JP4441076B2 - Ultrasonic vortex flowmeter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic vortex flow meter, and more particularly to an ultrasonic vortex flow meter that measures the flow rate of a fluid to be measured using an ultrasonic sensor.
[0002]
[Prior art]
In general, in a conventional ultrasonic vortex flowmeter, a vortex generator extending in a direction perpendicular to the flow direction is provided in a flow path in which a fluid to be measured flows, and one or two vortex generators are provided downstream of the vortex generator. A set of ultrasonic sensors is provided to detect Karman vortices generated downstream of the vortex generator. One set of ultrasonic sensors is provided in the flow path so as to face each other, one is a transmitting side that transmits ultrasonic waves, and the other is a receiving side that receives ultrasonic waves propagated in the fluid to be measured It becomes.
[0003]
In this type of ultrasonic vortex flowmeter, a phase comparison is made between the ultrasonic reception signal that has been propagated through the Karman vortex generated in the flow path and the ultrasonic transmission signal supplied to the transmission side. By doing so, the Doppler effect that the ultrasonic wave receives from the Karman vortex is detected as phase modulation.
[0004]
In addition, in an ultrasonic vortex flowmeter using two sets of ultrasonic sensors, by comparing the phases of two ultrasonic signals that propagate the fluid from the opposite directions relative to the Karman vortex flow, Only the phase change received from the Karman vortex is extracted by canceling the influence of the sound velocity change of the fluid to be measured.
[0005]
[Problems to be solved by the invention]
The conventional ultrasonic vortex flowmeter configured as described above is theoretically configured to extract the Doppler effect received by the ultrasonic wave from the Karman vortex as a phase change, so that it is independent of the type of fluid being measured. Vortices can be detected.
[0006]
However, in reality, in the path through which the ultrasonic wave is propagated, resonance may be generated by the ultrasonic wave propagating between the sensors or the ultrasonic wave reflected by the inner wall of the flow path. In that case, the signal received by the reception-side ultrasonic sensor is transmitted from the transmission-side ultrasonic sensor, propagates in the fluid and directly reaches the reception-side ultrasonic sensor, and from the transmission-side ultrasonic sensor. After being radiated, the reflected wave propagates in a complicated manner on the inner wall of the path and becomes a composite wave with the ultrasonic wave that reaches the reception-side ultrasonic sensor.
[0007]
For this reason, when resonance or the like occurs in the ultrasonic propagation path, even if a slight change in sound velocity of the fluid under measurement causes the resonance state to collapse, the received synthesized wave and the ultrasonic source signal When the phase comparison is performed, the modulation amount may be extremely larger or smaller than the phase modulation amount that should be received from the sound velocity change of the fluid to be measured and the flow velocity component of the Karman vortex.
[0008]
In such a state, accurate flow measurement could not be performed. As a countermeasure, by attaching a sound-absorbing member to the inner surface of the propagation path of the ultrasonic wave, the ultrasonic wave propagating while being reflected in a complicated manner is eliminated. Only the phase modulation that the ultrasonic wave receives from the Karman vortex is detected by increasing the ratio of the ultrasonic wave that has directly propagated through the fluid to be measured to the ultrasonic sensor.
[0009]
In this case, the propagation path of the ultrasonic wave that is the mounting portion of the sound absorbing member is often a narrow passage, and the sound absorbing member should not interfere with the flow generated by the Karman vortex. The method of pasting with is often used.
[0010]
However, since the place where the sound absorbing member is fixed is often a place where pressure pulsation or movement of the fluid to be measured occurs, the adhesive may peel off when used for a long time. In this case, the sound absorbing member peeled off from the inner wall of the flow path may interfere with the propagation of the ultrasonic wave to reduce the detection accuracy of the Karman vortex, and at the same time, the flow rate may not be measured.
[0011]
Accordingly, an object of the present invention is to provide an ultrasonic vortex flowmeter that solves the above-described problems.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, the present invention has the following features.
[0013]
The invention described in claim 1 includes a sandwiching member that contacts both ends of a cylindrical sound absorbing member inserted into an ultrasonic wave propagation path formed in the vortex generator and sandwiches the sound absorbing member from both ends. The sound absorbing member can be stably fixed to the inner wall of the ultrasonic wave propagation path.
[0014]
The invention according to claim 2 is characterized in that the sound absorbing member is sandwiched between the ultrasonic transmission side and the ultrasonic reception side, and is received by the ultrasonic wave and the ultrasonic sensor transmitted from the ultrasonic sensor. Ultrasonic resonance can be prevented.
