JPH07128133A - Method and apparatus for measuring vibration of rotary wing - Google Patents

Abstract

PURPOSE:To perform an automatic vibrating frequency analysis of a partial vibration waveform in which a vibration waveform is not continuous vibration waveform in a rotating period and to improve a function of a wind vibration measurement. CONSTITUTION:The method for measuring a vibration of a rotary wing comprises the steps of inputting an output of a tachometer 50 to a CPU 60, operating a relay contact 45 in a predetermined small range of speed variation, automating collection of data, calculating a vibration waveform by the CPU 60 from obtained time data, then identifying whether the waveform is a partial vibration waveform or not, and analyzing a vibration frequency of the partial waveform. In the case of the partial waveform, vibrating frequency information in the rotation change is automatically obtained, a measuring function of a wing vibration is improved, and an online monitoring function by a Campbell's diagram, etc., is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for contactlessly measuring rotor blade vibration of a rotary machine having a rotor wheel.

[0002]

2. Description of the Prior Art It is extremely important to measure the vibration of a moving blade during rotation of a compressor, a turbine, a fan, etc., and confirm the generation state and the stress generated by the vibration in order to ensure its reliability. Recently, rotating machines such as turbines and compressors tend to be high speed, high pressure, and high temperature, and the demand for ensuring reliability is increasing, and the need for vibration measurement of the blades is increasing.

Conventionally, for this purpose, a method is known in which a strain gauge is attached to the blade and vibration of the rotating blade is taken out by a slip ring or a telemeter. Further, as a method for measuring the vibration of a rotor when this method is difficult, Japanese Patent Publication No. 1-56694 and 1983-Tokyo-
ITC 123 (1983-TOKYO-Inte
953 of the rnational Gas Turbine Congress-123)
The methods described on pages 960 to 960 have been proposed. These methods calculate the time difference due to the vibration of the moving blade from the time data of the moving blade obtained by many optical non-contact detectors arranged on the casing containing the rotating blade, and based on these, the displacement of each moving blade is calculated. Is obtained. Since these methods can obtain the vibration waveform, they have an advantage that not only the vibration amplitude but also the vibration frequency can be obtained.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to measure a rotor blade vibration in which a rotor blade pulse is obtained from time data of rotor blade pulses of a large number of non-contact detectors. In the case of partial vibration waveforms that are not continuous vibration waveforms, the problem that frequency analysis by normal Fourier transform is difficult is solved, and automatic vibration frequency analysis of partial vibration waveforms during rotation changes is possible. It is an object of the present invention to provide a method and an apparatus for measuring vibration of a rotating blade by a detector.

[0005]

The above object is to identify whether or not a vibration waveform obtained from time data of blade pulses by a plurality of non-contact detectors is a partial vibration waveform, and to determine the vibration frequency in the case of a partial vibration waveform. It is achieved by taking analytical means. That is, the partial vibration waveform is obtained by complementing the waveform data in the rotation cycle other than the partial vibration waveform cycle,
It is possible to perform frequency analysis by Fourier transformation, but paying attention to the fact that the obtained frequency will be lower than the actual frequency by a constant ratio, and a means to correct this will be provided based on the ratio of the rotation cycle and the partial vibration waveform cycle. Achieved by

[0006]

According to the present invention, it is possible to analyze the frequency of the partial vibration waveform while the rotation speed is increasing or decreasing. Based on such an action, it is possible to achieve the effect that the information of the blade vibration amplitude and the vibration frequency can be automatically measured even when the probe cannot be arranged on the entire circumference of the casing.

