JP2022188333A - ultrasonic flow meter - Google Patents

Abstract

To suppress reduction of the intensity of a reception signal more.SOLUTION: The ultrasonic flow meter includes: a measurement pipe 101; an ultrasonic sending-receiving unit 102 attached to an upstream side of the measurement pipe 101, the ultrasonic sending-receiving unit 102 sending or receiving an ultrasonic wave with the downstream side; an ultrasonic sending-receiving unit 103 attached to a downstream side of the measurement pipe 101, the ultrasonic sending-receiving unit 103 sending or receiving an ultrasonic wave with the upstream side. The ultrasonic waves used by the ultrasonic sending-receiving units 102 and 103 are reflected at least one time in the measurement pipe 101 and the incident angle is an angle that does not cause a surface wave.SELECTED DRAWING: Figure 1

Description

The present invention relates to an ultrasonic flowmeter that uses ultrasonic waves to measure a fluid.

2. Description of the Related Art Conventionally, an ultrasonic flowmeter is known that measures a fluid to be measured based on the difference in propagation time of ultrasonic waves transmitted and received by a pair of ultrasonic transmitter/receivers.
In such an ultrasonic flowmeter, it is necessary to increase the propagation length in order to increase the propagation time difference. Therefore, as an ultrasonic wave propagation method, a reflection method such as a V-pass (one-time reflection) or a triangle-pass (two-time reflection) is known (see Patent Documents 1 and 2, for example).

JP 2019-196905 A JP 2013-178125 A

On the other hand, when the fluid to be measured by the ultrasonic flowmeter is water and the measurement tube of the ultrasonic flowmeter is made of a brass-based material, when the incident angle of ultrasonic waves reaches a certain angle, the surface A wave is generated, and the strength of the received signal (reception strength) decreases. The incident angle of the ultrasonic wave is the angle at which the ultrasonic wave is incident with respect to the normal direction of the reflecting surface on which the ultrasonic wave is reflected.

FIG. 5 shows the presence or absence of occurrence of surface waves due to the difference in the incident angle of ultrasonic waves. 5A shows the case where the incident angle of the ultrasonic waves is 35°, FIG. 5B shows the case where the incident angle of the ultrasonic waves is 40°, FIG. 5C shows the case where the incident angle of the ultrasonic waves is 45°, and FIG. 5D. indicates the case where the incident angle of ultrasonic waves is 50°. Note that FIG. 5 shows a case where the fluid to be measured is water and the measurement tube is made of brass.
Here, as shown in FIGS. 5A and 5B, no surface wave is generated when the incident angles of the ultrasonic waves are 35° and 40°. On the other hand, as shown in FIGS. 5C and 5D, surface waves are generated when the incident angles of the ultrasonic waves are 45° and 50°. In FIGS. 5C and 5D, reference numeral 51 denotes surface waves.

Moreover, FIG. 6 shows the difference in received signal intensity due to the difference in the material of the measurement tube when the incident angle of the ultrasonic wave is 48°. FIG. 6A shows a case where the measuring tube is made of brass, and FIG. 6B shows a case where the measuring tube is made of stainless steel. Note that FIG. 6 shows a case where the fluid to be measured is water.
As shown in FIG. 6, the intensity of the received signal is lower when the measuring tube is made of brass than when the measuring tube is made of stainless steel (the intensity of the received signal is about 1/3). It has become).

Also, FIG. 7 shows the difference in received signal intensity due to the difference in the incident angle of the ultrasonic waves. Note that FIG. 7 shows a case where the fluid to be measured is water and the measurement tube is made of brass.
As shown in FIG. 7, when the measurement tube is made of brass, the intensity of the received signal decreases when the incident angle of the ultrasonic waves is between 45° and 55°. The intensity of the received signal drops most near 50°.

Such surface waves are generated not only when the measuring tube is made of a brass-based material, but also when the measuring tube is made of a material other than the brass-based material.
The incident angle of the ultrasonic waves that generate the surface waves varies depending on the physical properties of the constituent material of the measurement tube and the fluid flowing through the measurement tube. Then, the value of the incident angle of the ultrasonic waves generated by the surface waves can be estimated by Snell's law. For example, when the measurement tube is made of stainless steel and the fluid flowing through the measurement tube is water, Snell's law shows that the incident angle of the ultrasonic waves that generate the surface waves is around 30°.

