High speed imaging device for swallowing birds of an aeroengine based on a multi-segment flexible image fiber bundle

Abstract

This invention belongs to the field of airworthiness testing for aero-engines and provides a high-speed imaging device for aero-engines that simulates birds swallowing flocks, based on a multi-splitter flexible imaging fiber bundle. This device is used to simultaneously observe the flight trajectories of multiple simulated birds between the air cannon and the engine inlet. It includes a first multi-splitter flexible imaging fiber bundle, with multiple first split ends each equipped with a first fiber optic lens aligned with the flight path of each simulated bird. A first high-speed imaging component is optically coupled to a first convergence end, simultaneously recording the dynamic images of all paths in a single frame. Each split end is positioned in the free space to the side of the flight path, without penetrating the engine casing. Furthermore, both the convergence and split ends of the fiber bundle have rectangular end faces, with aspect ratios matching the high-speed camera's image sensor, avoiding invalid imaging areas. This invention achieves high-speed imaging of multiple targets, high synchronization, and high space utilization in bird-swallowing tests, and has the advantages of compact structure and strong anti-interference capability.

Description

Technical Field

[0001] This invention belongs to the field of airworthiness testing for aero-engines and relates to the design technology for bird-swallowing tests. Specifically, it relates to a high-speed imaging device for bird-swallowing tests for aero-engines based on a one-to-many flexible imaging fiber bundle. It is suitable for high-precision measurement of the flight speed and trajectory of test birds in bird-swallowing tests, as well as dynamic deformation observation of fan blades during bird collisions. Background Technology

[0002] Before obtaining airworthiness certification, aircraft engines must undergo bird ingestion tests. According to relevant airworthiness regulations, the number of birds swallowed must be determined based on the compressor's frontal area at the air intake, which can be as many as ten or more small birds. During the test, it is necessary to accurately measure the flight speed and trajectory of the test birds, as well as the dynamic deformation of the fan blades after the bird strike.

[0003] Currently, bird-swallowing tests typically employ multiple air cannons, each capable of simultaneously launching multiple test birds, accompanied by high-speed cameras capturing images from the side or front to record the birds' motion parameters and impact process. To meet the accuracy requirements for velocity measurement, a "one cannon, one camera" approach is often used, meaning each air cannon is paired with a high-speed camera. For example, Chinese patent CN116593164A, "A Key Point Control Method for Bird Swallowing Test of an Aircraft Turbofan Engine," explicitly uses no fewer than five high-speed cameras for simultaneous imaging. However, high-speed cameras are expensive, and multiple devices require high-precision synchronization controllers, significantly increasing testing costs and making it difficult to completely eliminate microsecond-level delays between channels, affecting the consistency and reliability of multi-view data.

[0004] If a single high-speed camera is used to cover all the air cannons, the image clarity of all areas cannot be guaranteed at the same time because each cannon position is in a different spatial location and depth range. This results in insufficient accuracy in velocity measurement and trajectory reconstruction, making it difficult to meet the requirements of airworthiness testing.

[0005] On the other hand, existing methods for measuring the dynamic deformation of fan blades during bird strikes mostly rely on post-experiment disassembly and inspection, which can only obtain static final-state data and cannot capture the transient response of the impact, thus hindering the analysis of structural strength and impact resistance. Although some studies have attempted to use a binocular high-speed vision system combined with digital image correlation (DIC) speckle technology to achieve dynamic deformation measurement, this approach requires the deployment of two high-speed cameras, which is not only costly and complex, but also results in extremely limited physical space for installing a binocular system, as the area in front of the engine is usually occupied by air cannons.

