Transparent fluid concentration real-time monitoring device and method based on Michelson interferometer

Abstract

The invention discloses a transparent fluid concentration real-time monitoring device and method based on a Michelson interferometer, and belongs to the technical field of fluid concentration monitoring. The device comprises a Michelson interferometer, a drainage tube, a fluid supply device, a discharging device, a backflow device, an image collector, a data processor and a controller, the drainage tube is axially perpendicular to the first center line and installed between the compensating mirror and the fixed mirror, the feeding end of the drainage tube is communicated with the discharging end of the fluid supply device, and the drainage tube is provided with a light-transmitting channel corresponding to the first center line. The discharging device is communicated with the discharging end of the drainage pipe; the feeding end of the backflow device is communicated with the discharging end of the drainage pipe, and the discharging end is communicated with the backflow end of the fluid supply device; the data processor is electrically connected with the image collector, and the controller is electrically connected with the image collector and the data processor. By arranging the drainage tube, the concentration condition of the fluid in the drainage tube is monitored by utilizing the equal inclination interference phenomenon of the Michelson interferometer, so that the real-time non-contact monitoring of the fluid concentration is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of fluid concentration monitoring, and more specifically, to a real-time monitoring device and method for the concentration of transparent fluids based on a Michelson interferometer. Background Art

[0002] Fluid concentration is an important parameter characterizing the properties and quantities of fluids, and plays a crucial role in fields such as chemical engineering, environmental protection, aerospace, medicine and biotechnology, and energy. For example, fluid concentration will affect the intensity of chemical reactions and the accuracy of results, and plays a key role in reaction control during chemical processes; in the environmental field, the measurement of fluid concentration is widely used to monitor water quality and air pollution to ensure that air quality and water quality meet standards; fluid concentration measurement technology can be used in the aerospace field to simulate and optimize the airflow around aircraft to improve their safety; in biopharmaceuticals, the accurate measurement of the concentration of solutes in fluids (mainly solutions) is widely applied in diagnosing diseases, evaluating the efficacy of drug treatments, and studying cell culture, etc. Therefore, the monitoring of fluid concentration widely and deeply affects all aspects of modern industrial technology and production, and has important research value.

[0003] Currently, the measurement of fluid concentration mainly focuses on the measurement of the concentration of non-flowing and fixed-concentration solutions. The measurement methods include refractometer method, spectroscopy method, chromatography method, electrochemistry method, ultrasonic testing method, hydrometer method, densitometer method, etc. For example: in industrial applications, the refractometer method and spectroscopy method are particularly popular due to their fast, accurate, and easy-to-operate characteristics, while the chromatography method and electrochemistry method are more common in occasions where more complex analysis is required, and the ultrasonic testing method is widely adopted due to its non-invasive and non-interfering characteristics with samples. These measurement methods have their own characteristics. For example: the refractometer method and spectroscopy method respectively utilize the critical angle principle and the absorption characteristics of substance molecules for specific wavelength light to measure the concentration of liquids, and are applicable to the concentration measurement of various liquids, but the measurement range and accuracy have certain limitations; the chromatography method separates mixtures based on the principle that different components in the mixture are differently distributed between two phases to measure the concentration of liquids, with fast analysis speed, high detection sensitivity, but requires direct contact between the sample and multiple parts of the chromatography system, and has a certain destructive effect on liquid samples; both the electrochemistry method and ultrasonic testing method are non-contact measurement of samples, but the measurement accuracy of the electrochemistry method has certain limitations, and the measurement range and precision of the ultrasonic testing method will be limited in the case of signal attenuation. All in all, each method has its advantages and limitations, but in actual industrial production processes, in many cases, the concentration of fluids changes in real time, and there should be no artificial contact during the fluid concentration measurement process. Therefore, exploring a real-time detection device that can simultaneously achieve high-precision and non-contact detection of fluid concentration has important research value and significance. Summary of the Invention

[0004] In view of this, the present invention aims to provide a real-time monitoring device and method for the concentration of transparent fluids based on a Michelson interferometer to achieve high-precision and non-contact real-time monitoring and adjustment of fluid concentration.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A real-time monitoring device for the concentration of transparent fluids based on a Michelson interferometer includes: a Michelson interferometer, a drainage tube, a fluid supply device, a discharging device, a reflux device, an image collector, a data processor, and a controller;

[0007] The Michelson interferometer includes a light source, a beam splitter, a compensating mirror, a fixed mirror, a moving mirror, and a receiving screen. The light source, the beam splitter, the compensating mirror, and the fixed mirror are arranged collinearly along a first center line. The moving mirror, the beam splitter, the receiving screen, and the image collector are arranged collinearly along a second center line, and the moving mirror can be translated along the second center line. The first center line is perpendicular to the second center line;

[0008] The drainage tube is axially perpendicular to the first center line and is installed between the compensating mirror and the fixed mirror. Its feeding end is connected to the discharging end of the fluid supply device, and a light-transmitting channel is provided corresponding to the first center line; the discharging device is connected to the discharging end of the drainage tube; the feeding end of the reflux device is connected to the discharging end of the drainage tube, and the discharging end is connected to the reflux end of the fluid supply device;

[0009] The data processor is electrically connected to the image collector, and the controller is electrically connected to the image collector and the data processor.

