A fish-shaped fiber Bragg grating large-range pressure sensor
Through the design of the fish-type fiber grating sensor, the bionic principle of the fish body structure is used, combined with longitudinal and radial fiber sensors, high-precision pressure detection in the hydraulic tube is achieved, solving the problem of small measurement range of traditional fiber sensors and avoiding the Pipeline damaged.
Patent Information
- Application Number
- CN202010132426.8
- 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
When detecting pressure in hydraulic pipelines, existing fiber grating sensors have problems such as small measurement range and insufficient range, which is difficult to meet the needs of engineering hydraulic machinery. In addition, traditional methods will damage the pipeline structure or increase liquid flow disturbance.
Design a fish-type fiber grating large-range pressure sensor, adopting the bionic principle of subsymmetric structure of fish body, using metal sheet and airbag structures of different stiffness, combined with longitudinal and radial fiber grating sensors, and realizes the principles of forward and reverse deformation and elliptical deformation. Temperature self-compensation and high-precision pressure detection.
It realizes high-precision pressure detection in hydraulic pipes, expands the measurement range, avoids pipeline damage, and the structural design is suitable for inspection under various pressure conditions.
Smart Images
Figure CN113324694B_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 large-range pressure sensor. Background Art
[0002] From the Bernoulli equation, we know that the liquid pressure in the pipeline is also a form of energy. In the hydraulic transmission system, the flow rate (kinetic energy) of the medium is low, and the potential energy generated is relatively low, which can be ignored. The power is transmitted only by the pressure of the working medium, which is the so-called hydrostatic transmission. In hydrostatic transmission, the opening and closing of the pump or valve, or the dynamic change of the load, will cause the change of the fluid pressure in the pipeline. In particular, the research on the distribution and dynamic characteristics of the pressure in the spiral pipeline is still a technical blank.
[0003] Traditional liquid pressure sensing devices are mainly mechanical pressure gauges or resistive pressure sensors. The advantages of these detection methods are that the measurement theory and technology are relatively mature and the equipment cost is low. However, when detecting the internal pressure or pressure response of the hydraulic pipeline, the method usually adopted is to open a detection process hole in the pipeline path and install a pressure or high-frequency response pressure sensor probe on the side wall of the pipeline path.
[0004] However, the above method has certain problems: first, it destroys the side wall structure of the pipeline; 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 flow velocities inside and outside the spiral pipeline are different, and the pressure states are different. It is difficult to accurately measure the pressure distribution and change law in the pipeline using a fixed pressure sensor probe.
[0005] Considering the many disadvantages of the above methods, the prior art has developed instruments that can be used to measure the pressure of liquids in pipelines. Most of these instruments use the fiber Bragg grating principle, but when using fiber Bragg grating pressure sensors for pressure measurement, there are problems such as small load-bearing capacity 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-bearing capacity, but this will also increase the volume of the sensor, and encapsulating the sensor cannot solve the problem of its small measurement pressure range, that is, the sensor range still cannot meet the actual needs of engineering hydraulic machinery.
[0006] There are two main methods for measuring pressure using fiber Bragg grating in the prior art: one is to use the fiber Bragg grating wavelength to establish a certain linear relationship with the physical quantity to be measured, and by calibrating the linear coefficient within the linear range, the corresponding pressure value is converted from the wavelength drift value caused by the change of the physical quantity to be measured. For example, when the fiber grating is subjected to the external field (stress field, temperature field, etc.), its grating period or effective refractive index will change, thereby causing the grating reflection (or transmission) wavelength drift. Most of the fiber Bragg grating sensors in the grating sensors we commonly use now belong to this category; the second is that the fiber Bragg grating polarization characteristics can establish a linear relationship with the physical quantity to be measured. The polarization characteristics change with the change of the physical quantity to be measured. It is the resonant wavelength splitting of the fiber Bragg grating under the pressure load condition. The external pressure is detected by the offset of the center wavelength of the amplitude spectrum of the x-polarized light and the y-polarized light. However, when this method encounters a low pressure condition, the total amplitude spectrum is difficult to detect the difference between the center wavelengths of the two eigenmodes, and the detection is more difficult.
[0007] In summary, due to the high sensitivity of the fiber Bragg grating sensor itself, whether it is the detection method using the grating center wavelength drift or the birefringence caused by the fiber elliptical deformation, there is a detection range that can only detect low pressure and a relatively high pressure range, which greatly limits the range of pressure measurement. As a result, the lower or upper limit of the pressure detectable by the current fiber Bragg grating sensor cannot meet the actual needs of engineering hydraulic machinery.
[0008] Therefore, there is an urgent need for a pipeline nondestructive testing system that can achieve high-precision fiber Bragg grating large-range pressure sensors in hydraulic pipes, which can be used to collect high-precision pressure data of the oil pressure in the pipeline. This technology mainly relies on the innovation of sensor packaging and calibration detection methods to promote in-depth research and optimization of hydraulic pipelines.