SUMMARY OF THE INVENTION An object of the present invention is to provide an ultrasonic flowmeter capable of suppressing a decrease in the intensity of a received signal as compared with the conventional art.

An ultrasonic flowmeter according to the present invention comprises a measuring pipe, a first ultrasonic transmitter/receiver attached to the upstream side of the measuring pipe and transmitting/receiving ultrasonic waves to/from the downstream side, and and a second ultrasonic transmitter/receiver for transmitting/receiving ultrasonic waves to/from the upstream side, wherein the ultrasonic waves used in the first ultrasonic transmitter/receiver and the second ultrasonic transmitter/receiver are transmitted within the measurement pipe. , and the incident angle is an angle at which no surface wave is generated.

According to the present invention, since it is configured as described above, it is possible to suppress the decrease in strength of the received signal compared to the conventional art.

1A and 1B are diagrams showing a configuration example (in the case of V-pass) of the ultrasonic flowmeter according to Embodiment 1, where FIG. 1A is a transparent perspective view and FIG. 1B is a cross-sectional view. FIG. 4 is a diagram for explaining the calculation principle (in the case of V-path) of the ultrasonic flowmeter according to Embodiment 1; 3A and 3B are diagrams showing a configuration example (in the case of a triangle path) of the ultrasonic flowmeter according to Embodiment 1, where FIG. 3A is a transparent perspective view and FIG. 3B is a cross-sectional view. 4A and 4B are diagrams showing a configuration example (in the case of V-pass) of an ultrasonic flowmeter according to Embodiment 2, where FIG. 4A is a transparent perspective view and FIG. 4B is a cross-sectional view. 5A to 5D are diagrams for explaining the difference in the presence or absence of generation of surface waves due to the difference in the incident angle of ultrasonic waves in a conventional ultrasonic flowmeter. 6A and 6B are diagrams for explaining the difference in received signal intensity due to the difference in the constituent material of the measuring tube in the conventional ultrasonic flowmeter. FIG. 10 is a diagram for explaining a difference in intensity of a received signal due to a difference in incident angle of ultrasonic waves in a conventional ultrasonic flowmeter;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Embodiment 1.
FIG. 1 is a diagram showing a configuration example of an ultrasonic flowmeter 1 according to Embodiment 1. As shown in FIG.
The ultrasonic flowmeter 1 uses ultrasonic waves to measure a fluid. This ultrasonic flowmeter 1, as shown in FIG. A section 104 is provided. 1, illustration of the calculation unit 104 is omitted. In FIG. 1, reference numeral 11 indicates the tube axis of the measuring tube 101, and reference numeral 12 indicates the propagation path (V path) of ultrasonic waves.

The measurement tube 101 is a cylindrical member in which a fluid to be measured flows. The measurement tube 101 is made of brass material, for example. Also, the fluid to be measured is, for example, water.

The measurement tube 101 is provided with a mounting portion 1011 to which the ultrasonic transmitter/receiver 102 is mounted on the upstream side of the side wall. The mounting portion 1011 is a hole that extends from the outer wall to the inner wall of the measuring tube 101 .
Further, the measurement tube 101 is provided with a mounting portion 1012 to which the ultrasonic transmitter/receiver 103 is mounted on the downstream side of the side wall. The mounting portion 1012 is a hole that extends from the outer wall to the inner wall of the measurement tube 101 .

The positional relationship between the mounting portion 1011 and the mounting portion 1012 is designed according to the propagation path of ultrasonic waves used in the ultrasonic transmitter/receiver 102 and the ultrasonic transmitter/receiver 103 .
The propagation paths of the ultrasonic waves used in the ultrasonic transmitter/receiver 102 and the ultrasonic transmitter/receiver 103 are designed so that they are reflected one or more times within the measurement tube 101 in order to increase the propagation length. As a reflection method of the ultrasonic flowmeter 1 according to Embodiment 1, a reflection method such as a V pass or a triangle pass can be used. The ultrasonic flowmeter 1 shown in FIG. 1 shows a case where a V-path is adopted.

