JPH0450725A - Vortex flowmeter - Google Patents

Abstract

PURPOSE:To obtain the vortex flowmeter which makes a small pressure drop by providing a vortex generating column in a duct and forming a flow passage which communicate an upstream with a downstream side. CONSTITUTION:The vortex generating column 11 is formed of a long hole which has a lengthwise communication hole (flow passage) 13 communication with the upstream side and downstream side. The width L of the downstream- side front surface 2 of the vortex generating column 11 is about 30% of the internal diameter D of the duct 3 and suitable for the generation of a Karman vortex street on the downstream side. Fluid which flows in between flanks 12 and the inner peripheral surface 3A of the duct 3 separate and become vortexes alternately by the flanks 12 and 12 to generate a Karman vortex street on the downstream side of the vortex generating column 11. The flow rate of the fluid is measured according to the detection result of the generation period of the vortexes. further, the fluid can be made to flow even to the communication hole 13, so the fluid resistance is reduced and the pressure drop is reducible greatly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a vortex flowmeter, and particularly relates to a vortex flowmeter with low pressure loss.

[Prior Art] A vortex flowmeter has conventionally been used as a flowmeter for measuring flow rate.

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. .

By the way, various shapes have been considered for the above-mentioned vortex generation column, but in general, since the separation point of vortex generation is clear and constant, it is as shown in Fig. 4 or 5. , one having a triangular or trapezoidal cross section is preferable.

Further, it is said that it is desirable for the width of the upstream front surface 2 of the vortex generating column 1 to be approximately 30% of the diameter of the conduit 3 in order to generate a Karman vortex street.

In addition, in order to detect the generation period of the Karman vortex street, an ultrasonic wave is emitted into the pipe 3 on the downstream side of the vortex generating column l, and when the ultrasonic wave propagates, the interval changes due to the vortex. vortex generation column 1 by the detection method or the generation of Karman vortex street
There is a method of detecting the cycle of vortex generation by measuring the stress acting on the vortex using a piezoelectric element or the like.

[Problems to be Solved by the Invention] However, in the vortex flowmeter as described above, the vortex generating column 1 having a width of about 30% of the diameter of the pipe 3 is connected to the pipe 3. Since it is installed inside the tank, there is a drawback that the pressure loss is large.

This invention was made in view of the above circumstances, and an object thereof is to provide a vortex flow meter with less pressure loss.

[Means for Solving the Problems] The vortex flowmeter of the present invention is a vortex flowmeter that provides a vortex generation column in a pipe and measures the flow rate based on the Karman vortex street generated by the vortex generation column. The vortex generating column is characterized in that a flow path communicating between an upstream side and a downstream side is formed in the vortex generating column.

[Operation] According to the vortex flow meter of the present invention, a vortex is generated by separation of the fluid that has flowed into between the surface of the vortex generating column and the inner circumferential surface of the conduit. Then, the flow and amount of fluid can be measured based on the generation period of this vortex.

In addition, the fluid flowing approximately at the center of the pipe passes through the flow path formed in the vortex generating column and flows downstream, so that it flows between the surface of the vortex generating column and the inner circumferential surface of the pipe. By slowing down the flow rate of the fluid, the fluid resistance can be reduced, and the pressure loss of the fluid can be reduced.

[Example] Hereinafter, an example of the vortex flowmeter of the present invention will be described with reference to the drawings.

Note that the same reference numerals are given to the same structural parts as in the conventional example, and the explanation thereof will be omitted.

In FIG. 1, reference numeral 11 is a vortex generating column used in the vortex flowmeter of the present invention.

This vortex generating column 11 has a side surface 12. which is gradually spaced apart from the inner circumferential surface 3A of the conduit 3 as it goes from upstream to downstream. ．． 12. Further, this vortex generating column 11 is formed with a communication hole (flow path) 13 that communicates between the upstream side and the downstream side. As shown in FIG. 2, the communication holes 13 are elongated holes that are formed in parallel in the longitudinal direction of the vortex generating column 11.

The width of the upstream front surface 2 of this vortex generating column 11 is as follows:
It is approximately 30% of the inner diameter of the pipe 3, and is a suitable size for generating a Karman vortex street on the downstream side of the vortex generating column 11.

