JP3436247B2 - Ultrasonic flow meter - Google Patents

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, for this type of flow rate measuring device, for example, an ultrasonic type disclosed in Japanese Patent Laid-Open No. 9-189591 is known, and as shown in FIG. 13, a pipe 1 for flowing a fluid from one side to the other side is known. The upstream ultrasonic transmitter / receiver 2a and the downstream ultrasonic transmitter / receiver 2b are provided so as to face each other across the center line and have a predetermined angle with respect to the center line, and the fluid of the pipe 1 is provided. A rectifying body 4 composed of a plurality of thin tubes 4a arranged in parallel is provided in the suction port 3 in the same direction as the piping 1.

Then, the flow velocity of the fluid flowing through the pipe 1 is transmitted and received between the ultrasonic transmitters / receivers 2a and 2b and measured from the difference in propagation time, and the flow rate is calculated from the cross-sectional area of the pipe 1. At this time, the flow entering the pipe 1 is regulated in the same direction as that of the pipe 1 by the thin pipe 4a forming the rectifying body 4 to reduce the inclination of the streamline in the measuring section and suppress the generation of vortices. The fluctuation of the ultrasonic wave reception level due to the reflection and refraction of the ultrasonic wave at the boundary surface of the flow turbulence is reduced to prevent the deterioration of the measurement accuracy.

[0004]

However, in the conventional configuration, the rectifying body 4 and the ultrasonic wave propagation path are installed apart from each other, and the distance between the rectifying body 4 and the ultrasonic wave transceiver 2a side and the ultrasonic wave transceiver 2b side is large. Since there is a large difference between the flow velocity and the flow velocity, a difference in the development state of the flow passing through the rectifying body is generated, and the average flow velocity in the cross section orthogonal to the measurement flow channel and the measurement between the ultrasonic transmitters / receivers 2a and 2b obliquely intersecting the measurement flow channel It makes a difference in the average flow velocity in the cross section,
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 is intended to solve the above problems, and it is an object of the present invention to improve the measurement accuracy by reducing the change in the correction coefficient over the entire flow rate measurement range.

[0006]

In order to solve the above-mentioned problems, the present invention provides a measurement flow path through which a fluid to be measured flows and the measurement.
An introduction part and a derivation part provided on the upstream side and the downstream side of the flow path, at least a pair of ultrasonic transceivers provided so that the ultrasonic wave propagates across the measurement flow path, and the ultrasonic transmission.
Ultrasonic waves are transmitted and received between receivers and based on the transmitted and received signals.
Equipped with a flow rate calculation means for calculating the flow rate
Both Placing signal device in the center portion of the measurement flow path, the meter
The velocity distribution is maximized by making the velocity distribution asymmetric at the inlet side of the measurement flow path.
Non-pair that biases the value generation position to one side from the center of the measurement flow path
It is provided with a flow promoting means.

According to the above invention, in the laminar region where the velocity distribution has a convex shape, the maximum value of the velocity is biased to increase the portion where the velocity is slow and the correction coefficient is increased to increase the velocity.
In the turbulent flow region where the distribution is relatively flat, by measuring the flow velocity region that does not differ much from the maximum value of the flow velocity, the difference between the correction factor between the laminar flow region and the turbulent flow region is reduced as a correction factor that does not differ much from the conventional one. The change of the correction coefficient can be reduced over the entire measurement range, the error due to the correction coefficient can be prevented from expanding, and the measurement accuracy can be improved. 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.

[0008]

DETAILED DESCRIPTION OF THE INVENTION The present invention includes a measurement flow path which a fluid to be measured flows, the introduction portion and outlet portion provided on the upstream side and the downstream side of the measurement flow path, the measurement flow path ultrasonic across For transmitting and receiving ultrasonic waves between at least one pair of ultrasonic transceivers that are installed to propagate
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 unpaired on the inlet side of the measurement flow path.
The position where the maximum value of the flow velocity is generated from the center of the measurement flow path
It is provided with an asymmetrical flow promoting means that biases it to one side.
It

In the laminar flow region where the velocity distribution is convex, the correction coefficient is increased by biasing the maximum value of the velocity and increasing the portion where the velocity is slow, and the velocity distribution becomes relatively flat. In the turbulent flow region, the flow velocity region that is not much different from the maximum value of the flow velocity is measured to reduce the difference between the correction factors for the laminar flow region and the turbulent flow region as a correction factor that does not differ much from the conventional one, and The flow rate change characteristic is flattened 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.

Further, the asymmetrical flow promoting means of the present invention has an introduction part.
It is formed by eccentricizing the measurement flow path with respect to
It Further, the flow path shape can be simplified, the workability can be improved, and the cost can be reduced.

Further , the asymmetrical flow promoting means of the present invention includes a guide.
Configured by connecting the inlet part and the measurement channel via the bent part
It was done. Then, the centrifugal force at the bent portion causes the flow to be biased toward the outer peripheral side of the bent portion to make the velocity distribution asymmetric.
It is possible to flatten the flow rate change characteristic of the correction coefficient, and by bending and arranging the inlet and outlet inlets and outlets with respect to the measurement channel, the width can be reduced and the size can be reduced. You can improve your sex.

