JP3497279B2 - Ultrasonic flow meter - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic flowmeter for measuring a flow rate by ultrasonic waves.

[0002]

2. Description of the Related Art In a conventional measuring device of this type, as shown in FIG. 9, ultrasonic transducers 2 and 3 are installed so as to face each other with a measurement channel 1 in between, and an ultrasonic transducer Sound wave oscillator 3
The time until it was detected was measured, the velocity of the fluid was calculated from this time, and the flow rate was calculated from this.

[0003]

However, in general,
To place diagonally ultrasonic transducer 2 and 3 to the measuring channel 1, depression occurs the recess between the measurement channel 1 and the ultrasonic transducer 2 and 3 the end surface produces a turbulent flow However, the measurement accuracy was adversely affected.

The present invention is intended to solve the above-mentioned problems, and a chamber is provided upstream and downstream of a measurement flow path, and an ultrasonic transducer is arranged in this chamber, thereby causing turbulence in the flow in the measurement flow path. The purpose is to measure the flow rate with high accuracy.

[0005]

In order to achieve the above-mentioned object, the present invention is provided with a flow rate measuring unit, and is disposed upstream and downstream of the flow rate measuring unit, respectively , and is larger than the flow rate measuring unit.
An upstream chamber and a downstream chamber having a specific cross-sectional area, a first ultrasonic transducer arranged in the upstream chamber, a second ultrasonic transducer arranged in the downstream chamber, and the ultrasonic transducer. And a flow rate calculation unit that calculates a flow rate based on the signal, and the ultrasonic transducers are arranged in the upstream chamber and the downstream chamber so that signals are transmitted and received at an angle with respect to the flow of the fluid flowing in the flow rate measurement unit. It was done.

[0006]

According to the present invention, since the ultrasonic transducers are arranged in the chambers provided upstream and downstream of the flow rate measuring unit with the above-described structure, the flow rate measuring unit can accurately measure without disturbing the flow. Is what you can do.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS.
Will be described with reference to.

In FIG. 1, 4 is a flow rate measuring unit, and 5
Is an upstream chamber provided upstream of the flow rate measuring unit 4, and 6 is a downstream chamber provided downstream of the flow rate measuring unit 4. 7 is the upstream chamber 5
And 8 is an outlet connected to the downstream chamber 6. The cross-sectional areas s1 and s2 of the upstream chamber 5 and the downstream chamber 6 are set sufficiently larger than the cross-sectional area s of the flow rate measurement unit 4. The method of this setting will be described later.

Reference numeral 9 is a first ultrasonic transducer arranged in the upstream chamber 5, and 10 is a second ultrasonic transducer arranged in the downstream chamber 6. Reference numerals 11 and 12 denote walls of the upstream chamber 5 and the downstream chamber 6, respectively. 13a and 13b are corners where the upstream chamber 5 and the flow rate measuring unit 4 are connected, 1
Reference numerals 4a and 14b are corners where the downstream chamber 6 and the flow rate measuring unit 4 are connected.

In FIG. 3, reference numeral 15 is a flow rate calculation unit which receives signals from the first and second ultrasonic transducers 9 and 10 and calculates the flow rate. Among them, 16 is a start signal generating section, 17 is a transmitting section, 18 is a receiving section, and 19 is a switching section.

The transmission section 17 comprises a trigger signal generation section 20 and an oscillation section 21. The receiving unit 18 includes an amplifying unit 22 for a received signal and a comparing unit 23 with a reference value.

Reference numeral 24 is a repeating unit, 25 is a clocking unit, and 26 is an arithmetic unit.

Next, the operation will be described.

Now, it is assumed that the fluid flows in through the inlet portion 7, passes through the flow rate measuring portion 4, and flows out through the outlet portion 8. The flow that has flowed in from the inlet section 7 once enters the upstream chamber 5, and in this upstream chamber 5, the first ultrasonic transducer 9 is connected to the flow rate measuring section 4.
Is located away from the entrance to the wall 11
Since it is integrally disposed in the flow rate measuring unit 4, it does not significantly affect the flow of the flow rate measuring unit 4. This situation also applies to the second ultrasonic transducer 10 arranged in the downstream chamber 6.

