JPH0620972Y2 - Vortex flowmeter - Google Patents

Description

TECHNICAL FIELD The present invention relates to a structure of a vortex generator in a vortex flowmeter.

2. Description of the Related Art The applicant of the present application discloses, in Japanese Patent Publication No. 55-40804, a vortex generating element provided in the direction of fluid flow, and a Karman vortex generating element plate having a desired thickness is integrally provided behind the vortex generating element. Furthermore, there has been proposed a Karman vortex forming device in which at least one or more Karman vortex generating element plates similar to those described above are arranged behind the Karman vortex generating element plate at desired intervals and independently of each other. The above-mentioned vortex generating element has a cross-sectional shape of an isosceles triangle having an apex on the flow axis, and one or more Karman vortex generating element plates provided at the rear of the vortex generated here. (Hereinafter, simply referred to as a flat plate), the vortex is developed to have an optimum strength, and the vortex is separated from the final flat plate. In this way, the vortex generated by the Karman vortex generating element can be developed as a sufficiently strong vortex, so that a stable vortex generator can be obtained.

Problems of the prior art In the above prior art, since the vortex amplification effect is obtained by arranging flat plates on the wake side of the vortex generator, separation from the final flat plate by selecting an appropriate number of flat plates. In this case, the fully developed vortex has been generated so far, so the time required for separation is shortened and the vortex with extremely stable frequency is generated. Had a problem that it had a positively increasing characteristic.

Means for Solving the Problems To solve the above problems, the present applicant has proposed that when the vortex generating element forming the vortex generator is arranged independently in a state where the vortex generator is arranged in the flow path. Focusing on the Reynolds number characteristic of the instrumental error, especially in the low Reynolds number region, when the vortex frequency ratio of each vortex generated from the upstream side vortex generator and the downstream side vortex generator is a predetermined ratio. did. For example, as a vortex generator including a plurality of vortex generators, an acute-angled isosceles triangular vortex generator having an apex on the above-mentioned flow axis and one or more flat plates on the downstream side of the vortex generator. In the case of the vortex generating element consisting of, the cross section of the upstream isosceles triangular vortex generating element has a bottom length of d and a height of 0.6d, and faces the flow of the flat plate at the final stage. The length in the direction is d, the thickness of the flat plate is 0.2 to 0.3d, and the space between the vortex generating elements is
When 0.1 to 0.9d is set, the ratio of the vortex frequency of the vortex independently generated from the final flat plate to the vortex frequency independently generated from the upstream vortex generating element is 0.7 to 0.9. It was confirmed that the Reynolds number instrumental error characteristic was obtained. Furthermore, as a result of testing the shape of the vortex generating element that satisfies the above frequency ratio, the cross-sectional shape of the upstream vortex generating element is arcuate with an arc on the upstream side, and the length in the direction facing the flow of the cross-sectional shape of the downstream vortex generating element. In the case of a T-shape having a base parallel to the chord of the bow and having a length substantially equal to the length of the chord and a side projecting to the downstream side, a constant instrumental error characteristic is obtained over a wide flow range. A vortex flowmeter with a gyro was realized.

Embodiment FIG. 1 is a side sectional view of a vortex flowmeter according to the present invention, and FIG. 2 is a plan sectional view, in which a vortex generating element 2a, 2b in a flow path 1 is vertically opposed to and parallel to a flow direction Q. It is arranged. The vortex generator 2a has an arcuate shape with a flow-facing arc, and has a semicircle with a diameter d ₁ in the figure. 2b is T-shaped, and the bottom has a width of d ₂ and is parallel to the chord of the vortex generating element 2a. Flat plates 2c having a width d ₂ are arranged at equal intervals between the vortex generating elements 2a and 2b. The widths d ₁ , d ₂ , d ₃ of the vortex generating elements 2a, 2b and the flat plate 2c are preferably equal to each other, and the interval t is a value of 0.1 to 0.9d. The vortex signal is converted into an electric signal by a vortex detector (not shown), shaped and amplified by the preamplifier 3, and processed. Although the flat plate provides a vortex amplification effect, the conventional vortex generator combining the triangular prism and the flat plate in the prior art has a characteristic that the instrumental error increases in the low flow region. The vortex frequency is proportional to the Strouhal number, but the Strouhal number becomes smaller as the vortex strength becomes stronger. Therefore, the vortex frequency becomes an inverse function of the vortex strength. When flat plates are combined, the vortex strength increases due to the vortex amplification effect, but the vortex strength of the triangular prism at the tip is low. In a vortex generator that combines these, each vortex characteristic affects each other,
In addition, since a combination of characteristics is generated in relation to the flow velocity, in the prior art as described above, the influence of the triangular prism at the tip is large in the low flow region, which is the device difference increasing characteristic in the low flow region. The Applicant, as stated earlier,
Set the vortex frequency ratio of the vortex generators on the downstream side and the upstream side to 0.7.
It was proposed to set the value to ~ 0.9, but in the present invention, the third
As shown in FIGS. 4 and 5, an arcuate vortex generating element (FIG. 3) having a chord length d ₁ facing the flow Q in the channel 1 and having a width d
Vortex frequency ratio of the vortex generating elements ₂ of T-shaped (FIG. 4) is in the range described above, the width _{d 1 =} d 2 ₌ d, the flat plate of width d _{3 =} d disposed in the central position , This interval t is 0.1 to 1.9
It was confirmed that when d is set, the flow rate is flat and the instrumental error characteristic is wide in a wide flow range from a small flow area to a large flow area. Also,
These properties are stable and emit strong eddy signals.

Effect As described above, according to the present invention, a highly accurate and stable vortex flowmeter with a small instrumental error can be realized in a wide flow range, that is, a wide Reynolds number range.

[Brief description of drawings]

FIGS. 1 and 2 are side and plan sectional views of the vortex flowmeter according to the present invention, and FIGS. 3 and 4 are used for explaining the present invention. The vortex generating elements 2a and 2b are used as flow paths. It is a figure which shows the case where it is arrange | positioned independently. 1 ... Channel, 2a ... Bow-shaped vortex generating element, 2b ... T-shaped vortex generating element, 2c ... Flat plate.

Claims (1)

[Scope of utility model registration request] 1. A vortex generator disposed in a flow path so as to face a flow is composed of a plurality of vortex generators having the same width facing the flow, and the cross-sectional shape of the vortex generator is sequentially arranged from upstream. A vortex flowmeter, wherein the vortex flowmeter has a bow shape having an arc facing the flow, a flat plate, and a T shape having a bottom portion parallel to the flat plate, and the vortex generating elements are arranged at predetermined intervals.