JP2003302266A - Ultrasonic flow measuring apparatus - Google Patents

Ultrasonic flow measuring apparatus

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Publication number
JP2003302266A
JP2003302266A JP2002106163A JP2002106163A JP2003302266A JP 2003302266 A JP2003302266 A JP 2003302266A JP 2002106163 A JP2002106163 A JP 2002106163A JP 2002106163 A JP2002106163 A JP 2002106163A JP 2003302266 A JP2003302266 A JP 2003302266A
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Japan
Prior art keywords
flow
measurement
ultrasonic
height
flow path
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JP2002106163A
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Japanese (ja)
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JP3438734B1 (en
Inventor
Shigeru Iwanaga
茂 岩永
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Matsushita Electric Ind Co Ltd
松下電器産業株式会社
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Priority to JP2002106163A priority Critical patent/JP3438734B1/en
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Publication of JP3438734B1 publication Critical patent/JP3438734B1/en
Publication of JP2003302266A publication Critical patent/JP2003302266A/en
Expired - Fee Related legal-status Critical Current

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Abstract

<P>PROBLEM TO BE SOLVED: To increase measurement accuracy by reducing the variation of the correction factor of a measured flow. <P>SOLUTION: This ultrasonic flow measuring apparatus comprises a measurement flow passage 5 for flowing measured fluid, an inlet part 11 and an outlet part 12 provided on the upstream side and downstream side of the measurement flow passage 5, at least a pair of ultrasonic transceivers 7 and 8 installed so that ultrasonic wave can cross and propagate in the lateral direction of the measurement flow passage 5, and a asymmetrical flow promoting means 15 for deflecting the occurrence position of the maximum value of a flow velocity in height direction from the center of the height to one side by making asymmetric a velocity distribution in the height direction of the measurement flow passage 5. In a laminar flow area where the flow velocity distribution is projected, the maximum value of the flow velocity is deflected and a slow flow velocity is measured to increase the correction factor and, in a turbulent flow area where the flow velocity distribution is flattened, a flow velocity area where the flow velocity is not so different from the maximum value of the flow velocity is measured to reduce a difference between the values of the correction factors for the laminar flow area and the turbulent flow area. Thus an error at the time of correction can be reduced to increase the measurement accuracy by providing characteristics in which the variation of the correction factors is flattened. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow rate measuring device for measuring the flow rate and flow velocity of gas or liquid.

[0002]

2. Description of the Related Art Conventional ultrasonic flow rate measuring devices of this type include
For example, Japanese Unexamined Patent Publication No. 11-351926 is known, and as shown in FIG. The ultrasonic transmitter / receiver 2a on the upstream side is inclined at a predetermined angle.
And the ultrasonic transmitter / receiver 2b on the downstream side are provided so as to face each other, and these ultrasonic transmitter / receivers 2a and 2b are housed in the recesses 3a and 3b provided in the measurement flow path 1 and at the inlet side of the measurement flow path 1. A rectifying body 4 is provided. Then, the flow velocity of the fluid flowing through the measurement flow path 1 is transmitted and received between the ultrasonic wave transmitters / receivers 2a and 2b, measured from the propagation time difference, and the flow rate is calculated from the cross-sectional area of the measurement flow path 1. At this time, the flow entering the measurement flow path 1 is regulated by the rectifying body 4 to reduce the inclination of the streamline in the measurement unit and suppress the generation of vortices, and to suppress the ultrasonic waves at the boundary surface of the flow turbulence. The fluctuation of the reception level of ultrasonic waves due to reflection and refraction is reduced to prevent the deterioration of measurement accuracy.

[0003]

However, in the conventional configuration, the rectifying body and the ultrasonic wave propagation path are set apart from each other, and the distance between the rectifying body is on the ultrasonic transmitter / receiver 2a side and the ultrasonic wave transmitter / receiver 2b side. There is a difference in the development state of the flow passing through the rectifying body because of the large difference, or the ultrasonic wave transmitted from the ultrasonic transmitter / receiver has an intensity distribution in the height direction although the entire width W direction of the measuring tube 1 is measured. By doing so, the flow velocity distribution on the central axis of the ultrasonic transmitter / receiver is mainly measured. Therefore, the average flow velocity in the cross section orthogonal to the measurement flow passage and the measurement between the ultrasonic transmitter / receivers 2a and 2b oblique to the measurement flow passage are measured. A difference occurs in the average flow velocity in the cross section, and in order to calculate the true flow rate, a correction coefficient corresponding to the flow rate is necessary for the measured value. In particular, since the correction coefficient greatly changes in the flow rate range where laminar flow changes to turbulent flow, even if there is a slight error in the flow velocity measurement at the measurement cross section, the correction coefficient expands the error and deteriorates the measurement accuracy. was there.

The present invention has been made to solve the above problems, and an object of the present invention is to improve the measurement accuracy by reducing the change in the correction coefficient over the entire flow rate measurement range.

[0005]

In order to solve the above problems, the present invention provides a measurement flow path through which a fluid to be measured flows, and an introduction section and a discharge section provided on the upstream side and the downstream side of the measurement flow path, respectively.
At least a pair of ultrasonic transceivers provided so that ultrasonic waves propagate across the width direction of the measurement flow path, and the velocity distribution in the height direction of the measurement flow path is made asymmetric to maximize the flow velocity in the height direction. An asymmetric flow promoting means for biasing the position where the value is generated from the height center to one side, and a flow rate calculating means for transmitting and receiving ultrasonic waves between the ultrasonic transceivers and calculating the flow rate based on the transmitted and received signals Is.

According to the above invention, in the laminar flow region in which the velocity distribution in the height direction is convex, the maximum value of the flow velocity is biased and the slow velocity region is measured in many places to increase the correction coefficient to increase the high velocity. In the turbulent flow region where the velocity distribution in the depth direction is relatively flat, the maximum value of the flow velocity is measured and the correction coefficient, which was larger than the laminar flow region in the past, is made slightly smaller. It is possible to reduce the difference between the correction coefficients and reduce the change in the correction coefficient over the entire flow rate measurement range, prevent the error from being increased by the correction coefficient, and improve the measurement accuracy. Further, even if the Reynolds number changes due to the change of the kinematic viscosity of the fluid, the change of the correction coefficient is small, so the measurement accuracy is maintained, and it is possible to realize a measuring device that is strong against changes in the fluid temperature and changes in the fluid components. Can be increased.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 is a measurement flow path through which a fluid to be measured flows, an introduction part and a discharge part provided on the upstream side and the downstream side of the measurement flow path, and the measurement flow path. At least a pair of ultrasonic transceivers provided so that ultrasonic waves propagate across the width direction, and the maximum value in the velocity distribution in the height direction by positively asymmetricalizing the flow distribution in the height direction of the measurement flow path. Asymmetrical flow promoting means for biasing the generation position of one side from the height center to one side, and flow rate calculating means for transmitting and receiving ultrasonic waves between the ultrasonic transceivers and calculating the flow rate based on the transmitted and received signals. is there. Then, in the laminar region where the velocity distribution in the height direction is convex, the maximum correction value of the velocity is biased to increase the correction factor by increasing the number of places where the velocity is slow, and comparing the velocity distribution in the height direction. In the turbulent flow area, which is generally flat, the maximum value of the flow velocity is measured, and the correction coefficient, which was conventionally larger than the laminar flow area, is made slightly smaller to reduce the difference in the correction coefficient between the laminar flow area and the turbulent flow area. However, the flow rate change characteristic of the correction coefficient is flattened over the entire flow rate measurement range, and the measurement accuracy can be improved. Further, even if the physical property value of the fluid changes, the measurement accuracy is maintained, and the practicality and convenience can be improved.

According to a second aspect of the present invention, the asymmetrical flow promoting means is an enlarged slope portion in which the height of the measurement flow passage gradually increases toward the downstream side. Then, the generation position of the maximum value of the flow velocity distribution in the expansion gradient part can be biased in the direction in which the height is expanded, and the generation direction and the magnitude of the bias of the flow velocity distribution in the ultrasonic propagation path can be controlled. In addition, the flatness of the flow rate change characteristics of the correction coefficient can be improved and the degree of freedom of the ultrasonic transmitter / receiver installation position in the height direction can be improved. The cost can be reduced by simplifying and improving the workability.

According to a third aspect of the present invention, the enlarged slope portion is formed by disposing the slope portion on one surface in the height direction. In addition, the bending of the measurement flow path can be reduced to reduce the size, and the simplification of the configuration can be further improved to reduce the cost.

According to a fourth aspect of the present invention, the enlarged slope portion is formed by disposing the slope portions on both surfaces in the height direction.
Then, the bending amount of the measurement flow path can be increased to increase the deviation amount of the maximum value of the flow velocity distribution, the flatness of the flow rate change characteristic of the correction coefficient can be promoted, and the measurement accuracy can be improved.

