JP4769774B2 - Turbine blade shroud clearance measuring apparatus and measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently measure a clearance between shrouds when rotating a turbine. <P>SOLUTION: This clearance measuring device 40 comprises an optical sensor 46 arranged on the respective blade tips of a plurality of turbine blades 14 implanted in the peripheral direction of a turbine rotor 12 and receiving and converting the reflected light into an electric signal by emitting the light toward the shrouds 16 from the outside in the radial direction of the turbine blades 14 for measuring an adjacent clearance of the shrouds 16 capable of mutually contacting between the adjacent blades in response to rotation of the turbine when rotating the turbine, and an arithmetic operation device 48 for arithmetically operating the adjacent clearance of the shrouds based on the time ratio of a received part &Delta;t<SB>h</SB>and an unreceiving part &Delta;t<SB>1</SB>of the reflected light from the shrouds 16 of this electric signal (a waveform 52) and a dimension L in the peripheral direction of the shrouds 16. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a turbine blade shroud gap measuring device and a measuring method, and more particularly to a technique for measuring a gap between shrouds during turbine rotation.

  Regardless of whether the current power plant is a steam turbine plant or a combined cycle power plant in which a steam turbine is combined with a gas turbine, high efficiency and high output are required, and both the gas turbine and the steam turbine have a tendency to increase the single unit output. Along with this, the stage near the turbine outlet including the final stage has a longer blade length, and various measures have been taken to avoid excessive vibration during operation.

  For example, a moving blade implanted in a turbine rotor has a continuous structure in which each section of the blade profile is twisted from the root part (root part) to the tip part (tip part), and is twisted by rotational centrifugal force during operation. Since the return (hereinafter referred to as untwist) acts, it is known to use this action to connect the turbine blades during operation and suppress the vibration of the turbine blades.

  In other words, the shroud that covers the entire blade profile at the tip of each blade tip has a gap between adjacent shrouds when the turbine is stationary, and the gap decreases due to untwisting as the turbine rotor speed increases, and eventually the shrouds contact each other. Is provided. Thereby, a high vibration damping characteristic can be obtained by connecting shrouds adjacent in the circumferential direction. In addition, the shroud gap is designed so that the shrouds come into contact with each other with the contact force set during the rated rotation in consideration of vibration damping characteristics and the like.

  The variation in the gap size between the shrouds means the variation in the rotational speed at which the shrouds of the blades are in contact with each other, and also affects the variation in the contact force of the contact surface. Therefore, tolerance management of the gap size is required.

  As a method for managing the tolerance of the gap dimension, conventionally, the gap dimension between the shrouds has been measured with a caliper while the turbine is stationary. However, there are large variations in measurement and several tens of times along the circumferential direction. It is inefficient to measure and manage gaps in excess of locations using this method.

  In particular, in the case of a moving blade having an axial entry groove (hereinafter referred to as Ax groove as appropriate) structure, since there is no gap between the rotor side Ax groove for the first time due to centrifugal force due to rotation, there is a gap in the Ax groove when stationary, and the shroud The gap of the gap easily changes, and the tolerance management of the gap is not easy.

  Therefore, Patent Document 1 describes a technique for measuring a gap between shrouds during turbine rotation. Specifically, first, a plurality of measurement reference lines are drawn in advance at predetermined intervals on the shroud, and an image is obtained by photographing with a camera while illuminating the shroud with a strobe light emitter. Then, a ratio between a known dimension between measurement reference lines and a dimension between measurement reference lines on an image is obtained, and a gap between shrouds is obtained based on this ratio.

Japanese Patent No. 2678647

  However, in the technique disclosed in Patent Document 1, the gap between the shrouds may not be efficiently measured during turbine rotation.

  That is, when it is desired to measure all the shroud gaps in the circumferential direction of the turbine during turbine rotation by the method of Patent Document 1 above, a plurality of measurement standards can be accurately applied to all the shrouds of tens or hundreds. It is necessary to draw a line in advance, which is not efficient.

