Ultrasonic flowmeter

Abstract

To provide an ultrasonic flowmeter that has a compact outer shape, and with which yet it is possible to realize highly accurate measurement.SOLUTION: An ultrasonic flowmeter 1 comprises: a fluid passage 2 in which the fluid to be measured flows; a pair of ultrasonic transducers 6, 7 that are capable of transmitting and receiving an ultrasonic signal; a flow rate calculation unit 21 that calculates the flow rate of the fluid to be measured, on the basis of the propagation time of the ultrasonic signal; and a passage body 19 in which the fluid passage 2 is formed. The fluid passage 2 includes a main passage 4 that is composed of a plurality of divided passages in which the passage that is rectangular in cross section is divided with the same width, and sub-passages 22a, 22b that are composed of additional passages whose heights are lower than the divided passages and which have a rectangular cross section. The ultrasonic signal propagates through the fluid to be measured that flows inside the main passage 2. The sub-passages 22a, 22b are arranged so as to be symmetrical to the main passage 4. The sub-passages 22a, 22b are arranged in a smallest circle that includes the passage cross section of the main passage 4, and the smallest circle is located in the inside of the passage body 19.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to an ultrasonic flowmeter that measures the flow rate of a fluid to be measured by dividing a measurement flow path into multi-layered flow paths using a partition plate. [Background technology]

[0002] As a conventional ultrasonic flowmeter of this type, for example, the ultrasonic flowmeter disclosed in Patent Document 1 is known. Figs. 13A to 13E are diagrams showing the conventional ultrasonic flowmeter disclosed in Patent Document 1. Fig. 13A is a perspective view of the conventional ultrasonic flowmeter. Fig. 13B is a view taken along the S arrow in Fig. 13A. Fig. 13C is a view taken along the T arrow in Fig. 13A. Fig. 13D is a cross-sectional view taken along the 13D-13D line in Fig. 13A. Fig. 13E is a cross-sectional view taken along the 13E-13E line in Fig. 13A.

[0003] As shown in Figures 13A to 13E, particularly Figure 13E, the ultrasonic flowmeter has a pair of ultrasonic transmitters / receivers, consisting of a first ultrasonic transmitter / receiver 6 and a second ultrasonic transmitter / receiver 7, disposed in a measurement flow path 4 having a rectangular cross section. A swirling flow suppression sheet 8 having openings 9, 10 smaller than the openings of the recesses 11, 12 is disposed in the path from the ultrasonic transmission surfaces of the first ultrasonic transmitter / receiver 6 and the second ultrasonic transmitter / receiver 7 to the measurement flow path 4. This suppression sheet 8 suppresses attenuation of ultrasonic waves and also suppresses the generation of vortex flows p, q in the recesses 11, 12, which are a cause of measurement errors, thereby ensuring measurement accuracy. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-215060 A Summary of the Invention

[0005] Recently, there has been an increasing demand for ultrasonic flowmeters to be installed in gas meters for measuring gas flow rates, ranging from general household gas meters to commercial gas meters for large and small stores and other facilities. In response to this growing demand, ultrasonic flowmeters with flow paths of a size appropriate to the gas flow rate to be measured are required.

[0006] For example, in the conventional ultrasonic flowmeter described in Patent Document 1, the flow paths through which the measured fluid flows are rectangular and have substantially the same cross-sectional shape. That is, when the total number of flow paths including the measurement flow path 4 is three, the width and height of each flow path cross-sectional shape are the same for all three. However, in such a configuration, when, for example, two flow paths are added to make the total number of flow paths five in order to measure a larger gas flow rate, two flow paths having the same width and height as the existing flow paths are added, so that the external size of the ultrasonic flowmeter increases significantly, making it difficult to assemble the ultrasonic flowmeter into a gas meter box that houses the ultrasonic flowmeter. Note that the total number of flow paths in the measurement flow paths 4 shown in Figures 13B to 13D is four.

[0007] The ultrasonic flowmeter according to the present disclosure includes a fluid flow path through which a fluid to be measured flows, a pair of ultrasonic transmitters and receivers arranged upstream and downstream of an upper portion of the fluid flow path and capable of transmitting and receiving ultrasonic signals, a flow rate calculation unit that calculates a flow velocity or flow rate of the fluid to be measured based on a propagation time required for an ultrasonic signal transmitted from one of the pair of ultrasonic transmitters to propagate through the fluid to be measured and be received by the other of the pair of ultrasonic transmitters and receivers, and a flow path body in which the fluid flow path is configured. With multiple partitions, A main flow path is composed of a plurality of divided flow paths obtained by dividing a flow path having a rectangular cross section by the same width; With multiple sub-partitions, a secondary flow passage formed of an additional flow passage having a rectangular cross section whose width is the same as that of the divided flow passages and whose height is less than that of the divided flow passages. The plurality of partition plates and the plurality of sub-partition plates are provided parallel to a plane including a propagation path of an ultrasonic signal transmitted and received by a pair of ultrasonic transmitters and receivers. The ultrasonic transducer transmits The aboveThe ultrasonic signal propagates through the measured fluid flowing in the main flow path. The sub-flow paths are arranged symmetrically with respect to the main flow path. The sub-flow paths are arranged within a minimum circle that includes a flow path cross section of the main flow path, and the minimum circle is located inside the flow path body. Furthermore, the flow rate calculation unit is configured to calculate the flow rate of the measured fluid flowing through the fluid flow path from the flow velocity or flow rate of the measured fluid obtained based on the propagation time.