[0009] The present invention speculates on the neural perception principle of the fish's "fish line" to liquid pressure, and with the help of the development of today's fiber grating technology, comprehensively utilizes the complementarity of the two outstanding characteristics of fiber grating that the measurement range is different in the longitudinal and radial directions as the pressure changes, and mainly innovates a bionic fish-shaped fiber grating large-range pressure sensor. Summary of the invention
[0010] The present invention provides a fish-shaped fiber grating large-range pressure sensor, which has a reasonable structural design. According to the bionic principle of the fish body's sub-symmetrical structure, fishbone-shaped metal sheets with different stiffness are designed on the left and right sides of the fish body, and there are air bags similar to fish bubbles inside. Elastic fillers are arranged between the air bags and the metal sheets, and grating sensors are arranged on the optical fibers on the inner and outer sides of the central axis of the metal sheets. The metal sheets of the sensor skeleton are divided into positive metal sheets and negative metal sheets. The negative metal sheets have transparent grooves excavated along the upper and lower sides of the grating, which plays the role of a strain diaphragm under low pressure, so that the negative metal sheets can quickly deform and respond under low pressure. The fiber gratings on its surface are numbered 1 and 2 from the outside to the inside; within the low-pressure measurement range, the positive and negative deformation principles of the two grating sensors are used to eliminate the temperature influence, thereby realizing the detection of temperature self-compensated pressure; the thickness of the positive metal sheet can be thickened relative to the negative metal sheet as needed, or convex or concave shapes can be arranged along the surface of the positive metal sheet. The concave reinforcing rib groove makes the deformation resistance of the positive metal sheet greater than that of the negative metal sheet, so that the outermost grating is supported to undergo radial elliptical deformation first in response to external pressure, so that the characteristic light signal produces resonant wavelength splitting under pressure load conditions, and the external pressure is detected by the change of the characteristic light signal. Due to the energy absorption of the elastic part of the fish body, the grating on the inner side of the positive metal sheet undergoes elliptical deformation only when it is subjected to greater external pressure, thereby detecting higher pressures. Moreover, the elliptical deformation of the gratings on the inner and outer sides of the positive metal sheet is not affected by temperature. Therefore, this structure is suitable for a large range of hydraulic pressure detection, thereby solving the problem of low pressure detection and small range of the current fiber Bragg grating sensor.
[0011] The technical solution adopted by the present invention to solve the above technical problems is: a fish-shaped fiber Bragg grating large-range pressure sensor suitable for detecting the liquid pressure in a pipeline, comprising:
[0012] A skeleton, wherein the skeleton is composed of two metal sheets arranged symmetrically with each other, wherein the metal sheets are arranged as thin sheet structures that are long in the longitudinal direction and short in the transverse direction, wherein the middle parts of the two metal sheets are respectively raised outwards, so that a cavity is formed between the two metal sheets, wherein 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; wherein at least two grooves are opened in the transverse direction of the metal sheet, and the grooves are arranged symmetrically about the longitudinal center axis of the metal sheet, so that the parts left beside the grooves of the two metal sheets form a plurality of mutually matched supporting parts;
[0013] Two optical fibers are arranged along the central axis of the side wall of each metal sheet, and the two optical fibers are symmetrical about the inside and outside of the metal sheet. A grating is engraved on each optical fiber in the middle of the metal sheet, and the grating characteristic values on each metal sheet are the same. The same grating characteristic values mean that the grating grid period, the engraving depth and the grid length are the same. The four optical fibers on the two metal sheets are numbered and arranged, and four optical fibers with different numbers are sequentially formed into an optical cable from both ends of the skeleton, and the optical cable can be connected to a four-channel optical fiber connector.
[0014] Each metal sheet is provided with a connecting hole at both ends in the longitudinal direction, and a connecting piece is provided between the two metal sheets, and the connecting piece is arranged along the two connecting holes so that the two metal sheets form a mutually connected structure; the connecting piece is connected to the optical fiber connector via a traction rope, and the traction rope is built into the optical cable formed by the optical fiber;
[0015] When the fish-shaped fiber Bragg grating large-range pressure sensor is subjected to the liquid pressure in the pipeline, the fiber Bragg gratings on the inner and outer walls of the metal sheet with weak deformation resistance in the two metal sheets of the skeleton first undergo positive and negative deformations along the longitudinal direction of the skeleton, and the temperature self-compensated pressure detection is realized by collecting the difference in the central wavelength drift of the two fiber Bragg gratings with positive and negative deformations; when the pressure in the pipeline rises to a certain threshold, the outer fiber Bragg grating on the metal sheet with strong deformation resistance in the two metal sheets of the skeleton is firstly elliptical deformed in the radial direction due to the mutual contact and support of the supporting parts of the two metal sheets, resulting in the change of characteristic light signal to detect the external pressure; secondly, when the pressure continues to rise and reaches a higher threshold, the liquid pressure acts on the fiber Bragg grating on the inner side of the other metal sheet through the metal sheet with weak deformation resistance, the air bag and the filler in the two metal sheets of the skeleton, so that the cross section of the fiber Bragg grating on the inner side of the metal sheet with strong deformation resistance in the two metal sheets of the skeleton undergoes elliptical deformation in the radial direction, resulting in the change of characteristic light signal to detect higher external pressure; the threshold is the critical value of the corresponding light signal that can be detected by the relevant fiber Bragg grating;
[0016] The skin is a film that wraps the skeleton and the optical cable externally, and the film is compatible with the hydraulic medium material in the pipeline.
