JP4048964B2 - Ultrasonic flow meter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic flowmeter that measures the flow rate of a fluid such as gas or water using ultrasonic waves.
[0002]
[Prior art]
The conventional ultrasonic flowmeter has a structure as shown in FIG. That is, a flow rate measuring unit 3 provided with a layered flow path 2 partitioned by a partition plate 1, an inlet unit 4 for flowing fluid into the flow rate measuring unit 3, and an outlet unit 5 for flowing fluid out And an upstream connection part 6 for connecting the inlet part 4 and the flow rate measuring part 3, and a downstream side connection part 7 for connecting the outlet part 5 and the flow rate measuring part 3.
[0003]
The layered channels provided in the flow rate measuring unit 3 are formed with substantially uniform channel heights, and this structure ensures two-dimensional flow and realizes highly accurate flow rate measurement. (For example, refer to Patent Document 1).
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 9-43015 (2nd, 3rd page, FIG. 1)
[0005]
[Problems to be solved by the invention]
However, in the above conventional technique, the flow rate distribution of the fluid at the inlet 4 is measured when the flow rate measurement unit 3 measures the flow rate using ultrasonic waves because the partition plate 1 simply divides the layered flow channel 2. There was a problem that the accuracy was reduced due to the influence of.
[0006]
In view of the above problems, an object of the present invention is to provide an ultrasonic flowmeter with high accuracy that suppresses the influence of the flow velocity distribution at the inlet when the flow rate is measured in the flow rate measuring unit.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, an ultrasonic flowmeter of the present invention is provided in a flow tube through which a fluid flows, a plurality of divided flow paths formed by dividing the inside of the flow tube with a partition plate, and the flow tube. And at least a pair of ultrasonic transducers and flow rate measuring means for calculating the flow rate of the fluid according to the propagation time of the ultrasonic waves measured by the ultrasonic transducers, the ultrasonic transducers In the measurement area to be measured, the number of the divided flow paths is increased from the upstream side to the downstream side, and the fluid divided in the upstream divided flow path is sequentially subdivided in the divided flow path in the next stage. is there.
[0008]
According to the present invention, since the flow velocity distribution of the fluid at the inlet is distributed to each divided flow channel, the flow velocity in each divided flow channel can be made uniform and a highly accurate ultrasonic flowmeter can be realized.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The present invention includes a flow tube through which a fluid flows, a plurality of divided flow paths formed by dividing the inside of the flow tube with a partition plate, at least a pair of ultrasonic transducers provided in the flow tube, Flow rate measuring means for calculating the flow rate of the fluid according to the propagation time of the ultrasonic wave measured by the ultrasonic transducer, and from the upstream side to the downstream side in the measurement region measured by the ultrasonic transducer Accordingly, the number of the divided flow paths is increased, and the fluid divided in the upstream divided flow path is sequentially re-divided in the subsequent divided flow path .
[0010]
With this configuration, since the fluid is sequentially divided from the upstream side to the downstream side in the measurement region measured by the ultrasonic transducer, the flow velocity in the divided flow path is made uniform, and a high-accuracy ultrasonic flowmeter is installed. Can be realized.
[0011]
The number of divided flow paths is increased stepwise, for example, and the cross-sectional areas of the divided flow paths are made equal for each stage. Moreover, the flow tube was made into the rectangle of a cross-sectional rectangle shape, and the partition plate was provided in parallel with the long side.
[0012]
【Example】
Example 1
Embodiments of the present invention will be described below with reference to the drawings. 1 to 3, the ultrasonic flowmeter has a flow tube 11. Ultrasonic transducers 12 and 13 are arranged on the upstream side and the downstream side of the flow tube 11 as if they face each other diagonally.
[0013]
The flow rate of the fluid flowing through the flow tube 11 is measured by the flow rate measuring means 14 based on the time during which the ultrasonic wave propagates between the ultrasonic transducers 12 and 13.
[0014]
The ultrasonic transducers 12 and 13 are disposed in recessed portions 15a and 15b provided on the side surface of the flow tube 11 so as not to adversely affect the flow of fluid.
