Three-dimensional high-speed background schlieren experiment table based on flexible optical fiber bundle

Abstract

The invention discloses a three-dimensional high-speed background schlieren experiment table based on a flexible optical fiber bundle. The three-dimensional high-speed background schlieren experiment table comprises a high-speed camera, the flexible optical fiber bundle, an imaging lens, a background plate, a direct light source, a four-degree-of-freedom sliding block, a sliding rail and a jet device, wherein the sliding rail is a circular sliding rail; the four-degree-of-freedom sliding block is placed on the sliding rail; the jet device is placed in the center of the slide rail and used for generating a to-be-measured target flow field; one end of the flexible fiber bundle is a mother fiber, the other end is a plurality of son fibers, and optical signals of the son fibers are transmitted to the mother fiber through fiber filaments; each sub-optical fiber corresponds to one group of imaging lenses, one group of background plates, one group of direct light sources and one group of four-degree-of-freedom sliding blocks, so that an independent imaging unit is formed; the high-speed camera is used for collecting optical signals of the mother fiber. By combining the flexible optical fiber bundle and the imaging lens, three-dimensional background schlieren measurement of the single high-speed camera is achieved, and the problem that a three-dimensional high-speed background schlieren measurement system is too complex in operation is solved.

Description

Technical Field

[0001] The invention relates to the field of experimental testing devices, and more specifically to a three-dimensional high-speed background schlieren experimental platform based on a flexible optical fiber bundle. Background Art

[0002] Complex turbulent flames are widely present in many industrial combustion processes, promoting mixing and heat transfer, and their research covers a wide range of length and time scales. The propagation of the flame front is closely related to the local stoichiometric state and turbulent mixing. Considering the formation of pollutants such as nitrogen oxides and soot, the occurrence of flashback and detonation, and the overall efficiency of energy conversion, the interaction between turbulence and chemical reactions is crucial for the ignition and stability of flames. Benchmark test data on parameters such as temperature, velocity, species concentration and flame morphology are particularly important for the design of new clean gas turbines, coal burners, chemical reactors and engines, which can effectively reduce combustion costs and mitigate harmful effects.

[0003] In recent years, the measurement of unsteady three-dimensional flows has become a research focus. Optical diagnostic methods not only avoid the interference of traditional physical contact measurements on the flow, but also can capture key structural information in complex flows with high resolution, and have significant application potential. Background-guided schlieren technology can effectively measure the refractive index field and visualize the density gradient, thereby estimating the temperature distribution in the flow and analyzing the flow structure. Conventional three-dimensional high-speed background schlieren systems require multiple high-speed cameras, which are too expensive. In addition, multiple high-speed cameras also need to be controlled synchronously, which brings great complexity to the three-dimensional high-speed background schlieren experiment.

[0004] Based on the above requirements, designing a low-cost, low-complexity three-dimensional high-speed background schlieren experimental platform is an urgent problem that technical personnel in this field need to solve. Summary of the invention

[0005] In view of this, the present invention provides a three-dimensional high-speed background schlieren experimental platform based on a flexible optical fiber bundle. By combining the flexible optical fiber bundle with an imaging lens, three-dimensional background schlieren measurement with a single high-speed camera is realized, thereby reducing the cost of the three-dimensional high-speed background schlieren measurement system. The optical fiber bundles used are of equal length, thereby avoiding the need for synchronous control. The four-degree-of-freedom slider used can conveniently adjust the distance between the imaging lens and the background plate, thereby solving the problem of overly complicated operation of the three-dimensional high-speed background schlieren measurement system.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A three-dimensional high-speed background schlieren experimental platform based on a flexible optical fiber bundle, comprising a high-speed camera, a flexible optical fiber bundle, an imaging lens, a background plate, a direct light source, a four-degree-of-freedom slider, a slide rail and a jet device;

[0008] Wherein, the slide rail is a circular slide rail;

[0009] The four-degree-of-freedom slider is placed on the slide rail;

[0010] The jet device is placed at the center of the slide rail and is used to generate a target flow field to be measured;

[0011] One end of the flexible optical fiber bundle is a mother optical fiber, and the other end is a plurality of daughter optical fibers, and the optical signals of the daughter optical fibers are transmitted to the mother optical fiber through optical fiber filaments; each daughter optical fiber corresponds to a group of imaging lenses, background plates, direct light sources and four-degree-of-freedom sliders, forming an independent imaging unit;

[0012] The high-speed camera is used to collect the optical signal of the mother optical fiber.

[0013] Furthermore, the independent imaging unit includes:

[0014] The same group of flexible fiber bundle sub-fibers, imaging lenses, and direct light sources are fixed on a four-degree-of-freedom slider as an imaging end slider;

[0015] The corresponding background plate is fixed on another four-degree-of-freedom slider as a background end slider;

[0016] The imaging end slider and the background end slider are symmetrically placed on the slide rail with an interval of 180°.