[0017] Furthermore, the traction rope forms two end optical cables along the arrangement direction of the four optical fibers and the four optical fibers, and the optical cables can be connected to a four-channel optical fiber connector, or connected to the end optical cable of the next fish-shaped fiber grating large-range pressure sensor; two anti-torsion ropes are provided between the connecting parts between adjacent skeletons, and the anti-torsion ropes are connected to the two ends of the connecting parts passing through the metal sheet.
[0018] Furthermore, the positions of the corresponding connection holes of the two metal sheets are arranged without contacting each other, and when the filler and the airbag are in a state of maximum deformation, the gap between the connection hole positions of the two metal sheets is not less than the diameter of the optical fiber.
[0019] Furthermore, the airbag is filled with an inert gas, the filler is an elastic filler, and the elastic filler includes a rubber or resin model.
[0020] Furthermore, the number of support parts arranged on the same side of the metal sheet is set to 3 to 5. 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.
[0021] Furthermore, an angle is formed between the support part and the metal sheet, so that the support part is tilted and the corresponding support parts of the two metal sheets form a contact surface; when the skeleton 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 part and the filler abut against each other.
[0022] Furthermore, the skeleton is provided with a positive side and a negative side, and the metal sheet corresponding to the negative side is dug with transparent grooves along the upper and lower sides of the grating, so that the metal sheet between the grooves can also quickly deform and respond to low pressure, becoming a movable metal sheet, and the fiber gratings on its surface are numbered 1 and 2 from the outside to the inside; the thickness of the metal sheet corresponding to the positive side can be thickened relative to the negative side as needed, or convex or concave reinforcing rib grooves can be set along the surface of the positive side metal sheet, so that the deformation resistance of the positive side metal sheet is greater than that of the negative side metal sheet, and the fiber gratings on the surface of the positive side metal sheet are numbered 3 and 4 from the inside to the outside.
[0023] Furthermore, the skeleton is fish-shaped, and the support parts on both sides of the metal sheet are trapezoidal toe-shaped, ensuring that the abutting parts between the two arched metal sheets are in large-area reliable contact, so as to enhance the ability of the skeleton as a whole to withstand the liquid pressure in the pipeline.
[0024] Furthermore, when the skeleton is subjected to a liquid pressure that changes from small to large, the deformation characteristic of its shape is a step-like shape, and the pressure detection is completed by the grating groups on both sides of the skeleton;
[0025] The cavity portion corresponding to the metal sheet has different longitudinal and transverse deformations under different pressures. In the process of increasing the liquid pressure from small to large, the deformation of the skeleton first increases mainly toward the longitudinal sides, driving the grating grid period to increase, and the deformation of the negative metal sheet is greater than that of the positive metal sheet. In this stage, the longitudinal changes of the two optical fiber gratings on both sides of the negative metal sheet are mainly used to eliminate the influence of temperature on the longitudinal change of the grating by using the positive and negative deformation principle of the metal sheet, so as to realize temperature self-compensated pressure detection;
[0026] In the second stage, as the liquid pressure continues to increase, the supporting parts of the metal sheets close together and abut against each other, the entire elastic modulus increases stepwise, the deformation of the two longitudinal ends of the metal sheets slows down, and the detection sensitivity of the longitudinal deformation of the two fiber gratings on both sides of the metal sheet on the negative side of the skeleton decreases. The fiber gratings arranged on the outside of the positive side metal sheet with strong anti-deformation ability first undergo elliptical deformation under the action of liquid pressure and the supporting force of the metal sheet, causing the resonant splitting of the optical signal. The external pressure is detected by collecting the changes in the characteristic optical signal in the grating.
[0027] In the third stage, as the liquid pressure continues to increase, the liquid pressure acts on the fiber grating on the inner side of the positive metal sheet through the movable metal sheet, air bag, and elastic filler on the negative metal sheet, causing the cross-section of the fiber grating on the inner side of the positive metal sheet to subsequently become elliptical, resulting in resonant splitting of the optical signal. By collecting changes in the characteristic optical signal in the grating, higher external pressure can be detected.
[0028] Furthermore, a plurality of the fish-shaped fiber Bragg grating large-range pressure sensors are connected in series via optical fibers or four-channel optical fiber connectors, so that the plurality of fish-shaped fiber Bragg grating large-range pressure sensors can be used in a combined state, with the outer gratings connected to the outer ones, the inner gratings connected to the inner ones, and the gratings on the same side being ensured to be grouped, and the optical fiber connector interface numbers are clearly marked and in a regular order.