In such a state, the start signal generator 16
When a signal is input from the trigger signal generator 20, the trigger signal generator 20 operates and the oscillator 21 sends the signal to the switching unit 19. Initially, the switching unit 19 includes the transmitting unit 17 in the first ultrasonic transducer 9 and
The receiving unit 18 is set to be connected to the second ultrasonic transducer 10. Therefore, an ultrasonic signal is emitted from the first ultrasonic transducer 9 into the flow rate measuring unit 4 by the trigger signal. This signal is received by the second ultrasonic transducer 10, amplified by the amplification unit 22, compared with the reference signal by the comparison unit 23, and when a signal exceeding the reference value is obtained, the trigger signal generation unit 20 is again activated. To drive. This process is performed the number of times set by the repeater 24.

When the predetermined number of repetitions is completed, the timer unit 25
Signal is sent to the terminal, and the elapsed time (T1) from the generation of the trigger signal to the signal sent at this time is measured. Also, on the other hand,
When the predetermined number of repetitions are completed, the repeater 24 disconnects
A signal is sent to the conversion unit 19, and the transmission unit 17 is connected to the second ultrasonic transducer 10 and the reception unit 18 is connected to the first ultrasonic transducer 9.

At the same time, a drive signal is sent again to the trigger signal generator 20, the same operation as above is performed in the opposite direction to the flow, and the elapsed time (T2) is measured.

Now, the ultrasonic wave propagation path is connected to the flow rate measurement unit 4
(Length L), upstream chamber 5 parts (L1), downstream chamber 6 parts (L2)
And the flow velocities in the respective portions L, L1, L2 are v, v1, and v2, and the angles formed by the respective flows with the ultrasonic wave propagation path are θ, θ1, and θ2. Speed of sound c
Then, T1 and T2 are as follows.

[0019]

[Equation 1]

[0020]

[Equation 2]

Now, the cross-sectional area s1 of the upstream chamber 5 is set as follows.

First, assuming that the measured flow rate is Q, the following relationship is established.

[0023] Q = s · v = s1 · v1 = s2 · v2 (1) From this, s1 is determined by the following equation.

[0024] s1 = (V / V1) · s (2) Now, assuming that the error accuracy is p% v1 / v = p / 100 (3) Substituting (3) into (2) gives the following equation.

S1 = (100 / p) · s (4) s2 of the downstream chamber 6 is determined by the same method. Next, T1
When the denominator and the numerator of the second term of are divided by v, the following equation is obtained.

[0026]

[Equation 3]

Usually, the accuracy (percentage) of the error is at most 1
Since it is a digit, 0 <(v1 / v) << 1 from the formula (3) (6) Further, | cos θ1 | <1 (7) From (6) and (7), the following formula is established.

0 <(v1 / v) | cos θ1 | << 1 (8) Now, when measuring a flow velocity much lower than the speed of sound, c / v >> 1 (9) (8), (9) The second term of the denominator in equation (5) can be ignored. Therefore, the equation (5) is as follows.

[0029] L1 / c (10) If the same thing is done, the third term of T1 becomes like the following expression.

[0030] L2 / c (11) Therefore, T1 becomes the following formula.

[0031]

[Equation 4]

The same applies to T2 and the following equation is obtained.

[0033]

[Equation 5]

The second term in equations (12) and (13) is set as follows.

T = (L1 + L2) / c Since this value is already known, it is transferred to the left side of equations (12) and (13), and the reciprocal of each is taken to perform subtraction to obtain the flow velocity in the flow rate measuring section. v is calculated by the following equation.

[0036]

[Equation 6]

The flow rate (Q) is calculated by multiplying this flow rate by the cross-sectional area (s) of the flow rate measuring section 4 and the flow rate correction coefficient (k).

