JP3357499B2 - Whirlpool velocimeter and whirlpool flowmeter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vortex flowmeter and a vortex flowmeter for measuring the velocity and flow rate of a fluid by utilizing the principle of a vortex.

[0002]

2. Description of the Related Art In recent years, a vortex flowmeter and a vortex flowmeter which measure the flow velocity and flow rate of a gas such as a gas flowing through a pipeline by a whirlpool have been developed. In general, a vortex flute generates a fluid vibration having a frequency proportional to the instantaneous flow rate or flow velocity. Conversely, the instantaneous flow rate or flow velocity can be obtained by measuring the generated frequency. When the fluid to be applied is a gas such as a gas, the fluid vibration becomes a sound wave. Therefore, an acoustic signal is collected using a microphone, a frequency is obtained, and a flow velocity and a flow rate can be calculated. Further, by using the underwater microphone in the same structure, the flow velocity and the flow rate of the liquid can be calculated.

FIG. 13 is a schematic configuration diagram of a conventional vortex-type current meter 201. Whirlpool 202 of the whirlpool current meter 201
Is composed of a blowing port 203, a chamber 205, and a blowing port 207. The blowing port 203 is connected to a gas pipe or the like, and corresponds to the upstream side of the vortex-type current meter 201. The downstream side of the outlet 207 is open to the atmosphere.
Is provided. The microphone 209 includes a signal processing unit 211
Are connected, and the display unit 213 is further connected.

When a fluid is applied to the outlet 203 from a connection portion with a gas pipe or the like, the fluid rotates in the chamber 205 and flows out to the outlet 207, and the outlet 207
Collides with the external fluid flowing from Outlet 20
The natural frequency of the compression wave of the sound due to the simple vibration generated inside 7 is proportional to the instantaneous volume flow rate flowing through the gas pipe. The generated sound is detected by the microphone 209, the frequency is calculated by the signal processing unit 211 to calculate the flow rate and the flow velocity, and the obtained result is displayed on the display unit 213.

FIG. 14 is a schematic diagram of a conventional whirlpool-type current meter 301 with a hood. This is the one in which the outlet 307 similar to that of the vortex flowmeter 201 in FIG. 13 is covered with a hood 315, and the tip of the hood 315 is connected to the downstream side of a gas pipe or the like. The microphone 309 is
It is provided inside the hood 315.

[0006]

However, the microphones 209 and 309 have high sensitivity in the audible band, and the sounds emitted by the whistles 202 and 302 are also included in the same audible band. When the band of the sound signal generated by the whistle overlaps with the band of the sound, it is difficult to remove the influence of noise by signal processing such as a filter, and the flow velocity and the flow rate cannot be measured accurately. there were. Further, since the diaphragms of the microphones 209 and 309 are very sensitive, there is a problem that even when an external vibration propagates, the flow velocity and the flow rate cannot be accurately measured for the same reason.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a vortex flow meter and a vortex flow meter having a high signal / noise ratio and high accuracy. That is.

[0008]

In order to achieve the above-mentioned object, a first aspect of the present invention is to provide a whistle that emits an acoustic signal having a frequency corresponding to the flow velocity of a fluid to be applied, and a vicinity of an outlet of the whistle. A pair of microphones provided to face each other, a subtractor for subtracting output signals of the pair of microphones, and signal processing means for calculating a flow rate of the fluid from the output signals of the subtractor. And the pair of
The ichrophone is one of the acoustic signals emitted from the whistle
This is a vortex-type current meter that collects signals that are substantially 180 degrees out of phase .

According to a second aspect of the present invention, there is provided a whistle which emits an acoustic signal having a frequency corresponding to the flow velocity of a fluid to be applied, and a whistle provided near the outlet of the whistle so as to face each other.
Comprising a pair of microphones, a subtractor for subtracting an output signal of the pair of microphones, and a signal processing means for calculating the flow rate of the fluid from the output signal of the subtractor, before
The pair of microphones is the sound emitted from the whistle
A Uzufue flow meter characterized by the this <br/> for collecting approximately 180 degrees different from the phase of the signal out of the signal.

[0010]

The flow rate or flow velocity of the fluid is calculated from the output signal obtained by subtracting the output signal of a pair of microphones provided in the vicinity of the outlet of the whistle so as to be opposed to each other by a subtractor. In addition, the signal / noise ratio of the vortex whistle flow meter is increased to improve the measurement accuracy.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of a vortex-type current meter 1 according to a first embodiment of the present invention. The whirlpool 2 of the whirlpool-type current meter 1 comprises an inlet 3, a chamber 5, and an outlet 7. The blowing port 3 is connected to a gas pipe or the like, and corresponds to the upstream side of the whistle 2. The downstream side of the outlet 7 is open to the atmosphere, and a pair of microphones 9a and 9b are provided near the outlet 7 so as to face each other. To the microphones 9a and 9b, a subtractor 11 is connected, and further, a signal processing means 13 is connected. Signal processing means 13
Comprises a low-pass filter 15, a comparator 17, a counter / timer 19, and a multiplier 21. The multiplier 21 is connected to a display device 23.

