Ultrasonic flowmeter

Abstract

To suppress the influence of flow disturbance or resistance due to condensation on measurement accuracy in measuring the flow rate of fluid containing moisture.SOLUTION: An ultrasonic flow meter includes: a measurement channel 1 with a rectangular cross section through which fluid to be measured flows; partition plates 2 arranged to divide the short side of the measurement channel 1 into a plurality of parts; a pair of ultrasonic transducers 5 and 6 arranged on the short side of the measurement channel 1 so that ultrasonic waves cross the measurement channel 1; a measurement circuit 11 that performs an operation of transmitting from one of the pair of ultrasonic transducers 5 and 6 and receiving at the other; and a calculation circuit 12 that calculates a received signal of the pair of ultrasonic transducers 5 and 6. A downstream end 10 of the partition plates 2 is formed so that the downstream end downstream of a downstream-side ultrasonic propagation path 8b is approximately parallel to a propagation path, which makes it possible to reduce pressure loss of the fluid, reduce the influence of flow due to water droplets adhering to the partition plates 2, and suppress a decrease in measurement accuracy.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a configuration of an ultrasonic flowmeter that measures a flow rate by using ultrasonic waves. [Background technology]

[0002] Conventionally, as this type of ultrasonic flowmeter, a flowmeter that measures a flow rate by dividing the inside of a rectangular cross-section flow channel into multiple layers is known (see, for example, Patent Document 1).

[0003] 4 shows a cross section of a measurement flow path of the ultrasonic flowmeter described in Patent Document 1. In this ultrasonic flowmeter, ultrasonic transmitter / receivers 102 are arranged on the upstream and downstream sides of the short side of a measurement flow path 101 with a rectangular cross section, and rectangular partition plates 103 are arranged so as to divide the short side direction of the rectangular cross section into multiple layers. Ultrasonic waves form a propagation path 105 between the ultrasonic transmitter / receivers 102 via a reflecting portion 104, and flow measurement is performed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2012-247299 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the conventional configuration has a problem that the pressure loss due to the multiple partitions is large. Also, when measuring a gas containing moisture, condensation on the partitions causes disturbance in the flow or creates resistance, which affects the measurement accuracy.

[0006] The present invention is intended to solve the above-mentioned problems in the conventional art, and has an object to provide an ultrasonic flowmeter which has a small pressure loss and can be used with fluids which contain moisture and may cause condensation. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the ultrasonic flowmeter of the present invention has a rectangular cross section through which a fluid to be measured flows. Measurement The flow path and measurement A partition plate is arranged to divide the short side of the flow path into several parts, measurement The ultrasonic transducer includes a pair of ultrasonic transmitters and receivers disposed on the short sides of the flow path so that ultrasonic waves cross the flow path, a measurement circuit that transmits from one of the pair of ultrasonic transmitters and receives from the other, and a calculation circuit that calculates the reception signals of the pair of ultrasonic transmitters and receivers, an upstream end of the partition plate along the measurement flow path is provided upstream of the ultrasonic propagation path; The downstream end of the partition plate is formed almost parallel to the center line of the ultrasonic propagation path. The partition plate overlaps with the entire ultrasonic propagation path in the measurement flow path when viewed from a direction perpendicular to both the direction in which the measured fluid flows and the direction in which the ultrasonic waves propagate. By configuring it in this manner, the length of the partition plate can be shortened, the effect of water droplets adhering to the partition plate can be reduced, preventing a decrease in measurement accuracy, making it possible to reduce fluid pressure loss, and the surface area of ​​the partition plate can be reduced to reduce the adhesion of water droplets due to condensation.

[0008] Furthermore, the downstream end of this partition is configured to be substantially parallel to the center line of the downstream ultrasonic propagation path and at least half the width r of the ultrasonic transmitter / receiver downstream of this center line.By placing the partition at the downstream end of the multilayer section to an extent that does not affect ultrasonic propagation, it is possible to further reduce fluid pressure loss and reduce the surface area of ​​the partition, minimizing the adhesion of water droplets due to condensation. Effect of the Invention

[0009] The ultrasonic flowmeter of the present invention can reduce pressure loss by cutting the downstream side of the partition plate that divides the flow path into multiple layers. In addition, it can reduce the probability of condensation occurring even for a measured fluid that contains humidity. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view of an ultrasonic flowmeter according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view of a flow path taken along line AA in FIG. 1 according to the first embodiment of the present invention; [Diagram 3] 1 is a graph showing the relationship between flow rate and pressure loss in the first embodiment of the present invention, and a schematic cross-sectional view of a flow path used in an experiment. [Figure 4] Cross-sectional view showing the configuration of a conventional ultrasonic flowmeter. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The first invention comprises a flow path with a rectangular cross-section through which a fluid to be measured flows, a partition plate arranged to divide the short side of the flow path into multiple parts, a pair of ultrasonic transmitters and receivers arranged on the short side of the flow path so that ultrasonic waves cross the flow path, a measurement circuit that transmits from one of the pair of ultrasonic transmitters and receives from the other, and a calculation circuit that calculates the received signals of the pair of ultrasonic transmitters and receivers, and the downstream end of the partition plate is formed downstream of the center line of the ultrasonic propagation path and approximately parallel to the propagation path, thereby reducing pressure loss and the probability of water droplets adhering on the partition plate.

