JP5815437B2 - Ultrasonic fluid measuring device - Google Patents

Description

  The present invention relates to an ultrasonic fluid measuring apparatus that measures the flow rate of a fluid using ultrasonic waves.

  Conventionally, as this type of ultrasonic fluid measuring device, an ultrasonic flowmeter that measures the flow rate of fluid using ultrasonic waves has been used. In this ultrasonic flow meter, as shown schematically in FIG. 18, the first ultrasonic transmitter / receiver 2 is disposed on the outer peripheral surface on the upstream side of the measurement tube 1 through which the fluid to be measured flows, and the outer periphery on the downstream side. The second ultrasonic transmitter / receiver 3 is arranged on the surface, and the flow velocity V of the fluid is measured based on the difference in ultrasonic propagation time between the ultrasonic transmitter / receiver 2 and the ultrasonic transmitter / receiver 3, and this measurement is performed. From the flow velocity V and the cross-sectional area S of the measuring tube 1, the flow rate of the fluid is obtained as Q = V × S.

Calculation formulas for obtaining the flow rate Q are shown as the following formulas (1) to (4).
t1 = L / (c + V · cos θ) (1)
t2 = L / (c−V · cos θ) (2)
V = c ² · (t2−t1) / (2 · L · cos θ) (3)
Q = S · V (4)

  However, in the above formulas (1) to (4), t1 is the time required for the ultrasonic transmitter / receiver 3 to receive the ultrasonic wave transmitted from the ultrasonic transmitter / receiver 2, and t2 is from the ultrasonic transmitter / receiver 3. The time required for the transmitted ultrasonic wave to be received by the ultrasonic transmitter / receiver 2, c is the propagation velocity of the ultrasonic wave in the fluid, and L is between the ultrasonic transmitter / receiver 2 and the ultrasonic transmitter / receiver 3. The distance (distance of the ultrasonic propagation path (path)), θ is the inclination of the ultrasonic propagation path with respect to the tube axis O of the measuring tube 1.

  In this ultrasonic flowmeter, since the average flow velocity V ′ on the ultrasonic propagation path is measured as the flow velocity V, the measured flow rate Q ′ calculated by V ′ × S is slightly different from the true flow rate Q. If the ratio V ′ / V = Q ′ / Q = k between the average flow velocity V ′ measured by this ultrasonic wave and the average flow velocity (true flow velocity) V of the pipe cross section is known beforehand by actual flow calibration or the like, this ratio By using as the flow rate correction coefficient k, the true flow rate Q can be obtained using the average flow velocity V ′ on the ultrasonic wave propagation path measured by ultrasonic waves and the flow rate correction coefficient k.

However, the flow rate correction coefficient k has the following characteristics.
The flow velocity distribution of the fluid in the measuring tube 1 changes depending on the flow rate. That is, when the flow rate is low, the flow becomes laminar, and when the flow rate is high, the flow becomes turbulent. For this reason, the flow velocity distribution in the pipe on the ultrasonic propagation path has a parabolic convex shape in a laminar flow region with a small flow rate (see FIG. 19A), and a relatively flat shape in a turbulent flow region with a large flow rate. (See FIG. 19B).

  Therefore, the flow rate correction coefficient k, which is the ratio of the average flow velocity V ′ measured with the ultrasonic propagation path and the true flow velocity V, does not become the same value for the laminar flow and the turbulent flow. That is, in the laminar flow region, when the average flow velocity V ′ measured by the ultrasonic wave propagation path is V1 ′ and the true flow velocity is V1, the flow rate correction coefficient k1 is k1 = V1 ′ / V1. In the turbulent region, when the average flow velocity V ′ measured by the ultrasonic wave propagation path is V2 ′ and the true flow velocity is V2, the flow rate correction coefficient k2 is k2 = V2 ′ / V2. In this case, if the difference between V1 and V1 ′ in the laminar flow area is a deviation ΔV1, and the difference between V2 and V2 ′ in the turbulent flow area is a deviation ΔV2, the deviation ΔV1 in the laminar flow area and the deviation ΔV2 in the turbulent flow area Since the difference is large, the flow rate correction coefficient k1 in the laminar flow region and the flow rate correction coefficient k2 in the turbulent flow region are not equal (k1 ≠ k2).

