JP2005195374A - Ultrasonic flowmeter, and wedge used therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a measuring error caused by generation of two kinds of waves to provide a technique for measuring an accurate flow rate, in particular, for conducting precise measurement in several mm-several tens mm of small aperture pipe. <P>SOLUTION: In this ultrasonic flowmeter, a sound wave propagating medium (wedge when it is a solid) is interposed between an ultrasonic oscillator for generating a longitudinal ultrasonic wave and the pipe, and the ultrasonic oscillator is inclined to bring the incident ultrasonic wave into a critical angle or more in the longitudinal wave calculated pursuant to Snell's law, when the incident ultrasonic wave is transmitted through a fluid pipe wall, by interposing the medium. Only a transverse wave is thereby transmitted into a measured fluid. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ultrasonic flowmeter capable of instantaneously measuring a flow rate of a fluid to be measured from a flow velocity distribution in a measurement region in a time-dependent manner and a technique related thereto.

  Various techniques have been provided for Doppler ultrasonic flowmeters capable of measuring the flow rate without contact. (For example, JP 2000-97742 A)

JP 2000-97742 A

  The above technique will be specifically described. The Doppler type ultrasonic flowmeter disclosed in the above document is an ultrasonic transmission that causes an ultrasonic pulse of a required frequency to enter a measured fluid in a fluid (for example, water) pipe along a measurement line from an ultrasonic transducer. Means, a fluid velocity distribution measuring means for receiving an ultrasonic echo reflected from the measurement area among ultrasonic pulses incident on the measurement fluid, and measuring a flow velocity distribution of the measurement fluid in the measurement area; and the measurement A flow rate calculation means for calculating the flow rate of the fluid under measurement in the measurement region is provided based on the flow velocity distribution of the fluid, and the flow rate of the fluid under measurement is measured.

  This technique measures the flow velocity distribution of the fluid to be measured flowing in the pipe, and is excellent in responsiveness to the transient flow rate that varies with time. In addition, the flow rate of the fluid to be measured even in places where the flow of the fluid is not sufficiently developed or where the flow is three-dimensional, such as an elbow pipe or a bent pipe such as a U-shaped inverted pipe Can be measured efficiently and instantaneously. Compared to the ultrasonic flowmeters provided before that, there is a feature that accurate measurement is possible without the "flow rate correction coefficient" calculated from experimental values and experience values, etc. Has been.

  Now, as shown in FIG. 6, when the material (acoustic impedance) of the wedge 30 and the fluid pipe 10 is different, the ultrasonic wave incident from the ultrasonic transducer 20 is separated from the longitudinal wave, which is a dense wave, It is known that transverse waves due to shear stress are generated by mode conversion at the interface. Then, it enters the measured fluid 11 as two parallel longitudinal waves.

  The incident angle is determined by the sound speed in the contact medium (wedge 30) and the sound speed of the fluid to be measured according to Snell's law. In a general case where acrylic resin is used for the wedge 30 and aluminum is used for the fluid pipe 10, the speed of the transverse wave is slower in the fluid pipe 10 than the longitudinal wave, and the path through the measured fluid 11 is also vertical. Different from waves. Also, as shown in FIG. 7, the echo signal (longitudinal ultrasonic wave) from the reflector existing in the fluid to be measured is converted again to the mode conversion at the interface between the two when returning from the fluid to be measured to the inside of the pipe. It is divided into two waves, a longitudinal wave and a transverse wave.

  When the measurement line is calculated using the longitudinal wave as a reference in the ultrasonic flowmeter, the reflected wave (ultrasonic echo) incident and reflected from the transverse wave may become noise in measurement. In this way, the measurement error due to overlapping detection due to the generation of two waves is not a problem when the pipe diameter is large, but in the case of a small diameter pipe of several mm to several tens of mm. When measuring with high accuracy, there may be a problem.

