JP2004212180A - Flow rate measuring instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flow rate measuring instrument that is further improved in measurement accuracy. <P>SOLUTION: On the upstream side and downstream side of a conduit having a rectangular cross section and forming the flow passage W10 of a gas, ultrasonic transmitters/receivers 12A and 12B are disposed to face each other. The transmitter/receiver 12A is disposed at a first position SA provided on the first ridgeline section 11A of the conduit 11, and the other transmitter/receiver 12B is disposed at a second position SB provided on the second ridgeline section 11B of the conduit 11. The distance from the first position SA to the second position SB is the longest distance in the flow rate measuring section I of the conduit 11. In the conduit 11, flow passages W11, W12, W13, W14, and W15 are formed by providing rectifying members 13 constituted by bending one plate-shaped member into stages in the conduit 11. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a flow measurement device for measuring the flow rate of a fluid such as city gas using sound waves.
[0002]
[Prior art]
For example, in a flow rate measuring device such as a gas meter, an ultrasonic wave is propagated to a fluid to be measured such as city gas flowing through a conduit, and the propagation time or propagation speed of the ultrasonic wave changes depending on the flow velocity of the fluid to be measured. Thus, a so-called ultrasonic wave propagation type flow rate measuring device for measuring the flow rate of a fluid to be measured has been put to practical use.
[0003]
In the flow measuring device of the ultrasonic wave propagation method, a linear average flow velocity having a correlation with the average flow velocity in the cross section of the conduit is measured, and the flow rate is calculated based on the linear average flow velocity. Therefore, in order to reduce the measurement error, it is necessary to equalize or stabilize the flow velocity distribution of the fluid to be measured in the cross section of the conduit.
[0004]
Therefore, in a conventional flow rate measuring device, as shown in FIG. 8, for example, a wire mesh such as a wire mesh is provided in a conduit 102 upstream of a propagation path P100 formed by a pair of ultrasonic transmitters / receivers 101A and 101B. A rectifying grid 103 is provided. According to this flow rate measurement device, as schematically shown in FIG. 9, the flow resistance of the rectifying grid 103 with respect to the flow of the fluid to be measured is appropriately orthogonal to the flow line of the flow upstream of the rectifying grid 103. By positively generating the momentum transmission in the direction, the flow velocity distribution in the cross section of the flow conduit 102 downstream of the flow straightening grid 103 is uniformed or stabilized.
[0005]
However, even with this flow measuring device, it is difficult to sufficiently reduce the measurement error. This is because the calibration is generally performed in a state where the flow velocity distribution of the fluid to be measured is stable. However, in this flow measurement device, the ultrasonic wave is disposed downstream of the rectifying grid 103 over a predetermined length. Even if the flow velocity distribution in the cross section of the conduit 102 of the fluid to be measured is stabilized or uniformized by the rectification grid 103, the rectification grid 103 causes fluctuations in the supply pressure and pressure fluctuations caused by peripheral devices. Alternatively, the flow velocity distribution of the fluid to be measured is disturbed by disturbance such as a substance attached to the channel wall surface, and a difference occurs in the flow velocity distribution of the fluid to be measured between the time of measurement and the time of calibration.
[0006]
In order to solve this problem, a plate-like member is provided in parallel with the wall surface of the conduit to divide the flow path of the fluid to be measured into a plurality of flow paths, and the ultrasonic wave is transmitted to one of the flow paths. There is a flow measurement device provided with a pair of ultrasonic transmitters / receivers (see Patent Document 1).
[0007]
[Patent Document 1]
JP-A-9-43015
[Problems to be solved by the invention]
However, this flow measurement device has a problem that the propagation path of the ultrasonic wave is short, and it is difficult to measure a wide area in the cross section of the conduit. Further, since the flow path is divided into two or more, a plurality of plate-like members are required, and they must be individually fixed to the conduit, which is troublesome, and productivity and economy are low. There are also problems.
[0009]
The present invention has been made in view of such a problem, and a first object of the present invention is to provide a flow measurement device capable of further improving measurement accuracy.
[0010]
Further, a second object of the present invention is to provide a flow rate measuring device excellent in productivity and economy.
[0011]
[Means for Solving the Problems]
A flow rate measuring device according to the present invention forms a fluid flow path having a polygonal cross section having a plurality of ridges, a conduit having a flow rate measuring section of a predetermined length along a flow direction, and a flow measuring section of the conduit. Wherein the first and second transmitters / receivers disposed at a first position and a second position, respectively, at one or two of the plurality of ridges, are configured to include: A sound wave propagating means for propagating sound waves to the fluid, a rectifying member disposed in the flow rate measuring section in the conduit and dividing the fluid flow path into a plurality of parts, and a propagation time or propagation of the sound waves between the pair of transmitters / receivers And a flow rate calculating means for calculating a flow rate value of the fluid based on the speed.
