Patent Publication Number: US-2015075265-A1

Title: Measurement device and method for evaluating turbomachine clearances

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims filing benefit of U.S. Provisional Patent Application Ser. No. 61/878,776 having a filing date of Sep. 17, 2013, which is incorporated by reference herein in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present disclosure relates generally to turbomachines, such as gas turbine systems, and more particularly to methods and apparatus for evaluating clearances in turbomachines. 
     BACKGROUND OF THE INVENTION 
     Turbomachines are widely utilized in fields such as power generation. For example, a conventional gas turbine system includes a compressor section, a combustor section, and at least one turbine section. The compressor section is configured to compress air as the air flows through the compressor section. The air is then flowed from the compressor section to the combustor section, where it is mixed with fuel and combusted, generating a hot gas flow. The hot gas flow is provided to the turbine section, which utilizes the hot gas flow by extracting energy from it to power the compressor, an electrical generator, and other various loads. 
     Various clearances are required in a turbomachine for the components thereof to properly operate relative to one another. For example, clearances are defined between blade tips and adjacent shroud surfaces in the turbine section of a gas turbine, and clearances are defined between blade tips and compressor casings in the compressor section of a gas turbine. Engineering clearance limits for the various components are predetermined during design of a turbomachine, and typically include ranges of appropriate clearances for relative components which include maximum and minimum clearances. During construction and maintenance of the turbomachine, present clearances may be compared to the required engineering clearance limits to ensure that the various components are positioned within the required specifications for the turbomachine. 
     Such comparison of present clearances to engineering clearance limits is particularly appropriate during maintenance of a turbomachine. During a typical maintenance period or outage, clearances are measure at the beginning of the outage, when the turbomachine is opened, and at the end of the outage, when the turbomachine is closed. These measurements are then compared to each other and/or to the engineering clearance limits, and modifications are made to bring the present clearances within the required engineering clearance limits. 
     Currently, however, such clearance measurement operations are tedious and inefficient. For example, current practice is to utilize shim stock or manual gauges to take clearance measurements. These measurements are then each manually compared to the required engineering clearance limits. Such process significantly increases outage times. 
     Accordingly, improved methods and apparatus for evaluating clearances in turbomachines are desired. In particular, methods and apparatus which facilitate efficient and accurate clearance measurement and analysis would be advantageous. 
     BRIEF DESCRIPTION OF THE INVENTION 
     Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention. 
     In one embodiment, the present disclosure is directed to a measurement device for evaluating a clearance between adjacent components in a turbomachine. The measurement device may include a tool and a controller. The tool and controller may determine the clearance by measuring the distance between the adjacent components. The controller may compare the clearance to a predetermined engineering clearance limit and/or a previously measured clearance. 
     In another embodiment, the present disclosure is directed to method for evaluating a clearance in a turbomachine. The method may include, for example, measuring the clearance with a device which includes a controller. The method may further include comparing the clearance in the controller to a predetermined engineering clearance limit and/or a previously measured clearance. 
     These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which: 
         FIG. 1  is a schematic view of a gas turbine system according to one embodiment of the present disclosure; 
         FIG. 2  is a cross-sectional view of a portion of a turbine section according to one embodiment of the present disclosure; 
         FIG. 3  is a close-up view of a portion of a turbine section, as indicated in  FIG. 2 , according to one embodiment of the present disclosure; 
         FIG. 4  is another close-up view of a portion of a turbine section, as indicated in  FIG. 2 , according to one embodiment of the present disclosure; and 
         FIG. 5  is a cross-sectional view of a portion of a compressor section according to one embodiment of the present disclosure; 
         FIG. 6  is a perspective view of a measurement device mounted to a gas turbine system according to one embodiment of the present disclosure; and 
         FIG. 7  illustrates a measurement device measuring various clearance points in a compressor section according to one embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
       FIG. 1  is a schematic diagram of a turbomachine, which in the embodiment shown is a gas turbine system  10 . It should be understood that the turbomachine of the present disclosure need not be a gas turbine system  10 , but rather may be any suitable turbine system or other turbomachine, such as a steam turbine system or other suitable system. The system  10  as shown may include a compressor section  12 , a combustor section  14  which may include a plurality of combustors as discussed below, and a turbine section  16 . The compressor section  12  and turbine section  16  may be coupled by a shaft  18 . The shaft  18  may be a single shaft or a plurality of shaft segments coupled together to form shaft  18 . The shaft  18  may further be coupled to a generator or other suitable energy storage device, or may be connected directly to, for example, an electrical grid. An inlet section  19  may provide an air flow to the compressor section  12 , and exhaust gases may be exhausted from the turbine section  16  through an exhaust section  20  and exhausted and/or utilized in the system  10  or other suitable system. Exhaust gases from the system  10  may for example be exhausted into the atmosphere, flowed to a steam turbine or other suitable system, or recycled through a heat recovery steam generator. 