A conventional whirlpool-type current meter 201 shown in FIG.
Similarly, the natural frequency of the sound wave oscillated by the whirlpool 2 is proportional to the instantaneous flow rate flowing through the gas pipe.

The microphones 9a and 9b detect the generated sound, and the subtracter 11 subtracts the output signals of both microphones 9a and 9b to reduce the influence of external noise. In the case of only the sound signal from the whirlpool 2, a sine wave is obtained,
The waveform is distorted when noise is added. This external noise is, in the case of a gas meter, the internal noise. The low-pass filter 15 in the signal processing means 13 removes noise in a higher frequency band than a predetermined cutoff frequency. The comparator 17 compares the magnitude of the amplitude with a predetermined threshold, shapes the waveform into a simple waveform, and forms a pulse. counter·
The timer 19 measures how many times the pulse is observed within a predetermined time. The multiplier 21 obtains the frequency from the measurement result of the counter / timer 19 to calculate the flow rate and the flow velocity of the fluid, and the display device 23 displays the obtained result.

FIG. 2 is a diagram showing a second embodiment, and FIG.
The microphones 9a and 9b provided on the side of the outlet 57 are provided in the fluid at the center of the outlet 57.

FIG. 3 is a schematic configuration diagram of a vortex-type current meter 51 for analyzing a power spectrum according to a third embodiment of the present invention. It comprises a blowing port 53, a chamber 55, and a blowing port 57. The difference from the vortex whistle current meter 1 of FIG.
The following is the signal processing part. The signal processing means 63 is connected to the subtracter 61, and is connected to the display device 71 via the band pass filter 65, the peak detector 67, and the flow rate / flow rate calculator 69.

In the vortex flowmeter 51, as in the vortex flowmeter 1 of FIG.
The output signal of 59b is subtracted. Next, the signal processing means 6
The band pass filter 65 within 3 extracts and processes only the acoustic signal of a predetermined band, and the peak detector 67 specifies the oscillation frequency of the peak. Next, the flow velocity / flow rate calculation device 69 calculates the flow velocity and the flow rate of the fluid from the peak frequency by calculation, and displays the obtained result on the display device 71.

In order to measure the frequency from the power spectrum obtained by frequency-analyzing the waveform, the frequency at the highest point of the spectrum is read as the frequency of the whistle oscillating sound, so that the signal processing method becomes complicated. Is high.

FIG. 4 is a view showing a fourth embodiment. In FIG. 3, microphones 59a and 59b provided on the side of the outlet 57 are provided in the fluid at the center of the outlet 57.

As described above, the place where the pair of microphones is installed is, as shown in FIGS.
2 and 4, or may be provided in the fluid at the center of the outlets 7 and 57, as shown in FIGS. 2 and 4. When it is small, the whistle 2, 52 on the side of the outlet 7, 57
When is large, it is easy to design if it is provided in the fluid at the center of the outlets 7, 57. In order to reduce the influence of noise, it is better to arrange the microphones 9a, 9b, 59a, 59b at the center of the outlets 7, 57, but the microphones 9a, 9b, 59a due to wind pressure from the outlets 7, 57. , 59b may be disposed on the side of the outlets 7, 57 when there is a risk of fatigue or breakage.

In the case of actual measurement using a vortex flute, if sound is collected by only one microphone, the waveform or power spectrum abnormality is caused by a change in gas flow rate, or is caused by external noise. Although it is difficult to determine whether the noise is a noise, the noise portion can be determined by collecting the sound with two microphones and performing the subtraction process.

FIG. 5 is a layout diagram for explaining an example of an experiment for reducing the influence of external noise on an acoustic signal generated from the whirlpool 102 of the vortex current meter 101. Installed in a sound-insulated room that shuts The gas flows from the direction A into the blow port 103 of the whirlpool 102.

Microphones 109a and 109b are provided near the outlet 107 of the whirlpool 102 so as to face each other, and a stereo microphone 11 is provided in the fluid near the center of the outlet 107. The stereo microphone 121 is held by a support 133 so as not to hinder exhaust from the outlet 7.

The microphones 109a and 109b are shown in FIG.
3 or the microphones 59a and 59b in FIG. 3, and the stereo microphone 131 corresponds to the microphones 9a and 9b in FIG. 2 or the microphones 59a and 59b in FIG.

