Accumulated water level measuring device based on distributed temperature sensor

Abstract

The invention provides a distributed temperature sensor-based accumulated water level measuring device, which comprises an optical fiber rod, a base, a polygonal rod and a shell, the polygonal rod and the shell are fixed on the base, a vertical polygonal through hole matched with the polygonal rod in shape is formed in the optical fiber rod, and the optical fiber rod is fixed on the base after the polygonal rod is inserted into the optical fiber rod. The bottom of the shell is of a mesh structure, the optical fiber rod is located in the shell, and sensing optical fibers of the distributed temperature sensors are wound on the optical fiber rod. The winding length of the sensing optical fiber in the corresponding height in the vertical direction of the optical fiber rod is adjusted, and the temperature measurement precision of the distributed temperature sensor is smaller than or equal to the minimum difference value of the air temperature and the accumulated water temperature. The device is passive equipment, is low in energy consumption, has universality and is high in measurement accuracy.

Description

Technical Field

[0001] The invention belongs to the field of optical fiber sensing, and in particular relates to a water level measuring device based on a distributed temperature sensor. Background Art

[0002] Traditional waterlogging monitoring methods mostly rely on active devices such as electrode sensors or ultrasonic sensors and image recognition, which are susceptible to environmental interference and have high maintenance costs. With the development of technology, a distributed sensing method for tunnel waterlogging based on distributed temperature sensing (DTS) is proposed. The spatial resolution of the sensor is improved by packaging the sensing fiber in a two-dimensional plane spiral. The temperature difference of the water-air interface sensing fiber is significantly improved by using the active heating method, thereby realizing the identification of waterlogging events and waterlogging range. However, this method requires active heating of active equipment, which is more energy-consuming and easily affected by the external environment whether the active equipment is allowed to operate. The installation and subsequent maintenance workload is greater. In addition, when the heating method is used to increase the temperature difference of the water-air interface sensing fiber, if the water level in a fixed container is measured and heated in a fixed container, the water-air interface can be determined based on the heating time and the corresponding temperature difference. However, if the waterlogging range and water level are unknown, it will be impossible to determine how long the heating should be and how much the temperature difference should be to accurately reflect the water-air interface. It can be seen that this heating method is not universal and has low measurement accuracy. Summary of the invention

[0003] The present invention provides a water level measurement device based on a distributed temperature sensor to solve the problems that the current water level measurement device based on a distributed temperature sensor needs to rely on active equipment, has high energy consumption, is not universal and has low measurement accuracy.

[0004] According to a first aspect of an embodiment of the present invention, there is provided a device for measuring accumulated water level based on a distributed temperature sensor, comprising an optical fiber rod, a base, a polygonal rod fixed on the base, and a shell, wherein the optical fiber rod is provided with a vertical polygonal through hole matching the shape of the polygonal rod, and the polygonal rod is inserted into the optical fiber rod to fix the optical fiber rod on the base, and the bottom of the shell is a mesh structure, the optical fiber rod is located in the shell and a sensing optical fiber of the distributed temperature sensor is wound thereon, and the winding length of the sensing optical fiber within the corresponding height in the vertical direction of the optical fiber rod is adjusted according to the spatial resolution requirement of the accumulated water level and the spatial resolution of the corresponding sensing optical fiber of the distributed temperature sensor, and the temperature measurement accuracy of the distributed temperature sensor is less than or equal to the minimum difference between the air temperature and the accumulated water temperature.

[0005] In an optional implementation, when the spatial resolution of the accumulated water level is required to be k1, it means that the minimum value required for the optical fiber rod to distinguish the change of the accumulated water level through the temperature difference in the vertical direction is k1. When the spatial resolution of the distributed temperature sensor corresponding to the sensing optical fiber is k2, it means that the length of the sensing optical fiber in the temperature change area must be at least k2 to distinguish the temperature change. At this time, the length L of the sensing optical fiber that needs to be wound within every height of k1 in the vertical direction of the optical fiber rod is greater than or equal to k0*k2, where k1 and k2 are arbitrary values ​​greater than 0, and k0 is an arbitrary value greater than 1 set artificially to ensure measurement accuracy.

