Fiber optic strain low flow sensor with temperature compensation and method

Abstract

This invention discloses a fiber optic strain gauge low-flow-velocity sensor and method with temperature compensation. The sensor includes a rigid insulating base, a fiber optic strain sensing unit, a pre-tightening fixing assembly, a temperature sensing unit, and a support fixing unit. The fiber optic strain sensing unit is radially arranged through the base, with its axis perpendicular to the fluid flow direction. The temperature sensing unit is sealed and embedded in the sidewall of the base, adjacent to the fiber optic strain sensing unit. The pre-tightening fixing assembly tensions and positions the fiber optic cable, and the support fixing unit mounts the base onto the flow field to be measured. This sensor utilizes an insulating base to resist electromagnetic interference and corrosion, making it suitable for harsh environments; the radially perpendicular arrangement enhances low-flow-velocity sensitivity; the pre-tightening structure provides stable tension, suppressing baseline drift; and the adjacent arrangement of the temperature sensing unit achieves synchronous thermal balance, ensuring accurate compensation, effectively reducing measurement errors, and improving measurement stability and service life.

Description

Technical Field

[0001] This invention belongs to the field of fiber optic sensing and fluid measurement technology, specifically relating to a fiber optic strain gauge low-flow-rate sensor with temperature compensation and a method thereof. Background Technology

[0002] Flow velocity measurement is widely used in industrial control, energy metering, environmental monitoring and aerospace. Traditional devices such as Pitot tubes, turbine flow meters and thermal flow meters are susceptible to electromagnetic interference, electrochemical corrosion or material failure under harsh conditions such as strong electric fields, strong corrosion, high temperature and high pressure, which seriously affects the measurement accuracy and safety of use. Fiber optic sensing technology, with its inherent insulation, anti-electromagnetic interference and corrosion resistance, has been gradually applied to the field of flow velocity measurement.

[0003] Existing fiber optic flow velocity sensors mostly employ a cantilever beam fiber optic deployment structure, which results in low sensitivity in low-velocity measurement scenarios. Furthermore, the simple design of the fiber fixing and tensioning structure makes it impossible to apply stable and precise pre-tension, easily causing sensor baseline drift and poor measurement repeatability. Simultaneously, changes in ambient temperature induce thermo-induced strain in the fiber, which couples with the flow-induced strain generated by the fluid, leading to a significant increase in measurement error.

[0004] Existing temperature compensation schemes often separate the temperature sensing unit from the fiber optic sensing unit, making it difficult for the two to achieve synchronous thermal balance. This results in limited compensation effects and an inability to guarantee low-flow-rate measurement accuracy under fluctuating temperature conditions. Summary of the Invention

[0005] The purpose of this invention is to provide a fiber optic strain gauge low flow velocity sensor and method with temperature compensation, in order to solve the technical defects of traditional flow velocity measurement devices that are easily interfered with and corroded under harsh working conditions, as well as the low sensitivity, unstable fiber tension, baseline drift, and inaccurate temperature compensation of existing fiber optic flow velocity sensors.

[0006] To achieve the above objectives, this application provides the following technical solution: In a first aspect, this application provides a temperature-compensated fiber optic strain gauge low-flow-rate sensor, comprising: Rigid insulating base; The fiber optic strain sensing unit is arranged radially through the rigid insulating base; A pre-tightening fixing assembly is connected to the end of the fiber optic strain sensing unit to tension and position the fiber optic strain sensing unit radially along the rigid insulating base, and the axis of the fiber optic strain sensing unit is perpendicular to the direction of fluid flow. The temperature sensing unit is sealed and embedded in the side wall of the rigid insulating base and is disposed adjacent to the fiber optic strain sensing unit. A support and fixing unit is fixed to the outer periphery of the rigid insulating base and is used to fix the rigid insulating base in the flow field to be measured.

[0007] In one alternative embodiment, the rigid insulating base is a rigid insulating ring, which is made of insulating ceramic.

[0008] In one alternative embodiment, the fiber optic strain sensing unit is disposed through the rigid insulating base in a horizontal radial direction.

[0009] In one alternative embodiment, both ends of the fiber optic strain sensing unit extend outward to the outside of the rigid insulating base.

[0010] In one optional embodiment, the sidewall of the rigid insulating base is provided with a micro-blind hole, and the temperature sensing unit is housed within the micro-blind hole.

