Patent Document

BACKGROUND OF THE INVENTION 
   The present invention relates generally to in-situ inspection of rotating machinery components and, more particularly to in-situ ultrasonic inspection of turbine and compressor components, for example, blades, buckets or airfoils in turbines and compressors. 
   At least some known gas turbine engines include a compressor for compressing air, which is mixed with a fuel and channeled to a combustor wherein the mixture is ignited within a combustion chamber for generating hot combustion gases. The hot combustion gases are channeled downstream to a turbine, which extracts energy from the combustion gases for powering the compressor, as well as producing useful work to propel an aircraft in flight or to power a load, such as an electrical generator. 
   Known compressors include a rotor assembly that includes at least one row of circumferentially spaced rotor blades. Each rotor blade includes an airfoil that includes a pressure side and a suction side connected together at leading and trailing edges. Each airfoil extends radially outward from a rotor blade platform. Each rotor blade also includes an attachment portion, such as, a dovetail that extends radially inward from the platform, and is used to mount the rotor blade within the rotor assembly to a rotor disk or spool. 
   During operation, the rotor blades and dovetails are subjected to loading forces that may cause in-service cracking, micro-fractures or other damage that is visually imperceptible. Known inspection techniques are limited in their ability to assess the integrity of the blades while the blades are in-place. More specifically, a visual inspection only permits a limited examination of the blades for cracks in the airfoil. To thoroughly examine the blade and dovetail regions, where cracking or other damage may originate, at least a portion of the engine casing may need to be removed to facilitate removal of each blade, and subsequent inspection of the blades and dovetails with visual, magnetic particle, liquid penetrant, or other techniques. However, because of labor and cost constraints such techniques may be impracticable in some instances. To examine the blades without disassembly, a technician must manually reach into the machine. This can be a potentially hazardous action as any movement in the rotor blades or inlet guide vanes would likely result in the loss of a limb. Accordingly, a new method and apparatus for the in-situ inspection of rotating machinery components is needed. 
   BRIEF DESCRIPTION OF THE INVENTION 
   In one aspect, a method of testing a component of a rotary machine while the component remains coupled within an assembled rotary machine is provided. The method includes positioning a transceiver on a face of the component, transmitting ultrasonic waves into the component, receiving ultrasonic echoes, and analyzing the ultrasonic echoes. 
   In another aspect, an ultrasonic testing system for testing a component of a rotatable member of a rotary machine while the rotatable member remains coupled within an assembled rotary machine is provided. The system includes an ultrasonic transceiver configured to transmit ultrasound waves into and receive ultrasound echoes from the component, a processor for controlling outputs from the transmitter/receiver and receiving inputs from the transmitter/receiver, and a display for outputting information based on the ultrasonic echo data. 
   In another aspect, an in-situ ultrasonic testing apparatus for testing a component of a rotatable member of a rotary machine while the rotatable member remains coupled within an assembled rotary machine is provided. A positioning fixture includes clamping means for clamping onto the component, transceiver support means for mounting an ultrasonic transceiver, and manipulator rod means for enabling the transceiver to be moved to different positions along said component. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side elevation view of an exemplary gas turbine engine; 
       FIG. 2  is a perspective view of a portion of a row one (R 1 ) compressor wheel that may be used with the gas turbine engine shown in  FIG. 1 ; 
       FIG. 3  is an enlarged axial cross-sectional view of a portion of a compressor blade that may be used with the compressor wheel shown in  FIG. 2 ; 
       FIG. 4  is a perspective view of the clamp and manipulating means. 
       FIG. 5  is a radial perspective view of a row of inlet guide vanes and a row of compressor blades that may be used with the gas turbine engine shown in  FIG. 1 . 
       FIG. 6  is a cross-sectional view of the clamp and manipulating means attached to a compressor blade that may be used with the compressor wheel shown in  FIG. 2 . 
