A liquid flow rate monitoring system and method based on an optical fiber probe

Abstract

The application provides a liquid flow rate monitoring system and method based on an optical fiber probe. The liquid flow rate monitoring system comprises a liquid storage tank, the sealed tank body is divided into an inner central cylindrical chamber and an outer annular cavity by a cylindrical partition, both upper and lower parts are connected, and liquid can circulate in the tank; an arc or U-shaped ring channel connected with the annular cavity and a heating wire wound on the ring channel are arranged on the sealed tank body, bubbles are generated by heating the heating wire after the liquid passes through the ring channel, and a double-probe optical fiber probe sensor is arranged at the position where the liquid passes through. The time difference of the bubbles passing through the two probes of the optical fiber probe sensor is determined by an optical fiber cavity demodulator receiving the optical signals collected by the two probes of the optical fiber probe sensor, and then the moving speed of the bubbles, i.e. the liquid speed, is calculated. The application has high safety and can realize accurate and rapid measurement of the liquid flow rate in the sealed storage tank.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of optical fiber sensing, and particularly relates to a liquid flow rate monitoring system and method based on an optical fiber probe. BACKGROUND

[0002] Optical fiber sensing technology is a new sensing technology developed along with optical fiber and optical fiber communication technology, and is the fastest high-tech application technology in the world since the mid-1970s. With the gradual maturity of optical fiber manufacturing technology, optical fiber sensors are widely used in many occasions such as temperature monitoring and pressure measurement due to their advantages of high temperature and pressure resistance, electrical passivity, and strong anti-interference ability of strong electricity, strong magnetism and strong radiation. In the 1980s, optical fiber sensor technology ushered in an important technical breakthrough, and various new optical fiber sensors such as interference type optical fiber sensors and optical fiber grating sensors were successively put into use. Not only the measurement accuracy and stability are improved, but also the application field of optical fiber sensing technology is expanded.

[0003] In the chemical industry, general chemical reactions occur in sealed storage tanks, so there are strict requirements for liquid flow rate. Too fast liquid flow rate may cause equipment damage or leakage; too slow liquid flow rate may affect the reaction rate or product quality. In order to ensure production safety and quality control and monitoring, the liquid flow rate in the sealed tank needs to be monitored. At present, the most commonly used way for liquid flow rate measurement is ultrasonic flow meter, which uses the principle that the time difference between the upstream and downstream propagation of sound waves in the fluid is proportional to the liquid flow rate to measure the liquid flow rate. However, this method requires high purity of the liquid, and impurities or bubbles in the liquid will cause the incident angle of ultrasonic waves to deviate, reducing the accuracy of measurement. In view of the problems existing in ultrasonic flow meter, the application uses optical fiber double probe sensor to measure the liquid flow rate in the sealed storage tank. This method is less affected by the environment, has strong anti-electromagnetic interference ability, can be remotely monitored, and provides a new technical means for liquid flow rate measurement. SUMMARY

[0004] The application provides a liquid flow rate monitoring system and method based on an optical fiber probe to meet the demand for measuring the liquid flow rate in a sealed storage tank. The system combines an optical fiber demodulation system to realize accurate and rapid measurement of the liquid flow rate in the sealed storage tank, and provides a new technical method for measuring the liquid flow rate in the sealed tank.

[0005] In order to achieve the above technical purpose, the application provides a liquid flow rate monitoring system based on an optical fiber probe, which comprises a liquid storage tank, a bubble generating device, an optical fiber probe sensor and an optical fiber demodulation system.

[0006] The liquid storage tank comprises a sealed tank body, the sealed tank body is divided into an inner central cylindrical chamber and an outer annular cavity by a cylindrical partition plate, a plurality of holes are formed in the upper part of the cylindrical partition plate, and the central cylindrical chamber and the annular cavity are communicated through the plurality of holes; a first liquid flow hole is arranged at the bottom of the central cylindrical chamber, a second liquid flow hole is arranged at the bottom of the annular cavity, and the first liquid flow hole and the second liquid flow hole are communicated.