[0008] With this configuration, the rectangular additional flow paths of the sub-flow paths have the same width and lower height as the rectangular shapes of the flow paths of the measurement flow paths, so that the external size of the ultrasonic flow meter can be made relatively compact, and high-precision measurement can be achieved even for large flow rates of the measured fluid.

[0009] According to the present disclosure, it is possible to provide an ultrasonic flowmeter that has a compact outer shape and can achieve high-precision measurement when measuring a fluid with a large flow rate. [Brief description of the drawings]

[0010] [Figure 1A] FIG. 1A is a perspective view of an ultrasonic flowmeter according to a first embodiment of the present disclosure. [Figure 1B] FIG. 1B is a view taken along the arrow A in FIG. 1A. [Figure 1C] FIG. 1C is a view taken along the arrow B in FIG. 1A. [Figure 1D] FIG. 1D is a cross-sectional view taken along line 1D-1D of FIG. 1A. [Figure 1E] FIG. 1E is a cross-sectional view taken along line 1E-1E of FIG. 1A. [Diagram 2] FIG. 2 is an enlarged view of FIG. 1C. [Figure 3A] FIG. 3A is an exploded perspective view of a flow path body and partition plates according to the first embodiment of the present disclosure. [Figure 3B] FIG. 3B is a cross-sectional view taken along line 3B-3B of FIG. 3A. [Figure 3C] FIG. 3C is a view taken along the arrow C in FIG. 3A. [Figure 4]FIG. 4 is an assembly structure diagram of the ultrasonic flowmeter according to the first embodiment of the present disclosure. [Figure 5A] FIG. 5A is a diagram showing a flow path configuration in a conventional ultrasonic flowmeter that is capable of measuring a large flow rate. [Figure 5B] FIG. 5B is a comparison diagram between the conventional ultrasonic flowmeter and the ultrasonic flowmeter according to the first embodiment. [Figure 6A] FIG. 6A is a diagram showing another flow path configuration in a conventional ultrasonic flowmeter that allows a large flow rate to be measured. [Figure 6B] FIG. 6B is a cross-sectional view taken along line 6B-6B of FIG. 6A. [Figure 6C] FIG. 6C is a view taken along the arrow J in FIG. 6A. [Figure 7] FIG. 7 is a graph showing the flow rate measurement results in the ultrasonic flowmeter shown in FIGS. 6A to 6C. [Figure 8] FIG. 8 is a graph showing a flow rate measurement result in the ultrasonic flowmeter according to the first embodiment of the present disclosure. [Figure 9A] FIG. 9A is a diagram showing a flow path configuration of an ultrasonic flowmeter according to a first modified example of the present disclosure. [Figure 9B] FIG. 9B is a cross-sectional view taken along line 9B-9B of FIG. 9A. [Figure 9C] FIG. 9C is a view taken along the arrow N in FIG. 9A. [Figure 10] FIG. 10 is a graph showing a flow rate measurement result in the ultrasonic flowmeter according to the first modified example of the present disclosure. [Figure 11] FIG. 11 is a graph showing a comparison between a flow rate measurement result for h1=0.68h in an ultrasonic flowmeter according to a first modified example of the present disclosure and a flow rate measurement result in an ultrasonic flowmeter according to a second modified example of the present disclosure. [Figure 12A] FIG. 12A is a flow path configuration diagram of an ultrasonic flowmeter according to a second modified example of the present disclosure. [Figure 12B] FIG. 12B is a cross-sectional view taken along line 12B-12B of FIG. 12A. [Figure 12C] FIG. 12C is a view taken along the arrow Q in FIG. 12A. [Figure 13A]FIG. 13A is a perspective view of a conventional ultrasonic flowmeter. [Figure 13B] FIG. 13B is a view taken along the arrow S in FIG. 13A. [Figure 13C] FIG. 13C is a view taken along the line T in FIG. 13A. [Figure 13D] FIG. 13D is a cross-sectional view taken along line 13D-13D of FIG. 13A. [Figure 13E] FIG. 13E is a cross-sectional view taken along line 13E-13E of FIG. 13A. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0012] (First embodiment) (Configuration of ultrasonic flowmeter) Fig. 1A is a perspective view of an ultrasonic flowmeter according to a first embodiment of the present disclosure. Fig. 1B is a view seen from an arrow A in Fig. 1A. Fig. 1C is a view seen from an arrow B in Fig. 1A. Fig. 1D is a cross-sectional view taken along line 1D-1D in Fig. 1A. Fig. 1E is a cross-sectional view taken along line 1E-1E in Fig. 1A. Fig. 2 is an enlarged view of Fig. 1C.