  Accordingly, an object of the present invention is to efficiently measure a gap between shrouds during turbine rotation.

  In order to solve the above-described problems, a turbine blade shroud clearance measurement apparatus according to the present invention is provided at the tip of each blade of a plurality of turbine blades implanted along the circumferential direction of the turbine rotor, and is accompanied with the rotation of the turbine. The adjacent gap of the shroud that can contact each other between adjacent blades is measured during turbine rotation. It emits light from the outside in the radial direction of the turbine rotor blade toward the shroud and receives reflected light to generate an electrical signal. And an arithmetic means for calculating an adjacent gap of the shroud based on a change with time of the electric signal and a circumferential dimension of the shroud.

  That is, when the turbine rotates, for example, laser light is emitted from the radially outer side of the turbine blade toward the shroud, and when the reflected light is received, the reflected light from the shroud has a high light reception level, while in the shroud gap Since the reflectance is low, the received light level of the reflected light is lower than this. Then, a portion corresponding to the shroud and a portion corresponding to the gap appear in the electrical signal converted according to the light receiving level, and this change with time and the known circumferential dimension of the shroud , The adjacent gap of the shroud can be calculated.

More specifically, the calculation means calculates the adjacent gap of the shroud based on the time ratio between the portion where the reflected light from the shroud of the electrical signal is received and the portion where the reflected light is not received and the circumferential dimension of the shroud. can do.
The converted electric signal has a waveform in which, for example, a portion having a high signal level corresponding to the shroud and a portion having a low signal level corresponding to the gap appear alternately. The ratio of the length of time of these parts corresponds to the ratio of the shroud circumferential dimension and the shroud gap, so the known shroud circumferential dimension and the time ratio obtained from the electrical signal Based on this, the shroud gap can be calculated.

  As described above, according to the present invention, it is not necessary to perform a measurement operation on the shroud in advance, and a plurality of adjacent shroud gaps can be efficiently measured continuously in the circumferential direction while rotating the turbine. be able to.

  Also, at least one of the circumferential direction of the turbine rotor, turbine rotor blade, and shroud is physically provided differently from the other parts, and a physical change due to the rotation reference is measured to measure the electrical change. A reference signal generating device for converting the signal into a signal, and the calculating means recognizes the rotation reference of the turbine based on the change over time of the electrical signal output from the reference signal generating device, and identifies the adjacent gap portion of the calculated shroud be able to.

  According to this, since the rotation reference of one rotation of the turbine can be recognized, a set of a high level portion and a low level portion appearing in the electric signal waveform is a set of a plurality of shrouds and shroud adjacent gaps existing in the circumferential direction of the turbine. It is possible to specify which one of these corresponds to.

  For example, the rotation reference is provided in a circumferential portion of at least one of the turbine rotor, the turbine rotor blade, and the shroud with a light reflectance different from that of the other portion, and the reference signal generator is directed to the rotation reference. The reflected light can be received and converted into an electrical signal.

  In this way, since the adjacent gap of the shroud can be measured while rotating the turbine, it is difficult to measure the gap when the turbine is stationary, as in the turbine in which the turbine rotor blade is implanted in the turbine rotor by the axial entry groove structure. Even if it is a thing, the clearance gap between shrouds can be measured efficiently.

  In order to solve the above-described problem, the turbine blade shroud clearance measuring method of the present invention is provided at the tip of each blade of a plurality of turbine blades implanted along the circumferential direction of the turbine rotor. Accordingly, the adjacent gap of the shroud that can contact each other between the adjacent blades is measured while the turbine is rotating, and emits light from the radially outer side of the turbine blade toward the shroud and receives the reflected light. It is converted into an electric signal, and the adjacent gap of the shroud is calculated based on the change over time of the electric signal and the circumferential dimension of the shroud.

  According to the present invention, it is possible to efficiently measure a gap between shrouds during turbine rotation.

  Embodiments of a turbine blade shroud clearance measuring apparatus and method to which the present invention is applied will be described below with reference to FIGS.

