JPH0554889B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to an ultrasonic flow rate measuring device that calculates a flow rate based on the propagation time of ultrasonic waves in a fluid in a pipe, and in particular to acoustic propagation due to temperature changes in a fluid to be measured. Concerning the modification of roads.

[Conventional technology]

In a flow measuring device that uses ultrasonic waves to measure the flow velocity 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 rate of fluid in the pipe. This method is disclosed in Utility Model Publication No. 44-25837, "Ultrasonic Flow Measuring Device" and Patent Publication No. 1987-25750, "Ultrasonic Flow Measuring System."

A pair of ultrasonic transducers is installed on the outer periphery of the pipe along the pipe axis, which is the flow direction of the fluid.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 measured fluid changes, the sound velocity of the medium such as a 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 a pipe with an inner diameter of D, 3-1, 3-2 is an ultrasonic transducer (hereinafter referred to as transducer), 11 is a wedge made of synthetic resin, and L is a set of transducers 3.
-1, 3-2 are the intervals between the positions of incidence of the ultrasonic beams on 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. In the transducers 3-1 and 3-2, a wedge body 11 made of a synthetic resin material is provided on the radiation surface of an ultrasonic transducer (hereinafter referred to as a transducer), and the fluid in the pipe 1 is water.

At the boundary surface of the medium in the acoustic propagation path, refraction of the ultrasonic wave occurs depending on the sound velocity of the medium and the angle of incidence. (Snell's Law) When the temperature of the fluid changes, the sound speed of the medium changes, so the refraction angle changes and the sound propagation path changes. Therefore, the ultrasonic beam emitted from the transducer 3-1 reaches a position deviated from a predetermined position of the transducer 3-2 due to a change in the acoustic propagation path.

For example, JIS-G-3452 carbon steel pipes are used, the transducer is PZT, the wedge body 11 is made of acrylic, and in the conduit 1 of the reflective acoustic propagation path shown in FIG. Assuming that the angle of incidence of the ultrasonic beam emitted by the ultrasonic beam on pipe 1 is 47°, when the temperature of the fluid changes from 10°C to 60°C, the pipe size is 25A,
Predetermined incident interval L of the transducer 3-1, 3-2 at the arrival position of the ultrasonic beam at 50A, 100A, 200A
The deflection positions are 5.4 mm, 8.8 mm, 15.6 mm, and 30.3 mm, and as the fluid temperature changes, the arrival position of the ultrasonic beam changes, so the received signal level of the ultrasonic wave at the transducer 3-2 decreases.

On the other hand, C: Sound velocity of the fluid, φ: Refraction angle of the ultrasonic wave into the fluid τ: Fixed delay time, V: Fluid flow rate td: Flow from the transducer 3-1 to the transducer 3-2 Forward propagation time, tu; Assuming the propagation time in the reverse direction from the transducer 3-2 to the transducer 3-1, td=D/(C+Vsinφ)cosφ+τ tu=D/(C−Vsinφ)cosφ+τ Δt=tu−td T=1/2 (Tu+Td) V=D・Δt/sin2φ・(T−τ) ^2When the temperature changes, the speed of sound in 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, which changes the flow velocity V, resulting in a measurement error.

The flow rate and flow rate of the fluid are determined by the propagation time difference between the pair of ultrasonic transducers 3-1 and 3-2 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,
The ultrasonic beam transmitted from the transducer 3-1 reaches a position deviated from a predetermined position of the transducer 3-2. This state becomes more noticeable as the fluid temperature changes and the pipe size increases, so the ultrasonic level received by the transducer 3-2 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 reception sensitivity decreases, measurement errors may intervene and measurement may become impossible.

In particular, when measuring the flow rate in the pipe line 1 in an industrial plant, there are many factors that change the acoustic propagation path, such as pipe size, pipe material, type of fluid (fluid other than water), and temperature of the fluid. To modify the acoustic propagation path, change the shape of the wedge body 11 provided on the transducer radiation surface of the transducers 3-1 and 3-2 to change the incident angle of the ultrasonic beam to the conduit 1. 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 Transducer/receiver 3-1, 3-2
The acoustic propagation path of the ultrasonic wave is stabilized so that 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 angle of incidence of ultrasonic beams emitted from transducers 3-1 and 3-2 into a conduit 1.

