Calibration device and calibration method for particle image velocity measurement method

Abstract

The invention provides a calibration device and a calibration method for a particle image velocity measurement method, and relates to the technical field of fluid mechanics, and the calibration device comprises a calibration plate module which is installed on a casing of a gas compressor and comprises a calibration plate suitable for moving along the radial direction of the casing; the calibration plate extends in a plane perpendicular to the radial direction so as to simulate target view fields at different radial positions in the cartridge receiver, and a plurality of calibration points are arranged on the calibration plate; the transparent window module is configured on the window of the casing so as to form a transparent window on the casing; the camera module is arranged outside the cartridge receiver and is suitable for penetrating through the transparent window to shoot the calibration plates at different radial positions, and calibration images corresponding to the different radial positions are obtained respectively; wherein the spatial relationship between the camera module and the target view field is obtained according to the information of the calibration points of the calibration plate and the information of the representation calibration points displayed on the plurality of calibration images.

Description

Technical Field

[0001] At least one embodiment of the present invention relates to the technical field of fluid mechanics, and specifically to a calibration device and a calibration method for a particle image velocimetry method. Background Art

[0002] The full-field, non-contact particle image velocimetry method can be used to obtain flow field data at different blade height positions inside the rotor channel of the compressor. Furthermore, the three velocity components at different radial positions in the rotor channel can be obtained using the volumetric particle image velocimetry method. To measure the motion data of the flow field using the particle image velocimetry method, first, the camera module needs to be calibrated, that is, to determine the coefficients of the fitting function between the three-dimensional coordinate size of the actual shooting section and the imaging size of the camera, accurately realize the conversion of pixel coordinates to physical coordinates, and then obtain the actual physical size corresponding to the pixel point of the photo taken by the camera, and finally determine the displacement of the tracer particles.

[0003] The compressor is equipped with a casing, and the camera needs to shoot the tracer particle flow field inside the rotor channel inside the casing from the outside of the casing. Therefore, the compressor casing needs to be made of transparent optical glass. After the light passes through the glass, it will be refracted to a certain extent, and calibration is also required to solve the field of view distortion caused by the above problem.

[0004] In the related art, the calibration work of the particle image velocimetry method uses a specially processed calibration plate. Based on the universality of the specially processed calibration plate, its size is usually large, which causes certain difficulties in the calibration work of the rotor channel on the inner side of the casing near the casing. In the case where the window retained on the casing is a glass window, an additional multi-degree-of-freedom coordinate frame is required to fix the glass window. When the position of the calibration plate is changed, the glass window needs to be disassembled, thereby increasing the experimental cost and reducing the efficiency of the calibration work. Moreover, it is difficult to accurately simulate and restore the relative position relationship between the camera and the calibration plate during real shooting, thereby affecting the measurement accuracy of the particle image velocimetry method. Summary of the invention

[0005] In view of this, the present invention provides a calibration device and a calibration method for a particle image velocimetry method, which can improve the efficiency of the calibration work.

[0006] The calibration device for the particle image velocimetry method according to the embodiment of the present invention is suitable for measuring the flow field of the rotor channel of the compressor, comprising: a calibration plate module, installed on the casing 21 of the compressor, and comprising a calibration plate 11 suitable for moving along the radial direction of the casing 21; the calibration plate 11 extends in a plane perpendicular to the radial direction to simulate a target field of view at different radial positions in the casing 21, and a plurality of calibration points are provided on the calibration plate 11; a transparent window module, arranged on the window 211 of the casing 21 to form a transparent window on the casing 21; and a camera module, arranged outside the casing 21, suitable for photographing the calibration plate 11 at different radial positions through the transparent window, and obtaining calibration images corresponding to the different radial positions respectively; wherein, according to the information of the calibration points of the calibration plate 11 and the information representing the calibration points displayed on the plurality of calibration images, the spatial relationship between the camera module and the target field of view is obtained.

[0007] According to an embodiment of the present invention, the calibration plate module further includes: a supporting mechanism, mounted on the casing 21, the calibration plate 11 mounted on the supporting mechanism, and the supporting mechanism being configured to position the calibration plate 11 at the different radial positions in the radial direction, so that the camera module obtains the calibration images corresponding to the different radial positions respectively.

[0008] According to an embodiment of the present invention, the supporting mechanism comprises: a first mounting assembly mounted on the casing 21 ; and a calibration plate base 14 movably mounted on the first mounting assembly in the radial direction and configured to fix the calibration plate 11 .