     Referring now to  FIG. 2 , a side cross-sectional view of a portion of a turbine section  16  of a gas turbine system  10  is illustrated. Turbine section  16  may include various rotary and stationary components which form various turbine stages. In some embodiments, turbine section  16  may have three stages. In other embodiments, a turbine section  16  may have one, two, four or more stages. A single stage of turbine section  16  is generally illustrated in  FIG. 2 . Such stage may include a plurality of circumferentially spaced nozzles  30  and buckets  32  (one of each of which is shown). The nozzles  30  may be disposed and fixed circumferentially about shaft  18 . The buckets  32  may be disposed circumferentially about the shaft  18  and coupled to the shaft  18 . 
     The nozzle  30  may generally include an outer platform  42 , an inner platform  44 , and a stator vane  46  extending generally radially therebetween. Stator vane  46  may be generally airfoil shaped, having a pressure side and a suction side extending between a leading edge and a trailing edge. An inner stage seal  48  may be coupled to the inner platform  44 . 
     The bucket  32  may include a platform  52 , a rotor blade  54  extending radially outward from the platform  32 , and a shank  56  extending radially inward from the platform  52 . Rotor blade  54  may be generally airfoil shaped, having a pressure side and a suction side extending between a leading edge and a trailing edge. Shank  56  may further include a plurality of angel wings  58  extending therefrom, such as along a generally axial direction. 
     A dovetail (not shown) extending radially inward from the shank  56  may couple to the bucket  32  to a rotor wheel  60 . Additionally, a shroud  62  may be positioned radially outwardly from the bucket  32 . Outer platform  42  may be coupled to the shroud  62  to position the nozzle  30  within the turbine section  16 . 
     Referring now to  FIG. 5 , a side cross-sectional view of a portion of a compressor section  12  of a gas turbine system  10  is illustrated. Turbine section  16  may include various rotary and stationary components which form various compressor stages. In some embodiments, compressor section  12  may have between 10 and 20 stages. In other embodiments, a compressor section  12  may have less than 10 or greater than 20 stages. Four stages of compressor section  12  are generally illustrated in  FIG. 5 . A stage may include a plurality of circumferentially spaced stationary airfoils  70  and rotating airfoils  72  (one of each of which is shown). The stationary airfoils  70  may be disposed and fixed circumferentially about shaft  18 . The rotating airfoils  72  may be disposed circumferentially about the shaft  18  and coupled to the shaft  18 . 
     The stationary airfoils  70  may generally include a stator vane  82  which extends radially inwardly from an outer body  84 . The outer body  84  may be coupled to a compressor casing  86  or compressor discharge casing  88  to position the stationary airfoil  70  within the compressor section  12 . Compressor casing  86  and compressor discharge casing  88  may additionally be coupled together to form an outer casing of the compressor section  12 . (Alternatively, a single outer casing may be utilized). 
     The rotating airfoils  72  may include a rotor blade  100  extending radially outward from a platform (not shown). A dovetail (not shown) extending radially inward from the platform may couple the rotating airfoils  72  to a rotor wheel  102 . 
     Various clearances may be defined by the various components of a system  10 . A clearance is generally a distance between two components. As discussed above, it is desirable to ensure that present clearances between components are within required engineering clearance limits, such as within the ranges and tolerances defined by the predetermined engineering clearance limits. Referring now to  FIGS. 3-5 , various clearances are illustrated. In the embodiments shown, radial clearances  90  and axial clearances  92  are illustrated. However, any suitable clearances in any suitable direction between any suitable components are within the scope and spirit of the present disclosure. 
