Patent Application
20110110760
The present application relates generally to a method and a system for increasing efficiency of a pressurized machine, such as a steam turbine; and particularly relates to a steam turbine using a steam seal header for preventing steam leakage.
Various types of pressurized machines, such as, but not limiting of, a steam turbine, are used in power generation applications. The steam turbine may have one or more turbine units, each operating within a pressure range. These units may include: a high-pressure (HP) turbine unit, an intermediate-pressure (IP) turbine unit, and a low-pressure (LP) turbine unit. Each turbine unit may have a stationary housing that partially encloses a shaft. One or more turbine stages may be axially disposed around the shaft; and each turbine stage may have a plurality of turbine blades that are circumferentially mounted on the shaft. A steam flow path may be considered the area between the stationary housing and the shaft. Under normal operating conditions the pressurized steam, which is injected into the turbine unit, rotates the plurality of turbine blades, causing the shaft to rotate. Typically, the shaft passes through the stationary housing to transfer the generated rotational power outside the turbine unit.
The clearance between the shaft and the stationary housing of a turbine unit, may cause the pressurized steam to leak out of the unit, or, may allow air to enter the unit. In various known solutions, techniques such as pressure packing and/or vacuum packing is used to reduce leakage.
In addition to the pressure packing and the vacuum packing, a shaft sealing system may also be used for preventing steam leakage from the pressure packing into the turbine room. Typically, the shaft sealing system includes a Steam Seal Header (SSH), typically maintained at a pre-determined pressure. Under the normal operating conditions of the steam turbine, the SSH may trap the steam leaked from the pressure packings in the HP and IP turbines and direct that steam to seal the vacuum packings in the LP turbine. The shaft sealing system may also include a steam packing exhauster (SPE); which may maintains a vacuum and discharge the excess steam in the shaft sealing system.
Typically, in known steam sealing systems, the SSH may be maintained at constant pressure via a pressure regulator, when pressure is low external steam from an auxiliary boiler is provided; when pressure is high the excess of steam is directed to the condenser. Under normal operating conditions, a change in the steam turbine load changes the amount of steam from the HP and IP turbines; and as load increases the auxiliary boiler steam is no longer required, the auxiliary boiler steam production is only required during start-up and relative low loads. The higher the SSH pressure set point, the bigger the auxiliary boiler. At full load the lower the SSH pressure set point, the lower efficiency. Current systems utilized a compromised SSH set point.
As a result, there is a desire for an improved steam sealing method and system that addresses the aforementioned issues of some known steam sealing systems.
In accordance with an embodiment of the present invention, a sealing system configured for increasing an efficiency of a machine, the system including a pressurized machine, for example a steam turbine, the pressurized machine including a rotatable shaft partially enclosed by a stationary housing, a flow path defined by the area between the shaft and the housing; a shaft sealing system configured for controlling a flow of fluid within the pressurized machine; the shaft sealing system including a pressure packing configured for substantially barring a fluid, for example steam from escaping the pressurized machine, and a header configured for maintaining the pressure packing at an optimized pressure range; wherein a magnitude of the optimized pressure range varies on an operating status of the pressurized machine; a header bleed system configured for regulating the header at the optimized pressure range; wherein the header bleed system includes a valve adapted for removing a portion of the fluid within the header; and a controller configured for determining the optimized pressure range; wherein the optimized pressure allows for operating the shaft sealing system with the header having a varying pressure; allowing for a reduction in the quantity of fluid used to maintain the header.
In accordance with an alternate embodiment of the present invention, a method for increasing an efficiency of a machine, the method including providing a pressurized machine including a rotatable shaft partially enclosed by a stationary housing, a flow path defined by the area between the shaft and the housing; a shaft sealing system configured for performing the step of controlling a flow of fluid within the pressurized machine at an optimized pressure range; and determining the optimized pressure range; wherein the optimized pressure allows for operating the shaft sealing system with a header having a varying pressure; allowing for a reduction in the quantity of fluid used to maintain the header.
The method may further include the steps of determining the operating status of the pressurized machine; determining the fluid flow entering the header; and determining the fluid flow exiting the header.
These and other features of the present application will become apparent upon review of the following detailed description of the preferred embodiments when taken in conjunction with the drawings and the appended claims.
