JPS638515A - Ultrasonic flow rate measuring instrument - Google Patents

Abstract

PURPOSE:To enable a flow rate to be accurately measured regardless of the changes in the temperature of a fluid being measured by arranging a plurality of vibrators in an ultrasonic wave transmitter and receiver and adjusting the phases of signals for exciting the vibrators in accordance with the temperature of the fluid. CONSTITUTION:An ultrasonic wave transmitter and receiver 3 is composed of a plurality of ultrasonic vibrators 2 and excitation by the pulse signals of the ultrasonic vibrators 2 is applied from a pulse circuit 4 via delay circuits 5. Since the quantities delayed by the delay circuits 5 in prescribed mutual relationships are automatically controlled (7) in correspondence with the output of a temperature detector 6 for a fluid being measured, the excitation phases of the pulse signals of the ultrasonic vibrators 2 are adjusted by a fluid temperature. Accordingly, by changing the incident angles of ultrasonic beams emitted from the transmitter and receiver 3 to a pipe line, an acoustic transmitting path is properly maintained.

Description

Detailed Description of the Invention [Industrial Application Field] This invention relates to an ultrasonic flow rate determination device that calculates the flow rate based on the propagation time of ultrasonic waves in a conduit countercurrent flow body, for example, and in particular, to Concerning the modification of the acoustic propagation path by changes.

[Conventional technology]

In a sight measurement device using ultrasonic waves that controls the flow rate or flow rate of fluid in a pipe, a pair of ultrasonic transducers are placed around the outer circumference of the pipe to measure the flow of IIL bodies in the pipe. .

Regarding the measurement of quantity, see 1972-25838 Utility Model Publication [
"Ultrasonic Flow Measuring Apparatus" and Japanese Patent No. 51-25750 "Ultrasonic Flow Measuring Apparatus".

A pair of ultrasonic transducers is installed along the pipe axis, which is the flow direction of the fluid, on the outer circumference of the pipe, and the installation position of the ultrasonic transducer on the pipe is determined by the pipe dimensions and pipe Depending on the material and type of fluid, the acoustic propagation path is determined so that the ultrasonic waves emitted from one ultrasonic transducer can be received with sufficient sensitivity by the other ultrasonic transducer.

When a set of ultrasonic transducers is installed under the above conditions, if the temperature of the fluid to be measured changes, the sound velocity of the medium such as the wedge, pipe, or fluid that forms the acoustic propagation path changes, causing the acoustic propagation path to change. changes.

Fig. 4 is an explanatory diagram of a conventional reflection type acoustic propagation path, and shows an example in which the acoustic propagation path utilizes reflection within the pipe, where 1 is an inner diameter pipe, 3-1.3-2 is an ultrasonic transducer (hereinafter referred to as transducer); 11 is a wedge made of synthetic resin; L;
is the interval between the incident positions of the ultrasonic beams of the pair of transducers 3-1, 3-2 into the conduit 1.

FIG. 5 is an explanatory diagram of a conventional transmission type acoustic propagation path, and shows an example in which the acoustic propagation path utilizes direct propagation of ultrasonic waves within the conduit.The conduit 1 is made of iron-based material and has an inner diameter of D. , transducer 3-1
, 3-2, a wedge body 11 made of a synthetic resin material is provided on the radiation surface of an ultrasonic vibrator (hereinafter referred to as a vibrator), and the fluid in the pipe line 1 is water.

Place it on the boundary surface of the medium in the above sound propagation path!・Ultrasonic waves are refracted depending on the sound speed of the medium and the angle of incidence. (
Snell's law) When the temperature of the fluid changes, the speed of sound in the medium changes, so the angle of refraction changes and the acoustic propagation path changes. Therefore, the ultrasonic beam emitted from the transducer 6-1 reaches a position deviated from the predetermined position of the transducer 3-2 due to the change in the acoustic propagation path.

For example, JIS-G-3452 carbon steel pipes are used, the vibrator is PZT, the i-body 11 is made of acrylic, and the fourth
In conduit 1 of the reflective acoustic propagation path shown in the figure, if the angle of incidence of the ultrasonic beam emitted by the transducer 3-1 into conduit 1 is 47, the temperature of the fluid changes from 10°C to 60°C. When changed, pipe size 25A, 50A, 100A, 20
Transducer/receiver 3-1 at the arrival position of the ultrasonic beam at 0A
．． 3-2 (7) Predetermined incidence interval V4 L Yo! l) (
7) Deflection X 5.4 m, a 8 m.

