JP6909100B2 - Ultrasonic flow meter and ultrasonic flow measurement method - Google Patents

Description

The present invention relates to an ultrasonic flow rate measurement technique for reducing a noise component of ultrasonic waves propagating in an ultrasonic absorber attached to an outer peripheral surface of a pipe during flow rate measurement.

In general, a clamp-on type ultrasonic flowmeter transmits ultrasonic waves into the pipe from one transducer mounted on the outside of the pipe, and the other transducer also mounted on the outside of the pipe transmits ultrasonic waves into the pipe. It receives ultrasonic waves that have passed through the fluid flowing through the pipe, and measures the flow velocity and flow rate of the fluid according to the reception result.
At this time, in the reception result obtained by the ultrasonic transmitter, in addition to the signal component consisting of the fluid propagating wave propagating in the fluid flowing in the pipe, the pipe propagating propagating in the outer peripheral surface, the inner peripheral surface, or the wall portion of the pipe. A noise component consisting of waves is included. Therefore, this noise component lowers the measurement accuracy of the flow rate.

Conventionally, as a technique for reducing such a noise component, a mat-shaped ultrasonic absorber is attached to the outer peripheral surface of the pipe to absorb the pipe propagating wave propagating in the outer peripheral surface, the inner peripheral surface, or the wall of the pipe. A technique has been proposed (see, for example, Patent Document 1).
This ultrasonic absorber is made of an elastic mat-like elastic body whose main material is rubber or a polymer material, such as uncrosslinked buruchi rubber.

When ultrasonic waves propagate in different media, the transmittance and reflectance at the medium interface change depending on the magnitude of the difference in acoustic impedance between the media. In general, since the acoustic impedance difference between the pipe and the atmosphere outside the pipe is large, the ratio of the pipe propagating wave propagating through the pipe to the atmosphere is small. On the other hand, since the ultrasonic absorber has a larger acoustic impedance than the atmosphere, the difference in acoustic impedance from the pipe is smaller than the difference in acoustic impedance between the pipe and the atmosphere outside the pipe. As a result, the noise component composed of the pipe propagating wave can be reduced by attaching the ultrasonic absorber to the outer peripheral surface of the pipe.

Japanese Unexamined Patent Publication No. 2014-157129

However, in such a conventional technique, although the noise component consisting of the pipe propagating wave propagating in the pipe can be reduced by the ultrasonic absorber attached to the outer peripheral surface of the pipe, the absorber propagating wave propagating in the ultrasonic absorber itself. There was a problem that a noise component consisting of the above was generated.
In particular, when the pipe is a small-diameter pipe having a diameter of 25 A or less, the distance between the transducers that transmit and receive ultrasonic waves is short, and the ultrasonic absorber attached between these transducers on the outer peripheral surface of the pipe is also short. Therefore, the noise component composed of the absorber propagating wave tends to be large, and the measurement accuracy of the flow rate tends to be lowered.

The present invention is for solving such a problem, and provides an ultrasonic flow measurement technique capable of reducing noise components caused by ultrasonic waves propagating in an ultrasonic absorber attached to an outer peripheral surface of a pipe. I am aiming.

In order to achieve such an object, the ultrasonic flow meter according to the present invention is based on ultrasonic waves transmitted and received so as to pass through the fluid flowing in the pipe by a transducer provided on the outer peripheral surface of the pipe. An ultrasonic flowmeter that measures the flow rate, and is an ultrasonic absorber that is provided on the outer peripheral surface of the pipe and absorbs the pipe propagating wave propagating in the pipe among the ultrasonic waves, and the outer peripheral surface of the pipe. Among them, a propagation suppressing unit provided between the ultrasonic absorber and the transducer and suppressing the propagation of the absorber propagating wave of the ultrasonic waves that has propagated through the ultrasonic absorber to the transducer is provided. ing.