[0012]
More specifically, the first transmitter / receiver has a first position at one of the plurality of ridges, and the second transmitter / receiver has a linear distance from the first position. Are disposed opposite to each other at the second position on the other longest ridge line portion. Further, the first transmitter / receiver is the most upstream side in the flow rate measurement section, and the second transmitter / receiver is the flow rate detector. It is arranged at the most downstream position in the measurement section.
[0013]
In this flow measurement device, transmission and reception of sound waves in a wide range between the first transmitter / receiver and the second transmitter / receiver disposed at the ridge of the conduit in the flow measurement section of the conduit, respectively. The flow rate of a fluid such as a gas is calculated based on the propagation time or velocity of the sound wave.
[0014]
Note that, in the flow rate measuring device of the present invention, a plurality of sets each including the first transmitter / receiver and the second transmitter / receiver may be provided. The rectifying member may form a flow path parallel to the sound wave propagation path, or may form a flow path that intersects the sound wave propagation path and have a through hole through which the sound wave passes. You may.
[0015]
Further, in the flow rate measuring device of the present invention, a large number of depressions (dimples) may be provided on the surface of the rectifying member, and further, the rectifying member is formed by a single plate-like member forming a plurality of flow paths. It may be formed by folding or bending.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0017]
[First Embodiment]
FIG. 1 shows a schematic configuration of a part of a gas meter according to a first embodiment of the present invention. The gas meter is of an ultrasonic wave propagation type, and a flow rate calculation circuit system (flow rate calculation means) for calculating a flow rate value based on a propagation time or a propagation speed of an ultrasonic wave, and an integrated flow rate value calculation for calculating an integrated flow rate value. Circuit system, integrated flow value counter that displays the integrated flow value, abnormality detection device that detects an abnormality such as gas leakage, and shut-off valve that closes the valve and stops gas supply when an abnormality is detected However, since they are not directly related to the gist of the present invention, illustration and detailed description thereof are omitted.
[0018]
This gas meter has a conduit 11 serving as a gas flow path W10, and a flow rate measurement section I is provided between an upstream side and a downstream side of the conduit 11. In the flow rate measurement section I, the distal ends of the ultrasonic transmitters / receivers 12A and 12B are inserted into the conduit 11 through insertion holes (not shown) provided in the wall surface of the conduit 11. The ultrasonic transmitters / receivers 12A and 12B are arranged to face each other, and transmit and receive ultrasonic waves in a gas flow. In the present embodiment, the cross section of the conduit 11 has a polygonal shape, for example, a rectangular shape. One ultrasonic transmitter / receiver 12A is disposed at the most upstream position (first position SA) in the flow rate measurement section I on the first ridgeline portion 11A, and the other ultrasonic transmitter / receiver is provided. 12B is disposed at the most downstream position (second position SB) within the flow rate measurement section I on the second ridgeline portion 11B.
[0019]
As described above, in the present embodiment, the ultrasonic transmitters / receivers 12A and 12B are not disposed so that the propagation path of the ultrasonic waves is parallel to the wall surface of the conduit 11, but the two opposing ridge portions 11A. , 11B such that the ultrasonic wave propagation path P10 is inclined with respect to the bottom surface of the conduit 11. Hereinafter, the reason will be described.
[0020]
First, the ultrasonic wave propagation path P10 is made longer than before so as to increase the resolution with respect to the measurement time. Second, the ultrasonic waves are propagated over a wide area in the cross section of the conduit 11. FIG. 2 shows an ultrasonic wave propagation path P <b> 10 in a cross section of the conduit 11. As can be seen from FIG. 2, in this flow measurement device, the propagation path P10 is longer than the propagation path P200 when ultrasonic waves are propagated in parallel to the wall surface of the conduit 11, and the propagation path P10 is It is formed in a wide area in the cross section of the conduit 11.
[0021]
Third, by making the protruding portions of the ultrasonic transmitters / receivers 12A and 12B into the conduit 11 into the corners of the flow passage having a rectangular cross section, the flow turbulence caused by the protruding portions is relative to the entire flow passage. This is to reduce the influence and to secure the uniformity of the flow velocity distribution. As described above, the influence of the projecting portions of the ultrasonic transmitters / receivers 12A and 12B into the conduit 11 on the entire flow path is reduced. It is possible to insert the inside of the meter for a long time, whereby the protruding portion outside the conduit 11 is reduced, and the size of the entire meter can be reduced. That is, in this gas meter, the measurement accuracy can be sufficiently improved and the size can be reduced.
