Apparatus and method for measuring inlet sand dust concentration distribution of an aeroengine

Abstract

The application discloses a device and method for measuring the inlet sand dust concentration distribution of an aero-engine, belongs to the field of sand swallowing test of an aero-engine, and comprises a pulsed laser light source, a shaping module, an optical image acquisition module and a data post-processing module; the pulsed laser light source is arranged at a preset position around the aero-engine and is used for emitting a laser beam; the aero-engine is located in a sand dust environment to be measured; the shaping module is used for receiving the laser beam and outputting a sheet-shaped light beam; the optical image acquisition module is used for receiving the coherent scattering light emitted by sand in a sheet-shaped light beam irradiation area, forming a laser speckle image, and transmitting the obtained laser speckle image to the data post-processing module; the data post-processing module adopts an inlet sand dust concentration measurement algorithm to process the laser speckle image, and obtains the inlet sand dust concentration distribution of the aero-engine. The application has a simple structure and is suitable for measuring the inlet sand dust concentration distribution in the sand swallowing experiment of aero-engines of different sizes or stages.

Description

Technical Field

[0001] This invention relates to the field of sand ingestion testing for aero-engines, and particularly to an apparatus and method for measuring the concentration distribution of sand and dust at the inlet of an aero-engine. Background Technology

[0002] To ensure the stable operation of aero-engines under harsh flight conditions with high sand and dust content, such as desert environments and sandstorms, during takeoff, landing, and flight, sand ingestion tests have become a crucial test item in the design and finalization of new engines. Sand ingestion tests involve introducing test sand and dust into the aero-engine using a sand ingestion device to simulate the state of sand and dust ingestion during actual use. Currently, research on sand ingestion tests mainly focuses on the impact of sand and dust particles on the performance of turboshaft / turbofan engines. Limited by existing measurement technology, the amount of sand ingested in sand in these tests can only be derived from parameters such as the feed rate of the feeding mechanism and the sand and dust particle size range. The sand and dust concentration distribution near the engine inlet section and the instantaneous sand ingestion mass flow rate are still unavailable, limiting the breadth of data for engine performance testing.

[0003] The sand-swallowing device consists of a sand bucket, a sand-scraping mechanism, a feeding mechanism, a mixer, a distributor, compressed air pipelines, a mounting bracket, and a measurement and control system. Its working principle is as follows: the sand-scraping mechanism, driven by the feeding mechanism, rotates and descends at a constant speed within the sand bucket, causing sand to be blown into the mixer by high-pressure air from the sand outlet pipeline. The sand, uniformly mixed with air, is then transported to the distributor via several hoses and sprayed out from nozzles. The sand diffuses through the nozzles to completely cover the engine intake grille (diameter ≥ 800 mm) before being sucked into the engine intake duct, completing the sand-swallowing process. The amount of sand swallowed is obtained by inverting the travel distance of the feeding mechanism and the instantaneous rotational speed of the drive motor. The sand swallowing amount obtained by the above method only represents the total mass of sand swallowed by the aero-engine within a certain time interval, and the reliability of the inversion algorithm is lower than that of visual measurement methods. Therefore, to meet the practical needs of measuring the total amount of sand swallowed, the spatial distribution of sand, and the instantaneous distribution characteristics of sand in sand-swallowing experiments, specialized measurement technologies need to be developed.

[0004] Currently, techniques for measuring the concentration distribution of discrete phases such as solid particles generally employ visual image measurement techniques such as holography and shadowing. These techniques use a camera to capture as many particles as possible within the field of view, thereby obtaining accurate information on the concentration distribution of the discrete phase. Holography, based on Huygens-Fresnel diffraction theory and light scattering theory, works by using a laser beam to illuminate a cloud field, creating scattered light. A holographic plate or camera records the interference fringes generated by the scattered light and the original laser beam, and the particle position and size information are obtained through optical or numerical reconstruction. Shadowing, on the other hand, captures particles based on the differences in light transmission characteristics between different media, and then uses image processing techniques to obtain particle size and distribution information. It offers advantages such as simple principle, convenient testing, and low cost. However, the above methods cannot be directly applied to the sand ingestion test of aero-engines. On the one hand, both the holographic method and the shadow method require the optical axis of the light source end to coincide with that of the camera acquisition end. When measuring the sand and dust distribution at the engine inlet section, this arrangement will inevitably affect the engine intake airflow, thus causing the ground simulation conditions of the sand ingestion test to deviate from the actual engine operating conditions. On the other hand, one of the measurement / imaging principles of the holographic method and the shadow method is to perform two-dimensional compression of the lens imaging area. Therefore, there are a large number of particles stacked and interacting in the image, which makes it impossible to accurately obtain the particles and their distribution in a single plane section.

[0005] Therefore, it is necessary to conduct research on the measurement technology and development of measurement devices for the sand ingress concentration distribution and sand ingress amount of aero-engines, specifically for sand ingress tests. Summary of the Invention

[0006] The purpose of this invention is to provide an apparatus and method for measuring the sand and dust concentration distribution at the inlet of an aero-engine, so as to solve the problems of low reliability of the backtracking algorithm for calculating the sand ingestion amount in traditional sand ingestion experiments and the inability to monitor or obtain the sand and dust concentration at different cross sections of the inlet.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] The device for measuring the concentration distribution of sand and dust at the inlet of an aircraft engine includes a pulsed laser source, a shaping module, an optical image acquisition module, and a data post-processing module.

[0009] The pulsed laser source is placed at a preset position around the aero-engine to emit a laser beam, and the aero-engine is located in the sand and dust environment to be tested;

[0010] The shaping module is used to receive the laser beam and output a sheet-like beam.

[0011] The optical image acquisition module is used to receive coherent scattered light emitted by the sand and gravel in the area irradiated by the sheet beam, form a laser speckle image, and transmit the obtained laser speckle image to the data post-processing module.

[0012] The data post-processing module uses an imported sand and dust concentration measurement algorithm to process the laser speckle image to obtain the sand and dust concentration distribution at the aero-engine inlet.

[0013] Furthermore, the optical image acquisition module includes a distributed optical acquisition unit and a timing trigger controller. The timing trigger controller is used to control the distributed optical acquisition unit to capture coherent scattered light emitted by the sand and gravel to form a laser speckle image.