[0007] The bubble generating device comprises an arc-shaped or U-shaped ring channel arranged on the sealed tank body and a heating wire wound on the ring channel, the ring channel is communicated with the annular cavity, and the heating wire is used for generating bubbles by heating after the liquid passes through the ring channel.

[0008] The fiber probe sensor is a double-probe fiber probe sensor, which is arranged directly below the bubble generating device, two probes of the fiber probe sensor are arranged in the annular cavity, and the two probes are arranged on the moving path of the bubbles generated by the bubble generating device.

[0009] The fiber demodulation system comprises a fiber cavitation demodulator, a sensing optical cable and a fiber cavitation demodulation module in an upper computer, the fiber probe sensor is signal-connected with the fiber cavitation demodulator through the sensing optical cable, and the fiber cavitation demodulator is signal-connected with the fiber cavitation demodulation module in the upper computer.

[0010] The fiber cavitation demodulator is used for receiving optical signals collected by the two probes of the fiber probe sensor, transmitting the optical signals to the fiber cavitation demodulation module in the upper computer after processing, and judging gas-liquid by the fiber cavitation demodulation module in the upper computer, so that the time difference of the bubbles passing through the two probes of the fiber probe sensor is judged. 气泡 The moving speed V of the bubbles is calculated according to the time difference, and the calculation formula is as follows:

[0011]

[0012] Wherein, S is the distance between the two probes of the fiber probe sensor.

[0013] t is the time difference of the bubbles passing through the two probes of the fiber probe sensor.

[0014] Without considering the buoyancy of the bubbles, the moving speed of the bubbles is the flow rate of the liquid in the tank, that is, V 气泡 = V 液体 .

[0015] The vertical distance between the two probes of the fiber probe sensor is greater than the diameter of a single bubble and less than the diameter of two bubbles.

[0016] The preferred technical technical scheme of the present application: the optical fiber probe sensor includes a connector, a pigtail segment, an FC / APC joint and two groups of optical fiber probes, the two groups of optical fiber probes are arranged side by side, the lengths of the two probes are different, the two probes are connected with the pigtail segment through the connector, and the two probes are output through the FC / APC joint.

[0017] The preferred technical technical scheme of the present application: the bubble generating device is provided with four groups, which are arranged at the positions with the same height in the four directions of the liquid storage tank, two groups of optical fiber probe sensors are arranged below each group of bubble generating devices, the probes of the two groups of optical fiber probe sensors are inserted into the annular cavity, and the two groups of optical fiber probe sensors are arranged side by side on the bubble moving path generated by the corresponding bubble generating device.

[0018] The preferred technical technical scheme of the present application: the optical fiber probe sensor is fixed on the liquid storage tank by using the sealing assembly in the transverse direction.

[0019] The present application also provides a liquid flow rate monitoring method based on an optical fiber probe, which uses the above-mentioned liquid flow rate monitoring system based on an optical fiber probe to monitor the liquid flow rate in a sealed liquid storage tank, and the specific steps are as follows:

[0020] S1. The multiple holes on the upper part of the cylindrical partition in the sealed liquid storage tank, the first liquid flow hole at the bottom of the central cylindrical chamber and the second liquid flow hole at the bottom of the annular cavity are arranged to circulate the liquid between the cylindrical chamber and the external annular cavity of the tank body;

[0021] S2. After the liquid reaches the external annular cavity, the liquid is heated by the heating wire wound on the arc-shaped or U-shaped ring channel, so that the liquid generates bubbles;

[0022] S3. The bubbles follow the liquid flow direction, pass through the double-probe optical fiber probe sensor, and are monitored by the two probes of the double-probe optical fiber probe sensor;

[0023] S4. The two probes of the double-probe optical fiber probe sensor transmit the monitored signals to the optical fiber demodulation system, and the signals are transmitted to the optical fiber cavity demodulation module in the host computer after being processed by the optical fiber demodulation system, and the gas-liquid judgment is performed by the optical fiber cavity demodulation module in the host computer, so as to judge the time difference of the bubbles passing between the two probes of the optical fiber sensor, and calculate the bubble rate according to the time difference of the bubbles passing between the two probes of the double-probe optical fiber sensor, and calculate the flow rate of the liquid in the storage tank according to the bubble rate.

