A rotating fluid test platform and method based on optical fiber transmission and quasi-synchronous time-sharing measurement

Abstract

The application discloses a rotating fluid test platform and method based on optical fiber transmission and quasi-synchronous time-sharing measurement, belongs to the technical field of fluid mechanics experiment equipment, and aims to solve the problems of optical lever, signal crosstalk and poor universality of the existing platform. The platform comprises a rotating system, a fluid mixing system, a fluid test system and a control and data processing system. The rotating system provides rotation and inclination adjustment for the liquid-filled cylinder; the fluid mixing system comprises the liquid-filled cylinder, a rotating water liner and a working medium with added tracer particles and fluorescent dye; the fluid test system adopts an optical fiber coupling head to divide laser into two paths, one of which is connected with an optical fiber delay line, two-path laser passes through a collimator and a Powell prism to form sheet light, and multiple CMOS cameras cooperate with polarizing plates and optical filters to collect images; the control and data processing system realizes parameter control and data processing. The optical fiber delay line realizes quasi-synchronous time-sharing collection of PIV and PLIF. The application has high measurement precision and strong universality, and is suitable for rotating fluid working condition research.

Description

Technical Field

[0001] This invention relates to the field of fluid mechanics experimental equipment technology, specifically to a rotating fluid testing platform and method based on fiber optic transmission and quasi-synchronous time-division measurement, which is particularly suitable for high-precision synchronous measurement of velocity field and concentration field in the flow and mixing characteristics of liquids in a rotating cylinder. Background Technology

[0002] Rotating fluid dynamics is an important branch of fundamental research in fluid mechanics. Precise testing and analysis of the flow characteristics of rotating fluids and their fluid-structure interaction with solids have broad application prospects in aerospace, machinery manufacturing, and defense industries. In the study of rotating cylindrical flows, accurately obtaining the velocity and concentration field distributions is crucial for revealing the fluid mixing mechanism.

[0003] In the prior art, patent CN 121877339 A discloses a rotating fluid testing platform and method for a turntable. By integrating PIV and PLIF technologies, multi-camera synchronous acquisition, and refractive index matching design, it solves problems such as the inability to simultaneously measure velocity and concentration fields, difficulties in multi-section measurement, and optical distortion interference. However, this technical solution still has the following shortcomings: First, the use of a reflective optical path to transmit laser light results in significant optical levering. Minor vibrations generated during turntable operation are amplified by the reflectors, causing light jitter and deviation, especially at high speeds, severely affecting measurement accuracy. Second, relying solely on a beam-splitting cube to synchronously distribute the light signal to the PIV and PLIF cameras, without microsecond-level time staggering and corresponding filtering configurations, not only leads to laser energy distribution loss, but also potential crosstalk between the scattered light signal from the PIV and the fluorescence signal from the PLIF, resulting in measurement deviations. Third, the fixed installation of the optical system and cameras only accommodates liquid-filled cylinders of specific sizes. When testing cylinders of different specifications or cross-sections at different locations, the optical path must be rebuilt, resulting in poor platform versatility. Summary of the Invention

[0004] (a) Technical problems to be solved The present invention aims to solve the problems of optical levering phenomenon, PIV and PLIF signal crosstalk, and poor platform versatility in the existing rotating fluid testing platform.

[0005] (II) Technical Solution To address the aforementioned issues, this invention proposes a rotating fluid testing platform and method based on fiber optic transmission and quasi-synchronous time-division measurement. The core idea is to replace the traditional reflective free-space optical path with fiber optic transmission to reduce optical leverage effects; to achieve quasi-synchronous time-division measurement of PIV and PLIF signals by cascading a fiber delay line in one fiber to solve signal crosstalk problems; and to install multi-dimensional adjustment mechanisms at key components to achieve flexible adaptation to liquid-filled cylinders of different specifications.

[0006] The rotating fluid testing platform includes a rotating system, a fluid mixing system, a fluid testing system, and a control and data processing system.