According to a fifth aspect of the present invention, the asymmetrical flow promoting means is formed by a measurement flow path bent portion in which the measurement flow path is bent in the height direction. Then, the bending portion causes a bias in the flow velocity distribution in the ultrasonic wave propagation path to promote the flatness of the flow rate change characteristic of the correction coefficient, and the cross-sectional area of the measurement flow path is kept constant to change the cross-sectional area. It is possible to reduce error generation and improve measurement accuracy.

According to a sixth aspect of the present invention, the ultrasonic transmitter / receiver is eccentric from the center in the height direction of the measurement flow channel to one side, and the expansion gradient part is expanded to the side where the ultrasonic transmitter / receiver is eccentric. It is a thing. The eccentric position in the height direction of the ultrasonic transmitter / receiver can be optimally eccentrically set so that the value of the correction coefficient in the low velocity region flowing in the laminar flow state is close to the value in the large velocity region flowing in the turbulent state. Moreover, by eccentrically arranging in the direction in which the maximum value of the flow velocity distribution deviates, it is possible to mainly measure the region where the flow velocity is large and to make the correction coefficient in the large flow velocity region close to the value in the low flow velocity region. The region where the change is flat can be expanded to the low flow velocity side.

According to a seventh aspect of the invention, the ultrasonic transmitter / receiver is eccentric from the center in the height direction of the measurement flow path to one side, and the measurement flow path bent portion is bent to the side where the ultrasonic transmitter / receiver is eccentric. It was made. Moreover, the deviation of the flow velocity distribution due to the bent portion of the measurement flow path can be promoted as the flow rate increases, and since the ultrasonic transmitter / receiver is eccentric to the side where the flow velocity distribution is fast, the correction coefficient in the large flow rate region can be set to the laminar flow state. It is possible to get close to the low flow velocity region, and the cross-sectional area of the measurement flow path is kept constant to improve the measurement accuracy by reducing the occurrence of errors due to cross-sectional area changes, and a wide measurement range from the low flow velocity region to the large flow velocity region. The flatness of the correction coefficient can be improved.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIGS. 1 and 2 are a longitudinal sectional view and a transverse sectional view of an ultrasonic flow rate measuring apparatus showing Embodiment 1 of the present invention. In the figure, 5 is a measurement flow path surrounded by a flow path wall 6, and 7 and 8 are upstream and downstream ultrasonic transceivers attached to the flow path wall 6 so as to face each other. The upstream ultrasonic transmitter / receiver 7 and the downstream ultrasonic transmitter / receiver 8 are separated from each other by a distance L so as to cross the width W direction of the measurement flow path 5 and inclined by an angle θ with respect to the flow direction of the fluid in the measurement flow path 5. The measurement flow path 5 is installed at approximately the center of the height H direction. Reference numerals 9a and 9b denote upstream and downstream opening holes that expose the ultrasonic transceivers 7 and 8 to the measurement flow path 5. Reference numeral 10 denotes an ultrasonic wave propagation path (indicated by a chain double-dashed line) in which ultrasonic waves transmitted between the ultrasonic wave transmitters / receivers 7 and 8 which oppose each other propagate directly to the other party. Reference numeral 11 is an introduction portion which is provided on the upstream side of the measurement flow path 5 and serves as an inlet for the fluid to be measured, and 12 is a derivation portion which is provided on the downstream side of the measurement fluid path 5 and serves as an outlet for the measurement fluid. 13 is a measurement channel 5 and an introduction part 1
1, which is a bent portion on the upstream side connecting with 1, and the bent portion 13 is bent in the height H direction of the measurement flow path 5. Reference numeral 14 is a downstream bent portion that connects the measurement flow path 5 and the lead-out portion 12, and the bent portion 14 is bent in the height H direction of the measurement flow path 5.

Reference numeral 15 indicates that the velocity distribution S in the height H direction of the measurement flow path 5 is made asymmetric with respect to the height center so that the generation position T of the maximum value of the flow velocity in the height H direction is biased to one side from the height center. This is an asymmetrical flow promoting means. This asymmetrical flow promoting means 15
Is formed by the enlarged slope portion 16 provided on the downstream side of the measurement flow path 5, and here, the slope portion 17 and the upper slope portion 17 provided on the upper side in the height direction are provided with a slope of an angle α toward the downstream side. An enlarged sloped portion 16 in which the height of the measurement flow path 5 is sequentially increased is formed by a lower sloped portion 18 provided on the lower side in the depth direction and having a slope of an angle β (α> β) toward the downstream side. There is. The expansion gradient portion 16 causes a deviation in the flow velocity distribution in the height direction of the measurement flow path 5. 19 is the outer peripheral surface 1 of the bent portion 13 on the upstream side.
It is a stepped portion provided on the 3a side.

Reference numeral 20 denotes a flow stabilizing means provided between the asymmetrical flow promoting means 15 and the ultrasonic wave propagation path 10, and a grid-like direction regulating portion 20a for dividing the cross section of the measurement flow path 5 to adjust the flow direction. A fluctuation suppressing portion 20b formed of a mesh-like body such as a mesh for reducing fluctuations in flow velocity is provided. Reference numeral 21 is a flow rate calculation provided with a measurement control section 22 connected to the ultrasonic wave transmitters / receivers 7 and 8 for transmitting and receiving ultrasonic waves, and a calculation section 23 for calculating a flow rate based on a signal from the measurement control section 22 to calculate a flow rate. It is a means.

Next, the operation of this ultrasonic flow rate measuring device will be described. The fluid to be measured that has flowed in from the introduction section 11 is an asymmetrical flow promoting means 15 provided on the inlet side of the measurement flow path 5.
As a result, the velocity distribution in the height H direction of the measurement flow path 5 is not substantially symmetrical with respect to the height center but has an asymmetric shape. That is, in the transition region in which the flow of the measurement flow path 5 is changing from the laminar flow region or the laminar flow to the turbulent flow, as shown by the velocity distribution S in FIG. 1, a parabolic convex shape in which the velocity gradually increases as the distance from the wall surface increases. Yes The position T at which the maximum flow velocity is generated is slightly biased to one side (upper in the drawing) from the vicinity of the center of the height.
On the other hand, when the flow rate flowing through the measurement flow path 5 increases and enters the turbulent flow region, the speed change in the height direction decreases as shown by the speed distribution R in FIG. The generation position U is biased to one side (upward in the drawing) from the vicinity of the center of height.

Next, the flow rate measuring operation using ultrasonic waves will be described. In the measurement flow path 5, the measurement controller 22 acts so as to cross the width W of the flow path cross section of the measurement flow path 5 between the ultrasonic transceivers 7 and 8 with respect to the flow in which the velocity distribution in the height direction is asymmetrical. Then, ultrasonic waves are transmitted and received. That is, the propagation time T1 until the ultrasonic waves emitted from the upstream ultrasonic transceiver 7 are received by the downstream ultrasonic transceiver 8 is measured. On the other hand, the propagation time T2 until the ultrasonic wave emitted from the ultrasonic wave transmitter / receiver 8 on the downstream side is received by the ultrasonic wave transmitter / receiver 7 on the upstream side is measured.

Based on the propagation times T1 and T2 measured in this way, the flow rate is calculated by the calculation unit 23 by the following calculation formula.

Now, the angle formed by the flow velocity V of the fluid to be measured in the flow direction of the measurement flow path 5 and the ultrasonic wave propagation path 10 is θ, the distance between the ultrasonic transceivers 7 and 8 is L, and the distance of the fluid to be measured is L. When the speed of sound is C, the flow velocity V is calculated by the following formula.

T1 = L / (C + Vcosθ) T2 = L / (C-Vcosθ) V = (L / 2cosθ) ((1 / T1) by eliminating the sound velocity C from the equation of subtracting the inverse of T2 from the inverse of T1. -(1 / T2)) Since θ and L are known, the flow velocity V is calculated from the values of T1 and T2.
Can be calculated.

However, the flow velocity V obtained here is measured by the ultrasonic wave propagation path 10 that obliquely crosses the measurement flow path 5, and the average flow speed measured by the ultrasonic wave propagation path 10 is a state of flow development depending on the cross-sectional position. However, since the entire flow passage is not measured in the cross section in the height H direction, there is a difference in the average flow velocity obtained from the entire cross section orthogonal to the measurement flow passage 5. Moreover, since the intensity distribution of the ultrasonic waves in the ultrasonic wave propagation path 10 has a characteristic that the center of the ultrasonic wave transmitters / receivers 7, 8 which is on the central axis side becomes strong, the central portion of the ultrasonic wave propagation path 10 in the height direction is Will be measured mainly.

For this reason, the flow rate is calculated by adding the correction coefficient, and from the cross-sectional area S orthogonal to the flow direction of the measurement flow path 5,
The flow rate Q is Q = KVS, where K is a correction coefficient considering the flow velocity distribution in the cross-sectional area S.

In this way, the calculation unit 23 can determine the flow rate.

