JP4789435B2 - Ultrasonic flow meter - Google Patents

Description

The present invention relates to an ultrasonic flow measuring apparatus you measure the flow rate of a fluid such as gas and water.

Conventionally, there is an apparatus using ultrasonic waves as an apparatus for measuring the flow rate of a rectangular channel (see, for example, Patent Document 1).
As shown in FIG. 3, the ultrasonic measurement apparatus includes an ultrasonic flow meter 32 including a pair of ultrasonic transmission / reception units 32A and 32B between left and right side walls 31a of a tubular body 31 having a rectangular cross section. The flow rate calculating unit 33 measures the flow velocity of the fluid based on the propagation time of the ultrasonic wave detected by the ultrasonic flow meter 32, and calculates the flow rate of the fluid flowing in the tubular body 31 from the measured flow velocity. Is provided. In addition, the measurement flow path portion K of the tubular body 31 in which the ultrasonic flow meter 32 is disposed has a parallel and high flow R3 in order to enhance the two-dimensionality of the flow velocity distribution of the fluid flowing in the tubular body 31. Two partition plates 34 are arranged at equal intervals in the vertical direction.

According to this, a three-dimensional flow velocity distribution P31 having a parabolic distribution in the height direction and depth direction (used in the sense of being close to a parabola, and the same shall apply hereinafter) on the upstream side of the measurement flow path portion K. The flow in the depth direction is flattened by dividing the current flow into three flow velocity distributions P32 at the measurement flow path portion K, that is, by dividing the flow path with a small aspect ratio into a flow path with a large aspect ratio. Thus, by arranging the partition plate 34, the two-dimensionality in the measurement flow path part K is enhanced, and the ultrasonic flow meter 32 is easily included in the entire flow velocity distribution, thereby increasing the measurement accuracy. Improvements are being made.
JP-A-9-43015 (page 2-3)

  When the ultrasonic measuring device having the conventional configuration is applied to a flow path having a larger pipe cross-sectional area (so-called large flow rate type), the size of the ultrasonic transducer that can be manufactured is limited as follows. Two measurement methods are conceivable.

1. Bypass-type measurement method As shown in FIG. 4, the pipe body 41 is divided into a measurement flow path section 42 and a pipe body section 43, and a flow R4 is a flow R4a on the measurement flow path section 42 side and a flow on the pipe body section 43 side. The flow rate of the flow R4a is measured by an ultrasonic flow meter 44 that is branched into the R4b and is provided in the measurement flow path section.

2. Built-in Measurement Method As shown in FIG. 5, a measurement flow path unit 52 is built in a pipe body 51, and a flow R <b> 5 is a flow R <b> 5 a in the measurement flow path unit 52 and a flow R <b> 5 b outside the measurement flow path unit 52. The flow rate of the flow R5a is measured by the ultrasonic flow meter 53 provided on the measurement flow path section 52.

  However, in the two measurement methods described above, the flow velocity of the fluid flowing in the measurement flow path portions 42 and 52 can be correctly measured by the conventional configuration (FIG. 3), but the partition included in the measurement flow path portions 42 and 52 The friction resistance is generated by the plate, and the pressure difference necessary for flowing the fluid through the narrow channel surrounded by the partition plate cannot be secured, so that the fluid is difficult to flow, and the average in the measurement channel units 42 and 52 There is a problem that the flow velocity becomes smaller than the average flow velocity other than the measurement flow path portions 42 and 52.

The present invention is intended to solve the conventional problems, Ri velocity of the measurement flow path portion the name equal the flow rate of the non-measurement flow path unit, the ultrasonic flow rate measuring device which can work to increase the flow rate of measurement accuracy The purpose is to provide.

In order to achieve the above object, an ultrasonic flow measuring device according to claim 1 of the present invention opens an inlet portion of an inner tube, and extends from the periphery of the inlet portion of the inner tube to the wall surface of the tube. In addition to providing a resistor only on the head, an ultrasonic current meter is provided to measure the flow rate of the fluid flowing through the inner tube. According to this, the flow to the outer channel of the inner tube is suppressed by the resistor. Thus, the average flow velocity can be made uniform, and the average flow velocity of the fluid flowing through the inner tube can be measured, whereby the fluid flow rate can be measured more accurately.