Further , the asymmetrical flow promoting means of the present invention is
It is composed of a stepped portion provided on the inlet side of the measurement channel.
Then, by adjusting the size of the step, the maximum flow velocity in the measurement channel
Since the upper limit of the flow rate that maintains the position deviation can be changed, it can be applied to the flattening of the flow rate change characteristics of the correction coefficient over a wide measurement range, and the adaptability to specifications with different measurement ranges can be improved. Productivity can be improved.

The asymmetrical flow promoting means of the present invention is
The shape of the one end and the other end on the inlet side of the measurement
The deformed shape portion is formed. Then, the maximum flow velocity of the measurement flow path can be changed by changing the shapes of the upper and lower ends.
The positional deviation can be increased, the flatness of the flow rate change characteristic of the correction coefficient can be promoted, and the measurement accuracy can be improved.

The asymmetrical flow promoting means of the present invention is
The stepped part provided on the inlet side of the measurement flow path and the inlet side of the measurement flow path
With a different shape part where the shape of one end and the other end is different
It is composed.

By adjusting the size of the step, the flow rate change characteristic of the correction coefficient can be flattened for specifications with different measurement ranges, and the maximum flow velocity of the measurement flow path can be obtained by the different shape portion.
The deviation of the position is enlarged to promote the flatness of the flow rate change characteristic of the correction coefficient, and the flatness of the correction coefficient is promoted over a wide measurement range to improve the measurement accuracy.

Further , the asymmetrical flow promoting means of the present invention includes
The bent portion that connects the inlet and the measurement flow path, and the outside of the bent portion.
Due to the stepped portion provided on the inlet side of the measurement flow path connected to the peripheral surface side
It is composed.

The interaction between the bent portion and the stepped portion promotes the asymmetry of the velocity distribution of the measurement flow path to promote the flattening of the correction coefficient over a wide measurement range, and adapts to the specifications of different measurement ranges. A highly compact and compact device can be realized.

Further , the asymmetrical flow promoting means of the present invention includes
The bent portion that connects the inlet and the measurement flow path, and the outside of the bent portion.
The stepped portion provided on the inlet side of the measurement flow path connected to the peripheral surface side,
The shape of the one end and the other end on the inlet side of the measurement
The deformed shape portion is formed.

Further, the interaction of the bent portion, the step portion and the irregular shape portion promotes the flattening of the correction coefficient over a wide measurement range and improves the flatness of the correction coefficient, so that the measurement accuracy can be improved and the size is small. Installation can be improved by making it compact.

Further , the asymmetrical flow promoting means of the present invention is
It is installed on the inlet side of the measurement channel to promote eccentricity of velocity distribution.
It is composed of rectifiers with different flow resistance.
Then, by making the flow resistance depending on the position of the measurement flow path arbitrarily different, the asymmetry of the velocity distribution can be optimized, and the flattening of the correction coefficient can be improved.

Further, the deformed portion of the present invention is provided with an inlet for the measurement flow path.
One end on the mouth side is stepped, and the other end has a curvature.
It has a smooth shape. And of the measurement flow path
The deviation of the maximum flow velocity position can be increased, and the flow stability can be improved by the shape having a curvature and smoothly changing, and the measurement accuracy can be stabilized.

Further, the deformed portion of the present invention is provided with an inlet for the measurement flow path.
It is constructed by shifting the positions of one end on the mouth side and the other end.
It is a thing. And deviation of the maximum flow velocity position of the measurement flow path
The possible further increase, thereby improving the flatness of the correction factor.

The introduction part and the derivation part of the present invention are coaxial.
Rui are arranged in parallel. Further, simplification of the flow path shape can be further promoted, and cost reduction and size reduction can be improved.

Further , the ultrasonic transmitter / receiver of the present invention is provided with a measuring flow.
It is arranged eccentrically from the center of the road. And
The eccentric position 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 turbulent flow region, and the change in the correction factor is flat. This region can be expanded to the low flow velocity side.

The ultrasonic transmitter / receiver is located at the center of the measurement flow path.
Is eccentrically arranged on the outer peripheral surface side of the bent portion.
It Further, since the bias of the flow toward the outer peripheral side of the bent portion due to the action of the centrifugal force at the bent portion can be promoted as the flow rate increases, the correction coefficient in the large flow area can be made small and the correction coefficient in the small flow area can be reduced. It is possible to reduce the difference between the two and improve the flatness of the correction coefficient over a wide measurement range.

Further , the ultrasonic transmitter / receiver is more
It is provided with a small ultrasonic wave emitting surface. And super sound
Even if the wave transceiver is arranged with some eccentricity, it is possible to effectively emit ultrasonic waves to the ultrasonic wave propagation path, prevent deterioration of ultrasonic wave transmission / reception sensitivity, and improve measurement accuracy by measurement with an increased S / N. Further, the degree of freedom of eccentricity can be increased, and the flatness of the correction coefficient can be improved by propagating the ultrasonic wave to the region of the representative portion of the measurement flow channel and performing measurement.