     For example,  FIG. 3  illustrates various clearances between a rotor blade  54  and a shroud  62 . As shown, a radial clearance  90  may be defined between a tip  112  of the blade  54 , such as the rail  114  thereof, and an abradable material block  116  of the shroud  62 . An axial clearance  92  may be defined between the rail  114  and an axially adjacent surface  118  of the shroud  62 . An axial clearance  92  may additionally be defined between axially adjacent surfaces  120 ,  122  of the tip  102  and shroud  62 , respectively. 
       FIG. 4  illustrates various clearances between a bucket  32  and a nozzle  30  and inner stage seal  48 . As shown, a radial clearance  90  may be defined between each angel wing  58  and a radially adjacent surface, such as a radially adjacent inner stage seal surface  132 . A radial clearance  90  may additionally be defined between a seal tooth  133  of a spacer wheel  134  that is between axially adjacent rotor wheels  60  and an abradable material block  136  of the inner stage seal  48 . An axial clearance  92  may be defined between each angel wing  58  and an axially adjacent surface, such as an axially adjacent inner platform surface  140  or an axially adjacent inner stage seal surface  142 . An axial clearance  92  may additionally be defined between a platform leading edge  144  and an axially adjacent inner platform surface  146 . An axial clearance  92  may additionally be defined between a seal tooth  133  and an end  148  of the inner stage seal  48 . 
       FIG. 5  illustrates various clearances between various components in a compressor section  12 . As shown, a radial clearance may be defined between a blade  100  and casing  86 , and between a vane  82  and rotor wheel  102 . Further, a clearance  94  may be defined for an airslot between the compressor casing  86  and compressor discharge casing  88 . Such clearance  94  may be defined at an angle to the radial and axial clearance directions. 
     It should be understood that the present disclosure is not limited to the above-disclosed clearances. Rather, any suitable clearance in any section of a gas turbine system  10  or other turbomachine is within the scope and spirit of the present disclosure. 
     As discussed above, accurate and efficient apparatus for measuring such clearances  90 ,  92 ,  94  are desired. Accordingly, and referring to  FIGS. 6 and 7 , the present disclosure is further directed to measurement devices  200  for measuring such clearances  90 ,  92 ,  94 . 
     As illustrated, a measuring device  200  may include a tool  202 . The tool  202  may operate to measure relative locations of various system  10  components, to calculate present clearances  90 ,  92 ,  94 , or measure the clearances  90 ,  92 ,  94  themselves. In some embodiments, for example, a tool  202  may be a coordinate measuring machine, as illustrated. Tool  202  in these embodiments may include a base  210  and an articulated arm  212 . The base  210  may be connectable to a suitable location in the system  10 , such as to a casing thereof. In exemplary embodiments, base  210  may be magnetic, and may thus be magnetically connectable to a component of the system  10  as shown. The articulated arm  212  may include various portions and hinges which provide the arm  212  with, for example, six degrees of freedom, such that a wide variety of movements of the arm  212  are available. A probe tip  214  may be provided on an end of the arm  212 . The tool  202  in these embodiments may operate to measure relative locations of various system  10  components. For example, referring to  FIG. 7 , tool  202  is illustrated measuring relative locations for two radial clearances  90 . The tip  214  may be initially brought into contact with a first surface that defines a clearance, such as a rotor blade  100  or stator vane  82  as shown. A location measurement may be taken with the tip  214  in such contact. The tip  214  may then be brought into contact with a second surface that defines a clearance, such as a compressor casing  86  or rotor wheel  102  as shown. A location measurement may be taken with the tip  214  in such contact. The tool  202  may be capable of defining these measurements relative to each other in 3-dimensional space, such that a clearance  90 ,  92 ,  94  can be determined based on the relative locations. 
     As further shown with respect to the clearance  90  defined by the stator vane  82  and rotor wheel  102 , in some embodiments, the tip  214  may take contact measurements along a 2-dimensional distance (as shown) or within a 3-dimensional plane for each component. The tool  202  may be capable of defining these 2-dimensional or 3-dimensional measurements relative to each other in 3-dimensional space, such that clearances  90 ,  92 ,  94  can be determined based on the relative locations. 
     Suitable coordinate measuring machines are commercially available from, for example, ARGON 3D MEASUREMENT SERVICES, with a place of business in Belgium, and FARO TECHNOLOGIES, with a place of business in Florida, USA. 
