Patent Application
20110129331
The present invention relates generally to the operation of a turbomachine, and more particularly, to a system for reducing the axial thrust load acting on a turbomachine rotor.
Turbomachines, such as steam turbines, gas turbines, and the like, operate in a wide variety of applications, including, but not limited to, power generation and propulsion. As the turbomachine operates, the turbomachine rotor experiences high levels of axial thrust (hereinafter “thrust”, “thrust load”, or the like). A known solution for transferring the thrust load from rotating to stationary components employs thrust bearings, which absorb the thrust load without interfering with the rotation of the rotor and associated components. In general, the level of thrust experienced by thrust bearings varies. Differences in rotor manufacture, and changes in flow path pressure, can produce large fluctuations in the thrust load. Some turbomachines employ large thrust bearings to reduce these large fluctuations.
Turbomachines tend to operate best when the thrust load remains relatively constant or varies slowly. Large thrust bearings require substantial amounts of fluid and experience large friction losses; which may cause excessive power losses and reduce the overall efficiency of the turbomachine.
Some known solutions for addressing those issues transfer a portion of an operating fluid (derived from the turbomachine) to provide a force that opposes the thrust. However, this solution decreases the overall efficiency of the turbomachine.
Therefore, there is a desire for an improved system for reducing the thrust load and/or minimizing thrust variation experienced by a turbomachine. This system should be more efficient and cost-effective than currently known systems. This system may allow a turbomachine to use smaller thrust bearings.
The present application describes embodiments of a system for controlling a thrust load experienced by a turbomachine rotor. An embodiment of the system may include a chamber that partially surrounds a portion of the rotor (hereinafter “rotor portion”, or the like). This chamber may be substantially filled with a pressurized fluid that does not derive from the turbomachine. The chamber may include a first port and a second port that allow the fluid to flow through the chamber. The system may also include a seal system configured for operatively connecting the chamber and the rotor portion. A controller may determine the position of the rotor portion; and utilize the pressurized fluid to move the rotor in a direction that lessens the thrust load.
The system may also include a fluid supply system that provides the external fluid to the chamber and regulates fluid pressure within the chamber. The fluid supply system may comprise: an accumulator, an upper limit switch and a lower limit switch, a supply tank, and a pump. If an upper lower limit switch is triggered, a portion of the fluid within the accumulator may exit the chamber and return to the supply tank. If a lower limit switch is triggered, the pump may replenish the accumulator with the external fluid. Further, the system may contain a pneumatic supply system that provides pneumatic fluid to the chamber. The pneumatic supply system may include at least one pressure-reducing valve for regulating pressure of the pneumatic fluid within the chamber.
These and other features of the present application are discussed in the following detailed description, drawings and claims.
An embodiment of the present invention provides a system for controlling the thrust experienced by a rotor in a turbomachine. This turbomachine may take the form of, but is not limited to, a steam turbine, a heavy-duty gas turbine, an aero-derivative gas turbine, and the like. The system may employ a chamber, enclosing a rotor portion. The chamber may be filled with a pressurized fluid, such as, but not limiting of, a hydraulic fluid. The fluid may derive from a source external to the turbomachine. A seal system may engage the rotor portion, dividing the chamber into separate portions. Each portion may include at least one port and structure to move the fluid into and out of (through) the chamber. This may allow the rotor to be subjected to bidirectional forces. A control system may vary the pressure of the fluid within the chamber in order to bias the rotor in a desired direction. This may control the overall thrust, and may prevent large variations in the overall thrust. This may reduce the energy losses in the turbomachine.
Certain terminology may be used herein for convenience only and is not to be taken as a limitation on the invention. For example, words such as “upper”, “lower”, “left”, “front”, “right”, “horizontal”, “vertical”, “upstream”, “downstream”, “fore”, and “aft” merely describe the configuration illustrated in the Figures (FIGS). Indeed, the components may be oriented in any direction and the terminology, therefore, should be understood as encompassing such variations unless specified otherwise. The terms “downstream” and “upstream” indicate directions relative to the flow of the working fluid through the turbomachine, “downstream” being the direction of flow and “upstream” is the opposite direction. Related to these terms, “aft” and/or “trailing edge” refer to the downstream direction or end, and “forward” or “leading edge” refers to the upstream direction or end. Further, an “axial” direction or position lies parallel to an axis.
Detailed example embodiments are disclosed herein. However, specific structural and functional details disclosed herein are merely representative for purposes of describing example embodiments. Example embodiments may, however, be embodied in many alternate forms, and should not be construed as limited to only the embodiments set forth herein.
Accordingly, while example embodiments are capable of various modifications and alternative forms, embodiments thereof are illustrated by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit example embodiments to the particular forms disclosed. Example embodiments are to cover all modifications, equivalents, and alternatives falling within the scope of example embodiments.
It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and/or” includes any, and all, combinations of one or more of the associated listed items.
The terminology used herein is for describing particular embodiments only and is not intended to be limiting of example embodiments. 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”, “comprising”, “includes” and/or “including”, when used herein, 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.