Further, one configuration example of the ultrasonic flowmeter according to the present invention is made of a mat-like elastic porous body provided on the outer surface of the ultrasonic absorber, and is formed at an interface between the pipe and the ultrasonic absorber. For operation, an ultrasonic shock absorber that buffers the reflection of the pipe propagating wave, and a tightening portion that is provided on the outer surface of the ultrasonic shock absorber and presses and tightens the ultrasonic shock absorber in the direction of the pipe. By changing the tightening force of the tightening portion accordingly and changing the degree of deformation of the ultrasonic shock absorber due to the pressing to change the acoustic impedance of the ultrasonic shock absorber, it is reflected at the interface. The pipe, the ultrasonic absorber, and an acoustic matching adjusting unit for adjusting the acoustic matching status regarding the acoustic impedance of the ultrasonic buffer, which influence the intensity of the pipe propagating wave, are further provided, and the propagation suppressing unit is provided. Of the outer peripheral surfaces of the pipe, the ultrasonic absorber, the ultrasonic shock absorber, and the tightening portion and the transducer are provided.

Further, in one configuration example of the ultrasonic flow meter according to the present invention, the propagation suppressing portion is made of a porous material or an air layer having a large number of voids for containing air.

Further, the ultrasonic flow rate measuring method according to the present invention measures the flow rate of the fluid based on the ultrasonic waves transmitted and received so as to pass through the fluid flowing in the pipe by a transducer provided on the outer peripheral surface of the pipe. An ultrasonic flow measurement method used in a meter, wherein an ultrasonic absorber provided on the outer peripheral surface of the pipe absorbs a pipe propagating wave propagating in the pipe among the ultrasonic waves, and an ultrasonic absorption step. The propagation suppressing portion provided between the ultrasonic absorber and the transducer on the outer peripheral surface of the pipe is the absorber propagating wave of the ultrasonic waves that has propagated through the ultrasonic absorber with respect to the transducer. It includes a propagation suppression step that suppresses propagation.

According to the present invention, it is possible to reduce the noise component composed of the pipe propagating wave propagating in the pipe, and also reduce the noise component composed of the absorber propagating wave propagating in the ultrasonic absorber itself. Therefore, it is possible to improve the S / N ratio indicating the ratio of the noise component to the signal component corresponding to the fluid propagating wave propagating in the fluid X, and as a result, it is possible to obtain extremely good measurement accuracy.

It is an external view of an ultrasonic flow meter. It is sectional drawing of the ultrasonic flowmeter in the radial direction of a pipe. It is sectional drawing of the ultrasonic flowmeter about the longitudinal direction of a pipe. It is explanatory drawing which shows the principle of acoustic matching. It is a graph which shows the acoustic matching characteristic. It is a signal waveform diagram which shows absorption of a noise component.

Next, an embodiment of the present invention will be described with reference to the drawings.
[Ultrasonic flowmeter]
First, the ultrasonic flow meter 1 according to the embodiment of the present invention will be described with reference to FIGS. 1 to 3. FIG. 1 is an external view of an ultrasonic flowmeter. FIG. 2 is a cross-sectional view of an ultrasonic flowmeter in the radial direction of the pipe. FIG. 3 is a cross-sectional view of an ultrasonic flowmeter in the longitudinal direction of the pipe.

The ultrasonic flowmeter 1 is composed of a clamp-on ultrasonic flowmeter as a whole, and transmits ultrasonic waves from one of the transducers 13A (13B) attached to the outer peripheral surface 31 of the pipe 30 toward the inside of the pipe 30. The other transducer 13B (13A) attached to the outer peripheral surface 31 of the pipe 30 receives ultrasonic waves that have passed through the fluid X such as steam flowing in the pipe 30, and measures the flow rate of the fluid X according to the reception result. Has the function of

As shown in FIG. 1, the ultrasonic flow meter 1 according to the present embodiment mainly includes a flow meter main body 10, transducers 13A and 13B, an ultrasonic absorber 14, an ultrasonic buffer 21, and tightening. A unit 22, an acoustic matching adjustment unit 23, and propagation suppression units 24A and 24B are provided. Of these configurations, the ultrasonic shock absorber 21, the tightening section 22, the acoustic matching adjustment section 23, and the propagation suppression sections 24A and 24B constitute the ultrasonic shock absorber 20.

The flow meter main body 10 is composed of a housing in which various circuit units for ultrasonic flow rate measurement are housed, and a switching unit 11 and a measurement processing unit 12 are provided as main circuit units.

