A method for measuring a flow field of a space guide vane body based on V3V technology

Abstract

The present application relates to the technical field of hydraulic machinery measurement, and discloses a kind of measurement method of space guide vane body flow field based on V3V technology, by being set between the space guide vane body of hydraulic machinery and V3V camera array in the region to be measured of the space guide vane body of hydraulic machinery a calibration container filled with water, and the calibration container is provided with target target disc, and after the space position and camera parameter of V3V camera array are calibrated remotely using the target target disc, the flow field of the space guide vane body of hydraulic machinery is measured according to the current position and camera parameter of V3V camera array.The present application can well avoid and reduce optical error caused by the installation of space guide vane body and calibration before and after by using remote calibration method, and ensures the accuracy of three-dimensional measurement result.

Description

Technical Field

[0001] This invention relates to the field of hydraulic machinery measurement technology, and in particular to a method for measuring the flow field of a spatial guide vane based on V3V (Volumetric 3-component Velocimetry System) technology. Background Technology

[0002] The internal flow of hydraulic machinery not only exhibits general turbulent properties but also, due to impeller rotation and blade bending, becomes multi-wall shear rotational turbulence. This involves more than 20 complex flow phenomena, including dynamic-static coupling, mainstream-boundary layer interaction, adverse pressure gradient, flow separation, wake-jet, gap flow, and transition flow, making the rotational, transient, and nonlinear characteristics of the internal flow of hydraulic machinery particularly prominent. The spatiotemporal distribution characteristics of the internal flow of hydraulic machinery directly determine its macroscopic hydraulic performance and dynamic characteristics. Therefore, the analysis of the complex multi-scale flow within hydraulic machinery is fundamental to conducting related research.

[0003] Currently, the solution of multi-scale flows inside hydraulic machinery is mainly achieved through numerical calculation methods. However, due to the limitations of scale-based methods, such as the LES series of models (Sub-grid Scale Model, SGS; Dynamic Subgrid-scale Model, DSM), and hybrid models (Detached Eddy Simulation, DES and Scale Adaptive Simulation, SAS) considered as alternatives to LES before its widespread engineering application, analytical methods for complex flows inside hydraulic machinery still require substantial computational resources. In addition, the most common approach is to indirectly reflect the temporal evolution characteristics of complex flows by drilling holes in the casing of the flow-through components of the hydraulic machinery under test to obtain discrete dynamic signals. Installing pressure sensors to collect fluid pulsating pressure to understand the internal flow field is limited by the casing, resulting in a limited number and location of measurement points. Embedding sensors on the blades is further constrained by space volume, signal transmission, waterproofing, and shock resistance, significantly increasing the cost, complexity, and difficulty in implementation for such experiments. Meanwhile, with the development of experimental measurement technology, more detailed measurements and visualizations of flow fields have gradually become possible, such as high-speed imaging, laser Doppler anemometry, and Particle Image Velocity (PIV) measurement. However, hydraulic machinery has multiple blades (including rotating impellers and stationary guide vanes) within a limited space, and the complex blade profiles make the internal flow field structure complex and variable, making it difficult for general measurement methods to meet the requirements.

[0004] Furthermore, due to the significant spatiotemporal evolution characteristics of the internal flow in hydraulic machinery, simply measuring its discrete dynamic characteristics or low spatial resolution is far from sufficient. Predicting its three-dimensional flow field is necessary. The main challenge in measuring the three-dimensional flow field within the spatial guide vanes of hydraulic machinery lies in determining the calibration method. Various factors must be considered, including measurement errors, lighting arrangements, and the imaging effects of tracer particles. The accuracy of the three-dimensional flow field measurement is largely determined by the ideality of the calibration results. Therefore, the precise measurement of the flow field inside the spatial guide vanes of hydraulic machinery has always been a research focus for those skilled in the art. Summary of the Invention

[0005] To address the aforementioned problems, this invention discloses a method for measuring the flow field of a spatial guide vane based on V3V technology, thereby solving the problem that calibration methods for measuring the three-dimensional flow field within the spatial guide vane of hydraulic machinery are very difficult in the existing technology.

[0006] A method for measuring the flow field of a spatial guide vane based on V3V technology, applied to the measurement of the flow field of a spatial guide vane in hydraulic machinery, includes the following steps:

[0007] A V3V measurement system is provided, comprising a V3V camera array, a camera optical three-dimensional coordinate frame, a laser light guide arm, an image acquisition card, a computer, a synchronizer, and a laser source. The V3V camera array is mounted on the camera optical three-dimensional coordinate frame and is communicatively connected to the computer via the image acquisition card. The laser source is connected to the laser light guide arm, and the synchronizer is connected to both the V3V camera array and the laser source.