[0027]

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,
Reference numeral 5 denotes a measurement flow path surrounded by the flow path wall 6, and reference numerals 7 and 8 denote upstream and downstream ultrasonic transmitter / receivers 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 ultrasonic transmitters / receivers 7 and 8 for measuring the flow path 5.
These are the opening holes on the upstream side and the downstream side that are exposed to. 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 that 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 the measurement flow path 5
It is a lead-out portion which is provided on the downstream side of and serves as an outlet for the fluid to be measured.
Reference numeral 13 is an upstream bent portion that connects the measurement flow path 5 and the introduction portion 11, 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 is an asymmetric flow in which the velocity distribution S in the height H direction of the measurement flow path 5 is made asymmetric with respect to the height center and 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. It is a means of promotion. Here, the asymmetrical flow promoting means 15 includes a bent portion 13 on the upstream side, a step portion 16 provided in the height H direction on the inlet side of the measurement flow path 5, and a height H direction on the inlet side of the measurement flow path 5. The one end 17 and the other end 18 are formed of differently shaped portions 19 formed differently. Further, the step portion 16 is provided on the outer peripheral surface 13a side of the bent portion 13 on the upstream side. Further, the irregular shape portion 19 has one end 17 in the height H direction on the inlet side of the measurement flow path 5 which has a stepped shape with no corner R at the tip, and the other end 18
Has a smooth shape with a curvature and a smoothly changing cross section in the height direction.

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 lattice-shaped 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. The flow stabilizing means 20 holds the velocity distribution asymmetrical by the asymmetrical flow promoting means 15 and adjusts the flow direction and velocity fluctuation to send the flow to the ultrasonic wave propagation path 10. 21
Is a flow rate calculation means including a measurement control unit 22 connected to the ultrasonic wave transmitters / receivers 7 and 8 for transmitting and receiving ultrasonic waves, and a calculation unit 23 for calculating a flow rate based on a signal from the measurement control unit 22 to calculate a flow rate. Is.

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 where the maximum flow velocity is generated is slightly deviated to one side (downward 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 becomes a turbulent flow region, as shown by a velocity distribution R in FIG. 3 (a longitudinal sectional view of the ultrasonic flow rate measuring device showing the velocity distribution in the turbulent flow region), The velocity change is small and the plateau is relatively flat, but the position U where the maximum flow velocity is generated is biased to one side (downward in the drawing) from the vicinity of the center of the height. The asymmetrical velocity distribution generated by the asymmetrical flow promoting means 15 has its flow direction regulated by the flow stabilizing means 20 and its velocity fluctuation is stabilized to maintain its velocity distribution shape until it reaches the ultrasonic wave propagation path 10. Is.

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 wave transmitters / receivers 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) By subtracting the reciprocal of T2 from the reciprocal of T1, the sound velocity C is eliminated and V = (L / 2cosθ) ((1 / 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. Considering to measure the flow rate of air, angle θ = 45 degrees, distance L = 70 mm, sound velocity C = 340 m / s,
Assuming a flow velocity V = 8 m / s, T1 = 2.0 × 10 -4
Second, T2=2.1.times.10@-4 second, and instantaneous measurement is possible.

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 the 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.

Therefore, 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 channel 5,
The flow rate Q is Q = KVS, where K is a correction coefficient considering the velocity distribution in the cross-sectional area S.

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

In particular, in the case where the asymmetrical flow promoting means 15 is not provided, the maximum flow velocity portion having a parabolic convex shape is located in the central portion of the ultrasonic wave propagation path 10 in the height direction in the laminar flow region. Is considerably smaller than that in the turbulent region.
Therefore, as shown in FIG. 4 (characteristic diagram of the correction coefficient when there is no asymmetrical flow promoting means), the correction coefficient greatly changes in the transition region where the laminar flow region changes to the turbulent flow region, and the measurement flow rate is corrected by the error ΔQm. The error is magnified because the coefficient greatly changes from ΔK1. 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 the flow rate change characteristics of the correction coefficient when the asymmetrical flow promoting means 15 is installed on the inlet side of the measurement flow path 5, centering on the velocity distribution in the height direction of the measurement flow path 5. In the laminar flow area where the velocity distribution in the height direction is convex by biasing it toward one side, the maximum correction value of the velocity is biased and the slow velocity is increased to increase the correction coefficient. In the turbulent flow region where the velocity distribution in the direction is relatively flat, by measuring the flow velocity region that is not much different from the maximum value of the flow velocity, the difference between the correction factor between the laminar flow region and the turbulent flow region is reduced as a correction factor that does not differ much from the conventional one. Therefore, the difference from the correction coefficient in the originally turbulent flow area where the flow velocity is high can be made small, and the change in the correction coefficient is small even in the transition region where the laminar flow changes to the turbulent flow, and the correction coefficient is flattened. Therefore, the measured flow rate has an error ΔQ.
Even if m is generated, the change in the correction coefficient can be made sufficiently small as ΔK2 (K2 <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, 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 to increase the correction factor by increasing the portion where the flow velocity is slow,
In the turbulent flow region where the velocity distribution in the height direction is relatively flat, by measuring the flow velocity region that is not much different from the maximum value of the flow velocity, the difference between the correction factors of the laminar flow region and the turbulent flow region is the same as before. Therefore, it is possible to reduce the change in the correction coefficient over the entire flow rate measurement range, prevent the error from increasing due to 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.