[0011] In one optional embodiment, the micro-blind hole is filled with a high thermal conductivity sealant, and the temperature sensing unit is fixed in the micro-blind hole by the high thermal conductivity sealant.

[0012] In one alternative embodiment, the support fixing unit is vertically fixed to the outer peripheral wall of the rigid insulating base.

[0013] In one optional embodiment, the pre-tightening fixing assembly is fixedly connected to the rigid insulating base, and the clamping end of the pre-tightening fixing assembly is pressed against the end of the fiber optic strain sensing unit.

[0014] In one optional embodiment, one end of the support fixing unit is fixedly connected to the outer peripheral wall of the rigid insulating base, and the other end is used for fixed engagement with an external mounting structure.

[0015] A second aspect of this application provides a method for measuring low flow rates with temperature compensation, the method employing a temperature-compensated fiber optic strain gauge low flow rate sensor as described above, comprising: Place the sensor in the flow field to be measured, so that the axis of the fiber optic strain sensing unit is perpendicular to the direction of fluid flow, and at the same time, place the temperature sensing unit, the fiber optic strain sensing unit and the flow field to be measured in the same thermal environment. When the fluid flows through the fiber optic strain sensing unit, it generates an impact force and causes the fluid to undergo strain deformation. The fiber optic strain sensing unit converts the strain deformation into a corresponding strain signal and outputs it. The ambient temperature signal of the flow field under test is collected in real time using a temperature sensing unit, and the strain signal output by the fiber optic strain sensing unit is corrected by temperature compensation based on the ambient temperature signal to eliminate the influence of temperature change on the measurement results. Based on the strain signal after temperature compensation correction, and combined with the preset strain-flow velocity correspondence, the low flow velocity value of the fluid under test is calculated.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. The rigid insulating base avoids electromagnetic interference and corrosion, solving the problem of traditional devices being prone to failure under harsh working conditions; the fiber optic strain sensing unit is arranged radially along the base and its axis is perpendicular to the incoming flow direction, improving the measurement sensitivity in low flow velocity scenarios and overcoming the shortcomings of insufficient sensitivity of existing sensors; the pre-tightening fixing component achieves precise fiber tensioning, solving the problems of rough fiber fixing, baseline drift, and poor measurement repeatability; the temperature sensing unit is embedded in the base and adjacent to the sensing unit, achieving synchronous thermal balance, solving the problems of inaccurate temperature compensation and separation of the sensing and temperature measurement units; the support fixing unit ensures stable sensor installation, ensures stable measurement, and guarantees measurement stability and repeatability, significantly reducing measurement errors and extending the service life of the equipment.

[0017] 2. The rigid insulating base is a rigid insulating ring made of insulating ceramic material. Ceramic has high rigidity, high insulation, high temperature resistance and corrosion resistance. It can work stably in harsh environments such as strong electric field, strong corrosion and high temperature and high pressure, avoiding electromagnetic interference, electrochemical corrosion and material failure. The ring structure facilitates the radial installation of optical fiber, provides a stable and unchanging installation reference for the sensing unit, ensures that the base has no deformation, and ensures that the detected strain comes only from the fluid action. This structurally improves the measurement accuracy, long-term stability and sensor lifespan.

[0018] 3. The fiber optic strain sensing unit is arranged horizontally and radially along the base, which can keep the axis of the sensing unit perpendicular to the direction of fluid flow at the best angle, maximize the fluid force, and significantly improve the detection sensitivity at low flow rates. The horizontal radial arrangement results in a symmetrical structure and uniform stress, which can effectively reduce the measurement error caused by installation deviation, ensure stable and controllable deformation of the sensing unit, improve the problem of insufficient sensitivity and weak response of the existing cantilever beam structure, and improve the measurement accuracy and linearity at low flow rates.

[0019] 4. The fiber optic strain sensing unit extends to the outside of the base at both ends, providing ample installation and operation space for the pre-tensioning fixing components, facilitating precise application, adjustment, and maintenance of pre-tension. The extended structure avoids interference from the clamping parts with the sensing area inside the base, ensuring the stability of the effective detection section length of the fiber optic cable. It also facilitates connection between the fiber optic cable and the external demodulation system, improving assembly efficiency and debugging convenience, ensuring stable tension, reducing baseline drift, and improving measurement repeatability and signal output reliability.

