JPH10274551A - Ultrasonic flow meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To diffuse ultrasonic wave coming in contact with the pipe wall surface, by a protruding face so as to reduce a flow rate measuring error by forming sectional shape orthogonal to the axis of a passage in the pipe wall surface forming a linear passage, of a face with a protruding face. SOLUTION: A fluid flowing in from an inflow port 5 flows into a buffer chamber 3 and is stabilized in flow, and then flows into a linear passage 8 from a horn-shaped opening part 8a on the inlet side of the linear passage 8. At the time of flowing in, the fluid is guided by the outer surface of a conical cover 11 and the horn-shaped inner peripheral surface 8c of the opening part 8a so as to flow into the linear passage without flow becoming turbulent. At the time of flowing into an outlet side buffer chamber 4 from an outflow port 8b, the fluid is guided by the outer surface of a conical cover 12 and the horn- shaped inner peripheral surface 8d of an opening part 8b so as to flow out without flow becoming turbulent. The fluid flowing into the buffer chamber 4 is fed to a specified feed part from an outflow port 6. An echo sounder transducer 9, 10 measure propagation time in a forward direction and a reverse direction to the flow of the fluid and computes the flow rate from the difference of arrival time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an ultrasonic flowmeter.

[0002]

2. Description of the Related Art Conventionally, the propagation time of ultrasonic waves in the forward and reverse directions with respect to the flow of a fluid is measured, and the flow rate is calculated from the propagation time to determine the flow rate, and further, the integrated flow rate is determined. Sonic flow meters are well known.

In such an ultrasonic flowmeter, conventionally,
As shown in FIGS. 11 and 12, a straight flow path 101 is provided in the main body 100, and the fluid to be measured flowing from the inflow port 102 flows through the flow path 101 through the buffer chamber 103, and flows through the other buffer chamber 104. Outlet 105
Some of the flow paths 101 have ultrasonic transducers 106 and 107 disposed relative to each other on the inlet side and the outlet side.

[0004] The cross-sectional shape of the tube wall 108 forming the flow path 101 is formed in a perfect circular cross-sectional shape as shown in FIG. The mounting surfaces 109 and 110 are formed as surfaces orthogonal to the axis of the straight flow path 101.

[0005]

By the way, the measuring principle of the ultrasonic flowmeter as described above is based on the two transducers 106,
In step 107, the flow rate is calculated from the arrival time difference corresponding to the flow rate of the ultrasonic wave transmitted and received. Therefore, the ultrasonic wave that linearly arrives between the transducers is measured as a true acoustic wave, but the acoustic wave transmitted from the transducer is, as shown in FIG. There is an ultrasonic wave B reflected on the tube wall forming the straight flow path 101.

[0006] Such a reflected ultrasonic wave B hits the tube wall 108 and reflects in the same direction as the incident direction in the case where the straight flow path 101 is formed in the same perfect circular cross section over the entire length as in the conventional case. However, there is a case where a large measurement error occurs due to being received by interfering with the ultrasonic wave A traveling straight.

That is, it is considered that a reflected wave arrives with a delay corresponding to its reflection path with respect to an ultrasonic wave that arrives linearly, and becomes large when the phases of the plurality of ultrasonic waves match, and becomes a large wave. If the wavelength shifts, they will cancel each other.

As a result of experimentally measuring the effect of the reflected wave, a reception waveform as shown by a solid line C in FIG. 14 is shown. Compared with the reception waveform D (broken line) in the open space, the interference amplification component E due to the reflected wave is smaller. Appeared.

In such a state, the degree of interference fluctuates in a complicated manner due to a change in flow velocity from a state in which there is no flow of fluid, making accurate reception difficult and causing a large error.
Further, as in the above-described conventional case, when the surfaces 109 and 110 facing the entrance and exit of the straight flow passage 101 are formed on a surface orthogonal to the axis of the straight flow passage 101, the central portion of the flow passage is used. , And ultrasonic waves other than the ultrasonic waves received by one of the transducers are reflected by the other transducer. Therefore, the ultrasonic wave transmitted from one of the transducers may be reciprocated one and a half times and received by the other transducer. Therefore, measurement cannot be performed continuously or at arbitrary intervals, and the number of measurements is reduced. As a result, there is a problem that the measurement resolution is deteriorated, the measurement accuracy is reduced, and the measurement error is increased.