[0015]
And perforated plates 16a and 16b, such as a wire mesh, are provided at the intersection with the flow tube 11 so that the flow of fluid enters the recessed portions 15a and 15b and vortices are not generated.
[0016]
The flow tube 11 is set to have a rectangular cross-section, and a plurality of partition plates 17a, 17b, 17c are arranged in parallel with the long sides thereof, thereby dividing the flow paths 18a, 18b, 18c, 18d, 18e, 18f is formed.
[0017]
More specifically, the central partition plate 17b is longer forward than the other partition plates 17a and 17c, whereby the flow tube 11 is first divided into two divided flow paths 18a and 18b, and the short partition plate 17a. , 17c further divides the two divided flow paths 18a, 18b into four divided flow paths 18c, 18d, 18e, 18f.
[0018]
The four divided flow paths 18c, 18d, 18e, and 18f are set in a flat shape so that fluid flows in a laminar flow state.
[0019]
The flow tube 11 has running channels 19 and 20 on the upper and lower sides, an upstream chamber 21 is provided in the upstream running channel 19, and a downstream chamber 22 is provided in the downstream running channel 20. Yes.
[0020]
Reference numerals 23 and 24 denote flow path folding plates.
[0021]
The operation of the ultrasonic flowmeter configured as described above will be described. The fluid enters the flow pipe 11, first decelerated in the upstream chamber 21, and then passes through the run-up channel 19, so that the fluid flow is made uniform.
[0022]
The homogenized fluid is first divided into the divided flow paths 18a and 18b, then again divided into the divided flow paths 18c, 18d, 18e, and 18f, and flows in a laminar flow state, and then downstream through the auxiliary flow path 20. Exit the flow tube 11 through the chamber 22.
[0023]
Now, assuming that the partition plates 17a, 17b, and 17c have the same length, and the fluid is immediately divided into the four divided flow paths 18c, 18d, 18e, and 18f, the flow velocity distribution of the fluid flowing through the flow pipe 11 is as shown in FIG. become.
[0024]
In the figure, an arrow represents a flow velocity vector, and in the divided flow paths 18c, 18d, 18e, and 18f obtained by dividing the flow velocity distribution of the fluid flowing into the running flow path 19 of the flow tube 11, the flow velocity at the center portion becomes faster, and the outer peripheral wall portion. The flow velocity is greatly affected by the flow velocity distribution in the run-up channel 19 such that the flow velocity is slow.
[0025]
Here, as shown in FIGS. 1 to 3, the length of the partition plate 17 b provided in the central portion of the flow tube 11 is increased, and the length of the partition plates 17 a and 17 c provided in the outer peripheral wall portion is decreased. Thus, in the measurement area by the ultrasonic transducers 12 and 13, the flow is first divided into two divided flow paths 18a and 18b from the upstream side to the downstream side, and then divided into four divided flow paths 18c, 18d, 18e and 18f. Thus, by substantially increasing the number of flow paths, the flow velocity distribution of the fluid is equalized.
[0026]
That is, first, the flow divided by the partition plate 17b provided in the central portion of the flow pipe 11 is distributed again by the partition plates 17a and 17c provided outside.
[0027]
As described above, according to the present embodiment, since the flow is divided, the flow speeds are uniformized in the four divided flow paths 18c, 18d, 18e, and 18f, and the flow velocity distribution of the fluid in the run-up flow path 19 is achieved. Therefore, it is possible to realize an ultrasonic flowmeter with high accuracy.
[0028]
Further, since the flow velocity distribution can be made uniform using the partition plates 17a, 17b, and 17c, accurate measurement can be performed in a wide flow region regardless of the type of fluid.
[0029]
In the present embodiment, the measurement area measured by the ultrasonic transducers 12 and 13 in the flow tube 11 has been described. However, the lengths of the partition plates 17a, 17b, and 17c are not limited to the measurement area but also on the downstream side. Alternatively, the number of divided flow paths may be changed.