  Now, when the data was acquired by changing the incident angle of the ultrasonic wave, the following could be confirmed. That is, as the incident angle increases, the transmitted sound pressure of the longitudinal wave decreases, and hardly transmits when the “critical angle” calculated from Snell's law is exceeded. On the other hand, as the incident angle increases, the transmitted sound pressure of the transverse wave increases and reaches a maximum value near the critical angle. When the incident angle is set to be equal to or smaller than the critical angle of the longitudinal wave, longitudinal and transverse ultrasonic waves enter the flow path. Specifically, when the incident angle is less than the critical angle of longitudinal waves, specifically when the wedge is made of acrylic resin and the fluid piping is made of iron, the angle is about 10 to 20 degrees. It has been found that the transmissivity of the longitudinal wave is low and exceeds the critical angle of the longitudinal wave and becomes less than half the transmissivity of the transverse wave when only the transverse wave is generated (from the ultrasonic handbook). If the transmittance is low, there is a possibility that the reception of reflected waves may be hindered.

In the ultrasonic flowmeter, the flow velocity of the fluid is calculated by using the echo signal from the reflector existing in the fluid to be measured. Even when only the transverse wave is transmitted and applied to the measurement, ringing ( (Internal repetitive reflection) needs to be considered.
At a relatively shallow incident angle that exceeds the critical critical angle of the longitudinal wave and only the transverse wave begins to be generated, the transmitted intensity of the transverse wave is large and a plurality of measurement lines due to ringing are hardly generated. Even when multiple measurement lines are generated due to ringing, if the pipe diameter is thin enough for the pipe wall thickness, the multiple measurement lines have a short time difference with respect to the propagation time in the measured fluid. Therefore, if the time difference is within the allowable range of measurement error, good measurement can be performed.
On the other hand, if the incident angle is gradually increased, the velocity component in the direction of the ultrasonic transducer increases, which is advantageous for measurement. In the case of a pipe material having a high ultrasonic attenuation rate, the ultrasonic wave generated by ringing is not generated. There is also a possibility of sufficient attenuation while propagating in the pipe. However, the transverse wave transmittance decreases as the incident angle is gradually increased.
In consideration of the above, it is necessary to select an optimum incident angle.

The problem to be solved by the present invention is a technique for measuring a more accurate flow rate by reducing measurement errors caused by the occurrence of two types of waves, in particular, small-diameter piping of several mm to several tens of mm. In this case, a technique suitable for high-precision measurement is provided.
An object of the present invention is to provide an ultrasonic flow meter that measures a more accurate flow rate by reducing measurement errors caused by the occurrence of two types of waves. .
The object of the invention described in claim 7 and claim 8 is to provide a wedge for use in an ultrasonic flowmeter for measuring a more accurate flow rate by reducing measurement errors caused by the occurrence of two types of waves. There is.

  The invention described in claims 1 to 6 is a so-called clamp-on type ultrasonic flow meter, and the invention described in claims 7 to 8 is a wedge used for a so-called clamp-on type ultrasonic flow meter. .

(Claim 1)
According to the first aspect of the present invention, there is provided an ultrasonic transmission means for causing an ultrasonic pulse having a required frequency to enter a fluid to be measured in a fluid pipe along a measurement line from an ultrasonic transducer, and an ultrasonic wave incident on the fluid to be measured. A fluid velocity distribution measuring means for receiving an ultrasonic echo reflected from the measurement region of the pulse and measuring a flow velocity distribution of the fluid under measurement in the measurement region; and based on the flow velocity distribution of the fluid under measurement in the measurement region A flow rate calculating means for calculating the flow rate of the fluid to be measured, and a wedge interposed between the fluid pipe (10) and an ultrasonic transducer (20) for generating longitudinal ultrasonic waves provided in the ultrasonic wave transmitting means. (30) and an ultrasonic flowmeter for measuring the flow rate of the fluid to be measured (11).
The wedge (30) includes an ultrasonic transmission unit (32) positioned between the ultrasonic transducer (20) and the outer surface of the fluid pipe (10), and an ultrasonic transmission to the ultrasonic transmission unit (32). The ultrasonic transducer (20), and the ultrasonic transmission unit (32) is made of a material having sound wave propagating properties.The fixed unit (31) is an ultrasonic transducer ( 20) is incident on the outer surface of the pipe (10) and the incident angle formed by the direction perpendicular to the pipe (10) is greater than the critical angle of the longitudinal wave calculated from Snell's law. Thus, the ultrasonic transducer (20) is formed so as to be fixed.