[0022]
A straightening member 13 is also provided inside the conduit 11 (FIG. 1). The rectifying member 13 divides the flow path W10 into flow paths W11, W12, W13, W14, and W15 parallel to the propagation path P10. The propagation path P10 is formed in the flow path W13. This suppresses a change in the gas flow velocity distribution in the propagation path P10 due to disturbance, and reduces the difference between the gas flow velocity distribution during calibration and the gas flow distribution during measurement.
[0023]
The rectifying member 13 is formed of, for example, a single plate-shaped member made of the same material as the conduit 11. Specifically, the plate-shaped member is folded so as to fit into the conduit 11. The reason why the rectifying member 13 is constituted by one plate-like member is to save the trouble of individually fixing a plurality of plate-like members to the conduit 11 and to improve productivity and economy. It is preferable that a depression (dimple) 13A is provided on the surface of the rectifying member 13. This is because measurement accuracy can be further improved by generating turbulent flow in the depression 13A and making the flow velocity distribution uniform throughout the gas flow path.
[0024]
In this flow measuring device, when the gas reaches the upstream end of the flow regulating member 13, the velocity distribution in the cross section of the conduit 11 is made uniform to some extent by the flow regulating action of the upstream end of the flow regulating member 13. After that, the gas whose velocity distribution has been made uniform flows into the flow paths W11, W12, W13, W14, and W15.
[0025]
On the other hand, the ultrasonic transmitters / receivers 12A and 12B intermittently transmit ultrasonic waves to the flow path W13, for example, at a predetermined frequency per one measurement period. The propagation of the ultrasonic waves is performed so that the propagation from the upstream side to the downstream side and the propagation from the downstream side to the upstream side are alternately repeated. The flow rate calculating means (not shown) measures the gas flow rate based on the propagation time of the ultrasonic wave from the upstream side to the downstream side and from the downstream side to the upstream side, and then calculates the gas flow rate based on the flow rate. Thereby, the flow rate of the gas is obtained.
[0026]
As described above, in the present embodiment, the ultrasonic transmission / reception devices 12A and 12B are arranged such that the ultrasonic wave propagation path is inclined with respect to the two ridge portions 11A and 11B of the conduit 11 with respect to the bottom surface of the conduit 11. Since it is arranged, the propagation path P10 of the ultrasonic wave can be lengthened, the resolution with respect to the measurement time can be increased, and the ultrasonic wave can be propagated over a wide area in the cross section inside the conduit 11. Further, since the protruding portions of the ultrasonic transmission / reception devices 12A and 12B into the conduit 11 can be reduced, uniformity of the gas flow velocity distribution can be ensured. Therefore, measurement accuracy can be sufficiently improved, and downsizing can be achieved.
[0027]
In particular, if a large number of depressions 13A are provided on the surface of the rectifying member 13, a turbulent flow can be generated in each of the depressions 13A to make the gas flow velocity distribution uniform, thereby further improving measurement accuracy. Can be done.
[0028]
In addition, if the flow regulating member 13 is constituted by one plate-like member, there is no need to individually fix a plurality of plate-like members to the conduit, and excellent productivity and economic efficiency can be obtained.
[0029]
Hereinafter, other embodiments (second to fourth embodiments) of the present invention will be described. In these embodiments, the same components as those in the first embodiment are denoted by the same reference numerals. However, a detailed description of the same part will be omitted.
[0030]
[Second embodiment]
FIG. 3 shows a schematic configuration of a part of a gas meter according to a second embodiment of the present invention. This gas meter has a configuration similar to that of the first embodiment, except that a gas flow member 23 is provided instead of the flow straightening member 13.
[0031]
The flow regulating member 23 forms flow paths W21, W22, W23, W24, and W25 that intersect with the ultrasonic wave propagation path P10. The rectifying member 23 has a through-hole 23A through which ultrasonic waves penetrate, and is configured by folding one plate-shaped member so as to intersect with the propagation path P10. Specifically, for example, it is constituted by a member such as a mesh member or a shadow mask having a large number of slits, and particularly preferably constituted by a mesh member. This is because there is a depression on the surface of the mesh member, and a turbulence is generated by the depression, so that the flow velocity distribution becomes uniform. In addition, it may be configured by providing a through-hole corresponding to the cross-sectional shape of the ultrasonic wave only at the position where the ultrasonic wave propagates.
[0032]
The operation and effect of this gas meter are the same as those of the first embodiment.
