JPH0499917A - Vortex flowmeter - Google Patents

Abstract

PURPOSE:To measure correctly by providing an ultrasonic wave sending element within a vortex generating column, and ultrasonic wave receiving elements at the downstream side of the vortex generating column in symmetric relation to a conduit. CONSTITUTION:A vortex generating column 22 is fixed within a conduit 23, having an ultrasonic wave generating element 24. Moreover, two ultrasonic wave receiving elements 25, 26 are provided in symmetric relation to an inner wall of the conduit 23 at the downstream side of the vortex generating column 22. When a fluid starts flowing in the conduit 23, a von Karman's vortex street 29 is generated at the downstream side of the vortex generating column 22. At this time, when an ultrasonic wave is sent into the conduit 23 from the ultrasonic wave generating element 24 driven by an oscillating circuit 27, the ultrasonic wave is propagated in the fluid and modulated alternatingly by the von Karman's vortex street 29, and detected by the receiving elements 25, 26. The alternatingly modulated signal is demodulated to a vortex frequency by a demodulating circuit 28 and output. Accordingly, the flow rate of the fluid running in the conduit 23 can be correctly measured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to vortex flowmeters, and more particularly to vortex flowmeters that do not require phase compensation when fluid temperature changes significantly.

[Prior Art] As a conventional flowmeter for measuring flow rate, a vortex flowmeter that detects vortices using ultrasonic waves is known.

This vortex flowmeter generates a so-called Karman vortex street on the downstream side of a vortex generating column installed in a pipe, and measures the flow rate of fluid flowing in the pipe based on the generation period of the vortex. .

Hereinafter, the vortex flowmeter 1 that has been commonly used will be explained based on FIG. 2.

The vortex flowmeter 1 is approximately composed of a vortex generating column 2, a conduit 3, an ultrasonic transmitter 4, an ultrasonic receiver 5, an oscillation circuit 6, a demodulation circuit 7, and a phase shift circuit 8.

The vortex generating column 2 is fixed within the conduit 3. Further, the ultrasonic transmitter 4 and the ultrasonic receiver 5 are respectively attached at symmetrical positions on the inner wall of the conduit 3 on the downstream side of the vortex generating column 2. An oscillation circuit 6 is attached to the ultrasonic transmitter 4, a demodulation circuit 7 is attached to the ultrasonic receiver 5, and a circuit branched from the oscillation circuit 6 passes through a phase shift circuit 8 to the demodulation circuit 7. It is connected to the.

A method of measuring flow rate using this vortex flow meter 1 will be explained.

When fluid flows through the pipe 3, this flow generates a Karman vortex 9 on the downstream side of the vortex generating column 2 provided within the pipe 3. Here, when an ultrasonic wave is transmitted into the pipe line 3 from the ultrasonic transmitter 4 driven by the oscillation circuit 6, this ultrasonic wave propagates in the flow and is modulated by the Karman vortex 9.
, is detected by the ultrasonic receiver 5, and further demodulated into a vortex frequency by the demodulation circuit 7 and output. During demodulation, the phase shift circuit 8 constantizes the reference signal.

In this way, the flow rate of the fluid flowing in the pipe line 3 can be measured by the vortex flow meter 1.

Further, as an improved version of the conventional vortex flowmeter 1, a vortex flowmeter I+ as shown in FIG. 3 has been proposed and put into practical use.

This vortex flow meter 11 includes a pipe line I in which a vortex generation column I2 is provided.
3.2 ultrasonic transmitters +4. It is approximately composed of +5.2 ultrasonic receivers +6.17, an oscillation circuit 18, and a demodulation circuit 19.

The vortex generating column I2 is fixed within the conduit +3.

Further, the two ultrasonic transmitters 14.15 and the ultrasonic receivers 16.17 each connect to the pipe line 13 on the downstream side of the vortex generating column 12.
They are arranged in such a way that they correspond to the symmetrical positions of the inner walls. An oscillation circuit I8 is attached to these ultrasonic transmitters 14.15, and ultrasonic receivers 16.17
A demodulation circuit 19 is attached to the. The ultrasonic wave transmitted from the ultrasonic transmitter I4 (+5) propagates through the fluid and is detected by the ultrasonic receiver 1.6 (+7).

A method of measuring flow rate using this vortex flow meter 11 will be explained.