Further, the asymmetrical flow promoting means 15 has the introduction part 1
1 and the measurement flow channel 5 are formed by connecting the measurement flow channel 5 via the bent portion 13 that bends in the height direction of the measurement flow channel 5,
By the action of the centrifugal force in the bent portion 13, the flow is biased to the flow passage wall 6a of the measurement flow passage 5 on the outer peripheral surface 13a side of the bent portion 13 to make the velocity distribution in the height direction asymmetric. The flow rate change characteristics of the correction coefficient can be flattened, and the inlet and outlet inlets and outlets can be bent and arranged with respect to the measurement channel to reduce the width and reduce the size. You can improve your sex.

Further, the asymmetrical flow promoting means 15 is formed by the step portion 16 provided in the height direction on the inlet side of the measurement flow path 5, so that the step causes a contraction in the flow and biases the velocity distribution. By adjusting the size of the step, it is possible to change the upper limit value of the flow rate that maintains the bias of the maximum flow velocity position in the height direction of the measurement flow channel 15 in the turbulent flow region shown in FIG.
By increasing the step, the upper limit of the flow rate at which the flow coefficient can be flattened can be increased, and the step size can be set according to the required specifications of the measurement range. Therefore, it is possible to adapt to the flattening of the flow rate change characteristic of the correction coefficient over a wide measurement range, and it is possible to improve the adaptability to the specifications with different measurement ranges and improve the productivity.

The asymmetrical flow promoting means 15 includes one end 17 in the height direction on the inlet side of the measurement flow path 5 and the other end 1 in the height direction.
By using the differently shaped portions 19 formed by making the shapes of 8 different, it is possible to largely deviate the maximum flow velocity position in the height direction of the measurement flow path 5 by largely changing the shapes of the upper and lower end portions in the figure. Therefore, the flatness of the flow rate change characteristic of the correction coefficient can be promoted to improve the measurement accuracy.

The asymmetrical flow promoting means 15 includes a step portion 16 provided in the height direction on the inlet side of the measurement flow path 5, one end 17 in the height direction on the inlet side of the measurement flow path 5, and the other. By forming the end portion 18 of the different shape with the different shape portion 19, the flow rate change characteristic of the correction coefficient can be flattened for the specifications with different measurement ranges by adjusting the size of the step, and the different shape portion can be formed. The deviation of the maximum flow velocity position in the height direction of the measurement flow path 5 is expanded by 19 to promote the flatness of the flow rate change characteristic of the correction coefficient, and to promote the flatness of the correction coefficient over a wide measurement range. The measurement accuracy can be improved.

FIG. 6 is a vertical cross-sectional partial view of an ultrasonic flow rate measuring device according to another embodiment, in which the introduction portion 11 and the measurement flow path 5 are arranged in parallel or coaxially, and the height of the measurement flow path 5 on the inlet side is set. The stepped portions 16 are provided at both ends in the direction, and the one-sided end portion 17 and the other-sided end portion 18 are formed to have different shapes.
Since the asymmetrical flow promoting means 15 is formed in this way, the introduction part 11 which is the inlet of the fluid to be measured and the measurement flow path 5 can be connected in a short manner to form a compact flow path structure.

The asymmetrical flow promoting means 15 is connected to the bent portion 13 that bends in the height direction of the measurement flow passage that connects the introduction portion 11 and the measurement flow passage 5, and the measurement continuous to the outer peripheral surface 13a side of the bent portion 13. It is formed by the step portion 16 provided on the inlet side of the flow path 5. The velocity distribution in the height direction of the measurement channel is promoted to be asymmetrical due to the interaction between the bent part and the stepped part, and the asymmetrical shape can be maintained even in the large flow rate region where turbulent flow is advancing. It is possible to promote the flattening of the coefficient and realize a compact and compact device that is highly adaptable to specifications with different measurement ranges.

The asymmetrical flow promoting means 15 is connected to the bent portion 13 that bends in the height direction of the measurement flow path that connects the introduction portion 11 and the measurement flow path 5, and the measurement that is continuous to the outer peripheral surface 13a side of the bent portion 13. Formed by a step portion 16 provided on the inlet side of the flow channel 5, and a different-shaped portion 19 formed by making one end 17 and the other end 18 in the height direction on the inlet side of the measurement flow channel 5 different from each other. It was done. The interaction between the bent portion 13, the step portion 16, and the irregular shape portion 19 promotes the maintenance and expansion of the asymmetric shape in the large flow rate region and the expansion of the deviation of the maximum flow velocity position, and the correction coefficient for a wide measurement range. The measurement accuracy can be improved by promoting the flattening and the flatness of the correction coefficient, and the installability can be improved by downsizing.

