High speed engine blade deformation measurement system and method for wind tunnel test

Abstract

The high-speed engine blade deformation measurement system and measurement method for wind tunnel test belong to the technical field of full-surface deformation measurement of engine blades. In order to realize the full-surface deformation measurement of blades, the present invention includes a first imaging device and a second imaging device connected to a digital pulse signal delay generator and a computer respectively, the digital pulse signal delay generator is connected to a laser, the laser is connected to a beam expander, the beam expander is connected to an optical fiber image transmission bundle, and the optical fiber image transmission bundle is connected to a zoom lens; the beam expander, the optical fiber image transmission bundle, and the zoom lens constitute a laser homogenization device, and the laser emitted by the zoom lens is irradiated onto the blades and the fairing; the first imaging device and the second imaging device are aligned with the position where the laser irradiates the high-speed engine blades to shoot. The present invention significantly improves the measurement accuracy and the comprehensiveness of the data, and improves the overall performance and reliability of the engine.

Description

Technical Field

[0001] The invention belongs to the technical field of full-surface deformation measurement of engine blades, and in particular relates to a deformation measurement system and a measurement method for high-speed engine blades used in wind tunnel tests. Background Art

[0002] High-speed engines are core components in modern aviation, aerospace and industrial fields, directly affecting the performance and reliability of aircraft and industrial equipment. Engine blades are subjected to complex stresses and deformations under high speed and high temperature conditions, and these deformations are directly related to the efficiency, stability and life of the engine. Accurately measuring and analyzing blade deformation is of great significance for optimizing blade design, improving material selection and improving overall engine performance. With the development of aerospace technology, engine blade materials have gradually evolved from traditional metal materials to advanced composite materials. These new materials have higher strength, high temperature resistance and corrosion resistance, but they also bring new measurement challenges. Accurate measurement of blade deformation is crucial to verify the performance of new materials and improve their application technology.

[0003] Wind tunnel testing is a key experimental method for studying the aerodynamic performance of aircraft and the dynamic behavior of engine blades. In wind tunnel testing, engine blades operate under high airflow speeds and complex aerodynamic environments to simulate actual flight conditions. Measuring the deformation of blades in wind tunnel testing can provide real engineering data, guide blade design and improvement, and ensure its reliability and safety in actual flight. Therefore, it is particularly important to develop a deformation measurement method for high-speed engine blades suitable for wind tunnel testing.

[0004] The traditional strain gauge method measures the strain generated during operation by pasting strain gauges on the surface of the blade. However, due to the need for precise pasting and wiring, the installation is complicated, the surface treatment of the blade is required, and only local measurements can be performed. It is impossible to obtain deformation information on the entire surface of the blade, and it is easy to be damaged in high temperature and high-speed airflow environments. Traditional optical measurement methods, such as the optical method with added marking points, measure deformation by arranging marking points on the surface of the blade and using an optical system to track the position changes of the marking points. The number of marking points is sparse and cannot reflect the deformation of the entire surface of the blade with complex shapes, resulting in incomplete data and low data analysis. When rotating at high speed, motion blur occurs, which will also seriously affect the data quality.

[0005] In summary, the traditional blade deformation measurement method has many limitations in high-speed and wind tunnel test environments. Therefore, the development of new methods suitable for high-speed engine blade deformation measurement is of great significance for improving measurement accuracy, obtaining comprehensive deformation data, optimizing blade design and improving engine performance. Summary of the invention

[0006] The problem to be solved by the present invention is to realize the deformation measurement of the entire surface of a blade, and a deformation measurement system and a measurement method for a high-speed engine blade used in a wind tunnel test are proposed.

[0007] To achieve the above object, the present invention is implemented through the following technical solutions:

[0008] A high-speed engine blade deformation measurement system for wind tunnel testing, comprising a first imaging device, a second imaging device, a digital pulse signal delay generator, a laser, a beam expander, an optical fiber image transmission bundle, a zoom lens, and a computer;

[0009] The first imaging device and the second imaging device are connected to a digital pulse signal delay generator and a computer respectively, the digital pulse signal delay generator is connected to a laser, the laser is connected to a beam expander, the beam expander is connected to an optical fiber image transmission bundle, and the optical fiber image transmission bundle is connected to a zoom lens;

[0010] The beam expander, the optical fiber image transmission bundle, and the zoom lens constitute a laser homogenization device, and the laser emitted by the zoom lens irradiates the blades and the fairing;

[0011] The first imaging device and the second imaging device are aimed at the position where the laser is irradiated to the high-speed engine blades to take pictures.

[0012] Furthermore, the first imaging device and the second imaging device are composed of a camera, a lens and a filter.

[0013] Furthermore, the blade surface is provided with speckle dots based on fluorescent dyes and positioning mark points based on matte paint, the diameter of the speckle dots in the image is set to 3-4 pixels, the diameter of the positioning mark points in the image is set to 8-10 pixels, and the number of the positioning mark points is 12-18.