[0008] A calibration container filled with water is placed between the test area of ​​the space guide vane of the hydraulic machinery and the V3V camera array. A target disk is placed in the calibration container, and the target disk is aligned with the vertical projection plane of the test area of ​​the space guide vane. After adjusting the spatial position of the camera array so that the center of the V3V camera array coincides with the center of the target disk, the distance between the target disk and the V3V camera array is measured and recorded.

[0009] Based on the test area of ​​the spatial guide vane of the hydraulic machinery, the thickness of the target disk calibration space is determined, and the position of each calibration section is determined based on the thickness of the target disk calibration space, and the thickness of the target disk calibration space is not less than the thickness of the test area of ​​the spatial guide vane.

[0010] Adjust the camera parameters of the V3V camera array to achieve the preset requirements for saturation and image clarity of the calibration points on the target disk. After recording the camera parameters of the V3V camera array, move the target disk in the standard container toward the direction of the space guide vane. Then, use the V3V camera array to take pictures of the target disk according to the position of the calibration section of the target disk, and transmit the pictures of the target disk to the computer through the image acquisition card.

[0011] The computer is used to evaluate the current position and camera parameters of the V3V camera array based on the images of the target disk captured by the V3V camera array. If the evaluation of the current position and camera parameters of the V3V camera array is valid, the flow field of the space guide vane of the hydraulic machinery is measured based on the current position and camera parameters of the V3V camera array.

[0012] In some embodiments, the step of measuring the flow field of the space guide vane of the hydraulic machinery based on the current position of the V3V camera array and camera parameters includes:

[0013] Remove the calibration container and the target disk, and adjust the optical part by installing a bulk light source in the optical path of the laser light source to expand the laser emitted by the laser light source into a laser bulk light source that can cover and illuminate the flow field of the space guide vane;

[0014] The V3V camera array is translated on the camera optical three-dimensional coordinate frame to adjust the distance between the V3V camera array and the test area of ​​the space guide vane so that it is equal to the distance between the recorded target disk and the V3V camera array;

[0015] The pre-mixed tracer particle suspension is added to the flow channel of the hydraulic machine, and the hydraulic machine is started.

[0016] Set the laser intensity of the laser source and the measurement and shooting parameters of the synchronizer;

[0017] The V3V camera array is used to photograph the spatial guide vane of the hydraulic machinery, and the captured images of the spatial guide vane are transmitted to the computer through the image acquisition card;

[0018] The computer processes images of the space guide vane captured by the V3V camera array to obtain velocity data of tracer particles within the space guide vane, and obtains flow field data of the space guide vane based on the velocity data of the tracer particles within the space guide vane.

[0019] In some of these embodiments, the volume light source adjustment optics includes two lenses.

[0020] In some of these embodiments, the tracer particles are fluorescent particles.

[0021] In some embodiments, the step of translating the V3V camera array on the camera optical three-dimensional coordinate frame to adjust the distance between the V3V camera array and the test area of ​​the space guide vane to be equal to the recorded distance between the target disk and the V3V camera array further includes a step of calibrating the position of the V3V camera array using a camera calibration laser.

[0022] The specific steps for calibrating the position of the V3V camera array using a camera calibration laser include:

[0023] The camera calibration laser calibration is used to ensure that the central area of ​​the flow channel captured by the V3V camera array is aligned with the camera optical axis of the V3V camera array.

[0024] The camera calibration laser calibration is used to make the imaging plane of the V3V camera array parallel to the plane of the area to be measured of the space guide vane.

[0025] The camera calibration laser calibration ensures that the imaging surface of the V3V camera array covers the entire flow channel of the space guide vane.

[0026] In some embodiments, the V synchronizer measures the following imaging parameters: pulse repetition frequency, laser pulse delay time, exposure time, and frame span time of the captured image.

[0027] In some embodiments, the step of the computer processing images of the space guide vane captured by the V3V camera array to obtain velocity data of tracer particles within the space guide vane specifically includes:

[0028] The computer sequentially performs image preprocessing, particle identification, particle matching and spatial reconstruction, velocity synthesis calculation and velocity field spatial reconstruction, and velocity field post-processing on the images of the space guide vane captured by the V3V camera array to obtain velocity data of the tracer particles in the space guide vane.

