JPH0337522A - Current meter - Google Patents

Abstract

PURPOSE:To measure flow speed with excellent linearily, stability and reproducibility with a signal having a high S/N ratio by mixing bubbles into fluid, and detecting ultrasonic waves which are generated by the collapse of the bubbles. CONSTITUTION:The output of a bubble generator 2 is engaged with fluid in a pipe 1. The generator 2 feeds compressed air from a pressure source 3 into a bubbler 6 which is provided on the inner wall surface of the pipe 1 and has many through-holes on the surface through a pressure regulating valve 4 and an opening and closing valve 5. Many generated bubbles are mixed into the fluid. The bubbles which are mixed into a conducting body are fixed with a holding rod 8 at the approximately central position in the pipe 1. The bubbles hit an obstacle 7 having discontinuous surface for the flow. When the bubbles collapse, ultrasonic waves in a broad frequency band are generated in the fluid. The ultrasonic waves from sound sources in the fluid due to the hit of the bubbles are propagated in the fluid in the pipe 1. The ultrasonic waves are received with an ultrasonic wave detector 9 which is mounted at the downstream side. The signals in response to the ultrasonic wave levels are obtained. The flow speed of the fluid is measured in a measuring circuit 12, and the result is displayed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a current meter that measures the flow rate of a fluid flowing in a pipe, for example, and particularly a current meter that measures the flow rate by detecting ultrasonic waves generated in the fluid. Regarding.

[Prior art] For measuring the flow rate of liquid in pipes, see "Flow Measurement Handbook" (July 1978), Nikkan Kogyo Shimbun, p. 264, "
Other Flow Measurement Methods”.

According to this, the liquid flowing inside the pipe has a shearing effect on the liquid due to vortices and turbulence, and ultrasonic waves with a wide frequency band are generated within the fluid, and these ultrasonic waves are transmitted to a detector attached to the outer circumferential surface of the pipe. It is described that when detected using this method, the flow velocity can be measured from the signal.

[Problems to be Solved by the Invention] In the conventional flow meter as described above, the level of ultrasonic waves generated by the shearing action of the liquid in the pipe is relatively low.
The signal level received by the detector is low and a sufficient signal-to-noise ratio cannot be obtained. In addition, although flow rate measurements based on these signals can be used to identify the presence or absence of liquid flow in a pipe, they do not have the required linearity, stability, and reproducibility as a flow meter.
The problem was that it could not actually be used to measure flow velocity.

This invention was made to solve this problem, and by mixing air bubbles into a fluid and detecting the ultrasonic waves generated by the collapse of the air bubbles, a signal with a large signal-to-noise ratio is detected. The purpose of the present invention is to obtain a current meter capable of measuring flow velocity with excellent linearity, stability, and reproducibility.

[Means for Solving the Problems] A current meter according to the present invention includes a bubble generator that supplies air to a pipe-directed fluid to generate bubbles in the fluid, and a bubble generator that is disposed in the fluid in which the bubbles are mixed. an obstacle having a discontinuous surface with respect to the flow of the fluid; an ultrasonic detector attached to the outer peripheral surface of the downstream side of the obstacle and sensitive to ultrasound mainly generated by the collapse of bubbles in the fluid; A measurement circuit that outputs a signal responsive to the amplitude of the received signal from the device is provided.

[Function] In this invention, since an obstacle is placed in the fluid mixed with air bubbles, a large number of air bubbles collide with the obstacle and collapse or recombine, resulting in a high level in the fluid. Ultrasonic waves are generated.

The ultrasonic detector provided on the outer peripheral surface of the pipe outputs an electrical signal proportional to the ultrasonic level within the fluid, and the fluid flow velocity is measured based on the amplitude of the signal in a frequency band higher than the audible band.

Since air bubbles are artificially mixed into the fluid and interference from the surrounding environment is avoided, a received signal with a high signal-to-noise ratio can be obtained, allowing measurements with excellent linearity, stability, and reproducibility. measurement accuracy can be improved.

