JPH06117891A - Karman vortex flowmeter - Google Patents

Abstract

PURPOSE:To improve the flow rate measuring accuracy of a Karman vortex flowmeter by adequately setting the degree of projection of a projecting body against a flow. CONSTITUTION:A vortex generating body 2 is provided with an upstream-side columnar body 11 and downstream-side columnar body 12 inside a conduit 1 and external threads are respectively cut at the parts of the bodies 11 and 12 which are fitted to the conduit 1. The cylindrical nuts 5a and 5B are engaged with the threads as projecting bodies so that the bodies can be moved in the axial direction of the conduit 1 and the projecting dimensions (a) and (b) of the bodies can be decided so that the Karman vortex generating condition of the body 2 can be optimized by adjusting the positions of the nuts 5A and 5B against the body 2. Therefore, the K-value (=velocityXflow rate Q/Karman vortex frequency f) of a fluid to be measured can be made almost constant against the variation of the Re-number by adequately setting the dimensions (a) and (b).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flowmeter in which a vortex generator is provided at each position where the vortex generator is fitted with the peripheral wall of a pipe, and a protrusion is provided to promote the Karman vortex generation. The present invention relates to a Karman vortex flowmeter which has an adjustable structure for optimizing the degree of protrusion and thereby improves the accuracy of flow rate measurement.

[0002]

2. Description of the Related Art A conventional example will be described with reference to the side sectional view of FIG. In the figure, reference numeral 1 is a conduit through which a measurement fluid flows. Reference numeral 22 denotes a vortex generator, which is inserted into the pipe line 1 so as to penetrate along the diameter thereof, and the penetrating portion is composed of an upstream side columnar body 23 having a triangular cross section and a downstream side columnar body 24 having a trapezoidal cross section. Moreover, cylindrical projections 25 and 26 for promoting the generation of Karman vortices are integrally formed at the fitting positions above and below the conduit 1. It should be noted that O-rings, which are not labeled, are inserted at the fitting positions above and below the conduit 1 for fluid sealing or vibration isolation. 3 is a vortex detector, which is a disk-shaped diaphragm 3a, and a mandrel 3b extending inward in the axial direction thereof.
It consists of a threaded rod that extends outwardly. Mandrel 3b is 2
The small diameter portion on the tip side is located inside the hole formed in the columnar body 24, and the cushioning material 4 is inserted at the root of the small diameter portion for resonance prevention. On the upper surface side of the diaphragm 3a, the insulating plate 6, the piezoelectric element 8,
Insulating plate 9 and Belleville spring 9 are stacked and balance weight
It is fixed by 10 screws. Here, the piezoelectric element 8
Detects a minute displacement of the mandrel 3b of the vortex detector 3 as a displacement of the diaphragm 3a, converts it into an electric signal, and outputs it. The balance weight 10 has a function of a nut for fixing a screw and a function of canceling an influence of a vibration factor other than the Karman vortex that the vortex detector 3 receives, for example, a vibration of the conduit 1 or the like.

In the conventional example, when a fluid flows through the conduit 1, a Karman vortex is generated in the vicinity of the column 24 by the upstream column 23 and the downstream column 24, and is generated by the generated Karman vortex. The change in fluid pressure is transmitted to the small diameter portion of the mandrel 3b of the vortex detector 3. To transmit this pressure change, a pressure guide hole (not shown) is formed in the columnar body 24 at a position corresponding to the small diameter portion of the mandrel 3b so as to communicate with the hole of the columnar body 24. It is done through. Now,
The small displacement of the mandrel 3b of the vortex detector 3 is converted into the displacement of the diaphragm 3a and then converted into a corresponding electric signal by the piezoelectric element 8 and output.

[0004]

The conventional example has the following problems. That is, as already mentioned, the vortex generator
The cylindrical projecting bodies 25 and 26 are integrally formed at the upper and lower fitting points of the pipe line 1, respectively.
Is an essential component for promoting the Karman vortex to be generated in a periodic and stable manner. And each protrusion
The dimensions a and b projecting inside the conduit 1 of 25 and 26 have a great influence on the performance of the Karman vortex flowmeter. Generally, for the velocity flow rate Q of the measurement fluid and the frequency f of the Karman vortex, Q =
The relationship of Kf is established. Here, K is a constant unique to the Karman vortex flowmeter, and it is desirable that it is as constant as possible with respect to the change in the velocity flow rate Q. With respect to this change of the K value, the dimensions a and b projecting inside the conduit 1 of each projecting portion 25 and 26 have a great influence, in other words, to the accuracy of measuring the flow rate by the Karman vortex flowmeter. It has a great influence.

An object of the present invention is to provide a Karman vortex flowmeter which solves the above problems of the prior art, optimizes the degree of protrusion of the projecting body with respect to the flow, and thereby improves the accuracy of flow rate measurement. is there.

[0006]

A Karman vortex flowmeter according to a first aspect of the present invention is a flow rate in which a protrusion for promoting Karman vortex generation is provided at each position where the vortex generator is fitted with the peripheral wall of the conduit. In the total, the projecting body is a cylindrical member provided so as to be positionally adjustable with respect to the vortex generator in the axial direction.

A Karman vortex flowmeter according to a second aspect is the flowmeter according to the first aspect, wherein the projecting body is a cylindrical nut screwed to a male thread portion provided on the vortex generator.

