JP2004264064A - Ultrasonic flow meter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve measurement accuracy of a flow rate measuring apparatus and to adapt to alterations in specifications etc. <P>SOLUTION: In a measuring part 1, a fluid supply path 3 is connected to an upstream side, and a fluid outflow path 5 is connected to a downstream side. The inside of a measuring flow path 15 is divided into a plurality of laminar flow paths 22a-22d. The measuring part 1 includes the measuring flow path 15 and is provided with both ultrasonic transducers 13 and 14 for measuring the flow velocity of the fluid flowing through the laminar flow paths of the measuring flow path 15 and a computing means 19 for computing the quantity of a fluid on the basis of output of the ultrasonic transducers 13 and 14. The measuring flow path 15 is constituted as an separate body from the measuring part 1. Therefore it is possible to separately handle the measuring flow path 15. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ultrasonic flow rate measuring device that measures a flow rate of a gas or the like.
[0002]
[Prior art]
As shown in FIG. 7, a conventional flow measuring device of this type includes a pair of ultrasonic transducers and the like in a measuring flow path 53 in which a fluid supply path 51 is connected to an upstream side and a fluid outflow path 52 is connected to a downstream side. The flow rate detecting means consisting of
[0003]
Further, the inside of the measurement flow path 53 is divided by a plurality of partition plates 54 so that the fluid has a two-dimensional laminar flow.
[0004]
Then, the flow velocity of the fluid flowing through the measurement flow path 53 is measured by the flow velocity detecting means, and the flow rate is calculated based on the measured flow velocity (Patent Document 1).
[0005]
[Patent Document 1]
JP-A-9-43015
[Problems to be solved by the invention]
However, in the above-mentioned conventional flow measuring device, since the flow path and the measuring unit are integrated, measures for improving the accuracy, for example, high-precision processing is difficult, and the flow path specification when the measurement specification is changed. Changing was not easy either.
[0007]
The present invention solves such a conventional problem, and realizes high accuracy of measurement by rationally configuring a measurement unit, and can surely respond to a specification change or the like. It was made.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a measuring section in which a fluid supply path is connected to an upstream side and a fluid outflow path is connected to a downstream side, a measuring flow path body included in the measuring section, At least one pair of ultrasonic transducers for measuring the flow velocity of the fluid flowing through the flow path body, and arithmetic means for calculating the amount of fluid flowing through the measurement flow path body based on the output of the ultrasonic transducer. The measurement flow path body is configured separately from the measurement unit, and the inside is divided into a plurality of laminar flow paths. Thus, the measurement flow path body is separate from the measurement unit. Since it is configured, the measurement flow path body can be processed independently, and the high precision can be promoted.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention relates to a measuring section in which a fluid supply path is connected to an upstream side and a fluid outflow path is connected to a downstream side, a measuring flow path body included in the measuring section, and a flow velocity of a fluid flowing through the measuring flow path body. At least one pair of ultrasonic transducers for measuring the flow rate, and calculating means for calculating the amount of fluid flowing through the measurement flow path body based on the output of the ultrasonic transducer, the measurement flow path body Has a structure separate from the measuring unit and is divided into a plurality of laminar flow passages.
[0010]
As described above, since the measurement flow path body is configured separately from the measurement unit, the measurement flow path body can be processed independently to promote high precision, and the specification can be easily changed. It becomes.
[0011]
If the flow velocity detecting means is arranged on the measurement section side, the handling of the measurement flow path body is further facilitated.
[0012]
The laminar flow passage is defined by a plurality of partition plates. Further, the measurement flow path body is a rectangle having a rectangular cross section, and a short side is divided by the plurality of partition plates.
[0013]
In the laminar flow passage, the spacing between the partition plates is selected so as to be set in the boundary layer region of the fluid flow, so that the laminar flow passage is not affected by external factors.
[0014]
The flow velocity measurement by the ultrasonic transducer may be performed not on the whole of the plurality of laminar flow paths but on at least a part of the laminar flow paths. For example, the flow velocity of a fluid having an even number of laminar flow paths and flowing through two adjacent laminar flow paths located at the center is measured.
[0015]
In addition, at least one pair of ultrasonic transducers face each other so that the ultrasonic waves cross the fluid diagonally, and the laminar flow passage in the measurement channel has a length corresponding to the ultrasonic transmission and reception area of the ultrasonic transducer. Is set, the flow resistance of the partition plate or the like can be reduced as much as possible.
[0016]
Furthermore, by forming the opening end of the measurement channel body and the tip of the partition plate to be tapered, the flow of the fluid can be further smoothed, and the accuracy of measurement can be promoted.