[0013] As shown in Figures 1A to 1E and 2, the ultrasonic flowmeter 1 has a flow path body 19 in which a fluid flow path 2 through which a fluid to be measured flows is configured. A pair of ultrasonic transmitters and receivers, consisting of a first ultrasonic transmitter and receiver 6 and a second ultrasonic transmitter and receiver 7 capable of transmitting and receiving ultrasonic signals, are arranged upstream and downstream of an upper portion of the fluid flow path 2. The ultrasonic flowmeter 1 also includes a flow rate calculation unit 21 that measures the flow velocity or flow rate of the contacted fluid based on the propagation time required for an ultrasonic signal transmitted from one of the pair of ultrasonic transmitters and receivers consisting of the first ultrasonic transmitter and receiver 6 and the second ultrasonic transmitter and receiver 7 to propagate through the fluid to be measured and be received by the other ultrasonic transmitter and receiver.

[0014] In the fluid flow path 2, the measurement flow path 4, which is a main flow path with a rectangular cross section, is divided by partition plates 20a, 20b, and 20c to form a plurality of divided flow paths 5a, 5b, 5c, and 5d of the same width w and height h. The fluid flow path 2 is also provided with sub-flow paths 22a and 22b, which are formed of additional flow paths 24a, 24b, 24c, and 24d having a rectangular cross section with the same width w as the divided flow paths 5a, 5b, 5c, and 5d that constitute the measurement flow path 4 and lower than the height h of the divided flow paths 5a, 5b, 5c, and 5d. The measurement flow path 4, which is the main flow path, and the sub-flow path 22a are divided by a sub-partition plate 23a, and the measurement flow path 4, which is the main flow path, and the sub-flow path 22b are divided by a sub-partition plate 23b. Furthermore, the sub-flow path 22a is divided by a sub-partition plate 23c, and additional flow paths 24a and 24b are provided, which have the same width w as the divided flow paths 5a, 5b, 5c, and 5d and have rectangular cross sections that are lower than the height h of the divided flow paths 5a, 5b, 5c, and 5d. The sub-flow path 22b is divided by a sub-partition plate 23d, and additional flow paths 24c and 24d are provided, which have the same width w as the divided flow paths 5a, 5b, 5c, and 5d and have rectangular cross sections that are lower than the height h of the divided flow paths 5a, 5b, 5c, and 5d.

[0015] The flow path body 19 has a trumpet-shaped inlet 19a through which the measured fluid flows in and an outlet 19b through which the measured fluid flows out, and may be formed, for example, by injection molding of resin. The partition plates 20a, 20b, 20c and the sub-partition plates 23a, 23b, 23c, 23d are made of, for example, stainless steel metal plates, and have the same plate thickness t, which is about 0.3 mm, as shown in FIG. 1D. The partition plates 20a, 20b, 20c and the sub-partition plates 23a, 23b, 23c, 23d are attached to the flow path body 19.

[0016] Fig. 3A is an exploded perspective view of a flow path body and partition plates according to the first embodiment of the present disclosure, Fig. 3B is a cross-sectional view taken along line 3B-3B in Fig. 3A, and Fig. 3C is a view taken along arrow C in Fig. 3A.

[0017] As shown in Fig. 3B, inflow side fixed grooves 29a, 29b, 29c, 29d, 29e, 29f, and 29g and outflow side fixed grooves 30a, 30b, 30c, 30d, 30e, 30f, and 30g are provided on the reflection surface 25 side of the space through which the measured fluid flows. The reflection surface 25 is a plane that reflects an ultrasonic signal transmitted from one of a pair of ultrasonic transmitter-receivers consisting of the first ultrasonic transmitter-receiver 6 and the second ultrasonic transmitter-receiver 7 until it propagates through the measured fluid and reaches the other ultrasonic transmitter-receiver.

[0018] Furthermore, as shown in FIG. 3C, inlet side slits 27a, 27b, 27c, 27d, 27e, 27f, and 27g and outlet side slits 28a, 28b, 28c, 28d, 28e, 28f, and 28g are provided on the entrainment flow suppression sheet installation surface 26 side of the flow path body 19.

[0019] Here, the inlet side fixed grooves 29a-29g, the outlet side fixed grooves 30a-30g, the inlet side slits 27a-27g, and the outlet side slits 28a-28g all have the same width, which is slightly larger than the plate thickness t of the partition plates 20a-20c and the sub-partition plates 23a-23d, for example, about 0.32 mm. Also, the shape of the partition plates 20a-20c and the sub-partition plates 23a-23d is provided with two protrusions 23e, as shown in the shape of the sub-partition plate 23d in FIG. 3A.

[0020] In the above-described structure, when the partition plates 20a to 20c and the sub-partition plates 23a to 23d are attached to the flow path body 19, they are inserted from the side of the entrainment-flow suppression sheet installation surface 26, as shown in Fig. 3A. The protrusions 23e of the partition plates 20a to 20c and the sub-partition plates 23a to 23d are fitted into the inflow-side fixing grooves 29a to 29g and the outflow-side fixing grooves 30a to 30g, and the sides opposite to the protrusions 23e are sandwiched between the inflow-side slits 27a to 27g and the outflow-side slits 28a to 28g, and are fixed by a clearance fit.

