WO2007074779A1

WO2007074779A1 - Ultrasonic flowmeter and wedge for use in ultrasonic flowmeter

Info

Publication number: WO2007074779A1
Application number: PCT/JP2006/325795
Authority: WO
Inventors: Michitsugu Mori; Kenichi Tezuka; Takeshi Suzuki
Original assignee: The Tokyo Electric Power Company, Incorporated
Priority date: 2005-12-27
Filing date: 2006-12-25
Publication date: 2007-07-05
Also published as: JP2007178244A

Abstract

An ultrasonic flowmeter contributive to more accurate measurement of flow rate even when the surface temperature of piping is high. An ultrasonic transmission means and a means for receiving an ultrasonic echo are formed integrally into a transducer (20). A wedge (30) for securing the ultrasonic transmission means (transducer (20)) to the outer wall surface of fluid piping (10) concerning fluid (11) to be measured is provided, and that wedge (30) is formed by sintering and molding graphite. Distance from the outer wall surface to the inner wall surface of the fluid piping (10) is equal to integral multiples of the half wavelength of incident ultrasonic wave, and the distance from the transducer (20) to the outer wall surface of the fluid piping (10) in the wedge (30) is equal to integral multiples of the half wavelength of incident ultrasonic wave.

Description

Wedge used for ultrasonic flowmeter and ultrasonic flowmeter

Technical field

TECHNICAL FIELD [0001] The present invention relates to an ultrasonic flowmeter and a related technique capable of solving the problems that occur when measuring the flow velocity of fluid in a pipe when the surface temperature of the pipe is high.

Background art

[0002] Various techniques have been provided for Doppler type ultrasonic flowmeters capable of measuring flow rates without contact. For example, the technique described in Patent Document 1.

[0003] Patent Document 1: JP 2000-97742 A

[0004] The above technique will be specifically described. The Doppler type ultrasonic flowmeter disclosed in the above document is an ultrasonic wave that makes an ultrasonic pulse of a required frequency incident on a fluid to be measured in a fluid (for example, water) pipe along an ultrasonic transducer force measurement line. Transmitting means and fluid velocity distribution measuring means for receiving the ultrasonic echo reflected from the measurement area among the ultrasonic pulses incident on the measured fluid and measuring the flow velocity distribution of the measured fluid in the measurement area And a flow rate calculation means for calculating the flow rate of the fluid under measurement in the measurement region based on the flow velocity distribution of the fluid under measurement to measure the flow rate of the fluid under measurement.

[0005] In an ultrasonic flowmeter, when the fluid to be measured is a liquid, a “clamp-on type” is often used in which the ultrasonic wave transmission means is fixed to the pipe via a wedge. This is because there is an advantage that “retrofitting” is possible for piping. The first condition for the wedge is that it should be easy to pass ultrasonic waves. On the other hand, a synthetic resin (for example, acrylic resin) is generally employed for the convenience of fixing the ultrasonic transmission means after determining the ultrasonic incident angle.

[0006] In recent ultrasonic flowmeters, an ultrasonic oscillator (emission) and an apparatus (receiver) for receiving the reflected wave of the ultrasonic are often provided as one ultrasonic transmission / reception apparatus. In an ultrasonic flowmeter that has an ultrasonic oscillator and a device that receives the reflected wave of the ultrasonic wave separately, each must be attached to the fluid piping with strict positioning. However, the ultrasonic flowmeter provided as an ultrasonic transmission / reception device has the advantage that it only needs to be attached to the fluid piping once.

[0007] When an ultrasonic flowmeter with high measurement accuracy is to be used for equipment piping of a nuclear power plant, the following techniques are provided. For example, the techniques described in Patent Document 2 and Patent Document 3.

Patent Document 2: Japanese Patent Application Laid-Open No. 11 230801

Patent Document 3: Japanese Patent Application Laid-Open No. 2001-141534

[0010] The technique described in Patent Document 2 is a technique for reducing the temperature to a temperature that can be withstood by an ultrasonic transducer in an ultrasonic flowmeter by providing a radiation fin on the outer surface of a measurement tube.