15.6 cod, 30.3 m υ, as the fluid temperature changes, the arrival position of the ultrasonic beam changes, so the transducer 3-
The received signal level of the ultrasonic waves at 2 decreases.

On the other hand, C: sound velocity of the fluid, φ: angle of refraction of the ultrasonic wave into the fluid τ
; Fixed delay time; V: Fluid flow rate td; Propagation time in the forward direction from the transducer 3-1 to the transducer 6-2; 1++: From the transducer 3-2 to the transducer 3-1. Assuming that the propagation time is in the opposite direction to the flow, ``'' (c+veroφ)■φ +7 1°=death; ``+7 When the temperature changes, the sound speed of each medium that makes up the acoustic propagation path changes.Therefore, If the angle of incidence of the ultrasonic beam on the conduit 1 is constant, the angle of refraction φ changes, so the flow velocity V changes, resulting in a measurement error.

The fluid flow rate and flow rate are determined by a pair of ultrasonic transducers 3-1.
Since it is determined by the propagation time difference between 3 and 2 and the angle between the tube axis and the propagation direction of the ultrasonic wave, if the fluid temperature changes at the same flow rate or flow rate, the output will change and a measurement error will occur.

[Problem that the invention seeks to solve]

In the conventional ultrasonic flow measurement device as described above, when the temperature of the fluid changes, the sound velocity of the medium forming the acoustic propagation path changes, and the refraction angle of the ultrasonic wave at the interface between each medium changes, so the acoustic propagation path changes. is deviated, and the ultrasonic beam transmitted from the transducer 3-1 reaches a position of the transducer 3-2 that is deviated from the predetermined position. This state becomes more noticeable as the fluid temperature changes and the pipe size increases, so the ultrasonic level received by the transducer 6-2 decreases, resulting in a decrease in reception sensitivity, and in extreme cases, The deviation of the acoustic propagation path becomes large, and the ultrasonic beam does not reach the ultrasonic beam, making it impossible to receive it. Furthermore, with conventional methods, measurement errors due to temperature changes cannot be avoided. Therefore, as the receiving sensitivity decreases, measurement errors may intervene and measurement may become impossible.

Especially when measuring the internal flow of pipe 1 in an industrial plant, pipe dimensions, pipe material, type of fluid (fluid other than water)
There are many factors that change the acoustic propagation path, such as the temperature of the fluid. In order to modify the acoustic propagation path, the incident angle of the ultrasonic beam to the conduit 1 must be changed by changing the shape of the bare body 11 provided on the transducer radiation surface of the transducer 3-1.3-2. There was a problem that it had to be done.

This invention was made to solve this problem, and in order to expand the range of applications for flow measurement, even if the pipe dimensions, pipe material, sound velocity of the fluid, fluid temperature, etc. change, one set of K, the transducer 3-1.3-2 so that the acoustic propagation path of the ultrasonic wave of the transducer 3-1.3-2 is stabilized, a normal reception signal is always obtained, and measurement errors are suppressed. It is an object of the present invention to provide an ultrasonic flow rate measuring device that can automatically control the incident angle of an ultrasonic beam emitted from a pipe 1 into a conduit 1.

[Means for solving problems]

In an ultrasonic flow measurement device that measures the ultrasonic propagation time of the fluid in the pipe and the flow rate of the fluid by arranging one set of ultrasonic transducers in a column Vc in the pipe axis direction on the outer circumference of the pipe, a plurality of individual An ultrasonic transducer is arranged on an inclined plane in the axial direction of a naked body made of synthetic resin, and an ultrasonic transducer is excited at one end of the ultrasonic transducer. A plurality of delay circuits with adjustable delay amounts that give delays of Δt, 2Δt, 3Δt, etc. in the order of arrangement based on the transducer, and a pulse circuit that supplies pulse signals to the 7 ultrasonic transducers via the delay circuits. The temperature detecting means detects the temperature of the fluid, and the control circuit generates a control signal that corresponds to the delay amount of the delay circuit in accordance with the output signal of the temperature detecting means.

[Effect]

In this invention, each transducer is composed of a plurality of oscillators, and the excitation of each oscillator by a pulse signal is applied from a pulse generation circuit through a delay circuit, and is delayed by a certain relationship between the respective delay circuits. The delay amount is automatically controlled according to the fluid temperature to be measured, so the excitation phase of the pulse signal of each vibrator is adjusted according to the fluid temperature, and by changing this excitation phase, the amount of delay emitted from the transducer is adjusted. The acoustic propagation path is maintained properly by changing the angle of incidence of the ultrasonic beam on the pipe.