  FIG. 20 shows a change characteristic of the flow rate correction coefficient k. Thus, the flow rate correction coefficient k has a flow rate dependency that changes abruptly on the laminar flow side. When the flow rate correction coefficient k showing such a change characteristic is used, where the change amount of the flow rate correction coefficient k changes abruptly, the flow rate correction coefficient k applied to the flow rate correction coefficient k can be applied even if the flow rate measurement error is slight. The error is large, and as a result, the required flow rate error becomes large.

  Therefore, in order to measure the flow rate with high accuracy over a wide flow range, it is desired to make the change amount of the flow rate correction coefficient k as small as possible. That is, as shown in FIG. 21, it is desired that the change characteristic I having a flow rate dependency that changes suddenly on the laminar flow side approaches the flat change characteristic II (ideally a constant value).

  For this reason, for example, in Patent Document 1, as shown in FIG. 22, the built-in member 4 is provided in the measurement tube 1. This built-in member 4 is formed in a star shape, and has a central portion as a blocking surface 4a and arms 4b to 4e extending in four directions from the blocking surface 4a. When such a built-in member 4 is provided, as shown in FIG. 23, when the fluid flowing through the measuring tube 1 passes through the built-in member 4, the flow velocity of the fluid at the central portion is reduced by the blocking surface 4a, and the fluid at the peripheral portion The flow rate increases. As a result, the flow velocity distribution can be an averaged flow velocity distribution that does not have a conspicuous maximum value at the center of the pipe in both the laminar flow region and the turbulent flow region. That is, the laminar flow becomes turbulent, and the deviation ΔV2 between the true flow velocity V2 in the turbulent flow region and the average flow velocity V2 ′ measured in the ultrasonic propagation path, and the true flow velocity V1 in the laminar flow region The difference from the deviation ΔV1 from the average flow velocity V1 ′ measured in the sound wave propagation path becomes small, and the change characteristic of the flow rate correction coefficient k becomes closer to the flat change characteristic II.

Japanese Patent Publication No. 3-11648

  However, in the technique disclosed in Patent Document 1 described above, since the built-in member is provided between the pair of ultrasonic transmitters / receivers, the ultrasonic waves propagating between the transmitters / receivers are partially blocked to propagate the ultrasonic waves. The received signal is attenuated. There is a problem in that the signal-to-noise ratio of the signal is lowered due to the attenuation of the received signal, and the measurement accuracy is lowered. In addition, if an attempt is made to increase the voltage applied to the sensor in order to improve the SN ratio, there is a problem that the power consumption of the device is increased.

  The present invention has been made to solve such problems, and the object of the present invention is to enable highly accurate flow measurement over a wide flow range without lowering the SN ratio or increasing power consumption. An ultrasonic fluid measuring device is provided.

In order to achieve such an object, the present invention provides a measurement tube through which a fluid to be measured flows, a first ultrasonic transmitter / receiver disposed on the upstream peripheral surface of the measurement tube, and a downstream side of the measurement tube The flow rate of the fluid is measured based on the difference in the propagation time of the ultrasonic waves between the second ultrasonic transmitter / receiver disposed on the peripheral surface of the first ultrasonic transmitter / receiver and the second ultrasonic transmitter / receiver In the ultrasonic fluid measuring device including the measuring unit, the first ultrasonic transmitter / receiver and the second ultrasonic transmitter / receiver are connected to a pipe upstream of the first ultrasonic transmitter / receiver of the measuring tube. A cross-section in which a part of the shape projected on the cross-section orthogonal to the tube axis of the measurement tube of the member is orthogonal to the tube axis of the measurement tube of the ultrasonic wave propagation path with the placed flow velocity distribution adjusting member so as to overlap a portion of the projected trajectory, the propagation path of the ultrasonic wave, its The trajectory projected on the cross section of the propagation path perpendicular to the tube axis of the measurement tube is a triangle, and the flow velocity distribution adjusting member has a cross-sectional shape perpendicular to the tube axis of the measurement tube. The inner annular surface to be divided, the outer annular surface surrounding the peripheral edge of the measuring tube, and the connecting surface that divides the space surrounded by the inner annular surface and the outer annular surface into a plurality of spaces, and the inner annular surface. The surface, the outer annular surface, and the connecting surface are characterized by extending in parallel to the direction of the tube axis of the measuring tube .