[0014] The distributed optical acquisition unit includes several cameras and telephoto camera lenses that work in conjunction with the cameras.

[0015] Furthermore, the shaping module includes a zero-order waveplate, a reflecting mirror, a plano-convex cylindrical mirror, and a plano-concave cylindrical mirror arranged in sequence. The shaping module is used to make the plane containing the sheet beam perpendicular to the optical axis of the camera.

[0016] Furthermore, the data post-processing module is a computer with a built-in algorithm for measuring the concentration of imported sand and dust. Specifically, the algorithm for measuring the concentration of imported sand and dust is as follows:

[0017] The laser speckle image obtained in the actual scene is input into the pre-established sand and gravel morphology and particle size inversion model to obtain the morphology and particle size information of the sand and gravel.

[0018] Based on the morphology and particle size information of the sand and gravel, the sand and gravel are modeled using basic geometric shapes and the equivalent mass is calculated.

[0019] A reference coordinate system is constructed based on the center position of the aero-engine inlet. The laser speckle image is divided into grids according to the reference coordinate system. The grid size is determined according to the maximum particle size of the sand and gravel. The number of sand and gravel in each grid and the equivalent mass are converted into values ​​between 0 and 1, and then a statistical chart of the relative concentration of sand and gravel is obtained. The sand and dust concentration distribution at the aero-engine inlet is obtained from the statistical chart of the relative concentration of sand and gravel.

[0020] Furthermore, the process of establishing the sand and gravel morphology and grain size inversion model is as follows:

[0021] A simulation calculation model for sand speckle is obtained based on the mapping relationship between the pre-acquired sand and gravel morphology and the laser speckle image;

[0022] Several gravel morphology images were automatically generated using the maximum inscribed rhombus method, which served as an irregular gravel morphology dataset. The irregular gravel morphology dataset was then imported into the gravel speckle simulation model, and several laser speckle images corresponding to the gravel morphology images were output, resulting in an irregular gravel speckle image dataset.

[0023] A deep learning network was used to train an image dataset of irregularly shaped gravel speckle to establish a gravel morphology and particle size inversion model.

[0024] Furthermore, the mapping relationship between the gravel morphology and the laser speckle image is obtained through a calibration device, which includes an ultrasonic suspension stage, a speckle image acquisition device, and a gravel morphology acquisition device. The ultrasonic suspension stage is installed in the imaging focal plane of the speckle image acquisition device and the gravel morphology acquisition device, and the force field center of the ultrasonic suspension stage is aligned with the center of the imaging area and the irradiation area of ​​the sheet beam.

[0025] The ultrasonic levitation stage includes an upper part and a lower part, and the upper part and the lower part are used to suspend multi-morphological gravel.

[0026] Gravel morphology and speckle image acquisition devices were used to acquire gravel morphology and speckle image data respectively, and the mapping relationship between gravel morphology and speckle image was obtained.

[0027] A method for measuring the dust concentration distribution at the inlet of an aircraft engine includes the following steps:

[0028] A laser beam is emitted by a pulsed laser source placed at a predetermined position around the aircraft engine under test;

[0029] The laser beam is received by the shaping module and output as a sheet-like beam;

[0030] The optical image acquisition module receives coherent scattered light emitted by the sand and gravel in the area illuminated by the sheet beam, forms a laser speckle image, and transmits the obtained laser speckle image to the data post-processing module.

[0031] The speckle image was processed by the data post-processing module to obtain the dust concentration distribution at the aero-engine inlet.

[0032] Furthermore, the laser speckle image is processed by the data post-processing module to obtain the dust concentration distribution at the aero-engine inlet, specifically as follows:

[0033] The laser speckle image obtained in the actual scene is input into the pre-established sand and gravel morphology and particle size inversion model to obtain the morphology and particle size information of the sand and gravel.

[0034] Based on the morphology and particle size information of the sand and gravel, the sand and gravel are modeled using basic geometric shapes and the equivalent mass is calculated.

[0035] A reference coordinate system is constructed based on the center position of the aero-engine inlet. The speckle image is divided into grids according to the reference coordinate system. The grid size is determined according to the maximum particle size of the sand and gravel. The number of sand and gravel in each grid and the equivalent mass are converted into values ​​between 0 and 1, and then a statistical chart of the relative concentration of sand and gravel is obtained. The sand and dust concentration distribution at the aero-engine inlet is obtained from the statistical chart of the relative concentration of sand and gravel.

[0036] Furthermore, the process of establishing the sand and gravel morphology and grain size inversion model is as follows:

[0037] A simulation calculation model for sand speckle is obtained based on the mapping relationship between the pre-acquired sand and gravel morphology and the laser speckle image;

[0038] Several gravel morphology images were automatically generated using the maximum inscribed rhombus method, which served as an irregular gravel morphology dataset. The irregular gravel morphology dataset was then imported into the gravel speckle simulation model, and several laser speckle images corresponding to the gravel morphology images were output, resulting in an irregular gravel speckle image dataset.

[0039] A deep learning network was used to train an image dataset of irregularly shaped gravel speckle to establish a gravel morphology and particle size inversion model.

[0040] Furthermore, the mapping relationship between the gravel morphology and the laser speckle image is obtained through a calibration device, which includes an ultrasonic suspension stage, a speckle image acquisition device, and a gravel morphology acquisition device. The ultrasonic suspension stage is installed in the imaging focal plane of the speckle image acquisition device and the gravel morphology acquisition device, and the force field center of the ultrasonic suspension stage is aligned with the center of the imaging area and the irradiation area of ​​the sheet beam.

[0041] The ultrasonic levitation stage includes an upper part and a lower part, and the upper part and the lower part are used to suspend multi-morphological gravel.

[0042] Gravel morphology and speckle image acquisition devices were used to acquire gravel morphology and speckle image data respectively, and the mapping relationship between gravel morphology and speckle image was obtained.

