Abstract:
A method and a system for determining radial clearances in a rotating machine are provided. The rotating machine includes at least one shell, at least one rotor, and at least one stationary component. The method includes creating a finite element model for at least one component within the rotating machine, creating a cycle deck data file for the rotating machine, determining an initial clearance versus time, and determining an initial clearance versus location. The system includes a client system including a browser, a centralized database for storing machine information, and a server system configured to be coupled to the client system and the database wherein the server system is further configured to receive machine information from the client system, store finite element model information in the centralized database, track machine information, update the centralized database periodically with newly received machine information to maintain machine information, and provide machine information in response to an inquiry.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates generally to rotating machinery, and more particularly to steam turbines, and methods and system for calculating steam path clearances in steam turbines. 
   A steam turbine includes a steam path which typically includes, in serial-flow relationship, a steam inlet, a turbine, and a steam outlet. At least some known turbine rotor assemblies include a plurality of rows of blades coupled to a rotor wheel. The blades are arranged in axially-spaced stages that extend circumferentially around the rotor wheel. More specifically, each stage includes a set of stationary blades or nozzles, and a set of cooperating rotating blades, known as buckets. The tips of the rotating blades are surrounded by a turbine casing such that a radial gap is defined between the rotor blade tips and the casing. 
   An operating efficiency of the turbine is at least partially dependent upon the radial clearance or gap between rotor blade tips and the casing. For example, if the clearance between the rotor blade tips and the surrounding casing is too large, flow may leak through the gap between the rotor blade tips and the surrounding casing, decreasing the turbine&#39;s efficiency. However, if the clearance is too small, the rotor blade tips may strike the surrounding casing during certain turbine operating conditions. To facilitate optimizing the turbine efficiency, the clearance is adjusted to enhance steady-state performance while maintaining an adequate clearance margin as the turbine accelerates and decelerates through the rotor train vibration criticals. A cold clearance, which is initially tight, can result in excessive regenerative rubs. Over time, continued rubs may cause loss of material and/or a blunt or mushroomed seal tooth which may change the flow characteristics and adversely affect the performance of the turbine. A balanced design may provide tight average operating clearances as well as facilitate avoiding rubs during transients and operating at off-design conditions. 
   Turbine radial clearances may change during periods of acceleration or deceleration due to changing centrifugal force induced to the blade tips, and/or due to relative thermal growth between the rotating rotor and stationary casing. During periods of differential centrifugal and thermal growth, clearance changes may result in rubbing of the moving blade tips against the stationary casing. Such an increase in blade tip clearance results in efficiency loss. Since components of steam turbines are made of different materials with different thicknesses, such components exhibit different rates of thermal growth from a cold startup condition to steady state operating condition and during transient operating conditions. Additionally, turbine components are subject to vibratory excitement during transient operation that also affects steam path clearances. Such differences make calculating steam path clearances difficult and time consuming. 
   BRIEF DESCRIPTION OF THE INVENTION 
   In one aspect, a method of determining radial clearances in a rotating machine is provided. The rotating machine includes at least one shell, at least one rotor, and at least one stationary component. The method includes creating a finite element model for at least one component within the rotating machine, creating a cycle deck data file for the rotating machine, determining an initial clearance versus time, and determining an initial clearance versus location. 
   In another aspect, a computer program embodied on a computer readable medium for determining a rotating machine radial clearance is provided. The program includes a code segment that prompts a user to input at least one of a machine identifier, a user identifier, a current date and time, and a comment retrieves stored data for the machine identified, prompts a user to input data from a selection of data exclusive to the machine identified, provides a user with an input file status for the machine identified, and provides a graphical output of calculations based on data input by the user and data retrieved from storage. 
   In yet another aspect, a system for determining radial clearances in a rotating machine is provided. The rotating machine includes at least one shell, at least one rotor, and at least one stationary component. The system includes a client system including a browser, a centralized database for storing machine information, and a server system configured to be coupled to the client system and the database wherein the server system is further configured to: receive machine information from the client system, store finite element model information in the centralized database, track machine information, update the centralized database periodically with newly received machine information to maintain machine information, and provide machine information in response to an inquiry. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective partial cut away view of an exemplary steam turbine. 