[0021] Here, the flow path body 19, the partition plates 20a to 20c, and the sub-partition plates 23a to 23d are constructed as separate parts and fixed together with a clearance fit, but the partition plates 20a to 20c and the sub-partition plates 23a to 23d, and the flow path body 19 may also be constructed as a single unit molded from resin, for example.

[0022] 4 is an assembly structure diagram of the ultrasonic flowmeter 1 according to the first embodiment of the present disclosure. As shown in FIG. 4, the first ultrasonic transmitter / receiver 6 and the second ultrasonic transmitter / receiver 7 are set at predetermined positions in the ultrasonic transmitter / receiver fixing body 31 made of resin, and fixed by the ultrasonic transmitter / receiver fixing tool 33 made of resin. A protrusion 31a is provided on the ultrasonic transmitter / receiver fixing body 31 side, and a fitting hole 33a provided on the ultrasonic transmitter / receiver fixing tool 33 side is fitted into the protrusion 31a, so that the first ultrasonic transmitter / receiver 6 and the second ultrasonic transmitter / receiver 7 are sandwiched and fixed between the ultrasonic transmitter / receiver fixing body 31 and the ultrasonic transmitter / receiver fixing tool 33. In addition, the signal lines 6a, 7a of the first ultrasonic transmitter / receiver 6 and the second ultrasonic transmitter / receiver 7 are connected to the flow rate calculation unit 21.

[0023] The ultrasonic transmitter / receiver unit 32 thus assembled is attached to the upper part of the flow path body 19 via the entanglement flow suppression sheet 8. The ultrasonic transmitter / receiver fixing body 31 can be attached to the flow path body 19 by, for example, thermal welding if both are made of resin.

[0024] As shown in Fig. 2, the divided flow paths 5a, 5b, 5c, and 5d of the measurement flow path 4 each have a rectangular cross-sectional shape with a width w and a height h, and partition plates 20a, 20b, and 20c of the same thickness t are disposed between them. The additional flow path 24a of the sub-flow path 22a has a rectangular cross-sectional shape with a width w and a height h2, and the additional flow path 24b has a rectangular cross-sectional shape with a width w and a height h1. A sub-partition plate 23c having a thickness t is disposed between the additional flow paths 24a and the additional flow paths 24b. The additional flow path 24d of the sub-flow path 22b has a rectangular cross-sectional shape with a width w and a height h2, and the additional flow path 24c has a rectangular cross-sectional shape with a width w and a height h1.

[0025] Here, for the height, h2

[0026] (Action and effect of ultrasonic flowmeter) First, a first function and effect of the ultrasonic flowmeter according to the first embodiment of the present disclosure will be described.

[0027] FIG. 5A shows a flow path configuration diagram of an ultrasonic flowmeter 100 using a flow path body 35 to which a flow path is added in order to measure a larger gas flow rate in the conventional ultrasonic flowmeter according to Patent Document 1. The example shows a fluid flow path in which a sub-flow path 52a having two flow paths and a sub-flow path 52b having two flow paths are added to a measurement flow path 40 having four flow paths, making the total number of flow paths eight. Here, the rectangular cross-sectional shapes of the flow paths 54a and 54b of the added sub-flow path 52a and the flow paths 54c and 54d of the sub-flow path 52b are configured with the same width w and height h as the flow paths 45a, 45b, 45c, and 45d of the measurement flow path 4. That is, this corresponds to the case where h=h1=h2 in the first embodiment.

[0028] ​FIG. 5B is a comparative diagram of the outlet 35b shown in FIG. 5A, which is a view seen from an arrow E of the ultrasonic flowmeter 100 in which the outer diameter of the outlet 35b is ΦD2, and the outlet 19b shown in FIG. 1C, which is a view seen from an arrow B of the ultrasonic flowmeter 1 in FIG. 1A, which is a view seen from an arrow B of the ultrasonic flowmeter 1 in which the outer diameter of the outlet 19b is ΦD1, and the outlet 19b shown in FIG. 2. In the ultrasonic flowmeter 1 according to the first embodiment, the fluid flow path 2 is contained within a circle F shown by a dotted line, whereas in the ultrasonic flowmeter 100, the fluid flow path 2 is contained within a circle G larger than the circle F. The circles F and G correspond to the minimum diameter of the flow path body 35 required to form the fluid flow path therein. That is, as can be seen from FIG. 5B, ΦD1<ΦD2, and according to the ultrasonic flowmeter 1 according to the first embodiment of the present disclosure, it can be seen that a compact configuration can be realized by arranging the sub-flow paths 22a and the sub-flow paths 22b within the smallest circle F that contains the measurement flow path 4.

[0029] Next, a second function and effect of the ultrasonic flowmeter 1 according to the present embodiment will be described.

[0030] As shown in FIG. 2, which is a view taken along the arrow B in FIG. 1A, in the ultrasonic flowmeter 1 according to this embodiment, the added sub-flow paths 22a and 22b are arranged symmetrically in the vertical and horizontal directions with respect to the width direction center line X and height direction center line Y of the measurement flow path 4, including the same plate thickness t of the partition plates 20a, 20b, and 20c and the sub-partition plates 23a, 23b, 23c, and 23d.

