KR100732116B1 - Vortex flowmeter - Google Patents

Abstract

The present invention relates to a vortex flow meter, comprising: a vortex generating unit for generating a vortex in an oil conduit, and a Karman vortex operating range downstream of the vortex generating unit to measure deformation amount due to vortex through a piezoelectric element connected at both ends of the housing. In the configuration including the flow sensor, the eddy current in the pipe through the piezoelectric element provided with the housing is characterized in that the stress can be generated simultaneously in the transverse direction and the thickness direction to increase the output sensitivity of the electrical signal.

Carman vortex, frequency, piezoelectric element

Description

Vortex Flowmeter {VORTEX FLOWMETER}

1 is a side view showing an ultrasonic flowmeter according to the prior art.

Figure 2 is a perspective view of a vortex flow meter according to the present invention.

3a and 3b is an operating state diagram showing the flow sensor portion of the vortex flow meter according to the invention.

4A and 4B are sectional views showing a flow sensor part of a vortex flow meter according to a modification of the present invention.

5 is a perspective view showing a vortex flowmeter according to a modification of the present invention.

Figure 6 is a perspective view of a vortex flow meter according to another variant of the present invention.

<Code Description of Main Parts of Drawing>

100 Vortex generator 200 Flow sensor

210.Housing 220.Piezoelectric element

300 support 400 pipe

The present invention relates to a vortex flow meter, and relates to a vortex flow meter that can increase the output sensitivity of an electrical signal through a piezoelectric element provided with a housing when the vortex occurs in the oil pipe.

In general, there are various types of flowmeters for measuring the flow rate of the fluid flowing in the duct, but in particular, an ultrasonic flowmeter using the speed of the ultrasonic wave varies with the speed of the fluid, and a vortex type for generating the vortex in the fluid and measuring the flow rate. Flow meters are attracting attention.

Ultrasonic flowmeters are widely used in ultrasonic transit time difference flow rate measurement method. As illustrated in FIG. 1, the ultrasonic flowmeters have a pair of ultrasonic wave receivers 20 and 30 installed oppositely in the oil pipe 10 to alternately fire or receive each other to calculate flow rates. For example, an ultrasonic transceiver uses piezoelectric vibrators such as piezoelectric ceramics as electrical energy and mechanical energy conversion elements. That is, when the driving bus voltage signal is radiated by applying the driving bus voltage signal to the ultrasonic wave transceiver 20 on one side, the ultrasonic burst signal reaches the ultrasonic wave receiver 30 on the other side after t hours through the L path of the figure. The ultrasonic transmitter 30 on the other side converts only the transmitted ultrasonic burst signal into an electrical burst signal, and radiates the ultrasonic burst signal back to the ultrasonic transmitter 20 on one side using the electrical burst signal as a trigger signal. The ultrasonic burst signal reaches the ultrasonic transceiver 20 on one side after t hours through the L path. Such a device is called a singaround device, and the time required for the ultrasonic wave 20 to be radiated from the ultrasonic wave receiver 20 on one side to reach the ultrasonic wave 30 on the other side is called a singaround period, and the inverse thereof is referred to as a singa frequency. do.

The flow velocity of the liquid flowing through the duct is V, the velocity of the ultrasonic wave in the fluid is C, the angle between the direction in which the fluid flows and the ultrasonic pulse is θ, and the ultrasonic pulse from the ultrasonic wave transmitter 20 on one side is the ultrasonic wave receiver on the other side. If the singaround period t, the time to reach (30), is t, and the singaround frequency is f, then

<Equation 1>

f = 1 / t = (C + Vcosθ) / L

Singaround period, which is the time when the ultrasonic pulse from one side of the ultrasonic wave receiver 20 reaches the ultrasonic wave receiver 30 of the other side is called t1, the singing frequency of f1 is called, the ultrasonic pulse from the other side of the ultrasonic wave receiver 30 If the singaround period, which is the time to reach the ultrasonic transceiver 20 on one side, is t2, and the singaround frequency is f2, the following equation is established.

