KR100937472B1 - Differential pressure flow meter - Google Patents

Abstract

The present invention relates to a differential pressure flow meter in which a pressure gauge for measuring the pressure of a fluid is composed of an optical fiber pressure sensor, and the differential pressure flow meter according to the present invention has an internal space through which a fluid can flow, and an throttle portion having an narrow internal cross section. A main body having a main body, detecting means installed at upper and lower sides of the throttle part to detect a pressure of the fluid, and receiving the pressure detected by the detecting means as an electrical signal, and the pressure difference at each point. It is provided with a control means for calculating the flow rate of the fluid passing through the main body and displaying it, the detection means is an optical fiber pressure sensor.

Differential pressure flow meter according to the present invention has the advantage that can accurately calculate the flow rate by measuring the exact pressure of the fluid inside the pipe through the optical fiber pressure sensor.

Differential pressure flow meter, optical fiber, pressure sensor

Description

Differential pressure flowmeter

The present invention relates to a differential pressure flow meter, and more particularly, to a differential pressure flow meter in which a pressure gauge for measuring the pressure of a fluid comprises an optical fiber pressure sensor.

There are various types of flowmeters, but there are relatively widely used flowmeters such as vane flowmeters, differential pressure flowmeters and area flowmeters. Among them, the vane flow meter is the simplest, and the vane is turned by the flow, and the rotation speed is instructed by the mechanism of the gear. As you can see in the surroundings, water meters use this.

The area expression puts a float in the pressure detector tube that is widened upwards, flows the fluid from the bottom up, and balances the weight of the float with the buoyancy caused by the differential pressure before and after the float pushed up into the fluid stream. Know the flow rate at the location. In addition, the volume of the fluid is directly measured in a container of a constant volume, the gas meter of the city gas is a kind.

Differential pressure flowmeters are mainly used in the industrial field, and the flow rate is detected by using the pressure difference of the fluid generated at the front and rear of the throttle by installing the cooking utensils, venturi tubes, flow nozzles, etc. in the pipeline. That's the way it is.

Bernoulli's law states that shrinking a portion of a pipeline through which a fluid flows increases the velocity and decreases the pressure as the fluid passes through the section, creating a constant relationship between the flow rate and the back and forth pressure of the pipeline. The differential pressure is converted into the measured flow rate.

Therefore, the pressure sensor for measuring the pressure in the differential pressure flow meter is very important. Conventional sensors for measuring pressure can be classified into mechanical, electrical, and semiconductor types according to the detection method. For these pressure sensors, precise pressure measurement is difficult, and to compensate for this, if pressure sensitivity is increased, pressure measurement is performed. The range becomes very narrow and there is a problem that it is difficult to accurately measure the pressure to be measured in order to calculate the accurate flow rate if the sensitivity is not good if you want to measure a wide range of pressure.

An object of the present invention is to provide a differential pressure flow meter for measuring the pressure of the fluid before and after the throttle using an optical fiber pressure sensor for accurate measurement of the flow rate.

The differential pressure flow meter according to the present invention for achieving the above object has an internal space through which fluid can flow, and a main body having an throttle portion whose inner cross-sectional area is narrowed, and fixed portions on the upper and downstream sides of the throttle portion, respectively. A detection means installed to detect the pressure of the fluid, and a control means for receiving the pressure detected by the detection means as an electrical signal to calculate and display a flow rate of the fluid passing through the main body using the pressure difference between the points. It is provided, the detection means is made of an optical fiber pressure sensor.

The fixing part may be formed as a fixing band for tightly fixing the optical fiber pressure sensor to the outer peripheral surface of the main body so that the optical fiber pressure sensor can measure the pressure of the fluid through the deformation amount of the main body according to the pressure of the fluid.

The main body has first and second pressure outlets formed on the upstream side and the downstream side of the throttle part, respectively, and communicates with the inside of the main body from the first and second pressure outlets. The detection tube is extended, and the fixing portion secures the optical fiber pressure sensor to be introduced into the first and second pressure detection tube to a predetermined depth, and includes a housing coupled to the main body to seal the first and second pressure outlets. In addition, the control means may be installed on the upper portion of the housing.