       FIG. 7  is a block diagram of an exemplary method for ultrasonically testing a component of a rotating machine. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  is a side elevation view of an exemplary gas turbine engine  10  that includes a compressor section  12 , a turbine section  14  and a plurality of combustors  16  (only one combustor is shown in  FIG. 1 ). Engine  10  includes a rotor  40  including a plurality of rotor wheels  42 . Each rotor wheel  42  is configured to mount a plurality of components, such as, but not limited to, buckets or blades  44 , which in conjunction with a respective number of stator vanes  46 , form the various stages of engine  10 . Hereafter, the description of the invention references the component as a blade, however, this description is merely exemplary. It is not intended to limit the invention in any manner. The invention herein contemplates use with any such component. In the exemplary embodiment, a plurality of compressor blades  44  are coupled to a first row  48  that includes a first-stage rotor wheel  50 . Each blade  44  includes an airfoil  52  that is mounted in opposition to respective stator vanes  46 . Blades  44  are spaced circumferentially about first-stage wheel  50 . Inlet guide vanes  54  serve to properly orient the incoming airflow. The inlet guide vanes can be of the fixed or variable type. The variable type can open or close by varying amounts to adjust the angle of the incoming airflow. Turbine engine  10  may drive a generator (not shown) for producing electrical power 
     FIG. 2  is a perspective view of a portion of first stage rotor wheel  50 . Rotor wheel  50  includes a plurality of axially aligned dovetail slots  202  that are spaced circumferentially about a radially outer periphery of wheel  50 . Slots  202  receive an attachment portion, such as a dovetail  206  of blade  44 , therein. More specifically, blades  44  are removably coupled within disk slot  202  by each respective blade dovetail  206 . Accordingly, slot  202  is shaped to generally compliment a shape of each dovetail  206  received therein, and accordingly, in the exemplary embodiment, includes a pair of wheel post tangs  222  and a disk slot bottom  224  that extends between wheel post tangs  222 . In the exemplary embodiment, disk slot  202  also includes a pair of opposed wheel faces  230  and  232 . 
     FIG. 3  is an enlarged axial cross-sectional view of a portion of rotor blade  44 . Each rotor blade  44  includes a dovetail  206  used for mounting each respective airfoil  52  to rotor wheel  50 . More specifically, each airfoil  52  extends radially outward from a platform  208  formed integrally with, and extending between dovetail  206  and airfoil  52 . Each airfoil  52  includes a first contoured sidewall  210  and a second contoured sidewall  212 . First sidewall  210  defines a suction side of airfoil  52 , and second sidewall  212  defines a pressure side of airfoil  52 . Sidewalls  210  and  212  are joined at a leading edge  214  and at an axially spaced trailing edge  216  of airfoil  52 . More specifically, airfoil trailing edge  216  is spaced downstream from airfoil leading edge  214 . First and second sidewalls  210  and  212 , respectively, extend longitudinally or radially outward in span from a blade root  218  positioned adjacent dovetail  206 , to an airfoil tip  220 . 
   Each blade dovetail  206  is mounted within dovetail slot  202  (refer to  FIG. 2 ), and cooperates with dovetail slot  202 , to form rotor wheel  50 . In the exemplary embodiment, each dovetail  206  includes a pair of opposed dovetail shoulders  234  and  236 , and a dovetail bottom  238  that extends between dovetail shoulders  234  and  236 . A dovetail base  240  extends circumferentially between dovetail shoulders  234  and  236 . Shoulders  234  and  236  are sized to be received within respective wheel post tangs  222  and engage disk slot  202 , such that blades  44  are radially retained within wheel  50 . In an alternative embodiment, each blade dovetail includes a plurality of pairs of wheel post tangs  222 . 
   During operation, centrifugal forces force rotor blades  44  outward and induce loading forces into dovetail  206  and blade  44 . Over time, such forces may induce cracking within dovetail  206  at such locations that may be radially inward or outward from platform  208 , and thus not easily accessible to conventional testing techniques. As one example, an area where cracks may develop is indicated by the circle  270 . 