The switching unit 11 is a circuit unit that switches and connects the measurement processing unit 12 and the transducers 13A and 13B according to the switching signal output from the measurement processing unit 12. As a result, when transmitting ultrasonic waves from the transducer 13A, the electric transmission signal from the measurement processing unit 12 is output to the transducer 13A, and the electric reception signal from the transducer 13B is output to the measurement processing unit 12, and the transducer is When the ultrasonic waves are transmitted from the 13B, the electric transmission signal from the measurement processing unit 12 is output to the transducer 13B, and the electric reception signal from the transducer 13A is output to the measurement processing unit 12.

The measurement processing unit 12 is composed of a CPU and a signal processing circuit as a whole, and has a function of generating an electric transmission signal composed of a pulse signal modulated at a constant frequency, and the generated electric transmission signal is transmitted to the transducers 13A and 13B by the switching unit 11. Based on the function of exchanging ultrasonic waves in the up and down directions between the transducers 13A and 13B by switching output, and the propagation time difference obtained from the uplink and downlink electric reception signals obtained thereby. It has a function of calculating the speed and the flow rate of the fluid flowing in the pipe 30.

The transducers 13A and 13B are composed of an ultrasonic transmitter / receiver as a whole, convert an electric transmission signal output from the flow meter main body 10 into ultrasonic waves, and convert the electric transmission signal into ultrasonic waves into a body X in the pipe 30 via the pipe wall 32 of the pipe 30. It has a function of transmitting the ultrasonic waves toward the pipe wall 32 and a function of receiving ultrasonic waves arriving from the inside of the pipe 30 via the pipe wall 32, converting the ultrasonic waves into an electric reception signal, and outputting the ultrasonic waves to the flow meter main body 10. These transducers 13A and 13B are obliquely inclined to the upstream position and the downstream side position of the fluid X with the reference measurement point P provided at the center position inside the pipe 30 on the outer peripheral surface 31 of the pipe 30. It is arranged to face each other.

Generally, when ultrasonic waves are transmitted and received between the transducers 13A and 13B in the up direction U and the down direction D with respect to the flow direction F of the fluid X, the fluid propagating the fluid according to the flow velocity of the fluid X due to such an obliquely opposed arrangement. There is a propagation time difference in the propagated wave. Therefore, the flow rate of the fluid X can be calculated from this propagation time difference and the angle of the ultrasonic wave with respect to the fluid X. In the present embodiment, as in Patent Document 1 described above, a case where the flow rate is measured by such a propagation time difference method will be described as an example, but the present invention is not limited to this, and the Doppler method is also used. The embodiments can be applied in the same manner.

The ultrasonic absorber 14 is made of a mat-like elastic body mainly made of rubber or a polymer material such as uncrosslinked buruchi rubber, and is provided on the outer peripheral surface 31 of the pipe 30 from the transducers 13A and 13B. Among the transmitted ultrasonic waves, it has a function of absorbing a pipe propagating wave propagating in the pipe 30 itself, such as in the outer peripheral surface 31, the inner peripheral surface 32, or the wall portion 33 of the pipe 30.

The ultrasonic shock absorber 21 is made of an open-cell mat-like elastic porous body mainly made of an organic material such as a silicone resin, such as a silicone rubber sponge, and is formed on the outer surface of the ultrasonic absorber 14. It is provided and has a function of buffering the reflection of the pipe propagating wave at the interface between the pipe 30 and the ultrasonic absorber 14.
When the fluid X has a high temperature such as steam, a heat-resistant silicone resin may be used. In addition, if a sponge made of a polyimide resin is used, for example, a fluid X having a higher temperature can be used. ..

The tightening portion 22 is provided on the outer surface of the ultrasonic shock absorber 21 and has a function of pressing and tightening the ultrasonic shock absorber 21 in the direction of the pipe 30, and includes the pressing plate 22A and the tightening band 22B. It is composed of.

The pressing plate 22A is made of a metal plate such as stainless steel, is provided on the outer surface of the ultrasonic shock absorber 21, and has a function of dispersing the tightening force of the tightening band 22B.
The tightening band 22B is made of, for example, a metal plate such as stainless steel, is provided so as to orbit the outer surface of the pressing plate 22A, and by tightening the pressing plate 22A, the ultrasonic shock absorber 21 further via the pressing plate 22A. Has a function of evenly pressing the entire ultrasonic absorber 14 against the outer surface of the pipe 30.