Q = kvs That is, the upstream chamber 5 and the downstream chamber 6 are set to have such sizes, and the first ultrasonic transducer 9 and the second ultrasonic wave are set in the chambers 5 and 6 . By arranging the vibrator 10, the existence of the vibrator does not adversely affect the flow rate measurement, and accurate flow rate measurement is realized.

[0039] Particularly arrangement of vibrators 9 and 10, the ultrasonic wave propagation path, wherein the substantially parallel section in the flow direction of the flow measuring portion 4 rectangular flow measuring portion 4 is cut (in FIG. 1 13a-13b The average flow velocity can be measured by the flow rate measuring unit 4 by arranging the rectangle p) formed in -14a-14b in a position substantially in the diagonal direction, and more accurate measurement is possible. .

Further, when the cross-sectional shape of the flow rate measuring unit 4 is rectangular, the flow in the flow rate measuring unit 4 is maintained in a two-dimensional shape, so that the measurement accuracy is further improved.

Although the measurement of T1 and T2 is repeated in the above description, it may be performed once if accurate measurement is performed.

Next, the second embodiment will be described.

Since the constituent elements in FIG. 4 are exactly the same as those in the first embodiment, the respective elements are designated by the same reference numerals. The difference from the first embodiment is the arrangement of the components. In the case of this example, the inlet portion 7, the outlet portion 8 and the flow rate measuring portion 4 are relatively arranged so that the flow directions inside thereof are perpendicular to each other.
Further, the connection between the flow rate measuring unit 4 and the upstream chamber 5 is set to be performed at a position farthest from the inlet 7. Along with this, the first ultrasonic transducer 9 is arranged at the farthest position from the inlet portion 7 corresponding to the position of the flow rate measuring unit 4.

The flow of signal processing is the same as in FIG.

Next, the operation will be described.

In this arrangement, the first ultrasonic transducer 9 is placed in the upstream chamber 5 at a position where the flow velocity from the inlet portion 7 is further reduced, and the flow velocity v in the upstream chamber 5 is reduced.
Since it is more guaranteed that 1 is within the error range of the flow velocity v of the flow rate measuring unit 4, it is possible to perform measurement in a state with less error.

Next, a third embodiment will be described.

In FIG. 5, 27 is a circular flow rate measuring unit, 28 is a cylindrical upstream chamber provided upstream of the flow rate measuring unit 27, and 29 is a cylindrical flow chamber provided downstream of the flow rate measuring unit 27. It is a downstream chamber. Also in this case, the cross-sectional areas sa1 and sa2 of the upstream chamber 28 and the downstream chamber 29 are set sufficiently larger than the cross-sectional area sa of the flow rate measuring unit 27. Three
0 is an inlet connected to the upstream chamber 28, 31 is a downstream chamber 29
Is an outlet connected to.

Reference numeral 32 is a first ultrasonic transducer arranged in the upstream chamber 28, and 33 is a second ultrasonic transducer arranged in the downstream chamber 29.

The flow of signal processing is the same as in FIG.

Next, the operation will be described.

Now, it is assumed that the fluid flows in through the inlet portion 30, passes through the flow rate measuring portion 27, and flows out through the outlet portion 31. The flow that has flowed in from the inlet portion 30 once enters the upstream chamber 28, but since this upstream chamber 28 is set large, the condition of the equation (8) is satisfied as in the first embodiment, and accurate measurement is possible. Is performed.

Further, in the case of this example, since the shapes of the flow rate measuring unit 27, the upstream chamber 28 and the downstream chamber 29 are axisymmetric, the selection range of the ultrasonic wave propagation path is wide. This allows
The first ultrasonic transducer 32 can be arranged at the farthest position from the inlet of the flow rate measuring unit 27, and has a configuration that makes it easier to satisfy the condition (8). In addition, this position is also a position that does not easily affect the flow of the flow rate measuring unit 27.

The flow of signal processing is the same as in FIG.

By thus forming the upstream chamber 28 and the downstream chamber 29 in a cylindrical shape and setting the cross section of the flow rate measuring unit 27 in a circular shape, the first ultrasonic transducer 32 and the second ultrasonic transducer 32 are formed. The arrangement of the sound wave oscillator 33 can be set at any position around these axes (p), and the degree of freedom in design is further improved.

