JPH08261806A - Edge tone flowmeter - Google Patents

Abstract

PURPOSE: To realize a highly accurate edge tone flowmeter by restricting changes in a Reynolds number-strouhal curve over a wide range. CONSTITUTION: An oscillation frequency based on an edge tone oscillation of a measuring fluid is detected to measure a flow rate. This flowmeter includes an internal void 12 provided in the course of a measuring passage, a slit-shaped nozzle 13 which is provided on the upstream side of the internal void 12 to jet the measuring fluid into the internal void, a throttle 21 which is provided on the downstream side to choke the flow of the measuring fluid from the internal void, a flat sheet-shaped edge 22 having a plane arranged in the internal void parallel in the direction of a measuring path, a rod body 24 arranged almost at the right angle to the flow of the fluid roughly at the center in the course of the nozzle while facing the flat sheet-shaped edge along the length and an oscillation frequency detecting means which is arranged in the internal void to detect an oscillation frequency by an edge tone oscillation of the measuring fluid.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an edge tone flowmeter which can obtain stable oscillation and has a wide dynamic range.

[0002]

2. Description of the Related Art FIG.
It is an edge tone flow meter filed on the date. In FIG. 3, 11 is a pipe through which the measurement fluid flows, and 12 is an internal space provided in the middle of the pipe 11. 13 is an internal space 12
Is a slit-shaped nozzle that is provided upstream of the nozzle and ejects the measurement fluid to the internal space 12. Reference numeral 21 is a throttle provided downstream of the internal space 12 for restricting the flow of the measurement fluid from the internal space 12.

Reference numeral 22 is a thin flat plate-shaped edge which is arranged in the inner space 12 in parallel with the direction of the conduit 11. 23
Is a pressure fluctuation detecting means which is arranged in the internal space 12 and detects a pressure fluctuation due to edge tone oscillation of the measurement fluid. In this case, the pressure introducing hole 231 and the pressure introducing hole 231
And a pressure detector 232 (not shown) for detecting the pressure fluctuation of the measurement fluid introduced from.

In the above structure, the fluid to be measured is the conduit 11
The jet flow flowing out of the nozzle 13 and exiting from the nozzle 13 is
It collides with the tip of and causes edge tone oscillation. By detecting the pressure fluctuation of the measurement fluid based on this oscillation frequency by the pressure fluctuation detection means 23, the flow velocity flow rate of the measurement fluid can be measured. Generally, the relationship between the oscillation frequency and the average flow rate of the jet flow has a proportional range.

FIG. 4 shows experimental data of Reynolds number (Re) -Strohal number (St) characteristics of the conventional device shown in FIG. Such an edge tone type flow meter has a higher oscillation frequency than other oscillation type flow meters and is characterized by stable oscillation.

[0006]

However, in such a device, a fluid having a Reynolds number (Re) of 1800 or less has a non-linear characteristic, and a correction means must be provided in such a fluid. There was a problem.

The present invention solves this problem. An object of the present invention is to provide an edge tone flowmeter with improved non-linear characteristics in a fluid having a low Reynolds number (Re).

[0008]

In order to achieve this object, the present invention provides an edge tone flow meter which detects an oscillation frequency based on an edge tone oscillation of a measurement fluid to measure a flow rate, in the middle of a measurement flow path. An internal void provided in the internal void, a slit-shaped nozzle provided upstream of the internal void for ejecting a measurement fluid to the internal void, and a measurement from the internal void provided downstream of the internal void A throttle for narrowing the flow of fluid, a thin plate-like edge whose plane is arranged parallel to the measurement flow channel direction in the internal space, and a direction substantially perpendicular to the flow of fluid at approximately the center of the nozzle. And a rod arranged in the longitudinal direction opposite to the edge of the thin flat plate, and an oscillation frequency detecting means arranged in the internal space for detecting an oscillation frequency due to edge tone oscillation of the measurement fluid. It is also characterized by It is.

[0009]

With the above construction, when the fluid to be measured flows in the pipe and the fluid flows to the nozzle, Karman vortices are generated behind the rod. The cooperation between the vortex generation frequency and the self-excited oscillation frequency of the jet stream stabilizes the oscillation frequency and suppresses the change in the Reynolds number-Strohhal number curve. Hereinafter, detailed description will be given based on examples.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view of the essential structure of an embodiment of the present invention. In the figure, the same symbols as those in FIG. 3 represent the same functions. Only parts different from FIG. 3 will be described below. Reference numeral 24 denotes a rod body provided in the middle of the nozzle 13 for generating a Karman vortex. The rod body 24 has a thin plate-like edge 2 at a substantially central portion of the slit-shaped nozzle in a direction substantially perpendicular to the fluid flow.
2 is disposed so as to face the longitudinal direction.

