JPS5827017A - Vortex flowmeter - Google Patents

Abstract

PURPOSE:To detect a stable vortex frequency signal and to detect an analog signal corresponding to a mean flow speed at the same time, by detecting the change in the flow of fluid due to the vortex by heat sensitive elements which are provided so as to widen an effective area. CONSTITUTION:A pair of heating wires 31, which are provided behind a vortex yielding body 2, are approximately vertically stretched within a lateral width D of the yielding body 2. Then the wires are bent and stretched to the outside of the lateral width D in a V shape. Thus the effective area is widened. The heating wires 31 are also provided at the opposite side. The detection is performed in the wider area in comparison with the case the change in the flow speed is detected by dot or a piece of wire. Therefore the stable detection of the vortex signal can be expected. An electric signal corresponding to the mean flow speed can be concurrently detected by a part protruded from the width D. As a result, the stable vortex frequency signal can be detected, and the analog signal corresponding to the mean flow speed can be also detected.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a vortex flow needle, and more particularly to a vortex detection section.

This kind of vortex flow meter is known as a force μ-man vortex type type or a swirl type type, and both output a frequency signal that is approximately proportional to the flow rate or flow velocity. When a vortex generator is inserted into the fluid to be measured, a vortex is stably generated downstream of the vortex generator. As vortices are generated, regular flow changes occur around the vortex generator,
Various methods have been put into practical use for detecting such changes based on changes in pressure, changes in flow velocity, changes in propagation of ultrasonic waves, changes in heat radiation of heat-sensitive elements, etc.

However, it is not possible to obtain a stable frequency signal unless the sensor is installed in an appropriate position to obtain an electrical signal corresponding to the vortex frequency. A method for installing this sensor at an appropriate position is described in detail in Japanese Patent Publication No. 88518/1983.

FIG. 1 shows an example of a vortex generator and the flow of fluid around it.

In the figure, (1) is a conduit, (2) is a vortex generator, and (3)
is a force μ-man vortex. In the figure, when the fluid to be measured flows, a regular Karman vortex street (3) is generated in the wake of the vortex generator (2). The shaded parts (4) and (5) in the figure are
This is the part where changes in flow velocity corresponding to the frequency of the force μ-Man vortex can be stably observed. Among these, the flow velocity change signal can be observed most clearly in the parts (6) and (7) immediately after the last flat plate of the vortex generator (2), but on the other hand, unnecessary noise signals are superimposed on the parts (6) and (7). It's also big. Conversely, as the distance from parts (6) and (7) increases, the noise signal superimposed on the flow velocity change signal becomes smaller;
Since the flow rate becomes faster than the flow rate, the obtained flow velocity change signal becomes smaller. Of course, the diagonal lines (4) and (6) and (5)
The directions of changes in flow velocity in part (7) are in opposite phase to each other,
Geometrically symmetrical.

This figure shows how the fluid flows around the vortex generating column when the other vortex generating column shown in FIG. 2 is used. The shaded area is obviously different because the shape of the vortex generator (2) is different, but the shaded area (4) (6
), the characteristics of the shaded area (s) (7) are as explained in FIG.

Now, assume that a thermistor or a hot wire is used when converting a change in flow velocity due to a vortex into an electrical signal using a heat-sensitive element. These heat-sensitive elements can only detect changes in flow velocity within a narrow range in which they are installed, and are sensitive to misalignment of the installation location. In addition, even when heat-sensitive elements are arranged in symmetrical positions and a vortex signal is detected based on the difference signal between them, the influence of deviation from the symmetrical position is very large, and the positional accuracy must be maintained sufficiently. be.

Furthermore, when trying to detect an analog signal corresponding to the flow velocity from among the electrical signals of the heat-sensitive element, there is a drawback that good signals cannot be obtained in the shaded areas (6) and (7) within the width of the vortex generator (2). be.

This invention attempts to eliminate the above-mentioned drawbacks; its first purpose is to detect a stable, undisturbed vortex frequency signal, and its second purpose is to detect a frequency signal corresponding to a flow rate as well as an analog signal. This is for the purpose of detection.

FIG. 8 is a partial explanatory diagram of one embodiment of the present invention, and in the figure, the button) is a hot wire. A pair of hot wires rAO are installed behind the rearmost part of the vortex generator (2), and the installation method is as follows:
) is approximately perpendicular to the area within width ID1 of A-A',
Then turn around and move the width TD above to the outside as well.
-eA" and are stretched in a "V" shape. The opposite side is symmetrical.

With the hot wire installed as described above, it is possible to detect changes in flow velocity over a wider surface than when detecting changes in flow velocity at a point or a single line, and stable detection of vortex signals can be expected.

In addition, it is possible to simultaneously detect electrical signals corresponding to the average flow velocity of multiple fluids at the part of X → M which extends beyond the width ID).This detection principle is the same as that of a normal hot wire anemometer. In the above embodiment, the case where the hot wires are stretched in series in a "V" shape is described, but the "W"
” shape or any other tension is fine. Also, they may be connected in parallel instead of in series, or there may be multiple thermistors in place of the hot wire.

Further, in the above embodiment, the case of detecting the Karman vortex street was described, but it goes without saying that similar effects can be expected in the case of a swirl type vortex flow meter.

As explained above, according to the present invention, a stable vortex frequency signal can be detected with a simple configuration in which regular changes in fluid flow caused by vortices are detected using heat-sensitive elements installed to spread over 16 areas. At the same time, there is an effect that an analog signal corresponding to the average flow velocity can also be detected at the same time.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the flow of fluid around the vortex generator, FIG. 2 is a diagram showing another vortex generator and the flow of fluid around it, and FIG. 8 is an embodiment of the present invention. FIG. 2 is a structural diagram showing an example. In the figure, (1) is a conduit, (2) is a vortex generator, and (3) is a hot wire. Agent Shin Kuzuno (1 other person)

Claims (2)

[Claims] (1) A vortex generator installed in the fluid to be measured captures the air flow rate as a change in the fluid vortex, and changes the frequency of the electrical signal by using at least one heat-sensitive element to detect the change in the fluid vortex. For signals to be detected as change signals, it is specially mandated that a heat-sensitive element consisting of a first element provided within the width of the vortex generator in the flow direction of the fluid and a second element provided outside the said width is provided. Vortex flowmeter with. (2) The vortex flowmeter according to claim 1, wherein the heat-sensitive element is composed of a first heating wire and a second heating wire.