As described above, according to the ultrasonic flow measuring device of the first aspect of the present invention, the entrance portion of the inner tube is opened, and the periphery of the entrance portion of the inner tube extends from the periphery of the tube to the wall surface of the tube. Only, the resistance body has a resistance that matches the fluid resistance of the measurement flow path section of the inner tube. According to this, the flow to the outer flow path section of the inner tube body is suppressed by the resistance body. By doing so, the average flow velocity of the measurement flow path section and the outer flow path section can be made more equal, and furthermore, by measuring the average flow velocity of the fluid flowing through the measurement flow path section with an ultrasonic velocimeter, The flow rate can be measured more accurately.

Hereinafter, an average flow velocity uniform structure in a flow channel according to an embodiment of the present invention will be described with reference to the drawings.
(Embodiment 1)
FIG. 1 shows an average flow velocity uniform structure according to the first embodiment. As the tubular body (which is also a flow path and a pipeline) 11 through which a fluid (for example, gas, water, etc.) according to the first embodiment flows, a pipe having a round cross section is used.

  In the flow path formed by the tube body 11, the elongated inner tube body 12 is arranged coaxially with the central axis of the tube body 11, so that the measurement flow path section 13 formed in the inner tube body 12 and the measurement The flow R1 is divided into an outer flow path portion 14 other than the flow path portion 13, and the flow R1 is coaxially branched into a flow R1a in the measurement flow path portion 13 and a flow R1b in the outer flow path portion 14.

  A resistance body 15 having a resistance that matches the fluid resistance (resistance component) of the measurement flow path section 13 of the inner tube body 12 is installed at the entrance of the outer flow path section 14. The inner end portion of the resistor 15 is fixed to the start position 16 (the entrance portion of the inner tube body 12) of the measurement flow path portion 13, and the outer end portion is fixed to the start position 17 on the inner wall surface of the tube body 11. . The start position 17 with respect to the flow direction must be disposed at the same position or upstream of the start position 16 of the measurement flow path section 13 along the flow direction. As the resistor 15, for example, a metal or resin porous plate, a metal or resin net, a plate or block made of a polymer porous material, or the like is employed.

In the configuration of the first embodiment, the flow velocity distribution P11 in the tube body 11 becomes a flow velocity distribution P12 that is almost flat immediately before the branch inlets to both flow path portions 13 and 14 due to the suppression of the flow by the resistor 15. Branches with the vectors of the same size. In addition, since the measurement flow path portion 13 is coaxially arranged on the central axis of the tube body 11, the vicinity of the maximum flow velocity of the flow velocity distribution P12 flows into the measurement flow path portion 13, and the resistance of the resistor 15 is reduced. Can be reduced.
(Embodiment 2)
The ultrasonic flow rate measuring device according to the second embodiment uses the flow rate uniformizing structure of the pipe line according to the first embodiment, and the fluid to be measured is, for example, gas or water.

  As shown in FIG. 2, this ultrasonic flow measuring device has a flow equalization structure described in the first embodiment, that is, an elongated inner tube 22 is formed in a flow path formed by the tube 21. By being arranged coaxially with the central axis of 21, it is divided into a measurement channel part 23 formed in the inner tube 22 and an outer channel part (pipe) 24 other than the measurement channel part 23, In the entrance portion of the outer flow path portion 24, a flow rate equalizing structure in which a resistor 25 having a resistance corresponding to the fluid resistance (resistance component) of the measurement flow path portion 23 of the inner tube body 22 is installed is used. A sonic velocimeter (using an ultrasonic transducer or the like) 26 and a flow rate calculation unit 27 are added.

  Here, the inner tube body 22 has a rectangular cross section, the measurement flow path portion 23 is formed in a rectangular shape, and the ultrasonic type including a pair of ultrasonic transmission / reception portions 26A and 26B between the left and right side wall portions 22a. A flow meter 26 is provided to detect the propagation time (also referred to as transmission time and arrival time) of ultrasonic waves between the ultrasonic transmission units 26A and 26B, and after obtaining the flow velocity based on the propagation time, The flow rate calculation unit 27 calculates the flow rate of the fluid based on the above.