It should also be noted that in some alternative implementations, the functions/acts noted might occur out of the order noted in the FIGS. For example, two successive FIGS. may be executed substantially concurrently or may sometimes be executed in the reverse order, depending upon the functionality/operations involved.
Embodiments of the present invention provide systems that comprise a fluid filled chamber that partially surrounds a portion of a turbomachine rotor. The chamber may be filled with a pressurized fluid that creates a pressure distribution around the rotor portion. The pressure distribution may be considered a force that counteracts the thrust experience by the rotor by impacting the rotor position, possibly moving the rotor and/or lessening the thrust load on the rotor. Referring now to the FIGS., where the various numbers represent like parts throughout the several views.
The chamber 100 may be filled with a pressurized fluid deriving from a source independent of the turbomachine. For example, but not liming of, with a steam turbine, the fluid within the chamber 100 may be separate from the steam path. Here, the operating fluid (steam) may not be extracted for adjusting the thrust load; possibly avoiding any degradation of the steam turbine efficiency due to the present invention. An embodiment of the chamber 100 may also be referred to as a hydraulic chamber; which may be filled with a fluid that may substantially surrounds the rotor portion 102. Here, the fluid may be a hydraulic fluid. In other embodiments of the chamber 100, the fluid may be compressed air, or any other hydraulic or pneumatic fluid capable of use in similar applications.
The rotor portion 102 rotates within the chamber 100. A circular rotor portion 103 may extend outward from the rotor portion 102, substantially filling the chamber 100. In an embodiment of the present invention, the rotor portion 102 may be a machined structure of the turbomachine rotor. The rotor portion 103 may be a new structure added, via welding or the like, to the turbomachine rotor. A sealing system 104 may seal the inner gap between the rotor portion 102 and the chamber wall; dividing the interior of the chamber 100 into portions 106 and 108. The operative connection between the seal system 104 and the chamber 100 may be of a conventional design known in the art.
Ports 110 and 112 may be located on one side of chamber 100, and ports 114 and 116, may be located on the opposite side, as illustrated in
Operationally, the pressurized fluid may enter the chamber 100 via at least one of the ports 110, 112, 114 or 116. The pressurized fluid may then impact the rotor portion 102; possibly with sufficient force to bias the net thrust a desired amount and/or to move the rotor in a desired direction. The external pressure sources connected to ports 110, 112, 114, 116 coupled with normal operating variances, may cause one portion 106, 108 of the chamber 100 to experience a higher pressure than does the other portion 106, 108 creating “high pressure” and “low pressure” portions of the chamber 100. In an embodiment of the present invention, either portion 106, 108 may function as the “high pressure” portion.
In embodiments of the present invention, the high-pressure fluid may be pumped into the upstream end of the rotor portion 102/202 to reduce the thrust load. Here, the thrust acting on each portion 106, 108//206, 208 of the chamber 100 may be controlled independently, as further described in connection with
To counter the thrust, the system 300 may include pressure sources, such as, but limiting of pressure tanks, 302, 306 connected to each side of the chamber 100. The upstream port 112 of the chamber 100 may be connected to pressure tank 302 and the downstream port 116 may be connected to pressure tank 304. The pressure tanks 302 and 304 may contain a fluid used to control the pressure acting on each portion of the chamber 100, which may reduce the rotor thrust. The pressure tank 302 may be connected to an accumulator 306, an upper limit switch 308, and a lower limit switch 310, as illustrated. Similarly, the pressure tank 304 may be connected to an accumulator 312, an upper limit switch 314, and a lower limit switch 316. The accumulators 306 and 312 may be configured to regulate fluid pressure within the chamber 100. The system 300 may also include a fluid supply system 318 supplying fluid to or receiving fluid from the pressure tanks 302 and 304. The fluid supply system 318 may be connected to control valves 320, 322, 324, and 326; and a pump 328, to allow entry or exit of fluid.
As illustrated in
In an embodiment of the present invention, a pump 330 may pump the pressurized fluid from the pressure tank 302 into the upstream port 112 of the chamber 100. This high-pressure fluid serves to oppose the thrust load, as described. Downstream fluid leakage may result in a constant reduction of the fluid level in the pressure tank 302. Here, the pump 328 may restore the fluid level to the desired range. The downstream fluid leakage may result in a continuous rise in the pressure tank 304 via a pump 332. Here, the control valve 326 may allow the extra fluid from the pressure tank 304 to flow into the fluid supply system 318.
To overcome this leakage, the system 300 may include independent pressure controls on either side of the chamber 100. The lower limit switch 310 and the upper limit switch 314 may operate to maintain the fluid level between selected levels. As known in the art, a variety of control mechanisms and strategies can be employed to accomplish this control result.
The system 300 may also include a control system, such as, but not limiting of, a controller 340 to monitor the position of the rotor portion 102. Based on the value of the thrust load, the controller 340 may control the fluid pressure from the pressure source (pressure tank 302 or 304) to the chamber 100, with the goal of reducing the thrust load to a desirable value and/or positioning the rotor at a desire position. The controller 340 may also drive the activation or deactivation of the control valves (320, 322, 324, and 326) and the limit switches (308, 310, 314, and 316), with the goal of maintaining the fluid on either side of the chamber 100 to a desired range.