<Equation 2>

Δf = f1-f2 = 2Vcosθ / L

That is, the flow rate V of the fluid can be obtained from the distance L of the ultrasonic wave propagation path and the frequency difference Δf, and the flow rate is irradiated from the flow rate V.

However, when the ultrasonic flowmeter has a long interval between the ultrasonic wave receiver on the one side and the ultrasonic wave receiver on the other side, or when vortices of various sizes occur in the fluid flow, the ultrasonic pulses are refracted, diffused, or absorbed attenuation changes, thereby causing errors in the measurement. Can be. In addition, the ultrasonic flowmeter has a problem in that the configuration is complicated and the manufacturing cost is high.

 On the other hand, the vortex flowmeter using the vortex sensor uses that the Karman swirling flow frequency is proportional to the flow rate of the fluid. For example, when the column-shaped vortex generator is installed in the oil pipe, the vortices generate a stable and regular vortex as the fluid flows. This vortex occurs as a result of the separation of the boundary layer between the object and the fluid and is called the Karman vortex. In this case, it is well known in the art that the number of vortices (frequency of vortices) generated in unit time on the right side of an object is proportional to the flow velocity of the fluid. Therefore, when the number of vortices generated in unit time is known, the flow velocity or flow rate of the fluid can be known. That is, the vortex flowmeter generates vortices in the vortex generator to generate vortex signals due to changes in stress, pressure, and the like, and the vortex sensor receives the vortex signals and outputs them as pulse signals.

However, such a vortex flowmeter has a problem that the vortex signal measured at the time of detection of the vortex signal generated from the vortex generator is weak and can be used only at a minute flow rate of less than a certain amount.

SUMMARY OF THE INVENTION An object of the present invention is to provide a vortex flow meter which can increase the output sensitivity of the vortex signal generated by the vortex generating unit.

In order to achieve the above object, the present invention provides a vortex generating unit for generating a Karman vortex in the fluid flowing and installed in the duct, and a Karman vortex installed in the operating range of the Karman vortex downstream of the vortex generating unit. And a flow sensor unit fixed in the housing to which the vortex is applied and including a piezoelectric element for measuring the amount of deformation caused by the vortex.

In this case, the housing includes first and second housings having one end portion and the other end portion fixed to both ends of the piezoelectric element, and disposed on opposite sides of the piezoelectric element, respectively, and the piezoelectric element includes the first and second housings. A predetermined space is formed between the housings. In addition, the housing of the flow sensor unit is installed to face the traveling direction of the Karman vortex.

An embodiment of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 2, the present invention includes a vortex generating unit 100 for generating a Karman vortex in the duct 400, and a flow sensor unit 200 for measuring a frequency generated by the Karman vortex.

Specifically, the vortex generating unit 100 is satisfactory if the shape of the obstacles that can form the vortex in the fluid flowing in the flow pipe 400 is not particularly limited in shape. The vortex generator 100 according to the present embodiment is formed in a cylindrical shape in which both ends are vertically arranged and fixed to an inner wall of the oil pipe 400.

In addition, the vortex generating unit 100 is inserted into the oil pipe 400 to determine a proper position, and by fixing the inner wall of the welding by irradiation with an electron beam or a laser or the like, or fixed by tightening with screws or bolts. It can also be bonded and fixed.

As described above, Karman vortices are generated from both sides of the surface of the vortex generating unit 100 in the flow direction of the fluid in the oil pipe 400 through the vortex generating unit 100 fixed in the oil pipe 400. The Karman vortex is maintained in an active state within a predetermined distance to the rear of the vortex generating unit 100 disposed in the fluid flow, and the flow sensor unit 200 is disposed within the range in which the active state is maintained.

