JPH03239914A - Fluidic flowmeter - Google Patents

Abstract

PURPOSE:To measure a flow rate up to a logical lower measurement limit and to expand a flow rate measurement range by forming at least one set of mutually opposite slots at right angles to the flow direction of fluid. CONSTITUTION:The fluid 100 which flows in a flow passage flows in the jet nozzle 40 of a fluid oscillator 30 and is jetted as a jet flow 200 to a target 42. At this time, vortex flows are formed in the slots 46a and 46a with the jet flow 200 in the nozzle 40. The size of the generated vortex flows is prescribed by the size of the slots and the flow velocity of the part of the jet flow 200 contacting vortex rings is equalized to the flow velocity of the vortex rings. Namely, the slots 46a and 46a are provided to prescribe the flow velocities of the parts of the jet flow 200, which contact the slots 46a and 46b, with the vortex. Thus, the border layer of the jet flow 200 in the nozzle 200 is prevented from being developed and the flow velocity of the vortex peripheries affect the flow velocity distribution nearby the wall surface of the nozzle.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention uses a fluidic flowmeter, particularly a fluidic oscillator that alternately vibrates the flow direction of a jet ejected from a nozzle force at a frequency corresponding to the flow rate. Concerning improvements to fluidic flowmeters.

[Prior Art] As is well known, when a columnar object is placed facing a jet flow with its axis perpendicular to the flow, the direction of flow of the jet oscillates to the left and right of the object behind the object, causing the wall surfaces on the left and right sides of the flow path to oscillate. A fluid oscillator is formed which is attached alternately to the fluid oscillator. Since the frequency of vibration of this jet flow is proportional to the flow velocity, the flow velocity or flow rate can be determined by measuring the frequency of vibration of the jet flow.

The full-ink flowmeter utilizes this principle.
This flowmeter is expected to have a long life and high reliability because the moving parts are not combined, and it can be used in various fields such as an intake flow meter for automobiles and a gas meter for home use.

FIG. 12 shows the membrane structure of a conventional full-ink flowmeter. This fluidinok flow is 1;1
is 71111 constant, and the fluid 1. which becomes the l-elephant. It includes a pipe line 11 flowing in the direction (1 ( ) or χIl + /, in the figure) and a fluid equalizer 12 provided in the pipe line 10 (I).

The fluid vibrator 12 has two jet nozzles]/1 and a jet nozzle/16 with a pipe vertically attached to the outlet of the jet nozzle/1. −f.And
A jet stream 2 is ejected from the jet 14 toward the target 16.
00, the flow direction vibrates alternately at a frequency proportional to the flow velocity in the order of ■, ■, ■, ■ in the figure.

The full-ink flowmeter thus operates as a fluid oscillator 1.
2. Measure the vibration frequency of the jet 200 formed by
The flow velocity or flow rate of the fluid 100 is determined.

By the way, when such a full ink flow meter is used as a household gas meter, for example, the ratio between the lower limit and the upper limit of the measurable flow rate, that is, the flow ffl,'+1
11 constant range is required to be 1:100 or more.

In particular, in the case of household gas meters, it is necessary to accurately measure small flow rates.

[Problems to be Solved by the Invention] However, in the conventional full-ink flowmeter, when the flow rate decreases, the jet 200 vibrates irregularly and becomes unstable, making measurement difficult.
It becomes Noh. This flow rate measurement limit is theoretically determined by the Reynolds number, but in reality, the flow rate is determined by the Reynolds number.
It20 (II vibrates, but at higher flow speeds it vibrates or stops (I-S), or there is a problem that the proportionality between flow velocity and vibration frequency deteriorates.

This is because the boundary layer has a constant velocity near the wall surface of the jet nozzle 14, and the actual jet/7t near the outlet of the nozzle 14.
This is because 2 (10) becomes the three-dimensional flow velocity m shown in FIG.
It is possible to eliminate the flow velocity distribution i).

However, if the above-mentioned rectifying grid or the like is installed inside the nozzle 14, the flow path resistance increases. As a result, in the Sung Dynasty, the f-force loss in the Ryu-0 man-friendly region became large, and the Ryu-2, iFI
Since the fixed upper limit is low, the flowmeter jLL'
5 The problem is that if we set ↓L and 2 becomes smaller, we will newly define ′1 and 2.