In addition, the main body has a bellows-type expansion and contraction is formed in the longitudinal direction by the pressure of the fluid on the upstream side and the downstream side around the throttle portion, respectively, the optical fiber pressure sensor measures the pressure by the amount of deformation of the expansion portion It may be installed so as to contact the expansion and contraction.

Differential pressure flow meter according to the present invention has the advantage that can accurately calculate the flow rate by measuring the exact pressure of the fluid inside the pipe through the optical fiber pressure sensor.

Referring to the accompanying drawings in more detail with respect to the differential pressure type flow meter according to the present invention.

1 and 2 show a first embodiment of a differential pressure flow meter 10 according to the invention. Referring to the drawings, the differential pressure flow meter 10 includes a main body 11 having an internal flow path, first and second optical fiber pressure sensors 14 and 15 provided on an outer circumferential surface of the main body 11, and a main body 11. It is coupled to the outer circumferential surface, the housing 16 surrounding the first and second optical fiber pressure sensors 14 and 15, and the inside of the housing 16 is installed in the first and second optical fiber pressure sensor (14, 15) Control means 20 to calculate the flow rate through the measured measurement value, and display so that the user can recognize.

The main body 11 is provided with a flow path through which fluid can move. And the throttle part 12 which becomes narrow gradually the width | variety of a flow path on the inner flow path, The both ends of the main body 11 is provided with the flange part 13 so that it may be connected to the conveying pipe of a fluid. The main body 11 is made of a material having an elastic force to be expanded by the pressure of the fluid when the fluid moves through the inner flow path.

First and second optical fiber pressure sensors 14 and 15 are attached to the outer circumferential surface of the main body 11. The first and second optical fiber pressure sensors 14 and 15 are for measuring the pressure of the fluid flowing inside the body 11, and the first optical fiber pressure sensor 14 is upstream of the throttle part 12. It is provided so as to measure the pressure of the fluid on the side, and the second optical fiber pressure sensor 15 is provided in the main body 11 so as to measure the pressure of the fluid on the downstream side.

The first and second optical fiber pressure sensors 14 and 15 all have the same structure.

The first and second optical fiber pressure sensors 14 and 15 have an optical fiber for reference signal, an optical fiber for pressure measurement, and a light source for supplying light to the two optical fibers, and an optical signal for detecting an optical signal passing through the optical fiber. With a detector. In the optical fiber for the reference signal, a constant optical signal is detected regardless of the pressure of the fluid. On the other hand, the pressure measuring optical fiber is installed to surround the elastic body in contact with the outer circumferential surface of the main body 11, and when the main body 11 expands or deforms due to the pressure of the fluid, the elastic body deforms together according to the deformation of the main body 11. This will happen. The optical fiber for pressure measurement changes in length, refractive index, and diameter in accordance with the shape deformation of the elastic body. Accordingly, even when an optical signal is applied from the same light source, an optical signal having a phase difference from that of the reference signal optical fiber is detected. Therefore, the pressure of the fluid can be measured through the phase difference of the optical signal according to the externally applied pressure.

The control means 20 calculates the flow rate of the fluid based on the pressure measurement values of the fluids measured by the first and second optical fiber pressure sensors 14 and 15, and displays the numerical value for the user to recognize. The means 20 includes a calculation unit 21 and a display unit 22 exposed to the upper surface of the housing 16 so that the calculation result of the calculation unit 21 can be recognized from the outside.

The calculation unit 21 calculates the flow rate based on the pressure values measured at each point, that is, the first and second optical fiber pressure sensors 14 and 15, and the flow rate calculation is based on the continuous law and the Bernoulli equation.

Assuming that the density is constant irrespective of the pressure change of the fluid, the area of the point where the first optical fiber pressure sensor is installed is A ₁ [㎥], the flow rate is V ₁ [㎨], and the pressure is P ₁ [㎏ / ㎡]. When the area of the point where the second optical fiber pressure sensor is installed is A ₂ [㎥], the flow rate is V ₂ [㎨], and the pressure is P ₂ [㎏ / ㎡], the upstream point and the downstream point if the pipeline is horizontal. The flow rate of the fluid flowing through the same is the same.