The acoustic matching adjustment unit 23 changes the tightening force of the tightening unit 22 by the tightening band 22B by the tightening operation of the operator, and changes the degree of deformation of the ultrasonic shock absorber 21 due to pressing, thereby changing the pipe 30. Ultrasonic waves that influence the acoustic matching status regarding the acoustic impedance of the pipe 30, the ultrasonic absorber 14, and the ultrasonic shock absorber 21, which influence the intensity of the pipe propagating wave reflected at the interface between the ultrasonic absorber 14 and the ultrasonic absorber 14. It has a function of adjusting the acoustic impedance of the buffer 21.

The propagation suppression portion 24A is located between the ultrasonic absorber 14 and the transducer 13A, and further between the ultrasonic shock absorber 21 and the tightening portion 22 (holding plate 22A) and the transducer 13A in the outer peripheral surface 31 of the pipe 30. It has a function of suppressing the propagation of the absorber-propagated wave propagating in the ultrasonic absorber 14 among the ultrasonic waves transmitted from the transducer 13B to the transducer 13A.

The propagation suppression portion 24B is located between the ultrasonic absorber 14 and the transducer 13A, and further between the ultrasonic shock absorber 21 and the tightening portion 22 (holding plate 22A) and the transducer 13A in the outer peripheral surface 31 of the pipe 30. It is provided in and has a function of suppressing the propagation of the absorber-propagated wave propagating in the ultrasonic absorber 14 among the ultrasonic waves transmitted from the transducer 13A to the transducer 13B.

The propagation suppressing portions 24A and 24B are made of a continuous cell type porous material having a large number of voids for containing air. When the fluid X has a high temperature such as steam, a heat-resistant silicone resin may be used. In addition, if a sponge made of a polyimide resin is used, for example, a fluid X having a higher temperature can be used. .. Further, as the propagation suppressing portions 24A and 24B, inorganic fibers such as glass wool, rock wool and urethane foam, which are open cell type porous materials, may be used. The propagation suppression units 24A and 24B may be composed of an air layer in addition to such a porous material, and the propagation suppression units 24A and 24B can be realized with a simple configuration.

[How to attach the ultrasonic shock absorber]
Next, a method of attaching the ultrasonic buffer 21 to the ultrasonic flow meter 1 will be described with reference to FIGS. 1 to 3.
Here, as in Patent Document 1 described above, a case where the ultrasonic shock absorber 20 is later attached to the ultrasonic flow meter 1 in which the ultrasonic absorber 14 is already provided in the pipe 30 will be described as an example. ..

First, the ultrasonic shock absorber 21 is attached to the outer surface of the ultrasonic absorber 14 by a process such as winding and bonding, and then ultrasonic waves are provided by a tightening portion 22 provided on the outer surface of the ultrasonic shock absorber 21. The shock absorber 21 is pressed and tightened in the direction of the pipe 30. At this time, with respect to the tightening portion 22, after the pressing plate 22A is wound around the outer surface of the ultrasonic shock absorber 21, the tightening band 22B is circulated around the outer surface of the pressing plate 22A.

After that, the acoustic matching adjustment unit 23 is operated to change the tightening force of the tightening band 22B of the tightening unit 22. As a result, the degree of deformation of the ultrasonic buffer 21 due to the pressing of the tightening portion 22 changes, and the acoustic impedance of the ultrasonic buffer 21 changes. Therefore, the acoustic matching status regarding the acoustic impedance of the pipe 30, the ultrasonic absorber 14, and the ultrasonic shock absorber 21 is adjusted, and the intensity of the pipe propagating wave reflected at the interface between the pipe 30 and the ultrasonic absorber 14 is adjusted. Is reduced.

In this embodiment, the case where the pressing plate 22A is used has been described as an example, but if the ultrasonic buffer 21 is not partially deformed by the tightening band 22B, the pressing plate 22A is omitted and tightening is performed. The ultrasonic buffer 21 may be directly tightened by the band 22B.
Further, in the present embodiment, the case where the tightening band 22B is used has been described as an example, but the holding plate 22A may be directly tightened by the acoustic matching adjusting unit 23.