[0014] A method for measuring deformation of a high-speed engine blade for a wind tunnel test is implemented based on the high-speed engine blade deformation measurement system for a wind tunnel test, and comprises the following steps:

[0015] S1. Surface treatment is performed on the blade and the fairing, and positioning marking points based on fluorescent dyes and matte paint are set on the surface of the blade, and registration marking points based on fluorescent dyes are arranged on the surface of the fairing;

[0016] S2. Building a high-speed engine blade deformation measurement system for wind tunnel testing, first determining the position of the photographed blade, installing a first imaging device, a second imaging device, and a laser according to the position, and adjusting the optical path so that the laser emits laser light to illuminate the area to be measured;

[0017] S3. Timing adjustment: through the digital pulse signal delay generator, phase-locking is performed according to the signal returned by the motor encoder to control the laser light emission, the first imaging device, and the second imaging device to collect data, so that the first imaging device and the second imaging device collect the leaves at the same position, and at the same time ensure that the laser light emission is within the exposure time of the first imaging device and the second imaging device;

[0018] S4. Obtaining camera parameters: placing checkerboard calibration plates at different locations in the test area, and solving the camera internal and external parameters based on Zhang's calibration method;

[0019] S5. Collecting blade images when there is no wind and no speed and blade images during the test;

[0020] S6. Data processing, based on the blade image collected in step S5, obtain the three-dimensional coordinates of the scattered spots on the blade surface in the camera coordinate system in the windless and speedless state and the test state;

[0021] S7. Ground three-dimensional coordinate mapping, measuring the three-dimensional coordinates of the positioning points of the blade in the ground coordinate system;

[0022] S8. Deformation calculation: calculate the deformation of the blade in the ground coordinate system.

[0023] Furthermore, the specific implementation method of step S3 includes the following steps:

[0024] S3.1. Every time the blade rotates one circle, the motor encoder returns a phase-locked control signal and sets the delay. , so that the blade in the image currently captured by the camera is in the measurement position, and the laser emission time is , illuminating the speckle area on the target leaf, the lifetime of the fluorescent dye rhodamine is , the time the speckle is illuminated is + ; Set the time the speckle is illuminated within the camera exposure time To achieve effective lighting;

[0025] S3.2. The camera delay from the time the camera is triggered to the time the camera is captured is , the camera is triggered earlier than the laser emits light The timing control ensures that each image collected during the experiment is of the same leaf and in the same position.

[0026] Furthermore, step S4 solves the camera intrinsic parameters based on Zhang's calibration method. , external parameters ;

[0027] in, is the focal length in the u and v directions, is the radial distortion parameter, is the image principal point coordinate, R and t They are the rotation matrix and translation vector from the world coordinate system to the camera coordinate system respectively.

[0028] Furthermore, the specific implementation method of step S5 includes the following steps:

[0029] S5.1. When the distortion of the images from the two camera perspectives is not affected, collect the image from the perspective of the first imaging device when there is no wind and no speed. and the image from the perspective of the second imaging device ;

[0030] S5.2. In the wind tunnel test, first reach the test condition, and after the blade speed stabilizes, adjust the , the position of the blade captured by the real-time image display is the same as the blade position captured when there is no wind and no speed, and the degree of distortion of the imaging under the two camera perspectives is not affected, and then the image sequence under the perspective of the first imaging device is collected and the sequence from the perspective of the second imaging device , n is the number of images collected.

[0031] Furthermore, the specific implementation method of step S6 includes the following steps:

[0032] S6.1. Extract the image coordinate sequence of blade positioning mark points of the image collected by the first imaging device when there is no wind and no speed by artificial selection or by combining image binarization with contour extraction , the image coordinate sequence of the registration mark points on the fairing of the image collected by the first imaging device ;

[0033] Then, based on the image cross-correlation method, , Obtain the image coordinate sequence of the leaf positioning mark points of the image collected by the second imaging device , the image coordinate sequence of the registration mark points on the fairing of the image collected by the second imaging device ;

[0034] A maximum bounding rectangle is artificially drawn for the leaf region in the image under the viewing angle of the first imaging device, and an equidistant rectangular grid G ​​is defined based on the rectangle, and a mask M is determined for the leaf region to distinguish the model region from the non-model region in the bounding rectangle. = ,set up for The image is 1 i m, 1 j n ;

[0035] According to M, the grid points in G that are not in the leaf area are deleted to obtain the image coordinates of the speckle grid points under the viewing angle of the first imaging device only in the leaf area. ;

[0036] Assume that the image coordinates of the speckle grid points under the viewing angle of the second imaging device are , aligning the speckle on the leaf at the viewing angle of the second imaging device to the speckle on the leaf at the viewing angle of the first imaging device, and obtaining a transformation relationship between the speckle on the leaf at the viewing angle of the second imaging device and the speckle on the leaf at the viewing angle of the first imaging device through a cubic polynomial transformation;

[0037] set up for The image coordinates of any point in for The neutralization point P is the image coordinate of the same-named marking point. Then, the expression for aligning the speckle on the leaf under the viewing angle of the second imaging device to the leaf under the viewing angle of the first imaging device is:

[0038] + + + ;

[0039] + + + ;

[0040] in, for The i-th coefficient of the polynomial, i=0,1…9, for The i-th transformation coefficient of the polynomial, i=0,1…9;

[0041] Will and Substitute into the expression for realizing the alignment of the speckle on the leaf under the perspective of the second imaging device to the leaf under the perspective of the first imaging device, and solve the equation group to obtain the aligned image , the image cross-correlation method can be used to obtain The speckle grid image coordinates , then The inverse transformation of the cubic polynomial can accurately obtain the speckle grid point image coordinates of the leaf area under the perspective of the second imaging device. ;