Accordingly, an object of the present invention is to solve the above-mentioned problems and to provide an ultrasonic flowmeter capable of reducing a flow measurement error.

[0011]

Means for Solving the Problems In order to solve the above-mentioned problems, the invention according to claim 1 includes a pair of transducers provided on an inflow side and an outflow side of a straight flow path. The cross-sectional shape of the pipe wall surface forming the straight flow path in a direction orthogonal to the axis of the flow path is formed by a surface having a convex surface.

In the present invention, of the ultrasonic waves transmitted from one of the transducers, the ultrasonic waves that pass straight through the axis of the straight flow path are received by the other transducer. Further, the ultrasonic waves hitting the convex surface forming the flow path are diffused and do not collect sound again, so that the diffused ultrasonic waves are prevented from interfering with the linearly transmitted ultrasonic waves, and the flow rate measurement error is prevented. Is reduced.

According to a second aspect of the present invention, the convex surface is formed as a curved surface. Also in the present invention, the ultrasonic waves hitting the curved surface forming the straight flow path are diffused, and the same operation and effect as described above are achieved.

According to a third aspect of the present invention, a pair of transducers are provided on an inflow side and an outflow side of a straight flow path. A diffusing surface for diffusing an ultrasonic wave other than that received by the vessel outward.

In the present invention, of the ultrasonic waves transmitted from one of the transducers, the ultrasonic waves that pass straight through the axial center of the straight flow path are received by the other transducer, and The ultrasonic waves other than the ultrasonic waves that pass through the surface strike the surface for diffusion and are diffused outward. Therefore, it is possible to prevent the ultrasonic wave received from one of the transducers from being reciprocated one and a half times and received by the other transducer. Therefore, the transmission and reception of ultrasonic waves are performed continuously or at arbitrary intervals to increase the resolution and reduce the flow rate measurement error.

According to a fourth aspect of the present invention, in the third aspect of the present invention, the diffusing surface is provided with a transmitting / receiving hole in the center at the front side of the transmitter / receiver and an ultrasonic wave on the outer peripheral surface. It is formed by a cover provided with a surface that diffuses to the surface.

According to the present invention, the same operation as that of the third aspect of the invention is provided. In a fifth aspect of the present invention, a pair of transducers are provided on the inflow side and the outflow side of the straight flow path, and the axial center of the flow path on the pipe wall surface forming the straight flow path. The cross-sectional shape in the orthogonal direction is formed by a surface having a convex surface, and further, to the transducer section, for diffusing outwardly the ultrasonic waves other than received by the transducer by going straight through the straight flow path. A surface is provided.

In the present invention, the operation of the first aspect and the operation of the third aspect are exhibited.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described based on an embodiment shown in FIGS.

FIGS. 1 to 4 show an embodiment in which the present invention is applied to an ultrasonic flowmeter provided with a buffer chamber. In the main body 1 constituting the ultrasonic flow meter, an inlet buffer chamber 3 is formed on one side by the partition wall 2, and an outlet buffer chamber 4 is formed on the other side. Is formed in the outlet-side buffer chamber 4.

Further, a flow pipe 7 is provided in the main body 1 and penetrates through the partition wall 2 and opens to both buffer chambers 3 and 4. In the flow pipe 7, a straight flow path 8 is formed. Have been.
Inner peripheral surface 8 of both openings 8a, 8b in the straight channel 8
Each of c and 8d is formed in a trumpet shape expanding toward the outside, and has an open end surface on the inner surface of both side walls 1a and 1b of the main body 1 with a gap through which a fluid can flow therebetween. And are arranged in close proximity.

On one side wall 1a of the main body 1, one transducer 9 is located on the axis of the straight flow path 8 and is disposed so as to be directed to the straight flow path 8. On the other side wall 1b, Straight channel 8
The other transducer 10 is positioned on the axis of the straight line so as to face the straight flow path 8. Therefore, the two transducers 9,
As shown in the drawing, 10 is disposed on the same axis with the straight flow path 8 interposed therebetween. The two transducers 9 and 10 are:
As is well known, it has a vibrator, a reception wave detection unit, and the like, and is further driven to transmit and receive waves by a drive unit (not shown).