In addition, the technique described in Patent Document 3 provides a cooling space between the pipe surface and the ultrasonic vibrator, and lowers the cooling space to a temperature that the ultrasonic vibrator can withstand by water cooling or the like. This is a technology intended for

Disclosure of the invention

Problems to be solved by the invention

[0011] However, it has been found that the engineering plastic that is usually selected as the material of the wedge in such an environment greatly varies the speed of sound of the ultrasonic wave that passes through depending on the temperature. The speed of sound increases at low temperature. That is, there is a complicated layer of members and shoes with different sound speeds between the part of 220 degrees Celsius in contact with the pipe surface and the part of 100 degrees Celsius or less reaching the transducer. The same.

[0012] It is well known that ultrasonic waves are reflected and refracted at the interface of members with different acoustic impedances expressed by the product of sound velocity and density, but this is also true for members whose sound velocity changes due to temperature gradients. Phenomenon is expected. For this reason, as shown in FIG. 5, the incident angle of the ultrasonic wave transmitted by the ultrasonic transducer force is different from the installation angle of the wedge, and the flow velocity distribution cannot be measured accurately.

[0013] The problem to be solved by the present invention is to provide a technique that contributes to more accurate flow rate measurement even when the temperature of the pipe surface is high.

An object of the invention described in claim 1 is to provide an ultrasonic flowmeter that contributes to more accurate flow rate measurement even when the pipe surface temperature is high.

The inventions of claims 2 to 4 may be used even if the temperature of the piping surface is high. It is to provide a wedge for an ultrasonic flow meter that contributes to more accurate flow rate measurement. Means for solving the problem

[0014] (Claim 1)

The invention according to claim 1 is an ultrasonic transmission means (20) in which an ultrasonic pulse of a required frequency is incident from a ultrasonic transducer along a measurement line into a fluid to be measured (11) in a fluid pipe (10). A fluid velocity distribution measuring means for receiving an ultrasonic echo reflected from the measurement region force among ultrasonic pulses incident on the fluid to be measured (11) and measuring the flow velocity distribution of the fluid to be measured in the measurement region; The present invention relates to an ultrasonic flowmeter that includes flow rate calculation 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 and that measures a flow rate of the fluid under measurement. In the ultrasonic flow meter, the ultrasonic transmission means and the reception means for receiving the ultrasonic echo are integrally formed.

A wedge (30) is provided for fixing the ultrasonic transmission means (20) to the outer wall surface of the fluid pipe (10) related to the fluid to be measured (11), and the wedge (30) is made of graphite. It is characterized by being formed by sintering.

[0015] (Glossary)

The above ultrasonic flowmeter includes a general Doppler ultrasonic flowmeter and an ultrasonic flowmeter using a correlation method. The ultrasonic flow meter using the correlation method is, for example, an ultrasonic flow meter as disclosed in Japanese Patent Application Laid-Open No. 2003-344131.

In both cases, an ultrasonic transmission means for injecting an ultrasonic pulse of a required frequency along the measurement line from the ultrasonic transducer into the fluid to be measured in the fluid pipe, and an ultrasonic pulse incident on the fluid to be measured. The measurement area force is reflected by the reflected ultrasonic echo, the fluid velocity distribution measuring means for measuring the flow velocity distribution of the fluid under measurement in the measurement area, and the measurement based on the flow velocity distribution of the fluid under measurement! A flow rate calculating means for calculating a flow rate of the fluid to be measured in the region, and measuring the flow rate of the fluid to be measured.

[0016] For "molding", surface coating is possible without interfering with the transmission of ultrasonic waves. If necessary in sintering and molding, noder is mixed. The condition for the “binder” is that it does not interfere with the transmission of ultrasonic waves. For example, shape graphite fiber Don't make it! This is because the mesh structure blocks the ultrasonic waves.

[0017] (Action)

Graphite has almost no change in sound speed up to 25 degrees Celsius and 230 degrees Celsius, as shown in Figure 2. Therefore, even when a wedge formed by sintering and molding graphite is installed on the surface of a pipe at 230 degrees Celsius, the flow velocity distribution can be measured as a homogeneous material. Therefore, it can be used as an ultrasonic flowmeter that contributes to more accurate flow rate measurement even when the temperature of the piping surface in a nuclear power generation facility is high.