[Embodiment] An embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram of a flowmeter according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along line AA in FIG. In the figure, 1 is a conduit through which fluid flows, and 2 is a bubble generator that generates bubbles and mixes the bubbles into the fluid. 3 is a pressure source that generates air pressure using a near compressor, etc.; 4
5 is a pressure regulating valve that adjusts the level of air pressure, 5 is an on-off valve, and 6 is a bubble generator provided on the inner wall surface of the conduit 1, and these constitute the bubble generator 2. Reference numeral 7 indicates an obstacle provided in the fluid on the downstream side of the bubble generator 2, and reference numeral 8 indicates a holding rod for disposing the obstacle 7 at a predetermined position within the conduit 1. Reference numeral 9 denotes an ultrasonic detector that detects ultrasonic waves generated in the fluid, and is mounted on the outer circumferential surface of the conduit 1 on the downstream side of the obstacle 7.

12 is a measurement circuit that measures the flow velocity based on the detection signal of the ultrasonic detector 9. 13 is an amplifier; 14 is a filter that limits the frequency band of the received signal from the ultrasonic detector 9;
15 is a detection circuit, 1G is an integration circuit, device 7 is a sample and hold circuit, 18 is a control circuit, and 19 is an indicator, which constitute the measurement circuit 12.

In the current meter configured as described above, the output of the bubble generator 2 is engaged with the fluid in the pipe 1 1 that flows in the direction of the arrow. The bubble generator 2 is installed on the inner wall surface of the conduit 1 to supply pressurized air from a pressure source 3 using a near compressor or the like via a pressure regulating valve 4 and an on-off valve 5. The fluid is supplied to a bubbler 6 having a through hole, and a large number of generated bubbles are mixed into the fluid.

The bubbles mixed in the fluid are fixed at a substantially central position in the pipe line 1 by a holding rod 8, and collide with an obstacle 7 having a discontinuous surface against the flow. Ultrasonic waves with a wide frequency band are generated. FIG. 3 is an external view showing an example of the obstacle 7, in which (a) is a conical shape, and (b) is a conical shape.
) show examples of cylindrical obstacles.

When the bubble hits the obstacle 7, it becomes a sound source within the fluid, and the level of the resulting ultrasound wave is proportional to the flow rate of the fluid.

The ultrasonic waves generated in the fluid propagate through the fluid and the pipe line 1, and are received by the ultrasonic detector 9 mounted on the outer peripheral surface of the downstream side of the pipe line 1 in which the obstacle 7 is installed. Then, the ultrasonic detector 9 outputs an electrical signal according to the ultrasonic level.

In this case, if the ultrasonic detector 9 uses, for example, a bimorph structure in which two piezoelectric vibrators are superimposed and their additive output is obtained, highly sensitive detection can be performed in a wide frequency band. Furthermore, if the mounting surface of the ultrasonic detector 9 to the conduit 1 is flattened and the ultrasonic detector 9 is housed in a container made of acoustic insulation material to suppress external noise, low-level ultrasonic waves in the conduit 1 can be suppressed. can be received.

Figure 4 is a time chart showing an example of the waveform received by the ultrasonic detector. The ultrasonic waves generated by the collapse of bubbles are in the form of pulses, and the amount of bubbles is larger than when no bubbles are mixed into the fluid. increases, and the level increases as ultrasonic waves are added due to the collapse of the bubbles.

The output of the ultrasonic detector 9 is applied to the measurement circuit 12, and the received signal with a wide frequency band is amplified by a high gain amplifier I3, and then filtered by a filter 14 to eliminate interference in the audible frequency band such as electrical noise and low frequency vibrations. Received signals are limited to high frequency bands that avoid For example, the signal is applied to the detection circuit 15 through a band-limited filter 14 with a pass band of 10 to 50 Hz.