[0017] Furthermore, the angular interval between the imaging end sliders is adjusted according to the measured flow field characteristics.

[0018] Furthermore, the imaging lens on the imaging end slider coincides with the optical axis of the sub-optical fiber and is parallel to the direction of the direct light source.

[0019] Furthermore, the background plate on the background end slider is oriented perpendicular to the optical axis direction of the corresponding imaging lens, and the optical axis of the imaging lens passes through the center of the background plate.

[0020] Furthermore, the distance between the imaging lens and the background plate is adjusted by the four-degree-of-freedom slider.

[0021] Furthermore, the high-speed camera synchronously collects the background schlieren signals on all sub-optical fibers, and quantitatively reconstructs the three-dimensional results of the flow field by combining with a tomography algorithm.

[0022] It can be seen from the above technical solution that compared with the prior art, the present invention discloses a three-dimensional high-speed background schlieren experimental platform based on a flexible optical fiber bundle, which introduces a flexible optical fiber bundle and can realize three-dimensional background schlieren measurement of a single high-speed camera, while avoiding the problem of synchronous control, and effectively reducing the complexity of the three-dimensional background schlieren system; the distance between the imaging lens and the background plate can be adjusted by a four-degree-of-freedom slider, which is convenient for experimental operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0024] Figure 1 A schematic structural diagram of a three-dimensional high-speed background schlieren experimental platform based on a flexible optical fiber bundle provided by the present invention.

[0025] Description of the drawings: 1 is a high-speed camera, 2 is a flexible optical fiber bundle, 3 is an imaging lens, 4 is a background plate, 5 is a direct light source, 6 is a four-degree-of-freedom slider, 7 is a slide rail, and 8 is a jet device. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] The embodiment of the present invention discloses a three-dimensional high-speed background schlieren experimental platform based on a flexible optical fiber bundle, referring to Figure 1 As shown, it includes a high-speed camera 1, a flexible optical fiber bundle 2, an imaging lens 3, a background plate 4, a direct light source 5, a four-degree-of-freedom slider 6, a slide rail 7 and a jet device 8;

[0028] Wherein, the slide rail 7 is a circular slide rail;

[0029] The four-degree-of-freedom slider 6 is placed on the slide rail 7;

[0030] The jet device 8 is placed at the center of the slide rail 7 and is used to generate the target flow field to be measured;

[0031] One end of the flexible optical fiber bundle 2 is a mother optical fiber, and the other end is a plurality of daughter optical fibers. The main function of the flexible optical fiber bundle 2 is to efficiently transmit the optical signals collected from each daughter optical fiber end to the mother optical fiber through the optical fiber filaments. In this way, even if the imaging lenses are distributed in different positions, all image information can be concentrated to one point and captured by a single high-speed camera.

[0032] In this embodiment, the number of sub-fibers is consistent with the number of imaging lenses 3, background plates 4 and direct light sources 5; each sub-fiber corresponds to a group of imaging lenses 3, background plates 4, direct light sources 5 and four-degree-of-freedom sliders 6, forming an independent imaging unit.

[0033] By using the flexible optical fiber bundle 2, multiple imaging units can work simultaneously and synchronously observe the same flow field from different angles, thereby obtaining a comprehensive three-dimensional data set.

[0034] Each independent imaging unit includes an imaging end slider and a background end slider.

[0035] Among them, the same group of flexible fiber bundle sub-fibers 2, imaging lens 3, and direct light source 5 are fixed on a four-degree-of-freedom slider 6 as an imaging end slider; the corresponding background plate 4 is fixed on another four-degree-of-freedom slider 6 as a background end slider.

[0036] Each group of imaging end sliders and background end sliders are symmetrically placed on the circular slide rail 7 with an interval of 180°.

[0037] The circular slide allows the imaging end slider (containing the imaging lens, sub-fiber and direct light source) and the background end slider (containing the background plate) to be evenly distributed around the jet device, and the angular spacing between the imaging end sliders can also be adjusted according to the measured flow field characteristics. This layout allows the same flow field to be observed from multiple different angles, thereby obtaining a more comprehensive data set.

[0038] In this embodiment, the sub-optical fiber of each imaging unit is respectively connected to the imaging lens 3, and the optical axes coincide and are parallel to the optical axis of the direct light source 5, ensuring uniform illumination on the background plate 4, reducing errors caused by shadows and uneven lighting, and thus producing a clear background schlieren pattern.

[0039] The sub-optical fiber and the corresponding imaging lens 3 and the direct light source 5 are all installed on a four-degree-of-freedom slider 6, and the position can be adjusted along the optical axis by the four-degree-of-freedom slider 6, which makes it easier to achieve standardized settings; each time an experiment is performed, it is only necessary to move the four-degree-of-freedom slider 6 to a predetermined position to ensure the same observation conditions, thereby improving the consistency and repeatability of the experimental results.

