JP2005195371A - Ultrasonic flowmeter, and sound absorbing material for ultrasonic flowmeter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a measuring error resulting from a reflected waves from a pipe to measure an accurate flow rate. <P>SOLUTION: This ultrasonic flowmeter is provided with an ultrasonic transmission means 20 for making a prescribed frequency of ultrasonic pulse get incident into a measured fluid 11 inside the fluid pipe 10 along a measuring line from an ultrasonic transducer, a fluid velocity distribution measuring means 20 for receiving an ultrasonic echo (reflected wave A) reflected from a measuring area out of the ultrasonic pulses incident into the measuring fluid 11 to measure a flow velocity distribution of the measured fluid 11 in the measuring area, and a flow rate computing means for computing the flow rate of the measuring fluid in the measuring area, based on the flow velocity distribution of the measured fluid 11. The ultrasonic flowmeter is provided also with a sound absorbing material 40 fixed onto a pipe outer wall in an arrival position of the ultrasonic pulse in the fluid pipe 10 for the measured fluid 11, and the sound absorbing material 40 comprises a high density material to bring an acoustic impedance thereof into an approximate value close to that of the fluid pipe 10. <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, with the above-mentioned Doppler type ultrasonic flowmeter, aiming for further improvement in measurement accuracy, the following problems emerged.
This will be described with reference to FIGS. For the ultrasonic wave transmitted by the ultrasonic wave transmitting means, it is desired to use only the reflected wave that is normally reflected by the bubbles in the fluid to be measured ("reflected wave A" shown in FIGS. 5 and 6). However, as shown in FIG. 5, the transmitted ultrasonic wave reaches the fluid pipe 10, and the reflected wave from the fluid pipe 10 (“reflected wave B” in FIG. 5) hits another bubble and reflects the reflected wave A. It was found that the ultrasonic transmission / reception means 20 received by following the same path, causing measurement errors. In addition, as shown in FIG. 6, when an ultrasonic wave enters the fluid pipe 10, the reflected wave is transmitted through the fluid pipe 10 without entering the non-measurement fluid 11, and then enters the measured fluid 11. It was found that there was also a measurement error caused by the collision with the bubble and reflection, and the reflected wave B being measured by the ultrasonic transmitting / receiving means 20.
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 the bubbles in the fluid to be measured, the measurement result should theoretically draw a parabola. As a result of this measurement, a flat straight part is drawn near the top of the parabola.

The problem to be solved by the present invention is to provide a technique for measuring a more accurate flow rate by reducing a measurement error caused by a reflected wave from a pipe.
An object of the invention described in claims 1 to 4 is to provide an ultrasonic flowmeter that measures a more accurate flow rate by reducing a measurement error caused by a reflected wave from a pipe.
Another object of the present invention is to provide a sound absorbing material for an ultrasonic flowmeter that reduces a measurement error caused by a reflected wave from a pipe and measures a more accurate flow rate.

(Claim 1)
The invention according to claim 1 is an ultrasonic transmission means (20) for causing an ultrasonic pulse of a required frequency to enter a measured fluid (11) in a fluid pipe (10) along a measurement line from an ultrasonic transducer; A fluid velocity that receives an ultrasonic echo (reflected wave A) reflected from the measurement region among the ultrasonic pulses incident on the fluid to be measured (11) and measures the flow velocity distribution of the fluid to be measured (11) in the measurement region. A distribution measuring means (20); and a flow rate calculating means for calculating a flow rate of the fluid under measurement in the measurement region based on a flow velocity distribution of the fluid under measurement (11). Related to sonic flow meter.
Then, a sound absorbing material (40) that can be fixed to the pipe outer wall at the arrival position of the ultrasonic pulse in the fluid pipe (10) of the fluid to be measured (11), and the acoustic impedance of the sound absorbing material (40) is the fluid pipe ( The material is characterized by a high-density material that approximates the acoustic impedance of 10).

(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 tube wall.