[0033]
[Third Embodiment]
FIG. 4 shows a schematic configuration of a gas meter according to the third embodiment of the present invention. This gas meter has the same configuration as the second embodiment except that the gas meter further includes a pair of ultrasonic transmitters / receivers 32A and 32B in addition to the ultrasonic transmitters / receivers 12A and 12B of the second embodiment. It has the same configuration, operation and effect.
[0034]
The ultrasonic transmitters / receivers 32A and 32B form another propagation path P30 different from the propagation path P10, and are disposed on the first ridge 11A and the second ridge 11B of the conduit 11, respectively. ing.
[0035]
As described above, in the present embodiment, the ultrasonic transmitters / receivers 32A and 32B are provided in addition to the ultrasonic transmitters / receivers 12A and 12B, so that gas lines in various portions of the flow path W10 are provided. The average flow velocity can be measured. Therefore, the measurement accuracy can be further improved as compared with the second embodiment.
[0036]
[Fourth Embodiment]
FIG. 5 shows a schematic configuration of a gas meter according to a fourth embodiment of the present invention. This gas meter has the same configuration, operation and effect as the first embodiment except that an ultrasonic transmitter / receiver 42B is provided instead of the ultrasonic transmitter / receiver 12B.
[0037]
The ultrasonic transmitter / receiver 42B has a second ridge 11B that transmits ultrasonic waves to a second position SC on the first ridge 11A of the conduit 11 downstream of the first position SA. It is arranged to head to. Thereby, the ultrasonic waves transmitted from the ultrasonic transmitters / receivers 12A and 42B are reflected on the side wall of the conduit 11, and the reflected ultrasonic waves are received by the ultrasonic transmitters / receivers 12A and 42B. I have. Therefore, the propagation path P40 of the ultrasonic wave becomes V-shaped and the distance becomes long. In this case, it is preferable that the conduit 11 be made of a material that is durable against impact by ultrasonic waves.
[0038]
As described above, in the present embodiment, the ultrasonic transmitter / receiver 42B is disposed at the second position SC so that the part transmitting the ultrasonic waves is directed to the second ridgeline portion 11B. The distance of the route P30 increases. Therefore, the resolution with respect to the measurement time can be increased, and the linear average flow velocity of the gas in various portions of the flow path W10 can be measured. As a result, the measurement accuracy can be sufficiently improved.
[0039]
By changing the direction in which the ultrasonic transmitters / receivers 12A and 42B are arranged, the propagation path of the ultrasonic waves may be formed in a W-shape or a zigzag shape. In this case, the measurement accuracy can be further improved for the reasons described above.
[0040]
As described above, the embodiments of the present invention have been described, but the present invention is not limited to the above embodiments, and various modifications are possible. For example, in the above embodiment, one or two pairs of ultrasonic transmitters / receivers are provided, but three or more pairs of ultrasonic transmitters / receivers may be provided. Thereby, the measurement accuracy can be further improved.
[0041]
Further, in the above embodiment, the case where the conduit 11 having a rectangular cross section is used has been described. However, a conduit having another shape, for example, a conduit having a polygonal shape such as a triangular, pentagonal, or hexagonal cross section is used. May be used. Note that when the number of ridge lines is infinitely large, a circular cross section is obtained. In the case of a conduit having a circular cross section, the positions of the two ultrasonic transmitters / receivers (first and first positions) are set so that the ultrasonic wave propagation path is the longest. (Second position) may be determined.
[0042]
Further, in the above-described embodiment, the rectifying members 13 and 23 are configured by a single plate-shaped member that is stepped, but may be configured by another plate-shaped member. For example, when a conduit having a circular cross section is used, it can be configured by a wound plate-like member 33 as shown in FIG. 6 instead of step folding. Further, it is not necessary to form a plate-like member, and as an example, for example, a honeycomb structure 43 as shown in FIG. 7 can be cited.
[0043]
In addition, in the above embodiment, the flow paths W11, W12, W13, W14, W15, W21, W22, W23, W24, and W25 are formed by the rectifying members 13 and 23 formed of a single plate-like member. However, it is not necessary to form with a rectifying member composed of one plate-shaped member, and it may be formed with a plurality of plate-shaped members as in the related art.
[0044]
Further, the present invention can be applied to a flow rate measuring device for measuring a flow velocity and a flow rate of a liquid fuel or a material gas for a chemical industry, for example, in addition to the gas meter.