[0008]

In the Karman vortex flowmeter according to the first aspect, by adjusting the position of the projecting body in the axial direction with respect to the vortex generating body, the projecting degree with respect to the flow of the projecting body is properly adjusted, and the Karman vortex generating condition is set. Optimization can be achieved. Particularly, in the Karman vortex flowmeter according to claim 2, a cylindrical nut as a projecting body which is screwed to the male thread portion of the vortex generator is rotated,
Aligned axially.

[0009]

Embodiments of the Karman vortex flowmeter according to the present invention will be described below with reference to the drawings. FIG. 1 is a side sectional view of the embodiment, and FIG. 2 is a main portion thereof, that is, a transverse sectional view taken along a section AA of FIG. In this embodiment, in the conventional example, the cylindrical protrusions 25 and 26 are provided on the pipe line 1,
Unlike the case where it is integrally molded with the vortex generator 22 at each mating point below, each cylindrical nut 5A, 5B corresponding to each protrusion 25, 26 can be adjusted axially with respect to the vortex generator 2. Use a screw connection configuration. That is, in FIG. 1, the vortex generator 2 is
The upstream side columnar body 11 and the downstream side columnar body 12 are provided at locations inside the pipeline 1 (see FIG. 2), and male threads are cut at the respective fitting points with the pipeline 1 and the protrusions in the invention are shown here. The cylindrical nuts 5A and 5B as the body are screw-coupled so as to be positionally movable in the axial direction. The other members are the same as those in the conventional example, and therefore, the same members are designated by the same reference numerals.
In FIG. 2, a pressure guiding hole 13 is formed in the columnar body 12 so as to intersect the hole into which the tip of the mandrel 3b is inserted at a right angle, and a Karman vortex is generated through this pressure guiding hole 13. The pressure related to is transmitted to the vortex detector 3.

In the embodiment, by adjusting the positions of the cylindrical nuts 5A and 5B with respect to the vortex generator 2, the protrusion dimensions a and b can be appropriately determined so that the Karman vortex generation condition can be optimized. The influence of the protrusion dimensions a and b on the flow rate measurement will be described with reference to FIG. FIG. 3 is a characteristic diagram of the K value with respect to the Re number, in which the degree of protrusion of the nut as the protrusion is used as a parameter. In FIG. 3, the horizontal axis represents the Reynolds number (Re number) of the measured fluid, and the vertical axis represents the K value described in the conventional example (K = Q / f for the velocity flow rate Q of the measured fluid and the frequency f of the Karman vortex). Then, the characteristics of the K value with respect to the Re number are shown using the respective dimensions a and b as parameters. The characteristic curve shows that when the dimensions a and b are proper values, the characteristic curve is when the dimensions a and b are smaller than proper values, and the characteristic curve is when the dimensions a and b are larger than proper values. Are shown respectively. When the dimensions a and b are proper values, the K value becomes almost constant with respect to the change in Re number. On the other hand, when the dimensions a and b are too small or too large, the K value tends to increase or decrease particularly in a region where the Re number is low, in other words, when the flow rate is low. This reduces the accuracy of flow rate measurement.

[0011]

According to the Karman vortex flowmeter of claim 1,
By adjusting the position of the protrusion with respect to the vortex generator in the axial direction, the degree of protrusion of the protrusion with respect to the flow can be appropriately adjusted, and the Karman vortex generation condition can be optimized. Therefore, it is possible to easily obtain optimal conditions for Karman vortex generation that slightly change according to each Karman vortex flowmeter, enable highly accurate flow rate measurement, and have a simple structure for that.
Not only the cost increase is small, but on the other hand, the requirement for the dimensional accuracy of the related parts can be relaxed, so that the cost can be reduced as a whole.

Particularly, in the Karman vortex flowmeter according to the second aspect, since the cylindrical nut as the projecting body screw-connected to the male thread portion of the vortex generator is rotated, the position is adjusted in the axial direction. The adjustment is accurate, easy, and quick, and the structure is simple and easy to manufacture.

[Brief description of drawings]

FIG. 1 is a side sectional view of an embodiment according to the present invention.

[FIG. 2] Similarly, a cross-sectional view of the main part thereof.

FIG. 3 is a characteristic diagram of the K value with respect to the Re number using the protrusion degree as a parameter.

FIG. 4 is a side sectional view of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pipe line 2 Vortex generator 3 Vortex detector 3a Diaphragm 3b Mandrel 4 Buffer material 5A Nut (protruding body) 5B Nut (projecting body) 6 Insulating plate 7 Insulating plate 8 Piezoelectric element 9 Disc spring 10 Balance weight 11 Columnar body (upstream) Side) 12 columnar body (downstream side) 13 pressure guide hole

Claims (2)

[Claims] 1. A flowmeter in which a protrusion for promoting the generation of Karman's vortex is provided at each position where the vortex generator is fitted with the peripheral wall of the pipeline, wherein the protrusion has an axis line with respect to the vortex generator. A Karman vortex flowmeter, which is a cylindrical member that is positionally adjustable in a direction. 2. The Karman vortex flowmeter according to claim 1, wherein the projecting body is a cylindrical nut screw-coupled to a male thread portion provided on the vortex generator.