Also, the arrangement angles of the mounting portions 1011 and 1012 are designed so that the incident angle of the ultrasonic waves used in the ultrasonic transmitter/receiver 102 and the ultrasonic transmitter/receiver 103 does not generate surface waves. The incident angle of ultrasonic waves is the angle at which the ultrasonic waves are incident with respect to the normal direction of the reflecting surface on which the ultrasonic waves are reflected.
In the ultrasonic flowmeter 1 shown in FIG. 1, in order to realize a short distance between the measurement pipe 101 made of a brass-based material (to shorten the propagation distance of ultrasonic waves in the axial direction of the measurement pipe 101) , is designed so that the incident angle of ultrasonic waves is 45° or less.

The ultrasonic transmitter/receiver 102 is an ultrasonic transducer that is attached to the upstream side (mounting portion 1011 ) of the measurement tube 101 and transmits/receives ultrasonic waves to/from the ultrasonic transmitter/receiver 103 within the measurement tube 101 . That is, the ultrasonic transmitter/receiver 102 transmits ultrasonic waves to the downstream side (ultrasonic transmitter/receiver 103) within the measurement tube 101, and receives ultrasonic waves from the downstream side (ultrasonic transmitter/receiver 103).

The ultrasonic transmitter/receiver 103 is an ultrasonic transducer that is attached to the downstream side (mounting portion 1012 ) of the measurement pipe 101 and transmits/receives ultrasonic waves to/from the ultrasonic transmitter/receiver 102 within the measurement pipe 101 . That is, the ultrasonic transmitter/receiver 103 transmits ultrasonic waves to the upstream side (ultrasonic transmitter/receiver 102) within the measurement tube 101, and receives ultrasonic waves from the upstream side (ultrasonic transmitter/receiver 102).

The computation unit 104 computes the flow velocity of the fluid in the measurement tube 101 based on the transmission/reception result of the ultrasonic transmitter/receiver 102 and the transmission/reception result of the ultrasonic transmitter/receiver 103 . Moreover, the calculation unit 104 may calculate the flow rate of the fluid based on the flow velocity of the fluid.
The principle of operation in this operation unit 104 will be described below with reference to FIG.

Here, as shown in FIG. 2, the case where the ultrasound reflection method is V-pass will be described as an example, but the same applies to other reflection methods.
In FIG. 2, S indicates the cross-sectional area (cross _- sectional area) perpendicular to the tube axis in the measurement tube 101, V indicates the flow velocity of the fluid, and L1 indicates the L ₂ indicates the propagation length (first propagation length) from the transmitting/receiving surface of the ultrasonic transmitter/receiver 103 to the reflecting surface (second propagation length), and t ₁ indicates the upstream side in the measurement tube 101 to the downstream side (forward propagation time), t2 indicates the ultrasonic propagation time (backward propagation time) from the downstream side to the upstream _side in the measurement pipe 101, and θ is The angle at which the ultrasonic wave is incident on the reflecting surface of the measurement tube 101 is shown, and _θi is the incident angle of the ultrasonic wave.

In this case, first, the calculation unit 104 calculates the propagation time (t ₁ ) and the propagation time (t ₂ ) of the ultrasonic wave from the downstream side to the upstream side in the measurement pipe 101 (Δt) is calculated. Then, the calculation unit 104 calculates the flow velocity (V) of the fluid from the following equation (1) based on this time difference (Δt). Further, the calculation unit 104 may calculate the flow rate (Q) of the fluid from the following equation (2) based on the flow velocity (V) of the fluid. In Equation (1), c indicates the speed of sound, and L (=L ₁ +L ₂ ) indicates the propagation length.
V=(c ² /2Lcos θ)·(t ₂ −t ₁ )=(c ² /2Lcos θ)·Δt (1)
Q=S・V (2)