       FIG. 2  is a simplified block diagram of a clearance synthesis dashboard computer system. 
       FIG. 3  is an expanded version block diagram of an example embodiment of a server architecture of the clearance synthesis dashboard computer system shown in FIG.  2 . 
       FIG. 4  is an exemplary data flow diagram of a clearance synthesis dashboard that may be used with the clearance synthesis dashboard computer system shown in FIG.  2 . 
       FIG. 5  is an exemplary process flow diagram that may be used to generate input data for the clearance synthesis dashboard shown in FIG.  3 . 
       FIG. 6  is a screen shot of an exemplary user interface input screen that may be used with clearance synthesis dashboard shown in FIG.  3 . 
       FIG. 7  is a screen shot of an exemplary “Select Machine” screen that may be used with clearance synthesis dashboard shown in FIG.  3 . 
       FIG. 8  is a screen shot of an exemplary “Input Status” screen that may be used with clearance synthesis dashboard shown in FIG.  3 . 
       FIG. 9  is a screen shot of an exemplary “Select Stages” screen that may be used with clearance synthesis dashboard shown in FIG.  3 . 
       FIG. 10  is a screen shot of an exemplary “Main Menu” screen that may be used with clearance synthesis dashboard shown in FIG.  3 . 
       FIG. 11  is a screen shot of an exemplary “Output Status” screen that may be used with “View Output Status” shown in FIG.  9 . 
       FIG. 12  is a screen shot of an exemplary display that may output from clearance synthesis dashboard shown in. FIG.  3 . 
       FIG. 13  is a screen shot of an exemplary display that may output from clearance synthesis dashboard shown in FIG.  3 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  is a perspective partial cut away view of an exemplary steam turbine  10  including a rotor  12  that includes a shaft  14  and a plurality of turbine stages  16 . Turbine rotor  12  includes a plurality of axially spaced rotor wheels  18 . A plurality of buckets  20  are mechanically coupled to each rotor wheel  18 . More specifically, buckets  20  are arranged in rows that extend circumferentially around each rotor wheel  18 . A plurality of stationary nozzles  22  extend circumferentially around shaft  14  and are axially positioned between adjacent rows of buckets  20 . Nozzles  22  cooperate with buckets  20  to form each turbine stage  16  and to define a portion of a steam flow path through turbine  10 . Shaft  14  is supported and guided in rotation by a plurality of bearings  23  and  24 . 
   In operation, steam  25  enters an inlet  26  of turbine  10  and is channeled through nozzles  22 . Nozzles  22  direct steam  25  downstream against buckets  20 . Steam  25  passes through the remaining stages  16  imparting a force on buckets  20  which causes rotor  12  to rotate. At least one end of turbine  10  may extend axially away from rotor  12  and may be attached to a load or machinery (not shown), such as, but not limited to, a generator, and/or another turbine. Accordingly, a large steam turbine unit may actually include several turbines that are all co-axially coupled to the same shaft  14 . Such a unit may, for example, include a high-pressure (HP) turbine coupled to an intermediate-pressure (IP) turbine, which is coupled to a low-pressure (LP) turbine. In one embodiment, steam turbine  10  is commercially available from General Electric Power Systems, Schenectady, N.Y. 
     FIG. 2  is a simplified block diagram of a clearance synthesis dashboard computer system  100  including a server system  112  including a disk storage unit  113  for data storage, and a plurality of client sub-systems, also referred to as client systems  114 , connected to server system  112 . In one embodiment, client systems  114  are computers including a web browser, such that server system  112  is accessible to client systems  114  via the Internet. Client systems  114  are interconnected to the Internet through many interfaces including a network, such as a local area network (LAN) or a wide area network (WAN), dial-in-connections, cable modems and special high-speed ISDN lines. Client systems  114  could be any device capable of interconnecting to the Internet including a web-based phone, personal digital assistant (PDA), or other web-based connectable equipment. A database server  116  is connected to a database  120  containing information on a variety of matters, as described below in greater detail. In one embodiment, centralized database  120  is stored on server system  112  and can be accessed by potential users at one of client systems  114  by logging onto server system  112  through one of client systems  114 . In an alternative embodiment database  120  is stored remotely from server system  112  and may be non-centralized. 
