Fluid refractive index measuring device and method suitable for wide-range temperature and pressure working conditions

Abstract

The application discloses a fluid refractive index measuring device and method suitable for wide-range temperature and pressure working conditions. The device comprises an optical measuring unit, a fluid passage and parameter sensing unit, a data processing and display unit and an instrument box. The optical measuring unit is integratedly installed in the instrument box and comprises a fluid optical prism with an equilateral triangle measuring cavity, an incident optical system and an emergent optical image acquisition system. The fluid passage and parameter sensing unit comprises a temperature sensor installed in a temperature sensor mounting hole, a pressure sensor installed in a pressure sensor mounting hole, a fluid inlet connected with a fluid inlet hole, a fluid outlet connected with a fluid outlet hole and an end cover installed in an end cover mounting hole. The data processing and display unit comprises a circuit board and a display screen. The display screen is installed on a front side panel of the instrument box and is electrically connected with the circuit board. The device has the advantages of high measuring precision and high speed and can provide technical support for fluid refractive index measurement in different fields.

Description

Technical Field

[0001] This application relates to the field of optical detection technology, specifically to a fluid refractive index measurement device and method applicable to a wide range of temperature and pressure conditions. Background Technology

[0002] In fields such as atmospheric science, environmental monitoring, and industrial manufacturing, optical technology can be used to achieve online measurement of various physical quantities of fluids. However, the refractive index of the fluid (including gases and liquids) under operating conditions is a key parameter of optical detection technology, which determines the propagation characteristics of the light beam in the medium.

[0003] Existing research indicates that the refractive index of a fluid is closely related to operating conditions. Operating temperature and pressure affect the intermolecular forces, causing changes in the fluid's composition and density, which in turn alters its refractive index. Therefore, the accuracy of the fluid's refractive index significantly impacts the design, calibration, and measurement of precision instruments. For example, in the natural gas field, when using optical technology for component analysis and leak monitoring, the refractive index of pure methane under standard conditions (1.0004) is typically used as the key measurement benchmark. However, changes in the temperature and pressure of natural gas within pipelines cause two main issues: liquefaction of some gas components, altering the natural gas composition; and compression or expansion, changing its density. Ultimately, this results in the refractive index of natural gas changing in real-time with operating parameters, leading to zero-point drift and measurement errors in natural gas measurement sensors. Therefore, the current standardized approach, which does not fully consider the coupling effects between composition, pressure, and temperature under actual operating conditions, is often a significant factor limiting sensor performance improvement.

[0004] The existing techniques for measuring the refractive index of fluids mainly include interferometry, total internal reflection critical angle method, polarization method, resonant cavity method, and speed of light measurement method. These methods mainly focus on single or simple component fluids and are mostly applicable to normal temperature and pressure conditions. They cannot meet the refractive index measurement requirements of complex component mixed fluids and non-normal temperature and pressure coupling conditions in industrial and other fields. Summary of the Invention

[0005] In view of this, embodiments of this application provide a fluid refractive index measurement device suitable for wide-range temperature and pressure conditions, including: an optical measurement unit, a fluid passage and parameter sensing unit, a data processing and display unit, and an instrument box; The optical measurement unit is integrated into the instrument box and includes a fluid optical prism with an equilateral triangular measurement cavity, an incident optical system, and an outgoing optical image acquisition system. The fluid optical prism has a first optical window mounting hole, a second optical window mounting hole, a temperature sensor mounting hole, a pressure sensor mounting hole, a fluid inlet hole, a fluid outlet hole, and an end cap mounting hole on its base. The incident optical system is mounted to the first optical window mounting hole via a connector and is used to emit monochromatic incident light. The outgoing optical image acquisition system is mounted to the second optical window mounting hole via a connector and is used to receive the outgoing light signal after refraction by the fluid and acquire optical images. The fluid passage and parameter sensing unit includes a temperature sensor installed in a temperature sensor mounting hole, a pressure sensor installed in a pressure sensor mounting hole, a fluid inlet connected to a fluid inlet hole, a fluid outlet connected to a fluid outlet hole, and an end cap installed in an end cap mounting hole. The data processing and display unit includes a circuit board and a display screen. The circuit board is electrically connected to the incident optical system, the outgoing optical image acquisition system, the temperature sensor, and the pressure sensor. It is used to acquire optical images, temperature data acquired by the temperature sensor, and pressure data acquired by the pressure sensor. It also calculates the refractive index parameters of the fluid under test using a preset algorithm. The display screen is mounted on the front panel of the instrument box and is electrically connected to the circuit board. It is used to display the temperature data, pressure data, and refractive index parameters of the fluid under test in real time.

[0006] Optionally, the first optical window mounting hole and the second optical window mounting hole are symmetrically arranged on the left and right end faces of the fluid optical prism substrate, and a flat window glass is installed in both the first optical window mounting hole and the second optical window mounting hole; the material of the flat window glass is one of alkali-free aluminosilicate tempered glass, lithium aluminum silicon transparent microcrystalline glass, and fused silica glass.

[0007] Optionally, a metal graphite gasket is used to seal between the planar viewing window glass and the substrate of the fluid optical prism, and a surface contact seal is achieved through a threaded pre-tightening structure, with a sealing pressure rating of 25 MPa; a metal graphite sealing structure is used between the end cap and the substrate of the fluid optical prism.

[0008] Optionally, the fluid optical prism is made of one or more of the following materials: carbon steel, low alloy steel, alloy structural steel, heat-resistant steel, or non-ferrous metal alloy, and the outer surface of the fluid optical prism is coated or installed with a heat insulation layer.