[0030]
In this case, even if a reverse flow such as a pulsating flow is generated, the flow velocity of the pulsating flow becomes uniform on the downstream side, so that it can be accurately measured.
[0031]
In this embodiment, the flow tube 11 is finally divided into four divided flow paths 18c, 18d, 18e, and 18f by the three divider plates 17a, 17b, and 17c, but the number of divider plates is changed. However, the same effect can be obtained even if the number of the divided flow paths is increased or decreased.
[0032]
In addition, when increasing or decreasing the number of divided flow paths, the number of partition plates may be increased so as to be symmetric with respect to the partition plate provided in the central portion of the flow tube in order to obtain a uniform flow rate by distributing the flow. preferable.
[0033]
Further, preferably, the number of divided flow paths is increased stepwise from the upstream side to the downstream side of the flow tube, and the flow is equally distributed by equalizing the cross-sectional areas of the divided flow paths for each stage. .
[0034]
In the present embodiment, the ultrasonic transducers 12 and 13 are arranged in an I-path system in which the upstream and downstream sides of the flow tube 11 are diagonally opposed to each other. The same effect can be obtained even if the V-pass method is used in which an ultrasonic transducer is arranged in the V-pass method. Furthermore, the same effect can be obtained even if the number of ultrasonic transducers is increased.
[0035]
In the present embodiment, the partition plates 17a, 17b, and 17c are provided in parallel to the long side of the rectangular flow tube 11 having a rectangular cross section. However, the partition plate may be provided in parallel to the short side of the flow tube 11. Moreover, the shape of the flow tube 11 is not limited to a rectangle.
[0036]
(Example 2)
Hereinafter, another embodiment will be described with reference to FIG. In FIG. 5, the same members as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted. The operation of the ultrasonic flowmeter is the same as that of the first embodiment.
[0037]
In FIG. 5, the pipe 19 is divided into six divided flow paths 18g, 18h, 18i, 18j, 18k, and 18m by five partition plates 17d, 17e, 17f, 17g, and 17h.
[0038]
Then, by making the three partition plates 17e, 17f, and 17g in the central part longer than the other partition plates 17d and 17h on the outside, the length of the two divided flow channels 18i and 18j in the center is changed to that on the other side. It is set longer than the divided flow paths 18g, 18h, 18k, and 18m.
[0039]
With this configuration, the divided flow paths 18i and 18j in the central portion of the flow tube 19 are longer than the other divided flow paths 18g, 18h, 18k, and 18m, so that the resistance when the fluid flows through the divided flow paths 18i and 18j is different. It becomes larger than the resistance when flowing through the divided flow paths 18g, 18h, 18k, 18m.
[0040]
As a result, the flow speeds of the divided flow paths 18i, 18j in the portion where the flow velocity is high and the divided flow paths 18g, 18h, 18k, 18m in the portion where the flow velocity is low are equalized.
[0041]
The number of the divided flow paths is not limited as long as it corresponds to the flow velocity distribution, and the length change of the divided flow paths is generally performed stepwise.
[0042]
Of course, as a method of providing the partition plate, it is conceivable to arrange in parallel with the long side or the short side in the rectangular flow path having a rectangular cross section, and the shape of the flow tube is not limited to the rectangular shape. Absent.
[0043]
(Example 3)
Hereinafter, another embodiment will be described with reference to FIG. In FIG. 6, the same members as those in the first embodiment and the second embodiment are denoted by the same reference numerals and the description thereof is omitted. In FIG. 6, the operation of the ultrasonic flowmeter is the same as that of the first embodiment.
[0044]
FIG. 7 shows an embodiment of a case where the flow velocity distribution is such that the flow velocity at the center portion of the flow tube 9 is large and the flow velocity decreases as the outer peripheral wall portion is reached.
[0045]
In FIG. 6, a rectangular flow path 11 having a rectangular cross section is divided into six divided flow paths via five partition plates 17i, 17j, 17k, 17m, and 17n that are parallel to the long side and have the same length. 18n, 18o, 18p, 18q, 18r, and 18s are divided, and in addition, their cross-sectional areas are increased stepwise from the central portion of the flow tube 11 to the outside.
