Temperature sensor for measuring internal temperature in granular mixture compression molding process, preparation method and application

Abstract

The invention relates to the technical field of sensing and measurement, in particular to a temperature sensor for measuring the internal temperature in the granular mixture compression molding process, a preparation method and application. The single-mode fiber laser is composed of a cylindrical metal sleeve, a single-mode fiber and a compressible spring-shaped metal capillary tube, the compressible spring-shaped metal capillary tube is composed of straight tubes at the two ends and a spiral tube in the middle, the end portion of the straight tube at one end is closed, and the end portion of the straight tube at the other end is open; the Bragg grating fiber is arranged in the compressible spring-shaped metal capillary in a penetrating mode, the fiber Bragg grating at one end of the metal capillary is located in the straight pipe at the closed end, and the other end of the metal capillary extends out of the open straight pipe end. The spiral tube part of the compressible spring-shaped metal capillary tube is arranged in the metal sleeve, and the part provided with the fiber bragg grating fiber is located outside the sleeve.

Description

Technical Field

[0001] The present invention relates to the technical field of sensing and measurement, and more specifically, to a temperature sensor for measuring the internal temperature during the compacting process of granular materials, a preparation method thereof, and an application thereof. Background Art

[0002] In the technology of compacting granular materials, the detection of physical quantities such as temperature, pressure, displacement, and stress is of great significance. Among them, temperature, as one of the core parameters for controlling the forming process, its accurate monitoring is crucial for ensuring the forming quality. By real-time monitoring and adjusting the temperature distribution of granular materials and molds, quality defects caused by temperature differences can be effectively avoided. Temperature monitoring can not only provide real-time feedback on the temperature fluctuations during the forming process but also provide data support for the optimization of the temperature control system to ensure that the material is always within an appropriate temperature range for forming. In addition, too high or too low temperature may have an adverse impact on the forming quality, such as causing excessive sintering or incomplete compaction of particles, thereby weakening the stability and consistency of the product. Therefore, accurate temperature detection plays an irreplaceable role in improving product quality, increasing production efficiency, optimizing equipment protection, and achieving energy conservation and consumption reduction.

[0003] Currently, for the temperature monitoring during the compacting process of granular materials, traditional measurement techniques such as CT scanning and ultrasonic detection have obvious deficiencies when applied to high-pressure complex environments (such as explosive pressing). CT scanning is based on the principle of X-ray imaging and can construct high-resolution images of the internal structure of materials, with the advantage of non-contact detection. However, its radiation risk, high cost, and lack of real-time performance severely restrict its large-scale application in industrial fields. Ultrasonic detection technology monitors the changes in the internal structure through the propagation characteristics of sound waves in materials. Although it is suitable for non-destructive detection of sensitive materials, due to the low correlation between the change in sound velocity and temperature, it is difficult to achieve high-precision temperature measurement. In addition, ultrasonic signals are easily affected by environmental noise and material non-uniformity, resulting in a decrease in the stability and reliability of measurement results.

[0004] With the rapid development of fiber optic sensing technology, fiber Bragg grating (FBG) sensors, as an emerging technology, due to their Bragg reflection principle based on the periodic microstructure of optical fibers, have the ability to monitor temperature and stress changes in real time and have strong anti-electromagnetic interference capabilities. For example, in the document with the application number "202110939985.4", "A Fiber Bragg Grating Temperature Sensor" is disclosed, which includes a Bragg grating optical fiber and a capillary tube. The capillary tube is sleeved on the Bragg grating optical fiber, and the fiber Bragg grating section in the Bragg grating optical fiber is located inside the capillary tube. The gap between the capillary tube and the Bragg grating optical fiber located inside the capillary tube is filled with epoxy resin.

