Ultrasonic flow meter

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

[Technical field]

[0001] The present invention relates to an ultrasonic flowmeter that uses ultrasonic waves to measure a fluid. [Background technology]

[0002] 2. Description of the Related Art Conventionally, ultrasonic flowmeters are known that perform measurements on a fluid to be measured based on the difference in propagation time of ultrasonic waves transmitted and received by a pair of ultrasonic transmitters and receivers. In such an ultrasonic flowmeter, in order to increase the propagation time difference, it is necessary to increase the propagation length. For this reason, reflection methods such as V-path (single reflection) and triangle-path (double reflection) are known as ultrasonic propagation methods (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-196905 A [Patent Document 2] JP 2013-178125 A Summary of the Invention [Problem to be solved by the invention]

[0004] 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 the ultrasonic wave reaches a certain angle, a surface wave is generated and the strength of the received signal (reception strength) decreases. Note that 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 where the ultrasonic wave is reflected.

[0005] Figure 5 shows the difference in the occurrence of surface waves depending on the ultrasonic incidence angle. Figure 5A shows the case where the ultrasonic incidence angle is 35°, Figure 5B shows the case where the ultrasonic incidence angle is 40°, Figure 5C shows the case where the ultrasonic incidence angle is 45°, and Figure 5D shows the case where the ultrasonic incidence angle is 50°. Note that Figure 5 shows the case where the fluid to be measured is water and the measurement tube is made of brass. Here, as shown in Figures 5A and 5B, when the ultrasonic wave incidence angle is 35° and 40°, no surface wave is generated. On the other hand, as shown in Figures 5C and 5D, when the ultrasonic wave incidence angle is 45° and 50°, a surface wave is generated. In Figures 5C and 5D, reference numeral 51 denotes a surface wave.

[0006] Also, Fig. 6 shows the difference in the strength of the received signal due to the difference in the material of the measurement tube when the ultrasonic wave incidence angle is 48°. Fig. 6A shows the case where the measurement tube is made of brass, and Fig. 6B shows the case where the measurement tube is made of stainless steel. Note that Fig. 6 shows the case where the fluid to be measured is water. As shown in FIG. 6, when the measurement tube is made of brass, the strength of the received signal is lower than when the measurement tube is made of stainless steel (the strength of the received signal is about 1 / 3).

[0007] Fig. 7 shows the difference in the strength of the received signal due to the difference in the incident angle of the ultrasonic wave. In Fig. 7, the fluid to be measured is water, and the measurement tube is made of brass. As shown in Figure 7, when the measuring tube is made of brass, the strength of the received signal decreases when the ultrasonic incident angle is between 45° and 55°, and the strength of the received signal is lowest when the ultrasonic incident angle is around 50°.

[0008] Such surface waves are generated not only when the measurement tube is made of a brass-based material, but also when the measurement 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 material that makes up the measurement tube and the fluid that flows through the measurement tube. The value of the incident angle of the ultrasonic waves that generate the surface waves can be estimated by Snell's law. For example, if the measurement tube is made of stainless steel and the fluid that flows through the measurement tube is water, it can be seen from Snell's law that the incident angle of the ultrasonic waves that generate the surface waves is approximately 30°.

[0009] The present invention has been made to solve the above-mentioned problems, and has an object to provide an ultrasonic flowmeter capable of suppressing a decrease in the strength of a received signal compared to the conventional ultrasonic flowmeter. [Means for solving the problem]

[0010] The ultrasonic flowmeter of the present invention comprises a measuring tube, a first ultrasonic transceiver attached to the upstream side of the measuring tube and transmitting and receiving ultrasonic waves between the downstream side, and a second ultrasonic transceiver attached to the downstream side of the measuring tube and transmitting and receiving ultrasonic waves between the upstream side, and is characterized in that the ultrasonic waves used by the first ultrasonic transceiver and the second ultrasonic transceiver are reflected one or more times within the measuring tube and the angle of incidence is an angle at which no surface waves are generated. Effect of the Invention

[0011] According to the present invention, since it is configured as described above, it is possible to suppress a decrease in the strength of the received signal compared to the conventional case. [Brief description of the drawings]