Note that the minimum value of the incident angle of the ultrasonic waves is determined by the minimum time difference that can guarantee accuracy determined by the performance of the computing unit 104 . The minimum time difference is the time difference when the fluid has the minimum flow rate.
For example, the minimum flow rate of the fluid is 0.1 m ³ /h, the cross-sectional area of the measuring tube 101 is 200 mm ² , the speed of sound is 1500 m/s, and the propagation length is 100 mm. Let the minimum time difference be 2000 ps. In this case, the minimum value of the incident angle of ultrasonic waves is 9.3° from the following equations (3) to (6). That is, in order to satisfy the minimum time difference that can ensure accuracy when the fluid has a minimum flow rate, the incident angle of the ultrasonic waves must be 9.3° or more.
0.1/3600=0.0002×V (3)
V≈0.139 (4)
θ=Cos ⁻¹ ((c ² /2LV)·Δt) ≈Cos ⁻¹ ((1500 ² /(2×0.1×1.39))×2000×10 ⁻¹² )≈80.7° (5 )
θ _i =90°−θ=90°−80.7°=9.3° (6)

Next, the effect of the ultrasonic flowmeter 1 according to Embodiment 1 shown in FIG. 1 will be described.
Here, as shown in FIG. 7, in the conventional ultrasonic flowmeter 1, the fluid to be measured is water, and the measurement tube 101 is made of a brass-based material (brass in FIG. 7). In this case, when the incident angle of the ultrasonic wave becomes a certain angle (45° to 55° in FIG. 7), a surface wave is generated and the strength of the received signal is reduced.

Therefore, in the ultrasonic flowmeter 1 according to Embodiment 1, the arrangement angles of the ultrasonic transmitter/receiver 102 and the ultrasonic transmitter/receiver 103 are designed so that the incident angle of the ultrasonic waves is an angle at which surface waves are not generated. ing. When the measurement tube 101 is made of a brass-based material, it is designed so that the incident angle of the ultrasonic wave is 45° or less or 55° or more (45° or less when realizing short-face distance). there is As a result, in the ultrasonic flowmeter 1 according to Embodiment 1, it is possible to avoid the generation of surface waves and prevent the intensity of the received signal from decreasing.

Note that FIG. 1 shows a case where the ultrasonic wave reflection method in the ultrasonic flowmeter 1 is V-pass (one-time reflection). However, the ultrasonic wave reflection method in the ultrasonic flowmeter 1 is not limited to this, and may be a triangle pass (twice reflection) or multiple reflections.
For example, in FIG. 3, the shape of the cross section orthogonal (including the meaning of approximately orthogonal) to the tube axis in the measurement tube 101 is configured to be hexagonal, and a triangle path reflection method in which the propagation path is a triangle is adopted. indicates the case. In this case, the incident angle of the ultrasonic wave with respect to all reflecting surfaces (reflecting surface 1013 and reflecting surface 1014 in FIG. 3) on which the ultrasonic wave is reflected in the measurement tube 101 should be an angle at which surface waves are not generated. designed to

In addition, in the ultrasonic flowmeter 1 shown in FIG. The rectifying member 105 is provided on the upstream side of the measuring tube 101 and is a member for rectifying the fluid inside the measuring tube 101 .

In FIG. 3, reference numeral 31 denotes the tube axis of the measuring tube 101, reference numeral 32 denotes the propagation path (triangle path) of ultrasonic waves, and reference numeral 33 denotes the incident angle of the ultrasonic waves (in FIG. 3, the incident angle is 36° ).
In FIG. 3B, reference numeral 321 denotes the first propagation path in the triangle path, reference numeral 322 denotes the second propagation path in the triangle path, and reference numeral 323 denotes the third propagation path in the triangle path.

In the above description, it is assumed that the measurement tube 101 is made of a brass-based material. A case of designing an angle that does not occur is shown. However, the arrangement angle of the ultrasonic transmitter/receiver 102 and the ultrasonic transmitter/receiver 103 is not limited to this, and by adjusting the constituent material of the measurement tube 101, the angle of incidence of the ultrasonic waves can be adjusted so that surface waves do not occur. You may design so that it may become an angle.
For example, if the fluid to be measured is water and the incident angle of the ultrasonic waves is to be within the range of 45° to 55°, surface waves will be generated if the measurement tube 101 is made of a brass-based material. put away. Therefore, in such a case, a material (for example, stainless steel) that does not generate a surface wave when the incident angle of the ultrasonic wave is within the range of 45° to 55° may be used as the constituent material of the measurement tube 101 .