Particularly, in the case where the asymmetrical flow promoting means 15 is not provided, in the laminar flow region, the parabolic convex maximum flow velocity portion is located at the central portion in the height direction within the ultrasonic wave propagation path 10. Is considerably smaller than that in the turbulent region.
Therefore, as shown in FIG. 4, the correction coefficient greatly changes in the transition region where the laminar flow region transitions to the turbulent flow region, and the correction coefficient greatly changes to ΔK1 due to the occurrence of the error ΔQm in the measured flow rate, so that the error is magnified. This error may occur due to a difference in flow state due to a difference in Reynolds number due to a change in kinematic viscosity coefficient due to a change in fluid temperature or a change in fluid composition ratio. In particular, when measuring the flow rate of city gas, LPG (liquefied petroleum gas), etc., it is necessary to consider when the gas composition change due to the difference of seasons or regions.

FIG. 5 shows an asymmetrical flow promoting means 1 in the measurement channel 5.
5 shows the flow rate change characteristic of the correction coefficient when 5 is installed. By biasing the velocity distribution in the height direction of the measurement flow path 5 to one side from the center, the velocity distribution in the height direction becomes convex. In the laminar flow region, the maximum flow velocity is biased to increase the correction coefficient by increasing the number of slow flow velocity areas, and the maximum flow velocity is obtained in the turbulent flow region where the velocity distribution in the height direction is relatively flat. By measuring the side, by slightly reducing the correction coefficient that was conventionally larger than the laminar flow area, it is possible to reduce the difference in the correction coefficient between the laminar flow area and the turbulent flow area, and Difference can be reduced,
Even in the transition region where the laminar flow changes to the turbulent flow, the change of the correction coefficient is small, and the correction coefficient is flattened. Therefore, even if an error ΔQm occurs in the measured flow rate, the change in the correction coefficient is ΔK2 (K2
It can be made sufficiently small as <K1), and measurement with high measurement accuracy can be performed. It is effective to flatten the correction coefficient when there is a temperature change or composition change of the fluid. Especially, when measuring the flow rate of fuel gas such as city gas or LPG where composition change and temperature change are considered, the accuracy is further improved. Measurement can be realized.

As described above, the asymmetric flow promoting means for making the velocity distribution in the height direction of the measurement flow path asymmetric so that the generation position of the maximum value of the flow velocity in the height direction is deviated from the height center to one side, In a laminar region where the velocity distribution is convex, the maximum velocity is biased to increase the correction factor by increasing the number of slow velocity regions and making the velocity distribution relatively flat in the height direction. In the turbulent flow region, the maximum value of the flow velocity is measured so that the correction coefficient that was conventionally larger than that in the laminar flow region is slightly reduced to reduce the difference in the correction coefficient between the laminar flow region and the turbulent flow region, and the flow rate measurement range. It is possible to reduce the change in the correction coefficient over the entire area, and it is possible to prevent the error from increasing due to the correction coefficient and improve the measurement accuracy.
Furthermore, even if the Reynolds number changes due to the change in the kinematic viscosity of the fluid, the change in the correction coefficient is small, so the measurement accuracy is maintained, and a measuring device that is robust against changes in the fluid temperature and changes in the fluid components can be realized. Can be increased.

Further, as in the present embodiment, the asymmetrical flow promoting means 15 is provided with the expansion slope portion 16 in which the height of the measurement flow path 5 is gradually increased toward the downstream side, so that the position where the maximum value of the flow velocity distribution is generated is generated. Can be biased in the direction in which the height increases,
Since the generation direction and the magnitude of the deviation of the flow velocity distribution in the ultrasonic wave propagation path 10 can be controlled by the size of the enlarged gradient portion and the position where the gradient starts, the flatness of the flow rate change characteristic of the correction coefficient is increased and the ultrasonic wave is generated. The degree of freedom in the installation position of the transceivers 7 and 8 in the height direction can be improved, and a simple shape can be provided only by providing a gradient on the wall surface of the measurement flow path 5, so that the configuration can be simplified and the workability can be improved, and the cost can be reduced. Can be converted.

Further, in the structure of this embodiment, the lower slope portion 18 provided with a slope of the angle β on the lower side in the height direction of the measurement flow path 5 is removed, and the enlarged slope portion 16 is provided with the height of the measurement flow path 5. By forming the inclined portion on one surface of only the upper inclined portion 17 provided on the upper side in the vertical direction, the bending of the measurement flow path can be reduced and downsized, and the simplification of the configuration can be further improved and reduced. Cost can be reduced.

Further, as in this embodiment, the expansion gradient part 16
Is formed by arranging the sloped portions 17 and 18 on both sides in the height direction, the amount of expansion of the cross-sectional area is set to an appropriate value by the difference between the upper and lower angles α and β even if the bending of the measurement flow path 5 is increased. Can be maintained
It is possible to increase the bending amount of the measurement flow path to increase the deviation amount of the maximum value of the flow velocity distribution, promote the flatness of the flow rate change characteristic of the correction coefficient, and improve the measurement accuracy.

Although the start point of the gradient of the expanded gradient section 16 starts in the middle of the ultrasonic wave propagation path 10, the same operational effect can be obtained even if it is provided after the ultrasonic wave propagation path 10 is finished. At the same time, since the cross-sectional area of the measurement flow path in the ultrasonic wave propagation path 10 can be made constant, the measurement accuracy can be improved. Further, the start point of the gradient of the expansion gradient section 16 is the ultrasonic propagation path 10
The position of the maximum value of the flow velocity distribution can be largely displaced by providing it on the upstream side of, and it is possible to improve the flatness of the correction coefficient or increase the degree of freedom in the shape of the flow rate change characteristic of the correction coefficient.

(Embodiment 2) FIG. 6 is a sectional view of an ultrasonic flow rate measuring apparatus showing Embodiment 2 of the present invention. In FIG.
The same members and functions as those of the embodiment shown in FIGS. 1 to 5 are designated by the same reference numerals, detailed description thereof will be omitted, and different points will be mainly described.

Reference numeral 24 denotes a measurement flow path bent portion provided in the ultrasonic flow path 10 of the measurement flow path 5, and the measurement flow path bent portion 24 is directed to the upper side and the lower side in the height direction H toward the downstream side. The asymmetrical flow promoting means 15 is formed by bending the measurement flow path 5 in the height direction by the upper and lower slope portions 17 and 18 provided with the gradient of the angle γ in the same direction.

Next, the operation of this ultrasonic flow rate measuring device will be described. The fluid to be measured that has flowed in from the introduction portion 11 is bent in the upward direction in the drawing by the measurement flow path bending portion 24, and a deviation occurs in the height direction position of the maximum value of the flow velocity distribution.
In, the velocity distribution in the height direction is made asymmetric. For this reason,
As described in the first embodiment, the change in the correction coefficient of the flow rate value is reduced from the laminar flow area to the turbulent flow area, and the flow rate change characteristic of the flat correction coefficient is obtained.

As described above, the asymmetrical flow promoting means 15 is formed by the measurement flow path bent portion in which the measurement flow path 5 is bent in the height direction. Then, the bending portion causes a bias in the flow velocity distribution in the ultrasonic wave propagation path to promote the flatness of the flow rate change characteristic of the correction coefficient, and the cross-sectional area of the measurement flow path is kept constant to change the cross-sectional area. It is possible to reduce error generation and improve measurement accuracy.

Although the bending start point of the measurement flow path bending portion 24 is shown to start from the middle of the ultrasonic wave propagation path 10, the same operational effect can be obtained even if the measurement flow path bending part 24 is provided after the ultrasonic wave propagation path 10 is finished. In addition to being obtained, the cross-sectional area of the measurement flow path in the ultrasonic wave propagation path 10 can be made constant, so that the measurement accuracy can be improved. Further, by providing the bending start point of the measurement flow path bending portion 24 on the upstream side of the ultrasonic wave propagation path 10, the position of the maximum value of the flow velocity distribution can be largely displaced, and the flatness of the correction coefficient or the correction coefficient can be improved. The degree of freedom with respect to the shape of the flow rate change characteristic can be increased.

(Embodiment 3) FIGS. 7 and 8 are sectional views of an ultrasonic flow rate measuring apparatus showing Embodiment 3 of the present invention. 7 and 8, the same members and functions as those of the embodiment shown in FIGS. 1 to 6 are designated by the same reference numerals, detailed description thereof will be omitted, and different points will be mainly described.

Reference numeral 25 denotes a transmission / reception axis which is a central axis of the ultrasonic wave transmitters / receivers 7 and 8. The transmission / reception axis 25 is located above the measurement flow path axis 26, which is the central axis in the height direction of the measurement flow path 5, above the drawing. Is eccentric by ΔY.

Here, the ultrasonic transmitters / receivers 7 and 8 have the maximum eccentric directions indicated by velocity distributions S and R in the eccentric direction of the transmission / reception shaft 25 as shown in FIG. 7 showing a laminar flow region and FIG. 8 showing a turbulent flow region. This is the upper direction of the drawing in which the flow velocity generation positions T and U exist.