  First, an outline of a turbine to which a turbine blade shroud clearance measurement device (hereinafter simply referred to as a clearance measurement device) of the present invention is applied will be described with reference to FIG. A turbine rotor 12 is provided for the turbine rotating shaft 10, and a plurality of turbine blades 14 are implanted along the circumferential direction of the turbine rotor 12. Usually, about tens to hundreds of turbine blades 14 are implanted.

  Each blade tip is provided with a shroud 16 that can contact each other between adjacent blades as the turbine rotates. For convenience of explanation, the turbine is drawn in a single stage, but actually, a plurality of stages of turbines are provided along the turbine rotation shaft 10.

  Next, details of the turbine rotor blade 14 and the shroud 16 will be described with reference to FIG. FIG. 2 is a perspective view of the turbine rotor blade and the shroud. As shown in FIG. 2, the turbine rotor blade 14 has a continuous structure from the root portion (root portion) 20 to the tip portion (tip portion) 22 so that each cross section of the blade profile is twisted. Further, the turbine rotor blade 14 has a root portion 20 extending along the rotation axis direction, and is gradually twisted toward the outer side in the radial direction with respect to the rotation axis, so that the tip portion 22 rotates the turbine. It is formed so as to extend along the circumferential direction.

  The shroud 16 is a plate-like member provided substantially orthogonal to the radial direction so as to cover the tip portion 22, and is formed so as to extend longer in the circumferential direction than the rotation axis direction in accordance with the tip portion 22. ing. Further, the shroud 16 has recesses formed on two sides facing each other in the circumferential direction so that the shrouds between adjacent blades can be brought into contact with each other by untwisting due to turbine rotation.

  Further, in the present embodiment, an axial entry groove (Ax groove) structure is employed for the connection between the turbine rotor blade 14 and the turbine rotor 12, that is, the implantation of the turbine rotor blade 14 into the turbine rotor 12. As shown in FIGS. 2 and 3, the Ax groove structure corresponds to the unevenness of the fitting member 24 provided on the inner side in the radial direction of the root portion 20 of the turbine rotor blade 14 and having unevenness as shown in the drawing. Then, it is inserted into the Ax groove provided in the turbine rotor 12 by sliding in the axial direction.

  By the way, such turbine rotor blades 14 have been noticeably increased in length due to the demand for high efficiency and high output of the power plant, resulting in a rapid increase in torsion and a thin profile of the blade profile in the vicinity of the tip portion. There is also a need for suppression of excessive vibration during turbine operation. Therefore, as described above, the shroud is provided in the tip portion 22 of the turbine rotor blade 14 and the adjacent shrouds are connected to each other in the circumferential direction of the turbine to improve the rigidity. As a result, high vibration damping characteristics are obtained. .

  Specifically, when assembling the turbine rotor blade, a gap is provided in the shroud between adjacent blades, and this gap decreases due to the occurrence of untwisting with the increase in the rotational speed of the rotor, and eventually the shroud. The shrouds are designed to come into contact with each other and with the contact force set during rated rotation.

Therefore, the variation in the gap size between the shrouds means the variation in the rotational speed at which the shrouds of the blades come into contact with each other, and also affects the variation in the contact force on the contact surface. When an excessively large contact force is generated due to the variation in the gap size, fretting is caused, and wear of the contact surface due to this may cause a change in blade vibration characteristics. As a result, if the initial vibration damping characteristics cannot be obtained, the blades may be damaged. Therefore, the tolerance management of the gap dimension is necessary.
In particular, in the case of a rotor blade having an Ax groove structure as in the present embodiment, the rotor side contacts the Ax groove on the rotor side without any clearance for the first time due to the centrifugal force caused by rotation. There is a gap and the shroud gap changes easily. Even if a shim is inserted into the gap of the Ax groove and the gap is filled to reduce the backlash, the shroud gap is not uniform between the same blades. Therefore, it is difficult to manage the tolerance of the clearance when the turbine is stationary.