[0029] The beneficial effect of the above structure adopted in the present invention is that its structural design is reasonable. According to the bionic principle of the sub-symmetrical structure of the fish body, fishbone-shaped metal sheets with different stiffness are designed on the left and right sides of the fish body, and there are air bags similar to fish bubbles inside. Elastic fillers are provided between the air bags and the metal sheets, and grating sensors are arranged on the optical fibers on both sides of the central axis of the metal sheet. The metal sheet of the sensor skeleton is divided into a positive metal sheet and a negative metal sheet. The negative metal sheet has transparent grooves excavated along the upper and lower sides of the grating, which plays the role of a strain diaphragm under low pressure, so that the negative metal sheet can quickly deform and respond under low pressure. The fiber gratings on its surface are numbered 1 and 2 from outside to inside. In the low-pressure measurement range, the positive and negative deformation principles of the two grating sensors are used to eliminate the temperature influence, thereby realizing the detection of temperature self-compensated pressure. The thickness of the positive metal sheet can be thickened relative to one side of the negative metal sheet as needed, or convex or concave reinforcing rib grooves are set along the surface of the positive metal sheet, so that the deformation resistance of the positive metal sheet is greater than that of the negative metal sheet, so that the outermost grating is first supported to undergo radial elliptical deformation in response to the external pressure, so that the optical signal undergoes resonant wavelength splitting, and the external pressure is detected by the change of the characteristic optical signal. Due to the energy absorption of the elastic part of the fish body, the grating on the inner side of the positive metal sheet undergoes elliptical deformation only when it is subjected to a greater external pressure, thereby detecting a higher pressure. Moreover, this elliptical deformation of the gratings on the inner and outer sides of the positive metal sheet is not affected by temperature. Therefore, through the packaging of this fish-shaped sensor, the staged collection of the fiber Bragg grating axial signal and radial elliptical deformation information is realized, overcoming the problem that traditional fiber Bragg grating sensors are difficult to measure high and low pressures at the same time, and expanding the pressure detection range; thereby solving the current fiber Bragg grating sensor's low detection pressure and small range problem.
[0030] Secondly, the streamlined and floating fish-shaped sensor with a bionic fish structure can be built into the middle of the liquid in the hydraulic pipeline without damaging the pipeline wall. The optical fiber is set in series in the pipeline, which also reduces the leakage points of the process holes in the pipeline wall.
[0031] Finally, the sensor encapsulates multi-channel fiber Bragg gratings in a fish-shaped sensor with a sub-symmetrical structure, utilizing the supporting effect of the liquid pressure in the pipeline on the outer wall of the fish-shaped sensor, as well as the elastic absorption effect of the airbag and the fish body, so that the fiber Bragg grating on the inner side of the positive metal sheet will only undergo radial elliptical deformation when the ambient pressure is very high, thereby realizing the detection of ultra-high pressure through different packaging materials.
[0032] Therefore, this structure is suitable for a wide range of hydraulic pressure detection, thereby solving the problem of low pressure detection and small range of current fiber grating sensors. BRIEF DESCRIPTION OF THE DRAWINGS
[0033] Figure 1 It is a cross-sectional structural schematic diagram of the present invention.
[0034] Figure 2 It is a schematic diagram of the unfolded structure of the negative metal sheet of the present invention at corresponding angles.
[0035] Figure 3 It is a schematic diagram of the unfolded structure of the positive metal sheet of the present invention at corresponding angles.
[0036] Figure 4 It is a schematic diagram of the three-dimensional structure of the skeleton part of the present invention.
[0037] Figure 5 for Figure 4 Schematic diagram of the side structure.
[0038] In the figure, 1, skeleton; 2, metal sheet; 201, negative metal sheet; 202, positive metal sheet; 3, cavity; 4, airbag; 5, filler; 6, groove; 7, support part; 8, optical fiber; 9, grating; 10, optical cable; 11, connecting hole; 12, traction rope; 13, connecting piece; 14, anti-torsion rope; 15, optical fiber connector; 16, groove; 17, convex or concave reinforcing rib groove. DETAILED DESCRIPTION
[0039] 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.
[0040] 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.
[0041] 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.
[0042] 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.
[0043] 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.
[0044] 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.