[0043] Compared with the prior art, the present invention has the following beneficial technical effects:

[0044] This invention provides a device for measuring the sand and dust concentration distribution at the inlet of an aero-engine. It utilizes a laser-irradiated irregularly shaped gravel to generate a laser speckle image by propagating coherent scattered light to the far field. An inlet sand and dust concentration measurement algorithm is employed to achieve high-precision measurement of the gravel morphology / particle size and sand and dust concentration distribution at the inlet cross-section of the aero-engine during sand ingestion experiments. This solves the problems of low reliability of backtracking algorithms for calculating sand ingestion volume in traditional sand ingestion experiments, and the inability to monitor or obtain sand and dust concentrations at different inlet cross-sections. This invention can improve the design capabilities of sandblasting devices used in sand ingestion experiments. Furthermore, this invention employs visual measurement technology, resulting in high-precision measurement results and a clear physical basis for the measurement process. Due to its modular design, this invention has a simple structure, is easy to transport, and is suitable for measuring the sand and dust concentration distribution at the inlet of aero-engines of different sizes or stages during sand ingestion experiments.

[0045] Furthermore, by designing the structure of the shaping module so that the plane of the sheet beam is perpendicular to the optical axis of the camera, the imaging position can be made to be more than 1.5m away from the inlet of the aero-engine. This can significantly reduce the influence of the measuring device on the airflow at the inlet of the aero-engine, and thus make the sand swallowing experiment more in line with the harsh environmental conditions of reality.

[0046] Furthermore, a sand speckle simulation calculation model is obtained by mapping the sand speckle morphology to the laser speckle image. By learning and training the sand speckle simulation calculation model, a sand morphology and particle size inversion model is obtained. Measurements are performed based on the sand morphology and particle size inversion model. This not only allows the calculation of the true morphology and particle size of the sand using the speckle imaging principle, but also enables the identification or detection of tiny sand particles smaller than those in traditional image measurement techniques at far-field (imaging distance > 1500 mm), thereby improving the testing accuracy and applicability. Attached Figure Description

[0047] The accompanying drawings are provided to further understand the invention and constitute a part of this invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0048] Figure 1 This is a structural diagram of the device for measuring the concentration distribution of sand and dust at the inlet of an aircraft engine according to the present invention;

[0049] Figure 2 This is a structural diagram of the calibration device of the present invention;

[0050] Figure 3 This is a structural diagram of the distributed optical data acquisition device of the present invention;

[0051] Figure 4 This is a schematic diagram illustrating a specific implementation scheme for the dust concentration distribution during the aero-engine sand ingestion test of the present invention.

[0052] Figure 5 This is a diagram illustrating the algorithm steps of the gravel morphology and particle size inversion model of the present invention.

[0053] Figure 6 This is a flowchart illustrating the algorithm steps for measuring the concentration of imported sand and dust according to the present invention.

[0054] Among them, 1. Short pulse width low frequency laser; 2. Air gap zero-order waveplate; 3. 532nm laser reflector; 4. 532nm laser plano-convex cylindrical mirror; 5. 532nm laser plano-concave cylindrical mirror; 6. Ultrasonic levitation stage; 7. Sheet beam; 8. Coherent scattered light from sand and gravel; 9. Distributed optical collector; 10. Timing trigger controller; 11. Computer; 12. Speckle image collector; 13. Sand and gravel morphology collector; 14. Irregularly shaped sand and gravel; 1 5. Lighting source; 16. Upper part of ultrasonic suspension platform; 17. Lower part of ultrasonic suspension platform; 18. Gravel storage tank; 19. Gravel conveying pipe; 20. Gravel fluidization section; 21. Gravel dispersion pipe; 22. Harsh sand and dust environment; 23. Aircraft engine inlet; 24. Pressure plate; 25. Support; 26. Support rod; 27. Distributed fixed bracket; 28. Telephoto camera lens; 29. ​​Horizontal rotating bracket; 30. Vertical rotating bracket; 31. Camera. Detailed Implementation

[0055] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0056] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0057] Example 1

[0058] like Figure 1As shown, this invention provides an optical device for measuring the concentration distribution of sand and dust at the inlet of an aero-engine, including a pulsed laser source, a shaping module, an optical image acquisition module, and a data post-processing module. In the sand and dust environment to be measured, the pulsed laser source is placed at a preset position around the aero-engine to emit a laser beam. The shaping module receives the laser beam and outputs a sheet-like beam 7. The optical image acquisition module receives the coherent scattered light emitted by the sand and gravel within the area illuminated by the sheet-like beam 7 and transmits the resulting laser speckle image to the data post-processing module. The data post-processing module's built-in inlet sand and dust concentration measurement algorithm can quickly process the laser speckle image and accurately obtain the concentration distribution of sand and dust at the aero-engine inlet. The shaping module includes several optical elements, including a zero-order waveplate, a reflecting mirror, a plano-convex cylindrical mirror, and a plano-concave cylindrical mirror arranged sequentially. Its function is to shape the circular output light spot into a sheet-like beam 7 (illumination area ≥ 0.64m). 2 This causes the sand and gravel within the illuminated area to emit high-intensity coherent scattered light. See also Figure 1 and Figure 3 The optical image acquisition module includes a distributed optical acquisition unit 9 and a timing trigger controller 10. The timing trigger controller 10 is used to control the distributed optical acquisition unit 9 to capture coherent scattered light emitted by the sand and gravel to form a laser speckle image. The distributed optical acquisition unit 9 includes several cameras 31 (specifically, high-resolution CCD cameras) and a telephoto camera lens 28 that works in conjunction with the cameras 31.

[0059] It also includes a calibration device, which includes an ultrasonic suspension stage 6, a speckle image acquisition device 12, and a gravel morphology acquisition device 13. The ultrasonic suspension stage 6 includes an upper ultrasonic suspension stage 16 and a lower ultrasonic suspension stage 17. Multi-morphological gravel is arranged between the upper ultrasonic suspension stage 16 and the lower ultrasonic suspension stage 17. The size range of the gravel is 50μm-3000μm, and the morphology of the gravel includes regular circles, approximately circles, approximately regular polygons, and various irregular morphologies. The speckle image acquisition device 12 consists of an industrial lens and a high-resolution CCD (Charge Coupled Device) camera. The gravel morphology acquisition device 13 consists of a high-magnification morphology observation lens and a high-resolution CCD camera.