[0020] 5. By creating micro-blind holes on the sidewall of the base and housing the temperature sensing unit within these holes, the temperature sensing unit can be positioned adjacent to the strain sensing unit, achieving synchronous thermal equilibrium between the two and improving the real-time performance and accuracy of temperature acquisition. The micro-blind holes also provide protection for the temperature sensing unit, preventing direct fluid erosion and mechanical damage, ensuring stable temperature detection, and resolving the problems of inaccurate compensation and coupling interference between temperature-induced strain and flow-induced strain measurements inherent in traditional separate arrangements.

[0021] 6. The micro-blind hole is filled with high thermal conductivity sealant and potted to fix the temperature sensing unit. This allows for rapid conduction of ambient temperature, ensuring high consistency between the measured temperature and the strain detection temperature, thus improving compensation accuracy. The sealant also serves to fix, seal, and conduct heat, preventing the intrusion of fluids, moisture, and dust, protecting the temperature sensing unit from corrosion and external forces, ensuring long-term stable temperature measurement, providing reliable data for accurate temperature compensation, and significantly reducing measurement errors caused by temperature fluctuations.

[0022] 7. The support and fixing unit is vertically fixed to the outer peripheral wall of the base. The force direction is reasonable and the support is stable, which can ensure that the base does not shake, deflect or shift under fluid impact, and always keep the axis of the sensing unit perpendicular to the direction of the incoming flow. The vertical connection structure is firmly installed and has strong impact resistance, which can keep the sensor posture stable, ensure that the measurement reference remains unchanged, improve the reliability of operation under harsh flow fields, and ensure the stability and consistency of low flow velocity measurement.

[0023] 8. The pre-tensioning and fixing components are fixedly connected to the base, and the clamping end presses the end of the optical fiber, which can apply constant and precise pre-tension to the optical fiber, so that it is stably tensioned in the radial direction and always kept in a taut state; the stable pre-tension can eliminate the baseline drift caused by the slackness and sway of the optical fiber, ensure the pre-tension consistency of different sensors, solve the problems of roughness and unstable pre-tensioning force in traditional tensioning methods, and improve measurement repeatability, signal stability and long-term working reliability.

[0024] 9. The support unit is fixed to the base at one end and connected to the external mounting structure at the other end. The installation method is simple and universal. It can be quickly and stably installed in various flow fields such as pipelines and open channels, ensuring accurate positioning and stable attitude of the sensor, unaffected by fluid impact, facilitating on-site installation and maintenance, improving the sensor's adaptability and versatility, ensuring long-term stable measurement, and meeting the low flow velocity detection needs under different working conditions. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0026] Figures 1-2 A schematic diagram of a fiber optic strain gauge low-flow-rate sensor with temperature compensation provided by the present invention. In the figure: 1. Rigid insulating base; 2. Fiber optic strain sensing unit; 3. Pre-tightening fixing assembly; 4. Temperature sensing unit; 5. Support fixing unit. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0028] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0029] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0030] To address the technical deficiencies mentioned in the background section, this embodiment provides a fiber optic strain gauge low-flow-rate sensor and method with temperature compensation.

[0031] The present invention will now be described in further detail with reference to the accompanying drawings: like Figures 1-2 As shown, in a first aspect of the present invention, a temperature-compensated fiber optic strain gauge low-flow-rate sensor is provided, comprising a rigid insulating base 1; a fiber optic strain sensing unit 2, which is radially arranged through the rigid insulating base 1; a pre-tightening fixing assembly 3, connected to the end of the fiber optic strain sensing unit 2, for tensioning and positioning the fiber optic strain sensing unit 2 radially along the rigid insulating base 1, wherein the axis of the fiber optic strain sensing unit 2 is perpendicular to the direction of fluid flow; a temperature sensing unit 4, which is sealed and embedded in the side wall of the rigid insulating base 1 and disposed adjacent to the fiber optic strain sensing unit 2; and a support fixing unit 5, which is fixed to the outer periphery of the rigid insulating base 1, for fixing the rigid insulating base 1 in the flow field to be measured.