  According to the present invention, on the ultrasonic wave propagation path, the flow velocity of the fluid after the portion having the member shape of the flow velocity distribution adjusting member can be decreased, and the flow velocity of the fluid after the portion having no member shape is increased. Therefore, the flow velocity V ′ measured by the ultrasonic flowmeter can be changed by changing the flow velocity distribution on the ultrasonic propagation path even if the flow rate of the fluid is the same.

  Further, a deviation ΔV2 between the true flow velocity V2 in the turbulent flow region and the average flow velocity V2 ′ measured in the ultrasonic propagation path, and the true flow velocity V1 in the laminar flow region and the average flow velocity V1 ′ measured in the ultrasonic propagation path. If the shape of the flow velocity distribution adjusting member is determined so that the difference from the deviation ΔV1 is as small as possible, the characteristic change of the flow rate correction coefficient k from the turbulent flow region to the laminar flow region can be brought close to a flat characteristic.

According to the present invention, the measurement tube of the member is arranged so as not to interfere with the propagation of the ultrasonic wave between the first ultrasonic transmitter / receiver and the second ultrasonic transmitter / receiver in the upstream line of the measurement tube. A flow velocity distribution adjusting member arranged so that a part of the shape projected on the cross section orthogonal to the tube axis of the tube overlaps a part of the locus projected on the cross section orthogonal to the tube axis of the measurement pipe of the ultrasonic wave propagation path. Since it is provided, the flow velocity of the fluid after the portion with the member shape of the flow velocity distribution adjusting member can be decreased, the flow velocity of the fluid after the portion without the member shape can be increased, and the propagation of the ultrasonic wave can be inhibited. Without changing the flow velocity distribution on the ultrasonic wave propagation path, the change characteristic of the flow rate correction coefficient from the turbulent flow region to the laminar flow region is brought closer to a flat change characteristic without lowering the SN ratio or increasing the power consumption. Highly accurate flow rate over a wide flow range Measurement is possible.
Further, in the present invention, the flow velocity distribution adjusting member is formed such that the cross-sectional shape orthogonal to the tube axis of the measurement tube has an inner annular surface that divides the central portion and the peripheral portion of the measurement tube, and an outer surface that surrounds the peripheral portion of the measurement tube. An annular surface and a connecting surface that divides a space surrounded by the inner annular surface and the outer annular surface into a plurality of spaces, and the inner annular surface, the outer annular surface, and the connecting surface are tube axes of the measuring tube. Since the fluid flowing through the measurement tube passes through the flow velocity distribution adjusting member, the velocity component in the tube radial direction of the fluid is removed, and the flow of the fluid is regulated in the same direction. (Rectified).