     FIG. 3  is an expanded version block diagram  122  of an example embodiment of a server architecture of clearance synthesis dashboard computer system  100  shown in FIG.  2 . Components in diagram  122 , identical to components of system  100  (shown in FIG.  2 ), are identified in  FIG. 3  using the same reference numerals as used in FIG.  2 . System  122  includes server system  112  and client systems  114 . Server system  112  further includes database server  116 , an application server  124 , a web server  126 , a fax server  128 , a directory server  130 , and a mail server  132 . Disk storage unit  113  is coupled to database server  116  and directory server  130 . Servers  116 ,  124 ,  126 ,  128 ,  130 , and  132  are coupled in a local area network (LAN)  136 . In addition, a system administrator&#39;s workstation  138 , a user workstation  140 , and a supervisor&#39;s workstation  142  are coupled to LAN  136 . Alternatively, workstations  138 ,  140 , and  142  are coupled to LAN  136  via an Internet link or are connected through an Intranet. 
   Each workstation,  138 ,  140 , and  142  is a personal computer having a web browser. Although the functions performed at the workstations typically are illustrated as being performed at respective workstations  138 ,  140 , and  142 , such functions can be performed at one of many personal computers coupled to LAN  136 . Workstations  138 ,  140 , and  142  are illustrated as being associated with separate functions only to facilitate an understanding of the different types of functions that can be performed by individuals having access to LAN  136 . In an example embodiment, client system  114  includes workstation  140  which can be used by an internal analyst or a designated outside field engineer to review clearance information relating to an analyzed machine. 
   Server system  112  is configured to be communicatively coupled to various individuals, including employees  144  and to field engineers  146  via an ISP Internet connection  148 . The communication in the example embodiment is illustrated as being performed via the Internet, however, any other wide area network  150  (WAN) type communication can be utilized in other embodiments, i.e., the systems and processes are not limited to being practiced via the Internet. In addition, and rather than WAN  150 , local area network  136  could be used in place of WAN  150 . 
   In the exemplary embodiment, any authorized individual having a workstation  154  can access clearance synthesis dashboard computer system  100 . At least one of the client systems includes a manager workstation  156  located at a remote location. Workstations  154  and  156  are personal computers having a web browser. Also, workstations  154  and  156  are configured to communicate with server system  112 . Furthermore, fax server  128  communicates with remotely located client systems, including a client system  156  via a telephone link. Fax server  128  is configured to communicate with other client systems  138 ,  140 , and  142  as well. 
     FIG. 4  is an exemplary data flow diagram  200  of a clearance synthesis dashboard  201  that may be used with clearance synthesis dashboard computer system  100  shown in FIG.  2 . Clearance synthesis dashboard  201  includes a plurality of input data files  202 . In the exemplary embodiment, input data files  202  are formatted Excel™ input files. Input data files  202  are derived from finite element analysis models  204 . Each component of interest, for example, but not limited to, an HP/IP turbine shell, an LP shell, an N 1  packing, an N 2  packing, an N 3  packing, a plurality of diaphragms, an HP turbine rotor, and an LP turbine rotor in steam turbine  10  is modeled In one embodiment, finite element models of the components are created by a third party and files of the components are transmitted to clearance synthesis dashboard  201 . A type of finite element model used for each component is variably selected depending on the affect of each component on radial clearances in steam turbine  10 . In the exemplary embodiment, the finite element models used to describe the HP/IP turbine shell, the N 1  packing, the N 2  packing, the N 3  packing, and diaphragms are 180°, three-dimensional models. The LP shell finite element model is a 180/90°, three dimensional model. The HP rotor and LP rotor finite element models are two-dimensional axi-symmetric models. 
   Input data files  202  include component deflections versus time, and component deflection versus location data. 