[0006] In another optional implementation, the optical fiber rod is cylindrical, and the length L of the sensing optical fiber that needs to be wound within each k1 height in the vertical direction of the optical fiber rod is n*2πr, wherein n is the number of winding turns, r is the radius of the optical fiber rod, n is an integer greater than 0, and r is any value greater than 0. According to the formula n*r≥k0*k2 / 2π, the number n of winding turns of the sensing optical fiber within each k1 height in the vertical direction of the optical fiber rod and the radius r of the optical fiber rod are designed.

[0007] In another optional implementation, during measurement, the accumulated water enters the shell through the mesh structure at the bottom of the shell, so that the water levels inside and outside the shell remain consistent. The sensing optical fiber in the shell performs temperature measurement, and the length of the sensing optical fiber located in the accumulated water is determined based on the temperature difference on the sensing optical fiber. The water level of the accumulated water is determined based on the length of the sensing optical fiber located in the accumulated water and the winding length of the sensing optical fiber at the corresponding height in the vertical direction of the optical fiber rod.

[0008] In another optional implementation, after the threaded column at the top end of the polygonal rod passes through the polygonal through hole in the optical fiber rod, the optical fiber rod is fixed to the base through a nut.

[0009] In another optional implementation, the optical fiber rod and the housing are both cylindrical.

[0010] In another optional implementation, the upper end of the shell is provided with a protective cover and a through hole for the sensing optical fiber to pass through.

[0011] In another optional implementation, the base, the polygonal rod and the shell are integrally formed, and a screw hole is provided on the base, and the base is fixed by passing a screw through the screw hole.

[0012] In another optional implementation, the bottom of the optical fiber rod is a mesh structure, and the optical fiber rod has transverse flow guide holes distributed in the vertical direction.

[0013] In another optional implementation, the sensing optical fiber is wound on the optical fiber rod in a spiral manner.

[0014] The beneficial effects of the present invention are:

[0015] 1. The present invention sets a shell outside the optical fiber rod wound with the sensing optical fiber, and designs the bottom of the shell into a mesh structure to filter foreign matter in the accumulated water, which can not only protect the sensing optical fiber and prevent external foreign matter from entering the shell and directly acting on the sensing optical fiber to affect the temperature measurement of the sensing optical fiber, but also ensure that the water level inside and outside the shell is consistent, and the water level inside the shell will not fluctuate greatly, thereby further ensuring the temperature measurement accuracy of the sensing optical fiber; the present invention also sets a polygonal rod in the shell, and after the polygonal rod fixed on the base is inserted into the optical fiber rod, the optical fiber rod is fixed in On the base, on the one hand, it is convenient to remove and install the optical fiber rod, and it is convenient to perform daily inspection and maintenance on the sensing optical fiber on the optical fiber rod. On the other hand, the polygonal rod can prevent the optical fiber rod from rotating under the action of accumulated water. In addition, the optical fiber rod and the base are not tightly connected. The accumulated water will enter the space between the optical fiber rod and the polygonal rod through the gap between the optical fiber rod and the base. The accumulated water in the space can also transfer the temperature to the sensing optical fiber through the optical fiber rod, so that the sensing optical fiber can sense the accumulated water temperature in all directions, increase the difference between the measured accumulated water temperature and the air temperature, and thus further ensure the accuracy of the temperature measurement of the sensing optical fiber.

[0016] The present invention proposes a new measurement method based on the above structure, which selects a distributed temperature sensor with a temperature measurement accuracy less than or equal to the minimum difference between the air temperature and the accumulated water temperature, and adjusts the winding length of the sensing optical fiber in the corresponding height in the vertical direction of the optical fiber rod according to the spatial resolution requirement of the accumulated water level and the spatial resolution of the sensing optical fiber corresponding to the distributed temperature sensor. Since the above structure can ensure that the accumulated water air temperature has obvious differences, even if the accumulated water range and the accumulated water level are unknown, the measurement method of the present invention can also realize accurate measurement of the accumulated water level. Winding the sensing optical fiber on the optical fiber rod makes up for the insufficient resolution of the sensing optical fiber when measuring the accumulated water level. The long temperature measurement distance and passive characteristics also enable the device to be placed in remote and complex environments, greatly expanding the monitoring range, making the measuring device universal.