+, Ming was made in view of such problems in the Song Dynasty.The purpose of this was to prevent the constant velocity of the boundary layer near the wall 111 of the jet nozzle, Furthermore, by smoothing the nozzle]':ii (5 flow velocity'->Q+, it is possible to measure the flow rate up to the theoretical lower limit of measurement, and to provide a full-ink flowmeter capable of expanding the flow rate measurement range. It is in.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a fluid oscillator that alternately vibrates the flow direction of the jet jet ejected from the jet nozzle at a frequency depending on the flow rate, In a full-ink flowmeter that measures the vibration frequency of a jet, the jet nozzle is formed as a rectangular nozzle composed of four wall surfaces, and the jet nozzle is formed as a rectangular nozzle consisting of four wall surfaces, and the jet nozzle is formed in the vicinity of the outlet of at least one pair of opposing wall surfaces. It is characterized in that at least one set of slots are formed to intersect five directions of fluid flow.

[Work] Next, the present invention will be explained in detail.

FIG. 1 shows the fluid flow ff1g according to the present invention.
A diagram of the principle of + is shown.

The feature of the present invention is that the jet nozzle 40 is a nozzle with a rectangular cross section of 11"/11" formed by four wall surfaces 44, and in the vicinity of the outlet of at least one pair of opposing wall surfaces 44a, The present invention is characterized in that at least one set of slots 46a, 46a are formed to intersect the flow direction of the jet 200. Here, the slots 46a, 46a are preferably formed to be perpendicular to the flow direction. .

As a result, a vortex is formed in the jet 200 flowing within the jet nozzle 40 by the slots 46a, 46a. The size of the vortex formed is the same as that of the slots 46a, 46a.
The flow velocity of the portion of the jet flow 200 in contact with the vortex ring is adjusted to be equal to the flow velocity of the vortex ring.

That is, by providing the slots 46a, 46a, the flow velocity at the portion of the jet 200 that contacts the slots 46a, 46a is determined by the vortices.

By generating the vortex in this manner, the development of the boundary layer of the jet 200 flowing within the jet nozzle 40 is hindered, and the flow velocity around the vortex influences the flow velocity distribution near the nozzle wall surface.

According to Helmholtz's vortex theorem, which is known in the field of fluid mechanics, in the case of a vortex ring having the same cross-sectional area, the flow velocity around the vortex is guaranteed to be constant. Furthermore, it follows that the circulation of vortices remains unchanged on the membrane surface. In other words, the smaller the diameter of the vortex ring, the higher the altitude and the faster the flow velocity around the vortex. Conversely, as the diameter of the vortex ring increases, the altitude decreases and the flow velocity around the vortex decreases.

In this way, since the flow velocity around the vortex is guaranteed to be constant, the wall surface 4 is placed inside the slots 46a, 46a.
By generating vortex rings having the same cross-sectional area along the walls 4a, 44a, the flow velocity distribution near the wall surfaces 44a, 44a can be made uniform.

As a result, in the fluid oscillator 12 used in the present invention, stable vibration can be obtained even at low flow velocity, and proportionality between the flow velocity and the vibration frequency can be maintained.

Therefore, it is possible to obtain a fluidinok flow rate 51 that can accurately measure the flow rate or flow velocity up to the theoretical lower limit of measurement.

[Effects of the Invention] As explained above, according to the present invention, by preventing the development of a boundary layer near the wall surface of a jet flowing in a jet nozzle of a fluid oscillator and by lowering the flow velocity distribution, Reynolds This has the advantage that it is possible to obtain a fluidic flowmeter capable of measuring a flow rate up to around the lower limit value of flow jl 61, which is determined by a number.

[Example] Next, a preferred example of the present invention will be described in detail based on the drawings.

2 to 4 show a first preferred embodiment of the fluidic flowmeter according to the present invention.

As shown in FIG. 2, the fluidic flowmeter of the embodiment has a pipe 2 in which a fluid 100 flows through a flow path 22 formed inside.
0, a fluid oscillator 30 provided within this conduit 20,
and a sensor 50 for detecting the vibration frequency of the jet flow 200.

The fluid oscillator 30 includes a jet nozzle 40 that forms a jet 200 and a columnar target 42 that faces the outlet of the jet nozzle 40 and is provided so that its axis intersects the jet 200 perpendicularly.

The sensor 50 detects vibrations of the jet stream 200 as a change in pressure or a change in flow velocity. This sensor 200,
When forming it as a pressure sensor, a piezoelectric element such as PVDF may be used, and when forming it as a flow rate sensor, a hot wire current meter or the like may be used. In the embodiment, PVDF membranes are bonded to both sides of the target 42, and the differential pressure caused by the jet flow is detected using differential manual power on both sides. Note that the sensor 50 may be installed at a position other than this, for example, as shown by A in the figure, or on the inner wall surface of the conduit 200, as shown by B in the figure.