[Operation of the present embodiment]
Next, with reference to FIG. 4, the absorption action of the pipe propagating wave propagating in the pipe 30 will be described as the operation of the ultrasonic flow meter 1 according to the present embodiment. FIG. 4 is an explanatory diagram showing the principle of acoustic matching.

When ultrasonic waves propagate in an arbitrary medium, the speed at which the medium particles vibrate at a constant sound pressure differs depending on the medium. Generally, the ease (difficulty) of vibration of such medium particles is called acoustic impedance, and the acoustic impedance Z is the product of the density ρ of the medium and the speed of sound c in which ultrasonic waves propagate in the medium, Z =. It is represented by ρ · c.

When ultrasonic waves propagate between different media, the transmittance and reflectance of ultrasonic waves at the medium interface change according to the difference in acoustic impedance of each medium, and the larger the difference in acoustic impedance, the higher the reflectance.
When propagating between media having such a large difference in acoustic impedance, there is a method of matching the acoustic impedance by inserting a third medium called an acoustic matching layer between the two media.

As shown in FIG. 4, if between the medium M ₁ and the medium M ₂ of the acoustic impedance Z ₂ of the acoustic impedance Z _1, was inserted medium M ₃ in the acoustic impedance Z ₃ in the width L, the medium M _1, M _{3. The} acoustic matching conditions for matching the acoustic impedance in the entire M ₂ are expressed by the following equations (1) and (2).
L = λ ₃ /4… (1)
Z ₃ = √ Z _{1 Z 2} … (2)
Note that lambda ₃ is the characteristic wavelength of the medium M _3, if the density of the medium M ₃ and the speed of sound in the medium M ₃ and C ₃ has a [rho _3, obtained by _{λ 3 = C 3 / ρ 3} .

When such an acoustic matching condition is satisfied, the acoustic matching condition becomes a matching state, _{the reflectance at each medium interface R 13} and R ₂₃ becomes zero, and the intensity I of the reflected wave with respect to the ultrasonic wave incident on the _{medium M 1 3} becomes the cello. As a result, the reflection loss becomes zero, and _{the intensity I 1 of the} ultrasonic waves incident on the _{medium M 1} becomes equal to _{the intensity I 2 of the} ultrasonic waves emitted from the medium M 2.

The present invention provides good propagation of ultrasonic waves by improving the acoustic matching condition even when the acoustic impedances Z ₁ , Z ₃ , and Z _{2 of these three media M 1} , M ₃ , and M _{2 are different from each other.} Focusing on the fact that the characteristics can be obtained, these media M ₁ and M ₃ are regarded as the wall 33 of the pipe 30 and the ultrasonic absorber 14, and the ultrasonic shock absorber 21 corresponding to the _{medium M 2 is regarded as the ultrasonic absorber 14.} It is provided on the outer surface of the pipe 30 so as to efficiently absorb the pipe propagating wave propagating in the pipe 30.

Further, in an elastic porous body such as a silicone rubber sponge, attention is paid to the fact that the volume of bubbles is reduced and the density is changed by pressing and deforming, and the acoustic impedance is also changed. By providing a tightening portion 22 on the outer surface of the pipe and adjusting the tightening force, that is, the pressing pressure on the ultrasonic shock absorber 21 by the acoustic matching adjusting portion 23, the pipe 30 is adjusted according to the acoustic impedance of the pipe 30 which differs depending on the pipe material. , The acoustic impedance of the ultrasonic shock absorber 21, which affects the acoustic matching status of the ultrasonic absorber 14 and the ultrasonic shock absorber 21, is adjusted.

FIG. 5 is a graph showing the acoustic matching characteristics, in which the horizontal axis represents the pipe acoustic impedance Z ₁ and the vertical axis represents the ultrasonic buffer acoustic impedance Z ₂ . In FIG. 5, the acoustic matching characteristic Q is _{the pipe acoustic impedance Z 1 in} which the _{acoustic matching self-requirement is satisfied when the acoustic impedance Z 3} of the ultrasonic absorber 14 is fixed to 1.9e + 06 [Pa · s / m]. The relationship with the ultrasonic buffer acoustic impedance Z _{2 is shown.}