Embodiments of the present invention have been described herein referring to the accompanying FIGS. The accompanying drawings are solely for the purpose of illustration and are not intended to limit the scope of the invention. Other embodiments having different structural arrangement of elements do not depart from the scope of the invention.
Certain terminology is used herein for the convenience of the reader only and is not intended as a limitation on the scope of the invention. For example, words such as “upper,” “lower,” “left,” “right,” “front”, “rear” “top”, “bottom”, “horizontal,” “vertical,” “upstream,” “downstream,” “fore”, “aft”, and the like; merely describe the configuration illustrated in the FIGS. Indeed, the element or elements of an embodiment of the present invention may be oriented in any direction and the terminology, therefore, should be understood as encompassing such variations unless specified otherwise.
The present invention has the technical effect of improving an efficiency of a pressurized machine, such as, but not limiting of, a steam turbine.
The efficiency of the pressurized machine may be considered as the ratio of an output power by the pressurized machine to the input energy of the pressurized machine. Hence, the efficiency may be considered the fraction of input energy that is converted to useful output power.
The present invention may be applied to a variety of pressurized machines that use pressurized steam, such as, but not limiting to, a steam turbine. An embodiment of the present invention may be applied to either a single steam turbine or a plurality of steam turbines. An embodiment of the present invention may be applied to a steam turbine operating in a simple cycle or a combined cycle configuration.
Referring now to the FIGS., where the various numbers represent like elements throughout the several views,
Under normal operating conditions, pressurized steam from a main source of steam, such as, but not limiting of, a HRSG, a steam generator, or the like; may be supplied to the high-pressure turbine unit 102 through a steam line 122. In an embodiment of the present invention, pressurized steam may be supplied by opening an inlet valve 120 provided on the steam line 122. Here the high-pressure turbine unit 102 may operate within a pressure range, such as, but not limited to, of about 4500 psia to about 900 psia (of about 31000 kP to about 6200 kP).
The steam leaving the high-pressure turbine unit 102 may enter the intermediate-pressure turbine 104 through a steam line 124. The pressure of the steam entering the intermediate-pressure turbine 104 may be within a pressure range, such as, but not limited to, of about 900 psia to about 300 psia (of about 6200 kP to about 2100 kP). After leaving the intermediate-turbine unit 104 the steam may enter the low-pressure turbine unit 106 through a steam line 126, which may be operating within a pressure range, such as, but not limited to, of about 250 psia to 40 psia (of about 1700 kP to about 250 kP). In other embodiments of the present invention, the number of the turbine units and the operating pressure ranges may vary depending on, but not limited to, the application, output power requirements, and cycle configuration.
In an embodiment of the present invention, a shaft sealing system may be provided for controlling the flow of the pressurized steam in the steam turbine 100. In an embodiment of the present invention, the shaft sealing system may include pressure packing 128. The pressure packing 128 may be provided on the shaft 108 adjacent to a clearance area provided between the shaft 108 and the stationary housings 112 and 114. Under normal operating conditions, the pressure packing 128 may reduce leakage of the pressurized steam from the turbine units 102 and 104 into the turbine room 118. The pressure packing 128 may include one or more sealing rings, which may have segmented circumferential packing or labyrinth packing. In other embodiments of the present invention, variation in the shape of packing rings or labyrinth structure may be provided in accordance with the pressure of the steam, application, or the like. In an embodiment of the present invention, the shaft sealing system may also include a Steam Seal Header 130 (hereinafter referred to as “SSH”), which may be connected to the pressure packing 128. In an embodiment of the present invention, the SSH 130 may also be connected to a LP turbine vacuum packing 132. Here, the vacuum packing 132 may be located on the shaft 108 adjacent to a clearance area where the shaft 108 passes through the stationary housing 116. The vacuum packing 132 may reduce the leakage of air into the low-pressure turbine unit 106. In an embodiment of the present invention, the SSH 130 may direct the steam, which may leak from the pressure packing 128 to the vacuum packing 132, and maintain the vacuum packing 132 at an above-atmospheric pressure. The vacuum packing 132 may reduce a leakage of the air into the low-pressure turbine unit 106.