[0015]
According to a third aspect of the present invention, the clamping member is formed in a ring shape, and the ultrasonic wave propagation path is formed with a concave part for attaching sound absorbing members provided at both ends of the ultrasonic wave propagation path, and the concave part. And an annular groove into which each of the ring-shaped sandwiching members is fitted, and the sound absorbing member is sandwiched by the sandwiching member in a state of being inserted into the concave portion of the ultrasonic wave propagation path. The sound absorbing member can be securely fixed.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0017]
FIG. 1 is a cross-sectional view of an embodiment of an ultrasonic vortex flow meter according to the present invention. FIG. 2 is a longitudinal sectional view of an embodiment of the ultrasonic vortex flowmeter according to the present invention.
[0018]
As shown in FIGS. 1 and 2, the ultrasonic vortex flowmeter 10 includes a flowmeter body 14 having a flow path 12 through which a gas (gas) as a fluid to be measured flows, and a flow path 12 of the flowmeter body 14. And a vortex generator 16 extending in a vertical direction perpendicular to the flow direction of the fluid to be measured (indicated by an arrow in FIG. 1). The vortex generator 16 has a substantially triangular cross section when viewed from above.
[0019]
Then, in the process in which the fluid to be measured flows downstream while colliding with the front surface 16 a of the vortex generator 16 facing the upstream side, Karman vortices are alternately generated on the left and right sides of the vortex generator 16. Since the cycle in which the Karman vortex is generated is proportional to the flow velocity of the fluid to be measured, the flow rate of the fluid to be measured can be obtained by detecting the Karman vortex generated in the fluid to be measured.
[0020]
The vortex generator 16 has a pair of passages 18 and 20 extending in the longitudinal direction penetrating as an ultrasonic wave propagation path. The passages 18 and 20 communicate with first to fourth pressure introduction passages 22, 24, 26, and 28 that open to oblique sides 16 b and 16 c formed on the downstream side of the vortex generator 16, respectively. The pressure introduction paths 22, 24, 26, and 28 are shifted in the longitudinal direction (height direction) of the vortex generator 16, and are provided so as not to cross each other.
[0021]
One end of the first pressure introduction path 22 opens to the hypotenuse 16 b and the other end communicates with the passage 18. Further, one end of the second pressure introduction path 24 opens to the hypotenuse 16 c and the other end communicates with the passage 20. The third pressure introduction path 26 has one end opened to the hypotenuse 16 b and the other end connected to the path 20. The fourth pressure introduction path 28 has one end opened to the hypotenuse 16 c and the other end connected to the passage 18.
[0022]
Accordingly, when a Karman vortex is generated in the fluid to be measured flowing downstream of the vortex generator 16, a pressure difference is generated on both the left and right sides of the vortex generator 16 due to a pressure change caused by the generation of the Karman vortex. , 20 generates a fluid flow to be measured. That is, in the passages 18 and 20, a reverse flow alternately occurs at the same cycle as the generation of the Karman vortex.
[0023]
A holding member 38 that holds the transmission ultrasonic sensors 30 and 32 is provided at the upper end of the vortex generator 16. Further, a holding member 40 that holds the receiving ultrasonic sensors 34 and 36 is provided at the lower end of the vortex generator 16. Each ultrasonic sensor 30, 32, 34, 36 is inserted into mounting holes 38 a, 38 b, 40 a, 40 b provided in the holding members 38, 40, and further sealed by a ring-shaped packing (or O-ring) 42. Is done.
[0024]
The material of the packing 42 includes a Teflon-based packing and a resin ring made of asbestos containing Teflon.
[0025]
The mounting holes 38a, 38b, 40a, 40b into which the ultrasonic sensors 30, 32, 34, 36 are inserted communicate with the upper and lower openings of the passages 18, 20, respectively. The ultrasonic waves transmitted from the transmission ultrasonic sensors 30 and 32 propagate through the fluid in the passages 18 and 20 and are received by the reception ultrasonic sensors 34 and 36. At that time, the ultrasonic wave propagating in the passages 18 and 20 is modulated by the flow velocity of the fluid to be measured flowing in the passages 18 and 20 due to the pressure difference between the left and right sides of the vortex generator 16 accompanying the generation of Karman vortex. Therefore, the detection signals output from the reception ultrasonic sensors 34 and 36 are demodulated to detect the Karman vortex generation frequency, and the flow rate of the fluid to be measured flowing in the flow path 12 is measured based on this frequency. it can.
