JP4172091B2 - Ultrasonic vortex flowmeter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic vortex flowmeter that measures the flow rate of a fluid.
[0002]
[Prior art]
A conventional ultrasonic vortex flowmeter will be described with reference to FIG.
[0003]
In the conventional ultrasonic vortex flowmeter 51, a substantially triangular prism-shaped vortex is generated in a pipe 52 through which a gas as a fluid to be measured flows, and the diameter direction and the axial direction of the pipe 52 are parallel to each other through the center of the pipe 52. The vortex generator 53 has a side face corresponding to the base of the triangle directed in the upstream direction of the fluid to be measured, and an internal space 54 opened at both ends of the vortex generator 53 is formed therein. Yes.
[0004]
Further, holes 55, 55 communicating the inner space 54 and the inside of the pipe 2 are formed in the peripheral wall portion of the vortex generator 53 so as to be displaced from each other in the axial direction of the vortex generator 53 on the side surfaces corresponding to both sides of the triangle. One by one.
[0005]
Transmitters 56 a and 56 b that transmit ultrasonic waves toward the internal space 54 are provided in an opening on one side of the internal space 54, and the transmitter 56 transmits in an opening on the other side of the internal space 54. Receivers 57a and 57b that receive the ultrasonic waves and output them as ultrasonic signals are provided.
[0006]
The input terminals of the transmitters 56a and 56b are connected to the output terminal of an oscillation circuit 58 that transmits an ultrasonic signal having a frequency of the oscillation signal by outputting an oscillation signal having a predetermined frequency to the transmitters 56a and 56b. The output terminals of the receivers 57a and 57b are connected to input terminals of amplification circuits 59a and 59b that amplify the ultrasonic signals (the electric signals obtained from the received ultrasonic signals).
[0007]
The output terminal of the oscillation circuit 58 is also connected to one input terminal of the phase comparison circuits 60a and 60b, and the other input terminal of the phase comparison circuits 60a and 60b is connected to the amplification circuits 59a and 59b. Yes.
[0008]
The phase comparison circuits 60a and 60b compare the phases of the oscillation signal of the oscillation circuit 58 and the amplified ultrasonic signals from the amplification circuits 59a and 59b, and the phase difference signal (the phase delay of the ultrasonic signal relative to the oscillation signal). Output a signal indicating a change in decimal).
[0009]
The output terminals of the phase comparison circuits 60a and 60b are connected to the input terminals of an amplification / waveform shaping circuit (not shown), and the amplification / waveform shaping circuit amplifies and pulsates the phase difference signal, which is an analog signal, and further performs an operation (not shown) The circuit is connected so as to calculate the flow rate in the tube 52 from the frequency of the pulsed phase difference signal and output it to a display or control device (not shown). In this case, since two flow rate values are obtained corresponding to the outputs from the phase comparison circuits 60a and 60b, they are output by taking an average or the like.
[0010]
Alternatively, the output terminals of the amplifier circuits 59a and 59b are connected to the input terminal of a phase difference comparison circuit (not shown), and the output terminal of the phase difference comparison circuit (not shown) is connected to the input terminal of an amplification / waveform shaping circuit (not shown). The phase difference signal, which is an analog signal, is amplified and pulsed by the amplification / waveform shaping circuit, and the flow rate in the tube 52 is calculated from the frequency of the pulsed phase difference signal by the calculation circuit (not shown) and displayed (not shown). You may connect so that it may output to a device or a control device. In this case, the required flow rate value is one.
[0011]
In the flow meter 51, when a fluid to be measured flows in the pipe 52, Karman vortices are alternately formed on the side surfaces corresponding to both sides of the triangle of the vortex generator 53 in the downstream of the vortex generator 53 by the vortex generator 53. appear.
[0012]
When a Karman vortex is generated on one side of the side surfaces corresponding to both sides of the triangle of the cross section of the vortex generator 53, negative pressure is generated on one side, and the fluid to be measured in the internal space 54 from the hole 55 on the one side. Flows out from the hole 55 on the other side surface, and the fluid to be measured flows into the internal space 54 from the hole 55 on the other side surface to the hole 55 on the one side surface.
[0013]
Similarly, when a Karman vortex is generated on the other side surface of the vortex generator 53, a fluid to be measured flows from the hole 55 on one side surface to the hole 55 on the other side surface in the internal space 54.