[0045] like Figure 1-5As shown, a fish-shaped fiber Bragg grating large-range pressure sensor is suitable for detecting the liquid pressure in a pipeline, comprising a frame 1, the frame 1 is composed of two symmetrically arranged female metal sheets 201 and male metal sheets 202, the female metal sheets 201 and male metal sheets 202 are configured as thin sheet structures that are long in the longitudinal direction and short in the transverse direction, the middle parts of the two metal sheets 2 are respectively bulged outwards to form a cavity 3 between the two metal sheets 2, an air bag 4 similar to a fish bubble is provided in the cavity 3, and a filler 5 is provided between the air bag 4 and the metal sheet 2; the metal sheet 2 is provided with at least two grooves 6, the grooves 6 are symmetrically arranged about the longitudinal center axis of the metal sheet 2, so that the two metal sheets 2 A plurality of mutually cooperating supporting parts 7 are formed; two optical fibers 8 are arranged on the side wall of each metal sheet 2 along the central axis, the two optical fibers 8 are symmetrical about the inside and outside of the metal sheet 2, a grating 9 is engraved on each optical fiber 8, the characteristic values of the grating 9 on each metal sheet 2 are the same (the grating grid period is the same, the engraving depth is the same, and the grid length is the same), and the grating 9 on each metal sheet 2 is symmetrical inside and outside along the longitudinal length of the metal sheet 2; the four optical fibers 8 on the two metal sheets are numbered and arranged, and four optical fibers 8 with different numbers are sequentially formed into an optical cable 10 from both ends of the skeleton 1, and the optical cable 10 can be connected to a four-channel optical fiber connector 15; each metal sheet 2 is arranged at both ends in the longitudinal direction A connecting hole 11, a connecting piece 13 is provided between the two metal sheets 2, and the connecting piece 13 is arranged along the two connecting holes 11, so that the two metal sheets 2 form a mutually connected structure; the connecting piece 13 is connected to the optical fiber connector 15 through the traction rope 12, and the traction rope 12 is built into the optical cable 10 formed by the optical fiber 8; when the fish-shaped fiber Bragg grating large-range pressure sensor is subjected to the liquid pressure in the pipeline, the female metal sheet 201 is more easily deformed after the grooves are symmetrically opened along the two sides of the fiber Bragg grating, and plays the role of a strain diaphragm, thereby playing a similar working principle of the spring tube fiber Bragg grating pressure sensor to eliminate the influence of temperature, and realizing temperature self-compensation Compensated pressure detection; when the pressure in the pipeline rises to a certain threshold, the support parts 7 of the two metal sheets 2 contact and support each other, so that the fiber Bragg grating on the outer side of the positive metal sheet 202 undergoes elliptical deformation in the radial direction, resulting in the splitting of the resonant wavelength of the optical signal, and the external pressure is detected by the change of the characteristic optical signal. When the pressure rises to a higher threshold, the fiber Bragg grating on the inner side of the positive metal sheet 18 also undergoes elliptical deformation in the radial direction, resulting in the splitting of the resonant wavelength of the optical signal, and the higher external pressure is detected by detecting the change of the characteristic optical signal; a skin is packaged on the outside of the skeleton 1 and the optical cable 10, and the skin is set to a thin film, which is compatible with the hydraulic medium material in the pipeline.When in use, according to the bionic principle of deep-sea fish's perception of water pressure, a fishbone-shaped metal sheet is designed. According to the bionic principle of fish's "fish line"'s perception of water pressure and the sub-symmetrical structure commonly existing in the biological world, the skeleton 1 is provided with a positive side and a negative side, and a fishbone-shaped negative side metal sheet 201 and a positive side metal sheet 202 are designed, and two optical fibers are arranged at both sides of the "fish line" of the metal sheet, and grating sensors are arranged on both sides of the central axis of the metal sheet 2. The negative side metal sheet 201 has transparent grooves 16 excavated along the upper and lower sides of the grating, which plays the role of a strain diaphragm under low pressure; within the low-pressure measurement range, the positive and negative deformation principles of the two grating sensors are used to eliminate the temperature influence, thereby realizing the detection of temperature self-compensated pressure; within the medium and high pressure measurement range, the optical fiber and the grating between the pipeline liquid and the positive side metal sheet 202 undergo radial elliptical deformation under the action of pressure, so that the resonance wavelength of the characteristic light signal of the grating under the pressure load condition is split, and the external pressure is detected by changing the characteristic light signal, and this elliptical deformation is not affected by temperature. Thus, higher pressure can be detected, so this structure is suitable for a large range of hydraulic pressure detection, thereby solving the problem of low pressure detection and small range of current fiber grating sensors.
[0046] It is worth mentioning that the optical fiber 8 is attached along the surface of the female metal sheet 201 and the male metal sheet 202 , and the female metal sheet 201 and the male metal sheet 202 are made of titanium or titanium alloy with light weight and high strength.
[0047] In a preferred embodiment, the traction rope 12 forms two end optical cables 10 along the arrangement direction of the four optical fibers 8 and the four optical fibers 8, and the optical cable 10 can be connected to a four-channel optical fiber connector 15, or connected to the end optical cable 10 of the next fish-shaped fiber grating large-range pressure sensor; two anti-torsion ropes 14 are provided between the connecting parts 13 between adjacent skeletons 1, and the anti-torsion ropes 14 are connected to the two ends of the connecting parts 13 passing through the metal sheet 2, so as to establish an anti-torsion torque arm with the help of the hole spacing between the metal sheets 2 on the positive and negative sides.