[0006] Therefore, there is an urgent need for a low-cost, compact, high-precision high-speed imaging device that can simultaneously measure multiple bird trajectories and observe dynamic deformation of blades within a limited space. Summary of the Invention

[0007] To address the technical challenges of high testing costs, limited installation space, difficulties in simultaneous observation of multiple targets, and the inability to measure the dynamic deformation of fan blades in real time in existing bird-swallowing experiments, this invention provides a high-speed imaging device for aero-engines based on a multi-point flexible imaging fiber bundle. This device can simultaneously acquire high-resolution dynamic images from multiple observation positions using only one or two high-speed cameras, achieving high-precision, low-cost, and compact measurement of the flight speed and trajectory of multiple simulated birds, as well as the impact deformation process of fan blades. Specifically, the high-speed imaging device for aero-engines includes a first multi-point flexible imaging fiber bundle and a first high-speed imaging component.

[0008] The first flexible optical fiber bundle has a first converging end and multiple first split ends. Each first split end is equipped with a first optical fiber lens at its front end, and each first optical fiber lens is aligned with a simulated bird's flight path from the air cannon to the inlet of the aircraft engine.

[0009] The first high-speed imaging component is optically docked with the first converging end, including a first high-speed camera, a first close-up lens and a first high-speed camera lens connected in sequence. The first high-speed camera lens is used to image the composite image output from the first converging end onto the first high-speed camera to record the multi-channel dynamic images transmitted by the first one-to-many flexible image transmission fiber bundle. In this configuration, all the first beam splitters are arranged in the lateral free space of their corresponding flight paths, and the first high-speed imaging component synchronously records dynamic images from each of the first beam splitters in the same frame.

[0010] Furthermore, in an improved embodiment of the above-mentioned high-speed imaging device for catching birds in an aero-engine, the device further includes a second one-to-many flexible imaging fiber bundle, having a second converging end and multiple second split ends. Each second split end is provided with a second fiber lens at its front end, and each second fiber lens is respectively aligned with another or more simulated bird flight paths from the air cannon to the aero-engine inlet. The second high-speed imaging component is optically connected to the second converging end and is used to receive and record dynamic images transmitted by the second one-to-many flexible imaging fiber bundle. All of the second beam splitters are arranged in the free space to the side of their respective flight paths.

[0011] Furthermore, the second high-speed imaging component includes a second high-speed camera, a second close-up mount, and a second high-speed camera lens connected in sequence, wherein the second high-speed camera lens is used to image the composite image output from the second converging end onto the second high-speed camera.

[0012] Furthermore, the first beam splitter and its corresponding first fiber optic lens, as well as the second beam splitter and its corresponding second fiber optic lens, are all provided with detachable anti-splash protection covers.

[0013] Furthermore, both the first high-speed imaging component and the second high-speed imaging component are equipped with external trigger interfaces, which are electrically connected to the firing controller of the air cannon via signal lines to achieve microsecond-level synchronization between image acquisition and simulated bird shot firing.

[0014] In an improved embodiment of the above-mentioned high-speed imaging device for birds that swallow flocks in an aero-engine, the device further includes a calibration plate and a light source. The calibration plate is temporarily placed in front of either the first or second beam splitter to establish a coordinate mapping relationship between the simulated bird flight space and the pixels of the high-speed camera image.

[0015] Furthermore, the end faces of the first converging end, the first beam splitting end, the second converging end, and the second beam splitting end are all rectangular, and the aspect ratio of the rectangular end faces matches the aspect ratio of the image sensor chip of the high-speed camera, so that the sub-images imaged by each beam splitting end can completely cover the camera's image screen.

[0016] Furthermore, the end face dimensions of the first and second converging ends are r1 × c1, where r1 is the lateral length, c1 is the longitudinal length, and r1 ≥ dr0, c1 ≥ dc0, d is the fiber core diameter, and r0 and c0 are the lateral and longitudinal dimensions of a single pixel of the high-speed camera, respectively.

[0017] Compared with the prior art, the beneficial effects that at least one technical solution adopted in the embodiments of this specification can achieve include at least: 1. This invention uses a single flexible imaging fiber bundle in conjunction with a small number of high-speed cameras (e.g., two) to achieve simultaneous observation of multiple trajectories in a flock-swallowing bird experiment. It eliminates the need to configure a separate high-speed camera and high-precision synchronization controller for each path, significantly reducing the number of equipment to be purchased. At the same time, it simplifies the installation, debugging and maintenance process, effectively reducing the overall test cost.