[0046]
The change in the cross-sectional area of the divided flow paths 18n, 18o, 18p, 18q, 18r, and 18s is realized by adjusting the adjacent intervals of the partition plates 17i, 17j, 17k, 17m, and 17n.
[0047]
As described above, according to the present embodiment, the sectional area of the divided flow path 31 is increased from the central portion of the flow tube 11 to the outside. Correspondingly, since the sectional areas of the divided flow paths 18n, 18o, 18p, 18q, 18r, and 18s, that is, the fluid resistance is set, the flow rates in the divided flow paths 18n to 18s become uniform.
[0048]
And since the flow velocity in each division | segmentation flow path 18n-18s can be equalized, highly accurate flow volume measurement can be implement | achieved.
[0049]
In addition, the cross-sectional area of each division | segmentation flow path 18n-18s is realizable also by changing the thickness of the partition plates 17o, 17p, and 17q like FIG. FIG. 7 shows an example in which four divided flow paths 18t, 18u, 18v, and 19w are provided.
[0050]
In this example, the cross-sectional area was increased stepwise from the center of the flow tube in the outward direction, but the main point is how to change the cross-sectional area as long as it corresponds to the flow velocity distribution in the run-up channel. Will not be constrained at all.
[0051]
Moreover, while changing the cross-sectional area of a division | segmentation flow path according to flow-velocity distribution, you may change the length of a flow path according to flow-velocity distribution like Example 2. FIG. That is, the length of the divided flow path in the portion where the fluid flow rate is large may be longer than the length of the other divided flow paths, and the cross-sectional area thereof may be smaller than the cross-sectional area of the other divided flow paths.
[0052]
In general, at least one of the change in the cross-sectional area and the change in the length of the divided flow path appears stepwise. Furthermore, the length may be shortened stepwise and the cross-sectional area may be increased stepwise as the flow rate of the fluid in the flow tube is changed from the flow passage of the portion where the flow velocity is high to the flow passage of the portion where the flow velocity is low.
[0053]
【The invention's effect】
As described above, according to the ultrasonic flowmeter of the present invention, the flow velocity distribution in each divided flow path can be made uniform and highly accurate measurement can be performed.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an ultrasonic flowmeter in Embodiment 1 of the present invention. FIG. 2 is a transverse sectional view of the same. FIG. 3 is a flow velocity distribution diagram in Embodiment 1 of the present invention. Flow velocity distribution diagram corresponding to Example 1 [FIG. 5] Longitudinal sectional view of the ultrasonic flowmeter in Example 2 of the present invention [FIG. 6] Longitudinal sectional view of the ultrasonic flowmeter in Example 3 of the present invention [FIG. FIG. 8 is a longitudinal sectional view showing another example of the ultrasonic flowmeter according to the third embodiment of the present invention. FIG. 8 is a schematic sectional view of a flow path in a conventional ultrasonic flowmeter.
DESCRIPTION OF SYMBOLS 11 Flow pipe 12, 13 Ultrasonic wave transmitter / receiver 14 Flow rate measuring means 17a-17q Partition plate 18a-18w Divided flow path

Claims (3)

A flow tube through which fluid flows, a plurality of divided flow paths formed by dividing the inside of the flow tube with a partition plate, at least a pair of ultrasonic transducers provided in the flow tube, and the ultrasonic transmission / reception wave Flow rate measuring means for calculating the flow rate of the fluid according to the propagation time of the ultrasonic waves measured by the measuring device, and the division as the upstream side becomes the downstream side in the measurement region measured by the ultrasonic transducer An ultrasonic flowmeter in which the number of flow paths is increased and the fluid divided in the upstream divided flow path is sequentially subdivided in the divided flow path in the next stage .   The ultrasonic flowmeter according to claim 1, wherein the number of the divided flow paths is increased stepwise, and the sectional areas of the divided flow paths are made equal for each stage. The ultrasonic flowmeter according to claim 1 or 2, wherein a partition plate is provided in parallel to a long side of the rectangular flow tube having a rectangular cross section .

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