(Glossary)
The ultrasonic flow meter includes a general Doppler ultrasonic flow meter and an ultrasonic flow meter using a correlation method. The ultrasonic flow meter using the correlation method is, for example, an ultrasonic flow meter as disclosed in JP-A-2003-344131.
In both cases, an ultrasonic transmission means for injecting an ultrasonic pulse of a required frequency from an ultrasonic transducer along a measurement line into a fluid to be measured in a fluid pipe, and a measurement region of the ultrasonic pulses incident on the fluid to be measured A fluid velocity distribution measuring means for receiving the ultrasonic echo reflected from the measurement region and measuring a flow velocity distribution of the fluid under measurement in the measurement region; and a flow rate of the fluid under measurement in the measurement region based on the flow velocity distribution of the fluid under measurement. The flow rate of the fluid to be measured is measured.

の演算を行う手段である。 The “flow rate calculation means” has a flow rate of m (t),

It is a means to perform the calculation.

Further, from the above equation (1), the flow rate m (t) of the time t flowing through the fluid piping can be rewritten as the following equation.

ここで、αとは、超音波トランスジューサから発振される超音波の入射角度、すなわち流体配管の管壁への垂線に対してなす角度である。 If the flow of the fluid to be measured flowing in the pipe is a flow in the tube axis direction and the flows vr and vθ in the radial direction and the angle θ can be ignored, vx >> vr = vθ, and the flow rate measurement is simplified. It is expressed by the following formula.

Here, α is an incident angle of the ultrasonic wave oscillated from the ultrasonic transducer, that is, an angle formed with respect to a perpendicular to the pipe wall of the fluid piping.

  As the incident angle increases, the transmitted sound pressure of longitudinal waves decreases. When the angle exceeds the “critical angle” calculated from Snell's law, it hardly transmits. Therefore, by making the ultrasonic wave incident at an incident angle exceeding the “critical angle”, it is possible to prevent the presence of longitudinal waves and transverse waves inside the pipe. Only ultrasonic waves are incident.

  The “wedge” may be formed of the same material as the ultrasonic transmission part (32) and the fixing part (31), or may be formed of different materials, as defined in claim 2 and below. .

(Function)
First, the ultrasonic transmission means causes an ultrasonic pulse of a required frequency to enter the measured fluid in the fluid pipe along the measurement line from the ultrasonic transducer via the ultrasonic transmission section of the wedge. If the material (acoustic impedance) of the ultrasonic transmission part of the wedge and the fluid pipe (10) are different in the fluid pipe, the incident ultrasonic wave will be shear stress at the interface between them, apart from the longitudinal wave which is a dense wave. However, the incident angle between the direction in which the ultrasonic transducer is incident on the outer surface of the pipe and the direction perpendicular to the pipe is calculated from Snell's law. When the ultrasonic transducer is fixed so that it is above the critical angle of the longitudinal wave, the longitudinal wave disappears and only the transverse wave passes through the fluid pipe (10).
Also, the echo signal (longitudinal ultrasonic wave) from the reflector existing in the fluid to be measured also disappears when returning from the fluid to be measured to the inside of the pipe, and only the transverse wave passes through the inside of the pipe. It is received by the ultrasonic transducer 20 that has been switched to the reception mode (see FIG. 2).