[0032] In this embodiment, the rigid insulating base 1 adopts a rigid insulating ring structure, and the whole is made of insulating ceramic material, preferably one of aluminum nitride, silicon nitride, or high-purity alumina ceramic. The above-mentioned ceramic material has high insulation, high temperature resistance, and corrosion resistance, which can effectively isolate external electromagnetic interference and avoid signal crosstalk and electrical failure in strong electric field environments. At the same time, it can withstand long-term use under high temperature conditions, maintain the stability of material mechanical properties and structural dimensions, and does not undergo thermal deformation, thermal embrittlement, or thermal softening. In corrosive media environments such as acids, alkalis, salt spray, and oil and gas, it will not produce electrochemical corrosion, surface peeling, or structural deterioration, significantly improving the service life and operational reliability of the sensor in harsh environments.

[0033] The rigid insulating base 1 remains completely rigid and fixed during operation, without any deformation. This provides a stable and unchanging installation and measurement reference for the fiber optic strain sensing unit 2, ensuring that the strain detected by the fiber optic strain sensing unit 2 originates only from hydrodynamic forces rather than from the deformation of the base itself. This improves measurement accuracy and long-term repeatability from the structural source.

[0034] The fiber optic strain sensing unit 2 is arranged radially through the rigid insulating base 1, preferably through the horizontal radial direction of the rigid insulating base 1, so that the axis of the fiber optic strain sensing unit 2 is strictly perpendicular to the direction of fluid flow, maximizing the effect of fluid dynamics on the fiber optic strain sensing unit 2 and significantly improving the sensor's sensitivity to low-velocity fluids.

[0035] Furthermore, the fiber optic strain sensing unit 2 extends through the rigid insulating base 1, with both ends extending outward to the outside of the rigid insulating base 1, which facilitates connection and fixation with the pre-tightening fixing assembly 3, while providing operating space for applying the pre-tightening force.

[0036] In practice, the fiber optic strain sensing unit 2 adopts a single-mode fiber or fiber grating structure, which can convert its own minute deformation into changes in the wavelength, phase or intensity of the optical signal, and has the advantages of high strain detection accuracy, fast response speed and long transmission distance.

[0037] In a static state without fluid action, the fiber optic strain sensing unit 2 maintains a straight and taut shape, providing a stable initial reference for strain detection under subsequent fluid action. When fluid flows through the fiber optic strain sensing unit 2, the fluid resistance acts directly on the fiber surface, causing the fiber to undergo slight bending and tensile deformation, thereby changing the physical characteristics of the internal transmitted optical signal and realizing the core function of converting flow velocity information into detectable optical signals.

[0038] The pre-tightening fixing component 3 is disposed on the outside of the rigid insulating base 1 and is fixedly connected to the rigid insulating base 1. The clamping end of the pre-tightening fixing component 3 and the end of the fiber optic strain sensing unit 2 extending to the outside form a pressing fit.

[0039] The pre-tightening fixing component 3 is used to apply a constant, precise and long-term maintainable pre-tightening force to the fiber optic strain sensing unit 2, and to stably tension and position the fiber optic strain sensing unit 2 radially along the rigid insulating base 1, ensuring that the fiber optic cable is always taut throughout the entire measurement cycle and will not slacken, shake or bend.

[0040] The locking action of the pre-tension fixing component 3 can precisely control the initial pre-tension magnitude, ensuring the consistency of pre-tension between different sensors, and effectively solving problems such as baseline drift and poor measurement repeatability caused by coarse fiber tensioning and unstable pre-tension in the existing technology.

[0041] The clamping part of the pre-tightening fixing component 3 adopts a flexible anti-slip structure, which ensures that the clamping is firm and reliable, and will not damage the surface and internal structure of the optical fiber, avoid optical fiber breakage, increased loss or signal distortion, and ensure the long-term stable operation of the optical fiber strain sensing unit 2.

[0042] In this embodiment, the temperature sensing unit 4 is sealed and embedded inside the side wall of the rigid insulating base 1, and is arranged adjacent to the fiber optic strain sensing unit 2, so that the temperature sensing unit 4 and the fiber optic strain sensing unit 2 are in the same thermal environment, achieving a real-time and synchronous thermal equilibrium state.

[0043] The rigid insulating base 1 has micro blind holes on its side wall. The micro blind holes are preferably opened on the outer wall of the horizontal radial end of the rigid insulating base 1, and are located close to the area where the fiber optic strain sensing unit 2 is arranged. The temperature sensing unit 4 is housed inside the micro blind holes.

