JP5168722B2 - Ultrasonic flow meter and sound absorbing material for ultrasonic flow meter - Google Patents

Description

  The present invention relates to an ultrasonic flowmeter capable of measuring a flow rate of a fluid to be measured from a flow velocity distribution in a measurement region, and more particularly to a technique of an ultrasonic flowmeter in an open eye having a free water surface.

  For example, Patent Document 1 discloses a technique for measuring a flow rate using an ultrasonic flowmeter in Kaiai. The technology disclosed here acquires flow velocity distributions from the water surface side and bottom surface side of the flow path through which the fluid flows, obtains the flow velocity distribution in the depth direction of the flow path based on these acquired flow velocity distributions by calibration processing, By integrating the obtained flow velocity distribution in the depth direction along the channel width direction, the flow rate can be obtained with high accuracy.

  In the case of flow measurement with an ultrasonic flowmeter in such an opening, if an ultrasonic wave is transmitted from the bottom of the channel toward the water surface, the ultrasonic echo reflected by particles (reflectors) such as bubbles mixed in the water In addition to the signal, a signal or the like caused by the reflected wave reflected on the water surface is received by the receiving unit on the bottom surface of the flow path, which may cause a measurement error.

  This will be described with reference to FIG. As the ultrasonic wave transmitted by the ultrasonic wave transmitting / receiving means 30, it is desirable to use only the reflected wave 91a reflected from the reflector (bubble) 20 in the fluid to be measured. Further, on the water surface 70 where the transmitted ultrasonic wave 90 has arrived, a reflected wave 91b in a direction returning to the ultrasonic wave transmitting / receiving unit 30 is also generated, but if the reflected wave 91b is received by the ultrasonic wave transmitting / receiving unit 30, position information on the water surface is obtained. This is not a problem, but rather a desirable signal for flow measurement. However, as shown in FIG. 4, the reflected wave 91 c generated on the water surface 70 is reflected on the water bottom 71, and the reflected wave 91 e reflected on the water surface 70 is again received by the ultrasonic transmission / reception means 30. This can cause measurement errors.

  Although illustration is omitted, if the flow velocity distribution of the fluid to be measured can be measured only with the reflected wave reflected by bubbles in the fluid to be measured, the measurement result should theoretically draw a smooth curve. , The actual measurement result will draw a distorted curve.

The above-mentioned problem in the flow measurement by the ultrasonic flow meter is the same in the flow measurement by the ultrasonic flow meter that measures the flow velocity distribution of the fluid to be measured flowing in the pipe by making the ultrasonic wave incident from the outside of the pipe. For example, Patent Literature 2 discloses a technique for improving measurement accuracy by reducing a measurement error caused by a reflected wave from a pipe. Provide a sound-absorbing material that can be fixed to the pipe outer wall at the ultrasonic wave arrival position in the fluid piping of the fluid to be measured, and make the acoustic impedance of the sound-absorbing material close to the acoustic impedance of the fluid piping. This is to solve the problem.
JP-A-2005-321314 JP-A-2005-195371

  However, the above-described solution is provided with a sound absorbing material on the outer wall of a solid pipe, and is not directly applicable to the flow measurement in opening. For example, if a sound absorbing material is floated and arranged on an open pier that has a free water surface, the presence of the portion under the water surface of the sound absorbing material near the water surface becomes a resistance against the flow of the fluid to be measured. The problem arises that the measurement of the flow velocity distribution in a natural flow state is hindered. Also, if there is an air flow, the presence of the sound absorbing material on the surface of the water acts as a resistance to the air flow, which affects the flow below the surface of the water, resulting in the state of the natural flow of the fluid being measured. To change.

  In view of such problems, the present invention prevents reflection of ultrasonic waves on the water surface, eliminates interference with the natural flow of the fluid to be measured, and keeps the flow as close to the water surface as possible. It is an object of the present invention to provide a sound-absorbing material that contributes to improving the accuracy of flow measurement using an ultrasonic flowmeter in the open eye, and an ultrasonic flowmeter using such a sound-absorbing material.