[0048] In addition, the length of the optical cable 10 or the traction rope 12 can be greater than ten times the transverse length of the fish-shaped sensor or the optical fiber connector 15 at the front end thereof to prevent the upstream object from affecting the rear turbulence and the pressure of the next sensor. A film compatible with oil is hung between the anti-torsion rope 14 and the optical cable 10 to achieve anti-torsion balance with the help of liquid flow.
[0049] Specifically, the connecting member 13 is configured as a metal rod structure, and connecting rings are respectively provided at the middle and both ends of the connecting member 13 . The connecting ring structure can be directly produced by knotting the connecting member 13 itself, so as to connect the traction rope 12 and the anti-torsion rope 14 .
[0050] In a preferred embodiment, the positions of the connection holes 11 of the two metal sheets 2 are not in contact with each other, and when the filler 5 and the airbag 4 are in the maximum deformation state, the gap between the connection holes 11 of the two metal sheets 2 is not less than the diameter of the optical fiber 8. Figure 5 As shown, notches are set at corresponding positions at both ends of the metal sheet 2. When the main parts of the metal sheet 2 are in contact with each other, there are still gaps at the two ends where the optical fiber passes, which will not cause squeezing damage to the optical fiber. In this embodiment, the gap between the two metal sheets 2 is limited to prevent the female metal sheet 201 and the male metal sheet 202 from squeezing the optical fiber 8 against each other after the skeleton 1 receives external pressure, thereby protecting the optical fiber 8.
[0051] In a preferred embodiment, the airbag 4 is filled with an inert gas or other non-toxic gas, and the filler 5 is an elastic filler, which includes a rubber or resin type.
[0052] In a preferred embodiment, the number of support portions 7 arranged on the same side of the metal sheet 2 is set to 3 to 5. When the skeleton 1 is subjected to liquid pressure, the support portions 7 corresponding to the negative metal sheet 201 and the positive metal sheet 202 can abut against each other to increase the overall elastic modulus of the skeleton 1.
[0053] In a preferred embodiment, an angle is formed between the support portion 7 and the metal sheet, so that the support portion 7 is tilted, and the support portions of the two metal sheets 2 corresponding to each other form a contact surface; when the skeleton 1 is subjected to pressure, the corresponding support portions 7 abut against each other, or fillers 5 are arranged between the support portions 7, so that the support portions 7 abut against the fillers 5. This embodiment further optimizes the setting of the support portion 7, so that the support portion 7 forms a structure similar to the shape of a toe, forming multiple surface contacts, so as to improve the stability of the entire skeleton 1.
[0054] In a preferred embodiment, the skeleton 1 is provided with a positive side and a negative side, and the metal sheet corresponding to the negative side is a negative side metal sheet 201. Transparent grooves 16 are excavated along the upper and lower sides of the grating 9, so that the negative side metal sheet 201 between the grooves 16 can quickly deform and respond under low pressure, becoming a movable metal sheet, and the fiber gratings on its surface are numbered 1 and 2 from the outside to the inside; the metal sheet corresponding to the positive side is the positive side metal sheet 202, and the thickness can be thickened relative to the negative side as needed, or convex or concave reinforcing rib grooves 17 can be set along the surface of the positive side metal sheet 202, so that the deformation resistance of the positive side metal sheet 202 is greater than that of the negative side metal sheet 201, and the fiber gratings on the surface of the positive side metal sheet 202 are numbered 3 and 4 from the inside to the outside.
[0055] In a preferred embodiment, the skeleton 1 is fish-shaped, and support portions 7 are arranged on both lateral sides of the metal sheet 2 in the shape of trapezoidal toes to ensure that the abutting portions between the two arched metal sheets 2 are in reliable contact over a large area, so as to enhance the overall ability of the skeleton 1 to withstand the liquid pressure in the pipeline.
[0056] In a preferred embodiment, when the frame 1 is subjected to a liquid pressure that changes from small to large, its deformation characteristic is a step-like shape, and the pressure detection is completed by the grating groups on both sides of the frame 1;
[0057] The longitudinal and transverse deformation amounts of the cavity 3 corresponding to the metal sheet 2 are different under different pressures. In the process of increasing the liquid pressure from small to large, the deformation amount of the skeleton 1 first increases mainly toward the longitudinal sides, driving the grating grid period attached thereto to increase, and the deformation of the negative metal sheet 201 is greater than that of the positive metal sheet 202. At this stage, the two fiber gratings on both sides of the negative metal sheet 201 are mainly used to eliminate the influence of temperature on the grating by using the positive and negative deformation principle of the metal sheet 2, so as to realize temperature self-compensated pressure detection;
[0058] In the second stage, as the liquid pressure continues to increase, the supporting parts of the metal sheet 2 close together and abut against each other, the entire elastic modulus increases stepwise, the deformation at both ends of the metal sheet 2 in the longitudinal direction slows down, and the detection sensitivity of the two groups of fiber gratings on both sides of the skeleton 1 for the longitudinal deformation decreases. The fiber gratings arranged on the outside of the metal sheet 2 with strong anti-deformation ability will first undergo an elliptical change in cross section on the outside of the positive metal sheet 202 under the action of the liquid pressure and the supporting force of the metal sheet 2, causing the resonant splitting of the optical signal, and detecting the external pressure by collecting the changes in the characteristic optical signal in the grating;
[0059] In the third stage, as the liquid pressure continues to increase, the liquid pressure acts on the fiber grating on the inner side of the positive metal sheet 202 through the negative metal sheet 201, the airbag 4, and the elastic filler 5, causing the cross-section of the fiber grating on the inner side of the positive metal sheet 202 to subsequently become elliptical, resulting in resonant splitting of the optical signal. The external pressure is detected by collecting changes in the characteristic optical signal in the grating.
