Liquid flow rate monitoring system and method based on optical fiber probe

Abstract

The invention 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 interior of a sealed tank body is divided into an internal central cylindrical cavity and an external annular cavity through a cylindrical partition plate, the upper portions and the lower portions of the internal central cylindrical cavity and the external annular cavity are communicated, and liquid can circulate in the tank; an arc-shaped or U-shaped annular channel communicated with the annular cavity and a heating wire wound on the annular channel are arranged on the sealed tank body, after liquid passes through the annular channel, bubbles are generated through heating of the heating wire, and a double-probe optical fiber probe sensor is installed at the position where the liquid passes through. The optical fiber cavitation demodulator receives optical signals collected by the two probes of the optical fiber probe sensor to judge the time difference of bubbles passing through the two probes of the optical fiber probe sensor, and then the moving speed of the bubbles, namely the liquid speed, is calculated. The device has high safety, and the flow velocity of the liquid in the sealed storage tank can be accurately and rapidly measured.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical fiber sensing, and in particular relates to a liquid flow rate monitoring system and method based on an optical fiber probe. Background Art

[0002] Fiber optic sensing technology is a new sensing technology that has developed along with the development of optical fiber and fiber optic communication technology. It is the fastest-growing high-tech application technology in the world since the mid-1970s. With the gradual maturity of optical fiber manufacturing technology, fiber optic sensors have been widely used in many occasions, such as temperature monitoring and pressure measurement, due to their advantages of high temperature and high pressure resistance, electrical passivity, and resistance to strong electrical / magnetic / radiation interference. In the 1980s, fiber optic sensor technology ushered in important technological breakthroughs, and a variety of new fiber optic sensors were introduced, such as interferometric fiber optic sensors and fiber grating sensors. Not only has it improved the measurement accuracy and stability, but it has also expanded the application field of fiber optic sensing technology.

[0003] In the chemical industry, general chemical reactions occur in sealed storage tanks, so there are strict requirements for the liquid flow rate. Too fast a liquid flow rate may cause equipment damage or leakage; too slow a 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 method for measuring liquid flow rate is the ultrasonic flow meter, which uses the principle that the time difference between the downstream and upstream propagation of sound waves in the fluid is proportional to the liquid flow rate to measure the liquid flow rate; but at the same time, this method has extremely high requirements for the purity of the liquid. Impurities or bubbles in the liquid will cause the ultrasonic incident angle to shift, reducing the accuracy of the measurement. In response to the problems existing in the ultrasonic flow meter, the present invention uses an optical fiber dual-probe sensor to measure the liquid flow rate in a sealed storage tank; this method is less affected by the environment, has strong anti-electromagnetic interference ability, and can be remotely monitored, providing a new technical means for liquid flow rate measurement. Summary of the invention

[0004] Aiming at the demand of measuring the flow rate of liquid in a sealed storage tank, the present invention provides a liquid flow rate monitoring system and method based on an optical fiber probe. The system is combined with an optical fiber demodulation system to achieve accurate and rapid measurement of the flow rate of liquid inside a sealed storage tank, providing a new technical method for measuring the flow rate of liquid in a sealed tank.

[0005] In order to achieve the above technical purpose, this patent provides a liquid flow rate monitoring system based on an optical fiber probe, the liquid flow rate monitoring system includes 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, which is divided into an inner central cylindrical chamber and an outer annular chamber by a cylindrical partition, a plurality of holes are provided on the upper part of the cylindrical partition, and the central cylindrical chamber and the annular chamber are connected through the plurality of holes; a first liquid flow hole is provided at the bottom of the central cylindrical chamber, and a second liquid flow hole is provided at the bottom of the annular chamber, and the first liquid flow hole is connected with the second liquid flow hole;

[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, wherein the ring channel is connected with the annular cavity, and after the liquid passes through the ring channel, the liquid is heated by the heating wire to generate bubbles;

[0008] The optical fiber probe sensor is a dual-probe optical fiber probe sensor, which is arranged directly below the bubble generating device, and the two probes of the optical fiber probe sensor extend into the annular cavity, and the two probes are arranged side by side up and down on the bubble moving path generated by the bubble generating device;

[0009] The optical fiber demodulation system includes an optical fiber cavitation demodulator, a sensing optical cable and an optical fiber cavitation demodulation module located in a host computer. The fiber probe sensor is connected to the optical fiber cavitation demodulator signal through the sensing optical cable, and the optical fiber cavitation demodulator is connected to the optical fiber cavitation demodulation module in the host computer signal.