  Further, the measurement flow path portion 23 of the inner tube body 22 in which the ultrasonic flowmeter 26 is disposed is parallel to the flow direction R2a in order to improve the two-dimensionality of the flow velocity distribution of the fluid flowing in the inner tube body 22. In addition, two partition plates 28 are arranged at equal intervals in the height direction (short side direction), so that the measurement flow path section 23 has three (plural) flow path sections, that is, three ultrasonic measurement areas S. It is divided into

  The ultrasonic flow meter 26 is attached at a position where the ultrasonic wave crosses the intermediate part of the measurement flow path part 23. Further, in this flow rate calculation unit 27, the relationship between the flow velocity in the ultrasonic measurement region S and the average flow velocity in the measurement flow path portion 23 and the tube body 21 according to various flows of the fluid to be measured in advance. The relationship between the average flow velocity and the average flow velocity in the measurement flow path section 23 is stored as a correction coefficient, and the average flow velocity in the tube body 21 is obtained from the measured flow velocity using the correction coefficient.

  Note that the ultrasonic flowmeter 26 is attached in the horizontal direction with respect to the flow direction R2a at a predetermined angle θ (however, it is in the range of 0 ° <θ <90 °, but is preferably close to 0 °). It is attached so as to be inclined.

  In the configuration of the second embodiment, the flow velocity distribution in the tube body 21 becomes a flow velocity distribution close to flat just before the branch inlets to both flow path portions 23 and 24 due to the suppression of the flow by the resistor 25, and the flow velocity vector Branches with the same size. Further, since the measurement flow path portion 23 is coaxially arranged on the central axis of the tube body 21, the vicinity of the maximum flow velocity of the flow velocity distribution flows into the measurement flow path portion 23, and the resistance of the resistor 25 is reduced. can do.

  Then, the flow velocity of the fluid flowing in the measurement flow path unit 23 is detected as the propagation time of the ultrasonic waves transmitted and received alternately between the ultrasonic transmission / reception units 26A and 26B, and the average of the fluid is determined based on the difference in the propagation time. The flow rate is obtained, and the flow rate of the fluid flowing in the tube body 21 can be obtained, that is, measured, by multiplying the flow rate by the cross-sectional area of the flow path.

  As described above, when the flow rate is obtained by measuring the velocity of the fluid flowing through the measurement flow path unit 23, the measurement flow path is connected to the pipeline other than the measurement flow path unit 23, that is, the entrance of the outer flow path unit 24. Since the resistance body 25 having a resistance force commensurate with the fluid resistance of the portion 23 is arranged so that the velocity distribution of the fluid flowing into the branch portion is flattened, the flow velocity vectors have the same size. The flow rate can be measured more accurately.

  In the first and second embodiments described above, the tubular bodies 11 and 21 have a round cross section, but this may be a form using a tubular body having a rectangular cross section.

Fluid to be ultrasonic type flow measuring device of the present invention, the gas, the other, such as water, gas such as air (combustion air), and liquid such as chemical solution or oil of interest.

1 is a schematic perspective view of a flow channel according to Embodiment 1 of the present invention. Schematic perspective view of the flow path in Embodiment 2 of the present invention Schematic cross section of conventional flow path Schematic perspective view of conventional channel Schematic perspective view of conventional channel

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Tube 12 Inner tube 13 Measurement flow path part 14 Outer flow path part 15 Resistor R1 Flow R1a Flow R1b Flow P11 Flow rate distribution P12 Flow rate distribution 21 Tube 22 Inner tube 23 Measurement flow path part (rectangular flow path part)
24 Outer channel portion 25 Resistor 26 Ultrasonic velocity meter 26A Ultrasonic transmission / reception unit 26B Ultrasonic transmission / reception unit 27 Flow rate calculation unit 28 Partition plate S Ultrasonic measurement region (flow channel unit)
R2a Flow direction

Claims (2)

This is an ultrasonic flow measuring device that divides the flow rate of the fluid flowing in the flow path into and out of the inner tube body by coaxially incorporating an elongated inner tube body in the flow path formed by the tube body. And
Opening the entrance part of the inner tube, a resistance having a resistance corresponding to the fluid resistance of the measurement flow path part of the inner tube only from the periphery of the entrance part of the inner tube to the wall surface of the tube An ultrasonic flow rate measuring device characterized in that an ultrasonic current meter is provided for measuring the flow rate of a fluid flowing through a measurement flow path while providing a body.   2. The ultrasonic flow rate according to claim 1, wherein the inner tube body has a rectangular cross section and forms a rectangular flow channel portion therein, and the rectangular flow channel portion is divided into a plurality of flow channel portions by a partition plate. Measuring device.

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