In an embodiment of the present invention, an auxiliary boiler 134 may be provided to supply steam to the SSH 130, such that the auxiliary boiler 134 may maintain a required quantity of the steam in the SSH 130 if the steam flow provided by the HP and IP turbines is inadequate. In an embodiment of the present invention, the SSH 130 may maintain the pressure packing 128 within an optimized pressure range. In an embodiment of the present invention, the optimized pressure range for the pressure packing 128 may depend on an operating status of the steam turbine 100. In an embodiment of the present invention, the operating status of the steam turbine 100 may be the percentage loading of the steam turbine 100, for example, but not limited to, a start-up loading condition, an intermediate part-load condition and a full-load condition. In an alternate embodiment of the present invention, the operating status of the steam turbine 100 may be defined as the ratio of a current power output to a rated or full load power of the steam turbine 100.
In an embodiment of the present invention, a header bleed system may be provided to regulate the steam pressure in the SSH 130 within the optimized pressure range. This may be necessary if excess of steam is provided by the HP and IP turbines; particularly at higher steam turbine loads. The header bleed system may include a steam line 138, which may be connected to a condenser system 140. The steam line 138 may be used to remove a portion of the steam from the SSH 130 to achieve the optimized pressure range at the pressure packing 128. In an embodiment of the present invention, a valve 136 may be provided in the steam line 138. The valve 136 may be opened to allow steam in the SSH 130 to exit through the valve 136 and flow to the condenser system 140. In an embodiment of the present invention, the valve 136 may be integrated with the condenser system 140. In an embodiment of the present invention, the condenser system 140 may be associated with the steam turbine 100.
In an embodiment of the present invention, an active controller 142 may be provided to determine the optimized pressure for the pressure packing 128. The controller 142 may include a control system, or the like, that has the technical effect of determining the operating status of the steam turbine 100, determining quantity of steam entering the SSH 130 and determining quantity of the steam exiting the SSH 130. In an embodiment of the present invention, the controller 142 may communicate with (as illustrated by the dashed-line in the
In an embodiment of the present invention, by utilizing the header bleed system and the controller 142, the pressure in the SSH 130 may vary within a range of approximately above-atmospheric pressure to about an optimum performance pressure. The range of the optimum performance pressure may be specific to steam turbine 100. In an alternate embodiment of the present invention, the pressure in the SSH 130 may vary within a range, such as, but not limiting to, of from about 15.5 psia to about 50 psia (from about 107 kP to about 345 kP).
In an embodiment of the present invention, the shaft sealing system may also include a steam packing exhauster header (SPE) 144. The SPE 144 may be maintained at a sub-atmospheric pressure and connected to a steam packing exhauster pump 146. In an alternate embodiment of the present invention, the SPE 144 may be maintained at a pressure, such as, but not limiting to, about −0.2 psig, at an outermost portion of the pressure packing 128 and the vacuum packing 132. The SPE 144 may exhaust the steam collected from the packing 128 and 132 to the atmosphere through the steam packing exhauster pump 146.
An optimization of the pressure in the SSH 130, according to the operating status of the steam turbine 100, may reduce the amount of steam required in the SSH 130 during the start-up loading condition. In an embodiment of the present invention, the shaft sealing system may decrease the load on the auxiliary boiler 134 during the start-up loading as the amount of steam required in the SSH 130 may be less. Similarly, during part-load operation and full-load operation, the SSH 130 may be maintained within the optimized pressure range and the steam requirement from the auxiliary boiler 134 may vary, so that an overall increase in the efficiency or decrease heat rate of the steam turbine 100 may be achieved. Further, in an embodiment of the present invention, the operational envelope of the steam turbine 100 may increase, and hence the turbine may be capable of operating in a wider pressure range. In an embodiment of the present invention, the overall efficiency of the steam turbine 100 may increase as the load on the auxiliary boiler 134 decreases.
As will be appreciated, the present invention may be embodied as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects all generally referred to herein as a “circuit”, “module,” or “system”. Furthermore, the present invention may take the form of a computer program product on a computer-usable storage medium having computer-usable program code embodied in the medium.
Any suitable computer readable medium may be utilized. The computer-usable or computer-readable medium may be, for example but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, device, or propagation medium. More specific examples (a non exhaustive list) of the computer-readable medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a transmission media such as those supporting the Internet or an intranet, or a magnetic storage device. Note that the computer-usable or computer-readable medium could even be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, via, for instance, optical scanning of the paper or other medium, then compiled, interpreted, or otherwise processed in a suitable manner, if necessary, and then stored in a computer memory. In the context of this document, a computer-usable or computer-readable medium may be any medium that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device.