[0060] During use, the industrial lens should be at least 120cm away from the inlet section of the aircraft engine, and the sheet-like beam 7 output by the shaping module should be perpendicular to the optical axis of the telephoto camera lens 28 of the optical image acquisition module. Finally, the image data acquired by the optical image acquisition module is transmitted to the data post-processing module via a communication optical cable. After processing, the morphology, particle size, sand and dust concentration distribution within the cross-section, and instantaneous mass flow rate of the gravel are obtained.

[0061] The main component of the data post-processing module is a high-performance computer 11. The detailed processing procedure of this data post-processing module is as follows:

[0062] The first step is to acquire images of different gravel morphology and corresponding laser speckle images using a calibration device, forming a gravel speckle image-morphology database, which is the mapping relationship between gravel morphology and speckle images.

[0063] The second step is to develop a sand speckle simulation calculation model based on ray tracing and laser speckle imaging theory, based on the mapping relationship between sand and gravel morphology and speckle image.

[0064] The third step is to automatically generate several gravel morphology images using the maximum inscribed rhombus method, i.e., irregular gravel morphology dataset, and import them as input into the gravel speckle simulation calculation model. The gravel speckle simulation calculation model will output the corresponding speckle images, thereby obtaining a large number of speckle images corresponding to the gravel morphology images, i.e. irregular gravel speckle image dataset.

[0065] The fourth step involves training a deep learning network on the irregularly shaped speckle image dataset obtained in the third step to establish a sand and gravel morphology and particle size inversion model. The function of this sand and gravel morphology and particle size inversion model is to process the input speckle image and directly output the corresponding sand and gravel morphology and particle size information.

[0066] The fifth step is to acquire laser speckle images of sand and gravel in the actual scene, input them into the sand and gravel morphology and particle size inversion model, and obtain the morphology and particle size information of the sand and gravel.

[0067] The sixth step is to model the irregularly shaped gravel using basic geometric shapes and calculate its equivalent mass.

[0068] The seventh step is to construct a reference coordinate system based on the center position of the aero-engine inlet, and to divide the speckle image into grids accordingly. The grid size is determined based on the maximum particle size of the gravel in the experiment. The number of gravel particles and their equivalent mass in each grid are converted into values ​​between 0 and 1, thereby obtaining a statistical chart of the relative concentration of gravel.

[0069] This invention relies on a sheet-like light beam 7 to induce coherent scattered light from irregularly shaped sand grains. By utilizing the interference phenomenon of scattered light during the far-field propagation of this coherent scattered light, on the one hand, the imaging thickness can be limited to the camera's focal plane, avoiding the additional influence of out-of-focus sand grains on the measurement; on the other hand, this method can achieve the measurement of small sand grains at a relatively long distance, thereby avoiding the measurement equipment from affecting the inlet flow field of the aero-engine in the sand swallowing experiment and deviating from the actual process.

[0070] The pulsed laser source, shaping module, and optical image acquisition module are the key components of the device of this invention. Capturing an image of the sand and gravel distribution within a specific cross-section can be achieved through the following two different techniques.

[0071] In the first technical solution, a coaxial arrangement is used to align the optical axes of the pulsed laser source and the high-resolution CCD camera. When it is necessary to measure the sand and gravel distribution image within a certain cross-section, the lens of the high-resolution CCD camera is adjusted so that the focal plane coincides with the cross-section. Then, the pulsed laser source is turned on and directly illuminated by the high-resolution CCD camera. When the sand and gravel pass through the test area, a shadow area will appear in the high-resolution CCD camera. Parameters such as the sand and gravel concentration distribution within the cross-section can be obtained by reading the area and position coordinates of the shadow area in the image. This solution has advantages such as a simple optical system and flexible adjustment of the test cross-section; however, the lens depth of field causes the halo of out-of-focus sand and gravel to have a significant impact on the measurement results (especially at high concentrations); the imaging principle indicates that the focal plane should be very close to the lens when measuring sand and gravel, which has a significant impact on the airflow at the inlet of the aero-engine; and the pulsed laser source is arranged in the opposite direction to the airflow at the inlet of the aero-engine, making it difficult to fix the pulsed laser source. Therefore, it is not suitable for measuring the sand and dust concentration distribution in aero-engine sand ingestion experiments.

[0072] In the second technical solution, a cross-arrangement is used to make the optical axes of the pulsed laser source and the high-resolution CCD camera perpendicular. When measuring the distribution image of sand and gravel in a certain cross section, the sheet-like beam 7 and the focal plane of the lens are adjusted to coincide with the measurement cross section. The sheet-like beam 7 induces irregularly shaped sand and gravel to emit coherent scattered light, and the high-resolution CCD camera captures the laser speckle image generated during the far-field propagation of the coherent scattered light. Based on the mapping relationship between the sand and gravel morphology and the speckle image obtained by the calibration device, the morphology and particle size information of the sand and gravel are measured. By reading the area and position coordinates of the shadowed area in the speckle image, parameters such as the sand and gravel concentration distribution in the cross section are obtained. This solution includes a laser beam shaping optical path, which is relatively complex in arrangement. However, the pulsed laser source and shaping module can be arranged outside the airflow area of ​​the aero-engine inlet, which can avoid interference with the airflow. The far-field propagation characteristics of coherent scattered light can improve the measurement accuracy of small sand and gravel, and thus the high-resolution CCD camera can be installed at a distance far from the aero-engine inlet, minimizing the impact on the inlet airflow. Therefore, the present invention adopts the second technical solution.

[0073] The technical solution for measuring the dust concentration distribution at the inlet of an aero-engine using the aforementioned device is as follows:

[0074] The main steps for measuring the concentration distribution of sand and dust at the inlet of an aero-engine include: static calibration, constructing a sand and gravel morphology and particle size inversion model, measurement and debugging, sand ingestion environment simulation, image acquisition, and concentration distribution determination. Specifically, these steps are as follows:

[0075] A. Static calibration: Install two high-resolution CCD cameras with an industrial lens and a high-magnification topography observation lens, respectively. The optical axis of the industrial lens must be aligned with the central longitudinal axis of the airflow in the aero-engine intake. Using the optical axis of the industrial lens as a reference, tilt the optical axis of the high-magnification topography observation lens by 1-2° to ensure that the center of the imaging images of the two high-resolution CCD cameras is aligned with the same spatial area. Install the ultrasonic levitation stage 6 within the imaging focal plane of the high-resolution CCD camera, aligning the weightless zone of the ultrasonic levitation stage 6 with the center of the imaging area and the area irradiated by the sheet beam 7. The ultrasonic levitation stage 6 includes an upper ultrasonic levitation stage 16 and a lower ultrasonic levitation stage 17. Place sand grains of different morphologies / sizes multiple times in the weightless zone of the ultrasonic levitation stage 6 (i.e., between the upper ultrasonic levitation stage 16 and the lower ultrasonic levitation stage 17). Use the timing trigger controller 10 to control the high-resolution CCD camera to capture and save speckle images and high-resolution sand grain topography images.

