JPH11295118A - Vortex flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vortex flowmeter enhanced in long-term reliability. SOLUTION: A vortex flowmeter for measuring the flow rate by detecting the frequency of Karman vortexes caused by a columnar vortex generator 31 inserted into a measurement pipeline 10 is provided with a hollow vortex generator 31 having a circumferential surface part 32 constituted by a thin plate, a supporting part provided to the hollow part of the vortex generator 31 and whose peripheral part is fixed to the circumferential surface part 32, a supporting bar 34 fixed to this supporting part on the way, and a strain sensor for detecting the deformation of the vortex generator 31.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vortex flowmeter having improved long-term reliability.

[0002]

2. Description of the Related Art FIG. 10 is a diagram for explaining the structure of a conventional example generally used in the prior art.
No. 18 (Japanese Patent Application No. 1-033256).

[0003] line 10 is conduit through which measurement fluid FL _o,
The nozzle 11 is provided at a right angle to the pipe 10 and has a cylindrical shape.
The vortex generator 12 is separated from the nozzle
At right angles to each other, have a trapezoidal cross section, and have a columnar shape.

[0004] One end thereof is supported by the pipe 10 by a screw 13 and the other end is fixed to the nozzle 11 by a screw or welding by a flange portion 14. The recess 15 is provided in the vortex generator 1.
2 is provided on the flange portion 14 side.

In the recess 15, a first common electrode 16 made of metal, a piezoelectric element 17, an electrode plate 18, an insulating plate 19, an electrode plate 20, and a piezoelectric element 21 are arranged in order from the bottom. These are pressed and fixed by a pressing rod 22 made of metal. Further, a lead wire 23 from the electrode plate 18 and a lead wire 24 from the electrode plate 20 are led to terminals A and B, respectively.

Each of the piezoelectric elements 17 and 21 is
The left and right sides of the paper 21 are polarized in opposite directions, respectively, and generate opposite-polarity charges on the upper and lower electrodes with respect to the stress in the same direction.

The electric charge generated in the piezoelectric element 17 is applied to the electrode plate 1.
The electric charge generated between the terminal A connected to the electrode 8 and the conduit 10 connected via the pedestal 16 and generated in the piezoelectric element 21 is transferred to the terminal B connected to the electrode plate 20 and the pressing rod 20. And the connected pipeline 10.

The charges generated on the two electrode plates 18 and 20 are input to charge amplifiers 25 and 26 as shown in FIG. The output of the charge amplifier 25 and the output of the charge amplifier 26 via the volume 27 are added by an adder 28 to obtain a flow signal.

This flow signal is converted into, for example, a current output and transmitted to a load via two wires (not shown). Next, the operation of the vortex flowmeter configured as described above will be described with reference to FIGS.

When the fluid flows through the conduit 10, vibrations are generated in the vortex generator 12 by Karman vortices in the direction indicated by the arrow F. Due to this vibration, the vortex generator 12
The stress distribution shown in FIG. 1A and the reverse stress distribution are repeated.

Each of the piezoelectric elements 17 and 21 has a structure shown in FIG.
+ Q,-corresponding to the signal stress having the vortex frequency shown in
Q repetition occurs. In FIG. 12, for convenience of explanation, the electrode plate 18 or 21 is divided into two parts on the left and right with respect to the paper surface, and one of the upper and lower electrodes corresponds to the pedestal 16 or the pressing rod 22. .

On the other hand, the pipe line 10 also generates pipe line vibrations that cause noise. The pipeline vibration is divided into a drag direction in the same direction as the fluid flow, a lift direction perpendicular to the fluid flow, and a longitudinal component of the vortex generator.

Among them, the stress distribution with respect to the vibration in the drag direction is as shown in FIG. 12 (b). Positive and negative charges are canceled in one electrode, and no noise charge is generated.
In addition, the vibration in the longitudinal direction is canceled in the electrode as shown in FIG. 12C, and no noise charge is generated as in the case of the drag direction.

However, the vibration in the lift direction has the same stress distribution as the signal stress, and generates noise charges. Therefore, the following calculation is executed to eliminate the noise charge.

The electric charges of the piezoelectric elements 17 and 21 are represented by Q ₁ , Q ₂ ,
The signal components are S ₁ and S ₂ , and the noise components in the lift direction are N ₁ and N ₂
When the polarization is reversed by the piezoelectric elements 17 and 21, Q ₁ and Q ₂
Is represented by the following equation. Q ₁ = S ₁ + N ₁ -Q ₂ = -S ₂ -N ₂

However, the vector directions of S ₁ and S ₂ and N ₁ and N ₂ are the same. Here, the relationship between the signal component and the noise component of the piezoelectric elements 17 and 21 is as shown in FIG. 13 (this diagram shows the relationship between the noise in the lift direction and the bending moment of the vortex generator with respect to the signal). ing.