[0042] Then, according to the internal and external parameters obtained in step S4 and the above-mentioned image coordinates, the three-dimensional coordinates of the positioning mark point on the blade in the camera coordinate system when there is no wind and no speed are obtained. , the three-dimensional coordinates of the registration mark points on the fairing in the camera coordinate system , the three-dimensional coordinates of the speckle on the blade in the camera coordinate system ;

[0043] S6.2. Obtain the three-dimensional coordinates of the positioning mark points on the blade, the registration mark points on the fairing, and the speckle on the blade in the camera coordinate system during the test;

[0044] Image coordinates of the registration mark points on the fairing on the blade under the viewing angles of the first imaging device and the second imaging device during the test , Combined with image correlation technology , , , Then, the image coordinates of the positioning mark points on the fairing on the blade under the perspective of the first imaging device and the second imaging device during the test are obtained. , ;

[0045] Assume that the speckle grid image coordinates of the image under the viewing angle of the first imaging device during the experiment are ,Considering that the image distortion is consistent under the same camera perspective, the image during the test is aligned to the image when there is no wind and no speed through the affine transformation method;

[0046] According to step S6.1 The image coordinates of any point in ,set up for The image coordinates of the same-named marked points in the test image are completed by the following formula: The alignment expression is:

[0047] ;

[0048] Among them, af is the transformation coefficient to be solved. and Substituting into the above formula, we can solve the equation system and get;

[0049] After the radiometric transformation, the aligned image is obtained. , based on the image cross-correlation method The speckle grid image coordinates , then Perform the inverse transformation of the cubic polynomial to obtain ; Similarly, the speckle grid image coordinates of the image under the viewing angle of the second imaging device are obtained ;

[0050] Then, according to the camera parameters obtained in step S4 and the above-mentioned image coordinates, the three-dimensional coordinates of the positioning mark point on the blade in the camera coordinate system, the three-dimensional coordinates of the registration mark point on the fairing in the camera coordinate system, and the three-dimensional coordinates of the speckle on the blade in the camera coordinate system are obtained during the test;

[0051] Then, for the image sequence under the viewing angle of the first imaging device and the image sequence from the perspective of the second imaging device All images in the above method are used to obtain the three-dimensional coordinates of the positioning mark points, registration mark points, and speckle, and then summed and averaged respectively to obtain the three-dimensional coordinates of the positioning mark points on the leaves in the final test under the camera coordinates. , the three-dimensional coordinates of the registration mark points on the fairing in the camera coordinates , the three-dimensional coordinates of the speckle on the blade in the camera coordinate system ;

[0052] S6.3. Registration. Considering that the rotation of the fairing conforms to the rigid body transformation, the registration mark points arranged on the fairing are used to eliminate the deviation of the blades in the windless and non-rotating speed and the phase during the test caused by the system and manual determination of the blade position. According to the Kabsch algorithm, calculate The rotation and translation transformation relationship , then the expression of the three-dimensional coordinates of the speckle after blade registration during the test is:

[0053] = ;

[0054] The three-dimensional coordinates of the speckle pattern are obtained when the blade is in phase with that in the test and when there is no wind and no speed.

[0055] Furthermore, the specific implementation method of step S7 is to use a three-dimensional coordinate measuring machine, calibrate and set it, place the blade firmly on the measuring platform to ensure that it does not move during the measurement process, use the measuring probe to touch the positioning mark points on the blade one by one, and record its coordinate data in three-dimensional space. , and then measure the three-dimensional coordinates of the positioning calibration points on the blade in the ground coordinate system.

[0056] Furthermore, the specific implementation method of step S8 includes the following steps:

[0057] S8.1. First, the three-dimensional coordinates of all scattered spots need to be converted into the blade numerical model coordinate system. According to the Kabsch algorithm, the The rotation and translation transformation relationship ;

[0058] Then the three-dimensional coordinates of the blade speckle in the ground coordinate system when there is no wind and no speed are: = , and then calculate the three-dimensional coordinates of the blade speckle in the ground coordinate system during the test ;

[0059] S8.2. Subtract the three-dimensional coordinates of the blade speckle in the ground coordinate system when there is no wind and no speed from the three-dimensional coordinates of the blade speckle in the ground coordinate system during the test to obtain the deformation of the blade in the ground coordinate system;

[0060] S8.3. Construct a triangular mesh for the speckled cloud based on the triangulation and display it as a map.

[0061] Beneficial effects of the present invention:

[0062] The method for measuring deformation of high-speed engine blades for wind tunnel tests described in the present invention is based on a binocular vision three-dimensional reconstruction method, and realizes transient high-definition imaging by exciting speckles prepared by fluorescent dyes; accurately aligns the blade phase based on the alignment mark points on the fairing, and uses the positioning mark points on the blades for three-coordinate mapping, establishes a transformation relationship from the camera coordinate system to the ground coordinate system, and realizes accurate measurement of the full surface of the high-speed blade, which is beneficial to the subsequent design analysis and shape structure optimization of the blade;

[0063] The method for measuring deformation of high-speed engine blades for wind tunnel testing described in the present invention solves the problems of traditional strain gauge methods and optical measurement methods that are easy to damage in high-temperature and high-speed airflow environments, are complex to install, have partial measurements and incomplete data, and have motion blur. Ultimately, the full-surface deformation data of the blades under actual working conditions is obtained, which significantly improves the measurement accuracy and comprehensiveness of the data, lays a foundation for subsequent blade design optimization, and improves the overall performance and reliability of the engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 It is a structural schematic diagram of a high-speed engine blade deformation measurement system for wind tunnel testing according to the present invention;

[0065] Figure 2 It is a schematic diagram of the timing control relationship of the present invention;

[0066] Figure 3 It is a partial enlarged schematic diagram of the timing control relationship of the present invention;

[0067] Figure 4 The present invention provides a flow chart of a method for measuring deformation of high-speed engine blades for wind tunnel testing. DETAILED DESCRIPTION

[0068] In order to make the purpose, technical solution and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the specific embodiments described are only part of the embodiments of the present invention, rather than all of the specific embodiments. The components of the specific embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations, and the present invention can also have other embodiments.