Although the signal processing device and the display device are not shown, the signals from the microphones are shown in FIGS.
And the power spectrum processing apparatus shown in FIGS. 3 and 4 are switched and connected.

Approximately 2 m away from the whistle 102
5, and a precision sound level meter 137 is provided behind the whistle 102. An artificial noise whose frequency, level, and directivity are controlled is generated from the speaker 135, and the noise is emitted from the outlet 107.
It is measured by a precision sound level meter 137 installed in the vicinity. Generally, in octave analysis, which is one method of noise analysis, the center frequency and cutoff frequency of sound waves in octave steps used in the analysis are specified by standards.
The analysis is performed by adding white noise of only one octave having a center frequency of 125 Hz and cutting frequencies of 90 Hz and 180 Hz on both sides, which are close to the frequency band of the transmission sound of No. 2. The sound level of this noise was measured using a precision sound level meter 1
The measured value of 37 is 120 dB, which is close to the upper limit of general environmental noise.

FIG. 6 shows a whistle 102 and a microphone 10
9A and 109B are arrangement diagrams of a stereo microphone 131. In FIG. 3, the gas blowing direction B is from the back to the front. A microphone 109a is provided immediately above the air outlet 103, and a microphone 109b is provided at a position 180 degrees opposite to the microphone 109a at the center of the air outlet 107. The stereo microphone 131 is provided such that the front end portion is inserted into the center of the front end side of the outlet 107, and the right microphone is located immediately above the outlet 103. The stereo microphone 131 is unidirectional, and is held downward by the support 133 at the center of the outlet 107.

Next, the experimental results of each of the first to fourth embodiments will be briefly described with reference to waveform diagrams or power spectrum diagrams of FIGS. FIG. 7 shows a microphone 1 that has acquired an acoustic signal emitted from a whistle 102.
9A and 9B are diagrams showing waveforms output from 09a and 109b.
This corresponds to the first embodiment shown in FIG. 1 and is a case where a large amount of gas is introduced from the blowing port 103. FIG. 7 (b)
In the portion C of the waveform of the microphone 109b, the amplitude is equal to or smaller than a predetermined value, and is not recognized as a pulse. Also in the waveform of the microphone 109a in FIG. 7A, the amplitude is slightly smaller in the time zone corresponding to C in FIG. 7B. FIG. 7C shows the microphone 109a.
And a waveform obtained by inverting the waveform of the microphone 109b, and the influence of noise is removed.
Since the sine wave has almost the same amplitude, accurate pulsing and frequency measurement can be performed.

FIG. 8 is a power spectrum diagram obtained by frequency-analyzing the waveform shown in FIG. 7, and corresponds to the third embodiment shown in FIG. However, in FIGS. 8A and 8B, the peaks of the peaks of the spectra of the microphones 109a and 109b are both located at portions where the frequency is not correct, and the correct frequency is buried in noise. As shown in FIG. 8C, the spectrum of the microphone 109a and the microphone 10a
In the case of adding the inverted version of the spectrum of 9b, the noise portion is reduced and the acoustic signal component of the whistle 102 is added, so that the peak of the peak of the spectrum is restored to the correct frequency position, Can be read.

FIG. 9 is a waveform diagram in the case where a small amount of gas enters through the blowing port 103, and FIG. 10 is a power spectrum diagram obtained by frequency-analyzing the waveform shown in FIG.

FIG. 9 shows a comparison of these waveforms.
(A) The phase of the acoustic signal collected by the microphone 109a and the phase of the acoustic signal collected by the microphone 109b in FIG. 9B are not aligned. This is because the rotating airflow inside the whistle 102
It is considered that the air inlet 103 is tilted or biased due to the influence of the position. Since the phases are not aligned, the acoustic signal collected by the microphone 109a and the microphone 109
Even if the acoustic signal collected in b is superimposed, the superimposed waveform does not become twice as large as the individual waveform. 9 (b), the waveform is disturbed and a correct frequency cannot be obtained. However, in FIG. 10 (b), the peaks of the spectrum peaks are in the same portions as (a) and (c). It can be seen that the correct frequency can be read even when the gas liquid amount is small.

The waveform diagram of FIG. 11 corresponds to the second embodiment shown in FIG. 2, and the power spectrum diagram of FIG. 12 corresponds to the fourth embodiment shown in FIG. To allow a small amount of gas to enter.

In FIG. 11, a stereo microphone 131 is shown.
Is provided at the center of the outlet 107, and the left microphone and the right microphone are close to each other. Therefore, the waveform obtained by adding the acoustic signals collected by the microphones on both sides is almost twice the individual waveform. In addition, outlet 1
In the central part of 07, the flow rate sensitivity of the microphone is nearly three times as large as that in the outer peripheral part, and the influence of noise is reduced. Compared to the noise of 120 dB, it is considered that at least the central microphone detects the incompressible vibration of the exhaust gas from the outlet 107.