[0026]
A sound absorbing member 43 formed in a cylindrical shape and a ring-shaped holding member 44 that holds both ends of the sound absorbing member 43 are attached to both ends of the passages 18 and 20. Further, the inner walls at both ends of the passages 18 and 20 are provided with recesses 45 in which the sound absorbing member 43 and the clamping member 44 are accommodated on the entire circumference. The sound absorbing member 43 is formed of a porous material so as to be able to absorb sound waves. For example, the sound absorbing member 43 is formed of a material having elasticity such as a sponge.
[0027]
Accordingly, the sound absorbing member 43 is accommodated in the recess 45 and inserted so as not to protrude into the passages 18 and 20, and the upper and lower ends are sandwiched by the sandwiching member 44. Temperature limit can be eliminated. In addition, the sound absorbing member 43 can be securely fixed, and the passage 18 as the ultrasonic propagation path is not narrowed, and the ultrasonic reception efficiency can be stabilized.
[0028]
FIG. 3 is a block diagram showing a circuit configuration connected to each of the ultrasonic sensors 30, 32, 34, 36.
[0029]
As shown in FIG. 3, the transmission ultrasonic sensors 30 and 32 are connected to the oscillation circuit 46 and vibrate in response to a signal from the oscillation circuit 46 to transmit ultrasonic waves into the fluid in the passages 18 and 20. To do. The ultrasonic waves propagated in the passages 18 and 20 are received by the reception ultrasonic sensors 34 and 36. The receiving ultrasonic sensors 34 and 36 are connected to a calculation unit 47 that calculates the flow rate.
[0030]
The calculation unit 47 includes amplifier circuits 48 and 50, waveform shaping circuits 52 and 54, a phase comparison circuit 56, an amplifier circuit 58, a filter circuit 60, a flow rate calculation circuit 62, a display circuit 64, and an output circuit 66. In the flow rate calculation circuit 62, the flow rate of the fluid to be measured flowing through the flow path 12 based on the frequency of the Karman vortex obtained from the phase difference of the detection signals output from the receiving ultrasonic sensors 34 and 36 as will be described later. Is calculated.
[0031]
Here, the mounting structure of the sound absorbing member 43 constituting the main part of the present invention will be described. Since the ultrasonic sensors 30, 32, 34, and 36 have the same structure and the same mounting structure, the mounting structure of the ultrasonic sensor 30 and the sound absorbing member 43 will be described below.
[0032]
FIG. 4 is an enlarged longitudinal sectional view showing a mounting structure of the ultrasonic sensor 30 and the sound absorbing member 43. In FIG. 4, since it is bilaterally symmetrical, only the left side of the center line is displayed.
[0033]
As shown in FIG. 4, the ultrasonic sensor 30 has a cylindrical holder 67 in which a piezoelectric element 68 is inserted into an internal space 67a, and the bottom surface of the internal space 67a is a diaphragm 67b. . In addition, the holder 67 is provided with a flange 67c that protrudes in the radial direction from the outer periphery of the bottom. The flange portion 67c is sealed by compressing the packing 42.
[0034]
The piezoelectric element 68 is excited by a signal supplied from the oscillation circuit 46 while being fixed to the diaphragm 67b, and vibrates the diaphragm 67b. The diaphragm 67b is in contact with the fluid to be measured that is filled in the passage 18, and propagates ultrasonic waves into the fluid to be measured. A sealing stepped portion 70 with which the packing 42 abuts is formed in the mounting hole 38a into which the holder 66 is inserted.
[0035]
In addition, annular grooves 45a and 45b for fitting a holding member 44 formed in a ring shape are provided at the entrance and the back of the recess 45 provided at the end of the passage 18. The sandwiching member 44 is partly cut in a ring shape, and can be inserted into the annular groove 45b formed in the inner part of the recess 45 from the inner peripheral side. The sandwiching member 44 has an L-shaped cross section, and has an annular locking portion 44a that protrudes in the axial direction from the inner peripheral portion.
[0036]
Therefore, since the pair of clamping members 44 are fitted in the annular grooves 45 a and 45 b, both ends of the sound absorbing member 43 formed in a cylindrical shape are clamped from the axial direction, and the annular locking portion 44 a is the sound absorbing member 43. Are sandwiched between the inner ends. Therefore, the sound absorbing member 43 is sandwiched in the axial direction and the radial direction by the pair of sandwiching members 44, and is securely held in the recess 45 provided at the end of the passage 18, and is prevented from falling off.