For example, when the pipe 30 is made of an aluminum pipe (AL), its acoustic impedance Z ₁ is about 17e + 06 [Pa · s / m]. _{Therefore, it can be seen from the acoustic matching characteristic Q that the ultrasonic buffer acoustic impedance Z 2} from which a good acoustic matching condition can be obtained with the pipe 30 is about 0.22e + 06 [Pa · s / m].
On the other hand, when the pipe 30 is made of stainless steel pipe (SUS), the pipe acoustic impedance Z ₁ is about 45 to 46e + 06 [Pa · s / m], and _{when the pipe 30 is made of SGP pipe (SGP), the pipe acoustic impedance Z 1} is. It becomes about 46e + 06 [Pa · s / m]. _{Therefore, it can be seen from the acoustic matching characteristic Q that the ultrasonic buffer acoustic impedance Z 2} from which a good acoustic matching condition can be obtained with these pipes 30 is about 0.08e + 06 [Pa · s / m].

On the other hand, since the ultrasonic buffer acoustic impedance Z ₂ of the bubble-free silicone rubber (SG) itself is about 0.2e + 06 [Pa · s / m], in the case of aluminum piping, the bubble-free silicone By using the rubber as the ultrasonic buffer 21, a good acoustic matching condition can be obtained.
On the other hand, since the acoustic impedance of the ultrasonic shock absorber of air (Air) is about 0.0004e + 06 [Pa · s / m], a good acoustic matching condition can be obtained by using the silicone rubber sponge as the ultrasonic shock absorber 21. Will be.

Therefore, by using a silicone rubber sponge as the ultrasonic buffer 21 and pressing and deforming it, it is possible to obtain a good acoustic matching condition with various pipes from aluminum pipes to stainless steel pipes and SGP pipes. Z ₂ can be obtained.
As a result, the acoustic matching condition of the pipe 30, the ultrasonic absorber 14, and the ultrasonic buffer 21 can be improved by an extremely simple operation of changing the tightening force of the tightening portion 22 by the tightening operation. , The pipe propagating wave propagating in the pipe 30, that is, the noise component can be efficiently absorbed.

Further, in the present invention, among the outer peripheral surfaces 31 of the pipe 30, propagation suppressing portions 24A and 24B are provided between the ultrasonic absorber 14 and the transducers 13A and 13B, and the absorber propagates through the ultrasonic absorber 14. The propagation of the wave to the transducers 13A and 13B is suppressed.
At this time, the propagation from the ultrasonic absorber 14 to the propagation suppression units 24A and 24B and the propagation from the propagation suppression units 24A and 24B to the transducers 13A and 13B are determined by the acoustic impedance of these media through which the ultrasonic waves pass. Will be done.

In general, if the two acoustic impedance of the medium M _1, M ₂ and the Z _1, Z _2, the reflectance r in the boundary between the two M _1, M ₂ is obtained by the following expression (3).
r = {(Z ₂ −Z ₁ ) / (Z ₂ + Z ₁ )} ² … (3)
Therefore, the _{larger the difference between Z 1} and Z ₂ , the larger the reflectance r tends to be.

_{For example, as described above, the acoustic impedance Z 1} of the stainless steel pipe (SUS) or the SGP pipe (SGP) is about 46e + 06 [Pa · s / m], and the acoustic impedance Z _{2 of the} air is about 0.0004e + 06 [Pa ·. Since it is s / m], according to the above-mentioned equation (3), the reflectance r between the two is about 99.9%, and the propagation of ultrasonic waves is almost suppressed.

Usually, the wedge resin used when fixing the transducers 13A and 13B diagonally to the outer peripheral surface 31 of the pipe 30 is mostly polyimide-based, and its acoustic impedance is 3e + 06 [Pa · s / m]. Therefore, as described above, when an elastic body having an acoustic impedance of 1.9e + 06 [Pa · s / m] is used as the ultrasonic absorber 14, the acoustic impedance between the transducers 13A and 13B and the ultrasonic absorber 14 becomes high. Get closer. In this case, according to the above-mentioned equation (3), the reflectance r between the two is about 0.08%, which makes it easier for ultrasonic waves to propagate.