[0010] The beneficial effects that the present invention can achieve: By introducing a drainage tube provided with a light-transmitting channel, the equal-inclination interference phenomenon of the Michelson interferometer is used to monitor the concentration of the fluid in the drainage tube, realizing non-contact real-time monitoring of the fluid concentration. And the controller controls the fluid flow direction in real time so that the fluid enters the next production link only after the concentration meets the standard, achieving strict control of the fluid concentration.

[0011] Furthermore, it further includes a support device. The support device includes a support platform and a support frame. The support platform is placed below the support frame and is spaced from the support frame without contact. The Michelson interferometer is installed on the top of the support platform, and the drainage tube is installed on the support frame.

[0012] Further, the fluid supply device includes a feeding device, a sample cell, and a discharge pump. The feeding device is installed at the feeding port of the sample cell. The feeding end of the discharge pump is communicated with the discharge port of the sample cell, and the drainage tube is communicated with the discharge end of the discharge pump.

[0013] Further, the feeding device includes a solute feeding component, a solvent feeding component, and a mixer. The discharge ends of the solute feeding component and the solvent feeding component are both communicated with the mixer, and the discharge end of the mixer is communicated with the feeding port of the sample cell.

[0014] Further, the solute feeding component includes a solute storage tank, a solute discharge tube, and a solute flowmeter. The feeding end of the solute discharge tube is communicated with the discharge end of the solute storage tank, and the discharge end is communicated with the feeding end of the mixer. The solute flowmeter is installed on the solute discharge tube.

[0015] Further, the solvent feeding component includes a solvent storage tank, a solvent discharge tube, and a solvent flowmeter. The feeding end of the solvent discharge tube is communicated with the discharge end of the solvent storage tank, and the discharge end is communicated with the feeding end of the mixer. The solvent flowmeter is installed on the solvent discharge tube.

[0016] Further, the discharging device includes a discharge tube and a discharge solenoid valve. The discharge tube is installed at the discharge end of the drainage tube, and the discharge solenoid valve is installed at the feeding end of the discharge tube and is electrically connected to the controller.

[0017] Further, the reflux device includes a reflux tube and a return material solenoid valve. The feeding end of the reflux tube is communicated with the discharge end of the drainage tube, and the discharge end is communicated with the reflux port of the sample cell. The return material solenoid valve is installed at the feeding end of the reflux tube and is electrically connected to the controller.

[0018] Further, an alarm is provided, and the alarm is electrically connected to the controller.

[0019] The real-time monitoring method for the concentration of transparent fluid based on a Michelson interferometer adopts the above-mentioned real-time monitoring device for the concentration of transparent fluid based on a Michelson interferometer, and includes the following steps:

[0020] S1. Laboratory measurement stage: According to the needs of the actual fluid production application link, a simulation test is carried out in the laboratory using a Michelson interferometer and a cuvette. Through calculation and analysis, the corresponding relationship between the fluid concentration and the change amount of equal-inclination interference fringes is obtained and imported into the data processor;

[0021] S2. Production equipment installation stage: Connect the fluid supply device, the reflux device and the drainage tube; Set up a Michelson interferometer at the drainage tube, place the drainage tube between the compensating mirror and the fixed mirror of the Michelson interferometer, ensure that the light-transmitting channel on the drainage tube corresponds to the second center line, and then debug the Michelson interferometer. After debugging, it is reserved for use;

[0022] S3. Monitoring stage: Turn on the light source, use the pattern collector to collect the image on the receiving screen, and import the image into the data processor for analysis and calculation to obtain the current fluid concentration;

[0023] S4. Feedback stage: Compare the current fluid concentration with the set value. If the concentration reaches the set value, control the fluid in the drainage tube to enter the next production process through the discharging device. If the concentration does not reach the set value, make it flow back to the fluid supply device through the reflux device. At the same time, adjust the fluid concentration in the sample cell and re-detect until the detected concentration is within the set value range. Then turn off the reflux device and introduce it into the next production process through the discharging device.

