JPH0156694B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotor blade vibration measuring device that detects vibrations when a rotor blade is rotating by detecting displacement from a normal position.

Currently, it is difficult to accurately predict the dynamic stress associated with blade vibration through calculations, and it is difficult to measure the vibration of rotor blades such as fans, compressors, and turbine blades as accurately as possible under operating conditions. This is extremely important.

Conventionally, strain gauges were attached to the blade to be measured for this purpose, but there were various problems such as high temperature, large centrifugal force, corrosion, noise caused by slip rings, etc., and it was difficult to measure easily and accurately. It was difficult to do so.

Another example of detecting vibrations of rotating blades is described in Japanese Patent Laid-Open No. 133401/1983. This is the ratio of the time required for two adjacent blades to successively pass under one inductive detector mounted on the rotor casing and the rotational speed of the rotor at that time. The vibration of the blade is statistically measured based on the variation width of the value.

With this configuration, even though the statistical vibrations (in this case only the amplitude) of the blades at the location where the inductive detector is mounted on the casing are separated, the temporal change in displacement during the rotation of each blade, i.e. It was impossible to observe the vibration waveform during rotation of the blade of interest.

This invention has been made in view of the above points, and includes detecting the position of a blade to be measured while rotating without contact, and detecting how much the blade to be measured has displaced from its normal position at each detected position. The vibration of the rotor blade is detected by The present invention will be explained in detail below based on the drawings.

FIG. 1 is a diagram illustrating the principle of the present invention. Reference numeral 1 denotes a rotary blade, and blade pieces 4 are fixed to a rotating body 3 of a rotating shaft 2 at equal intervals. 5 is a circular plate on which a reference point α is provided. Note that the disc 5 is not necessarily required, and in that case, the reference point α may be provided on the rotating body 3. S is a wing tip detector, and its output reaches its maximum at the moment it faces the tip of the wing piece 4. P is a reference point detector, and its output becomes maximum at the moment it faces the reference point α.

FIG. 2a shows an example of a wing tip detector S or a reference point detector P (hereinafter simply referred to as a detector), and FIG. 2b shows an example of its output waveform.

In FIG. 2a, light from light source 11 passes through optical fiber 12 and is emitted from the tip. At this time, if the tip of the wing piece 4 faces the tip of the optical fiber 12, the reflected light passes through the optical fiber 13 and enters the photoelectric converter 14, so that an output is obtained from the photoelectric converter 14. That is, the optical fibers 12 and 13 are plotted on the horizontal axis.
If the facing distance d between the tip of the blade 4 and the tip of the blade 4 is taken, and the output voltage is plotted on the vertical axis, the output of the photoelectric converter 14 becomes as shown in FIG. 2b. As can be seen from this, when the rotary blade 1 rotates, each time the blade 4 passes the tips of the optical fibers 12 and 13, the photoelectric converter 1
4 provides a pulse-like output. Detection of the reference point α is performed in exactly the same manner.

Note that as the detectors P and S, other types of detectors such as electromagnetic pickups can also be used.

In FIG. 1, the distance between the reference point α and any one of the blades 4, that is, the blade to be measured in the blade 4 (hereinafter referred to as the blade 4') can be measured in advance. Since the rotation speed, that is, the speed of the rotor blade 1 can also be measured by other methods, the time from when the reference point α is detected by the detector P to when the blade piece 4' is detected by the detector S is measured. Comparing this time with the time calculated in advance assuming that there is no displacement (vibration) in the blade 4', we can see how much the blade 4' moves forward or backward in the direction of rotation at that moment, based on the size relationship. You can tell if it has shifted. By arranging a large number of detectors S on the rotating circumference, it is possible to measure the displacement from the normal position at the time when the blade 4' passes through the position of each detector S on the rotating circumference. From this, a time-dependent change waveform (vibration waveform) of the displacement of the blade 4' can be obtained.

The above is an explanation of the principle of this invention, and further embodiments of this invention will be explained.

FIG. 3 shows an embodiment of the present invention, in which a detector P and k detectors S ₁ to S _k are connected to a casing 6.
It was placed in A total of m blades 4 are arranged at equal pitch intervals p, and each tip is located on a pitch circle C of the blade tip of the blade 4. Then, the blade tip pitch distance l ₁ between the detector S ₁ and the detector P is determined accurately. The other detectors S ₁ to S _k are equally pitched.
Place it in However, l=・p+0.5p...(1) Here, it is preferable that: natural number, p: blade tip pitch. Although the pitch circle C at the tip of the blade is strictly different from the pitch circle at the tip of the detectors S ₁ to S _k , there is almost no difference between the two, so the pitch circle C at the tip of the blade will be used in the following explanation. do.