[0018] (Claim 2)

The invention described in claim 2 is a wedge for use in the ultrasonic flowmeter according to claim 1, characterized in that it is formed by sintering and molding black lead.

[0019] (Function)

The wedge according to this claim can be used for an ultrasonic flowmeter that contributes to more accurate flow rate measurement even when the temperature of the piping surface in a nuclear power generation facility or the like is high.

Since the wedge is a member that determines the incident angle of the ultrasonic wave by the ultrasonic transmission means, it is common to prepare a plurality of types and select and use an appropriate one at the site. Therefore, if several types of wedges are prepared by sintering and molding graphite, it will contribute to the efficiency of on-site installation and subsequent measurement.

[0020] (Claim 3)

The invention according to claim 3 is a fixing portion for fixing the ultrasonic transmission means to the fluid piping related to the fluid to be measured, and an outer wall surface of the fluid piping from the ultrasonic transmission means fixed to the fixing portion. The ultrasonic transmission part is a wedge characterized by being formed by sintering and molding graphite.

[0021] The difference from the wedge according to claim 2 is as follows. That is, in contrast to the wedge according to claim 2 formed as a homogeneous material, the wedge according to claim 3 uses only the portion that becomes the path of ultrasonic waves as graphite.

If such a rust is used, a rust can be formed more appropriately according to the environment and conditions to be installed. For example, if you have to fix to a vibrating pipe, It is possible to use a material (for example, metal) having a higher strength than graphite for the portion other than the portion serving as the ultrasonic path.

[0022] (Claim 4)

The invention described in claim 4 limits the wedge described in either claim 2 or claim 3.

That is, the outer wall force of the fluid pipe is the integral multiple of the half wave length of the incident ultrasonic wave, and the distance to the outer wall surface of the fluid pipe is incident on the wedge. It is characterized by being formed to be an integral multiple of half the wavelength of the ultrasonic wave.

[0023] It is necessary to adjust the transmission frequency of the ultrasonic transmission means (20) so that the distance Lx2 passing through the pipe wall of the fluid pipe (10) is an integral multiple of half the wavelength (e / 2) of the transmission frequency. There is.

In this way, the transmission frequency of the ultrasonic transmission means (20) is adjusted. Then, according to this transmission frequency, the distance Lxl of the wedge (30) is adjusted to be an integral multiple of a half wavelength. Then, the transmittance is improved dramatically.

It should be noted that the Lxl distance can be as small as possible to suppress the attenuation of ultrasonic waves in the wedge (30).

The invention's effect

[0024] According to the invention described in claim 1, it is possible to provide an ultrasonic flowmeter that contributes to more accurate flow rate measurement even when the pipe surface temperature is high.

According to the inventions described in claims 2 to 4, it is possible to provide a wedge for an ultrasonic flowmeter that contributes to more accurate flow rate measurement even when the temperature of the pipe surface is high. .

In particular, according to the invention described in claim 4, it is possible to increase the transmittance when passing through Lxl and Lx2. In other words, it efficiently penetrates both the wedge and the piping wall surface, contributing to more accurate flow rate measurement.

Brief Description of Drawings

FIG. 1 is a conceptual diagram showing an ultrasonic path.

FIG. 2 is a graph showing the relationship between temperature and sound velocity for several materials including graphite. FIG. 3 is a conceptual diagram for showing a dimensional ratio in a wedge.

FIG. 4 is a view showing a wedge provided with an ultrasonic transmission portion that is a graphite force and an ultrasonic transducer fixing portion that is a separate member force.

[Fig. 5] An illustration of the change in sound velocity due to the temperature gradient and the resulting refraction of incident ultrasound.