[0031] Furthermore, the ultrasonic flowmeter 1 has a pair of ultrasonic transmitters / receivers, consisting of a first ultrasonic transmitter / receiver 6 and a second ultrasonic transmitter / receiver 7, arranged upstream and downstream of the upper part of the fluid flow path 2. The ultrasonic signal transmitted from one of the pair of ultrasonic transmitter / receivers is propagated through the fluid to be measured and is received by the other ultrasonic transmitter / receiver, and based on the propagation time, the flow velocity or flow rate of the fluid to be measured is calculated. Therefore, since the ultrasonic signal is propagated only through the measurement flow path, the flow velocity or flow rate of the fluid to be measured passing through the added sub-flow paths 22a and 22b is not directly measured.

[0032] Therefore, the flow rate of the measured fluid passing through the measurement flow path 4, the sub-flow paths 22a, and the sub-flow paths 22b is calculated as the total flow rate of the measured fluid, including the sub-flow paths 22a and 22b, from the measurement results in the measurement flow path 4, which directly measures the measured fluid passing through.

[0033] For example, it can be calculated by multiplying the flow rate of the fluid to be measured obtained in the measurement flow path 4 by the flow rate cross-sectional area of ​​the fluid flow path 2 (the sum of the flow rate cross-sectional areas of the measurement flow path 4, the sub-flow paths 22a, and the sub-flow paths 22b). Alternatively, the ratio of the flow rate of the measurement flow path 4 to the flow rates of the sub-flow paths 22a and the sub-flow paths 22b may be calculated in advance, and the flow rates of the sub-flow paths 22a and the sub-flow paths 22b may be calculated from the flow rate of the measurement flow path 4, and then the total may be calculated. However, in either case, it is preferable that the flow rates of the measurement flow path 4, the sub-flow paths 22a, and the sub-flow paths 22b are the same even if the flow rate changes.

[0034] Therefore, it is necessary to make the flow velocity distribution of the measured fluid passing through the measurement flow path 4, the sub-flow paths 22a, and the sub-flow paths 22b as uniform as possible. In this embodiment, by making the sub-flow paths 22a and the sub-flow paths 22b symmetrical in the vertical and horizontal directions with respect to the measurement flow path 4, a more uniform flow of the measured fluid passing through can be achieved, thereby enabling highly accurate measurement.

[0035] Even if the added sub-flow paths 22a and 22b are arranged symmetrically in the vertical and horizontal directions with respect to the measurement flow path 4 and are arranged to fit within the circle F of the outlet portion 19b of the first embodiment described as "In the case of FIG. 2" at the bottom of Figure 5B, the measurement results may not be satisfactory.

[0036] Figures 6A to 6C show an example of an ultrasonic flowmeter 200. Figure 6A is a diagram showing another flow path configuration in a conventional ultrasonic flowmeter that allows a large flow rate to be measured. Figure 6B is a cross-sectional view taken along line 6B-6B in Figure 6A. Figure 6C is a view taken along the arrow J in Figure 6A.

[0037] 6A, in ultrasonic flowmeter 200, sub-flow paths 37a and sub-flow paths 37b are arranged symmetrically on the left and right of measurement flow path 60 with respect to width-direction center line X and height-direction center line Y. However, the flow path cross-sectional shapes of sub-flow paths 37a and sub-flow paths 37b are substantially semicircular, unlike the rectangular shapes of divided flow paths 65a, 65b, 65c, and 65d of measurement flow path 60, and the flow path cross-sectional areas of sub-flow paths 37a and sub-flow paths 37b are approximately 2.6 times larger than each of divided flow paths 65a to 65d of measurement flow path 60.

[0038] 7 is a graph showing the flow measurement results in ultrasonic flowmeter 200 shown in Fig. 6A to Fig. 6C, in terms of actual flow rate and flow coefficient. Here, the flow coefficient (denoted as k) is a coefficient for calculating the actual flow rate from the measured flow rate, and is defined as k = Qt / Qm, where Qt is the actual flow rate and Qm is the measured flow rate. Note that the measured flow rate Qm is calculated as the total flow rate by multiplying the flow velocity determined in measurement flow path 60 by the sum of the flow path cross-sectional areas of measurement flow path 60, sub-flow paths 37a, and sub-flow paths 37b.

[0039] Ideally, this flow coefficient k should be 1 relative to the actual flow rate Qt on the horizontal axis, and at this time, it indicates that the actual flow rate Qt of the passing fluid to be measured matches the calculated flow rate of the entire fluid to be measured, including the sub-flow paths 37a and 37b, based on the flow rate measured in the measurement flow path 60. Therefore, it is ideal for the flow coefficient k on the vertical axis to fluctuate near the value 1 relative to the actual flow rate Qt on the horizontal axis, indicating high measurement accuracy.

[0040] 7 shows that at low flow rates, the flow coefficient k is greater than 1, and at high flow rates, the flow coefficient k gradually approaches 1. This shows that at low flow rates, the calculated flow rate of the entire measured fluid, including the sub-flow paths 37a and 37b, based on the flow rate actually measured in the measurement flow path 60 is smaller than the actual flow rate Qt, and therefore the calculated flow rate does not match the actual flow rate Qt unless the flow coefficient k is multiplied by a value greater than 1, which shows that the measurement accuracy is low.