The pitch l also needs to be chosen so that l≦ _ld . However, l _d can be obtained from the following formula.

l _d ≦K・N・D _s /F _nax・N _s ...(2) where, N: Number of rotations of rotor blade 1 (rotations/second) K: π/60 F _nax : Number of rotations of blade 4 per second Maximum measurement frequency N: Number of samples required to observe one cycle of blade vibration D: Diameter of blade tip pitch circle C Now, in Fig. 3, the blade to be measured is determined from m blades 4, and this Let be the wing piece 4'. and,
Blade tip pitch circle C between detector _S1 and detector P, and between detector P and blade piece 4' when rotor blade 1 is stationary at the position where reference point α is detected by detector P
The distances between the upper blade tips are l ₁ and l _s , and the numbers of blades 4' between l ₁ and l _s are n ₁ and n _s . Furthermore, it is assumed that the rotational speed N of the rotary blade 1 remains unchanged during the measurement period in question. Note that the above-mentioned l ₁ , l _s , n ₁ , n _s , N, etc. can all be accurately measured in advance regardless of the arrangement state of the reference point α and the detectors P and S. The blade to be measured can be changed from the blade 4' to any other blade 4.
If you want to replace it with , just change the above values of n _s and l _s to values corresponding to the blade 4. Furthermore, l ₁ =0 may be used as a special case.

FIG. 4 is a block diagram showing an embodiment for processing the output signals from the detectors P and S to obtain a vibration waveform. In the following description, the operation of the embodiment shown in FIG. 9, which will be described later, will be shown in brackets.

In Figure 4, FF is a flip-flop;
It has input terminals S' and R', and when the set signal S is input, the output terminal Q is set to "H" and the gates of the preset counters PC-0 and PC-1 (Fig. 9) are opened. When the reset signal R is input, the output terminal is set to “H” and the preset counter PC
-0, Close the gate of PC-1 (Figure 9). W _p
and W ₁ to W _k are waveform shaping circuits composed of, for example, amplifiers, Schmitt circuits, one-shot multivibrators, and the like. Preset counter
PC-0 is for specifying the blade to be measured, and detector S ₁
and the number of blades between the blade 4', that is, n ₁ + n _s
is set. Preset counter PC
1 is set to n in FIG. 3 (the number of blades between detectors S _i and S _i+1 , where i is an arbitrary integer from 1 to (k-1)). SC is an input selection circuit,
One of the outputs of the waveform shaping circuits W ₁ to W _k is selected. The preset counter PC-1 increments the count every time one pulse is input from the input selection circuit SC, and when it reaches the preset value n, it generates a pulse-like count end signal _I1 , which is used for timekeeping as described later. Sends one pulse to counter CNTR and clears preset counter PC-1.
Reset the pull set value and start the next count. SCC is an input signal selection counter, and the counter contents are determined by the pulse-like count end signal _I1 .
The codes corresponding to S ₂ , S ₃ ... are changed one after another, and the input selection circuit SC is changed depending on the contents of this counter.
are driven to input only the signals from the respective detectors S ₂ , S ₃ . . . to the preset counter PC-1. The time counter CNTR calculates the time △T _{1 required for the tip of the blade 4' to move from the position shown in Figure 3 to the detector S 1 and} the time required for the tip to move from the detector S _i to S _{i +1.} This is a circuit for counting the time ΔT _i (i≧2), and is configured as shown in FIG. 5, for example.

In Figure 5, SE is a sequential circuit,
C' is a counter and B is an output latch. This operation will be explained with reference to the timing diagram of FIG.

Count end signal M of time counter CNTR
is the preset counter PC-1 or PC- which indicates that the tip of the blade 4' is directly below the detector S _i .
OR of the 0 count end signals I ₀ , I ₁ and the signal I _p obtained by shaping the output signal of the detector P
This is a signal that, in response to this input, transfers the contents of the previous count of the reference clock signal KL by counter C' to output latch B, and also instructs (IN) the data storage/calculation device DPU to read the count value. Counter content transfer strobe signal ST,
Figure 6 shows a count stop signal SP for stopping the count of the reference clock signal KL, a clear signal CR for clearing the contents of the count C', and a start signal SR for restarting the count of the reference clock signal KL. Activate the sequential circuit SE that emits at the timing shown in . The reference clock signal KL is a stabilized clock signal with a frequency high enough to measure the time interval ΔT _i with the required accuracy. Output latch B is a circuit for adjusting the processing speed of the data storage/calculation device DPU and the counting speed of the time counter CNTR, and the contents △T _i of the time counter CNTR are sent to the data storage/calculation device DPU one after another. The data will be stored in and used for later analysis.

