Ultrasonic flow meter

Abstract

To provide an ultrasonic flowmeter which makes it less frequent to suffer from dust jams and pressure loss compared to traditional ones and which can mitigate measurement errors due to elbow piping.SOLUTION: An ultrasonic flowmeter comprises: a measurement pipe 1 having a circular tube shape area 101 the profile in a direction perpendicular to an axial direction of which is configured to be a circular tube shape and to which fluid that is a measuring object flows, a rectangular tube shape area 103 the profile in a direction perpendicular to the axial direction of which is configured to be a rectangular tube shape, and a loft shape area 104 that is configured to be a loft shape for connecting the circular tube shape area 101 to the rectangular tube shape area 103; an ultrasonic sensor 2 arranged on an upstream side in the rectangular tube shape area 103 of the measurement pipe 1 and performing ultrasonic transmission / reception to / from the downstream side; and a an ultrasonic sensor 3 arranged on the downstream side in the rectangular tube shape area 103 of the measurement pipe 1 and performing ultrasonic transmission / reception to / from the upstream side.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an ultrasonic flowmeter that measures flow rate using ultrasonic waves. [Background technology]

[0002] Conventionally, ultrasonic flowmeters have been known that measure the flow rate of a fluid by measuring the flow velocity (flow velocity in a pipe) of the fluid to be measured based on the difference in propagation time of ultrasonic waves transmitted and received by a pair of ultrasonic sensors. In this case, ultrasonic flowmeters create and adjust a flow rate correction coefficient for when the measurement pipe through which the fluid flows is a straight pipe, and use the flow rate correction coefficient to correct the flow rate, thereby enabling measurement of the flow rate. The flow rate correction coefficient is a coefficient that depends on the flow velocity in the pipe.

[0003] On the other hand, flow rate measurement using an ultrasonic flow meter directly measures the flow velocity inside the pipe, so it is affected by the piping connected upstream of the measurement pipe (upstream piping).In particular, elbow piping generates drift and swirling flow, so if the upstream piping is an elbow piping, errors will occur in the flow rate measurement by the ultrasonic flow meter.

[0004] In response to this, conventionally, methods have been proposed, such as a method of rectifying the flow using a mesh or a rectifier (see, for example, Patent Documents 1 to 3), a method of creating an asymmetric flow (see, for example, Patent Documents 4 and 5), or a method of making the measuring tube rectangular (see, for example, Patent Document 6). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-198372 [Patent Document 2] Patent No. 4453341 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-178125 [Patent Document 4] Patent No. 3436247 [Patent Document 5] Patent No. 4936856 [Patent Document 6] Patent No. 3217021 Summary of the Invention [Problem to be solved by the invention]

[0006] However, all of the above methods have problems such as clogging with dust and increased pressure loss.

[0007] The present invention has been made to solve the above-mentioned problems, and aims to provide an ultrasonic flowmeter that is less prone to clogging with debris and pressure loss than conventional flowmeters, and that can reduce measurement errors caused by elbow piping. [Means for solving the problem]

[0008] An ultrasonic flowmeter according to the present invention comprises a measuring pipe having a first circular pipe-shaped region whose cross section in a direction perpendicular to the axial direction is circular pipe-shaped and into which a fluid to be measured flows, a rectangular pipe-shaped region whose cross section in a direction perpendicular to the axial direction is rectangular pipe-shaped, and a first loft-shaped region that is loft-shaped and connects the first circular pipe-shaped region and the rectangular pipe-shaped region, a first ultrasonic sensor attached to the upstream side of the rectangular pipe-shaped region of the measuring pipe and transmitting and receiving ultrasonic waves to and from the downstream side, and a second ultrasonic sensor attached to the downstream side of the rectangular pipe-shaped region of the measuring pipe and transmitting and receiving ultrasonic waves to and from the upstream side, The loft shape is a shape in which the length and width of the measuring pipe in a direction perpendicular to the axial direction change by a uniform amount in the axial direction in accordance with the ratio of the position coordinate in the axial direction to the total length in the axial direction of the area configured in the loft shape. It is characterized by: [Effects of the Invention]