[0009] Optionally, an independent optical platform is provided inside the instrument box; the optical platform is connected to the instrument box housing by a rubber vibration damping pad, and heat insulation cotton is provided between the optical platform and the fluid pipeline and circuit board; the fluid pipeline includes an inlet pipeline connected to the fluid inlet, an outlet pipeline connected to the fluid outlet, and a flow channel inside the substrate of the fluid optical prism.

[0010] Optionally, the fluid inlet channel has a gradually expanding structure, the fluid outlet channel has a gradually contracting structure, and the inner wall of the channel is chamfered.

[0011] Optionally, the fluid outlet is integrated with a back pressure regulating valve to achieve cavity back pressure control in the range of 0~20MPa.

[0012] Optionally, a temperature sensor is embedded 2 mm from the inner wall of the equilateral triangular measuring cavity through a temperature sensor mounting hole to collect temperature data of the fluid under test in real time; a pressure sensor is embedded 2 mm from the inner wall of the equilateral triangular measuring cavity through a pressure sensor mounting hole to collect pressure data of the fluid under test in real time; the operating temperature range of the fluid refractive index measuring device suitable for wide temperature and pressure conditions is -40℃ to 200℃.

[0013] This application provides a fluid refractive index measurement method applicable to a wide range of temperature and pressure conditions. This method is implemented using the fluid refractive index measurement device applicable to a wide range of temperature and pressure conditions provided in this application, and includes the following steps: S1. Integrate the optical measurement unit, fluid passage and parameter sensing unit, and circuit board into the instrument box. Set the display screen on the front side panel of the instrument box and complete the electrical connection. Fill the fluid optical prism with air under normal temperature and pressure conditions. Adjust the incident optical system so that the outgoing light is in the same direction as the incident light and the outgoing light spot is located at the initial position of the outgoing optical image acquisition system. Record the first pixel coordinate of the initial position. S2. The fluid to be measured is introduced into the equilateral triangular measuring cavity of the fluid optical prism through the fluid inlet and discharged through the fluid outlet, so that the measuring cavity is filled with the fluid to be measured and the temperature and pressure of the fluid to be measured meet the stability conditions. S3. Start the incident optical system and adjust the incident angle until the displacement of the outgoing light spot relative to the initial position is minimized by the outgoing optical image acquisition system. Record the second pixel coordinate of the outgoing light spot at the deflection angle corresponding to the minimum displacement of the outgoing light spot. S4. Calculate the pixel displacement based on the first pixel coordinates and the second pixel coordinates; S5. Based on geometric relationships Calculate the minimum deflection angle ,in Pixel-to-physical size calibration factor This refers to the fixed distance between the imaging surface of the outgoing optical image acquisition system and the center of the fluid optical prism. This is the pixel displacement. S6. Determine the refractive index of the ambient air. ; S7. According to the minimum deflection angle formula Calculate the refractive index of the fluid to be tested. ,in, Let α be the refractive index of the ambient air, where α = 60°. S8. The refractive index of the fluid to be tested calculated in S7. The refractive index measurement results are used as the current temperature and pressure conditions, and the current temperature, current pressure and refractive index of the fluid under test are used as the data. The output is displayed on the screen.

[0014] Optionally, the determination of the refractive index of the ambient air... ,include: If the fluid to be tested is a liquid, then determine the refractive index of the ambient air. =1; If the fluid to be tested is a gas, the temperature, pressure, and humidity parameters of the ambient air are acquired and input into a preset air refractive index calculation model to determine the refractive index of the ambient air. .

[0015] In this embodiment, the fluid refractive index measurement device under wide-range temperature and pressure conditions includes an optical measurement unit, a fluid path and parameter sensing unit, a data processing and display unit, and an instrument box, forming an independent and complete measurement device. It eliminates the need for an external computer and optical experimental platform, realizing the transformation of the minimum deflection angle method from a laboratory discrete device to a field instrument. It can independently complete the entire process of fluid refractive index measurement, calculation, and display. The fluid optical prism has an equilateral triangular measurement cavity, which, combined with a highly sealed end cap and optical window mounting hole, maintains optical path stability and sealing integrity under wide-range temperature and pressure conditions of -40℃ to 200℃ and 0 to 20MPa, providing a structural foundation for online measurement under wide-range conditions. By opening functional holes in the prism substrate, the optical path... The optical path (first optical window mounting hole, second optical window mounting hole), fluid path (fluid inlet hole, fluid outlet hole), and sensing path (temperature sensor mounting hole, pressure sensor mounting hole) are integrated on the same fluid optical prism substrate, allowing the optical path and fluid flow path to intersect within an equilateral triangular measurement cavity. The temperature and pressure sensors collect real-time temperature and pressure data of the fluid under test, which are used to characterize the current operating conditions corresponding to the refractive index measurement results, improving the measurement accuracy over a wide range of operating conditions. The circuit board simultaneously acquires optical images, temperature data, and pressure data, and automatically calculates the refractive index parameters through a preset algorithm without manual intervention. The display screen provides real-time visual display of the measurement results, enabling automated measurement with immediate reading. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein: Figure 1 A partial structural schematic diagram of a fluid refractive index measuring device suitable for wide-range temperature and pressure conditions, provided in an embodiment of this application; Figure 2 A schematic diagram of the structure of a substrate for a fluid optical prism provided in this application embodiment. Figure 1 ; Figure 3 A schematic diagram of the structure of a substrate for a fluid optical prism provided in this application embodiment. Figure 2 ; Figure 4 A schematic diagram of the simulation results of stress distribution in a fluid optical prism provided in this application embodiment; Figure 5 A schematic diagram of the simulation results of the deformation distribution of a fluid optical prism provided in this application embodiment; Figure 6 A schematic diagram of a fluid inlet and a fluid outlet provided for an embodiment of this application; Figure 7 This is a schematic diagram of the structure of an end cap provided in an embodiment of this application; Figure 8 A schematic diagram of the installation position of a display screen provided in an embodiment of this application; Figure 9 This is a schematic diagram of a fluid refractive index measurement method based on geometric optics, provided as an embodiment of this application. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. The following embodiments are used to illustrate this application, but are not intended to limit the scope of this application. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0018] In the following description, references are made to “some embodiments,” which describe a subset of all possible embodiments. However, it is understood that “some embodiments” may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0019] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments of this application pertain. It should also be understood that terms such as those defined in general dictionaries should be understood to have a meaning consistent with their meaning in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined as herein.

