Devices and methods for testing of a turbine moving blade while the turbine moving blade is mounted on a turbine rotor

Abstract

The present disclosure relates to a device for testing of a turbine moving blade. The device comprises a body configured to be immovably fitted around the turbine moving blade, wherein the body comprises at least six transducers arranged such that when the body is fitted around the turbine moving blade at least three transducers are arranged on a pressure side of the airfoil and at least three transducers are arranged on a suction side of the airfoil. The present disclosure further relates to methods of testing using such devices.

Description

DEVICES AND METHODS FOR TESTING OF A TURBNE MOVING BLADE WHILE THE TURBINE MOVING BLADE IS MOUNTED ON A TURBINE ROTOR

[0001] The present disclosure relates generally to testing of rotating machinery components and, more particularly to ultrasonic inspection of turbine moving blades, for example, airfoils and dovetails thereof.BACKGROUND

[0002] Modern turbines, which include gas and steam turbines, are used in a wide variety of applications, such as for power generation or for conducting industrial processes. Power generation is done, for example, at fossil, nuclear or renewable plants.

[0003] A turbine includes a rotor which includes a shaft, and a plurality of blades arranged in rows. The rotor blades may be referred to as moving blades. The rotor is supported by bearings and is housed in a casing, e.g. a cylinder-shaped casing. Stator vanes or nozzles may be arranged in between rows of the turbine blades and have a fixed position.

[0004] During operation of the turbine, the nozzles or vanes direct the flow of steam (or gas) between a preceding row of moving blades and the next row of moving blades. The shaft to which the moving blades are attached therefore turns. And the shaft may for example turn a generator for producing electric power.

[0005] During operation, moving rotors are subjected to loading forces that may cause cracking, micro-fractures or other damage that is visually imperceptible. A visual inspection only permits a limited examination of the blades for cracks in the airfoil. A better approach is to use ultrasonic measurements. The ultrasonic measurements can provide a better insight into the internal structure of a moving blade. Ultrasonic measurements can also be done when a moving blade has been detached from a rotor. It is preferred however to have the ultrasonic measurements done while a moving blade is still attached to a rotor. This avoids the need for dismounting and remounting a moving blade and so the risks of damaging the moving blade during the dismounting and mounting process can be avoided.

[0006] In order to thoroughly examine the blade and dovetail regions, where cracking or other damage may originate, at least a portion of the turbine casing may need to be removed to allow subsequent inspection of the blades and dovetails with visual, magneticparticle, liquid penetrant, ultrasound, or other techniques. This is especially relevant for the techniques that require access from both sides of a steam turbine blade, i.e., from a suction side and from a pressure side of said steam turbine blade. Said dovetail region comprises or consists of a part of a steam turbine blade that is inserted in a rotor and which is responsible for mounting the steam turbine blade to the rotor.

[0007] However, the cost of such techniques is significant. Moreover, blades or buckets may be damaged in the process of removal, transport and testing.

[0008] The techniques based on ultrasonic measurements performed while blades are mounted on a rotor face problems with accuracy and precision as well as with the time needed to examine every blade in a turbine. Accuracy and precision are essential for a proper evaluation of a condition of a moving blade and those two parameters suffer due to measurements that cannot be repeated, turned out to be incomplete during data processing or measurements that lack sufficient redundancy to obtain meaningful data or due to time constraints. There is interest in performing tests in a shortest possible time as tests prolong outage which means that the longer the tests are being conducted, the longer the facility is not operating. At the same time, as mentioned earlier, time constraints have a negative impact on the quality of tests.

[0009] Accordingly, there is still a need for methods and systems that are both accurate and precise and can perform tests in a shortest possible time and at the same time, without the need to dismantle any part of a steam turbine casing. The present invention addresses this need by providing devices and methods that allow for fast, precise and accurate determination of a condition of a turbine moving blade.SUMMARY

[0010] In an aspect of the present disclosure, a device for testing of a turbine moving blade while the turbine moving blade is mounted on a turbine rotor is provided. The turbine moving blade includes an airfoil and a dovetail region, and the airfoil comprises an airfoil pressure side and an airfoil suction side. The device comprises a body configured to be immovably fitted around the turbine moving blade. The body comprises at least six transducers arranged such that when the body is fitted around the turbine moving blade, at least three transducers are arranged on the airfoil pressure side and at least three transducers are arranged on the airfoil suction side. The transducers are 2Dmatrix phased array transducers. The transducers are configured to emit one or more ultrasonic waves towards at least a portion of the dovetail region.

