JP2003177059A - Method and apparatus for measuring vibration - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an apparatus for highly accurately measuring a mode of vibration of a turbine rotor blade or the like in a noncontact fashion. <P>SOLUTION: A displacement sensor 20 is set at a stationary part which is nearly perpendicular or nearly parallel to a rotation face of a rotary body and is out of contact with the rotary body. The displacement sensor 20 is of a type that can measure even under a measurement environment filled with a lubricating oil mist, such as a capacitance type displacement sensor. The vibration of the rotary body is measured by receiving the sensor signal. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration measuring method and apparatus for measuring a vibration mode of a rotating body such as a turbine rotor blade with high accuracy in a non-contact manner.

[0002]

2. Description of the Related Art There are various types of rotating bodies to which the present invention is applied, but for simplicity, a steam turbine rotor blade will be described here as an example. In general, knowing the vibration characteristics of rotating steam turbine blades, especially the resonance characteristics, is an essential item for plant reliability diagnosis and performance improvement, and detailed vibration measurements are made before the plant is shipped. .

FIG. 9 schematically shows a test chamber for carrying out a rotary vibration test of a steam turbine rotor blade. The test chamber 1 is divided into upper and lower halves (not shown). Test room 1 above
Two pedestals 2 and 2 are arranged inside, and a bearing 3 is provided on each pedestal 2. At the time of the test, the turbine moving blade 4 is loaded into the test chamber 1 by using a transport crane (not shown), the shaft of the turbine moving blade 4 is supported by the bearing 3 on the pedestal 2, and the turbine moving blade 4 is rotated. A motor or an engine (not shown) is connected via 5 so that the turbine moving blade 4 can be rotated at a set rotational speed by the motor or the like. Then, in order to avoid the influence of aerodynamics on the rotational vibration characteristics, the test chamber 1 during the rotational vibration test
Has a structure in which a vacuum pump (not shown) realizes a substantially vacuum of about -0.2 to -0.3 atm. Also,
Since the inside of the test chamber 1 is substantially vacuumed, the seeping out of the lubricating oil occurs from the bearing 3 of the pedestal 2 that supports the turbine blade 4 for the test. Therefore, an oil reservoir (not shown) is prepared in the lower portion of the test blade in preparation for such leaked oil in the test chamber 1, and a shield 6 is further provided. In recent years, steam turbine blades are becoming longer with the aim of improving turbine output.Therefore, the test blade often scrapes the lubricating oil in the oil pool during the test. Therefore, the environment in which the scraped lubricating oil is filled with mist will be created in the test chamber.

By the way, in the steam turbine moving blades of recent years in which the blades are becoming longer as described above, as shown in FIG. 10, all the shrouds of the moving blades are connected to each other and the entire circumference is integrated. It is a group of infinite wings that make up the structure. The vibration characteristics of the rotor blades of this infinite blade group are that each rotor blade does not individually vibrate, but rotor blades around the entire circumference vibrate as if they were one disk. It has been known. FIG. 11 shows an example of the rotational vibration mode. FIG. 11 is a schematic drawing of how the vibration of each moving blade 7 around the entire circumference with reference to any one moving blade. The vibration displacement is in phase with the reference moving blade. If there is a + (plus) sign if there is an opposite phase, it is drawn with a- (minus) sign. Figure 1
In the case of No. 1, there are three petals in the rotational vibration mode, and three straight lines can be drawn by connecting the nodes of amplitude (points of 0 amplitude) in axisymmetric fashion with straight lines. Such a rotational vibration mode is called a three-node diameter. It should be noted that the number of node diameters is up to tenth order or more, though it varies depending on the test blade, which is an important index representing the pattern of rotational vibration.

Further, in the rotational vibration test of the steam turbine rotor blade, it is important to consider the vibration mode in the blade axis direction.
FIGS. 12 (a) and 12 (b) schematically show the vibration in the blade axial direction when the blade row group is viewed from the side, based on the FEM analysis results. FIG. 12 (a) shows the axial direction 1 The next mode (b) shows the axial secondary mode. For ease of explanation, the vibration amplitude is enlarged and emphasized in both figures. Since it is difficult to identify such vibration modes in the axial direction only by the displacement of the blade tip, the FEM analysis as described above is often used together.