The independent pressure source of an embodiment of the present invention may be connected to each side of the chamber 100, and varied to manipulate the rotor thrust to a desired range and/or to keep the thrust biased in a desired direction.
In alternate embodiment of the present invention, the system 300 may also include a cooler 334, which may be connected to the chamber 100 through the ports 110 and 114. The cooler 334 may absorb the heat associated with the rotor thrust and with the process of pumping high-pressure fluid to counter that thrust. The heat absorption may reduce power losses within the turbomachine, possibly increasing the efficiency.
The system 400 may also include a fluid supply system, for example, but not limiting of a conventional lube oil system 410 that provides oil to the chamber 100. A pump 412, which may be connected to a downstream port of the lube oil system 410, may provide constant pressure output to the chamber 100. Further, a bypass valve 414 may be attached to the lube oil system 410 to vary the pressure exerted by the oil entering the chamber 100. An embodiment of the present invention may include a bypass valve 414 that may operate from a fully open position to a fully closed position. In the fully closed position, the oil flowing from the lube oil system 410 may exert maximum pressure on the upstream end of the rotor 102. If the bypass valve 414 operates in the fully open position, the oil may apply minimum pressure on the upstream end of the rotor 102. Furthermore, the position of the bypass valve 414 may vary the thrust acting on the rotor 102.
An embodiment of the system 400 may operate in multiple modes, one with control valves 402 and 406 activated, and another with control valves 404 and 408 activated. In the first mode of operation, control valves 402 and 406 may be open and the control valves 404 and 408 may be closed. Here, the pump 412 may provide high-pressure fluid to the upstream end of the rotor 102, through the control valve 402, to control the thrust. The leakage fluid from the downstream port 114 of the chamber 100 may return to the lube oil system 410 through the control valve 406.
In another mode of operation, the control valves 404 and 408 may be open and the control valves 402 and 406 may be closed. Here, the pump 412 may provide fluid from the lube oil system 410 to the high-pressure side, and the leakage fluid may be returned to the lube oil system 410 via the control valve 408.
During operation, a control system 440 may monitor the thrust acting on the chamber 100 and control the operation of the bypass valve 414 to maintain a desired thrust within the chamber 100.
An embodiment of the system 500 may include the chamber 100 (illustrated in
In an embodiment of the present invention, the pressure on either side of the chamber 100 may be adjusted using reducing valves, such as reducing valves 510 and 512, which may be configured to regulate the pressure of the pneumatic fluid within the chamber 100. The system 500 may activate the reducing valve located upstream of the high-pressure side to control the overall thrust.
An embodiment of the system 500 may also include a reducing valve 514, which may operate in a manner opposite to that of the reducing valves 510 and 512. The reducing valve 514, located upstream of the control valves 502 and 506, may function as a backpressure regulator, controlling the pressure acting on the low-pressure side. The reducing valve 514 may be configured for regulating a supply pressure of the pneumatic fluid. The system 500 functions to provide capabilities of controlling the thrust on the upstream end and the downstream end of the rotor 102. During operation, a control system 540 may operate the system 500 to control the thrust acting on the rotor, as described.
An embodiment of the blocking valve 602 may include a single valve conventionally used in hydraulic systems and may operate in three positions. As illustrated in
In position 612, physically shifting the blocking valve 602 to a lower position may result in pumping the high-pressure fluid to the chamber 100 via the downstream port 116. This fluid may return to the lube oil system 604 via the port 112 through the blocking valve 602. In the third position, the blocking valve 602 may block the passage of fluid between the chamber 100 and the lube oil system 604.
A controller 640 may monitor the thrust exerted on the rotor and control the position of the blocking valve 602 to manipulate the overall thrust of the turbomachine via the rotor portion 102.
Embodiments of the present invention may provide the benefit of allowing for a smaller thrust bearing. Conventionally, due to the configuration and complexity of the turbomachine, at least two thrust bearings are typically employed to absorb the thrust. If the design of the turbomachine machine requires that the thrust be biased in one direction, then an embodiment of the chamber 100 may be employed to keep this thrust biased in the desired direction. Controlling the thrust in the desired direction and reducing the overall net thrust may allow for one thrust bearing. As a result, an embodiment of the present invention may eliminate the need of a second thrust bearing and/or reduce the size of the bearing(s) needed.
As one of ordinary skill in the art will appreciate, the many varying features and configurations described above in relation to the several exemplary embodiments may be further selectively applied to form the other possible embodiments of the present invention. Those in the art will further understand that all possible iterations of the present invention are not provided or discussed in detail, even though all combinations and possible embodiments embraced by the several claims below or otherwise are intended to be part of the instant application. In addition, from the above description of several exemplary embodiments of the invention, those skilled in the art will perceive improvements, changes, and modifications. Such improvements, changes, and modifications within the skill of the art are also intended to be covered by the appended claims. Further, it should be apparent that the foregoing relates only to the described embodiments of the present application and that numerous changes and modifications may be made herein without departing from the spirit and scope of the application as defined by the following claims and the equivalents thereof.