Therefore, it is desirable that the propagation suppression units 24A and 24B are made of materials having a certain degree of difference from these acoustic impedances. If an air layer is used as the propagation suppressing portions 24A and 24B, the reflectance r between the elastic body of the ultrasonic absorber 14 and the air is about 99.9% according to the above-mentioned equation (3), which is super. Propagation of sound waves will be almost suppressed.
In general, the higher the porosity (ratio of the gap volume per unit volume), the closer the porous material is to the air layer, and the lower the acoustic impedance. Therefore, as the propagation suppressing portions 24A and 24B, a porous material having a higher porosity than the ultrasonic absorber 14 and closer to the acoustic impedance of air, for example, a porous material such as glass wool, rock wool, or urethane foam may be used. I understand.

FIG. 6 is a signal waveform diagram showing absorption of noise components, FIG. 6 (a) shows a received ultrasonic waveform (electrically received waveform) without the propagation suppression units 24A and 24B, and FIG. 6 (b) is a signal waveform diagram. The received ultrasonic waveforms (electrically received waveforms) in the case where the propagation suppression units 24A and 24B are present are shown. At this time, the fluid X was steam flowing in the pipe 30 at a pressure of 0.9 MPaG at a flow rate of 12 m / s, the pipe 30 used an SGP pipe of 25 A, and the ultrasonic frequency was set to 1 MHz.

In FIG. 6, the signal component corresponds to the fluid propagating wave propagating in the fluid X, and the noise component corresponds to the pipe propagating wave propagating in the pipe 30 itself.
Comparing these FIGS. 6 (a) and 6 (b), the amplitude of the absorber propagating wave, that is, the noise component is significantly attenuated by adjusting the acoustic impedance by providing the ultrasonic buffer 21. It can be seen that the propagation suppression units 24A and 24B are effectively suppressed.

[Effect of this embodiment]
As described above, in the present embodiment, the ultrasonic absorber 14 for absorbing the pipe propagating wave propagating in the pipe 30 among the ultrasonic waves is provided on the outer peripheral surface 31 of the pipe 30, and the outer peripheral surface 31 of the pipe 30 is super-ultrasonic. The propagation suppression units 24A and 24B provided between the sound absorber 14 and the transducers 13A and 13B suppress the propagation of the absorber propagating wave that has propagated through the ultrasonic absorber 14 among the ultrasonic waves to the transducers 13A and 13B. It is something that I tried to do.

As a result, the noise component composed of the pipe propagating wave propagating in the pipe 30 can be reduced, and the noise component caused by the absorber propagating wave propagating in the ultrasonic absorber 14 itself can also be reduced. Therefore, it is possible to improve the S / N ratio indicating the ratio of the noise component to the signal component corresponding to the fluid propagating wave propagating in the fluid X, and as a result, it is possible to obtain extremely good measurement accuracy.

Further, in the present embodiment, the pipe 30 and the pipe 30 are made of a mat-like elastic porous body provided on the outer surface 31 of the ultrasonic absorber 14 and are caused by the difference in acoustic impedance between the pipe 30 and the ultrasonic absorber 14. An ultrasonic shock absorber 21 for buffering the reflection of the pipe propagating wave at the interface with the ultrasonic absorber 14 is provided, and the acoustic matching adjustment unit 23 tightens the tightening portion 22 provided on the outer surface of the ultrasonic shock absorber 21. By changing the applying force according to the tightening operation and changing the degree of deformation of the ultrasonic shock absorber 21 due to pressing, the acoustic matching status of the pipe 30, the ultrasonic absorber 14, and the ultrasonic shock absorber 21 is affected. The acoustic impedance of the ultrasonic shock absorber 21 is adjusted, and the propagation suppression portions 24A and 24B are connected to the ultrasonic absorber 14, the ultrasonic shock absorber 21, the tightening portion 22 and the transducer on the outer peripheral surface of the pipe 30. It may be provided between 13A and 13B.

As a result, the acoustic matching condition of the pipe 30, the ultrasonic absorber 14, and the ultrasonic buffer 21 can be improved by an extremely simple operation of changing the tightening force of the tightening portion 22 by the tightening operation. The same ultrasonic absorber 14 can efficiently absorb the pipe propagating wave propagating in the pipe 30, that is, the noise component, and the ultrasonic absorber 14 and the ultrasonic shock absorber can be used without replacing the ultrasonic absorber 14. It is possible to suppress the propagation of the ultrasonic waves propagating through the 21 and the tightening portion 22 to the transducers 13A and 13B, and it is possible to obtain extremely good measurement accuracy.

