KR100436620B1 - Cavity flowmeter - Google Patents

Abstract

The present invention is a cavity flowmeter for measuring the flow rate of the fluid in the cavity installed in the pipe portion, by measuring the flow rate of the fluid flowing through the pipe portion, it is possible to accurately and easily measure the frequency due to pressure vibration of the fluid in the cavity A noise filter is installed at the inlet of the pipe so that the sound wave propagating along the fluid flowing into the inlet does not interfere with the pressure vibration of the fluid generated in the cavity.

In addition, the present invention facilitates the measurement of the flow rate of the fluid flowing at a low speed, thereby providing a flow path contraction part and a flow path expansion part in the pipe part to widen the flow measurement range of the common flow meter.

Description

Cavity Flowmeters {CAVITY FLOWMETER}

The present invention relates to a flow meter for measuring the flow rate of a gas or liquid flowing in a pipe, that is, a fluid, and more particularly, by accurately detecting the frequency of the vibration wave generated when the fluid is pressure oscillated in a cavity in the pipe part. It relates to the joint flowmeter to measure.

In general, there are various kinds of flowmeters for measuring the flow rate of a fluid flowing in a pipe, such as differential pressure type, turbine type, electronic type, volume type, mass type, ultrasonic type, and vortex type, depending on the operation principle. Comparing the vortex flowmeter and the vortex flowmeter, both have a common point in that they measure the flow rate by detecting a frequency proportional to the flow rate, but in the case of the vortex flowmeter, the generation period of the vortex generated in the vortex generator is measured. In contrast to the apparatus for calculating the flow rate, the cavity flowmeter differs in that it calculates the flow rate by detecting a frequency proportional to the flow velocity of the fluid passing through the cavity.

Compared with the various flowmeters described above, the common flowmeter has great advantages such as the simplicity of design and manufacture and the need for maintenance, but the conventional flowmeter has a problem of interference with external noise during frequency measurement. The frequency has not been measured accurately and its utilization is insufficient, and it has not been commercialized yet.

The operation principle of a conventional cavity flowmeter will be described with reference to the accompanying drawings, in which FIG. 1 shows a configuration of a conventional cavity flowmeter, in which the flowmeter measures the cavity 2 and the pressure in the cavity to generate pressure vibration of the fluid. It consists of a pressure sensor (3) for sensing, by measuring the frequency of the pressure in the cavity sensed by the pressure sensor (3) to measure the flow rate.

However, in the conventional cavity flowmeter, it is impossible to detect the pressure vibration in the cavity substantially accurately, or it is difficult to detect it manually by equipment such as a signal automatic tracker, and thus it is difficult to detect it manually. Not only is this poor, it has not yet been commercialized.

In order to solve the above problems, the present invention is a cavity flow meter for measuring the flow rate of the fluid flowing in the pipe by detecting the frequency in the cavity, by blocking the interference of external noise, etc. to easily and accurately measure the common vibration frequency flow rate It is an object of the present invention to provide a common flow meter that can accurately calculate

It is yet another object of the present invention to provide a cavity flowmeter for accurately measuring the frequency in the cavity of a cavity flowmeter at low cost by introducing a simple device.

1 is a schematic diagram showing the configuration of a conventional cavity flow meter.

2 is a schematic diagram schematically showing the configuration of a cavity flowmeter for explaining the operation principle of the cavity flowmeter of the present invention.

FIG. 3 is a graph schematically showing the relationship between the waveform of the time versus pressure wave and the frequency versus flow rate detected by the pressure sensor 3 of the common flow meter of FIG. 2.

4 is a configuration diagram showing a first embodiment of the present invention.

5 is a configuration diagram showing a second embodiment of the present invention.

6 is an enlarged view of the A-A cross section of FIGS. 4 and 5.

7 is a perspective view of a cavity installed in the pipe portion of the present invention.

8 is an enlarged view of the noise filter 12 of FIG. 4 and FIG. 5.

9 is an enlarged perspective view of the noise suppressor of the spherical ball shape of FIG. 8.

10 is a graph showing the frequency vs. peak size of the frequency spectrum detected in the cavity of a conventional cavity flowmeter without a noise filter.

11 is a graph showing the frequency versus the peak size of the frequency spectrum detected in the cavity of the cavity flowmeter with a noise suppressor of the present invention.