[0012] [Figure 1] 1A and 1B are diagrams showing a configuration example (in the case of a V-path) of an ultrasonic flowmeter according to the first embodiment, where FIG. 1A is a transparent perspective view and FIG. 1B is a cross-sectional view. [Diagram 2] FIG. 2 is a diagram for explaining the calculation principle (in the case of a V path) of the ultrasonic flowmeter according to the first embodiment. [Diagram 3] 3A and 3B are diagrams showing a configuration example (in the case of a triangle path) of the ultrasonic flowmeter according to the first embodiment, where FIG. 3A is a transparent perspective view and FIG. 3B is a cross-sectional view. [Figure 4] 4A and 4B are diagrams showing a configuration example (in the case of a V-path) of an ultrasonic flowmeter according to the second embodiment, where FIG. 4A is a transparent perspective view and FIG. 4B is a cross-sectional view. [Diagram 5] 5A to 5D are diagrams for explaining the difference in the occurrence or absence of surface waves depending on the incident angle of ultrasonic waves in a conventional ultrasonic flowmeter. [Figure 6] 6A and 6B are diagrams for explaining differences in the strength of a received signal due to differences in the constituent materials of a measuring tube in a conventional ultrasonic flowmeter. [Figure 7] 1A and 1B are diagrams for explaining differences in intensity of received signals due to differences in the incidence angle of ultrasonic waves in a conventional ultrasonic flowmeter. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment 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 the first embodiment. The ultrasonic flowmeter 1 measures a fluid using ultrasonic waves. As shown in Fig. 1, the ultrasonic flowmeter 1 includes a measurement tube 101, an ultrasonic transmitter / receiver (first ultrasonic transmitter / receiver) 102, an ultrasonic transmitter / receiver (second ultrasonic transmitter / receiver) 103, and a calculation unit 104. Note that the illustration of the calculation unit 104 is omitted in Fig. 1. Also, in Fig. 1, reference numeral 11 denotes the tube axis of the measurement tube 101, and reference numeral 12 denotes the propagation path (V path) of the ultrasonic waves.

[0014] The measurement tube 101 is a cylindrical member through which a fluid to be measured flows. The measurement tube 101 is made of, for example, a brass-based material. The fluid to be measured is, for example, water.

[0015] A mounting portion 1011 for mounting an ultrasonic transmitter / receiver 102 is provided on the upstream side of the side wall of this measuring pipe 101. The mounting portion 1011 is a hole that connects the outer wall of the measuring pipe 101 to the inner wall. Furthermore, a mounting portion 1012 for mounting an ultrasonic transmitter / receiver 103 is provided on the downstream side of the side wall of the measuring pipe 101. The mounting portion 1012 is a hole that connects the outer wall of the measuring pipe 101 to the inner wall.

[0016] The positional relationship between the attachment parts 1011 and 1012 is designed according to the propagation paths of the ultrasonic waves used in the ultrasonic transmitter-receiver 102 and the ultrasonic transmitter-receiver 103 . The ultrasonic waves used in the ultrasonic transmitter / receiver 102 and the ultrasonic transmitter / receiver 103 have a propagation path designed to be reflected one or more times in the measuring pipe 101 in order to increase the propagation length. Examples of the reflection method of the ultrasonic flowmeter 1 according to the first embodiment include a V-path or a triangle-path reflection method. The ultrasonic flowmeter 1 shown in FIG. 1 shows a case where a V-path is adopted.

[0017] The arrangement angles of the mounting parts 1011 and 1012 are designed so that the incident angle of the ultrasonic waves used in the ultrasonic transceiver 102 and the ultrasonic transceiver 103 is an angle at which no surface waves are generated. The incident angle of the ultrasonic waves is the angle at which the ultrasonic waves are incident with respect to the normal direction of the reflecting surface from which the ultrasonic waves are reflected. In the ultrasonic flowmeter 1 shown in FIG. 1, in order to realize a short face-to-face distance for the measuring tube 101 made of a brass-based material (in order to shorten the propagation distance of the ultrasonic waves in the axial direction of the measuring tube 101), the ultrasonic flowmeter is designed so that the incident angle of the ultrasonic waves is 45° or less.

[0018] The ultrasonic transmitter / receiver 102 is attached to the upstream side (attachment portion 1011) of the measurement pipe 101, and is an ultrasonic transducer that transmits and receives ultrasonic waves between the ultrasonic transmitter / receiver 103 within the measurement pipe 101. That is, the ultrasonic transmitter / receiver 102 transmits ultrasonic waves to the downstream side (ultrasonic transmitter / receiver 103) within the measurement pipe 101, and receives ultrasonic waves from the downstream side (ultrasonic transmitter / receiver 103).

[0019] The ultrasonic transmitter / receiver 103 is attached to the downstream side (attachment portion 1012) of the measurement pipe 101, and is an ultrasonic transducer that transmits and receives ultrasonic waves between 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 pipe 101, and receives ultrasonic waves from the upstream side (ultrasonic transmitter / receiver 102).

[0020] The calculation unit 104 calculates the flow velocity of the fluid in the measuring pipe 101 based on the transmission and reception results by the ultrasonic transmitter / receiver 102 and the transmission and reception results by the ultrasonic transmitter / receiver 103. The calculation unit 104 may also calculate the flow rate of the fluid based on the flow velocity of the fluid. The calculation principle in the calculation unit 104 will be described below with reference to FIG.