The flow sensor unit 200 is a piezoelectric element 220 for outputting an electrical signal proportional to the flow rate through the alternating pressure of the generated Karman vortex, and the housing 210 for interconnecting the ends of the piezoelectric element 220 It is composed. At this time, the support 300 is provided within the range in which the active state of the vortex is maintained to the rear of the vortex generating unit 100 so that the flow sensor unit 200 can be fixed in the oil pipe 400 by the support 300. Do. In addition, the support 300 may be provided with a lead wire (not shown) connected to the piezoelectric element 220, and a connection between the piezoelectric element 220 and an electric measurement circuit may be made through the lead wire.

In general, piezoelectric elements can switch between mechanical energy and electrical energy. When pressure is applied to the polarization crystal of a piezoelectric element to cause mechanical deformation, an electric field is formed to induce a voltage. On the contrary, when a voltage is applied to the polarization crystal, mechanical deformation may be caused.

The piezoelectric element 220 according to the present exemplary embodiment converts the physical energy due to the Karman vortex generated from the vortex generator 100 into electrical energy. For example, when a force is applied to the polarization direction of the piezoelectric element 220, electric charges are generated at both sides, thereby generating a potential difference. This potential difference is proportional to the magnitude of the applied force.

For example, the piezoelectric element 220 detects a change in stress of the alternating stress as a change in an electrical signal, and detects a vortex generation frequency in accordance with detecting the number of changes. The piezoelectric element 220 is satisfied as long as it can detect a stress. For example, a piezoelectric element made of lithium niobate can be used.

On the other hand, in order to obtain sufficient detection sensitivity in the piezoelectric element 220, it is advantageous that the distortion on the surface is large, and for this purpose, the piezoelectric element 220 is provided with a housing 210.

As shown in FIGS. 3A and 3B, the housing 210 includes a first housing 210a having one end and the other end connected to both ends of one side of the piezoelectric element 220, and the other of the piezoelectric element 220. The second housing 210b has one end and the other end connected to both side ends thereof.

At this time, the first and second housing (210a, 210b) is formed on the outer surface portion 211 extending horizontally formed on one side of the upper surface, the lower surface of the other side connected to the piezoelectric element 220 An inner curved portion 212 is formed to extend in a curved shape.

In addition, each end of the first and second housings 210a and 210b is connected to an end of the piezoelectric element 220, and an intermediate portion thereof is spaced apart from each other so that a predetermined space is formed between the piezoelectric elements 220. At this time, the housing 210 is preferably composed of a flexible member that can be deformed by a predetermined space 230 formed between the piezoelectric element 220 and the housing 210 when the external stress caused by the vortex. Through this, external stresses caused by vortices applied to the first and second housings 210a and 210b can be simultaneously transmitted in the transverse direction and the thickness direction of the piezoelectric element 220. Accordingly, the electric signal output sensitivity of the piezoelectric element 220 through external stress can be increased.

As shown in FIG. 4A, the housing 210 may include first and second housings 210a and 210b having an outer horizontal portion 213 and an inner curved portion 212. That is, the first and second housings 210a and 210b are formed with an outer horizontal portion 213 extending horizontally on one upper surface thereof, and the other lower surface connected to the piezoelectric element 220. An inner curved portion 212 is formed to extend in a curved shape.

In addition, as shown in FIG. 4B, the housing 210 has first and second housings 210a and 210b having an outer horizontal portion 213, a bent portion 215, and an inner horizontal portion 216. It may be configured as. That is, the first and second housings 210a and 210b are formed with an outer horizontal portion 213 and an inner horizontal portion 216 horizontally extending on the upper and lower surfaces thereof, respectively. The bent portion 215 is formed to be bent to both sides of the horizontal portion 213, 216 is formed. In this case, an end portion of the bent portion 215 is connected to both ends of the piezoelectric element 220.

The flow sensor unit 200 is installed so that the housing 210, which is opposite to each other, faces the traveling direction of the Karman vortex in the oil pipe 400, and the size and arrangement interval of the piezoelectric element 220 can be variously changed. However, as the number of piezoelectric elements 220 increases, the sensing sensitivity increases.