[0011] In accordance with this aspect, the device is fitted around the turbine moving blade such that testing can be performed without the need to remove the turbine moving blade from a rotor. Immovably fitting the device around the turbine moving blade together with the described configuration of transducers allows for high-precision and high-accuracy measurements with any needed redundancy in a single step for each blade to determine a condition of that blade. The device allows for testing of a turbine moving blade. Additionally, this device does not require to have access from both sides of a steam turbine blade, i.e., suction and pressure sides. It follows that in order to perform testing there is no need to remove any part of a steam turbine casing.

[0012] The device comprises at least six transducers which, when the device is fitted around the turbine moving blade, are held in known predetermined positions with respect to the airfoil and dovetail. The arrangement of three transducers on the pressure side and three transducers on the suction side means that after fixing the device on the turbine moving blade, the transducers do not need to be displaced or translated in the axial direction to be able to inspect different parts of the dovetail. By maintaining the transducers in a fixed axial position, the determination of where damage may be is much more reliable. Moreover, since transducers are provided on both the suction side and pressure side, analysis can cover the whole dovetail area, and the different information obtained from the individual transducers can be combined to obtain an overall picture of the status or damage of the component.

[0013] The transducers are 2D matrix phased array transducers. 2D stands for two dimensional. The use of 2D matrix phased array transducers allows one or more ultrasonic waves to be emitted in various planes to achieve a comprehensive volumetric inspection. In particular, the use of such transducers together with the FMC techniques reduces the time needed for testing of a moving blade and for a complete testing of a blade. Additionally, the use of such transducers together with the FMC techniques in the device allows to observe parts of the dovetail region that are not possible to be observed using known methods.

[0014] With examples of such a solution, previously mentioned problems relating to e.g., limitation in inspection coverage of the dovetail region can be reduced or avoided.

[0015] In a further aspect of the present disclosure, a method for testing of a turbine moving blade while the turbine moving blade is mounted on a turbine rotor, the turbine moving blade includes an airfoil and a dovetail region, the airfoil comprises an airfoil pressure side and an airfoil suction side. The method comprises immovably fitting a device for testing according to the disclosure around the turbine moving blade such that at least three transducers are arranged on a pressure side of the airfoil, and at least three transducers arranged on a suction side of the airfoil. A plurality of the transducers of the device emitting one or more ultrasonic waves towards a portion of the dovetail region. The method further comprises the transducers receiving echoes of the ultrasonic waves; and combining the received echoes using Full Matrix Capture (FMC) techniques to obtain an image of the internal structure of the portion of the dovetail region.

[0016] The turbine moving blade is mounted on the turbine rotor, and the testing may be performed without dismounting the turbine moving blade from the turbine rotor. Inspecting the turbine moving blade without the need for disassembly is cost-effective and can save a significant amount of time. It also allows mitigating risks associated with dismounting of a turbine moving blade from a rotor. Specifically, it can also avoid damage that may occur when removing the turbine moving blade from a rotor.

[0017] In some examples, reorienting of individual transducers allows gathering improved data from a particular region in a turbine moving blade. This is relevant when echoes are somehow distorted and as a result the internal image of a turbine moving blade does not clearly show all combined regions of the turbine moving blade.

[0018] Each of the transducers is a 2D matrix phased array transducer and thereby configured to emit one or more ultrasonic waves in different directions. Each of the transducers may preferably be fixed on the body.

[0019] In accordance with some examples, at least one of the transducers may be configured to send ultrasonic waves towards an end portion in the longitudinal direction of the dovetail region. In the prior art, the end portions at the leading and trailing edges are areas that are often neglected and constitute inaccessible areas for inspection of the dovetail region.