When fluid flows through pipe +3, this flow causes pipe +3 to flow.
A Karman vortex 2 is located downstream of the vortex generation column 12 installed inside the
0 is generated. The oscillation circuit 18 is modulated by this Karman vortex 20. Here, when ultrasonic waves are transmitted into the conduit 13 from each of the two ultrasonic transmitters I4.15 driven by the oscillation circuit I8, these ultrasonic waves propagate through the flow and form a Karman vortex 20. These ultrasonic waves are respectively subjected to different modulations and detected separately by two ultrasonic receivers 16 and 17. Thereafter, a phase difference between these ultrasonic waves is determined by the demodulation circuit 7, and a vortex signal is detected based on this phase difference.

In this way, the flow rate of the fluid flowing in the pipe line 13 can be measured by the vortex flowmeter 11.

[Problems to be Solved by the Invention] By the way, in the vortex flowmeter 1 described in ``2'', when the fluid temperature changes, the sound speed of the ultrasonic wave changes greatly, so it is not possible to constantize the signal that serves as a reference during demodulation. , there is a problem that correct eddy signal detection cannot be performed unless the phase shift circuit 8 continuously changes t:I.

Especially if the temperature of the fluid changes significantly and rapidly.
In the conventional vortex flow meter 1, since there is a time difference in the constantization of the reference signal by the phase shift circuit 8, it is not possible to follow this sudden change, resulting in a large error in the measured value. Therefore, the conventional vortex flowmeter 1 has a limitation in measurement, and has the drawback that accurate measurement is impossible, especially when the temperature of the fluid changes significantly and rapidly.

In addition, the vortex flowmeter I+ has been put into practical use as an improved version of the conventional vortex flowmeter 1, but the vortex flowmeter II has the following features:
Although the phase shift circuit 8 becomes unnecessary, two ultrasonic transmitters 14, 15 and two ultrasonic receivers 16, 17 are installed downstream of the vortex generating column 12 at regular intervals along the fluid flow. ζ'J, which has the disadvantage that the pipe line 13 becomes long. In this case, the product will have a large distance between surfaces, which may cause various problems in design and mounting. In addition, two ultrasonic transmitters 1 each
4.15 and ultrasonic receiver 16.17, if the electrical characteristics of these elements are different, the optimum conditions for each element will also be different. It is nearly impossible to drive the element.

Therefore, it is extremely difficult to drive this vortex flow meter 11 under conditions with the best efficiency (Q value). Furthermore,
2 ultrasonic transmitters each + 4. , 15 and ultrasonic receivers 16 and 17, there is also the disadvantage that power consumption doubles.

This invention was made in view of the two circumstances, and it effectively solves the following problems and drawbacks, and also enables correct measurement even when the fluid temperature changes significantly and rapidly. The purpose of the present invention is to provide a vortex flowmeter.

[Means for Solving the Problems] In order to solve the problems described above, the present invention employs the following vortex flowmeter. In other words, a vortex generating column is provided in the pipe,
In a vortex flowmeter that measures the flow rate based on the Karman vortex street generated by this vortex generating column, an ultrasonic transmitter is provided in the vortex generating column, and the ultrasonic transmitter is provided on the downstream side of the local main phase and symmetrically of the pipe line. It is characterized by having an ultrasonic receiver installed at each position.

[Function] In this invention, an ultrasonic transmitter is installed in the vortex generating column i:
I', ultrasonic receivers are provided downstream of the surface vortex generating column and at symmetrical positions of the pipe, thereby transmitting ultrasonic waves propagating through the fluid at symmetrical positions on the inner wall of the pipe. is detected by an ultrasonic receiver, and phase shifts due to fluid temperature changes are removed.

Further, by configuring a circuit using one ultrasonic transmitter, it becomes possible to drive this ultrasonic transmitter under optimal conditions (conditions with the highest efficiency (Q value)).

[Embodiment] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a vortex flow meter 21 according to the present invention.

This vortex flow meter 21 includes a vortex generation column 22, a pipe line 23, an ultrasonic transmitter 24, ultrasonic receivers 25 and 26, an oscillation circuit 27,
It is roughly composed of a demodulation circuit 28.

The vortex generating column 22 is fixed within the conduit 23, and the vortex generating column 22 is provided with an ultrasonic transmitter 24. Further, two ultrasonic receivers 25 and 26 are respectively attached at symmetrical positions on the inner wall of the conduit 23 on the downstream side of the vortex generating column 22. An oscillation circuit 27 is attached to the ultrasonic transmitter 24, and a demodulation circuit 28 is attached to the ultrasonic receivers 25 and 26. And ultrasonic transmitter 2
The ultrasonic waves transmitted from 4 propagate through the fluid and are detected by ultrasonic receivers 25 and 26, respectively.