Computer program code for carrying out operations of the present invention may be written in an object oriented programming language such as Java7, Smalltalk or C++, or the like. However, the computer program code for carrying out operations of the present invention may also be written in conventional procedural programming languages, such as the “C” programming language, or a similar language. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer. In the latter scenario, the remote computer may be connected to the user's computer through a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).
The present invention is described below with reference to flowchart illustrations and/or block diagrams of methods, apparatuses (systems) and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a public purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function/act specified in the flowchart and/or block diagram block or blocks. The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions/acts specified in the flowchart and/or block diagram block.
The present invention may include a control system, or the like, that has the technical effect of determining the optimized pressure range for a SSH 1.30 for a steam turbine 100. The control system may be configured to automatically or continuously monitor the operating status of the steam turbine and vary pressure in the SSH 130 according the operating status of the steam turbine 100. Alternatively, the control system may be configured to require a user action to initiate the operation. An embodiment of the control system of the present invention may function as a stand-alone system. Alternatively, the control system may be integrated as a module, or the like, within a broader system, such as a steam turbine control or a power plant control system.
Referring now to
In step 310, of the method 300, the controller 142 may monitor and vary the pressure of steam in the SSH 130 in accordance with an embodiment of the present invention. The pressure inside the SSH 130 may vary within a range of about above atmospheric pressure to an optimum performance pressure. In an embodiment of the present invention, the pressure inside the SSH 130 may vary within a range, such as, but not limited to, of from about 15.5 psia to about 50 psia (from about 107 kP to about 345 kP).
In step 320, the method 300 may determine the operating status of the steam turbine 100. In an embodiment of the present invention, a plurality of temperature and pressure sensors may be used to determine the operating status of the steam turbine 100. The sensors may be connected to the turbine units 102, 104, and 106 and may communicate with the controller 142. The controller 142 may estimate the operating status of the steam turbine 100 based on data obtained from the sensors. In another embodiment of the present invention, the power output of the load 110 may be measured to determine the operating status of the steam turbine 100. Alternatively, the torque and rotational speed of the shaft 108 may be used for estimating the operating status of the steam turbine 100. In an embodiment of the present invention, the operating status of the steam turbine 100 may be a start-up, part-load or full-load, as described.
In step 330, the method 300 may determine a target quantity of steam in the SSH 130. In an embodiment of the present invention, the target quantity of the steam may be equal to the quantity of the steam in the SSH 130 at which the performance of the steam turbine 100 may be optimal for the given operating status of the steam turbine 100.
In step 340, the method 300 may determine a current quantity of steam in the SSH 130. In an embodiment of the present invention, the current quantity of steam in the SSH 130 may be determined by using a plurality of pressure and temperature sensors. The plurality of sensors may be connected to the SSH 130 and the data from the sensors may be received by the controller 142 to calculate the current quantity of the steam in the SSH 130. In other embodiments of the present invention, at least one flow-metering device may be used to monitor the quantity of steam entering and exiting the SSH 130. The flow-metering devices may be connected to the steam line 138 and the SSH 130 and the data from the flow-metering devices may be received by the controller 142 to calculate the current quantity of the steam in the SSH 130.
In step 350, the method 300 may determine whether the current quantity of the steam in the SSH 130 may be nearly equal to the target quantity of the steam in the SSH 130. In the step 350, the method 300 may compare the target quantity of the steam in the SSH 130, and the current quantity of the steam in the SSH 130. If the current quantity is not nearly equal to the target quantity of the steam in the SSH 130, then the method 300 may proceed to step 360; otherwise the method 300 may revert to step 310 where the steps 310-350 may repeat.
In step 360, the method 300 may control the quantity of the steam in the SSH 130. In an embodiment of the present invention, the controller 142 may determine the position of the valve 136. The controller 142 may further regulate the opening and closing of the valve 136 in order to increase and decrease the quantity of the steam in the SSH 130.
By varying the quantity of the steam, the pressure of steam in the SSH 130 may be varied within an optimized pressure range. This may help to improve the performance of the steam turbine 100. During the start-up mode, as the required target quantity of steam in the SSH 130 is less, the load on the auxiliary boiler 134 may be relatively low. Also at part-load and the full-load, the pressure in the SSH 130 may vary, and improve the overall heat rate of the steam turbine 100.
All steps of the method 300 may be repeated periodically to constantly monitor the operating status of the steam turbine 100 and vary the pressure of steam in the SSH 130 in accordance with the operating status of the steam turbine 100.
