JP4092977B2 - Flow measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flow rate measuring apparatus 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. 7 (a) and 7 (b) show a conventional ultrasonic flow measuring device 1. FIG. FIG. 1A shows a horizontal cross section of the ultrasonic flow rate measuring apparatus 1, and FIG. The measurement channel 2 has a width W, a height H, a rectangular ratio (W / H) of several times or more, and a laminar flow having a length H in the short side direction as a representative length. . Transmit and receive ultrasonic waves from a pair of ultrasonic transmitters / receivers 3 and 4 provided on the upstream side and downstream side, and measure each ultrasonic propagation time from the upstream side to the downstream side, or from the downstream side to the upstream side, The fluid velocity was calculated from the propagation time difference, and the fluid flow rate was measured.
[0003]
The arrow 5 and the alternate long and short dash 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 crossing angle with the direction in which the fluid flows is denoted by θ.
[0004]
[Problems to be solved by the invention]
However, in the conventional ultrasonic flow measuring device, the ultrasonic wave that has spread in the middle of the ultrasonic wave transmitted from one ultrasonic wave transmitter / receiver reaches the ultrasonic wave transmitter / receiver on the receiving side is not measured. There is a problem that the measurement accuracy of the ultrasonic wave propagation time is deteriorated due to the direct reflection and the direct wave.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, in the ultrasonic flow measuring device of the present invention , at least a pair of ultrasonic transmitters / receivers are provided on the measurement flow channel for flowing the fluid to be measured, on the upstream side and the downstream side of the measurement flow channel, and A shape in which a plurality of partition plates are provided at intervals equal to or less than the last maximum of the ultrasonic transmitter / receiver between the ultrasonic transmitter / receiver in parallel with the flow direction of the fluid to be measured, and the ultrasonic transmitter of the ultrasonic transmitter / receiver is projected onto the partition plate open the ultrasound transparent window, by Rukoto provided a pseudo interface by attaching the mesh to the ultrasonic transmission window, so as not affected by the ultrasonic wave reflected by the measurement flow path, also ultrasonic transducer The ultrasonic wave does not spread even at a distance longer than the last max, and the propagation time of the ultrasonic wave can be accurately measured without being affected by reflection.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The ultrasonic flow rate measuring device of the present invention includes a measurement channel for flowing a fluid to be measured, and at least a pair of ultrasonic transmitters / receivers on the upstream side and the downstream side of the measurement channel, and between the ultrasonic transmitters / receivers. In parallel with the flow direction of the fluid to be measured, a plurality of partition plates are provided at intervals equal to or less than the last maximum of the ultrasonic transmitter / receiver, and an ultrasonic transmission window having a shape in which the ultrasonic transmitter of the ultrasonic transmitter / receiver is projected on the partition plate. By opening and pasting the mesh to the ultrasonic transmission window, a pseudo boundary surface is provided so that it is not affected by the ultrasonic wave reflected by the measurement flow path, and even at a distance longer than the last max of the ultrasonic transceiver. The ultrasonic wave does not spread, and the ultrasonic wave propagation time can be accurately measured without being affected by reflection.
[0007]
In addition, 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 set to the ultrasonic transmission unit of the ultrasonic transceiver. By making the width less than or equal to the width, the ultrasonic wave can be easily transmitted to the receiver with a uniform intensity in the vertical direction, and the flow velocity of the fluid to be measured in the measurement channel can be accurately measured.
[0008]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
[0009]
Example 1
A flow rate measuring apparatus according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows the propagation state 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 with a plane wave, becomes a spherical wave when it reaches the last max 9 or more, 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.
[0010]
X = D2 / 4λ
Here, D is the diameter of the transmission part of the ultrasonic transceiver, and λ represents the wavelength of the ultrasonic wave. Moreover, the arrow 8 in the figure represents the traveling direction of the ultrasonic wave.
[0011]
FIG. 2 is a diagram 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 in which ultrasonic waves propagate between the ultrasonic transceivers is measured from the ultrasonic transceiver to the last max 9. The feature is that the distance is X or less. By doing this, the range in which the ultrasonic wave does not spread can be used for propagation time measurement, so that it is possible to measure the propagation time of only the direct wave without being affected by the reflected wave of the ultrasonic wave generated in the measurement channel 2. Thus, the propagation time measurement system is improved.
[0012]
(Example 2)
FIG. 3 is a block diagram showing a horizontal cross section of the flow rate measuring apparatus according to the second embodiment of the present invention.
[0013]
The basic configuration is the same as that of the first embodiment of the present invention, and the difference from this embodiment is that the configuration of the measurement channel 2 is a structure that uses the wall surface reflection of the measurement channel 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 propagation distance of the ultrasonic wave is the same as that in the first embodiment. By doing in this way, even if the horizontal direction dimension W of the measurement flow path 2 is shortened, the measurement accuracy of the propagation time can be improved as in the first embodiment.
[0014]
(Example 3)