[0010] The preferred technical solution of the present invention is as follows: the optical fiber cavitation demodulator is used to receive the optical signals collected by the two probes of the optical fiber probe sensor, process them, and then transmit them to the optical fiber cavitation demodulation module in the host computer, and the optical fiber cavitation demodulation module in the host computer performs gas-liquid judgment, thereby judging the time difference of the bubble passing through the two probes of the optical 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 optical fiber probe sensor 气泡 , the calculation formula is:

[0011]

[0012] Where S is the distance between the two probes of the fiber optic probe sensor;

[0013] t is the time difference of the bubble passing through the two probes of the optical fiber probe sensor;

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

[0015] A more preferred technical solution of the present invention is as follows: the vertical distance between the two probes of the optical fiber probe sensor is greater than the diameter of a single bubble and less than the sum of the diameters of the two bubbles.

[0016] The preferred technical solution of the present invention is as follows: the fiber optic probe sensor includes a connector, a pigtail segment, an FC / APC connector and two groups of fiber optic probes. The two groups of fiber optic probes are arranged in parallel, and the two probes are of different lengths. They are respectively connected to the pigtail segment through a connector and output through the FC / APC connector.

[0017] The preferred technical solution of the present invention is as follows: the bubble generating devices are provided with four groups, which are respectively placed at equal heights in four directions of the liquid storage tank; two groups of fiber optic probe sensors are correspondingly arranged under each group of bubble generating devices; the probes of the two groups of fiber optic probe sensors are both extended into the annular cavity; the two groups of fiber optic probe sensors are arranged side by side up and down on the bubble movement path generated by the corresponding bubble generating devices; the eight groups of fiber optic probe sensors are respectively connected to the signal of the fiber optic cavitation demodulator through sensing optical cables.

[0018] A more preferred technical solution of the present invention: the optical fiber probe sensor is laterally fixed to the liquid storage tank by a sealing component.

[0019] The present invention also provides a liquid flow rate monitoring method based on an optical fiber probe, wherein the monitoring method uses the 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 liquid in the sealed liquid storage tank is sealed by a plurality of holes in the upper part of the cylindrical partition of the tank body, 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, so that the liquid circulates between the cylindrical chamber of the tank body and the outer annular cavity;

[0021] S2. After the liquid reaches the external annular cavity, it passes through the arc-shaped or U-shaped ring channel, and the liquid in the arc-shaped or U-shaped ring channel is heated by the heating wire wrapped around the arc-shaped or U-shaped ring channel, so that bubbles are generated in the liquid;

[0022] S3. The bubble follows the liquid flow direction, passes through the dual-probe fiber optic probe sensor, and is monitored by the two probes of the dual-probe fiber optic probe sensor;

[0023] S4. The two probes of the dual-probe fiber optic probe sensor transmit the monitoring signal to the fiber optic demodulation system, which is processed by the fiber optic demodulation system and then 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, thereby judging the time difference between the bubbles passing through the two probes of the fiber optic sensor, and calculating the bubble rate based on the time difference between the bubbles passing through the two probes of the dual-probe fiber optic sensor. The flow rate of the liquid in the storage tank can be calculated based on the bubble rate.

[0024] The preferred technical solution of the present invention: In the step S4, the bubble velocity is calculated according to the time difference between the two probes of the dual-probe optical fiber sensor when the bubble passes through, and the specific process of calculating the flow rate of the liquid in the storage tank by the bubble velocity is as follows:

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

[0026]

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

[0028] ② If the buoyancy of bubbles 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] Among them, ρ 液 is the density of the liquid in the sealed tank;

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

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

[0035] g represents the acceleration due to gravity.

