A fish-shaped fiber Bragg grating pressure and temperature sensor
Through the design of the fish-type fiber grating sensor, combined with the principles of fish-body bionics and computer computing, the accuracy and range of pressure and temperature detection in the hydraulic tube are solved, and high-precision pressure and temperature distribution detection is achieved.
Patent Information
- Application Number
- CN202010132414.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2020-02-29
- Publication Date
- 2025-01-03
- Estimated Expiration
- 2040-02-29
AI Technical Summary
The existing fiber grating sensors have problems such as small load, narrow measurement range, insufficient structural strength and slow response speed in the pressure and temperature detection of hydraulic pipes, making it difficult to achieve high-precision pressure and temperature distribution detection at the same time.
A fish-type fiber grating pressure and temperature sensor was designed, using the principle of fish-body bionics, using fish bone-shaped metal sheets and fiber grating sensors, eliminating the temperature influence through the principle of forward and reverse deformation of the grating, combining with computer large-capacity calculation to expand the detection range, and Thermal silicone oil and partitions slow down external pressure interference, achieving high-precision temperature and pressure detection.
High-precision temperature and pressure distribution detection in the hydraulic tube is realized, the detection range is expanded, the sensitivity and response speed of the sensor are improved, and the problem of insufficient structural strength and response speed in the prior art is overcome.
Smart Images
Figure CN113405720B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical fields of optical fiber sensing and hydraulic detection, and in particular to a fish-shaped optical fiber grating pressure and temperature sensor. Background Art
[0002] Fiber Bragg grating is a diffraction grating formed by axially periodically modulating the refractive index of the optical fiber core through a certain method. It is a passive filtering device. Because grating fiber has the advantages of small size, small fusion loss, full compatibility with optical fiber, and ability to be embedded in smart materials, and its resonant wavelength is sensitive to changes in external environment such as strain, refractive index, and concentration, it has been widely used in the field of optical fiber communication and sensing.
[0003] Ordinary fiber Bragg gratings have poor tensile and bending resistance when exposed, so it is necessary to encapsulate and protect the fiber Bragg grating. Because the temperature resistance of fiber Bragg grating is poor, if the operating temperature is higher than the heat resistance temperature of the fiber Bragg grating, the central wavelength of the grating will drift greatly, resulting in the calibration method of fiber Bragg grating through linear fitting, and the range is limited.
[0004] At present, when detecting the pressure or temperature in the hydraulic pipeline, the method of opening a detection process hole in the pipeline path and installing a pressure or temperature sensor probe on the pipeline path side wall is usually adopted. However, this method has certain problems: first, it destroys the pipeline side wall structure; second, the radial sensor probe destroys the laminar flow morphology of the inner wall liquid flow and increases the internal disturbance of the liquid flow; third, the inner and outer flow velocities of the spiral pipeline are different, and the pressure state is different. It is difficult to accurately measure the pressure distribution and change law in the pipeline by using a fixed pressure sensor probe. Most of the liquid pressure measurements in the pipeline are carried out using the fiber grating principle, but when using the fiber grating pressure sensor for pressure measurement, there are problems such as small load and small measurement pressure range. For this reason, the cantilever beam amplification principle is usually used to encapsulate the pressure sensor to solve the problem of small sensor load. However, this will also cause the problem of increased sensor volume; and encapsulating the sensor cannot solve the problem of its small measurement pressure range, that is, the range of this pressure sensor still cannot meet the actual needs of engineering hydraulic machinery.
[0005] The biggest feature of fiber Bragg grating temperature sensors is that they can connect multiple sensors in series to achieve distributed temperature measurement. A maximum of 35 temperature sensors can be connected in series on a single optical fiber, which greatly reduces the number of wiring connections. It is simple, reliable and economical. Existing fiber Bragg grating temperature sensors encounter two types of problems when used in engineering structures. One is the strength of the fiber Bragg grating temperature sensor itself, and the other is the time response problem. High strength will inevitably lead to a large packaging shell thickness, which affects the response speed to the ambient temperature. In order to increase the response speed, the thickness of the packaging tube must be reduced, which in turn reduces the protection strength. In the prior art, the packaging structure of the fiber Bragg grating temperature sensor cannot simultaneously have strong protection strength and fast response speed.
[0006] The invention (CN201010141147.4 A fiber grating temperature sensor) ensures strong protection for the fiber grating by encapsulating it in a packaging tube made of metal, glass or ceramic materials; however, since the grating mainly senses the ambient temperature outside the packaging tube by sensing the heat of the enclosed gas in the packaging tube, it is easy for the grating to deform due to the expansion pressure of the internal gas at high temperatures, and it is also easy for the internal heat dissipation speed to be affected when the ambient temperature drops, resulting in a delayed response. Moreover, this sensor can only detect temperature, but cannot simultaneously detect pressure in the same environment.