[0041] The reason is that the flow path cross-sectional area of ​​the sub-flow path 37a or the sub-flow path 37b is larger than the divided flow paths 65a to 65d of the measurement flow path 60, so that at low flow rates the fluid does not flow to the measurement flow path 60 side, which has a large flow path resistance, but tends to flow to the sub-flow path 37a or the sub-flow path 37b side, which has a small flow path resistance, and the measured fluid does not flow uniformly and the flow velocity distribution of the measured fluid becomes large. Also, at high flow rates, the measured fluid cannot flow sufficiently through the flow path cross-sectional area of ​​the sub-flow path 37a or the sub-flow path 37b alone, so the measured fluid also flows into the measurement flow path 60 side, gradually changing to a uniform flow.

[0042] Even if the added sub-flow paths 37a and 37b are arranged symmetrically in the vertical and horizontal directions with respect to the measurement flow path 60, the measurement accuracy may not be satisfactory, and it is important to make the flow velocity distribution of the measured fluid as uniform as possible from the low flow rate region to the high flow rate region.

[0043] In contrast, the flow rate measurement results of the ultrasonic flowmeter 1 according to the first embodiment of the present disclosure shown in Figures 1A to 1E and 2 are as shown in Figure 8. According to Figure 8, the flow coefficient k changes in the vicinity of 1.10 in the flow rate range from the low flow rate range to the high flow rate range, and there is almost no change in the flow coefficient as in Figure 7, indicating that the characteristics of the flow coefficient are flat and the measurement accuracy is high. This is because the flow path widths of the additional flow paths 24a, 24b of the sub-flow path 22a and the additional flow paths 24c, 24d of the sub-flow path 22b are set to the same width w as the flow path widths of the divided flow paths 5a, 5b, 5c, 5d of the measurement flow path 4, which is the main flow path, thereby making it possible to reduce the difference in flow path resistance.

[0044] As described above, according to this embodiment, it is possible to provide an ultrasonic flowmeter that has a compact outer shape and can achieve high-precision measurement when measuring a large flow rate of a fluid to be measured.

[0045] (First Modification) In the ultrasonic flowmeter 1 according to the first embodiment of the present disclosure shown in Figures 1A to 1E and Figure 2, the flow path heights of the additional flow path 24b of the sub-flow path 22a and the additional flow path 24c of the sub-flow path 22b are selected as h1 and the flow path heights of the additional flow path 24a of the sub-flow path 22a and the additional flow path 24d of the sub-flow path 22b are selected as h2 so as to fall within circle F, as shown in the view of arrow B in Figure 1A shown below in Figure 5B. However, if the flow path width is set to width w, high-precision measurement is possible even if the flow path height is changed.

[0046] Figures 9A to 9C are configuration diagrams of an ultrasonic flowmeter 300 according to a first modified example. Figure 9B is a cross-sectional view taken along line 9B-9B in Figure 9A. Figure 9C is a view taken along the arrow N in Figure 9A.

[0047] Measurement flow path 80 is configured with divided flow paths 85a, 85b, and 85c having a rectangular cross-sectional shape with width w and height h via partition plates 90a and 90b. Sub-flow paths 92a and 92b are added to measurement flow path 80 via sub-partition plates 93a and 93b, respectively, and are configured with a rectangular cross-sectional shape with width w and height h1.

[0048] Here, the flow rate measurement results when the flow path height h1 of the sub-flow path 92a and the sub-flow path 92b is changed are shown in FIG. 10. FIG. 10 is a graph showing the flow coefficient against the actual flow rate when the flow path height h1 is set to 0.68h, 0.66h, 0.58h, and 0.50h. As can be seen from this graph, if the flow path width of the divided flow paths 85a, 85b, and 85c of the measurement flow path 80 and the sub-flow paths 92a and 92b is set to width w, there is no significant difference in the results even if the flow path height is changed to four types, and stable and highly accurate measurement is possible. Therefore, when there is a restriction on the external size of the ultrasonic flowmeter, the flow path height can be changed arbitrarily after the flow path width is set to width w, allowing for flexible design.

[0049] (Second Modification) The graph shown in Fig. 10 shows the flow coefficient k when the actual flow rate Qt is in the range of 360 L / h to 25,000 L / h in the ultrasonic flowmeter 300 according to the first modification. When the actual flow rate Qt is in the smaller flow rate range of 50 L / h to 25,000 L / h and the flow path height h1 is 0.68h, the flow coefficient k is represented by a solid line in the graph shown in Fig. 11.

[0050] As can be seen from Figure 11, when the flow path height h1 is 0.68h, the actual flow rate Qt peaks at around 2,500 L / h, and the flow coefficient k decreases both on the low flow rate side and the high flow rate side. The tendency to decrease significantly in the low flow rate side is particularly evident, which indicates that at low flow rates, the flow in the measurement flow path 80 and the sub-flow paths 92a and 92b is non-uniform, with more of the measured fluid flowing toward the measurement flow path 80. In order to further suppress the fluctuation range of the flow coefficient k and improve measurement accuracy, we therefore considered increasing the flow path cross-sectional area of ​​the sub-flow paths 92a and 92b to achieve a more uniform flow at low flow rates.