[0060] In a preferred embodiment, the optical fibers where the fiber gratings are numbered 1, 2, 3, and 4 are located, and the corresponding optical fibers 8 or optical fiber connector 15 interfaces are also numbered 1, 2, 3, and 4; multiple skeletons 1 are arranged in series via optical fibers 8 or four-channel optical fiber connectors 15, so that multiple fish-shaped fiber grating large-range pressure sensors are used in a combined state, the outer gratings 9 are connected to the outer ones, the inner gratings 9 are connected to the inner ones, the gratings 9 on the same side are guaranteed to be grouped, and the interface numbers of the optical fiber connector 15 are clearly marked and the sequence is regular.
[0061] It should be noted that in order to prevent the optical fiber outside the sensor frame from being subjected to elliptical deformation caused by the liquid pressure in the pipeline and causing interference to the collected characteristic light signal, the optical fiber outside the sensor frame is armored so that the armored optical fiber segment can basically eliminate the elliptical deformation caused by the pressure in the pipeline, thereby making the characteristic light signal output by the optical fiber more accurate.
[0062] 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.
[0063] 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 large-range pressure sensor suitable for detecting liquid pressure in a pipeline, characterized in that: include: A skeleton, wherein the skeleton is composed of two metal sheets arranged symmetrically with each other, wherein the metal sheets are arranged as thin sheet structures that are long in the longitudinal direction and short in the transverse direction, wherein the middle parts of the two metal sheets are respectively raised outwards, so that a cavity is formed between the two metal sheets, wherein 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; wherein at least two grooves are opened in the transverse direction of the metal sheet, and the grooves are arranged symmetrically about the longitudinal center axis of the metal sheet, so that the parts left beside the grooves of the two metal sheets form a plurality of mutually matched supporting parts; Two optical fibers are arranged along the central axis of the side wall of each metal sheet, and the two optical fibers are symmetrical about the inside and outside of the metal sheet. A grating is engraved on each optical fiber in the middle of the metal sheet, and the grating characteristic values on each metal sheet are the same. The same grating characteristic values mean that the grating grid period, the engraving depth and the grid length are the same. The four optical fibers on the two metal sheets are numbered and arranged, and four optical fibers with different numbers are sequentially formed into an optical cable from both ends of the skeleton, and the optical cable can be connected to a four-channel optical fiber connector. Each metal sheet is provided with a connecting hole at both ends in the longitudinal direction, and a connecting piece is provided between the two metal sheets, and the connecting piece is arranged along the two connecting holes so that the two metal sheets form a mutually connected structure; the connecting piece is connected to the optical fiber connector via a traction rope, and the traction rope is built into the optical cable formed by the optical fiber; When the fish-shaped fiber Bragg grating large-range pressure sensor is subjected to the liquid pressure in the pipeline, the fiber Bragg gratings on the inner and outer walls of the metal sheet with weak deformation resistance in the two metal sheets of the skeleton first undergo positive and negative deformations along the longitudinal direction of the skeleton, and the temperature self-compensated pressure detection is realized by collecting the difference in the central wavelength drift of the two fiber Bragg gratings with positive and negative deformations; when the pressure in the pipeline rises to a certain threshold, the outer fiber Bragg grating on the metal sheet with strong deformation resistance in the two metal sheets of the skeleton is firstly elliptical deformed in the radial direction due to the mutual contact and support of the supporting parts of the two metal sheets, resulting in the change of characteristic light signal to detect the external pressure; secondly, when the pressure continues to rise and reaches a higher threshold, the liquid pressure acts on the fiber Bragg grating on the inner side of the other metal sheet through the metal sheet with weak deformation resistance, the air bag and the filler in the two metal sheets of the skeleton, so that the cross section of the fiber Bragg grating on the inner side of the metal sheet with strong deformation resistance in the two metal sheets of the skeleton undergoes elliptical deformation in the radial direction, resulting in the change of characteristic light signal to detect higher external pressure; the threshold is the critical value of the corresponding light signal that can be detected by the relevant fiber Bragg grating; The skin is a film that wraps the skeleton and the optical cable externally, and the film is compatible with the hydraulic medium material in the pipeline.