Q = A ₁ v ₁ = A ₂ v ₂

The energy relationship at the upstream and downstream locations is:

와 같이 표기될 수 있으며,If the tube is horizontal, the potential energy is the same.

Can be written as:

로 나누게 되면

과 같은 결과가 도출된다.On both sides

Divided by

The result is as follows.

이므로

이며,

Because of

,

에 대해 정리한 것을 대입하면

가 된다.In the Law of Consecutive Continuity

Substituting the summation for

Becomes

)은

(n:기준상태,T:절대온도(T=273.15+℃,P:절대압력)In the case of measuring the gas fluid, the gas flow rate varies greatly depending on the temperature and pressure. Therefore, an error occurs when the differential pressure flow meter 10 calculates and measures the same with the incompressible fluid. If the measurement gas is an ideal gas, Boyle-Charles' law states that

)silver

(n: reference condition, T: absolute temperature (T = 273.15 + ℃, P: absolute pressure)

If the weight flow rate of the compressive fluid is substituted into the equation

= 기체 팽창 보정계수(0.01252),

= 유량계수(

)}{

= Gas expansion correction factor (0.01252),

= Flow coefficient (

)}

Get

Therefore, as can be seen from this, it is possible to obtain a correct flow rate by measuring the differential pressure of the fluid and at the same time measuring the pressure and temperature of the fluid and accurately correcting the reference value and obesity in the design of the flowmeter.

The calculating unit 21 calculates the flow rate through the pressure values measured by the first and second optical fiber pressure sensors 14 and 15 through the above process.

In the present embodiment, since the differential pressure flow meter 10 measures the flow rate of the incompressible fluid, a temperature sensor is not installed. However, in the case of the differential pressure flow meter 10 for measuring the flow rate of the compressive fluid such as gas as described above, A separate temperature sensor for measuring the temperature of the side point and the downstream point to transmit information to the calculation unit 21 will be further provided.

The flow rate calculated by the calculator 21 is displayed to be recognized by the manager through the display 22.

The display unit 22 is connected to the operation unit 21 and is exposed to the outside through the upper surface of the main body 11. Since the flow rate calculated by the calculator 21 is numerically displayed through the liquid crystal display 23 of the display unit 22, the manager can easily grasp the flow rate.

The housing 16 is coupled to the main body 11 so as to surround the first and second optical fiber pressure sensors 14 and 15, and a power button for intermittent the power of the differential pressure flow meter 10 on the upper portion of the housing 16. (17), a reset button 18 for re-measurement of the flow rate, and a start button 19 for starting the flow rate measurement are provided.

3 shows a second embodiment of the differential pressure flow meter 30 according to the present invention. Referring to FIG. 3, the differential pressure flow meter 30 extends into the main body 31 and an internal flow path of the main body 31. First and second pressure detection pipes 35 and 36, third and fourth optical fiber pressure sensors 37 and 38 and control means inserted into the first and second pressure detection pipes 35 and 36. 20 is provided.

The main body 31 of this embodiment is open at both sides so that the fluid can be introduced and discharged, the flange portion 33 is formed to facilitate the connection with the outer tube. In addition, an throttle portion 32 is formed on the inner flow path so that the width of the pipe narrows, and the outer and inner spaces of the main body 31 communicate with the upstream side and the downstream side of the main body 31 around the throttle portion 32, respectively. A pressure outlet 34 is formed.

The first and second pressure detection pipes 35 and 36 provide an installation space in which the third and fourth optical fiber pressure sensors 37 and 38 can be installed, and the pressure outlet 34 of the main body 31 is provided. It is installed to extend into the body 31 through. It is preferable to perform a sealing treatment on the coupling portion with the first and second pressure detection pipes 35 and 36 to prevent the external air from flowing into the main body 31 through the pressure outlet 34.

The first and second pressure detection pipes 35 and 36 are open downward so that the fluid pressure is lowered through the lower portions of the first and second pressure detection pipes 35 and 36 when the fluid passes through the main body 31. The first and second pressure detection pipes 35 and 36 are transferred into the interior.