That is, in the rotary vibration test of the steam-turn rotor blade, the vibration frequency and vibration amplitude for each rotation speed are measured using the rotation speed as a test parameter, and the rotation vibration mode generated in the blade row and the blade axial direction at that time are also measured. Analyze the mode of. It should be noted that as shown in FIG. 13, the resonance frequency is plotted in a graph for each node diameter number, where the horizontal axis is the rotor rotation frequency and the vertical axis is the blade frequency, and is called a Campbell diagram. A straight line that sequentially represents the doubled frequency is called a harmonics line (1H, 2H, 3H ... in FIG. 13).

In FIG. 13, the final purpose of the rotational vibration test is to clarify the resonance amplitude and frequency at the intersection of the nodal diameter line and the harmonics line having the same coefficient, and to investigate and confirm that there is no hindrance during operation of the actual machine. is there.

By the way, conventionally, as shown in FIG. 14, a strain gauge 8 is attached to the moving blade 4, and the vibration is measured through the telemeter transmitting section 9 and the telemeter receiving section 10. However, in the method using the strain gauge 8 as described above, not only it takes a great deal of time to directly attach it to the turbine rotor blade, but also a slip ring or a telemeter is used to extract the strain gauge signal in the rotating field to the stationary field. Therefore, there is a problem that it is difficult to cure the wiring and secure the power supply for this purpose.

[0009]

As one of the techniques for overcoming the above-mentioned drawbacks of the vibration measuring method using the strain gauge, the tip of the reflection type moving blade made of an optical fiber is detected on the casing around the moving blade by using the laser beam. A non-contact method in which a device is attached in the circumferential direction (for example, Endo / Matsuda / Matsuki, non-contact measurement method of blade vibration, GTSJ 22-86 (1994)) has been proposed. This method generates a pulse signal when each blade passes through this detector, and utilizes the fact that the time of generation of this pulse signal causes a time difference between when the blade does not vibrate and when it vibrates. The vibration characteristics of the blade are measured based on the vibration waveform in the circumferential direction.

However, this non-contact measurement method using a laser beam is effective for a single blade structure in which each blade is separated, such as a compressor blade, but a steam turbine that often uses a large blade is used. In rotor blades, not only are the lashing wires connected to the middle portion of the blade, but also shroud blades that connect the blade tips of all blades are often used, so the entire blade row has a configuration like a disk. There was a problem that the vibration of the wings could not be sensed well.

A vibration measurement system using a laser displacement sensor (Japanese Patent Laid-Open No. 7-27601) has also been proposed.
As mentioned above, the rotational vibration test is carried out in a special vacuum chamber, so that the lubricating oil mist of rotating equipment is filled in the test chamber, and the sensing part of the optical fiber sensor becomes soiled, making measurement difficult in practice. was there. As a measure against pollution, it is expected to use a sensor with a large laser output, but a small high output sensor that meets these high requirements has not been developed at present, and a sensor that has a laser light source outside Not only is a high-power laser light source expensive, but the laser body must be installed in the atmosphere when performing a rotational vibration test in a special vacuum chamber, such as a steam turbine blade test. Since it is necessary (there is no operation record of the laser body under vacuum), there is a drawback that it is necessary to prepare an optical fiber that is as long as several tens of meters outside the vacuum chamber, and the measurement system itself becomes very expensive. It was difficult to do.

The present invention has been made based on such a situation, and even with a structure in which the blade tips are connected like a steam turbine rotor blade, the vibration characteristics of the blade can be measured with high accuracy. In addition, it is possible to obtain a device that can measure vibration characteristics of a rotating body such as a rotating turbine blade with high accuracy and at low cost even under a measurement environment in which the lubricating oil mist in the vacuum chamber is filled. To aim.