[0024] As can be seen from the above technical solutions, compared with the prior art, the present invention discloses a real-time monitoring device and method for the concentration of a transparent fluid based on a Michelson interferometer. This device integrates the monitoring and feedback functions, so it can monitor and adjust the concentration of the fluid in real time to make the fluid concentration reach the required concentration range for production; Since the Michelson interferometer is a precision measuring instrument and its characterization of the optical path difference can reach the order of the wavelength of the incident light, therefore, this device can achieve high-precision measurement of the fluid concentration; During the process of monitoring the fluid concentration, this device is assisted by the drainage tube and does not require manual contact with the fluid sample. Therefore, this device can achieve non-contact measurement of the fluid concentration. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0026] Figure 1 FIG. is a schematic structural diagram of a real-time monitoring device for the concentration of a transparent fluid based on a Michelson interferometer provided by the present invention.

[0027] Figure 2 FIG. is a schematic installation structure diagram of a Michelson interferometer and a drainage tube.

[0028] Figure 3 is Figure 1 The enlarged structural diagram of part A in

[0029] Figure 4 It is a schematic diagram of the working principle of a Michelson interferometer.

[0030] Figure 5 It is an optical path diagram when light enters the colorimetric cell.

[0031] Figure 6 It is a flowchart of the real-time monitoring method for the concentration of transparent fluid based on the Michelson interferometer provided by the present invention.

[0032] In the figure: 1. Michelson interferometer, 11. Light source, 12. Beam splitter, 13. Compensating mirror, 14. Fixed mirror, 15. Moving mirror, 16. Receiving screen, 17. Virtual image of the fixed mirror, 2. Drainage tube, 3. Fluid supply device, 31. Feeding device, 311. Mixer, 312. Solute storage tank, 313. Solute outlet pipe, 314. Solute flowmeter, 315. Solvent storage tank, 316. Solvent outlet pipe, 317. Solvent flowmeter, 32. Sample cell, 33. Export pump, 4. Discharge device, 41. Discharge pipe, 42. Discharge solenoid valve, 5. Return device, 51. Return pipe, 52. Return material solenoid valve, 6. Image collector. Detailed implementation manners

[0033] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0034] Please refer to Figures 1 - 3 , the embodiments of the present invention disclose a real-time monitoring device for the concentration of transparent fluid based on a Michelson interferometer, including: a Michelson interferometer 1, a drainage tube 2, a fluid supply device 3, a discharge device 4, a return device 5, an image collector 6, a data processor, and a controller;

[0035] The Michelson interferometer 1 includes a light source 11, a beam splitter 12, a compensator 13, a fixed mirror 14, a movable mirror 15, and a receiving screen 16. The light source 11 uses a laser light source. When the laser light source passes through the fluid, it has a high transmittance, is not absorbed, and does not undergo non-linear optical effects or photoreactions with the fluid. The light source 11, the beam splitter 12, the compensator 13, and the fixed mirror 14 are arranged collinearly in sequence along the first center line. The movable mirror 15, the beam splitter 12, the receiving screen 16, and the image collector 6 are arranged collinearly in sequence along the second center line, and the movable mirror 15 can be translated along the second center line. The first center line is perpendicular to the second center line. Among them, the adjusting device for translating the movable mirror 15 is a prior art and will not be elaborated here. The image collector 6 uses a CCD camera and can quickly capture the image changes on the receiving screen 16.

[0036] The drainage tube 2 is arranged axially perpendicular to the first center line and is installed between the compensator 13 and the fixed mirror 14. Its feed end is connected to the discharge end of the fluid supply device 3, and it is provided with a light-transmitting channel corresponding to the first center line. The discharge device 4 is connected to the discharge end of the drainage tube 2. The feed end of the reflux device 5 is connected to the discharge end of the drainage tube 2, and the discharge end is connected to the reflux end of the fluid supply device 3. The data processor is electrically connected to the image collector, and the controller is electrically connected to the image collector 6 and the data processor.

[0037] Among them, the transparent channel means that the drainage tube 2 can be a fully transparent pipeline, so that the light beam between the compensator 13 and the fixed mirror 14 can pass through. The drainage tube 2 can also be a corrosion-resistant metal pipeline with transparent windows symmetrically installed on both sides. The light beam can pass through the transparent windows. The metal pipeline has a certain weight, stronger compressive and impact resistance, and can effectively prevent the drainage tube 2 from vibrating under the strong impact of the fluid, thus affecting the detection results, and prolong the service life of the drainage tube 2. The fully transparent pipeline or both transparent windows of the transparent pipeline are made of materials with the same material and thickness.