[0014]
The flow of the fluid to be measured generated in the internal space 54 by the Karman vortex propagates the ultrasonic wave transmitted from the transmitter 56a to the receiver 57a and the ultrasonic wave transmitted from the transmitter 56b to the receiver 57b. The direction of the ultrasonic wave advances when the flow of the measured fluid in the same direction as the propagation direction of the ultrasonic wave is generated, and the measured fluid in the direction opposite to the propagation direction of the ultrasonic wave. When the flow of is occurring, the phase of the ultrasonic wave is delayed.
[0015]
The ultrasonic phase delay frequency is synchronized with the Karman vortex generation frequency. Since the Karman vortex generation frequency is proportional to the flow velocity in the tube 52, the ultrasonic phase delay frequency is measured. Thus, the flow rate of the fluid to be measured in the pipe 52 can be calculated.
[0016]
[Problems to be solved by the invention]
The conventional ultrasonic vortex flowmeter has two pairs of ultrasonic transmitters and ultrasonic receivers for comparing received signals for the purpose of canceling noise or the like.
[0017]
In such a configuration, since the propagation direction of each pair of ultrasonic waves is substantially the same direction (reverse direction), the respective ultrasonic waves may interfere with each other such as canceling or strengthening, and good flow measurement is possible. May be disturbed.
[0018]
[Means for Solving the Problems]
In order to solve the above problem, the invention of claim 1 is provided with a pipe through which a fluid to be measured flows, a vortex generator that is provided in the pipe and generates a Karman vortex downstream, and is provided in the vortex generator. A first hole that is perforated on an inner space and one side surface of the vortex generator facing the inner wall of the tube, communicates the inner space with the inside of the tube, and a side surface that opposes the one side surface of the vortex generator. A second hole that communicates between the internal space and the inside of the pipe, and is provided in the internal space. A proximal end is located at one end of the internal space, and a distal end is located in the other end of the internal space. By projecting from the line connecting the first hole and the second hole toward the end side, one end side of the internal space is divided into two sides, one side and the other side of the vortex generator. A partition and a partition provided on the other end side of the internal space, and transmit ultrasonic waves to one end of the internal space. A receiver, two receivers each provided on one end side partitioned by the partition, and receiving ultrasonic waves transmitted from the transmitter; and ultrasonic waves received by the two receivers from the two receivers to the tube. And a flow rate measuring means for obtaining a flow rate of the fluid to be measured.
[0019]
Thereby, since the ultrasonic waves received by the two receiving means take different propagation paths, they can be prevented from interfering with each other.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIG.
[0021]
The ultrasonic vortex flowmeter 1A shown in FIG. 1 passes through the center of the tube 2 in the tube 2 through which the gas to be measured, which is the fluid to be measured, flows, and the diameter direction of the tube 2 is substantially parallel to the axial direction. A prismatic vortex generator 3 is provided, and the vortex generator 3 has a side face corresponding to the base of the triangle facing the upstream direction of the fluid to be measured.
[0022]
Inside the vortex generator 3, an internal space 4 formed along the axial direction of the vortex generator 3 is provided, and in the vicinity of the center of the tube 2 on the side surface corresponding to both sides of the triangle of the vortex generator 3 cross section Are provided with holes 5a and 5b communicating with the internal space 4 and the inside of the pipe 2, respectively.
[0023]
In the internal space 4, the base end is located in the opening 4 a on one end side of the internal space 4, and the tip 5 a and the hole 5 b are directed toward the opening 4 b on the other end side of the internal space 4. A partition 4c protruding from the connecting line is provided, and the partition 4c partitions one end side of the internal space 4 into a space 4d on the hole 5a side and a space 4e on the hole 5b side.
[0024]
A transmitter 6 that transmits ultrasonic waves to the openings 4aa and 4ab on one end side partitioned by the partition 4c is provided in the opening 4b on the other end side of the internal space 4. 4aa and 4ab are provided with receivers 7a and 7b for receiving the ultrasonic waves transmitted from the transmitter 6 and outputting them as ultrasonic signals.
[0025]
An input terminal of the transmitter 6 is connected to an output terminal of an oscillation circuit 8 that transmits an ultrasonic wave having a frequency of the oscillation signal by outputting an oscillation signal having a predetermined frequency to the transmitter 6. The output terminals 7a and 7b are connected to input terminals of amplification circuits 9a and 9b that amplify the ultrasonic signals (the electric signals obtained from the received ultrasonic signals).
[0026]
The output terminals of the amplification circuits 9a and 9b are connected to the input terminals of the phase comparison circuit 10, and the phase comparison circuit 10 compares the phases of the amplified ultrasonic signals from the amplification circuits 9a and 9b. The phase difference signal (a signal indicating a change in the phase delay of the two ultrasonic signals) is output.