  The `` arrival position of the ultrasonic pulse in the fluid pipe (10) of the fluid to be measured (11) '' means the incident angle of the ultrasonic wave oscillated from the ultrasonic transducer (20), the pipe material, the inner diameter and the outer diameter of the pipe Alternatively, it is specified by specifying variable conditions such as the wall thickness and the type of fluid to be measured. For example, the pipe outer wall on the opposite side across the fluid to be measured (11) (FIG. 1), the pipe outer wall on the incident side of the ultrasonic wave oscillated from the ultrasonic transducer (20) (FIG. 4), etc. .

  The acoustic impedance of the sound-absorbing material is “high density material that approximates the acoustic impedance of the fluid piping”. Otherwise, the ultrasonic waves will be reflected at the interface between the sound-absorbing material and the piping. Because. As a specific material, a material formed by blending a synthetic resin (for example, an epoxy resin) with a high-density metal powder (for example, a fine powder of tungsten) was preferable. As the high-density metal, chromium, molybdenum, or the like can be used.

(Function)
First, an ultrasonic pulse having a required frequency is caused to enter the measured fluid (11) in the fluid pipe (10) along the measurement line from the ultrasonic transducer (20). Then, among the ultrasonic pulses incident on the fluid to be measured (11), the one reflected from the measurement region (reflected wave A) becomes the measurement object, and a part of the ultrasonic pulses is the fluid of the fluid to be measured (11). It reaches the pipe (10) or reflects inside the fluid pipe (10) without reaching the fluid to be measured (11). However, the sound absorbing material (40) is fixed to the outer wall of the pipe at the reaching position, and the acoustic impedance of the sound absorbing material (40) is so high as to be close to the acoustic impedance of the fluid pipe (10). Because it is a material, most of it is absorbed. Therefore, it is possible to suppress a reflected wave from the fluid pipe (10) from being a measurement object and causing a measurement error.
Fluid velocity distribution measuring means (the ultrasonic transducer (20) receives an ultrasonic echo and measures the flow velocity distribution of the fluid to be measured (11) in the measurement region. Based on the flow velocity distribution of the fluid to be measured (11)) Then, the flow rate calculation means calculates the flow rate of the fluid to be measured (11) in the measurement region.

(Claim 2)
The invention according to claim 2 limits the ultrasonic flowmeter according to claim 1,
A sound absorbing material holder (41) that holds the sound absorbing material (40) and is fixed to the outer wall of the pipe, and a slider (42) that enables the position of the sound absorbing material holder (41) to be changed. The fixed position of the sound absorbing material (40) with respect to is formed to be changeable.

(Function)
It is assumed that a situation has occurred in which a part of the ultrasonic pulse that has not been reflected in the measurement region reaches the fluid piping of the fluid to be measured and is reflected to cause a measurement error. In that case, it is considered that the fixing position of the sound absorbing material (40) with respect to the outer wall of the pipe is not appropriate. Therefore, the sound absorbing material (40) may be moved to an appropriate position. That is, the position of the sound absorbing material (40) relative to the outer wall of the pipe is adjusted by changing the position of the sound absorbing material (40) relative to the sound absorbing material holder (41) using the slider (42). If the sound absorbing material (40) with respect to the outer wall of the pipe can be moved to an appropriate position, it can contribute to the reduction of the measurement error.

(Claim 3)
According to a third 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 The present invention relates to an ultrasonic flowmeter that includes a flow rate calculation unit that calculates a flow rate of a fluid to be measured and that measures the flow rate of the fluid to be measured.
That is, it comprises a wedge (30) for fixing the ultrasonic transmission means (20) at a predetermined angle and clamping it to the outer wall of the fluid pipe (10) of the fluid to be measured (11), the wedge (30) A sound absorbing material (40) is provided at a predetermined position on the surface in contact with the pipe outer wall side, and the acoustic impedance of the sound absorbing material (40) is so high as to be close to the acoustic impedance of the fluid piping (10). It is characterized by the material.