[0017] 2. The present invention designs the optical fiber rod and the shell to be cylindrical. Even if a small-scale fluctuation occurs in the shell, the fluctuation can be quickly balanced. The present invention designs the bottom of the optical fiber rod to be a mesh structure. Transverse guide holes are distributed in the vertical direction of the optical fiber rod, and the space between the optical fiber rod into which the accumulated water flows and the polygonal rod is made polygonal, which can stabilize the fluctuation and further weaken the formed fluctuation, thereby further ensuring the temperature measurement accuracy of the sensing optical fiber; in addition, transverse guide holes are distributed in the vertical direction of the optical fiber rod, which can make the accumulated water further affect the temperature measured by the sensing optical fiber from another aspect, increase the difference between the measured accumulated water temperature and the air temperature, thereby further ensuring the temperature measurement accuracy of the sensing optical fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a component exploded view of an embodiment of a water level measuring device based on a distributed temperature sensor of the present invention;

[0019] Figure 2 It is a schematic diagram of the assembly structure of an embodiment of a water level measuring device based on a distributed temperature sensor of the present invention;

[0020] Figure 3 is a schematic diagram of the structure of an optical fiber rod wound with a sensing optical fiber;

[0021] Figure 4 It is a schematic diagram of the measurement results. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention and to make the above-mentioned purposes, features and advantages of the embodiments of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0023] In the description of the present invention, unless otherwise specified and limited, it should be noted that the term "connection" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the internal connection between two elements. It can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0024] See also Figure 1 , is a component exploded view of an embodiment of a water level measurement device based on a distributed temperature sensor of the present invention. Figure 2 and Figure 3As shown, the accumulated water level measuring device may include an optical fiber rod 1, a base 2, a polygonal rod 3 fixed on the base 2, and a shell 4. The optical fiber rod 1 is provided with a vertical polygonal through hole matching the shape of the polygonal rod 3. After the polygonal rod 3 is inserted into the optical fiber rod 1, the optical fiber rod 1 is fixed on the base 2. The bottom of the shell 4 is a mesh structure 41. The optical fiber rod 1 is located in the shell 4 and a sensing optical fiber 5 of a distributed temperature sensor is wound thereon. According to the spatial resolution requirement of the accumulated water level and the spatial resolution of the corresponding sensing optical fiber 5 of the distributed temperature sensor, the winding length of the sensing optical fiber 5 in the corresponding height in the vertical direction of the optical fiber rod 1 is adjusted. The temperature measurement accuracy of the distributed temperature sensor is less than or equal to the minimum difference between the air temperature and the accumulated water temperature.

[0025] In this embodiment, the polygonal rod 3 can be a square cylinder, and the corresponding polygonal through hole in the optical fiber rod 1 can be a square through hole. The sensing optical fiber can be wound on the optical fiber rod in a spiral manner. The length of the sensing optical fiber can reach tens of kilometers, and one device can be connected to multiple temperature measuring optical fibers. Therefore, the monitoring device can be placed in various remote tunnels or urban drainage pipe networks and other environments where existing equipment is difficult to place for water level monitoring, and a modulation and demodulation device can be used to achieve real-time measurement of water levels in multiple scenes. When the spatial resolution of the accumulated water level is required to be k1, it means that the minimum value of the accumulated water level change that can be distinguished by the temperature difference in the vertical direction of the optical fiber rod is k1. When the spatial resolution of the sensing optical fiber corresponding to the distributed temperature sensor is k2, it means that the length of the sensing optical fiber in the temperature change area is at least k2 to distinguish the temperature change. At this time, the length L of the sensing optical fiber that needs to be wound in the vertical direction of the optical fiber rod per k1 height is greater than or equal to k0*k2, where k1 and k2 are any values ​​greater than 0, and k0 is an arbitrary value greater than 1 set artificially to ensure measurement accuracy, which can generally be 1.5 or 2.