[0020] This application provides a fluid refractive index measuring device suitable for a wide range of temperature and pressure conditions. The fluid refractive index measuring device suitable for a wide range of temperature and pressure conditions includes an optical measurement unit, a fluid passage and parameter sensing unit, a data processing and display unit, and an instrument box.

[0021] In some embodiments, such as Figure 1 As shown, the optical measurement unit includes a fluid optical prism 1, an incident optical system 3, and an exit optical image acquisition system 4. The optical measurement unit is integrated and installed inside the instrument box 20.

[0022] In some embodiments, such as Figure 2 As shown, the fluid optical prism 1 has a first optical window mounting hole 5, a second optical window mounting hole 6, a temperature sensor mounting hole 8, and a pressure sensor mounting hole 10 on its substrate. Figure 3 As shown, the fluid optical prism 1 has an equilateral triangular measuring cavity 2 inside, and the fluid optical prism 1 also has a fluid inlet hole 12, a fluid outlet hole 14 and an end cap mounting hole 16 on its base.

[0023] In some embodiments, the fluid optical prism 1 is an integrated core carrier for optical measurement, pressure bearing and temperature resistance. The fluid optical prism is made of one or more of the following materials: carbon steel, low alloy steel, alloy structural steel, heat-resistant steel or non-ferrous metal alloy. The outer surface of the fluid optical prism is coated or installed with a heat insulation layer, which can isolate the heat of the fluid inside the fluid optical prism 1 from external heat conduction and radiation, so that the internal fluid maintains thermal stability.

[0024] In some embodiments, the various mounting holes (first optical window mounting hole 5, second optical window mounting hole 6, temperature sensor mounting hole 8, pressure sensor mounting hole 10, fluid inlet hole 12, fluid outlet hole 14, and end cap mounting hole 16) formed on the substrate of the fluid optical prism 1 have different sizes. For example, the first optical window mounting hole 5 and the second optical window mounting hole 6 have the same size, the temperature sensor mounting hole 8 and the pressure sensor mounting hole 10 have the same size, and the fluid inlet hole 12 and the fluid outlet hole 14 have the same size. The end cap mounting hole 16 is larger than the first optical window mounting hole 5 (or the second optical window mounting hole 6), the first optical window mounting hole 5 is larger than the temperature sensor mounting hole 8 (or the pressure sensor mounting hole 10), and the temperature sensor mounting hole 8 is larger than the fluid inlet hole 12 (or the fluid outlet hole 14).

[0025] In some embodiments, the first optical window mounting hole 5 and the second optical window mounting hole 6 are symmetrically arranged on the left and right end faces of the substrate of the fluid optical prism 1. A planar window glass (optical window) is installed in both the first optical window mounting hole 5 and the second optical window mounting hole 6. The material of the planar window glass is one of alkali-free aluminosilicate tempered glass, lithium aluminum silicon transparent microcrystalline glass, or fused silica glass. In practice, the material of the planar window glass can be selected according to different working conditions.

[0026] In some embodiments, a metal graphite gasket is used to seal between the planar viewing window glass and the substrate of the fluid optical prism, and a surface contact seal is achieved through a threaded pre-tightening structure, with a sealing pressure rating of 25 MPa.

[0027] In some embodiments, the pressure resistance of the fluid optical prism 1 is analyzed. 40CrNiMoA is selected as the core component material for numerical simulation. Its key thermo-mechanical performance parameters, such as density, thermal conductivity, specific heat capacity, coefficient of linear expansion, elastic modulus, Poisson's ratio, and yield strength, are all taken from the standard material handbook. The specific parameters are shown in Table 1.

[0028] Table 1 Performance parameters of fluid optical prism substrate materials

[0029] Simulation results are as follows Figure 4 and Figure 5 As shown. From Figure 4It can be seen that the maximum stress of the substrate structure of the fluid optical prism 1 under an internal pressure of 20 MPa is 138.13 MPa, while the yield strength of 40CrNiMoA is 850~1000 MPa, which is only about 14%~16% of the yield strength, far below the material's yield limit. This indicates that the substrate structure of the fluid optical prism 1 has sufficient strength reserve under an internal pressure of 20 MPa and will not experience plastic yield failure. It should be noted that the high-stress areas are concentrated at the edges of the sensor mounting holes (temperature sensor mounting hole 8 and pressure sensor mounting hole 10) and at the transition between the hole wall and the cylinder wall. This is a typical stress concentration effect of openings. The stress level in the remaining areas of the cylinder wall is low and relatively uniformly distributed, indicating that the overall structure is reasonably stressed and there are no large-area high-stress areas. Figure 5 It can be seen that the maximum total deformation of the substrate structure of the fluid optical prism 1 is 2.0979 × 10⁻⁶. -5 The small deformation (m) indicates that the structure exhibits good overall rigidity under an internal pressure of 20 MPa, with the deformation remaining within the elastic deformation range. This will not affect the sealing accuracy of the optical window or the alignment stability of the optical path. It should be noted that the maximum deformation occurs in the middle of the base wall of the fluid optical prism 1, away from the end constraints, and in the local edge region of the sensor mounting hole, corresponding to the high-stress areas in the stress distribution. The deformation in the end support constraint areas is zero, meeting the boundary condition settings; the uniform deformation in the middle of the cylinder wall, without any local abnormal bulging or warping, indicates uniform internal pressure load transmission and stable structural deformation behavior.