[0076] B. Constructing a gravel morphology and particle size inversion model: First, using a calibration device, acquire gravel morphology images of different gravels and their corresponding laser speckle images, i.e., a gravel speckle-morphology database, to obtain the mapping relationship between gravel morphology and speckle images; second, based on the mapping relationship between gravel morphology and speckle images, develop a gravel speckle simulation calculation model based on ray tracing and laser speckle imaging theory; third, automatically generate a large number of gravel morphology images using the maximum inscribed rhombus method, i.e., an irregular gravel morphology dataset, and import it as input into the gravel speckle simulation calculation model. This gravel speckle simulation calculation model will output the corresponding speckle images, thus obtaining a large number of speckle images corresponding to the gravel morphology images, i.e., an irregular gravel speckle image dataset; then, use a deep learning network to train the irregular gravel speckle image dataset to establish a gravel morphology and particle size inversion model. The function of this gravel morphology and particle size inversion model is to process the input speckle images and directly output the corresponding gravel morphology and particle size information;

[0077] C. Measurement and Debugging: Following the requirement that the sheet-like laser beam 7 be perpendicular to the optical axis of the high-resolution CCD camera, the pulsed laser source and shaping module, along with the optical image acquisition module, are arranged separately in suitable locations. Specifically, the laser beam is emitted from the pulsed laser source, its polarization angle is adjusted by a zero-order waveplate, and its exit direction is adjusted by a mirror to align with the beam shaping section. The beam shaping section consists of a plano-convex cylindrical mirror and a plano-concave cylindrical mirror. The optical axis is located horizontally and vertically along the longitudinal axis of the aero-engine's airflow center. The laser beam is then... x Directional compression and yDirectional stretching is used to achieve the output of the sheet-like beam 7, while maintaining its uniform thickness within an area of ​​800mm in length. Specifically, the pulsed laser source and shaping module should ensure that the optical path is at least 50cm away from the aero-engine inlet airflow area, and the telephoto lens 28 of the high-resolution CCD camera in the optical image acquisition module is at least 120cm away from the aero-engine inlet section.

[0078] D. Sand ingestion environment simulation: After disassembling the calibration device, install the sand and dust supply and dispersion device, connect the required air pipeline and turn on the sand and dust supply and dispersion device. When the sand and dust flow steadily towards the inlet of the aero-engine with the airflow of the aero-engine, adjust the adjustment knob of the sand and dust supply and dispersion device and observe whether the response of the sand and dust supply and dispersion device is normal and whether the particle size of the outflowing sand and gravel changes. If everything is normal, keep the operation status.

[0079] E. Image acquisition: Adjust the experimental conditions according to the requirements of the sand swallowing experiment, and use the timing trigger controller 10 to control the sheet beam 7 and the high-resolution CCD camera under each experimental condition to capture and save the speckle image of the sand.

[0080] F. Concentration Distribution Measurement: The saved full-field speckle image of the aero-engine inlet section is imported into the inlet dust concentration measurement algorithm. The algorithm first segments the full-field speckle image to obtain speckle images of each gravel and saves them independently. Second, based on the gravel morphology and particle size inversion model, the two-dimensional morphology of each gravel is output. S Then, the algorithm for measuring the concentration of imported sand and dust is based on the basic geometric filling method, utilizing circles to represent two-dimensional morphology. S Fitting was performed, and the equivalent particle size was calculated. D i equivalent volume V i and equivalent quality m i Furthermore, a reference coordinate system was constructed based on the center position of the aero-engine inlet, and the speckle image was divided into grids according to this system, based on the maximum particle size observed in the experiment. D max Determine the grid size, and map the values ​​into the interval [0, 1] based on the number of gravels and equivalent mass in each grid (0 represents empty, 1 represents all gravels), thereby obtaining a statistical chart of the relative concentration of gravels.

[0081] Example 2

[0082] Reference Figure 1This invention proposes a device for measuring the concentration distribution of sand and dust at the inlet of an aero-engine, comprising a short-pulse low-frequency laser 1 (corresponding to the pulsed laser source in Embodiment 1), an air gap zero-order waveplate 2 (corresponding to the zero-order waveplate in Embodiment 1), a 532nm laser reflector 3 (corresponding to the reflector in Embodiment 1), a 532nm laser plano-convex cylindrical mirror 4 (corresponding to the plano-convex cylindrical mirror in Embodiment 1), a 532nm laser plano-concave cylindrical mirror 5 (corresponding to the plano-concave cylindrical mirror in Embodiment 1), a distributed optical acquisition unit 9, a timing trigger controller 10, and a computer 11.

[0083] Reference Figure 2 During the calibration test, an ultrasonic levitation stage 6, consisting of the upper part 16 and the lower part 17, was used to form an ultrasonic standing wave force field. Irregularly shaped gravel 14 (corresponding to the multi-morphological gravel in Example 1) was suspended in this ultrasonic standing wave force field and irradiated by a sheet beam 7 and an illumination source 15, respectively. A speckle image acquisition device 12 was used to acquire speckle images of the gravel generated by the sheet beam 7, and a gravel morphology acquisition device 13 was used to acquire gravel morphology images generated by the illumination source 15. The speckle images and morphology images of the same irregularly shaped gravel 14 were stored one-to-one in the computer 11 to obtain the mapping relationship between the gravel morphology and the speckle images.

