JPS6226408B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a Karman vortex flow meter, and particularly to measures for promoting the growth of Karman vortices on the side surfaces of a vortex generator.

As an example of the Karman vortex flowmeter is shown in Fig. 1, one end of the Karman vortex flow meter is installed in a duct 1 where fluid flows in the direction of arrow 9 (Fig. 1 shows a cross-sectional view, so the installed state is A vortex generator 2 (not shown) is arranged, and the generation frequency of Karman vortices 4, which are generated alternately on the left and right sides on the downstream side by this vortex generator 2, is proportional to the flow velocity of the fluid, and therefore the flow rate. This is used to detect the frequency or period of the Karman vortices that occur and measure the flow rate or velocity of the fluid.

To detect the frequency of Karman vortices, for example,
A communication hole 3 is provided in the vortex generator 2 and extends through the vortex generator 2 perpendicularly to the flow direction of the fluid, and a resistance wire 5 in a self-heating state is stretched inside the communication hole 3. In the communication hole 3, alternating flows 6 (a flow from top to bottom and a flow from bottom to top in the plane of FIG. 1) are generated in synchronization with the generation of the Karman vortex. This alternating current 6 cools the resistance wire 5 which is in a state of self-heating, and its resistance value changes. This change in resistance value is synchronized with the alternating current 6 and therefore with the Karman vortex 4. By electrically measuring this change in resistance value, the generation frequency of the Karman vortex 4 is determined, and the flow rate of the fluid is measured.

In such a Karman vortex flowmeter, communication as shown in FIG. It has been previously proposed to have a hole configuration (see Japanese Patent Publication No. 50-3180). FIG. 2a shows a cross-sectional view of the vortex generator, and FIG. 2b shows a side view. That is, a plurality of through passages 7 and 8 which penetrate the vortex generator 2 from its diagonally upstream side to its diagonally downstream side, intersecting with the flow direction of the fluid, and are independent from each other, are provided in the axial direction of the vortex generator 2. It is provided so that the direction changes alternately each time the position changes.

By providing a plurality of through passages 7 and 8 in the vortex generating body 2 as shown in FIG. However, in the configuration shown in FIG. 2, the alternating current flow 6 in the through passages 7 and 8 is blown diagonally downstream, so the vortex growth on the downstream side of the vortex generating body 2 is promoted. 4
This has the disadvantage that separation of the vortex and entrainment of the vortex on both sides of the vortex generator 2 are hindered.

An object of the present invention is to provide a Karman vortex flowmeter that can eliminate the above-mentioned disadvantages of the prior art and promote vortex growth without preventing vortex separation and entrainment on both sides of a vortex generator. be.

In order to achieve the above object, the features of the present invention are as follows:
A plurality of communication holes are provided that communicate with both sides of the vortex generator in a direction substantially perpendicular to the fluid flow, and each of these communication holes is provided in a substantially parallel direction. The vortex detector is provided in a passage connecting substantially the center of two communicating holes.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a diagram showing the first embodiment of the present invention, a
is a cross-sectional view of the vortex generator 2, b is a side view, and c is a sectional view taken along line A--A in a. Two communication holes 10 and 11 that communicate with each other on both sides of the vortex generator 2 are provided so that the communication holes 10 and 11 are parallel to each other in a direction substantially orthogonal to the fluid flow. The communication holes 10 and 11 are connected at their central portions by a passage 12, and a resistance wire 5 is stretched approximately at the center of this passage 12. 10' and 11' are communication holes 1
0 and 11 are openings on the side surfaces of the vortex generators 2, respectively.

Now, when the fluid flows in the direction of arrow 9, Karman vortices 4 and 4' are created alternately and regularly on the downstream side of the vortex generator 2. At this time, alternating flows 6 are generated in the communication holes 10 and 11 in the same direction in synchronization with the Karman vortices 4 and 4'. As shown in Fig. 3a, it is assumed that a Karman vortex 4 is generated on the upper side. At this time, on both the upper and lower sides of the vortex generator 2, the upper side becomes more negative pressure than the lower side based on the generation of Karman vortices, and the communication hole 1
0 and 11, a fluid flow occurs from the bottom side to the top side. Conversely, when the next Karman vortex (not shown) is created on the lower side, a flow is generated in the communicating holes 10 and 11 from the upper side to the lower side. These communication holes 10 and 11
The fluid flow generated in the above creates a flow in the passage 12, which cools the resistance wire 5 and changes the resistance value. By counting this change in resistance value, the cycle of the alternating current is determined, and the frequency at which the Karman vortex occurs is determined. Since the generation frequency of Karman vortices is proportional to the passing flow rate, the passing flow rate can be determined.