[0007] Therefore, there is an urgent need for a detection system that can achieve high-precision temperature and pressure distribution in hydraulic pipes, which can be used for high-precision detection of oil temperature in pipelines and lossless collection of internal pressure data at multiple points on the pipeline wall. This technology mainly relies on the innovation of sensors and calibration detection methods to promote in-depth research and optimization of hydraulic pipelines. The present invention speculates on the neural perception principle of fish to liquid pressure and temperature, combines the structure of fish body in water, and mainly innovates bionic fish-type pressure and temperature sensors. Summary of the invention
[0008] The present invention provides a fish-shaped fiber Bragg grating pressure and temperature sensor, which has a reasonable structural design. According to the bionics principle of fish body, a fishbone-shaped metal sheet is designed, and fiber Bragg grating sensors are arranged on both sides of the central axis of the metal sheet, which plays the role of a strain diaphragm under low pressure. Two optical fibers are arranged on both sides of the "fish line" of the metal sheet, and the positive and negative deformation principles of two grating sensors are used to eliminate the temperature influence, so as to realize the pressure detection with temperature self-compensation. The present invention makes full use of the characteristics of large-capacity and high-speed operation of computers, and overcomes the problem that the linear fitting method used in sensor calibration causes information loss and cannot expand the detection range. The invention solves the problem, thereby expanding the range of pressure detection of the current fiber Bragg grating sensor, solves the problems existing in the prior art, and utilizes the sub-symmetrical structure of the fish body. On the other side, the temperature is transmitted to the wall of the temperature measuring cavity built into the skeleton through the beard-shaped temperature measuring metal wire protruding to the outside, and then transmitted to the temperature measuring grating sensitivity enhancement component by the partition on the wall of the temperature measuring cavity and the thermal conductive silicone oil in the temperature measuring cavity. The fiber Bragg grating is fixed on the temperature measuring grating sensitivity enhancement component, which enhances the timeliness of the fiber Bragg grating to collect the environmental temperature change and improves the sensitivity coefficient to the temperature signal. At the same time, because the elastic modulus of the partition and the wall of the temperature measuring cavity is much larger than that of the surrounding airbag and elastic The elastic modulus of the fish's body skeleton greatly reduces the interference of the external pressure strain of the fish body on the longitudinal deformation of the grating on the temperature measuring grating sensitive component in the temperature measuring metal shell. On the other hand, since the temperature measuring grating sensitive component is fixedly connected to the partition at only one arc-shaped cross section, even if the partition is slightly deformed due to external stress, it will not affect the longitudinal deformation of the optical fiber pasted on the longitudinal axis of the arc-shaped temperature measuring grating sensitive component, thereby avoiding the interference of external pressure on the longitudinal deformation of the grating on the temperature measuring grating sensitive component in the temperature measuring metal shell, and thus overcoming the cross-interference of the longitudinal signal of the fiber Bragg grating measuring the temperature caused by the deformation caused by external stress. ; Furthermore, since only one end of the temperature measuring grating sensitizer is fixed when it deforms longitudinally and the other end is freely suspended, the cross-interference of the longitudinal signal of the fiber grating measuring temperature caused by the inherent thermal stress deformation caused by thermal expansion and contraction is overcome, thereby achieving high-precision temperature detection by the fiber grating; Finally, in order to make full use of the information collected by the above-mentioned temperature signal and expand the pressure detection range of the fiber grating group on both sides of the negative metal sheet, the fiber grating on the outside of the positive metal sheet can be used to simultaneously detect the pressure and temperature data of the liquid in the pipeline, and the pressure measurement of the fiber grating on the outside of the positive metal sheet is realized by table lookup and inverse calculation after the temperature data is collected.
[0009] The technical solution adopted by the present invention to solve the above technical problems is: a fish-shaped fiber Bragg grating pressure and temperature sensor, suitable for detecting the pressure and temperature of the liquid in the pipeline, comprising:
[0010] The skeleton is composed of two metal sheets symmetrically arranged with each other, and the metal sheets are set as thin sheet structures that are long in the longitudinal direction and short in the transverse direction, one of the metal sheets is provided with longitudinal grooves symmetrically on both sides of its longitudinal central axis, and is set as a female metal sheet; the other metal sheet is provided with longitudinal outwardly protruding rib grooves symmetrically on both sides of its longitudinal central axis, and is set as a male metal sheet; the middle parts of the male metal sheet and the female metal sheet are respectively bulged outwards, so that a cavity is formed between the two metal sheets, and an air bag similar to a fish bubble is arranged in the cavity, and a filler is arranged between the air bag and the metal sheet;
[0011] A direct pressure measuring unit, the direct pressure measuring unit comprising a No. 1 optical fiber and a No. 2 optical fiber, the No. 1 optical fiber and the No. 2 optical fiber are symmetrically arranged along the longitudinal axis of the inner and outer side walls of the negative metal sheet, the No. 1 optical fiber and the No. 2 optical fiber are symmetrically engraved with gratings corresponding to the middle of the negative metal sheet, and the grating characteristic values on the No. 1 optical fiber and the No. 2 optical fiber are the same; when the skeleton is subjected to the liquid pressure in the pipeline, the gratings on the No. 1 optical fiber and the No. 2 optical fiber undergo positive and negative deformations along the longitudinal direction of the skeleton, thereby realizing temperature self-compensated pressure detection;
[0012] A temperature measuring unit, the temperature measuring unit comprises a temperature measuring metal shell arranged in a cavity, the temperature measuring metal shell is connected to the inner wall of the positive metal sheet to form a temperature measuring cavity, at least two partitions connected to the inner wall of the temperature measuring metal shell are arranged in the temperature measuring cavity, a temperature measuring grating sensitivity enhancement component is arranged in the temperature measuring cavity, one end of the temperature measuring grating sensitivity enhancement component is fixedly connected to one of the partitions, and the other end of the temperature measuring grating sensitivity enhancement component passes through another partition and is suspended, so that the temperature measuring grating sensitivity enhancement component can freely expand and contract when thermal expansion and contraction occur, A heat-conducting medium is provided in the temperature measurement cavity, so that the temperature-measuring grating sensitizing component is immersed in the heat-conducting medium, the temperature-measuring grating sensitizing component is connected to the No. 3 optical fiber, the No. 3 optical fiber is recorded with a grating corresponding to the position of the temperature-measuring grating sensitizing component, the grating on the No. 3 optical fiber is tightly adhered to the temperature-measuring grating sensitizing component, and has the same characteristic value as the gratings on the No. 1 optical fiber and the No. 2 optical fiber, the No. 3 optical fiber is arranged through a temperature-measuring metal shell, the temperature-measuring metal shell is connected to a temperature-measuring metal wire, and the temperature-measuring metal wire is arranged to extend outward through a skeleton;
[0013] An indirect pressure measuring unit, wherein the indirect pressure measuring unit comprises a No. 4 optical fiber, wherein the No. 4 optical fiber is arranged along the longitudinal axis of the outer side wall of the positive side metal sheet, and a grating is engraved on the No. 4 optical fiber corresponding to the middle part of the positive side metal sheet, and the grating on the No. 4 optical fiber has the same characteristic value as the gratings on the No. 1 optical fiber, the No. 2 optical fiber, and the No. 3 optical fiber;
[0014] Four optical fibers with different numbers are sequentially assembled into optical cables from both ends of the skeleton, and the optical cables are connected to a four-channel optical fiber connector;
[0015] The skin is encapsulated outside the skeleton and the optical cable, and the skin is compatible with the hydraulic medium material in the pipeline; the temperature measuring metal wire passes through the skeleton and the skin and then extends outward.