[0020] In some examples, the device may comprise one or more transducers which are configured to be reoriented. In these examples, the transducers may stay in the same axial position on the device (and thereby in the same chordwise position of the turbinemoving blade), but they can be redirected e.g., tilted or rotated to send ultrasound waves in different directions.

[0021] In some examples, the device may be configured to be fitted around the turbine moving blade by sliding the device over a tip area of the airfoil portion towards the root of the airfoil portion. The internal shape of the device may be adapted for inspection of specific blades, i.e., in case of inspection of another blade, a new device that is tailored for this specific component may be prepared and used.

[0022] In some examples, the device is configured to be opened, and the body comprises a pressure side part and a suction side part. The device may be mounted around the component by arranging the parts on the sides of the airfoil and connecting the pressure side part to the suction side part at the trailing edge and leading edge region. In a further example, the pressure side part may be hingedly connected to the suction side part. Providing a device in two parts allows for faster gathering of data for a single blade, thereby allowing fast inspection for whole rows of moving blades with precision and accuracy . Additionally, transportation to and from the customer side is easier as such two-part device can be better packed.

[0023] In yet a further aspect, a system for testing is provided. The system comprises the device according to any of the examples herein disclosed and a data processor, wherein the data processor is configured to receive data obtained from the transducers and to combine the received data.

[0024] The data processor may be configured to combine the received data using Full Matrix Capture (FMC) techniques. The data obtained from the several transducers may be stitched together to get a complete picture of potential damage in the turbine moving blade, and particularly in the dovetail portion thereof.

[0025] In the method for inspection, the plurality of the transducers can be activated in a sequential manner, i.e., at any time only one transducer is active in sending ultrasound waves and receiving the echoed ultrasound waves. This ensures that the sound waves received by any of the transducers also originated at the same transducers and this allows an accurate determination of the status of a component that is being inspected.

[0026] In some examples, the system may further comprise a display for outputting the combined data. The data processor may be wirelessly connected to the device andremotely located, i.e., analysis of the obtained data may be performed at a remote location. In other examples, the analysis of the obtained data may be carried out in situ. The analysis may be carried out in real-time or at a later stage.

[0027] Examples of the present disclosure are specifically aimed at steam turbine blades or buckets in view of their size and complexity of inspection of the dovetail portion, particularly curved dovetail portions, but it will be clear that examples of the present disclosure may be used for inspection of e.g., gas turbine blades with similar effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Non-limiting examples of the present disclosure will be described in the following, with reference to the appended drawings, in which:Figure 1 A schematically illustrates a perspective view of an example of a turbine moving blade according to the prior art;Figure 1B schematically illustrates a perspective view of one example of a turbine assembly according to the prior art;Figure 2A schematically illustrates an example of a device for testing mounted on a turbine moving blade;Figure 2B schematically illustrates the functioning of the device of figure 2A;Figure 2C schematically illustrates an example of a system for testing according to the present disclosure;Figures 3A and 3B schematically illustrate top views of different examples of devices for testing;Figure 4 schematically illustrates a side view of yet a further example of a device that may be used for testing; andFigure 5 schematically illustrates a flowchart of an example of a method for testing of a turbine moving blade in accordance with the present disclosure.DETAILED DESCRIPTION

[0029] Reference now will be made in detail to embodiments of the present disclosure, one or more examples of which are illustrated in the drawings. Each exampleis provided by way of explanation only, not as a limitation. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure. 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 disclosure covers such modifications and variations as come within the scope of the appended claims and their equivalents.

[0030] Figure 1A illustrates a perspective view of an example of a conventional turbine moving blade. The turbine moving blade depicted in this example may be a blade 100 for a steam turbine. As shown, turbine moving blade component 100 includes an airfoil 110 comprising a pressure side 120 and a suction side 130, and a dovetail region 140.

[0031] Figure 1B illustrates an example of a turbine assembly comprising a turbine moving blade 100, mounted to a turbine wheel 150. Turbine wheel 150 includes a plurality of dovetail slots that are spaced circumferentially about a radially outer periphery of the turbine wheel 150. The slots receive an attachment portion of the blade, such as the dovetail region 140 of the turbine moving blade 100, therein.