[0005] However, for the detection of the internal temperature of granular materials during the pressing process, the above-mentioned sensors are difficult to meet the measurement requirements and have the following problems. First, the sensor needs to withstand an extreme pressure of up to 200 MPa, and such a high-pressure environment may cause damage to the sensor. Second, the high pressure may cause the flow and rearrangement of granular materials during the pressing process, thereby changing the original stress distribution. Due to the influence of this rearrangement, the anti-interference ability of the sensor is insufficient, reducing the measurement accuracy. In addition, the implantation of the sensor may hinder the natural movement of granular particles, forming a "blocking point" effect, changing the local stress distribution, resulting in the measurement result deviating from the actual value and low measurement accuracy. Importantly, around the sensor, the forces between particles may concentrate on its surface or nearby, resulting in too concentrated local stress, which will not only have a destructive effect on the sensor, but also may cause an unnatural force field distribution. Especially for highly sensitive materials such as explosives, the implantation of the sensor may cause additional mechanical or thermal interference, significantly increasing the thermal sensitivity or friction sensitivity of the materials, thereby increasing the explosion risk. Therefore, it cannot fully meet the requirements of complex working conditions. Summary of the Invention

[0006] The present invention provides a temperature sensor for measuring the internal temperature during the pressing process of granular materials, a preparation method and an application to solve the problem in the prior art that the internal temperature of granular materials during the pressing process cannot be measured under high-pressure conditions.

[0007] To achieve the above object, the present invention provides the following technical solutions: An elastic temperature sensor for measuring the internal temperature during the pressing process of granular materials, which is composed of a cylindrical metal sleeve, a single-mode optical fiber and a compressible spring-shaped metal capillary;

[0008] The compressible spring-shaped metal capillary is composed of straight pipes at both ends and a spiral pipe in the middle. One end of the straight pipe is closed, and the other end of the straight pipe is open;

[0009] The single-mode optical fiber is arranged inside the compressible spring-shaped metal capillary. The Bragg grating at one end is located in the straight pipe at the closed end, and the other end extends out from the open straight pipe end;

[0010] The spiral pipe part of the compressible spring-shaped metal capillary is arranged inside the metal sleeve, and the part provided with the Bragg grating is located outside the sleeve.

[0011] Further, spiral grooves are arranged inside the above-mentioned metal sleeve, and the compressible spring-shaped metal capillary is embedded in the spiral grooves.

[0012] Further, the cross-section of the above-mentioned spiral groove is arc-shaped.

[0013] Furthermore, the preparation method of the elastic temperature sensor for measuring the internal temperature during the granule pressing process includes the following steps:

[0014] Step 1: Push the single-mode optical fiber through the metal capillary tube so that the Bragg grating optical fiber is located inside the front end of the compressible spring-shaped metal capillary tube, and seal the front end of the compressible spring-shaped metal capillary tube;

[0015] Step 2: Screw the compressible spring-shaped metal capillary tube into the metal sleeve so that the spiral tube in the middle of the metal capillary tube is embedded in the spiral groove, and use strong curing glue to fill the gap and firmly encapsulate and fix it.

[0016] Furthermore, the application of the above elastic temperature sensor in the granule pressing process specifically includes the following steps:

[0017] Step 1: Conduct a temperature calibration experiment on the elastic temperature sensor to establish the relationship between the reflection wavelength and the temperature value. The Bragg wavelength shift satisfies the following formula: Δλ = λ 0 (α + ξ)ΔT, where α is the thermal expansion coefficient of the single-mode optical fiber material, ξ is the thermo-optic coefficient, and ΔT is the temperature change;

[0018] Step 2: Install the elastic temperature sensor at the bottom of the mold and fill the granule powder into the mold;

[0019] Step 3: Based on the broadband light source to provide incident light waves, the light waves are transmitted to the elastic temperature sensor through the circulator and reflected in the Bragg grating optical fiber. Then the reflected light is guided by the circulator to the spectrometer for spectral analysis measurement method to complete the installation and debugging of the device;

[0020] Step 4: Start pressurizing and simultaneously acquire and record the reflected spectrum data;