[0024] The preferred technical technical scheme of the application: in the S4 step, the bubble rate is calculated according to the time difference of the bubble passing between the two probes of the double-probe optical fiber sensor, and the specific process of calculating the flow rate of the liquid in the storage tank by the bubble rate is as follows:

[0025] ①If the buoyancy of the bubble in the liquid is not considered, the bubble rate is the liquid flow rate, and the calculation formula is as follows:

[0026]

[0027] Wherein, S is the distance between the two probes, and t is the time difference of the bubble passing through the two probes;

[0028] ②If the buoyancy of the bubble in the liquid is considered, according to Stokes law; when the liquid flows from top to bottom, the liquid flow rate is calculated as follows:

[0029]

[0030] When the liquid flows from bottom to top, the liquid flow rate is calculated as follows:

[0031]

[0032] Wherein, p 液 is the density of the liquid in the sealed tank;

[0033] p 气 is the density of the gas in the bubble, generally taking the density of air;

[0034] C d is the drag coefficient, and the drag coefficient is 0.45;

[0035] g represents the acceleration of gravity.

[0036] The preferred technical technical scheme of the application: in the S4 step, the bubble rate is calculated according to the time difference of the bubble passing between the two probes of the double-probe optical fiber sensor, and the specific process of calculating the flow rate of the liquid in the storage tank by the bubble rate is as follows:

[0037] The liquid circulates from bottom to top, specifically, from the flow hole at the bottom of the central cylindrical chamber of the tank body upwards, enters the external annular cavity through the multiple holes at the upper part of the cylindrical partition, and after reaching the external annular cavity, flows downwards through the arc-shaped or U-shaped ring channel, the liquid in the arc-shaped or U-shaped ring channel is heated by the heating wire wound on the arc-shaped or U-shaped ring channel, so that the liquid generates bubbles; the bubbles enter the peripheral annular cavity of the tank body again from the arc-shaped or U-shaped ring channel along the liquid flow direction, and flow again to the bottom of the central cylindrical chamber through the multiple holes at the upper part of the cylindrical partition.

[0038] The liquid circulates from bottom to top, specifically, from the flow hole at the bottom of the central cylindrical chamber of the tank body upwards, enters the external annular cavity through the multiple holes at the upper part of the cylindrical partition, and after reaching the external annular cavity, flows downwards through the arc-shaped or U-shaped ring channel, the liquid in the arc-shaped or U-shaped ring channel is heated by the heating wire wound on the arc-shaped or U-shaped ring channel, so that the liquid generates bubbles; the bubbles enter the peripheral annular cavity of the tank body again from the arc-shaped or U-shaped ring channel along the liquid flow direction, and flow again to the bottom of the central cylindrical chamber through the multiple holes at the upper part of the cylindrical partition.

[0039] The cavitation demodulator amplifies, denoises and converts the optical signal returned by the sensor into an electrical signal through a hardware mode, and does not have a built-in CPU; the cavitation demodulation software compares the electrical signal with a certain threshold value, judges the gas-liquid, and visualizes the signal.

[0040] The optical fiber probe sensor can be electrically passive, so it has high safety; this method has high safety, high measurement accuracy, good corrosion resistance and chemical stability, and provides a new technical method for measuring the liquid flow rate in a sealed tank, and can realize accurate and rapid measurement of the liquid flow rate in the sealed storage tank. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 It is a system schematic diagram of the present application;

[0042] Figure 2 It is an optical fiber probe sensor in the present application;

[0043] Figure 3 It is an enlarged schematic view of the probe part of the optical fiber probe sensor in the present application;

[0044] Figure 4 It is an internal structure diagram of the liquid storage tank in the present application.