     In other embodiments, a tool  202  may measure the clearances  90 ,  92 ,  94 . For example, a suitable laser device may direct a laser between two components that define a clearance, such that the length of the laser may be the clearance  90 ,  92 ,  94 . A suitable photo- or video-graphic device may be utilized to record clearances  90 ,  92 ,  94  for analysis. 
     A device  200  according to the present disclosure may further include a controller  204 , which may be in communication with the tool  202 . Controller  104  may provide a variety of functions, including calculating clearances  90 ,  92 ,  94  based on data, such as location data, from the tool  202 , and comparing clearance measurements to, for example, predetermined engineering clearance limits and other clearance measurements. 
     It should be appreciated that the controller  204  may generally comprise a computer or any other suitable processing unit. Thus, in several embodiments, the controller  204  may include one or more processor(s) and associated memory device(s) configured to perform a variety of computer-implemented functions. As used herein, the term “processor” refers not only to integrated circuits referred to in the art as being included in a computer, but also refers to a controller, a microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific integrated circuit, and other programmable circuits. Additionally, the memory device(s) of the controller  204  may generally comprise memory element(s) including, but are not limited to, computer readable medium (e.g., random access memory (RAM)), computer readable non-volatile medium (e.g., a flash memory), a floppy disk, a compact disc-read only memory (CD-ROM), a magneto-optical disk (MOD), a digital versatile disc (DVD) and/or other suitable memory elements. Such memory device(s) may generally be configured to store suitable computer-readable instructions that, when implemented by the processor(s), configure the controller  204  to perform various computer-implemented functions. In addition, the controller  204  may also include various input/output channels for receiving inputs from and sending control signals to sensors and/or other measurement devices, such as the tool  202 . 
     It should be understood that tool  202  and controller  204  may be separate components or themselves components of a single device. Further, a single controller  204  or multiple controllers  204  may be utilized. For example, tool  202  may include an integrated controller  204 , and may further be connected to an additionally controller  204 . 
     Device  200  may thus determine present clearances  90 ,  92 ,  94  as required. In exemplary embodiments, the device  200  may further be utilized to analyze such clearances  90 ,  92 ,  94 . For example, the device  200 , such as the controller  204  thereof, may compare present clearances  90 ,  92 ,  94  to predetermined engineering clearance limits, or to previously measured clearances. Such predetermined engineering clearance limits and/or previously measured clearances may be programmed into and/or stored in the controller  204 . As discussed, present clearance measurements may be taken in some embodiments at the beginning of an outage and at the end of an outage. Thus, for example, present clearance measurements taken at the end of an outage may be compared to present clearance measurements taken at the beginning of an outage and to predetermined engineering clearance limits. Thus, adjustments can be made to various system  10  components if necessary to ensure that all clearances are correct and all components are correctly positioned before the system  10  is operated. 
     Additionally, in exemplary embodiments, the device  200  can be utilized for documentation of clearances  90 ,  92 ,  94 . For example, clearances  90 ,  92 ,  94  and engineering clearance limits stored in the device  200 , such as in the controller  204  thereof, can be output into summary reports or other suitable documentation, to document the clearances. Such documentation may be prepared, for example, when clearances are evaluated at the beginning and at the end of an outage. 
     The present disclosure is further directed to methods for evaluating clearances between components in turbomachines. A method may include, for example, determining a clearance utilizing, for example, a device comprising a controller. The method may further include utilizing the controller to compare the clearance to another clearance, such as a predetermined engineering clearance limit or a previously determined clearance. The method may further include, for example, displaying the clearance. Such comparison and display may be performed in exemplary embodiments in real time. For example, after determining a clearance, the controller may compare the clearance and display an indication on, for example, a screen thereof, relative to the clearance. The indication may indicate whether, for example, the measure clearance is within a predetermined engineering clearance limit and/or is approximately equal to (with a suitable tolerance) a previously determined clearance. Further, the method may include, for example, documenting the clearance, as discussed above. 
     Advantageously, use of a device  200  according to the present disclosure may facilitate efficient and accurate clearance measurements and analysis. For example, the present inventors have estimated that use of such device  200  according to the present disclosure may save between one and two days of outage time. Further, such devices  200  provide more accurate clearance measurements and analysis relative to previously known measurement methods and apparatus. 
     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 include 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.