Therefore, as shown in FIG.
When the output of the charge amplifier 25 on the 7 side is added by the adder 28, the output of the charge amplifier 25 is multiplied by N ₁ / N ₂ together with the volume 27, and
When added to the output of the charge amplifier 26 on the first side, Q ₁ −Q ₂ (N ₁ / N ₂ ) = S ₁ −S ₂ (N ₁ / N ₂ ), and the line noise is removed.

Then, the first common electrode 16, the piezoelectric element 1
7, electrode plate 18, insulating plate 19, electrode plate 20, piezoelectric element 2
1 is pressed and fixed to the recess 15 by a pressing rod 22.

Here, the vortex generator 12 and the first common electrode 1
6, piezoelectric element 17, electrode plate 18, insulating plate 19, electrode plate 2
If the temperature expansion of 0, the piezoelectric element 21 and the pressure rod 22 are made equal, there is no problem since the initial pressing force does not change even if the temperature of the measurement fluid changes.

[0020]

The feature of the prior art shown in FIG. 10 is that there is a difference in distribution of bending moment due to Karman vortex and pipe vibration. For this reason, the stress detection unit
It is configured above the vortex generator 12.

Therefore, as a structural disadvantage, a gap is required between the vortex generator 12 and the measurement pipe 10. For this reason, when a highly rigid object adheres to the gap, the bending moment decreases and the distribution of the bending moment changes.

As a result, the detection sensitivity decreases and the vibration characteristics deteriorate. In addition, in the configuration of the fixed end and the support end, the structure becomes complicated, and the manufacturing cost is increased.

The present invention solves this problem. An object of the present invention is to provide a vortex flowmeter with improved long-term reliability.

[0024]

In order to achieve the above object, the present invention provides: (1) a Karman vortex frequency generated by a columnar vortex generator inserted into a measurement pipe, and a flow rate is measured. In a vortex flowmeter, a hollow vortex generator having a peripheral surface portion formed of a thin plate, a support portion provided in a hollow portion of the vortex generator and having a peripheral portion fixed to the peripheral surface portion, A vortex flowmeter, comprising: a support rod to which the vortex generator is fixed; and a strain sensor that detects deformation of the vortex generator. (2) The vortex flowmeter according to (1), wherein the strain sensor is provided on the support portion. (3) A sensor fixing plate provided outside the measurement pipe and to which the other end of the support rod is fixed, and a strain sensor provided on the sensor fixing plate for detecting deformation of the vortex generator. The vortex flowmeter according to (1), which is characterized in that: (4) The vortex flowmeter according to any one of (1) to (3), wherein a semiconductor strain gauge is used as the strain sensor. (5) The vortex flowmeter according to any one of (1) to (4), wherein the vortex generator is formed by extrusion forming. It is what constituted.

[0025]

In the above configuration, when the measurement fluid is flown,
The vortex is released from the vortex generator, and a vortex street is formed downstream of the vortex generator. A negative pressure is generated by the circulating flow of the Karman vortex.

The vortex generator that has been subjected to the alternating pressure due to the vortex in the measurement fluid includes: Translational movement in the direction perpendicular to the flow direction of the measurement fluid due to the lift due to the vortex. 2. A torsional motion about the center of gravity of the vortex generator due to the torsional moment of the vortex. Receive the two forces.

This deformation is greatest at the longitudinal center of the vortex generator when both ends of the vortex generator are fixed. The deformation at this point is detected by the support portion, the deformation is transmitted to the sensor fixing plate by the support rod, and the deformation due to the transmitted force is detected by the two strain sensors.

The signal detected by the strain sensor may be both or one of the above two forces. By detecting lift and torsion simultaneously, a large signal is obtained.

However, it is presumed that the vibration noise due to the vibration of the pipe or the like enters the strain sensor in the same phase. Therefore, the output signals of the two strain sensors are subjected to differential processing to detect only the twist signal. By doing so, a sensor having a high S / N ratio can be realized.

However, in the structure of the vortex generator, the mass of the vortex generator itself is smaller than that of the conventional bulk vortex generator.
Since it is overwhelmingly small, it originally has a strong property against vibration.
Hereinafter, a detailed description will be given based on embodiments.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view of a main part of an embodiment of the present invention, FIG. 2 is a side view of FIG. 1, FIG. 3 is a plan view of FIG.
4 is an operation explanatory diagram of FIG. 1, FIG. 5 is an operational explanatory diagram of FIG. 1, and FIG. 6 is an operational explanatory diagram of FIG. In the figure, the configuration of the same symbol as in FIG. 10 indicates the same function. Hereinafter, only differences from FIG. 10 will be described.