[0040] In this embodiment, the background plate 4 is mounted on a four-degree-of-freedom slider 6, the background plate 4 is oriented perpendicular to the optical axis of the imaging lens 3, and its position is adjusted along the optical axis by the four-degree-of-freedom slider 6, ensuring that the light is directly reflected back to the imaging lens 3, avoiding refraction or reflection loss caused by tilt, thereby ensuring image quality.

[0041] In this embodiment, the jet device 8 is placed at the center of the slide rail to ensure symmetry and uniformity when observed from all angles, thereby avoiding data deviation caused by position offset and improving the accuracy and reliability of the reconstructed three-dimensional results.

[0042] The sub-fiber transmits the collected background schlieren image of the background plate 4 to the imaging lens mother fiber, and uses the high-speed camera 1 to collect the optical signal of the mother fiber, records the change of the flow field over time, and reconstructs the three-dimensional flow field characteristics by combining the background schlieren images of all sub-fibers and the distance between the corresponding objective lens and the background plate, thereby revealing key information such as the density distribution and velocity field inside the flow field.

[0043] In this embodiment, a tomographic algorithm is used to quantitatively reconstruct the three-dimensional characteristics of the flow field. Specifically, algebraic reconstruction technology ART, filtered back projection FBP, simultaneous algebraic reconstruction technology SART, maximum likelihood expectation maximization MLEM, compressed sensing CS and Bayesian algorithm can be used to reconstruct the three-dimensional structure of the flow field to be measured from the two-dimensional background schlieren images collected from different angles.

[0044] The present invention adopts a flexible optical fiber bundle to transmit optical signals, which can realize single-camera high-speed three-dimensional background schlieren test while avoiding the difficulty of synchronous control; the flexible optical fiber bundle is combined with an imaging lens to realize real-time high-speed transmission of multi-angle background schlieren images; the equipment is installed on a slide rail through a four-degree-of-freedom slider, which is convenient for adjusting the distance and angle in the experiment.

[0045] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0046] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may 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 the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A three-dimensional high-speed background schlieren experimental platform based on a flexible optical fiber bundle, characterized in that: It includes a high-speed camera, a flexible optical fiber bundle, an imaging lens, a background plate, a direct light source, a four-degree-of-freedom slider, a slide rail, and a jet device; Wherein, the slide rail is a circular slide rail; The four-degree-of-freedom slider is placed on the slide rail; The jet device is placed at the center of the slide rail and is used to generate a target flow field to be measured; One end of the flexible optical fiber bundle is a mother optical fiber, and the other end is a plurality of daughter optical fibers, and the optical signals of the daughter optical fibers are transmitted to the mother optical fiber through optical fiber filaments; each daughter optical fiber corresponds to a group of imaging lenses, background plates, direct light sources and four-degree-of-freedom sliders, forming an independent imaging unit; The high-speed camera is used to collect the optical signal of the mother optical fiber.

2. A three-dimensional high-speed background schlieren test bench based on a flexible optical fiber bundle as claimed in claim 1, characterized in that: The independent imaging unit comprises: The same group of flexible fiber bundle sub-fibers, imaging lenses, and direct light sources are fixed on a four-degree-of-freedom slider as an imaging end slider; The corresponding background plate is fixed on another four-degree-of-freedom slider as a background end slider; The imaging end slider and the background end slider are symmetrically placed on the slide rail with an interval of 180°.

3. A three-dimensional high-speed background schlieren test bench based on a flexible optical fiber bundle as claimed in claim 2, characterized in that: The angular interval between the imaging end sliders is adjusted according to the measured flow field characteristics.

4. A three-dimensional high-speed background schlieren test bench based on a flexible optical fiber bundle as claimed in claim 3, characterized in that: The imaging lens on the imaging end slider coincides with the optical axis of the sub-fiber and is parallel to the direction of the direct light source.

5. A three-dimensional high-speed background schlieren test bench based on a flexible optical fiber bundle as claimed in claim 4, characterized in that: The background plate on the background end slider is oriented perpendicular to the optical axis direction of the corresponding imaging lens, and the optical axis of the imaging lens passes through the center of the background plate.

6. A three-dimensional high-speed background schlieren test bench based on a flexible optical fiber bundle as claimed in claim 5, characterized in that: The distance between the imaging lens and the background plate is adjusted by the four-degree-of-freedom slider.

7. A three-dimensional high-speed background schlieren test platform based on a flexible optical fiber bundle as claimed in claim 6, characterized in that: The high-speed camera synchronously collects background schlieren signals on all sub-optical fibers, and quantitatively reconstructs the three-dimensional result of the flow field by combining with a tomography algorithm.

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