[0069] Therefore, the following detailed description of the specific embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents the selected specific embodiments of the present invention. Based on the specific embodiments of the present invention, all other specific embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0070] In order to further understand the content, features and effects of the present invention, the following specific implementation methods are given as examples, and the attached Figure 1 -Attached Figure 4 The detailed instructions are as follows:

[0071] Embodiment 1:

[0072] A high-speed engine blade deformation measurement system for wind tunnel testing, comprising a first imaging device 1, a second imaging device 2, a digital pulse signal delay generator 3, a laser 4, a beam expander 5, an optical fiber image transmission bundle 6, a zoom lens 7, and a computer 8;

[0073] The first imaging device 1 and the second imaging device 2 are connected to a digital pulse signal delay generator 3 and a computer 8 respectively, the digital pulse signal delay generator 3 is connected to a laser 4, the laser 4 is connected to a beam expander 5, the beam expander 5 is connected to an optical fiber image transmission bundle 6, and the optical fiber image transmission bundle 6 is connected to a zoom lens 7;

[0074] The beam expander 5, the optical fiber image transmission bundle 6, and the zoom lens 7 constitute a laser homogenization device, and the laser emitted by the zoom lens 7 irradiates the blades 9 and the fairing 10;

[0075] The first imaging device 1 and the second imaging device 2 aim at the position where the laser irradiates the high-speed engine blade 9 to take a picture.

[0076] Furthermore, the first imaging device 1 and the second imaging device 2 are composed of a camera, a lens and a filter.

[0077] Furthermore, the surface of the blade 9 is provided with speckle dots based on fluorescent dye and positioning mark points based on matte paint, the diameter of the speckle dots in the image is set to 3-4 pixels, the diameter of the positioning mark points in the image is set to 8-10 pixels, and the number of the positioning mark points is 12-18.

[0078] Embodiment 2:

[0079] A method for measuring deformation of a high-speed engine blade for a wind tunnel test is implemented based on a system for measuring deformation of a high-speed engine blade for a wind tunnel test described in Example 1, and includes the following steps:

[0080] S1. Surface treatment is performed on the blade and the fairing, and positioning marking points based on fluorescent dyes and matte paint are set on the surface of the blade, and registration marking points based on fluorescent dyes are arranged on the surface of the fairing;

[0081] Furthermore, firstly, alcohol is used to clean the surface of the model to ensure that there is no oil on the surface, then a layer of white primer is evenly sprayed on the surface of the blade to be tested and the surface of the fairing, and then a hollow speckle mask sticker is used to fit the blade surface, and a hollow dot mask sticker is used to fit the fairing, and a fluorescent dye (preferably a fluorescent solvent made of rhodamine dye and alcohol) is evenly brushed on the surface of the blade and the fairing. After the dye dries naturally, the hollow speckle mask sticker and the hollow dot sticker are torn off to complete the preparation of the blade surface speckle and fairing registration mark points based on the fluorescent dye. Then, black matte paint is used to prepare positioning mark points on the blade surface, and the mark points are evenly distributed on the blade surface.

[0082] Furthermore, the diameter of the speckle dots in the image is 3-4 pixels; the diameter of the positioning mark points in the image is 8-10 pixels; the number of positioning mark points is 12-18;

[0083] S2. Building a high-speed engine blade deformation measurement system for wind tunnel testing, first determining the position of the photographed blade, installing a first imaging device, a second imaging device, and a laser according to the position, and adjusting the optical path so that the laser emits laser light to illuminate the area to be measured;

[0084] Furthermore, firstly, according to CATIA software, a real shooting environment is simulated, and under the premise of ensuring that the two cameras shoot the blades as completely as possible, the distance between the two cameras and the shooting blades, the corresponding angles of the two cameras, and the approximate positions of the two cameras are determined. The field of view of the shooting should cover the blade to be measured, as well as the fairing part on the same side of the blade. A suitable camera lens is selected according to the field of view of the shooting and the shooting distance. Considering that the present invention uses a laser for lighting, it is necessary to install a suitable filter on the camera lens to filter stray light.

[0085] In order to obtain a uniform and appropriately sized laser area, the laser is first made uniform during transmission through the mixing effect of multiple optical fibers in the fiber optic image transmission bundle, and then the divergence angle and focus position of the laser beam are controlled through a zoom lens to adjust the size of the laser area to an appropriate size.