[0007] The rotating system includes a turntable surface, a rotating shaft, and turntable control software, used to provide rotation and tilt adjustment for the liquid-filling cylinder. The rotating shaft is driven by a high-precision servo motor and is vertically mounted at the end of the turntable shaft. It has a 0-90 degree tilt adjustment function. The turntable adopts a dynamic balance counterweight design and vibration isolation measures.

[0008] The fluid mixing system includes a liquid-filled cylinder, a rotating water liner, and a working fluid, used to contain the test working fluid and provide a refractive index matching environment. The liquid-filled cylinder and the rotating water liner are made of transparent acrylic glass or quartz glass. The rotating water liner is filled with a refractive index matching solution and remains stationary relative to the fluid testing system. Tracer particles and fluorescent dyes are added to the working fluid inside the liquid-filled cylinder, providing signal sources for PIV and PLIF tests, respectively.

[0009] The fluid testing system includes a laser generation module, an optical fiber transmission module, a sheet light generation module, a signal synchronization module, and an image acquisition module, which are used to realize the acquisition of multi-section, multi-physics field signals.

[0010] The laser generating module includes a laser and an optical fiber coupler. The laser output from the laser is coupled into an optical fiber beam splitter via the optical fiber coupler, and then split into two optical fiber lasers by the optical fiber beam splitter.

[0011] The optical fiber transmission module includes an optical fiber bundle splitter and two optical fibers, one of which has an adjustable optical fiber delay line connected in series. The reference optical path of the two optical fibers remains consistent when no delay is introduced.

[0012] The sheet light generation module includes a first sheet light generation unit and a second sheet light generation unit. The first sheet light generation unit includes a first fiber collimator, a first Powell prism, and a total reflection mirror; the second sheet light generation unit includes a second fiber collimator and a second Powell prism. Each sheet light generation unit is equipped with an adjustment mechanism, which includes a horizontal slide rail, a vertical slide rail, a slider, and a rotary table, used to adjust the position and incident angle of the sheet light. After adjustment, it can be fixed by a locking structure.

[0013] The image acquisition module includes a first PIV CMOS camera, a first PLIF CMOS camera, a second PIV CMOS camera, and a second PLIF CMOS camera. The PIV CMOS camera has a polarizer and a narrowband filter that allows only the original laser wavelength to pass through. The PLIF CMOS camera has a polarizer and a high-pass filter that allows only the excitation fluorescence wavelength to pass through. A beam-splitting cube is incorporated in part of the camera's optical path to distribute the light signal corresponding to the field of view to the PIV and PLIF imaging channels. The image acquisition module also includes an adjustment mechanism comprising a horizontal slide rail, a vertical slide rail, a slider, and a telescopic support rod for adjusting the camera's shooting position, focal length direction, and shooting angle.

[0014] The signal synchronization module includes a synchronizer for synchronously triggering the laser and all CMOS cameras. The fiber optic delay line provides a fixed optical path delay, ensuring that the acquisition time difference between the corresponding PIV and PLIF images is less than 1% of the fluid characteristic motion time. This, in conjunction with the synchronizer, enables quasi-synchronous time-division data acquisition.

[0015] The control and data processing system includes a computer and data processing software. The computer is connected to the turntable control software, synchronizer, and all CMOS cameras to enable parameter setting, startup control, and data acquisition for the entire experimental platform. The data processing software analyzes and processes the acquired image information to obtain velocity and concentration field distribution data of the flow field.