[0009] According to the present invention, as configured as described above, clogging with dust and pressure loss are less likely to occur than in the past, and measurement errors due to elbow piping can be reduced. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram illustrating a configuration example of an ultrasonic flowmeter according to a first embodiment. [Figure 2] 2A and 2B are diagrams showing an example of the configuration of a measurement tube in embodiment 1, where FIG. 2A is a partial cross-sectional view seen from the XZ plane side and a diagram showing the taper, and FIG. 2B is a partial cross-sectional view seen from the XY plane side and a diagram showing the taper. [Figure 3] 3A to 3G are cross-sectional views showing configuration examples of the loft-shaped region of the measurement pipe in the first embodiment. [Figure 4] FIG. 4 is a diagram showing an example of each dimension of a loft-shaped region of a measurement pipe in the first embodiment. [Figure 5] 5A and 5B are diagrams for explaining the effects of the ultrasonic flowmeter according to the first embodiment, and are diagrams showing a configuration example in which a conical region (taper angle 30°) is provided in a measuring pipe. [Figure 6] 6A and 6B are diagrams for explaining the effects of the ultrasonic flowmeter according to the first embodiment, and are diagrams showing a configuration example in which a conical region (taper angle 50°) is provided in a measuring pipe. [Figure 7] 7A and 7B are diagrams for explaining the effects of the ultrasonic flowmeter according to the first embodiment, and are diagrams showing a configuration example in which a loft-shaped region is provided in a measuring pipe. [Figure 8] 8A and 8B are diagrams showing examples of analysis results in the configuration examples shown in FIGS. [Figure 9] FIG. 6 is a diagram showing an example of an analysis result in the configuration example shown in FIG. 5 (when a straight pipe is connected). [Figure 10] FIG. 7 is a diagram showing an example of an analysis result in the configuration example shown in FIG. 6 (when a straight pipe is connected). [Figure 11] FIG. 8 is a diagram showing an example of an analysis result in the configuration example shown in FIG. 7 (when a straight pipe is connected). [Figure 12] FIG. 6 is a diagram showing an example of an analysis result in the configuration example shown in FIG. 5 (when an elbow pipe is connected). [Figure 13] FIG. 7 is a diagram showing an example of an analysis result in the configuration example shown in FIG. 6 (when an elbow pipe is connected). [Figure 14]FIG. 8 is a diagram showing an example of an analysis result in the configuration example shown in FIG. 7 (when an elbow pipe is connected). DETAILED DESCRIPTION OF THE INVENTION

[0011] 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 according to the first embodiment. An ultrasonic flowmeter measures a fluid using ultrasonic waves. As shown in Fig. 1, this ultrasonic flowmeter includes a measuring pipe 1, an ultrasonic sensor (first ultrasonic sensor) 2, an ultrasonic sensor (second ultrasonic sensor) 3, and a calculation unit 4.

[0012] The measuring pipe 1 is a cylindrical member through which a fluid to be measured flows. Details of the measuring pipe 1 will be described later.

[0013] The ultrasonic sensor 2 is an ultrasonic transducer that is attached to the upstream side of the side wall of the measuring pipe 1 (a rectangular pipe-shaped region 103 described later) and transmits and receives ultrasonic waves to and from the ultrasonic sensor 3 inside the measuring pipe 1. That is, the ultrasonic sensor 2 transmits ultrasonic waves to the downstream side (ultrasonic sensor 3) inside the measuring pipe 1, and receives ultrasonic waves from the downstream side (ultrasonic sensor 3) as a reception signal.

[0014] From the viewpoint of measurement, it is preferable that the ultrasonic sensor 2 has a width that is approximately 80 to 90% of the width of the surface of the rectangular tubular region 103 to which it is attached.

[0015] The ultrasonic sensor 3 is an ultrasonic transducer that is attached to the downstream side of the side wall of the measuring pipe 1 (a rectangular pipe-shaped region 103 described later) and transmits and receives ultrasonic waves to and from the ultrasonic sensor 2 within the measuring pipe 1. That is, the ultrasonic sensor 3 transmits ultrasonic waves to the upstream side (ultrasonic sensor 2) within the measuring pipe 1, and receives ultrasonic waves from the upstream side (ultrasonic sensor 2) as a reception signal.

[0016] From the viewpoint of measurement, it is preferable that the ultrasonic sensor 3 has a width that is approximately 80 to 90% of the width of the surface of the rectangular tubular region 103 to which it is attached.

[0017] The positional relationship between the ultrasonic sensors 2 and 3 is designed according to the propagation paths of the ultrasonic waves used by the ultrasonic sensors 2 and 3. Moreover, it is desirable that the propagation path is designed to pass through the center of a rectangular tubular region 103 in the measuring tube 1, which will be described later.

