JPH0727601A - Method and apparatus for measuring vibration in non-contact - Google Patents

Abstract

PURPOSE:To measure the vibration of a rotary body such as a steam turbine rotor highly accurately in a non-contact state. CONSTITUTION:A laser light emitting body is provided at a stationary part not in contact with an object part to be measured. The laser light from the laser light emitting body is cast on the object part to be measured. The reflected light from the object part to be measured is received and the vibration of the object part is measured. For example, the laser light is emitted from a sensor head 22 in turbine wheel chamber 6 toward a shroud 5 at the tip of a turbine bucket 4. The vibration of the bucket 4 is measured based on the displacement of the incident position of the reflected light. For a bucket 3, which does not have the shroud 5, the laser light is emitted to the tip of the bucket, and the vibration of the bucket 3 is measured based on the Doppler displacement of the reflected signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for non-contact measurement of rotational vibrations of various rotary machines such as steam turbine rotors, rotor blades of axial flow type compressors, impeller blades of superchargers. Regarding the device.

[0002]

2. Description of the Related Art A conventional method of measuring rotational vibration of a steam turbine rotor will be described with reference to FIG. FIG. 17 shows the final stage portion of the steam turbine rotor, which is the L-0 rotor blade 3 of the final stage and the first stage counted from the final stage, which are provided on the peripheral edge of the disk 2 formed integrally with the rotary shaft 1. The stage L-1 rotor blade 4 is shown. A shroud 5 is provided at the tip of the L-1 rotor blade 4. The rotary shaft 1, the disk 2, the L-0 moving blades 3, the L-1 moving blades 4 and a number of stages of moving blades (not shown) are collectively referred to as a rotor. This rotor is housed in the passenger compartment 6.

A strain gauge 11 is attached to the root of each L-1 rotor blade 4 to be measured, and a telemeter transmitter 12 is fixed to the rotor portion near the passenger compartment 6. Strain gauge 11 and telemeter transmitter 1
2 is connected by a lead wire 13, but the lead wire 13 is firmly fixed with an adhesive or the like so that the rotor surface crawls from the blade surface and is not scattered by centrifugal force during rotation. . On the other hand, a receiving antenna 14 is provided inside the stationary cabin 6, and the receiving antenna 14 is connected to a receiver 16 via a high frequency cable 15.

Now, the vibration of the moving blade is measured in the following manner by the above-mentioned structure. That is, the strain gauge 11 attached to the L-1 rotor blade 4 is
Rotation of the rotor causes dynamic strain, and electric resistance changes in proportion to the dynamic strain. This change is received by the telemeter transmission device 12, FM-modulated, and radiated as a radio wave. By capturing this radio wave with the receiving antenna 14 and demodulating it with the receiver 16, an analog signal proportional to the vibration of the L-1 rotor blade 4 is obtained, and a desired vibration analysis is performed by an FFT analyzer (not shown) or the like, and rotation is performed. Measure the vibration characteristics of the inner rotor blade.

[0005]

As described above, conventionally, the vibration of the moving blade is measured by the telemeter method, but this method has the following problems. That is, the frequencies that can be used under the Radio Law are 88 MHz to 108
Since the frequency is MHz, the frequency to be distributed to the telemeter transmission device 12 for each strain gauge 11 can be set to at most 6 channels within this range, and therefore only 6 points can be measured at the same time. It was Therefore, it is possible to measure only the vibration characteristics of six moving blades in one measurement, and to grasp the overall vibration characteristics of rotating moving blades with 100 to 120 implanted in one stage. I couldn't.

Further, a great deal of labor is required for attaching the strain gauge to the moving blade and for attaching the lead wire connecting the strain gauge and the telemeter transmitting device, and the vibration characteristics of all moving blades are required. It was extremely difficult to measure.

The present invention has been made in order to solve the problems of the prior art as described above, and it is possible to highly accurately measure the vibration of a rotating body such as a moving blade without contacting the telemeter system. It is an object to provide a method and a device.

[0008]

In order to solve the above-mentioned problems, according to the present invention, a laser light emitter is placed on a stationary part which does not contact the measurement object part, and the laser beam from this laser light emitter is applied to the measurement object part. Irradiation is performed, and the reflected light from the measurement target portion is received to measure the vibration of the measurement target portion.