[0021] Step 5: Use the upper computer to process the reflected spectrum data and calculate and determine the temperature through the calibration coefficient.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The present invention adopts the structure combining the compressible spring-shaped metal capillary tube and the Bragg grating. For the high-pressure environment, the compressible spring-shaped metal capillary tube can effectively avoid the measurement error caused by the friction and collision between granule particles during the pressing process through its elastic deformation and adaptive design. Especially during the pressing process of sensitive materials such as gunpowder, this design can avoid potential safety hazards caused by local overheating, improve the operation safety and maximize the protection of personnel and equipment safety.

[0024] 2. The structure provided by the present invention can effectively reduce or eliminate the adverse effects caused by the "blocking point effect" in traditional methods. The compressible spring-shaped metal capillary can dynamically adapt to the changes between granular materials, reducing local stress concentration. During the pressing process of granular materials, the flexible spring-shaped probe (Bragg grating optical fiber and compressible spring-shaped metal capillary) given by the present invention can adapt to the dynamic changes in the pressing environment. Therefore, during the pressing process, the external pressure is evenly distributed, avoiding probe damage or poor contact caused by excessive or uneven local pressure, effectively avoiding excessive local pressure and blocking point effect caused by the extrusion and friction between particles and the probe, and reducing the phenomenon of being unable to collect some temperature data; through this design, the probe maintains good contact with the surface of granular materials, ensuring the accuracy and efficiency of temperature measurement; at the same time, the flexible spring structure helps to slow down the pressing pressure between granular materials and the probe, significantly reducing the risk of spontaneous combustion of gunpowder caused by local overheating, thereby improving the safety of the experimental process. By using a spectrometer to record the change of the reflection wavelength of the single-mode optical fiber in real time, based on the numerical fitting relationship between temperature and reflection wavelength, the temperature inside the granular materials can be accurately calculated through the upper computer. The test results confirm that this method effectively avoids the failure of traditional temperature sensors in high-pressure and high-temperature environments and is a more stable and accurate temperature monitoring method.

[0025] 3. Since the structure of the present invention can significantly improve the temperature measurement accuracy and stability during the pressing and forming process of granular materials, it is particularly suitable for use under complex working conditions such as high-pressure, dynamic, and extreme environments. Description of the Drawings

[0026] Figure 1 is a schematic diagram of the principle of Bragg optical fiber;

[0027] Figure 2 is a schematic diagram of the structure of the compressible spring-shaped metal capillary and the metal sleeve;

[0028] Figure 3 is a schematic diagram of the structure of the combination of Bragg grating optical fiber and compressible spring-shaped metal capillary;

[0029] Figure 4 is a schematic diagram of the overall structure of the present invention;

[0030] Figure 5 is a schematic diagram of the method for measuring the internal temperature during the pressing process of granular materials;

[0031] Figure 6 is a graph showing the relationship between the internal temperature change of granular materials during the pressing process of granular materials;

[0032] The accompanying reference numerals are as follows: 1 - straight tube, 2 - helical tube, 3 - single-mode optical fiber, 4 - helical groove, 5 - Bragg grating, 6 - metal sleeve, 10 - broadband light source, 11 - circulator, 12 - spectrometer, 13 - upper computer, 14 - mold, 15 - granular powder. Specific embodiments

[0033] The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0034] See Figures 1 - 4 , the working principle of the present invention is as follows: An elastic temperature sensor for measuring the internal temperature during the granule compression molding process is composed of a cylindrical metal sleeve 6, a single-mode optical fiber 3 with a Bragg grating provided at one end, and a compressible spring-shaped metal capillary tube. The compressible spring-shaped metal capillary tube is composed of a straight tube 1 at both ends and a helical tube 2 in the middle. One end of the straight tube 1 is closed, and the other end of the straight tube 1 is open;

[0035] Considering the outer diameter of the bare fiber and subsequent encapsulation, a compressible spring-shaped metal capillary tube with an inner diameter of 200 μm is selected in this embodiment; the single-mode optical fiber 3 is inserted into the compressible spring-shaped metal capillary tube, and the Bragg grating at one end is located in the straight tube 1 at the closed end, and the other end extends out from the open end of the straight tube 1; through the comparison of the effects of different fiber Bragg gratings, a Bragg grating 5 with a length of 4 mm is selected in this embodiment.