[0007]

Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a flow of data collection in an embodiment of a rotor blade vibration measuring apparatus of the present invention. The rotor blade vibration measuring apparatus of the present invention automatically collects vibration data in order to facilitate online measurement. This will be described in more detail with reference to FIG. 1. During the change in the measured rotational speed when the rotational speed increases and when the rotational speed decreases, the rotational speed change width ΔR and the measured rotational speed are stored in advance in a central processing unit (hereinafter abbreviated as CPU). There is. Output speed R of tachometer 50
Is also directly input to the CPU 60, and when this rotational speed reaches the measured rotational speed after the start of measurement, the CPU 60 activates the contact input start terminal 451 in the timing device 40. When the time measurement data of the required number of revolutions is collected, the contact input stop terminal 452 is activated, and the data collection at the measured number of revolutions R is completed. The collected time data is CPU6
At 0, the vibration waveform calculation and the frequency analysis processing of the vibration waveform are performed and displayed on the CRT 62 or the like. If the measurement is not completed, collect the above data by using the rotation speed data acquisition command rotation speed as the measurement rotation speed when the speed changes in the + direction when the speed increases and in the − direction when the speed decreases. Repeat automatically. The judgment of measurement start and measurement end is made in advance by C
It is performed by the CPU 60 based on the measurement start rotation speed R _S and the measurement end rotation speed R _E stored in the PU 60. However, the values of the measurement start rotation speed R _S and the measurement end rotation speed R _E or a specific measurement rotation speed R can be manually input to the CPU 60 as appropriate. However, in this case, although the collection of the vibration data with respect to the change of the rotation speed is not necessarily automatic, the calculation of the vibration waveform and the frequency analysis thereof at the manually input measured rotation speed are automatically performed. The measured rotation speed R is stored in the external storage device 61 together with the time measurement data.

FIG. 2 shows a rotor blade vibration measuring apparatus showing an embodiment of the present invention. In FIG. 2, a rotary impeller 10 is composed of a rotary disc 101 rotatably supported by a shaft 11 and a plurality of moving blades 12 supported on the rotary disc. A rotation reference mark 13 for generating a reference pulse according to the rotation of the moving blade 12 is provided at the root portion of the rotating chassis 101 where vibration does not occur. A plurality of first non-contact detectors 211 to 216 that generate a moving blade pulse train when the tip of the blade 12 reaches a predetermined position are provided on a casing 14 that houses the rotary impeller 10. Each non-contact detector detects the tip of the moving blade as each moving blade comes to the opposing position, and generates a moving blade pulse train. Therefore,
The pulse generated by each non-contact detector is a pulse train delayed by the pitch angle of the moving blade.

The detector 22 generates a rotation reference pulse train when the rotation reference mark 13 reaches a predetermined position. The optical fiber cable 24 branches the light from the light source 30 into the branch section 23.
Through the first non-contact detectors 211 to 216, and irradiates the tip of the moving blade 12. The reflected light from the moving blade 12 is again guided to the photoelectric converter 31 via the optical fiber cable 24. The timing device 40 includes a waveform shaping section 41, a counting storage section 42, a control section 43, an interface 44, and a contact input terminal 45. The tachometer 50 is the waveform shaping unit 4
Rotating impeller 1 at the time of measurement according to the output of the rotation reference pulse 1
The number of rotations of 0 is calculated and input to the CPU 60. CPU6
A storage device 61, a CRT display 62, and a printer plotter 63 are connected to 0.

A plurality of first non-contact detectors 211-216
Are installed on the casing 14 at predetermined intervals in the circumferential direction, and light is supplied from the light source 30 through the optical fiber cable 24 and the branch 23 to irradiate the tip of the moving blade 12. A laser diode, for example, is adopted as the light source 30 and supplies light to each of the plurality of non-contact detectors 211 to 216. In this state, the rotary impeller 10 rotates, and the tip of the moving blade 12 has non-contact detectors 211 to 216.
After passing through the detection part of the above, reflected light is generated for each moving blade, and this reflected light is guided again to the photoelectric conversion device 31 through the optical fiber cable 24, converted into an electric signal by the photoelectric conversion element, and taken out as an electric signal pulse. . This moving blade pulse is waveform-shaped by the comparator of the waveform shaping unit 41 in the timing device 40, and is then guided to the instrumentation storage unit 42 as rectangular-wave moving blade pulse data. The counting storage unit 42 has a built-in clock clock pulse generator and a storage element (RAM), and the number of clock pulses until each blade pulse is generated is based on the first rotation reference pulse after the start of measurement. The counting storage unit 42 for each of the contact detectors 211 to 216
Is stored as time data.