[0018] 2. By configuring an independent fiber optic lens at the front end of each fiber optic bundle splitter and combining it with targeted imaging calibration, it is ensured that each simulated bird is within the optimal depth of field of the corresponding lens, resulting in high image clarity. Combined with image segmentation, enhancement algorithms, and precise pixel-space coordinate mapping calibration methods, image distortion and background interference are effectively suppressed, ensuring that the accuracy of bird speed measurement meets the requirements of airworthiness specifications for trajectory measurement errors.

[0019] 3. The system has a simple structure and is easy to operate. The connection relationship between the components of the device is clear and the layout is flexible. There is no need for complex multi-camera synchronous control circuits. The test process is clear and the calibration operation is simple. Only a few high-speed cameras are needed to complete all data acquisition, which reduces the professional skill requirements of the operators and improves the efficiency and repeatability of the test.

[0020] 4. The number of split ends of the flexible image transmission fiber bundle can be flexibly configured according to the actual number of air guns, making it suitable for bird-swallowing test platforms of different sizes; moreover, the flexible image transmission fiber bundle is a passive optical element, which is not sensitive to electromagnetic interference, vibration and temperature changes, and can work stably in harsh impact test environments, with good engineering applicability. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the high-speed imaging device for aero-engines based on a one-to-many flexible image transmission fiber bundle disclosed in this invention. Figure 2 This is a schematic diagram of the first one-to-many flexible imaging fiber bundle disclosed in an embodiment of the present invention; Figure 3 This is a schematic diagram of the second one-to-many flexible imaging fiber bundle disclosed in an embodiment of the present invention; Figure 4 The speckle pattern prepared on the surface of the fan blades in this embodiment of the invention; The components include: 1. First one-to-many flexible image transmission fiber bundle; 2. First high-speed camera; 3. First fiber optic lens; 4. First close-up lens; 5. First high-speed camera lens; 6. Calibration plate; 7. Light source; 8. Air cannon; 9. Computer; 10. Second one-to-many flexible image transmission fiber bundle; 11. Second fiber optic lens; 12. Second high-speed camera; 13. Second close-up lens; 14. Second high-speed camera lens; 15. First converging end; 16. First splitting end; 17. Second converging end; 18. Second splitting end. Detailed Implementation

[0023] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0024] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features of the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] This invention provides a high-speed imaging device for aero-engines that simulates flocking birds, based on a one-to-many flexible image transmission fiber bundle. This device can simultaneously acquire high-definition dynamic images from multiple observation positions using only one or two high-speed cameras, enabling high-precision, low-cost, and compact measurement of the flight speed and trajectory of multiple simulated birds, as well as the impact deformation process of fan blades.

[0026] like Figure 1 and Figure 2 As shown, the high-speed imaging device for aero-engine swallowing birds includes a first one-to-many flexible image transmission fiber bundle 1 and a first high-speed imaging component. The first one-to-many flexible image transmission fiber bundle 1 has a first converging end 15 and multiple first split ends 16. Each first split end 16 is provided with a first fiber optic lens 3 at its front end. Each first fiber optic lens 3 is aligned with a simulated flight path of a bird from the air cannon 8 to the aero-engine inlet. The first high-speed imaging component is optically docked with the first converging end 15, including a first high-speed camera 2, a first close-up lens 4 and a first high-speed camera lens 5 connected in sequence. The first high-speed camera lens 5 is used to image the composite image output from the first converging end 15 onto the first high-speed camera 2 to record the multi-channel dynamic images transmitted by the first one-to-many flexible image transmission fiber bundle 1. In this configuration, all the first beam splitters 16 are arranged in the free space to the side of their respective flight paths, and the first high-speed imaging component synchronously records dynamic images from each of the first beam splitters 16 in the same frame.