[0036] The helical tube 2 of the compressible spring-shaped metal capillary tube is partially arranged inside the metal sleeve 6, and the part provided with the Bragg grating 5 is located outside the sleeve 6. In this embodiment, half of the helical tube 2 is arranged inside the metal sleeve 6.

[0037] An arc-shaped helical groove 4 is provided on the inner part of the metal sleeve 6, and the compressible spring-shaped metal capillary tube is embedded in the helical groove 4, and the shape of the helical groove is adapted to the outer diameter of the helical tube 2 in the middle of the compressible spring-shaped metal capillary tube.

[0038] The preparation method of the elastic temperature sensor for measuring the internal temperature during the granule compression molding process includes the following steps:

[0039] Step 1: Since the diameter of the single-mode optical fiber 3 provided with the Bragg grating 5 is matched with the inner diameter of the metal capillary tube, the single-mode optical fiber 3 can be gently pushed manually through the metal capillary tube, so that the Bragg grating 5 is located in the straight tube 1 at the front end of the compressible spring-shaped metal capillary tube and the closed end is sealed;

[0040] Step 2: Screw the compressible spring-shaped metal capillary into the metal sleeve 6, so that the helical tube 2 in the middle of the metal capillary is embedded in the helical groove 4, and part of the helical tube 2 is arranged outside the metal sleeve 6. The end (front end) of this part of the helical tube 2 and the part with the Bragg grating are also located outside the technical sleeve 6. Use strong curing glue to fill the gap and firmly encapsulate and fix it.

[0041] See Figure 5 , the application of the elastic temperature sensor in the compacting of granular materials specifically includes the following steps:

[0042] Step 1: Conduct a temperature calibration experiment on the elastic temperature sensor to establish the relationship between the reflection wavelength and the temperature value. That is, due to the thermal expansion of the single-mode fiber 3 material, the grating period increases, and at the same time, the thermo-optic effect causes the refractive index of the fiber core to change. The combined effect of these two effects makes the Bragg wavelength shift satisfy the following formula: Δλ = λ 0 (α + ξ)ΔT, where α is the thermal expansion coefficient of the single-mode fiber 3 material, ξ is the thermo-optic coefficient, and ΔT is the temperature change;

[0043] Step 2: Install the elastic temperature sensor at the bottom of the mold 14, and fill the granular powder 15 into the mold 14;

[0044] Step 3: Based on the broadband light source 10 to provide incident light waves, the light waves are transmitted to the elastic temperature sensor through the circulator 11 and reflected in the Bragg grating optical fiber 5. The reflected light is then guided by the circulator 11 to the spectrometer 12 for spectral analysis measurement method to complete the installation and debugging of the device;

[0045] Step 4: Start pressurizing, and at the same time obtain and record the reflected spectrum data;

[0046] Step 5: Use the host computer 13 to process the reflected spectrum data and determine the temperature by calculating the calibration coefficient.

[0047] During the pressing process, according to the working principle of the Bragg grating optical fiber 5: when the incident light passes through the single-mode fiber 3, part of the light will be reflected by the Bragg grating 5 in the single-mode fiber 3. This reflection wavelength is closely related to the refractive index of the single-mode fiber 3, and at the same time, the refractive index changes with the temperature, thus causing a displacement of the reflection wavelength. Through numerical fitting and experimental calibration, the numerical relationship between the reflected light wavelength and the temperature field is established.