It is a schematic diagram of the ultrasonic flowmeter which shows one Embodiment (Embodiment 1) of the ultrasonic fluid measuring apparatus which concerns on this invention. It is a figure which compares and shows the flow velocity distribution in the pipe | tube on the ultrasonic wave propagation path in the case of a turbulent flow about the case where there is no flow velocity distribution adjustment member in this ultrasonic flowmeter. It is a figure which compares and shows the flow velocity distribution in the pipe | tube on the ultrasonic wave propagation path in the case of a laminar flow in the case where there is no flow velocity distribution adjustment member in this ultrasonic flowmeter. It is a figure which shows the change characteristic of a flow volume correction coefficient with and without the flow velocity distribution adjustment member in this ultrasonic flowmeter. It is a figure which shows the modification of a flow velocity distribution adjustment member. It is a figure which shows the modification of a flow velocity distribution adjustment member. It is a figure which shows the modification of a flow velocity distribution adjustment member. It is a figure which shows the modification of a flow velocity distribution adjustment member. It is a figure which shows the modification of a flow velocity distribution adjustment member. It is a figure which shows the modification of a flow velocity distribution adjustment member. It is a figure which shows the specific example (Embodiment 2) of the ultrasonic flowmeter using the flow-velocity distribution adjustment member shown in FIG. It is the front view which looked at this ultrasonic flowmeter from the side in which the flow velocity distribution adjustment member was inserted. It is a figure which compares and shows the flow velocity distribution in the pipe | tube on the ultrasonic wave propagation path in the case of a turbulent flow about the case where there is no flow velocity distribution adjustment member in this ultrasonic flowmeter. It is a figure which compares and shows the flow velocity distribution in the pipe | tube on the ultrasonic wave propagation path in the case of a laminar flow in the case where there is no flow velocity distribution adjustment member in this ultrasonic flowmeter. It is a figure which shows the relationship with the locus | trajectory of a triangle path | pass at the time of using the flow-velocity distribution adjustment member which provided the cross-section Y-shaped convex wall in this ultrasonic flowmeter. The flow velocity distribution in the tube on the ultrasonic wave propagation path in the case of turbulent flow when there is no flow velocity distribution adjusting member in the ultrasonic flowmeter using the flow velocity distribution adjusting member provided with the convex wall having a Y-shaped cross section. It is a figure shown in comparison. In an ultrasonic flowmeter using a flow velocity distribution adjusting member provided with a convex wall having a Y-shaped cross section, the flow velocity distribution in the tube on the ultrasonic propagation path in the case of laminar flow when there is no flow velocity distribution adjusting member and when there is no flow velocity distribution adjusting member It is a figure shown in comparison. It is a schematic diagram of the conventional ultrasonic flowmeter. It is a figure which shows the flow-velocity distribution in the case of the laminar flow and the turbulent flow in the pipe on the ultrasonic propagation path. It is a figure which shows the change characteristic of the flow volume correction coefficient in this ultrasonic flowmeter. It is a figure which shows the change characteristic of the flow volume correction coefficient desired in this ultrasonic flowmeter. It is a figure which shows the star-shaped integration member shown by patent document 1. FIG. It is a figure explaining the change of the velocity distribution in a pipe | tube at the time of providing a star-shaped built-in member.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, in the following description, what is not included in the scope of the right of the present invention is described as an embodiment, but here, it will be described as an embodiment.

[Embodiment 1]
FIG. 1 is a schematic diagram of an ultrasonic flowmeter showing an embodiment (Embodiment 1) of an ultrasonic fluid measuring apparatus according to the present invention. In the figure, the same reference numerals as those in FIG. 18 denote the same or equivalent components as those described with reference to FIG.

  In this ultrasonic flowmeter 100, the flow velocity distribution adjusting member 5 is provided in a pipe line upstream of the measurement pipe 1 (a pipe line upstream of the first ultrasonic transmitter / receiver 2). The flow velocity distribution adjusting member 5 includes a first rectangular parallelepiped member 5-1 positioned on the upper side of the inner peripheral surface of the measurement tube 1 and a second rectangular parallelepiped shape positioned on the lower side of the inner peripheral surface of the measurement tube 1. The longitudinal direction of the measurement tube 1 is arranged as the direction of the tube axis O of the measurement tube 1.

  In the ultrasonic flowmeter 100, the flow velocity distribution adjusting member 5 has a part of the shape projected onto the cross section orthogonal to the tube axis O of the measuring tube 1 of the members 5-1 and 5-2, and the ultrasonic propagation path. It arrange | positions so that it may overlap with a part of locus | trajectory projected on the cross section orthogonal to the tube axis | shaft O of the measurement tube 1 of this.