[0029] In some embodiments, the step of obtaining the flow field data of the space guide vane body based on the velocity data of tracer particles within the space guide vane body specifically includes:

[0030] Based on ParaView 5.10 and MATLAB, the velocity data of tracer particles in the space guide vane are calculated and analyzed to obtain the flow field data of the space guide vane. The flow field data includes the average flow field, the flow statistics, the transient flow field, the transient flow field feature extraction, and the flow field reconstruction.

[0031] In some embodiments, both the calibration container and the space guide vane are made of acrylic.

[0032] In some embodiments, the step of using a computer to evaluate the current position and camera parameters of the V3V camera array based on images of the target disk captured by the V3V camera array specifically includes:

[0033] The computer uses images of the target disk captured by the V3V camera array to determine whether the center trajectory line, linear magnification, and warping error of the three cameras of the V3V camera array meet preset requirements. If the preset requirements are met, the current position and camera parameters of the V3V camera array are evaluated as valid. If the preset requirements are not met, the current position and camera parameters of the V3V camera array are evaluated as invalid, and the process returns to adjusting the camera parameters of the V3V camera array so that the saturation and image clarity of the calibration points on the target disk meet the preset requirements.

[0034] Compared with the prior art, the above invention has at least the following advantages or beneficial effects:

[0035] This invention, by employing a heterogeneous calibration method, can effectively avoid and reduce optical errors caused by the installation of the spatial guide vane and calibration, thus ensuring the accuracy of the three-dimensional measurement results. Attached Figure Description

[0036] The invention, its features, shape, and advantages will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings. Like reference numerals denote like parts throughout the drawings. The drawings are not drawn to scale; their focus is on illustrating the gist of the invention.

[0037] Figure 1 This is a flowchart of a method for measuring the flow field of a space guide vane based on V3V technology in an embodiment of the present invention;

[0038] Figure 2 This is a schematic diagram of the center trajectory lines of the three cameras in the V3V calibration result analysis of this embodiment of the invention;

[0039] Figure 3 This is a schematic diagram of the linear magnification of the three cameras in the V3V calibration result analysis of this embodiment of the invention;

[0040] Figure 4 This is a schematic diagram of the warping error of the three cameras in the V3V calibration result analysis in an embodiment of the present invention. Detailed Implementation

[0041] V3V calibration is a crucial part of the entire three-dimensional flow field measurement process. The main challenge in measuring the spatial guide vane of hydraulic machinery lies in determining the calibration method. The measurement scheme must consider various factors such as measurement errors, lighting arrangements, and the imaging effect of tracer particles. The ideality of the calibration results largely determines the accuracy of the three-dimensional flow field measurement. Conventional in-situ calibration (where the measurement area and calibration area completely overlap) is extremely difficult for calibrating the spatial guide vane of hydraulic machinery. This is because after the hydraulic machinery loop system is installed and debugged, the spatial guide vane is removed, then placed in the calibration container, and after calibration, the spatial guide vane is reassembled for measurement. During this process, the emptying and reassembly of the measurement space cannot guarantee that the optical path between the camera and the calibration / measurement area is completely consistent, leading to significant errors caused by the two installation and measurement processes. Therefore, this application adopts a heterogeneous calibration method (the calibration area and the test area have a fixed optical path relationship) to achieve the calibration of the flow field of the spatial guide vane of hydraulic machinery before measurement, and performs optical path calculation and analysis on the test area of ​​the spatial guide vane, in which the optical path error caused by the vertical distance noise of the test area can be ignored.

[0042] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the present invention.

[0043] like Figure 1 As shown, this invention discloses a method for measuring the flow field of a spatial guide vane body based on V3V technology. This method is applied to measure the flow field of a spatial guide vane body in hydraulic machinery, such as a waterjet propulsion pump. The invention is illustrated using a waterjet propulsion pump test bench system as an example. Specifically, the method includes the following steps:

[0044] Step S1, Calibration Preparation: A V3V measurement system is provided, which includes a V3V camera array, a camera optical three-dimensional coordinate frame, a laser light guide arm, an image acquisition card, a computer, a synchronizer, and a laser light source. The V3V camera array is mounted on the camera optical three-dimensional coordinate frame and is connected to the computer via the image acquisition card. The laser light source is connected to the laser light guide arm, and the synchronizer is connected to both the V3V camera array and the laser light source. The V3V camera array includes three CCD cameras: Camera Right, Camera Left, and Camera Top.