[0009] According to an embodiment of the present invention, the above-mentioned first mounting assembly includes: a support frame 12, which is installed on the above-mentioned casing 21 and extends in the above-mentioned radial direction, and the above-mentioned support frame 12 is provided with a plurality of groups of first positioning holes 122 extending in the above-mentioned radial direction, and is configured to be connected to the above-mentioned calibration plate base 14 to adjust the position of the above-mentioned calibration plate 11 along the above-mentioned radial direction with a first step length; and a first translation mechanism 13, the above-mentioned calibration plate base 14 is installed on the above-mentioned first translation mechanism 13, and the above-mentioned first translation mechanism 13 is configured to be connected to different groups of first positioning holes 122 of the above-mentioned support frame 12 to adjust the position of the above-mentioned calibration plate 11 along the above-mentioned radial direction.

[0010] According to an embodiment of the present invention, the first translation mechanism 13 is configured to continuously move the calibration plate 11 in the radial direction relative to the support frame 12 .

[0011] According to an embodiment of the present invention, the support frame 12 further includes: a support plate 121 extending in the radial direction; and two opposite mounting arms protruding from one end of the support plate 121, and an edge of the casing 21 adjacent to the window 211 is clamped between the mounting arms.

[0012] According to an embodiment of the present invention, the camera module includes: a support column 34, suitable for adjusting the height of the field of view of the camera module; a second mounting assembly 31, mounted on the support column 34; a flat plate 32, mounted on the second mounting assembly 31, and provided with a plurality of groups of second positioning holes on the flat plate 32; and a camera assembly 33, mounted on the flat plate 32, configured to connect different groups of second positioning holes of the flat plate 32 to adjust the field of view of the camera assembly 33.

[0013] According to an embodiment of the present invention, the second mounting assembly 31 includes: a second translation mechanism, adapted to adjust the position of the camera assembly 33 along the radial direction; and a rotation mechanism, adapted to adjust the shooting angle of the camera assembly 33 .

[0014] According to an embodiment of the present invention, the transparent window module includes: a transparent plate 22, installed at the position of the window 211 of the casing 21; and two pressing blocks, installed at both ends of the window 211, so that the transparent plate 22 cooperates with the window 211 to seal the airflow.

[0015] Another aspect of the present invention provides a calibration method using a calibration device for a particle image velocimetry method, the calibration method comprising: positioning a calibration plate at a reference position in a radial direction of an inner side of a casing by a calibration plate module, the calibration plate being used to simulate a target field of view; a plurality of calibration points are arranged on the calibration plate; photographing the calibration plate at the reference position by a camera module to obtain a calibration image at the reference position; obtaining a pixel coordinate of the camera module and a pixel coordinate of the target field of view according to information of the calibration point and information representing the calibration point displayed on the calibration image at the reference position. The method comprises the following steps: obtaining a conversion relationship between the two-dimensional physical coordinates of the target field of view and the calibration plate; moving the calibration plate along the radial direction through the calibration plate module to record multiple sliding positions of the calibration plate at different radial positions; photographing the calibration plate at different sliding positions using the camera module to obtain calibration images of each of the multiple sliding positions; and obtaining a spatial relationship between the camera module and the three-dimensional physical coordinates of the target field of view according to the conversion relationship, the reference position, the multiple sliding positions, the information of the calibration points and the information representing the calibration points displayed on the calibration images of each of the multiple sliding positions.

[0016] The calibration device for the particle image velocimetry method of the embodiment of the present invention sets the calibration plate on the inner side of the casing through the calibration plate module, and moves the calibration plate along the radial direction, which can simulate the cross-sectional area of ​​the flow field at different radial positions inside the casing, and can also avoid multiple disassembly of the transparent window, thereby reducing the experimental cost, improving the efficiency of the calibration work, and can more accurately obtain the spatial relationship between the camera module and the target field of view, thereby improving the measurement accuracy of the particle image velocimetry method. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings.

[0018] Figure 1 A schematic diagram showing the principle of a calibration scheme for a particle image velocimetry method in the related art is shown.

[0019] Figure 2 A schematic diagram showing the principle of a calibration device for a particle image velocimetry method according to an embodiment of the present invention is shown.

[0020] Figure 3 A schematic diagram showing multiple calibration points of a calibration plate of a calibration device for a particle image velocimetry method according to an embodiment of the present invention is shown.

[0021] Figure 4 A schematic diagram of a calibration plate base of a calibration device for a particle image velocimetry method according to an embodiment of the present invention is shown.

[0022] Figure 5 A schematic diagram of a translation mechanism of a calibration device for a particle image velocimetry method according to an embodiment of the present invention is shown.

[0023] Figure 6 A schematic diagram of a support frame of a calibration device for a particle image velocimetry method according to an embodiment of the present invention is shown.

[0024] Figure 7 A schematic diagram of a casing of a calibration device for a particle image velocimetry method according to an embodiment of the present invention is shown.

[0025] Figure 8 A schematic diagram of a transparent plate of a calibration device for a particle image velocimetry method according to an embodiment of the present invention is shown.

