JPH01136024A - Vortex flowmeter - Google Patents

Abstract

PURPOSE:To realize a vortex flowmeter having a good characteristic, by distributing a fluid to be measured by a distributor to bring the same to a turbulent flow state and subsequently measuring the flow speed of the fluid to be measured by the vortex generator arranged to a downstream piping. CONSTITUTION:The low flow speed fluid 2 low in a Reynolds' number of a pipeline 1 flows in a flow smoother 3 in a laminar flow or turbulent flow state. After the fluid 2 to be measured is distributed by the smoother 3 to be brought to the turbulent flow state, the flow speed of the fluid 2 to be measured is measured by the vortex generator 4 arranged on the downstream side. As mentioned above, by adapting the smoother 3 consisting of a disc-shape distribution plate main body 31 and the through-holes 32 provided thereto, the discharge of a vortex of 1 X 10<3> <= Reynolds' number <= 2 X 10<4> is stabilized and linearity is improved. As a result, the magnitude (amplitude) of a vortex signal is increased by about 5 times or more within a range of 1 X 10<3> <= Reynolds' number Re <= 2 X 10<4> and the vortex signal can be stabilized.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to improving the flow characteristics of a vortex flowmeter in a low Reynolds number region using a perforated plate. As for the flow rate characteristics, as shown in FIG. 7, when the Reynolds number is less than 5X103, the vortex shedding becomes unstable, so the lower limit of the operable range was about 5X103.

<Problems to be solved by the invention> Therefore, (1) When measuring high viscosity fluids such as chemical fluids and oil with a vortex flow meter, the measurement range is narrow and Reynolds number < 5
There is a problem that measurement at 10' is not possible.

(2) When the Reynolds number is 2×10' or less, as shown in FIG. 7, there is a problem that the K factor ((vortex frequency)/(flow rate)) increases rapidly and the linearity deteriorates.

The present invention solves this problem.

An object of the present invention is to provide a vortex flowmeter with good characteristics by reducing the Reynolds number near the lower measurement limit, lowering the measurable lower limit and widening the measurable range, and improving linearity near the measurement lower limit. be.

Means for Solving the Problems To achieve this object, the present invention provides a rectifying device that is provided in a pipe through which a measuring fluid flows and acts to rectify the measuring fluid, and a rectifying device that is disposed downstream of the rectifying device. In a vortex flowmeter comprising a vortex generator, the vortex generator has a ratio of (width dimension facing the flow of the vortex generator)/(pipe inner diameter) of 0.2 to 0.3, and a current plate main body. The rectifying plate body is divided into at least three equal area parts and the orifice pressure loss formula is used to give a pressure loss inversely proportional to the laminar flow velocity distribution of the measured fluid to create a turbulent flow velocity distribution. The vortex flow meter is characterized in that it comprises a rectifying device including a plurality of through holes provided in the rectifying plate body so as to have an aperture ratio determined by the flow rate meter.

Effect> In the above configuration, the low flow velocity fluid with a low Reynolds number flows into the rectifier in a laminar flow or turbulent flow state. After the flow is rectified into a turbulent state by the rectifier, the flow velocity of the measurement fluid is measured by a vortex generator disposed downstream.

Hereinafter, a detailed explanation will be given based on examples.

<Example> FIG. 1 is an explanatory diagram of the configuration of an embodiment of the present invention.

In the figure, 1 is a conduit through which a measuring fluid 2 flows, and 3 is a rectifier. The rectifying device 3 consists of a disc-shaped rectifying plate main body 31 and a through hole 32 (described later) provided in the rectifying plate main body 31, 4 is a vortex generator, and 5 is the number of vortices generated by the vortex generator 4. 6 is an output terminal of a conversion circuit which converts a signal corresponding to the signal into an output signal.

In the above configuration, the low flow velocity fluid 2 with a low Reynolds number
flows into the rectifier 3 in a laminar or turbulent state.

After being rectified into a turbulent state by the rectifier 3, the flow velocity of the measurement fluid 2 is measured by the vortex generator 4 disposed downstream.

By the way, in a conventional vortex flowmeter, the relationship between the vortex shedding mechanism and linearity is as follows.

(1) When the Reynolds number Re≧2X10', the second
As shown in the figure, since the flow has a turbulent flow velocity distribution, the flow velocity distribution B becomes almost flat right next to the vortex generator 2 due to the occlusion effect of the vortex generator.

Therefore, the vortex shedding is stable and has good linearity.

However, in order to provide the above-mentioned flat flow velocity distribution, (dimension of the width of the vortex generator facing the flow)/(pipe inner diameter) is 0.2.
A value of ~0.3 is required, and vortex generators with a single vortex current, which are commercialized for use in circular pipes, have a hollow value.

(2) When the Reynolds number Re≦2XLO', the flow velocity distribution cannot be flattened only by the above-mentioned occlusion effect, but since the degree of bending of the yarn is small, vortex shedding is possible. However, the linearity deteriorates.6 (3) When the Reynolds number Re≦5X10', the flow of the measured fluid approaches the flow velocity distribution C of laminar flow.

For this reason, as shown in FIG. 3, the curvature of the yarn becomes large D, making it difficult to release the vortex.