[0030] In some embodiments, such as Figure 1 As shown, the incident optical system 3 is installed in conjunction with the first optical window mounting hole 5 via the connector 7, and is used to emit monochromatic incident light. The incident optical system 3 integrates components such as a light source, lens group, and slit aperture, and can provide a stable and parameter-controllable incident light source to project incident light of a specific wavelength and angle onto the fluid optical prism 1.

[0031] In some embodiments, the outgoing optical image acquisition system 4 is installed in conjunction with the second optical window mounting hole 6 via the connector 7, and is used to receive the outgoing light signal after refraction by the fluid and acquire optical images. This can provide raw optical measurement data for subsequent calculation of the refractive index of the fluid to be measured.

[0032] It is understandable that the flat viewing window glass is installed in conjunction with the incident optical system 3 and the outgoing optical image acquisition system 4 through the connector 7, so that the optical path remains horizontal.

[0033] In some embodiments, the fluid passage and parameter sensing unit includes a temperature sensor 9 installed in the temperature sensor mounting hole 8, a pressure sensor 11 installed in the pressure sensor mounting hole 10, and a fluid inlet 13 connected to the fluid inlet hole 12 (e.g., a temperature sensor 9 installed in the temperature sensor mounting hole 8, a pressure sensor 11 installed in the pressure sensor mounting hole 10, and a fluid inlet 13 connected to the fluid inlet hole 12). Figure 6As shown, the fluid inlet 13 is located on the surface of the instrument box 20, and the fluid outlet 15 is connected to the fluid outlet hole 14 (as shown). Figure 6 As shown, fluid outlet 15 is located on the surface of instrument box 20, and end cap 17 is installed in end cap mounting hole 16 (as shown). Figure 7 As shown, a metal-graphite sealing structure is used between the end cap 17 and the substrate of the fluid optical prism 1.

[0034] In some embodiments, temperature sensor 9 is embedded 2 mm from the inner wall of equilateral triangular measuring cavity 2 through temperature sensor mounting hole 8, for real-time acquisition of temperature data of the fluid to be measured; pressure sensor 11 is embedded 2 mm from the inner wall of equilateral triangular measuring cavity 2 through pressure sensor mounting hole 10, for real-time acquisition of pressure data of the fluid to be measured.

[0035] In some embodiments, the fluid refractive index measuring device provided in this application, which is suitable for a wide range of temperature and pressure conditions, maintains the stability of the internal fluid temperature through a heat insulation layer coated on the outer surface, and the material of its structural components can withstand fluid conditions ranging from -40°C to 200°C.

[0036] In some embodiments, fluid inlet 12 and fluid inlet 13 are fitted with pressure-resistant pipes and connectors for connecting to an external fluid source and introducing the external fluid source into the equilateral triangular measuring cavity 2. Fluid outlet 14 and fluid outlet 15 are fitted with pressure-resistant pipes and connectors for connecting to an external fluid discharge device to discharge fluid. The flow channel of fluid inlet 13 has a gradually expanding structure, and the flow channel of fluid outlet has a gradually contracting structure. The inner wall of the flow channel is chamfered to avoid air bubble retention and dead zone formation.

[0037] In some embodiments, the fluid outlet 15 is integrated with a back pressure regulating valve to achieve cavity back pressure control in the range of 0~20MPa.

[0038] In some embodiments, such as Figure 1 and Figure 8 As shown, the data processing and display unit includes a circuit board 18 and a display screen 19; the circuit board 18 is electrically connected to the incident optical system 3, the exit optical image acquisition system 4, the temperature sensor 9, and the pressure sensor 11, and is used to acquire optical images, temperature data acquired by the temperature sensor 9, and pressure data acquired by the pressure sensor 11, and calculate the refractive index parameters of the fluid under test by combining them with a preset algorithm. Figure 8 As shown, the display screen 19 is mounted on the front panel of the instrument box 20. It is a visual interactive interface and is electrically connected to the circuit board 18. It is used to display the temperature data, pressure data and refractive index parameters of the fluid under test in real time, so that users can read the measurement results intuitively.

[0039] In some embodiments, the display screen 19 may also display auxiliary parameters such as the density and medium type of the fluid being tested. These auxiliary parameters are optional display parameters used to assist in characterizing the state of the fluid being tested and do not participate in the refractive index of the fluid being tested. The calculation process does not affect the refractive index of the fluid being measured. The measurement results.

[0040] In some embodiments, auxiliary parameters may be input by the user via the display screen 19 or an external input interface, or provided by an external process system that is communicatively connected to this device. The external process system may be a process control system, a data acquisition system, a component analysis device, a density measurement device, or a pre-established process database, used to provide the circuit board 18 with the name, medium type, component information, or density data of the fluid to be tested.

[0041] In some embodiments, the circuit board 18 may also obtain auxiliary parameters according to conventional physical property calculation methods in the art. For example, when the medium name or composition information of the fluid to be tested is known, the circuit board 18 may calculate the density auxiliary parameter based on the current temperature, current pressure, and a preset physical property model or equation of state; or it may obtain the density auxiliary parameter by looking up a table or interpolation based on a pre-established temperature-pressure-density calibration relationship, refractive index-density calibration relationship, or process database. The medium type may be input by the user, provided by an external process system, or obtained by calling up the medium category information in a preset process database.