[Extension of Embodiment]
Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made to the structure and details of the present invention within the scope of the present invention.

1 ... Ultrasonic flow meter, 10 ... Flow meter body, 11 ... Switching unit, 12 ... Measurement processing unit, 13A, 13B ... Transducer, 14 ... Ultrasonic absorber, 20 ... Ultrasonic shock absorber, 21 ... Ultrasonic shock absorber , 22 ... Tightening part, 22A ... Holding plate, 22B ... Tightening band, 23 ... Acoustic matching adjustment part, 24A, 24B ... Propagation suppression part, 30 ... Piping, 31 ... Outer surface surface, 32 ... Inner peripheral surface, 33 ... The wall part.

Claims (3)

An ultrasonic flowmeter that measures the flow rate of the fluid based on ultrasonic waves transmitted and received so as to pass through the fluid flowing in the pipe by a transducer provided on the outer peripheral surface of the pipe.
An ultrasonic absorber provided on the outer peripheral surface of the pipe and absorbing the pipe propagating wave propagating in the pipe among the ultrasonic waves, and an ultrasonic absorber.
An ultrasonic shock absorber made of a mat-like elastic porous body provided on the outer surface of the ultrasonic absorber and buffering the reflection of the pipe propagating wave at the interface between the pipe and the ultrasonic absorber.
A tightening portion provided on the outer surface of the ultrasonic shock absorber and pressing and tightening the ultrasonic shock absorber in the direction of the pipe.
Reflection at the interface by changing the tightening force of the tightening portion according to the operation and changing the degree of deformation of the ultrasonic shock absorber due to the pressing to change the acoustic impedance of the ultrasonic shock absorber. An acoustic matching adjustment unit that adjusts the acoustic matching status regarding the acoustic impedance of the piping, the ultrasonic absorber, and the ultrasonic shock absorber, which influences the intensity of the pipe propagating wave .
The ultrasound absorber of the outer peripheral surface of the front Symbol pipe, the ultrasonic shock absorber, and said provided between the fastening portion and the transducer, propagating the ultrasonic absorber of the ultrasonic A propagation suppression unit that suppresses the propagation of the absorber-propagated wave to the transducer,
An ultrasonic flowmeter characterized by being equipped with. In the ultrasonic flow meter according to claim 1,
The ultrasonic flowmeter is characterized in that the propagation suppressing portion is made of a porous material or an air layer having a large number of voids for containing air. An ultrasonic flow rate measuring method used in an ultrasonic flow meter that measures the flow rate of the fluid based on ultrasonic waves transmitted and received so as to pass through the fluid flowing in the pipe by a transducer provided on the outer peripheral surface of the pipe.
An ultrasonic absorption step in which an ultrasonic absorber provided on the outer peripheral surface of the pipe absorbs a pipe propagating wave propagating in the pipe among the ultrasonic waves.
An ultrasonic shock absorber made of a mat-like elastic porous body provided on the outer surface of the ultrasonic absorber buffers the reflection of the pipe propagating wave at the interface between the pipe and the ultrasonic absorber. Steps and
A tightening step in which a tightening portion provided on the outer surface of the ultrasonic shock absorber presses and tightens the ultrasonic shock absorber in the direction of the pipe.
The acoustic matching adjustment unit changes the tightening force of the tightening portion according to the operation to change the degree of deformation of the ultrasonic shock absorber due to the pressing to change the acoustic impedance of the ultrasonic shock absorber. The acoustic matching adjustment step for adjusting the acoustic matching status regarding the acoustic impedance of the pipe, the ultrasonic absorber, and the ultrasonic shock absorber, which influences the intensity of the pipe propagating wave reflected at the interface.
The ultrasonic absorber, the ultrasonic shock absorber, and the propagation suppressing portion provided between the tightening portion and the transducer on the outer peripheral surface of the pipe make the ultrasonic absorber of the ultrasonic waves. A propagation suppression step that suppresses the propagation of the propagating absorber-propagated wave to the transducer , and
An ultrasonic flow rate measuring method characterized by being provided with.

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