Again in FIG. 4, OR is an OR circuit, CR is a clear signal, and after clearing the preset counter PC-0, the initial value is set. I ₀ and I ₁ are count end signals as described above, I _p is the waveform shaping circuit
This is the output signal of W _p and represents the signal that tells the time counter CNTR to start counting.

Next, the operation shown in FIG. 4 will be explained with reference to FIG. 3.

First, n ₁ +n _s and n are set in preset counters PC-0 and PC-1, respectively. The rotational speed N of the rotor blade 1 and the adjacent detectors S _i on the blade tip pitch circle C
The frequency of the reference clock signal KL to obtain the necessary calculation accuracy is determined from the distance l from S _i+1 . Next, when the pulse-like start signal SRT is issued, the preset counters PC-0, PC-1, and the time counter
The contents of CNTR are cleared, and n ₁ + n _s ,
n is set. _At the same time, the contents of the input signal selection counter SCC are set to a value that does not correspond to any of the detectors S _{2 to} S _k . Detector S ₂ ~ until changed to the corresponding value
Both outputs of S _k are preset counter PC-1.
is not reached and counting does not start.

Now, when the reference point α comes under the detector P, the gate of the preset counter PC-0 is opened, and the preset counter PC-0 starts counting, and the clock counter CNTR is opened by the output signal I _p .
also starts counting. When the blade 4' comes directly under the detector _S1 and the preset counter PC-0 finishes counting _n1 +n _s , the count end signal _I0 closes the gate of the preset counter PC-0 and starts the time counter. Sends a signal to CNTR to end the time counting, and sends a read command signal IN to the data storage/calculation device DPU, as well as the contents of the time counter CNTR△
Send T _i . The count end signal I ₀ also changes the contents of the input signal selection counter SCC, the signal of the detector S ₂ ,
In other words, the output of the waveform shaping circuit _W2 is selected.

While the blade 4' moves from directly below the detector S ₁ to directly below the detector S ₂ , the detector S ₂ detects n blades 4, and the waveform shaping circuit W ₂ pre-processes n output signals. Send to set counter PC-1. When the blade 4' reaches directly below the detector and the preset counter PC-1 completes n counts, a count end signal _I1 is sent to the time counter CNTR, and the sequential circuit SE in the time counter CNTR is activated. Then, the time counting ends, and the content ΔT ₂ of the time counter CNTR is sent to the data storage/calculation device DPU.
The count end signal I ₁ is also input signal selection circuit SCC
, and select the signal of the detector _S3 , that is, the output of the waveform shaping circuit _W3 . Thereafter, in the same process, the blade 4' is moved from directly below the detector S ₂ to the detectors S ₃ and S ₄ .
...In general, each time the sensor S _i reaches the bottom, the contents of the time counter CNTR change to △T _i (i=1, 2,
) is stored in the data storage/computing unit DPU.

Next, by the above data storage and computing device DPU
Measured value of time counter CNTR stored in △
Using T _i (1, 2, . . . ), the data storage/calculation unit DPU calculates the change in displacement of the blade 4' over time, that is, the vibration waveform.

First, the concept of calculating vibration waveforms according to the present invention is shown in FIG. In Fig. 7a, the solid line indicates that the tip of the blade 4' is the detector, for example, during vibration measurement.
It shows the situation when the blades 4' are moving one after another directly below S ₁ , S ₂ ..., S ₇ , and the broken line shows the situation when the blade 4' is moving without being displaced from its normal position. It represents. h ₁ , h ₂ , _{. .} . h ₇ in FIG _. ) is the reference point α, assuming that there is no displacement of the blade 4' from its normal position.
is detected by detector P until blade 4' is detected by detector S _i (i = 1, 2 _... ). After being detected by P, the blade 4' is transferred to the detector S _i
Assuming that the time required for detection is given by (i=1, 2, . . . ), it is easy to see that the displacement h _i of the blade 4' can be obtained by equation (3).

h _i (i = 1, 2, ...) = (T _si - T _i ) (πD _s N)...
... (3) However, T _si and T _i in equation (3) are determined by equation (4), and h _i is the displacement of the blade 4' in the rotational direction as positive, and the displacement in the counter-rotational direction as negative. .