[0027] In one embodiment, such as Figure 1 and Figure 2 As shown, in addition to the first one-to-one flexible imaging fiber bundle 1, it also has a second one-to-one flexible imaging fiber bundle 10, which is arranged in front of the engine inlet to capture the process of bird hitting the engine blade and to obtain the blade deformation during the process.

[0028] The structure of the second one-to-many flexible imaging fiber bundle 10 is basically the same as that of the first one-to-many flexible imaging fiber bundle 1, having a second converging end 17, multiple second splitting ends 18, and a second high-speed imaging component. Each second splitting end 18 has a second fiber optic lens 11 at its front end, and each second fiber optic lens 11 is respectively aligned with another one or more simulated bird flight paths from the air cannon 8 to the aircraft engine inlet. The second high-speed imaging component is optically connected to the second converging end 17 for receiving and recording the dynamic images transmitted by the second one-to-many flexible imaging fiber bundle 10; wherein, all the second splitting ends 18 are arranged in the free space to the side of their corresponding flight paths.

[0029] In addition, such as Figure 1 As shown, the second high-speed imaging assembly includes a second high-speed camera 12, a second close-up lens 13, and a second high-speed camera lens 14 connected in sequence. The second high-speed camera lens 14 is used to image the composite image output from the second converging end 17 onto the second high-speed camera 12. The position of the second high-speed camera lens 14 should be as close as possible to the corresponding air cannon barrel, located midway between the air cannon outlet and the engine inlet, directly facing the vertical plane of the cannon barrel outlet. Furthermore, the high-speed camera imaging chip, lens, and the center point of the fiber optic bundle converging end are aligned on the same straight line and stably fixed.

[0030] In one embodiment, the minimum bending radius of the flexible segment of the first split-multiplex flexible imaging fiber bundle 1 and the second split-multiplex flexible imaging fiber bundle 10 is not greater than 50 mm, and in the bent state, its modulation transfer function (MTF) is not less than 0.3 at a spatial frequency of 50 lp / mm.

[0031] The first beam splitter 16 and the second beam splitter 18 are adjusted during installation to be as perpendicular as possible to the surface of the observed target in order to reduce imaging perspective distortion.

[0032] In an embodiment where no accompanying drawings are shown, the first beam splitter 16 and its corresponding first fiber optic lens 3, as well as the second beam splitter 18 and its corresponding second fiber optic lens 11, are all provided with detachable anti-splash protection covers to prevent debris from impacting the optical components during the test.

[0033] In one embodiment, a surface preparation such as... can be made on the fan blade surface before the test. Figure 4 The speckle pattern shown has speckle diameters preferably not less than 2 pixels and speckle density not less than 70%.

[0034] In an embodiment where no accompanying drawings are shown, both the first high-speed imaging component and the second high-speed imaging component are provided with external trigger interfaces, which are electrically connected to the firing controller of the air cannon 8 via signal lines to achieve microsecond-level synchronization of image acquisition and simulated bird bullet firing.

[0035] Furthermore, the first high-speed imaging component is configured to continuously acquire image data for at least 200 ms at a frame rate of not less than 10,000 fps after receiving an external trigger signal.

[0036] In one embodiment, such as Figure 1 As shown, the device also includes a calibration plate 6, which is temporarily positioned in front of either the first beam splitter 16 or the second beam splitter 18 to establish a coordinate mapping relationship between the simulated bird flight space and the pixels of a high-speed camera image. The calibration plate 6 has a checkerboard pattern with known spacing on its surface to establish a mapping relationship between physical space coordinates and camera pixel coordinates.

[0037] In practice, when calibrating the first flexible image transmission fiber bundle 1, a high-speed camera and light source are activated during calibration. The first high-speed camera 2 acquires the calibration board image transmitted by the first fiber lens 3. The acquired calibration board image is transmitted to the computer 9, and the standard scale or feature marks on the calibration board 6 are extracted using image processing software. The mapping relationship between the image pixel coordinates and the actual spatial coordinates of each fiber channel is established, and the imaging calibration of each fiber lens is completed. The image magnification factor of the i-th fiber lens corresponding to the i-th (i is a positive integer, 1≤i≤n) air cannon barrel is determined to be λ. i .