[0012] In the second invention, the downstream end of the partition plate is configured to be substantially parallel to the center line of the downstream ultrasonic propagation path and at least 1 / 2 the width r of the ultrasonic transmitter / receiver downstream of the center line, thereby making it possible to obtain a more quantitative guideline.

[0013] Hereinafter, the embodiments will be described in detail with reference to the drawings. However, more detailed explanation than necessary may be omitted. For example, detailed explanation of already well-known matters or duplicate explanation of substantially the same configuration may be omitted. This is to avoid the following explanation becoming more redundant than necessary and to facilitate understanding by those skilled in the art.

[0014] It should be noted that the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0015] (Embodiment 1) The first embodiment will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a structural cross-sectional view of an ultrasonic flowmeter according to the first embodiment of the present invention, and Fig. 2 is a cross-sectional view of the ultrasonic flowmeter showing the AA cross section of Fig. 1 according to the first embodiment of the present invention.

[0016] 1 and 2, measurement flow channel 1, in which a fluid to be measured flows in the direction of the white arrow, has a rectangular cross-section with a long side width W and a short side height H, and the short side height is divided equally inside by multiple partition plates 2. This measurement flow channel 1 is provided with an upstream inlet 3 and a downstream outlet 4 on the upstream and downstream sides.

[0017] An upstream ultrasonic transmitter / receiver 5 and a downstream ultrasonic transmitter / receiver 6 are arranged on the short sides of the measurement flow path 1 having a rectangular cross section, and a reflecting surface 7 that reflects ultrasonic waves is formed on the opposing short side.

[0018] A pair of ultrasonic transmitters and receivers 5 and 6 have a dimension of width r, and open into the measurement flow path 1 with the same opening dimension of width r for transmitting and receiving ultrasonic waves.

[0019] In the pair of ultrasonic transmitters and receivers 5 and 6 and the multiple divided flow paths 1a divided into multiple layers, ultrasonic waves form a V-shaped ultrasonic propagation path 8 indicated by the path P1-P2-P3. In the case of such V-shaped ultrasonic propagation, the ultrasonic propagation path 8 is divided into an upstream ultrasonic propagation path 8a (P1-P2) and a downstream ultrasonic propagation path 8b (P2-P3).

[0020] In Fig. 1, the upstream ultrasonic propagation path 8a and the downstream ultrasonic propagation path 8b are both depicted as representatives of the center lines of ultrasonic waves with strong ultrasonic propagation strength. In this sense, the upstream ultrasonic propagation path 8a and the downstream ultrasonic propagation path 8b represent the center lines of the upstream ultrasonic propagation path and the downstream ultrasonic propagation path, respectively.

[0021] The upstream end 9 of the partition plate 2 is formed in a direction perpendicular to the flow of the fluid to be measured, as indicated by the outline arrow. The downstream end 10 of the partition plate 2 is formed downstream of the downstream ultrasonic propagation path 8b, approximately parallel to the downstream ultrasonic propagation path 8b, and inclined with respect to the flow direction of the fluid to be measured.

[0022] A pair of ultrasonic transmitters 5 and 6 that form an ultrasonic propagation path 8 are each electrically connected to a measurement circuit 11, which switches between transmitting and receiving the ultrasonic transmitters 5 and 6 to measure the propagation time of the ultrasonic waves between the ultrasonic transmitters 5 and 6, and a calculation circuit 12 electrically connected to the measurement circuit 11 receives a signal from the measurement circuit 11 and calculates the flow velocity and flow rate of the fluid.

[0023] Furthermore, the downstream end 10 of the partition plate 2 is configured to be substantially parallel to the downstream ultrasonic propagation path 8b and to be at least 1 / 2 the width r of the ultrasonic transmitter / receiver 6 downstream of the downstream ultrasonic propagation path 8b, thereby making it possible to effectively measure the propagation of ultrasonic waves within the divided flow path 1a.

[0024] Next, the operation of the ultrasonic flowmeter of the present invention will be described.

[0025] The fluid to be measured flowing through the measurement flow path 1 flows in from the upstream inlet 3 as shown by the white arrow in Figure 1, passes through the ultrasonic propagation path 8 formed in a V shape by the ultrasonic transmitters and receivers 5 and 6, and flows out from the downstream outlet 4 of the measurement flow path 1.