[0051] 12A to 12C show the configuration of an ultrasonic flowmeter 400 according to a second modified example.

[0052] 12A to 12C, the difference from the shape of the ultrasonic flowmeter 300 shown in Fig. 9A to 9C is that the shape of the sub-flow paths 94a and 94b of the ultrasonic flowmeter 400 is trapezoidal rather than rectangular. That is, the flow path width (the distance between the parallel sides of the trapezoid) of the sub-flow paths 94a and 94b is the same as the flow path width of the divided flow paths 86a, 86b, and 86c of the measurement flow path 81, the flow path height is the same as the flow path height of the divided flow paths 86a, 86b, and 86c on the long side, and the short side is the height h1 shorter than the height h, and the sides corresponding to the legs of the trapezoid are configured obliquely along the circle including the divided flow paths 86a, 86b, and 86c. Therefore, the flow path cross-sectional area of ​​the sub-flow paths 94a and 94b in this modification can be made larger than that of the rectangular sub-flow paths shown in Fig. 9A to 9C. Compared with the total flow path cross-sectional area in the ultrasonic flowmeter 300 shown in Figures 9A to 9C, the ultrasonic flowmeter 400 has an increased area of ​​approximately four triangles shown by diagonal lines in the enlarged view of Figure 12C per upper and lower ends of the sub-flow paths 94a, 94b.

[0053] 12A to 12C. The ultrasonic flowmeter 400 shown in FIG. 12A to 12C differs from the structure shown in FIG. 3A to 3C in that the flow path body 19, partition plates 20a, 20b, and sub-partition plates 23a, 23b shown in FIG. 3A to 3C are integrally molded from the same material (e.g., resin). The ultrasonic flowmeter 400 may also be configured to be integrally molded from the same material including the ultrasonic transmitter / receiver fixing body 31 shown in FIG. 4.

[0054] In the enlarged view shown in Figure 12C, which is a view taken from the Q arrow in Figure 12A, the added approximately triangular corner portion indicated by diagonal lines has a moderately rounded shape, which is expected to have the effect of reducing the mold release resistance when, for example, the flow path body 19, partition plates 91a, 91b, and sub-partition plates 95a, 95b are integrally molded from resin.

[0055] The flow rate measurement results for the ultrasonic flowmeter 400 configured as above, particularly when h1=0.68, are shown by the dashed line in Fig. 11. As can be seen from the graph in Fig. 11, the fluctuation range of the flow coefficient k is suppressed (from about 4% to about 1%) and the measurement accuracy is improved, particularly at low flow rates of 50 L / h to 1,000 L / h in the actual flow rate Qt range, compared to the solid line showing the results for the ultrasonic flowmeter 300 shown in Figs. 9A to 9C. This is believed to be because the increased flow cross-sectional area of ​​the sub-flow paths 94a and 94b allows a more uniform flow to be achieved in the measurement flow path 81 and the sub-flow paths 94a and 94b at low flow rates.

[0056] Furthermore, in the ultrasonic flowmeter 400 shown in Figures 12A to 12C, if it is considered that the ultrasonic transmitter / receiver fixing body 31a is also integrated by resin molding of the same material, with a configuration such as that shown in Figures 12A to 12C, the resin will be thick at the joint between the flow path body 19a and the ultrasonic transmitter / receiver fixing body 31a. However, by providing an approximately triangular flow path cross-sectional increased portion on the upper side of the sub-flow paths 94a, 94b, the resin thickness will become more uniform, and it is expected that resin molding with higher dimensional accuracy will be achieved.

[0057] Therefore, when there is a restriction on the external size of the ultrasonic flowmeter, the cross-sectional shape of the sub-channels is basically a rectangular cross-section with the channel width aligned to width w and the channel height changed as desired. However, in order to achieve a more uniform flow and more accurate measurement, the cross-sectional shapes of the sub-channels 94a, 94b are trapezoidal cross-sections with the channel width aligned to width w of the divided channel 86a-86c of the measurement channel 81, and the channel height direction is parallel within a predetermined range of the height of the divided channel 86a-86c of the measurement channel 81, and the cross-sectional shapes are arranged symmetrically with respect to the measurement channel 81, which is the main channel, thereby enabling a flexible design for achieving a uniform flow.

[0058] (Other embodiments) From the above description, many improvements and other embodiments of the present disclosure will be apparent to those skilled in the art. Therefore, the above description should be interpreted as merely illustrative and is provided for the purpose of teaching those skilled in the art the best mode for carrying out the present disclosure. The details of the structure and function thereof may be substantially changed without departing from the spirit of the present disclosure.