[0086] S3. Timing adjustment: through the digital pulse signal delay generator, phase-locking is performed according to the signal returned by the motor encoder to control the laser light emission, the first imaging device, and the second imaging device to collect data, so that the first imaging device and the second imaging device collect the leaves at the same position, and at the same time ensure that the laser light emission is within the exposure time of the first imaging device and the second imaging device;

[0087] Furthermore, the specific implementation method of step S3 includes the following steps:

[0088] S3.1. Every time the blade rotates one circle, the motor encoder returns a phase-locked control signal and sets the delay. , so that the blade in the image currently captured by the camera is in the measurement position, and the laser emission time is , illuminating the speckle area on the target leaf, the lifetime of the fluorescent dye rhodamine is , the time the speckle is illuminated is + ; Set the time the speckle is illuminated within the camera exposure time To achieve effective lighting;

[0089] Further, the blade is in the measurement position where the blade is least obscured in both camera viewing angles;

[0090] S3.2. The camera delay from the time the camera is triggered to the time the camera is captured is , the camera is triggered earlier than the laser emits light The timing control ensures that each image collected during the experiment is of the same leaf and in the same position;

[0091] S4. Obtaining camera parameters: placing checkerboard calibration plates at different locations in the test area, and solving the camera internal and external parameters based on Zhang's calibration method;

[0092] Furthermore, step S4 solves the camera intrinsic parameters based on Zhang's calibration method. , external parameters ;

[0093] in, is the focal length in the u and v directions, is the radial distortion parameter, is the image principal point coordinate, R and tThey are the rotation matrix and translation vector from the world coordinate system to the camera coordinate system respectively;

[0094] S5. Collecting blade images when there is no wind and no speed and blade images during the test;

[0095] Furthermore, the specific implementation method of step S5 includes the following steps:

[0096] S5.1. When the distortion of the images from the two camera perspectives is not affected, collect the image from the perspective of the first imaging device when there is no wind and no speed. and the image from the perspective of the second imaging device ;

[0097] Furthermore, through real-time image display, the rotor blades are manually adjusted to the appropriate position to ensure that the blades are not obscured as much as possible under the two camera viewing angles and the degree of image distortion is minimized.

[0098] S5.2. In the wind tunnel test, first reach the test condition, and after the blade speed stabilizes, adjust the , the position of the blade captured by the real-time image display is the same as the blade position captured when there is no wind and no speed, and the degree of distortion of the imaging under the two camera perspectives is not affected, and then the image sequence under the perspective of the first imaging device is collected and the sequence from the perspective of the second imaging device , n is the number of images collected;

[0099] S6. Data processing, based on the blade image collected in step S5, obtain the three-dimensional coordinates of the blade spots in the camera coordinate system in the windless and speedless state and the test state;

[0100] Furthermore, the specific implementation method of step S6 includes the following steps:

[0101] S6.1. Extract the image coordinate sequence of blade positioning mark points of the image collected by the first imaging device when there is no wind and no speed by artificial selection or by combining image binarization with contour extraction , the image coordinate sequence of the registration mark points on the fairing of the image collected by the first imaging device ;

[0102] Then, based on the image cross-correlation method, , Obtain the image coordinate sequence of the leaf positioning mark points of the image collected by the second imaging device , the image coordinate sequence of the registration mark points on the fairing of the image collected by the second imaging device ;

[0103] A maximum bounding rectangle is artificially drawn for the leaf region in the image under the viewing angle of the first imaging device, and an equidistant rectangular grid G ​​is defined based on the rectangle, and a mask M is determined for the leaf region to distinguish the model region from the non-model region in the bounding rectangle. = ,set up for The image is 1 i m, 1 j n ;

[0104] According to M, the grid points in G that are not in the leaf area are deleted to obtain the image coordinates of the speckle grid points under the viewing angle of the first imaging device only in the leaf area. ;

[0105] Assume that the image coordinates of the speckle grid points under the viewing angle of the second imaging device are , aligning the speckle on the leaf at the viewing angle of the second imaging device to the speckle on the leaf at the viewing angle of the first imaging device, and obtaining a transformation relationship between the speckle on the leaf at the viewing angle of the second imaging device and the speckle on the leaf at the viewing angle of the first imaging device through a cubic polynomial transformation;

[0106] set up for The image coordinates of any point in for The neutralization point P is the image coordinate of the same-named marking point. Then, the expression for aligning the speckle on the leaf under the viewing angle of the second imaging device to the leaf under the viewing angle of the first imaging device is:

[0107] + + + ;

[0108] + + + ;

[0109] in, for The i-th coefficient of the polynomial, i=0,1…9, for The i-th transformation coefficient of the polynomial, i=0,1…9;

[0110] Will and Substitute into the expression for realizing the alignment of the speckle on the leaf under the perspective of the second imaging device to the leaf under the perspective of the first imaging device, and solve the equation group to obtain the aligned image , the image cross-correlation method can be used to obtain The speckle grid image coordinates , then The inverse transformation of the cubic polynomial can accurately obtain the speckle grid point image coordinates of the leaf area under the perspective of the second imaging device. ;

[0111] Then, according to the internal and external parameters obtained in step S4 and the above-mentioned image coordinates, the three-dimensional coordinates of the positioning mark point on the blade in the camera coordinate system when there is no wind and no speed are obtained. , the three-dimensional coordinates of the registration mark points on the fairing in the camera coordinate system , the three-dimensional coordinates of the speckle on the blade in the camera coordinate system ;

[0112] S6.2. Obtain the three-dimensional coordinates of the positioning mark points on the blade, the registration mark points on the fairing, and the speckle on the blade in the camera coordinate system during the test;

[0113] Image coordinates of the registration mark points on the fairing on the blade under the viewing angles of the first imaging device and the second imaging device during the test , Combined with image correlation technology , , , Then, the image coordinates of the positioning mark points on the fairing on the blade under the perspective of the first imaging device and the second imaging device during the test are obtained. , ;