[0044] The size of the micro-blind hole matches the shape of the temperature sensing unit 4, ensuring its stable installation without shaking. The micro-blind hole is filled with a high thermal conductivity sealant, which fixes the temperature sensing unit 4 within it. This sealant provides thermal conductivity, sealing, and fixation, rapidly conducting ambient temperature to enable the temperature sensing unit 4 to accurately acquire the temperature of the flow field under test in real time, maintaining temperature synchronization with the fiber optic strain sensing unit 2. It also seals the micro-blind hole opening, preventing external fluids, moisture, and dust from entering and protecting the temperature sensing unit 4 from mechanical stress, media corrosion, or environmental interference, ensuring stable and reliable temperature detection. The temperature sensing unit 4 is used to acquire ambient temperature signals in real time, providing accurate reference for subsequent temperature compensation and resolving measurement errors caused by the coupling of temperature-induced strain and flow-induced strain.

[0045] The support and fixing unit 5 is fixed to the outer periphery of the rigid insulating base 1, preferably vertically fixed to the outer peripheral wall of the rigid insulating base 1. One end of the support and fixing unit 5 is fixedly connected to the outer peripheral wall of the rigid insulating base 1, and the other end is used to fix and cooperate with the external mounting structure, so as to realize the stable installation of the rigid insulating base 1 in the flow field to be measured. The support and fixing unit 5 adopts a rigid support structure, which has sufficient mechanical strength and impact resistance, and can withstand the force generated by the continuous impact of the fluid, ensuring that the rigid insulating base 1 is stable in attitude and fixed in position in the flow field, without shaking, deflection or displacement, and maintaining the perpendicular relationship between the fiber optic strain sensing unit 2 and the fluid flow direction. The installation method of the support and fixing unit 5 is simple and reliable, and can be adapted to various flow field installation scenarios such as pipelines, open channels, and monitoring chambers, improving the installation versatility and scenario adaptability of the sensor.

[0046] In this embodiment, after the sensor is assembled, the rigid insulating base 1, the fiber optic strain sensing unit 2, the pre-tightening fixing component 3, the temperature sensing unit 4, and the support fixing unit 5 form a collaborative working system. The rigid insulating base 1 provides rigid support and environmental protection, the fiber optic strain sensing unit 2 realizes the conversion of flow velocity, strain, and optical signal, the pre-tightening fixing component 3 ensures stable tension of the fiber optic cable, the temperature sensing unit 4 realizes synchronous temperature measurement and temperature compensation, and the support fixing unit 5 ensures the stability of the overall structure. Each component works together and is indispensable to achieve high-precision measurement of low flow velocity in harsh environments.

[0047] In this embodiment, the resistance experienced by the fiber optic strain sensing unit 2 can be described by the following formula:

[0048] Where: F: Force exerted by the fluid on the optical fiber / N; ρ: Density of the fluid / kg / m³; V: Flow velocity of the fluid / m / s; C d : Drag coefficient, dimensionless number, which can be approximated as a constant under low-velocity laminar flow conditions; D: diameter of optical fiber / m; L: effective length of optical fiber exposed in the fluid / m.

[0049] The force F acting on the optical fiber is proportional to the strain ε of the optical fiber, that is:

[0050] Ks: The structural sensitivity coefficient of optical fiber, which includes the elastic modulus and geometric dimensions of the optical fiber.

[0051] Combining the two formulas above, we can obtain:

[0052] By transforming the above formula, we can obtain the formula for calculating flow velocity by measuring strain, that is, the flow velocity v is proportional to the square root of the measured strain ε.

[0053]

[0054] Temperature sensing unit 4, serving as a temperature compensation device, is installed to ensure it is not affected by mechanical stress. Real-time wavelength data from strain sensor 2 and temperature sensor 4 are simultaneously acquired using fiber optic demodulation equipment. By subtracting the wavelength change of the temperature sensor from the wavelength change of strain sensor 2, the wavelength change purely caused by hydrodynamics is obtained. The drift wavelength of the fiber optic strain sensor caused by hydrodynamics is then calculated using a formula. This is converted into strain ε caused by hydrodynamics.