As described above, according to the first embodiment, the ultrasonic flowmeter 1 includes the measuring pipe 101 and the ultrasonic wave flow meter 1 attached to the upstream side of the measuring pipe 101 and transmitting/receiving ultrasonic waves to/from the downstream side. A transmitter/receiver 102 and an ultrasonic transmitter/receiver 103 attached to the downstream side of the measurement pipe 101 for transmitting/receiving ultrasonic waves to/from the upstream side, and are used in the ultrasonic transmitter/receiver 102 and the ultrasonic transmitter/receiver 103. The ultrasonic wave is reflected one or more times within the measurement tube 101, and the angle of incidence is such that no surface wave is generated. As a result, the ultrasonic flowmeter 1 according to Embodiment 1 can suppress a decrease in the intensity of the received signal compared to the conventional art.

Embodiment 2.
FIG. 4 is a diagram showing a configuration example of the ultrasonic flowmeter 1 according to the second embodiment. The ultrasonic flowmeter 1 according to the second embodiment shown in FIG. 4 has a reflecting member 106 added to the ultrasonic flowmeter 1 according to the first embodiment shown in FIG. Other configuration examples of the ultrasonic flowmeter 1 according to the second embodiment shown in FIG. 4 are the same as the configuration example of the ultrasonic flowmeter 1 according to the first embodiment shown in FIG. Only the different parts will be explained.

The reflecting member 106 is made of a material other than the constituent material of the measuring tube 101 and attached to a reflecting surface of the measuring tube 101 that reflects the ultrasonic waves used in the ultrasonic transmitter/receiver 102 and the ultrasonic transmitter/receiver 103 . For example, if the measuring tube 101 is made of a brass-based material, the reflecting member 106 is made of stainless steel or the like.
In this case, the incident angle of the ultrasonic waves is designed at an angle at which surface waves are not generated, based on the physical properties of the constituent material of the reflecting member 106 and the fluid to be measured.

As a result, for example, even if the measurement tube 101 is made of a brass-based material, the incident angle of the ultrasonic waves can be reduced by attaching the reflecting member 106 made of a material other than the brass-based material only to the reflecting surface of the ultrasonic waves. It can be set within the range of 45° to 55°.

Note that FIG. 4 shows a case where the ultrasonic wave reflection method in the ultrasonic flowmeter 1 is V-pass (one-time reflection). However, the ultrasonic wave reflection method in the ultrasonic flowmeter 1 is not limited to this, and may be a triangle pass (twice reflection) or multiple reflections.

Further, within the scope of the present invention, it is possible to freely combine each embodiment, modify any component of each embodiment, or omit any component in each embodiment. be.

1 ultrasonic flowmeter 101 measuring tube 102 ultrasonic transmitter/receiver (first ultrasonic transmitter/receiver)
103 ultrasonic transmitter/receiver (second ultrasonic transmitter/receiver)
104 calculation unit 105 rectifying member 106 reflecting member 1011 mounting portion 1012 mounting portion 1013 reflecting surface 1014 reflecting surface

Claims (4)

a measuring tube;
a first ultrasonic transmitter/receiver attached to the upstream side of the measurement pipe and transmitting/receiving ultrasonic waves to/from the downstream side;
a second ultrasonic transmitter/receiver attached to the downstream side of the measurement pipe and transmitting/receiving ultrasonic waves to/from the upstream side;
The ultrasonic waves used in the first ultrasonic transmitter/receiver and the second ultrasonic transmitter/receiver are reflected one or more times in the measurement tube, and the incident angle is an angle at which surface waves are not generated. and ultrasonic flowmeter. 2. The ultrasonic flowmeter according to claim 1, wherein the measuring pipe is made of a brass-based material. 3. The ultrasonic flowmeter according to claim 2, wherein an incident angle of ultrasonic waves used in said first ultrasonic transmitter/receiver and said second ultrasonic transmitter/receiver is 45[deg.] or less. A reflector made of a material other than the constituent material of the measuring tube and attached to a reflecting surface of the measuring tube that reflects the ultrasonic waves used in the first ultrasonic transmitter/receiver and the second ultrasonic transmitter/receiver. 3. The ultrasonic flowmeter according to claim 1, further comprising a member.

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