[0026] Fig. 9 A schematic diagram of a pressing block of a calibration device for a particle image velocimetry method according to an embodiment of the present invention is shown.

[0027] Fig.10 A schematic diagram of a second mounting assembly of a calibration device for a particle image velocimetry method according to an embodiment of the present invention is shown.

[0028] Fig.11 A schematic diagram of a plate of a calibration device for a particle image velocimetry method according to an embodiment of the present invention is shown.

[0029] Fig.12 A schematic flow chart of a calibration method using a calibration device for a particle image velocimetry method according to an embodiment of the present invention is shown.

[0030] Description of reference numerals:

[0031] 11: Calibration board;

[0032] 12: support frame;

[0033] 121: support plate;

[0034] 122: first positioning hole;

[0035] 123_1: first mounting arm;

[0036] 123_2: second mounting arm;

[0037] 124: second threaded hole;

[0038] 13: first translation mechanism;

[0039] 131: Main body;

[0040] 132: Slider;

[0041] 133: first threaded hole;

[0042] 14: Calibration plate base;

[0043] 141: Page 1;

[0044] 142: first through hole;

[0045] 21: Receiver;

[0046] 212: Threaded blind hole

[0047] 211: Window;

[0048] 213: Edge;

[0049] 22: Transparent plate;

[0050] 23: Briquetting;

[0051] 231: third threaded hole;

[0052] 31: second installation component;

[0053] 311: second translation mechanism;

[0054] 312: Rotating mechanism;

[0055] 313: rotating table;

[0056] 314: fourth threaded hole;

[0057] 32: Flat plate;

[0058] 321: second positioning hole;

[0059] 33: Camera assembly;

[0060] 34: Support column. DETAILED DESCRIPTION

[0061] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0062] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0063] All terms used herein, including technical and scientific terms, have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification, and should not be interpreted in an idealized or overly rigid manner.

[0064] When using expressions such as "at least one of A, B, and C, etc.", it should generally be interpreted as the meaning of the expression generally understood by those skilled in the art. For example, "a system having at least one of A, B, and C" should include but not be limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc. When using expressions such as "at least one of A, B, or C, etc.", it should generally be interpreted as the meaning of the expression generally understood by those skilled in the art. For example, "a system having at least one of A, B, or C" should include but not be limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.

[0065] It should also be noted that the directional terms mentioned in the embodiments, such as "upper", "lower", "front", "back", "left", "right", etc., are only reference directions of the drawings and are not intended to limit the scope of protection of the present invention. Throughout the drawings, the same elements are represented by the same or similar reference numerals. Conventional structures or configurations will be omitted when they may cause confusion in the understanding of the present invention.

[0066] Figure 1 A schematic diagram showing the principle of a calibration scheme for a particle image velocimetry method in the related art is shown.

[0067] like Figure 1 As shown, in the related art, the calibration plate is fixed at the target flow field, and a precisely movable calibration plate mechanism is not designed to calibrate different radial positions, which makes it difficult to adapt to the flow field measurement requirements at different radial positions.

[0068] The present invention provides a calibration device for a particle image velocimetry method, in order to solve at least one of the above technical problems.

[0069] Figure 2 A schematic diagram showing the principle of a calibration device for a particle image velocimetry method according to an embodiment of the present invention is shown.

[0070] According to an embodiment of the present invention, the particle image velocimetry method is suitable for measuring the flow field of a rotor channel of a compressor.

[0071] Particle image velocimetry is a non-contact fluid dynamics velocimetry technique.

[0072] In one example, the compressor can be an axial flow compressor, and the rotor of the compressor works on the gas by rotating at high speed, compressing the gas and increasing the pressure. The flow area between different rotor blades of the compressor is called the rotor channel, and the gas flows along the rotor channel to form a flow field. The particle image velocimetry method scatters some tracer particles with good tracking and reflective properties in the flow field, uses a laser sheet light source to illuminate the cross-sectional area of ​​the flow field, and continuously captures the particle images of the tracer particles exposed multiple times through a camera module. The particle image is analyzed using the image cross-correlation method, and the average displacement of the particle image in each small area can be obtained, thereby determining the motion data of the cross-sectional area.

[0073] The purpose of calibration is to determine the spatial relationship between the optical axis of the camera module and the cross-sectional area of ​​the flow field, and further determine the spatial relationship between the pixel coordinates of the camera module and the three-dimensional physical coordinates of the cross-sectional area of ​​the flow field to eliminate field of view distortion.

[0074] like Figure 2 As shown, the calibration device 100 for the particle image velocimetry method includes a calibration plate module, a transparent window module and a camera module.