[0018] The calculation unit 4 calculates the flow rate of the fluid by calculating the flow velocity of the fluid in the measuring pipe 1 based on the transmission and reception results of the ultrasonic sensor 2 and the transmission and reception results of the ultrasonic sensor 3. Note that the calculation method used by the calculation unit 4 can be any conventional calculation method, and a description thereof will be omitted.

[0019] The calculation unit 4 is realized by a processing circuit such as an IC (Integrated Circuit) or a system LSI (Large Scale Integration), or a CPU (Central Processing Unit) that executes a program stored in a memory or the like.

[0020] Next, an example of the configuration of the measuring pipe 1 will be described with reference to FIGS. As shown in Figures 1 to 3, the measuring tube 1 has a circular tube-shaped region (first circular tube-shaped region) 101, a circular tube-shaped region (second circular tube-shaped region) 102, a rectangular tube-shaped region 103, a loft-shaped region (first loft-shaped region) 104, and a loft-shaped region (second loft-shaped region) 105.

[0021] The circular pipe-shaped region 101 is a region whose cross section in a direction perpendicular to the axial direction of the measuring pipe 1 is configured to have a circular pipe shape. This circular pipe-shaped region 101 is located on the upstream side of the measuring pipe 1. An upstream pipe 11 (see FIG. 7) is connected to the outer end face of this circular pipe-shaped region 101, and the fluid to be measured flows from the upstream pipe 11 into the measuring pipe 1 side. The upstream pipe 11 can be, for example, a straight pipe or an elbow pipe.

[0022] 2 and 3, the cylindrical region 101 does not have a width in the axial direction of the measuring pipe 1, but it may have a width.

[0023] The circular pipe-shaped region 102 is a region configured so that the cross section in a direction perpendicular to the axial direction of the measuring pipe 1 has a circular pipe shape. This circular pipe-shaped region 102 is located on the downstream side of the measuring pipe 1. The downstream pipe 12 (see FIG. 7) is connected to the outer end face of this circular pipe-shaped region 102, and the fluid to be measured flows out from the measuring pipe 1 to the downstream pipe 12 side.

[0024] 2 and 3, the cylindrical region 102 does not have a width in the axial direction of the measuring pipe 1, but it may have a width.

[0025] The rectangular tubular region 103 is a region configured to have a rectangular tubular cross section in a direction perpendicular to the axial direction of the measuring tube 1. The rectangular tubular region 103 is located between the circular tubular region 101 and the circular tubular region 102 in the measuring tube 1. 2 and 3 show a case where the cross-sectional shape of the rectangular tubular region 103 is a rectangular tubular shape. In addition, in FIGS. 2 and 3, the cross-sectional area of ​​the rectangular tubular region 103 is configured to be smaller than the cross-sectional areas of the circular tubular regions 101 and 102.

[0026] In the configuration shown in FIGS. 2 and 3, the ultrasonic sensors 2 and 3 are attached to the short sides (top and bottom surfaces shown in FIG. 2A) of the rectangular pipe-shaped region 103 of the measuring pipe 1.

[0027] The loft-shaped region 104 is located between the circular tubular region 101 and the rectangular tubular region 103, and is a region configured in a shape (loft shape) that smoothly connects the circular tubular region 101 and the rectangular tubular region 103. Here, the loft shape is a shape in which the amount of change in the length and width in a direction perpendicular to the axial direction of the measuring tube 1 (the amount of reduction in Figs. 2 and 3) changes uniformly (including the meaning of approximately uniformly) in accordance with the length ratio (decreases in Figs. 2 and 3). Note that in Figs. 2 and 3, the loft shape region 104 is configured as a reducing pipe that is shaped to reduce in size from the circular pipe shape region 101 side toward the rectangular pipe shape region 103 side. Also, in Figs. 2 and 3, the cross section of the rectangular pipe shape region 103 is configured as a rectangular pipe shape, and the vertical and horizontal taper angles of the loft shape region 104 are different.

[0028] The loft-shaped region 105 is located between the circular tubular region 102 and the rectangular tubular region 103, and is a region configured in a shape (loft shape) that smoothly connects the circular tubular region 102 and the rectangular tubular region 103. 2 and 3, the loft-shaped region 105 is configured as a tapered pipe having a shape that narrows from the circular pipe-shaped region 102 side toward the rectangular pipe-shaped region 103 side. Also, in FIGS. 2 and 3, the cross-sectional shape of the rectangular pipe-shaped region 103 is configured as a rectangular pipe shape, and the vertical and horizontal taper angles of the loft-shaped region 105 are different from each other.