  In order to solve the above problems, a typical structure of the sound absorbing material according to the present invention used in an ultrasonic flowmeter is to superimpose a fluid to be measured in an open mouth having a free water surface from the flow path bottom to the water surface. An ultrasonic transmission means for making a sound wave incident; an ultrasonic reception means for receiving a reflected ultrasonic echo of an ultrasonic wave incident on a fluid to be measured; and a flow velocity of the fluid to be measured by processing the received ultrasonic echo A fluid velocity distribution measuring means for measuring the distribution and a flow rate calculating means for calculating the flow rate of the fluid to be measured based on the flow velocity distribution of the fluid to be measured are used for an ultrasonic flowmeter for measuring the flow rate of the fluid to be measured. It is a sound-absorbing material that floats on the surface of the open water and absorbs ultrasonic waves, a floating support that places the main body in the vicinity of the water surface, and a position where ultrasonic waves reach the surface of the water in the open surface To be connected to external fixed objects It includes a connection portion, the bottom surface of the body portion, characterized by being formed in the shape of a curved surface having a curvature to reduce the frictional resistance to the flow of the fluid to be measured.

  According to the above configuration, the ultrasonic wave transmitted from the bottom surface of the flow path during the opening and reaching the water surface is absorbed by the sound absorbing material arranged so as to float on the water surface, thereby preventing reflection on the water surface. Therefore, the signal caused by the reflected wave on the water surface is suppressed from reaching the ultrasonic wave transmitting / receiving means on the bottom surface, and the accuracy of flow rate measurement can be improved.

  In addition, since the bottom surface of the main body is formed in a curved surface shape having a curvature that reduces the frictional resistance against the flow of the fluid to be measured, the bottom of the main body is located between the main body and the flow of the fluid to be measured that collides with the bottom surface. Since the generated frictional resistance is minimized, the natural flow of the fluid to be measured is prevented from being disturbed.

  The technology related to the measurement means such as the flow rate calculation means of the ultrasonic flowmeter is described in, for example, the above-mentioned Patent Document 2 and is a general matter, and thus the description thereof is omitted here.

  Another typical configuration of the sound absorbing material according to the present invention is an ultrasonic transmission means for injecting an ultrasonic wave into a fluid to be measured in an opening having a free water surface from the bottom surface of the channel toward the water surface, and a fluid to be measured. An ultrasonic receiving means for receiving a reflected ultrasonic echo of the ultrasonic wave incident on the fluid; a fluid velocity distribution measuring means for processing the received ultrasonic echo and measuring a flow velocity distribution of the fluid to be measured; A sound-absorbing material that is used in an ultrasonic flowmeter that measures the flow rate of a fluid to be measured based on the flow velocity distribution of the fluid and that has a flow rate calculation means for calculating the flow rate of the fluid to be measured. Main body part that absorbs ultrasonic waves, floating support part that floats the main body part in the vicinity of the water surface, and connection part that is connected to an external fixed object in order to stay at the ultrasonic wave arrival position on the water surface in the culvert The body part is friction against air flow Reducing anti and characterized by being formed into a shape having a path of air.

  According to this configuration, reflection of ultrasonic waves on the water surface is prevented, and the main body is formed in a shape having an air passage that reduces frictional resistance against the air flow, so there is an air flow. In such a case, the presence of the sound absorbing material on the surface of the water does not become a resistance to the air flow, which affects the flow below the water surface and changes the natural flow state of the fluid to be measured. Preventing the occurrence of

  You may comprise as invention of an ultrasonic flowmeter provided with the sound-absorbing material concerning this invention. A typical configuration of such an ultrasonic flowmeter is an ultrasonic transmission means for injecting ultrasonic waves into the fluid to be measured in the open channel having a free water surface from the bottom surface of the flow path toward the water surface, and the ultrasonic fluid is incident on the fluid to be measured. Ultrasonic receiving means for receiving reflected ultrasonic echoes, fluid velocity distribution measuring means for processing the received ultrasonic echoes and measuring the flow velocity distribution of the fluid to be measured, and the flow velocity of the fluid to be measured An ultrasonic flowmeter comprising a flow rate calculation means for calculating the flow rate of the fluid to be measured based on the distribution and measuring the flow rate of the fluid to be measured, wherein the ultrasonic flowmeter is provided with the sound absorbing material. it can.