[0036] The preferred technical solution of the present invention: The process of judging 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 light signals collected by the two probes of the dual-probe fiber optic probe sensor, and converts them into electrical signals and transmits them to the fiber optic cavitation demodulation module in the host computer. The fiber optic cavitation demodulation module compares the signal strength with the set threshold. If the signal strength is lower than the set threshold, it means that the probes of the dual-probe fiber optic sensor are located in the liquid; otherwise, the probes of the dual-probe fiber optic sensor are located in the air, that is, it is judged that the probes of the dual-probe fiber optic sensor are located in the bubble, thereby judging the time difference t of the bubble passing through the two probes of the fiber optic probe sensor.

[0037] The preferred technical solution of the present invention is as follows: the liquid circulates from bottom to top, specifically flows upward from the flow hole at the bottom of the central cylindrical chamber of the tank body, passes through the multiple holes on the upper part of the cylindrical partition and enters the external annular cavity; after the liquid reaches the external annular cavity, it passes downward through the arc-shaped or U-shaped loop; the liquid in the arc-shaped or U-shaped loop is heated by the heating wire wound on the arc-shaped or U-shaped loop, so that bubbles are generated in the liquid; the bubbles follow the flow direction of the liquid, enter the outer annular cavity of the tank body from the arc-shaped or U-shaped loop again, and flow to the bottom of the central cylindrical cavity through the bottom of the annular cavity;

[0038] The liquid circulates from top to bottom specifically by flowing downward from the upper part of the central cylindrical chamber of the tank body, and flows downward into the external annular chamber through the flow hole at the bottom of the central cylindrical chamber. After reaching the external annular chamber, the liquid passes upward through an arc-shaped or U-shaped loop, and the liquid in the arc-shaped or U-shaped loop is heated by a heating wire wound on the arc-shaped or U-shaped loop, so that bubbles are generated in the liquid; the bubbles follow the flow direction of the liquid, enter the outer annular cavity of the tank body from the arc-shaped or U-shaped loop again, and flow into the central cylindrical chamber through multiple holes on the upper part of the cylindrical partition.

[0039] The cavitation demodulator amplifies, removes noise, and converts the optical signal returned by the sensor into an electrical signal through hardware, and has no built-in CPU; the cavitation demodulation software compares the electrical signal with a certain threshold, makes a gas-liquid judgment, and visualizes the signal.

[0040] The optical fiber probe sensor of the present invention can be electrically passive and therefore 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 flow rate of liquid in a sealed tank, which can achieve accurate and rapid measurement of the flow rate of liquid inside a sealed storage tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is the system principle diagram of the present invention;

[0042] Figure 2 The optical fiber probe sensor of the present invention;

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

[0044] Figure 4 This is a diagram showing the internal structure of the liquid storage tank in the present invention.

[0045] In the figure: 1—optical fiber cavitation demodulator, 2—host computer, 3—liquid storage tank, 300—sealed tank body, 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 loop, 6—optical fiber probe sensor, 601—optical fiber probe, 602—connector, 603—pigtail segment, 604—FCA connector; 7—sensing optical cable. DETAILED DESCRIPTION

[0046] In order to make the technical solutions and advantages of the present invention easier to understand, the present invention is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings. The accompanying drawings are drawn in a simplified manner and are only used to clearly and concisely illustrate the purpose of this patent. The technical solutions shown in the following drawings are specific solutions of this patent and are not intended to limit the scope of the invention to be protected. Based on the embodiments of the present invention, all other patents obtained by ordinary technicians in this field without making creative work are within the scope of protection of this patent.

[0047] Embodiment 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, the sealed tank body 300 is divided into an inner central cylindrical chamber 303 and an outer annular cavity 302 by a cylindrical partition, a plurality of holes 301 are opened on the upper part of the cylindrical partition, and the central cylindrical chamber 303 and the annular cavity 302 are connected through the plurality of holes 301; a first liquid flow hole 304 is provided at the bottom of the central cylindrical chamber 303, and a second liquid flow hole 305 is provided at the bottom of the annular cavity 302, and the first liquid flow hole 304 is connected with the second liquid flow hole 305; the bubble generating device includes an arc-shaped or U-shaped ring channel 5 arranged on the sealed tank body 300 and a heating wire 4 wound on the ring channel 5, the ring channel 5 is connected with the annular cavity 302, and after the liquid passes through the ring channel, it is heated by the heating wire 4 to generate bubbles.