The transmitted ultrasonic wave is reflected by a reflector (for example, a bubble) in the measurement region and receives the ultrasonic echo, and the fluid velocity distribution measuring means measures the flow velocity distribution of the fluid to be measured in the measurement region. Based on the flow velocity distribution of the measured fluid, the flow rate calculation means calculates the flow rate of the measured fluid in the measurement region.
Longitudinal waves and transverse waves are mixed inside the pipe, and there is no measurement error that occurs when two types of ultrasonic waves are incident on the fluid to be measured. Such measurement is suitable for performing highly accurate measurement in the case of a small-diameter pipe having a diameter of several millimeters to several tens of millimeters, in which an error is likely to occur when a longitudinal wave and a transverse wave are incident.

(Claim 2)
The invention according to claim 2 limits the ultrasonic flowmeter according to claim 1,
The ultrasonic transmission part of the wedge is a sound-propagating solid such as acrylic or iron.

(Function)
If the ultrasonic transmission part of the wedge is made of a sound-propagating solid such as acrylic or iron, it is easy to process or actually fix the ultrasonic transducer fixing structure based on the setting of the incident angle.

(Claim 3)
The invention described in claim 3 limits the ultrasonic flowmeter according to claim 1,
The ultrasonic transmission part of the wedge is a fluid excellent in sound wave propagation properties such as water, oil, air and the like.
When the ultrasonic transmission portion of the wedge is a fluid, the wedge fixing portion includes a portion that holds the fluid.

(Function)
If the ultrasonic transmission part of the wedge is a fluid having excellent sound wave propagation properties such as water, oil, air, etc., it is easy to adjust the incident angle.

(Claim 4)
Invention of Claim 4 limited the ultrasonic flowmeter in any one of Claims 1-3,
The fluid pipe is made of a metal such as carbon steel, aluminum, or stainless steel.

(Claim 5)
Invention of Claim 5 limited the ultrasonic flowmeter in any one of Claims 1-3,
The fluid pipe is a resin such as acrylic.

(Claim 6)
Invention of Claim 6 limited the ultrasonic flowmeter in any one of Claims 1-5,
An incident angle adjusting means capable of adjusting the incident angle of the ultrasonic wave; and a data receiving means for receiving the incident angle set by the incident angle adjusting means as data, the fluid velocity distribution measuring means receiving the data The flow velocity distribution of the fluid to be measured in the measurement region is measured based on the data received by the means.

(Function)
The incident angle adjusting unit adjusts the incident angle of the ultrasonic wave, and the data receiving unit receives the incident angle set by the incident angle adjusting unit as data. The fluid velocity distribution measuring means measures the flow velocity distribution of the fluid to be measured in the measurement region based on the data received by the data receiving means. If it is determined that the measurement result is not highly accurate, or if longitudinal wave generation is detected by measuring the transmitted sound pressure using a hydrophone, the incident angle adjustment means readjust the ultrasonic incident angle. The measurement can be performed again at the incident angle of the ultrasonic wave after readjustment.

(Claim 7)
The invention according to claim 7 is an ultrasonic transmitting means for causing an ultrasonic pulse of a required frequency to enter the fluid under measurement in the fluid pipe along the measurement line from the ultrasonic transducer, and the ultrasonic wave incident on the fluid under measurement. A fluid velocity distribution measuring means for receiving an ultrasonic echo reflected from the measurement region of the pulse and measuring a flow velocity distribution of the fluid under measurement in the measurement region; and based on the flow velocity distribution of the fluid under measurement in the measurement region A wedge interposed between an ultrasonic transducer that generates longitudinal wave ultrasonic waves and the pipe in an ultrasonic flowmeter that includes a flow rate calculation unit that calculates a flow rate of the fluid to be measured and measures the flow rate of the fluid to be measured. Concerning.
The wedge includes an ultrasonic transmission unit located between the ultrasonic transducer and the outer surface of the fluid pipe, and a fixing unit that fixes the ultrasonic transducer to the ultrasonic transmission unit. The fixing part is made up of Snell's law, where the incident angle between the direction in which the ultrasonic transducer enters the outer surface of the pipe and the direction perpendicular to the pipe. The ultrasonic transducer is fixed so as to be equal to or greater than the critical angle of the longitudinal wave calculated from the equation (1).