FIG. 4 is a vertical sectional view of the measurement flow path 2 of the flow rate measuring device according to the third embodiment of the present invention. The features of this measurement channel 2 are that the ultrasonic propagation distance L of the ultrasonic transmitters / receivers 3 and 4 is set to be equal to or shorter than the distance X to the last max 9, and the height H is adjusted to the diameter D of the ultrasonic transmitter / receiver. It is. By doing so, all cross sections in the measurement flow path 2 can be measured with ultrasonic waves of plane waves with little 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 waves and the flow velocity distribution.
[0015]
Example 4
FIG. 5A is a configuration diagram showing a horizontal cross section of a flow rate measuring apparatus 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 the 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 where 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 transmission unit of the ultrasonic transceivers 3 and 4 from the propagation direction of the ultrasonic wave. The purpose of the partition plate 10 is to create a pseudo boundary surface in the ultrasonic wave propagation direction. By creating a pseudo boundary surface in this way, the ultrasonic propagation mode changes from the ultrasonic transceiver to the partition plate and after the partition plate, so that the ultrasonic wave propagates from the partition plate in a new mode. The distance which propagates by the plane wave 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 is extended to X + α.
[0016]
Therefore, by providing the plurality of partition plates 10, the distance L between the ultrasonic transmitters / receivers 3 and 4 can be increased without changing the frequency of the ultrasonic transmitter / receiver or the diameter of the transmitter.
[0017]
(Example 5)
FIG. 6 is a view showing a partition plate 10 of a flow rate measuring device according to a fifth embodiment of the present invention.
[0018]
The basic configuration of the flow rate measuring apparatus according to the fifth embodiment is the same as that of the fourth embodiment. 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. As for the dimensions of the rectangle, the vertical direction is set to the height H of the measurement channel 2 and the horizontal direction is 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 channel 2 with the same width, so that the ultrasonic wave is equally received in the state of the flow rate in the measurement channel 2, so the flow rate is more accurate. Can be measured.
[0019]
As described above, according to the flow rate measuring apparatus according to the first embodiment, the ultrasonic wave propagation time can be accurately measured without being affected by the reflected wave of the ultrasonic wave generated in the measurement flow path. Will improve.
[0020]
According to the flow rate measuring device of 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 channel is narrowed. It becomes possible.
[0021]
According to the flow rate measuring apparatus of the third embodiment, in addition to the effects of the first embodiment, all the cross-sectional directions in the measurement flow path can be measured, so that the flow rate can be measured without being affected by the flow velocity distribution. Become.
[0022]
According to the flow rate measuring apparatus of the fourth embodiment, in addition to the effects of the first embodiment, the measurement channel can be enlarged without changing the frequency of the ultrasonic transmitter / receiver or the diameter of the transmitter, so that measurement is possible. It is possible to widen the flow range.
[0023]
According to the flow rate measuring apparatus of the fifth embodiment, in addition to the effects of the fourth embodiment, the vertical direction of the measurement channel can be measured uniformly, so that the flow rate is more accurate without being affected by the flow velocity distribution. Can be measured.
[0024]
【The invention's effect】
As described above, the present invention can measure the flow rate more accurately in a wider range.
[Brief description of the drawings]
FIG. 1 is a diagram showing an ultrasonic wave propagation state from an ultrasonic transmitter / receiver. FIG. 2 is a detailed diagram showing a flow rate measuring apparatus according to a first embodiment of the invention. FIG. 3 is a measurement of a second embodiment of the invention. Cross-sectional view in the horizontal direction of the flow path [FIG. 4] Cross-sectional view in the vertical direction of the measurement flow path in the third embodiment of the present invention [FIG. 5] Configuration diagram showing the flow rate measuring device in the fourth embodiment of the present invention [FIG. FIG. 7 is a block diagram of a fifth embodiment of the present invention. FIG. 7 is a block diagram showing a conventional flow rate measuring apparatus.
DESCRIPTION OF SYMBOLS 1 Flow measuring device 2 Measurement flow path 3 Ultrasonic transmitter / receiver 4 Ultrasonic transmitter / receiver 5 Fluid flow direction to be measured 6 Fluid flow direction to be measured 7 Ultrasonic propagation direction 8 Ultrasonic propagation direction 9 Last Max 10 Partition plate 11 Ultrasonic wave Transmission window 12 Ultrasonic transmission window

Claims (2)

A measurement channel for flowing the fluid to be measured, and at least a pair of ultrasonic transmitters / receivers are provided on the upstream side and the downstream side of the measurement channel, and the flow direction of the fluid to be measured is parallel between the ultrasonic transmitters / receivers A plurality of partition plates are provided at intervals equal to or less than the last max of the ultrasonic transmitter / receiver, and an ultrasonic transmission window having a shape in which the ultrasonic transmission unit of the ultrasonic transmitter / receiver is projected is opened on the partition plate. ultrasonic wave flow measurement apparatus in which a pseudo-interface by attaching a mesh. 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 flow path, and the horizontal dimension of the ultrasonic transmission window is set to the ultrasonic transmission part of the ultrasonic transmitter / receiver. The ultrasonic flow measuring device according to claim 1, wherein the ultrasonic flow rate measuring device has a width or less .

Images