<Explanation of symbols for the main parts of the drawings>

1: tube 2: joint

3: pressure sensor 5: outlet

6 inlet part 7 flow path shrinking part

8: Euro 9: static pressure sensing hole

10: temperature sensor insertion hole 11: flow path expansion portion

12: Noise Filter 13: Electronic part

20 case 21 screw tightening unit

In the cavity flowmeter of the present invention, if the cavity vibration frequency is f, the cavity length is L, and the flow velocity is V, a dimensionless number S having a relationship of S = f * L / V is obtained, and this relation is a mathematical model of vibration. Here, S is referred to as the strouhal number.

The number of straw holes depends on the shape and size of the cavity, and if the number of straw holes is not constant, a large error occurs in the flow rate value. However, the cavity flowmeter is almost constant within the range of a constant Reynolds number, It is well known that cavity flowmeters can accurately measure flow rates by reducing errors.

However, in the case of such a collective flowmeter, the principle of measuring the pressure vibration occurring in the cavity is known, and there is a lack of data or research on the specific measurement method or configuration of the flow measurement. It is not used as a situation.

The flow measurement principle of the cavity flowmeter according to the present invention will be described with reference to Figures 2 and 3, Figure 2 is a schematic diagram showing the configuration of the cavity flowmeter for explaining the operation principle of the cavity flowmeter of the present invention. In the drawing, the flow meter is a cavity (2) for generating a pressure vibration of the fluid and a pressure sensor (3) for detecting the pressure in the cavity and converting it into a frequency signal, and a pressure sensor for installing the pressure sensor for measuring the pressure of the fluid 9), it is composed of a temperature sensor insertion hole 10 and the electronic portion 13 is provided with a temperature sensor for measuring the temperature of the fluid, the electronic portion 13 is the pressure (15) measured in the positive pressure sensing hole (9) ) And the frequency signal 14 output from the temperature 16 and the pressure sensor 3 measured by the temperature sensor insertion hole 10 are input to the data input terminal 17, and the frequency signal is output to the screen output unit 20. ) And FFT transform (Fast Fourier Transform) Signal auto tracker for detecting a maximum peak of the frequency signal consists of a (19, Signal Tracker).

3 is a simplified graph showing the input of the pressure sensor 3 in the cavity as time versus pressure vibration in the cavity flowmeter, and a simplified graph showing the output of the pressure sensor 3 as frequency versus flow rate. It can be seen that the ratio of the linearly proportional.

However, in the case of the cavity flowmeter having only the above configuration, when detecting the frequency due to the pressure vibration of the fluid in the cavity obtained from the cavity, the frequency peak of the noise component is superior to or similar to the frequency peak due to the pressure vibration of the fluid. Since the signal-to-noise ratio (SNR) of the frequency spectrum captured by the signal is close to 1.0, there is a problem that automatic peak detection cannot be performed by a signal tracker.

In order to solve this problem, the present invention provides a cavity flow meter for measuring the flow rate by measuring the frequency caused by the pressure vibration of the fluid in the cavity (2) is installed in the cavity (1) In order to prevent noise propagating along the fluid flowing into the inlet 6 of the pipe 1 from interfering with the pressure vibration in the cavity 2, the spherical body or the fiber in the case 20 is screwed. (21) is a cavity flowmeter characterized in that a noise filter (12), which is densely packed in a maximum dense structure, is provided upstream of the cavity (2).

More preferably, in the present invention, a nozzle-shaped flow path contracting portion 7 is provided between the noise filter 12 and the cavity 2 of the pipe portion 1, and the cavity 2 and the outlet portion ( It is a cavity flowmeter characterized in that a diffuser-shaped flow path expansion part (1) is provided between 5).

That is, the present invention installs a noise filter 12 to remove noise that may interfere with the cavity vibration at the inlet of the pipe through which the fluid flows, thereby generating a fluid generated in the cavity installed at a predetermined position of the pipe. By detecting the vibration of the pressure to remove the noise caused by noise when measuring the frequency, the frequency peak by the noise component is removed, it is possible to accurately measure the flow rate of the fluid flowing through the pipe (1).

In the cavity flow meter without the noise filter according to FIG. 2, when the flow rate of the fluid is small, the cavity flow rate to be measured by the pressure caused by noise generated by the pipe part itself or the outside or generated by the fluid flow is measured. In many cases, the intensity of the pressure vibration is weak, and even if the flow rate of the fluid is higher than a certain level, the pressure due to the noise cannot detect or accurately detect the frequency peak due to the joint pressure vibration.