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

[0049] In Example 1, in order to ensure accurate monitoring, the bubble generating device is provided with four groups, which are respectively placed at equal heights in four directions of the liquid storage tank, and two groups of fiber optic probe sensors 6 are correspondingly arranged under each group of bubble generating devices. The probes of the two groups of fiber optic probe sensors 6 are both extended into the annular cavity 302, and the two groups of fiber optic probe sensors 6 are arranged side by side up and down on the bubble movement path generated by the corresponding bubble generating device.

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

[0051] In the first embodiment, the optical fiber demodulation system receives the optical signal collected by the two probes of the dual-probe optical fiber probe sensor, and converts it into an electrical signal and transmits it to the optical fiber cavitation demodulation module in the upper computer. The optical 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 means that the probes of the dual-probe optical fiber sensor are located in the liquid; otherwise, the probes of the dual-probe optical fiber sensor are located in the air, that is, it is determined that the probes of the dual-probe optical fiber sensor are located in the bubble, thereby determining the time difference t of the bubble passing through the two probes of the optical fiber probe sensor. Then, the moving speed V of the bubble is calculated based on the time difference of the bubble passing through the two probes of the optical fiber probe sensor 6. 气泡 , the calculation formula is:

[0052]

[0053] Where S is the distance between the two probes of the fiber optic 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 flow rate of the liquid in the tank, that is, V 气泡 =V 液体 .

[0056] The fiber optic probe sensor is a dual-probe type, which is fixed in the liquid storage tank horizontally by a sealing component, and the dual probes are placed in the peripheral annular flow channel. After the bubble generating device generates bubbles, the bubbles flow from the "handle"-shaped annular channel again into the peripheral annular flow channel and are monitored by the fiber optic probe sensor. After passing through the two probes of the sensor, the fiber optic demodulation system processes and demodulates the signal sent back by the sensor to obtain the time difference of the bubble passing through the two probes to calculate the bubble rate, thereby obtaining the liquid flow rate in the storage tank. In order to avoid the error in calculating the liquid flow rate due to the error in monitoring the bubble by a single fiber optic probe sensor, a total of 4 groups of bubble generating devices and sensors are set in four directions of the liquid storage tank.

[0057] In the embodiment, the liquid circulates from bottom to top, specifically flowing upward from the flow hole at the bottom of the central cylindrical chamber of the tank body, passing through the multiple holes at the upper part of the cylindrical partition to enter the external annular cavity, and after reaching the external annular cavity, the liquid passes downward through the arc-shaped or U-shaped loop, and the liquid in the arc-shaped or U-shaped loop is heated by the heating wire wound on the arc-shaped or U-shaped loop, so that bubbles are generated in the liquid; the bubbles follow the flow direction of the liquid, enter the outer annular cavity of the tank body from the arc-shaped or U-shaped loop again, and flow to the bottom of the central cylindrical cavity through the bottom of the annular cavity; The liquid circulates from top to bottom specifically by flowing downward from the upper part of the central cylindrical chamber of the tank body, and flows downward into the external annular chamber through the flow hole at the bottom of the central cylindrical chamber. After reaching the external annular chamber, the liquid passes upward through an arc-shaped or U-shaped loop, and the liquid in the arc-shaped or U-shaped loop is heated by a heating wire wound on the arc-shaped or U-shaped loop, so that bubbles are generated in the liquid; the bubbles follow the flow direction of the liquid, enter the outer annular cavity of the tank body from the arc-shaped or U-shaped loop again, and flow into the central cylindrical chamber through multiple holes on the upper part of the cylindrical partition.

[0058] In the embodiment, the density of the gas in the bubble is obtained based on the liquid in the sealed can. If the liquid is water, the gas is air. It mainly depends on what the gas produced after the liquid in the sealed can is heated. Generally, for the convenience of calculation, the gas in the bubble can be regarded as air.