[0017]
The flow of the fluid can be improved by providing a flow straightening means, for example, a net-like member or a porous body at the opening of the measurement flow path body.
[0018]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0019]
(Example 1)
1 and 2, the measuring unit 1 is a rectangle having a rectangular cross section. A fluid supply path 3 is connected to the upstream chamber 2 and a fluid outflow path 5 is connected to the downstream chamber 4 at substantially right angles. It is set in the shape.
[0020]
The fluid supply path 3 has a valve seat 8 which is opened and closed by a valve 7 which is linked to a drive unit 6 such as an electromagnetic device or a stepping motor. The introduction passage 9 downstream of the valve seat 8 and connected to the upstream chamber 2 of the measuring unit 1 is rectangular.
[0021]
Reference numeral 10 denotes an inlet of the fluid supply passage 3, reference numeral 11 denotes an outlet of the fluid outflow passage 5 formed in a rectangular shape, and reference numeral 12 denotes an outlet.
[0022]
As shown in FIG. 2, at least one pair of ultrasonic transducers 13 and 14 constituting the flow velocity detecting means are arranged in the measuring section 1 so as to face diagonally.
[0023]
A rectangular measurement flow path body 15 that is included in the measurement unit 1 and that has a rectangular cross-section that is separate from the measurement unit 1 has an opening 16 a in a wall on the short side facing the ultrasonic transducers 13 and 14. , 16b.
[0024]
The openings 16a and 16b are covered with ultrasonically permeable porous materials 17a and 17b made of a wire mesh, punched metal, or the like so that the fluid does not enter the ultrasonic transducers 13 and 14 (see FIG. In the figure, a counterpart of the ultrasonic transducer 13 on the upstream side is shown as a representative).
[0025]
Further, each end of the measurement flow path body 15 extends to a position facing the introduction path 9 of the fluid supply path 3 and the lead-out path 11 of the fluid outflow path 5, and therefore, via the introduction path 9. The introduced fluid flows as it bypasses and reaches the measurement channel body 15, and the fluid from the measurement channel body 15 flows as it bypasses and reaches the outlet channel 11 of the fluid outflow channel 5.
[0026]
The bypass flow form on the fluid supply side is effective for suppressing drifting of the fluid and the like. In addition, the bypass flow form on the fluid outflow side is effective in suppressing drift or the like at the time of fluid reverse flow due to the occurrence of pulsation.
[0027]
The ultrasonic propagation time between the ultrasonic transducers 13 and 14 is measured by the measurement control means 18 (details will be described later), and the calculation means 19 calculates the flow rate based on the result. These measurement control means 18 and calculation means 19 are driven by a battery power supply 20 such as a lithium battery.
[0028]
The drive unit 6, the measurement control unit 18, the calculation unit 19, and the like of the valve body 7 are arranged in a portion surrounded by a U-shaped flow path component, and are collectively compacted as a whole. I have.
[0029]
By the way, the short side of the measurement flow path body 15 is divided into a plurality of laminar flow paths 22a, 22b, 22c, and 22d via partition plates 21a, 21b, and 21c. That is, the fluid flow in the laminar flow passages 22a, 22b, 22c, and 22d is made two-dimensional.
[0030]
In this embodiment, the number of the partition plates 21a, 21b, 21c is an odd number (three), and therefore, the laminar flow passages 22a, 22b, 22c, 22d are even-numbered passages (four passages).
[0031]
The height centers of the transmitting and receiving surfaces of the ultrasonic transducers 13 and 14 are opposed to the central partition plate 21b, and the transmitting and receiving surfaces are mainly opposed to the two adjacent laminar flow passages 22b and 22c at the center. are doing.
[0032]
In the above configuration, the operation of measuring the flow rate of the fluid is briefly described. First, an ultrasonic wave is generated from the ultrasonic transducer 13 on the upstream side so as to cross the flow in the forward direction and obliquely.
[0033]
This ultrasonic wave propagates in the flow of the fluid at the speed of sound, is detected by the ultrasonic wave transmitter / receiver 14 on the downstream side, is converted into an electric signal, and the signal is amplified by the amplifier of the measurement control means 18 and is compared by the comparator. It is compared with the reference signal to detect that the ultrasonic signal has been received.
[0034]
This change in the comparison signal is sent to the repetition means, and is transmitted again by the trigger means via the delay means.
[0035]
The number of repetitions ends with the number set by the number setting means. The timer means resets the timer when the first trigger signal is transmitted, and measures the time until the repetition ends.
[0036]
When the transmission of the ultrasonic waves from the upstream to the downstream ends, the direction of transmission and reception is switched by the switching means.