The wall surface of the pipe forming the straight flow path 8 is formed such that the cross section perpendicular to the axial direction has a convex surface. In this embodiment, it is formed in a shape as shown in FIG. That is, each surface of the virtual square is formed as a convex surface 8e which is expanded in an arc shape inward. The radius of the convex surface 8e is, for example, R10. Further, a corner 8f between adjacent portions of the four convex surfaces 8e.
Is formed with a concave surface having a small radius to facilitate the processing of the flow channel 8. However, the corner 8f may be a pointed concave portion as shown in FIG. In addition, the above-mentioned cross-sectional shape is the same as that of the opening 8
It is formed over the entire length of the straight channel extending between a and 8b.

Covers 11 and 12 are provided in front of the two transducers 9 and 10, respectively. The two covers 11, 1
2 are formed on the conical surfaces for diffusion 11a and 12a having the apex on the axis of the straight flow path 8, and the top thereof is provided so as to face the straight flow path 8 side. Of the ultrasonic waves transmitted from the other transducer, the transmitting and receiving holes 13 and 14 capable of receiving only the linearly arriving ultrasonic waves, that is, the ultrasonic waves passing through the axial center portion of the linear flow path 8 are formed through. Have been. Further, the inner surfaces of the covers 11, 12 are also formed as conical surfaces substantially along the conical surfaces of the outer surfaces. Further, the covers 11 and 12 are formed integrally with the cases 15 and 16 of the transducers 9 and 10, respectively.

In the above-described configuration, the fluid flowing from the inlet 5 enters the buffer chamber 3 on the inlet side to stabilize the flow of the fluid. Flows into the straight channel 8 from At the time of this inflow, the fluid flows into the straight flow passage 8 without being disturbed by being guided by the outer surface of the conical cover 11 and the flared inner peripheral surface 8c of the opening 8a.

The fluid flowing in the straight flow path 8 in a rectified state flows from the outlet 8 b of the straight flow path 8 to the outlet buffer chamber 4.
Spills into. At the time of the outflow, the fluid is guided by the outer surface of the conical cover 12 and the trumpet-shaped inner peripheral surface 8d of the opening 8b and flows out without being disturbed.

The fluid flowing into the outlet buffer chamber 4 flows out of the outlet 6 and is supplied to a predetermined supply unit. In a state where the fluid is flowing through the straight flow path 8 or in a state where the fluid is not flowing, the transmission and reception of the ultrasonic wave are repeated between the two transducers 9 and 10 in a well-known manner, so that the fluid flows in the forward direction with respect to the flow of the fluid. The propagation time is measured in the opposite direction to the propagation time, and the flow rate is calculated from the difference between the arrival times.

At the time of such flow rate measurement, of the ultrasonic waves transmitted from one of the transducers 9 or 10, the ultrasonic waves transmitted linearly in parallel with the axis at the axis of the straight flow path 8. The sound wave is directly received by the other transducer 10 or 9 through the transmission / reception hole 14 or 13.

Among the ultrasonic waves transmitted from one of the transducers 9 or 10, the ultrasonic wave that hits the convex surface 8e of the tube wall forming the straight flow path 8 bends and diffuses to the side and collects sound again. Never do.

Therefore, the received ultrasonic signal is only the above-mentioned linear ultrasonic wave, and there is no measurement error caused by interference of the delayed ultrasonic wave as in the conventional case. As a result of forming and projecting the convex surface 8e as in the embodiment of the present invention,
The reception waveform becomes as shown by the solid line F in FIG. 13, approximating the reception waveform D in the open space, and the above-described interference amplification component E as in the conventional case disappears.

Furthermore, if the lower limit flow rate of measurement is supposed to be 1 cm / s, the flow rate multiplied by the cross-sectional area becomes the lower limit flow rate of measurement. Micro flow rate measurement with a small cross-sectional area flow path became possible.

Further, conventionally, even in a flow path having a relatively large sectional area, which is considered to have a small influence of the reflected wave on the pipe wall surface of the straight flow path, the reflected wave interferes as the flow velocity increases. According to this, it was possible to measure up to a large flow velocity (flow rate).