[0021] Here, as shown in FIG. 2, a case where the ultrasonic wave reflection method is a V-path will be described as an example, but the same applies to the cases of other reflection methods. In FIG. 2, S indicates the cross-sectional area of ​​the section perpendicular to the tube axis in the measuring tube 101, V indicates the flow velocity of the fluid, and L 1 indicates the propagation length (first propagation length) from the transmitting / receiving surface to the reflecting surface of the ultrasonic transmitter / receiver 102, and L 2 indicates the propagation length (second propagation length) from the transmitting / receiving surface to the reflecting surface of the ultrasonic transmitter / receiver 103, and t 1 indicates the propagation time (forward propagation time) of the ultrasonic wave from the upstream side to the downstream side in the measuring pipe 101, and t 2 indicates the propagation time of the ultrasonic wave from the downstream side to the upstream side in the measuring pipe 101 (reverse propagation time), θ indicates the angle at which the ultrasonic wave is incident on the reflecting surface in the measuring pipe 101, and θ i indicates the angle of incidence of the ultrasonic wave.

[0022] In this case, first, the calculation unit 104 calculates the propagation time (t 1 ) and the propagation time of the ultrasonic wave from the downstream side to the upstream side in the measuring pipe 101 (t2 ) is calculated. Then, the calculation unit 104 calculates the flow velocity (V) of the fluid from the following formula (1) based on this time difference (Δt). The calculation unit 104 may also calculate the flow rate (Q) of the fluid from the following formula (2) based on the flow velocity (V) of the fluid. In formula (1), c represents the speed of sound, L (=L 1 +L 2 ) indicates the propagation length. V = (c 2 / 2Lcosθ)·(t 2 -t 1 )=(c 2 / 2Lcosθ)·Δt (1) Q = S V (2)

[0023] The minimum value of the ultrasonic wave incidence angle is determined by the minimum time difference for which the accuracy can be guaranteed, which is determined by the performance of the calculation unit 104. The minimum time difference is the time difference when the fluid has a minimum flow rate. For example, if the minimum flow rate of a fluid is 0.1 m 3 / h, and the cross-sectional area of ​​the measuring tube 101 is 200 mm 2 Assume that the speed of sound is 1500 m / s, the propagation length is 100 mm, and the minimum time difference for which accuracy can be guaranteed by the calculation unit 104 is 2000 ps. In this case, the minimum value of the incidence angle of the ultrasonic waves is 9.3° from the following formulas (3) to (6). That is, in order to satisfy the minimum time difference for which accuracy can be guaranteed when the fluid has a minimum flow rate, the incidence angle of the ultrasonic waves needs to 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)

[0024] Next, effects of the ultrasonic flowmeter 1 according to the first embodiment shown in FIG. 1 will be described. Here, as shown in FIG. 7, in a conventional ultrasonic flowmeter 1, when the fluid to be measured is water and the measuring tube 101 is made of a brass-based material (brass in FIG. 7), when the incident angle of the ultrasonic waves reaches a certain angle (45° to 55° in FIG. 7), a surface wave is generated and the strength of the received signal decreases.

[0025] Therefore, in the ultrasonic flowmeter 1 according to the first embodiment, 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. When the measuring pipe 101 is made of a brass-based material, the incident angle of the ultrasonic waves is designed to be 45° or less or 55° or more (45° or less when a short face distance is realized). As a result, in the ultrasonic flowmeter 1 according to the first embodiment, it is possible to avoid the generation of surface waves and prevent a decrease in the strength of the received signal.

[0026] 1 shows a case where the ultrasonic wave reflection method in the ultrasonic flowmeter 1 is a V-path (single reflection). However, the ultrasonic wave reflection method in the ultrasonic flowmeter 1 is not limited to this, and may be a triangle path (two reflections) or multiple reflections. For example, Fig. 3 shows a case where the shape of the cross section perpendicular (including the meaning of approximately perpendicular) to the tube axis in measuring tube 101 is configured to be hexagonal, and a triangle path reflection method in which the propagation path is triangular is adopted. In this case, the incident angle of the ultrasonic wave is designed to be an angle at which no surface wave is generated for all reflection surfaces (reflection surfaces 1013 and 1014 in Fig. 3) that reflect the ultrasonic wave in measuring tube 101.

[0027] 3, a flow straightening member 105 is attached to the measurement pipe 101. The flow straightening member 105 is provided on the upstream side of the measurement pipe 101, and is a member for straightening the flow of the fluid in the measurement pipe 101.

[0028] 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 the ultrasonic waves, and reference numeral 33 denotes the incident angle of the ultrasonic waves (the incident angle is 36° in FIG. 3). In FIG. 3B, reference numeral 321 denotes a first propagation path in the triangular path, reference numeral 322 denotes a second propagation path in the triangular path, and reference numeral 323 denotes a third propagation path in the triangular path.