[Means for solving problems]

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 is arranged on an inclined surface in the tube axis direction of a wedge made of a synthetic resin material, 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... in the order of arrangement with the transducer as a reference, and a pulse circuit that supplies pulse signals to the ultrasonic transducer via the delay circuits. , temperature detection means for detecting the temperature of the fluid;
The control circuit includes a control circuit that generates a control signal that corresponds to the delay amount of the delay circuit and the output signal of the temperature detection 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 the respective delay circuits are connected in a certain manner. The amount of delay to be delayed 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 radiation from the transducer is The acoustic propagation path is maintained properly by changing the angle of incidence of the ultrasonic beam onto the pipe.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the present invention, and numeral 1 is the same as the conventional device described above. 2 is a vibrator that performs electro-acoustic conversion to generate ultrasonic waves; 3
is a transducer consisting of a plurality of oscillators 2 which are individually excited and arranged in a row; 4 is a transducer consisting of a plurality of oscillators 2;
5 is a delay circuit provided for each of the plurality of transducers and provides a delay in a certain relation to the excitation phase of the pulse signal of the pulse circuit 4; 6 is a delay circuit for generating a pulse signal to individually excite the fluid to be measured; A temperature detector generates a temperature signal, 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 rate measuring device configured as described above, the transducer 3 includes, for example, four individually excited vibrators 2, and a pulse circuit 4.
The pulse signals branched into four circuits excite the vibrator 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 individually excited oscillators 2
The radiation direction 8 of the ultrasonic beam radiated from the transducer 3 is perpendicular to the radiation surface of the transducer 3.

Temperature detector 6 when fluid temperature rises above room temperature
When the output signal of the control circuit 7 changes, the connection position of the output of the control circuit 7 to the delay amount switching tap provided in the delay circuit 5 is changed, and the delay amount of the excitation pulse signal applied to each vibrator 2 is controlled. Fig. 2 shows the radiation characteristics of the ultrasonic beam emitted from the transducer 3 when the phases of the excitation pulse signals of the plurality of transducers 2 are changed respectively. In the explanatory diagram, 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 deviation angle of the ultrasonic beam in the radiation direction, and the pulse signal to each transducer 2 is As shown in the figure, the delay amount is
By the arrangement ^of Δt from one end of the array in order of array,
By changing the phase of the excitation pulse signal by giving different delays to each transducer 2 of 2Δt, 3Δt, etc., the radiation direction of the combined ultrasound beam radiated from the plurality of transducers 2 is determined by the radiation direction of the transducer 2. It is possible to deviate from the direction perpendicular to the plane in the arrangement direction of the vibrators 2 so that the deviation angle increases in proportion to the amount of delay. Further, by sequentially increasing the delay amount with the reference position of the delay amount applied to the transducer 2 as the other end, the deflection angle of the ultrasonic beam can be deviated from the vertical direction in the opposite direction to the above-mentioned deflection direction.

FIG. 3 shows an example of a structural diagram 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 molded into an integral structure of synthetic resin. Furthermore, when the transducer 3 is attached to the pipe line 1 with the radiation surface adhered to the wedge body 11, the ultrasonic beam is radiated into the pipe line 1 through the wedge body 11.

In the above structure, when the incident angle of the ultrasonic beam emitted from the transducer 3-1 to the pipe line 1 using 50A of JIS G 3452 piping carbon steel pipe is 47° and the fluid temperature is 20°C, one set of Transducer/receiver 3-1, 3
-2 ultrasonic beam incident position interval L into conduit 1
is 56.0mm. When the fluid temperature rises, pipe 1
Although the sound speed of the wedge 11 made of the material and the acrylic material decreases, the sound speed 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 rises from 20°C to 60°C, the value of the above-mentioned incident position interval L becomes 62.7 mm. At this time, by adjusting the delay amount of the delay circuit 5 so that the angle of incidence of the ultrasonic beam of the transducer 3-1 on the pipe line 1 is from 47° to 44.6°, the acoustic propagation path due to the change in the refraction angle is adjusted. The change is corrected so that the reflected position of the ultrasonic beam in the conduit 1 matches the position when the fluid temperature is normal temperature, and the arrival position also matches the position of the transducer 3-2.