[0009]

[Operation] According to the above means, it is possible to measure the vibration characteristics of the target portion in a non-contact state with the measurement target portion, and to replace the sensors with the vibration characteristics of a large number of measurement target portions. Can be measured without. Further, by using the laser light, it is possible to measure a minute vibration as displacement of the target portion or interference of the laser light.

[0010]

Embodiments of the non-contact vibration measuring method and apparatus according to the present invention will be described below in detail with reference to FIGS. Note that in these figures, FIG.
The same parts as 7 are designated by the same reference numerals and the description thereof will be omitted.

First, a first embodiment will be described with reference to FIGS. 1 to 9.

FIG. 1 shows a final stage portion of a steam turbine rotor similar to that shown in FIG. 17, and in the case where a rotary vibration test is performed, the rotor portion is installed in a special vacuum casing and is rotated. Then, the vibration state of the rotor blade with respect to the rotation change is tested. Here, in order to measure the vibration of the L-1 rotor blade 4, laser light is emitted from the axial direction of the rotating shaft 1 toward the side surface of the shroud 5 provided at the tip of the rotor blade 4, so that A sensor head 22 is fixed to a mounting base 21 mounted inside the chamber 6. This sensor head 22 is
It is firmly fixed so as not to vibrate due to the rotation of the rotor. Even in the vacuum chamber, the rotor heats up due to the rotational friction with the residual air and expands by several mm in the axial direction. Therefore, the sensor head 22 should be separated by about 10 mm to avoid contact with the rotor due to this thermal expansion. Must be installed. Further, a light reflecting tape 23 is attached to a part of the rotary shaft 1, and a photodetector 24 is provided at a position facing the light reflecting tape 23 so that the number of rotations of the rotary shaft 1 can be detected. Other known means can be appropriately used for detecting the rotation speed.

FIG. 2 is an enlarged view of a part of the L-1 rotor blade 4. The shrouds 5 are integrally attached to the tips of the respective blades, and when the blades 4 are implanted on the entire circumference of the disk 2, only a small gap is formed between the shrouds 5,
When the rotor rotates, the rotor blades 4 are twisted back by the centrifugal force, so that the adjacent shrouds 5 come into contact with each other, and the shroud 5 forms one ring during the rotation of the rotor. Toward the side surface of such a shroud 5, as shown in FIG.
Laser light is emitted from the sensor head 22 shown in FIG.

Next, regarding the details of the sensor head 22,
This will be described with reference to FIG. The sensor head 22 constitutes a laser displacement meter, and a semiconductor laser element 32 excited by a semiconductor laser driving unit 31 is provided inside the sensor head 22, and the laser light emitted from the sensor head 22 is projected by a light projecting lens 33. Are focused by the laser beam and are irradiated onto the side surface of the shroud 5. Further, a light receiving lens 34 and a light receiving element 35 are also provided inside the sensor head 22, and the laser light reflected by the side surface of the shroud 5 is focused and received, and the light receiving element 35 outputs an electric signal corresponding to the light receiving position. Send a signal. Electric signals from the light receiving element 35, electric power supplied to the semiconductor laser driving unit 31, and the like are transmitted and received through the cable 36.

Since most of the inside of the sensor head 22 is composed of semiconductor circuit elements, it is necessary to take measures against heat. Therefore, the sensor head 22 is completely inserted into the water-cooled container 37 and the internal temperature during the test. Is 40
It is continuously cooled so that it does not exceed ℃. The water cooling container 37 is provided with a cooling water inlet 38 below and a cooling water outlet 39 above, and a waterproof packing 40 is packed in a penetrating portion of the cable 36.

Now, regarding the method of measuring the vibration of the L-1 rotor blade 4 using such a sensor head 22, a system diagram of one embodiment of the non-contact vibration measuring device by the laser displacement meter shown in FIG. Will be described with reference to. When the rotor blade 4 vibrates while the rotor is rotating, the vibration is transmitted to the shroud 5, and when the shroud 5 meanders due to the vibration, the shroud 5 is displaced in the rotation axis direction. Therefore, in FIG. 3, assuming that the shroud 5 is in the B position in the absence of vibration, the shroud 5 is displaced between the A position and the C position in the vibrating state. Therefore, depending on the position of the shroud 5, the distance and the angle of the laser light reflected on the side surface of the shroud 5 to reach the light receiving element 35 are slightly changed, and the electric signal output from the light receiving element 35 is also displaced accordingly. become.