FIG. 3 is an explanatory diagram showing this situation. The rotation reference pulse (A) is a pulse signal generated once when the rotation reference mark 13 is detected by the rotation detector 22, and the waveform signal is shaped in the timing device 40 through the optical fiber cable 24 and the photoelectric converter 31. The portion 41 is shaped into a rectangular wave. The moving blade pulse train (B) shows an example of moving blade pulse data obtained from the signals of the non-contact detectors 211 to 216 as described above. The pulse timing output (C) is
The number of clock pulses P1, P2, up to each blade pulse measured in the counting storage unit 42 with the rotation reference pulse as a reference
Indicates P3 .... These values are stored in the RAM of the counting storage unit 42 as moving blade pulse clock data.
See (D). Rotation reference pulse timing outputs Q1, Q2
Similarly, the RAM for the rotation reference pulse in the counting storage unit 42
Remembered above. See (E). Pulse time output (C)
Indicates the two rotations of the measured rotation number, and this rotation number is controlled by the control unit 43 according to a preset value. In the embodiment, the maximum value of the clock pulse clock output is 2 ¹⁶ -1 (65535) because the CPU 60 is a 16-bit machine.
A CPU having a larger number of bits may be adopted for speeding up or the like.

In FIG. 2, the moving blade clock pulse data and the rotation reference clock pulse data stored in the counting storage unit 42 are transferred to the CPU 60 via the control unit 43 and the interface 44, and the vibration waveform and its frequency component are transferred. Calculation and processing for obtaining are performed. These vibration data are output or displayed online or offline on the CRT 62 and the printer plotter 63. After the online processing is completed, the moving blade clock pulse data and the rotation reference clock pulse data are stored in the external storage device 61.

Next, a method of obtaining a vibration waveform from the time measurement data by the CPU 60 will be described in detail. First, the procedure for measuring the vibration waveform will be described with reference to FIGS. First, the rotor blade clock pulse data as shown by the solid line in FIG. 4 is measured at the reference rotational speed R ₀ which is considered to be free of vibration, and then the measured rotational speed R
Then, blade clock pulse data as shown by the dotted line in FIG. 4 is measured, and these data are multiplied by the clock period to obtain time data. This is the step (I) in FIG. Next in FIG.
In step (II), the time difference Δt of the time data between the vibration measurement rotation and the reference rotation is obtained. Assuming that the time data at the time of reference rotation is t ′ and the time data at the time of vibration measurement is t, the time difference Δt can be obtained from the equation (1) in consideration of the difference in the rotation speeds of the both.

[0014]

[Equation 1]

This is shown in the case of the moving blade number 1 of the detector 1 and the detector 2 in FIG. 4, which are Δt ₁ and Δt ₂ , respectively. t ₁ and t ₂ are time data of the moving blade 1 at the time of vibration measurement rotation, that is, the time until the moving blade reaches the detector 1 and the detector 2, respectively. This time difference Δt is caused by the vibration of the blade. Then, the process (I
In II), the time difference data is converted into displacement data. When the circumferential speed of the blade tip and the pitch circle diameter of the blade tip at the measured rotation speed are U and D, respectively, the vibration displacement is calculated by the equation (2).

[0016]

[Equation 2]

However, the displacement represented by the equation (2) is a displacement in the circumferential direction. Since the displacement data obtained by the equation (2) is obtained for all target blades for all non-contact detectors, the data for each blade is extracted from these data in step (IV) of FIG. . For example, referring to the rotor blade 1 of FIG. 4, it is possible to extract displacement data δ ₁ corresponding to Δt ₁ from the data of the detector ₁ and displacement data δ ₂ corresponding to Δt ₂ from the data of the detector 2. means. Finally, the displacement data of all the detectors are aligned in time series, and the points of each displacement data are connected by a straight line to obtain a vibration waveform. This is Figure 5
This is the step (V).