[0045] Specifically, the pre-experiment preparations are as follows: The waterjet propulsion pump experimental platform mainly includes a waterjet propulsion pump model, motor, torque meter, encoder, pressure tank, booster pump, inlet and outlet pressure gauges, flow meter, and piping system. The operational stability of the waterjet propulsion pump experimental platform is debugged, and repeatability measurements are performed to ensure stable operation of the waterjet propulsion pump. The optical measurement hardware in the V3V measurement system is debugged, especially when installing the camera optical 3D coordinate frame, ensuring sufficient space is reserved for the parallel movement of the camera array to facilitate equipment movement during fine-tuning. Before the experiment, it is also essential to ensure that all ground objects are properly placed and ground connections are properly handled to avoid personnel injury and equipment damage in insufficient light. It is worth noting that due to the special environmental requirements of this V3V experiment, the darker the indoor lighting during the experimental filming, the better. During the measurement process, a black curtain is used to cover the spatial guide vane measurement area to reduce the influence of natural light on the measurement results, and matte tape is used to cover areas outside the spatial guide vane measurement area that are prone to light oversaturation.

[0046] Step S2, determining the camera position using a different location: A calibration container filled with water is placed between the area to be measured on the space guide vane of the water jet propulsion pump and the V3V camera array. A target disk is placed inside the calibration container, and the vertical projection of the target disk and the plane of the area to be measured (i.e., the surface of the area to be measured) of the space guide vane is made to coincide. After adjusting the spatial position of the camera array so that the center of the V3V camera array coincides with the center of the target disk, the distance between the target disk and the V3V camera array is measured and recorded.

[0047] Specifically, considering that the space guide vane of the water jet propulsion pump test bench system is made of pure acrylic material with a shell thickness of 20mm, a smooth and flat surface, and good light transmission, the calibration container is made of pure acrylic material with the same wall thickness as the space guide vane of the water jet propulsion pump test bench system. The target disk is 200*200mm in size, with a grid spacing of 5mm. Three points around the center point are deliberately missing to facilitate finding the center point of the target disk. Place the calibration container in front of the plane of the area to be measured on the space guide vane (the plane of the area to be measured on the space guide vane is parallel to the surface of the calibration container). Ensure that the observation plane of the calibration container is parallel to the plane of the area to be measured on the space guide vane, and that the projection plane of the target disk and the plane of the area to be measured on the space guide vane coincides in the vertical direction. Use the camera optical three-dimensional coordinate frame to adjust the spatial position of the V3V camera array so that it is directly in front of the center of the target disk (i.e., the calibration center) (so that the center of the V3V camera array coincides with the center of the target disk). Then, ensure that the positions of the V3V camera array in the x, y, and z directions remain unchanged, and measure and record the distance L between the target disk and the V3V camera array inside the calibration container.

[0048] Step S3: Determine the thickness of the target disk calibration space and the position of each calibration section: Based on the measurement area of ​​the space guide vane of the water jet propulsion pump, determine the thickness of the target disk calibration space, and determine the position of each calibration section based on the thickness of the target disk calibration space, and the thickness of the target disk calibration space is not less than the thickness of the space guide vane.

[0049] Specifically, based on the measurement area of ​​the guide vane body of the waterjet propulsion pump (x*y*z = 60mm*50mm*30mm, where x is the axial direction and z is the guide vane flow channel width / thickness direction), the calibration space thickness is determined to be 50mm (not less than the thickness direction of the guide vane), and there are 21 calibration sections in the calibration space, with thicknesses of 0, 2.5, 5, ..., 45, 47.5, and 50mm. The camera reference plane is defined as a reference plane with the same field of view for all three CCD cameras. The distance from this reference plane to the camera plane is an important parameter in the calibration and V3V camera array setup. Under the existing experimental conditions, a continuous LED light source is used in the rear to uniformly illuminate the target, resulting in a relatively clear array of light spots on the target disk.

[0050] Step S4, V3V calibration process: Adjust the camera parameters (e.g., aperture) of the V3V camera array to ensure that the saturation and image clarity of the calibration points on the target disk meet the preset requirements, and record the camera parameters of the V3V camera array. Move the target disk in the standard container toward the direction of the space guide vane, and take pictures of the target disk according to the position of the calibration section of the target disk using the V3V camera array. Transmit the pictures of the target disk to the computer through the image acquisition card.