  According to such a configuration, it is possible to suppress the reflection of ultrasonic waves on the water surface during opening, eliminate interference with the natural flow of the fluid to be measured, and measure the flow rate with high accuracy up to the vicinity of the water surface.

  According to the present invention, in the flow measurement with an ultrasonic flowmeter in the open sea, the reflection of ultrasonic waves on the water surface is prevented, and interference with the natural flow of the fluid to be measured is eliminated, so that the natural flow to the vicinity of the water surface is eliminated. The flow rate can be measured in the flow state, and the measurement accuracy can be improved.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are omitted. To do.

  FIG. 1 is an external view of a sound absorbing material according to the present embodiment. Fig.1 (a) is the figure which looked at the sound-absorbing material from the side, FIG.1 (b) is a top view, FIG.1 (c) is a front view. The sound absorbing material 10 includes a main body part 11, a connection part 12 for connecting a connection wire 13, and a floating support part 14. The sound absorbing material 10 is floated on the water surface in the unfolding and absorbs ultrasonic waves that reach the lower surface of the main body 11.

  The main body 11 has a density smaller than that of the fluid to be measured so as to float on the water surface. Depending on the density, the floating assisting portion 14 plays a role of imparting buoyancy to the sound absorbing material 10 so that the sound absorbing material 10 can float on the water surface when the sound absorbing material 10 cannot obtain sufficient buoyancy. When the sound absorbing material 10 is placed near the water surface and floats by the action of the floating support unit 14, a flow velocity distribution up to a region closer to the water surface can be obtained, and the flow rate can be measured with higher accuracy.

  In order to fulfill this role, the floating support unit 14 is made of, for example, foamed polystyrene. In FIG. 1, the floating support portion 14 has a substantially triangular prism shape and is fixed to the main body portion 11 by fitting. The fixing method of the floating support portion 14 and the main body portion 11 is, for example, the floating support portion 14. Alternatively, the main body 11 may be provided with a male screw and a female screw and screwed together. The shape and size of the floating support part 14 are not particularly limited as long as they fulfill the above role.

  At least the lower surface of the main body 11 is made of a porous member, a foamed resin, and a fiber-like plate member, so that ultrasonic waves can be absorbed. For example, the foamed polyurethane itself or foamed polyurethane having a felt bonded to the lower surface with an adhesive can be used as the main body 11.

  The lower surface of the main body 11 is also formed in a curved shape having a curvature that reduces the frictional resistance against the flow of the fluid to be measured. By forming in this shape, the frictional resistance generated between the main body 11 and the flow of the fluid to be measured that collides with the bottom surface of the main body 11 can be minimized. Therefore, by preventing the natural flow of the fluid to be measured from being disturbed, the flow rate can be measured in a natural flow state up to the vicinity of the water surface, and the measurement accuracy can be improved.

  For example, the connecting portion 12 connects the connecting wire 13 connected to the scaffold 41 (see FIG. 3) and the main body portion 11 and plays a role of keeping the sound absorbing material 10 at a predetermined position where the ultrasonic waves reach. In the present embodiment, the connection portion 12 is illustrated as having a hand ring (annular metal fitting), but the shape of the connection portion 12 is not limited to this, and a groove is provided on the outer periphery of the main body portion 11. Alternatively, a hole for connecting the connection wire 13 to the main body 11 may be provided.

  The connection means between the scaffold 41 and the sound absorbing material 10 is not limited to the connection wire 13, and may be a rope or a string as long as the sound absorbing material 10 is held at a predetermined position. The shape and size of the sound absorbing material 10 are not particularly limited as long as they can absorb ultrasonic waves that reach the water surface.

  FIG. 2 is an external view of a sound absorbing material according to another embodiment of the present invention. 2A is a cross-sectional view taken along the line BB in FIG. 2B, FIG. 2B is a cross-sectional view taken along the line AA in FIG. 2A, and FIG. It is CC sectional drawing of b). The sound absorbing material 10 according to the present embodiment is composed of a main body portion 11a, a connecting portion 12 for connecting a connecting wire 13, and a floating assisting portion 14, like the sound absorbing material 10 shown in FIG. As shown in FIG. 2, the portion 11 a is formed from an upper plate 111, a lower plate 112, a side structure material 113, and a center structure material 114.