In order to solve this problem, the present invention introduces a noise filter 12 into the inlet part 6 of the pipe part 1 to remove the noise component of the frequency caused by the noise, thereby accurately measuring the flow rate of the fluid. Make sure

In addition, in the present invention, in order to solve the disadvantage that the strength of the pressure vibration in the cavity is small and cannot be measured when the flow velocity of the fluid is small, the flow path of the flow path downstream of the noise filter 12 of the inlet part 6 is solved. By installing a nozzle-shaped flow path contracting portion 7 that has a narrow area and allowing the fluid flow rate to be small, a certain flow rate or more can be output through the flow path contracting portion 7 to measure the frequency by the pressure vibration of the fluid when the flow rate is small. The fluid flow rate measurement range of the fluid was broadened easily.

In addition, a diffuser-shaped flow path expansion part 11 is installed at the end of the tube so that the fluid can be reduced to the state before passing through the flow path contraction part 7.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The cavity flow meter of the present invention detects and converts the pipe part 1 through which the fluid flows, the cavity 2 through which the fluid flowing through the pipe part 1 generates pressure vibration, the pressure vibration generated in the cavity, and converts it into frequency. It is composed of an electronic unit 13 for displaying the accumulated frequency formed on the detected pressure accumulation on the screen.

More specifically, in the pipe part 1, the inlet part 6 of the fluid is a noise filter 12, which is densely packed with a spherical body or a fiber so that noise propagating along the fluid does not interfere with the cavity vibration. And a cavity (2, Cavity) is installed at the downstream side of the noise filter (12, Noise Filter) to allow the introduced fluid to generate a cavity vibration, and the pipe part (1) can measure the pressure of the flow fluid. There is a static pressure detection hole (9) and the temperature sensor insertion hole (10) that can detect the temperature of the flow fluid can measure the thermodynamic state of the fluid by measuring the pressure and temperature of the flow fluid. By knowing the thermodynamic state of the fluid, it is possible to convert the measured volume flow of the fluid into the mass flow of the fluid.

More specifically, the outer shape of the noise filter 12 is formed along the shape of the pipe 1, and as shown in FIG. 8, the case 20 of the noise filter 12 is shown. ) And the spherical body or fiber in the case 20 to be densely packed in the maximum density structure by filling the screw fastener 21, and filled in the noise filter (12, Noise Filter) By allowing the amount of spherical body or fiber to be adjusted, the fluid flowing into the inlet part 6 of the pipe part 1 is disturbed in the flow rate distribution and the structure of the sound wave existing therein, so that the fluid is a noise suppressor (12). , The noise wave and the like cannot be transmitted downstream through the Noise Filter. Further, the spherical body and the fiber may be made of steel or ceramic in the case of the spherical body, and may be made of fiber such as an optical fiber or a polyester in the case of the fiber according to the type and chemical characteristics of the fluid used. Various materials are available. For example, in general, a spherical body of steel is used, but a ceramic or the like is used to measure the flow rate of a corrosive or hot fluid. In addition, the size of the spherical body may also vary depending on the use environment. In general, the larger the size of the unit spherical body is, the smaller the void loss due to the flow of fluid due to the larger air gap, and easier to manufacture. On the contrary, the smaller the size of the unit spherical body is, after passing through the noise filter 12, NoiseFilter Since the blocking effect of the sound waves of the fluid is large, it is necessary to appropriately control such conflicting requirements. This may also depend on the average flow rate of the fluid and the nature of the fluid. In addition, the arrangement of the fibers may also be various, such as a net-shaped form or simply entangled with each other.

4 is a cross-sectional view showing a noise filter 12 attached to a cavity flowmeter. As shown in the drawing, the inlet part 6 of the pipe part 1 is provided with a noise filter 12, and the fluid flowing along the flow path 8 is discharged from the cavity 2 to which the pressure sensor 3 is attached. It is provided to generate the cavity vibration, the positive pressure sensing hole 9 and the temperature sensing hole 10 is installed at the end of the pipe part 1 to detect the pressure and temperature of the fluid.

5 shows another embodiment of the cavity flowmeter, the nozzle-shaped flow path contracting portion 7 and the cavity 2 between the noise filter 12 and the cavity 2 in the cavity flowmeter of FIG. A diffuser-shaped flow path expansion portion 11 is further included between the outlet portion 5 and the outlet portion 5.