[0026] For the flow in this measurement flow path 1, a pair of ultrasonic transmitters and receivers 5, 6 are used to measure the forward propagation time from the ultrasonic transmitter and receiver 5 to the ultrasonic transmitter and receiver 6, as well as the reverse propagation time, using a measurement circuit 11. The flow velocity and flow rate are calculated by a calculation circuit 12 using the well-known reciprocal propagation time difference method.

[0027] The downstream end 10 of the partition plate 2, which is used to rectify and stabilize the flow during propagation time measurement, is cut at an angle to the flow direction. However, its position is downstream of the downstream ultrasonic propagation path 8b, where the ultrasonic propagation strength is strong, i.e., downstream of the center line of the downstream ultrasonic propagation path 8b by half the width r of the ultrasonic transmitter / receiver 6, and therefore does not have a significant effect on the ultrasonic measurement.

[0028] Figure 3(a) is a graph showing the experimental relationship between flow rate (Q) and pressure loss (ΔP) due to differences in the shape of the partition plate. Figures 3(b) and (c) are cross-sectional views showing the outline of the two measurement flow paths used in this experiment. Flow path 21 has a rectangular cross section with long sides of 30 mm and short sides of 9.3 mm, and is divided equally by five partition plates to form six divided flow paths, with ultrasonic transmitters 22 and 23 arranged opposite each other on both short sides. Propagation path P1 is set at an angle of 50° to the flow.

[0029] In Fig. 3(a), the conventional data is for the case where the partition plate 24 shown in Fig. 3(b) is rectangular, and the data marked with the symbol CM is for the case where the downstream end of the partition plate shown in Fig. 3(c) is parallel to the ultrasonic propagation path and the partition plate is cut downstream by the width of the ultrasonic transmitter / receiver (corresponding to r in this embodiment). Comparing these, it can be seen that the CM has less pressure loss than the conventional one.

[0030] In other words, since the area of ​​the partition plate in the CM is smaller than that of conventional devices, measurements can be made with little pressure loss.

[0031] In addition, when measuring the flow rate of a humid fluid, moisture in the airflow may condense on the partition and adhere to partition 2, thereby affecting the measurement, such as increasing pressure loss. However, in this case, the probability of condensation is reduced because the area is smaller than when a conventional rectangular partition is used.

[0032] As described above, by shortening the length of the partition plate downstream of the center line of the downstream ultrasonic propagation path 8b, the pressure loss can be reduced. In addition, since the surface area of ​​the partition plate 2 is reduced, the probability of condensation occurring can be reduced.

[0033] The graph shown in Figure 3(a) is for a so-called Z-shaped configuration in which ultrasonic transmitters and receivers are arranged on opposing short sides, and there is only one ultrasonic propagation path, with no distinction between upstream and downstream. However, by regarding this propagation path as the downstream ultrasonic propagation path and shortening the length of the partition plate downstream of it, it goes without saying that the same action and effect can be expected even in the case of a V-shaped ultrasonic propagation path as shown in Figure 1. [Industrial Applicability]

[0034] As described above, the ultrasonic flowmeter of the present invention makes it possible to reduce pressure loss and the probability of condensation of humid airflow by removing a portion of the downstream portion of the partition plate that forms the multilayer flow path, and therefore has a wide range of applications, particularly as a flowmeter for flows that contain moisture. [Explanation of symbols]

[0035] 1 Measurement flow path 2 Partition 3 Upstream entrance 4 downstream outlet 5, 6 Ultrasonic Transducer 7 Reflective surface 8 Ultrasonic propagation path 8a Upstream ultrasonic propagation path 8b Downstream ultrasonic propagation path 9 Upstream end 10 Downstream end 11 Measurement circuit 12 Arithmetic circuit

Claims

1. a measurement flow path having a rectangular cross section through which a fluid to be measured flows; A partition plate arranged to divide a short side of the measurement flow path into a plurality of parts; a pair of ultrasonic transmitters and receivers disposed on short sides of the measurement flow path so that ultrasonic waves cross the measurement flow path; a measurement circuit that performs an operation of transmitting from one of the pair of ultrasonic transmitters and receiving from the other; a calculation circuit for calculating a reception signal of the pair of ultrasonic transmitters and receivers, an upstream end of the partition plate along the measurement flow path is provided upstream of an ultrasonic propagation path; The downstream end of the partition plate is formed substantially parallel to the ultrasonic propagation path downstream of a center line of the ultrasonic propagation path, An ultrasonic flowmeter, wherein the partition plate overlaps with the entire ultrasonic propagation path in the measurement flow path when viewed from a direction perpendicular to both the direction in which the measured fluid flows and the direction in which the ultrasonic waves propagate.

2. 2. The ultrasonic flowmeter according to claim 1, wherein the downstream end of the partition plate is substantially parallel to the center line of the downstream ultrasonic propagation path and is configured to be at least one-half the width r of the ultrasonic transmitter / receiver downstream of the center line.

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