[0016] Furthermore, there is a gap at both ends of the two metal sheets in the longitudinal direction, the size of the gap changes due to the deformation of the two metal sheets, and the minimum size of the gap is not less than the diameter of the optical fiber.
[0017] Furthermore, the positive metal sheet is provided with an outwardly protruding rib groove, the temperature measuring metal shell and the rib groove on the inner wall of the positive metal sheet are matched, and the connection position between the temperature measuring metal shell and the rib groove is provided by a colloid seal.
[0018] Furthermore, the temperature measuring cavity is filled with 1 / 2 to 4 / 5 of a heat-conducting medium, and the heat-conducting medium is selected from heat-conducting silicone oil or heat-conducting silicone grease.
[0019] Furthermore, two connecting rods are respectively provided at both ends of the cavity in the skeleton, and the two ends of each connecting rod are respectively passed through the female metal sheet and the male metal sheet. The connecting rod is provided with an intermediate connecting ring between the female metal sheet and the male metal sheet, and the intermediate connecting ring is connected to the traction rope, and the traction rope is connected to the optical fiber connector.
[0020] Furthermore, both ends of the connecting rod are located on the outside of the skeleton and are respectively provided with end connecting rings, and the two end connecting rings are connected to the anti-torsion rope. The anti-torsion rope is connected to the end connecting rings of the connecting rods of the skeletons of other fish-type sensors in series, or is connected to the corresponding holes on the optical fiber connectors at the corresponding ends thereof, so as to enhance the connection stability between adjacent skeletons.
[0021] Furthermore, each of the metal sheets is provided with at least two side grooves, which are symmetrically arranged about the longitudinal center axis of the metal sheet, so that the parts left beside the side grooves form a plurality of mutually cooperating support parts; when the skeleton is subjected to liquid pressure, the support parts corresponding to the two metal sheets can abut against each other to increase the overall elastic modulus of the skeleton.
[0022] Furthermore, the two metal sheets are symmetrically provided with end grooves at both longitudinal ends, and the gap is formed between the parts left beside the end grooves. The intermediate connecting ring can abut against the parts left beside the end grooves of the two metal sheets, so that the minimum size of the gap is not less than the diameter size of the optical fiber.
[0023] Furthermore, the support parts are bent so that the corresponding side support parts of the two metal sheets form corresponding contact surfaces; when the frame is subjected to pressure, the corresponding support parts abut against each other, or the filler is arranged between the support parts so that the support parts and the filler abut against each other.
[0024] Furthermore, transparent grooves are excavated on the negative metal sheet along the upper and lower sides of the optical fiber, so that the negative metal sheet can quickly deform and respond under low pressure. Optical fiber No. 1 is arranged on the outer side of the negative metal sheet, and optical fiber No. 2 is arranged on the inner side; the gratings on optical fiber No. 1 and optical fiber No. 2 are combined to measure the liquid pressure in the pipeline, and the grating on optical fiber No. 3 is suitable for measuring the liquid temperature in the pipeline; the grating on optical fiber No. 4 is suitable for measuring the comprehensive value of liquid pressure and temperature in the pipeline, and indirectly measures the pressure through the temperature detection of the grating on optical fiber No. 3, and can be combined with calibration equipment to recheck and verify the temperature value detected by optical fiber No. 3 under a given pressure.
[0025] The calibration equipment mainly calibrates pressure and temperature; the pressure calibration mainly involves setting the pressure step by step within the working pressure range according to the accuracy requirement, collecting the difference in characteristic center wavelength offset of the grating group on the No. 1 optical fiber and the No. 2 optical fiber under the set pressure, and establishing a one-to-one correspondence table between the pressure and the collected signal (difference in offset); the temperature calibration mainly involves setting the temperature step by step within the working temperature range according to the accuracy requirement, collecting the characteristic center wavelength offset of the grating group on the No. 3 optical fiber under the set temperature, and establishing a one-to-one correspondence table between the temperature and the collected signal (offset); Step by step, the temperature is set step by step, and within each given temperature level, the pressure is increased step by step, and the pressure is set step by step with the required pressure accuracy as the step size. Under the set pressure, the grating characteristic center wavelength offset on the No. 3 optical fiber and the No. 4 optical fiber is collected, and the grating characteristic center wavelength offset on the No. 4 optical fiber corresponding to each level of pressure at different temperatures is established. The center wavelength offset is calibrated in a fishing net-shaped data table formed by pressure and temperature. By searching the temperature signal on the No. 3 optical fiber and the grating characteristic center wavelength offset on the No. 4 optical fiber, and then screening through the above-mentioned fishing net-shaped data table, the corresponding pressure value or the pressure value and accuracy range of the grid attachment can be obtained.