A method of measuring flow rate using this vortex flow meter 21 will be explained.

When fluid flows through the pipe line 23, this flow causes the pipe line 23 to
A Karman vortex 29 is located downstream of the vortex generation column 22 provided within the
occurs. Here, when an ultrasonic wave is transmitted into the conduit 23 from the ultrasonic transmitter 24 driven by the oscillation circuit 27, this ultrasonic wave propagates through the flow and is alternately modulated by the Karman vortex 29. (', 11 ultrasound receiver 25.26
are detected respectively. This alternately modulated signal is demodulated into a vortex frequency by a demodulation circuit 28 and output.

In this way, the flow rate of the fluid flowing in the pipe line 23 can be measured by the vortex flow meter 21.

As explained above, according to the vortex flowmeter 21 of the present invention,
An ultrasonic transmitter 24 is provided in the vortex generating column 22, and ultrasonic receivers 25 and 26 are provided downstream of the i-+1 vortex generating column 22 and at symmetrical positions on the inner wall of the conduit 23, so that the ultrasonic waves propagate through the fluid. The ultrasonic waves generated are detected by a plurality of ultrasonic receivers 2526 installed at symmetrical positions on the inner wall of the conduit 23, and by removing the phase shift caused by temperature changes in the fluid, the influence of temperature fluctuations in the fluid can be reduced. It is possible to make accurate measurements without any problems.

Further, since the ultrasonic receivers 25 and 26 can be provided on the inner wall of the conduit 23 near the vortex generating column 22, the conduit 23 can be made short.

Furthermore, since the circuit can be configured using one ultrasonic transmitter 24, the optimum conditions for this ultrasonic transmitter 24 (
The vortex flowmeter 21 can be driven under the most efficient conditions (conditions with the best Q value), and power consumption can also be reduced compared to the case where two ultrasonic transmitters are used.

As described above, it is possible to provide a vortex flowmeter 21 which solves the problems and drawbacks of conventional vortex flowmeters in terms of load movement, and which enables correct measurement even when the fluid temperature changes significantly and rapidly.

[Effects of the Invention] As explained in detail above, according to the present invention, a vortex flowmeter is provided in which a vortex generating column is provided in a pipe and the flow rate is measured based on the Karman vortex street generated by the vortex generating column. In,
An ultrasonic transmitter was provided in the vortex generating column, and ultrasonic receivers were provided downstream of the vortex generating column and at symmetrical positions in the pipe, so that the ultrasonic waves propagating in the fluid were transmitted through the pipe. Detection is performed using multiple ultrasonic receivers installed at symmetrical positions on the inner wall of the fluid, and by eliminating phase shifts due to fluid temperature changes, accurate measurement is possible without the influence of fluid temperature fluctuations.

Furthermore, since the ultrasonic receiver can be installed on the inner wall of the conduit near the vortex generating column, the conduit can be made short.

In addition, since the circuit can be configured using one ultrasonic transmitter, the vortex flowmeter can be driven under the optimal conditions (conditions with the highest efficiency (Q value)) for this ultrasonic transmitter. This effectively solves the problems and shortcomings of conventional vortex flowmeters, and significantly reduces the fluid temperature. In addition, it is possible to provide a vortex flowmeter that allows accurate measurement even when there is a sudden change.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a vortex flowmeter which is an embodiment of the present invention.
2 and 3 are circuit diagrams of a conventional vortex flowmeter,
FIG. 2 is a circuit diagram of a vortex flowmeter using a phase shift circuit, and FIG. 3 is a circuit diagram of a vortex flowmeter that does not require phase compensation due to fluid temperature fluctuations. 25 26... Shaking circuit, 28 Mann height.・Vortex flowmeter, 22 ・・Vortex generation column, pipe line, 24 ・
・Ultrasonic transmitter, ・Ultrasonic receiver, 27 ・ ・ ・ Full demodulation circuit, 29 ・ ・ Cal

Claims (1)

[Claims] A vortex flow meter that includes a vortex generating column in a pipe and measures a flow rate based on the Karman vortex street generated by the vortex generating column, comprising: an ultrasonic transmitter in the vortex generating column; and ultrasonic receivers are provided downstream of the vortex generating column and at symmetrical positions of the conduit.