[0045] In the diagram: 1—Fiber optic cavitation demodulator, 2—Host computer, 3—Liquid storage tank, 300—Sealed tank, 301—Hole, 302—Annular cavity, 303—Central cylindrical chamber, 304—First liquid flow hole, 305—Second liquid flow hole, 4—Heating device, 5—Arc-shaped or U-shaped ring channel, 6—Fiber optic probe sensor, 601—Fiber optic probe, 602—Connector, 603—Pigtail, 604—FCA connector; 7—Sensing optical cable. Detailed Implementation

[0046] To make the technical solutions and advantages of the present invention easier to understand, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. The accompanying drawings are drawn in a simplified manner and are only used for the purpose of clearly and concisely illustrating the purpose of this patent. The technical solutions shown in the accompanying drawings below are specific solutions of this patent and are not intended to limit the scope of the claimed invention. Based on the embodiments of the present invention, all other patents obtained by those skilled in the art without inventive effort are within the scope of protection of this patent.

[0047] Example 1 provides a liquid flow rate monitoring system based on an optical fiber probe, such as... Figures 1 to 4 As shown, the liquid flow rate monitoring system includes a liquid storage tank 3, a bubble generating device, an optical fiber probe sensor 6, and an optical fiber demodulation system. The liquid storage tank 3 includes a sealed tank body 300, which is divided into an inner central cylindrical chamber 303 and an outer annular chamber 302 by a cylindrical partition. Multiple holes 301 are provided in the upper part of the cylindrical partition, and the central cylindrical chamber 303 and the annular chamber 302 are connected through the multiple holes 301. The bottom of the central cylindrical chamber 303 is provided with a first liquid flow hole 304, and the bottom of the annular chamber 302 is provided with a second liquid flow hole 305. The first liquid flow hole 304 and the second liquid flow hole 305 are connected. The bubble generating device includes an arc-shaped or U-shaped ring channel 5 disposed on the sealed tank body 300 and a heating wire 4 wound on the ring channel 5. The ring channel 5 is connected to the annular chamber 302, and bubbles are generated by heating the liquid through the heating wire 4 after it passes through the ring channel.

[0048] Example 1 provides a liquid flow rate monitoring system based on an optical fiber probe, such as... Figures 1 to 4As shown, the fiber probe sensor 6 is a double-probe fiber probe sensor, which includes a connector 602, a pigtail segment 603, an FC / APC joint 604, and two groups of fiber probes 601 arranged side by side, connected with the pigtail segment 603 through the connector 602, and output through the FC / APC joint 604. The vertical distance between the two probes of the fiber probe sensor 6 is greater than the diameter of a single bubble and less than the diameter of two bubbles. The fiber probe sensor 6 is arranged directly below the bubble generating device, the two probes of the fiber probe sensor 6 extend into the annular cavity 302, and the two probes are arranged side by side above and below the moving path of the bubbles generated by the bubble generating device; the fiber probe sensor 6 is fixed on the liquid storage tank 3 laterally by using a sealing assembly.

[0049] In the embodiment, in order to monitor accurately, the bubble generating device is provided with four groups, which are arranged at the same height in four directions of the liquid storage tank. Two groups of fiber probe sensors 6 are arranged below each group of bubble generating devices. The probes of the two groups of fiber probe sensors 6 extend into the annular cavity 302, and the two groups of fiber probe sensors 6 are arranged side by side above and below the moving path of the bubbles generated by the corresponding bubble generating device.

[0050] In the embodiment, the fiber demodulation system includes a fiber cavitation demodulator 1, a sensing optical cable 7, and a fiber cavitation demodulation module in the upper computer 2. Eight groups of fiber probe sensors 6 are connected with the fiber cavitation demodulator through the sensing optical cable 7, and the fiber cavitation demodulator is connected with the fiber cavitation demodulation module in the upper computer. The fiber cavitation demodulator amplifies, denoises, and converts the optical signal returned by the sensor into an electrical signal through a hardware mode, and has no built-in CPU. The fiber cavitation demodulation module in the upper computer compares the electrical signal with a certain threshold value, judges the gas-liquid, and visualizes the signal.

