JP3142015B2 - Vortex flow meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a structure of a vortex flow meter, and more particularly to a structure of a vortex flow meter which is less affected by piping.

[0002]

2. Description of the Related Art As is well known, a vortex flow meter is a flow meter utilizing the fact that the number of Karman vortices flowing out of a vortex generator per unit time is constant over a wide range of Reynolds numbers. This relationship depends only on the Reynolds number, is not affected by the physical properties of the fluid, and has the same flow characteristics for liquids and gases, so it can be used not only as an industrial flow meter but also as an air flow meter for controlling automobile engines. Used. In addition, the vortex flowmeter has a simple structure in which a vortex generator is provided in the flow tube and vortex detection means for detecting the vortex flowing out of the vortex generator is used. The flow meter has a high characteristic and is inexpensive.

However, in order for the vortex generated from the vortex generator of the vortex flowmeter to be constant in a predetermined Reynolds number range as described above, the flow of the fluid flowing into the vortex flowmeter is an axially symmetric flow, The condition was that the condition for separation of the vortex flowing out of the vortex generator was kept constant. Generally, a fluid flowing through a flow tube includes a deviated flow and a swirling flow.In order to make the fluid an axisymmetric flow, a rectifying device is disposed on the upstream side, and the rectifying device removes the deflected flow and the swirling flow. Piping conditions for providing a straight pipe section of a predetermined length on the downstream side are also required. If there is no rectifier, a straight pipe section is provided on the upstream side, and the straight pipe section has a length sufficient to attenuate and remove the drift or swirl flow contained in the flow by the viscosity of the pipe wall surface and the fluid itself. Stipulated.

In evaluating the stability of vortex generation in a vortex flowmeter, the number of vortices generated per unit time, that is, the Strauhal, which is a proportional constant of the vortex frequency to the flow velocity, within a predetermined Reynolds number range. The rate of change of the number or the rate of change of the meter constant (the number of vortices generated per unit volume) is investigated. Conventional vortex flowmeters are susceptible to piping with fluctuations in flow velocity distribution, and the flow of the fluid to be measured flowing into the vortex flowmeter must have a normal distribution, as described above, for stable and accurate flow measurement. was there. However, the upstream straight pipe length L for obtaining a predetermined measurement accuracy is not uniquely determined for all vortex flow meters, but is determined by the shape and dimensions of the vortex generator. Although the upstream straight pipe length L is dimensionlessly displayed as a multiple (L / D) of the pipe inner diameter D, in a vortex flow meter of a system in which a vortex generator having a uniform cross-sectional shape is fixedly supported on both ends on a cylindrical body. , L / D greatly changed the instrumental difference (flow rate characteristic indicating the accuracy with respect to the flow rate).

FIG. 3 is a diagram showing the deviation of the instrumental error due to the L / D of the vortex flowmeter. The horizontal axis represents L / D and the vertical axis represents the instrumental error deviation.
The instrumental error deviation shown is based on L / D = 100.
The instrumental error curve A shows an example of a conventional vortex flowmeter, and an instrumental error occurs in the plus direction in the range of L / D = 10 to 30 tested. For this reason, a similar instrument error deviation tendency is expected as a piping system on the rectifier and the extension of the instrument error deviation curve in the range where the test was performed. There is a problem that a long straight pipe section is required and the device becomes large.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a vortex flowmeter having a simple structure and a flow rate characteristic which is hardly affected by piping.

[0007]

To achieve the above object, the present invention provides (1)
In a vortex flowmeter comprising a tubular main body and a vortex generator fixed at both ends on a diameter inside the main body and obtaining a flow rate from the number of vortices generated per unit time, in the vicinity of the both ends fixed position of the vortex generator A through-hole penetrating in the flow direction is provided. (2) In the above (1), the cross-sectional shape of the through-hole penetrating in the flow direction in the vicinity of both ends of the vortex generator is circular. It is what it was. Hereinafter, a description will be given based on examples of the present invention.

FIGS. 1A and 1B are views for explaining an embodiment of a vortex flowmeter according to the present invention. FIG. 1A is a view as viewed from the flow direction, and FIG. View A in FIG.
It is -A sectional drawing. In the figure, 1 is a main body (circular pipe), 1a is a pipe wall, 2 is a vortex generator, and 3, 3 are through holes.