[0038] Specifically, a support device is also provided. The support device includes a support platform and a support frame. The support platform is placed below the support frame and is spaced from the support frame without contact. The Michelson interferometer is installed on the top of the support platform, and the drainage tube is installed on the support frame. The Michelson interferometer 1 has a high measurement accuracy and is highly sensitive to the environment. Therefore, each component of the Michelson interferometer 1 is installed on a relatively stable anti-vibration support platform. The drainage tube 2 is erected above the anti-vibration platform through the support frame, and a certain interval is maintained between the support frame and the support platform, so that the drainage tube 2 does not contact the Michelson interferometer 1, preventing the drainage tube 2 from driving the Michelson interferometer 1 to vibrate when vibrating under the impact of the fluid inside it, and affecting the optical path stability of the Michelson interferometer 1.

[0039] The Michelson interferometer 1 and the drainage tube 2 are placed in the same protective cover to ensure the stability of the monitoring environment, avoid the influence of external air flow changes on the Michelson interferometer 1, and prevent the interference fringes from jittering, thereby affecting the accuracy of the measurement results.

[0040] As Figures 1 - 3 , the fluid supply device 3 includes a feeding device 31, a sample cell 32, and a discharge pump 33. A stirring device is installed inside the sample cell 32. The feeding device 31 is installed at the feeding port of the sample cell 32. The feeding end of the discharge pump 33 is connected to the discharge port of the sample cell 32, and the drainage tube 2 is connected to the discharge end of the discharge pump 33, so as to continuously introduce the solution in the sample cell 32 into the drainage tube 2 to detect the concentration of the sample solution.

[0041] The feeding device 31 includes a solute feeding component, a solvent feeding component, and a mixer 311. The discharge ends of the solute feeding component and the solvent feeding component are both connected to the mixer 311. A spiral feeder is built in the mixer 311, and its discharge end is connected to the feeding port of the sample cell 32, so that the solute and the solution are mixed evenly during the spiral falling process in the mixer 311 and then enter the sample cell 32.

[0042] The solute feeding component includes a solute storage tank 312, a solute discharge pipe 313, and a solute flow meter 314. The feeding end of the solute discharge pipe 313 is connected to the discharge end of the solute storage tank 312, and the discharge end is connected to the feeding end of the mixer 311. The solute flow meter 314 is installed on the solute discharge pipe 313.

[0043] The solvent feeding component includes a solvent storage tank 315, a solvent discharge pipe 316, and a solvent flow meter 317. The feeding end of the solvent discharge pipe 316 is connected to the discharge end of the solvent storage tank 315, and the discharge end is connected to the feeding end of the mixer 311. The solvent flow meter 317 is installed on the solvent discharge pipe 316. It realizes the adjustment and control of the addition amounts of the solute and the solvent, thereby adjusting the concentration of the solution in the sample cell 32.

[0044] The discharging device 4 includes a discharge pipe 41 and a discharge solenoid valve 42. The discharge pipe 41 is installed at the discharge end of the drainage tube 2. The discharge solenoid valve 42 is installed at the feeding end of the discharge pipe 41 and is electrically connected to the controller. When the concentration reaches the standard, the discharge solenoid valve 42 is opened, and it is introduced into the next processing link through the discharge pipe 41.

[0045] The reflux device 5 includes a reflux pipe 51 and a return material solenoid valve 52. The feeding end of the reflux pipe 51 is connected to the discharge end of the drainage tube 2, and the discharge end is connected to the reflux port of the sample cell 32. The return material solenoid valve 52 is installed at the feeding end of the reflux pipe 51 and is electrically connected to the controller. When the concentration does not reach the standard, the return material solenoid valve 52 is opened, and it is re-introduced into the sample cell 32 through the reflux pipe 51, and the concentration of the fluid solution is readjusted through the feeding device 31 and re-detected until it reaches the standard and then is introduced into the next processing link through the discharge pipe 41.

[0046] An alarm is also provided, and the alarm is electrically connected to the controller. The alarm is a warning light, a sound alarm, or an audible and visual alarm, which alarms when the concentration of the solution does not meet the standard, serving the purpose of warning the staff.

[0047] The working principle of the present invention:

[0048] See Figure 4 , according to the principle of equal inclination interference of the Michelson interferometer 1: The light emitted from the light source 11 is divided into two beams of light with similar amplitudes by the semi-transparent and semi-reflective film on the back surface of the beam splitter 12: the reflected light ① and the transmitted light ②. After the reflected light ① is reflected by the movable mirror 15, it passes through the beam splitter 12 again and reaches point D. The transmitted light ② passes through the compensating mirror 13, is reflected by the fixed mirror 14, and then reaches the back surface of the beam splitter 12 again and is reflected to point D. These two beams of light have the same frequency and vibration direction, and the optical path difference is constant. Therefore, the phase difference is constant, and thus interference fringes are generated on the receiving screen in the space where they meet.