[0055]

[0056] In the formula: : The amount of wavelength change of the strain sensor; The amount of wavelength change of the temperature sensor; λ: Drift wavelength of the fiber optic strain sensor caused by hydrodynamics; λ: Original wavelength of the fiber optic strain sensor; : Effective elastic coefficient; ε: Strain caused by hydrodynamics.

[0057] Combining the above formulas, we can obtain:

[0058] Wherein: K is a comprehensive constant, which needs to be determined through calibration.

[0059] In a second aspect, this invention provides a low-flow-velocity measurement method based on temperature compensation. This method employs the aforementioned temperature-compensated fiber optic strain gauge low-flow-velocity sensor, and the specific steps are as follows: Step 1: Place the sensor in the flow field to be measured, so that the axis of the fiber optic strain sensing unit is perpendicular to the direction of fluid flow, and at the same time, make the temperature sensing unit, the fiber optic strain sensing unit and the flow field to be measured are in the same thermal environment. For example, the sensor is placed in the flow field to be measured and fixed to the external mounting structure by the support and fixing unit 5. The sensor posture is adjusted to ensure that the axis of the fiber optic strain sensing unit 2 is strictly perpendicular to the direction of fluid flow. At the same time, the temperature sensing unit 4, the fiber optic strain sensing unit 2 and the flow field to be measured are in full contact and in the same thermal environment to ensure the environmental consistency of temperature detection and strain detection, and to provide the basic conditions for subsequent measurement and temperature compensation.

[0060] Step 2: When the fluid flows through the fiber optic strain sensing unit, it generates an impact force and causes the fluid to undergo strain deformation. The fiber optic strain sensing unit converts the strain deformation into a corresponding strain signal and outputs it. For example, when the fluid flows steadily through the fiber optic strain sensing unit 2, the fluid exerts a continuous impact force and resistance on the surface of the fiber, causing the fiber optic strain sensing unit 2, which was originally in a taut state, to undergo a slight strain deformation. The fiber optic strain sensing unit 2 converts this strain deformation into a corresponding optical signal change, forming a strain signal, which is output to an external demodulation device in real time. The demodulation device acquires, amplifies, and performs preliminary processing on the received strain signal to obtain the raw strain detection data.

[0061] Step 3: The ambient temperature signal of the flow field under test is collected in real time using the temperature sensing unit, and the strain signal output by the fiber optic strain sensing unit is corrected by temperature compensation based on the ambient temperature signal to eliminate the influence of temperature change on the measurement results. For example, the ambient temperature signal of the flow field under test is acquired in real time using the temperature sensing unit 4, and the temperature signal is synchronously transmitted to the demodulation device or signal processing unit. Based on the ambient temperature signal, the original strain signal output by the fiber optic strain sensing unit 2 is temperature compensated and corrected, the temperature-induced strain component caused by temperature change is removed, and the flow-induced strain component generated purely by hydrodynamic action is retained, thus eliminating the interference of temperature fluctuations on the measurement results and solving the error problem caused by the coupling of temperature-induced strain and flow-induced strain.

[0062] Step 4: Based on the strain signal after temperature compensation correction, and combined with the preset strain-flow velocity correspondence, calculate the low flow velocity value of the fluid to be measured.

[0063] For example, based on the accurate strain signal after temperature compensation correction, combined with the strain-flow velocity correspondence established in advance through calibration experiments, the strain signal value is converted into the corresponding fluid flow velocity value through the built-in algorithm of the signal processing unit, and finally the low flow velocity measurement result of the fluid under test is obtained. The result is then output in real time through the display module or data transmission interface, thus completing the entire low flow velocity measurement process.

[0064] In actual measurement, the resistance of the fluid acting on the fiber optic strain sensing unit 2 is proportional to the square of the flow velocity, and the fiber strain is proportional to the resistance. Therefore, after temperature compensation, there is a stable quantitative correspondence between the strain signal and the flow velocity. The pre-tightening fixing component 3 ensures the stability of the initial tension of the fiber, the rigid insulating base 1 ensures the measurement reference remains unchanged, and the temperature sensing unit 4 achieves accurate temperature compensation. This ensures that the sensor has high sensitivity, good linearity, and small measurement error in the low flow velocity range. Even in environments with strong electric fields, strong corrosion, high temperature and high pressure, and drastic temperature fluctuations, it can still maintain long-term stable, high-precision, and high-repeatability measurement performance.