[0075] According to an embodiment of the present invention, the calibration plate module is installed on the casing 21 of the compressor, and includes a calibration plate 11 suitable for moving along the radial direction of the casing 21; the calibration plate 11 extends in a plane perpendicular to the radial direction to simulate the target field of view at different radial positions in the casing 21, and a plurality of calibration points are provided on the calibration plate 11. The transparent window module is arranged on the window 211 of the casing 21 to form a transparent window on the casing 21. The camera module is arranged outside the casing 21 and is suitable for photographing the calibration plate 11 at different radial positions through the transparent window to obtain calibration images corresponding to different radial positions.

[0076] According to an embodiment of the present invention, the casing 21 of the compressor may be a cylindrical shell, and the casing 21 is coaxial with the rotor of the compressor. The rotor and blades of the compressor are arranged on the inner side of the casing 21. The radial direction of the casing 21 refers to the straight line direction from the casing 21 to the rotor.

[0077] According to an embodiment of the present invention, the target field of view is the cross-sectional area of ​​the flow field irradiated by the laser sheet light source in the particle image velocimetry method.

[0078] In one example, the tip region of the blade mainly includes the position between the 80% relative height position of the blade and the wall of the casing 21. For example, 80% relative blade height, 89% relative blade height, 90% relative blade height, and the blade tip clearance. In the tip region of the blade, the calibration plate 11 moves along the radial direction to simulate the cross-sectional area of ​​the flow field to achieve the calibration of the above-mentioned different radial positions.

[0079] Figure 3 FIG. 1 is a schematic diagram showing multiple calibration points of a calibration plate of a calibration device for a particle image velocimetry method according to an embodiment of the present invention. Figure 3 As shown, the multiple calibration points of the calibration plate 11 can be homemade small-sized equidistant square grid points.

[0080] According to an embodiment of the present invention, the transparent window has a certain curvature based on the arc-shaped inner wall surface of the casing 21. The curvature will cause the imaging of the camera module to be distorted. According to the information of the calibration points of the calibration plate 11 and the information representing the calibration points displayed on the multiple calibration images, the spatial relationship between the camera module and the target field of view is obtained.

[0081] The calibration device for the particle image velocimetry method of the embodiment of the present invention sets the calibration plate on the inner side of the casing through the calibration plate module, and moves the calibration plate along the radial direction, which can simulate the cross-sectional area of ​​the flow field at different radial positions inside the casing, and can also avoid multiple disassembly of the transparent window, thereby reducing the experimental cost, improving the efficiency of the calibration work, and can more accurately obtain the spatial relationship between the camera module and the target field of view, thereby improving the measurement accuracy of the particle image velocimetry method.

[0082] like Figure 2 As shown, the calibration plate module also includes a support mechanism. The support mechanism is mounted on the casing 21, and the calibration plate 11 is mounted on the support mechanism. The support mechanism is configured to position the calibration plate 11 at different radial positions in the radial direction, so that the camera module obtains calibration images corresponding to different radial positions.

[0083] like Figure 2 As shown, the support mechanism includes a first mounting assembly and a calibration plate base 14. The first mounting assembly is mounted on the casing 21. The calibration plate base 14 is movably mounted on the first mounting assembly in a radial direction and is configured to fix the calibration plate 11.

[0084] Figure 4 A schematic diagram of a calibration plate base of a calibration device for a particle image velocimetry method according to an embodiment of the present invention is shown.

[0085] like Figure 4 As shown, the calibration plate base 14 is provided with a plurality of first through holes 142 extending in the radial direction, and the plurality of first through holes 142 may be three rows of discrete equidistant through holes. The calibration plate base 14 is provided with a base plate in a direction perpendicular to the radial direction.

[0086] In one example, the calibration plate 11 can be fixed to the first surface 141 of the substrate or the reverse side of the first surface 141 of the substrate by gluing, so that the calibration plate 11 can simulate the target field of view perpendicular to the radial direction.

[0087] like Figure 2 As shown, the first mounting assembly includes a support frame 12 and a first translation mechanism 13. The support frame 12 is mounted on the casing 21 and extends in the radial direction. The support frame 12 is provided with a plurality of first positioning holes 122 extending in the radial direction, and is configured to connect to the calibration plate base 14 to adjust the position of the calibration plate 11 in the radial direction with a first step length. The calibration plate base 14 is mounted on the first translation mechanism 13, and the first translation mechanism 13 is configured to connect to different groups of first positioning holes 122 of the support frame 12 to adjust the position of the calibration plate 11 in the radial direction. The connection method may be bolt connection.

[0088] According to an embodiment of the present invention, the first translation mechanism 13 connects different groups of first positioning holes 122 of the support frame 12 so that the calibration plate 11 can change the radial position at a first fixed interval according to the layout of the first positioning holes 122 .