[0013]

The invention according to claim 1 is
In the vibration measuring method, a static capacitance type displacement sensor is provided on a stationary portion that is substantially perpendicular or parallel to the rotation surface of the rotating body and does not contact the rotating body, and the rotating body receives the sensor signal from the displacement sensor. It is characterized by measuring the vibration of.

According to a second aspect of the present invention, in a vibration measuring device, a static portion such as a capacitance type displacement sensor is lubricated on a stationary portion which is substantially perpendicular or substantially parallel to the rotating surface of the rotating body and which does not contact the rotating body. The present invention is characterized in that a displacement sensor of a type that can measure even under a measurement environment in which oil mist is filled is provided, and the vibration of the rotating body is measured by receiving a sensor signal from the displacement sensor.

The invention according to claim 3 is characterized in that, in the invention according to claim 2, a plurality of displacement sensors are arranged at different circumferential positions of the rotating body.

The invention according to claim 4 is characterized in that, in the invention according to claim 2, a plurality of displacement sensors are arranged at different radial positions on the substantially same radial line of the rotating body.

According to a fifth aspect of the invention, in the invention according to the second aspect, the plurality of displacement sensors are arranged at different circumferential positions of the rotating body and also at different radial positions on the substantially same radial line. Characterize.

Further, the invention according to claim 6 is the invention according to claim 3.
The invention according to any one of claims 1 to 5 is characterized in that the vibration mode of the rotating body is identified by using sensor signals obtained from a plurality of displacement sensors.

In the invention according to claim 7, in the invention according to claim 6, the inclination of the vibration waveform is obtained from the sensor signals obtained from the plurality of displacement sensors, and the vibration mode is identified using the value of this inclination. It is characterized by having done.

The invention according to claim 8 is the invention according to any one of claims 2 to 7, wherein a displacement sensor for sensing the axial extension of the rotating body is provided, and the sensor signal is used to provide the rotating body. It is characterized in that the vibration displacement sensor signal is processed so as to cancel the axial extension of the.

The invention according to claim 9 is the invention according to any one of claims 2 to 7, further comprising a mechanism for moving the displacement sensor so as to cancel the axial extension of the rotating body. Is characterized by.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a non-contact vibration measuring device according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a view showing a first embodiment of the present invention, in which a shield 6 erected between left and right pedestals 2 and 2 is provided.
A shield wall 6a extending in the left-right direction is formed so as to cover the outer periphery of the test turbine blade 4 supported on the pedestal 2 and not to contact the tip of the blade, and the inner surface of the shield wall 6a is formed. Further, a capacitance type displacement sensor 20 is attached so as to face the outer peripheral surface of the turbine rotor blade 4. That is, the capacitance type displacement sensor 20 is attached to the shield wall 6a which is perpendicular to the rotating surface of the test turbine blade 4. In addition, the above-mentioned mount 2
A rotational position sensor 21 is provided above the turbine rotor blade 4 at a position facing the shaft.

However, by using the capacitance type displacement sensor 20 as described above, in the blade vibration measurement of a single blade or a group blade connected by a lashing wire as in the optical fiber sensor, the phase due to blade twist during vibration The delay can be measured with high accuracy. In addition, since the sensor type is a capacitance type, even in a measurement environment where the lubricating oil mist in the vacuum chamber is full, it is possible to significantly reduce the measurement error compared to optical measurement using a laser. You can

FIG. 2 schematically shows a second embodiment of the present invention in which a capacitance type displacement sensor is attached near the tip of the blade on a plane parallel to the test blade. A sensor support leg 22 is provided so as to project from the gantry 4, and an electrostatic capacitance type displacement sensor 23 is attached to the upper end portion of the sensor support leg 22 so as to face the blade tip vicinity. That is, the capacitance type displacement sensor 23 is attached to a stationary portion parallel to the rotating surface of the test turbine rotor blade 4 so as to face the blade tip vicinity portion.