[0042] In some embodiments, an independent optical platform is provided inside the instrument box 20; the optical platform is connected to the instrument box housing by a rubber vibration damping pad, and heat insulation cotton is provided between the optical platform and the fluid pipeline and the circuit board 18, which can reduce the impact of vibration and temperature fluctuations on the optical path. The fluid pipeline includes an inlet pipeline connected to the fluid inlet 13, an outlet pipeline connected to the fluid outlet 15, and a flow channel inside the substrate of the fluid optical prism 1.

[0043] Understandably, the instrument box 20 serves as an integrated protection and installation carrier for fluid refractive index measurement devices applicable to a wide range of temperature and pressure conditions. It provides installation, fixation, and protection for internal components such as optical systems, sensors, circuit boards, and displays, ensuring the relative stability of each component. At the same time, it provides interface positioning for fluid inlets and outlets, realizing the integrated and miniaturized design of the device, making it easy to install and use.

[0044] In this embodiment, the fluid refractive index measurement device under wide-range temperature and pressure conditions includes an optical measurement unit, a fluid path and parameter sensing unit, a data processing and display unit, and an instrument box, forming an independent and complete measurement device. It eliminates the need for an external computer and optical experimental platform, realizing the transformation of the minimum deflection angle method from a laboratory discrete device to a field instrument. It can independently complete the entire process of fluid refractive index measurement, calculation, and display. The fluid optical prism has an equilateral triangular measurement cavity, which, combined with a highly sealed end cap and optical window mounting hole, maintains optical path stability and sealing integrity under wide-range temperature and pressure conditions of -40℃ to 200℃ and 0 to 20MPa, providing a structural foundation for online measurement under wide-range conditions. By opening functional holes in the prism substrate, the optical path... The optical path (first optical window mounting hole, second optical window mounting hole), fluid path (fluid inlet hole, fluid outlet hole), and sensing path (temperature sensor mounting hole, pressure sensor mounting hole) are integrated on the same fluid optical prism substrate, allowing the optical path and fluid flow path to intersect within an equilateral triangular measurement cavity. The temperature and pressure sensors collect real-time temperature and pressure data of the fluid under test, which are used to characterize the current operating conditions corresponding to the refractive index measurement results, improving the measurement accuracy over a wide range of operating conditions. The circuit board simultaneously acquires optical images, temperature data, and pressure data, and automatically calculates the refractive index parameters through a preset algorithm without manual intervention. The display screen provides real-time visual display of the measurement results, enabling automated measurement with immediate reading.

[0045] This application provides a fluid refractive index measurement method applicable to a wide range of temperature and pressure conditions, implemented using the fluid refractive index measurement device provided in this application. The method includes the following steps: S1. Integrate the optical measurement unit, fluid passage and parameter sensing unit, and circuit board 18 into the instrument box 20. Set the display screen 19 on the front side panel of the instrument box 20 and complete the electrical connection. Fill the fluid optical prism 1 with air under normal temperature and pressure conditions. Adjust the incident optical system 3 so that the direction of the outgoing light is consistent with that of the incident light, and the outgoing light spot is located at the initial position of the outgoing optical image acquisition system 4. Record the first pixel coordinate of the initial position.

[0046] In some embodiments, the relative positions of each module are fixed with the instrument box 20 as the installation reference to ensure the coaxiality and stability of the optical path and the fluid path. Pressure-resistant glass windows are installed at the first optical window mounting hole 5 and the second optical window mounting hole 6, respectively, and precisely connected to the incident optical system 3 and the exit optical image acquisition system 4 via connectors 7 to form a horizontally sealed optical path. A temperature sensor 9 is installed at the temperature sensor mounting hole 8 to collect fluid temperature data in real time, and a pressure sensor 11 is installed at the pressure sensor mounting hole 10 to collect fluid pressure data in real time. The fluid inlet hole 12 is connected to the fluid inlet 13 via a pressure-resistant connector, and the fluid outlet hole 14 is connected to the fluid outlet 15 via a pressure-resistant connector, constructing a leak-free, continuous fluid path under a wide temperature and pressure range. An end cap 17 is installed at the end cap mounting hole 16 to seal the equilateral triangular measuring cavity 2 of the fluid optical prism 1, ensuring the cavity's sealing performance under high-pressure conditions.

[0047] In some embodiments, the incident optical system 3 (integrated light source, lens group, slit aperture) is fixed inside the instrument box 20 and aligned with the planar glass window of the first optical window mounting hole 5 on the fluid optical prism 1; the outgoing optical image acquisition system 4 is aligned with the planar glass window of the second optical window mounting hole 6 on the fluid optical prism 1, forming a complete incident-refracted-outgoing optical path.

[0048] In some embodiments, the circuit board 18 is fixed inside the instrument box 20 and electrically connected to the incident optical system 3, the outgoing optical image acquisition system 4, the temperature sensor 9, the pressure sensor 11, and the display screen 19 to realize signal acquisition, calculation control, and data transmission; the display screen 19 is installed on the front side panel of the instrument box 20 for parameter visualization display.

[0049] In some embodiments, after the assembly of the various components in the device is completed, 20 MPa of high-purity nitrogen gas is introduced into the equilateral triangular measuring cavity 2 of the fluid optical prism and the pressure is maintained for 24 hours. The pressure drop is less than or equal to 0.01 MPa, which is considered qualified.

[0050] S2. The fluid to be measured is introduced into the equilateral triangular measuring cavity 2 of the fluid optical prism 1 through the fluid inlet and discharged through the fluid outlet, so that the equilateral triangular measuring cavity 2 is filled with the fluid to be measured and the temperature and pressure of the fluid to be measured are determined to meet the stability conditions.