  With this structure, the main body 11a forms an air passage that reduces the frictional resistance against the air flow when there is an air flow. That is, the air that has entered from one end of the main body portion 11a passes through the air passage formed by the upper plate 111, the lower plate 112, the side structural member 113, and the central structural member 114, and from the other end of the main body portion 11a. to go out. Here, the air passage is formed so that the presence of the portion of the main body portion 11a on the water surface does not become a resistance to the air flow, so that the influence on the flow below the water surface is reduced, and the measurement is made. By preventing the occurrence of a situation where the state of the natural flow of the fluid changes, the measurement accuracy up to the vicinity of the water surface can be improved.

  In order to obtain such an effect, it is desirable that part of the lateral structural member 113 and the central structural member 114 are formed into a substantially streamlined shape as shown in FIG. When it is difficult to form a substantially streamlined shape, it is possible to reduce the air resistance by increasing the cross-sectional area of the air passage or reducing the thickness of the structural material.

  FIG. 3 is a diagram for explaining an ultrasonic flowmeter having a sound absorbing material. As shown in FIG. 3, the sound absorbing material 10 is floated by being placed in the vicinity of the water surface 70 of the flow path, and is connected to a scaffold 41 fixed to a guide 40 a assembled by a single pipe or the like by a connection wire 13. The That is, the guide 40a functions as an external fixed object for keeping the sound absorbing material 10 at a predetermined position. The sound absorbing material 10 may be suspended from the scaffold 41 fixed above and floated on the water surface 70.

  When there is not enough reflector 20 (such as bubbles) for measurement in the fluid 80 to be measured, the bubble generator 50 supplies the reflector 20 (bubbles). The bubble generating device 50 is fixed by a guide 40a. The ultrasonic transmission / reception means 30 (transducer) that transmits and receives ultrasonic waves is disposed on the water bottom 71 on the downstream side of the flow path and is fixed by the guide 40b. The ultrasonic transmission / reception means 30 is connected to an arithmetic processing unit (not shown), and the flow velocity distribution is measured based on the signal transmitted / received by the ultrasonic transmission / reception means 30 and the flow rate is measured. The white arrow in FIG. 3 indicates the direction in which the fluid 80 to be measured flows.

  The transmitted ultrasonic wave 90 transmitted from the ultrasonic transmission / reception means 30 is reflected by a large number of reflectors 20 existing on the measurement line, and the reflected wave 91 a is received by the ultrasonic transmission / reception means 30. The transmitted ultrasonic wave 90 is, for example, a straight beam having a pulse width of about 5 mm and hardly spreading, and reaches the water surface 70.

  In the absence of the sound absorbing material 10, the transmitted ultrasonic wave 90 that has reached the water surface 70 is reflected by the water surface 70, and the reflected wave 91c (see the vicinity of the water surface 100) causes measurement errors as described above.

  On the other hand, the case where the sound absorbing material 10 according to the present invention is on the water surface 70 is as follows. For example, the main body 11 is a foamed polyurethane foam and the fluid 80 to be measured is water. The transmitted ultrasonic wave 90 enters the foamed polyurethane by reflection or transmission at the interface between the foamed polyurethane and water (ultrasonic wave 92 in FIG. 3).

  Since the polyurethane foam has a large number of small and large holes, the ultrasonic wave 92 incident on the polyurethane foam is reflected in various directions at the interface between the polyurethane foam and water. In the process of irregular reflection, the energy of the ultrasonic wave 92 is converted into heat by friction with water, or is lost by being converted into vibration energy of the polyurethane foam, and the ultrasonic wave 92 is absorbed by the polyurethane foam.

  Therefore, the transmitted ultrasonic wave 90 that has reached the water surface 70 is almost absorbed by the sound absorbing material 10, and the generation of the reflected wave 91c that causes an error in flow rate measurement is suppressed. Further, it can be suppressed that the ultrasonic wave 92 incident on the sound absorbing material 10 is reflected again at the interface between the sound absorbing material 10 and the air and is received by the ultrasonic wave transmitting / receiving means 30 and becomes an error factor in flow rate measurement.