[0038] When calibrating the second flexible imaging fiber bundle 10, the calibration board 6 is placed on the fan plane and controlled to generate different postures. The high-speed camera and light source are turned on, and the calibration board images transmitted by each second high-speed camera lens 14 are acquired through the second high-speed camera 12. The acquired calibration board images are transmitted to the computer, and the intrinsic and extrinsic parameters of the second fiber lens 11 are obtained using the Zhang Zhengyou calibration method.

[0039] In one embodiment, such as Figure 1 As shown, the device also includes a light source 7, which can be arranged on the same side of the fiber optic lens and with the air cannon outlet section facing the engine inlet, for imaging illumination.

[0040] In one embodiment, the end faces of the first converging end 15, the first beam splitting end 16, the second converging end 17, and the second beam splitting end 18 are all rectangular, and the aspect ratio of the rectangular end faces matches the aspect ratio of the image sensor chip of the high-speed camera, so that the sub-images imaged by each beam splitting end can completely cover the camera image, avoiding the occurrence of invalid imaging areas.

[0041] In one embodiment, if the resolution of the high-speed camera in the flock-swallowing experiment is defined as r0×c0, where r0 and c0 are the lateral and vertical dimensions of a single pixel in the high-speed camera, respectively, the camera sensitivity is S0, the pixel size is d0, and the light intensity of the shooting area is I0; and the imaging end face size of the image transmission fiber bundle matching the application scenario of the high-speed camera is defined as r×c, and the fiber core diameter is defined as d, then for a given length L of one-to-many flexible image transmission fiber bundle, the parameter range of the one-to-many flexible fiber bundle suitable for the flock-swallowing experiment can be calculated according to the following empirical formula: ; ; ; Taking the first one-to-many flexible imaging fiber bundle 1 as an example, such as Figure 2 As shown, it consists of a first converging end 15 and n first beam splitters 16. If the imaging end face area of ​​the first converging end 15 is defined as r1×c1, where r1 is the lateral length of the first converging end 15 and c1 is the longitudinal length of the first converging end 15, and since the shape of the converging end face is mathematically similar to the shape of the high-speed camera imaging chip, then the imaging end face area of ​​each first beam splitter 16 is r1×c1. The number of beam splitters n is the same as the number of cannon barrels in the air cannon 8; this ensures that the image fills the camera's field of view and avoids invalid image areas.

[0042] Before use, the distance between the first high-speed camera 2 and its corresponding first converging end 15, as well as the focal length of the first high-speed camera lens 5, can be adjusted to ensure that the imaging end face of the first converging end 15 fills the camera's image frame. If it cannot be completely filled, priority should be given to ensuring that the vertical image is completely filled. In addition, the first fiber optic lens 3 can be adjusted so that the air cannon 8 outlet and engine inlet are just visible in the image; the second fiber optic lens 11 can be adjusted so that the center of the fan is at the center of the split image, and the split image can just contain the entire fan; preferably, auxiliary reference lines are generated on the camera screen to ensure that the proportion of the air cannon outlet and engine inlet captured by each lens, and the proportion of the fan occupying the split field of view are consistent.

[0043] It should be noted that the adjustment method of the second one-to-one flexible image transmission fiber bundle 10 is the same as that of the first one-to-one flexible image transmission fiber bundle 1, and will not be described again here.

[0044] In one embodiment, the device further includes the computer 9, which processes the fiber optic convergence end image acquired by the high-speed camera and subsequently performs image segmentation, image enhancement, and bird velocity trajectory calculation.