[0089] According to an embodiment of the present invention, the first translation mechanism 13 is configured to continuously move the calibration plate 11 in a radial direction relative to the support frame 12 .

[0090] Figure 5 A schematic diagram of a translation mechanism of a calibration device for a particle image velocimetry method according to an embodiment of the present invention is shown.

[0091] like Figure 5 As shown, the first translation mechanism 13 includes: a main body 131 and a slider 132. The main body 131 is configured to be connected to different groups of first positioning holes 122 of the support frame 12, and the connection method can be bolt connection. The main body 131 is provided with a track extending in the radial direction. The slider 132 is provided with a matching groove that matches the track of the main body 131, so that the slider 132 can be slidably installed on the main body 131, and the calibration plate 11 is installed on the slider 132 to move in the radial direction with the slider 132. The connection method can be bolt connection.

[0092] In one example, three rows of discrete, equidistant multiple first threaded holes 133 are provided on the slider 132 of the first translation mechanism 13, and the multiple first threaded holes 133 cooperate with the multiple first through holes 142 of the calibration plate base 14, so that the calibration plate 11 can slide along the slider 132 in the radial direction and change the radial position in a second step length, and the value of the second step length is not fixed.

[0093] Figure 6 A schematic diagram of a support frame of a calibration device for a particle image velocimetry method according to an embodiment of the present invention is shown.

[0094] like Figure 6 As shown, the support frame 12 also includes a support plate 121, a first mounting arm 123_1, a second mounting arm 123_2 and a plurality of second threaded holes 124. The support plate 121 extends in the radial direction. Two opposing mounting arms are formed protruding from one end of the support plate 121, and the edge of the casing 21 adjacent to the window 211 is clamped between the mounting arms. The plurality of second threaded holes 124 are provided on at least one of the mounting arms, so that the support frame 12 is mounted on the casing 21 by threading the plurality of bolts with the plurality of second threaded holes 124.

[0095] Figure 7 A schematic diagram of a casing of a calibration device for a particle image velocimetry method according to an embodiment of the present invention is shown.

[0096] like Figure 7 As shown, the first mounting arm 123_1 and the second mounting arm 123_2 are clamped on the edge 213 of the casing 21, and the edge 213 is located near the edge of the window 211, so that the calibration plate 11 appears in the shooting field of the camera module. By selecting a suitable material for the support frame 12, it is expected that non-destructive installation can be achieved.

[0097] According to an embodiment of the present invention, the transparent window module includes: a transparent plate 22 and two pressing blocks.

[0098] Figure 8 A schematic diagram of a transparent plate of a calibration device for a particle image velocimetry method according to an embodiment of the present invention is shown.

[0099] Fig. 9 A schematic diagram of a pressing block of a calibration device for a particle image velocimetry method according to an embodiment of the present invention is shown.

[0100] like Figure 7 , Figure 8 and Fig. 9 As shown, a window 211 is provided on the casing 21, and a transparent plate 22 is installed at the position of the window 211 of the casing 21. Two pressing blocks are installed at both ends of the window 211 so that the transparent plate 22 cooperates with the window 211 to seal the airflow. The connection method can be bolt connection.

[0101] In one example, three equally spaced threaded blind holes 212 are provided at both ends of the window 211 in the circumferential direction. The pressing block 23 is provided with three equally spaced third threaded holes 231, which are connected to the three equally spaced threaded blind holes 212 of the casing 21. The transparent plate 22 can be a transparent acrylic plate in a flat ring shape. Female stoppers are provided on the four peripheries of the transparent plate 22, and the female stoppers are closely matched with the window 211 of the casing 21.

[0102] According to an embodiment of the present invention, a visual window is provided for the camera module during calibration work, a flow field can be sealed during the testing process of the particle image testing method, and an air flow can be sealed during the operation of the compressor.

[0103] According to an embodiment of the present invention, Figure 2 As shown, the camera module includes a support column 34, a second mounting assembly 31, a flat plate 32 and a camera assembly 33. The support column 34 is suitable for adjusting the height of the field of view of the camera module. The second mounting assembly 31 is mounted on the support column 34. The flat plate 32 is mounted on the second mounting assembly 31, and a plurality of groups of second positioning holes 321 are provided on the flat plate 32. The camera assembly 33 is mounted on the flat plate 32 and is configured to connect different groups of second positioning holes 321 of the flat plate 32 to adjust the field of view of the camera assembly 33. The connection method can be bolt connection.

[0104] According to an embodiment of the present invention, the camera assembly 33 may include two cameras, and the relative position relationship between the two cameras may be set based on different groups of second positioning holes to adjust the range of the field of view of the camera module.

[0105] Fig.10 A schematic diagram of a second mounting assembly of a calibration device for a particle image velocimetry method according to an embodiment of the present invention is shown.

