KR920009907B1 - Swirling flow meter - Google Patents

Abstract

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Description

Vortex flowmeter

1 to 3 are schematic explanatory diagrams showing the configuration of the vortex flow meter of the present invention.

1 is a planar cross-sectional view,

2 is a side cross-sectional view,

3 is a front sectional view seen from the flow direction,

4 shows a signal detection circuit from a column sensor,

FIG. 5: is a figure which shows the example of waveform observation in the air flow measurement of this invention.

* Explanation of symbols for the main parts of the drawings

1: Euro 2: Vortex generator

5 differential amplifier 6 trigger circuit

7: output terminal 11: flow path wall

21, 22, 23: vortex generating element 31, 32: thermal sensor

41, 42: set temperature heating circuit 41a, 41b: amplifier

101, 102, 103: Vortex 311: hot wire

312 frame 313: disconnection frame

314: protective support 315, 316: lead wire

Tr ₁ , Tr ₂ : Transistor

R ₁₁ , R ₁₂ , R ₂₁ , R ₂₂ , R ₃₁ , R ₃₂ , R ₄₁ , R ₄₂ , R ₅₁ , R ₅₂ , R ₆₁ , R ₆₂ , R ₇₁ , R ₇₂ , R ₈₁ , R ₈₂ : resistance

R _S1 , R _S2 : resistance

The present invention relates to vortex detection in a vortex flowmeter, and more particularly in a vortex flowmeter.

Conventionally, the vortex flowmeter uses a Karman swirling flow frequency proportional to the flow rate. Usually, the eddy current signal includes a lot of high frequency and low frequency noise, but is removed by a filter of these noise components. It is shaped close to the sine wave signal and output as a pulse signal.

The detection of the vortex signal is a thermal change in the deformation or stress generated in the vortex generator due to the lifting force acting on the vortex generator, the change in the pressure acting on the vortex generator, or the generation of the vortex itself. This is detected by the change of the ultrasonic wave propagation speed.

As for these eddy current signals, the former is a signal proportional to the density of the rapeseed to be measured and proportional to the square of the flow rate. Therefore, in order to make the signal level constant in the measurement range of the flow rate, 1/2 of the frequency is used. An amplification circuit with gain of power is required.

In this case, the gain becomes very large in the low range, but the noise effect increases in the low flow rate region because the signal of the low frequency such as vibration increases in the signal.

For this reason, although the signal of a small flow area is interrupted | blocked, there exists a problem that a flow volume range cannot be enlarged when it blocks.

On the other hand, in the latter case, the physical phenomenon caused by partial change in density, density change, etc. caused by the vortex is detected. Therefore, the vortex detection is sufficient as a detector having a responsiveness proportional to the flow rate, which is advantageous compared to the former. Do. As a representative example of the method of detecting the vortex itself, it is possible to use the heat radiation of the resistor due to the flow generated by the vortex, but the resistor is disposed on the front side of the vortex generator, inside the vortex generator, and the back side of the vortex generator. It was.

The thermal detection method of the vortex is simple and inexpensive, unlike the method using the amplitude or phase modulation by the vortex of the ultrasonic wave. In addition, since the noise components of the streams included in the flow are also detected, error pulses are often transmitted, and noise removal circuits such as a tracking filter that follows the eddy signal frequency are required to remove them. This has risen.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, using a thermal sensor as a condition to take advantage of the direct detection of vortices, and experimenting on the best arrangement of S / N (signal-to-noise ratio) of the thermal sensor. It is decided.

As a result, it is confirmed that the best position of the thermal sensor is downstream of the vortex generator, and is within a range between the inner wall of the flow path where the vortex generator is arranged and the vortex heat. S / N is extremely good, thus complicated and expensive tracking filter is unnecessary.

EXAMPLE

An embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a plan view for explaining one embodiment of the present invention, FIG. 2 is a side sectional view, FIG. 3 is a front sectional view seen from the flow direction, in which, (1) is a fluid flow path, In the center of the flow path 1, a vortex generator 2 is arranged to face the flow Q.

The vortex generator 2 has a vortex generating element 21 having an isosceles triangular cross section whose bottom surface is downstream, and the vortex generating element 21 described above on the downstream side of the vortex generating element 21. Vortex generating element 22, which is a flat plate arranged at predetermined intervals, and a T-shaped vortex generating element having a cross section arranged at equal intervals as described above on the rear flow side of the vortex generating element 22 ( It consists of the composite vortex generator element 23), and constitutes the stable vortex generator 2.