For example, as shown in FIG. 5, two flow sensor 200 may be installed in a direction facing the traveling direction of the Karman vortex with respect to the support 300 supporting the oil pipe 400. Through this, it is possible to increase the detection sensitivity than when measuring the vortex through one flow sensor unit 200. That is, in consideration of the diameter of the oil pipe 400 in which the flow sensor 200 is installed, a plurality of flow sensor 200 may be installed in the oil pipe 400.

In addition, as shown in FIG. 6, the flow sensor 200 may be disposed such that the curvature direction of the housing 210 is bent in the radial direction of the oil pipe 400. That is, the flow sensor unit 200 satisfies the configuration of the present invention when the housing 210, which is the opposite surface thereof, is installed to face the traveling direction of the Karman vortex in the oil pipe 400.

Meanwhile, Each piezoelectric element 220 may be provided with a circuit composed of a resistor and a capacitor to generate a piezoelectric voltage output from the piezoelectric current (piezoelectric charge) generated by the applied pressure. In addition, a signal amplifier (not shown) may be further provided to amplify the output sensitivity output from the piezoelectric element 220 to a predetermined size. The signal amplifier is composed of an amplifier circuit corresponding to each piezoelectric element 220 circuit, and since the signal amplifier is implemented using a general signal amplifier circuit, a detailed description thereof will be omitted. The signal amplifier may further include a low frequency band filter to remove white noise included in the signal.

Referring to the operation of the present invention made of such a configuration as follows.

Karman vortices are generated from both sides of the surface of the vortex generator 100 facing the flow direction of the fluid through the vortex generator 100 disposed in the oil pipe 400. The Karman vortex is transmitted to the flow sensor unit 200 within a predetermined distance in which the active state is maintained to the rear of the vortex generating unit 100 disposed in the fluid flow.

At this time, the alternating stress acting by the Karman vortex is transmitted to the housing 210 of the flow sensor unit 200. Referring again to FIGS. 3A and 3B, when an external stress is applied to the housing 210 in the direction A, the displacement of the piezoelectric element 220 increases in the direction of the arrow B, and the piezoelectric element 220 is increased. Through the housing 210 can detect the variation of the pressure caused by the Karman vortex as a large displacement amount. As a result, the measurement sensitivity can be remarkably improved. When the displacement amount by the housing 210 is transmitted to the piezoelectric element 220, the piezoelectric element 220 is converted into an electrical signal and then supplied to the circuit of the electrical measurement through a lead wire (not shown), The flow velocity and flow rate of the measured fluid can be measured.

While the invention has been shown and described with respect to specific embodiments thereof, it will be appreciated that the invention can be variously modified and modified without departing from the spirit or scope of the invention as provided by the following claims. It will be clear to those skilled in the art that they can easily know.

As described above, according to the present invention, when the vortex is generated by the vortex generating unit in the pipe, stress is simultaneously generated in the transverse direction and the thickness direction of the piezoelectric element provided with the housing, thereby increasing the output sensitivity of the electrical signal through the piezoelectric element. It can be effective.

In addition, the present invention can improve the productivity of the product through the price competitiveness by implementing a structure for generating a vortex in the pipe, and measuring the flow rate by detecting the electrical signal by the stress caused by the vortex generated through a simple configuration There is an advantage.

Claims (4)

A vortex generating unit for generating a Karman vortex in the fluid flowing in the duct The flow sensor unit is installed in the Karman vortex action range downstream of the vortex generating unit and is provided with a housing to which the Karman vortex is applied by the vortex generating unit and both ends thereof are fixed in the housing to measure a deformation amount caused by the Karman vortex. Vortex flow meter comprising a. The method according to claim 1, The housing is First and second housings disposed on opposite sides of the piezoelectric elements, respectively, and having one end and the other end fixed to both ends of the piezoelectric element, And the piezoelectric element forms a predetermined space between the first and second housings. The method according to claim 1 or 2, The housing of the flow sensor unit is a vortex flow meter, characterized in that it is installed so as to face the traveling direction of the Karman vortex. The method according to claim 3, The housing is A vortex flow meter comprising a flexible member.

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