[0016] The rotating fluid testing method based on the above platform includes the following steps: S1 Preparation of working medium and installation of cylinder: Prepare the test working medium in the liquid-filled cylinder, add the tracer particles and fluorescent dye in the preset proportion, fill the liquid-filled cylinder with working medium and seal it, install the liquid-filled cylinder on the rotating platform, and adjust the attitude and motion parameters. S2 Optics and Image Adjustment: Based on the size of the liquid-filled cylinder and the position of the test section, adjust the horizontal slide rail, vertical slide rail, slider, and rotating slide in the sheet light generation unit so that the planar laser formed by the Powell prism is perpendicular to the target cross-section and longitudinal section; adjust the horizontal slide rail, vertical slide rail, slider, and telescopic support rod in the camera bracket so that the PIV / PLIF CMOS camera is aligned with the shooting area and the corresponding shooting parameters are set; S3 Delay Parameter Setting: Based on the fluid motion characteristics, set the delay time of the fiber delay line to ensure that the PIV and PLIF signals are quasi-synchronous and free from crosstalk; S4 Data Acquisition and Processing: The turntable and fluid testing system are started synchronously, and the synchronizer triggers the laser and each CMOS camera; the laser enters the fiber beam splitter through the fiber coupler and is split into two paths. One path is delayed by a preset time through the fiber delay line. The two lasers are respectively collimated by the fiber collimator and the Powell prism to form sheet light and illuminate the test section; each CMOS camera acquires PIV scattered light images and PLIF excited fluorescence images in a time-division manner. The computer receives and processes the image data to obtain the velocity field and concentration field distribution results of the flow field.

[0017] (III) Beneficial Effects Compared with the prior art, the present invention has the following beneficial effects: 1. This invention achieves fiber-optic transmission of laser by using fiber optic couplers and fiber optic beam splitters, reducing the need for multiple mirror adjustments in traditional reflective optical paths. It also effectively isolates turntable vibration by utilizing the flexible transmission characteristics of optical fibers, avoiding beam jitter and offset, thereby significantly improving measurement accuracy and data reliability under high-speed operating conditions.

[0018] 2. The fiber delay line of this invention achieves time-staggered PIV and PLIF illumination light, and, in conjunction with polarizers, narrowband filters, high-pass filters, and beam splitters, completes channel separation of optical signals, so that scattered light and fluorescence signals are distinguished in both time and spectrum, thereby reducing crosstalk and improving data accuracy.

[0019] 3. By adding a multi-dimensional adjustment mechanism to the sheet light generation unit and the camera, the present invention can flexibly adjust the incident position and angle of the sheet light, as well as the shooting position and angle of the camera. This allows the platform to quickly adapt to various sizes of liquid-filled cylinders and supports testing of cross-sections of arbitrary height and longitudinal sections of arbitrary angle without the need to rebuild the optical path, thus significantly improving experimental efficiency.

[0020] 4. The optical fiber path of this invention does not require complex multi-stage mirror adjustment. The direction of the sheet light can be quickly set by the optical fiber collimator, Powell prism, total reflection mirror, as well as slide rail, slider and rotating slide, which greatly reduces the time and difficulty of optical path adjustment. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of the rotating fluid testing platform provided in an embodiment of the present invention; Figure 2 This is a partial schematic diagram of the sheet light generation unit adjustment mechanism provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the adjustment mechanism of the top-firing system provided in an embodiment of the present invention; In the diagram: 1. Laser, 2. Fiber optic coupler, 3. Fiber optic beam splitter, 4. First fiber optic collimator, 5. First Powell prism, 6. Total reflection mirror, 7. Third fiber optic collimator, 8. Fiber optic delay line, 9. Third fiber optic collimator, 10. Second Powell prism, 11. Liquid-filled cylinder, 12. Polarizer, 13. Narrow-band filter, 14. CMOS camera for first PIV, 15. Polarizer, 16. High-pass filter, 17. CMOS camera for first PLIF, 18. Beam splitter cube, 19. 20. Vibrating plate, 21. Narrow-band filter, 22. CMOS camera for second PIV, 23. Polarizer, 24. High-pass filter, 25. CMOS camera for second PIV, 26. Synchronizer, 27. Computer, 28. Horizontal slide rail, 29. Slider, 30. Slider, 31. Slider, 32. Rotary slide, 33. Slider, 34. Vertical slide rail, 35. Slider, 36. Slider, 37. Rotary slide, 38. Horizontal slide rail, 39. Slider, 40. Vertical slide rail, 41. Slider, 42. Telescopic support rod. Detailed Implementation

[0022] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings, so that those skilled in the art can accurately implement the present invention.

[0023] Example 1 This embodiment provides a rotating fluid testing platform based on fiber optic transmission and quasi-synchronous time-division measurement, the overall structure of which is as follows: Figure 1 As shown.