Next, a fourth embodiment will be described.

Since the components of FIG. 6 are exactly the same as those of the third embodiment, they are designated by the same reference numerals. The difference from the third embodiment is the arrangement of the components. In the case of this example, the entrance 3
0, the outlet portion 31 and the flow rate measuring portion 27 are relatively arranged so that the flow directions inside thereof are perpendicular to each other.
Under this condition, the first ultrasonic transducer 32 moves the upstream chamber 28
It can be arranged at a position farthest from the entrance portion 30 inside.

The flow of signal processing is the same as in FIG.

Next, the operation will be described.

Now, it is assumed that the fluid flows in through the inlet portion 30, passes through the flow rate measuring portion 27, and flows out through the outlet portion 31. The flow that has flowed in from the inlet portion 30 once enters the upstream chamber 28, but since this upstream chamber 28 is set large, the condition of the equation (8) is satisfied as in the first embodiment, and accurate measurement is possible. Is performed. Further, in this case, since the first ultrasonic transducer 32 is arranged at the farthest position from the inlet portion 30 in the upstream chamber 28, the condition (8) is more easily satisfied.

In such an arrangement state, the first ultrasonic transducer 32 is placed in the upstream chamber 28 at a position where the flow velocity from the inlet portion 30 is further reduced, so that the measurement can be performed with less error. Is something that can be done.

Next, a fifth embodiment will be described.

7 and 8, except for the first ultrasonic transducer 34, the second ultrasonic transducer 35, the third ultrasonic transducer 36, and the fourth ultrasonic transducer 37, Since they are the same as the fourth embodiment, they are designated by the same reference numerals. Further, the flow rate calculation circuit corresponding to each pair of ultrasonic transducers is omitted because it is the same as in FIG. 3, but in this case, for the first and second ultrasonic transducers 34 and 35, There are respective arithmetic circuits for the third and fourth ultrasonic transducers 36 and 37.

Next, the operation will be described.

The procedure for measuring the flow rate with the first ultrasonic transducer 34 and the second ultrasonic transducer 35 is the same as in the first embodiment. The procedure for measuring the flow rate with the third ultrasonic transducer 36 and the second ultrasonic transducer 37 is also the same as in the first embodiment.

The flow velocities thus obtained are defined as w1 and w2. When the flow rate measuring unit 27 has a circular shape as in this example, the internal flow may include a three-dimensional element. However, by averaging the flow velocities thus obtained as described below, higher accuracy can be obtained. You can get the value.

W = (w1 + w2) / 2 As described above, in order to obtain a more accurate flow velocity, a method of performing measurement using a plurality of ultrasonic wave propagation paths is a method that is often used in this field, but is usually used. The oscillator is the flow rate measurement unit 2
Since the number of the vibrators is increased, the influence of the dents when the vibrators are installed is increased as the number of the vibrators is increased, and the measurement accuracy may be deteriorated. On the other hand, in the present embodiment, plural pairs of ultrasonic transducers 3 are provided in the upstream chamber 28 and the downstream chamber 29.
Since 4, 35 , 36, and 37 can be arranged, the measurement accuracy can be improved without affecting the flow due to the installation of the ultrasonic transducer.

In the present embodiment, an example in which two pairs of ultrasonic transducers are used has been shown, but the measurement accuracy can be further improved by arranging more pairs of ultrasonic transducers.

The arithmetic processing according to the present invention can be realized by software using a microcomputer such as a one-chip microcomputer.

Further, since the flow rate calculation in the present invention is performed based on the flow velocity measurement, the measuring method described in the present invention can be applied to the ultrasonic velocity meter.

As described above, according to this embodiment, the following effects can be obtained.

(1) Flow rate measurement using an ultrasonic transducer for flow rate measurement
Upstream and downstream arranged upstream chamber of tough, oblique to the downstream chamber
To face each other, and the upstream chamber and the downstream chamber are set to have a cross-sectional shape of such a size that the flow velocities inside the upstream chamber and the downstream chamber are within the range of the measurement error. It is possible to perform accurate flow rate measurement without causing any disturbance in the flow rate.