[0106] Fig.11A schematic diagram of a plate of a calibration device for a particle image velocimetry method according to an embodiment of the present invention is shown.

[0107] like Fig.10 As shown, the second installation assembly 31 includes: a second translation mechanism 311 and a rotation mechanism 312. The second translation mechanism 311 is suitable for adjusting the position of the camera assembly 33 along the radial direction. The rotation mechanism 312 is suitable for adjusting the shooting angle of the camera assembly 33.

[0108] In one example, if Fig.10 and Fig.11 As shown, the second translation mechanism 311 is provided with a sliding track, and the bottom of the rotation mechanism 312 is provided with a sliding groove that cooperates with the sliding track, so that the camera assembly 33 can be adjusted along the radial direction. The rotation mechanism 312 is also provided with a precise rotating table 313, and the four fourth threaded holes 314 on the rotating table 313 can be connected with different groups of second positioning holes 321 of the flat plate 32.

[0109] In one example, if Figure 2 and Fig.11 As shown, the flat plate 32 is arranged to be inclined along the installation angle direction of the blade tip.

[0110] Fig.12 A schematic flow chart of a calibration method using a calibration device for a particle image velocimetry method according to an embodiment of the present invention is shown.

[0111] like Fig.12 As shown, the calibration method includes operations S121 to S126.

[0112] In operation S121, a calibration plate module is used to position a calibration plate at a reference position in a radial direction inside the casing, and the calibration plate is used to simulate a target field of view. A plurality of calibration points are arranged on the calibration plate.

[0113] In operation S122, the calibration plate at the reference position is photographed by using a camera module to obtain a calibration image of the reference position.

[0114] In operation S123, a conversion relationship between the pixel coordinates of the camera module and the two-dimensional physical coordinates of the target field of view is obtained according to the information of the calibration points and the information representing the calibration points displayed on the calibration image of the reference position.

[0115] In operation S124, the calibration plate is moved along the radial direction by the calibration plate module, and a plurality of sliding positions of the calibration plate at different radial positions are recorded.

[0116] In operation S125 , the calibration plate at different sliding positions is photographed by using a camera module to obtain calibration images of the respective sliding positions.

[0117] In operation S126, a spatial relationship between the camera module and the spatial 3D physical coordinates of the target field of view is obtained according to the conversion relationship, the reference position, the plurality of sliding positions, the information of the calibration points, and the information representing the calibration points displayed on the calibration images of the plurality of sliding positions.

[0118] The calibration method of the calibration device for the particle image velocimetry method of the present invention is further described by a specific embodiment below.

[0119] Under the condition that the imaging optical path of the camera module is not changed, the rotor of the compressor is pushed out, leaving only the compressor casing 21. The calibration plate module of the calibration device for the particle image velocimetry method of the present invention is installed.

[0120] When the first translation mechanism 13 is positioned in the first positioning hole 122 of the first group of the support frame 12, the calibration plate 11 is positioned in the middle position of the first translation mechanism 13 and recorded as the first reference position. The field of view of the camera assembly 33 is adjusted to be able to shoot clearly, and the spatial position of the camera assembly 33 is kept fixed, which is recorded as the first radial position of the camera assembly 33. The camera module shoots the calibration plate 11 to obtain a calibration image of the first reference position. Since the aperture parameters of the camera are not precise values ​​and cannot be reproduced, the aperture and other parameters of the subsequent shooting camera cannot be changed.

[0121] According to the information of the calibration points and the calibration image of the first reference position, a first conversion relationship between the pixel coordinates of the camera module and the two-dimensional physical coordinates of the target field of view at the first reference position can be obtained.

[0122] For example, the radial position of the first reference position may be r1=0 mm, and the first radial position of the camera assembly 33 may be r 01 =20mm. The first conversion relationship includes the two-dimensional physical coordinates z1 and θ1 directions of the target field of view perpendicular to the radial direction.

[0123] The calibration plate 11 is slid relative to the first reference position on the first translation mechanism 13 with a second step length, so that the radial position of the calibration plate 11 can cover the depth of field of the camera module, and a clear shooting picture can be obtained. During the sliding process with the second step length, multiple first sliding positions are recorded. The camera assembly 33 is used to shoot, and corresponding calibration images of each of the multiple first sliding positions are obtained.

[0124] Based on the first conversion relationship, the first reference position, multiple first sliding positions, information of the calibration points and the calibration images of each of the multiple first sliding positions, the first inclination angle of the optical axis of the camera module and multiple first conversion relationships corresponding to the three-dimensional physical coordinates of the camera module and multiple target fields of view at the first reference position can be obtained, thereby obtaining the first spatial relationship at the first reference position.