[0024] The liquid-filled cylinder 11 in the fluid mixing system is made of transparent plexiglass, with a diameter of 200 mm and a height of 300 mm. The working fluid inside the liquid-filled cylinder 11 is deionized water, with tracer particles and Rhodamine B fluorescent dye added. The concentration of the tracer particles is 0.01 g / L, and the concentration of the fluorescent dye is 0.05 mg / L.

[0025] The fluid testing system includes a laser generation module, an optical fiber transmission module, a sheet light generation module, a signal synchronization module, and an image acquisition module.

[0026] The laser generation module includes a 532nm laser 1 and an optical fiber coupler 2. The output power of the laser 1 is 10W. The laser output from the laser 1 is coupled into the optical fiber beam splitter 3 via the optical fiber coupler 2, and then split into two optical fiber lasers by the optical fiber beam splitter 3.

[0027] The fiber optic transmission module includes a fiber optic beam splitter 3, two optical fibers, and a fiber optic delay line 8. One fiber optic laser beam passes through a first fiber optic collimator 4 and enters the first light-generating unit; the other fiber optic laser beam passes through a third fiber optic collimator 7 and the fiber optic delay line 8, and then passes through a second fiber optic collimator 9 before entering the second light-generating unit. The delay range of the fiber optic delay line 8 is 0-20 microseconds, with an adjustment accuracy of 0.1 microseconds.

[0028] The sheet light generation module comprises two independent sheet light generation units. The first sheet light generation unit consists of a first fiber collimator 4, a first Powell prism 5, and a total reflection mirror 6; the second sheet light generation unit consists of a second fiber collimator 9 and a second Powell prism 10. The planar laser generated by the first Powell prism 5 is redirected by the total reflection mirror 6 and then incident on the target longitudinal section of the liquid-filled cylinder 11; the planar laser generated by the second Powell prism 10 is incident on the target cross section of the liquid-filled cylinder 11. The local adjustment mechanism of the sheet light generation unit is as follows: Figure 2 As shown, it includes a horizontal slide rail 27, a slider 28, a vertical slide rail 29, a slider 30, a slider 31, a rotary slide 32, a slider 33, a vertical slide rail 34, a slider 35, a slider 36, and a rotary slide 37. These adjustment mechanisms allow for precise control of the position and incident angle of the light beam, with a positioning accuracy better than 0.1 mm.

[0029] The image acquisition module includes four 2048×2048 pixel CMOS cameras, operating at a frame rate of 200fps. For example... Figure 1 As shown, a polarizer 12 and a narrowband filter 13 (center wavelength 532nm, bandwidth 10nm) are sequentially arranged in front of the first PIV CMOS camera 14; a polarizer 15 and a high-pass filter 16 (cutoff wavelength 550nm) are sequentially arranged in front of the first PLIF CMOS camera 17; a polarizer 19 and a narrowband filter 20 are sequentially arranged in front of the second PIV CMOS camera 21; and a polarizer 22 and a high-pass filter 23 are sequentially arranged in front of the second PLIF CMOS camera 24. A beam splitter cube 18 is arranged in the imaging optical path of the second field of view to distribute the light signal of the corresponding field of view to the second PIV CMOS camera 21 and the second PLIF CMOS camera 24. The adjustment mechanism of the top shooting system is as follows... Figure 3 As shown, it includes a horizontal slide rail 38, a slider 39, a vertical slide rail 40, a slider 41, and a telescopic support rod 42. The telescopic support rod 42 has a telescopic range of 200-800mm and an angle adjustment range of ±90°, thus allowing for flexible adjustment of the camera's shooting height and angle.

[0030] The signal synchronization module includes a synchronizer 25 with a time synchronization accuracy of 0.5 microseconds. The synchronizer 25 is connected to the laser 1 and four CMOS cameras 14, 17, 21, and 24, respectively. The fiber optic delay line 8 provides a preset microsecond-level optical path delay, which is set to 5 microseconds in this embodiment.

[0031] The control and data processing system includes a computer 26 and data processing software. The computer 26 is an industrial control computer configured with an Intel Core i7 processor, 32GB of RAM, and a 1TB solid-state drive. The data processing software uses commercial PIV / PLIF processing software, capable of image preprocessing, cross-correlation calculation, velocity field, and concentration field reconstruction.