In the above flow rate measurement,
Of the ultrasonic waves transmitted from one of the transducers 9 or 10, those other than those received by the other transducer 10 or 9 are diffusely reflected laterally on the tapered outer surface of the cover 11. . Therefore, it is possible to prevent the light from being reflected by the transducer unit and reaching the other transducer unit as in the related art. Therefore, it is possible to prevent the ultrasonic wave transmitted from one of the transducers from being reciprocated for one and a half times and received by the other transducer. This means that the transmission and reception of ultrasonic waves can be performed continuously or at arbitrary intervals, the measurement resolution can be improved according to the number of measurements, and the measurement accuracy can be improved.

FIG. 6 is a view in which a tube wall of a cross section in a direction orthogonal to the axial direction of the straight flow path 8 is formed as a convex surface 8e in which each surface of a virtual equilateral triangle is bulged inward in an arc shape. Also in the present straight flow path 8, the same function and effect as the straight flow path shown in FIG. 4 can be exerted by the convex surface 8e.

FIG. 7 is a view in which a pipe wall of a cross section in a direction orthogonal to the axial direction of the straight flow path 8 is formed as a convex surface 8e in which each surface of a virtual regular hexagon is expanded inward in an arc shape. Also in the present straight flow path 8, the same operation and effect as the above-mentioned straight flow path 8 can be exerted by the convex surface 8e.

FIG. 8 shows an alternative to the covers 11 and 12
The outer peripheral surfaces of the outer peripheral holding walls 11b of the transducers 9 and 10 are formed as diffusion conical surfaces 11a and 12a. The diffusing conical surfaces 11a and 12a exhibit the same operation and effect as described above.

FIG. 9 shows an embodiment in which the present invention is applied to an ultrasonic flowmeter having no buffer chamber. In this embodiment,
An inflow port 5 and an outflow port 6 are provided at both ends of a main body 20 constituting the ultrasonic flowmeter, and the above-mentioned straight flow path 8 is formed on a straight line connecting these axes. The cross-sectional shape of the straight flow path 8 in a direction orthogonal to the axial direction is formed to be the same as the shape shown in FIG. The cross-sectional shape of the straight flow path 8 may be a curved surface such as the shape shown in FIGS.

The two openings 8a and 8b of the straight flow path 8 are
It is formed by the same trumpet-shaped inner peripheral surfaces 8c and 8d as described above. Further, the transducers 9, 9 are provided in the openings 8 a, 8 b.
Reference numeral 10 is positioned on the axis of the straight flow path 8 and is arranged such that a flow passage is formed on the outer periphery thereof. Furthermore,
The two transducers 9 and 10 are fixedly installed on the main body 1 via plate-shaped fixing ribs 21 via cases 15 and 16.

Further, a conical cover 11 similar to the cover 11 shown in FIG. 3 is fixed to the front side of the two transducers 9, 10. In this embodiment, the inlet 5
Is supplied from the outlet 6 through the opening 8a, the straight flow path 8, and the opening 8b. In addition, ultrasonic waves are transmitted and received by the opposed transducers 9 and 10, and the flow rate is measured.

Also in this embodiment, the pipe wall 8 of the straight flow path 8
By forming the cover e and the covers 11 and 12 as described above, the same operation as that of the structure shown in FIGS. 1 to 7 is exerted, and the measurement error of the flow rate can be reduced.

FIG. 10 shows that the inlet 5 is provided on one side of the straight flow path 8, the outlet 6 is provided on the other side of the straight flow path 8, and a pair of transducers is provided at both ends of the straight flow path 8. An embodiment in which the present invention is applied to an ultrasonic flowmeter provided with 9 and 10 facing each other will be described.

In this embodiment, the pipe wall 8 of the straight flow path 8
"e" is formed in a sectional shape as shown in FIGS. 4 to 7, and the conical covers 11 and 12 as described above are provided at the front portions of the two transducers 9 and 10.

Also in this embodiment, the pipe wall 8 of the straight flow path 8
By forming the cover e and the covers 11 and 12 as described above, the same operation as that of the structure shown in FIGS. 1 to 7 is exerted, and the measurement error of the flow rate can be reduced.