[0029] A specific configuration example of the loft-shaped region 104 will be described below with reference to FIGS. 2 and 3, the length (taper length) of the loft shape region 104, which is a tapered portion, in the axial direction is represented by L. In FIGS. 2 and 3, L=6 mm. Furthermore, each position (taper coordinate) in the axial direction on the loft shape region 104 is represented by L. x In Figures 2 and 3, L x are arranged at 1 mm intervals from the rectangular tubular region 103 side to the circular tubular region 101 side. S ,L1,L2,L3,L4,L5,L E In this case, the expansion ratio (rectangular expansion ratio) for the rectangular tubular region 103 at each taper coordinate can be expressed by the following formula (1). Rectangle magnification ratio [%] = 100 × L x / L (1)

[0030] The length of the short side of the pipe at each taper coordinate in the loft shape region 104 (taper short side length) is expressed as y x The length of the short side within the tube of the rectangular tubular region 103 (the length of the short side of the rectangle) is represented by y0. The taper angle in the xy plane in the loft shape region 104 is represented by θy. In this case, the length of the short side of the taper can be represented by the following formula (2) or (3): y x [mm]=y0+(LL x ) × Rectangle magnification ratio / 100 (2) y x [mm]=y0+{(LL x )·tanθy}×2 (3)

[0031] In addition, the length of the long side in the pipe at each taper coordinate in the loft shape region 104 (taper long side length) is z x The length of the long side within the rectangular tubular region 103 (the rectangular long side length) is represented by z0. The taper angle in the xz plane in the loft shape region 104 is represented by θz. In this case, the taper long side length can be represented by the following formula (4) or (5). z x [mm]=z0+(LL x ) × Rectangle magnification ratio / 100 (4) z x [mm]=z0+{(LL x )·tanθz}×2 (5)

[0032] FIG. 4 shows the taper short side length, taper long side length, and rectangle enlargement ratio at each taper coordinate calculated using equations (1) to (5).

[0033] Although the detailed configuration of the loft shape region 104 has been described above, the same applies to the details of the loft shape region 105.

[0034] In the above description, the case has been described in which the loft-shaped region 105 is provided between the circular tubular region 102 and the rectangular tubular region 103 in the measuring pipe 1. However, the present invention is not limited to this, and the loft-shaped region 105 does not have to be provided between the circular tubular region 102 and the rectangular tubular region 103 in the measuring pipe 1. In other words, the downstream side of the measuring pipe 1 does not have to be configured in a loft shape, and may be configured in a conical shape, for example. It should be noted that since the ultrasonic flowmeter can measure not only the flow velocity in the forward direction but also the flow velocity in the reverse direction, it is preferable that the measuring pipe 1 be provided with a loft-shaped region 105 .

[0035] Next, the effects of the ultrasonic flowmeter according to the first embodiment will be described. Below, a comparison is made between a case where conical regions 104b and 104c configured in a conical shape are provided between the circular tubular region 101 and the rectangular tubular region 103 in the measuring pipe 1 (as in FIGS. 5 and 6) and a case where a loft-shaped region 104 configured in a loft shape is provided (as in FIG. 7). The conical region 104b shown in FIG. 5 has a cone-shaped taper angle of 30°, and the conical region 104c shown in FIG. 6 has a cone-shaped taper angle of 50°. A comparison is also made between a case where the upstream pipe 11 connected to the upstream side of the measuring pipe 1 is a straight pipe and a case where it is an elbow pipe. FIGS. 5 to 7 show a case where an elbow pipe is connected as the upstream pipe 11.

[0036] FIG. 8 shows an example of the results of analyzing the flow rate error in the configurations shown in FIGS. 5 to 7 when the upstream pipe 11 is a straight pipe and when it is an elbow pipe. In the graph shown in Figure 8A, the horizontal axis represents the Reynolds number (Re') and the vertical axis represents the flow error (%RD). The Reynolds number decreases when the flow velocity and water temperature are low, and conversely, increases when the flow velocity and water temperature are high. Furthermore, the flow error decreases when the difference from the average flow velocity in the pipe is large and the flow velocity on the propagation path is low, and conversely, increases when the difference from the average flow velocity in the pipe is small and the flow velocity on the propagation path is high.