   An ultrasonic transceiver  250  may be placed in a position contacting blade  44  radially outward from platform  208  to interrogate, inspect and scan, as described hereinafter a volume of dovetail  206  that is inaccessible to known testing techniques. Inaccessible is defined as a location that cannot be reached without disassembling parts of the machine, or that poses a hazardous condition to a testing technician. For example, to access the R 0  blades (i.e., the first row of blades) in a compressor, a technician must reach through the inlet guide vanes (IGVs)  54  with his hand and arm. This is extremely dangerous for the technician as any movement of the IGVs or the R 0  blades could result in the loss of a hand and/or an arm. Accordingly, the present invention provides an improved safer method and apparatus for inspecting rotary machine components. 
   In the exemplary embodiment, transceiver  250  is a monolithic type ultrasonic transceiver wherein an angle and focus of a single ultrasonic beam  254  are selected by controlling the physical orientation of transceiver  250 . The beam spread  252  is selected to cover the desired area to be inspected, such as, that indicated by region  270 . During scanning, or the inspection process, an ultrasonic beam  254  from transceiver  250  penetrates into blade  44  and dovetail  206 . As each blade  44  is scanned, the ultrasonic transceiver  250  generates ultrasonic pulses, and then receives echoes from blade  44  to facilitate detecting flaws, which may have developed within blade  44  or dovetail  206 . The data received is indicative of the structure and/or a flaw in blade  44  or dovetail  206 . This process of steps can be referred to as interrogating, inspecting or scanning. In alternative embodiments, transducer  250  comprises at least one non-phased array transducer configured to transmit ultrasonic beams into a component at a plurality of steering angles or at least one linear phased array type. Using one or more transducers may permit ultrasonic viewing of portions of the component that may not be able to be viewed using traditional techniques. 
   A monolithic transceiver is a device that generates only one ultrasonic beam at a time, however, there may be one or more ultrasonic generating elements in this type of transceiver. A phased array ultrasonic transceiver generates one or more ultrasonic beams simultaneously (or in rapid sequence) at multiple angles. This allows dynamic focusing and “electronic” steering of the beam and multiple beam widths. Another advantage of phased array type transceivers is their wide field of view. Components may be tested separately from other pieces of an assembly as well as part of the assembly. In addition, components with portions that are inaccessible to known testing methods may be tested using one or more monolithic transceivers, one or more non-phased-array transceivers and/or one or more phased-array transducers. 
     FIG. 4  is an enlarged perspective view of an exemplary clamp and manipulating means  401 , as embodied by the invention. The clamps  402 ,  403  attach to the leading and trailing edges of the blade  44 . The clamps comprise elongated slots  404  which engage the edges of blades  44  to securely mount the clamp and manipulating means  401  to the blade  44 . Handle  405  is used to maneuver and navigate the clamp and manipulating means  401  inside the rotary machine and onto a blade  44 . Clamp  402  is hingedly connected to base  406 . This hinge or pivot  602  (not illustrated in  FIG. 4 , but shown in  FIG. 6 ) allows the clamps  402  and  404  to open to accept the blade, then close to engage and securely mount to the blade  44 . The handle  405  is used to pivot clamp  402  between open and closed positions. Additionally, clamp  402  functions as a docking member for transceiver mount  407 . As the clamp and manipulating means  401  is inserted inside the rotary machine, clamp  402  secures transceiver mount  407  and prevents any unwanted movement. 
   Manipulator rod  408  is used to move transceiver mount  407  back and forth along a rail  409  on the base  406 . During the inspection procedure, manipulator rod  408  is used to reposition the transceiver  250  along the face of the component to be tested. The manipulator rod  408  is threaded into base  410  and fastened to a pivot arm  411  with suitable fasteners. Manipulator rod  408  can be passed through a support means  422 . By rotating manipulator rod  408 , the pivot arm  411  is forced away from or pulled towards threaded base  410 , by pivoting on pivot  412 . This enables the skew angle of the scan to be adjusted to re-aim the scan on specific areas of interest. The skew angle is the angle the incident beam  254  makes with the surface of the blade  44  or dovetail  206 . Typically, the skew angle is about 90°, but can be changed to scan other areas, or to obtain a “different view” of a specific area of interest. The manipulator rod  408  enables the skew angle to be adjusted between about −45° to +45°. 