[0125] For example, the radial positions of the four first sliding positions may be r 11 =-1mm, r 12 =-0.5mm, r 13 =0.5mm, r 14 =1mm. The plurality of first conversion relationships may be five first conversion relationships corresponding to the first reference position and the four first sliding positions. The first spatial relationship includes the r1 radial direction, and the two-dimensional physical coordinate z1 direction and θ1 direction of the target field of view perpendicular to the r1 radial direction.

[0126] At this point, the spatial relationship calibration of the three-dimensional physical coordinates of multiple target fields of view based on the first reference position is completed.

[0127] When the first translation mechanism 13 is positioned in the first positioning hole 122 of the second group of the support frame 12, the radial position of the calibration plate 11 at this time is recorded as the second reference position. At this time, the camera assembly 33 may no longer be able to capture a clear image. The camera assembly 33 is moved a small distance in the radial direction following the first translation mechanism 13 and fixed, and recorded as the second radial position of the camera assembly. The small distance is recorded as the camera displacement, and the camera displacement can be recorded and accurately reproduced by the second translation mechanism. The camera module shoots the calibration plate 11 to obtain a calibration image of the second reference position.

[0128] According to the second reference position, the information of the calibration point and the calibration image of the second reference position, a second conversion relationship between the pixel coordinates of the camera module and the two-dimensional physical coordinates of the target field of view at the second reference position can be obtained.

[0129] For example, the radial position of the second reference position may be r2=3 mm, and the second radial position of the camera assembly 33 may be r2=3 mm. 02 =25mm. The second conversion relationship includes the two-dimensional physical coordinates z2 and θ2 of the target field of view perpendicular to the radial direction.

[0130] The calibration plate 11 is slid relative to the second reference position on the first translation mechanism 13 by a third step length, so that the radial position of the calibration plate 11 can cover the depth of field of the camera module, and a clear shooting picture can be obtained. During the sliding process by the third step length, a plurality of second sliding positions are recorded, and the camera assembly 33 is used to shoot, and corresponding calibration images of the plurality of second sliding positions are obtained.

[0131] Based on the second conversion relationship, the second reference position, multiple second sliding positions, the information of the calibration points and the calibration images of each of the multiple second sliding positions, the second inclination angle of the optical axis of the camera module and multiple second conversion relationships corresponding to the three-dimensional physical coordinates of the camera module and the multiple target fields of view at the second reference position can be obtained, thereby obtaining the second spatial relationship at the second reference position.

[0132] For example, the radial positions of the four second sliding positions may be r 21 =2mm, r 22 =2.5mm, r 23 =3.5mm, r 24 =4mm. The plurality of second conversion relationships may be five second conversion relationships corresponding to the second reference position and the four second sliding positions. The second spatial relationship includes the r2 radial direction, and the two-dimensional physical coordinate z2 direction and θ2 direction of the target field of view perpendicular to the r2 radial direction.

[0133] At this point, the spatial relationship calibration of the three-dimensional physical coordinates of multiple target fields of view based on the second reference position is completed.

[0134] The calibration result of the calibration device for the particle image velocimetry method of the present invention can obtain the spatial relationship at different radial positions. After the calibration work is completed, the rotor of the compressor is pushed into the compressor casing again, and the position of the camera module and the casing are kept unchanged, thereby retaining the relative position relationship and improving the measurement accuracy.

[0135] According to an embodiment of the present invention, two adjacent first sliding positions among a plurality of first sliding positions can be used as a group, corresponding to two positions of a calibration plate, and the two-position spacing of a calibration plate of a group and the calibration images of the two corresponding first sliding positions are used to simulate the information of two layers of different heights of the calibration plate in the related art to calibrate the radial direction coordinates, which can reduce the volume of the calibration plate. In addition, during the calibration process, there are many radial positions to move, and a higher-order polynomial fitting can be used to improve the calculation accuracy of the calibration result.

[0136] In one example, when the particle image velocimetry method is used to measure the flow field of a compressor, when it is difficult to adjust the position of the actually generated light sheet along the radial direction, for example, the radial position of the light sheet is located at r s =2.8mm, at this time, the second spatial relationship of the target field of view at the radial position r2=3mm of the second reference position can be selected, which is approximately r s =2.8 mm, and adjust the camera assembly 33 to the second radial position r 02 =25mm to accurately reproduce the absolute position of the camera assembly 33 in the calibration result.

[0137] The embodiments of the present invention are described above. However, these embodiments are only for the purpose of illustration, and are not intended to limit the scope of the present invention. Although each embodiment is described above, it does not mean that the measures in each embodiment cannot be used in combination advantageously. Without departing from the scope of the present invention, those skilled in the art may make various substitutions and modifications, which should all fall within the scope of the present invention.