(Function)
Wedges can be supplied independently, and setting and maintenance can be performed using wedges. When passing through the fluid piping by the wedge according to the present claim, the longitudinal wave does not pass through, but is incident on the fluid to be measured after becoming a transverse wave whose speed is slower than that of the longitudinal wave. The ultrasonic wave becomes a reflected wave by the reflector. In the case of a small-diameter pipe having a diameter of several millimeters to several tens of millimeters where errors are likely to occur when a longitudinal wave and a transverse wave are incident, it is suitable for highly accurate measurement.

(Claim 8)
Invention of Claim 8 limited the wedge for ultrasonic flowmeters of Claim 7,
The acoustic impedance is made of a material different from the acoustic impedance of the fluid piping.

According to the first to sixth aspects of the invention, it is possible to provide an ultrasonic flowmeter that can measure a more accurate flow rate by reducing measurement errors caused by the occurrence of two types of waves. It was.
According to invention of Claim 7 and Claim 8, the wedge used for the ultrasonic flowmeter which measures a more exact flow volume is reduced by reducing the measurement error resulting from two types of waves being generated. I was able to.

Hereinafter, the present invention will be described in more detail based on embodiments and drawings. The drawings used here are FIGS. 1 to 5.
(Figure 1)
FIG. 1 shows a state in which an ultrasonic pulse is incident on the measured fluid 11 by the ultrasonic transducer 20 in an ultrasonic flowmeter for measuring the flow rate of the fluid pipe 10 through which the measured fluid 11 flows.
The ultrasonic transducer 20 is fixed to a predetermined portion of the pipe 10 with a medium wedge 30. That is, this ultrasonic flowmeter is not a liquid contact type but a clamp-on type. The material of the wedge 30 is a material having sound wave propagation properties, for example, an epoxy resin.

  The ultrasonic transducer 20 is configured to transmit an ultrasonic pulse having a required frequency (fundamental frequency) along the measurement line to the fluid to be measured 11 and to measure the ultrasonic pulse incident on the fluid to be measured. It also serves as fluid velocity distribution measuring means for receiving the ultrasonic echo reflected from the region and measuring the flow velocity distribution of the fluid to be measured in the measurement region. A computer such as a microcomputer, CPU, MPU or the like as a flow rate calculation means for obtaining the flow rate of the fluid to be measured in a time-dependent manner based on the flow velocity distribution, and a display device capable of displaying the output from the computer in time series It is connected.

Further, the ultrasonic vibrator 20 oscillates an ultrasonic pulse having a fundamental frequency along a measurement line by applying a pulse electric signal to the ultrasonic vibrator. The generated ultrasonic pulse is, for example, a straight beam that has a beam diameter of about several millimeters and hardly spreads.
The ultrasonic transducer 20 receives an ultrasonic echo that oscillates and an ultrasonic pulse is reflected by the reflector 12 in the fluid 11. Here, the reflector 12 is a bubble uniformly contained in the fluid 11 to be measured. Basically, the fluid to be measured 11 must be a foreign object having a different acoustic impedance.

  When the dimensions of the fluid pipe 10 (two or more of the outer diameter, the wall thickness, and the inner diameter), the material of the fluid pipe 10 and the type of the fluid 11 are known in advance, the incidence of the ultrasonic wave described above is performed. The angle α can be specified. The incident angle α is specified to be equal to or greater than the critical angle of the longitudinal wave calculated from Snell's law. When the incident angle α is specified so as to be equal to or greater than the critical angle of the longitudinal wave, the longitudinal wave disappears and only the transverse wave passes through the fluid pipe 10.

The transmitted ultrasonic wave is reflected by a reflector (for example, a bubble) in the measurement region and receives the ultrasonic echo, and the fluid velocity distribution measuring unit measures the flow velocity distribution of the fluid to be measured in the measurement region. Based on the flow velocity distribution of the measured fluid, the flow rate calculation means calculates the flow rate of the measured fluid in the measurement region.
When passing through the fluid piping, it becomes a transverse wave whose velocity is slower than the longitudinal wave, and then enters the fluid to be measured and becomes a reflected wave. Therefore, in the case of a small-diameter pipe of several mm to several tens of mm, it is suitable for high-precision measurement.