[0037]
Therefore, by adopting a configuration in which the sound absorbing member 43 is sandwiched by the pair of sandwiching members 44, the sound absorbing member 43 can be fixed to the passage 18 more reliably than the conventional method of fixing the sound absorbing member 43 with an adhesive. At the same time, it is possible to measure the flow rate of high-temperature fluid. In addition, there is no concern that the sound absorbing member 43 may be peeled off due to fluid fluctuations as in the case where the sound absorbing member 43 is fixed with an adhesive, and the variation in the sound absorbing effect due to the failure in applying the adhesive to the sound absorbing member 43 is also eliminated. be able to.
[0038]
Here, the propagation of the ultrasonic wave in the ultrasonic wave propagation path in which the sound absorbing member 43 is fixed immediately before the ultrasonic sensor 30 as described above will be described.
[0039]
The ultrasonic wave transmitted from the transmitting ultrasonic sensor 30 is radiated from the diaphragm 67b of the holder 67 into the passage 18 as a propagation path. Propagate while reflecting on the inner wall. Further, when the ultrasonic waves are radiated as a continuous wave, they are received as a composite of the ultrasonic waves that arrive while being reflected by the inner wall of the passage 18 in a complicated manner. It is a synthesis of what was received.
[0040]
Furthermore, when a standing wave or the like is generated between the reflected wave and the traveling wave in the propagation path, the wave is received as a synthesized wave having more complicated information. As a countermeasure, in the present invention, the sound absorbing member 43 is sandwiched by a pair of sandwiching members 44 in the ultrasonic wave propagation path, and the ultrasonic wave propagates directly into the measured fluid without being reflected by the inner wall of the passage 18. Only the signal is received by the reception ultrasonic sensor 34. Therefore, the resonance of the ultrasonic wave received by the ultrasonic sensor 32 for reception and the ultrasonic wave transmitted from the ultrasonic sensor 30 for transmission after the reflected wave in the passage (ultrasonic propagation path) 18 is absorbed by the sound absorbing member 43. Can be prevented.
[0041]
Next, the measurement operation of the ultrasonic vortex flowmeter 10 configured as described above will be described. When the fluid to be measured flows in the flow path 12 of the flow meter main body 14, regularly alternating Karman vortices proportional to the flow velocity of the fluid to be measured are generated downstream of the vortex generator 16.
[0042]
When Karman vortices are generated in the fluid to be measured in this manner, pressure changes synchronized with the Karman vortices are generated on the hypotenuses 16 b and 16 c on the downstream side of the vortex generator 16. Then, according to the pressure difference between the left and right flow sides of the vortex generator 16, an alternating flow synchronized with the Karman vortex in the longitudinal direction of the vortex generator 16 is generated in the passages 18 and 20.
[0043]
Here, the ultrasonic signal generated by the oscillation circuit 46 is transmitted to the transmission-side ultrasonic sensors 30 and 32 to excite the piezoelectric element 68. The vibration is propagated as ultrasonic waves into the fluid to be measured in the passage 18 through the diaphragm 67 c of the holder 67.
The ultrasonic wave propagated through the fluid to be measured is received by the receiving ultrasonic sensors 34 and 36 with the flow information in the passage 18 synchronized with the Karman vortex (the propagation speed is accelerated or decelerated) and is amplified as an ultrasonic signal. After being amplified by the circuits 48 and 50 and converted into rectangular waves by the waveform shaping circuits 52 and 54, the phases are compared by the phase comparison circuit 56. The signals input to the phase comparison circuit 56 are signals that have undergone phase modulation in opposite directions, and a phase difference is generated in synchronization with the flow in the space generated by the Karman vortex. The phase difference signal is amplified by the amplifier circuit 58, noise is removed by the filter circuit 60, and then input to the flow rate calculation circuit 62.
[0044]
Since this phase difference signal is synchronized with the Karman vortex, the flow rate calculation circuit 62 calculates the flow velocity from the frequency of the Karman vortex, calculates the volume flow rate and displays it on the display circuit 64, or outputs the flow rate signal to the output circuit 66. Output to.
[0045]
Here, if the sound velocity of the fluid changes due to temperature change or pressure change of the fluid to be measured, the ultrasonic waves propagated through the passages 18 and 20 are not detected as a phase difference because they propagate through the same environment. Therefore, it has a structure that can stably detect only the change in the flow in the passages 18 and 20 generated by the Karman vortex without being affected by the change in temperature and pressure of the fluid to be measured.