[0059] The second embodiment provides a method for monitoring liquid flow rate based on an optical fiber probe, using the liquid flow rate monitoring system based on an optical fiber probe provided in the first embodiment to monitor the liquid flow rate in a sealed liquid storage tank, and the specific steps are as follows:

[0060] S1. The liquid in the sealed liquid storage tank is sealed by a plurality of holes in the upper part of the cylindrical partition of the tank body, 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, so that the liquid circulates between the cylindrical chamber of the tank body and the outer annular cavity;

[0061] S2. After the liquid reaches the external annular cavity, it passes through the arc-shaped or U-shaped ring channel, and the liquid in the arc-shaped or U-shaped ring channel is heated by the heating wire wrapped around the arc-shaped or U-shaped ring channel, so that bubbles are generated in the liquid;

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

[0063] S4. The two probes of the dual-probe fiber optic probe sensor transmit the monitored signals to the fiber optic demodulation system, which is processed by the fiber optic demodulation system and then 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, thereby judging the time difference between the bubbles passing through the two probes of the fiber optic sensor. The specific judgment process is as follows: the fiber optic demodulation system receives the optical signals collected by the two probes of the dual-probe fiber optic probe sensor, and converts them into electrical signals and transmits them to the fiber optic cavitation demodulation module in the host computer. The fiber optic cavitation demodulation module compares the signal strength with the set threshold. If the signal strength is lower than the set threshold, it means that the probes of the dual-probe fiber optic sensor are located in the liquid; otherwise, the probes of the dual-probe fiber optic sensor are located in the air, that is, it is judged that the probes of the dual-probe fiber optic sensor are located in the bubble, thereby judging the time difference t between the bubbles passing through the two probes of the fiber optic probe sensor.

[0064] The bubble velocity is calculated based on the time difference between the two probes of the dual-probe optical fiber sensor when the bubble passes through. The flow rate of the liquid in the storage tank can be calculated based on the bubble velocity. The specific process is as follows:

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

[0066]

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

[0068] ② If the buoyancy of bubbles 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:

[0069]

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

[0071]

[0072] Among them, ρ 液 is the density of the liquid in the tank, ρ 气 is the density of the bubble gas, which is usually the density of air;

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

[0074] g represents the acceleration due to gravity.

[0075] The above is only an embodiment of this patent, and its description is relatively specific and detailed, but it cannot be understood as limiting the scope of this patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of this patent, which all belong to the protection scope of this patent. Therefore, the protection scope of this patent shall be based on the attached claims.

Claims

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

2. A liquid flow rate monitoring system based on an optical fiber probe according to claim 1, characterized in that: The optical fiber cavitation demodulator is used to receive the optical signals collected by the two probes of the optical fiber probe sensor (6), process them, and then transmit them to the optical fiber cavitation demodulation module in the host computer. The optical fiber cavitation demodulation module in the host computer performs gas-liquid judgment, thereby judging the time difference of the bubble passing through the two probes of the optical fiber probe sensor (6); Then, the moving speed V of the bubble is calculated based on the time difference between the two probes of the optical fiber probe sensor (6). 气泡 , the calculation formula is: Where S is the distance between the two probes of the fiber optic probe sensor; t is the time difference of the bubble passing through the two probes of the optical fiber probe sensor; Without considering the buoyancy of the bubble, the moving speed of the bubble is the flow rate of the liquid in the tank, that is, V 气泡 =V 液体 .

3. A liquid flow rate 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 optical fiber probe sensor (6) is greater than the diameter of a single bubble and 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 optical fiber probe sensor (6) comprises a connector (602), a pigtail segment (603), an FC / APC connector (604) and two groups of optical fiber probes (601). The two groups of optical fiber probes (601) are arranged in parallel, and the two probes (601) have different lengths and are respectively connected to the pigtail segment (603) through the connector (602) and output through the FC / APC connector (604).

5. A liquid flow rate monitoring system based on an optical fiber probe according to claim 1 or 2, characterized in that: The bubble generating devices are provided with four groups, which are respectively placed at equal heights in four directions of the liquid storage tank. Two groups of optical fiber probe sensors (6) are correspondingly provided below each group of bubble generating devices. The probes of the two groups of optical fiber probe sensors (6) are both extended into the annular cavity (302). The two groups of optical fiber probe sensors (6) are arranged side by side up and down on the bubble moving path generated by the corresponding bubble generating devices; the eight groups of optical fiber probe sensors (6) are respectively connected to the signal of the optical fiber cavitation demodulator through the sensing optical cable (7).