  FIG. 2 shows a comparison of flow velocity distributions in the tube on the ultrasonic wave propagation path in the case of turbulent flow, with and without the flow velocity distribution adjusting member 5. 2A shows a case where the flow velocity distribution adjusting member 5 is not provided, and FIG. 2B shows a case where the flow velocity distribution adjusting member 5 is provided. As can be seen by comparing these figures, in this ultrasonic flowmeter 100, when the fluid flowing through the measurement tube 1 passes through the flow velocity distribution adjusting member 5, the fluid after the portion where the member shape of the flow velocity distribution adjusting member 5 is present. The flow velocity of the fluid is decreased and the flow velocity of the fluid after the portion without the member shape is increased, but in the turbulent region, the average flow velocity measured on the ultrasonic propagation path with and without the flow velocity distribution adjusting member 5 V2 ′ may not change much.

  FIG. 3 shows a comparison of flow velocity distributions in the tube on the ultrasonic wave propagation path in the case of laminar flow, with and without the flow velocity distribution adjusting member 5. 3A shows a case where the flow velocity distribution adjusting member 5 is provided, and FIG. 3B shows a case where the flow velocity distribution adjusting member 5 is not provided. As can be seen by comparing these figures, in this ultrasonic flowmeter 100, when the fluid flowing through the measurement tube 1 passes through the flow velocity distribution adjusting member 5, the fluid after the portion where the member shape of the flow velocity distribution adjusting member 5 is present. The flow rate of the fluid decreases, and the fluid flow rate after the part without the member shape increases. In the case of a laminar flow region, the average flow velocity V1 'measured on the ultrasonic wave propagation path can vary greatly depending on whether or not the flow velocity distribution adjusting member 5 is present.

In this ultrasonic flow meter 100, by providing the flow velocity distribution adjusting member 5, as shown in FIG. 2B and FIG. 3B, measurement is performed with the true flow velocity V2 in the turbulent flow region and the ultrasonic propagation path. The difference between the deviation ΔV2 from the average flow velocity V2 ′ and the deviation ΔV1 between the true flow velocity V1 in the laminar flow area and the average flow velocity V1 ′ measured in the ultrasonic wave propagation path becomes small. As a result, the change characteristic of the flow rate correction coefficient k becomes closer to the flat change characteristic II (see FIG. 4), and high-precision flow rate measurement is possible over a wide flow rate range.

  In the first embodiment, the flow velocity distribution adjusting member 5 is provided with the rectangular parallelepiped members 5-1 and 5-2 above and below the measuring tube 1 as shown in FIG. The members 5-3 and 5-4 may also be provided on the left and right. Moreover, as shown in FIG. 6, the ring-shaped member 6 may be provided as a flow velocity distribution adjusting member, and as shown in FIG. 7, the ring-shaped member 6 in which a large number of through holes 6a are formed is flow velocity distribution. You may make it provide as an adjustment member.

  Further, as shown in FIG. 8, a member 7 in which an inner annular member 7-1 and an outer annular member 7-2 are connected by a large number of ribs 7-3 may be used as a flow velocity distribution adjusting member. The flow velocity distribution adjusting member 7 (7A) has a cross-sectional shape orthogonal to the tube axis O of the measuring tube 1 and an inner annular surface 7a that divides the central portion and the peripheral portion of the measuring tube 1 and the peripheral edge of the measuring tube 1 An outer annular surface 7b that surrounds the portion, and a connecting surface 7d that divides a space surrounded by the inner annular surface 7a and the outer annular surface 7b into a plurality of spaces 7c, the inner annular surface 7a, the outer annular surface 7b and the connecting surface 7d are shaped to have a length in the direction of the tube axis O of the measuring tube 1.