The positions T and U at which the maximum flow velocity is generated are present in the upward direction of the drawing because the asymmetrical flow is promoted by the enlarged gradient portion 16 provided on the downstream side of the measurement flow path 5 and having a gradient in the upward direction of the drawing. By the means 15, the measurement flow path 5
Since the downstream side is bent by the bent portion 14 upward in the drawing in the same direction as the enlarged gradient portion 16, the deviation of the flow becomes large and the deviation of the flow is maintained even at a large flow rate.

Next, the operation will be described. Ultrasonic transceiver 7,
8 is eccentric from the center of the measurement flow path 5 in the height direction, so that in the laminar flow region of low flow velocity where the velocity distribution shape is convex, the height center of the ultrasonic wave propagation path 10 is the position where the maximum flow velocity value is generated. The value of the correction coefficient increases as the distance from the position increases, and the eccentric position in the height direction of the ultrasonic transmitters / receivers 7 and 8 is set so as to approach the value of the turbulent flow area at the time of large flow rate, and the change in the correction coefficient is flat. Can be expanded to a low flow rate region on the low flow velocity side. In addition, the eccentric direction of the ultrasonic transmitters / receivers 7 and 8 is set to the direction in which the maximum value exists in the velocity distribution in the height direction, so that the position of the maximum velocity value in the laminar flow region or transition region where the flow velocity distribution shape is convex. The flow velocity between the wall and the wall can be made steeper, and the height of the ultrasonic transmitters / receivers 7 and 8 can be slightly adjusted to easily change the value of the correction coefficient to change the correction coefficient to the low flow rate side. The flat area can be enlarged. Further, on the large flow rate side, the place where the flow velocity is large is measured and the value of the correction coefficient is reduced to reduce the difference between the correction coefficient values on the large flow rate side and the low flow rate side, and the flatness can be improved. Therefore, the change of the correction coefficient can be flattened over a wide flow range of a large flow range.

The ultrasonic transmitters / receivers 7 and 8 are the measurement flow path 5.
In addition to eccentricity from the center of the height direction, the expansion gradient section 16 imparts a gradient in the direction in which the ultrasonic transmitters / receivers 7 and 8 are eccentrically expanded to expand the low-velocity region flowing in a laminar state. The eccentricity can be optimally set so that the value of the correction coefficient at is close to the value in the large flow velocity region that flows in the turbulent state. It is possible to make the correction coefficient in the large flow velocity region close to the value in the low flow velocity region by measuring the value in the above manner, and the region where the change of the correction coefficient is flat can be expanded to the low flow velocity side.

Further, the bent portion 14 on the downstream side of the measurement flow path 5
By setting the gradient direction of the enlarged gradient portion 16 on the bending direction side of the, the flow deviation can be promoted as the flow rate increases, and the ratio of the region of high velocity in the ultrasonic propagation path 10 decentered in the height direction. Can be increased to reduce the correction coefficient in the large flow rate range, and the correction coefficient value can be reduced at a larger flow rate value, and the flatness of the correction coefficient can be improved over a wider measurement range.

In FIG. 9, the ultrasonic transmitter / receivers 7 and 8 are connected to the measurement flow path 5.
Another example is shown in which the center is eccentric from the center of the height direction of the measurement flow path. The asymmetric flow promoting means 15 provided on the downstream side of the measurement flow path 5 is formed by the measurement flow path bent portion 24, and The sound wave transmitters / receivers 7 and 8 are arranged on the side where the measurement flow path bending portion 24 is bent, with eccentricity ΔY from the center of the measurement flow path 5 in the height H direction.

As in the case of the above-described enlarged slope portion 16, the measurement flow path bent portion 24 serving as the asymmetrical flow promoting means 15 can flatten the correction coefficient by biasing the maximum value position of the flow velocity distribution in the height direction. Since the measurement flow path bent portion 24 has a constant cross-sectional area of the measurement flow path 5, it is possible to reduce an error caused by a change in cross-sectional area and improve the measurement accuracy.

Further, the ultrasonic transmitters / receivers 7, 8 are the measurement flow path 5
In the low flow velocity region flowing in a laminar flow state, the measurement flow path bending portion 24 is bent in the direction in which the ultrasonic transceivers 7 and 8 are eccentric while being eccentric by ΔY from the center in the height direction. Optimum eccentricity can be set so that the value of the correction coefficient is close to the value in the large flow velocity range flowing in the turbulent state.Furthermore, by eccentrically arranging in the direction in which the maximum value of the flow velocity distribution is deviated, mainly in the region of large flow velocity The correction coefficient in the large flow velocity region can be measured to be close to the value in the low flow velocity region, and the region where the change of the correction coefficient is flat can be expanded to the low flow velocity side.

In this way, the ultrasonic wave transmitters / receivers 7, 8 are eccentric to the one side from the center in the height direction of the measurement flow path 5, and the measurement flow path bent portion 24 makes the ultrasonic wave transmitters / receivers 7, 8 eccentric. When the flow rate distribution is biased toward the side, the deviation of the flow velocity distribution can be promoted as the flow rate increases, and the ultrasonic transmitters / receivers 7, 8 are eccentric to the side where the flow velocity distribution is fast, so that the flow rate distribution is large. The correction coefficient of can be brought close to the low flow velocity region where a laminar flow is achieved. Further, by maintaining the cross-sectional area of the measurement flow path 5 constant, it is possible to improve the measurement accuracy by reducing the error occurrence due to the change in cross-sectional area and to improve the flatness of the correction coefficient over a wide measurement range from the low flow velocity region to the large flow velocity region. Can be improved.

Further, by setting the direction of the measurement flow path bent portion 24 on the bending direction side of the bent portion 14 on the downstream side of the measurement flow path 5, the flow deviation can be promoted as the flow rate increases, and the height direction can be increased. It is possible to increase the proportion of a region having a large flow velocity in the ultrasonic propagation path 10 that is eccentric to, and reduce the correction coefficient in a large flow rate range, and further reduce the correction coefficient value at a larger flow rate value, and to cover a wider measurement range. The flatness of the correction coefficient can be improved.

Although the start point of the bending of the enlarged gradient portion 16 and the measurement flow path bent portion 24 starts in the middle of the ultrasonic wave propagation path 10, it is provided even after the ultrasonic wave propagation path 10 is finished. The same effect can be obtained, and the cross-sectional area of the measurement flow path in the ultrasonic wave propagation path 10 can be made constant, so that the measurement accuracy can be improved. Further, by providing the bending start points of the enlarged gradient portion 16 and the measurement flow path bending portion 24 on the upstream side of the ultrasonic wave propagation path 10, the position of the maximum value of the flow velocity distribution can be largely displaced, and the correction coefficient is flat. It is possible to improve the flexibility or the degree of freedom of the shape of the flow rate change characteristic of the correction coefficient.

[0051]

As is apparent from the above description, according to the ultrasonic flow rate measuring apparatus of the present invention, the measurement accuracy can be improved by reducing the change of the correction coefficient over the entire flow rate measuring range.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an ultrasonic flow rate measuring device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the ultrasonic flow rate measuring device according to the first embodiment of the present invention.

FIG. 3 is a vertical cross-sectional view of the ultrasonic flow rate measuring device according to the first embodiment showing a velocity distribution in a turbulent flow region.

FIG. 4 is a characteristic diagram of a correction coefficient when there is no asymmetrical flow promoting means.

FIG. 5 is a characteristic diagram of a correction coefficient when there is an asymmetrical flow promoting means.

FIG. 6 is a vertical cross-sectional view of an ultrasonic flow rate measurement apparatus showing Embodiment 2 of the present invention.

FIG. 7 is a vertical cross-sectional view of an ultrasonic flow rate measurement apparatus showing Embodiment 3 of the present invention.

FIG. 8 is a vertical cross-sectional view of an ultrasonic flow rate measuring device according to a third embodiment showing a velocity distribution in a turbulent flow region.

FIG. 9 is a vertical cross-sectional view of an ultrasonic flow rate measuring device showing another embodiment.

FIG. 10 is a configuration diagram of a conventional ultrasonic flow rate measuring device.

[Explanation of symbols]

5 measurement channels 7, 8 Ultrasonic transceiver 11 Introduction 12 Derivation part 13 Bend 15 Asymmetric flow promoting means 16 Expanding slope section 17, 18 Gradient section 21 Flow rate calculation means 24 Measurement channel bend

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[Procedure amendment]

[Submission date] March 7, 2003 (2003.3.7)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

[Title of Invention] Ultrasonic flow rate measuring device

[Claims]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow rate measuring device for measuring the flow rate and flow velocity of gas or liquid.