According to the vortex flowmeter in which the vortex generating column 11 having the above-mentioned shape is provided in the conduit 3, when fluid flows in the direction of arrow A in FIG. and conduit 3
flows between the inner circumferential surface 3A, 3A and the side surface 12.12.

The fluid that has flowed into the communication hole 13 passes through the communication hole 13 and flows downstream without suffering any loss.

On the other hand, the fluid that has flowed into between the side surface 12.12 and the inner circumferential surfaces 3A, 3A of the conduit 3, because the side surface 12.12 is gradually separated from the inner circumferential surfaces 3A, 3A of the conduit 3, These side surfaces 12 and 12 separate alternately to form vortices, and a so-called Karman vortex street is generated on the downstream side of the vortex generating column 11.

Then, the generation period of this vortex can be detected, and the flow rate of the fluid can be measured based on the detection result.

As explained in the conventional technique, the method for detecting the vortex generation period is to radiate an ultrasonic wave into the pipe line 3 on the downstream side of the vortex generation column [l], and to determine the propagation time of the vortex. There are methods that detect the vortex generation period by measuring the stress generated in the vortex generation column 1 due to the generation of the Karman vortex street using a piezoelectric element, etc. The pillar 11 has a communication hole 13 formed therein, and since it is difficult to provide a piezoelectric element inside the communication hole 13, the former method using ultrasonic waves is appropriate.

According to the vortex flowmeter of the above embodiment, fluid can also flow through the communication hole 13 formed in the vortex generating column 11, so that the fluid can flow between the side surface 12.12 of the vortex generating column 11 and the inner circumferential surface 3A of the pipe line 3. ,3A
The flow rate of the fluid flowing between the two can be reduced.

As a result, the side surface 12.12 and the inner circumferential surface 3A of the conduit 3,
3 A, the fluid resistance can be reduced, and pressure loss can be significantly reduced. This also makes it possible to further increase the flow rate of the fluid flowing through the pipe line 3.

Incidentally, in the vortex generating column 11 of the vortex flowmeter of the above embodiment, a through hole 13 consisting of an elongated hole communicating with the upstream side and the downstream side is formed, and the fluid is made to flow into the communicating hole 13. For example, as shown in FIG. 4, a plurality of communication passages (flow passages) 14, 14, . Even if the light is allowed to pass through, the same effect as in the above embodiment can be obtained. In addition, in this case, the rigidity of the vortex generating column 11 can be increased, and the vortex generating column 11 is
deformation can be prevented.

Further, the outer cross-sectional shape of the vortex generating column in the above embodiments is not limited to the embodiments, and may be, for example, a circular shape or the like.

[Effects of the Invention] As described above, according to the vortex flowmeter of the present invention, the following effects can be obtained.

A vortex is generated when the fluid that has flowed into between the surface of the vortex generating column and the inner circumferential surface of the pipe is separated at the surface of the vortex generating column. Then, the flow rate of the fluid can be measured from the generation period of this vortex.

Here, the fluid flowing approximately at the center of the pipe passes through the flow path formed in the vortex generating column and flows downstream, so the fluid flowing between the surface of the vortex generating column and the inner peripheral surface of the pipe The flow velocity can be significantly reduced.

Therefore, fluid resistance between the surface and the inner circumferential surface of the pipe can be reduced, and fluid pressure loss can be significantly reduced.

[Brief explanation of the drawing]

1 to 3 are diagrams explaining the present invention in detail, in which FIG. 1 is a sectional view of a pipe line in which a vortex flowmeter is installed, and FIG.
The figure is a perspective view of a vortex generating column for explaining the vortex generating column, and FIG. 3 is a perspective view of another vortex generating column for explaining another vortex generating column. Furthermore, FIGS. 4 and 5 are diagrams for explaining conventional examples, in which FIG. 4 is a cross-sectional view of a conduit in which a vortex generating column with a triangular cross section is installed, and FIG. FIG. 3 is a cross-sectional view of a conduit in which a generating column is installed. 3...Pipe line! ! ... Vortex generation column, 13
...Communication hole (flow path), 14...Communication path (flow path). Figure 1: Tokiko Co., Ltd. Figure 2: Figure 3

Claims (1)

[Scope of Claims] A vortex flowmeter 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, wherein the vortex generating column has an upstream side and a downstream side. A vortex flowmeter characterized in that a flow path is formed that communicates with the vortex flowmeter.