In the present invention, the disc-shaped current plate main body 31 and the a current plate main body 31
By applying the rectifying device 3 consisting of the through hole 32 provided in the flowchart, the vortex shedding is stabilized and the linearity is improved when I×103≦Reynolds number≦2×10′.

For this purpose, a disc-shaped rectifying plate main body 31 and a rectifying plate main body 31 are used to convert the flow velocity distribution of laminar flow (Reynolds number Re of 1×103) into the flow velocity distribution of turbulent flow (Reynolds number Re of 2XIO'). A rectifier 3 consisting of a through hole 32 provided is used.

Here, the rectifier 3 is designed as follows.

As shown in FIG. 4, the ¥11fL plate main body 31 is divided into n equal parts so that each part has an equal area. In this case, the area is concentrically divided into three equal parts such that area St=area S2=area S.

Further, as shown in FIG. 5, the average flow velocity of each portion is set as 1 to 2 on the upstream side and Va to vb on the downstream side of the current plate main body 31.

At this time, the aperture ratio m of the area S, ~S, of the current plate main body 31
l~m3 respectively V, -+Va, V2-*Vb, ■3→V
Determine it to be C. The opening ratios m and ~m3 can be obtained from the empirical formula of the orifice by giving 1 to the pressure drop coefficient that gives the above flow velocity distribution, respectively, if each part is approximately regarded as an orifice. .

Here, in FIG. 5, the laminar flow velocity distribution on the upstream side of the rectifier 3 is expressed by the following equation.

+11=UL (1-(r/R) 2 )uL
; Flow velocity UL at distance r; Maximum flow velocity R; Radius r of pipe line 1 ; Arbitrary radial position The turbulent flow velocity distribution on the downstream side of the rectifying device 3 is expressed by the following equation.

uv = UT (1(r/R) I'')n=21
09 (Re/10) 11T; Flow velocity UT at distance r, maximum flow velocity R; Radius r of pipe 1: radial position of iF Re: Reynolds number As a result, the above rectifying device 3 is used. By this,
t:<t o'≦Reynolds number Re≦2X104
Within this range, it is possible to increase the amplitude of the vortex signal to about 51Δ or more and stabilize the vortex signal.

The dest data is shown in Fig. 6. Fig. 6 is an example of the vortex waveform at a Reynolds number Re of 2600.
(A) Figure shows the case without current flow device 3, (B) Figure shows the case with rectifier 3, (A) The X part in the figure shows that the transient type is unstable, (A) Figure vortex frequency fva:Q
, 71 [z, amplitude Va is approximately 0.02 V, vortex frequency fvb in figure (B): 0.62 Hz - @ width vb is approximately 0.1
■It is.

<Effects of the Invention> As explained above, the present invention includes a rectifier that is provided in a pipe through which a measurement fluid flows and acts as an Na effect on the measurement fluid, and a vortex generator disposed downstream of the rectification device. In a vortex flowmeter, (width dimension facing the flow of the vortex generator)
The vortex generating body (pipe inner diameter) is 0°2 to 0.3, and the pressure loss is inversely proportional to the laminar flow velocity distribution between the baffle plate body and the measured fluid to create a turbulent flow velocity distribution. The baffle plate body is divided into at least three equal area parts, and a plurality of through holes provided in the baffle plate body are formed so that an open ratio of 1 is determined using an orifice pressure loss formula. A vortex flowmeter is constructed, characterized in that it is equipped with a rectifying device.

As a result, by using the rectifier of the present invention,
In the range of I Xt o'≦Reynolds number Re≦2X104, the magnitude (amplitude) of the vortex signal can be increased by about 5 times or more, and the vortex signal can be stabilized.

Therefore, according to the present invention, by reducing the Reynolds number near the lower measurement limit, lowering the measurable lower limit and widening the measurable range, and improving the linearity near the lower measurement limit, a two-meter eddy current meter with good characteristics is realized. You can.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the configuration of one embodiment of the present invention, and FIGS. 2 to 5
FIG. 6 is an explanatory diagram of the operation of FIG. 1, FIG. 6 is an explanatory diagram of the effect of FIG. 1, and FIG. 7 is an explanatory diagram of the configuration of a conventional example that has been generally used. l...Pipeline, 2...Measurement fluid, 3...Third flow device,
4... Vortex generator, 5... Conversion circuit, 6... Output terminal. -2' Figure 1 Figure 2 Figure 3 Figure 4 Figure 6

Claims (1)

[Claims] In a vortex flowmeter, the vortex flowmeter is equipped with a rectifying device installed in a pipe through which the measured fluid flows and has a rectifying effect on the measured fluid, and a vortex generator disposed downstream of the rectifying device. A turbulent flow velocity is created by applying a pressure loss inversely proportional to the laminar flow velocity distribution of the current plate body and the measured fluid, using a vortex generator with a ratio of 0.2 to 0.3 (width dimension)/(pipe inner diameter). A plurality of through holes are provided in the current plate body so that the current plate body is divided into at least three equal area parts so as to have an opening ratio determined using an orifice pressure loss formula. A vortex flow meter characterized by comprising a rectifier having a hole.