[0026] In one example, urban flooding usually occurs in hot and rainy summers, when the temperature of the accumulated water is lower than the air temperature, and the temperature difference between the two is usually greater than 1°C. At this time, the temperature measurement accuracy of the selected distributed temperature sensor can be less than or equal to 1°C. When the spatial resolution of the sensing fiber corresponding to the distributed temperature sensor is 2m, that is, the length of the sensing fiber in the temperature change area must be at least 2m to distinguish the temperature change, if the spatial resolution of the accumulated water level is required to be at the cm level, then the length of the sensing fiber that needs to be wound in every 1cm height in the vertical direction of the optical fiber rod is L≥k0*2m. If higher accuracy is desired, k0 can take a value greater than 1. When k0=1.5, the length is Lπ1.5*2m.

[0027] When the optical fiber rod is cylindrical, the length L of the sensing optical fiber that needs to be wound within each k1 height in the vertical direction of the optical fiber rod is n*2πr, wherein n is the number of windings, r is the radius of the optical fiber rod, n is an integer greater than 0, and r is any value greater than 0. According to the formula n*r≥k0*k2 / 2π, the number n of windings of the sensing optical fiber within each k1 height in the vertical direction of the optical fiber rod and the radius r of the optical fiber rod can be designed to meet the required spatial resolution of the accumulated water level.

[0028] During measurement, the accumulated water enters the shell through the mesh structure at the bottom of the shell, so that the water levels inside and outside the shell remain consistent. The sensing optical fiber in the shell measures the temperature, and determines the length of the sensing optical fiber located in the accumulated water according to the temperature difference on the sensing optical fiber. The water level is determined according to the length of the sensing optical fiber located in the accumulated water and the winding length of the sensing optical fiber at the corresponding height in the vertical direction of the optical fiber rod. After the sensing optical fiber measures the corresponding temperature information, the temperature of each section of the sensing optical fiber is first compared to determine the temperature difference dividing line of the sensing optical fiber. The portion of the sensing optical fiber with a lower temperature below the dividing line is used as the sensing optical fiber section that measures the temperature of the accumulated water and is located in the accumulated water. In the experiment, the test data results are as follows: the immersion depth is 10 cm, and the measured length of the immersed part of the optical fiber is 30 meters; the immersion depth calculated according to the measured data is 30 ÷ 3.14 = 9.55 cm. The error is within 1 cm, which meets the requirements. In addition, if Figure 4 As shown, there is a clear temperature difference between the immersed and unimmersed parts.

[0029] It can be seen from the above embodiments that the present invention arranges a shell outside the optical fiber rod wrapped with the sensing optical fiber, and designs the bottom of the shell as a mesh structure to filter foreign matter in the accumulated water. This can not only protect the sensing optical fiber and prevent external foreign matter from entering the shell and directly acting on the sensing optical fiber and affecting the temperature measurement of the sensing optical fiber, but also ensure that the water level inside and outside the shell is consistent, and the water level inside the shell will not fluctuate greatly, thereby further ensuring the temperature measurement accuracy of the sensing optical fiber. The present invention also provides a polygonal rod in the shell. After the polygonal rod fixed on the base is inserted into the optical fiber rod, the optical fiber rod is fixed on the base. In this way, on the one hand, it is convenient to remove and install the optical fiber rod, and it is convenient to perform daily inspection and maintenance on the sensing optical fiber on the optical fiber rod. On the other hand, the polygonal rod can prevent the optical fiber rod from rotating under the action of accumulated water. Moreover, the optical fiber rod and the base are not tightly connected. The accumulated water will enter the space between the optical fiber rod and the polygonal rod through the gap between the optical fiber rod and the base. The accumulated water in the space can also transfer the temperature to the sensing optical fiber through the optical fiber rod, so that the sensing optical fiber can sense the accumulated water temperature in all directions, increase the difference between the measured accumulated water temperature and the air temperature, thereby further ensuring the accuracy of the temperature measurement of the sensing optical fiber.