[0037]
Transmission is performed from the ultrasonic transducer 14 on the downstream side to the ultrasonic transducer 13 on the upstream side, that is, from the downstream to the upstream, and transmission is repeatedly performed as described above, and the time is measured. Is done. Based on the time difference from the upstream to the downstream and the time difference from the downstream to the upstream, the flow rate is calculated by the calculation means 19 by a calculation formula such as a reciprocal difference of the propagation time.
[0038]
The valve 7 is closed when there is an abnormality in the fluid flow or when an earthquake occurs.
[0039]
By the way, as described above, since the measurement flow path body 15 is configured separately from the measurement unit 1, processing of the measurement flow path body 15 can be performed independently, and a high-precision measurement unit can be easily formed. It can be obtained, and it is possible to appropriately deal with changes in specifications and the like.
[0040]
The form of fluid flow to the measurement channel body 15 will be described. First, the fluid flowing into the fluid supply path 3 from the inflow port 10 flows from the valve seat 8 to the introduction path 9 and further to the upstream chamber 2 of the measurement unit 1.
[0041]
Since one end of the measurement flow path body 15 is located in the upstream chamber 2 in a protruding state, the fluid flowing into the upstream chamber 2 flows into the measurement flow path body 15 in such a way as to bypass the fluid. Become.
[0042]
Therefore, even if there is a drift or the like upstream, the detour corrects the drift, and as a result, the fluid flowing through the measurement flow path body 15 becomes stable, enabling accurate flow velocity measurement.
[0043]
As described above, the measurement flow path body 15 is divided into a plurality of laminar flow paths 22a, 22b, 22c, and 22d so that fluid flow becomes two-dimensional.
[0044]
Therefore, the fluid flows stably and evenly through the laminar flow passages 22a, 22b, 22c, and 22d, and the flow velocity measurement by the ultrasonic transducers 13 and 14 is performed over the entire height H of the measurement flow path body 15. There is no necessity, and the initial purpose can be achieved by mainly setting the height B of the laminar flow passages 22b and 22c adjacent to the center.
[0045]
In addition, at least the respective heights A of the central laminar flow paths 22b and 22c to be measured are set within the range of the boundary layer region so that the measurement accuracy is not affected by external factors.
[0046]
In general, when the target fluid is a gas such as a gas, the boundary layer of one partition plate is 15 mm. Therefore, if the target layer is to be within the boundary layer region, the heights of the laminar flow passages 22b and 22c are respectively set. The distance may be within 30 mm.
[0047]
(Example 2)
FIG. 3 shows an example in which the fluid flow in the measurement channel 15 is improved.
[0048]
The length of the partition plates 21a, 21b, 21c, that is, the lengths of the laminar flow passages 22a, 22b, 22c, 22d are made substantially equal to the ultrasonic transmission / reception area length W of the ultrasonic transducers 13, 14. is there.
[0049]
By doing so, the length of the partition plates 21a, 21b, 21c, that is, the length of the laminar flow passages 22a, 22b, 22c, 22d can be minimized, and the flow pressure loss of the fluid can be reduced accordingly. It becomes.
[0050]
(Example 3)
FIG. 4 shows a configuration in which turbulence preventing portions 23 and 24 are formed, for example, by forming the opening edges of both ends of the measurement channel body 15 into an arc shape or a tapered shape. In this case, a fluid is caused to flow so that no vortex is generated.
[0051]
Of course, if the turbulence prevention portions are formed at the ends of the partition plates 21a, 21b, 21c, further effects can be expected.
[0052]
(Example 4)
FIGS. 5 and 6 show an example in which a flow straightening means is provided at the opening of the fluid measurement flow path body 15 and the flow of the fluid into the inside is modified.
[0053]
First, the one shown in FIG. 5 is provided with mesh members 25 and 26 such as a wire mesh at the opening of the measurement channel body 15.
[0054]
According to this configuration, even when the upstream flow is in a turbulent state, the flow is rectified by the mesh member 25 and flows into the laminar flow passages 22a, 22b, 22c, and 22d of the measurement flow path body 15 in a stable flow form. This contributes to higher accuracy of measurement.
[0055]
It is needless to say that the same operation and effect can be obtained even if the honeycomb-shaped porous bodies 27 and 28 are adopted as the rectifying means as shown in FIG.
[0056]
In each of the above embodiments, measures were taken to stabilize the fluid flow to the measurement flow path body 15 even in the case of backflow. However, if there is no backflow, the fluid flow is stabilized only on the upstream side of the measurement flow path body 15. It is also conceivable to take countermeasures.