[0051] Specifically, adjust the camera parameters of the V3V camera array, observe the saturation level of the calibration points on the target disk, and ensure the calibration image is bright and clear (i.e., the saturation level and image clarity of the calibration points on the target disk can be considered to meet the preset requirements). Record the camera parameters (aperture, etc.). Sufficient space has been reserved for the parallel movement of the V3V camera array during the installation of the camera's optical 3D coordinate frame to facilitate equipment movement during fine-tuning. Furthermore, the movement of the target disk along the Z-axis must be along the camera's optical axis. The target disk movement must remain level so that each row of the target disk's dot matrix is ​​horizontal relative to the V3V camera array.

[0052] Step S5, Calibration Result Evaluation and Flow Field Measurement: The computer is used to evaluate the current position and camera parameters of the V3V camera array based on the image of the target disk captured by the V3V camera array. If the evaluation of the current position and camera parameters of the V3V camera array is valid, the flow field of the space guide vane of the hydraulic machinery is measured based on the current position and camera parameters of the V3V camera array.

[0053] In a preferred embodiment of the present invention, a computer is used to determine whether the target center trajectory line, linear magnification, and warping error of the three cameras of the V3V camera array meet preset requirements based on the image of the target disk captured by the V3V camera array. If the preset requirements are met, the current position and camera parameters of the V3V camera array are evaluated as valid. If the preset requirements are not met, the current position and camera parameters of the V3V camera array are evaluated as invalid, and the process returns to the step of adjusting the camera parameters of the V3V camera array so that the saturation and image clarity of the calibration point on the target disk meet the preset requirements. That is, the process returns to step S4 and repeats the V3V calibration process until the current position and camera parameters of the V3V camera array are evaluated as valid.

[0054] Specifically, after calibration, the first step in confirming the calibration results is to open the image of the target disk captured by the V3V camera array and evaluate the current position and camera parameters of the V3V camera array. This mainly involves analyzing the trajectory line of the target center of the three cameras in the V3V camera array, linear magnification, and warping error. The analysis also includes checking whether the movement of the origin positions of the three sets of cameras in the three images captured simultaneously by CameraRight, CameraLeft, and CameraTop follows a straight trajectory; whether the lines connecting the origins in the three images form triangles similar to the triangle formed by the lines connecting the three cameras; and whether the origins in the three images are evenly spaced and regularly distributed in a chart. If all these conditions are met, it indicates that the origin position data collected during calibration is stable and reliable. Figure 3 The structure shown; observe the magnification to ensure that the linear magnification laws followed by the three cameras (CameraRight, CameraLeft, and CameraTop) are almost completely consistent, such as... Figure 4 The structure shown; observe the degree of warping deformation after spatial reconstruction of the three camera groups, ensuring that the calibration warping error values ​​of the CameraRight, CameraLeft, and CameraTop cameras are stable between 10 and 12 μm, within the effective range, and without single-point jumps or abrupt changes. Figure 4 The structure shown.

[0055] In a preferred embodiment of the present invention, the step of measuring the flow field of the spatial guide vane of the hydraulic machinery based on the current position and camera parameters of the V3V camera array in step S3 specifically includes:

[0056] Step 1: Generate a laser volume source for V3V measurement: Remove the calibration container and target disk, and install a volume source adjustment optics unit on the optical path of the laser source to expand the laser emitted by the laser source into a laser volume source that can cover and illuminate the entire flow field of the space guide vane. Specifically, the aforementioned volume source adjustment optics unit includes two lenses.

[0057] The specific steps for generating the laser source for the V3V measurement are as follows: Due to the curvature of the guide vane, the laser projection should aim to cover the entire flow channel (i.e., the entire flow field of the guide vane body) while minimizing the irradiation area in other regions. Therefore, a lens (-25mm) is installed separately on the optical path of the laser source, and the laser sheet source is adjusted. Then, another lens (-50mm) is added to the optical path of the laser source to diffuse the laser sheet source in the depth direction, forming a laser source. Based on the experimental object (x*y*z = 60mm*50mm*30mm), the measurement space is approximately 150*100*50mm. After adjustment, this becomes the laser source required for the V3V experiment.

[0058] Step 2, Relative position adjustment between V3V measurement and the external landmark: Translate the V3V camera array on the camera optical 3D coordinate frame to adjust the distance between the V3V camera array and the area to be measured on the space guide vane so that it is equal to the distance between the recorded target disk and the V3V camera array.

