JP2004069520A - Flow rate measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent measurement accuracy in ultrasonic propagation time from becoming inferior by causing ultrasonic waves to be reflected on the upper surface or the lower surface of a measurement channel for affecting direct waves. <P>SOLUTION: The influence of ultrasonic waves reflected by the measurement channel is prevented by a measurement channel structure for measuring propagation time in ultrasonic waves at closer distance than last maximum where ultrasonic waves that are transmitted from an ultrasonic transceiver begin to spread. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a flow rate measuring device that measures the flow rate of a fluid using ultrasonic waves.
[0002]
[Prior art]
A conventional flow measuring device of this type is generally described in Japanese Patent Application Laid-Open No. 8-313316. FIGS. 7A and 7B show a conventional ultrasonic flow measuring device 1. FIG. FIG. 1A shows a horizontal cross section of the ultrasonic flow measuring device 1, and FIG. 1B shows a vertical cross section. The measurement flow path 2 is configured with a width W and a height H, has realized a laminar flow with a rectangular ratio (W / H) of several times or more and a length H in the short side direction as a representative length. . Transmits and receives ultrasonic waves from a pair of ultrasonic transceivers 3 and 4 provided on the upstream side and the downstream side, and measures each ultrasonic propagation time from the upstream side to the downstream side or from the downstream side to the upstream side, The flow velocity of the fluid is calculated from the propagation time difference, and the flow rate of the fluid is measured.
[0003]
The arrow 5 and the dashed-dotted line 6 indicate the direction in which the fluid flows, the broken line 7 indicates the direction in which the ultrasonic waves propagate, and the intersection angle with the direction in which the fluid flows is indicated by θ.
[0004]
[Problems to be solved by the invention]
However, in the conventional ultrasonic flow measurement device, the ultrasonic wave transmitted from one ultrasonic transceiver reaches the ultrasonic transmitter / receiver on the receiving side, and the ultrasonic wave that has spread on the way is the upper or lower surface of the measurement flow path. There is a problem that the measurement accuracy of the ultrasonic wave propagation time is deteriorated due to the direct reflection and the influence on the direct wave.
[0005]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, in the present invention, by measuring the propagation time of the ultrasonic wave at a distance closer to the last max where the ultrasonic wave transmitted from the ultrasonic transceiver starts to spread, the influence of the ultrasonic wave reflected on the measurement flow path Was not received.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
The flow measurement device according to the second aspect of the present invention is a measurement flow path for flowing a fluid to be measured, and a pair of ultrasonic transceivers are horizontally opposed to the upstream and downstream sides of the measurement flow path. Propagation time of the ultrasonic wave without being affected by the reflected wave by providing and attaching the distance at which the ultrasonic wave propagates between the two ultrasonic transceivers to be equal to or less than the last max of each ultrasonic transceiver. Can be measured with high accuracy.
[0007]
A flow rate measuring device according to a third aspect of the present invention has a structure in which ultrasonic waves propagate by reflecting a plurality of times on the wall surface of the measurement flow path while maintaining the distance between the ultrasonic transmitters and receivers according to claim 1. , It is possible to accurately measure the propagation time of the ultrasonic wave without being affected by reflection.
[0008]
The flow rate measuring device according to a fourth aspect of the present invention is a method of measuring the reflection and flow velocity distribution of ultrasonic waves by adjusting the vertical dimension of the ultrasonic transmission unit of the ultrasonic transceiver and the height dimension of the measurement flow path. This allows accurate measurement of the flow velocity of the fluid to be measured without being affected.
[0009]
According to a fifth aspect of the present invention, there is provided a flow rate measuring device, wherein a plurality of partition plates are provided between the ultrasonic transmitter and receiver in parallel with a flow direction of a fluid to be measured, and the ultrasonic transmitter and receiver provided on the partition plates transmit ultrasonic waves. By attaching a mesh to the ultrasonic transmission window of the projected shape of the part and providing a pseudo boundary surface, the ultrasonic wave will not spread even at a distance longer than the last maximum of the ultrasonic transceiver, and the ultrasonic wave will not be affected by reflection. This is to accurately measure the propagation time of a sound wave.
[0010]
According to a sixth aspect of the present invention, there is provided a flow rate measuring apparatus, wherein the ultrasonic transmission window shape of the partition plate is rectangular, the vertical dimension of the ultrasonic transmission window is adjusted to the height of the measurement flow path, and the horizontal direction of the ultrasonic transmission window is adjusted. By making the directional dimension equal to or smaller than the width of the ultrasonic transmission part of the ultrasonic transceiver, the ultrasonic waves can be easily transmitted to the receiver with uniform strength in the vertical direction, and the flow rate of the fluid to be measured in the measurement flow path can be accurately determined. Some measurements have been made.
