JP2017181230A - Flow measuring device - Google Patents

Abstract

An object of the present invention is to suppress the generation of vortices in the wake of a multilayer section in a flow meter using a multilayer divided flow path configuration. A flow path 2 having a rectangular cross section through which a fluid to be measured flows, partition plates 3, 4, 5 that divide the flow path 2 into a plurality of divided flow paths 6, 7, 8, and partition plates 3, 4, 5 is provided with an opening 5a, and the openings 5a communicate with the divided flow paths adjacent to each partition plate to eliminate the boundary layer developed in each divided flow path, thereby dividing the flow paths 6, 7, 8 Suppresses the generation of vortices that occur when the flows flowing out of [Selection] Figure 1

Description

  The present invention relates to a flow rate measuring device that measures a flow rate by dividing a flow into multiple layers, and more particularly, to a method of suppressing the generation of vortices in the wake of a multilayer portion.

  2. Description of the Related Art Conventionally, a method for changing the state of occurrence of a wake vortex in a pipeline placed in a flow is known (for example, see Patent Document 1).

  FIG. 6 is described in Patent Document 1. In FIG. 6, a through-hole 102 is provided on the downstream side of a pipe line 101 placed in a flow F1. The flow toward the pipe 101 is divided into an internal flow F2 inside the pipe 101 and an external flow F3 outside. These flows form a flow velocity distribution as indicated by D due to the influence of the boundary layer that develops on the boundary surface of the pipe 101.

  When there is no through-hole 102, an annular vortex that is circular with respect to the central axis of the pipe line 101 is generated, but when there is a through-hole 102, this annular vortex does not become circular as shown by V, The shape is shifted in the flow direction. As a result, the vortex further collapses into a discrete vortex as indicated by W on the downstream side. That is, compared with the case where no through hole is provided, the ratio of the discrete vortex occupying the vicinity of the outlet of the pipe line 101 is reduced, so that the upstream side is hardly affected.

JP-A-11-287686

  However, since the conventional configuration is not intended to eliminate the boundary layer developed on the wall surface of the pipe, it has a problem that the generation of discrete vortices cannot be avoided.

  The present invention solves the above-mentioned conventional problems, and has a configuration in which an opening is provided to eliminate the boundary layer developed from the upstream side over the entire area of the partition plate that divides the rectangular cross-section flow path into a plurality of parts. Thus, the object is to suppress the generation of vortices at the rectangular cross-section flow path outlet.

  In order to solve the conventional problem, a flow rate measuring device of the present invention includes a flow path having a rectangular cross section through which a fluid to be measured flows, a partition plate that divides the flow path into a plurality of divided flow paths, and at least one A flow rate sensor arranged to detect a flow rate in the divided flow path, a measurement unit for measuring a signal from the flow rate sensor, and a calculation unit for processing a signal from the measurement unit to calculate a flow rate. The partition plate has an opening that communicates between the adjacent divided flow paths, and the opening has a height and a width such that a boundary layer in the adjacent divided flow paths is substantially eliminated by the opening. Therefore, it is possible to suppress the generation of vortices that can be generated in the wake of the multilayer portion, and to avoid the adverse effect of the flow in the portion disposed in the wake.

  The flow rate measuring device of the present invention can eliminate the developed boundary layer by providing an opening in a plate that divides the flow path in the divided flow path divided into multiple layers. Can be suppressed. This does not adversely affect the fluid portion downstream from the multilayer portion.