T _si (i=1, 2,...)={l ₁ +l _s + (i-1)・l
} /(πD _s N) ...(4) T _i (i = 1, 2, ...) = _i 〓 ^{j = 1} △T _jNext , use the data storage/computing device DPU to perform the calculation in Figure 7b. The vibration waveform of the blade 4' can be obtained by plotting the displacement h _i (i=1, 2, . . . ) in correspondence with the time T _i (i=1, 2, . . . ) as shown in FIG.

Moreover, the number of detectors S may be one. In this case, only the portion surrounded by the dashed line in the embodiment shown in FIG. 4 may be used. When there is one detector S,
Since the displacement of the blade 4' is determined each time the rotor blade 1 rotates once, the displacement in the rotation direction and the displacement in the counter-rotation direction can be plotted after several rotations, as shown in FIG. 8, and the vibration amplitude a is calculated statistically.

Further, in the present invention, it is not necessary to specify the blade to be measured, and vibrations of an unspecified blade 4' can be measured. In this case _, in the embodiment shown in FIG.
PC-0 and its peripheral circuits are removed, the gate of preset counter PC-1 is opened by the start signal SRT, and the waveform shaping circuit W _k of the detector S _k is
The output signal causes the gate to close. The other parts function exactly the same as the embodiment shown in FIG. However, the input signal selection counter SCC is first set to the value corresponding to the detector _S1 . An embodiment constructed in this manner is shown in FIG.

In FIG. 9, an unspecified wing 4' passes through the detector S ₁ first after issuing the start signal SRT.
However, each time the detector moves from S ₁ to S ₂ , from S ₂ to S ₃ , and generally from S _i to S _i+1 , the fourth
Through the same process as in the embodiment shown in the figure, the time counter CNTR measures the time △ required from when the tip of the blade 4' is detected by the detector S _i until it is detected by the detector S _i+1 . Measure T _i sequentially, △T _i (i=1,
2,...) are stored in the data storage and computing unit DPU.

Next, by the above data storage and computing device DPU
Measured value of time counter CNTR stored in △
Using T ₁ (i=1, 2, . . . ), the data storage/calculation device DPU calculates the temporal change in displacement of the blade 4', that is, the vibration waveform.

First, the concept of calculating the vibration waveform is shown in FIG. In Fig. 10, a shows the blade under each of the detectors S 1 to S _{7 when the blade 4' moves one after another under the detectors S 1 , S 2 , . . . S 7 as an example .} 4', the solid line indicates the deformation during vibration measurement, and the dotted line indicates the previous detector,
In general, the displacement at the time of detector S _i remains the same for the next detector
In other words, it represents the deformation when it is assumed that it is below the detector S _i+1 . In the figure, δ ₁ , δ ₂ , ... δ ₇ , generally δ _i is an unspecified wing 4 generated while the wing 4' moves from below the detector S _i to below the detector S _i+1. ′, and △T _ni (i=1, 2,...) is the increase in the displacement of the blade 4′
The time required to move from detector S _i to S _i+1, assuming that the displacement of S does not increase while moving between detectors S _i and S _i+1 , and ΔT _i (i=1, 2,...)
If is the measured time required for blade 4' to move from detector S _i to S _i+1 during vibration measurement, then the increase in displacement of blade 4' δ _i is calculated using equation (5). It will be done.

δ _i (i = 1, 2, ...) = (△T _ni - △T _i ) (πD _s N) ... (5) However, △T _i (i = 1, 2, ...) is the data storage・Measurement data stored in the computing device DPU. Furthermore, δ _i is defined as positive when the displacement of the blade 4' in the rotational direction increases, and negative when the displacement in the rotational direction decreases.

Next, as shown in Fig. 10b, the displacement h ₀ of the blade 4' at the measurement start time is successively added to δ ₁ , δ ₂ , ... generally up to δ _i , which corresponds to time T _i. By displaying the vibration waveform of the blade 4', the vibration waveform of the blade 4' is obtained.
However, T _i is calculated using equation (6).

T _i (i = 1, 2, ...) = _i 〓 ^{j = 1} △T _j ... (6) However, the rotational displacement h ₀ in Fig. 7a cannot be obtained in this example; By simply changing the average value of the amplitude of the vibration waveform, the most important amplitude and frequency of blade vibration can be accurately determined. In order to detect the average vibration of many blades, it is sufficient to emit the start signal SRT several times, detect vibration waveforms of several blades, and statistically process the vibration waveforms.

Figures 11a and 11b show examples of experimental data according to the present invention, and data A shown in Figure 11a is
The vibration waveform of one of the 33 rotor blades (blade pieces to be measured) is shown.