[0002]

2. Description of the Related Art Conventional ultrasonic flow rate measuring devices of this type include
For example, Japanese Unexamined Patent Publication No. 11-351926 is known, and as shown in FIG. The ultrasonic transmitter / receiver 2a on the upstream side is inclined at a predetermined angle.
And the ultrasonic transmitter / receiver 2b on the downstream side are provided so as to face each other, and these ultrasonic transmitter / receivers 2a and 2b are housed in the recesses 3a and 3b provided in the measurement flow path 1 and at the inlet side of the measurement flow path 1. A rectifying body 4 is provided. Then, the flow velocity of the fluid flowing through the measurement flow path 1 is transmitted and received between the ultrasonic wave transmitters / receivers 2a and 2b, measured from the propagation time difference, and the flow rate is calculated from the cross-sectional area of the measurement flow path 1. At this time, the flow entering the measurement flow path 1 is regulated by the rectifying body 4 to reduce the inclination of the streamline in the measurement unit and suppress the generation of vortices, and to suppress the ultrasonic waves at the boundary surface of the flow turbulence. The fluctuation of the reception level of ultrasonic waves due to reflection and refraction is reduced to prevent the deterioration of measurement accuracy.

[0003]

However, in the conventional configuration, the rectifying body and the ultrasonic wave propagation path are set apart from each other, and the distance between the rectifying body is on the ultrasonic transmitter / receiver 2a side and the ultrasonic wave transmitter / receiver 2b side. There is a difference in the development state of the flow passing through the rectifying body because of the large difference, or the ultrasonic wave transmitted from the ultrasonic transmitter / receiver has an intensity distribution in the height direction although the entire width W direction of the measuring tube 1 is measured. By doing so, the flow velocity distribution on the central axis of the ultrasonic transmitter / receiver is mainly measured. Therefore, the average flow velocity in the cross section orthogonal to the measurement flow passage and the measurement between the ultrasonic transmitter / receivers 2a and 2b oblique to the measurement flow passage are measured. A difference occurs in the average flow velocity in the cross section, and in order to calculate the true flow rate, a correction coefficient corresponding to the flow rate is necessary for the measured value. In particular, since the correction coefficient greatly changes in the flow rate range where laminar flow changes to turbulent flow, even if there is a slight error in the flow velocity measurement at the measurement cross section, the correction coefficient expands the error and deteriorates the measurement accuracy. was there.

The present invention has been made to solve the above problems, and an object of the present invention is to improve the measurement accuracy by reducing the change in the correction coefficient over the entire flow rate measurement range.

[0005]

According to the present invention, a measurement flow path through which a fluid to be measured flows, an introduction part and a discharge part provided on the upstream side and the downstream side of the measurement flow path, and the measurement flow path are ultrasonic waves. At least a pair of ultrasonic transceivers provided so as to propagate across, and transmission and reception of ultrasonic waves between the ultrasonic transceivers.
Flow rate calculation that calculates the flow rate based on the transmitted and received signals
The ultrasonic transmitter / receiver is provided with
And the velocity distribution is made asymmetric,
In order to bias the generation position of the large value to one side, go downstream
Downstream of the measurement flow path with an enlarged slope part where the height of the measurement flow path expands
It is provided on the side.

According to the above invention, in the laminar flow region in which the velocity distribution in the height direction is convex, the maximum value of the flow velocity is biased and the slow velocity region is measured in many places to increase the correction coefficient to increase the high velocity. In the turbulent flow region where the velocity distribution in the depth direction is relatively flat, the maximum value of the flow velocity is measured and the correction coefficient, which was larger than the laminar flow region in the past, is made slightly smaller. It is possible to reduce the difference between the correction coefficients and reduce the change in the correction coefficient over the entire flow rate measurement range, prevent the error from being increased by the correction coefficient, and improve the measurement accuracy. Further, even if the Reynolds number changes due to the change of the kinematic viscosity of the fluid, the change of the correction coefficient is small, so the measurement accuracy is maintained, and it is possible to realize a measuring device that is strong against changes in the fluid temperature and changes in the fluid components. Can be increased.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is a meter in which a fluid to be measured flows.
The measurement channel and the upstream and downstream sides of the measurement channel
Ultrasound crosses the inlet and outlet and the measurement channel.
Transmission and reception of at least one pair of ultrasonic waves
The ultrasonic wave is transmitted and received between the ultrasonic wave transmitter and the ultrasonic wave transmitter / receiver.
Flow rate calculation means for calculating the flow rate based on the transmitted and received signals of
, And place the ultrasonic transceiver in the center of the measurement flow path.
In addition, the velocity distribution is made asymmetric and the maximum velocity is generated.
Measurement channel toward the downstream to bias the raw position to one side
An expansion slope part that expands the height of the
It is a thing. Then, in the laminar region where the velocity distribution in the height direction is convex, the maximum correction value of the velocity is biased to increase the correction factor by increasing the number of places where the velocity is slow, and comparing the velocity distribution in the height direction. In the turbulent flow area, which is generally flat, the maximum value of the flow velocity is measured, and the correction coefficient, which was conventionally larger than the laminar flow area, is made slightly smaller to reduce the difference in the correction coefficient between the laminar flow area and the turbulent flow area. However, the flow rate change characteristic of the correction coefficient is flattened over the entire flow rate measurement range, and the measurement accuracy can be improved. Further, even if the physical property value of the fluid changes, the measurement accuracy is maintained, and the practicality and convenience can be improved. Then, the flow velocity distribution
Biasing the position where the maximum value occurs in the direction in which the height increases
And the direction of the deviation of the flow velocity distribution in the ultrasonic wave propagation path.
And the amount of deviation can be controlled, so the flow rate
Height of the ultrasonic transmitter / receiver while increasing the flatness of the conversion characteristics
The degree of freedom of the installation position in the direction can be improved, and
Simplify the structure by simply adding a gradient
It is possible to improve the processability and processability and reduce the cost.

The enlarged slope portion of the present invention is provided on one side in the height direction.
It is formed by arranging the distribution portion. In addition, the bending of the measurement flow path can be reduced to reduce the size, and the simplification of the configuration can be further improved to reduce the cost.

The expansion slope portion of the present invention is provided on both sides in the height direction.
It is formed by arranging the distribution portion. Then, the bending amount of the measurement flow path can be increased to increase the deviation amount of the maximum value of the flow velocity distribution, the flatness of the flow rate change characteristic of the correction coefficient can be promoted, and the measurement accuracy can be improved.

In addition, whether the ultrasonic transmitter / receiver is at the center of the measurement flow path or not.
It is eccentric to one side, and the magnifying gradient part transmits ultrasonic waves.
The receiver is enlarged to the eccentric side. The eccentric position in the height direction of the ultrasonic transmitter / receiver can be optimally eccentrically set so that the value of the correction coefficient in the low velocity region flowing in the laminar flow state is close to the value in the large velocity region flowing in the turbulent state. ,
Furthermore, by eccentrically arranging in a direction in which the maximum value of the flow velocity distribution is biased, the region where the flow velocity is large can be measured mainly, and the correction coefficient in the large flow velocity region can be made close to the value in the low flow velocity region. The flat region can be expanded to the low flow velocity side.

The present invention also provides a measurement flow in which a fluid to be measured flows.
And the introduction provided on the upstream side and the downstream side of the measurement flow path.
Section and outlet section, and ultrasonic waves are transmitted across the measurement flow path.
At least a pair of ultrasonic transceivers provided so as to be carried
And transmitting and receiving ultrasonic waves between the ultrasonic transmitters and receivers
Flow rate calculation means that calculates the flow rate based on the transmitted and received signals
And arrange the ultrasonic transmitter / receiver in the center of the measurement channel.
At the same time, the velocity distribution is made asymmetric and the maximum value of the flow velocity is generated.
Measurement flow that inclines at the same angle to bias the position to one side
The curved road portion is provided on the downstream side.

[0012] Then, the bending portion causes a deviation of the flow velocity distribution in the ultrasonic wave propagation path to promote the flatness of the flow rate change characteristic of the correction coefficient, and at the same time, keeps the cross-sectional area of the measurement channel constant. It is possible to reduce the occurrence of errors due to area changes and improve the measurement accuracy.