  Further, since the lower surface of the main body 11 is formed in a curved surface shape having a curvature that reduces the frictional resistance against the flow of water, the frictional resistance of the water flowing in the direction of the main body and the arrow is minimized. Therefore, in the vicinity of the water surface 100, since the natural flow of water is not disturbed to the vicinity of the water surface, the flow rate can be measured without destroying the original flow state of the water.

  The present invention relates to a sound absorbing material that absorbs ultrasonic waves on the water surface, prevents reflection thereof, and realizes a natural flow to the vicinity of the water surface in the flow measurement by an ultrasonic flow meter in the open eye. It can be used as an ultrasonic flowmeter having

It is an external view of the sound absorbing material according to the present embodiment. It is an external view of the sound-absorbing material according to another embodiment. It is a figure explaining the ultrasonic flowmeter which has a sound-absorbing material. It is a figure explaining the problem of the prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Sound-absorbing material 11, 11a ... Main-body part, 12 ... Connection part, 13 ... Connection wire, 14, 14a ... Floating assistance part, 20 ... Reflector (bubble in fluid), 30 ... Ultrasonic transmission / reception means (transducer) , 40a, 40b ... guide, 41 ... scaffold, 50 ... bubble generator, 70 ... water surface, 71 ... water bottom, 80 ... fluid to be measured, 90 ... transmitted ultrasonic wave, 91a, 91b, 91c, 91d, 91e ... reflected wave, 92 ... Ultrasonic, 100 ... Near water surface, 111 ... Upper plate, 112 ... Lower plate, 113 ... Side structure material, 114 ... Center structure material

Claims (3)

Ultrasonic wave transmission means for making ultrasonic waves enter the fluid under measurement in the open channel with a free water surface from the channel bottom to the water surface, and receiving the reflected ultrasonic echo of the ultrasonic wave incident on the fluid under measurement An ultrasonic receiving means for processing, a fluid velocity distribution measuring means for processing the received ultrasonic echo and measuring a flow velocity distribution of the fluid to be measured, and a flow rate of the fluid to be measured based on the flow velocity distribution of the fluid to be measured. A sound-absorbing material for use in an ultrasonic flowmeter that measures the flow rate of a fluid to be measured,
A body that floats on the surface of the open water and absorbs ultrasound,
A floating aid part for placing the main body part near the water surface;
In order to stay at the ultrasonic wave arrival position on the water surface in the culvert, a connection part for connecting to an external fixed object is provided,
The sound absorbing material, wherein the bottom surface of the main body is formed in a curved shape having a curvature that reduces a frictional resistance against a flow of a fluid to be measured. Ultrasonic wave transmission means for making ultrasonic waves enter the fluid under measurement in the open channel with a free water surface from the channel bottom to the water surface, and receiving the reflected ultrasonic echo of the ultrasonic wave incident on the fluid under measurement An ultrasonic receiving means for processing, a fluid velocity distribution measuring means for processing the received ultrasonic echo and measuring a flow velocity distribution of the fluid to be measured, and a flow rate of the fluid to be measured based on the flow velocity distribution of the fluid to be measured. A sound-absorbing material for use in an ultrasonic flowmeter that measures the flow rate of a fluid to be measured,
A body that floats on the surface of the open water and absorbs ultrasound,
A floating aid part for placing the main body part near the water surface;
In order to stay at the ultrasonic wave arrival position on the water surface in the culvert, a connection part for connecting to an external fixed object is provided,
The sound-absorbing material, wherein the main body is formed in a shape having an air passage that reduces frictional resistance against air flow.   Ultrasonic wave transmission means for making ultrasonic waves enter the fluid under measurement in the open channel with a free water surface from the channel bottom to the water surface, and receiving the reflected ultrasonic echo of the ultrasonic wave incident on the fluid under measurement Ultrasonic wave receiving means, fluid velocity distribution measuring means for processing the received ultrasonic echoes and measuring the flow velocity distribution of the fluid under measurement, and the flow rate of the fluid under measurement based on the flow velocity distribution of the fluid under measurement. An ultrasonic flowmeter comprising a flow rate calculating means for calculating the flow rate of the fluid to be measured and comprising the sound absorbing material according to claim 1.

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