Further, in the irregularly shaped portion 19, one end portion 17 in the height direction on the inlet side of the measurement flow path 5 is a stepped step portion 16 and the other end portion 18 has a smooth shape having a curvature. Is. Further, due to the difference in the shape of the end portion on the inlet side of the measurement flow path 5, a symmetrical velocity distribution is not formed, and a contraction flow is generated by a stepped step, thereby increasing the deviation of the maximum flow velocity position in the measurement flow path height direction. In addition, it is possible to improve the stability of the flow and stabilize the measurement accuracy by forming the other end into a shape having a curvature and smoothly changing.

FIG. 7 is a vertical cross-sectional partial view of an ultrasonic flow rate measuring device according to another embodiment, and the irregular shape portion 19 is the measuring flow path 5.
One end 17 and the other end 18 in the height direction on the inlet side of the
Is formed by shifting the position in the flow direction of ΔX.
And since the position of the inflow end portion in the height direction of the measurement flow path is different, the deviation of the maximum flow velocity position in the height direction can be further increased,
The flatness of the correction coefficient can be improved by increasing the correction coefficient when the flow rate is low in the laminar flow area and decreasing the correction coefficient when the flow rate is high in the turbulent flow area. Although one end 17 is stepped and the other end 18 is provided with a curvature here, both ends 17 and 18 may be stepped, and either end 17 may be stepped. It goes without saying that both 17 and 18 may have a curvature.

FIG. 8 is a vertical sectional partial view of an ultrasonic flow rate measuring device according to another embodiment, in which 24 is a rectifying body provided on the inlet side of the measuring flow path 15, and this rectifying body 24 is the measuring flow path 5. The asymmetrical flow promoting means 15 is provided with a lattice-like direction regulating part 24a having a different length in the flow direction and a fluctuation suppressing part 24b formed of a mesh body such as a mesh to reduce flow velocity fluctuations. Is formed. As described above, the flow resistance in the height direction of the measurement flow path 5 is changed by changing the length of the direction restricting portion 24a in the flow direction with respect to the height direction of the measurement flow path 15. By arbitrarily varying the flow resistance depending on the position of the path 5 in the height direction, the asymmetry of the velocity distribution in the height direction can be optimized, and the flattening of the correction coefficient can be improved. Although the asymmetrical flow promoting means 15 is formed only by the rectifying body 24 having different flow resistances in the height direction, the rectifying body 24 and the above-described bent portion 13, step portion 16 or differently shaped portion 19 are shown. It goes without saying that the combination can further promote the asymmetry in the height direction and the flattening of the correction coefficient. The flow resistance may be changed by changing the size of the lattice instead of the length of the direction regulating portion 24a, and the fineness of the opening of the fluctuation suppressing portion 24b may be changed in the height direction of the measurement flow path 5. It goes without saying that the flow resistance may be different depending on.

In the above description, the cross section of the flow path of the measurement flow path 5 has been described as a rectangular shape having a width W and a height H. However, a substantially rectangular shape having a slight R at the corner portion of the rectangular shape, a trapezoidal shape, a circular shape, or a rectangular shape. It goes without saying that the cross-sectional shape may be an ellipse or the like. In addition, although the bent portion is an example of bending in the height direction of the measurement flow path and at a right angle, it is not always necessary to bend at a right angle, and it is sufficient if the angle is such that centrifugal force acts on the fluid due to the bend. Needless to say, may have an inclination in the width direction of the measurement channel.

(Embodiment 2) FIG. 9 is a sectional view of an ultrasonic flow rate measuring apparatus showing Embodiment 2 of the present invention. 9, the same members and functions as those of the embodiment of FIGS. 1 to 8 are designated by the same reference numerals, and detailed description thereof will be omitted.
The different points will be mainly explained.

Introducing section 11 and deriving section 12 arranged coaxially
The measurement flow path axis 26, which is the central axis of the measurement flow path 5, is arranged eccentrically in the height direction with respect to the connection axis 25 that is the central axis of the measurement flow path 5, and the one end 17 on the inlet side of the measurement flow path 5 is provided. An eccentric wall 27 is formed on the inner wall to form the asymmetrical flow promoting means 15. The eccentric wall 27 is provided with a curvature that changes smoothly in the height direction of the measurement flow path 5. The introduction unit 11 and the derivation unit 1
Although the connecting shaft 25, which is the central axis of the second shaft, is arranged on the same axis, the eccentric portion 27 may be arranged not on the same shaft but in parallel.
Needless to say, it is also possible to provide eccentric walls (not shown) of different sizes not only on the one end 17 on the inlet side of the measurement flow path 5 but also on the other end. Needless to say.