[0049] Taking the back surface of the beam splitter 12 as the dividing point, assuming that the fixed mirror 14 forms a virtual image 17 of the fixed mirror near the movable mirror 15, the reflection of light in the Michelson interferometer 1 between the movable mirror 15 and the fixed mirror 14 is equivalent to the reflection of light between the movable mirror 15 and the virtual image 17 of the fixed mirror. Based on this equivalence, when the movable mirror 15 and the fixed mirror 14 are parallel (at this time, the movable mirror 15 and the virtual image 17 of the fixed mirror), a uniform-thickness air film is formed between the movable mirror 15 and the virtual image 17 of the fixed mirror, and circular equal-inclination interference fringes are observed on the receiving screen 16 of the Michelson interferometer.

[0050] According to the principle of equal inclination interference, when the optical path difference between the two beams of light increases, the phenomenon of "ring spitting" will occur in the equal inclination interference fringes, and vice versa, the phenomenon of "ring swallowing" will occur. The interference pattern changes with the relative position of the movable mirror 15 and the virtual image 17 of the fixed mirror, and the change of the interference fringes depends on the optical path difference between the coherent light beams ① and ②:

[0051] δ = Δ1 - Δ2 (100)

[0052] Where Δ1 is the optical path of the reflected light ① passing through the AB section twice, and Δ2 is the optical path of the transmitted light ② passing through the BC section twice. Let n1 and r1 be the refractive index and geometric path of the medium through which the reflected light ① passes through the AB section, and n2 and r2 be the refractive index and geometric path of the medium through which the light beam ② passes through the BC section, then there is:

[0053] δ = Δ1 - Δ2 = n1r1 - n2r2 (200)

[0054] And from the bright fringe condition of the equal inclination interference of the Michelson interferometer, there is:

[0055] δ = Δ1 - Δ2 = kλ (300)

[0056] where λ is the wavelength of the incident laser, and K is a positive integer. Combining (200) and (300), we have:

[0057] n1r1 - n2r2 = kλn1r1 - n2r2 = kλ (400)

[0058] Therefore, by inserting the drainage tube 2 into one path of the Michelson interferometer to introduce the transparent fluid to be measured, the change in the refractive index of the fluid (caused by the change in the fluid concentration) will cause a change in the optical path difference between the two paths. When the change value of the optical path difference between the two paths of light is equal to Kλ, the equal-inclination interference fringe pattern will change accordingly, "swallowing rings" or "spitting rings". Whenever "swallowing one ring" or "spitting one ring", the optical path difference between the two paths of light changes by one wavelength λ. At this time, only by using the image collector 6 to record the number of "swallowing rings" or "spitting rings" of the equal-inclination interference rings on the receiving screen 16 in real time, the change in the refractive index of the fluid can be monitored in real time, and thus the change in the fluid concentration can be indirectly monitored in real time without contacting the fluid, improving the accuracy of fluid concentration monitoring; while monitoring the fluid concentration, a feedback mechanism is set up, and the controller is used to control the discharging device 4, the feeding device 31 and the recycling device 5 to perform feedback processing on the fluid, and the fluid concentration is adjusted in real time to make it reach the standard range required for production.

[0059] See Figure 6 This embodiment also provides a method for real-time monitoring of the concentration of a transparent fluid based on a Michelson interferometer. Using the above-mentioned device for real-time monitoring of the concentration of a transparent fluid based on a Michelson interferometer, it includes the following steps:

[0060] S1. Laboratory measurement stage: According to the needs of the actual fluid production application link, a simulation test is carried out in the laboratory using a Michelson interferometer and a cuvette. Through calculation and analysis, the corresponding relationship between the concentration of the fluid to be measured and the change amount of the equal-inclination interference fringes is obtained and imported into the data processor;

[0061] S2. Production equipment installation stage: Connect the fluid supply device 3, the reflux device 5 and the drainage tube 2; Build a Michelson interferometer 1 at the drainage tube 2, so that the drainage tube 2 corresponds to between the compensating mirror 13 and the fixed mirror 14 of the Michelson interferometer 1, ensure that the light-transmitting channel on the drainage tube corresponds to the second center line, and then turn on the light source to debug the Michelson interferometer 1. After debugging, turn off the light source and reserve it;

[0062] S3. Monitoring stage: Turn on the light source, use the pattern collector 6 to collect the image on the receiving screen 16, and import the image into the data processor for analysis and calculation to obtain the current fluid concentration;

[0063] S4. Feedback stage: Compare the current fluid concentration with the set value. If the concentration reaches the set value, control the fluid in the drainage tube 2 to enter the next production process through the discharging device 4. If the concentration does not reach the set value, make it flow back to the fluid supply device 3 through the reflux device 5. At the same time, adjust the fluid concentration in the sample cell 32 and re - conduct the detection until the detected concentration is within the set value range, then close the reflux device 5 and introduce it into the next production process through the discharging device 4.