Similar vibration waveform data can be obtained for other rotor blades. The operator can freely select which of the 33 moving blades to display.

In data A, the vibration waveform while the #1 rotor blade rotates a total of 20 times is obtained, and _T5 means that the #1 rotor blade rotates 5 times.
It represents the time required to rotate.

Moreover, data B shown in FIG. 11b is #1 rotor blade ~
#33 Vibration amplitude of rotor blade is displayed. This data B is the maximum displacement point Q and the minimum displacement point P in data A.
are connected in a bar graph and expressed as #1 of data B, and bar graphs can be created in the same manner for other rotor blades.

As described above in detail, the present invention includes a reference point detector and a blade tip detector, and after the reference point detector detects the reference point using a time counter, the blade to be measured is detected by the blade tip detector. The time until detection is measured, and this time and the time determined in advance assuming that there is no displacement of the blade to be measured are used to determine the displacement of the blade to be measured from its normal position, making it possible to use a non-contact method. Since it is possible to measure vibration and displacement, and there is no need to perform any processing or add a detector to the blade to be measured, the characteristics of the object to be measured are not disturbed due to vibration measurement.

Further, a plurality of blade tip detectors are provided at predetermined intervals, and a time counter measures the time it takes for the blade to be measured to move between two adjacent blade tip detectors,
On the other hand, in the case where this time is determined in advance assuming that there is no displacement of the blade to be measured, and the displacement of the blade to be measured is determined using this time and the time obtained by a timing counter, the reference point detector Displacement from the normal position caused by blade vibration during rotation can be immediately detected without the need for.

As described above, this invention is extremely significant because it can detect the vibrations of the rotor blade every moment without contact.

[Brief explanation of drawings]

Fig. 1 is a diagram explaining the principle of this invention, Fig. 2a is a configuration diagram showing an example of a detector, Fig. 2b is a waveform diagram showing an example of its output, and Fig. 3 is an embodiment of the invention. 4 is a block diagram showing an embodiment of the present invention. FIG. 5 is a block diagram showing an example of the structure of the time counter shown in FIG. 4.
The figures are a timing diagram of the output waveform of the time counter in Figure 5, Figure 7 is a diagram showing how to determine displacement, and Figure 8 is a diagram showing how to determine displacement.
The figure shows an example of displacement measurement using one detector, and FIG. 9 is a block diagram showing still another embodiment of the present invention.
FIG. 10 is a diagram showing how to obtain displacement, and FIG. 11 is a diagram showing an example of experimental data. In the figure, 1 is a rotating blade, 2 is a rotating shaft, 3 is a rotating body,
4 is a blade, 4' is a blade to be measured, 5 is a disk, α is a reference point, P is a reference point detector, S is a blade tip detector,
FF is a flip-flop, W _p , w ₁ to _{W k} are waveform shaping circuits, PC-0 and PC-1 are preset counters,
SC is an input selection circuit, SCC is an input signal selection counter, CNTR is a time counter, and DPU is a data storage/calculation device.

Claims (1)

[Scope of Claims] 1. A rotor blade consisting of a large number of blades arranged radially on a rotating body, comprising: a reference point detector for detecting a reference point provided on the rotating body in a non-contact manner; at least one blade tip detector for non-contact detection of passing; and from the time when an output is obtained from the reference point detector, a predetermined blade to be measured among the plurality of blades is detected by the blade tip. a time counter that measures the time until the blade is detected by the detector, and a time counter that measures the time until the blade is detected by the reference point detector; After determining the displacement of the blade to be measured from its normal position using the time until the blade to be measured is detected by the blade tip detector and the time obtained by the time counter, the time of this displacement is determined. A rotary blade vibration measuring device comprising: means for determining the vibration of the blade to be measured from changes. 2. In a rotor blade consisting of a large number of blades arranged radially on a rotating body, a plurality of blade tip detectors are provided at predetermined intervals to detect the passage of the blades in a non-contact manner. A timer that measures the time from when an unspecified blade to be measured is detected by one of the plurality of blade tip detectors to when it is detected by another adjacent blade tip detector. a time counter, a time during which the blade to be measured is detected by both wing tip detectors, which was determined in advance assuming that the blade to be measured has no displacement from its normal position, and a time obtained by the time counter. 1. A rotary blade vibration measuring device comprising: means for determining the displacement of the blade to be measured from a normal position using a rotary blade, and then determining the vibration of the blade to be measured from a temporal change in this displacement.