[0032] A large variety of different dovetail portions is known in the art. Dovetail portions can be curved along a chordwise (axial) direction as illustrated in figure 1A. Depending on the shape and size of the dovetail portion, it may be easier or more complicated to inspect for damage.

[0033] Figures 2A and 2B illustrate an example of a device according to the present disclosure mounted on the moving blade 100. A device for testing of a turbine moving blade 100 including an airfoil 110 and a dovetail region 140 is provided. The device comprises a body 200 configured to be immovably fitted around the turbine moving blade 100.

[0034] The body 200 comprises at least six transducers 300 arranged such that when the body 200 is immovably fitted around the turbine moving blade 100, at least three transducers 300 are arranged on a pressure side 120 of the airfoil 110 and at least three transducers 300 (not visible) are arranged on a suction side 130 of the airfoil 110. The transducers 300 are configured to emit one or more ultrasonic waves towards at least a portion of the dovetail region.

[0035] An ultrasound transducer 300 is a device that produces ultrasound waves that can bounce off and echo off a structure, and in this case a dovetail region 140 of the turbine moving blade 100. Depending on the internal structure of the airfoil portion (in particular depending on whether there are cracks, gaps, or other damage, the echoed waves will be different). The transducer also receives the echoes and can send them to a computer or data processor that can combine the echoes, and thereby construct an image of the internal structure of the turbine moving blade 100. In particular, location and type of damage may be detected in this manner.

[0036] The transducers 300 are 2D matrix phased array transducers.. As illustrated in figure 2B, each of the transducers 300 may be configured to emit one or more ultrasonic waves 400 in different directions.

[0037] Each one of the transducers 300 shown in figure 2B can send ultrasound waves within a range of directions. The three transducers illustrated on the suction side in figure 2B together can cover substantially the whole axial length of the dovetail portion. There is thus no need to move the transducers to obtain a complete picture of potential damage of the entire airfoil portion. Also, any movement is not desired as it may negatively affect the quality of data and redundancy thereof. It will be clear that in further examples (and depending on the component to be inspected), the number of transducers may vary.

[0038] In operation, each of the transducers may be activated sequentially. In an example, the transducer on the suction side and closest to the leading edge may be activated first, and send ultrasound waves in different directions throughout its operational range. The transducer receives the echoed waves. When the first transducer has finished, the next transducer may be activated e.g., the second transducer on the suction side. The rest of the transducers may be activated one after the other sequentially.

[0039] The body 200 may be formed of any suitable material that permits the transmission of ultrasonic waves e.g., suitable metals, plastics, ceramics or composites. The body 200 may further be configured to provide a cleaner and safer environment for the transducers.

[0040] Figure 2C illustrates an example of a system 270 for testing. The system 270 comprises the device (with body 200 and a plurality of transducers), and a data processor280. The data processor 280 is configured to receive data obtained from the transducers and to combine the received data. The system 270 may further comprise a display 290 for outputting and visualizing the combined data.

[0041] The data processor 280 may be configured to combine the received data using Full Matrix Capture (FMC) techniques. Full Matrix Capture is a technique for capturing all possible ultrasonic data from a phased array probe. Each element is fired in turn as mentioned before and the received signal is recorded at each of the other elements for each firing.

[0042] During FMC, each element in the array transmits a pulse one at a time, while all elements (including the transmitter) act as receivers. This process captures data for every possible combination of transmitter and receiver pairs, forming a complete dataset. FMC can collect all available data from the array, providing a complete representation of the interaction between the ultrasonic waves and the material.

[0043] As schematically illustrated in figure 2B, the range of angles of the individual transducers overlap at reference sign 450. This can occur for two or more transducers on the suction side, two or more transducers on the pressure side, but also for combinations of a transducer on the suction side and one on the pressure side.

[0044] At these intersections 450, the data from one transducer may be stitched together with data from another transducer to obtain an overall image of the dovetail portion.

[0045] In examples, the data processor 280 may be communicatively, e.g. wirelessly, coupled to the body 200 of the device. The data processor 280 can be located remotely from the device. For example, inspection of the blade may occur in a power plant, whereas the analysis (and potentially the visualization) may occur in a remotely located service center. The data from the process may be stored, e.g., the raw data (obtained from the individual transducers) may be stored and / or the processed data may be stored for later use.