[0084] Reference Figure 3 The distributed optical acquisition unit 9 includes a pressure plate 24, a support 25, a support rod 26, a distributed fixing bracket 27, a telephoto camera lens 28, a horizontal rotating bracket 29, a vertical rotating bracket 30, and a camera 31. Specifically, the distributed optical acquisition unit 9 includes four telephoto camera lenses 28 and four cameras 31, employing image stitching technology to achieve multi-camera coupling, thereby achieving the goal of covering the air intake duct of the aero-engine with a shooting area. The pressure plate 24, support 25, support rod 26, and distributed fixing bracket 27 are used to fix the aforementioned telephoto camera lenses 28 and cameras 31; the horizontal rotating bracket 29 and vertical rotating bracket 30 are used for fine-tuning the position of each telephoto camera lens 28 and camera 31.

[0085] Reference Figure 4The simulated harsh sand and dust environment 22 is generated by a sand and dust supply and dispersion device consisting of a sand and gravel storage tank 18, a sand and gravel conveying pipe 19, a sand and gravel fluidization section 20, and a sand and gravel dispersion pipe 21. Specifically, the sand and gravel in the sand and gravel storage tank 18 fall into the sand and gravel fluidization section 20 under the action of gravity, and after being mixed and fluidized with high-pressure air in the sand and gravel fluidization section 20, it flows through the sand and gravel conveying pipe 19, and is then sprayed out at the sand and gravel dispersion pipe 21, forming the harsh sand and dust environment 22. Furthermore, the measurement principle of the present invention can be summarized as follows: The sheet-like beam 7 is obtained by the shaping of a 532nm laser emitted by a short-pulse low-frequency laser 1 through optical elements such as an air gap zero-order waveplate 2, a 532nm laser reflector 3, a 532nm laser plano-convex cylindrical mirror 4, and a 532nm laser plano-concave cylindrical mirror 5. The sheet-like beam 7 is formed at the inlet 23 of the aero-engine. The sheet-like beam 7 irradiates the irregularly shaped sand and gravel 14 in the harsh sand and dust environment 22. The irregularly shaped sand and gravel 14 emits coherent scattered light 8 in all directions in space. The coherent scattered light 8 is collected by a distributed optical collector 9 fixed at the far field to obtain a laser speckle image. The speckle image is transmitted to a computer 11, and the built-in imported sand and dust concentration measurement algorithm is used to obtain the concentration data and concentration distribution of the local area in the harsh sand and dust environment 22.

[0086] Reference Figure 5 The implementation idea of ​​the gravel morphology and grain size inversion model is as follows:

[0087] a. Based on calibration experiments, a series of gravel morphology images and corresponding speckle images were obtained. A gravel speckle image-morphology database was established, and the mapping relationship between gravel morphology and speckle images was obtained based on the gravel speckle image-morphology database.

[0088] b. Import the gravel morphology image into the boundary recognition algorithm to read the morphology features, and import the morphology features as output into the gravel speckle simulation calculation model. Compare the simulation calculation results with the actual captured speckle image and verify the gravel speckle simulation calculation model.

[0089] c. A variety of irregularly shaped gravel morphology images are automatically generated using the maximum inscribed rhombus method, forming an irregularly shaped gravel morphology dataset. This dataset is then imported into a gravel speckle simulation model to obtain multiple sets of speckle images that correspond one-to-one with the gravel morphology images, forming an irregularly shaped gravel speckle image dataset. Using the speckle images from this dataset as input and the gravel morphology images as output, a deep learning network is used to train a gravel morphology and particle size inversion model. Specifically, the deep learning network employs cGAN (Conditional Generative Adversarial Network).

[0090] Reference Figure 6 The algorithm for measuring the concentration of imported sand and dust is implemented as follows:

[0091] The speckle images of the entire field acquired during the sand ingestion test are transmitted to computer 11 and imported into the inlet sand and dust concentration measurement algorithm. The inlet sand and dust concentration measurement algorithm first segments the entire field speckle images (i.e., image preprocessing), obtains speckle images of each sand grain, and saves them independently. Figure 6 middle( x 1, y 1), ( x 2, y 2), ( x 3, y 3) and ( x 4, y 4) The coordinates of the four gravels are given; secondly, based on the gravel morphology and grain size inversion model, the two-dimensional morphology of each gravel is output. S Then, the algorithm for measuring the concentration of imported sand and dust is based on the basic geometric filling method, utilizing circles to represent two-dimensional morphology. S Fitting was performed, and the equivalent particle size was calculated. D i ( D 1. D 2. D 3 and D 4 represents the equivalent particle size and equivalent volume of the four gravels. V i and equivalent quality m i Furthermore, a reference coordinate system was constructed based on the center position of the aero-engine inlet, and the speckle image was divided into grids according to this system, based on the maximum particle size observed in the experiment. D max Determine the grid size, and map the values ​​into the interval [0,1] based on the number of gravels and equivalent mass in each grid (0 represents empty, 1 represents all gravels), thereby obtaining a statistical chart of the relative concentration of gravels. The distribution of sand and dust concentration at the inlet of the aero-engine can be obtained from the statistical chart of the relative concentration of gravels.

[0092] Specifically, the method for measuring the dust concentration distribution at the inlet of an aero-engine, as proposed in this invention, taking a simulated harsh dust environment 22 in a laboratory as an example, uses the device involved in this invention to measure the dust concentration distribution, and includes the following specific steps:

[0093] (1) Static calibration: Install the speckle image acquisition device 12 and the gravel morphology acquisition device 13 with a small vertical tilt angle. The optical axis of the speckle image acquisition device 12 should be kept in conjunction with the central longitudinal axis of the airflow of the aero-engine. Using the optical axis of the speckle image acquisition device 12 as a reference, tilt the optical axis of the gravel morphology acquisition device 13 by about 1~2° to ensure that the center of the imaging screen of the speckle image acquisition device 12 and the gravel morphology acquisition device 13 is aligned with the same spatial area. Install the ultrasonic levitation stage 6 (composed of the upper part 16 and the lower part 17 of the ultrasonic levitation stage) in the imaging focal plane of the speckle image acquisition device 12 and the gravel morphology acquisition device 13, and align the center of the force field of the ultrasonic levitation stage 6 with the center of the imaging area and the area irradiated by the sheet beam 7. Different shaped gravel 14 with different morphologies / particle sizes are placed multiple times at the force field center of the ultrasonic suspension stage 6. A sheet beam 7 and an illumination source 15 (which cannot generate coherent scattered light) are used as light sources respectively. The timing trigger controller 10 controls the operation of the short pulse width low frequency laser 1, the speckle image acquisition device 12 and the gravel morphology acquisition device 13 to capture and save the gravel speckle image and the high resolution gravel morphology image.