〔Example〕

FIG. 1 is a block diagram showing one embodiment of the present invention,
1 is the same as the conventional device described above. 2 is a vibrator that performs electro-acoustic conversion to generate ultrasonic waves, 6 is individually excited, and -
A transducer consisting of a plurality of transducers 2 arranged in a row, 4
5 is a pulse circuit that generates a pulse signal to individually excite the plurality of oscillators 2; 5 is a delay circuit provided for each of the plurality of oscillators and delays the excitation phase of the pulse signal of the pulse circuit 4 in a certain relationship; 6 is a temperature detector that generates a temperature signal of the fluid to be measured; 7 is a control circuit that adjusts the delay amount of each delay circuit 5 based on the fluid temperature signal; and 8 is the radiation direction of the ultrasonic beam emitted by the transducer 3. .

In the ultrasonic flow measurement device configured as above,
Inside the transducer 3, for example, four oscillators 2 that are individually excited are provided, and a pulse signal branched from a pulse circuit 4 into four circuits excites the oscillators 2 through individual delay circuits 5. .

When the fluid temperature is equal to room temperature, the delay amount of each delay circuit 5 is the same, and the direction 8 is the direction 8 of the ultrasonic beam forest emitted from the transducer 3, which is an individually excited transducer 2. The direction is perpendicular to the radiation surface of the vessel 3.

When the fluid temperature rises above room temperature, the output signal of the temperature detection means changes and the output of the control circuit 7 is connected to the delay amount switching tap provided in the delay circuit 5 to switch the connection position to each vibrator 2.
The amount of delay of the excitation pulse signal applied to is controlled. Regarding the calibration characteristics of the ultrasonic beam emitted from the transducer 6 when the phases of the excitation pulse signals of the plurality of transducers 2 are changed respectively, Fig. 2 shows the emission of the ultrasonic beam from the transducer 3. In the explanatory diagram of the characteristics, d is the arrangement interval of the transducers 2, C is the sound velocity of the medium, Δt is the delay amount of the delay circuit 4, θ is the deflection angle of the ultrasonic beam in the radiation direction, and the deviation to each transducer 2. As shown in the figure, the delay amount of the Norculus signal is given according to ddnθ by the arrangement of the transducer 2, and the deflection angle of the ultrasonic beam is C・Δtθ=,1h1(−−7−). Δt, 2Δt from one end of the array in the order in which the oscillators 2 are arranged in pulse signals that individually excite the oscillators 2.

By applying a different delay to each transducer 2 of 3et... to change the phase of the excitation pulse signal, the radiation direction of the combined ultrasound beam emitted from the plurality of transducers 2 is directed to the radiation surface of the transducer 2. It is possible to deviate from the vertical direction in the arrangement direction of the vibrators 2 so that the deviation angle increases in proportion to the amount of delay. Furthermore, by sequentially adding delay amounts using the reference position of the delay amount given to the transducer 2 as the other end, the tilt angle of the ultrasonic beam can be deviated from the vertical direction in the opposite direction to the above deviation direction. .

FIG. 6 shows an example of a purchasing drawing of the transducer 3.

Reference numeral 12 denotes a back plate made of a synthetic resin material, on which four vibrators 2 are arranged at regular intervals d and are integrally molded from synthetic resin, and the vibrators 2 are arranged along the slope of the wedge body 11. When the transducer 3 is attached to the conduit 1 with its radiation surface adhered to the wedge 11, the ultrasonic beam is radiated into the conduit 1 through the wedge 11.

In the above structure, when the incidence angle of the ultrasonic beam emitted from the transducer 3-1 to the pipe line 1 using JIS G 3452 carbon steel pipe 50A is 47 and the fluid temperature is 20°C, one set of The incident position interval (L) of the ultrasonic beam of the transducer 6-1°3-2 into the conduit 1 is 56. O,
becomes. When the fluid temperature rises, the sonic dust of the pipe 1 material and the acrylic wedge 11 decreases, but the sonic dust of the fluid (water) increases, so the refraction angle at the boundary position of each medium in the acoustic propagation path, changes, and the acoustic propagation path changes.