  Hereinafter, a shroud clearance measuring apparatus for a turbine rotor blade of the present invention made in view of this point will be described. FIG. 4 is a diagram showing an overall configuration of the gap measuring device. FIG. 4 is a diagram showing an upper half of a cross section along the turbine rotation shaft 10 in FIG. 1.

  The gap measuring device 40 emits light from the outside in the radial direction of the turbine rotor blade 14 toward the shroud 16, receives the reflected light and converts it into an electrical signal, and changes in the electrical signal over time. Based on this, a calculation device 48 that calculates the adjacent gap of the shroud, a reference signal generator 50 that emits light toward the turbine rotor 12, receives reflected light and converts it into an electrical signal, and the like are provided.

  The optical sensor 46 converts the light-emitting and light-receiving optical fibers 42 fixed outside in the radial direction of the turbine rotor blade 14 and the electrical signals according to the light-emitting elements, the light-receiving elements, and the light-receiving levels at the light-receiving elements. It consists of a preamplifier 44 and the like. Note that a light emitting diode (LED), a semiconductor laser, or the like can be used as the light emitting element, for example. The light reception and the conversion of the electrical signal according to the light reception level can be performed using, for example, a photodiode (Photo Diode).

  The arithmetic device 48 is connected to the optical sensor 46, receives the output (electric signal) from the optical sensor 46, and based on the temporal change of the electric signal and the circumferential dimension of the shroud. Calculating means for calculating the adjacent gap of the shroud 16. A monitor is provided so that the received electrical signal and other information necessary for gap measurement can be confirmed in real time.

  In addition, the reference signal generator 50 emits light toward a rotation reference such as a reflective tape, which is provided at a part of the turbine rotor 12 in the circumferential direction with a light reflectance different from that of the other part. Is received and converted into an electrical signal. Light emission, light reception, conversion to an electrical signal, and the like can be configured in the same manner as the optical sensor 46 described above.

  Such an optical reference signal generator is a suitable example for obtaining a reference signal, but the reference signal generator is not limited to the optical type, and is provided on the side of a rotating body such as the turbine rotor 12. What is necessary is just to measure the physical change by the rotation reference provided in the circumferential direction partly different from other parts and to convert it into an electric signal.

  In addition to the optical type, a method using an eddy current sensor can be adopted. In this case, a rotation reference having different magnetism may be used. For example, by providing a ferromagnetic protrusion on a part of the circumferential direction of the turbine rotor, the change in magnetism due to this protrusion is detected by an eddy current sensor provided opposite to the turbine rotor and converted into an electric signal, thereby rotating the reference. A signal can be obtained. Further, a nonmagnetic material portion may be provided on the outer surface of the turbine rotor instead of the protrusion, and the nonmagnetic material may be embedded with a ferromagnetic material as a rotation reference.

  Next, the operation and action of the gap measuring device 40 will be described with reference to FIGS. While rotating the turbine, the optical sensor 46 emits, for example, highly directional laser light from the radial outside of the turbine rotor blade 14 toward the shroud 16, and sequentially receives reflected light and converts it into an electrical signal. To do.

  When the shroud 16 passes through the laser light, in other words, when the shroud 16 is hit by the laser light, the reflected laser from the surface of the shroud 16 is received. On the other hand, when the laser light passes through the gap between the shrouds, there is no reflection of light from the surface of the shroud 16, so the amount of light received is smaller than when the reflected laser from the shroud 16 is received.

  FIG. 5 shows an example of an electrical signal obtained by sequentially receiving reflected light in this way and converting it according to the light reception level. The waveform 52 in the figure shows the converted electric signal. A portion with a high output voltage corresponds to the converted reflected light from the surface of the shroud 16, and a portion with a low output voltage, which is approximately 0 V, corresponds to the gap between the shrouds with a small amount of reflected light. This electric signal is input to the arithmetic device 48.

  The arithmetic device 48 stores the electrical signal output from the optical sensor 46 in a memory, and measures the gap between the shrouds as follows. The waveform can also be reproduced on the monitor after the measurement.