[0048] During the pressing process of the granular powder 15 in the mold 14, the internal temperature continuously changes due to factors such as external pressure and friction. The fiber Bragg grating optical fiber 5 in the flexible spring-like probe captures these changes in real time. The external spectrometer 12 reads and records the changed reflected wavelength data. Using the host computer, based on the determined relationship between the reflected wavelength and temperature values, the real-time temperature inside the granular powder 15 is accurately calculated. The determined temperature inside the granular powder 15 is shown in Figure 6 . It can be seen that this solution can successfully monitor the entire process of the temperature during the compression molding process in a high-pressure environment.

[0049] The above description is an illustration of the specific implementation of the present invention, rather than a limitation thereof. Those skilled in the relevant technical field can also make various equivalent technical solutions without departing from the scope of the present invention. Therefore, all equivalent technical solutions should be included in the protection scope of the present invention.

Claims

1. An elastic temperature sensor for measuring the internal temperature of a granular body during a pressing process, characterized in that: The invention comprises a cylindrical metal sleeve (6), a single-mode optical fiber (3) with a Bragg grating arranged at one end, and a compressible spring-shaped metal capillary. The compressible spring-shaped metal capillary comprises straight tubes (1) at two ends and a spiral tube (2) in the middle. The straight tube (1) at one end is closed, and the straight tube (1) at the other end is open. The single-mode optical fiber (3) is inserted into the compressible spring-shaped metal capillary, and the Bragg grating at one end is located in the straight tube (1) at the closed end, and the other end extends out from the open straight tube (1). The spiral tube (2) part of the compressible spring-shaped metal capillary is arranged inside the metal sleeve (6), and the part with the Bragg grating is located outside the sleeve (6).

2. The elastic temperature sensor for measuring the internal temperature of a granular body during pressing and forming according to claim 1 is characterized in that: A spiral groove (4) is provided inside the metal sleeve (6), and a compressible spring-shaped metal capillary is embedded in the spiral groove (4).

3. The elastic temperature sensor for measuring the internal temperature of a granular body during pressing and forming according to claim 2 is characterized in that: The cross section of the spiral groove (4) is in the shape of an arc.

4. The method for preparing an elastic temperature sensor for measuring the internal temperature of a granular body during a pressing and forming process according to claim 1 comprises the following steps: Step 1, pushing the single-mode optical fiber (3) through the metal capillary, so that the Bragg grating (5) is located in the straight tube (1) at one end of the compressible spring-shaped metal capillary, and the end is closed; Step 2: Screw the compressible spring-shaped metal capillary into the metal sleeve (6) so that the spiral tube (2) in the middle of the metal capillary is embedded in the spiral groove (4), and the part with the Bragg grating is located outside the sleeve (6). Use strong curing glue to fill the gap and firmly encapsulate and fix it.

5. The application of an elastic temperature sensor in granular body pressing and forming according to claim 1 specifically comprises the following steps: Step 1: Perform a temperature calibration experiment on the elastic temperature sensor to establish the numerical relationship between the reflection wavelength and temperature. The Bragg wavelength shift satisfies the following formula: Δλ=λ0(α+ξ)ΔT, where, α is the thermal expansion coefficient of the single-mode optical fiber (3) material, ξ is the thermo-optic coefficient, and ΔT is the temperature change; Step 2: Install the elastic temperature sensor at the bottom of the mold (14) to fill the mold (14) with the granular powder (15); Step 3: Based on the broadband light source (10) providing an incident light wave, the light wave is transmitted to the elastic temperature sensor through the circulator (11) and reflected in the Bragg grating optical fiber (5), and the reflected light is then guided by the circulator (11) to the spectrometer (12) for spectral analysis, thereby completing the installation and commissioning of the device; Step 4, start pressurizing, and simultaneously acquire and record reflectance spectrum data; Step 5: Process the reflection spectrum data using the host computer (13) and determine the temperature by calculating the calibration coefficient.

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