[0046]
Therefore, most of the ultrasonic waves received by the reception-side ultrasonic sensors 34 and 36 are propagated through the fluid to be measured in the passages 18 and 20. Therefore, since the two signals propagating in the passages 18 and 20 are signals affected by the same sound speed change, the effects of the sound speed change in the fluid to be measured can be canceled by comparing the phases with each other. .
[0047]
In the above-described embodiment, the structure in which the sound absorbing member 43 is fixed to one end of the passage 18 has been described. However, the present invention is not limited to this, and can be applied to a structure in which the sound absorbing member 43 is fixed to the entire inner wall of the passage 18. It is.
[0048]
【The invention's effect】
As described above, according to the first aspect of the present invention, the holding of the sound absorbing member from both ends is brought into contact with both ends of the cylindrical sound absorbing member inserted into the ultrasonic wave propagation path formed in the vortex generator. Since the member is provided, the sound absorbing member can be reliably and stably fixed to the inner wall of the ultrasonic wave propagation path. In addition, unlike the conventional method of fixing the sound absorbing member to the ultrasonic wave propagation path with an adhesive, it is not peeled off due to fluid fluctuations, and the flow rate can be measured stably.
[0049]
According to the second aspect of the present invention, since the sound absorbing member is sandwiched between the ultrasonic transmitting side and the ultrasonic receiving side, the reflected wave in the ultrasonic propagation path is absorbed by the sound absorbing member and It is possible to prevent resonance between the transmitted ultrasonic wave and the ultrasonic wave received by the ultrasonic sensor.
[0050]
According to the invention of claim 3, the sandwiching member is formed in a ring shape, and the ultrasonic wave propagation path has a concave part for attaching the sound absorbing members provided at both ends of the ultrasonic wave propagation path, and the concave part And an annular groove into which each of the ring-shaped sandwiching members fits, and the sound absorbing member is sandwiched by the sandwiching member while being inserted into the concave portion of the ultrasonic wave propagation path. The member can be securely fixed, and the ultrasonic wave propagation path can be stabilized without narrowing the ultrasonic wave propagation path.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an embodiment of an ultrasonic vortex flowmeter according to the present invention.
FIG. 2 is a longitudinal sectional view of an embodiment of an ultrasonic vortex flowmeter according to the present invention.
3 is a block diagram showing a circuit configuration connected to each of the ultrasonic sensors 30, 32, 34, and 36. FIG.
4 is an enlarged longitudinal sectional view showing a mounting structure of an ultrasonic sensor 30 and a sound absorbing member 43. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Ultrasonic vortex flowmeter 12 Flow path 14 Flowmeter main body 16 Vortex generator 18, 20 Passage 22, 24, 26, 28 Pressure introduction path 30, 32 Transmission ultrasonic sensor 34, 36 Reception ultrasonic sensor 38, 40 Holding member 43 Sound absorbing member 44 Nipping member 45 Recess 46 Oscillation circuit 47 Calculation unit 48, 50 Amplifier circuit 52, 54 Waveform shaping circuit 56 Phase comparison circuit 62 Flow rate calculation circuit

Claims (3)

A flow meter body in which a gas flow path through which a gas as a measured fluid flows is formed; a vortex generator provided in the gas flow path so as to be orthogonal to the flow direction; and a superfluid formed in the vortex generator. An ultrasonic sensor that detects Karman vortices via a sound wave propagation path; a holding member that is fixed to the flowmeter body or the vortex generator and into which the ultrasonic sensor is inserted and held; and an ultrasonic sensor formed on the vortex generator. In an ultrasonic vortex flowmeter comprising a cylindrical sound absorbing member inserted into a sound wave propagation path,
An ultrasonic vortex flowmeter comprising a holding member that contacts both ends of the sound absorbing member and holds the sound absorbing member from both ends.   2. The ultrasonic vortex flowmeter according to claim 1, wherein the sound absorbing member is sandwiched between an ultrasonic transmission side and an ultrasonic reception side of the ultrasonic sensor. The clamping member is formed in a ring shape,
The ultrasonic propagation path includes
A recess for attaching the sound absorbing member provided at both ends of the ultrasonic wave propagation path;
An annular groove formed in the recess and into which each of the ring-shaped clamping members is fitted;
Formed,
2. The ultrasonic vortex flowmeter according to claim 1, wherein the sound absorbing member is clamped by the clamping member in a state of being inserted into a concave portion of the ultrasonic wave propagation path .

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