[0026] The beneficial effect of the above structure of the present invention is that its structural design is reasonable. According to the bionic principle of fish body, a fishbone-shaped metal sheet is designed, and fiber grating sensors are arranged on both sides of the central axis of the metal sheet, which plays the role of a strain diaphragm under low pressure. Two optical fibers are arranged on both sides of the "fish line" of the metal sheet, and the positive and negative deformation principles of two grating sensors are used to eliminate the temperature influence, thereby realizing the detection of pressure with temperature self-compensation; the present invention makes full use of the characteristics of large-capacity and high-speed computing of computers, overcomes the problem of information loss caused by the linear fitting method in sensor calibration and the inability to expand the detection range, thereby The invention expands the pressure detection range of the current fiber Bragg grating sensor, solves the problems existing in the prior art, and utilizes the sub-symmetrical structure of the fish body. On the other side, the temperature is transmitted to the wall of the temperature measuring cavity built into the skeleton through the beard-shaped temperature measuring metal wire protruding to the outside, and then transmitted to the temperature measuring grating sensitivity enhancement component by the partition on the wall of the temperature measuring cavity and the heat-conducting silicone oil in the temperature measuring cavity. The fiber Bragg grating is fixed on the temperature measuring grating sensitivity enhancement component, which enhances the timeliness of the fiber Bragg grating to collect environmental temperature changes and improves the sensitivity coefficient to the temperature signal. At the same time, since the elastic modulus of the partition and the wall of the temperature measuring cavity is much larger than that of the surrounding airbag and the elastic body bone The elastic modulus of the frame greatly reduces the interference of the pressure strain outside the fish body on the longitudinal deformation of the grating on the temperature measuring grating sensitivity member in the temperature measuring metal shell. On the other hand, since the temperature measuring grating sensitivity member is fixedly connected to the partition at only one arc-shaped cross section, even if the partition is slightly deformed due to external stress, it will not affect the longitudinal deformation of the optical fiber pasted on the longitudinal axis of the arc-shaped temperature measuring grating sensitivity member, thereby avoiding the interference of external pressure on the longitudinal deformation of the grating on the temperature measuring grating sensitivity member in the temperature measuring metal shell, and thus overcoming the cross-interference of the deformation caused by external stress on the longitudinal signal of the fiber Bragg grating measuring temperature; Furthermore, since only one end of the temperature measuring grating sensitizer is fixed when it deforms longitudinally and the other end is freely suspended, the cross-interference of the longitudinal signal of the fiber grating measuring temperature caused by the inherent thermal stress deformation caused by thermal expansion and contraction is overcome, thereby achieving high-precision temperature detection by the fiber grating; finally, in order to make full use of the information collected by the above-mentioned temperature signal and expand the pressure detection range of the fiber grating group on both sides of the negative metal sheet, the fiber grating on the outside of the positive metal sheet can be used to simultaneously detect the pressure and temperature data of the liquid in the pipeline, and the pressure measurement of the fiber grating on the outside of the positive metal sheet is realized by table lookup and inverse calculation after the temperature data is collected. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Figure 1 It is a three-dimensional structural schematic diagram of the main structure of the skeleton of the present invention.
[0028] Figure 2 It is a schematic diagram of the top view of the main structure of the skeleton of the present invention.
[0029] Figure 3It is a side view structural schematic diagram of the main structure of the skeleton of the present invention.
[0030] Figure 4 It is a schematic diagram of the cross-sectional structure after assembly of the present invention.
[0031] Figure 5 It is a structural schematic diagram of the combination state of multiple sensors of the present invention.
[0032] Figure 6 It is a structural schematic diagram of the optimized state of the positive metal sheet of the present invention.
[0033] Figure 7 It is a structural schematic diagram of the optimized state of the negative metal sheet of the present invention.
[0034] In the figure, 1, negative metal sheet; 2, rib groove; 3, positive metal sheet; 4, cavity; 5, air bag; 6, filler; 7, optical fiber No. 1; 8, optical fiber No. 2; 9, temperature measuring metal shell; 10, temperature measuring cavity; 11, partition; 12, temperature measuring grating sensitivity enhancement component; 13, optical fiber No. 3; 14, temperature measuring metal wire; 15, optical fiber No. 4; 16, optical fiber connector; 17, gap; 18, connecting rod; 1801, middle connecting ring; 1802, end connecting ring; 19, traction rope; 20, anti-torsion rope; 21, side groove; 22, support part; 23, end groove; 24, groove. DETAILED DESCRIPTION
[0035] In order to clearly illustrate the technical features of the present solution, the present invention is described in detail below through specific implementation methods and in conjunction with the accompanying drawings.
[0036] In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present application is not limited to the specific embodiments disclosed below.
[0037] In addition, in the description of the present application, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.
[0038] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.
[0039] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or a communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.
[0040] In the present application, unless otherwise clearly specified and limited, a first feature "above" or "below" a second feature may be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in an appropriate manner in any one or more embodiments or examples.
[0041] like Figure 1-7 As shown, a fish-shaped fiber Bragg grating pressure and temperature sensor is suitable for detecting the pressure and temperature of liquid in a pipeline, comprising a skeleton, a direct pressure measuring unit, a temperature measuring unit, an indirect pressure measuring unit and a skin, wherein the skeleton is composed of two metal sheets arranged symmetrically with each other, and the metal sheets are set as a thin sheet structure which is long in the longitudinal direction and short in the transverse direction, wherein one of the metal sheets has longitudinal grooves symmetrically opened on both sides of its longitudinal central axis, and is set as a female metal sheet 1; the other metal sheet has longitudinally outwardly protruding rib grooves symmetrically opened on both sides of its longitudinal central axis, and is set as a male metal sheet 3; the middle parts of the male metal sheet 3 and the female metal sheet 1 are respectively raised outwardly, so that a cavity 4 is formed between the two metal sheets, an air bag 5 similar to a fish bubble is set in the cavity 4, and a filler 6 is set between the air bag 5 and the metal sheet; an inert gas or other non-toxic gas is set in the air bag 5, and the filler 6 is set as an elastic filler, and the elastic filler includes a rubber or resin model.