   Spring biased mounting arms  414  retain ultrasonic transceiver  250  and maintain contact between the component under test and the transceiver  250 . For example, the spring biasing means could be a wire spring wound around shaft  420 , having one end contacting the mounting arm  414  and the other end contacting pivot arm  411 . Other spring biasing means that accomplish the same effect are also contemplated and within the scope of the invention. Height guides  416  contact the surface of the dovetail  206  or wheel  50  and maintain the correct spacing between the dovetail and transceiver  250 . This orients and aims the ultrasonic transceiver  250  at the desired area to be inspected (e.g., area  270 , as shown in  FIG. 3 ). Height guides  416  are adjustable and can be set to various vertical offsets. In one embodiment, height guides  416  can comprise threaded bolts, and the height is adjusted by turning the bolts clockwise or counter-clockwise. In alternative embodiments, height guides could be telescopically adjustable members or segmented members with sections that can be added or removed to adjust the height. 
     FIG. 5  is a radial perspective view of a row of inlet guide vanes  54  and a row of R 0  compressor blades  44  in a gas turbine engine  10  (shown in  FIG. 1 ). In one embodiment, transceiver  250  is transitioned from an accessible area  502  upstream from inlet guide vanes  54 , through inlet guide vanes  54  to inaccessible area  503 . In this exemplary embodiment, clamp and manipulating means  401 , together with transceiver  250 , are used in situ (i.e., the gas turbine engine  10  does not need to be dismantled). The inlet guide vanes  54  may be blocked in a full open position to facilitate testing of blades  44 . Accessible area  502  is located outside of the compressor and inaccessible area  503  is located behind inlet guide vanes  54 . Inaccessible area  503  was only previously accessible by dismantling the compressor and inlet guide vanes. This dismantling was a very time consuming and expensive process, as well as, costly due to the down time of the power generation equipment. Handle  405  and manipulator rod  408  can be extended to reach deeper rows of blades, such as, R 1 , R 2 , R 3 , etc. R 0  typically refers to the first row of blades, and R 1  to the second row and so on. 
   Transceiver  250  is held in place against each blade  44  in turn, and is translated mechanically, or by machine control, with manipulator rod  408 , in a substantially axial direction across blade pressure side  212 . During the scanning, an ultrasonic beam from transceiver  250  penetrates into blade  44  and dovetail  206 . As each blade  44  is interrogated, the ultrasonic transceiver  250  generates ultrasonic pulses, and then receives echoes from blade  44  to facilitate detecting flaws, which may have developed within blade  44  or dovetail  206 . The data received is indicative of the structure and/or a flaw in blade  44  or dovetail  206 . 
   In the exemplary embodiment, the data is transmitted to a processor  506  such as, but not limited to a laptop computer, a personal digital assistant (PDA), a data collector, or a network connection. In an alternative embodiment, the echo data and transceiver position data may be received by separate processors. In the exemplary embodiment, processor  506  includes a display  507  to monitor and display the results of each scan and operation of the scan. As used herein, the term “processor” also refers to microprocessors, central processing units (CPU), application specific integrated circuits (ASIC), logic circuits, and any other circuit or processor capable of executing inspection system, as described herein. 
     FIG. 6  is a cross sectional view of clamp and manipulating means  401  attached to a blade  44 . Pivot point  602  is located near one end of clamp  402 . Biasing means  604  biases clamp  402  in a closed position. In one embodiment, biasing means  604  is comprised of a spring-loaded plunger mechanism. In an alternative embodiment, the biasing means  604  could be a pneumatic operating element, or any other feature that biases clamp  402  into its closed position ( FIG. 6 ). An operator or technician can open clamp  402  by pulling on handle  405  pivoting  402  about pivot pin  602 . This enables the clamps  402  and  403  to expand and accept the blade  403 . When the handle  405  is released, clamp  402  closes and securely engages blade  44 . 