The convex surface in each of the above embodiments is not limited to an arc surface, but may be a curved surface such as a non-arc surface.
Furthermore, the surfaces 11a and 12a for diffusion in each of the above embodiments.
Is not limited to a conical surface, but may be formed on a surface such as a shell-shaped surface that can diffuse ultrasonic waves outward.

[0045]

As described above, according to the first aspect of the present invention, it is possible to reduce the error in the flow rate measurement by diffusing the ultrasonic waves impinging on the pipe wall forming the straight flow path on the convex surface. As a result, a small flow rate can be measured by the small cross-sectional area flow path, and further, the influence of the reflected wave is eliminated, and it is possible to measure a large flow velocity (flow rate).

According to the second aspect of the invention, the ultrasonic waves impinging on the wall of the tube forming the straight flow path can be diffused on the arc-shaped convex surface, and the same effect as the first aspect of the invention can be obtained. According to the third aspect of the present invention, it is possible to prevent generation of ultrasonic waves received by being reciprocated one and a half times between the transmitter and the receiver, and to reduce the flow rate measurement error by performing transmission and reception continuously or at arbitrary intervals.

According to the fourth aspect of the invention, the same effect as that of the third aspect of the invention can be exerted by the conical cover. According to the fifth aspect of the invention, the effect of the first aspect of the invention and the effect of the third aspect of the invention can be combined to further reduce the flow rate measurement error.

[Brief description of the drawings]

FIG. 1 is a side sectional view in which the present invention is applied to an ultrasonic flowmeter having a buffer chamber.

FIG. 2 is a bottom view of FIG. 1;

FIG. 3 is an enlarged side sectional view of a main part of FIG. 1;

FIG. 4 is a sectional view taken along line XX in FIG. 3;

FIG. 5 is a sectional view showing another example of the straight flow path.

FIG. 6 is a sectional view showing another example of the straight flow path.

FIG. 7 is a sectional view showing another example of the straight flow path.

FIG. 8 is a side sectional view showing another example of the conical surface for diffusion.

9A and 9B show an example in which the present invention is applied to an ultrasonic flowmeter having no buffer chamber, wherein FIG. 9A is a side sectional view, and FIG. 9B is a sectional view taken along line YY of FIG. 9A.

FIG. 10 is a side sectional view in which the present invention is applied to an ultrasonic flowmeter provided with inlets and outlets opposite to both side surfaces of a straight channel.

FIG. 11 is a side sectional view showing a conventional structure.

FIG. 12 is a sectional view taken along line ZZ in FIG. 12;

FIG. 13 is a diagram showing a signal waveform and a signal waveform in an open space according to the present invention.

FIG. 14 is a diagram showing a signal waveform in a conventional structure and a signal waveform in an open space.

[Explanation of symbols]

8 ... Linear flow path 8e ... Convex surface 9,10 ... Transducer / receiver 11,12 ... Cover 11a, 12a ... Diffusion surface 13,14 ... Transmission / reception hole

Claims (5)

[Claims] 1. A cross section in a direction perpendicular to the axis of a flow path on a pipe wall forming a straight flow path, wherein a pair of transducers are provided on the inflow side and the outflow side of a straight flow path. An ultrasonic flowmeter, wherein the shape is formed by a surface having a convex surface. 2. The ultrasonic flowmeter according to claim 1, wherein the convex surface is formed as a curved surface. 3. A device in which a pair of transducers are provided on the inflow side and the outflow side of a straight flow path, except that the transducer is moved straight through the straight flow path and received by the transducer. An ultrasonic flowmeter provided with a surface for diffusing the ultrasonic waves outward. 4. A diffusion surface is formed by a cover provided with a wave transmitting / receiving hole in the center and a surface on the outer peripheral surface for diffusing ultrasonic waves outward, in front of the transducer. An ultrasonic flowmeter as described. 5. A cross section in a direction perpendicular to an axis of a flow path on a pipe wall forming a straight flow path, wherein a pair of transducers are provided on an inflow side and an outflow side of a straight flow path. The shape is formed by a surface having a convex surface, and further, the transducer unit is provided with a diffusing surface that diffuses ultrasonic waves other than received by the transducer by going straight through the straight flow path. An ultrasonic flowmeter characterized by the above.