[0046] With examples of the present disclosure, an overview, e.g., length and width dimensions and the severity, e.g., the critical depth, of the defects that may compromise the structural integrity of the turbine moving blade 100 can be provided. Subsequently, by having access to the profile of the entire dovetail region, this may assist in the determination of which areas of the dovetail region 140 are most susceptible to defects,choosing appropriate mitigation measures according to defect characteristics obtained, and / or to provide the basis for an integrity management plan.

[0047] In the example of figure 2, the body 200 of the device may be configured to slide over the airfoil of the turbine moving blade 100 i.e., the body 200 may be arranged over a tip portion of the airfoil and may slide down. Depending on the shape of the turbine moving blade 100, such a mounting may be chosen.

[0048] Some turbine blades may include a platform at a root portion of the airfoil. The body 200 may be devised such that in use it is arranged on top of the platform and supported by the platform. For the accuracy of the detection of the damage, it is important that the precise position of the individual transducers is known and is constant. Mounting the body 200 on the platform can improve the accuracy of the detection of damage.

[0049] An inside of the body 200 may have a shape that is substantially complementary to an outer shape of the turbine moving blade 100.

[0050] Figure 3A schematically illustrates a device for testing. The body 200 comprises a pressure side part 220 and a suction side part 210, and wherein the device is configured to be opened by at least partially separating the suction side part 210 and the pressure side part 220 and configured to be closed. By opening and closing the body 200, the body can be immovably fitted around a variety of turbine blades. The inside surfaces of the body 200 may be adapted to fit or engage a specific turbine moving blade.

[0051] Figure 3A schematically illustrates that both near the leading edge and near the trailing edge, fasteners may be provided to releasably attach the pressure side part 220 and suction side part 210. In examples, one of the parts may include holes, and the other may include pins, screws or similar for fitting inside the holes. In some examples, the pressure side part and the suction side part may be releasably attached using e.g., magnets.

[0052] In this example, the suction side part 210 comprises five suction side transducers 310 to cover substantially the entire length of the dovetail portion of the turbine moving blade. The pressure side part 220 similarly comprises five pressure side transducers 320.

[0053] In a further example, illustrated in figure 3B, the pressure side part 220 is hingedly connected to the suction side part 210. In this particular example, a hinge 250is provided near a leading edge, and the body 200 may be opened and closed by rotating one part with respect to the other. In the example illustrated in figure 3B, each of the pressure side part and the suction side part includes three transducers.

[0054] In further examples, different numbers of transducers may be used. In some examples, the number of transducers on the suction side may be different from the number of transducers on the pressure side. In some examples, redundancy may be provided i.e., the number and type of transducers may be chosen such that there is sufficient overlap in the field of view of the individual transducers that the device can still function even if an individual transducer fails.

[0055] In some examples, not all the transducers need to be the same. As long as their position relative to each other and relative to the turbine moving blade 100 is known or can be accurately determined, the techniques described herein can be used.

[0056] In some examples, one or more of the transducers may be configured to be reoriented. An example hereof is illustrated in figure 4. A side view of a body 200 including transducers 330 is shown. The transducer 340 may be configured to be reoriented to increase the angular range of directions in which ultrasound waves can be emitted. The transducers 330 may be fixed in this example. The transducers 330 (and also 340) may be phased array transducers which can cover a range of angles without the need for reorienting.

[0057] Figure 5 provides a flowchart of an example of a method for the testing of a turbine moving blade in accordance with the present disclosure.

[0058] A method 500 for testing of a turbine moving blade while the turbine moving blade is mounted on a turbine rotor, the turbine moving blade including an airfoil and a dovetail region is provided. The method comprises, at block 510, immovably fitting a device for testing in accordance with any of the examples disclosed herein around the turbine moving blade, such that at least three transducers are arranged on a pressure side of the airfoil, and at least three transducers arranged on a suction side of the airfoil. The method then comprises, at block 520, a plurality of the transducers of the device emitting one or more ultrasonic waves towards a portion of the dovetail region. The transducers then receive echoes of the ultrasonic waves. In particular, individual transducers may be activated sequentially. In some examples, a single transducer may be emitting ultrasound waves, whereas multiple transducers are receiving the echoedwaves. The method further comprises combining the received echoes using Full Matrix Capture (FMC) techniques to obtain an image of the internal structure of the portion of the dovetail region.