[0051] In some embodiments, the fluid to be measured enters the equilateral triangular measuring cavity 2 of the fluid optical prism 1 through the fluid inlet 13 and the fluid inlet hole 12. After the equilateral triangular measuring cavity 2 is filled with the fluid, it is continuously discharged through the fluid outlet hole 14 and the fluid outlet 15, ensuring that there are no air bubbles or fluid stagnation in the equilateral triangular measuring cavity 2. The operating parameters (temperature and pressure) are collected in real time by the temperature sensor 9 and the pressure sensor 11 and transmitted to the circuit board 18. Within a set window time, if the difference between the maximum and minimum values ​​of the continuous temperature data is less than the set temperature threshold, and the difference between the maximum and minimum values ​​of the continuous pressure data is less than the set pressure threshold, then it is determined that the temperature and pressure of the fluid to be measured meet the stability conditions.

[0052] S3. Start the incident optical system 3, adjust the incident angle until the displacement of the outgoing light spot acquired by the outgoing optical image acquisition system relative to the initial position is the minimum, and record the second pixel coordinate of the outgoing light spot at the deflection angle corresponding to the minimum displacement of the outgoing light spot.

[0053] In some embodiments, the incident optical system 3 is activated to emit stable monochromatic incident light. The light beam enters the fluid to be tested within the fluid optical prism 1 through the planar glass window at the first optical window mounting hole 5. The light undergoes two refractions in the fluid medium within the fluid optical prism 1 and exits through the planar glass window at the second optical window mounting hole 6. The exited light signal is captured in real time by the CCD image sensor of the exiting optical image acquisition system 4. The incident angle is adjusted by (a rotatable mirror or a rotating stage) until the displacement of the exited light spot relative to the initial position is minimized. The second pixel coordinates of the exited light spot at the deflection angle corresponding to the minimum displacement of the exited light spot are recorded. The deflection angle corresponding to the minimum displacement of the exited light spot is the minimum deflection angle.

[0054] It should be noted that in S2 and S3, the operating conditions after the fluid to be tested is introduced are non-standard operating conditions relative to the normal temperature and pressure in S1, including but not limited to high temperature, high pressure, low temperature, low pressure or temperature-pressure coupling non-standard operating conditions.

[0055] S4. Calculate the pixel displacement based on the coordinates of the first pixel and the second pixel.

[0056] In some embodiments, the coordinates of the first pixel are set as follows: The coordinates of the second pixel are Then the pixel displacement is Since the light refraction of the fluid optical prism 1 only occurs within the horizontal plane where the prism's apex is located, and there is no theoretical displacement in the vertical direction (y-axis), the y-coordinate is fixed, i.e. The pixel displacement between the initial spot (initial position) and the emitted spot is calculated only along the x-axis. Therefore, the calculated pixel displacement amount for .

[0057] S5. Based on geometric relationships Calculate the minimum deflection angle ,in, Pixel-to-physical size calibration coefficient, representing the actual physical spatial size corresponding to one pixel on the CCD image sensor. This refers to the fixed distance between the imaging surface of the outgoing optical image acquisition system and the center of the fluid optical prism. This represents the pixel displacement.

[0058] S6. Determine the refractive index of the ambient air. .

[0059] In some embodiments, if the fluid to be measured is a liquid, the refractive index of the ambient air is determined. If the fluid to be measured is a gas, the temperature, pressure, and humidity parameters of the ambient air are acquired and input into a preset air refractive index calculation model to determine the refractive index of the ambient air. .

[0060] In some embodiments, the acquisition of ambient air temperature, pressure, and humidity parameters includes at least one of the following methods: using preset standard atmospheric parameters; receiving ambient air temperature, pressure, and humidity parameters input by the user through a display screen or external input interface; or receiving ambient air temperature, pressure, and humidity parameters collected by an environmental parameter sensor.

[0061] In some embodiments, an air refractive index calculation model is used to determine the refractive index of the ambient air. At that time, circuit board 18 will display the temperature of the ambient air. ,pressure ,humidity and the wavelength of the incident light As input parameters, the refractive index of the ambient air is calculated by substituting it into the preset air refractive index calculation model. Among them, the air refractive index calculation model can be based on humidity. and temperature Determine the partial pressure of water vapor in the ambient air, and based on the ambient air pressure... The partial pressure of dry air is determined by the partial pressure of water vapor, in order to correct for the refractive index of air.

[0062] In some embodiments, the air refractive index calculation model is expressed as: (1); in, This is an air refractive index correction function used to characterize the effects of ambient air temperature, pressure, humidity, and incident light wavelength on the air refractive index. Relative humidity or a humidity parameter that can characterize the moisture content of the ambient air.

[0063] In some embodiments, the preset air refractive index calculation model may employ a modified Edlén formula, a Ciddor formula, or an equivalent air refractive index calculation model.

[0064] In other embodiments, an air refractive index database can also be used to determine the refractive index of the ambient air. The air refractive index database pre-stores air refractive index data corresponding to different temperatures, pressures, humidity levels, and incident light wavelengths. After acquiring the temperature, pressure, and humidity parameters of the ambient air, circuit board 18 searches the air refractive index database for air refractive index data corresponding to the current parameters (the current temperature, pressure, and humidity parameters of the ambient air, and the incident light wavelength). If no parameter matching the current parameter exists in the air refractive index database, linear interpolation, bilinear interpolation, or trilinear interpolation methods are used to determine the ambient air refractive index under the current parameter conditions. .

[0065] S7. According to the minimum deflection angle formula Calculate the refractive index of the fluid to be tested. ,in, Let α be the refractive index of the ambient air, where α = 60°.