  The difference between the configuration of the invention according to claim 1 and the operation accompanying it is as follows. That is, the ultrasonic flowmeter according to claim 1 is arranged at a position where the ultrasonic transmission means (20) and the sound absorbing material (40) sandwich the fluid pipe (10). In the flow meter, the ultrasonic transmission means (20) and the sound absorbing material (40) are positioned in parallel. In other words, the ultrasonic flowmeter according to claim 1 absorbs the sound absorption material (40) at the place where the reflected wave is generated, whereas in the ultrasonic flowmeter according to claim 3, the sound absorption material (40) has a fluid velocity. This prevents the reflected wave (B) from the fluid pipe (10) in the distribution measuring means (20) from being measured.

(Claim 4)
Invention of Claim 4 limited the ultrasonic flowmeter of Claim 3,
An ultrasonic flowmeter characterized in that the position of the sound absorbing material (40) in the wedge (30) can be changed by providing the wedge with a slider, so that the fixed position of the sound absorbing material relative to the outer wall of the pipe can be changed. Related.

(Function)
Assume that a part of the ultrasonic pulse reaches the fluid piping of the fluid to be measured and is reflected, and the fluid velocity distribution measuring means receives the situation, so that a measurement error is considered to have occurred. In that case, since it is thought that the fixed position of the sound absorbing material with respect to the outer wall of the pipe is not appropriate, the sound absorbing material may be moved to an appropriate position. That is, the position of the sound absorbing material relative to the outer wall of the pipe is adjusted by changing the position of the sound absorbing material relative to the wedge using the slider. When the sound absorbing material with respect to the outer wall of the pipe can move to an appropriate position, it can contribute to the reduction of the measurement error.

(Claim 5)
The invention according to claim 5 can be fixed to the outer wall of the fluid piping of the fluid to be measured, and the synthetic resin is blended with high-density metal powder so that the acoustic impedance is approximate to the acoustic impedance of the piping. The present invention relates to a sound absorbing material for an ultrasonic flowmeter, which is formed of a molded material.
Here, examples of the “high density metal” include tungsten, chromium, and molybdenum.

(Function)
The invention according to claim 5 is used as a single member separated from the ultrasonic flowmeter.

According to the invention described in claims 1 to 4, it is possible to provide an ultrasonic flowmeter that measures a more accurate flow rate by reducing a measurement error caused by a reflected wave from a pipe. .
In addition, according to the invention described in claim 5, it is possible to provide a sound absorbing material for an ultrasonic flowmeter that reduces a measurement error caused by a reflected wave from a pipe and measures a more accurate flow rate. It was.

Hereinafter, the present invention will be described in more detail based on embodiments and drawings. The drawings used here are FIGS. 1 to 4.
(Figure 1)
FIG. 1 shows an ultrasonic flowmeter for measuring the flow rate of a fluid pipe 10 through which a fluid under measurement 11 flows, and receives an ultrasonic echo reflected from a measurement region of an ultrasonic pulse incident on the fluid under measurement 11. An ultrasonic transmission / reception means (transducer 20) also serving as a receiver is provided. The transducer 20 is fixed to a predetermined portion of the pipe 10 by a resin wedge 30. The material of the wedge 30 is, for example, an epoxy resin.

  The transducer 20 transmits ultrasonic pulses having a required frequency (fundamental frequency) along the measurement line to the fluid 11 to be measured, and reflects from the measurement region of the ultrasonic pulses incident on the fluid to be measured. It also serves as fluid velocity distribution measuring means for receiving the ultrasonic echo 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 transducer 20 is provided with a vibration amplifier as a signal generator for vibrating the transducer 20, so that a pulse electric signal having a required fundamental frequency is input from the vibration amplifier to the ultrasonic transducer. It has become. Then, an ultrasonic pulse having a fundamental frequency is oscillated along the measurement line by applying the pulse electric signal. The ultrasonic pulse is, for example, a straight beam having a pulse width of about 5 mm and hardly spreading.

  The transducer 20 is configured to receive 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.