   Clearance synthesis dashboard  201  also includes a plurality of input data files  206  that relate to system parameters that may affect turbine clearances. For example, in the exemplary embodiment, input data files  206  include system layout data, cycle deck, one dimensional component lengths and material properties for components, such as, for example, blades, packing teeth, and tip spill, cold clearance data, rotor vibration data, and bearing lift data. System layout data may include, but is not limited to, axial positioning and coordinate definition for components in steam turbine  10 . Cycle deck data may include temperature versus time data at various locations in steam turbine  10  for a plurality of turbine operations, including steady state, transient, trip, and abnormal operations. Some components of steam turbine  10  include a temperature influence in substantially only one dimension of interest when calculating radial clearances, for example, blades and/or buckets, packing teeth, and tip spill. For these components, a component length and material properties are used to determine the length of the component at a time or location of interest. 
   Cold clearance data includes initial clearances between components in a cold iron condition. A cold iron condition is a condition defined when steam turbine  10  has been idle for a sufficient period of time, such that steam turbine components achieve ambient temperature. Rotor vibration data for components of steam turbine  10  is used to calculate clearances during turbine operations wherein turbine vibration may occur, such as, but not limited to, steady state operations, passing through turbine critical speeds operations, abnormal load operations, overspeed operations, and carryover operations. Rotor vibration data may include a rotor resonance condition, a rotor vibration velocity amplitude versus rotor rotational speed, a rotor vibration displacement amplitude versus rotor rotational speed, and a rotor deflection versus location at a steady state operating condition of the machine. Bearing lift data includes data relating to deflections of rotor components as rotor  12  is re-positioned by changing oil film clearances at bearings  23  and  24 . Bearing oil film clearances may change during changes in turbine load, turbine speed changes during run-up and trip, and when oil temperature changes. 
   Input data files  202  and  206  are available to clearance synthesis dashboard  201  through either resident files stored on the same computer, or workstation, or through a network. 
   In operation, clearance synthesis dashboard  201  prompts a user to enter data. Based on information in input data files  202  and  206 , and data input into clearance synthesis dashboard  201 , clearance synthesis dashboard  201  calculates a deformed rotor solution in coordinate form, and a deformed stator solution in coordinate form. These solutions are then combined with initial clearance data to determine radial steam path clearances versus time and radial steam path clearances versus location. Clearance synthesis dashboard  201  then outputs  208  the radial steam path clearances data in a predetermined format selected by the user. The user may select an output, for example, in tabular form, as time-based graphs, as location-based polar charts, and as a computer file. 
   In operation, clearance synthesis dashboard  201  reads specific data from input files  202  and  206 , performs calculations, and displays results of the calculations in tables and graphs. In the exemplary embodiment, dashboard  201  calculates several results, such as, for example, rotor and stator totals, packing corrections, rotor dynamics. In another embodiment, dashboard  201  determines other turbine clearance statistics. In the exemplary embodiment, dashboard  201  is written in Visual Basic for Applications™ and is embedded in an Excel™ workbook named, “Clearance10&amp;11.xls” and resides on network drive  113  on server  112 . In another embodiment, dashboard  201  may located on a local drive or a remote drive accessible to users. 
     FIG. 5  is an exemplary process flow diagram  400  that may be used to generate input data for clearance synthesis dashboard  201 . Initially, a machine which clearance data will be determined is identified  402 . Parts or components that makeup the machine are then identified  404 , and an operating lifecycle of the machine is identified  406 . Existing finite element (FE) models for components is identified  408 . If an FE model does not exist for a component, inputs for an FE model are created  410 . In the exemplary embodiment, FE modeling inputs include, but are not limited to, FE modeling guidelines, loads and constraints, boundary conditions (BC), and material properties of the component. From the inputs created  410 , FE models are created  412 . The models are compared  414  to temperature data received  416  from the field, meaning operating installations or test installations. If the models and compare favorably to field data, the FE models are approved  418  and stored  420  on network drive  113  or other location accessible to users of clearance synthesis dashboard  201   
   A global coordinate system is then defined  422 , desired post-processing locations and time points are identified  424 , a displacement output format is also defined  426 . Input files are received  428 . In the exemplary embodiment, the input files are formatted Excel™ files. In another embodiment, the input files may be any suitable data files compatible with a computing platform being used. 