1 is a schematic configuration diagram of a flow rate measuring device according to Embodiment 1 of the present invention. 1 is a cross-sectional view taken along the line AA ′ of FIG. 1 in Embodiment 1 of the present invention. The perspective view of the partition plate in Embodiment 1 of this invention (A) Flow velocity distribution diagram of BB 'cross section when there is no opening, (b) Flow velocity distribution diagram of BB' cross section when there is an opening in the first embodiment of the present invention. Enlarged view of part Q in FIG. Diagram showing conventional annular vortex generation

  In a first aspect of the invention, a flow path having a rectangular cross section through which a fluid to be measured flows, a partition plate that divides the flow path into a plurality of divided flow paths, and a flow velocity in at least one of the divided flow paths are detected. A flow rate sensor disposed; a measurement unit that measures a signal from the flow rate sensor; and a calculation unit that calculates a flow rate by processing a signal from the measurement unit, wherein the partition plate is adjacent to the divided flow. An opening that communicates between the roads, and the opening has a height and a width such that a boundary layer in the adjacent divided flow path is substantially eliminated by the opening. The generation of vortices that can be generated can be suppressed, and the adverse effect of the flow in the portion arranged in the wake can be avoided.

  In the second invention, particularly in the first invention, since the opening is provided in the vicinity of the outlet portion of the partition plate, the boundary layer is not reconfigured. Can be suppressed.

  According to a third aspect of the invention, in particular, in the first or second aspect of the invention, the flow velocity sensor is configured by a pair of ultrasonic transducers, so that the entire flow cross section of the divided flow path is measured. Even if the flow on the upstream side of the opening is slightly affected, a large error does not occur.

  According to a fourth aspect of the present invention, in the first or second aspect of the invention, since the flow rate sensor is configured by a flow sensor, the second flow rate sensor is closer to the opening than when the flow rate sensor is a flow rate sensor using ultrasonic waves. Since the flow sensor can be arranged on the upstream side of the ultrasonic transducer, the influence on the measurement is less than that of the flow rate sensor using ultrasonic waves.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
The first embodiment will be described with reference to FIGS.

  FIG. 1 is a schematic configuration diagram of a flow rate measuring device 1 according to Embodiment 1 of the present invention. A cylindrical channel (channel) 2 having a rectangular cross section is divided into a first divided channel 6 and a second divided channel by a first partition plate 3, a second partition plate 4, and a third partition plate 5. 7, the third divided flow path 8 and the fourth divided flow path 9 are divided into a multilayer flow path 30 as a whole.

  Three rectangular openings 5 a are provided on the downstream side of the third partition plate 5, and the third divided flow path 8 and the fourth divided flow path 9 are communicated with each other through the openings 5 a.

  Although not shown in the drawing, the same opening is provided in the same position and the same shape as the third partition plate 5 in the first partition plate 3 and the second partition plate 4 respectively. The first divided flow path 6 and the second divided flow path 7, and the second divided flow path 7 and the third divided flow path 8 are formed so as to communicate with each other through these openings. The opening provided in the partition plate 3 is 3a, and the opening provided in the second partition plate 4 is 4a.

  In the flow path 2, an ultrasonic transducer holder 10 is attached to the upper part of the third divided flow path 8. The third divided flow path 8 is a flow path for measuring the flow rate. Hereinafter, the third divided flow path 8 is referred to as a measurement flow path 8, and the divided flow paths other than the measurement flow path 8 are referred to as non-measurement flow paths.

  FIG. 2 is a view showing the AA ′ cross section of FIG. 1, and the configuration and measuring method of the flow rate measuring apparatus 1 using ultrasonic waves will be described below with reference to FIG.

  The ultrasonic transducer holder 10 has a pair of ultrasonic transducers, a first ultrasonic transducer 11 disposed on the upstream side and a second ultrasonic transducer 12 disposed on the downstream side. Are held by the first holding unit 13 and the second holding unit 14, respectively.

  The first ultrasonic transducer 11 and the second ultrasonic transducer 12 constitute a flow rate sensor 50.

  The measurement channel 8 has an upper surface 15 and a lower surface 16. The upper surface 15 has a first ultrasonic transmission window 17 and a second ultrasonic transmission window 18. The lower surface 16 is configured to act as an ultrasonic reflection surface.