[0114] Assume that the speckle grid image coordinates of the image under the viewing angle of the first imaging device during the experiment are ,Considering that the image distortion is consistent under the same camera perspective, the image during the test is aligned to the image when there is no wind and no speed through the affine transformation method;

[0115] According to step S6.1 The image coordinates of any point in ,set up for The image coordinates of the same-named marked points in the test image are completed by the following formula: The alignment expression is:

[0116] ;

[0117] Among them, af is the transformation coefficient to be solved. and Substituting into the above formula, we can solve the equation system and get;

[0118] After the radiometric transformation, the aligned image is obtained , based on the image cross-correlation method The speckle grid image coordinates , then Perform the inverse transformation of the cubic polynomial to obtain ; Similarly, the speckle grid image coordinates of the image under the viewing angle of the second imaging device are obtained ;

[0119] Then, according to the camera parameters obtained in step S4 and the above-mentioned image coordinates, the three-dimensional coordinates of the positioning mark point on the blade in the camera coordinate system, the three-dimensional coordinates of the registration mark point on the fairing in the camera coordinate system, and the three-dimensional coordinates of the speckle on the blade in the camera coordinate system are obtained during the test;

[0120] Then, for the image sequence under the viewing angle of the first imaging device and the image sequence from the perspective of the second imaging device All images in the above method are used to obtain the three-dimensional coordinates of the positioning mark points, registration mark points, and speckle, and then summed and averaged respectively to obtain the three-dimensional coordinates of the positioning mark points on the leaves in the final test under the camera coordinates. , the three-dimensional coordinates of the registration mark points on the fairing in the camera coordinates , the three-dimensional coordinates of the speckle on the blade in the camera coordinate system ;

[0121] S6.3. Registration. Considering that the rotation of the fairing conforms to the rigid body transformation, the registration mark points arranged on the fairing are used to eliminate the deviation of the blades in the windless and non-rotating speed and the phase during the test caused by the system and manual determination of the blade position. According to the Kabsch algorithm, calculate The rotation and translation transformation relationship , then the expression of the three-dimensional coordinates of the speckle after blade registration during the test is:

[0122] = ;

[0123] The three-dimensional coordinates of the speckle pattern are obtained when the blade is in phase with that in the test and when there is no wind and no speed.

[0124] S7. Ground three-dimensional coordinate mapping, measuring the three-dimensional coordinates of the positioning points of the blade in the ground coordinate system;

[0125] Furthermore, the specific implementation method of step S7 is to use a three-dimensional coordinate measuring machine, calibrate and set it, place the blade firmly on the measuring platform to ensure that it does not move during the measurement process, use the measuring probe to touch the positioning mark points on the blade one by one, and record its coordinate data in three-dimensional space. , and then measure the three-dimensional coordinates of the positioning calibration points on the blade in the ground coordinate system;

[0126] S8. Deformation calculation, calculating the deformation of the blade in the ground coordinate system;

[0127] Furthermore, the specific implementation method of step S8 includes the following steps:

[0128] S8.1. First, the three-dimensional coordinates of all scattered spots need to be converted into the blade numerical model coordinate system. According to the Kabsch algorithm, the The rotation and translation transformation relationship ;

[0129] Then the three-dimensional coordinates of the blade speckle in the ground coordinate system when there is no wind and no speed are: = , and then calculate the three-dimensional coordinates of the blade speckle in the ground coordinate system during the test ;

[0130] S8.2. Subtract the three-dimensional coordinates of the blade speckle in the ground coordinate system when there is no wind and no speed from the three-dimensional coordinates of the blade speckle in the ground coordinate system during the test to obtain the deformation of the blade in the ground coordinate system;

[0131] S8.3. Construct a triangular mesh for the speckled cloud based on the triangulation and display it as a map.

[0132] It should be noted that relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0133] Although the present application has been described above with reference to specific embodiments, various modifications may be made thereto and parts thereof may be replaced with equivalents without departing from the scope of the present application. In particular, as long as there is no structural conflict, the various features in the specific embodiments disclosed in the present application may be used in combination with each other in any manner, and the fact that these combinations are not exhaustively described in this specification is only for the sake of omitting space and saving resources. Therefore, the present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for measuring deformation of a high-speed engine blade for a wind tunnel test, which is implemented by a system for measuring deformation of a high-speed engine blade for a wind tunnel test, comprising a first imaging device (1), a second imaging device (2), a digital pulse signal delay generator (3), a laser (4), a beam expander (5), an optical fiber image transmission bundle (6), a zoom lens (7), and a computer (8); The first imaging device (1) and the second imaging device (2) are connected to a digital pulse signal delay generator (3) and a computer (8) respectively; the digital pulse signal delay generator (3) is connected to a laser (4); the laser (4) is connected to a beam expander (5); the beam expander (5) is connected to an optical fiber image transmission bundle (6); and the optical fiber image transmission bundle (6) is connected to a zoom lens (7); The beam expander (5), the optical fiber image transmission bundle (6), and the zoom lens (7) constitute a laser homogenization device, and the laser emitted by the zoom lens (7) is irradiated onto the blades (9) and the fairing (10); The first imaging device (1) and the second imaging device (2) are aligned with the position where the laser irradiates the high-speed engine blade (9) to take a picture; The first imaging device (1) and the second imaging device (2) are composed of a camera, a lens and a filter; The surface of the blade (9) is provided with speckle dots based on fluorescent dye and positioning mark points based on matte paint, the diameter of the speckle dots in the image is set to 3-4 pixels, the diameter of the positioning mark points in the image is set to 8-10 pixels, and the number of the positioning mark points is 12-18; It is characterized in that The steps include: S1. Surface treatment is performed on the blade and the fairing, and positioning marking points based on fluorescent dyes and matte paint are set on the blade surface, and registration marking points based on fluorescent dyes are arranged on the fairing surface; S2. Build the high-speed engine blade deformation measurement system for wind tunnel test, first determine the position of the photographed blade, install the first imaging device, the second imaging device, and the laser according to the position, and adjust the optical path so that the laser emits laser to illuminate the area to be measured; S3. Timing adjustment: through the digital pulse signal delay generator, phase locking is performed according to the signal returned by the motor encoder to control the laser light emission, the first imaging device, and the second imaging device to collect, so that the first imaging device and the second imaging device collect the leaves at the same position, and at the same time ensure that the laser light emission is within the exposure time of the first imaging device and the second imaging device; S4. Obtaining camera parameters: placing checkerboard calibration plates at different locations in the area to be tested, and solving the camera internal and external parameters based on Zhang's calibration method; S5. Collecting blade images when there is no wind and no speed and blade images during the test; S6. Data processing, based on the blade image acquired in step S5, obtain the three-dimensional coordinates of the blade scattered spots in the camera coordinate system in the windless and speedless state and the test state; The specific implementation method of step S6 includes the following steps: S6.