The above content can be similarly modified by attaching a pair of transducers 3-1 and 3-2 to the conduit 1 of the transmission type acoustic propagation path shown in FIG. Transducer/receiver 3-
If you change the angle of incidence of the ultrasonic beam radiated from 1 into the pipe 1, the refraction angle at the interface between each medium in the acoustic propagation path will change depending on the fluid temperature, but the ultrasonic beam will not be transmitted or received for reception. A sound propagation path is always ensured correctly so that the sound propagation path can reach the predetermined position of the device 3-2.

Fluid temperature can be detected by attaching a temperature detector to the pipe line 1, or a pair of transducers 3-1, 3- can measure the flow rate by utilizing changes in sound velocity due to fluid temperature.
2, it can be calculated from the propagation time of the ultrasonic wave. When the excitation phase of each vibrator 2 is changed by automatically changing the delay amount of the delay circuit 4 based on the fluid temperature signal, the vibrators 2 in the transducer 3 are arranged in the tube axis direction of the conduit 1. Therefore, the radiation angle of the ultrasonic beam changes within a plane including the tube axis, so that the angle of incidence of the ultrasonic beam into the tube 1 can be changed.

In this ultrasonic flow rate measurement device, one set of transducers 3-1 and 3-2 performs alternate excitation, so
The same amount of delay is given when transmitting and receiving ultrasonic signals, and the angle between the ultrasonic beam radiation characteristics of the transducers 3-1 and 3-2 with the conduit 1 is the same when transmitting and receiving. Each is equal.

In the present invention, a plurality of oscillators 2 are arranged in a transducer 3, and the phase of a pulse signal that excites the oscillators 2 is determined by a fluid temperature signal so that the delay amount of a delay circuit 5 corresponds to the arrangement of the oscillators 2. By controlling and changing the amount of delay in a certain relationship, the angle between the beam radiation characteristics of one set of transducers 3 and the pipe 1 is constantly corrected, and an appropriate acoustic propagation path is always formed. By transmitting and receiving ultrasonic signals by the transducer 3 in the state of the best sensitivity, it is possible to correct changes in the refraction angle to the fluid and perform accurate measurements.

Furthermore, even if the dimensions of the pipe, the material of the pipe, the type of fluid, etc. change, the amount of delay of the delay circuit 4 can be adjusted so that an optimum acoustic propagation path can be formed.

〔Effect of the invention〕

As explained above, this invention has a simple structure in which multiple oscillators are arranged in a transducer and the phase of the signal that excites each oscillator is adjusted depending on the fluid temperature, so that the temperature of the measured fluid can be changed. The radiation characteristics of the ultrasonic beam emitted from the transducer can be adjusted by adjusting the mutual phases of the pulse signals that excite each transducer of the transducer in a certain relationship using the temperature signal of the measured fluid. Accurate measurements can be made by controlling the angle with the pipe to always form an optimal acoustic propagation path for one set of transducers. 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 the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram of the radiation characteristics of an ultrasonic beam,
FIG. 3 is an example of a structural diagram of a transducer, FIG. 4 is an explanatory diagram of a conventional reflection type acoustic propagation path, and FIG. 5 is an explanatory diagram of a conventional transmission type acoustic 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] 1 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, a plurality of an ultrasonic transducer in which individually excited ultrasonic transducers 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 delay amounts of Δt, 2Δt, 3Δt... based on the ultrasonic transducer in the order of arrangement, and a pulse signal to the ultrasonic transducer via the delay circuits. temperature detection means for detecting the fluid temperature; and a control circuit for generating a control signal in which the delay amount of the delay circuit corresponds to the 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 in the ultrasonic emission direction is adjusted by a signal.