[0094] (2) Constructing a gravel morphology and particle size inversion model: First, using a calibration device, gravel morphology images and corresponding speckle images of different gravels are obtained, i.e., a gravel speckle-morphology database, and then the mapping relationship between gravel morphology and speckle images is obtained; Second, based on the mapping relationship between gravel morphology and speckle images, a gravel speckle simulation calculation model based on ray tracing and laser speckle imaging theory is developed; Third, a large number of gravel morphology images are automatically generated using the maximum inscribed rhombus method, i.e., an irregular gravel morphology dataset, and it is used as input to the gravel speckle simulation calculation model. The gravel speckle simulation calculation model will output the corresponding speckle images, and thus a large number of speckle images corresponding to the gravel morphology images can be obtained, i.e., an irregular gravel speckle image dataset; Then, a deep learning network is used to train the irregular gravel speckle image dataset to establish a gravel morphology and particle size inversion model. The function of this gravel morphology and particle size inversion model is to process the input speckle images and directly output the corresponding gravel morphology and particle size information.

[0095] (3) Testing and debugging: Following the requirement that the optical axis of the sheet-like laser beam 7 be perpendicular to that of the distributed optical collector 9, the short-pulse low-frequency laser 1, the shaping module (composed of an air-gap zero-order waveplate 2, a 532nm laser reflector 3, a 532nm laser plano-convex cylindrical mirror 4, and a 532nm laser plano-concave cylindrical mirror 5), and the distributed optical collector 9 are arranged separately in suitable locations. Specifically, a circular laser beam is emitted from the short-pulse low-frequency laser 1, its polarization angle is adjusted by the air-gap zero-order waveplate 2, and its exit direction is adjusted by the 532nm laser reflector 3 to align with the beam shaping section. The beam shaping section consists of the 532nm laser plano-convex cylindrical mirror 4 and the 532nm laser plano-concave cylindrical mirror 5, and its optical axis is located in the horizontal and vertical direction of the longitudinal axis of the aero-engine intake airflow center. By adjusting the laser beam... x Directional compression and y Directional stretching is used to achieve the output of the sheet-like beam 7, while maintaining its uniform thickness within an 800mm length region. Specifically, the short-pulse-width low-frequency laser 1 and the shaping module should ensure that the optical path is at least 50cm away from the aero-engine inlet airflow area, and the distributed optical acquisition unit 9 in the optical image acquisition module is at least 150cm away from the aero-engine inlet cross-section.

[0096] (4) Simulate a harsh sand and dust environment 22: Install a sand and dust supply and dispersion device (composed of a sand and gravel storage tank 18, a sand and gravel conveying pipe 19, a sand and gravel fluidization section 20, a sand and gravel dispersion pipe 21, etc.), connect the required air pipeline and turn on the sand and dust supply and dispersion device, observe whether the sand and dust in the simulated harsh sand and dust environment 22 flows steadily towards the inlet of the aero-engine with the airflow of the aero-engine, and adjust the adjustment knob of the sand and dust supply and dispersion device, observe whether the response of the sand and dust supply and dispersion device is normal and whether the particle size of the outflowing sand and dust changes. If everything is normal, maintain the operation of the sand and dust supply and dispersion device.

[0097] (5) Adjust the experimental conditions, and under each experimental condition, use the timing trigger controller 10 to control the sheet beam 7 and the distributed optical collector 9 to capture and save the full-field speckle image of the aero-engine inlet section.

[0098] (6) Concentration distribution measurement: The saved full-field speckle image of the aero-engine inlet section is imported into the inlet dust concentration measurement algorithm. The inlet dust concentration measurement algorithm first segments the full-field speckle image to obtain speckle images of each gravel and saves them independently; secondly, based on the gravel morphology and particle size inversion model, the two-dimensional morphology of each gravel is output. S Then, the algorithm for measuring the concentration of imported sand and dust is based on the basic geometric filling method, utilizing circles to represent two-dimensional morphology. S Fitting was performed, and the equivalent particle size was calculated. D i equivalent volume Vi and equivalent quality m i Furthermore, a reference coordinate system was constructed based on the center position of the aero-engine inlet, and the speckle image was divided into grids according to this system, based on the maximum particle size observed in the experiment. D max Determine the grid size, and map the values ​​into the interval [0, 1] based on the number of gravel and equivalent mass in each grid (0 represents empty, 1 represents all gravel), thereby obtaining a statistical chart of the relative concentration of gravel. The distribution of sand and dust concentration at the inlet of the aero-engine can be obtained based on the statistical chart of the relative concentration of gravel.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit its scope of protection. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading the present invention, they can still make various changes, modifications or equivalent substitutions to the specific implementation of the invention, but these changes, modifications or equivalent substitutions are all within the scope of protection of the pending claims of the invention.