FIG. 3 shows a schematic perspective view of the flow path portion of the fluidic flowmeter formed in this manner. In the pipe line 20 of the embodiment, the flow path 22 thereof is formed to have a rectangular cross section.

The features of the present invention are: - The jet nozzle 40 is formed as a rectangular nozzle composed of four wall surfaces, and at least one pair of wall surfaces 44a facing each other.

At least one pair of opposing slots 46a, 46a are formed in the vicinity of the air outlet 44a so as to intersect with the flow direction of the jet stream 200.

Here, the slot 46 is preferably formed so as to be perpendicular to the flow direction of the jet stream 200.

FIG. 4 shows an enlarged view of the jet nozzle 40. The jet nozzle 40 of the embodiment is a rectangular nozzle with a long nozzle J-shape in cross section, with a pair of wall surfaces 44a, 44a facing each other with a width W, and another pair of wall surfaces 44b, 44b facing each other with a width W. (however, hew). and,
A pair of slots 46a, 46a are provided in the vicinity of the air outlet [1] of a pair of wall surfaces 44a, 44a standing upright in the same lj direction as the columnar target 42, so as to face each other. Each of the slots 46a has a rectangular cross section.

FIG. 1 shows an explanatory diagram of the [1F] of this practical example.

In the fluidic flowmeter of this embodiment, the fluid 100 flowing in the flow path 22 flows into the jet nozzle 40 of the fluid oscillator 30, becomes a jet 200, and is ejected toward the target 42.

At this time, the jet 200 flowing within the jet nozzle 40 forms a vortex within the slots 46a, 46a.

The size of the vortex formed is determined by the size of the slot, and the flow velocity of the portion of the jet 200 that contacts the vortex ring is made equal to the flow velocity of the vortex ring. That is, by providing the slots 46a, 46a, the flow velocity at the portion of the jet 200 that is in contact with the slots 46a, 46a is determined by the vortices.

By generating the vortex in this manner, the development of the boundary layer of the jet 200 flowing within the jet nozzle 40 is hindered, and the flow velocity around the vortex influences the flow velocity distribution near the nozzle wall surface.

According to Helmhorn's vortex theorem, which is known in the field of fluid mechanics, in the case of a vortex ring having the same cross-sectional area, it is guaranteed that the flow velocity around the vortex is constant. Furthermore, it follows that the circulation of vortices remains unchanged on the membrane surface. In other words, the smaller the diameter of the vortex ring, the higher the altitude and the faster the flow velocity around the vortex. Conversely, as the diameter of the vortex ring increases, the altitude decreases and the flow velocity around the vortex decreases.

In this way, since it has been proven that the flow velocity around the vortex is constant, a vortex ring with the same cross-sectional area (f) is generated inside the slots 46a, 46a along the wall surfaces 44a, 44a. As a result, the flow velocity distribution near the wall surfaces 44a, 44a can be made uniform as shown in FIG.

Taking advantage of this, the fluid oscillator 12 used in the present invention can provide stable vibration even at low flow velocities. , to,
Proportionality between flow velocity and vibration frequency is maintained.

It is possible to obtain a full-ink flowmeter that can accurately measure flow rate or flow velocity up to the theoretical lower measurement limit.

In addition, if the width and depth of the front 1° slots 46a and 46a are narrow or narrow, the effect will decrease.

Therefore, in the present invention, two sets of wall surfaces 44 facing each other
a, 44a, 44b, 44b, if the narrower one is W, each slot 46a, 46a is
It is preferable to form the width and depth in a range of 0.2 to 5 times W.

Moreover, if the slots 46a, 46a are formed too far away from the ejection port of the nozzle 40, the slots 46a, 46a will be removed from the wall surface again.
4) The developed boundary layer causes the flow velocity to have a distribution. For this reason, it is preferable that the slots and holes 46a, 46a be formed at a distance within 10 times W from the outlet of the nozzle 40.

As a result, the flow velocity distribution of the jet 200 near the outlet of the jet nozzle 40 is well smoothed as shown in FIG. 6, making it possible to accurately measure small flow rates with a gas meter or the like.

Furthermore, the larger the aspect ratio of the jet nozzle 40 is, the more uniform the flow velocity distribution in the height direction of the jet within the nozzle becomes, so the effect of the slot 46 becomes less. Therefore, in the present invention, it is preferable that the aspect ratio of the cross section of the jet nozzle 40 is in the range of 2 to 10.

Note that the present invention is not limited to the above embodiments, and various modifications can be made within the scope of the gist of the present invention.