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

7. A method for monitoring liquid flow rate based on an optical fiber probe, characterized in that: The monitoring method uses the liquid flow rate monitoring system based on the optical fiber probe according to any one of claims 1 to 6 to monitor the liquid flow rate in the sealed liquid storage tank, and the specific steps are as follows: S1. The liquid in the sealed liquid storage tank is sealed by a plurality of holes in the upper part of the cylindrical partition of the tank body, 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, so that the liquid circulates between the cylindrical chamber of the tank body and the outer annular cavity; S2. After the liquid reaches the external annular cavity, it passes through the arc-shaped or U-shaped ring channel, and the liquid in the arc-shaped or U-shaped ring channel is heated by the heating wire wrapped around the arc-shaped or U-shaped ring channel, so that bubbles are generated in the liquid; S3. The bubble follows the liquid flow direction, passes through the dual-probe fiber optic probe sensor, and is monitored by the two probes of the dual-probe fiber optic probe sensor; S4. The two probes of the dual-probe fiber optic probe sensor transmit the monitoring signal to the fiber optic demodulation system, which is processed by the fiber optic demodulation system and then 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, thereby judging the time difference between the bubbles passing through the two probes of the fiber optic sensor, and calculating the bubble rate based on the time difference between the bubbles passing through the two probes of the dual-probe fiber optic sensor. The flow rate of the liquid in the storage tank can be calculated based on the bubble rate.

8. The method for monitoring liquid flow rate 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 optical fiber sensor when the bubble passes through, and the specific process of calculating the flow rate of the liquid in the storage tank by the bubble velocity is as follows: ① If the buoyancy of bubbles in liquid is not considered, the bubble velocity is the liquid flow rate, and the calculation formula is as follows: Where S is the distance between the two probes, and t is the time difference between the bubble passing through the two probes; ② If the buoyancy of bubbles 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: When the liquid flows from bottom to top, the liquid flow rate is calculated as follows: Among them, ρ 液 is the density of the liquid in the sealed tank; ρ 气 is the gas density inside the bubble; C d is the drag coefficient, and the drag coefficient is 0.45; g represents the acceleration due to gravity.

9. The method for monitoring liquid flow rate based on an optical fiber probe according to claim 7, characterized in that: In step S4, the process of judging the time difference between the two probes of the dual-probe fiber optic sensor when the bubble passes through is as follows: the fiber optic demodulation system receives the optical signals collected by the two probes of the dual-probe fiber optic probe sensor, and converts them into electrical signals and transmits them to the fiber optic cavitation demodulation module in the host computer. The fiber optic cavitation demodulation module compares the signal strength with the set threshold. If the signal strength is lower than the set threshold, it means that the probes of the dual-probe fiber optic sensor are located in the liquid; otherwise, the probes of the dual-probe fiber optic sensor are located in the air, that is, it is judged that the probes of the dual-probe fiber optic sensor are located in the bubble, thereby judging the time difference t of the bubble passing through the two probes of the fiber optic probe sensor.

10. The method for monitoring liquid flow rate based on an optical fiber probe according to claim 8, characterized in that: Specifically, the liquid circulates upward from the flow hole at the bottom of the central cylindrical chamber of the tank body, flows upward through the multiple holes at the upper part of the cylindrical partition plate into the external annular cavity, and after reaching the external annular cavity, the liquid passes downward through the arc-shaped or U-shaped loop, and the liquid in the arc-shaped or U-shaped loop is heated by the heating wire wound on the arc-shaped or U-shaped loop, so that bubbles are generated in the liquid; the bubbles follow the flow direction of the liquid, enter the outer annular cavity of the tank body from the arc-shaped or U-shaped loop again, and flow to the bottom of the central cylindrical cavity through the bottom of the annular cavity; The liquid circulates from top to bottom specifically by flowing downward from the upper part of the central cylindrical chamber of the tank body, and flows downward into the external annular chamber through the flow hole at the bottom of the central cylindrical chamber. After reaching the external annular chamber, the liquid passes upward through an arc-shaped or U-shaped loop, and the liquid in the arc-shaped or U-shaped loop is heated by a heating wire wound on the arc-shaped or U-shaped loop, so that bubbles are generated in the liquid; the bubbles follow the flow direction of the liquid, enter the outer annular cavity of the tank body from the arc-shaped or U-shaped loop again, and flow into the central cylindrical chamber through multiple holes on the upper part of the cylindrical partition.

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