  As shown in FIG. 2, when the echo signal (longitudinal wave ultrasonic wave) from the reflector 12 existing in the fluid to be measured returns from the fluid to be measured 11 to the inside of the pipe 10, the longitudinal wave disappears and only the transverse wave is present. Is received by the ultrasonic transducer 20 that has been switched to the reception mode via the inside of the pipe 10. The received ultrasonic echo is received by a reflected wave receiver and converted into an echo electric signal by the reflected wave receiver. The echo electric signal is amplified by an amplifier and then digitized through an AD converter. Then, the digitized digital echo signal is input to a flow velocity calculation device provided with a flow velocity distribution measuring circuit.

  The flow velocity calculation device receives the digital signal of the fundamental frequency from the oscillation amplifier and measures the flow velocity using the change in flow velocity based on the Doppler shift or the cross-correlation value of both signals from the frequency difference between the two signals. The flow velocity distribution in the measurement area along the measurement line is calculated. When it is considered that longitudinal and transverse waves coexist due to the flow velocity distribution in the measurement area, etc., the flow velocity distribution is measured and the flow rate is calculated by resetting the ultrasonic incident angle α and re-measurement. To do.

The fluid to be measured 11 is water, and the material of the fluid pipe 10 related to the fluid to be measured 11 is aluminum. Only the ultrasonic longitudinal wave travels through the water at 1480m / s. The velocity of ultrasonic longitudinal waves traveling through aluminum is 6420 m / s, and the transverse wave is 3040 m / s.
When the critical angle is calculated from Snell's law, the critical angle of the longitudinal wave is 13.3 degrees and the critical angle of the transverse wave is 29.1 degrees. Therefore, in this embodiment, the incident angle that is greater than the critical angle of the longitudinal wave and less than the critical angle of the transverse wave is 28.0 degrees. That is, the critical angle of longitudinal waves <incident angle <critical angle of transverse waves.

  FIG. 3 is a plot of the relationship between the incident angle and the error rate. It was found that high-accuracy measurement was possible when the incident angle of the ultrasonic wave was 28.0 degrees.

If the reflector cannot secure a certain density, the reflector is artificially increased. As the method, there are a case where nylon particles are put and a case where cavitation bubbles are put.
FIG. 4 is a diagram showing a time-averaged flow velocity distribution when the material of the fluid pipe 10 is aluminum, the incident angle of ultrasonic waves is 28.0 degrees, and cavitation bubbles are generated as an ultrasonic reflector. FIG. 5 is a diagram showing a time-averaged flow velocity distribution when nylon particles are employed as the ultrasonic reflector.

Comparing the two, it can be seen that in the measurement on the side closer to the ultrasonic transducer (the center left side in the figure), the variation in flow velocity calculated for cavitation bubbles is smaller than that for nylon particles. This is because cavitation bubbles have a higher echo intensity.
That is, it can be understood from this example that cavitation bubbles are superior in the measurement of reflected waves by ultrasonic waves.

The present invention is not limited to the Doppler type ultrasonic flowmeter, but can also be adopted in a flowmeter belonging to a general ultrasonic flowmeter.
In addition to the manufacturing industry of ultrasonic flowmeters, it is also used in the installation and maintenance industries of ultrasonic flowmeters.