  In the ultrasonic flowmeter 100 using the flow velocity distribution adjusting member 7A, when the fluid flowing through the measurement tube 1 passes through the flow velocity distribution adjusting member 7A, it is divided by the space 7e having the inner diameter φ1 of the inner annular surface 7a and the connecting surface 7d. It passes through a plurality of spaces (divided spaces) 7c between the inner annular surface 7a and the outer annular surface 7b. A space 7e and a divided space 7c having an inner diameter φ1 of the inner annular surface 7a have a length in the direction of the tube axis O, and a passage (inner side) extending in the direction of the tube axis O of the space 7e having an inner diameter φ1 of the inner annular surface 7a. When the fluid passes through the passage (7f) and the passage (outer passage) 7g extending in the direction of the tube axis O of the divided space 7c, the velocity component in the tube radial direction of the fluid is removed and the flow of the fluid is regulated in the same direction. (Rectified).

  As a modification of the flow velocity distribution adjusting member 7, the flow velocity distribution adjusting member 7B having a reduced number of divided spaces 7c as shown in FIG. 9A, for example, three, and the dividing as shown in FIG. 9B. For example, a flow velocity distribution adjusting member 7C in which the number of spaces 7c is increased to twelve, for example, and a flow velocity distribution adjusting member 7D in which the size of the divided space 7c is changed as shown in FIG. Further, the flow velocity distribution adjusting member 7E in which the length of the outer annular member 7-2 as shown in FIG. 10 (a) is longer than that of the inner annular member 7-1, as shown in FIG. 10 (b). A flow velocity distribution adjusting member 7F in which the length of the annular member 7-1 is longer than that of the outer annular member 7-2 is also conceivable.

[Embodiment 2]
FIG. 11 shows a specific example of an ultrasonic flowmeter using the flow velocity distribution adjusting member 7A as the second embodiment. In this ultrasonic flowmeter 200, the flow velocity distribution adjusting member 7A is detachably fitted in the pipe line 1-1 on the inlet side of the measuring pipe 1. When the outlet side pipe line 1-2 is used as the inlet side, the flow velocity distribution adjusting member 7A is fitted into the outlet side pipe line 1-2.

  Further, in this ultrasonic flowmeter 200, the ultrasonic propagation path (ultrasonic propagation path) between the ultrasonic transmitter / receiver 2 and the ultrasonic transmitter / receiver 3 in FIG. The ultrasonic transmitter / receiver 2 and the ultrasonic transmitter / receiver 3 are connected to the outer peripheral surface of the measuring tube 1 so that the locus projected on the cross section orthogonal to the tube axis O of the measuring tube 1 of the sound wave propagation path 8 becomes a triangle (see FIG. 12). Is arranged. In this case, the ultrasonic propagation path 8 between the ultrasonic transmitter / receiver 2 and the ultrasonic transmitter / receiver 3 has two reflection points on the inner peripheral surface of the measuring tube 1.

  The ultrasonic wave propagation path 8 having two reflection points is a technique already known as a triangle path, and by passing the propagation path through the flow path so that the ultrasonic wave passes through almost the entire area of the flow path cross section. It is known as a technique that can average out the deviations well even for a flow with deviations and can measure the flow rate with high accuracy.

  FIG. 13 shows a comparison of flow velocity distributions in the tube on the ultrasonic wave propagation path in the case of turbulent flow with and without the flow velocity distribution adjusting member 7A. FIG. 13A shows a case where the flow velocity distribution adjusting member 7A is not provided, and FIG. 13B shows a case where the flow velocity distribution adjusting member 7A is provided. As can be seen by comparing this figure, in this ultrasonic flowmeter 200, when the fluid flowing through the measurement tube 1 passes through the flow velocity distribution adjusting member 7A, at each side of the triangular locus of the ultrasonic propagation path 8, The velocity distribution is such that the flow velocity at the center is smaller than the flow velocity at both ends. In this case, the amount of decrease in the flow rate at the center is small. Thereby, in the turbulent flow region, the average flow velocity V2 'measured in the ultrasonic wave propagation path does not change much.