[0030] In addition, for the structure of the present invention, although the sensing optical fiber measures the temperature of the accumulated water in the shell, since the accumulated water in the shell is connected to the external accumulated water, the accumulated water range and the accumulated water level are unknown, so it is still impossible to increase the temperature difference of the water-air interface by heating to measure the accumulated water level. To this end, the present invention proposes a new measurement method based on the above structure, selects a distributed temperature sensor with a temperature measurement accuracy less than or equal to the minimum difference between the air temperature and the accumulated water temperature, and adjusts the winding length of the sensing optical fiber in the corresponding height in the vertical direction of the optical fiber rod according to the spatial resolution requirement of the accumulated water level and the spatial resolution of the distributed temperature sensor corresponding to the sensing optical fiber. Since the above structure can ensure that the accumulated water air temperature has obvious differences, even if the accumulated water range and the accumulated water level are unknown, the measurement method of the present invention can also realize accurate measurement of the accumulated water level, and winding the sensing optical fiber on the optical fiber rod makes up for the lack of resolution of the sensing optical fiber when measuring the accumulated water level, and the longer temperature measurement distance and passive characteristics also allow the device to be placed in remote and complex environments, greatly expanding the monitoring range, so that the measurement device has universal applicability.

[0031] The measuring device of the present invention is a passive device, and the system mainly performs measurements through optical fiber. The passive characteristics of optical fiber mean that it does not require external power supply, thereby reducing the energy consumption and maintenance cost of the system. The present invention has strong anti-interference ability, and the optical fiber is mainly composed of silicon dioxide, which has good stability and resistance to electromagnetic interference, so that it can be widely used in various underground facilities in cities such as tunnels, underpasses, underground garages, urban drainage pipe networks and subway tracks, etc., greatly expanding the field and scope of urban waterlogging detection; especially in remote tunnels and urban drainage pipe networks, it can provide real-time monitoring capabilities that are difficult to achieve with other equipment.

[0032] In addition, in the above embodiment, the top of the polygonal rod 3 may be provided with a threaded column 6, and after the threaded column 6 passes through the polygonal through hole in the optical fiber rod 1, the optical fiber rod 1 is fixed to the base 2 by a nut 7. The optical fiber rod 1 and the housing 4 may both be cylindrical. The upper end of the housing 4 is provided with a protective cover 8 and a through hole 12 for the sensing optical fiber to pass through, wherein the protective cover 8 may be fixed to the housing 4 by a protective cover bolt 9 and a protective cover nut 10. The base 2, the polygonal rod 3 and the housing 4 may be integrally formed, and a screw hole 11 may be provided on the base 2, and the base 2 may be fixed by passing a screw through the screw hole 11. In another embodiment, the bottom of the optical fiber rod 1 may also be a mesh structure, and the optical fiber rod 1 may be provided with transverse guide holes distributed in the vertical direction. The present invention designs the optical fiber rod and the shell to be cylindrical, so that even if a small-scale fluctuation occurs in the shell, the fluctuation can be quickly balanced. The present invention designs the bottom of the optical fiber rod to be a mesh structure, and horizontal guide holes are distributed in the vertical direction of the optical fiber rod, and the space between the optical fiber rod into which the accumulated water flows and the polygonal rod is made polygonal, which can stabilize the fluctuation and further weaken the formed fluctuation, thereby further ensuring the temperature measurement accuracy of the sensing optical fiber; in addition, horizontal guide holes are distributed in the vertical direction of the optical fiber rod, so that the accumulated water can further affect the temperature measured by the sensing optical fiber from another aspect, increase the difference between the measured accumulated water temperature and the air temperature, thereby further ensuring the temperature measurement accuracy of the sensing optical fiber.

[0033] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art that are not disclosed by the present invention. The specification and examples are to be considered exemplary only, and the true scope and spirit of the present invention are indicated by the following claims.

[0034] It will be appreciated that the invention is not limited to the exact construction that has been described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the invention is governed solely by the appended claims.