In the above structure, the fluid to be measured is the conduit 11
And a Karman vortex is generated downstream of the rod body disposed in the middle of the nozzle 13. The fluid containing this vortex is ejected from the tip of the nozzle and collides with the tip of the edge 22, causing edge tone oscillation. By detecting the pressure fluctuation of the measurement fluid based on this oscillation frequency by the pressure fluctuation detection means 23, the flow velocity flow rate of the measurement fluid can be measured.

The inventors conducted an experiment of Reynolds number (Re) -Strohal number (St) characteristics using the conventional apparatus and the apparatus of the present invention in which a rod is arranged in the nozzle. The device used in the experiment was the width W ₁ = 2.5 mm of the nozzle and the diaphragm,
Width W ₂ = 57 mm, length W ₃ = 80 mm, plate thickness of edge 0.4 mm, diameter of rod body 0.8 mm (arranged on the upstream side of the jet outlet a = 22 mm), of the flow passage Depth (height)
The length was 30 mm, and the lengths of the edges and rods were the same as the depth of the channel.

FIG. 2 shows the experimental results. The line segment indicated by B is the conventional type, and the line segment indicated by A is the apparatus of the present invention. As can be seen from the figure, in the present invention in which the rods are arranged, the nonlinearity in the low Reynolds number region is improved.

The size of each part is not limited to the above embodiment. For example, the thickness of the edge 22 is determined by the nozzle 13
If the width is less than or equal to, the same edge tone oscillation can be obtained. Further, the shape of the rod body 24 is not limited to the round bar.
Further, the shape of the inner space 12 is not limited to the embodiment, and it is sufficient that the edge 22 can be arranged in the inner space 12.

The position of the pressure introducing hole 231 is not limited to that shown in FIG. However, the edge 22
The closer it is to, the larger the fluctuation in pressure can be detected, so the closer it is, the better.

In the embodiment, the oscillation detecting means has been described as the pressure fluctuation detecting means 23, but the invention is not limited to this, and for example, a strain gauge is attached to the edge 22 to detect from the fluctuation of strain. But it's okay. In short, it is only necessary that the oscillation of the edge 22 can be detected.

[0017]

As described above, according to the present invention, in an edge tone flow meter which measures the flow rate by detecting the oscillation frequency based on the edge tone oscillation of the measurement fluid, an internal space provided in the middle of the measurement flow path is used. And a slit-shaped nozzle that is provided upstream of this internal space to eject the measurement fluid to the internal space, and a throttle that is provided downstream of the internal space and that restricts the flow of the measurement fluid from the internal space, A thin plate-shaped edge in which a plane is arranged parallel to the measurement flow path direction in an internal space, and at a substantially center in the middle of the nozzle, in a direction substantially perpendicular to the flow of fluid, and in the thin plate-like shape. It is provided with a rod body arranged so as to face the edge in the longitudinal direction, and an oscillation frequency detecting means arranged in the internal space for detecting an oscillation frequency due to edge tone oscillation of the measurement fluid. Generation frequency of the Karman vortex And by cooperation with the self-oscillating frequency of the jet, it is possible to suppress a change in Reynolds number over Strouhal number curve over a wide range, it is possible to realize highly accurate edge tones flowmeter.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a main part configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing experimental results of Reynolds number (Re) -Strohal number (St) characteristics in the present invention and the conventional device.

FIG. 3 is an explanatory diagram of a configuration of a conventional example that is generally used in the past.

FIG. 4 is a diagram showing an experimental result of Reynolds number (Re) -Strohal number (St) characteristics in a conventional device.

[Explanation of symbols]

 11 ... Pipeline 12 ... Internal void 13 ... Nozzle 21 ... Restriction 22 ... Edge 24 ... Rod

Claims (1)

[Claims] 1. An edge-tone flowmeter for measuring a flow rate by detecting an oscillation frequency based on edge-tone oscillation of a measurement fluid, wherein an internal void provided in the middle of a measurement flow path and an upstream of the internal void. A slit-shaped nozzle provided to eject the measurement fluid to the internal space, a throttle provided downstream of the internal space to restrict the flow of the measurement fluid from the internal space, and the measurement flow to the internal space. A thin plate-shaped edge whose planes are arranged parallel to the road direction, and a substantially central part in the middle of the nozzle in a direction substantially perpendicular to the fluid flow, and the thin plate-shaped edge faces the longitudinal direction. An edge tone flowmeter, comprising: a rod body arranged in an inner space; and an oscillation frequency detecting means arranged in the internal space for detecting an oscillation frequency of an edge tone oscillation of a measurement fluid.