JPS6331041B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention provides a columnar vortex generator in the middle of a pipe through which a fluid to be measured flows, and measures the flow velocity or flow rate by detecting the vortex generated from the vortex generator. This relates to flow velocity/flow measuring devices.

2. Description of the Related Art Conventionally, a flow velocity/flow rate detection device shown in FIGS. 1-2 or 3 is known. That is, first, the first and second
In what is shown in the figure, 1 is a columnar vortex generator provided in the middle of the pipe, and the vortex generator 1 has a plane 1A facing the flow as shown in Figure 2, and decreases as it goes downstream of the flow. A pair of temperature sensing elements 2, such as a thermistor, are provided on the surface 1A facing the flow. The vortex generator 1 is provided through the diameter portion of the main body 3 of the flow rate/flow meter, which serves as a conduit, and is sealed air-liquid-tight by sealing members 4, 4. Further, a preamplifier 5 connected to the temperature sensing element 2 is provided at the upper part of the main body 3. When the fluid flows in the direction of the arrow, the vortex generator 1 generates vortices alternately on the left and right, and the flow velocity on the surface of the temperature sensing element 2 changes alternately, so this change can be detected differentially. and measuring flow rate or flow rate. However, in such a system, since the temperature sensing element 2 faces the flow, dust and dirt are likely to adhere to it, and there is a risk that dust and dirt will collide with the temperature sensing element 2 and cause it to be damaged. Element 2 had drawbacks such as weak strength and difficulty in electrical insulation, and was unsuitable for measuring fluids.

Further, in the one shown in FIG. 3, reference numeral 11 denotes a columnar vortex generator with a substantially square cross section, and metal diaphragms 12 and electrodes 13 are located above and below a surface 11B of the vortex generator 11 facing downstream of the flow. , the electrode 1
A pair of capacitance-type vortex detection sections are provided, each of which includes an insulating material 14 surrounding the diaphragm 3, a liquid 15 sealed between the diaphragm 12 and the electrode, a communication path 16, and the like. When the fluid flows in the direction of the arrow, vortices are alternately generated by the vortex generators 11, and the static pressure on the side where no vortices are generated is lowered, and this differential pressure causes the two diaphragms 12 to be slightly displaced from each other. , the sealed liquid 15 flows through the communication path 16. As a result, the capacitance between the diaphragm 12 and the electrode 13 changes differentially, and the flow rate or flow rate is measured by detecting this change. However, compared to the system shown in FIG.
In particular, since the electrode 13 is not exposed to the flow, dust and
It does not pose any problem when it comes to dust, etc., but since it mechanically detects changes in static pressure, the detection sensitivity is poor when measuring gases with low fluid density, making it unsuitable for practical use. It was hot.

Therefore, in order to take advantage of the features of FIGS. 2 and 3, the inventors manufactured a vortex generator having the shape shown in FIG. 4 and conducted various experiments. That is, in FIG. 4, the vortex generator 21 is located on the plane 2 facing the flow.
1A and a surface 21B that decreases as the flow moves downstream, and the metal diaphragm 22, the electrode 23, the insulating material 24, the sealed liquid 25, the communication path 26, etc. at the upper and lower positions of the decreasing surface 21B. The configuration is such that a pair of vortex detection sections are provided. However, even with this type of system, the strength of the generated vortices is weak, and it has been found that, like the system shown in FIG. 3, it is not suitable for measuring fluids with low fluid density such as gases.

The present invention improves the drawbacks of the conventional flow rate/flow rate detection apparatus shown in FIGS. 1 to 3 or used in the experiment shown in FIG. 4, and will be described below in conjunction with the embodiment shown in FIG.

In FIG. 5, the same components as those in FIG. It has been found that particularly strong vortices are generated when the ratio of 21C to the length d, that is, R/d is in the range of 1.4 to 2.5.

Similar to the vortex generator 1 shown in FIG. 1, the vortex generator 21 having such a shape is provided through the diameter portion of the main body 3 of the flow rate meter, which serves as a conduit.

Since the present invention is configured in this way, the second to fourth
Compared to what is shown in the figure, the signal based on the first generated vortex is very strong. This reason is the second
~For the one in Figure 4, the surface facing the flow is concave 2
1C, the front corner A becomes an acute angle, and the separation of the fluid that hits the concave surface 21C becomes more reliable and strong, and the strength of the vortex increases.

Second, as a result of experiments, we found that the instrumental error characteristics are excellent even in the low flow rate range. That is, the instrumental difference characteristic diagram of the one shown in FIG. 2 or 4 and the one according to the present invention is as shown in FIG. It was found that the instrumental error characteristics in the low flow rate range were greatly improved compared to the one shown in FIG. 3 as well as the one shown in FIG.

Although the embodiment shown in FIG. 5 is illustrated as a capacitance-type vortex detection section, the present invention is not limited to this, and it is possible to use a piezoelectric element, a piezoelectric element, etc. as well as one using the temperature sensing element shown in FIG. A well-known vortex detection unit such as a hot wire type or a strain gauge type may be used.

As described in detail above, the flow rate/flow rate measuring device of the present invention is provided with a columnar vortex generator in the middle of the pipe through which the fluid to be measured flows, and the width of the lateral cross section of the vortex generator is adjusted to the downstream side of the flow. In the flow velocity/flow measuring device formed so as to decrease toward the opposite direction, since the surface of the vortex generating body facing the flow is formed into a concave surface, the following effects can be achieved.

By making the surface facing the flow concave,
The front corner has an acute angle, and the separation of the fluid that hits the concave surface is reliable and strong, and the strength of the vortex can be increased.

As a result of the above, the flow velocity or flow rate can be reliably measured even in the case of a fluid to be measured having a low fluid density such as gas.

By making the surface facing the flow concave,
It is possible to improve the instrumental error characteristics in the low flow rate region.

If the ratio of the radius of curvature R of the concave surface to the length d of the concave surface is set to R/d=1.4 to 2.5, the effects of each of the above terms will be even more remarkable.

If the vortex detection section is provided on a surface where the vortex decreases toward the downstream side of the flow, measurement of the fluid to be measured including dirt and dust will not be hindered.

[Brief explanation of the drawing]

Figures 1 and 2 show a first embodiment of a conventional flow velocity/flow rate measuring device, with Figure 1 being a partially cutaway overall view, and Figure 2 being a cross-sectional view of the vortex generator in the transverse direction. 1 is a cross-sectional view in the direction of the − arrow in FIG. 1, FIG. 3 is a cross-sectional view in the same direction as FIG. 2 showing another embodiment of a conventional vortex generator, and FIG. 5 is a cross-sectional view in the same direction as FIG. 2 showing a vortex generator according to the present invention, and FIG. 6 is a cross-sectional view in the same direction as FIG. 2 showing a vortex generator according to the present invention. FIG. 3 is a flow rate-instrument difference characteristic diagram showing the instrumental difference characteristics of the vortex generator. 21... Vortex generator, 21B... Surface facing downstream,
21C...Concave.

Claims (1)

[Claims] 1. A column-shaped vortex generator is provided in the middle of the pipe through which the fluid to be measured flows, and the width of the lateral cross section of the vortex generator is formed to decrease as it goes downstream of the flow. - A flow velocity/flow rate measuring device, characterized in that a surface of the vortex generating body facing the flow is formed into a concave surface.