Explanation of symbols

[0026] 10 Fluid piping 11 Fluid to be measured

20 Ultrasonic transmitting / receiving means (transducer)

30 Wedge 31 Ultrasonic transmission means fixing part 32 Ultrasonic propagation part BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in more detail based on embodiments and drawings. The drawings used here are Figures 1 to 5. FIG. 1 is a conceptual diagram showing the whole of the present invention. FIG. 2 is a diagram showing the relationship between temperature and sound velocity in several materials including graphite. Fig. 3 is a conceptual diagram for showing the dimensional ratio in the wedge, and Fig. 4 is a diagram showing a wedge having an ultrasonic transducer fixing portion that is a separate member force and an ultrasonic transmission portion that is a graphite force. FIG. 5 is an explanatory diagram of the change in sound velocity due to the temperature gradient and the refraction of incident ultrasonic waves due to the change.

[0028] (Figure 1)

Fig. 1 shows an ultrasonic echo reflected from the measurement area of an ultrasonic pulse incident on the fluid 11 to be measured, as measured by an ultrasonic flowmeter for measuring the flow rate of the fluid pipe 10 through which the fluid 11 to be measured 11 flows. A state is shown in which an ultrasonic transmission / reception means (transducer 20) that also serves as a receiver for receiving the signal is provided. The transducer 20 is fixed to a predetermined portion of the pipe 10 by a wedge 30 made of resin.

[0029] The transducer 20 includes ultrasonic transmission means for transmitting an ultrasonic pulse having a required frequency (fundamental frequency) along the measurement line to the fluid to be measured 11, and measurement of the ultrasonic pulse incident on the fluid to be measured. Area force Receives reflected ultrasonic echoes and doubles as a fluid velocity distribution measuring means to measure the flow velocity distribution of the fluid under measurement in the measurement area. Although not shown, based on the flow velocity distribution, 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, and this computer It is connected to a display device capable of displaying power output in time series.

[0030] Further, the transducer 20 includes a vibration amplifier as a signal generator for vibrating the transducer 20, and a pulse electric signal having a required fundamental frequency is input to the ultrasonic transducer. It has come to be. Then, by applying the pulse electric signal, an ultrasonic pulse having a fundamental frequency is oscillated along the measurement line. An ultrasonic pulse is a straight beam with a pulse width of about 5mm and almost no spread!

The transducer 20 receives an ultrasonic echo that is reflected when an oscillated ultrasonic pulse hits a reflector (eg, “bubble” but not shown) in the fluid 11. It has become.

The ultrasonic echo by the longitudinal wave received by the transducer 20 is received by the reflected wave receiver also serving as the transducer 20 and converted into an echo electric signal by the reflected wave receiver. This echo electric signal is amplified by an amplifier and then digitized through an AD converter. The digitized digital echo signal is input to a flow velocity calculation device equipped with a flow velocity distribution measurement circuit.

FIG. 4 includes a fixing part for fixing the ultrasonic transmission means and an ultrasonic transmission part, and the ultrasonic transmission part shows a wedge formed by sintering and molding graphite. It has been. The basic configuration is the same as that shown in FIG. 1, but is different in that the fixing part for fixing the ultrasonic transmission means may be a member different from graphite.

[0033] (Fig. 2)

In FIG. 2, the temperature of the sound is measured by changing the temperature of graphite, a plurality of engineering plastics, and aluminum, which are the materials of the wedge according to the present embodiment. For example, aluminum is stable above 150 degrees Celsius, but the speed of sound continues to drop to 150 degrees Celsius.

In other engineering plastics, as the temperature increases, the speed of sound continues to decrease gradually.

[0034] However, for graphite, as shown in Fig. 2, the sound speed hardly changes until the force near 25 degrees Celsius is 230 degrees Celsius!

Therefore, by adopting graphite for the whole wedge or the part that becomes the path of ultrasonic waves, Even in environments where temperature gradients occur, it is possible to accurately measure the flow velocity distribution.

FIG. 3 shows the relationship between the transducer force in the wedge and the distance (Lxl) from the pipe surface to the fluid to be measured (Lx2).

The ultrasonic frequency is set to be an integral multiple of a half wavelength of the ultrasonic frequency by the transducer 20 at the distance Lx2. In other words, if the specifications (material and thickness) of the fluid pipe 10 are determined, the distance Lx2 that passes through the pipe wall is also determined.