[0064] In step 1, a simulation test should be first carried out in the laboratory to obtain the refractive indices of the fluid to be measured at different concentrations. The specific operation method is as follows:

[0065] Add the transparent fluid to be measured with a known concentration into the cuvette, and use the Michelson interferometer to obtain the refractive index of the fluid to be measured. Specifically, first make the incident light enter the cuvette at an angle θ0. Refer to Figure 5 , where r1 is the thickness of the front wall of the cuvette, r2 is the thickness of the rear wall of the cuvette, r is the inner diameter of the cuvette. n0 is the refractive index of air, and its value is 1.0; n1 is the refractive index of the cuvette; n is the refractive index of the fluid to be measured (unknown). θ0 is the incident angle of light entering the cuvette, θ1 is the refraction angle of light in the cuvette, and θ2 is the refraction angle of light in the fluid to be measured.

[0066] According to the law of refraction, we can get:

[0067] n0sinθ0 = n1sinθ1 = nsinθ2, (1)

[0068] Therefore, we have:

[0069]

[0070] Then:

[0071]

[0072] The distances that light travels in each section in the cuvette:

[0073]

[0074] The corresponding optical paths are:

[0075] Δ1 = n1L1; Δ2 = nL; Δ3 = n1L2 (7)

[0076] Therefore, the total optical path that light travels once in the cuvette is:

[0077] Δ total = n1(L1 + L2)+nL (8)

[0078] Substitute into equation (6), then we have:

[0079]

[0080] When the cuvette rotates through a certain angle dθ, the change in the optical path that the light travels in the cuvette is

[0081]

[0082] where

[0083]

[0084] Similarly,

[0085]

[0086] When the cuvette rotates through a certain angle dθ (which can cause obvious ring swallowing or ring spitting phenomena in the equal inclination interference generated by the Michelson interferometer), the change in the optical path (after passing through the cuvette once) of the light in the cuvette is at the cost of the corresponding change in the optical path of the light in air. Therefore, the true value of the optical path change (the optical path change value that causes ring spitting or ring swallowing in equal inclination interference) should be

[0087]

[0088] If the number of equal inclination interference ring spitting (or ring swallowing) observed on the observation screen is ΔN, then there is:

[0089]

[0090] By combining equation (13) and equation (14), there is:

[0091]

[0092] Substitute equations (11)-(12) into equation (15), then there is:

[0093]

[0094] In equation (16), r1, r2, r, n0, n1, θ0, dθ0, ΔN, λ are all known or can be directly measured through experiments. Therefore, through the above equation, the refractive index n of the fluid in the cuvette can be indirectly measured. Thus, equation (16) is transformed into

[0095]

[0096] Given r1, r2, r, n0, n1, θ0, dθ0, ΔN, λ, the right side of the equal sign is a constant. Let the right side of the equal sign be a constant C, that is

[0097]

[0098] Then equation (17) can be transformed into a polynomial equation of one variable:

[0099]

[0100] n 4 -2n 3 n0 + n 2 n0 2 = c 2 [n 6 + 3n 2 (n0sinθ0) 4 - 3n 4 (n0sinθ0) 2 -(n0sinθ0) 6 (19)

[0101] That is

[0102] c 2 n 6 + [-1 - 3(n0sinθ0) 2 n 4 + 2n0n 3 + [3(n0sinθ0) 4 - n0 2 n 2 -(n0sinθ0) 6 = 0 (20)

[0103] In summary, in the experiment of measuring the refractive index of a fluid using a Michelson interferometer, the following parameters are known:

[0104] r1 and r2 (the thicknesses of the front and rear walls of the cuvette, if the same, then r1 = r2),

[0105] r (the distance between the front and rear walls of the cuvette),

[0106] n0 (if the cuvette is placed in air, then n0 = 1.0),

[0107] n1 (the refractive index of the cuvette),

[0108] θ0 (the angle between the incident light and the cuvette),

[0109] λ (the wavelength of the incident light),

[0110] Rotate the cuvette by a certain angle dθ (usually about 10 degrees), and then record the number of fringes of equal inclination interference generated by the Michelson interferometer (i.e., the number of fringes swallowed or spit out) ΔN, then the constant c in equation (18) and all the coefficients of the variable n in equation (20) can be obtained. By solving the univariate polynomial equation (20), the refractive index n of the fluid to be measured at this concentration can be obtained.