[0037] In Fig. 8A, reference numeral 801 indicates a value when the upstream pipe 11 is a straight pipe in the configuration shown in Fig. 5, and reference numeral 802 indicates a value when the upstream pipe 11 is an elbow pipe in the configuration shown in Fig. 5. Reference numeral 803 indicates a value when the upstream pipe 11 is a straight pipe in the configuration shown in Fig. 6, and reference numeral 804 indicates a value when the upstream pipe 11 is an elbow pipe in the configuration shown in Fig. 6. Reference numeral 805 indicates a value when the upstream pipe 11 is a straight pipe in the configuration shown in Fig. 7, and reference numeral 806 indicates a value when the upstream pipe 11 is an elbow pipe in the configuration shown in Fig. 7.

[0038] 8B, "Vx" indicates the flow velocity in the axial direction of the measuring pipe 1, "Vy" indicates the flow velocity in the direction perpendicular to the axial center of the measuring pipe 1 (short side direction), and "Vz" indicates the flow velocity in the direction perpendicular to the axial center of the measuring pipe 1 (long side direction). Also, "Vx:Max" indicates the maximum value of "Vx", "Vy:Max" indicates the maximum value of "Vy", and "Vz:Max" indicates the maximum value of "Vz". In addition, in Figure 8B, for "Vx", "Vy", "Vz", "Vx:Max", "Vy:Max", and "Vz:Max", the values ​​shown in the first row indicate the values ​​for straight piping, and the values ​​shown in the second row indicate the values ​​for elbow piping.

[0039] 9 to 14 show examples of the results of analyzing the flow rate distribution in the configurations shown in FIGS. 5 to 7 at each position in the axial direction of the measuring pipe 1. In FIG. 9 to 14, the area from "X: -28 mm" to "X: -23 mm" corresponds to the loft-shaped area 104 or the conical-shaped areas 104b and 104c, and the area after the "rectangular inlet" corresponds to the rectangular pipe-shaped area 103. Furthermore, "upstream sensor" means the position where the ultrasonic sensor 2 is arranged, "measurement pipe center" means the central position of the measurement pipe 1, and "downstream sensor" means the position where the ultrasonic sensor 3 is arranged.

[0040] First, as shown in Figures 8, 9, and 12, in the case of the configuration shown in Figure 5 (when the conical region 104b is used), when the upstream pipe 11 is a straight pipe, the flow velocity distribution inside the pipe is most uniform. Furthermore, the flow velocity near the inner wall surface of the pipe is uniform due to the influence of the taper. Furthermore, when the upstream pipe 11 is an elbow pipe, the Vx component is uniform due to the vortex. On the other hand, the vortex is symmetrical vertically, but is biased to the right. Therefore, areas where the flow velocity is slow (areas circled in Figure 12) can be seen in the upper left and lower left parts of the measuring pipe 1.

[0041] Next, as shown in Figures 8, 10, and 13, in the case of the configuration shown in Figure 6 (when the conical region 104c is used), if the upstream pipe 11 is a straight pipe, the vertical direction contracts first, followed by the horizontal direction, so the flow toward the center becomes stronger and the Vx component at the center is large. On the other hand, the flow velocity on the inner wall surface of the pipe (the area circled in Figure 10) is slow. Also, if the upstream pipe 11 is an elbow pipe, the vortex is symmetrical vertically but biased to the right. Therefore, areas with slow flow velocity (the area circled in Figure 13) can be seen in the upper left and lower left parts of the measuring pipe 1. This tendency is stronger than when the conical region 104b is used.

[0042] Next, as shown in Figures 8, 11, and 14, in the case of the configuration shown in Figure 7 (when the loft-shaped region 104 is used), if the upstream pipe 11 is a straight pipe, the contraction is uniform in length up, down, left, and right, so the flow flows in uniformly in the left and right directions. On the other hand, the contraction in the up and down direction is steeper than the left and right, so the Vz component is large. Also, if the upstream pipe 11 is an elbow pipe, the vortex is symmetrical up and down and comes to the center, resulting in a flow that is symmetrical left and right. Therefore, the flow velocity distribution inside the pipe is uniform.