Next, the operation of this ultrasonic flow rate measuring device will be described. A part of the fluid to be measured that has flowed in from the introduction part 11 collides with the eccentric wall 27 formed on the inlet side of the measurement flow path 5 and flows into the measurement flow path 5, and the height of the measurement flow path 5 on the inlet side. On the other side of the direction, the fluid to be measured that has flowed in from the introduction part 11 flows in without colliding with the wall surface, and the flow distribution in the height direction in the measurement flow path 5 is asymmetric with respect to the measurement flow path axis 26 that is the central axis. Becomes

For this reason, in the laminar flow region, the maximum value of the flow velocity is biased to increase the portion where the flow velocity is slow and the correction coefficient is increased to make the velocity distribution in the height direction relatively flat. By measuring the flow velocity region that is not much different from the maximum value of the flow velocity, the difference between the correction factors of the laminar flow region and the turbulent flow region can be reduced as a correction factor that does not differ much from the conventional value, and the flow rate change characteristics of the flow rate correction factor can be flattened. The asymmetrical flow promoting means can simplify the flow path shape by arranging the measurement flow path eccentrically with respect to the introduction part, and the measurement flow path 5 and the introduction part 11 can be arranged close to each other to achieve a compact structure. The road shape can be simplified and the size can be reduced to improve the workability and reduce the cost.

Further, by disposing the introducing part and the extracting part coaxially or in parallel, it is possible to further facilitate the simplification of the flow path shape, and to arrange the introducing part 11 and the extracting part 12 close to each other, thereby reducing the cost and the size. Can be improved.

FIG. 10 is a longitudinal sectional view of an ultrasonic flow rate measuring device according to another embodiment, in which the connecting shaft 2 which is the central axis of the introducing portion 11 is shown.
5, the measurement flow path axis 26, which is the central axis of the measurement flow path 5, is arranged eccentrically, and one end 17 on the inlet side of the measurement flow path 5 is provided.
The eccentric wall 28 is formed in the asymmetrical flow promoting means 15, and the eccentric wall 28 is provided with a step-like step in the height direction of the measurement flow path 5. The center axis of the lead-out portion 12 is coaxial with the measurement channel axis 26 which is the center axis of the measurement channel 5. Here, the eccentric wall 28 having a step-like step
As a result, the flow that flows into the measurement flow path 5 is promoted to be asymmetric with respect to the center of the measurement flow path 5 in the height direction, and the flatness of the correction coefficient can be improved. Since they are coaxial, the flow path shape can be simplified and the size can be improved.

(Embodiment 3) FIG. 11 is a sectional view of an ultrasonic flow rate measuring apparatus showing Embodiment 3 of the present invention. 11, the same members and functions as those of the embodiment of FIGS. 1 to 10 are designated by the same reference numerals, detailed description thereof will be omitted, and different points will be mainly described.

Reference numeral 28 denotes a transmission / reception axis which is the central axis of the ultrasonic wave transmitters / receivers 7 and 8, and the transmission / reception axis 28 is deviated from the measurement channel axis 26, which is the central axis of the measurement channel 5, by ΔY in the lower part of the drawing. It is arranged with the core. Here, the ultrasonic transceiver 7,
Reference numeral 8 indicates the direction of eccentricity of the transmission / reception shaft 28, as shown by the velocity distribution R, in the direction below the drawing in which the maximum flow velocity generation position U is present. The generation position U of the maximum flow velocity exists in the downward direction of the drawing because the bent portion 13 on the inlet side of the measurement flow path 5 is present.
This is because the flow is biased toward the outer peripheral surface 13a side by the centrifugal force action due to the stepped portion 16 provided on the outer peripheral surface 13a side and the irregular shaped portion 19 in which the outer peripheral surface 13a side is stepped. At the same time, the flow deviation is maintained even when the flow rate is large.

FIG. 12 is a sectional view showing the height relationship between the ultrasonic transmitter / receiver 7 and the mounting portion of the measurement flow path 5. In FIG. 12, 29 is a case for hermetically housing the piezoelectric body 30 provided therein, 31 is an acoustic matching layer fixed to the outer wall surface of the case 29, 32 is a sealing body joined to the case 29, and 33 is a seal. Terminals provided on the stopper 32, 34 are lead wires connecting the piezoelectric body 30 and the terminals 33, 35 are holding the supporting portion 36 so as to be sandwiched, and are vibration-tight to the passage wall 6 The body 37 is a fixed body that holds the vibration transmission restraining body 35 so as not to fall off the flow path wall 6. Here, the ultrasonic wave transmitter / receiver 7 is arranged eccentrically with respect to the height direction of the measurement flow path 5, and the ultrasonic wave emission surface 38 of the acoustic matching layer 31 that emits ultrasonic waves into the fluid to be measured is It is smaller than the height dimension H of the measurement flow path 5. Since the same applies to the ultrasonic transmitter / receiver 8 on the downstream side, the description thereof will be omitted.