   Non-FE model factors that contribute to turbine clearances are identified  430  and retrieved or created  432 , such as, for example, blade growth, vane growth, bearing lift, and vibration. A respective contribution from each non-FE model factor is developed  434  in equation form for use in calculating clearances. Using FE model input files, and non-FE contributing factor input files, clearance synthesis dashboard  201  generates  436  clearance data and plots. In the exemplary embodiment, clearance data is generated in pre-determined formats selected by the user. The input and output files are saved  438  to a computer readable medium selected by the user. From the generated data in the output files, a statistical module predicts  440  turbine clearances based on statistical variations of the contributing factors. Empirical clearance data is retrieved  442  from field data acquired from an operational machine, or test facility, and compared  444  to the predictions received in block  440 . If the clearance predictions compare favorably to the field data, the clearance predictions are approved  446  and stored  448  on network drive  113  or other location accessible to users of clearance synthesis dashboard  201 . If the clearance predictions do not compare favorably to the field data, the input data is checked  450  for a missing contributing factor. If a contributing factor is determined to be missing and the factor is part of a component that is modeled using FE, a new FE model is created and process  400  restarts at block  412 . If the contributing factor determined missing is a non-FE contributing factor, the equation is re-developed and process  400  restarts at process block  430 . 
   In operation, clearance synthesis dashboard  201  receives a plurality of data files including FE model input files  202  and non-FE contributing factor input files  206 . Clearance synthesis dashboard  201  calculates turbine clearances versus time at locations selected by the user, and calculates turbine clearances versus location over a period of time selected by the user. After validation of results of the calculations, dashboard  201  generates data files, charts, and plots that represent the calculated results graphically and/or tabularly. 
     FIG. 6  is a screen shot of an exemplary user interface input screen  500  that may be used with clearance synthesis dashboard  201  shown in FIG.  3 . In the exemplary embodiment, screen  500  is a typical Windows™ input window  502  including three tabs  504 ,  506 , and  508  respectively. User information tab  504  prompts a user for administrative information to facilitate organizing databases and calculation results including, for example, a “Name of Machine or Machine Code” field  510 , an “Analyst&#39;s Initials” field  512 , a “Today&#39;s Date/Time” field  514 , a “Comments” field  516 , and a “Continue” button. Screen  502  is a first screen of user interaction and allows a user to input specific information that may be used in calculations and labeling of plots. For example, “Machine Information for X 1 ” tab  506  prompts a user for information specific to a selected machine, such as, for example, “Radius offset” and “Tolerances”. If a field is left blank or is filled in incorrectly, an error message may prompt a user to correctly complete input fields  510 ,  512 ,  514 , and  516 . After input fields  510 ,  512 ,  514 , and  516  are complete, a user may select a radio button  518  to continue with data input. In the exemplary embodiment, a user may select a machine designated as “X 1 ”. In another embodiment, any number of machines may have tabs from which a user may select. 
   “Machine Information for X 2 ” tab  508  prompts a user for information specific to a selected machine. In the exemplary embodiment, a user may select a machine designated as “X 2 ”. In the exemplary embodiment, tab  508  prompts the user for the same information as described above and includes user prompts for the user to input values for a specific machine that may be designated as X 2 , such as, for example, “Bearing Lift” and/or “Shell Arm Corrections”. The user may be prompted to enter these values when an appropriate radio button (bearing lift or shell arm) is selected. 
     FIG. 7  is a screen shot of an exemplary “Select Machine” screen  600  that may be used with clearance synthesis dashboard  201  shown in FIG.  3 . Screen  600  prompts the user to choose from a plurality of different types of machines for which a calculation will be determined. A drop-down menu button  602  permits the user to select one of the plurality of machines for which calculations may be determined. After selecting the desired machine, the user clicks on the “Continue” button  604 . 
     FIG. 8  is a screen shot of an exemplary “Input Status” screen  700  that may be used with clearance synthesis dashboard  201  shown in FIG.  3 . Screen  700  indicates if dashboard  201  has identified the appropriate input files based on the information collected from “User Input” screen  502 . If dashboard  201  has identified the file correctly, a filename will appear next to a corresponding indicator. In the exemplary embodiment, a plurality of arrows are used for the indicator. If the file is not identified, the text “FILE NOT FOUND” will appear next to corresponding indicator  702 . The user may browse  704  to the appropriate file name on network drive  113  or other storage media accessible to the user and manually select the appropriate file. 