For example, in the embodiment described above, the jet nozzle 4o is provided with a pair of slots 46a, 46a.

However, the present invention is not limited to this, and for example, as shown in FIG.
6a, 46a, 46b, 46b, 46c
, 46 c . . . may be formed in parallel.

Further, in the above embodiment, the slot 46 is formed to have a rectangular cross section, but the present invention is not limited to this. It may also be formed into a semicircular shape.

Further, in the embodiment, a pair of opposing wall surfaces 44a,
Although the explanation has been given by taking as an example the case where the slot 46 is formed only on the wall surface 44a, the present invention is limited to this. For example, as shown in FIG. 9, the slot 46 is formed on the four wall surfaces 44a.

A slot 46 may be formed in 44a, 44b, 44b to surround jet nozzle 40.

Furthermore, the vortex generated within the slot 46 is not necessarily equivalent to the size of the slot 46. Under the influence of the flow velocity distribution within the nozzle 40, a vortex ring with a small diameter may be formed at the center of the slot 46.

In such a case, as shown in FIG. 10, by forming a slot 46 whose width and depth are largest at the center of the wall surface 44, the same cross-sectional area can be created inside the slot 46 along the wall surface 44. It becomes possible to generate a vortex ring with

FIG. 11 shows experimental data for the fluidic flowmeter according to this embodiment and the conventional fluidic flowmeter. Here, the horizontal axis represents the flow jtQ, and the vertical axis represents the vibration frequency f.

During the experiment, the fluidic flowmeter of the embodiment has its jet nozzle 40 with a width w = 2B4° and a height h = 1.
It was formed to have a length of 2 mm and a length of e-10 mm. Further, the slot 46 was not rectangular in cross section as shown in FIG. 3, but had a semicircular cross section as shown in FIG. 8, and the radius was set to r -1 mm. This slot 46 was provided at a position 5 mm from the outlet of the jet nozzle 40.

In this experiment, we used such a fluidic flowmeter,
Data were measured when the slot 46 was provided (the present invention) and when it was not provided (the conventional device). In FIG. 11, A is actually measured data of the present invention, and B is actually measured data of the conventional device.

As is clear from this experimental data, according to the present invention, by providing the slot 46, a low Reynolds number,
In other words, it will be understood that vibrations occur in the jet stream 200 up to a low flow velocity. From this, it will be understood that according to the present invention, the flow force measurement of a small flow rate can be performed more accurately than the conventional device.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram of the fluidic flowmeter according to the present invention; FIG. 2 is a cross-sectional schematic explanatory diagram showing a preferred first embodiment of the fluidic flowmeter according to the present invention; 2 is a perspective explanatory view of the flow path portion of the embodiment shown in FIG. 2. FIG. 4 is a perspective explanatory view showing the detailed configuration of the jet nozzle of the present example. FIG. Fig. 6 is an explanatory diagram of the flow velocity distribution when a slot is not provided in the jet nozzle, and Figs. FIG. 11 is an explanatory diagram of actual measurement data of the present invention and a conventional fluidic flowmeter. FIG. 12 is an explanatory diagram of a conventional general fluidic flowmeter. 30...Fluid oscillator, 40. Jet nozzle, 42...
Target, 44...Wall surface, 46...Slot, 1
00...fluid, 200 jet.

Claims (5)

[Claims] (1) In a fluidic flowmeter that includes a fluid oscillator that alternately vibrates the flow direction of a jet jet ejected from a jet nozzle at a frequency corresponding to the flow rate, and measures the vibration frequency of the jet flow, the jet nozzle includes: The nozzle is formed as a rectangular nozzle composed of four wall surfaces, and at least one set of opposing slots are formed near the outlet of at least one pair of opposing wall surfaces so as to intersect with the flow direction of the fluid. A fluidic flowmeter featuring: (2) In claim (1), the jet nozzle has a cross-sectional aspect ratio of 2 to 10.
A fluidic flowmeter characterized by being formed in the range of. (3) The fluidics flowmeter according to any one of claims (1) and (2), wherein the width and depth of the slot are greatest at the center of the wall surface. (4) In any one of claims (1) to (3), the slot has a width and a depth of w for a narrower interval w among the two sets of walls facing each other. A fluidic flow meter characterized by a range of 0.2 times to 5 times. (5) In any one of claims (1) to (4), the slot is arranged from the jet outlet of the jet nozzle with respect to the narrower interval w of the intervals between the two sets of wall surfaces facing each other. A fluidic flowmeter characterized in that it is formed at a distance within 10 times w.