  The arrows indicated by P1 and P2 are ultrasonic wave propagation paths, and propagate so as to cross the measurement channel 8 diagonally.

  Signals from the first ultrasonic transducer 11 and the second ultrasonic transducer 12 are processed by the measurement circuit 20 (measurement means) and further calculated by the calculation circuit 21 (calculation means) to calculate the flow rate. Is done.

  The flow path portion including the second partition plate 4 is referred to as a multilayer portion 22. The first ultrasonic transducer 11, the second ultrasonic transducer 12, the multilayer unit 22, the measurement circuit 20, and the arithmetic circuit 21 form the flow rate measuring device 1.

  Next, flow measurement using ultrasonic waves will be described with reference to FIG.

  The flow velocity of the fluid to be measured flowing through the measurement flow path 8 is V, the sound velocity in the fluid to be measured is C, and the angle between the direction of flow of the fluid to be measured and the ultrasonic wave propagation direction until the ultrasonic wave is reflected by the lower surface 16 is θ. And Also, let L be the effective length of the propagation path of the ultrasonic wave propagating between the first ultrasonic transducer 11 and the second ultrasonic transducer 12.

  At this time, the propagation time t1 until the ultrasonic wave emitted from the first ultrasonic transducer 11 reaches the other second ultrasonic transducer 12 is expressed by the following equation.

t1 = L / (C + Vcos θ) (1)
Next, the propagation time t2 until the ultrasonic wave emitted from the second ultrasonic transducer 12 reaches the other first ultrasonic transducer 11 is expressed by the following equation.

t2 = L / (C−Vcos θ) (2)
When the sound velocity C of the fluid to be measured is deleted from the equations (1) and (2), the following equation is obtained.

V = (L / (2cos θ)) ((1 / t1) − (1 / t2)) (3)
As can be seen from Equation (3), if L and θ are known, the flow velocity V is obtained using the propagation times t1 and t2 measured by the measurement circuit 20.

  Next, as shown in the following equation, the flow rate Q of the entire flow path 2 is calculated by multiplying the flow velocity V by the cross-sectional area S of the flow path 2.

Q = V X S
However, in general, the flow velocity V of the measurement flow path 8 is different from the average flow speed Vave of the entire flow path 2, so the actual flow rate Qt is multiplied by the correction coefficient k as shown in the following equation. Ask.

Qt = k X Q
FIG. 3 is a perspective view of the third partition plate 5 of the present invention.

  The third partition plate 5 is formed with three rectangular openings 5a as already shown. The width La and the height Lb of the opening 5a have such values that the boundary layer developed on the upstream side is almost eliminated. That is, La has such a length that the boundary layer is eliminated in the flow direction.

  Further, Lb has such a ratio that the length of 3Lb occupies, for example, 90% or more with respect to the total length W in this direction, and the boundary layer is eliminated by the opening 5a. It is set to take a value that occupies a range that covers the entire area.

  The distance Lc from the opening 5a to the downstream end is appropriately set to a length that does not develop a boundary layer that has an effect.

  Further, the crosspieces 5b between the openings 5a are provided to ensure the strength against deformation of the openings 5a. If the strength of the openings 5a can be ensured, it is desirable to eliminate the crosspieces 5b and make one opening.

  FIG. 4 shows the flow velocity distribution of each divided layer in the BB ′ cross section of FIG. 1, where (a) shows a case where there is no opening, and (b) shows a case where there is an opening.

  When there is no opening shown in FIG. 4A, the flow velocity distribution at the inlet 23 where the flow path 2 is divided shows a flat shape, but a boundary layer develops while flowing through the multilayer part 22. The multi-layer outlet 24 has a parabolic flow velocity distribution.

  When the flow velocity distribution is larger than a certain level, the flow pattern fluctuates such that each jet flow is attracted or dispersed after leaving the multilayer portion 22. For the sake of clarity, when a state in which the main flow portion in the vicinity of the maximum flow velocity of the flow velocity distribution flows is displayed, at a certain moment, the state becomes large to meander as shown in S, and unstable such that a vortex is generated between the jets. Become a flow.