The user communication device 402 may include a system memory 404. The system memory 404 may include for example, but is not limited to, a Random Access Memory (RAM) and a Read Only Memory (ROM). The system memory 404 may have an operating system 406. The operating system 406 may controls the overall operations of the user communication device 402. The system memory 404 may also include a browser 408. The system memory 404 may also include data structures 410 or computer-executable code for varying the pressure of the steam in the SSH 130 that may be similar or include steps of the method 300 in
The system memory 404 may further include a template cache memory 412, which may be used in conjunction with the method 300 for varying the pressure of the steam in the SSH 130.
The user communication device 402 may also include a processor or a processing unit 414 to control operations of the other components in the user communication device 402. The operating system 406, the browser 408, and the data structures 410 may be operable on the processing unit 414. The processing unit 414 may be coupled to the system memory 404 and other components by a system bus 416.
The user communication device 402 may also include multiple input/output devices (I/O) 418. Each I/O device 418 may be coupled to the system bus 416 by an input/output interface (not illustrated in
The user communication device 402 may also have a monitor 422. The monitor 422 may be used for displaying certain parameters, such as, the operating status of the steam turbine 100, the current pressure of steam in the SSH 130, and current temperature of the steam in the SSH 130.
The user communication device 402 may also include a hard drive 424. The hard drive 424 may be coupled to the system bus 416 by a hard drive interface (not illustrated in
The user communication device 402 may be connected to a unit controller 426 via a network 428. The system bus 416 of the user communication device 402 may be coupled to the network 428 by a network interface 430. The network interface 430 facilitates the transfer of data from the user communication device 402 to external devices via the network 428 and vice versa. For example, but not limiting to, the user communication device 402 may communicate with similar communication devices or a central network server. The network interface 430 may be a modem, Ethernet card, router, gateway, or the like for coupling to the network 428. The coupling may be a wired or wireless connection. The network 428 here in might be a Local Area Network (LAN), Wide Area Network (WAN), Personal Area Network (PAN), an ad-hoc network, internet etc. The network 428 may be wired or wireless.
The unit controller 426 may also include a system memory 432, which may include a file system, ROM, RAM, and the like. The system memory 432 may also include an operating system 434. The operating system 434 may include a set of computer executable instructions for controlling the overall operations of the unit controller 426. The system memory 432 may also include data structures 436 for varying the pressure of the steam in the SSH 130. The data structures 436 may include operations similar to those described with respect to the method 300 for varying the pressure of the steam in the SSH 130. In accordance with an embodiment of the present invention, the data structures 436 may include, but not limited to, tabulated data of the steam turbine operating status and corresponding target quantity of steam in the SSH 130. The data structure 436 may further include data obtained from the user communication device 402 which may be required for effectively performing the steps of the method 300. The system memory 432 may also include a partition 438 for storing other files, applications, modules, and the like.
The unit controller 426 may also include a processor 442 to control the operations of the other components in the unit controller 426. The unit controller 426 may also include I/O device 444 and other devices 446, such as a monitor or the like to provide an interface along with the I/O devices 444 to the at least one unit controller 426. The unit controller 426 may also include a hard disk drive 448. A system bus 450 may connect the different components of the unit controller 426. A network interface 452 may couple the unit controller 426 to the network 428 via the system bus 450.
The flow charts and step diagrams described herein are for the purpose of illustration of the method, architecture and operation of various implementations and computer program products according to some embodiments of the present invention. The steps shown may involve one or more computer programs, modules or systems for performing various logical operations. It should be noted that the scope of the present invention is not limited to the sequence of the steps. In some alternative embodiments of the present invention, the steps may be performed simultaneously instead of serially. In other embodiments, the steps may be performed in reverse order. All such embodiments following the described steps in any order achieving the same end result do not depart from the scope of the invention.
Although the present invention has been described with reference to a steam turbine, it should be appreciated by a person skilled in the art that the teachings of the above invention could be applied for performance improvement of any rotating pressurized fluid machine that is susceptible to leakage of pressurized fluid from the machine housing.
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. For the sake of brevity and taking into account the abilities of one of ordinary skill in the art, all of the possible iterations are not provided or discussed in detail, though all combinations and possible embodiments embraced by the several claims below or otherwise are intended to be part of the present 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 following 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.