[0029] In the above, it is assumed that the measurement tube 101 is made of a brass-based material, and a case is shown in which the angle of incidence of the ultrasonic waves is designed to be an angle at which no surface waves are generated by adjusting the arrangement angles of the ultrasonic transmitter-receiver 102 and the ultrasonic transmitter-receiver 103. However, the present invention is not limited to this, and the arrangement angle of the ultrasonic transmitter-receiver 102 and the ultrasonic transmitter-receiver 103 may be set to a certain angle, and the material of the measurement tube 101 may be adjusted to design the angle of incidence of the ultrasonic waves to be an angle at which no surface waves are generated. For example, when the fluid to be measured is water and the ultrasonic wave incidence angle is desired to be within the range of 45° to 55°, if the measurement tube 101 is made of a brass-based material, surface waves will be generated. Therefore, in such a case, the measurement tube 101 may be made of a material (e.g., stainless steel) that does not generate surface waves when the ultrasonic wave incidence angle is within the range of 45° to 55°.

[0030] As described above, according to the first embodiment, the ultrasonic flowmeter 1 includes the measuring pipe 101, the ultrasonic transmitter / receiver 102 attached to the upstream side of the measuring pipe 101 and transmitting / receiving ultrasonic waves between the downstream side, and the ultrasonic transmitter / receiver 103 attached to the downstream side of the measuring pipe 101 and transmitting / receiving ultrasonic waves between the upstream side, and the ultrasonic waves used by the ultrasonic transmitter / receiver 102 and the ultrasonic transmitter / receiver 103 are reflected one or more times within the measuring pipe 101, and the incident angle is an angle at which no surface waves are generated. As a result, the ultrasonic flowmeter 1 according to the first embodiment can suppress a decrease in the strength of the received signal compared to the conventional one.

[0031] Embodiment 2 Fig. 4 is a diagram showing a configuration example of an ultrasonic flowmeter 1 according to embodiment 2. The ultrasonic flowmeter 1 according to embodiment 2 shown in Fig. 4 has a reflecting member 106 added to the ultrasonic flowmeter 1 according to embodiment 1 shown in Fig. 1. The other configuration example of the ultrasonic flowmeter 1 according to embodiment 2 shown in Fig. 4 is similar to the configuration example of the ultrasonic flowmeter 1 according to embodiment 1 shown in Fig. 1, and the same reference numerals are used to denote the same components, and only the different parts will be described.

[0032] The reflecting member 106 is made of a material other than the constituent material of the measuring tube 101, and is attached to a reflecting surface of the measuring tube 101 that reflects the ultrasonic waves used by the ultrasonic transmitter-receiver 102 and the ultrasonic transmitter-receiver 103. For example, when 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 based on the physical properties of the material constituting the reflecting member 106 and the fluid to be measured, so as to be an angle at which no surface waves are generated.

[0033] As a result, even if the measuring tube 101 is made of a brass-based material, for example, by attaching a reflecting member 106 whose ultrasonic reflecting surface is made of a material other than a brass-based material, the incident angle of the ultrasonic waves can be set within the range of 45° to 55°.

[0034] 4 shows a case where the ultrasonic wave reflection method in the ultrasonic flowmeter 1 is a V-path (single reflection). However, the ultrasonic wave reflection method in the ultrasonic flowmeter 1 is not limited to this, and may be a triangle path (two reflections) or multiple reflections.

[0035] Furthermore, within the scope of the present invention, the embodiments may be freely combined, any component of each embodiment may be modified, or any component of each embodiment may be omitted. [Explanation of symbols]

[0036] 1 Ultrasonic flowmeter 101 Measuring tube 102 ultrasonic transmitter / receiver (first ultrasonic transmitter / receiver) 103 Ultrasonic transmitter / receiver (second ultrasonic transmitter / receiver) 104 Arithmetic section 105 Straightening member 106 Reflective material 1011 Mounting part 1012 Mounting part 1013 Reflective surface 1014 Reflective surface

Claims

1. A measuring tube made of a brass-based material; a first ultrasonic transmitter / receiver attached to the upstream side of the measuring pipe and configured to transmit and receive ultrasonic waves between the upstream side and the downstream side; a second ultrasonic transmitter / receiver attached to the downstream side of the measuring pipe and configured to transmit and receive ultrasonic waves between the downstream side and the upstream side, The ultrasonic waves used by the first ultrasonic transmitter-receiver and the second ultrasonic transmitter-receiver are reflected one or more times within the measuring pipe, and the angle of incidence in said one or more reflections is between 45° and 55°; The measuring pipe further includes a reflecting member attached to a reflecting surface that reflects ultrasonic waves used in the first ultrasonic transmitter-receiver and the second ultrasonic transmitter-receiver, The reflecting member is made of stainless steel.

1. An ultrasonic flow meter comprising:

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