  FIG. 14 shows a comparison of flow velocity distributions in the tube on the ultrasonic wave propagation path in the case of laminar flow, with and without the flow velocity distribution adjusting member 7A. FIG. 14A shows a case where the flow velocity distribution adjusting member 7A is not provided, and FIG. 14B shows a case where the flow velocity distribution adjusting member 7A is provided. As can be seen by comparing this figure, in this ultrasonic flowmeter 200, when the fluid flowing through the measurement tube 1 passes through the flow velocity distribution adjusting member 7A, at each side of the triangular locus of the ultrasonic propagation path 8, The velocity distribution is such that the flow velocity at the center is smaller than the flow velocity at both ends. In this case, the amount of decrease in the flow rate at the center is large. As a result, in the laminar flow region, the average flow velocity V1 'measured by the ultrasonic wave propagation path greatly changes.

  In this ultrasonic flowmeter 200, by providing the flow velocity distribution adjusting member 7A, as shown in FIG. 13B and FIG. 14B, measurement is performed with the true flow velocity V2 in the turbulent region and the ultrasonic propagation path. The difference between the deviation ΔV2 from the average flow velocity V2 and the deviation ΔV1 between the true flow velocity V1 in the laminar flow area and the average flow velocity V1 ′ measured in the ultrasonic wave propagation path becomes small. As a result, the change characteristic of the flow rate correction coefficient k becomes closer to the flat change characteristic II (see FIG. 4), and high-precision flow rate measurement is possible over a wide flow rate range. Further, when the fluid passes through the flow velocity distribution adjusting member 7A, the flow of the fluid is rectified by the inner passage 7f and the outer passage 7g, so that the flow rate can be measured with high accuracy.

  In addition, when using a triangle path | pass, you may make it provide the flow velocity distribution adjustment member 7G as shown in FIG. In this flow velocity distribution adjusting member 7G, convex walls 71 to 73 having a Y-shaped cross section are provided so as to overlap each corner portion of the triangular locus of the triangle path. The convex walls 71 to 73 have a length in the direction of the tube axis O of the measuring tube 1.

  FIG. 16 shows a comparison of flow velocity distributions in the pipe on the ultrasonic wave propagation path in the case of turbulent flow, with and without the flow velocity distribution adjusting member 7G. FIG. 16A shows a case where there is no flow velocity distribution adjusting member 7G, and FIG. 16B shows a case where there is a flow velocity distribution adjusting member 7G. As can be seen by comparing these figures, when the convex walls 71 to 73 having a Y-shaped cross section are provided, when the fluid flowing through the measuring tube 1 passes through the flow velocity distribution adjusting member 7G, the triangle of the ultrasonic propagation path 8 is obtained. In each side of the trajectory, the velocity distribution is such that the flow velocity at both ends is smaller than the flow velocity at the central portion. In this case, the amount of decrease in the flow velocity at both ends is small. Thereby, in the turbulent flow region, the average flow velocity V2 'measured in the ultrasonic wave propagation path does not change much.

  FIG. 17 shows a comparison of flow velocity distributions in the tube on the ultrasonic wave propagation path in the case of laminar flow, with and without the flow velocity distribution adjusting member 7G. FIG. 17A shows a case where there is no flow velocity distribution adjusting member 7G, and FIG. 17B shows a case where there is a flow velocity distribution adjusting member 7G. As can be seen by comparing these figures, when the convex walls 71 to 73 having a Y-shaped cross section are provided, when the fluid flowing through the measuring tube 1 passes through the flow velocity distribution adjusting member 7G, the triangle of the ultrasonic propagation path 8 is obtained. In each side of the trajectory, the velocity distribution is such that the flow velocity at both ends is smaller than the flow velocity at the central portion. In this case, the amount of decrease in the flow velocity at both ends is large. As a result, in the laminar flow region, the average flow velocity V1 'measured by the ultrasonic wave propagation path greatly changes.

  Thus, in the same manner as when the flow velocity distribution adjusting member 7A is provided, the deviation ΔV2 between the true flow velocity V2 in the turbulent flow region and the average flow velocity V2 measured in the ultrasonic wave propagation path, and the true flow velocity in the laminar flow region. The difference between the difference ΔV1 between V1 and the average flow velocity V1 ′ measured by the ultrasonic wave propagation path is reduced, and the change characteristic of the flow rate correction coefficient k becomes closer to the flat change characteristic II (see FIG. 4). Highly accurate flow measurement is possible over a wide flow range.