FIG. 6 shows partial vibration waveforms for three rotations obtained by the above method. In FIG. 6, the horizontal axis represents time, T is the rotation cycle, and T'is the partial vibration waveform cycle. The present invention directly targets such a partial vibration waveform, and the occurrence situation thereof will be further described with reference to the probe layout diagram of FIG. 7. Figure 7
Indicates that 12 probes are arranged at a probe pitch angle of 10 °, and the distribution angle in the circumferential direction of the entire probe is 1
It is 10 °. Since each probe generates a blade pulse which becomes the data of the vibration waveform only when passing through its own probe in one rotation, the vibration waveform data can be obtained only in the range corresponding to the probe distribution angle. That is, the vibration waveform data in FIG. 6 can be obtained only during the period T ′ corresponding to the probe distribution angle of FIG. 7 with respect to the rotation period T. Therefore, the vibration waveform is not a continuous waveform with respect to rotation but a partial waveform. It suffices that the probe distribution angle can be set to 360 °, that is, the entire circumference, but due to physical restrictions of the casing 14, it can be arranged only in a part thereof, and as a result, only a partial vibration waveform can be obtained in many cases.

As the frequency information from the vibration waveform, it is useful to obtain the rotation frequency component and its harmonic components by frequency analysis by Fourier transform, etc., but in the case of the partial vibration waveform, there is no data for one rotation, so that No frequency analysis can be done. However, the missing data of the partial vibration waveform within the rotation cycle T is compensated by setting the sampling interval (probe pitch interval) to 0, which is the same as the portion of the partial vibration waveform, and the discrete Fourier transform (hereinafter referred to as the Fourier cycle) with the rotation cycle T as one cycle. It was found that it is sufficient to correct the obtained vibration frequency after DFT). That is, since the vibration frequency after DFT is lower than the actual value in relation to the rotation cycle T, the correct vibration frequency can be obtained by multiplying the vibration frequency by the coefficient α of the following equation (3).

[0020]

[Equation 3]

FIG. 8 shows an embodiment of the vibration measuring method according to the present invention, in which the vibration waveform is calculated in the above step (V) by using the rotation speed for instructing data acquisition of the tachometer as the measurement rotation speed, and then the partial vibration waveform is calculated. The frequency analysis step (VI) is included. The frequency analysis method of the partial vibration waveform in step VI will be described in more detail with reference to FIG. First, in step VI-1, it is identified whether the vibration waveform obtained in the step (V) is a partial vibration waveform. This is judged from the input values of the probe pitch angle and the number of probes whether the probe distribution angle as shown in FIG. 7 is 360 ° or less. Next, in step VI-2, the data deficiency of the partial vibration waveform is compensated, and the entire waveform of one rotation is assumed. As described above, the shortage data in the rotation period T has the same sampling interval as the sampling interval (probe pitch angle) of the partial vibration waveform and has a value of 0. Process VI
At -3, DFT is performed on the entire waveform with the rotation cycle T as one cycle. Finally, in step VI-4, the frequency of the DFT result is multiplied by the equation (3) to correct it and obtain the correct vibration frequency component.

Next, an example of measurement of rotor blade vibration in the embodiment of the present invention will be shown. FIG. 10 shows an example in which the partial vibration waveform due to the probe arrangement as shown in FIG. 7 is measured online while changing the rotation speed, and the frequency analysis result is displayed in a Campbell diagram. The size of the circle in FIG. 10 represents the amplitude, and the curve connecting the resonance points with the large amplitude in the figure shows the natural frequency line of this moving blade. The value of this natural frequency coincided with the calculated value. The Campbell diagram is most often used to describe the vibration characteristics of a wing. According to the present invention, even in the case of the partial vibration waveform, the online display by the Campbell diagram is possible in this way, and the function of measuring and monitoring the blade vibration is improved.

[0023]

As described above in detail, according to the rotor blade vibration measuring method and apparatus of the present invention, the frequency analysis of the partial vibration waveform during the rise or fall of the rotation speed is possible, so that the probe is installed in the entire casing. Even if it cannot be arranged around the circumference, not only the amplitude of the blade vibration but also the vibration frequency information can be automatically obtained. Further, for example, it is possible to simultaneously display the information on the amplitude and the frequency online with a Campbell diagram or the like, so that the function of monitoring the blade vibration can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a flow of data collection in an embodiment of a rotor blade vibration measuring apparatus of the present invention.