[0066] The following example illustrates the calculation of the refractive index of a fluid under test using the minimum deflection angle method. The implementation method. For example... Figure 9 As shown, the vertex angle of the equilateral triangle measuring cavity 2 is known to be... Under normal temperature and pressure conditions, light rays, after entering the first optical window along the incident light direction, are refracted by the first optical window and maintain their original direction before entering the second optical window. After being refracted again by the second optical window, they continue to exit in the original direction, reaching the acquisition position 1 of the CCD image sensor in the direction of exit light 1. Under extreme conditions, after light rays enter the first optical window along the incident light direction, the incident angle is... The angle of refraction is After being refracted through the first optical window, the light propagates along the refracted direction to the second optical window, at which point the angle of incidence is... After being refracted by the second optical window, the light is emitted along the direction of the emitted light 2 and reaches the acquisition position 2 of the CCD image sensor, with an emission angle of 2. .

[0067] According to the law of refraction: (2); (3); Based on geometric relationships, we obtain: (4); (5); but: (6); Furthermore, by geometric relations, in quadrilateral AFEG: (7); In quadrilateral ABCD: (8); In the above formulas (2) to (8), , , , Therefore, the deflection angle The size is: (9); For formula (9) Differentiate, where the vertex angle Since it is a constant, we can obtain: (10); To minimize the deflection angle δ, let ,have to .

[0068] Differentiate equations (2) and (3) and record the results. Given the relative refractive index, we have: (11); (12); Differentiating from formula (6), we get: Substituting these values ​​into formulas (11) and (12), and simplifying, we get: (13); Combined Then the minimum deflection angle is obtained. The conditions are: (14); In formula (14), if , Since all values ​​are less than 0, it has no practical significance, and in this case, the equation has a unique solution. , = That is, when the incident angle equals the exit angle, the light path is symmetrical, and the light rays enter and exit the hollow prism cell symmetrically. The deflection angle measured at this time is the minimum deflection angle. .

[0069] Combining formulas (6) and (9), we have: (15); (16); Substituting formulas (15) and (16) into formula (2), we get: (17); Right now: (18); Furthermore, the distance between the photosensitive surface of the CCD image sensor and the center of the equilateral triangular measurement cavity 2 is denoted as... (With the positions fixed), the distance between the emitted light position 1 and the emitted light position 2 under different operating conditions is denoted as... .

[0070] Based on geometric relationships, we obtain: (19); but Therefore, we get: (20); Therefore, it can be concluded that the known... , If the pixel displacement between the initial position 1 and the emitted light position 2 is measured... The refractive index of the fluid being tested can then be determined. .

[0071] S8. The refractive index of the fluid to be tested calculated in S7. As the refractive index measurement result under the current temperature and pressure conditions, the current temperature, current pressure, and refractive index of the fluid under test are used. The output is displayed on screen 19.

[0072] In some embodiments, the circuit board 18 determines the pixel displacement of the emitted light spot, the pixel-physical size calibration coefficient, the fixed distance between the photosensitive surface of the CCD image sensor and the center of the equilateral triangular measurement cavity 2, the apex angle of the fluid optical prism, and the refractive index of the ambient air. The refractive index of the fluid under test at the current temperature and pressure conditions is calculated. Temperature sensor 9 and pressure sensor 11 collect temperature and pressure data to characterize the operating conditions corresponding to the refractive index measurement results. Circuit board 18 displays the current temperature, current pressure, and refractive index of the fluid under test. The data is transmitted in real time to display screen 19 for visualization.

[0073] This application addresses the limitations of existing optical refractive index measurement technologies by proposing a fluid refractive index measurement device and method suitable for a wide range of temperature and pressure conditions. The device employs an integrated structure where the prism substrate is also the pressure-bearing cavity, including an optical measurement unit, a fluid path and parameter sensing unit, a data processing and display unit, and an instrument box. This achieves coaxial integration of the optical path, flow path, and circuitry, as well as reliable sealing under a wide temperature and pressure range. The method leverages the physical property of light deflection when passing through a prism to achieve high-precision measurement of the fluid refractive index. The fluid refractive index measurement device and method provided in this application, suitable for a wide range of temperature and pressure conditions, offers advantages such as high measurement accuracy and high speed, and can provide technical support for fluid refractive index measurement in various fields.

[0074] It should be noted that, depending on the implementation needs, the various steps / components described in the embodiments of this application can be broken down into more steps / components, or two or more steps / components, or parts of the operations of steps / components can be combined into new steps / components, in order to achieve the purpose of the embodiments of this application.

[0075] Those skilled in the art will recognize that the units and method steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the embodiments of this application.

[0076] The above embodiments are only used to illustrate the embodiments of this application, and are not intended to limit the embodiments of this application. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the embodiments of this application. Therefore, all equivalent technical solutions also fall within the scope of the embodiments of this application, and the patent protection scope of the embodiments of this application should be defined by the claims.