Claims

1. A device for measuring the concentration distribution of sand and dust at the inlet of an aircraft engine, characterized in that, Includes a pulsed laser source, a shaping module, an optical image acquisition module, and a data post-processing module: The pulsed laser source is placed at a preset position around the aero-engine to emit a laser beam, and the aero-engine is located in the sand and dust environment to be tested; The shaping module is used to receive the laser beam and output a sheet-like beam (7). The optical image acquisition module is used to receive coherent scattered light emitted by the sand and gravel in the area irradiated by the sheet beam (7), form a laser speckle image, and transmit the obtained laser speckle image to the data post-processing module. The data post-processing module uses an imported sand and dust concentration measurement algorithm to process the laser speckle image to obtain the sand and dust concentration distribution at the aero-engine inlet. The data post-processing module is a computer (11) with a built-in imported sand and dust concentration measurement algorithm. The imported sand and dust concentration measurement algorithm is as follows: The laser speckle image obtained in the actual scene is input into the pre-established sand and gravel morphology and particle size inversion model to obtain the morphology and particle size information of the sand and gravel. Based on the morphology and particle size information of the sand and gravel, the sand and gravel are modeled using basic geometric shapes and the equivalent mass is calculated. A reference coordinate system is constructed based on the center position of the aero-engine inlet. The laser speckle image is divided into grids according to the reference coordinate system. The grid size is determined according to the maximum particle size of the sand and gravel. The number of sand and gravel in each grid and the equivalent mass are converted into values ​​between 0 and 1, and then a statistical chart of the relative concentration of sand and gravel is obtained. The sand and dust concentration distribution at the aero-engine inlet is obtained from the statistical chart of the relative concentration of sand and gravel. The specific process for establishing the gravel morphology and grain size inversion model is as follows: A simulation calculation model for sand speckle is obtained based on the mapping relationship between the pre-acquired sand and gravel morphology and the laser speckle image; Several gravel morphology images were automatically generated using the maximum inscribed rhombus method, which served as an irregular gravel morphology dataset. The irregular gravel morphology dataset was then imported into the gravel speckle simulation model, and several laser speckle images corresponding to the gravel morphology images were output, resulting in an irregular gravel speckle image dataset. A deep learning network was used to train an image dataset of irregularly shaped gravel speckle to establish a gravel morphology and particle size inversion model.

2. The apparatus for measuring the concentration distribution of sand and dust at the inlet of an aircraft engine according to claim 1, characterized in that, The optical image acquisition module includes a distributed optical acquisition unit (9) and a timing trigger controller (10). The timing trigger controller (10) is used to control the distributed optical acquisition unit (9) to capture the coherent scattered light emitted by the sand and gravel to form a laser speckle image. The distributed optical acquisition unit (9) includes several cameras (31) and a telephoto camera lens (28) that works in conjunction with the cameras (31).

3. The apparatus for measuring the concentration distribution of sand and dust at the inlet of an aircraft engine according to claim 2, characterized in that, The shaping module includes a zero-order waveplate, a mirror, a plano-convex cylindrical mirror and a plano-concave cylindrical mirror arranged in sequence. The shaping module is used to make the plane of the sheet beam (7) perpendicular to the optical axis of the camera (31).

4. The apparatus for measuring the concentration distribution of sand and dust at the inlet of an aircraft engine according to claim 1, characterized in that, The mapping relationship between the gravel morphology and the laser speckle image is obtained by a calibration device, which includes an ultrasonic suspension stage (6), a speckle image acquisition device (12) and a gravel morphology acquisition device (13). The ultrasonic suspension stage is installed in the imaging focal plane of the speckle image acquisition device (12) and the gravel morphology acquisition device (13), and the force field center of the ultrasonic suspension stage is aligned with the center of the imaging area and the irradiation area of ​​the sheet beam (7). The ultrasonic levitation stage includes an upper part (16) and a lower part (17) of the ultrasonic levitation stage, and the upper part (16) and the lower part (17) of the ultrasonic levitation stage are used to suspend polymorphic gravel. Gravel morphology and speckle image are acquired by gravel morphology acquisition device (13) and speckle image acquisition device (12) respectively, and the mapping relationship between gravel morphology and speckle image is obtained.

5. A method for measuring the dust concentration distribution at the inlet of an aircraft engine, based on the apparatus for measuring the dust concentration distribution at the inlet of an aircraft engine as described in claim 1, characterized in that, The method includes the following steps: A laser beam is emitted by a pulsed laser source placed at a predetermined position around the aircraft engine under test; The laser beam is received by the shaping module and output as a sheet beam (7); The optical image acquisition module receives the coherent scattered light emitted by the sand and gravel in the area irradiated by the sheet beam (7) to form a laser speckle image, and transmits the obtained laser speckle image to the data post-processing module. The speckle image was processed by the data post-processing module to obtain the dust concentration distribution at the aero-engine inlet. The laser speckle image is processed by the data post-processing module to obtain the dust concentration distribution at the aero-engine inlet, specifically as follows: The laser speckle image obtained in the actual scene is input into the pre-established sand and gravel morphology and particle size inversion model to obtain the morphology and particle size information of the sand and gravel. Based on the morphology and particle size information of the sand and gravel, the sand and gravel are modeled using basic geometric shapes and the equivalent mass is calculated. A reference coordinate system is constructed based on the center position of the aero-engine inlet. The speckle image is divided into grids according to the reference coordinate system. The grid size is determined according to the maximum particle size of the sand and gravel. The number of sand and gravel in each grid and the equivalent mass are converted into values ​​between 0 and 1, and then a statistical chart of the relative concentration of sand and gravel is obtained. The sand and dust concentration distribution at the aero-engine inlet is obtained from the statistical chart of the relative concentration of sand and gravel. The specific process for establishing the gravel morphology and grain size inversion model is as follows: A simulation calculation model for sand speckle is obtained based on the mapping relationship between the pre-acquired sand and gravel morphology and the laser speckle image; Several gravel morphology images were automatically generated using the maximum inscribed rhombus method, which served as an irregular gravel morphology dataset. The irregular gravel morphology dataset was then imported into the gravel speckle simulation model, and several laser speckle images corresponding to the gravel morphology images were output, resulting in an irregular gravel speckle image dataset. A deep learning network was used to train an image dataset of irregularly shaped gravel speckle to establish a gravel morphology and particle size inversion model.

6. The method for measuring the dust concentration distribution at the inlet of an aircraft engine according to claim 5, characterized in that, The mapping relationship between the gravel morphology and the laser speckle image is obtained by a calibration device, which includes an ultrasonic suspension stage (6), a speckle image acquisition device (12) and a gravel morphology acquisition device (13). The ultrasonic suspension stage (6) is installed in the imaging focal plane of the speckle image acquisition device (12) and the gravel morphology acquisition device (13), and the force field center of the ultrasonic suspension stage is aligned with the center of the imaging area and the irradiation area of ​​the sheet beam (7). The ultrasonic suspension stage (6) includes an upper part (16) and a lower part (17) of the ultrasonic suspension stage, and the upper part (16) and the lower part (17) of the ultrasonic suspension stage are used to suspend polymorphic gravel. Gravel morphology and speckle image are acquired by gravel morphology acquisition device (13) and speckle image acquisition device (12) respectively, and the mapping relationship between gravel morphology and speckle image is obtained.

Images