Also, the ultrasonic transmitter / receiver should be placed at the center of the measurement flow path.
The other part is eccentric to the other side , and the measurement flow path bent part is the part where the ultrasonic transceiver is bent to the eccentric side. Moreover, the deviation of the flow velocity distribution due to the bent portion of the measurement flow path can be promoted as the flow rate increases, and since the ultrasonic transmitter / receiver is eccentric to the side where the flow velocity distribution is fast, the correction coefficient in the large flow rate region can be set to the laminar flow state. It is possible to get close to the low flow velocity region, and the cross-sectional area of the measurement flow path is kept constant to improve the measurement accuracy by reducing the occurrence of errors due to cross-sectional area changes, and a wide measurement range from the low flow velocity region to the large flow velocity region. The flatness of the correction coefficient can be improved.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIGS. 1 and 2 are a longitudinal sectional view and a transverse sectional view of an ultrasonic flow rate measuring apparatus showing Embodiment 1 of the present invention. In the figure, 5 is a measurement flow path surrounded by a flow path wall 6, and 7 and 8 are upstream and downstream ultrasonic transceivers attached to the flow path wall 6 so as to face each other. The upstream ultrasonic transmitter / receiver 7 and the downstream ultrasonic transmitter / receiver 8 are separated from each other by a distance L so as to cross the width W direction of the measurement flow path 5 and inclined by an angle θ with respect to the flow direction of the fluid in the measurement flow path 5. The measurement flow path 5 is installed at approximately the center of the height H direction. Reference numerals 9a and 9b denote upstream and downstream opening holes that expose the ultrasonic transceivers 7 and 8 to the measurement flow path 5. Reference numeral 10 denotes an ultrasonic wave propagation path (indicated by a chain double-dashed line) in which ultrasonic waves transmitted between the ultrasonic wave transmitters / receivers 7 and 8 which oppose each other propagate directly to the other party. Reference numeral 11 is an introduction portion which is provided on the upstream side of the measurement flow path 5 and serves as an inlet for the fluid to be measured, and 12 is a derivation portion which is provided on the downstream side of the measurement fluid path 5 and serves as an outlet for the measurement fluid. 13 is a measurement channel 5 and an introduction part 1
1, which is a bent portion on the upstream side connecting with 1, and the bent portion 13 is bent in the height H direction of the measurement flow path 5. Reference numeral 14 is a downstream bent portion that connects the measurement flow path 5 and the lead-out portion 12, and the bent portion 14 is bent in the height H direction of the measurement flow path 5.

Reference numeral 15 indicates that the velocity distribution S in the height H direction of the measurement flow path 5 is made asymmetric with respect to the height center so that the generation position T of the maximum value of the flow velocity in the height H direction is biased to one side from the height center. This is an asymmetrical flow promoting means. This asymmetrical flow promoting means 15
Is formed by the enlarged slope portion 16 provided on the downstream side of the measurement flow path 5, and here, the slope portion 17 and the upper slope portion 17 provided on the upper side in the height direction are provided with a slope of an angle α toward the downstream side. An enlarged sloped portion 16 in which the height of the measurement flow path 5 is sequentially increased is formed by a lower sloped portion 18 provided on the lower side in the depth direction and having a slope of an angle β (α> β) toward the downstream side. There is. The expansion gradient portion 16 causes a deviation in the flow velocity distribution in the height direction of the measurement flow path 5. 19 is the outer peripheral surface 1 of the bent portion 13 on the upstream side.
It is a stepped portion provided on the 3a side.

Reference numeral 20 denotes a flow stabilizing means provided between the asymmetrical flow promoting means 15 and the ultrasonic wave propagation path 10, and a grid-like direction regulating portion 20a for dividing the cross section of the measurement flow path 5 to adjust the flow direction. A fluctuation suppressing portion 20b formed of a mesh-like body such as a mesh for reducing fluctuations in flow velocity is provided. Reference numeral 21 is a flow rate calculation provided with a measurement control section 22 connected to the ultrasonic wave transmitters / receivers 7 and 8 for transmitting and receiving ultrasonic waves, and a calculation section 23 for calculating a flow rate based on a signal from the measurement control section 22 to calculate a flow rate. It is a means.

Next, the operation of this ultrasonic flow rate measuring device will be described. The fluid to be measured that has flowed in from the introduction section 11 is an asymmetrical flow promoting means 15 provided on the inlet side of the measurement flow path 5.
As a result, the velocity distribution in the height H direction of the measurement flow path 5 is not substantially symmetrical with respect to the height center but has an asymmetric shape. That is, in the transition region in which the flow of the measurement flow path 5 is changing from the laminar flow region or the laminar flow to the turbulent flow, as shown by the velocity distribution S in FIG. 1, a parabolic convex shape in which the velocity gradually increases as the distance from the wall surface increases. Yes The position T at which the maximum flow velocity is generated is slightly biased to one side (upper in the drawing) from the vicinity of the center of the height.
On the other hand, when the flow rate flowing through the measurement flow path 5 increases and enters the turbulent flow region, the speed change in the height direction decreases as shown by the speed distribution R in FIG. The generation position U is biased to one side (upward in the drawing) from the vicinity of the center of height.

Next, the flow rate measuring operation using ultrasonic waves will be described. In the measurement flow path 5, the measurement controller 22 acts so as to cross the width W of the flow path cross section of the measurement flow path 5 between the ultrasonic transceivers 7 and 8 with respect to the flow in which the velocity distribution in the height direction is asymmetrical. Then, ultrasonic waves are transmitted and received. That is, the propagation time T1 until the ultrasonic waves emitted from the upstream ultrasonic transceiver 7 are received by the downstream ultrasonic transceiver 8 is measured. On the other hand, the propagation time T2 until the ultrasonic wave emitted from the ultrasonic wave transmitter / receiver 8 on the downstream side is received by the ultrasonic wave transmitter / receiver 7 on the upstream side is measured.

Based on the propagation times T1 and T2 measured in this way, the flow rate is calculated by the calculation unit 23 by the following calculation formula.

Now, the angle formed by the flow velocity V of the fluid to be measured in the flow direction of the measurement flow path 5 and the ultrasonic wave propagation path 10 is θ, the distance between the ultrasonic transceivers 7 and 8 is L, and the distance of the fluid to be measured is L. When the speed of sound is C, the flow velocity V is calculated by the following formula.

T1 = L / (C + Vcosθ) T2 = L / (C-Vcosθ) V = (L / 2cosθ) ((1 / T1) by eliminating the sound velocity C from the equation of subtracting the inverse of T2 from the inverse of T1. -(1 / T2)) Since θ and L are known, the flow velocity V is calculated from the values of T1 and T2.
Can be calculated.

However, the flow velocity V obtained here is measured by the ultrasonic wave propagation path 10 that obliquely crosses the measurement flow path 5, and the average flow speed measured by the ultrasonic wave propagation path 10 is a state of flow development depending on the cross-sectional position. However, since the entire flow passage is not measured in the cross section in the height H direction, there is a difference in the average flow velocity obtained from the entire cross section orthogonal to the measurement flow passage 5. Moreover, since the intensity distribution of the ultrasonic waves in the ultrasonic wave propagation path 10 has a characteristic that the center of the ultrasonic wave transmitters / receivers 7, 8 which is on the central axis side becomes strong, the central portion of the ultrasonic wave propagation path 10 in the height direction is Will be measured mainly.

For this reason, the flow rate is calculated by adding the correction coefficient, and from the cross-sectional area S orthogonal to the flow direction of the measurement flow path 5,
The flow rate Q is Q = KVS, where K is a correction coefficient considering the flow velocity distribution in the cross-sectional area S.

In this way, the calculation unit 23 can determine the flow rate.

Particularly, in the case where the asymmetrical flow promoting means 15 is not provided, in the laminar flow region, the parabolic convex maximum flow velocity portion is located at the central portion in the height direction within the ultrasonic wave propagation path 10. Is considerably smaller than that in the turbulent region.
Therefore, as shown in FIG. 4, the correction coefficient greatly changes in the transition region where the laminar flow region transitions to the turbulent flow region, and the correction coefficient greatly changes to ΔK1 due to the occurrence of the error ΔQm in the measured flow rate, so that the error is magnified. This error may occur due to a difference in flow state due to a difference in Reynolds number due to a change in kinematic viscosity coefficient due to a change in fluid temperature or a change in fluid composition ratio. In particular, when measuring the flow rate of city gas, LPG (liquefied petroleum gas), etc., it is necessary to consider when the gas composition change due to the difference of seasons or regions.

FIG. 5 shows an asymmetrical flow promoting means 1 in the measurement channel 5.
5 shows the flow rate change characteristic of the correction coefficient when 5 is installed. By biasing the velocity distribution in the height direction of the measurement flow path 5 to one side from the center, the velocity distribution in the height direction becomes convex. In the laminar flow region, the maximum flow velocity is biased to increase the correction coefficient by increasing the number of slow flow velocity areas, and the maximum flow velocity is obtained in the turbulent flow region where the velocity distribution in the height direction is relatively flat. By measuring the side, by slightly reducing the correction coefficient that was conventionally larger than the laminar flow area, it is possible to reduce the difference in the correction coefficient between the laminar flow area and the turbulent flow area, and Difference can be reduced,
Even in the transition region where the laminar flow changes to the turbulent flow, the change of the correction coefficient is small, and the correction coefficient is flattened. Therefore, even if an error ΔQm occurs in the measured flow rate, the change in the correction coefficient is ΔK2 (K2
It can be made sufficiently small as <K1), and measurement with high measurement accuracy can be performed. It is effective to flatten the correction coefficient when there is a temperature change or composition change of the fluid. Especially, when measuring the flow rate of fuel gas such as city gas or LPG where composition change and temperature change are considered, the accuracy is further improved. Measurement can be realized.