[0045] Specifically, the processing of the multi-channel dynamic images obtained by the first flexible imaging fiber bundle 1 is as follows: Image segmentation algorithms can be used to separate the simulated bird target from the background in each fiber channel, removing environmental interference; image enhancement algorithms are used to improve the contrast and clarity of the bird image and repair blurred areas. Let z be an empirical constant (z is a positive integer, 2≤z≤5), and the centroid coordinates of the simulated bird in the j-th (j is a positive integer, j>z) frame image are extracted as (x... j ,y j Define V ij Let z be the horizontal velocity of the bird launched by the i-th air cannon in the j-th frame, and z be an empirical constant (z is a positive integer, 2≤z≤5). Then, the horizontal flight velocity of the bird in different frames can be calculated. for: ; By using the coordinates of the center of mass and velocity data of the simulated bird at each moment, the complete motion trajectory of each simulated bird is obtained through fitting, and the test results such as velocity-time curves and trajectory coordinate data are output.

[0046] The processing of the multi-channel dynamic images obtained by the second flexible imaging fiber bundle 10 is as follows: the computer 9 preprocesses the image data acquired by the second high-speed camera using image processing software; the fan rotation image in each fiber channel is separated by an image segmentation algorithm to remove environmental interference; the contrast and clarity of the fan image are improved by an image enhancement algorithm, the key frame image sequence of interest is extracted, and the deformation of the blade during the bird strike process is calculated by applying the digital correlation method (DIC).

[0047] This invention uses a typical flock-eating bird experiment scenario as an example to provide a detailed description of the above-mentioned device: (a) Equipment parameter selection The first flexible image transmission fiber bundle 1 has 5 split ends (compatible with 5 air guns), a fiber core diameter of 17μm, a numerical aperture of 0.22, and a transmission spectral range of 400–1100nm, ensuring high-fidelity image transmission. First high-speed camera 2: shooting frame rate ≥3000fps, resolution ≥1280×800 pixels, pixel size 20μm, to meet the requirements of clear capture of birds in high-speed flight; Second high-speed camera 12: shooting frame rate ≥20000fps, resolution ≥1280×800 pixels, pixel size 20μm, used for supplementary observation of key trajectories or specific perspectives with higher temporal resolution. First fiber optic lens 3: focal length 35mm, aperture F1.4, field of view 60°, matched with the beam splitter to ensure that the simulated bird is clearly imaged within the depth of field; Second fiber optic lens 11: focal length 135mm, aperture F2.8, used for high-magnification observation at long distances or in narrow field-of-view paths; First close-up adapter 4 and second close-up adapter 13: 80mm thick, used to adjust the distance between the high-speed camera lens and the fiber optic convergence end to achieve precise focusing; First high-speed camera lens 5 and second high-speed camera lens 14: focal length 50mm, aperture F2.8, minimum focusing distance 0.1m, ensuring that the composite image output from the fiber optic convergence end is completely imaged on the camera sensor; Calibration plate 6: 800mm×600mm in size, with a standard checkerboard pattern of 50mm×50mm on the surface; Light source 7: LED high-brightness surface light source, power 300W, color temperature 6500K, brightness continuously adjustable, providing uniform illumination; Air cannon 8: 5 in total, 150mm caliber, maximum working pressure 0.8MPa; Computer 9: Equipped with an Intel Core i7 processor, 16GB of RAM, and an NVIDIA GeForce RTX 3060 graphics card, running image processing and trajectory calculation software developed based on the MATLAB platform.

[0048] It should be noted that in this embodiment, the second one-to-many flexible imaging fiber bundle 10 is used to perform high frame rate supplementary observation of part of the trajectory in the same flight path, rather than for observation of the internal blades of the engine. All optical components are arranged in the open space between the air gun and the engine inlet.

[0049] (II) Implementation Process 1) Arrangement of components in the device: Five air cannons are evenly arranged about 4m in front of the engine inlet; the five first split ends 16 of the first one-to-one flexible imaging fiber bundle 1 are respectively aligned with the firing path of each air cannon and installed about 3m to the side of the path; the second split ends 18 of the second one-to-one flexible imaging fiber bundle 10 are aligned with 1-2 key paths for high frame rate observation; two high-speed cameras are aligned with the convergence end of their respective fiber bundles through a close-up adapter and camera lens, with an installation distance of about 100mm; the light source 7 is arranged 2m on the same side of the fiber lens to ensure uniform illumination of the flight area.