[0051] In the embodiment, the fiber demodulation system receives the optical signals collected by the two probes of the double-probe fiber probe sensor, converts the optical signals into electrical signals, and transmits the electrical signals to the fiber cavitation demodulation module in the upper computer. The fiber cavitation demodulation module compares the signal strength with the set threshold value, and the threshold value is 1.2V. If the signal strength is lower than the set threshold value, it indicates that the probe of the double-probe fiber sensor is located in the liquid. Otherwise, the probe of the double-probe fiber sensor is located in the air, that is, it is judged that the probe of the double-probe fiber sensor is located in the bubble, so as to judge the time difference t of the bubble passing through the two probes of the fiber probe sensor. Then, the moving speed V of the bubble is calculated according to the time difference of the bubble passing through the two probes of the fiber probe sensor 6 气泡 , and the calculation formula is:

[0052]

[0053] S is the distance between the two probes of the optical fiber probe sensor;

[0054] t is the time difference of the bubble passing through the two probes of the optical fiber probe sensor;

[0055] Without considering the buoyancy of the bubble, the moving speed of the bubble is the liquid flow rate in the tank, that is, V 气泡 = V 液体 .

[0056] The optical fiber probe sensor is a double-probe type, which is fixed in the liquid storage tank by a sealing assembly in a transverse direction, and the double probes are arranged in the peripheral annular flow channel. After the bubble generating device generates a bubble, the bubble enters the peripheral annular flow channel again from the "handle" shaped annular flow channel along with the liquid flow and is monitored by the optical fiber probe sensor, and then passes through the two probes of the sensor. The optical fiber demodulation system processes and demodulates the signal returned by the sensor to obtain the time difference of the bubble passing through the two probes, and then calculates the bubble rate, so as to obtain the liquid flow rate in the storage tank. In order to avoid the calculation error of the liquid flow rate caused by the error of the single optical fiber probe sensor in monitoring the bubble, the bubble generating device and the sensor are arranged in four directions of the liquid storage tank.

[0057] In the embodiment, the liquid flows upward from the flow hole at the bottom of the central cylindrical chamber of the tank body, enters the outer annular cavity through the plurality of holes at the upper part of the cylindrical partition, and then flows downward through the arc-shaped or U-shaped annular channel. The heating wire wound on the arc-shaped or U-shaped annular channel heats the liquid in the arc-shaped or U-shaped annular channel, so that the liquid generates bubbles. The bubbles enter the peripheral annular cavity of the tank body again from the arc-shaped or U-shaped annular channel along the flow direction of the liquid, and then flow to the bottom of the central cylindrical chamber again through the flow hole at the bottom of the annular cavity. In the embodiment, the liquid flows downward from the upper part of the central cylindrical chamber of the tank body, flows downward into the outer annular cavity through the flow hole at the bottom of the central cylindrical chamber, and then flows upward through the arc-shaped or U-shaped annular channel. The heating wire wound on the arc-shaped or U-shaped annular channel heats the liquid in the arc-shaped or U-shaped annular channel, so that the liquid generates bubbles. The bubbles enter the peripheral annular cavity of the tank body again from the arc-shaped or U-shaped annular channel along the flow direction of the liquid, and then flow to the central cylindrical chamber again through the plurality of holes at the upper part of the cylindrical partition.

[0058] In the embodiment, the gas density in the bubble is obtained according to the liquid in the sealed tank. If the liquid is water, the gas is air. Mainly, it is to see what gas is generated after the liquid in the sealed tank is heated. Generally, for the convenience of calculation, all the gas in the bubble can be regarded as air.