In addition, the vortex generator 2 is not limited to the thing of the structure mentioned above, For example, it may be triangular or other thing. Numerals 31 and 32 are heat sensors, and they have the same means of configuration, shape, and the like, and are arranged between the vortex heat VS and the oil pipe wall 11 downstream of the vortex generator.

The thermal sensors 31 and 32 are platinum wires welded between a frame 312 of an electrically conductive L-shaped elastic body such as nickel, and a disconnected frame 313 and the frames 312 and 313. A protective support 314 which insulates and protects the heating wires 311, the frames 312, and 313 from each other, and is introduced into the detection circuit of FIG. 4 by the lead wires 315 and 316. . The heating wire 311 of the thermal sensor 31 is introduced into the set temperature heating circuit 41 of the detection circuit. In the set temperature heating circuit 41, a bridge circuit is connected to the emitter of the transistor Tr ₁ with an emitter resistor, and forms an emitter follower.

The heating wire 311 forms one side of the bridge circuit together with the resistors R ₁₁ , R ₂₁ , and R ₃₁ , and the bridge output is connected to the amplifier 41a through the resistors R ₄₁ and R ₅₁ . Is entered.

When the resistance R _S1 of the heating wire 311 changes, a deviation signal is generated, and is negatively fed back to the transistor Tr ₁ through the amplifier 41a and the resistor R ₇₁ so that the temperature of the heating wire 311 is always constant. It works.

Resistor R ₈₁ is a bias resistor of transistor Tr ₁ and receives power from a power supply ( ⁺ B).

The thermal sensor 32 is also connected to the set temperature heating circuit 42 having the same circuit.

The circuit element of the set temperature heating circuit 42 denotes a single digit of the number in the circuit element of the set temperature heating circuit 41 as 2, and the description thereof is omitted.

The current change of each set temperature heating circuit is inputted to the differential amplifier circuit 5 and shaped, and is output from the output terminal 7 as a flow rate pulse through the trigger circuit 6.

Next, the positional relationship between the vortex generator 2 and the thermal sensors 31, 32 in the present invention will be described.

The vortex delaminates from the vortex generator 2 and flows out, but the vortex frequency is proportional to the flow rate, and the interval between the vortices VS is approximately h = 1.3 with respect to the width d of the vortex generator 2. a vortex (101), (102), (103) having a value of d, which satisfies the stable conditions of the Karman width; Flows alternately with, and spreads and disappears in the flow.

The vortex distance l between the vortices 101 and 103 can be easily calculated since the flow velocity and the number of strokes which are the proportional constants of the flow velocity and the vortex frequency are already known.

In the present applicant's experiment, the position b on the downstream side from the point P away from the vortex generator 2 of the thermal sensors 31 and 32 is greater than or equal to the distance l between the vortices. The disturbance increases, and conversely, the disturbance increases similarly even within 0.3 l.

In addition, when the distance a between the thermal sensors 31 and 32 is close to within the distance h between the vortex heats, the disturbance increases, and conversely, when the distance a exceeds 3h, the signal deteriorates.

That is, the position where the thermal sensors 31 and 32 are arranged is

It is widely in the range to satisfy S / N which is so great that a tracking filter is not necessary.

5 to 7 show examples of observation results of the eddy current waveform when a fluid is used as air. FIG. 5 shows frequency 8.9 Hz, 6 degrees 1070 Hz, and 7 degrees 2470 Hz. Are compared with the frequency analysis result (a) and the waveform (b), respectively.

In the experiment, a platinum wire having a diameter of 0.05 mm was used as the heating wire 311, but a thin film may also be used.

As described above, in the present invention, the vortex flowing out from the vortex generator is directly thermally detected, and the position of the heat sensor is arranged at a predetermined position to generate a very good S / N vortex signal, such as a tracking filter. Without using it, it was obtained by a simple method of directly amplifying and outputting a pulse, enabling a wide range of measurement of a frequency range of nearly 300 times.

Claims (1)

A vortex generator (2) arranged to face the flow in the fluid flow path and a pair of sensors (31), (32) arranged in parallel with the vortex generator (2) at the rear end of the vortex generator (2) In the vortex flow meter, the vortex body 2 is an isosceles triangular body 21 whose cross-sectional shape is a downstream side sequentially in the flow direction of the fluid, and a planar body 22 parallel to the base of the isosceles triangle. And a T-shaped body 23 having a base parallel to the isosceles triangular body 22, wherein the position of the thermal sensor is defined by the vortex generator 2 as the width d of the vortex generator 2 In the direction of the gap (a), the flow direction from the vortex separation breakpoint (b), the distance between the vortices (h), the distance between the vortices (l),

Vortex flow meter, characterized in that.

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