As described in detail above, in each of the above-described embodiments, a signal based on fluid vibration with noise is issued from the outlets 7 and 57. However, the microphones 9a and 59a and the microphones 9b and 59b generate signals. The signals based on the collected fluid vibrations output a symmetrical waveform having a phase difference of almost 180 degrees, so that the subtracters 11, 61
When the subtraction processing is performed in step (2), a signal almost twice as large as the original signal is obtained. However, since noises collected by the microphones 9a and 59a and the microphones 9b and 59b have almost the same phase, when the subtracters 11 and 61 perform a subtraction process, noise components are removed.

As described above, the signals output from the subtracters 11 and 61 have noise components removed, and the signal level is almost twice as high as the original signal. For this reason,
The output signals of the subtracters 11 and 61 are converted into signal processing means 13 and 63.
In the case where the flow rate is obtained by performing the signal processing in the above, the signal / noise ratio can be increased and the accuracy can be increased.

A hood concentric with the outlets 7 and 57 may be attached to the whirlpools 2 and 52, similarly to the conventional whisker-type current meter 301 with hood shown in FIG. In this case, the sound wave from the downstream side approaches the plane wave, so that the noise reduction effect can be enhanced.

Further, in this embodiment, the unidirectional stereo microphone 131 is used, but a combination of omnidirectional microphones back to back may be used.

Although the present embodiment has been described with respect to the case where gas is all measured, liquid can be measured when an underwater microphone is used.

[0038]

As described above in detail, according to the present invention, the influence of noise components due to extraneous noise and vibration is reduced, and a high signal / noise ratio and high precision vortex whistle flowmeter and vortex whistle are provided. A flow meter can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a vortex-type current meter 1.

FIG. 2 is an explanatory diagram of a position change of microphones 9a and 9b in FIG.

FIG. 3 is a schematic configuration diagram of a vortex-type current meter 51;

FIG. 4 is an explanatory diagram of a position change of the microphones 59a and 59b in FIG.

FIG. 5 is an experimental layout of the whirlpool 102

6 is a whirlpool 102 and a microphone 109 shown in FIG.
Layout diagram

FIG. 7 is a waveform diagram

FIG. 8 is a power spectrum diagram.

FIG. 9 is a waveform diagram when the flow rate is reduced as compared with the state of FIG. 7;

FIG. 10 is a power spectrum diagram when the flow rate is reduced as compared with the state of FIG. 7;

FIG. 11 is a waveform diagram when a stereo microphone 131 is used.

FIG. 12 is a power spectrum diagram when a stereo microphone 131 is used.

FIG. 13 is a schematic configuration diagram of a conventional vortex-type current meter 201;

FIG. 14 is a schematic configuration diagram of a conventional whirlpool-type current meter 301 with a hood.

[Explanation of symbols]

 1 whirlpool-type current meter 2 whirlpool 3 blow-in port 5 chamber 7 blow-out ports 9a, 9b microphone 11 subtractor 13 signal Processing means 15 Low-pass filter 17 Comparator 19 Counter / timer 21 Multiplier 23 Display device 51 Whirlpool velocimeter 63 Signal processing means 65 …… Band pass filter 67 …… Peak detector 69 ……… Flow velocity / flow rate calculation device

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01F 1/00-9/02

Claims (6)

(57) [Claims] 1. A whistle that emits an acoustic signal having a frequency corresponding to the flow velocity of a fluid to be applied, a pair of microphones provided near the outlet of the whistle so as to face each other, and the pair of microphones And a signal processing means for calculating the flow velocity of the fluid from the output signal of the subtractor. The pair of microphones includes a sound emitted from the whistle.
A vortex-type current meter characterized by collecting signals having phases substantially different from each other by 180 degrees among reverberation signals . 2. The vortex-type current meter according to claim 1, wherein the pair of microphones is provided on a side of an outlet of the whistle. 3. The vortex-type anemometer according to claim 1, wherein the pair of microphones are provided in a fluid blown out from the outlet of the whistle. 4. A whistle that emits an acoustic signal having a frequency corresponding to the flow velocity of a fluid to be applied, a pair of microphones provided so as to face each other near an outlet of the whistle, and the pair of microphones. And a signal processing means for calculating the flow rate of the fluid from the output signal of the subtractor, wherein the pair of microphones emit a sound emitted from the whistle.
A vortex-type flowmeter, which collects a signal having a phase difference of almost 180 degrees among reverberation signals . 5. The whistle flow meter according to claim 4, wherein the pair of microphones is provided on a side portion of the outlet of the whistle. 6. The vortex-type flowmeter according to claim 4, wherein the pair of microphones are provided in a fluid blown out from an outlet of the whirlpool.