[0027]
The output terminal of the phase comparison circuit 10 is connected to the input terminal of the amplification / waveform shaping circuit 11, and the output terminal of the amplification / waveform shaping circuit 10 is connected to the input terminal of the arithmetic circuit 12. The amplification / waveform shaping circuit 10 amplifies the phase difference signal, which is an analog signal, turns it into a pulse, and outputs it as a vortex signal. The arithmetic circuit 12 calculates the flow rate in the tube 2 from the frequency of the pulsed phase difference signal and outputs a flow rate signal. The output terminal of the arithmetic circuit 12 is connected to a display circuit 13 that displays the calculated flow rate and an output circuit 14 that outputs a flow rate signal to an external device.
[0028]
Next, the operation of the ultrasonic vortex flowmeter 1A configured as described above will be described.
[0029]
When the fluid to be measured flows through the pipe 2, Karman vortices are generated by the vortex generator 3 alternately downstream from the side surfaces corresponding to both sides of the triangle of the vortex generator 3 in the downstream of the vortex generator 3.
[0030]
When a Karman vortex is generated on one side (X side in the figure) of the side surfaces corresponding to both sides of the triangle of the cross section of the vortex generator 3, negative pressure is generated on the X side and Since the fluid to be measured in the space 4d flows out, the fluid to be measured flows into the space 4e of the internal space 4 from the hole 5b on the other side surface (Y side surface in the figure), and is partitioned from the hole 5b into the internal space 4. As shown by the dotted line in the figure, a substantially V-shaped fluid to be measured flows to the hole 5a via the vicinity of the tip of 4c.
[0031]
Similarly, when a Karman vortex is generated on the Y side surface of the vortex generator 3, a substantially V-shape is formed in the internal space 4 from the hole 5a through the vicinity of the tip of the partition 4c to the hole 5b as shown by a dotted line in the figure. A flow of the fluid to be measured is generated.
[0032]
At this time, if the tip of the partition 4c does not protrude beyond the line connecting the hole 5a and the hole 5b, the flow of the fluid to be measured is generated linearly from the hole 5a to the hole 5b. In this embodiment, the tip of the partition 4c protrudes beyond the line connecting the hole 5a and the hole 5b, so that the fluid to be measured generated in the internal space 4 by the Karman vortex is not used. The flow is substantially V-shaped, and in the vicinity of the propagation path of ultrasonic waves transmitted from the transmitter 6 to the receivers 7a and 7b (the portion indicated by the one-dot chain line in the figure), the direction is substantially the same as or opposite to the propagation direction. Become.
[0033]
Therefore, the phase of the ultrasonic wave advances when the flow of the fluid under measurement in the same direction as the propagation direction of the ultrasonic wave is generated, and the ultrasonic wave occurs when the flow of the fluid under measurement in the direction opposite to the propagation direction of the ultrasonic wave occurs. The phase of is delayed. For example, when the fluid to be measured flows from the hole 5a to the hole 5b, the phase of the ultrasonic wave received by the receiver 7a is delayed, and the phase of the ultrasonic wave received by the receiver 7b is advanced. Similarly, when a fluid to be measured flows from the hole 5b to the hole 5a, the phase of the ultrasonic wave received by the receiver 7a is advanced, and the phase of the ultrasonic wave received by the receiver 7b is delayed.
[0034]
As described above, since the phases of the ultrasonic waves received by the two receivers 7a and 7b are configured so that one of them is advanced and the other is delayed, the difference between the respective ultrasonic waves is obtained by the phase comparison circuit 10. Therefore, only the phase delay remains as a difference, and the ultrasonic component and the noise component are canceled. The phase delay frequency of this ultrasonic wave is synchronized with the Karman vortex generation frequency, and based on the fact that the Karman vortex generation frequency is proportional to the flow velocity in the tube 2, the fluid to be measured in the tube 2. Can be calculated.
[0035]
As described above, in the ultrasonic vortex flowmeter 1A of the present embodiment, the reception path and reception of the ultrasonic wave received by the receiver 7a by providing the partition 4c that partitions the internal space 4 into the space 4d and the space 4e. Since the propagation path of the ultrasonic wave received by the receiver 7b is different, the ultrasonic wave received by the receiver 7a and the ultrasonic wave received by the receiver 7b are prevented from interfering with each other and affecting flow measurement. it can.
[0036]
Further, the ultrasonic vortex flowmeter 1A of the present embodiment has an internal space 4 that is substantially V-shaped, and holes 5a and 5b that take in the flow of the fluid to be measured are formed in the spaces 4d and 4e. By making the flow of the measurement fluid substantially V-shaped, the propagation direction of the ultrasonic wave receiving the phase lag and advance can be made substantially the same direction, so only one transmitter 6 is required, and the number of parts can be reduced. I can plan.