The hollow vortex generator 31 has a peripheral surface portion 32 formed of a thin plate. Since the peripheral surface portion 32 has a small thickness, it can be easily deformed. In this case, the vortex generator 31
It is formed by extrusion molding and has a triangular cross section.

The support plate 33 is provided in a hollow portion of the vortex generator 31 and has a peripheral portion fixed to the peripheral surface portion 32.
In this case, the periphery of the support plate 33 is fixed to the two surfaces of the vortex generator 31, and the support plate 33 is deformed by the twist of the vortex generator 31.

The support plate 33 also serves as a support for ensuring the pressure resistance when the vortex generator 31 is exposed to a high pressure.

The support rod 34 is fixed to the support plate 33 in the middle. One end of the support rod 34 is fixed or rotatable to the measurement pipe 10. The sensor fixing plate 35 is connected to the measurement pipe 1
The other end of the support rod 34 is fixed, and is deformed by the rotation of the support rod 34.

In this case, both ends of the sensor fixing plate 35 are fixed to the outer wall 36 of the measuring pipe 10.

The strain sensor 37 is provided on the sensor fixing plate 35 and detects the deformation of the vortex generator 31. In this case, an inexpensive semiconductor strain sensor 37 having good sensitivity is used.

[0038] In the above configuration, when the measured fluid FL _o is flowed, vortices are released from the vortex generator 31, the vortex generator 3
A vortex street is formed downstream of 1. A negative pressure is generated by the circulating flow of the Karman vortex.

The measurement fluid FL _o in the vortex generation body 31 which receives an alternating pressure by eddy, the 1. Translation of the direction perpendicular to the flow direction of lift → measurement fluid FL _o eddy. 2. Torsion moment due to vortex → torsion motion about the center of gravity axis of vortex generator 31. Receive the two forces.

FIG. 4 shows an example of the analysis result of the vortex generator 31 deformed by the vortex. The degree of deformation of each side of the triangle is different. FIG. 5 shows a diagram of the deformation of the vortex generator 31 due to the above two forces.

That is, from the degree of deformation shown in FIG.
Force F applied to generator 31₁, F_Two, F _Three, F_FourSize is different
Become. The vortex generator 31 receives two forces of translation and rotation
That is, as a whole, the vortex generator 3
1 is deformed as shown in FIG.

In this deformation, when both ends of the vortex generator 31 are fixed, the central portion in the longitudinal direction of the vortex generator 31 becomes maximum. The deformation at this point is detected by the support plate 33, the deformation is transmitted to the sensor fixing plate 35 by the support rod 34, and the deformation due to the transmitted force is detected by the two strain sensors 37.

The signal detected by the strain sensor 37 may be both or one of the two forces. By detecting lift and torsion simultaneously, a large signal is obtained.

However, it is presumed that the vibration noise due to the vibration of the pipe or the like enters the same phase in the strain sensor. Therefore, the output signals of the two strain sensors 37 are subjected to differential processing,
By detecting only the twist signal, a sensor having a high S / N ratio can be realized.

However, in the structure of the vortex generator 31, since the mass of the vortex generator itself is overwhelmingly smaller than that of a conventional bulk vortex generator, the vortex generator 31 originally has a strong property against vibration.

Next, a method of manufacturing the vortex generator 31 will be described with reference to FIG. The thin vortex generator 31 is formed by extrusion molding. The assembly of the support rod 32 and the support plate 33 that enters the vortex generator 31 is inserted into the vortex generator 31 while being inclined (FIG. 6A). By making the support rod 32 vertical, the support plate 3 is attached to the vortex generator 31.
3 are fixed (FIG. 6b).

As a result, the Karman vortex is detected using the deflection of the mounting portion of the vortex generator 31 on the support plate 33.
For this reason, both ends of the vortex generator 31 are fixed to the measurement pipeline 10, and there is no gap.

Therefore, troubles such as reduction in sensitivity due to clogging with dust and the like do not occur. Therefore, a highly reliable vortex flowmeter can be realized.

(2) Since the portion for detecting the deformation of the vortex generator 31 is provided outside the measurement pipe 10, the vortex generator 31
There is no need to consider the airtight structure of the portion that detects the deformation of the vortex flowmeter, the structure is simplified, and an inexpensive vortex flowmeter can be obtained.

(3) Since semiconductor strain gauges are used as the strain sensors 37 and 41, an inexpensive vortex flowmeter having good sensitivity can be obtained.