Thus, the blade tip portion of the turbine rotor blade 4 can be measured in the axial direction by the capacitance type displacement sensor 23. As described above, since the measurement is performed from the axial direction of the turbine rotor blade 4, it is possible to directly measure the vibration of the blade with high accuracy even in the case of a shroud blade in which the entire blade tip is connected like a steam turbine rotor blade. Also in this case, since the sensor type is a capacitance type, even in a measurement environment where the lubricating oil mist in the vacuum chamber is full,
Compared with optical measurement using a laser, the measurement error can be greatly reduced.

The blade row group under test contains various disk-shaped rotational vibration modes and axial vibration modes, but not only the vibration amplitude can be known from the output of the displacement sensor, but also the output signal, for example, Imported into personal computer FF
By performing T analysis, it is possible to recognize a plurality of frequency peaks corresponding to those modes as shown in an example in FIG. In this way, the same measurement is repeated while changing the rotation speed, and the frequency peak is obtained for each rotor rotation speed. Next, a harmonics line that sequentially represents the frequency of an integer multiple of the rotor speed is entered, and a straight line connecting the frequency peak groups for each node diameter number is obtained. A stationary system similar to the Campbell diagram shown in FIG. 13 is obtained. The frequency characteristic diagram seen from is completed. When the blade frequency is fr (Hz), the blade row count is N (Hz), and the node diameter order is m, the blade row frequency f measured by the stationary system obtained as the output of the displacement sensor.
Since there is a relation of fs = fr ± mN between s (Hz) and the frequency of the blade viewed from the rotary system which is the final measurement target,
In order to obtain the blade vibration characteristics (Campbell diagram) of the rotating system, it is necessary to obtain the node diameter order by some method. For such a purpose, it is effective to use a plurality of displacement sensors as shown in the third embodiment. FIG. 4 shows a case in which a plurality of capacitance type displacement sensors 24a, 24b and 24c are attached at different circumferential positions parallel to the test blade for such a purpose. The sensors are installed appropriately adjacent to each other according to the rotational vibration mode (node diameter order) to be measured. In this way, a plurality of sensors 24a, 24
By arranging b and 24c, even if the vibration generated at the time of resonance is not fixed to the blade, the propagation velocity of the vibration can be known among a plurality of sensors by, for example, obtaining a cross-correlation coefficient. In addition, the rotational vibration mode at resonance can be identified from the relationship between the phase angle of the vibration waveform obtained from a plurality of sensor signals placed adjacent to each other and the measurement position (AIAA-87-1758). Alternatively, the inclination of the vibration waveform obtained from the sensor signal may be used.

This is because if the vibration amplitude at the radial position where the sensor is installed is known, the inclination of the vibration waveform is uniquely determined according to the rotational vibration mode generated on the circumference. More specifically, for example, three adjacent displacement sensors S1,
S2 and S3 are prepared, a trigger is applied at the time when the sensor S2 senses zero displacement, and the inclination of the vibration waveform is obtained using the sensors S1 and S3 (FIGS. 5A and 5B). The vibration amplitude may be the value sensed by any sensor.
If the amplitude is known, the slope of the vibration waveform at the time of triggering changes depending on the number of petals in the rotary vibration mode. Therefore, if the value of this slope is obtained, the rotary vibration mode can be specified. As described above, in the present embodiment, not only the vibration amplitude and the vibration cycle but also the propagation velocity of vibration and the rotational vibration mode can be obtained. As described in the second embodiment, the Campbell diagram is obtained and the resonance amplitude is calculated. The frequency can be clarified, and it is possible to investigate and confirm that there is no hindrance during actual operation.

When the vibration generated on the wing is fixed in the space as viewed from the stationary system, the maximum amplitude cannot be known depending on the installation position of the sensor, and when it happens to be installed at the node of vibration. In some cases, the vibration period itself cannot be measured. If it is possible to measure such an event, it is necessary to prepare as many displacement sensors as the number corresponding to the rotational vibration mode to be measured. Occurrence is extremely rare in practice, and the vibration measurement described here can be performed by using only a few displacement sensors in normal measurement.