[0059] The embodiment two provides a kind of liquid flow rate monitoring method based on optical fiber probe, using the liquid flow rate monitoring system based on optical fiber probe provided in embodiment one is monitored to the liquid flow rate in sealed liquid storage tank, its specific steps are as follows:

[0060] S1.the plurality of holes in the upper part of the cylindrical partition in the sealed liquid storage tank, the first liquid flow hole in the bottom of the central cylindrical chamber and the second liquid flow hole in the bottom of the annular cavity are provided with the circulation flow between the cylindrical chamber and the external annular cavity of the tank body;

[0061] S2.after liquid reaches the annular cavity outside, the liquid in the arc or U-shaped ring channel is heated by heating wire wound on the arc or U-shaped ring channel, so that the liquid generates bubble;

[0062] S3.bubble follows the direction of liquid flow, passes through double-probe optical fiber probe sensor and is monitored by the two probes of double-probe optical fiber probe sensor;

[0063] S4.the two probes of double-probe optical fiber probe sensor transmit the monitored signal to optical fiber demodulation system, which is transmitted to optical fiber cavity demodulation module in host computer after being processed by optical fiber demodulation system, and is judged by optical fiber cavity demodulation module in host computer, so as to judge the time difference of bubble passing between the two probes of optical fiber sensor, the specific judgment process is as follows: optical fiber demodulation system receives the optical signal collected by the two probes of double-probe optical fiber probe sensor, and converts it into electrical signal and transmits it to optical fiber cavity demodulation module in host computer, optical fiber cavity demodulation module compares the signal strength with the set threshold value, if the signal strength is lower than the set threshold value, it indicates that the probe of double-probe optical fiber sensor is located in liquid;On the contrary, the probe of double-probe optical fiber sensor is located in air, that is, it is judged that the probe of double-probe optical fiber sensor is located in bubble, so as to judge the time difference t of bubble passing between the two probes of optical fiber probe sensor.

[0064] And according to the time difference of bubble passing between the two probes of double-probe optical fiber sensor, bubble rate is calculated, and according to bubble rate, liquid flow rate in storage tank can be calculated, the specific process is as follows:

[0065] ①If the buoyancy of bubble in liquid is not considered, bubble rate is liquid flow rate, and the calculation formula is as follows:

[0066]

[0067] Wherein, S is the distance between the two probes, and t is the time difference of bubble passing between the two probes;

[0068] ②If the buoyancy of bubble in liquid is considered, according to Stokes law;When liquid flows from top to bottom, liquid flow rate is calculated as follows:

[0069]

[0070] When liquid flows from bottom to top, the liquid flow rate is calculated as follows:

[0071]

[0072] Where, p 液 is the density of liquid in the tank, p 气 is the density of bubble gas, generally the density of air is taken here;

[0073] C d is the drag coefficient, the drag coefficient is 0.45;

[0074] g represents the acceleration of gravity.

[0075] The above is only one embodiment of the patent, which is described in more detail and in detail, but it cannot be understood as a limitation on the scope of the patent. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the patent, a number of modifications and improvements can be made, which are within the scope of protection of the patent. Therefore, the scope of protection of the patent should be subject to the appended claims.