6 and 7 show an enlarged view of the A-A 'cross section of FIGS. 4 and 5 and a perspective view of the cavity attached to the tube.

The noise filter 12 installed in the pipe section 1 of the present invention has a noise filter 12 inside the noise filter 12, as shown in FIG. 8 showing an enlarged view of the noise filter 12. A spherical body or a fiber is densely packed in a maximum dense structure by tightening the screw fastening portion 21 to the case 20. Preferably, the spherical body is a steel ball or a ceramic ball, and the fiber is an optical fiber or a poly It is a fibrous material such as ester and the like, and the noise filter 12 serves to block noise propagating along the fluid flowing into the inlet 6 so as to automatically detect the frequency peak of the fluid generated in the cavity. 19) to be detected automatically.

FIG. 10 and FIG. 11 are frequency spectra of pressure fluctuations of a fluid generated in a cavity captured by a spectrum analyzer. Is a frequency spectrum detected in a conventional cavity flowmeter without a noise filter 12, and FIG. 11 shows a frequency spectrum detected in a cavity flowmeter of the present invention with a noise filter. .

As shown in Figs. 10 and 11, the peak was manually picked at 446 Hz in Fig. 10, but the peak was not detected automatically by the signal auto tracker 19 because the signal-to-noise ratio was close to 1.0. On the other hand, looking at the frequency spectrum of the present invention of Fig. 11, it can be seen that the signal-to-noise ratio of the peak at 448 Hz is large, so that the peak can be automatically detected by the signal auto tracker 19.

As described above, the present invention, despite the advantages of the cavity flowmeter, the signal-to-noise ratio of the frequency spectrum due to the pressure oscillation of the fluid generated in the cavity is small, so that the accurate flow rate cannot be measured automatically, its use is insufficient. In this way, the joint flowmeter could be actively used.

According to the cavity flowmeter with the noise filter 12 according to the present invention, the vibration frequency caused by the pressure vibration of the fluid can be accurately and conveniently by disturbing the cavity and the noise wave of the fluid causing the pressure vibration of the fluid. It can be measured.

In addition, in the joint flowmeter with a noise filter 12 according to the present invention, the noise filter 12 has a simple structure, simple structure, and no swinging part, so that its design and processing cost are high. Very little, and the cavity flowmeter also has a self-cleaning effect of foreign matter that can accumulate in the cavity when the cavity is positioned on the upper portion of the pipe 1, and thus does not require cleaning and maintenance. In view of the fact that the measuring equipment is much more expensive to maintain and repair than the initial design and installation cost, this joint flowmeter has no swinging part and has a self-cleaning effect.

In addition, according to the cavity type flow meter according to the present invention, the flow rate and the frequency are directly proportional to each other, and the detection of the frequency peak can be made accurately and simply so that the flow rate can be accurately measured. In addition, the cavity flowmeter of the present invention is easier to design and manufacture the signal processor because it is not sensitive to the pressure or temperature change of the fluid compared to the vortex flowmeter, and the cavity can use the same size standard cavity regardless of the pipe diameter. Therefore, the manufacturing cost of a large flow meter to be installed in a large diameter pipe is greatly reduced.

As such, the present invention provides a common flow meter that is accurate, reliable, and significantly reduced in cost.

Claims (5)

In the cavity 1, the cavity 2 for generating the pressure vibration of the fluid in the pipe part 1 is installed, and the flow rate is measured by measuring the frequency caused by the pressure vibration of the fluid in the cavity 2, A noise suppressor 12 is provided upstream of the cavity 2 to prevent noise propagating along the fluid entering the inlet 6 of the pipe 1 from interfering with the pressure vibration in the cavity 2 of the fluid. Joint flowmeter, characterized in that there is. The cavity type flow meter according to claim 1, wherein the silencer (12) is densely packed in a maximum dense structure by tightening a screw tightening portion (21) in the case (20). The cavity flow meter according to claim 1, wherein the noise suppressor (12) is filled with a fiber in the case (20) by tightening the screw tightening portion (21). The cavity according to any one of claims 1 to 3, wherein a nozzle-shaped flow path contracting portion (7) is provided between the noise suppressor (12) of the pipe portion (1) and the cavity (2). Food flow meter. The cavity flow meter according to claim 4, wherein a diffuser-shaped flow path expansion portion (1) is provided between the cavity (2) and the outlet portion (5).