  The ultrasonic echo received by the transducer 20 is received by a reflected wave receiver (not shown) and converted to an echo electrical 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. By calibrating the flow velocity distribution in the measurement region with the incident angle α of the ultrasonic wave, the flow velocity distribution in the cross section of the fluid piping can be measured.

  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. In that case, the wedge 30 can be omitted to form a “wetted” type.

When the incident angle α of the ultrasonic wave by the transducer 20 is determined, it can be calculated where the ultrasonic wave reaches on the tube wall opposite to the transducer 20 across the fluid pipe 10. The sound absorbing material 40 is fixed near the reaching position.
The acoustic impedance of the sound absorbing material 40 is a high-density material that approximates the acoustic impedance of the fluid piping 10. More specifically, it is a material formed by blending a synthetic resin (epoxy resin) with a high-density metal powder (tungsten powder) and has a diameter of about 10 to 20 mm and a thickness of about 10 to 15 mm. The presence of the sound absorbing material 40 can prevent the fluid pipe 10 from generating a reflected wave. Therefore, it can suppress that the reflected wave from the fluid piping 10 becomes a measuring object and causes a measurement error.
The material of the sound absorbing material is not limited to a material formed by blending tungsten powder with epoxy resin, and may be any material having a high density that approximates the acoustic impedance of the fluid pipe 10, for example, instead of tungsten. It is also possible to use lead.

  The reflected wave received by the receiver of the transducer 20 is amplified by an amplifier (not shown) and then digitized through an AD converter. Then, the sound speed calculation device calculates the sound speed using the digitized digital echo signal. The calculated sound speed is output to the ultrasonic flowmeter and used to calculate the flow rate, the flow velocity distribution, and the like in real time.

  It is assumed that a situation occurs in which it is considered that a measurement error has occurred due to a part of the ultrasonic pulse not reflected in the measurement region reaching the fluid piping of the fluid to be measured and reflected. In that case, since it is thought that the fixed position of the sound absorbing material 40 with respect to the outer wall of the pipe is not appropriate, the sound absorbing material 40 is moved to an appropriate position.

(Figure 2)
The embodiment shown in FIG. 2 includes a wedge 30 for fixing the transducer 20 at a predetermined angle and clamping it onto the outer wall of the fluid pipe 10 of the fluid 11 to be measured. A sound absorbing material 40 is provided at a predetermined position on the surface of the non-measurement fluid 11 that contacts the pipe outer wall side on the same side as the wedge 30. While the embodiment shown in FIG. 1 absorbs the sound absorbing material 40 at the place where the reflected wave is generated, the sound absorbing material 40 of the embodiment shown in FIG. 2 receives the reflected wave B from the fluid pipe 10 in the transducer 20. Prevent measuring.

(Figure 3)
The embodiment shown in FIG. 3 is a modification of the embodiment shown in FIG. That is, a sound absorbing material holder 41 that holds the sound absorbing material 40 and is fixed to the outer wall of the pipe, and a slider 42 that allows the position of the sound absorbing material holder 41 to be changed, so that the sound absorbing material 40 with respect to the outer wall of the pipe is provided. The fixed position can be changed.

It is assumed that a situation has occurred in which a part of the ultrasonic pulse that has not been reflected in the measurement region reaches the fluid piping of the fluid to be measured and is reflected to cause a measurement error. In that case, since it is thought that the fixing position of the sound absorbing material 40 with respect to the outer wall of the pipe is not appropriate, the position of the sound absorbing material 40 with respect to the sound absorbing material holder 41 is changed using the slider 42. Accordingly, the fixing position of the sound absorbing material 40 with respect to the outer wall of the pipe is adjusted. The sound absorbing material 40 with respect to the outer wall of the pipe can be moved to an appropriate position, which can contribute to the reduction of the measurement error.
If the fixed position of the sound absorbing material 40 is formed to be changeable as in this embodiment, it is possible to cope with a situation where the position of the reflected wave is changed, for example, a situation where the fluid to be measured is changed. is there.