[0065] The sensor and measurement method provided in this specific embodiment are structurally optimized and functionally enhanced to address the shortcomings of existing technologies. A rigid insulating base 1 is used to improve environmental adaptability, a radial through-hole and vertical arrangement is used to improve low flow velocity sensitivity, a pre-tightening fixing component 3 is used to improve measurement stability, and a nearby embedded temperature sensing unit 4 is used to improve temperature compensation accuracy. Comprehensive optimization is achieved in terms of structural design, installation method, signal detection, compensation algorithm, etc., to meet the needs of industrial process control, energy metering, environmental monitoring, aerospace and other fields for high-precision measurement of low flow velocities in harsh environments.

[0066] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A fiber optic strain gauge low-flow-rate sensor with temperature compensation, characterized in that, include: Rigid insulating base; The fiber optic strain sensing unit is arranged radially through the rigid insulating base; A pre-tightening fixing assembly is connected to the end of the fiber optic strain sensing unit to tension and position the fiber optic strain sensing unit radially along the rigid insulating base, and the axis of the fiber optic strain sensing unit is perpendicular to the direction of fluid flow. The temperature sensing unit is sealed and embedded in the side wall of the rigid insulating base and is disposed adjacent to the fiber optic strain sensing unit. A support and fixing unit is fixed to the outer periphery of the rigid insulating base and is used to fix the rigid insulating base in the flow field to be measured.

2. The fiber optic strain gauge low-flow-rate sensor with temperature compensation according to claim 1, characterized in that, The rigid insulating base is a rigid insulating ring, which is made of insulating ceramic.

3. The fiber optic strain gauge low-flow-rate sensor with temperature compensation according to claim 1, characterized in that, The fiber optic strain sensing unit is arranged radially through the rigid insulating base.

4. The fiber optic strain gauge low-flow-rate sensor with temperature compensation according to claim 1, characterized in that, Both ends of the fiber optic strain sensing unit extend outward to the outside of the rigid insulating base.

5. The fiber optic strain gauge low-flow-rate sensor with temperature compensation according to claim 1, characterized in that, The rigid insulating base has micro-blind holes on its sidewalls, and the temperature sensing unit is housed within the micro-blind holes.

6. The fiber optic strain gauge low-flow-rate sensor with temperature compensation according to claim 5, characterized in that, The micro-blind hole is filled with a high thermal conductivity sealant, and the temperature sensing unit is fixed in the micro-blind hole by the high thermal conductivity sealant.

7. The fiber optic strain gauge low-flow-rate sensor with temperature compensation according to claim 1, characterized in that, The support and fixing unit is vertically fixed to the outer peripheral wall of the rigid insulating base.

8. The fiber optic strain gauge low-flow-rate sensor with temperature compensation according to claim 1, characterized in that, The pre-tightening fixing component is fixedly connected to the rigid insulating base, and the clamping end of the pre-tightening fixing component is pressed against the end of the fiber optic strain sensing unit.

9. The fiber optic strain gauge low-flow-rate sensor with temperature compensation according to claim 1, characterized in that, One end of the support and fixing unit is fixedly connected to the outer peripheral wall of the rigid insulating base, and the other end is used for fixed cooperation with the external installation structure.

10. A method for measuring low flow rates with temperature compensation, characterized in that, The method employs the temperature-compensated fiber optic strain gauge low-flow-rate sensor as described in any one of claims 1-9, and includes: Place the sensor in the flow field to be measured, so that the axis of the fiber optic strain sensing unit is perpendicular to the direction of fluid flow, and at the same time, place the temperature sensing unit, the fiber optic strain sensing unit and the flow field to be measured in the same thermal environment. When the fluid flows through the fiber optic strain sensing unit, it generates an impact force and causes the fluid to undergo strain deformation. The fiber optic strain sensing unit converts the strain deformation into a corresponding strain signal and outputs it. The ambient temperature signal of the flow field under test is collected in real time using a temperature sensing unit, and the strain signal output by the fiber optic strain sensing unit is corrected by temperature compensation based on the ambient temperature signal to eliminate the influence of temperature change on the measurement results. Based on the strain signal after temperature compensation correction, and combined with the preset strain-flow velocity correspondence, the low flow velocity value of the fluid under test is calculated.

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