FIG. 2 is a block diagram showing an embodiment of a rotor blade vibration measuring apparatus of the present invention.

FIG. 3 is an explanatory diagram of a memory method of clock pulse data.

FIG. 4 is an explanatory diagram showing a time difference between blade pulse trains.

FIG. 5 is a flowchart showing a method of calculating a vibration waveform.

FIG. 6 is an explanatory diagram of a partial vibration waveform.

FIG. 7 is an explanatory diagram of a probe arrangement according to a partial vibration waveform.

FIG. 8 is a flow chart showing an embodiment of a method for measuring vibration of a rotor according to the present invention.

FIG. 9 is a flowchart showing a frequency analysis method for a partial vibration waveform.

FIG. 10 is a Campbell diagram showing an actual measurement result in an embodiment of the method and apparatus for measuring vibration of a rotary blade of the present invention.

[Explanation of symbols]

12 ... moving blade, 13 ... rotation reference mark, 30 ... light source, 40
... clock device, 50 ... tachometer, 60 ... central processing unit, 61
... External storage device, 101 ... Rotating chassis, 211-216 ...
Non-contact detector.

Claims (4)

[Claims] 1. A rotary vane wheel having a rotary wheel board rotatably supported and a plurality of moving vanes supported by the rotary wheel board, and a rotor vane installed on a casing accommodating the rotary vane wheel. A plurality of non-contact detectors for detecting the tip portion in a non-contact manner; and a reference position detector for detecting a reference position mark provided at a known position of the rotary impeller, wherein the rotary impeller rotates, When the non-contact detector detects the tip of the rotor blade, it generates a rotor blade pulse train, and when the reference position detector detects the reference position mark of the rotor wheel, it generates a rotation reference pulse train. The generation time data of the moving blade pulse train for each of the non-contact detectors based on the reference pulse train is obtained, the time difference data with the time data at the reference rotation speed is obtained, and the time difference data is converted into vibration displacement data. In obtaining a vibration waveform of each moving blade by extracting data of a specific moving blade from the vibration displacement data for each number of non-contact detectors, partial vibration that is not a continuous vibration waveform within a rotation cycle A method for measuring rotor blade vibration, characterized in that frequency analysis of waveforms is automatically performed. 2. The frequency of the partial vibration waveform is automatically determined from the ratio of the rotation cycle and the partial vibration waveform cycle based on the frequency analysis result by Fourier transform with the rotation cycle as one cycle. The method for measuring vibration of a rotor according to claim 1. 3. A rotor vane having a rotary wheel platform rotatably supported and a plurality of rotor blades supported by the rotary wheel platform, and a rotor vane installed on a casing for accommodating the rotary vane wheel. To a plurality of non-contact detectors that generate a blade pulse train when the rotor wheel rotates and the reflected light from the rotor is detected while irradiating the tip of the A light source that supplies light, a reference position detector that generates a rotation reference pulse train when a reference position mark provided at a known position on the rotating chassis is detected, and a photoelectric conversion that converts the output of the non-contact detector into an electric signal Device, means for obtaining a blade pulse train for each of the non-contact detectors for each blade of the impeller, and a timing device for measuring the generation time of the blade pulse train and time data of the rotation reference pulse with the rotation reference pulse as a reference , The moving blade pal A storage device for storing time data and rotation reference pulse time data, a central processing unit for calculating a vibration waveform of displacement for each moving blade from the time data, and means for displaying vibration data obtained from the vibration waveform 2. A vibration measuring apparatus for a rotary blade according to claim 1, further comprising means for automatically performing frequency analysis of a partial vibration waveform whose vibration waveform is not a continuous vibration waveform within a rotation cycle. 4. The frequency analysis means for the partial vibration waveform has means for automatically determining the frequency based on the ratio between the rotation cycle and the partial vibration waveform cycle based on the Fourier transform result in which the rotation cycle is one cycle. The vibration measuring device for a rotary blade according to claim 3.