[0050] System calibration: The calibration plate 6 is placed sequentially at the center of the exit section of each air cannon, and the first high-speed camera acquires the image; the computer calculates the image spatial resolution as 3.1 mm / pixel, the radial distortion parameters k1=-0.012, k2=0.003 through the calibration algorithm, and completes the construction of the coordinate mapping matrix.

[0051] Firing speed calibration: 50g of standard simulated bird was loaded into each air cannon, the working pressure was set to 0.5MPa, and the firing was repeated 5 times; the average flight speed of 80m / s was obtained through image analysis and used as the reference speed under this pressure.

[0052] Bird swallowing experiment: Three 50g simulated birds were loaded into each of the four air cannons, and four birds were loaded into the fifth cannon (a total of 16 birds); the light source, two high-speed cameras and five air cannons were started simultaneously; the first high-speed camera acquired full ballistic images at 3000fps, and the second high-speed camera recorded key paths at a high frame rate of 20000fps.

[0053] Image processing and result analysis: The computer extracts each bird target through image segmentation algorithm, enhances contrast by using histogram equalization, and calculates the spatial coordinates of the birds in consecutive frames by combining calibration parameters; based on the frame interval and displacement, the flight speed range is determined to be 78–85 m / s, the measurement error is less than ±1.0%, and the trajectory deviation of each bird is less than 5 mm, which meets the requirements of airworthiness regulations for the speed accuracy of bird swallowing tests.

[0054] This embodiment verifies that the device of the present invention can stably, efficiently, and accurately complete the synchronous measurement of the flight trajectories of multiple targets in the flock-swallowing bird experiment, and has good engineering practicality.

[0055] The embodiments of the present invention achieve the following technical effects: 1. Achieve multi-trajectory synchronous high-speed imaging. By using a one-to-many flexible image transmission fiber bundle, multiple split ends are aligned with the flight paths of different simulated birds. A single high-speed camera synchronously records the dynamic images of all paths in the same frame, effectively avoiding trajectory measurement errors caused by trigger timing deviations in multi-camera systems and ensuring the time consistency of multi-target flight speed and trajectory data.

[0056] 2. No modification to the engine casing is required, and the installation is flexible and safe. All beam splitters and fiber optic lenses are arranged in the free space on the side between the air cannon and the engine inlet. An external, non-intrusive observation method is adopted, which eliminates the need to open observation windows on the high-temperature, high-pressure engine casing, greatly reducing the complexity of test preparation and avoiding the impact on the structural integrity of the engine.

[0057] 3. High imaging efficiency with no invalid areas: The fiber end faces, such as the first convergence end 15 and the first split end 16, are all designed as rectangles, and their aspect ratios are matched with the high-speed camera's photosensitive chip. This allows each sub-image to be closely arranged and completely cover the effective area of ​​the sensor, significantly improving image utilization, reducing data redundancy, and facilitating subsequent image processing and trajectory extraction.

[0058] 4. Strong anti-interference capability and adaptability to harsh test environments. Each split end and its front-end fiber optic lens are equipped with a detachable anti-splash protection cover to effectively resist the impact of fragments generated during bird swallowing tests. At the same time, the flexible fiber bundle has a small bending radius (≤50 mm), which can be deployed in a narrow space and still maintain good imaging quality in a bent state.

[0059] 5. Supports high-precision spatiotemporal calibration and synchronization control. It can be linked with the air cannon firing controller through an external trigger interface to achieve microsecond-level image acquisition synchronization. With the calibration board and uniform light source, it can establish a precise mapping relationship between physical space coordinates and pixel coordinates, ensuring the accuracy of trajectory measurement.

[0060] In summary, the device of the present invention, with its simple, reliable, and efficient optical architecture, solves the technical challenge of simultaneous observation of multiple targets in the flock-swallowing bird test, and provides a key testing method for the airworthiness verification of aero-engines.