[0057]
In each of the above embodiments, the ultrasonic transducer is arranged in the measuring section. However, the ultrasonic transducer may be arranged on the measuring channel body side to form a kind of measuring channel unit.
[0058]
Further, as is clear from the above-described embodiment, the flow velocity measurement by at least one pair of ultrasonic transducers may be performed not on the entire measurement flow path body but on a part of the laminar flow paths. The areas need not all be the same.
[0059]
【The invention's effect】
As described above, the present invention relates to a measuring section in which a fluid supply path is connected to an upstream side and a fluid outflow path is connected to a downstream side, a measuring flow path body included in the measuring section, and the measuring flow path body. At least one pair of ultrasonic transducers for measuring the flow velocity of the flowing fluid, and computing means for computing the amount of fluid flowing through the measurement channel body based on the output of the ultrasonic transducer, The measurement flow path body is configured separately from the measurement unit, and the inside is divided into a plurality of laminar flow paths, so the measurement flow path body is independently processed and provided with a plurality of laminar flow paths. The measurement flow path section having a complicated configuration can be manufactured easily and with high precision, and the specification can be easily changed.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of an ultrasonic flow measuring device according to an embodiment of the present invention. FIG. 2 is a cross sectional view of the ultrasonic flow measuring device. FIG. 3 is an ultrasonic flow measuring device showing another embodiment of the present invention. FIG. 4 is a vertical cross-sectional view of a measurement flow path body showing another embodiment of the present invention. FIG. 5 is a vertical cross-sectional view of an ultrasonic flow measuring apparatus showing another embodiment of the present invention. 6 is a longitudinal sectional view of an ultrasonic flow rate measuring apparatus showing still another embodiment of the present invention. FIG. 7 is a schematic sectional view of a conventional ultrasonic flow rate measuring apparatus.
DESCRIPTION OF SYMBOLS 1 Measuring part 3 Fluid supply path 5 Fluid outflow path 13, 14 Ultrasonic transducer 15 Measurement flow path body 19 Calculation means 21a, 21b, 21c Partition plates 22a, 22b, 22c, 22d Laminar flow path 25 Reticulated member 26 Porous body

Claims (13)

A fluid supply path on the upstream side, a measurement unit to which a fluid outflow path is connected on the downstream side, a measurement channel body included in the measurement unit, and at least measuring a flow rate of the fluid flowing through the measurement channel body A pair of ultrasonic transducers, and computing means for computing the amount of fluid flowing through the measurement flow path body based on the output of the ultrasonic transducer, wherein the measurement flow path body has a measuring unit and Is an ultrasonic flow rate measuring device having a separate structure and dividing the inside into a plurality of laminar flow passages. The ultrasonic flow rate measuring device according to claim 1, wherein the ultrasonic transducer is arranged on the measuring unit side. 2. The ultrasonic flow measurement device according to claim 1, wherein the laminar flow passage of the measurement flow path body is defined by a plurality of partition plates. 4. The ultrasonic flow measuring device according to claim 3, wherein the measurement flow path body is a rectangle having a rectangular cross section, and a short side is divided by a plurality of partition plates. 4. The flow measuring device according to claim 3, wherein the distance between the partition plates is selected such that the laminar flow passage is set in the boundary layer region of the fluid flow. 2. The ultrasonic flow measuring device according to claim 1, wherein the flow velocity of the fluid flowing through at least a part of the laminar flow passages is measured by at least one pair of ultrasonic transducers. 7. The ultrasonic flow rate measuring device according to claim 6, further comprising an even number of laminar flow paths, wherein the flow velocity of the fluid flowing through two adjacent laminar flow paths located at the center is measured by at least one pair of ultrasonic transducers. apparatus. At least one pair of ultrasonic transducers face each other so that the ultrasonic waves cross the fluid diagonally, and the laminar flow path in the measurement channel is set to a length corresponding to the ultrasonic transmission and reception area of the ultrasonic transducer. The ultrasonic flow rate measuring device according to claim 1. 2. The ultrasonic flow rate measuring device according to claim 1, wherein an opening end of the measurement flow path body is formed in a tapered shape. 4. The ultrasonic flow rate measuring device according to claim 3, wherein a tip portion of the partition plate is tapered. The ultrasonic flow rate measuring device according to claim 1, wherein a rectifying means is provided at an opening of the measurement flow path body. The ultrasonic flow rate measuring device according to claim 11, wherein the rectifying means comprises a mesh member. The ultrasonic flow rate measuring device according to claim 11, wherein the rectifying means is formed of a porous body.

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