In the figure, a vortex generator 2 is fixed in a main body 1 on a diameter of a cross section of a circular pipe of the main body 1 by a double-supporting method. The cross-sectional shape of the vortex generator 2 may be a circle, a triangle, a trapezoid, or any other shape.
The bottom is disposed facing the upstream side. In the vicinity of both fixing positions of the vortex generator 2 to the main body 1, through holes 3, 3 having a circular cross section penetrating from the upstream side to the downstream side of the vortex generator 2 are provided.
The vortex flowmeter has the same inner diameter D as the main body 1 (not shown).
Used coaxially. Karman vortices are generated from the vortex generator 2, and the Karman vortices alternately form vortex tubes and peel off from both side walls of the vortex generator 2, but the vortex tubes extend from all sides over the length D of the vortex generator 2. Rather than peeling, the vortex tube closes in the central area of about 0.65D and peels off. The dead water area due to the dynamic pressure generated on the front surfaces of the both ends of the vortex generator 2 that influences the vortex tube is exerted on both ends of the vortex generator 2 that separates the vortex tube. Fluid flows, such as drifting and swirling flows, in the pipeline also cause changes in the dead water areas at both ends, so changes in pressure in the dead water areas affect the vortex tubes. The through holes 3, 3 reduce the pressure in the dead water area and stably generate Karman vortices.

The instrumental difference curve B shown in FIG. 3 is a vortex flowmeter having the same shape and dimensions as a conventional vortex flowmeter, in which the vortex generator 2 of the vortex flowmeter of the present invention has through holes 3,3. It shows an example of an instrument difference deviation curve. This is the instrumental error at a constant flow rate based on L / D = 100. In the range of L / D = 10 to 30, almost no difference is observed from the standard instrumental error.

FIGS. 2 (a) and 2 (b) show another embodiment of the vortex flowmeter of the present invention. FIG. 2 (a) is a diagram viewed from the flow direction, and FIG. It is an arrow AA sectional view of (a). In the drawing, 4 is a main body, 4a is an inner wall surface, 5 is a vortex generator, 5a is a flange, 5b is an inner surface, and 6, 6 are through holes.

The illustrated vortex generator 5 and the vortex generator 2 shown in FIG. 1 differ from each other in the shape of the vortex generator 5 and the method of fixing it to the main body 1. The vortex generator 1 of FIG.
2 has an end portion and is fixed at the end portion 1a.
In (2), the end of the vortex generator 5 is a cylindrical flange 5a, and is fixed to the main body 4 by the flange 5a. The inner surface portion 5b of the flange portion 5a is a flat surface, and both end portions are the inner wall 4a of the main body.
Dimensions are selected so that they touch. Accordingly, the central portion of the flange 5a protrudes from the tube wall 4a of the main body 4. Therefore, the through hole 6 penetrates the projecting portion of the flange 5 a in the axial direction of the main body 4. The function of the through holes 6 and 6 in FIG. 2 is the same as that of the through holes 3 and 3 in FIG. Can reduce the influence of the flow distribution.

[0013]

As is clear from the above description, the simple structure in which the through holes penetrate in the flow direction near both ends of the vortex generator is hardly affected by the piping, and changes even with a short upstream straight pipe. It is possible to provide a vortex flowmeter having a flow characteristic that does not have any problem.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining one embodiment of a vortex flowmeter of the present invention.

FIG. 2 is a diagram showing another embodiment of the vortex flowmeter of the present invention.

FIG. 3 is a diagram showing a deviation of an instrumental error of a vortex flow meter when L / D = 100 is used as a reference.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Body (circular channel), 1a ... Pipe wall, 2 ... Vortex generator, 3,
3 ... through-hole, 4 ... body, 4a ... inner wall surface, 5 ... vortex generator, 5
a ... flange, 5b ... inner surface, 6, 6 ... through-hole.

Continued on the front page (72) Inventor Yoshiya Terao 1-4-4 Umezono, Tsukuba, Ibaraki Pref., National Institute of Metrology (72) Inventor Hiroshi Kawaon 3-10-8 Kamiochiai, Shinjuku-ku, Tokyo Global equipment industry stock In-house (72) Inventor Katsuo Triangle Masayuki Mori, Examiner, Oval Equipment Industry Co., Ltd. 3-10-8, Kami-Ochiai, Shinjuku-ku, Tokyo (58) Field surveyed (Int.Cl. ⁷ , DB name) G01F 1 / 32

Claims (2)

(57) [Claims] 1. A vortex flowmeter comprising a tubular main body and a vortex generator fixed at both ends on a diameter inside the main body, wherein the flow rate is determined from the number of vortices generated per unit time. A vortex flowmeter characterized by providing a through hole in the flow direction in the vicinity of the fixed position at both ends. 2. The vortex flowmeter according to claim 1, wherein a cross-sectional shape of a through-hole penetrating in the flow direction near both ends of the vortex generator is circular.