As described above, the asymmetric flow promoting means for making the velocity distribution in the height direction of the measurement flow path asymmetric so that the generation position of the maximum value of the flow velocity in the height direction is deviated from the height center to one side, In a laminar region where the velocity distribution is convex, the maximum velocity is biased to increase the correction factor by increasing the number of slow velocity regions and making the velocity distribution relatively flat in the height direction. In the turbulent flow region, the maximum value of the flow velocity is measured so that the correction coefficient that was conventionally larger than that in the laminar flow region is slightly reduced to reduce the difference in the correction coefficient between the laminar flow region and the turbulent flow region, and the flow rate measurement range. It is possible to reduce the change in the correction coefficient over the entire area, and it is possible to prevent the error from increasing due to the correction coefficient and improve the measurement accuracy.
Furthermore, even if the Reynolds number changes due to the change in the kinematic viscosity of the fluid, the change in the correction coefficient is small, so the measurement accuracy is maintained, and a measuring device that is robust against changes in the fluid temperature and changes in the fluid components can be realized. Can be increased.

Further, as in the present embodiment, the asymmetrical flow promoting means 15 is provided with the expansion slope portion 16 in which the height of the measurement flow path 5 is gradually increased toward the downstream side, so that the position where the maximum value of the flow velocity distribution is generated is generated. Can be biased in the direction in which the height increases,
Since the generation direction and the magnitude of the deviation of the flow velocity distribution in the ultrasonic wave propagation path 10 can be controlled by the size of the enlarged gradient portion and the position where the gradient starts, the flatness of the flow rate change characteristic of the correction coefficient is increased and the ultrasonic wave is generated. The degree of freedom in the installation position of the transceivers 7 and 8 in the height direction can be improved, and a simple shape can be provided only by providing a gradient on the wall surface of the measurement flow path 5, so that the configuration can be simplified and the workability can be improved, and the cost can be reduced. Can be converted.

Further, in the structure of this embodiment, the lower slope portion 18 provided with a slope of the angle β on the lower side in the height direction of the measurement flow path 5 is removed, and the enlarged slope portion 16 is provided with the height of the measurement flow path 5. By forming the inclined portion on one surface of only the upper inclined portion 17 provided on the upper side in the vertical direction, the bending of the measurement flow path can be reduced and downsized, and the simplification of the configuration can be further improved and reduced. Cost can be reduced.

Further, as in this embodiment, the expansion gradient part 16
Is formed by arranging the sloped portions 17 and 18 on both sides in the height direction, the amount of expansion of the cross-sectional area is set to an appropriate value by the difference between the upper and lower angles α and β even if the bending of the measurement flow path 5 is increased. Can be maintained
It is possible to increase the bending amount of the measurement flow path to increase the deviation amount of the maximum value of the flow velocity distribution, promote the flatness of the flow rate change characteristic of the correction coefficient, and improve the measurement accuracy.

Although the start point of the gradient of the expanded gradient section 16 starts in the middle of the ultrasonic wave propagation path 10, the same operational effect can be obtained even if it is provided after the ultrasonic wave propagation path 10 is finished. At the same time, since the cross-sectional area of the measurement flow path in the ultrasonic wave propagation path 10 can be made constant, the measurement accuracy can be improved. Further, the start point of the gradient of the expansion gradient section 16 is the ultrasonic propagation path 10
The position of the maximum value of the flow velocity distribution can be largely displaced by providing it on the upstream side of, and it is possible to improve the flatness of the correction coefficient or increase the degree of freedom in the shape of the flow rate change characteristic of the correction coefficient.

(Embodiment 2) FIG. 6 is a sectional view of an ultrasonic flow rate measuring apparatus showing Embodiment 2 of the present invention. In FIG.
The same members and functions as those of the embodiment shown in FIGS. 1 to 5 are designated by the same reference numerals, detailed description thereof will be omitted, and different points will be mainly described.

Reference numeral 24 denotes a measurement flow path bent portion provided in the ultrasonic flow path 10 of the measurement flow path 5, and the measurement flow path bent portion 24 is directed to the upper side and the lower side in the height direction H toward the downstream side. The asymmetrical flow promoting means 15 is formed by bending the measurement flow path 5 in the height direction by the upper and lower slope portions 17 and 18 provided with the gradient of the angle γ in the same direction.

Next, the operation of this ultrasonic flow rate measuring device will be described. The fluid to be measured that has flowed in from the introduction portion 11 is bent in the upward direction in the drawing by the measurement flow path bending portion 24, and a deviation occurs in the height direction position of the maximum value of the flow velocity distribution.
In, the velocity distribution in the height direction is made asymmetric. For this reason,
As described in the first embodiment, the change in the correction coefficient of the flow rate value is reduced from the laminar flow area to the turbulent flow area, and the flow rate change characteristic of the flat correction coefficient is obtained.

As described above, the asymmetrical flow promoting means 15 is formed by the measurement flow path bent portion in which the measurement flow path 5 is bent in the height direction. Then, the bending portion causes a bias in the flow velocity distribution in the ultrasonic wave propagation path to promote the flatness of the flow rate change characteristic of the correction coefficient, and the cross-sectional area of the measurement flow path is kept constant to change the cross-sectional area. It is possible to reduce error generation and improve measurement accuracy.

Although the bending start point of the measurement flow path bending portion 24 is shown to start from the middle of the ultrasonic wave propagation path 10, the same operational effect can be obtained even if the measurement flow path bending part 24 is provided after the ultrasonic wave propagation path 10 is finished. In addition to being obtained, the cross-sectional area of the measurement flow path in the ultrasonic wave propagation path 10 can be made constant, so that the measurement accuracy can be improved. Further, by providing the bending start point of the measurement flow path bending portion 24 on the upstream side of the ultrasonic wave propagation path 10, the position of the maximum value of the flow velocity distribution can be largely displaced, and the flatness of the correction coefficient or the correction coefficient can be improved. The degree of freedom with respect to the shape of the flow rate change characteristic can be increased.

(Embodiment 3) FIGS. 7 and 8 are sectional views of an ultrasonic flow rate measuring apparatus showing Embodiment 3 of the present invention. 7 and 8, the same members and functions as those of the embodiment shown in FIGS. 1 to 6 are designated by the same reference numerals, detailed description thereof will be omitted, and different points will be mainly described.

Reference numeral 25 denotes a transmission / reception axis which is a central axis of the ultrasonic wave transmitters / receivers 7 and 8. The transmission / reception axis 25 is located above the measurement flow path axis 26, which is the central axis in the height direction of the measurement flow path 5, above the drawing. Is eccentric by ΔY.

Here, the ultrasonic transmitters / receivers 7 and 8 have the maximum eccentric directions indicated by velocity distributions S and R in the eccentric direction of the transmission / reception shaft 25 as shown in FIG. 7 showing a laminar flow region and FIG. 8 showing a turbulent flow region. This is the upper direction of the drawing in which the flow velocity generation positions T and U exist.

The positions T and U at which the maximum flow velocity is generated are present in the upward direction of the drawing because the asymmetrical flow is promoted by the enlarged gradient portion 16 provided on the downstream side of the measurement flow path 5 and having a gradient in the upward direction of the drawing. By the means 15, the measurement flow path 5
Since the downstream side is bent by the bent portion 14 upward in the drawing in the same direction as the enlarged gradient portion 16, the deviation of the flow becomes large and the deviation of the flow is maintained even at a large flow rate.

Next, the operation will be described. Ultrasonic transceiver 7,
8 is eccentric from the center of the measurement flow path 5 in the height direction, so that in the laminar flow region of low flow velocity where the velocity distribution shape is convex, the height center of the ultrasonic wave propagation path 10 is the position where the maximum flow velocity value is generated. The value of the correction coefficient increases as the distance from the position increases, and the eccentric position in the height direction of the ultrasonic transmitters / receivers 7 and 8 is set so as to approach the value of the turbulent flow area at the time of large flow rate, and the change in the correction coefficient is flat. Can be expanded to a low flow rate region on the low flow velocity side.

The eccentric direction of the ultrasonic transmitters / receivers 7 and 8 is set such that the maximum value exists in the velocity distribution in the height direction, so that the maximum flow velocity is obtained in the laminar flow region or transition region where the flow velocity distribution shape is convex. The flow velocity change between the position of the value and the wall surface can be made steeper, and the height position of the ultrasonic transmitters / receivers 7, 8 can be slightly adjusted to easily change the value of the correction coefficient to correct to the low flow rate side. It is possible to enlarge a region where the coefficient changes are flat. Further, on the large flow rate side, the place where the flow velocity is large is measured and the value of the correction coefficient is reduced to reduce the difference between the correction coefficient values on the large flow rate side and the low flow rate side, and the flatness can be improved. Therefore, the change of the correction coefficient can be flattened over a wide flow range of a large flow range.