[0111] In the experiment, if n0 = 1.0 and θ0 is very small (i.e., the cuvette is placed as perpendicular to the incident light as possible before rotation), so sinθ0 - θ0, cosθ0 - 1, θ0 n -0 (n≥2), then equations (18) and (20) are simplified to:

[0112]

[0113] c 2 n 6 -n 4 +2n 3 -n 2 = 0

[0114] That is

[0115] c 2 n 4 -n 2 +2n - 1 = 0 (22)

[0116] Change the concentration of the fluid to be measured and repeat the above experiment. The refractive index of the fluid to be measured at different concentrations can be obtained. By plotting the fitting relationship curve between the concentration and the refractive index, the fitting relationship formula between the refractive index n and the concentration w of the fluid to be measured can be obtained as;

[0117] n = f(w) (23)

[0118] For most transparent fluids, there is a linear or approximately linear relationship between the refractive index n and the concentration w of the fluid to be measured. Then, by differentiating equation (23), the relationship between the change in the refractive index Δn and the change in the concentration Δw of the fluid can be obtained.

[0119] Since the material and size of the drainage tube used for monitoring in actual production are constant, and the incident light remains perpendicular to the drainage tube, the factor causing the change in the interference fringes is the change in the fluid concentration. If the one-way path of the incident light in the drainage tube is l (i.e., the distance between the two transparent windows on both sides of the drainage tube), then:

[0120] δ 总 = Δn·l (24)

[0121] Combining equation (14) and equation (24), then

[0122]

[0123] It can be obtained that

[0124]

[0125] Therefore, during the use of the device, if the fluid concentration in the drainage tube changes, one only needs to observe and record the change amount ΔN of the interference fringes on the screen to know the change amount Δn of the refractive index of the fluid to be measured. Then, according to the fitting relationship formula (23) between the refractive index n of the fluid to be measured and the concentration w, the change amount Δw of the fluid concentration can be obtained, thereby knowing the current concentration of the fluid.

[0126] In step 2, during debugging, a fluid with a concentration within the set value range is introduced into the drainage tube 2 and the fluid is in a static state.

[0127] In step 3, the data processor analyzes the change amount of the equal-inclination interference fringes based on the collected equal-inclination interference images, calculates the change amount of the refractive index, thereby obtaining the change amount of the fluid concentration, and further knowing the current concentration of the fluid;

[0128] In step 4, if the concentration of the fluid sample does not exceed the set range, the alarm is turned off; if the concentration of the fluid sample exceeds the set range, the return solenoid valve is opened and the alarm is turned on at the same time, and it will not be turned off until it is monitored that the fluid concentration is within the set concentration range.

[0129] In this specification, the various embodiments are described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other. For the device disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the description of the method part.

[0130] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A real-time monitoring device for the concentration of transparent fluids based on a Michelson interferometer, characterized in that, Comprising: A Michelson interferometer (1), a drainage tube (2), a fluid supply device (3), a discharging device (4), a reflux device (5), an image collector (6), a data processor, and a controller; The Michelson interferometer (1) includes a light source (11), a beam splitter (12), a compensating mirror (13), a fixed mirror (14), a moving mirror (15), and a receiving screen (16). The light source (11), the beam splitter (12), the compensating mirror (13), and the fixed mirror (14) are arranged collinearly along a first center line. The moving mirror (15), the beam splitter (12), the receiving screen (16), and the image collector (6) are arranged collinearly along a second center line, and the moving mirror (15) can translate along the second center line. The first center line is perpendicular to the second center line; The drainage tube (2) is axially perpendicular to the first center line and is installed between the compensating mirror (13) and the fixed mirror (14). Its feeding end communicates with the discharging end of the fluid supply device (3), and a light-transmitting channel is provided corresponding to the first center line. The discharging device (4) communicates with the discharging end of the drainage tube (2). The feeding end of the reflux device (5) communicates with the discharging end of the drainage tube (2), and the discharging end communicates with the reflux end of the fluid supply device (3); The data processor is electrically connected to the image collector (6), and the controller is electrically connected to the image collector (6) and the data processor.

2. The real-time monitoring device for the concentration of transparent fluid based on a Michelson interferometer according to claim 1, characterized in that It further includes a supporting device. The supporting device includes a supporting platform and a supporting frame. The supporting platform is placed below the supporting frame and is spaced from the supporting frame without contact. The Michelson interferometer is installed on the top of the supporting platform, and the drainage tube is installed on the supporting frame.

