JPS5834765B2 - Karman vortex current meter - Google Patents

Description

[Detailed Description of the Invention] This invention provides a vortex generation column in the measurement fluid flowing in a conduit, and the number of Karman vortices (occurrence vortex frequency) generated downstream of the vortex generation column.
This paper relates to a Karman vortex current meter that measures flow velocity or flow rate by detecting it using ultrasonic waves, and its purpose is to provide a method that can easily detect even weak vortices at low flow speeds.

A method of installing a vortex generation column in a conduit and detecting the generation frequency of the Karman vortex generated downstream of the column using ultrasonic waves to determine the flow velocity or flow rate of the fluid flowing in the tube was developed in 1973.
1-24154.

When detecting the Karman vortex using this method, the ultrasound transmitted from the ultrasound transmitter propagates through the fluid, is modulated by the Karman vortex, and is received by the receiver.

However, when the flow velocity of the fluid is low, the Karman vortex is weak and the degree of modulation received by the propagating ultrasonic waves is also small.

For this reason, it is difficult to detect Karman vortices at low flow speeds.

This invention increases the degree to which ultrasonic waves propagating in a fluid is modulated in proportion to the number of Karman vortices, and
In order to facilitate the detection of Le Mans vortices, a temperature difference is created between the fluids flowing on the left and right sides of the vortex generating body, or a different fluid is mixed into one fluid to create a state between the left and right fluids. By applying a change, the propagation speed of the ultrasonic wave is changed between the Karman vortices generated by both the left and right fluids.

The embodiment shown in the figures will be described below.

In the figure, 1 is a conduit for flowing the measurement fluid, 2 is a vortex generation column installed approximately perpendicular to the flow of the measurement fluid, 3 and 4 are Karman vortices generated by the vortex generation column 2, and 5 is an ultrasonic wave generator. vessel,
6 is an oscillating device, 7 is an ultrasonic receiver, 8 is a receiving device, the ultrasonic transmitter 5, the oscillating device 6, the ultrasonic receiver 7,
The receiving device 8 constitutes an ultrasonic vortex detection device.

9 is a partition plate arranged upstream of the vortex generating column 2 and along the vortex generating column 2 to divide the flow of the measurement fluid into two flows A and B; 10 is a partition plate of the flow divided by this partition plate; On the other hand, an electric heater 11 provided to heat B is a battery.

In the above configuration, the inside of the conduit 1 is filled with a measuring fluid (for example, air).
flows in the direction of the arrow, Karman vortex 3 is created by vortex generation column 2
, 4 occurs.

The ultrasonic transmitter 5 is driven by an oscillation device 6 and transmits ultrasonic waves to a receiver 7.

At this time, the ultrasonic waves are modulated by the Karman vortices while propagating through the performer fluid, and the receiver 7 receives the modulated ultrasonic waves.

Then, the receiving device 8 detects the frequency at which the Karman vortex occurs.

When the flow velocity of the measurement fluid is low (for example, 3 rrV/s or less), the Karman vortex is weak, and therefore the degree of modulation received by the propagating ultrasonic wave becomes small, making it impossible to detect the Karman vortex.

In such a case, when the measurement fluid on the B side is heated by the electric heater 10 to create a temperature difference between the spring roll Karman vortex 3 and the left-handed Karman vortex 4, the propagation speed of the ultrasonic wave increases 3 and the Karman vortex 4 are significantly different from each other.

That is, the propagating ultrasonic waves are modulated in proportion to the frequency of occurrence of the Karman vortices 3 and 4 that occur alternately.

When the fluid to be measured is air, if the flow B on the transmitter 5 side is heated to a temperature several degrees higher than the flow A as shown in the figure, the propagating ultrasonic wave will be modulated by the Karman vortex and the Karman vortex 3.
The modulation caused by the difference in propagation velocity due to the temperature difference between

As described above, in this invention, the propagation speed of the ultrasonic wave is made different between the Karman vortex 3 and the Karman vortex 4, and either of the flows A and B may be heated or cooled. The same effect can also be obtained by mixing a different fluid with a different sound speed into one of the flows. For example, if the fluid to be measured is air,
By mixing water vapor into the flow B on the transmitter 5 side or gasoline vapor into the flow A on the receiver T side, the displacement of the propagating ultrasonic waves can be increased and the weak Karman vortices at low flow speeds can be increased. can also be detected.

The means for mixing this foreign fluid can be easily constructed using, for example, the principle of a normal vaporizer.

As described above, the present invention provides a temperature difference between the vortex generating column 2 disposed inside the conduit 1 and the measured fluid on both sides of the vortex generating column 2 on the upstream side of the vortex generating column 2, or By mixing a different fluid other than the fluid to be measured into one of the fluids to be measured on both sides of the column and changing the atmosphere (state) between the fluids to be measured on both sides of the vortex generating column, Karman vortices can be generated at low flow speeds. It is designed to easily detect the frequency of occurrence, and it is possible to obtain a Karman vortex current meter with excellent detection ability even at low flow speeds.

[Brief explanation of the drawing]

The figure is a configuration diagram showing an embodiment of the present invention. In the figure, 1 is a conduit, 2 is a vortex generation column, 3 and 4 are Karman vortices, and 5
is an ultrasonic transmitter, 1 is an ultrasonic receiver, 9 is a partition plate, 10
is an electric heater.

Claims (1)

[Scope of Claims] 1. A vortex generation column disposed inside a conduit substantially perpendicular to the flow of the fluid to be measured, and an ultrasonic vortex detection device that detects the number of Karman vortices generated downstream of this generation column. , and means for applying a temperature difference between the measured fluids on both sides of the vortex generating column on the upstream side of the vortex generating column. The Karman vortex current meter according to claim 1, which comprises a heater or a cooler for heating or cooling. 3. The means for providing a temperature difference includes a partition plate that divides the fluid to be measured into two along the vortex generating column on the upstream side of the vortex generating column, and a means for heating or cooling one of the two divided fluids to be measured. A Karman vortex current meter according to claim 1, comprising: 4. A vortex generating column disposed inside the conduit substantially perpendicular to the flow of the fluid to be measured, an ultrasonic detector for detecting the number of Karman vortices generated on the downstream side of this vortex generating column, and a A Karman vortex current meter comprising: a partition plate that divides a fluid to be measured into two along the vortex generation column on the upstream side; and means for mixing a foreign fluid into one of the fluids to be measured divided into two by the partition plate.