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 such that the maximum value exists in the velocity distribution in the height direction, and thus the position of the maximum velocity value in the laminar flow region or transition region where the 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 connected to the measurement channel 5.
By eccentrically arranging from the center in the height direction to the outer peripheral surface 13a side of the bending portion 13, the centrifugal force in the bending portion 13 causes the flow to be biased toward the outer peripheral surface 13a side by the centrifugal force. Is increased, the proportion of the region having a large flow velocity in the ultrasonic wave propagation path 10 decentered in the height direction can be increased to reduce the correction coefficient in the large flow amount region, and the correction coefficient can be increased at a larger flow amount value. The number can be reduced and the flatness of the correction coefficient can be improved over a wider measurement range. Further, the ultrasonic wave transmitters / receivers 7, 8 are provided with an ultrasonic wave emitting surface 38 smaller than the height dimension H of the measurement flow path 5, and the ultrasonic wave transmitter / receivers 7, 8 are
Since the ultrasonic wave emitting surface 38 can be installed in the measurement flow path 5 so as not to be hidden by the flow path wall 6 even if 8 is slightly eccentric, the ultrasonic wave can be effectively emitted to the ultrasonic wave propagation path 10, and the ultrasonic wave It is possible to improve the measurement accuracy by transmitting and receiving ultrasonic waves having an improved S / N by preventing the transmission / reception sensitivity from decreasing. Further, since the eccentricity region where the transmission / reception sensitivity of the ultrasonic wave transmitters / receivers 7 and 8 does not decrease can be expanded and the degree of freedom of the eccentricity can be increased, the ultrasonic wave is propagated to the region of the representative portion in the height direction of the measurement flow path. It is possible to improve the flatness of the correction coefficient.

As described above, the ultrasonic transmitter / receiver is arranged so as to be eccentric from the center of the measurement flow path in the height direction. Then, the eccentric position in the height direction of the ultrasonic transceiver can be optimally eccentrically set so that the value of the correction coefficient in the low flow velocity region flowing in the laminar flow state becomes a value close to the value of the turbulent flow region, A region where the change in the correction coefficient is flat can be expanded to the low flow velocity side.

The eccentric direction of the ultrasonic transmitter / receiver is the direction in which the maximum value exists in the velocity distribution in the height direction. Then, since a sharper flow velocity change can be obtained between the height position indicating the maximum flow velocity value and the wall surface of the measurement flow path, the correction coefficient can be easily adjusted by the change in the height position of the ultrasonic transceiver, A region where the change of the correction coefficient is flat can be further expanded to the low flow rate side. Further, since the large flow rate side, which is a turbulent flow, measures a large flow velocity, the value of the correction coefficient can be reduced, and the difference between the correction coefficient values on the large flow rate side and the low flow rate side can be reduced to improve the flatness. The change in the correction coefficient can be flattened over a wide flow rate range.

The ultrasonic transmitter / receiver is arranged so as to be eccentric from the center of the measurement channel in the height direction to the outer peripheral surface side of the bent portion. Further, since the bias of the flow toward the outer peripheral side of the bent portion due to the action of the centrifugal force at the bent portion can be promoted as the flow rate increases, the correction coefficient in the large flow area can be made small and the correction coefficient in the small flow area can be reduced. It is possible to reduce the difference between the two and improve the flatness of the correction coefficient over a wide measurement range.

Further, the ultrasonic transmitter / receiver is provided with an ultrasonic wave emitting surface smaller than the height dimension of the measurement flow path. Even if the ultrasonic transmitter / receiver is arranged with some eccentricity in the height direction of the measurement flow path, the ultrasonic wave can be effectively emitted to the ultrasonic wave propagation path, and the deterioration of the ultrasonic wave transmission / reception sensitivity can be prevented and the S / N ratio can be improved. The measurement accuracy can be improved by the increased measurement. Further, the degree of freedom of eccentricity can be increased, and the flatness of the correction coefficient can be improved by propagating the ultrasonic wave to the region of the representative portion in the height direction of the measurement flow path and performing the measurement.

[0067]

As is apparent from the above description, according to the ultrasonic flow rate measuring device of the present invention, the following effects can be obtained.

A measurement flow path through which the 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 at least an ultrasonic wave which propagates across the measurement flow path. and a flow rate calculation means for calculating a pair of ultrasonic transducers, the flow rate on the basis of the transmission and reception signals to send and receive ultrasonic waves between the ultrasonic transducers, ultrasonic transmitting and receiving
Place the receiver in the center of the measurement flow path and
The velocity distribution is maximized by making the velocity distribution asymmetric at the inlet side of the measurement flow path.
Non-pair that biases the value generation position to one side from the center of the measurement flow path
Since there is provided a universal flow promoting means, in the laminar flow region the velocity distribution becomes convex to increase the correction coefficient by measuring by many places slow flow rate to bias the maximum flow rate, fast
In the turbulent flow region where the degree distribution is relatively flat, by measuring the flow velocity region that does not differ much from the maximum value of the flow velocity, the difference between the correction factor between the laminar flow region and the turbulent flow region is reduced as a correction factor that does not differ much from the conventional one. There is an effect that 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. Even if the physical property value of the fluid changes, the measurement accuracy is maintained and the practicality and convenience are improved. The effect is that you can.