The electrical displacement signal from the light receiving element 35 is supplied to the processing device 41 through the cable 36, where it is subjected to data processing and converted into an analog electrical signal corresponding to the vibration of the shroud 5. This signal is supplied to a display device 42 such as a cathode ray tube oscilloscope and displayed as a vibration waveform. On the other hand, the rotation signal of the rotary shaft 1 detected by the photodetector 24 is amplified and waveform-shaped by the amplifier 43 to generate one pulse signal per one rotation. This pulse signal is supplied to the digital tachometer 44,
The number of rotations of the rotary shaft 1 is counted and displayed, and is also supplied to the display device 42 and displayed as a signal indicating a rotation cycle together with a vibration waveform. Although not shown in FIG. 4, an FFT analyzer, a data recorder, a data plotting device, etc. may be provided to analyze and record the change of the vibration data from moment to moment.

The vibration waveform displayed on the display device 42 is as shown in FIGS. 5 and 6. That is, when the shroud 5 is not vibrating, its end face is at the position B in FIG. 3 and is not displaced, so that the vibration waveform displayed on the display device 42 is a DC waveform with an amplitude B as shown in FIG. 45, which is displayed together with the pulse 46 indicating the rotation cycle. This amplitude B is determined by the shroud 5 and the sensor head 22.
It is a DC voltage component corresponding to the set distance between and. On the other hand,
The shroud 5 vibrates, and its end face is at position A and C in FIG.
When the displacement is between the position and the position, a vibration waveform 47 that is displaced between A and C with reference to the level B is displayed as shown in FIG. In this example, the vibration waveform 47 for exactly four cycles is displayed during one rotation cycle T of the rotary shaft 1, which means that the rotor blade 4 resonates at a frequency of four times the rotation speed. It is shown that.

By the way, when all the shrouds 5 of the L-1 moving blade 4 are connected to each other as shown in FIG. 2 and the entire circumference is integrated, this is called an infinite blade group. There is. The vibration characteristics of the rotor blades that make up this infinite blade group do not cause the rotor blades to individually vibrate individually, but the rotor blades around the entire circumference are related, as if they were one disk. It is known to vibrate.

FIG. 7 is an explanatory view shown for explaining a vibration mode in which all of the L-1 moving blades 4 are in a disk shape and are vibrating. This vibration mode is drawn by performing a static vibration test by hammering while the rotor is stationary, and actually measuring the vibration of each rotor blade around the entire circumference with reference to one rotor blade. If the vibration displacement is in phase with the reference moving blade, a + (plus) sign is attached, and if it is in antiphase, a minus sign is attached. In the example of FIG. 7, there are four petals in the vibration mode, and the nodes of the amplitude are symmetrical with respect to the axis (the point where the amplitude is 0).
You can draw four straight lines when you connect them with a straight line. Such a vibration mode is called 4ND (Nodal Dia ... Nodal diameter). In addition, the number of NDs will increase in sequence to 2
The 0th place is the observation target.

Now, when the horizontal axis is the ND frequency and the vertical axis is the resonance frequency, the relationship between the ND frequency and the resonance frequency is plotted in a graph as shown in FIG. This is measured while the rotor is stationary, and centrifugal force is applied during rotation of the rotor, so that each ND frequency tends to increase. A graph showing this relationship is called a Campbell diagram, which is a change curve of each ND frequency with respect to the rotation speed. As shown in FIG. 9, the horizontal axis is the rotation speed of the rotor, and the vertical axis is the blade frequency. ,
It is a plot for each ND number. In addition, FIG.
The straight lines indicated by 1H, 2H, 3H ... are called harmonics lines and represent the frequencies of integer multiples of the rotation speed in sequence. The intersections of the 4ND line and the 4H line in the figure are the 5ND line and the 5H line. The circles drawn at the intersections of both lines having the same coefficient, such as the intersections of, indicate that the resonance becomes particularly large at these intersections. The size of the circle represents the size of the resonance amplitude. The main purpose of the rotational vibration test is to actually measure the change curve of the ND frequency shown in FIG. 9, the magnitude of the resonance amplitude at the intersection of the ND line and the harmonics line, and the frequency thereof. .