Next, a fourth embodiment of the present invention will be described. FIG. 6 shows a plurality of capacitance type displacement sensors 24.
The case where a, 24b, and 24c are installed at different radial positions on the same radial line parallel to the test blade is shown. By installing a plurality of displacement sensors 24a, 24b, 24c at different radial positions on the same radial line in this way, the blade axis direction vibration waveform is obtained from the displacement information obtained by each sensor at the same time. The directional vibration mode can be identified. In addition, if a database concerning vibration amplitude in the blade axis direction is constructed in advance by FEM analysis, etc., it is possible to identify the vibration mode in the blade axis direction simply by installing multiple sensors adjacent to each other and obtaining the inclination of the vibration waveform. Is also possible. As described above, in the present embodiment, not only the vibration amplitude and the vibration cycle but also the vibration mode in the blade axis direction can be obtained. Therefore, the Campbell diagram is obtained, the resonance amplitude and the frequency are clarified, and there is no problem in operating the actual machine. It is possible to investigate and confirm. Further, as described in the present embodiment, if a plurality of sensors can be installed adjacent to each other, there is an advantage that the number of jigs for fixing the sensors can be reduced and the preparation work for the experiment can be reduced.

FIG. 7 is a diagram showing a fifth embodiment of the present invention, in which a plurality of capacitance type displacement sensors 24a, 24 are arranged at different circumferential positions in parallel with the turbine moving blade 4 for testing.
b and 24c are attached, and capacitance type displacement sensors 24b, 24d and 2 are also installed at different radial positions on the same radial line.
4e is attached. As described above, since the displacement sensors are installed at a plurality of different circumferential positions, the propagation velocity of the vibration waveform can be known and a plurality of adjacently placed sensors can be detected as described in the third embodiment of the present invention. It is possible to identify the rotational vibration mode at resonance from the sensor signal of. Further, since the displacement sensors are installed at a plurality of different radial positions, the vibration mode in the blade axis direction can be identified as described in the fourth embodiment.

As described above, in the present embodiment, not only the vibration amplitude and the vibration period but also the vibration propagation velocity and the rotational vibration mode as well as the vibration mode in the axial direction can be obtained. Therefore, a highly accurate Campbell diagram can be obtained. It is possible to draw and it is possible to obtain the resonance amplitude and frequency with high accuracy.

FIG. 8 is a diagram showing a sixth embodiment of the present invention. A traverse mechanism for moving the displacement sensor 23 described in the first to fifth embodiments of the present invention in the axial direction of the test blade. 3 shows a non-contact vibrating device equipped with. In this device, another displacement sensor 25 is provided near the base of the test blade to measure the axial travel distance (thermal elongation) of the test blade during the test and to measure the blade vibration by this thermal elongation. A traverse mechanism 26 for moving the displacement sensor 23 so as to cancel the movement of the test blade is provided. That is, the displacement sensor 23 for blade vibration measurement is attached to the tip of the traverse mechanism 26 which can be moved and adjusted in the axial direction of the steam turbine blade by the servo motor 27.

As described above, the rotary vibration test of the steam turbine rotor blade is performed substantially in the vacuum chamber, but frictional heat is generated due to the presence of residual air, and some thermal elongation of the test blade rotor shaft occurs. However, since this device is equipped with the traverse mechanism 26 that moves the base on which the displacement sensor for blade vibration measurement is placed so as to cancel the thermal expansion of the rotor shaft, the displacement sensor for blade vibration displacement and the measurement target are always provided. Since it is possible to keep the relative distance of the constant, it is possible to accurately measure the rotational vibration.

Although the traverse mechanism is provided in the above embodiment, a displacement sensor for detecting the axial extension of the rotating body is provided, and the sensor signal is used to detect the axial direction of the rotating body. The vibration displacement sensor signal may be processed so as to cancel the elongation of the vibration.

Although the displacement sensor used for the sake of simplicity has been described as a capacitance type displacement sensor, the lubricating oil mist may be full without departing from the scope of the present invention. It goes without saying that another type of displacement sensor that can measure even in a measurement environment may be used in combination, and the object of measurement is not limited to the rotational vibration measurement of the steam turbine blade.