[0011]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0012]
(Example 1)
A flow measurement device according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a state of propagation of ultrasonic waves from a general ultrasonic transceiver 3. The ultrasonic wave transmitted from the ultrasonic transmitter / receiver 3 travels straight to the last max 9 as a plane wave, and when the ultrasonic wave reaches the last max 9 or higher, it becomes a spherical wave and spreads at a certain angle. Here, the distance X from the ultrasonic transceiver to the last max 9 is expressed by the following equation.
[0013]
X = D ² / 4λ
Here, D is the diameter of the transmission unit of the ultrasonic transceiver, and λ represents the wavelength of the ultrasonic wave. The arrow 8 in the drawing indicates the traveling direction of the ultrasonic wave.
[0014]
FIG. 2 is a view showing a flow rate measuring apparatus according to the first means of the present invention. The difference from the conventional example is that the distance L between the ultrasonic transmitter and the ultrasonic transmitter propagates from the ultrasonic transmitter to the last max 9. The feature is that the distance is set to X or less. By doing so, the range in which the ultrasonic wave does not spread can be used for propagation time measurement, so that only the direct wave can be measured without being affected by the reflected wave of the ultrasonic wave generated in the measurement flow path 2. And the measurement accuracy of the propagation time is improved.
[0015]
(Example 2)
FIG. 3 is a configuration diagram showing a horizontal cross section of a flow rate measuring device according to a second embodiment of the present invention.
[0016]
The basic configuration is the same as that of the description of the first embodiment of the present invention. The difference from this embodiment is that the configuration of the measurement flow path 2 uses the wall reflection of the measurement flow path for ultrasonic wave propagation. That is. Here, the broken line 7 indicates the propagation direction of the ultrasonic wave as in the conventional example, and the ultrasonic wave propagation distance is the same as that of the first embodiment. In this manner, even when the horizontal dimension W of the measurement flow path 2 is reduced, the measurement accuracy of the propagation time can be improved as in the first embodiment.
[0017]
(Example 3)
FIG. 4 is a vertical sectional view of a measurement flow path 2 of a flow rate measuring device according to a third embodiment of the present invention. The features of this measurement channel 2 are that the ultrasonic wave propagation distance L of the ultrasonic transceivers 3 and 4 is set to be equal to or less than the distance X to the last max 9, and the height H is adjusted to the diameter D of the ultrasonic transceiver. It is. By doing so, the entire cross section in the measurement flow path 2 can be measured by the ultrasonic wave of the plane wave having a small spread, so that the flow velocity of the fluid to be measured can be accurately measured without being affected by the reflection of the ultrasonic wave and the flow velocity distribution.
[0018]
(Example 4)
FIG. 5A is a configuration diagram showing a horizontal cross section of a flow rate measuring device according to a fourth embodiment of the present invention. The basic configuration is the same as that of the first embodiment of the present invention. The difference from this embodiment is that a partition plate 10 is provided. As shown in FIG. 5B, the partition plate 10 has a configuration in which an ultrasonic transmission window 11 is provided in a portion through which ultrasonic waves pass, and a mesh is attached to the ultrasonic transmission window 11. The shape of the ultrasonic transmission window 11 is a shape obtained by projecting the shape of the ultrasonic transmitters of the ultrasonic transceivers 3 and 4 from the propagation direction of the ultrasonic waves. The purpose of this partition plate 10 is to create a pseudo boundary surface in the ultrasonic wave propagation direction. By creating a pseudo boundary in this way, since the propagation mode of the ultrasonic wave changes from the ultrasonic transceiver to the partition plate and thereafter, the ultrasonic wave propagates in a new mode from the partition plate. Thus, the distance that the plane wave propagates from the partition plate 10 is newly formed. This can be considered as if the propagation distance of the plane wave as viewed from the ultrasonic transceivers 3 and 4 has extended to X + α.
[0019]
Therefore, by providing the plurality of partition plates 10, the distance L between the ultrasonic transceivers 3 and 4 can be increased without changing the frequency of the ultrasonic transceiver or the diameter of the transmission unit.
[0020]
(Example 5)
FIG. 6 is a view showing a partition plate 10 of a flow measuring device according to a fifth embodiment of the present invention.