Claims

1. A water level measuring device based on a distributed temperature sensor, characterized in that: It comprises an optical fiber rod, a base, a polygonal rod fixed on the base, and a shell. A vertical polygonal through hole matching the shape of the polygonal rod is provided in the optical fiber rod. After the polygonal rod is inserted into the optical fiber rod, the optical fiber rod is fixed on the base. The bottom of the shell is a mesh structure. The optical fiber rod is located in the shell and a sensing optical fiber of a distributed temperature sensor is wound on the optical fiber rod. According to the spatial resolution requirement of the accumulated water level and the spatial resolution of the corresponding sensing optical fiber of the distributed temperature sensor, the winding length of the sensing optical fiber in the corresponding height in the vertical direction of the optical fiber rod is adjusted. The temperature measurement accuracy of the distributed temperature sensor is less than or equal to the minimum difference between the air temperature and the accumulated water temperature.

2. The water level measuring device based on distributed temperature sensor according to claim 1 is characterized in that: When the spatial resolution of the accumulated water level is required to be k1, it means that the minimum value required for the optical fiber rod to distinguish the change of the accumulated water level through the temperature difference in the vertical direction is k1. When the spatial resolution of the sensing optical fiber corresponding to the distributed temperature sensor is k2, it means that the length of the sensing optical fiber in the temperature change area must be at least k2 to distinguish the temperature change. At this time, the length L of the sensing optical fiber that needs to be wound within every height of k1 in the vertical direction of the optical fiber rod is greater than or equal to k0*k2, where k1 and k2 are arbitrary values ​​greater than 0, and k0 is an arbitrary value greater than 1 that is artificially set to ensure measurement accuracy.

3. The water level measuring device based on distributed temperature sensors according to claim 2 is characterized in that: The optical fiber rod is cylindrical, and the length L of the sensing optical fiber that needs to be wound within each k1 height in the vertical direction of the optical fiber rod is n*2πr, wherein n is the number of windings, r is the radius of the optical fiber rod, n is an integer greater than 0, and r is any value greater than 0. According to the formula n*rπk0*k2 / 2π, the number n of windings of the sensing optical fiber within each k1 height in the vertical direction of the optical fiber rod and the radius r of the optical fiber rod are designed.

4. The water level measuring device based on distributed temperature sensors according to claim 1 is characterized in that: During measurement, the accumulated water enters the shell through the mesh structure at the bottom of the shell, so that the water levels inside and outside the shell remain consistent. The sensing optical fiber in the shell performs temperature measurement, and the length of the sensing optical fiber located in the accumulated water is determined based on the temperature difference on the sensing optical fiber. The water level is determined based on the length of the sensing optical fiber located in the accumulated water and the winding length of the sensing optical fiber at the corresponding height in the vertical direction of the optical fiber rod.

5. The water level measuring device based on distributed temperature sensors according to claim 1 is characterized in that: After the threaded column at the top end of the polygonal rod passes through the polygonal through hole in the optical fiber rod, the optical fiber rod is fixed on the base through a nut.

6. The accumulated water level measuring device based on distributed temperature sensors according to claim 1 or 5, characterized in that: The optical fiber rod and the shell are both cylindrical.

7. The device for measuring accumulated water level based on distributed temperature sensors according to claim 6, characterized in that: The upper end of the shell is provided with a protective cover and a through hole for the sensing optical fiber to pass through.

8. The device for measuring accumulated water level based on distributed temperature sensors according to claim 7, characterized in that: The base, the polygonal rod and the shell are integrally formed, and a screw hole is provided on the base. The base is fixed by screws passing through the screw hole.

9. The device for measuring accumulated water level based on distributed temperature sensors according to claim 6, characterized in that: The bottom of the optical fiber rod is a mesh structure, and the optical fiber rod is provided with transverse flow guide holes distributed in the vertical direction.

10. The device for measuring accumulated water level based on distributed temperature sensors according to claim 1, characterized in that: The sensing optical fiber is wound on the optical fiber rod in a spiral manner.

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