For the received signal with a large signal-to-noise ratio, the envelope detection of the received signal is performed in the detection circuit 15, and the level information is held.
The integration circuit 16 converts the received signal into a DC signal and simultaneously averages it.

When measuring the DC signal corresponding to the average flow velocity of the fluid from the integrating circuit 16, the data is held in the sample hold circuit 17, and the average flow velocity is indicated to the indicator 19. Operation of integration circuit 16 and sample hold circuit 17
The sampling operation in is performed by the reference pulse of the control circuit 18.

FIG. 5 is a characteristic diagram showing an example of the correlation between the flow velocity and the measured output. The flow velocity of the fluid and the measured output of the measurement circuit 12 are in a proportional relationship, and a sufficient correlation is obtained. Since bubbles are mixed into the fluid and a sufficient level of ultrasonic waves are generated by collision with the obstacle 7, the amplitude of the received signal changes linearly with respect to the flow velocity, and furthermore, stability and reproducibility are improved. has been improved and flow velocity can be measured with sufficient accuracy.

As mentioned above, the collapse of air bubbles in the fluid flowing in the pipe 1 becomes a sound source and generates ultrasonic waves in the fluid, but the level of these ultrasound waves changes depending on the flow velocity of the fluid, and the ultrasonic waves in the fluid is detected using the ultrasonic detector 9 attached to the outer peripheral surface of the conduit 1, so the equipment configuration is simplified. Furthermore, since the ultrasonic detector 9 is attached to the outer circumferential surface of the conduit 1, maintenance and inspection can be easily performed, there is no adhesion of fluid contaminants, deterioration of detection sensitivity is avoided, and stable performance can be obtained over a long period of time.

[Effects of the Invention] As explained above, the present invention mixes a large amount of air bubbles into a fluid, causes the air bubbles to collide with an obstacle, generates high-level ultrasonic waves in the fluid, and increases the level of the ultrasonic waves. Since the flow velocity is measured by measuring the flow rate, the signal-to-noise ratio of the received signal is improved, and the linearity, stability, and reproducibility of the measurement can be improved. Furthermore, the received signal from the ultrasonic detector can be avoided from interference in the audible frequency band such as electrical noise and low-frequency vibrations, and stable measurements can be made in the high frequency band.

Furthermore, since it only receives the sound waves inside the pipe, the electrical measurement system can be simplified, and since the ultrasonic detector is not affected by the adhesion of fluid contaminants, it can be used for a long time without degrading the detector sensitivity. This has the advantage that stable performance can be obtained over a period of time, and maintenance and inspection can be easily performed.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of a current meter according to an embodiment of the present invention, Fig. 2 is a sectional view taken along line A-A in Fig. 1, and Fig. 3 (a) (b).
) is an outline diagram showing an example of an obstacle, FIG. 4 is a time chart showing an example of a waveform received by an ultrasonic detector, and FIG. 5 is a characteristic diagram showing an example of the correlation between flow velocity and measurement output. In the figure, 1 is a pipe line, 2 is a bubble generator, 3 is a pressure source,
4 is a pressure regulating valve, 5 is an on-off valve, 6 is a bubbler, 7 is an obstacle, 8 is a holding rod, 9 is an ultrasonic detector, 12 is a measurement circuit,
13 is an amplifier, 14 is a filter, 15 is a detection circuit, 1B
1 is an integrating circuit, 17 is a sample and hold circuit, 18 is a control circuit, and 19 is an indicator. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] A bubble generator that supplies air to a fluid flowing in a pipe to generate bubbles in the fluid; an ultrasonic detector mounted on the outer peripheral surface of the pipe on the downstream side of the obstacle and sensitive to ultrasonic waves mainly generated by the collapse of bubbles in the fluid; and a received signal from the ultrasonic detector. A current meter characterized in that it has a measurement circuit that outputs a signal responsive to the amplitude of.