The time of the part of the signal waveform that received the reflected light from the shroud is Δt _h, and the time of the part that did not receive the light is Δt _l . And let the dimension of the circumferential direction of the shroud 16 which is a known value shown in FIG. FIG. 6 is a diagram schematically showing two shrouds viewed from the outside in the radial direction.

Further, as shown in FIG. 7 an enlarged broken line in FIG. 6, a shroud gap to be finally determined is substantially vertical gap g _i to contact end face of the opposing shroud 16. An angle between the circumferential direction of the rotation of the turbine and the contact end surface of the shroud 16 is θ, and a gap between the end surfaces of the shroud 16 along the circumferential direction is L _g .

また、図５に示すように、基準信号発生装置５０から出力されるタービンの１回転の基準を認識するための回転基準信号５４を用いることにより、演算されたシュラウド間隙ｇ_ｉが、タービンの周方向に複数存在するシュラウド隣接間隙のいずれに対応するものであるかを特定することができる。 Then, the ratio between Δt _h and Δt _l , that is, the time ratio between the portion that received the reflected light from the shroud and the portion that did not receive the light, is the ratio between L and L _g , that is, the circumferential dimension of the shroud 16 and the adjacent shroud. Since it corresponds to the ratio of the gap, g _i can be obtained by the equation (1).

Further, as shown in FIG. 5, by using a rotating reference signal 54 for recognizing a reference for one rotation of the turbine output from the reference signal generator 50, the calculated shroud gap g _i is circumference of the turbine It is possible to specify which one of the plurality of shroud adjacent gaps exists in the direction.

That is, the reference signal generation device 50 emits light toward the turbine rotor 12 provided with a rotation reference mark such as a reflective tape while rotating the turbine and having a light reflectance different from that of the other part in the circumferential direction. Then, the reflected light is received and converted into an electric signal. Therefore, in the converted electrical signal, one part during one revolution of the turbine and a part with a high output voltage corresponding to the reflected light from the reflection tape appear, and the one revolution cycle of the turbine and the reference of the revolution are recognized. can do. As a result, a portion of the reflective tape, if you know the positional relationship between the shroud, computed shroud gap g _i is whether it corresponds to any of the shroud adjacent the gap there are a plurality in the circumferential direction of the turbine Can be identified.

このように、タービンの１回転を認識するための回転基準信号５４を得て、さらにタービン動翼の枚数ｋを入力して計測を行うことにより、Δｔの間に信号波形に現れるΔｔ_ｈの回数と、入力されたｋとを比較して、測定系が安定していることを確認した上でシュラウド間隙の計測を開始することができる。つまり、Δｔ_ｈの回数とｋとが同じであれば測定系が安定しており、一方、異なっていれば、何らかの要因で測定系が安定してないことを認識できる。これによれば、シュラウド間隙の計測精度をより向上させることができる。 Also, the time between the rotation reference signal 54 as a Delta] t, the the number of turbine blades 14 and k, it is possible to determine the shroud gap g _i from the equation (2).

As described above, the rotation reference signal 54 for recognizing one rotation of the turbine is obtained, and the number k of turbine rotor blades is input and measurement is performed, so that the number of Δt _h appearing in the signal waveform during Δt. And the input k can be compared to confirm that the measurement system is stable, and then measurement of the shroud gap can be started. That is, if the number of Δt _h is the same as k, the measurement system is stable. On the other hand, if they are different, it can be recognized that the measurement system is not stable for some reason. According to this, the measurement accuracy of the shroud gap can be further improved.

  As described above, according to the shroud gap measuring device for turbine blades of this embodiment, the shroud gap between all blades of the turbine blade can be efficiently measured during turbine rotation. Then, it becomes possible to capture the change in the gap corresponding to the change in the turbine rotation speed, and the contact rotation speed of all blades can be managed. As a result, more reliable tolerance management of the gap between the shrouds is possible.