[0059] As described above, the first disclosure includes a fluid flow path through which a fluid to be measured flows, and a pair of ultrasonic transmitters and receivers arranged upstream and downstream of the upper part of the fluid flow path and capable of transmitting and receiving ultrasonic signals. The first disclosure also includes a flow rate calculation unit that calculates the flow velocity or flow rate of the fluid to be measured based on the propagation time from when an ultrasonic signal transmitted from one of the pair of ultrasonic transmitters propagates through the fluid to when it is received by the other ultrasonic transmitter and receiver of the pair of ultrasonic transmitters. The fluid flow path also includes a main flow path composed of multiple divided flow paths obtained by dividing a flow path with a rectangular cross section by the same width, and a sub-flow path composed of an additional flow path having a rectangular cross section whose width is the same as the divided flow paths and whose height is lower than that of the divided flow paths. The flow rate calculation unit is an ultrasonic flowmeter that calculates the flow rate of the fluid to be measured flowing through the fluid flow path from the flow velocity or flow rate of the fluid to be measured obtained based on the propagation time.

[0060] With this configuration, the external size of the ultrasonic flowmeter is relatively compact, and high-precision measurement can be achieved even for a large flow rate of the fluid to be measured.

[0061] The second disclosure is characterized in that, particularly in the first disclosure, an ultrasonic signal transmitted from an ultrasonic transmitter / receiver propagates through the fluid to be measured flowing in the main flow path.

[0062] With this configuration, the propagation distance of the ultrasonic signal can be made longer than in the case of measurement in the sub-flow path, and measurement accuracy is improved.

[0063] In the third disclosure, particularly in the first disclosure, the secondary flow passages are arranged symmetrically with respect to the primary flow passage.

[0064] With this configuration, the sub-flow passage and the measurement flow passage are symmetrical in shape with respect to the flow direction of the fluid to be measured, so that a more uniform flow can be achieved, enabling highly accurate measurement to be achieved.

[0065] In the fourth disclosure, particularly in the second disclosure, the secondary flow paths are arranged symmetrically with respect to the primary flow path.

[0066] With this configuration, the sub-flow passage and the measurement flow passage are symmetrical in shape with respect to the flow direction of the fluid to be measured, so that a more uniform flow can be achieved, enabling highly accurate measurement to be achieved.

[0067] A fifth disclosure is particularly any one of the first to fourth disclosures, in which the sub-flow passages are arranged within a minimum circle including a flow passage cross section of the main flow passage.

[0068] A sixth disclosure is particularly any one of the first to fourth disclosures, wherein the additional flow passage has a trapezoidal cross section.

[0069] In the seventh disclosure, particularly in the fifth disclosure, the additional flow passage has a trapezoidal cross section. [Industrial Applicability]

[0070] In the present disclosure, for a measurement flow path equipped with a pair of ultrasonic transmitters and receivers capable of transmitting and receiving ultrasonic signals, the flow path width of each of the sub-flow paths added when measuring a larger flow rate of a measured fluid is made equal to the flow path width of each of the measurement flow paths. With this configuration, it is possible to provide an ultrasonic flow meter that has a relatively compact external shape and can achieve high-precision measurement. [Explanation of symbols]

[0071] 1, 100, 200, 300, 400 ultrasonic flowmeter 4, 80, 81 Measurement flow path (main flow path) 5a, 5b, 5c, 5d, 85a, 85b, 85c, 86a, 86b, 86c Divided channel 6 First ultrasonic transducer (ultrasonic transducer) 7 Second ultrasonic transducer (ultrasonic transducer) 21 Flow rate calculation section 22a, 22b, 92a, 92b, 94a, 94b Sub-channel 24a, 24b, 24c, 24d Additional flow paths

Claims

1. a fluid flow path through which a fluid to be measured flows; a pair of ultrasonic transmitters and receivers arranged upstream and downstream of an upper portion of the fluid flow path and capable of transmitting and receiving ultrasonic signals; a flow rate calculation unit that calculates a flow velocity or a flow rate of the fluid to be measured based on a propagation time of an ultrasonic signal transmitted from one of the pair of ultrasonic transmitter-receivers, propagating through the fluid to be measured and being received by the other of the pair of ultrasonic transmitter-receivers; a flow path body in which the fluid flow path is formed, The fluid flow path comprises a main flow path formed of a plurality of divided flow paths obtained by dividing a flow path having a rectangular cross section by a plurality of partition plates at the same width, and a sub-flow path formed of an additional flow path having a rectangular cross section, the width of which is the same as that of the divided flow paths and the height of which is lower than that of the divided flow paths, by a plurality of sub-partition plates; the plurality of partition plates and the plurality of sub-partition plates are provided parallel to a plane including a propagation path of an ultrasonic signal transmitted and received by the pair of ultrasonic transmitters and receivers, the ultrasonic signal transmitted from the ultrasonic transmitter-receiver propagates through the measurement target fluid flowing in the main flow path, The sub-flow passages are arranged symmetrically with respect to the main flow passage, The sub-flow passage is disposed within a minimum circle including a flow passage cross section of the main flow passage, and the minimum circle is located inside the flow passage body; The flow rate calculation unit calculates a flow rate of the fluid to be measured flowing through the fluid flow path from the flow velocity or flow rate of the fluid to be measured obtained based on the propagation time.

2. 2. The ultrasonic flowmeter according to claim 1, wherein the additional flow passage has a trapezoidal cross section.

3. 3. The ultrasonic flowmeter according to claim 1, wherein the sub-flow passages are arranged symmetrically with respect to the main flow passage and are arranged to sandwich the main flow passage.

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