  In the second embodiment, the locus projected on the cross section orthogonal to the tube axis of the measurement tube 1 of the ultrasonic wave propagation path 8 is a triangle. However, the locus is not limited to a triangle, and may be a quadrangle, a pentagon, or the like. Good. In the case of a quadrangular shape, there are three reflection points on the inner peripheral surface of the measuring tube 1, and in the case of a pentagonal shape, there are four reflection points on the inner peripheral surface of the measuring tube 1.

  Further, the flow velocity distribution adjusting member 7 (7A to 7G) is not necessarily provided so as to be detachable from the measuring tube 1, but may be fixed. Alternatively, the measurement tube 1 may be integrally formed. By making the flow velocity distribution adjusting member 7 (7A to 7G) detachable, maintenance becomes easy, and when foreign matters such as dust are clogged, they can be easily removed.

  In the first and second embodiments described above, the ultrasonic flowmeter for obtaining the flow rate from the measured fluid flow velocity has been described as an example. However, the ultrasonic flowmeter for obtaining the flow velocity of the fluid itself, and the ultrasonic wave for obtaining the heat amount from the flow rate. It goes without saying that a similar configuration can be adopted in a calorimeter or the like.

[Extension of the embodiment]
The present invention has been described above with reference to the embodiment. However, the present invention is not limited to the above embodiment. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the technical idea of the present invention. Each embodiment can be implemented in any combination within a consistent range.

  DESCRIPTION OF SYMBOLS 1 ... Measuring tube, O ... Tube axis, 2 ... 1st ultrasonic transmitter / receiver, 3 ... 2nd ultrasonic transmitter / receiver, 5, 6, 7 (7A-7G) ... Flow velocity distribution adjustment member, 7-1 ... Inner annular member, 7-2 ... outer annular member, 7-3 ... rib, 7a ... inner annular surface, 7b ... outer annular surface, 7c ... divided space, 7d ... connection surface, 7e ... space of inner diameter φ1, 7f ... inner passage, 7g ... outer passage, 8 ... ultrasonic propagation path.

Claims (1)

A measurement tube through which a fluid to be measured flows, a first ultrasonic transmitter / receiver disposed on a peripheral surface on the upstream side of the measurement tube, and a second ultrasonic wave disposed on a peripheral surface on the downstream side of the measurement tube An ultrasonic wave comprising: a transmitter / receiver; and a measurement unit that measures a flow velocity of the fluid based on a difference in propagation time of ultrasonic waves between the first ultrasonic transmitter / receiver and the second ultrasonic transmitter / receiver. In the fluid measuring device,
The propagation of the ultrasonic wave between the first ultrasonic transmitter / receiver and the second ultrasonic transmitter / receiver is not disturbed in the pipe line upstream of the first ultrasonic transmitter / receiver of the measurement tube. A part of the shape projected on the cross section perpendicular to the tube axis of the measurement tube of the member is part of the locus projected onto the cross section of the ultrasonic wave propagation path perpendicular to the tube axis of the measurement tube. It has a flow velocity distribution adjustment member arranged so as to overlap ,
The ultrasonic propagation path is:
The locus projected on the cross section perpendicular to the tube axis of the measurement tube of the propagation path is a triangle,
The flow velocity distribution adjusting member is
The shape of the cross section orthogonal to the tube axis of the measurement tube is an inner annular surface that divides the central portion and the peripheral portion of the measurement tube, an outer annular surface that surrounds the peripheral portion of the measurement tube, and the inner annular surface A shape having a connecting surface that divides a space surrounded by the outer annular surface into a plurality of spaces;
The inner annular surface, the outer annular surface and the connecting surface are:
2. An ultrasonic fluid measuring apparatus having a shape extending in parallel with a direction of a tube axis of the measuring tube .