For example, when the fluid temperature increases from 20° C. to 60° C., the value of the incident position interval (L) becomes 62.7 degrees. At this time, by adjusting the amount of delay in the channel 5 of the ultrasonic beam of the transducer 6-1, changes in the acoustic propagation path due to variations in the refraction angle are corrected, and the reflection position of the ultrasound beam in the channel 1 is corrected. corresponds to the position when the fluid temperature is room temperature, and the reached position also coincides with the position of the transducer 3-2. The same modification can be made even if the device is attached to the conduit 1 of the transmission type acoustic propagation path. If you change the angle of incidence of the ultrasonic beam emitted from the transducer 3-1 into the pipe line 1, the refraction angle at the interface between each medium in the acoustic propagation path will change, even if the refraction angle changes depending on the fluid temperature. The acoustic propagation path is always properly secured so that the beam can reach a predetermined position of the receiving transducer 3-2.

The fluid temperature is detected by attaching a temperature detector to the pipe line 1, or by using a set of transducers 3-1.3 to 2, which measure the flow rate by utilizing changes in sonic dust due to the fluid temperature. The propagation time of the ultrasonic wave can be calculated using Each vibrator 2 automatically changes the delay amount of the υ delay circuit 4 according to the fluid temperature signal.
When the excitation phase of The angle of incidence of the ultrasonic beam onto the conduit 1 can be changed.

In this ultrasonic flow measuring device, one set of transducer 3
-1 and 6-2 perform alternate excitation, so the same amount of delay is given when transmitting and receiving ultrasonic signals. Road 1
The angle between the two is the same at the time of transmission and at the time of reception.

The present invention arranges a plurality of vibrators 2 in a transducer 3,
(by controlling the phase of the pulse signal that excites the vibrator 2 by changing the delay amount of the delay circuit 5 using the fluid temperature signal by changing the delay amount in a certain relationship corresponding to the arrangement of the vibrator 2), one set is always set. The angle between the beam radiation characteristics of the transducer B and the pipe line 1 is corrected to always form an appropriate acoustic propagation path, and the ultrasonic signal is transmitted and received by the transducer B in the state of optimum sensitivity. Changes in the angle of refraction into the fluid can be corrected for accurate measurements.

Further, even if the dimensions of the pipe, the material of the pipe, the type of fluid, etc. change, the delay amount of the delay image path 4 can be adjusted so that an optimal sound propagation path can be formed.

〔Effect of the invention〕

As explained above, this invention has a simple structure in which a plurality of oscillators are arranged in a transducer and the phase of the signal that excites each oscillator is adjusted depending on the fluid temperature. The radiation characteristics of the ultrasonic beam emitted from the transducer can be controlled by adjusting the mutual phase of the pulse signals that excite each transducer of the transducer in a certain relationship even when the temperature signal of the measuring fluid changes. Accurate measurements can be made by controlling the angle between the acoustic propagation path and the 1flllll transducer to always form an optimal acoustic propagation path. Furthermore, the ultrasonic flowmeter can be widely applied to flow measurement in industrial plants where pipe dimensions, pipe materials, types of fluids to be measured, fluid temperatures, etc. are different, thereby expanding the range of applications of the ultrasonic flowmeter.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of this invention. IC
Figure 2 is an explanatory diagram of the radiation characteristics of an ultrasonic beam, Figure 3 is an example of a structural diagram of a transducer, Figure 4 is an explanatory diagram of a conventional reflective acoustic propagation path, and Figure 5 is an illustration of a conventional transmission acoustic propagation path. FIG. 3 is an explanatory diagram of a propagation path. In the figure, 2 is an ultrasonic transducer, 3 is an ultrasonic transducer,
4 is a pulse circuit, 5 is a delay circuit, 6 is a temperature detector, 7 is a control circuit, and 8 is the radiation direction of the ultrasonic beam. Note that the same reference numerals in each figure indicate the same or equivalent.

Claims (1)

[Claims] In an ultrasonic flow measurement device that measures the flow rate of a fluid based on the ultrasonic propagation time of the fluid in the pipe by arranging a set of ultrasonic transducers in tandem in the pipe axis direction on the outer circumference of the pipe, multiple individual an ultrasonic transducer in which ultrasonic transducers excited by the ultrasonic transducer are arranged on an inclined surface in the tube axis direction of a wedge made of a synthetic resin material, and one end arranged in the ultrasonic transducer A plurality of delay circuits whose delay amounts can be adjusted to give delays of Δt, 2Δt, 3Δt, etc. in the order of arrangement based on the ultrasonic transducer, and pulse signals are supplied to the ultrasonic transducer via the delay circuits. a pulse circuit that detects a fluid temperature, a temperature detection means that detects a fluid temperature, and a control circuit that generates a control signal in which a delay amount of the delay circuit corresponds to an output signal of the temperature detection means, An ultrasonic flow rate measurement device characterized in that the angle between the ultrasonic transducer and the pipe line in the ultrasonic emission direction is adjusted.