The ultrasonic transmitters / receivers 7 and 8 are used for the measurement flow path 5.
In addition to eccentricity from the center of the height direction, the expansion gradient section 16 imparts a gradient in the direction in which the ultrasonic transmitters / receivers 7 and 8 are eccentrically expanded to expand the low-velocity region flowing in a laminar state. The eccentricity can be optimally set so that the value of the correction coefficient at is close to the value in the large flow velocity region that flows in the turbulent state. It is possible to make the correction coefficient in the large flow velocity region close to the value in the low flow velocity region by measuring the value in the above manner, and the region where the change of the correction coefficient is flat can be expanded to the low flow velocity side.

Further, the bent portion 14 on the downstream side of the measurement flow path 5
By setting the gradient direction of the enlarged gradient portion 16 on the bending direction side of the, the flow deviation can be promoted as the flow rate increases, and the ratio of the region of high velocity in the ultrasonic propagation path 10 decentered in the height direction. Can be increased to reduce the correction coefficient in the large flow rate range, and the correction coefficient value can be reduced at a larger flow rate value, and the flatness of the correction coefficient can be improved over a wider measurement range.

FIG. 9 shows the ultrasonic transceivers 7 and 8 connected to the measurement channel 5.
Another example is shown in which the center is eccentric from the center of the height direction of the measurement flow path. The asymmetric flow promoting means 15 provided on the downstream side of the measurement flow path 5 is formed by the measurement flow path bent portion 24, and The sound wave transmitters / receivers 7 and 8 are arranged on the side where the measurement flow path bending portion 24 is bent, with eccentricity ΔY from the center of the measurement flow path 5 in the height H direction.

As in the case of the above-described enlarged gradient portion 16, the measurement flow path bent portion 24 serving as the asymmetrical flow promoting means 15 can flatten the correction coefficient by biasing the maximum value position of the flow velocity distribution in the height direction. Since the measurement flow path bent portion 24 has a constant cross-sectional area of the measurement flow path 5, it is possible to reduce an error caused by a change in cross-sectional area and improve the measurement accuracy.

The ultrasonic wave transmitters / receivers 7 and 8 are used for the measurement channel 5.
In the low flow velocity region flowing in a laminar flow state, the measurement flow path bending portion 24 is bent in the direction in which the ultrasonic transceivers 7 and 8 are eccentric while being eccentric by ΔY from the center in the height direction. Optimum eccentricity can be set so that the value of the correction coefficient is close to the value in the large flow velocity range flowing in the turbulent state.Furthermore, by eccentrically arranging in the direction in which the maximum value of the flow velocity distribution is deviated, mainly in the region of large flow velocity The correction coefficient in the large flow velocity region can be measured to be close to the value in the low flow velocity region, and the region where the change of the correction coefficient is flat can be expanded to the low flow velocity side.

In this way, the ultrasonic wave transmitters / receivers 7, 8 are eccentric to the one side from the center of the measurement flow path 5 in the height direction, and the measurement flow path bent portion 24 makes the ultrasonic wave transmitters / receivers 7, 8 eccentric. When the flow rate distribution is biased toward the side, the deviation of the flow velocity distribution can be promoted as the flow rate increases, and the ultrasonic transmitters / receivers 7, 8 are eccentric to the side where the flow velocity distribution is fast, so that the flow rate distribution is large. The correction coefficient of can be brought close to the low flow velocity region where a laminar flow is achieved. Further, by maintaining the cross-sectional area of the measurement flow path 5 constant, it is possible to improve the measurement accuracy by reducing the error occurrence due to the change in cross-sectional area and to improve the flatness of the correction coefficient over a wide measurement range from the low flow velocity region to the large flow velocity region. Can be improved.

Further, by setting the direction of the measurement flow path bent portion 24 on the bending direction side of the flow path bent portion 14 on the downstream side of the measurement flow path 5, the flow deviation can be promoted as the flow rate increases, and the height direction can be increased. It is possible to increase the proportion of a region having a large flow velocity in the ultrasonic propagation path 10 that is eccentric to, and reduce the correction coefficient in a large flow rate range, and further reduce the correction coefficient value at a larger flow rate value, and to cover a wider measurement range. The flatness of the correction coefficient can be improved.

Although the start point of the bending of the enlarged gradient portion 16 and the measurement flow path bending portion 24 starts in the middle of the ultrasonic wave propagation path 10, it is provided even after the ultrasonic wave propagation path 10 is finished. The same effect can be obtained, and the cross-sectional area of the measurement flow path in the ultrasonic wave propagation path 10 can be made constant, so that the measurement accuracy can be improved. Further, by providing the bending start points of the enlarged gradient portion 16 and the measurement flow path bending portion 24 on the upstream side of the ultrasonic wave propagation path 10, the position of the maximum value of the flow velocity distribution can be largely displaced, and the correction coefficient is flat. It is possible to improve the flexibility or the degree of freedom of the shape of the flow rate change characteristic of the correction coefficient.

[0052]

As is apparent from the above description, according to the ultrasonic flow rate measuring apparatus of the present invention, the measurement accuracy can be improved by reducing the change of the correction coefficient over the entire flow rate measuring range.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an ultrasonic flow rate measuring device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the ultrasonic flow rate measuring device according to the first embodiment of the present invention.

FIG. 3 is a vertical cross-sectional view of the ultrasonic flow rate measuring device according to the first embodiment showing a velocity distribution in a turbulent flow region.

FIG. 4 is a characteristic diagram of a correction coefficient when there is no asymmetrical flow promoting means.

FIG. 5 is a characteristic diagram of a correction coefficient when there is an asymmetrical flow promoting means.

FIG. 6 is a vertical cross-sectional view of an ultrasonic flow rate measurement apparatus showing Embodiment 2 of the present invention.

FIG. 7 is a vertical cross-sectional view of an ultrasonic flow rate measurement apparatus showing Embodiment 3 of the present invention.

FIG. 8 is a vertical cross-sectional view of an ultrasonic flow rate measuring device according to a third embodiment showing a velocity distribution in a turbulent flow region.

FIG. 9 is a vertical cross-sectional view of an ultrasonic flow rate measuring device showing another embodiment.

FIG. 10 is a configuration diagram of a conventional ultrasonic flow rate measuring device.

[Explanation of symbols] 5 measurement channels 7, 8 Ultrasonic transceiver 11 Introduction 12 Derivation part 13 Bend 15 Asymmetric flow promoting means 16 Expanding slope section 17, 18 Gradient section 21 Flow rate calculation means 24 Measurement channel bend

Claims (7)

[Claims]
1. A measurement flow path through which a fluid to be measured flows, an introduction part and a discharge part provided on the upstream side and the downstream side of the measurement flow path, and an ultrasonic wave so as to propagate across the width direction of the measurement flow path. At least a pair of ultrasonic transmitters and receivers provided in the asymmetrical flow promoting structure that makes the velocity distribution in the height direction of the measurement flow channel asymmetrical and biases the generation position of the maximum value of the flow velocity in the height direction to one side from the height center An ultrasonic flow rate measuring device comprising: means and a flow rate calculating means for transmitting and receiving ultrasonic waves between the ultrasonic transmitters and receivers and calculating a flow rate based on the transmitted and received signals.
2. The ultrasonic flow rate measuring device according to claim 1, wherein the asymmetrical flow promoting means is an enlarged slope portion in which the height of the measurement flow channel is gradually increased toward the downstream side.
3. The ultrasonic flow rate measuring device according to claim 2, wherein the enlarged gradient portion is formed by disposing the gradient portion on one surface in the height direction.
4. The ultrasonic flow rate measuring device according to claim 2, wherein the enlarged gradient portion is formed by arranging the gradient portions on both sides in the height direction.
5. The ultrasonic flow rate measuring device according to claim 1, wherein the asymmetric flow promoting means is formed by a measurement flow path bent portion in which the measurement flow path is bent in a height direction.
6. The ultrasonic transceiver according to claim 2, wherein the ultrasonic transmitter / receiver is eccentric from the center in the height direction of the measurement channel to one side, and the expansion gradient portion is expanded to the side where the ultrasonic transmitter / receiver is eccentric. The ultrasonic flow rate measuring device according to Item 1.
7. The ultrasonic transmitter / receiver is eccentric to the one side from the center in the height direction of the measurement flow path, and the measurement flow path bent portion is bent to the side on which the ultrasonic transmitter / receiver is eccentric. Ultrasonic flow rate measuring device.
JP2002106163A 2002-04-09 2002-04-09 Ultrasonic flow meter Expired - Fee Related JP3438734B1 (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2962073A4 (en) * 2013-02-27 2016-12-14 Daniel Measurement & Control Inc Ultrasonic flow metering with laminar to turbulent transition flow control

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2962073A4 (en) * 2013-02-27 2016-12-14 Daniel Measurement & Control Inc Ultrasonic flow metering with laminar to turbulent transition flow control
US10012521B2 (en) 2013-02-27 2018-07-03 Daniel Measurement And Control, Inc. Ultrasonic flow metering with laminar to turbulent transition flow control

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