to electrical or mechanical failure or malfunctions). As will be appreciated, the spring(s)/biasing members 100 may be located at any suitable location between the turbine housing 40 and the movable shroud portion 54.
The movable shroud portion 54 may be coupled to a clearance or proximity sensor 102 configured to detect clearance, i.e. the gap distance 56, by measuring a distance between the bottom surface 38 of the movable shroud portion 54 and the tip 58 of the blade 36. As will be appreciated, the sensor 102 may be any suitable type of proximity sensor, including capacitive, inductive, or photoelectric proximity sensors. An output 104 from the proximity sensor 102 may be sent to the clearance controller 46 as a feedback signal. Thus, by using the clearance data 104 provided by the proximity sensors 102 and/or feedback data 50 (e.g., temperature, vibration, flow, etc.) provided by other turbine sensors 48, as discussed above, the clearance controller 46 may adjust the radial gap 56 between the inner wall 38 of the turbine housing 40 and the tip 58 of the turbine blades 36 accordingly.
Before continuing, it should be noted that the above-described features of
Referring now to
Turning to
While only the movable shroud portions 54a-54e are specifically referenced in
As shown in
Turning to
For instance, as shown in
Continuing now to
The one or more parameters of the turbine engine 12 monitored at block 122 may then be used use to determine a desired clearance setting at decision blocks 124, 128, and 132. For instance, at decision block 124, a determination is made regarding whether the parameters indicate a transient state of the turbine engine 12, i.e. a state in which a changing parameter of the turbine engine 12 may have a tendency to cause rapid changes in the clearance. For example, one or more parameters may relate to a temperature of the turbine housing 40, the blades 36, or some other component of the turbine engine 12. If the temperature is detected as rapidly changing, this may indicate that the turbine engine 12 is in a transient state such as startup or shutdown.
If such a transient state is detected, the method 120 may proceed to block 126, at which the shroud is magnetically actuated to maintain a desired clearance setting that corresponds to a transient state of operation. In one embodiment, the method 120 may magnetically actuate the movable shroud portions 54 to a maximum clearance setting. By setting the clearance to a maximum level, the possibility of contact between the inner wall 38 of the shroud and the turbine blades 36 may be minimized. For instance, to achieve the maximum clearance setting, the clearance controller 46 may reduce or eliminate a current flow to the coils 74 of one or more of the magnets 70 and 72. Thus, as the repulsive force of the magnets is removed, the springs 100 may retract the movable shroud portions 54 outward and away from the rotational axis 62 (e.g., in the direction of arrow 98 of
In one embodiment, the determination of whether the turbine engine 12 is operating in a transient state or a steady-state condition may also be based on empirical measurements or theoretical estimates regarding the amount of time that the turbine engine 12 takes to reach a steady state after start-up or after some other change in the power setting of the turbine engine 12. The empirical data may be used to program specified time-constants into the clearance controller 46 representing the amount of time taken to achieve steady-state conditions after certain changes in the power setting of the turbine engine 12 have been initiated. For instance, after a particular change in the power setting of the turbine engine 12 has taken place, the clearance controller 46 may keep track of the amount of time that has elapsed since the change in the power setting to determine whether the turbine engine 12 is in a transient state or a steady state. If the elapsed time is greater than the specified time-constant, this may indicate that the turbine engine 12 has reached steady-state operating condition. If, however, the elapsed time is less than the specified time-constant, this may indicate that the turbine engine 12 is still in a transient operating state.
Returning to decision block 124, if the monitored parameters are not indicative of a transient state, then the method 120 may continue to one of the steady-state decision blocks 128 or 132. For example, if it is determined that the measured parameter (e.g., temperature) is relatively constant over a period of time, this may indicate that the turbine engine 12 has reached a steady-state operating condition. Thus, the method 120 may proceed through the decision logic depicted by blocks 128 and 130 to determine whether the turbine 20 is operating in a full-power steady-state condition or a turndown steady-state condition. Accordingly, the magnetic actuation of the movable shroud portions 54 may be determined based on the power setting of the turbine engine 12, as will be discussed below.
Continuing to decision block 128, a determination is made as to whether the parameters indicate that the turbine engine 12 is operating at full-power, steady-state conditions. If the monitored parameters indicate a full-power steady-state condition, the method 120 may magnetically actuate the movable shroud portions 54 at block 130 to a pre-determined displacement to provide a radial gap 56 that is intended to provide a minimum clearance for the full-power steady-state conditions. In some embodiments, the pre-determined displacement of each movable shroud portion 54 may be based on empirical measurements or theoretical estimates regarding the level and/or rate of expansion and/or distortion of the turbine housing 40, turbine blades 36, etc., that may be expected at full-power steady-state operating conditions. Thereafter, the method 120 may return to block 122 and continue to monitor operating parameter(s) of the turbine engine 12. By way of example only, the clearance setting for a full-power steady-state operating condition may be less than the clearance setting for the transient operating condition discussed above.
If at decision block 128, it is determined that the monitored parameters are not indicative of a full-power steady-state operating condition, the method 120 continues to decision block 132, wherein a determination is made as to whether the monitored parameters indicate that the turbine engine 12 is operating at turndown, steady-state conditions (e.g., 50% or less of the full-power setting). If so, the method 120 may magnetically actuate the movable shroud portions 54 at block 134 to a pre-determined displacement to provide a radial gap 56 that is intended to provide a minimum clearance for the turndown steady-state conditions. As mentioned above, the pre-determined displacement of each movable shroud portion 54 may be based on empirical measurements or theoretical estimates regarding the level and/or rate of expansion and/or distortion of the turbine housing 40, turbine blades 36, etc., that may be expected at turndown steady-state operating conditions. Furthermore, in some embodiments, several turndown settings may be programmed into the clearance controller 46 to correspond with various power settings of the turbine engine 12. Once the movable shroud portions 54 are adjusted accordingly, the method 120 may return to block 122 from block 134 and continue to monitor operating parameter(s) of the turbine engine 12. Additionally, the method 120 may also return to block 122 from decision block 132 and continue monitoring turbine parameters if a turndown steady-state condition is not detected at decision block 132.
As described above, the clearance controller 46 may be programmed to provide two or more discrete clearance settings which may be selected depending, at least in part, on whether the turbine engine 12 is operating in a steady-state operating condition (e.g., full-power and turndown). Turning now to
As shown in
The method 140 may also involve measuring the actual clearance, as indicated by block 144. For instance, the actual clearance may be measured by each of the proximity or clearance sensors 102 coupled to each of the movable shroud portions 54 around the circumference of the turbine housing 40 and sent to the clearance controller 46 (as feedback data signals 104 shown in
While the depicted method 140 shows that the adjustment process may end (block 150) once a desired clearance is achieved, in further embodiments the method 140 may be repeated at discrete short intervals to provide a near continuous, real-time monitoring and adjustment of the clearance. By continually adjusting the clearance in real time, a generally constant clearance may be maintained as the thermal response of the turbine 20 causes the blades 36 and/or the turbine housing 40 to contract or expand during operation. For example, as the turbine 20 heats up due to the combustion gases flowing out of the combustor section 18, the turbine blades 36 may tend to radially expand. As the turbine blades 36 radially expand, the movable shroud portions 54 may be adjusted outward (in direction of the arrow 98 in
It should be further appreciated that while the present examples have generally described the application of the clearance control techniques described herein with regard to a turbine of a turbine engine system, the foregoing techniques may also be applied to a compressor of the turbine engine system, as well as to any type of system that includes a stationary component and a rotary component and wherein a clearance is to be maintained between the stationary and rotary components.
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.
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