2. The fish-shaped fiber Bragg grating large-range pressure sensor according to claim 1, characterized in that: The traction rope forms two end optical cables along the arrangement direction of the four optical fibers and the four optical fibers, and the optical cables can be connected to a four-channel optical fiber connector, or connected to the end optical cable of the next fish-shaped fiber grating large-range pressure sensor; two anti-torsion ropes are arranged between the connecting parts between adjacent skeletons, and the anti-torsion ropes are connected to the two ends of the connecting parts passing through the metal sheet.
3. A fish-shaped fiber Bragg grating large-range pressure sensor according to claim 1 or 2, characterized in that: The positions of the corresponding connection holes of the two metal sheets are arranged without contacting each other. When the filler and the airbag are in a state of maximum deformation, the gap between the connection hole positions of the two metal sheets is not less than the diameter of the optical fiber.
4. The fish-shaped fiber Bragg grating large-range pressure sensor according to claim 3, characterized in that: The airbag is filled with inert gas, and the filler is an elastic filler, which includes a rubber or resin model.
5. The fish-shaped fiber Bragg grating large-range pressure sensor according to claim 4, characterized in that: The number of support parts arranged on the same side of the metal sheet is set to 3 to 5. 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.
6. The fish-shaped fiber Bragg grating large-range pressure sensor according to claim 5, characterized in that: An angle is formed between the support part and the metal sheet, so that the support part is tilted and the corresponding support parts of the two metal sheets form a contact surface; when the skeleton 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 part and the filler abut against each other.
7. The fish-shaped fiber Bragg grating large-range pressure sensor according to claim 6, characterized in that: The skeleton is provided with a positive side and a negative side. The metal sheet corresponding to the negative side is dug with transparent grooves along the upper and lower sides of the grating, so that the metal sheet between the grooves can also quickly deform and respond to low pressure, becoming a movable metal sheet, and the fiber gratings on its surface are numbered 1 and 2 from the outside to the inside; the thickness of the metal sheet corresponding to the positive side can be thickened relative to the negative side as needed, or convex or concave reinforcing rib grooves can be set along the surface of the positive side metal sheet, so that the deformation resistance of the positive side metal sheet is greater than that of the negative side metal sheet, and the fiber gratings on the surface of the positive side metal sheet are numbered 3 and 4 from the inside to the outside.
8. The fish-shaped fiber Bragg grating large-range pressure sensor according to claim 7, characterized in that: The skeleton is fish-shaped, and the support parts are trapezoidal toe-shaped on both sides of the metal sheet to ensure that the abutting parts between the two arched metal sheets are in large-area reliable contact, so as to enhance the ability of the skeleton as a whole to withstand the liquid pressure in the pipeline.
9. A fish-shaped fiber Bragg grating large-range pressure sensor according to claim 7 or 8, characterized in that: When the skeleton is subjected to liquid pressure that changes from small to large, its deformation characteristic is a step-like shape, and the pressure detection is completed by the grating groups on both sides of the skeleton; The cavity portion corresponding to the metal sheet has different longitudinal and transverse deformations under different pressures. In the process of increasing the liquid pressure from small to large, the deformation of the skeleton first increases mainly toward the longitudinal sides, driving the grating grid period to increase, and the deformation of the negative metal sheet is greater than that of the positive metal sheet. In this stage, the longitudinal changes of the two optical fiber gratings on both sides of the negative metal sheet are mainly used to eliminate the influence of temperature on the longitudinal change of the grating by using the positive and negative deformation principle of the metal sheet, so as to realize temperature self-compensated pressure detection; In the second stage, as the liquid pressure continues to increase, the supporting parts of the metal sheets close together and abut against each other, the entire elastic modulus increases stepwise, the deformation of the two longitudinal ends of the metal sheets slows down, and the detection sensitivity of the longitudinal deformation of the two fiber gratings on both sides of the metal sheet on the negative side of the skeleton decreases. The fiber gratings arranged on the outside of the positive side metal sheet with strong anti-deformation ability first undergo elliptical deformation under the action of liquid pressure and the supporting force of the metal sheet, causing the resonant splitting of the optical signal. The external pressure is detected by collecting the changes in the characteristic optical signal in the grating. In the third stage, as the liquid pressure continues to increase, the liquid pressure acts on the fiber grating on the inner side of the positive metal sheet through the movable metal sheet, air bag, and elastic filler on the negative metal sheet, causing the cross-section of the fiber grating on the inner side of the positive metal sheet to subsequently become elliptical, resulting in resonant splitting of the optical signal. By collecting changes in the characteristic optical signal in the grating, higher external pressure can be detected.
10. The fish-shaped fiber Bragg grating large-range pressure sensor according to claim 9, characterized in that: A plurality of the fish-shaped fiber Bragg grating large-range pressure sensors are connected in series via optical fibers or four-channel optical fiber connectors, so that the plurality of fish-shaped fiber Bragg grating large-range pressure sensors are used in a combined state, the outer gratings are connected to the outer ones, the inner gratings are connected to the inner ones, the gratings on the same side are guaranteed to be grouped, and the optical fiber connector interface numbers are clearly marked and in a regular order.