     FIG. 9  is a screen shot of an exemplary “Select Stages” screen  800  that may be used with clearance synthesis dashboard  201  shown in FIG.  3 . “Select Stages” screen  800  prompts the user to select particular stages for which output is desired. The user selects a checkbox  802  corresponding to each desired stage(s), and a continue radio button  804  to continue. In the exemplary embodiment, some checkboxes may not be available for selecting because dashboard  201  automatically reads the diaphragm data file and allows only the checkboxes that correspond to stages found in the diaphragm file to be available. Unavailable stages may be grayed out to indicate an unavailable status. 
     FIG. 10  is a screen shot of an exemplary “Main Menu” screen  900  that may be used with clearance synthesis dashboard  201  shown in FIG.  3 . In the exemplary embodiment, screen  900  includes four buttons: “Process Data”  902 , “Configure Plots”  904 , “View Output Status”  906 , and “Exit”  908 . “Process Data”  902  activates reading of data, performance of calculations, and formatting of data tables. “Configure Plots”  904  creates line and polar graphs presenting results of the calculations performed in “Process Data”  902 . “View Output Status”  906  opens an “Output Status” screen where the user may view opened output files and/or save the files. “Exit”  908  will exit the user from dashboard  201 . Upon exiting, dashboard  201  will close all input files. 
     FIG. 11  is a screen shot of an exemplary “Output Status” screen  1000  that may be used with “View Output Status”  906  shown in FIG.  9 . “Output Status” screen  1000  displays files that have been opened and written to. The files are divided into a plurality of types. In the exemplary embodiment, the files are divided into a component plot and data type  1002 , a cycle plot type  1004 , and an other output type  1006 . At the bottom of the screen, a “Save outputs” button  1008  and a “Close all outputs and return” button  1010  are shown. In the exemplary embodiment, the user has the option of saving the output files to a spreadsheet by clicking on “Save outputs” button  1008 , or the user may to close the output files and return to the main menu by clicking on “Close all outputs and exit” button  1010 . 
     FIG. 12  is a screen shot of an exemplary display  1100  that may output from clearance synthesis dashboard  201  shown in FIG.  3 . Display  1100  includes a graph  1101  of component deflection versus time that includes a heading  1102  that indicates, for example, a machine code, a graph type, and a location. A user information area  1104  includes data input by the user at tab  504 . An x-axis  1106  indicates a time elapsed starting at a time zero or event initiation and ending at a time selected by the user or calculated by clearance synthesis dashboard  201  based on data input by the user. A Y-axis  1108  indicates a deflection in a unit selected by the user for components of turbine  10  selected by the user to be analyzed. A total deflection for each of the rotor and the stator is also included in graph  1101 . 
     FIG. 13  is a screen shot of an exemplary display  1200  that may output from clearance synthesis dashboard  201  shown in FIG.  3 . Display  1200  includes a polar type graph  1202  that includes a heading  1204  that indicates, for example, a machine name, an operational cycle state, and a location of the analysis. Graph  1202  includes a polar scale that indicates an amount of deflection that takes place at a plurality of locations angularly displaced about a longitudinal axis of turbine  10 . 
   The above-described clearance synthesis dashboard is cost effective and highly reliable. The clearance synthesis dashboard includes a plurality of formatted input files and a calculation engine that determines turbine radial clearance changes that occur in a steam turbine for various operating cycles. The results are output in a format selected by the user. The output results facilitate visualizing changes occurring in a turbine. As a result, the clearance synthesis dashboard facilitates the design and maintenance of rotating machinery in a cost effective and reliable manner. 
   Exemplary embodiments of the clearance synthesis dashboard are described above in detail. The configurations are not limited to the specific embodiments described herein, but rather, components of the configuration may be utilized independently and separately from other components described herein. Each clearance synthesis dashboard component can also be used in combination with other clearance synthesis dashboard components. 
   While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.