  In the present embodiment, an axial entry groove (Ax groove) structure is employed for the connection between the turbine rotor blade 14 and the turbine rotor 12, that is, the implantation of the turbine rotor blade 14 into the turbine rotor 12. For example, the present invention can be similarly applied to a fork groove structure or a rectangular groove structure.

  In the present embodiment, in order to obtain the rotation reference signal 54, a reflection tape of a rotation reference mark is attached to the turbine rotor 12 to emit light, receive light, etc., but the present invention is not limited to this. For example, a rotation reference mark may be provided on one of the shrouds that exist in the circumferential direction. According to this, since the optical sensor 46 can be used in common for both obtaining a signal for recognizing the rotation reference and obtaining a signal for gap measurement, the reference signal generator 50 is unnecessary, and the configuration can be further simplified.

It is a figure explaining the outline of the turbine used as the application object of the shroud clearance measuring apparatus of the turbine rotor blade of this invention. It is a perspective view of a turbine rotor blade and a shroud. It is a figure explaining an axial entry groove | channel (Ax groove | channel) structure. It is a figure which shows the whole structure of the shroud clearance measuring apparatus of the turbine rotor blade of this invention. It is a figure which shows the example of the electrical signal converted according to the light reception level with the optical sensor. It is a figure which shows typically two shrouds seen from the outer side of radial direction. It is the figure which expanded the broken-line part of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Turbine rotating shaft 12 Turbine rotor 14 Turbine blade 16 Shroud 20 Root part (root part)
22 Tip (tip)
24 fitting member 40 gap measuring device 42 optical fiber 44 preamplifier 46 optical sensor 48 arithmetic unit 50 reference signal generator

Claims (6)

The adjacent gaps of shrouds provided at the tip of each turbine rotor blade implanted along the circumferential direction of the turbine rotor and capable of contacting each other between the adjacent blades as the turbine rotates are measured during turbine rotation. A turbine blade shroud clearance measuring device,
An optical sensor that emits light toward the shroud from the outside in the radial direction of the turbine rotor blade, receives the reflected light and converts it into an electrical signal, a change with time of the electrical signal, and a circumferential dimension of the shroud, And a calculating means for calculating the adjacent gap of the shroud based on the above.   The calculation means calculates an adjacent gap of the shroud based on a time ratio between a portion where the reflected light from the shroud of the electrical signal is received and a portion where the reflected light is not received and a circumferential dimension of the shroud. The shroud clearance measuring apparatus for a turbine rotor blade according to claim 1.   A rotation reference provided at a part of the circumferential direction of at least one of the turbine rotor, the turbine rotor blade, and the shroud physically different from other parts, and a physical change due to the rotation reference is measured. A reference signal generating device for converting into an electric signal, and the calculating means recognizes a rotation reference of the turbine based on a change with time of the electric signal output from the reference signal generating device, and calculates an adjacent gap of the calculated shroud. The turbine blade shroud clearance measuring apparatus according to claim 2, wherein the part is specified.   The rotation reference is provided in a part of the circumferential direction of at least one of the turbine rotor, the turbine rotor blade, and the shroud with a light reflectance different from that of the other part, and the reference signal generator is The turbine rotor blade shroud gap measuring device according to claim 3, wherein the turbine blade emits light toward the rotation reference and receives the reflected light to convert it into an electrical signal.   The shroud clearance measuring apparatus for a turbine rotor blade according to any one of claims 1 to 4, wherein the turbine rotor blade is implanted in the turbine rotor by an axial entry groove structure. The adjacent gaps of shrouds provided at the tip of each turbine rotor blade implanted along the circumferential direction of the turbine rotor and capable of contacting each other between the adjacent blades as the turbine rotates are measured during turbine rotation. A turbine blade shroud clearance measurement method,
Light is emitted toward the shroud from outside in the radial direction of the turbine rotor blade, and the reflected light is received and converted into an electrical signal. Based on the change over time of the electrical signal and the circumferential dimension of the shroud, A method for measuring a shroud gap of a turbine rotor blade, comprising calculating an adjacent gap of a shroud.

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