[0037]

EFFECTS OF THE INVENTION Since the present invention is constructed as described above, even if it is a rotating body having a structure in which the blade tips are joined like a steam turbine moving blade, the lubricating oil mist in the vacuum chamber is filled. Even under various measurement environments, it is possible to easily and accurately measure the vibration characteristics of the rotating body.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a first embodiment of a vibration measuring device of the present invention.

FIG. 2 is an explanatory diagram showing a second embodiment of the present invention.

FIG. 3 is an explanatory diagram for explaining frequency characteristics of vibration amplitude detected by a displacement sensor according to the second embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a third embodiment of the invention.

5A and 5B are explanatory diagrams shown for explaining a change in vibration amplitude per rotation detected by a displacement sensor according to a third embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a fourth embodiment of the present invention.

FIG. 7 is an explanatory diagram showing a fifth embodiment of the invention.

FIG. 8 is an explanatory diagram showing a sixth embodiment of the invention.

FIG. 9 is a schematic diagram of a steam turbine rotational vibration test apparatus as an example of a non-contact vibration measurement method.

FIG. 10 is a partially enlarged view of a steam turbine rotor blade.

FIG. 11 is an explanatory diagram shown for explaining a vibration mode in which all of the steam turbine blades are in a disk shape and are vibrating.

FIG. 12 is an explanatory diagram showing vibration modes in the axial direction.

FIG. 13 is a Campbell diagram showing a change curve of the node diameter order frequency with respect to the rotation speed.

FIG. 14 is a diagram showing an example of a conventional vibration measuring device.

[Explanation of symbols]

1 test room 2 mounts 3 bearings 4 turbine blades 5 rotation axes 6 shield 7 Moving blade 8 strain gauge 9 Telemeter transmitter 10 Telemeter receiver 20, 23 Displacement sensor 21 Rotational position sensor 22 Sensor support leg 24a, 24b, 24c Displacement sensor 25 Position displacement sensor 26 Traverse mechanism

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Kenichi Okuno, Inventor             2-4 Suehiro-cho, Tsurumi-ku, Yokohama-shi, Kanagawa               Toshiba Keihin Office F-term (reference) 2G064 AB03 BA02 BD05 CC13

Claims (9)

[Claims] 1. A capacitance type displacement sensor is provided at a stationary portion which is substantially perpendicular or substantially parallel to the rotation surface of the rotating body and which does not contact the rotating body, and receives a sensor signal from the displacement sensor to detect the rotating body. A non-contact vibration measuring method characterized by measuring vibration. 2. A measurement environment in which a lubricating oil mist, such as a capacitance type displacement sensor, is filled in a stationary portion that is substantially perpendicular or substantially parallel to the rotating surface of the rotating body and does not contact the rotating body. A non-contact vibration measuring device, characterized in that a displacement sensor of a type that can be measured even below is provided, and the vibration of the rotating body is measured by receiving a sensor signal from the displacement sensor. 3. The non-contact vibration measuring device according to claim 2, wherein a plurality of displacement sensors are arranged at different circumferential positions of the rotating body. 4. A plurality of displacement sensors are arranged at different radial positions on the substantially same radial line of the rotating body,
The non-contact vibration measuring device according to claim 2. 5. The non-contact vibration measuring device according to claim 2, wherein the plurality of displacement sensors are arranged at different circumferential positions of the rotating body and also at different radial positions on the substantially same radial line. . 6. The non-contact vibration measuring device according to claim 3, wherein the vibration mode of the rotating body is identified by using sensor signals obtained from a plurality of displacement sensors. 7. The method according to claim 6, wherein the inclination of the vibration waveform is obtained from sensor signals obtained from a plurality of displacement sensors, and the vibration mode is identified using the value of the inclination. Contact vibration measuring device. 8. A displacement sensor for detecting the axial extension of the rotating body is provided, and the vibration displacement sensor signal is processed so as to cancel the axial extension of the rotating body by using the sensor signal. Characterized by
The non-contact vibration measuring device according to any one of claims 2 to 7. 9. The non-contact vibration measuring device according to claim 2, further comprising a mechanism for moving the displacement sensor so as to cancel the axial extension of the rotating body. .