[0061] Obviously, those skilled in the art should understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Various modifications and variations of the embodiments of the present invention are possible for those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-speed imaging device for aero-engines that detects flocking birds based on a one-to-many flexible image transmission fiber bundle, characterized in that, include: The first flexible image transmission fiber bundle (1) has a first convergence end (15) and multiple first split ends (16). Each first split end (16) has a first fiber lens (3) at its front end. Each first fiber lens (3) is aligned with a simulated bird's flight path from the air cannon (8) to the inlet of the aircraft engine. The first high-speed imaging component is optically connected to the first converging end (15), including a first high-speed camera (2), a first close-up ring (4) and a first high-speed camera lens (5) connected in sequence. The first high-speed camera lens (5) is used to image the composite image output by the first converging end (15) onto the first high-speed camera (2) to record the multi-channel dynamic images transmitted by the first one-to-many flexible image transmission fiber bundle (1). All of the first beam splitters (16) are arranged in the free space to the side of their corresponding flight paths, and the first high-speed imaging component synchronously records dynamic images from each of the first beam splitters (16) in the same frame image.

2. The high-speed imaging device for aero-engines that swallows flocks of birds according to claim 1, characterized in that, It also includes a second one-to-many flexible image transmission fiber bundle (10), which has a second convergence end (17) and multiple second split ends (18). Each second split end (18) has a second fiber lens (11) at its front end. Each second fiber lens (11) is aligned with another or more simulated bird flight paths from the air cannon (8) to the aircraft engine inlet. The second high-speed imaging component is optically connected to the second converging end (17) for receiving and recording dynamic images transmitted by the second one-to-many flexible imaging fiber bundle (10); All of the second beam splitters (18) are arranged in the free space to the side of their respective flight paths.

3. The high-speed imaging device for aero-engines that swallows flocks of birds according to claim 2, characterized in that, The second high-speed imaging component includes a second high-speed camera (12), a second close-up mount (13), and a second high-speed camera lens (14) connected in sequence. The second high-speed camera lens (14) is used to image the composite image output from the second converging end (17) onto the second high-speed camera (12).

4. The high-speed imaging device for aero-engines that swallows flocks of birds according to claim 2, characterized in that, The first beam splitter (16) and its corresponding first fiber optic lens (3), as well as the second beam splitter (18) and its corresponding second fiber optic lens (11), are all provided with detachable anti-splash protection covers.

5. The high-speed imaging device for aero-engines that swallows flocks of birds according to claim 2, characterized in that, Both the first high-speed imaging component and the second high-speed imaging component are equipped with external trigger interfaces, which are electrically connected to the firing controller of the air cannon (8) through signal lines to achieve microsecond-level synchronization of image acquisition and simulated bird bullet firing.

6. The high-speed imaging device for aero-engines that swallows flocks of birds according to claim 2, characterized in that, It also includes a calibration plate (6) and a light source (7). The calibration plate (6) is temporarily set in front of either the first beam splitter (16) or the second beam splitter (18) to establish the coordinate mapping relationship between the simulated bird flight space and the high-speed camera image pixels.

7. The high-speed imaging device for aero-engines that swallows flocks of birds according to claim 2, characterized in that, The end faces of the first converging end (15), the first beam splitting end (16), the second converging end (17) and the second beam splitting end (18) are all rectangular, and the aspect ratio of the rectangular end faces matches the aspect ratio of the photosensitive chip of the high-speed camera, so that the sub-images imaged by each beam splitting end can completely cover the camera image.

8. The high-speed imaging device for aero-engines that swallows flocks of birds according to claim 7, characterized in that, The end face dimensions of the first converging end (15) and the second converging end (17) are r1×c1, where r1 is the horizontal length and c1 is the vertical length, and satisfy r1≥dr0, c1≥dc0, d is the fiber core diameter, and r0 and c0 are the horizontal and vertical dimensions of a single pixel of the high-speed camera, respectively.

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