Claims

1. A liquid flow velocity monitoring system based on an optical fiber probe, characterized in that: The liquid flow rate monitoring system includes a liquid storage tank (3), a bubble generating device, an optical fiber probe sensor (6), and an optical fiber demodulation system; The liquid storage tank (3) includes a sealed tank body (300), which is divided into an inner central cylindrical chamber (303) and an outer annular chamber (302) by a cylindrical partition. Multiple holes (301) are provided in the upper part of the cylindrical partition. The central cylindrical chamber (303) and the annular chamber (302) are connected through the multiple holes (301). The bottom of the central cylindrical chamber (303) is provided with a first liquid flow hole (304), and the bottom of the annular chamber (302) is provided with a second liquid flow hole (305). The first liquid flow hole (304) and the second liquid flow hole (305) are connected. The bubble generating device includes an arc-shaped or U-shaped ring channel (5) set on the sealed tank (300) and a heating wire (4) wound on the ring channel (5). The ring channel (5) is connected to the annular cavity (302), and bubbles are generated by heating the liquid through the heating wire (4) after the liquid passes through the ring channel. The fiber optic probe sensor (6) is a dual-probe fiber optic probe sensor, which is located directly below the bubble generating device. The two probes of the fiber optic probe sensor (6) extend into the annular cavity (302), and the two probes are arranged side by side on the bubble moving path generated by the bubble generating device. The fiber optic demodulation system includes a fiber optic cavitation demodulator (1), a sensing optical cable (7), and a fiber optic cavitation demodulation module located in the host computer (2). The fiber probe sensor (6) is connected to the fiber optic cavitation demodulator via the sensing optical cable (7), and the fiber optic cavitation demodulator is connected to the fiber optic cavitation demodulation module in the host computer.

2. The liquid flow velocity monitoring system based on an optical fiber probe according to claim 1, characterized in that: The fiber optic cavitation demodulator is used to receive the optical signals collected by the two probes of the fiber optic probe sensor (6), process them, and then send them to the fiber optic cavitation demodulation module in the host computer. The fiber optic cavitation demodulation module in the host computer performs gas-liquid judgment, thereby determining the time difference between the two probes of the fiber optic probe sensor (6) when the bubble passes through. Then, the bubble's speed is calculated based on the time difference between the two probes of the fiber optic probe sensor (6). The calculation formula is: ; Where S is the distance between the two probes of the fiber optic probe sensor; t is the time difference between the two probes of the fiber optic probe sensor as the bubble passes through. Neglecting the buoyancy of the bubble, the bubble's velocity is equal to the velocity of the liquid inside the container, i.e. .

3. A liquid flow velocity monitoring system based on an optical fiber probe according to claim 1 or 2, characterized in that: The vertical distance between the two probes of the fiber optic probe sensor (6) is greater than the diameter of a single bubble but less than the sum of the diameters of the two bubbles.

4. A liquid flow rate monitoring system based on an optical fiber probe according to claim 1 or 2, characterized in that: The fiber optic probe sensor (6) includes a connector (602), a pigtail (603), an FC / APC connector (604), and two sets of fiber optic probes (601). The two sets of fiber optic probes (601) are arranged side by side, and the two probes (601) have different lengths. They are connected to the pigtail (603) through the connector (602) and output through the FC / APC connector (604).

5. A liquid flow velocity monitoring system based on an optical fiber probe according to claim 1 or 2, characterized in that: The bubble generating device is provided in four groups, which are placed at the same height in four directions of the liquid storage tank. Each group of bubble generating devices is provided with two sets of fiber optic probe sensors (6) below it. The probes of the two sets of fiber optic probe sensors (6) are inserted into the annular cavity (302). The two sets of fiber optic probe sensors (6) are arranged side by side on the bubble moving path generated by the corresponding bubble generating device. The eight sets of fiber optic probe sensors (6) are respectively connected to the fiber optic cavitation demodulator through sensing optical cables (7).

6. A liquid flow velocity monitoring system based on an optical fiber probe according to claim 1 or 2, characterized in that: The fiber optic probe sensor (6) is laterally fixed to the liquid storage tank (3) using a sealing assembly.