FIG. 4 is a diagram showing a second embodiment of the present invention, a
is a cross-sectional view of the vortex generator, b is its side view, c is a
FIG. This is a case where a vortex generator 2 having a rectangular cross section is used, and the vortex generator 2 is arranged so that the flat front surface of the rectangle is perpendicular to the flow. Three communicating holes 10, 11, and 13 are provided in a direction perpendicular to the fluid flow and in parallel with each other, and two adjacent communicating holes 10,
11 are connected approximately in the center by a passage 12, and a resistance wire 5 is stretched approximately in the center of this passage 12. By making the front side of the generator 2 a flat surface perpendicular to the flow, the separation points of the vortices can be aligned, and stable vortex release can be achieved.

According to the present invention, the following effects are produced.

(1) By adopting a structure in which multiple communication holes are provided in a direction almost perpendicular to the direction of fluid flow, the fluid is blown out from the communication holes from multiple locations in a direction perpendicular to the flow, and the vortex can promote the growth and involvement of
Due to the suction and blowout of the fluid in the multiple communicating holes, the suction and blowout of the individual communicating holes interfere with each other, and the suction and blowout are performed according to the separation, growth, and entrainment of the vortex, so that the vortex can be released regularly. can be performed stably. As described above, since a stable and strong vortex can be created, it is particularly effective when applied to a turbulent flow caused by intake pulsation, such as when measuring the intake air amount of an internal combustion engine.

(2) The structure is such that the resistance wire of the vortex detector is placed in a passage that connects approximately the center of two adjacent communication holes, which makes it possible to remove disturbances outside the vortex generator and prevent vortex release. A synchronized and stable signal can be obtained, and dust and the like will not adhere to the vortex detector, improving durability.

(3) By providing the opening of the communication hole on the entire side surface of the vortex generator, the vortex can be emitted stably, and a stable signal can therefore be obtained. This is because the vortex is released in layers over the entire side surface.

(4) By making the upstream side of the vortex generator a flat surface that is almost perpendicular to the flow, as in the example shown in Fig. 4, the vortex separation points can be aligned, resulting in stable vortex release. can be made to do so.

[Brief explanation of the drawing]

Figure 1 is a general explanatory diagram of Karman vortex flowmeter, Figure 2
The figure shows a conventional example in which a plurality of through passages are provided for the vortex generator, and FIGS. 3 and 4 are examples of the present invention, respectively, in which a is a cross-sectional view of the vortex generator, b is a side view, and c is a a
FIG. Explanation of symbols, 1...datato, 2...vortex generator,
3...Communication hole, 4,4'...Karman vortex, 5...
Resistance wire, 6... Alternating current, 7, 8... Through path, 9...
...arrows indicating flow, 10, 11, 13... communicating holes, 12... passages, 10', 11', 13'... openings.

Claims (1)

[Claims] 1. A Karman vortex flow meter that measures the flow rate or flow velocity by detecting the generation frequency or circumference of the Karman vortex generated by a vortex generator installed in a duct through which fluid flows with a vortex detector. , a plurality of communication holes are provided that communicate with both side surfaces of the vortex generator in a direction substantially perpendicular to the fluid flow, and each communication hole is provided in a substantially parallel direction. A Karman overflow meter characterized in that a vortex detector is provided in a passage connecting approximately the center of two adjacent communicating holes. 2. The Karman vortex flowmeter according to claim 1, wherein each of the plurality of communication holes is a communication hole having an opening extending over the entire length of the side surface of the vortex generator. 3. The Karman vortex flowmeter according to claim 1 or 2, wherein the vortex generator has a front surface having a flat surface perpendicular to the flow of the fluid.