Claims

1. A fluid refractive index measuring device suitable for a wide range of temperature and pressure conditions, characterized in that, It includes an optical measurement unit, a fluid path and parameter sensing unit, a data processing and display unit, and an instrument box; The optical measurement unit is integrated into the instrument box and includes a fluid optical prism with an equilateral triangular measurement cavity, an incident optical system, and an outgoing optical image acquisition system. The fluid optical prism has a first optical window mounting hole, a second optical window mounting hole, a temperature sensor mounting hole, a pressure sensor mounting hole, a fluid inlet hole, a fluid outlet hole, and an end cap mounting hole on its base. The incident optical system is mounted to the first optical window mounting hole via a connector and is used to emit monochromatic incident light. The outgoing optical image acquisition system is mounted to the second optical window mounting hole via a connector and is used to receive the outgoing light signal after refraction by the fluid and acquire optical images. The fluid passage and parameter sensing unit includes a temperature sensor installed in a temperature sensor mounting hole, a pressure sensor installed in a pressure sensor mounting hole, a fluid inlet connected to a fluid inlet hole, a fluid outlet connected to a fluid outlet hole, and an end cap installed in an end cap mounting hole. The data processing and display unit includes a circuit board and a display screen. The circuit board is electrically connected to the incident optical system, the outgoing optical image acquisition system, the temperature sensor, and the pressure sensor. It is used to acquire optical images, temperature data acquired by the temperature sensor, and pressure data acquired by the pressure sensor, and calculate the refractive index parameters of the fluid under test by combining them with a preset algorithm. The display screen is mounted on the front panel of the instrument box and is electrically connected to the circuit board. It is used to display the temperature data, pressure data and refractive index parameters of the fluid being measured in real time.

2. The apparatus according to claim 1, characterized in that, The first optical window mounting hole and the second optical window mounting hole are symmetrically arranged on the left and right end faces of the fluid optical prism substrate, and a flat window glass is installed in both the first optical window mounting hole and the second optical window mounting hole; the material of the flat window glass is one of alkali-free aluminosilicate tempered glass, lithium aluminum silicon transparent microcrystalline glass, and fused silica glass.

3. The apparatus according to claim 2, characterized in that, The planar viewing window glass and the substrate of the fluid optical prism are sealed with a metal graphite gasket, and a surface contact seal is achieved through a threaded pre-tightening structure, with a sealing pressure rating of 25MPa; the end cap and the substrate of the fluid optical prism are sealed with a metal graphite sealing structure.

4. The apparatus according to claim 1, characterized in that, The fluid optical prism is made of one or more of the following materials: carbon steel, low alloy steel, alloy structural steel, heat-resistant steel, or non-ferrous metal alloy. The outer surface of the fluid optical prism is coated or installed with a heat insulation layer.

5. The apparatus according to claim 1, characterized in that, An independent optical platform is installed inside the instrument box; the optical platform is connected to the instrument box housing by a rubber vibration damping pad, and heat insulation cotton is installed between the optical platform and the fluid pipeline and circuit board; the fluid pipeline includes an inlet pipeline connected to the fluid inlet, an outlet pipeline connected to the fluid outlet, and a flow channel inside the substrate of the fluid optical prism.

6. The apparatus according to claim 1, characterized in that, The fluid inlet channel has a gradually expanding structure, and the fluid outlet channel has a gradually contracting structure, with the inner wall of the channel being chamfered.

7. The apparatus according to claim 1, characterized in that, The fluid outlet is integrated with a back pressure regulating valve to achieve cavity back pressure control within the range of 0~20MPa.

8. The apparatus according to claim 1, characterized in that, The temperature sensor is embedded 2 mm from the inner wall of the equilateral triangular measuring cavity through the temperature sensor mounting hole, and is used to collect the temperature data of the fluid to be measured in real time. The pressure sensor is embedded 2 mm from the inner wall of the equilateral triangular measuring cavity through the pressure sensor mounting hole, and is used to collect pressure data of the fluid to be measured in real time. The fluid refractive index measuring device applicable to a wide range of temperature and pressure conditions operates in a temperature range of -40℃ to 200℃.

9. A method for measuring the refractive index of a fluid suitable for a wide range of temperature and pressure conditions, implemented by the fluid refractive index measuring device suitable for a wide range of temperature and pressure conditions as described in any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Integrate the optical measurement unit, fluid passage and parameter sensing unit, and circuit board into the instrument box. Set the display screen on the front side panel of the instrument box and complete the electrical connection. Fill the fluid optical prism with air under normal temperature and pressure conditions. Adjust the incident optical system so that the outgoing light is in the same direction as the incident light and the outgoing light spot is located at the initial position of the outgoing optical image acquisition system. Record the first pixel coordinate of the initial position. S2. The fluid to be measured is introduced into the equilateral triangular measuring cavity of the fluid optical prism through the fluid inlet and discharged through the fluid outlet, so that the measuring cavity is filled with the fluid to be measured and the temperature and pressure of the fluid to be measured meet the stability conditions. S3. Start the incident optical system and adjust the incident angle until the displacement of the outgoing light spot relative to the initial position is minimized by the outgoing optical image acquisition system. Record the second pixel coordinate of the outgoing light spot at the deflection angle corresponding to the minimum displacement of the outgoing light spot. S4. Calculate the pixel displacement based on the first pixel coordinates and the second pixel coordinates; S5. Based on geometric relationships Calculate the minimum deflection angle ,in Pixel-to-physical size calibration factor This refers to the fixed distance between the imaging surface of the outgoing optical image acquisition system and the center of the fluid optical prism. This is the pixel displacement. S6. Determine the refractive index of the ambient air. ; S7. According to the minimum deflection angle formula Calculate the refractive index of the fluid to be tested. ,in, Let α be the refractive index of the ambient air, where α = 60°. S8. The refractive index of the fluid to be tested calculated in S7. The refractive index measurement results are used as the current temperature and pressure conditions, and the current temperature, current pressure and refractive index of the fluid under test are used as the data. The output is displayed on the screen.

10. The method according to claim 9, characterized in that, The determination of the refractive index of the ambient air ,include: If the fluid to be tested is a liquid, then determine the refractive index of the ambient air. =1; If the fluid to be tested is a gas, the temperature, pressure, and humidity parameters of the ambient air are acquired, and these parameters are input into a preset air refractive index calculation model to determine the refractive index of the ambient air. .

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