(4) Since the vortex generator 31 is formed by the extrusion forming process, the vortex generator 31 can be manufactured at a low cost, and the peripheral surface portion 32 of the vortex generator has no seams, so that airtightness and good vortex generation characteristics can be easily obtained. A vortex flowmeter which is inexpensive and has good characteristics can be obtained.

FIG. 7 is an explanatory view of a main part configuration of another embodiment of the present invention. Also in the present embodiment, the vortex generator 31 is soft and deformed by Karman vortex. Center support rod 34
Have both ends fixed to the measurement pipeline 10 and have high rigidity.

The strain gauge 41 is formed on a support plate 33 as shown in FIG.
The distortion of the vortex generator 31 having the shell structure deformed by the Karman vortex is detected.

Although the vortex generator 31 is made of a shell structure, as shown in FIG. 9, both ends are fixed to the measuring pipe 10 by welding A or the like, so that there is no gap. ing.

In this embodiment, on the support plate 33,
Since the strain gauge 41 is directly provided, the structure is simplified, and an inexpensive vortex flowmeter can be obtained.

[0056]

As described above in detail, according to the first aspect of the present invention, the Karman vortex is detected by using the deflection of the support mounting portion of the vortex generator. For this reason, both ends of the vortex generator can be fixed to the measurement pipe, and there is no gap.

Therefore, troubles such as reduction in sensitivity due to clogging of dust and the like do not occur. Therefore, a highly reliable vortex flowmeter can be realized.

According to the second aspect of the present invention, since the strain gauge is provided directly on the support portion, the structure is simplified and an inexpensive vortex flowmeter can be obtained.

According to the third aspect of the present invention, since the portion for detecting the deformation of the vortex generator is provided outside the measurement pipe,
There is no need to consider the confidential structure of the portion that detects the deformation of the vortex generator, the structure is simplified, and an inexpensive vortex flowmeter can be obtained.

According to the fourth aspect of the present invention, since the semiconductor strain gauge is used as the strain sensor, an inexpensive vortex flowmeter having good sensitivity can be obtained.

According to the fifth aspect of the present invention, since the vortex generator is formed by extrusion forming, the vortex generator can be manufactured at a low cost, the seam is eliminated on the peripheral surface of the vortex generator, and the confidentiality and good vortex generation characteristics are improved. Is easily obtained, and an inexpensive vortex flowmeter having good characteristics can be obtained.

Therefore, according to the present invention, a vortex flowmeter having improved long-term reliability can be realized.

[Brief description of the drawings]

FIG. 1 is a perspective view of a main part of an embodiment of the present invention.

FIG. 2 is a side view of FIG.

FIG. 3 is a plan view of FIG. 1;

FIG. 4 is an operation explanatory diagram of FIG. 1;

FIG. 5 is an operation explanatory diagram of FIG. 1;

FIG. 6 is an operation explanatory diagram of FIG. 1;

FIG. 7 is an explanatory view of a main part configuration of another embodiment of the present invention.

FIG. 8 is a detailed explanatory view of a main part of FIG. 7;

FIG. 9 is a detailed explanatory view of a main part of FIG. 7;

FIG. 10 is an explanatory diagram of a configuration of a conventional example generally used in the related art.

11 is an explanatory diagram of a main configuration of a conversion unit in FIG. 10;

FIG. 12 is an operation explanatory diagram of FIG. 10;

FIG. 13 is an operation explanatory diagram of FIG. 10;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Pipeline 31 Hollow vortex generator 32 Peripheral surface part 33 Support plate 34 Support rod 35 Sensor fixing plate 36 Outer wall of measurement pipeline 10 Strain sensor 41 Strain sensor

Claims (5)

[Claims] 1. A vortex flowmeter for measuring a flow rate by detecting a Karman vortex frequency generated by a columnar vortex generator inserted into a measurement pipe, wherein a hollow vortex generator having a peripheral surface portion made of a thin plate. A support portion provided in a hollow portion of the vortex generator and having a peripheral portion fixed to the peripheral surface portion; a support rod partially fixed to the support portion; and a strain sensor for detecting deformation of the vortex generator. And a vortex flowmeter comprising: 2. The vortex flowmeter according to claim 1, wherein the strain sensor is provided on the support. 3. A sensor fixing plate which is provided outside the measurement pipe and to which the other end of the support bar is fixed, and a strain sensor which is provided on the sensor fixing plate and detects a deformation of the vortex generator. The vortex flowmeter according to claim 1, wherein: 4. The vortex flowmeter according to claim 1, wherein a semiconductor strain gauge is used as said strain sensor. 5. The vortex flowmeter according to claim 1, wherein the vortex generator is formed by extrusion forming.