[0037]
Further, since the ultrasonic vortex flowmeter 1A of the present embodiment has holes 5a and 5b in the vicinity of the center of the pipe 2 having the highest flow velocity in the pipe 2, the energy of the Karman vortex is large and the internal space 4 The energy of the flow of the fluid to be measured generated inside increases, and the S / N ratio can be improved.
[0038]
In the ultrasonic vortex flowmeter 1A of the present embodiment, the cross-sectional area of the internal space 4 gradually decreases from the opening 4a on one end side to the opening 4b on the other end side, and accordingly, the cross-sectional area of the partition 4c is also reduced. Although configured so as to decrease, the cross-sectional area of the internal space 4 does not change between the opening 4a on one end side and the opening 4b on the other end side as in the ultrasonic vortex flowmeter 1B shown in FIG. The same effect can be achieved even if the plate is configured to have a constant cross-sectional area.
[0039]
Note that if the tip of the partition 4c has a planar shape parallel to the transmitter 6, the ultrasonic wave transmitted from the transmitter 6 may be reflected to generate a standing wave, which may adversely affect flow measurement. It is preferable to sharpen the tip as in the ultrasonic flow meter 1A of the form, or to round the tip as in the ultrasonic flow meter 1B in the modification.
[0040]
【The invention's effect】
As described above, the ultrasonic vortex flowmeter of the present invention is provided with a partition that divides the internal space into two, so that the ultrasonic reception path that one receiver receives and the ultrasonic wave that the other receiver receives. Since the propagation paths are different from each other, it is possible to prevent the ultrasonic wave received by one receiver and the ultrasonic wave received by another receiver from interfering with each other and affecting flow measurement.
[0041]
Further, the ultrasonic vortex flowmeter of the present invention does not provide the first hole and the second hole near the junction between the vortex generator and the tube, and the ultrasonic wave is generated by the flow of the fluid to be measured in the internal space. The distance subjected to the modulation can be increased, and therefore the S / N ratio can be improved without causing an error in the flow rate measurement.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an ultrasonic vortex flowmeter 1A according to an embodiment of the present invention.
FIG. 2 is a schematic view showing an ultrasonic vortex flowmeter 1B according to a modification of the embodiment of the present invention.
FIG. 3 is a schematic view showing a conventional ultrasonic vortex flowmeter.
[Explanation of symbols]
1A Ultrasonic Vortex Flowmeter 1B Embodiment Ultrasonic Vortex Flowmeter 2 Modification Example Embodiment Tube 3 Vortex Generator 4 Internal Space 4a Opening 4b on One End Side of Internal Space 4 Other End Side of Internal Space 4 Opening 4c partition 4d one space 4e partitioned by partition 4c other space 5a partitioned by partition 4c hole 5b hole 6 transmitter 7a receiver 7b receiver 8 oscillator circuit 9a amplifier circuit 9b amplifier circuit 10 phase comparison Circuit 11 Amplification / waveform shaping circuit 12 Arithmetic circuit 13 Display circuit 14 Output circuit 51 Conventional ultrasonic vortex flowmeter 52 Tube 53 Vortex generator 54 Internal space 55 Hole 56 Transmitter 57 Receiver 58 Oscillation circuit 59 Amplification circuit 60 Phase comparison Circuit 61 Amplification / waveform shaping circuit 62 Arithmetic circuit

Claims (1)

A tube through which the fluid to be measured flows;
A vortex generator that is provided in the tube and generates a Karman vortex downstream;
An internal space provided in the vortex generator;
A first hole that is formed in one side of the vortex generator facing the inner wall of the tube and that communicates the internal space with the inside of the tube;
A second hole that is drilled in a side surface that opposes the one side surface of the vortex generator and communicates the internal space with the inside of the tube;
Provided in the internal space, the base end is located at one end of the internal space, and the tip protrudes from the line connecting the first hole and the second hole toward the other end of the internal space. A partition for partitioning one end side of the internal space into two of one side and the other side of the vortex generator;
A transmitter that is provided on the other end side of the internal space and transmits ultrasonic waves to one end of the internal space;
Two receivers each provided on one end side partitioned by the partition and receiving ultrasonic waves transmitted from the transmitter;
Flow rate measuring means for obtaining a flow rate of the fluid to be measured flowing from the ultrasonic waves received by the two receivers to the tube;
An ultrasonic vortex flowmeter characterized by comprising:

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