[0032] The rotating fluid testing method based on the above platform is as follows: S1: Configure the test working medium in the filling cylinder 11 according to the above parameters and seal it. Install the filling cylinder 11 on the rotating platform and adjust the turntable to the preset speed through the turntable control software.

[0033] S2: Based on the test section location, through Figure 2 The adjustment mechanism shown adjusts the first and second light generating units, so that the two light beams are perpendicularly incident on the preset cross-section and longitudinal section of the liquid-filled cylinder 11, respectively. Figure 1 and Figure 3 The adjustment mechanism shown adjusts the four CMOS cameras to ensure that each camera is aligned with the shooting area and that the image is clear.

[0034] S3: Based on the fluid characteristic motion time, set the delay time of fiber delay line 8 to 5 microseconds.

[0035] S4: The turntable and fluid testing system are synchronously started via computer 26. Synchronizer 25 triggers laser 1 and all CMOS cameras. After transmission and beam splitting via optical fiber, one laser beam is delayed, and the two laser beams form sheet beams that illuminate the test section. The first PIV uses CMOS camera 14 and the second PIV uses CMOS camera 21 to acquire scattered light images, and the first PLIF uses CMOS camera 17 and the second PLIF uses CMOS camera 24 to acquire excited fluorescence images. After receiving the image data, computer 26 performs steps such as denoising, cross-correlation calculation, and concentration field reconstruction to obtain the velocity field and concentration field distribution of the flow field.

[0036] Experimental results show that the platform and method described in this embodiment can accurately obtain the velocity and concentration field distributions of the fluid inside the rotating cylinder. Under high-speed conditions, the stability of the sheet light is improved by more than 90% compared to the traditional reflective optical path, with no signal crosstalk. The optical path adjustment time is reduced by 90% compared to existing technologies, and it can be quickly adapted to liquid-filled cylinders of different sizes, significantly improving experimental efficiency.

[0037] This specific embodiment is for illustrative purposes only and is not intended to limit the scope of the invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention; therefore, all equivalent technical solutions also fall within the protection scope of this invention.

Claims

1. A rotating fluid testing platform based on fiber optic transmission and quasi-synchronous time-division measurement, characterized in that, Includes a rotating system, a fluid mixing system, a fluid testing system, and a control and data processing system; The rotating system includes a turntable, a rotating shaft, and turntable control software, which are used to provide rotation and tilt adjustment for the liquid filling cylinder (11); The fluid mixing system includes a liquid-filled cylinder (11), a rotating water liner, and a working fluid, which are used to contain the test working fluid and provide a refractive index matching environment. The working fluid in the liquid-filled cylinder (11) contains tracer particles and fluorescent dyes. The rotating water liner is filled with a refractive index matching solution and remains stationary relative to the fluid testing system. The fluid testing system includes a laser generation module, an optical fiber transmission module, a sheet light generation module, a signal synchronization module, and an image acquisition module, which are used to realize the acquisition of multi-section multi-physics field signals. The control and data processing system includes a computer (26) and data processing software for parameter control and data processing; The laser generating module includes a laser (1) and an optical fiber coupler (2). The laser output from the laser (1) is coupled into the optical fiber beam splitter (3) through the optical fiber coupler (2) and split into two optical fiber lasers by the optical fiber beam splitter (3). The optical fiber transmission module includes an optical fiber bundle splitter (3) and two optical fibers, one of which has an adjustable optical fiber delay line (8) connected in series. The light generation module includes a first light generation unit and a second light generation unit. The first light generation unit includes a first fiber collimator (4), a first Powell prism (5), and a total reflection mirror (6). The second light generation unit includes a second fiber collimator (9) and a second Powell prism (10). The image acquisition module includes a first PIV CMOS camera (14), a first PLIF CMOS camera (17), a second PIV CMOS camera (21), and a second PLIF CMOS camera (24); polarizers (12, 19) and narrowband filters (13, 20) are provided in front of the PIV CMOS cameras (14, 21), and polarizers (15, 22) and high-pass filters (16, 23) are provided in front of the PLIF CMOS cameras (17, 24). The signal synchronization module includes a synchronizer (25), which is used to synchronously trigger the laser (1) and each CMOS camera (14, 17, 21, 24); the fiber delay line (8) is used to provide a preset optical path delay to achieve quasi-synchronous time-division data acquisition.