[0036] As the actual procedure, first, the pipe wall thickness is obtained. This can be determined by actual measurement or piping specs.

Next, the distance Lx2 is calculated from the incident angle of the ultrasonic waves from the transducer 20, the material of the wedge 30 and the piping, and the like.

Then, the frequency of the ultrasonic wave oscillated by the transducer 20 is determined so that the Lx2 is an integral multiple of a half wavelength of the incident ultrasonic frequency. Using the determined frequency, Lxl is determined so as to be an integral multiple of a half wavelength.

In addition, since the ultrasonic wave is attenuated in the wedge 30, it is general to suppress the attenuation of the ultrasonic wave by making Lxl as close as possible.

Industrial applicability

[0037] The present invention is not limited to the Doppler type ultrasonic flowmeter, but can be applied to a flowmeter belonging to a general ultrasonic flowmeter.

In addition to the ultrasonic flow meter manufacturing industry, it is also used in the installation and maintenance industries of ultrasonic flow meters.

Claims

The scope of the claims

[1] Ultrasonic transmission means for injecting ultrasonic pulses of the required frequency along the ultrasonic transducer force measurement line into the fluid under measurement in the fluid pipe, and the measurement region of the ultrasonic pulses incident on the fluid under measurement The fluid velocity distribution measuring means for receiving the reflected ultrasonic echo and measuring the flow velocity distribution of the fluid to be measured in the measurement region, and the measurement based on the flow velocity distribution of the fluid to be measured! / An ultrasonic flowmeter for measuring a flow rate of a fluid to be measured, comprising a flow rate calculation unit for calculating a flow rate of the fluid to be measured in the region, and comprising an ultrasonic transmission unit and a reception unit for receiving an ultrasonic echo. Provided with a wedge for fixing the ultrasonic transmission means to the outer wall surface of the fluid pipe related to the fluid to be measured,

The wedge is an ultrasonic flowmeter characterized by being formed by sintering and molding graphite.

[2] Ultrasonic transmission means for injecting ultrasonic pulses of the required frequency along the ultrasonic transducer force measurement line into the fluid to be measured in the fluid pipe, and the measurement area of the ultrasonic pulses incident on the fluid to be measured The fluid velocity distribution measuring means for receiving the reflected ultrasonic echo and measuring the flow velocity distribution of the fluid to be measured in the measurement region, and the measurement based on the flow velocity distribution of the fluid to be measured! / An ultrasonic flowmeter for measuring the flow rate of the fluid to be measured, comprising a flow rate calculation means for calculating the flow rate of the fluid to be measured in the region, and integrally forming the ultrasonic transmission means and the reception means for receiving the ultrasonic echo A wedge used for the above, characterized by being formed by sintering and molding graphite.

[3] Ultrasonic transmission means for injecting an ultrasonic pulse of a required frequency along the ultrasonic transducer force measurement line into the fluid to be measured in the fluid pipe, and a measurement region of the ultrasonic pulse incident on the fluid to be measured The fluid velocity distribution measuring means for receiving the reflected ultrasonic echo and measuring the flow velocity distribution of the fluid to be measured in the measurement region, and the measurement based on the flow velocity distribution of the fluid to be measured! / An ultrasonic flowmeter for measuring the flow rate of the fluid to be measured, comprising a flow rate calculation means for calculating the flow rate of the fluid to be measured in the region, and integrally forming the ultrasonic transmission means and the reception means for receiving the ultrasonic echo A wedge for use in the above, a fixing portion for fixing the ultrasonic transmission means to the fluid piping related to the fluid to be measured; An ultrasonic transmission part that extends from the ultrasonic transmission means fixed to the fixed part to the outer wall surface of the fluid pipe,

The wedge is characterized in that the ultrasonic transmission part is formed by sintering and molding graphite. The outer wall force of the fluid pipe is an integral multiple of half the wavelength of the incident ultrasonic wave, and the distance to the outer wall surface of the fluid pipe is the incident ultrasonic wave. 4. The wedge according to claim 2, wherein the wedge is formed to be an integral multiple of a half wavelength.