Claims

1. A calibration device for a particle image velocimetry method, wherein the particle image velocimetry method is suitable for measuring the flow field of a rotor channel of a compressor, characterized in that: include: A calibration plate module is mounted on a casing (21) of the compressor and comprises a calibration plate (11) adapted to move in a radial direction of the casing (21); the calibration plate (11) extends in a plane perpendicular to the radial direction to simulate a target field of view at different radial positions in the casing (21); a plurality of calibration points are provided on the calibration plate (11); a transparent window module, configured on the window (211) of the casing (21) to form a transparent window on the casing (21); and A camera module, arranged outside the casing (21), adapted to photograph the calibration plate (11) at different radial positions through the transparent window, and to obtain calibration images corresponding to the different radial positions respectively; Wherein, the spatial relationship between the camera module and the target field of view is obtained based on the information of the calibration points of the calibration plate (11) and the information representing the calibration points displayed on the plurality of calibration images.

2. The calibration device for particle image velocimetry according to claim 1, characterized in that: The calibration board module also includes: A support mechanism is mounted on the casing (21), the calibration plate (11) is mounted on the support mechanism, and the support mechanism is configured to position the calibration plate (11) at different radial positions in the radial direction, so that the camera modules respectively obtain the calibration images corresponding to the different radial positions.

3. The calibration device for particle image velocimetry according to claim 2, characterized in that: The supporting mechanism comprises: A first mounting assembly mounted on the casing (21); and A calibration plate base (14) is movably mounted on the first mounting assembly in the radial direction and is configured to fix the calibration plate (11).

4. The calibration device for particle image velocimetry according to claim 3, characterized in that: The first installation component comprises: a support frame (12) mounted on the casing (21) and extending in the radial direction, the support frame (12) being provided with a plurality of first positioning holes (122) extending in the radial direction and configured to be connected to the calibration plate base (14) so ​​as to adjust the position of the calibration plate (11) along the radial direction by a first step; and A first translation mechanism (13), the calibration plate base (14) being mounted on the first translation mechanism (13), the first translation mechanism (13) being configured to be connected to different groups of first positioning holes (122) of the support frame (12) so as to adjust the position of the calibration plate (11) along the radial direction.

5. The calibration device for particle image velocimetry according to claim 4, characterized in that: The first translation mechanism (13) is configured to continuously move the calibration plate (11) in the radial direction relative to the support frame (12).

6. The calibration device for particle image velocimetry according to claim 5, characterized in that: The support frame (12) further comprises: A support plate (121) extending in the radial direction; and Two opposing mounting arms are formed protruding from one end of the support plate (121), and an edge of the casing (21) adjacent to the window (211) is clamped between the mounting arms.

7. The calibration device for particle image velocimetry according to claim 1, characterized in that: The camera module comprises: A support column (34) adapted to adjust the height of the field of view of the camera module; A second mounting assembly (31) mounted on the support column (34); a flat plate (32) mounted on the second mounting assembly (31), the flat plate (32) being provided with a plurality of groups of second positioning holes; and A camera assembly (33) is mounted on the flat plate (32) and is configured to connect different groups of second positioning holes of the flat plate (32) to adjust the field of view of the camera assembly (33).

8. The calibration device for particle image velocimetry according to claim 7, characterized in that: The second mounting component (31) comprises: A second translation mechanism, adapted to adjust the position of the camera assembly (33) along the radial direction; and The rotating mechanism is suitable for adjusting the shooting angle of the camera assembly (33).

9. The calibration device for particle image velocimetry according to claim 1, characterized in that: The transparent window module comprises: A transparent plate (22) is mounted on the window (211) of the casing (21); and Two pressing blocks are installed at both ends of the window (211), so that the transparent plate (22) cooperates with the window (211) to seal the airflow.

10. A calibration method using the calibration device for particle image velocimetry according to any one of claims 1 to 9, characterized in that: The calibration method comprises: The calibration plate is positioned at a reference position in the radial direction of the inner side of the casing by means of a calibration plate module, wherein the calibration plate is used to simulate the target field of view; and a plurality of calibration points are arranged on the calibration plate; Using a camera module to photograph the calibration plate at the reference position to obtain a calibration image of the reference position; Obtaining a conversion relationship between pixel coordinates of the camera module and two-dimensional physical coordinates of the target field of view according to information of the calibration points and information representing the calibration points displayed on the calibration image of the reference position; The calibration plate is moved along the radial direction by the calibration plate module to record a plurality of sliding positions of the calibration plate at different radial positions; Using the camera module to photograph the calibration plate at different sliding positions to obtain calibration images of the respective sliding positions; and The spatial relationship between the three-dimensional physical coordinates of the camera module and the target field of view is obtained according to the conversion relationship, the reference position, the multiple sliding positions, the information of the calibration points and the information representing the calibration points displayed on the calibration images of the multiple sliding positions.

Images