(2) In addition, the ultrasonic wave from the ultrasonic transducer flows.
Since it crosses diagonally to the flow direction of the body, it is possible to measure an average flow velocity in the flow rate measurement unit,
Higher precision measurement is possible.

(3) The flow path measuring section is formed in a flat rectangular cross section.
If the flow of the measurement part is formed two-dimensionally, it is possible to perform a more accurate flow rate measurement.

(4) If the flow path measuring section is formed in a circular shape,
The degree of freedom in arranging the ultrasonic transducer can be increased, and
Highly accurate measurement can be performed.

(5) Plural pairs of ultrasonic vibrations are provided in the upstream chamber and the downstream chamber.
If the pendulum is placed, the multi-directional ultrasonic wave propagation paths will be used.
Therefore, more accurate measurement can be performed.

[0077]

As described above, according to the present invention, it is possible to perform accurate flow rate measurement without causing flow turbulence in the measurement flow path.

[Brief description of drawings]

FIG. 1 is a horizontal sectional view of an ultrasonic flowmeter according to a first embodiment of the present invention.

FIG. 2 is a perspective view of the flow meter.

FIG. 3 is a control block diagram of the flow meter.

FIG. 4 is a perspective view of an ultrasonic flowmeter according to a second embodiment of the present invention.

FIG. 5 is a perspective view of an ultrasonic flowmeter according to a third embodiment of the present invention.

FIG. 6 is a perspective view of an ultrasonic flowmeter according to a fourth embodiment of the present invention.

FIG. 7 is a perspective view of an ultrasonic flowmeter according to a fifth embodiment of the present invention.

FIG. 8 is a horizontal sectional view of the same flow meter.

FIG. 9 is a vertical sectional view of a conventional ultrasonic flowmeter.

[Explanation of symbols]

4 Flow rate measurement unit 5 Upper chamber 6 Downstream chamber 9 First ultrasonic transducer 10 Second ultrasonic transducer 15 Flow rate calculator

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kenzo Ochi               1006 Kadoma, Kadoma-shi, Osaka Matsushitaden               Instrument industry Co., Ltd.                (56) References JP-A-60-115810 (JP, A)                 Special table 5-506092 (JP, A)

Claims (5)

(57) [Claims] And 1. A flow rate measuring section, the disposed respectively on the upstream and downstream of the flow measurement section, and than the flow rate measurement unit
An upstream chamber and a downstream chamber having a large cross-sectional area, a first ultrasonic transducer arranged in the upstream chamber, a second ultrasonic transducer arranged in the downstream chamber, and the ultrasonic transducer A flow rate calculation unit that calculates a flow rate based on a signal, and the ultrasonic transducers are arranged in the upstream chamber and the downstream chamber so as to transmit and receive a signal at an angle with respect to the flow of the fluid flowing in the flow rate measurement unit. Ultrasonic flow meter. 2. A flow rate measuring unit and upstream and downstream of the flow rate measuring unit, respectively , and more than the flow rate measuring unit.
An upstream chamber and a downstream chamber having a large cross-sectional area, a first ultrasonic transducer arranged in the upstream chamber, a second ultrasonic transducer arranged in the downstream chamber, and the ultrasonic transducer A flow rate calculation unit that calculates a flow rate based on a signal, the first and second ultrasonic transducers, the ultrasonic propagation path thereof,
An ultrasonic flow meter, which is cut substantially parallel to the flow direction of the flow rate measuring unit and is positioned substantially diagonally in a rectangular cross-sectional shape of the flow rate measuring unit. 3. The ultrasonic flowmeter according to claim 1, wherein the flow rate measuring section has a cross-sectional shape that forms a two-dimensional flow. 4. The ultrasonic flowmeter according to claim 1, wherein the flow rate measuring section has a circular cross section in a direction perpendicular to the flow. 5. The ultrasonic flowmeter according to claim 1, wherein the ultrasonic vibrator forms a plurality of pairs.