2. The rotating fluid testing platform according to claim 1, characterized in that, The narrowband filters (13, 20) allow only the original laser wavelength to pass through; the high-pass filters (16, 23) allow only the excitation fluorescence wavelength to pass through.

3. The rotating fluid testing platform according to claim 1, characterized in that, The reference lengths of the two optical fibers in the optical fiber transmission module are equal, and the delay time of the optical fiber delay line (8) is set to 1-10 microseconds, so that the acquisition time difference between the corresponding images of PIV and PLIF is less than 1% of the fluid feature motion time.

4. The rotating fluid testing platform according to claim 1, characterized in that, The light generation unit is equipped with a horizontal slide rail (27), a vertical slide rail (29, 34), a slider (28, 30, 31, 33, 35, 36), a rotating slide (32, 37), and a locking structure for fixing the adjustment position; the image acquisition module is equipped with a horizontal slide rail (38), a vertical slide rail (40), a slider (39, 41), and a telescopic support rod (42).

5. The rotating fluid testing platform according to claim 1, characterized in that, The rotating shaft is vertically installed at the end of the turntable shaft and is driven by a high-precision servo motor. It has a tilt angle adjustment function of 0-90 degrees. The turntable adopts a dynamic balance counterweight design and vibration isolation measures.

6. The rotating fluid testing platform according to claim 1, characterized in that, The liquid-filled cylinder (11) and the rotating water liner are made of transparent plexiglass or quartz glass.

7. A method for testing rotating fluid based on the platform described in any one of claims 1-6, characterized in that, Includes the following steps: S1 Preparation of working medium and installation of cylinder: Prepare the test working medium in the liquid-filled cylinder (11), add the tracer particles and fluorescent dye in a preset ratio, fill the liquid-filled cylinder (11) with working medium and seal it, install the liquid-filled cylinder (11) on the rotating platform, and adjust the attitude and motion parameters. S2 Optics and Image Adjustment: Based on the size of the liquid-filled cylinder (11) and the position of the test section, adjust the horizontal slide rail, vertical slide rail, slider and rotating slide in the sheet light generation unit so that the plane laser formed by the Powell prism is perpendicular to the target cross section and longitudinal section; adjust the horizontal slide rail, vertical slide rail, slider and telescopic support rod in the camera bracket so that the CMOS camera for PIV and the CMOS camera for PLIF are aligned with the shooting area and the corresponding shooting parameters are set; S3 Delay parameter setting: According to the fluid motion characteristics, set the delay time of the fiber delay line (8) to 1-10 microseconds to ensure that the PIV and PLIF signals are quasi-synchronous and without crosstalk; S4 Data Acquisition and Processing: The turntable and fluid testing system are started synchronously. The synchronizer (25) triggers the laser (1) and each CMOS camera. The laser enters the fiber beam splitter (3) through the fiber coupler (2) and is split into two paths. One path is delayed by the fiber delay line (8) to form a preset time delay. The two lasers are collimated by the fiber collimator and the Powell prism to form sheet light and illuminate the test section. Each CMOS camera acquires PIV scattered light image and PLIF excited fluorescence image in time division. The computer (26) receives the image data and processes it to obtain the velocity field and concentration field distribution results of the flow field.

8. The rotating fluid testing method according to claim 7, characterized in that, The test section in S2 includes the target cross section and the longitudinal section.

9. The rotating fluid testing method according to claim 7, characterized in that, The light generation unit and camera bracket in S2 are fixed by a locking structure after adjustment.

10. The rotating fluid testing method according to claim 7, characterized in that, In S4, the computer (26) receives the image data and processes it according to a preset algorithm to obtain the velocity field and concentration field distribution results.

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