  And this flow has a bad influence with respect to the fluid apparatus etc. which are arrange | positioned downstream of a measurement part. Especially when the pressure needs to be measured downstream, an unfavorable situation is caused.

  On the other hand, when there is an opening shown in FIG. 4 (b), the developed boundary layer is once eliminated due to the presence of the openings 3a, 4a, and 5a. Instead of the flow velocity distribution, the flow velocity distribution has a flat portion and the core portion of the jet is in close proximity.

  In this case, when a state in which the main flow portion in the vicinity of the maximum flow velocity of the flow velocity distribution flows is displayed, a state as indicated by T is obtained, and an unstable state as shown in FIG.

  FIG. 5 is an enlarged view of a portion Q in FIG. 4B, and as shown in the figure, the flow passing between the second partition plate 4 and the third partition plate 5 flows through the openings 4a and 5a. On the upstream side, a parabolic flow velocity distribution in which a boundary layer is developed as indicated by U in the figure is shown. However, the developed boundary layer is eliminated by the absence of walls when passing through the openings 4a, 5a. Therefore, on the downstream side of 4a and 5a, a relatively flat flow velocity distribution as shown in FIG.

  In the present embodiment, an opening is set only on the downstream side. However, for applications in which pulsation occurs in the flow and reverse flow occurs, the downstream side when the reverse flow occurs, That is, by providing an opening on the upstream side in the forward flow, the generation of vortices can be suppressed for both the forward and reverse flows.

  In this embodiment, a configuration in which a pair of ultrasonic transducers is provided in the upper part of the flow path and the flow velocity is measured by using the propagation time of a method (so-called V path) in which the ultrasonic waves are reflected on the opposing inner walls. However, it may be a so-called Z path in which a pair of ultrasonic transducers are provided facing each other.

  Moreover, the measurement of the flow velocity is not limited to this, and it goes without saying that, for example, a flow sensor may be provided as a flow velocity sensor to measure the flow velocity.

  As described above, since the flow rate measuring device according to the present invention can suppress the generation of vortices generated on the downstream side of the multilayer measuring unit, the influence on the components and the like arranged on the downstream side of the measuring unit may be reduced. it can. For this reason, it can be applied as a gas meter having an outlet channel on the downstream side of the measuring unit or an industrial flow meter arranged in a piping system.

1 Flow rate measuring device 2 Tubular channel (channel)
DESCRIPTION OF SYMBOLS 3 1st partition plate 4 2nd partition plate 5 3rd partition plate 3a, 4a, 5a Opening 6 1st divided flow path 7 2nd divided flow path 8 3rd divided flow path (measurement flow path)
9 Fourth Divided Channel 11 First Ultrasonic Transceiver 12 Second Ultrasonic Transceiver 20 Measuring Circuit (Measuring Means)
21 Arithmetic circuit (calculation means)
24 outlet 50 flow velocity sensor

Claims (4)

A flow path having a rectangular cross section through which the fluid to be measured flows;
A partition plate for dividing the flow path into a plurality of divided flow paths;
A flow rate sensor arranged to detect a flow rate in at least one of the divided flow paths;
Measuring means for measuring a signal from the flow velocity sensor;
Computing means for processing the signal from the measuring means to calculate the flow rate,
The partition plate has an opening communicating between the adjacent divided flow paths,
The opening is a flow rate measuring device having a height and a width such that a boundary layer in the adjacent divided flow path is substantially eliminated by the opening. The flow rate measuring device according to claim 1, wherein the opening is provided in the vicinity of an outlet portion of the partition plate. The flow rate measuring device according to claim 1, wherein the flow velocity sensor is configured by a pair of ultrasonic transducers. The flow rate measuring device according to claim 1, wherein the flow velocity sensor is configured by a flow sensor.