[0042] The direct pressure measurement unit includes optical fiber No. 1 7 and optical fiber No. 2 8, which are symmetrically arranged along the longitudinal axis of the inner and outer side walls of the negative metal sheet 1. Optical fiber No. 1 7 and optical fiber No. 2 8 are symmetrically engraved with gratings corresponding to the middle of the negative metal sheet 1, and the grating characteristic values on optical fiber No. 1 7 and optical fiber No. 2 8 are the same (the grating grid period is the same, the engraving depth is the same, and the grid length is the same); when the skeleton is subjected to the liquid pressure in the pipeline, the gratings of optical fiber No. 1 7 and optical fiber No. 2 8 undergo positive and negative deformations along the longitudinal direction of the skeleton, which is similar to the working principle of the spring tube fiber grating pressure sensor to eliminate the influence of temperature, thereby realizing temperature self-compensated pressure detection;
[0043] The temperature measuring unit includes a temperature measuring metal shell 9 arranged in the cavity 4, the temperature measuring metal shell 9 is connected to the inner wall of the positive metal sheet 3 to form a temperature measuring cavity 10, at least two partitions 11 connected to the inner wall of the temperature measuring metal shell 9 are arranged in the temperature measuring cavity 10, and a temperature measuring grating sensitivity enhancement component 12 is arranged in the temperature measuring cavity 10, one end of the temperature measuring grating sensitivity enhancement component 12 is fixedly connected to one of the partitions 11, and the other end of the temperature measuring grating sensitivity enhancement component 12 passes through another partition 11 through the suspension setting, so that the temperature measuring grating sensitivity enhancement component 12 can freely expand and contract at the suspension end due to thermal expansion and contraction, and the partitions 11 are arranged at intervals along the longitudinal axis of the temperature measuring cavity 10, and the partitions 11 are arranged at intervals. The temperature measuring cavity 10 has holes or openings on the edges to ensure light weight and good support strength. A heat-conducting medium is provided in the temperature measuring cavity 10, so that the temperature measuring grating sensitizing component 12 is immersed in the heat-conducting medium. The temperature measuring grating sensitizing component 12 is connected to the third optical fiber 13. The third optical fiber 13 is engraved with a grating corresponding to the position of the temperature measuring grating sensitizing component 12. The grating of the third optical fiber 13 is tightly attached to the temperature measuring grating sensitizing component 12, and has the same grating characteristic value as the first optical fiber 7 and the second optical fiber 8. The third optical fiber 13 is set through the temperature measuring metal shell 9, and the temperature measuring metal shell 9 is connected to the temperature measuring metal wire 14. The temperature measuring metal wire 14 passes through the skeleton and extends outward;
[0044] The partition 11 is connected to the temperature measuring metal shell 9, and can more reliably conduct the heat of the temperature measuring metal wire 14 to the temperature measuring grating sensitizer 12 through the temperature measuring metal shell 9 and the partition 11. The other parts of the temperature measuring grating sensitizer 12 can be suspended or movably connected on other partitions 11 to ensure that the temperature measuring grating sensitizer 12 is freely extended and deformed due to the influence of temperature. The temperature measuring grating sensitizer 12 can simultaneously receive the heat transferred by the heat-conducting medium and the partition 11. At the same time, the partition 11 can also play an auxiliary supporting role for the temperature measuring grating sensitizer 12, so that the temperature measuring grating sensitizer 12 maintains a stable posture, and avoids the external oil flow from disturbing the sensor and affecting the shaking of the No. 3 optical fiber 13, thereby affecting the detection accuracy of the temperature measurement.The entire sensor speculates on the neural perception principle of fish to liquid pressure and temperature. Combined with the structure of fish in water, it is designed with a fishbone-shaped metal sheet, and fiber grating sensors are set on both sides of the central axis of the metal sheet. It plays the role of a strain diaphragm under low pressure. Two optical fibers and fiber gratings symmetrically set inside and outside are set on both sides of the longitudinal axis of the metal sheet ("fish line"), and the positive and negative deformation principles of the two gratings are used to eliminate the temperature influence, thereby realizing the detection of temperature self-compensated pressure; the computer's large-capacity and high-speed computing characteristics are fully utilized to overcome the problem of information loss caused by the linear fitting method used in sensor calibration and the inability to expand the detection range. The invention expands the pressure detection range of the current fiber Bragg grating sensor, solves the problems existing in the prior art, and utilizes the sub-symmetrical structure of the fish body. On the other side, the temperature is transmitted to the temperature measuring metal shell 9 built into the frame through the beard-shaped temperature measuring metal wire 14 protruding to the outside, and then transmitted to the temperature measuring grating sensitization component 12 by the partition 11 on the temperature measuring metal shell 9 and the heat-conducting silicone oil in the temperature measuring cavity. The fiber Bragg grating is fixed on the temperature measuring grating sensitization component 12, which enhances the timeliness of the fiber Bragg grating to collect environmental temperature changes and improves the sensitivity coefficient to the temperature signal. At the same time, since the elastic modulus of the partition 11 and the wall of the temperature measuring cavity 10 is much larger than that of the surrounding airbag and The elastic modulus of the elastomeric skeleton greatly reduces the interference of the pressure strain outside the fish body on the longitudinal deformation of the grating on the temperature measuring grating sensitive component 12 in the temperature measuring metal shell 9. On the other hand, since the temperature measuring grating sensitive component 12 is fixedly connected to the partition 11 at only one arc-shaped cross section, even if the partition is slightly deformed due to external stress, it will not affect the longitudinal deformation of the optical fiber pasted on the longitudinal axis of the arc-shaped temperature measuring grating sensitive component 12, thereby avoiding the interference of external pressure on the longitudinal deformation of the grating on the temperature measuring grating sensitive component 12 in the temperature measuring metal shell 9, and thus overcoming the effect of deformation caused by external stress on the longitudinal signal of the fiber Bragg grating measuring temperature. Cross-interference; furthermore, since only one end of the temperature measuring grating sensitizer 12 is fixed when it is longitudinally deformed and the other end is freely suspended, the cross-interference of the longitudinal signal of the fiber grating measuring temperature caused by the inherent thermal stress deformation caused by thermal expansion and contraction is overcome, thereby achieving high-precision temperature detection by the fiber grating; finally, in order to make full use of the information collected by the above-mentioned temperature signal and expand the pressure detection range of the fiber grating group on both sides of the negative metal sheet 1, the fiber grating on the outside of the positive metal sheet 3 can be used to simultaneously detect the pressure and temperature data of the liquid in the pipeline, and the pressure measurement of the fiber grating on the outside of the positive metal sheet 3 is realized by table lookup and inverse calculation after the temperature data is collected.