As described above, in this embodiment, the sensor head is installed at one point on the stationary side toward the rotating blade, so that the amplitude and frequency in the vibration mode shown in FIG. Etc. can be measured.

Next, a second embodiment of the present invention will be described. In this embodiment, when the vibration mode shown in FIG. 7 has, for example, a vibration characteristic of fixing to the space instead of fixing to the rotor, the shroud 5 and the sensor head 2 are limited to this resonance.
This is for compensating for the fluctuation between 2 and 2 since it becomes a constant value and the fluctuation cannot be detected.

That is, as schematically shown in FIG. 10, a plurality of sensor heads 22 described in the first embodiment are arranged on the circumference toward the shroud 5 of the moving blade 4. A system diagram of the measuring device in this case is shown in FIG. That is, the plurality of sensor heads 22a, 22b, 2
2c ... The number of processing devices 41a, 41b, 41c
The output of each of the processing devices 41a, 41b, 41c ... Is supplied to the multiplexer 51, and the numerical data simultaneously sampled by the multiplexer 51 is input to the data processing device 52. For example, assuming that 16 sensor heads are arranged on the circumference, an amplitude signal as indicated by a black circle in FIG. 12 is input to the data processing device 52 from each sensor head. Therefore, in the data processing device 52, the cycle of the sine wave,
Amplitude and phase interpolation processing is executed, the waveform with the least calculation error is estimated, the dotted line waveform is displayed, and the amplitude, frequency, and phase at that time are also output.

In the case of this embodiment, the number of sensor heads arranged on the circumference needs to be twice or more the maximum ND number to be measured from the sampling theorem. By doing so, it becomes possible to measure even in the case of spatially fixing the vibration mode, which is a phenomenon that rarely occurs in a special case. If the vibration mode is fixed to the normal rotor,
It goes without saying that the same measurement method as in the first embodiment can be obtained by using one combination of the sensor head and the processing device.

Next, a third embodiment of the present invention will be described with reference to FIGS. 13 to 16. This example
This is suitable for measuring the vibration of the L-0 moving blade 3 by utilizing the Doppler displacement of the laser.

FIG. 13 shows that the tip of the L-0 rotor blade 3 of the turbine can be irradiated with laser light from the direction of the rotation axis.
FIG. 6 is a partially enlarged view showing a state in which a laser head 61 is provided, and the laser head 61 is firmly supported inside a vehicle interior 6 by a support base 63 together with a laser guide 62.

FIG. 14 is a view as seen from the tip side of the L-0 moving blade 3 shown in FIG. 13. The moving blade 3 does not have the shroud 5 like the moving blade 4, and the upper side of the moving blade 3 is Five moving blades 3 are welded and connected to each other via a stub 64 on the lower side so as to form one set.

A system diagram of the measuring device in this embodiment is shown in FIG. That is, laser light is emitted from the laser head 61 to the tip of the rotor blade 3, and the reflected light is received by the laser head 61 and introduced into the laser Doppler vibrometer 65 via the laser guide 62. In this case, since the L-0 moving blade 3 has no shroud and the laser irradiation surface is greatly cut for each blade, the laser Doppler vibrometer 65 is used.
A pulse train 66 as shown in FIG. 16 is output from the data processing device provided therein. This pulse train 66
The upper tip of the arrow indicates the vibration displacement of each blade. Therefore, the envelope 67 connecting the upper ends of the pulse trains 66 is
The vibration waveform of the entire L-0 moving blade 3 is calculated and processed by the envelope processor 68 to obtain the amplitude, the frequency, and the phase with respect to the rotation pulse. The method of measuring the rotation speed of the rotary shaft 1 is the same as in the first and second embodiments.