[0045]
【The invention's effect】
As described above, according to the flow rate measuring device according to any one of claims 1 to 9, the first and second transmitters / receivers are connected to one or two of the ridges of the polygonal conduit. Are arranged at the first position and the second position, respectively, in the ridge line portion, so that the propagation path of the ultrasonic wave can be lengthened, and the ultrasonic wave can be propagated over a wide area in the cross section of the conduit. Measurement accuracy can be sufficiently improved. In addition, since the relative influence of the protruding portion on the flow path in the conduit of the transmitter / receiver can be reduced, the uniformity of the gas flow velocity distribution due to the protruding portion is not lost, and the outside of the conduit is not affected. Since the projecting portion can be reduced, the size can be reduced.
[0046]
In particular, according to the flow rate measuring device of the eighth aspect, since the depression (dimple) is provided on the surface of the flow regulating member, a small turbulent flow is generated on the surface of the flow regulating member, and the flow velocity distribution can be made uniform. . Therefore, the measurement accuracy can be sufficiently improved.
[0047]
Furthermore, according to the flow rate measuring device of the ninth aspect, since a rectifying member configured by folding or bending one plate-like member is used, for example, a case where a plurality of plate-like members are used is used. Furthermore, there is no need to individually fix the plate members, and excellent productivity and economic efficiency can be obtained.
[Brief description of the drawings]
FIG. 1 is a perspective view illustrating a configuration of a gas meter according to a first embodiment of the present invention.
FIG. 2 is a diagram showing the propagation path shown in FIG. 1 in a cross section of a conduit.
FIG. 3 is a perspective view illustrating a configuration of a gas meter according to a second embodiment of the present invention.
FIG. 4 is a perspective view illustrating a configuration of a gas meter according to a third embodiment of the present invention.
FIG. 5 is a perspective view illustrating a configuration of a gas meter according to a fourth embodiment of the present invention.
FIG. 6 is a perspective view illustrating a configuration of a rectifying member according to a modification of the present invention.
FIG. 7 is a perspective view illustrating a configuration of another rectifying member according to a modification of the present invention.
FIG. 8 is a perspective view illustrating a configuration of a conventional gas meter.
FIG. 9 is a diagram schematically showing the operation of the rectifying grating shown in FIG.
[Explanation of symbols]
11, 102: conduit, 11A: first ridge, 11B: second ridge, 12A, 12B, 32A, 32B, 42B, 101A, 101B: ultrasonic transmitter / receiver, 13, 23: rectifying member, 13A: recess (dimple), 23A: through hole, 33: plate member, 34: honeycomb structure, 103: rectifying lattice, P10, P30, P40, P100: propagation path, SA: first position, SB, SC ... Second position, W10, W11, W12, W13, W14, W15, W21, W22, W23, W24, W25.

Claims (9)

A conduit having a fluid flow path having a polygonal cross section having a plurality of ridges, and having a flow rate measurement section having a predetermined length along the direction of flow,
In the flow rate measurement section of the conduit, first and second transmitters / receivers are respectively disposed at first and second positions on one or two of the plurality of ridges. A sound wave propagation means for propagating sound waves in the fluid flow path,
A rectifying member disposed in the flow rate measurement section in the conduit and dividing the fluid flow path into a plurality,
A flow rate calculating device for calculating a flow rate value of the fluid based on a propagation time or a propagation speed of the sound wave between the pair of transmitters / receivers. The flow rate measuring device according to claim 1, wherein the first and second positions are determined to be positions where the propagation path of the sound wave by the first and second transmitters / receivers is the longest. The first transmitter / receiver has a first position at one of a plurality of ridges, and the second transmitter / receiver has a longest linear distance from the first position. 3. The flow measuring device according to claim 1, wherein the flow measuring device is disposed so as to face each of the second positions on another ridge line portion. 2. The apparatus according to claim 1, wherein the first transmitter / receiver is disposed at a most upstream position in a flow rate measurement section, and the second transmitter / receiver is disposed at a most downstream position in a flow rate measurement section. The flow rate measuring device according to claim 3. The flow rate measuring device according to any one of claims 1 to 4, wherein a plurality of sets each including the first transmitter / receiver and the second transmitter / receiver are provided. . The flow measuring device according to any one of claims 1 to 5, wherein the rectifying member forms a flow path parallel to a propagation path of the sound wave. The flow rate according to any one of claims 1 to 5, wherein the flow regulating member forms a flow path intersecting with the propagation path of the sound wave and has a through hole through which the sound wave passes. Measuring device. The flow measuring device according to any one of claims 1 to 7, wherein the flow regulating member has a large number of depressions (dimples) on a surface thereof. 9. The rectifying member according to claim 1, wherein one plate-shaped member is formed by folding or bending to form a plurality of flow paths. Flow measuring device.

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