[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 partial vertical cross-sectional view of an ultrasonic flow rate measuring device showing another embodiment.

FIG. 7 is a partial vertical cross-sectional view of an ultrasonic flow rate measuring device showing another embodiment.

FIG. 8 is a partial vertical cross-sectional view of an ultrasonic flow rate measuring device showing another embodiment.

FIG. 9 is a vertical sectional view of an ultrasonic flow rate measuring device according to a second embodiment of the present invention.

FIG. 10 is a vertical cross-sectional view of an ultrasonic flow rate measuring device showing another embodiment.

FIG. 11 is a vertical sectional view of an ultrasonic flow rate measuring apparatus according to a third embodiment of the present invention.

FIG. 12 is a vertical sectional view of an ultrasonic transmitter / receiver unit according to a third embodiment.

FIG. 13 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 step 19 Deformed portion 21 Flow rate calculation means 38 Ultrasonic wave emitting surface

Claims (15)

(57) [Claims] 1. A measurement flow path through which a fluid to be measured flows, an introduction part and a derivation part provided on the upstream side and the downstream side of the measurement flow path, and an ultrasonic wave which propagates across the measurement flow path. at least a pair of ultrasonic transducers have the a flow rate calculating means for calculating a flow rate based on the transmission and reception signals to send and receive ultrasonic waves between the ultrasonic transducers, feed ultrasonic
The receiver is arranged in the central part of the measurement channel, and
The velocity distribution is asymmetrical at the inlet side of the measurement flow path,
Do not bias the generation position of large values from the center of the measurement channel to one side
An ultrasonic flow rate measuring device provided with a symmetrical flow promoting means . 2. The ultrasonic flowmeter-side device according to claim 1, wherein the asymmetrical flow promoting means is formed by arranging the measurement flow path eccentrically with respect to the introduction portion. 3. The asymmetrical flow promoting means is constituted by connecting the introduction part and the measurement flow path through a bent part.
The ultrasonic flow rate measuring device described. 4. The ultrasonic flow rate measuring device according to claim 1 , wherein the asymmetrical flow promoting means comprises a stepped portion provided on the inlet side of the measurement flow path. 5. The asymmetrical flow promoting means has a different shape in which one end and the other end on the inlet side of the measurement flow path have different shapes.
The ultrasonic flow rate measurement device according to claim 1, wherein the ultrasonic flow rate measurement device is configured by a unit. 6. The asymmetrical flow promoting means includes a step portion provided on the inlet side of the measurement flow passage, and one end portion on the inlet side of the measurement flow passage.
Claim consisting of differently shaped parts with different shapes at the other end
Item 2. The ultrasonic flow rate measuring device according to Item 1 . 7. The asymmetrical flow promoting means is constituted by a bent portion connecting the introduction portion and the measurement flow passage, and a step portion provided on the inlet side of the measurement flow passage connected to the outer peripheral surface side of the bent portion. 1. The ultrasonic flow rate measuring device according to 1. 8. The asymmetrical flow promoting means includes a bent portion connecting the introduction portion and the measurement flow passage, a step portion provided on the inlet side of the measurement flow passage connected to the outer peripheral surface side of the bent portion, and the measurement flow passage. Different shape with one end on the inlet side and the other end being different
The ultrasonic flow rate measurement device according to claim 1, wherein the ultrasonic flow rate measurement device is configured by: 9. The asymmetrical flow promoting means is provided on the inlet side of the measurement flow passage and has a flow resistance for promoting eccentricity of the velocity distribution.
The ultrasonic flow rate measuring device according to claim 1 , wherein the rectifying bodies are different from each other . 10. The deformed portion is one of the inlet side of the measurement flow path.
The end of the is stepped and the other end is smooth with curvature
The shape according to any one of claims 5, 6 and 8
Acoustic wave flow rate measuring device. 11. The deformed portion is one of the inlet side of the measurement flow path.
The ultrasonic flow rate measuring device according to any one of claims 5, 6, 8, and 10, wherein the positions of the end and the other end are offset from each other. 12. The ultrasonic flow rate measuring device according to claim 2, wherein the introducing part and the extracting part are arranged coaxially or in parallel. 13. The ultrasonic transmitter / receiver is at the center of the measurement flow path.
Any one of claims 1 arranged by Luo eccentric 12 of item 1
The ultrasonic flow rate measuring device described in. 14. The ultrasonic transmitter / receiver is at the center of the measurement channel.
The outer peripheral surface of the bent portion is eccentrically arranged.
7. The ultrasonic flow rate measuring device according to any one of 7 and 8. 15. The ultrasonic transmitter / receiver is smaller than the measurement flow path.
The ultrasonic flow rate measuring device according to claim 1, further comprising a supersonic wave emitting surface .