[0045] The indirect pressure measurement unit includes a fourth optical fiber 15, which is arranged along the longitudinal axis of the outer side wall of the positive metal sheet 3. The fourth optical fiber 15 corresponds to the middle part of the positive metal sheet 3 and has a grating engraved thereon. The grating on the fourth optical fiber 15 has the same characteristic value as the gratings on the first optical fiber 7, the second optical fiber 8, and the third optical fiber 13.
[0046] Four optical fibers with different numbers are sequentially assembled into an optical cable from both ends of the skeleton, and the optical cable is connected to a four-channel optical fiber connector 16;
[0047] The skin is encapsulated outside the frame and the optical cable, and the skin is compatible with the hydraulic medium material in the pipeline; the temperature measuring metal wire 14 passes through the frame and the skin and then extends outward.
[0048] It should be noted that there is a gap 17 at both ends of the two metal sheets in the longitudinal direction. The size of the gap 17 changes due to the deformation of the two metal sheets. The minimum size of the gap 17 is not less than the diameter of the optical fiber.
[0049] In a preferred embodiment, the positive metal sheet 3 is provided with an outwardly protruding rib groove 2, the temperature measuring metal shell 9 and the rib groove 2 on the inner wall of the positive metal sheet 3 are matched, and the connection position between the temperature measuring metal shell 9 and the rib groove 2 is provided by a colloid seal.
[0050] In a preferred embodiment, the temperature measuring cavity 10 is filled with 1 / 2 to 4 / 5 of a heat-conducting medium, and the heat-conducting medium is selected from heat-conducting silicone oil or heat-conducting silicone grease. The heat-conducting medium is not full, and the capacity of the heating medium is controlled within the range of 1 / 2 to 4 / 5. Under the premise of ensuring the heat-conducting capacity, the deformation factor of the outer wall of the temperature measuring cavity 10 is taken into account to absorb the influence of strain. The volume of the heat-conducting medium will increase by 10% after being heated from 20°C to 200°C. Therefore, the heat-conducting medium filled in the temperature measuring cavity 10 is filled with a maximum of 4 / 5 of the volume of the temperature measuring cavity 10 to ensure that the heat-conducting medium inside the temperature measuring cavity 10 will not squeeze the cavity wall of the temperature measuring cavity 10 after being heated and expanded.
[0051] In a preferred embodiment, two connecting rods 18 are respectively provided at both ends of the cavity 4 in the skeleton, and the two ends of each connecting rod 18 are respectively set through the female metal sheet 1 and the male metal sheet 3. The connecting rod 18 is located between the female metal sheet 1 and the male metal sheet 3 and is provided with an intermediate connecting ring 1801. The intermediate connecting ring 1801 is connected to a traction rope 19, and the traction rope 19 is connected to the optical fiber connector 16. The length of the traction rope 19 can be greater than ten times the longitudinal length of the skeleton, thereby avoiding the influence of the rear turbulence of the upstream object on the pressure detection of a sensor.
[0052] In a preferred embodiment, end connecting rings 1802 are respectively provided at both ends of the connecting rod 18 at the outer side of the skeleton, and the two end connecting rings 1802 are connected to the anti-torsion rope 20. The anti-torsion rope 20 is connected to the end connecting rings 1802 of the connecting rod 18 of the skeleton of other fish-type sensors in series, or is connected to the corresponding holes on the optical fiber connector 16 at the corresponding ends thereof, so as to enhance the connection stability between adjacent skeletons.
[0053] In a preferred embodiment, each metal sheet is provided with at least two side grooves 21, and the side grooves 21 are symmetrically arranged about the longitudinal center axis of the metal sheet, so that the portion left beside the side grooves 21 forms a plurality of mutually cooperating support portions 22; when the skeleton is subjected to liquid pressure, the corresponding support portions 22 of the two metal sheets can abut against each other to increase the overall elastic modulus of the skeleton.
[0054] In a preferred embodiment, the two metal sheets are symmetrically provided with end grooves 23 at both ends in the longitudinal direction, and a gap 17 is formed between the portions left beside the end grooves 23. The intermediate connecting ring 1801 can abut against the portions left beside the end grooves 23 of the two metal sheets, so that the minimum size of the gap 17 is not less than the diameter of the optical fiber. Figure 3 As shown, notches are set at the two end positions of the metal sheet compared to other positions. When the entire sensor is subjected to external oil pressure, when the main parts of the metal sheets abut against each other, the notch positions at both ends can ensure that the size of the gap 17 is larger than the diameter of the optical fiber, ensuring that the two ends of the two metal sheets will not contact each other and squeeze the optical fiber, thereby protecting the safety of the optical fiber.