   During operation, handle  405  and clamp and manipulating means  401  are extended through inlet guide vanes  54  from accessible area  502 , where an operator may then attach the clamps  402  and  403  onto blade  44 . The position of transceiver  250  with respect to blade  44  may be input by the user in response to prompts from processor  506 . Processor  506  may include data acquisition and/or analysis software executing thereon that receives data from transceiver  250  that displays simultaneously the data recorded for all beam angles as a polar plot, creating a cross-sectional view called a “linear scan”, “arc scan” or “sector scan” image. In the example of a linear scan, the ultrasonic transceiver is moved in a horizontal direction. For every scan line, a transmit pulse is sent and the reflected signals from different depths are recorded and scan-converted to be shown on a video display (e.g.,  507 ). The single transducer movement during image acquisition determines the shape of the image. This movement directly translates into the shape of a linear array transducer, i.e., for the linear scan, the array would be straight, while for the arc scan, the array would be concave. The resulting scan image may include the echoes received from blade  44  or dovetail  206  and cracks or flaws located therein. The positions of the reflections may be measured directly from the resulting scan image. If a crack or flaw is present, its image will be displayed among the reflectors on display  507  or sent directly over a network to an analysis location (not shown). The position, depth, and dimension of the crack or flaw may be measured directly from the image shown on display  507 . 
   The scan may be controlled manually by operator input to processor  506 . Scan control software executing in processor  506  may control transceiver  250 . At the end of the scan, processor  506  stops taking data and prompts the user to reposition clamp and manipulating means  401  to scan the next blade. Scanning continues with each blade scanned in turn until all blades and dovetails are scanned. Repositioning of rotor wheel  50  to maintain accessibility to blades  44  may be necessary. 
     FIG. 7  is a block diagram of an exemplary method  700  for ultrasonically testing a component  44  of a rotatable member  50  of a rotary machine  10  while the rotatable member remains positioned within a casing (not shown) of an assembled rotary machine  10 . In the exemplary embodiment, an ultrasonic transceiver is positioned at step  702 , on a face of a turbine blade attached to a turbine rotor wheel. The transceiver is positioned on each blade in turn during the testing procedure. Because the turbine remains assembled during the testing, the transceiver is fed through the turbine inlet guide vanes  54 , which may be blocked fully open. The transceiver is positioned at the base of the blade airfoil radially outward from the blade platform and slid axially along a predetermined scan path while in contact with the blade. During the scan, the transceiver transmits at step  704 , ultrasonic waves into an inaccessible portion of the blade and dovetail such that the blade and dovetail may be interrogated by the ultrasonic waves. The transceiver receives at step  706 , ultrasonic echoes as a result of the ultrasonic waves impinging on an acoustic impedance interface within the material and being reflected. The transceiver receives at least some of the ultrasonic energy that is reflected back into the transceivers&#39; field of view. The echoes may be indicative of flaws, such as cracks, that may have developed within the blade and/or dovetail. The echoes are transmitted to a processor for analyzing at step  708 , the ultrasonic echoes to determine the crack location and dimensions. The result may be displayed on a local display or may be transmitted to a remote location for further analysis. 
   The above-described ultrasonic testing method and apparatus is cost-effective and highly reliable for testing components that remain installed on a turbine rotor or compressor in an assembled machine. Specifically, the turbine or compressor blades are inaccessible to visual, eddy current, dye penetrant, and other test methods when the turbine is assembled. The method and apparatus permits an inspection of machine components without the heretofore attendant disassembly of the turbine and removal of the turbine or compressor blades to permit early detection of fatigue cracking in the primary location from which the cracks originate. The method and apparatus also enables a technician to perform an in-situ inspection without putting any part of their body in harm&#39;s way. By inspecting without removal of the component, the inspection is less disruptive to the commercial operation of the machines and can be easily scheduled and accomplished within scheduled downtimes. As a result, the methods and apparatus described herein facilitate ultrasonic testing in a cost-effective and reliable manner. The method and apparatus can be applied to the inspection of many types of rotating machines, such as, compressors, turbines, and generators, to name a few. 
   Exemplary embodiments of ultrasonic testing systems are described above in detail. The systems are not limited to the specific embodiments described herein, but rather, components of each system may be utilized independently and separately from other components described herein. Each system component can also be used in combination with other system components. For example, the ultrasonic transceiver could be replaced by an infrared, x-ray, electrical, resistive or other type of sensor. 
   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 following claims.

Technology Category: g