3. The real-time monitoring device for the concentration of transparent fluid based on a Michelson interferometer according to claim 1, wherein The fluid supply device (3) includes a feeding device (31), a sample cell (32), and an export pump (33). The feeding device (31) is installed at the feeding port of the sample cell (32). The feeding end of the export pump (33) communicates with the discharging port of the sample cell (32), and the drainage tube (2) communicates with the discharging end of the export pump (33).

4. The real-time monitoring device for the concentration of transparent fluid based on the Michelson interferometer according to claim 3, wherein, The feeding device (31) includes a solute feeding component, a solvent feeding component, and a mixer (311). The discharging ends of the solute feeding component and the solvent feeding component both communicate with the mixer (311), and the discharging end of the mixer (311) communicates with the feeding port of the sample cell (32).

5. The real-time monitoring device for the concentration of a transparent fluid based on a Michelson interferometer according to claim 4, characterized in that, The solute feeding component includes a solute storage tank (312), a solute export tube (313), and a solute flowmeter (314). The feeding end of the solute export tube (313) communicates with the discharging end of the solute storage tank (312), the discharging end communicates with the feeding end of the mixer (311), and the solute flowmeter (314) is installed on the solute export tube (313).

6. The real-time monitoring device for the concentration of transparent fluid based on a Michelson interferometer according to claim 5, characterized in that, The solvent feeding assembly includes a solvent storage tank (315), a solvent outlet pipe (316), and a solvent flowmeter (317). The feeding end of the solvent outlet pipe (316) communicates with the discharging end of the solvent storage tank (315), and the discharging end communicates with the feeding end of the mixer (311). The solvent flowmeter (317) is installed on the solvent outlet pipe (316).

7. The real-time monitoring device for the concentration of transparent fluid based on a Michelson interferometer according to any one of claims 1-6, characterized in that, The discharging device (4) includes a discharging pipe (41) and a discharging solenoid valve (42). The discharging pipe (41) is installed at the discharging end of the diversion pipe (2), and the discharging solenoid valve (42) is installed at the feeding end of the discharging pipe (41) and electrically connected to the controller.

8. The real-time monitoring device for the concentration of transparent fluid based on a Michelson interferometer according to any one of claims 3-6, characterized in that, The reflux device (5) includes a reflux pipe (51) and a return material solenoid valve (52). The feeding end of the reflux pipe (51) communicates with the discharging end of the diversion pipe (2), and the discharging end communicates with the reflux port of the sample cell (32). The return material solenoid valve (52) is installed at the feeding end of the reflux pipe (51) and electrically connected to the controller.

9. The real-time monitoring device for the concentration of transparent fluid based on a Michelson interferometer according to any one of claims 1-6, characterized in that, An alarm is further provided, and the alarm is electrically connected to the controller.

10. A real-time monitoring method for the concentration of a transparent fluid based on a Michelson interferometer (1), which uses the real-time monitoring device for the concentration of a transparent fluid based on a Michelson interferometer according to any one of claims 1-9, characterized in that, It includes the following steps: S1. Laboratory measurement stage: According to the needs of the actual fluid production application link, a simulation test is carried out in the laboratory using the Michelson interferometer 1 and the colorimetric cell. Through calculation and analysis, the corresponding relationship between the fluid concentration and the change amount of the equal inclination interference fringes is obtained and imported into the data processor. S2. Production equipment installation stage: Connect the fluid supply device (3), the reflux device (5), and the diversion pipe (2); Set up the Michelson interferometer (1) at the diversion pipe (2) so that the diversion pipe (2) is located between the compensating mirror (13) and the fixed mirror (14) of the Michelson interferometer (1), ensuring that the light transmission channel on the diversion pipe corresponds to the second center line. Then turn on the light source to debug the Michelson interferometer (1), and turn off the light source for standby after debugging. S3. Monitoring stage: Turn on the light source, use the pattern collector (6) to collect the image on the receiving screen (16), and import the image into the data processor for analysis and calculation to obtain the current fluid concentration. S4. Feedback stage: Compare the current fluid concentration with the set value. If the concentration reaches the set value, control the fluid in the diversion pipe (2) to enter the next production link through the discharging device (4). If the concentration does not reach the set value, make it reflux to the fluid supply device (3) through the reflux device (5). At the same time, adjust the fluid concentration in the sample cell (32) and re-detect until the detected concentration is within the set value range. Then turn off the reflux device (5) and import it into the next production link through the discharging device (4).

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