[0021]
The basic configuration of the flow rate measuring device according to the fifth embodiment is the same as that of the fourth embodiment, and the difference from this embodiment is that the shape of the ultrasonic transmission window 12 of the partition plate 10 is rectangular as shown in the figure. That is. The dimensions of the rectangle are set in the vertical direction to the height H of the measurement channel 2 and in the horizontal direction sufficiently shorter than the diameter D of the ultrasonic transceiver. By making the rectangular shape in this way, the ultrasonic wave propagates in the vertical direction in the measurement flow channel 2 with the same width, and the ultrasonic wave is uniformly received in the flow velocity state in the measurement flow channel 2, so that the flow velocity can be more accurately measured. Can be measured.
[0022]
As described above, according to the flow rate measuring apparatus according to the first embodiment, since the propagation time of the ultrasonic wave can be accurately measured without being affected by the reflected wave of the ultrasonic wave generated in the measurement flow path, the flow rate measurement accuracy Is improved.
[0023]
According to the flow rate measuring device according to the second embodiment, in addition to the effects of the first embodiment, the propagation distance can be increased even if the width of the measurement flow path is narrowed. Will be possible.
[0024]
According to the flow rate measuring device according to the third embodiment, in addition to the effects of the first embodiment, since all the cross-sectional directions in the measurement flow path can be measured, the flow rate can be measured without being affected by the flow velocity distribution. Become.
[0025]
According to the flow rate measuring device according to the fourth embodiment, in addition to the effects of the first embodiment, the measurement flow path can be enlarged without changing the frequency of the ultrasonic transceiver and the diameter of the transmission unit, so that measurement is possible. It is possible to widen the flow rate range.
[0026]
According to the flow rate measuring device according to the fifth embodiment, in addition to the effects of the fourth embodiment, since the vertical direction of the measurement flow path can be measured evenly, the flow rate can be more accurately measured without being affected by the flow velocity distribution. Can be measured.
[0027]
【The invention's effect】
As described above, the present invention can measure the flow rate in a wider range and more accurately.
[Brief description of the drawings]
FIG. 1 is a diagram showing the state of propagation of ultrasonic waves from an ultrasonic transmitter / receiver. FIG. 2 is a detailed diagram showing a flow rate measuring device in a first embodiment of the present invention. FIG. 3 is a diagram showing measurement in a second embodiment of the present invention. FIG. 4 is a vertical sectional view of a measurement flow channel according to a third embodiment of the present invention. FIG. 5 is a configuration diagram showing a flow rate measuring device according to a fourth embodiment of the present invention. FIG. 7 is a diagram showing a configuration of a partition plate according to a fifth embodiment of the present invention.
DESCRIPTION OF SYMBOLS 1 Flow rate measuring device 2 Measurement flow path 3 Ultrasonic transceiver 4 Ultrasonic transceiver 5 Measurement fluid flow direction 6 Measurement fluid flow direction 7 Ultrasonic propagation direction 8 Ultrasonic propagation direction 9 Last max 10 Partition plate 11 Ultrasonic Transmission window 12 Ultrasonic transmission window

Claims (6)

A measurement flow path for flowing a fluid to be measured, and at least a pair of ultrasonic transceivers provided on the upstream and downstream sides of the measurement flow path, and a distance over which ultrasonic waves propagate between the two ultrasonic transceivers The ultrasonic type flow rate measuring device which is attached so that it is not more than the last max of each ultrasonic transceiver. 2. The ultrasonic flow rate measuring device according to claim 1, wherein the ultrasonic transceivers provided on the upstream side and the downstream side are provided to face each other in the horizontal direction. 3. The ultrasonic type flow rate measuring device according to claim 1, wherein the ultrasonic type flow measuring device has a structure in which an ultrasonic wave propagates by reflecting the wall surface of the measurement flow path a plurality of times. 3. The ultrasonic flow rate measuring device according to claim 1, wherein a vertical dimension of an ultrasonic transmitting unit of the ultrasonic transceiver and a height dimension of the measurement flow path are matched. A plurality of partition plates are provided between the ultrasonic transmitter and receiver in parallel with the flow direction of the fluid to be measured, and an ultrasonic transmission window having a shape obtained by projecting the ultrasonic transmitter of the ultrasonic transmitter and receiver is opened on the partition plate, and the ultrasonic transmission is performed. An ultrasonic flow measurement device that has a pseudo boundary surface by attaching a mesh to a window. The shape of the ultrasonic transmission window of the partition plate is rectangular, the vertical dimension of the ultrasonic transmission window is adjusted to the height of the measurement channel, and the horizontal dimension of the ultrasonic transmission window is the width of the ultrasonic transmission unit of the ultrasonic transceiver. 6. The ultrasonic flow measuring device according to claim 5, wherein:

Images