1. Extract the image coordinate sequence of the blade positioning mark points of the image collected by the first imaging device when there is no wind and no speed by artificial selection or by combining image binarization with contour extraction The image coordinate sequence of the registration mark points on the fairing of the image collected by the first imaging device Then, based on the image cross-correlation method, Obtain the image coordinate sequence of the leaf positioning mark points of the image collected by the second imaging device The image coordinate sequence of the registration mark points on the fairing of the image collected by the second imaging device A maximum bounding rectangle is artificially drawn for the leaf area in the image under the viewing angle of the first imaging device, and an equidistant rectangular grid G ​​is defined based on the rectangle. A mask M is determined for the leaf area to distinguish the model area from the non-model area in the bounding rectangle, wherein Assume I1 base is m b ×n b For an image of , then 1≤i≤m,1≤j≤n; According to M, the grid points in G that are not in the leaf area are deleted to obtain the image coordinates S1 of the speckle grid points under the viewing angle of the first imaging device only in the leaf area. base ; Suppose the speckle grid point image coordinates S2 under the viewing angle of the second imaging device base , aligning the speckle on the leaf at the viewing angle of the second imaging device to the speckle on the leaf at the viewing angle of the first imaging device, and obtaining a transformation relationship between the speckle on the leaf at the viewing angle of the second imaging device and the speckle on the leaf at the viewing angle of the first imaging device through a cubic polynomial transformation; Let point P(u′,v′) be I1 base The image coordinates of any point in the image, (u,v) is I2 base The neutralization point P is the image coordinate of the same-named marking point. Then, the expression for aligning the speckle on the leaf under the viewing angle of the second imaging device to the leaf under the viewing angle of the first imaging device is: u′=a0+a1u+a2v+a3u 2 +a4uv+a5v 2 +a6u 3 +a7u 2 v+a8uv 2 +a9v 3 v′=b0+b1u+b2v+b3u 2 +b4uv+b5v 2 +b6u 3 +b7u 2 v+b8uv 2 +b9v 3 Among them, a i is the coefficient of the i-th term of the polynomial of u′, i=0,1…9, b i is the i-th transformation coefficient of the polynomial of v′, i=0,1…9; Will and Substitute into the expression for realizing the alignment of the speckle on the leaf under the perspective of the second imaging device to the leaf under the perspective of the first imaging device, and solve the equation group to obtain the aligned image The image cross-correlation method can be used to obtain The speckle grid image coordinates Then The inverse transformation of the cubic polynomial can accurately obtain the speckle grid point image coordinates S2 of the leaf area under the perspective of the second imaging device. base ; Then, according to the internal and external parameters obtained in step S4 and the above-mentioned image coordinates, the three-dimensional coordinates of the positioning mark point on the blade in the camera coordinate system when there is no wind and no speed are obtained. The three-dimensional coordinates of the registration mark points on the fairing in the camera coordinate system The three-dimensional coordinates of the speckle on the blade in the camera coordinate system S6.