[0059] As commented before, the transducers are 2D matrix phased array transducers capable of sending ultrasound waves in different directions. In accordance with FMC techniques, a single element in an array may be transmitting, while all elements of the array are receiving echoed ultrasound waves.

[0060] Method 500 further comprises, at block 530, combining the received echoes. The received echoes from the plurality of transducers are combined to detect damage in substantially the whole dovetail region. This may be achieved using full matrix capture techniques to combine the received echoes from the plurality of transducers.

[0061] Method 500 may further comprise, at block 540, displaying the result of the analyses. Any suitable display, including a computer monitor, tablet, PDA, mobile device or other may be used. The analyses may take place in real-time. Alternatively, the raw data obtained with the device may be stored for later processing.

[0062] In preferred examples, a turbine moving blade that is being analyzed is mounted on a turbine rotor, and a testing is performed without dismounting the turbine moving blade from the turbine rotor.

[0063] This written description uses examples to disclose the present teaching, including the preferred embodiments, and also to enable any person skilled in the art to practice it, including making and using any product and performing any incorporated methods. The patentable scope 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 have 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. Aspects from the various embodiments described, as well as other known equivalents for each such aspects, can be mixed and matched by one of ordinary skill in the art to construct additional embodiments and techniques in accordance with principles of this application. If reference signs related to drawings are placed in parentheses in a claim, they are solely for attempting to increase the intelligibility of the claim and shall not be construed as limiting the scope of the claim.

Claims

CLAIMS1. A device for testing of a turbine moving blade while the turbine moving blade is mounted on a turbine rotor,wherein the turbine moving blade includes an airfoil and a dovetail region, wherein the airfoil comprises an airfoil pressure side and an airfoil suction side, the device comprising:a body configured to be immovably fitted around the turbine moving blade, wherein the body comprises at least six transducers arranged such that when the body is fitted around the turbine moving blade, at least three transducers are arranged on the airfoil pressure side and at least three transducers are arranged on the airfoil suction side, andwherein the transducers are configured to emit one or more ultrasonic waves towards at least a portion of the dovetail region and the transducers are 2D matrix phased array transducers.

2. The device of claim 1 , wherein one or more of the transducers are configured to be reoriented.

3. The device of any of claims 1 - 2, wherein the body comprises a pressure side part and a suction side part, and wherein the device is configured to be opened by at least partially separating the suction side part and the pressure side part and configured to be closed.

4. The device of claim 3, wherein the pressure side part is hingedly connected to the suction side part.

5. The device of any of claims 1 - 4, wherein an inside of the body has a shape that is substantially complementary to an outer shape of the turbine moving blade.

6. The device of any of claims 1 - 5, wherein the turbine moving blade is a steam turbine moving blade or a gas turbine moving blade.

7. A system for testing comprising:the device of any of claims 1 - 6; anda data processor, whereinthe data processor is configured to receive data obtained from the transducers and to combine the received data.

8. The system of claim 7, wherein the data processor is configured to combine the received data using Full Matrix Capture (FMC) techniques.

9. A method for testing of a turbine moving blade while the turbine moving blade is mounted on a turbine rotor, wherein the turbine moving blade includes an airfoil and a dovetail region, wherein the airfoil comprises a pressure and a suction side,the method comprising:immovably fitting a device for testing according to any of claims 1 - 6 on the turbine moving blade such that at least three transducers are arranged on a pressure side of the airfoil, and at least three transducers arranged on a suction side of the airfoil;a plurality of the transducers of the device emitting one or more ultrasonic waves towards a portion of the dovetail region,wherein the transducers are 2D matrix phased array transducers;the transducers receiving echoes of the ultrasonic waves; andcombining the received echoes using Full Matrix Capture (FMC) techniques to obtain an image of the internal structure of the portion of the dovetail region.

10. The method of claim 9, wherein the turbine moving blade is a steam turbine moving blade or a gas turbine moving blade.

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