7. A method for monitoring liquid flow velocity based on an optical fiber probe, characterized in that, The monitoring method uses the liquid flow rate monitoring system based on fiber optic probes as described in any one of claims 1 to 6 to monitor the liquid flow rate in a sealed liquid storage tank. The specific steps are as follows: S1. The liquid in the sealed liquid storage tank has multiple holes at the top of the cylindrical partition, a first liquid flow hole at the bottom of the central cylindrical chamber, and a second liquid flow hole at the bottom of the annular cavity, which circulate between the cylindrical chamber and the outer annular cavity of the tank. S2. After the liquid reaches the external annular cavity, it passes through an arc-shaped or U-shaped channel. The heating wire wrapped around the arc-shaped or U-shaped channel heats the liquid inside the channel, causing the liquid to generate bubbles. S3. The bubble flows along the direction of liquid flow, passes through the dual-probe fiber optic sensor, and is monitored by the two probes of the dual-probe fiber optic sensor; S4. The two probes of the dual-probe fiber optic sensor transmit the monitored signal to the fiber optic demodulation system. After processing by the fiber optic demodulation system, the signal is transmitted to the fiber optic cavitation demodulation module in the host computer. The fiber optic cavitation demodulation module in the host computer performs gas-liquid judgment to determine the time difference between the two probes of the fiber optic sensor and calculates the bubble velocity based on the time difference between the two probes of the dual-probe fiber optic sensor. The flow rate of the liquid in the storage tank is then calculated based on the bubble velocity.

8. The liquid flow velocity monitoring method based on an optical fiber probe according to claim 7, characterized in that, In step S4, the bubble velocity is calculated based on the time difference between the two probes of the dual-probe fiber optic sensor, and the specific process of calculating the liquid flow rate in the storage tank based on the bubble velocity is as follows: ① If the buoyancy of the bubbles in the liquid is not considered, then the bubble velocity is the liquid flow velocity, and the calculation formula is as follows: ; in, S The distance between the two probes. t This represents the time difference between the two probes passing through the bubble. ② If we consider the buoyancy of the air bubbles in the liquid, according to Stokes' law, when the liquid flows from top to bottom, the liquid velocity is calculated as follows: ; When a liquid flows from bottom to top, the liquid velocity is calculated as follows: ； in, The density of the liquid inside the sealed container; The density of the gas inside the bubble; This is the drag coefficient, which is set to 0.

45. g represents the acceleration due to gravity.

9. A liquid flow velocity monitoring method based on an optical fiber probe according to claim 7, characterized in that, The process of determining the time difference between the two probes of the dual-probe fiber optic sensor in step S4 is as follows: The fiber optic demodulation system receives the optical signals collected by the two probes of the dual-probe fiber optic sensor and converts them into electrical signals, which are then transmitted to the fiber optic bubble demodulation module located in the host computer. The fiber optic bubble demodulation module compares the signal strength with a set threshold. If the signal strength is lower than the set threshold, it means that the probe of the dual-probe fiber optic sensor is located in the liquid; otherwise, the probe of the dual-probe fiber optic sensor is located in the air. That is, it is determined that the probe of the dual-probe fiber optic sensor is located inside the bubble, thereby determining the time difference t between the two probes of the fiber optic sensor as the bubble passes through.

10. A liquid flow velocity monitoring method based on an optical fiber probe according to claim 8, characterized in that: The liquid circulates from bottom to top, specifically flowing upwards from the flow hole at the bottom of the central cylindrical chamber of the tank. It then passes through multiple holes at the top of the cylindrical baffle and enters the outer annular chamber. After reaching the outer annular chamber, the liquid flows downwards through an arc-shaped or U-shaped channel. Heating wires wound around the arc-shaped or U-shaped channel heat the liquid inside, causing bubbles to form. The bubbles then flow in the same direction as the liquid, re-entering the outer annular chamber of the tank through the arc-shaped or U-shaped channel, and then flow back to the bottom of the central cylindrical chamber through the bottom of the annular chamber. The liquid circulates from top to bottom, specifically flowing downwards from the upper part of the central cylindrical chamber of the tank. It then flows downwards through the flow holes at the bottom of the central cylindrical chamber into the outer annular chamber. After reaching the outer annular chamber, the liquid flows upwards through an arc-shaped or U-shaped channel. The heating wires wound around the arc-shaped or U-shaped channel heat the liquid, causing bubbles to form. The bubbles then flow back into the outer annular chamber of the tank along the direction of liquid flow, and then flow back into the central cylindrical chamber through multiple holes at the top of the cylindrical baffle.

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