[0055] In a preferred embodiment, the support portion 22 is bent so that the side support portions 22 corresponding to each other on the two metal sheets form corresponding contact surfaces; when the skeleton is subjected to pressure, the corresponding support portions abut against each other, or fillers 6 are arranged between the support portions so that the support portions 22 and the fillers 6 abut against each other.
[0056] It is worth mentioning that transparent grooves 24 are excavated along the upper and lower sides of the optical fiber on the female metal sheet 1, so that the female metal sheet 1 can quickly deform and respond under low pressure. Optical fiber No. 1 7 is arranged on the outer side of the female metal sheet 1, and optical fiber No. 2 8 is arranged on the inner side; the gratings on optical fiber No. 1 7 and optical fiber No. 2 8 are combined to measure the liquid pressure in the pipeline, and the grating on optical fiber No. 3 13 is suitable for measuring the liquid temperature in the pipeline; the grating on optical fiber No. 4 15 is suitable for measuring the comprehensive value of liquid pressure and temperature in the pipeline, and indirectly measures the pressure through the temperature detection of the grating on optical fiber No. 3 13; in addition, the temperature value detected by the grating on optical fiber No. 3 13 can also be verified and calibrated under a given pressure through calibration equipment.
[0057] The calibration equipment mainly calibrates pressure and temperature; the pressure calibration mainly involves setting the pressure step by step within the working pressure range according to the accuracy requirement, collecting the difference in characteristic center wavelength offset of the grating group on the No. 1 optical fiber 7 and the No. 2 optical fiber 8 under the set pressure, and establishing a one-to-one correspondence table between the pressure and the collected signal (difference in offset); the temperature calibration mainly involves setting the temperature step by step within the working temperature range according to the accuracy requirement, and collecting the characteristic center wavelength offset of the grating group on the No. 3 optical fiber 13 under the set temperature, and establishing a one-to-one correspondence table between the temperature and the collected signal (offset); further , set the temperature step by step, within each given temperature level, increase the pressure step by step, set the pressure step by step with the required pressure accuracy as the step size, under the set pressure, collect the grating characteristic center wavelength offset on the third optical fiber 13 and the fourth optical fiber 15, establish the grating characteristic center wavelength offset on the fourth optical fiber 15 corresponding to each level of pressure at different temperatures, and calibrate it in a fishnet-shaped data table formed by pressure and temperature. By searching the temperature signal on the third optical fiber 13 and the grating characteristic center wavelength offset on the fourth optical fiber, and then filtering through the above-mentioned fishnet-shaped data table, the corresponding pressure value or the pressure value and accuracy range of the grid attachment can be obtained.
[0058] When using, if attached Figure 5 As shown, multiple skeletons are connected in series via optical fibers so that multiple sensors can be used in a combined state. The outer gratings are connected to the outer ones, and the inner gratings are connected to the inner ones. The gratings on the same side ensure grouping, and the optical fiber connectors are clearly marked and in a regular order.
[0059] The above specific implementation manner cannot be used as a limitation on the protection scope of the present invention. For those skilled in the art, any substitution, improvement or change made to the implementation manner of the present invention falls within the protection scope of the present invention.
[0060] The matters not described in detail in the present invention are all known technologies to those skilled in the art.
Claims
1. A fish-shaped fiber Bragg grating pressure and temperature sensor, suitable for detecting the pressure and temperature of liquid in a pipeline, characterized in that: include: The skeleton is composed of two metal sheets symmetrically arranged with each other, and the metal sheets are set as thin sheet structures that are long in the longitudinal direction and short in the transverse direction, one of the metal sheets is provided with longitudinal grooves symmetrically on both sides of its longitudinal central axis, and is set as a female metal sheet; the other metal sheet is provided with longitudinal outwardly protruding rib grooves symmetrically on both sides of its longitudinal central axis, and is set as a male metal sheet; the middle parts of the male metal sheet and the female metal sheet are respectively bulged outwards, so that a cavity is formed between the two metal sheets, and an air bag similar to a fish bubble is arranged in the cavity, and a filler is arranged between the air bag and the metal sheet; A direct pressure measuring unit, the direct pressure measuring unit comprising a No. 1 optical fiber and a No. 2 optical fiber, the No. 1 optical fiber and the No. 2 optical fiber are symmetrically arranged along the longitudinal axis of the inner and outer side walls of the negative metal sheet, the No. 1 optical fiber and the No. 2 optical fiber are symmetrically engraved with gratings corresponding to the middle of the negative metal sheet, and the grating characteristic values on the No. 1 optical fiber and the No. 2 optical fiber are the same; when the skeleton is subjected to the liquid pressure in the pipeline, the gratings on the No. 1 optical fiber and the No. 2 optical fiber undergo positive and negative deformations along the longitudinal direction of the skeleton, thereby realizing temperature self-compensated pressure detection; A temperature measuring unit, the temperature measuring unit comprises a temperature measuring metal shell arranged in a cavity, the temperature measuring metal shell is connected to the inner wall of the positive metal sheet to form a temperature measuring cavity, at least two partitions connected to the inner wall of the temperature measuring metal shell are arranged in the temperature measuring cavity, a temperature measuring grating sensitivity enhancement component is arranged in the temperature measuring cavity, one end of the temperature measuring grating sensitivity enhancement component is fixedly connected to one of the partitions, and the other end of the temperature measuring grating sensitivity enhancement component passes through another partition and is suspended, so that the temperature measuring grating sensitivity enhancement component can freely expand and contract when thermal expansion and contraction occur, A heat-conducting medium is provided in the temperature measurement cavity, so that the temperature-measuring grating sensitizing component is immersed in the heat-conducting medium, the temperature-measuring grating sensitizing component is connected to the No. 3 optical fiber, the No. 3 optical fiber is recorded with a grating corresponding to the position of the temperature-measuring grating sensitizing component, the grating on the No. 3 optical fiber is tightly adhered to the temperature-measuring grating sensitizing component, and has the same characteristic value as the gratings on the No. 1 optical fiber and the No. 2 optical fiber, the No. 3 optical fiber is arranged through a temperature-measuring metal shell, the temperature-measuring metal shell is connected to a temperature-measuring metal wire, and the temperature-measuring metal wire is arranged to extend outward through a skeleton; An indirect pressure measuring unit, the indirect pressure measuring unit comprising a No. 4 optical fiber, the No. 4 optical fiber is arranged along the longitudinal axis of the outer side wall of the positive side metal sheet, the No. 4 optical fiber corresponds to a grating engraved in the middle of the positive side metal sheet, and the grating on the No. 4 optical fiber has the same characteristic value as the gratings on the No. 1 optical fiber, the No. 2 optical fiber, and the No. 3 optical fiber; Four optical fibers with different numbers are sequentially assembled into optical cables from both ends of the skeleton, and the optical cables are connected to a four-channel optical fiber connector; The skin is encapsulated outside the skeleton and the optical cable, and the skin is compatible with the hydraulic medium material in the pipeline; the temperature measuring metal wire passes through the skeleton and the skin and then extends outward.