The laser Doppler vibrometer 65 applies the principle of Doppler interference of the laser wavelength to measure the vibration velocity at high speed with high sensitivity. When this is converted into a displacement amplitude, it has a vibration sensitivity and a frequency response of 1 nm to 5 mm and 1 Hz to 1 MHz. Therefore, even when the tip of the L-0 rotor blade 3 is rotating at a peripheral speed of 600 m / s, the vibration amplitude can be detected with an accuracy of each pitch of 600 × 103 mm / 1 MHz = 0.6 mm.

[0031]

As described in detail above, according to the present invention,
By arranging a measuring member such as a laser head on the stationary side, it is possible to measure the vibration of the measurement object on the rotating side in a non-contact manner, so the vibration characteristics of many measurement objects can be measured without replacing the sensor. can do. Further, by using the laser light, it is possible to measure a minute vibration as displacement of the target portion or interference of the laser light with extremely high sensitivity. Further, the labor required for the measurement preparation is reduced, and the work efficiency can be significantly improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a final stage portion of a steam turbine rotor shown for explaining a non-contact vibration measuring method according to the present invention.

FIG. 2 is an enlarged perspective view showing a part of the L-1 moving blade in FIG.

FIG. 3 is a configuration explanatory view showing an embodiment of a sensor head portion of the non-contact vibration measuring device according to the present invention.

FIG. 4 is a system diagram of an embodiment of a non-contact vibration measuring device according to the present invention.

FIG. 5 is a diagram showing an example of a vibration waveform displayed on a display device for explaining the operation of the present invention.

FIG. 6 is a diagram showing another example of the vibration waveform displayed on the display device for explaining the operation of the present invention.

FIG. 7 is an explanatory diagram shown for explaining a vibration mode in which all L-1 moving blades are vibrating in a disk shape.

FIG. 8 is a characteristic diagram showing the relationship between the ND number and the resonance frequency.

FIG. 9 is a Campbell diagram showing a change curve of the ND frequency with respect to the rotation speed.

FIG. 10 is a diagram showing an arrangement state of sensor heads for explaining a second embodiment of the present invention.

FIG. 11 is a system diagram of another embodiment of the non-contact vibration measuring device according to the present invention.

FIG. 12 is an explanatory diagram shown for explaining a vibration amplitude detected by each sensor head in the second embodiment of the present invention.

FIG. 13 is a diagram showing an arrangement state of sensor heads for explaining a third embodiment of the present invention.

FIG. 14 is a plan view of the L-0 moving blade shown in FIG. 13 viewed from the tip side.

FIG. 15 is a system diagram of another embodiment of the non-contact vibration measuring device according to the present invention.

FIG. 16 is a diagram showing an example of a vibration waveform displayed on the display device in the third embodiment of the present invention.

FIG. 17 is a configuration diagram of a final stage portion of a steam turbine rotor shown for explaining a conventional vibration measuring device.

[Explanation of symbols]

 1 rotating shaft 2 disk 3 L-0 rotor blade (final stage rotor blade) 4 L-1 rotor blade (first stage rotor blade counting from the last stage) 5 shroud 6 vehicle compartment 22 sensor head 23 light reflecting tape 24 Photo detector

Claims (4)

[Claims] 1. A laser light emitter is placed on a stationary portion that does not contact the measurement target portion, laser light from the laser light emitter is applied to the measurement target portion, and the reflected light from the measurement target portion receives the measurement target portion. A non-contact vibration measuring method, characterized by measuring the vibration of a. 2. A laser beam is radiated from a fixed portion inside the turbine casing toward a shroud provided at the tip of the turbine blade, and vibration of the turbine blade is caused based on displacement of an incident position of reflected light. A non-contact vibration measuring method characterized by measuring. 3. A laser beam is radiated from a fixed portion inside the turbine casing toward the tip of the turbine rotor blade, and the vibration of the turbine rotor blade is measured based on the Doppler displacement of the reflected signal. Contact vibration measurement method. 4. A sensor head portion fixed inside a turbine casing so as to irradiate a laser beam toward a shroud provided at the tip of a turbine rotor blade and receive the reflected light, and the sensor head. A non-contact vibration measuring device comprising: a processing device that receives a signal from the unit to analyze a vibration state of a turbine rotor blade.