2. Obtain the three-dimensional coordinates of the positioning mark points on the blade, the registration mark points on the fairing, and the speckle on the blade in the camera coordinate system during the test; Image coordinates of the registration mark points on the fairing on the blade under the viewing angles of the first imaging device and the second imaging device during the test Combined with I1 through image correlation technology base 、I2 base , Then, the image coordinates of the positioning mark points on the fairing on the blade under the perspective of the first imaging device and the second imaging device during the test are obtained. Assume that the speckle grid image coordinates of the image under the viewing angle of the first imaging device during the test are S1 exp ,Considering that the image distortion is consistent under the same camera perspective, the image during the test is aligned to the image when there is no wind and no speed through the affine transformation method; According to step S6.1, I1 base The image coordinates (u′, v′) of any point in exp ,v exp ) is the image coordinate of the same-named mark point in the test image at the test time point P, and the speckle on the leaf under the viewing angle of the first imaging device during the test is completed by the following formula to I1 base The alignment expression is: Among them, af is the transformation coefficient to be solved. and Substituting into the above formula, we can solve the equation system and get; After the radiometric transformation, the aligned image is obtained The image cross-correlation method is used to obtain The speckle grid image coordinates Then Perform the inverse transformation of the cubic polynomial to obtain S1 exp ; Similarly, the speckle grid image coordinates S2 of the image under the viewing angle of the second imaging device are obtained exp ; Then, according to the camera parameters obtained in step S4 and the above-mentioned image coordinates, the three-dimensional coordinates of the positioning mark point on the blade in the camera coordinate system, the three-dimensional coordinates of the registration mark point on the fairing in the camera coordinate system, and the three-dimensional coordinates of the speckle on the blade in the camera coordinate system are obtained during the test; Then, for the image sequence under the viewing angle of the first imaging device and the image sequence from the perspective of the second imaging device All images in the above method are used to obtain the three-dimensional coordinates of the positioning mark points, registration mark points, and speckle, and then summed and averaged respectively to obtain the three-dimensional coordinates of the positioning mark points on the leaves in the final test under the camera coordinates. The three-dimensional coordinates of the registration mark points on the fairing in camera coordinates The three-dimensional coordinates of the speckle on the blade in the camera coordinate system S6.

3. Registration. Considering that the rotation of the fairing conforms to the rigid body transformation, the registration mark points arranged on the fairing are used to eliminate the deviation of the blades in the windless and non-rotating speed and the phase during the test caused by the system and manual determination of the blade position. According to the Kabsch algorithm, calculate arrive The rotation and translation transformation relationship [R reg |T reg ], the expression of the three-dimensional coordinates of the speckle after blade registration during the test is: Then the three-dimensional coordinates of the speckle with the same phase as that of the blade in the test and in the absence of wind and speed are obtained; S7. Ground three-dimensional coordinate surveying, measuring the three-dimensional coordinates of the positioning points of the blade in the ground coordinate system; S8. Deformation calculation: calculating the deformation of the blade in the ground coordinate system.

2. A method for measuring deformation of high-speed engine blades for wind tunnel testing according to claim 1, characterized in that: The specific implementation method of step S3 includes the following steps: S3.

1. Every time the blade rotates one circle, the motor encoder returns a phase-locked control signal and sets the delay t A , so that the blade in the image currently captured by the camera is in the measurement position, and the laser emission time is t B , illuminating the speckle area on the target leaf, the lifetime of the fluorescent dye rhodamine is t c , the time the speckle is illuminated is t B +t c ; Set the time the speckle is illuminated within the camera exposure time t E To achieve effective lighting; S3.

2. Based on the camera delay from being triggered to capturing, t D , the camera is triggered earlier than the laser emits light t D The timing control ensures that each image collected during the experiment is of the same leaf and in the same position.

3. The method for measuring deformation of high-speed engine blades for wind tunnel testing according to claim 2, characterized in that: Step S4: Solve the camera intrinsic parameters based on Zhang's calibration method External parameter H = [R, t]; Among them, α, β are the focal lengths in the u and v directions, γ is the radial distortion parameter, ( u0 ,v0) are the coordinates of the image principal point, R and t are the rotation matrix and translation vector from the world coordinate system to the camera coordinate system respectively.

4. The method for measuring deformation of high-speed engine blades for wind tunnel testing according to claim 3, characterized in that: The specific implementation method of step S5 includes the following steps: S5.

1. When the distortion of the images from the two camera perspectives is not affected, collect the image I1 from the perspective of the first imaging device when there is no wind and no rotation speed. base and the image I2 from the perspective of the second imaging device base ; S5.

2. In the wind tunnel test, first reach the test condition, and after the blade speed stabilizes, adjust t in step S3 A , the position of the blade captured by the real-time image display is the same as the blade position captured when there is no wind and no speed, and the degree of distortion of the imaging under the two camera perspectives is not affected, and then the image sequence under the perspective of the first imaging device is collected and the sequence from the perspective of the second imaging device n is the number of images collected.

5. The method for measuring deformation of high-speed engine blades for wind tunnel testing according to claim 4, characterized in that: The specific implementation method of step S7 is to use a three-dimensional coordinate measuring machine, calibrate and set it, place the blade firmly on the measuring platform to ensure that it does not move during the measurement process, use the measuring probe to touch the positioning mark points on the blade one by one, and record its coordinate data in three-dimensional space. Then the three-dimensional coordinates of the positioning mark points on the blade in the ground coordinate system are measured.

6. A method for measuring deformation of high-speed engine blades for wind tunnel testing according to claim 5, characterized in that: The specific implementation method of step S8 includes the following steps: S8.

1. First, the three-dimensional coordinates of all scattered spots need to be converted into the blade numerical model coordinate system. According to the Kabsch algorithm, the arrive The rotation and translation transformation relationship [R real |T real ]; Then the three-dimensional coordinates of the blade speckle in the ground coordinate system when there is no wind and no speed are: Then calculate the three-dimensional coordinates of the blade speckle in the ground coordinate system during the test S8.

2. Subtract the three-dimensional coordinates of the blade speckle in the ground coordinate system when there is no wind and no speed from the three-dimensional coordinates of the blade speckle in the ground coordinate system during the test to obtain the deformation of the blade in the ground coordinate system; S8.

3. Based on the triangulation, construct a triangular mesh for the scattered speckle cloud and display it as a map.

Images