It is a conceptual diagram which shows embodiment. It is a conceptual diagram which shows embodiment. It is a graph of the Example which shows the relationship between an incident angle and an error incidence rate. It is the figure which showed the average flow velocity distribution in the case of generating cavitation bubbles as an ultrasonic reflector. It is the figure which showed the average flow velocity distribution in the case of employ | adopting nylon particles as an ultrasonic reflector. It is a conceptual diagram for showing a prior art and its problem. It is a conceptual diagram for showing a prior art and its problem.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fluid piping 11 Fluid to be measured 20 Ultrasonic vibrator 30 Wedge 31 Fixing part 32 Ultrasonic transmission part

Claims (8)

Ultrasonic transmission means for injecting ultrasonic pulses of the required frequency from the ultrasonic transducer along the measurement line into the fluid to be measured in the fluid piping, and reflected from the measurement area among the ultrasonic pulses incident on the fluid to be measured. A fluid velocity distribution measuring means for receiving the measured ultrasonic echo and measuring a flow velocity distribution of the fluid under measurement in the measurement region; and a flow rate for calculating a flow rate of the fluid under measurement in the measurement region based on the flow velocity distribution of the fluid under measurement. An ultrasonic flow rate for measuring the flow rate of the fluid to be measured, comprising: a calculation means; and a wedge interposed between the fluid pipe and an ultrasonic transducer for generating a longitudinal wave ultrasonic wave provided in the ultrasonic transmission means. A total of
The wedge includes an ultrasonic transmission unit located between the ultrasonic transducer and the outer surface of the fluid pipe, and a fixing unit that fixes the ultrasonic transducer to the ultrasonic transmission unit,
The ultrasonic transmission part is made of a material having sound wave propagation properties,
In the fixed part, the incident angle formed by the direction in which the ultrasonic transducer enters the outer surface of the pipe and the direction perpendicular to the pipe is equal to or greater than the critical angle of the longitudinal wave calculated from Snell's law. An ultrasonic flowmeter characterized by being formed so as to fix an ultrasonic transducer. The ultrasonic flowmeter according to claim 1, wherein the ultrasonic transmission unit of the wedge is a sound-propagating solid such as acrylic or iron. The ultrasonic flowmeter according to claim 1, wherein the ultrasonic transmission unit of the wedge is a sound-propagating fluid such as water, oil, or air. The ultrasonic flowmeter according to any one of claims 1 to 3, wherein the fluid pipe is made of a metal such as carbon steel, aluminum, or stainless steel.   The ultrasonic flowmeter according to claim 1, wherein the fluid pipe is a resin such as acrylic. An incident angle adjusting means capable of adjusting the incident angle of the ultrasonic wave;
Data receiving means for receiving the incident angle set by the incident angle adjusting means as data,
The superfluous velocity distribution measuring means according to any one of claims 1 to 5, wherein the fluid velocity distribution measuring means measures the flow velocity distribution of the fluid to be measured in the measurement region based on the data received by the data receiving means. Sonic flow meter. Ultrasonic transmission means for injecting ultrasonic pulses of the required frequency from the ultrasonic transducer along the measurement line into the fluid to be measured in the fluid piping, and reflected from the measurement area among the ultrasonic pulses incident on the fluid to be measured. A fluid velocity distribution measuring means for receiving the measured ultrasonic echo and measuring the flow velocity distribution of the fluid under measurement in the measurement region; and calculating the flow rate of the fluid under measurement in the measurement region based on the flow velocity distribution of the fluid under measurement. In an ultrasonic flowmeter that measures the flow rate of a fluid to be measured with a flow rate calculation means, a wedge interposed between an ultrasonic transducer that generates longitudinal ultrasonic waves and the pipe,
An ultrasonic transmission unit located between the ultrasonic transducer and the outer surface of the fluid pipe, and a fixing unit for fixing the ultrasonic transducer to the ultrasonic transmission unit,
The ultrasonic transmission part is made of a material having sound wave propagation properties,
In the fixed part, the incident angle formed by the direction in which the ultrasonic transducer enters the outer surface of the pipe and the direction perpendicular to the pipe is equal to or greater than the critical angle of the longitudinal wave calculated from Snell's law. A wedge for an ultrasonic flowmeter formed so as to fix the ultrasonic transducer. The wedge according to claim 7, wherein the acoustic impedance is made of a material different from the acoustic impedance of the fluid piping.

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