The third and fourth optical fiber pressure sensors 37 and 38 of the optical fiber received by the photodetector when the deformation is caused by the pressure of the fluid delivered through the first and second pressure detection pipes (35, 36). The phase difference is used to measure the pressure of the fluid at each point.

Since the third and fourth optical fiber pressure sensors 37 and 38 of the present embodiment measure the pressure of the fluid on the same principle as the first and second optical fiber pressure sensors 14 and 15 of the first embodiment, a detailed description thereof is omitted. do.

In addition, although not shown, the control means including the operation unit and the display unit of the present embodiment is installed so as to be adjacent to the main body 31, the operation unit in the same manner as the operation unit 21 of the first embodiment the third, fourth optical fiber pressure sensor The flow rate is calculated using the pressure measurement at (37,38), and the display unit digitizes it and displays it for the user to recognize.

In the present embodiment, the lower portions of the first and second pressure detection pipes 35 and 36 are open, and the pressure of the fluid flowing through the open portion is directly transmitted to the third and fourth optical fiber pressure sensors 37 and 38. It is intended to be authorized. However, when the fluid passing through the main body 31 is a fluid that cannot directly contact the optical fiber pressure sensor, such as causing corrosion to the optical fiber pressure sensor, it forms a separate protective layer for protecting the optical fiber pressure sensor, The deformation of the protective layer caused by the pressure of the optical fiber pressure sensor may be formed to measure the pressure of the fluid.

4 shows a third embodiment of a differential pressure flow meter 40 according to the present invention. Referring to the drawings, the differential pressure flow meter 40 includes a main body 41 and a fifth, And sixth optical fiber pressure sensors (45, 46) and control means.

The main body 41 has a narrow throttle portion 42 of the flow path therein, and a flange portion 44 is provided at both ends to facilitate engagement with the fluid transfer pipe, and on both sides of the throttle portion 42. An elastic bellows type elastic part 43 is formed. When the fluid flows, the elastic part 43 is elongated by a predetermined length along the longitudinal direction when the fluid is under pressure.

The fifth and sixth optical fiber pressure sensors 45 and 46 for measuring the pressure of the fluid are attached to the elastic part 43.

When the elastic part 43 is expanded by the pressure of the fluid, the fifth and sixth optical fiber pressure sensors 45 and 46 attached to the elastic part 43 are extended by the elastic part 43, and thus the fifth The phase difference between the optical signal received by the photodetector occurs as a difference in the refractive index and the length of the reference signal optical fiber and the pressure measuring optical fiber embedded in the sixth optical fiber pressure sensors 45 and 46. Based on this, the fifth and sixth optical fiber pressure sensors 45 and 46 measure the pressures on the upstream and downstream sides of the throttle portion 42.

Although not shown, the calculation unit of the control means is electrically connected to the fifth and sixth optical fiber pressure sensors 45 and 46 so as to receive the pressure measurement value of the fluid, and based on the pressure measurement values on both sides of the main body. The flow rate of the fluid passing through (41) is calculated. Since the calculation process of the flow rate and the display method of the display unit are the same as in the first embodiment, detailed description thereof will be omitted.

1 is a partially cut perspective view showing a first embodiment of a differential pressure flow meter according to the present invention;

2 is a block diagram showing the flow rate calculation and display step of FIG.

3 is a partially cut perspective view showing a second embodiment of a differential pressure flow meter according to the present invention;

4 is a sectional view showing a third embodiment of a differential pressure flow meter according to the present invention;

Claims (4)

delete delete delete A main body having an internal space through which the fluid can flow, and an throttle having an narrow internal cross section; Detecting means installed on the upstream and downstream sides of the throttle part by a fixing part to detect a pressure of the fluid; And control means for receiving the pressure detected by the detecting means as an electrical signal, calculating a flow rate of the fluid passing through the main body using the pressure difference between the respective points, and displaying the same. The detecting means is an optical fiber pressure sensor, The main body has a bellows type elastic part which is stretched along the longitudinal direction of the main body by the pressure of the fluid on the upstream side and the downstream side around the throttle part, respectively, The optical fiber pressure sensor is a differential pressure flow meter, characterized in that installed in contact with the expansion and contraction portion so that the pressure can be measured by the amount of deformation of the expansion and contraction portion.

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