2. A fish-shaped fiber Bragg grating pressure and temperature sensor according to claim 1, characterized in that: There is a gap at both ends of the two metal sheets in the longitudinal direction, the size of the gap changes due to the deformation of the two metal sheets, and the minimum size of the gap is not less than the diameter of the optical fiber.
3. A fish-shaped fiber Bragg grating pressure and temperature sensor according to claim 2, characterized in that: The positive metal sheet is provided with an outwardly protruding rib groove, the temperature measuring metal shell and the rib groove on the inner wall of the positive metal sheet are matched, and the connection position between the temperature measuring metal shell and the rib groove is sealed by colloid.
4. A fish-shaped fiber Bragg grating pressure and temperature sensor according to claim 3, characterized in that: The temperature measuring cavity is filled with 1 / 2 to 4 / 5 of a heat-conducting medium, and the heat-conducting medium is selected from heat-conducting silicone oil or heat-conducting silicone grease.
5. A fish-shaped fiber Bragg grating pressure and temperature sensor according to claim 3 or 4, characterized in that: Two connecting rods are respectively provided at the two ends of the cavity in the skeleton, and the two ends of each connecting rod are respectively passed through the female metal sheet and the male metal sheet. The connecting rod is provided with an intermediate connecting ring between the female metal sheet and the male metal sheet, and the intermediate connecting ring is connected to the traction rope, and the traction rope is connected to the optical fiber connector.
6. A fish-shaped fiber Bragg grating pressure and temperature sensor according to claim 5, characterized in that: The two ends of the connecting rod are located on the outside of the skeleton and are respectively provided with end connecting rings. The two end connecting rings are connected to the anti-torsion rope. The anti-torsion rope is connected to the end connecting rings of the connecting rods of the skeletons of other fish-shaped sensors in series, or is connected to the corresponding holes on the optical fiber connectors at the corresponding ends thereof to enhance the connection stability between adjacent skeletons.
7. A fish-shaped fiber Bragg grating pressure and temperature sensor according to claim 6, characterized in that: Each of the metal sheets is provided with at least two side grooves, which are symmetrically arranged about the longitudinal center axis of the metal sheet, so that the parts left beside the side grooves form a plurality of mutually cooperating support parts; when the skeleton is subjected to liquid pressure, the corresponding support parts of the two metal sheets can abut against each other to increase the overall elastic modulus of the skeleton.
8. A fish-shaped fiber Bragg grating pressure and temperature sensor according to claim 7, characterized in that: The two metal sheets are symmetrically provided with end grooves at both longitudinal ends, and the gap is formed between the parts left beside the end grooves. The intermediate connecting ring can abut against the parts left beside the end grooves of the two metal sheets, so that the minimum size of the gap is not less than the diameter size of the optical fiber.
9. A fish-shaped fiber Bragg grating pressure and temperature sensor according to claim 8, characterized in that: The support parts are bent so that the corresponding side support parts of the two metal sheets form corresponding contact surfaces; when the frame is subjected to pressure, the corresponding support parts abut against each other, or the filler is arranged between the support parts so that the support parts and the filler abut against each other.
10. The fish-shaped fiber Bragg grating pressure and temperature sensor according to claim 9, characterized in that: Transparent grooves are dug along the upper and lower sides of the optical fiber on the negative metal sheet, so that the negative metal sheet can quickly deform and respond under low pressure. Optical fiber No. 1 is arranged on the outer side of the negative metal sheet, and optical fiber No. 2 is arranged on the inner side; the gratings on optical fiber No. 1 and optical fiber No. 2 are combined to measure the liquid pressure in the pipeline, and the grating on optical fiber No. 3 is suitable for measuring the liquid temperature in the pipeline; the grating on optical fiber No. 4 is suitable for measuring the comprehensive value of liquid pressure and temperature in the pipeline, and indirectly measures the pressure through the temperature detection value obtained by the grating on optical fiber No. 3, and can be combined with calibration equipment to recheck and verify the temperature value detected by the grating on optical fiber No. 3 under a given pressure.