  In addition, although detailed illustration is abbreviate | omitted, the structure which can change the fixing position of the sound-absorbing material 40 is also employable also in the above-mentioned 2nd embodiment.

(Fig. 4)
In the embodiment shown in FIG. 4, a sound absorbing material 40 is provided so as to be incorporated into the wedge 30 at a position that absorbs ultrasonic waves reflected inside the fluid pipe 10 without reaching the fluid 11 to be measured. Also in this regard, it is possible to adopt a structure in which the fixing position of the sound absorbing material 40 can be changed as in the embodiment shown in FIG.

  As shown in FIGS. 1 to 3, the reflected wave that reaches the pipe on the opposite side across the fluid to be measured 11 is reflected inside the fluid pipe 10 without reaching the fluid to be measured 11 as shown in FIG. In order to absorb both ultrasonic waves, it is desirable to arrange the sound absorbing material 40 as in the first to third embodiments and the sound absorbing material 40 as shown in the fourth embodiment in combination.

  Both the prior art and the embodiment have been described as an ultrasonic flowmeter in which an ultrasonic transmission unit and an ultrasonic echo reception unit are integrally formed. However, even in an ultrasonic flowmeter provided with an ultrasonic transmitting means and an ultrasonic echo receiving means as separate bodies, the above-mentioned pipe can be fixed to the pipe outer wall at the arrival position of the ultrasonic pulse in the fluid pipe of the fluid to be measured. By providing such a sound absorbing material, it is possible to suppress the occurrence of measurement errors due to the reflected wave from the fluid piping.

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 1st embodiment. It is a conceptual diagram which shows 2nd embodiment. It is a conceptual diagram which shows 3rd embodiment. It is a conceptual diagram which shows 4th embodiment. It is a conceptual diagram for showing the problem of the prior art. It is a conceptual diagram for showing the problem of the prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fluid piping 11 Fluid 12 to be measured Bubble 20 in fluid Ultrasonic transmission / reception means (transducer)
30 Wedge 40 Sound absorbing material 41 Sound absorbing material holder 42 Slider

Claims (5)

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. An ultrasonic flowmeter comprising a flow rate calculation means for measuring the flow rate of a fluid to be measured,
A sound-absorbing material that can be fixed to the outer wall of the pipe at the arrival position of the ultrasonic pulse in the fluid pipe of the fluid to be measured,
The acoustic flowmeter is an ultrasonic flowmeter made of a high-density material whose acoustic impedance is close to the acoustic impedance of the fluid piping. A sound absorbing material holder that holds the sound absorbing material and is fixed to the outer wall of the pipe, and a slider that can change the position of the sound absorbing material holder, so that the fixing position of the sound absorbing material with respect to the outer wall of the pipe can be changed. The ultrasonic flowmeter according to claim 1, wherein 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. An ultrasonic flowmeter comprising a flow rate calculation means for measuring the flow rate of a fluid to be measured,
A wedge for fixing the ultrasonic transmission means at a predetermined angle and clamping on the outer wall of the fluid pipe of the fluid to be measured;
The wedge is provided with a sound absorbing material at a predetermined position on the surface in contact with the pipe outer wall side, and the acoustic impedance of the sound absorbing material is made of a high-density material that approximates the acoustic impedance of the fluid piping. Ultrasonic flow meter. 4. The ultrasonic flowmeter according to claim 3, wherein the wedge is provided with a slider capable of changing the position of the sound absorbing material in the wedge so that the fixing position of the sound absorbing material with respect to the outer wall of the pipe can be changed. 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. A sound-absorbing material for use in an ultrasonic flowmeter comprising a flow rate calculation means for measuring the flow rate of a fluid to be measured,
It can be fixed to the outer wall of the fluid piping of the fluid to be measured,
A sound-absorbing material for an ultrasonic flowmeter, characterized in that it is formed of a material obtained by blending a synthetic resin with a high-density metal powder so that its acoustic impedance is close to the acoustic impedance of a pipe.

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