[0043] As described above, in the ultrasonic flowmeter according to the first embodiment, a loft-shaped region 104 having a loft shape is provided between the circular pipe-shaped region 101 and the rectangular pipe-shaped region 103 in the measuring pipe 1. As a result, the ultrasonic flowmeter according to the first embodiment can reduce measurement errors compared to conventional flowmeters. That is, when the upstream pipe 11 is a straight pipe, the flow velocity in the measuring pipe 1 can be made uniform, and measurement errors can be reduced. Also, when the upstream pipe 11 is an elbow pipe, vortex deviation is unlikely to occur, so the flow velocity in the measuring pipe 1 can be made uniform, and measurement errors can be reduced. Furthermore, in the ultrasonic flowmeter according to embodiment 1, there is no component interposed between the circular pipe-shaped region 101 and the rectangular pipe-shaped region 103, and they are smoothly connected in a loft shape, so that clogging with dust and pressure loss are less likely to occur than in conventional flowmeters.

[0044] As described above, according to this embodiment 1, the ultrasonic flowmeter comprises the measuring pipe 1 having the circular pipe-shaped region 101, whose cross section in a direction perpendicular to the axial direction is configured to be circular pipe-shaped and into which the fluid to be measured flows, the rectangular pipe-shaped region 103, whose cross section in a direction perpendicular to the axial direction is configured to be rectangular pipe-shaped, and the loft-shaped region 104, which is configured to be loft-shaped and connects the circular pipe-shaped region 101 and the rectangular pipe-shaped region 103, the ultrasonic sensor 2 attached to the upstream side of the rectangular pipe-shaped region 103 of the measuring pipe 1 and transmits and receives ultrasonic waves to and from the downstream side, and the ultrasonic sensor 3 attached to the downstream side of the rectangular pipe-shaped region 103 of the measuring pipe 1 and transmits and receives ultrasonic waves to and from the upstream side. As a result, the ultrasonic flowmeter according to embodiment 1 is less likely to be clogged with dust and cause pressure loss than conventional ones, and can reduce measurement errors caused by elbow piping.

[0045] It should be noted that, within the scope of the present invention, any of the components of the embodiments may be modified or omitted. [Explanation of symbols]

[0046] 1 Measuring tube 2 ultrasonic sensor (first ultrasonic sensor) 3 Ultrasonic sensor (second ultrasonic sensor) 4 Arithmetic section 11 Upstream piping 12 Downstream piping 101 Circular pipe shaped region (first circular pipe shaped region) 102 Circular pipe shaped region (second circular pipe shaped region) 103 Rectangular tube shape area 104 Loft Shape Area (First Loft Shape Area) 105 Loft Shape Area (Second Loft Shape Area)

Claims

1. a measurement tube having a first circular tubular region whose cross section in a direction perpendicular to the axial direction is circular tubular and into which a fluid to be measured flows, a rectangular tubular region whose cross section in a direction perpendicular to the axial direction is rectangular tubular, and a first loft-shaped region that connects the first circular tubular region and the rectangular tubular region; a first ultrasonic sensor attached to an upstream side of the rectangular pipe-shaped region of the measuring pipe, for transmitting and receiving ultrasonic waves between the upstream side and the downstream side; a second ultrasonic sensor attached to the downstream side of the rectangular pipe-shaped region of the measuring pipe, for transmitting and receiving ultrasonic waves between the downstream side and the upstream side; Equipped with The loft shape is a shape in which the length and width of the measuring pipe in a direction perpendicular to the axial direction change by a uniform amount in the axial direction in accordance with the ratio of the position coordinate in the axial direction to the total length in the axial direction of the area configured in the loft shape.

1. An ultrasonic flow meter comprising:

2. The first loft-shaped region is formed by a contracting pipe having a shape that contracts from the first circular pipe-shaped region side toward the rectangular pipe-shaped region side.

2. The ultrasonic flowmeter according to claim 1.

3. The rectangular tubular region has a cross-sectional shape in a direction perpendicular to the axial direction that is a rectangular tubular shape, The first loft shape region has different vertical and horizontal taper angles in a direction perpendicular to the axial direction.

3. The ultrasonic flowmeter according to claim 1 or 2.

4. The measuring tube is The cross section in a direction perpendicular to the axial direction is configured to be circular pipe-shaped, and the fluid to be measured flows out from a second circular pipe-shaped region, and a second loft-shaped region is configured to be in the loft shape and connects the second circular pipe-shaped region and the rectangular pipe-shaped region.

4. The ultrasonic flowmeter according to claim 1, wherein the ultrasonic flowmeter comprises: a first electrode;

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