[0059] In a preferred embodiment of the present invention, after translating the V3V camera array on the camera optical three-dimensional coordinate frame to adjust the distance between the V3V camera array and the test area of ​​the space guide vane to be equal to the distance between the recorded target disk and the V3V camera array, the method further includes a step of calibrating (fine-tuning) the position of the V3V camera array using a camera calibration laser; specifically, the step of calibrating the position of the V3V camera array using a camera calibration laser includes:

[0060] Step a: Use camera calibration laser calibration to ensure that the central area of ​​the flow channel captured by the V3V camera array is aligned with the camera optical axis of the V3V camera array.

[0061] Step b: Use camera calibration laser calibration to make the shooting plane of the V3V camera array parallel to the plane of the area to be measured of the space guide vane.

[0062] Step c: Use camera calibration laser calibration to ensure that the shooting surface of the V3V camera array covers the entire flow channel of the space guide vane (that is, to obtain the intersection of the two laser beams, i.e., the reference plane is at the back of the shooting area).

[0063] Specifically, before moving the V3V camera array, ensure that all equipment power is off and camera connections are secure. Using the 3D coordinate optical support, slowly move the V3V camera array to the front of the space guide vane, keeping the V3V camera array plane parallel to the front surface of the space guide vane. Then, activate the camera calibration laser for calibration.

[0064] Step 3, add tracer particles: Add the pre-mixed tracer particle suspension to the flow channel of the water jet propulsion pump and start the water jet propulsion pump.

[0065] Specifically, a V3V measurement experiment was conducted using fluorescent particles (in conjunction with a green laser with a wavelength of 532nm). The V3V particle concentration was maintained at 0.0025–0.030 clearly identifiable particles per pixel. The powdered tracer particles were evenly sprinkled into a container filled with water and vigorously stirred until thoroughly mixed. A pre-prepared high-concentration suspension was reserved for later use. After each settling period, the suspension was vigorously stirred again to maintain its consistency. The water jet propulsion pump experimental platform was started, and the motor speed was adjusted. The pre-mixed high-concentration suspension of fluorescent tracer particles was slowly added to the experimental platform, allowing sufficient time for the particles to be evenly mixed within the water jet propulsion pump liquid. All experimental equipment was started, and it was confirmed that the laser source, synchronizer, and V3V camera array were in normal communication and operational status. Using the "Continuous" shooting mode, the laser energy was adjusted or the tracer particle suspension was added until a sufficiently large and evenly distributed distribution of particles was visible in the captured image.

[0066] Step 4, set measurement and shooting parameters: set the laser intensity of the laser source and the measurement and shooting parameters of the synchronizer.

[0067] Preferably, the measurement and imaging parameters of the synchronizer include: pulse repetition frequency, laser pulse delay time, exposure time, and frame span time of the captured image.

[0068] Specifically, the synchronizer's measurement and imaging parameters are set as follows: Pulse RepRate (Hz), Laser Pulse Delay (μs), and Exposure (μs). A straddle mode is used, where the camera captures two consecutive single-exposure images. The pulse repetition rate is selected as 15Hz (based on the operating conditions of the water jet propulsion pump). The laser pulse delay time must be greater than the Q-switch delay time, set to 220μs (estimated based on the measurement speed). The exposure time is the exposure time of the first frame (Frame A). Adjusting the exposure time of the first frame will correspondingly increase or decrease the exposure time of the second frame (Frame B). This time is not critical, but it is essential to ensure that the laser pulse falls within the time range of both the first (Frame A) and second (Frame B) frames, and is set to 300μs. Additionally, the estimated average flow velocity is 0.1–0.3 m / s, and the synchronizer timing parameters are adjusted to ensure that all shooting conditions are met. After repeated test shots and calculations, it was finally determined that when the frame span time Δt is 250μs, good and reliable flow field calculation results can be obtained, and sufficient storage space must be maintained.

[0069] Laser intensity settings for the laser source: Laser intensity directly affects the scattering of tracer particles. Experiments with insufficient light intensity will result in an inadequate number of particles; however, excessive light intensity will cause excessive particle scattering, also reducing the number of particles that can be identified. Therefore, the experiment requires setting a suitable light intensity, and it is essential to ensure that the laser beams from Laser A and Laser B have the same intensity. During setup, a lower power setting between 1 and 3 is sufficient; during imaging, a higher power setting, generally between 7 and 10, is recommended.

[0070] Step 5, V3V measurement image acquisition: Based on the above measurement and shooting parameters, use a V3V camera array to photograph the spatial guide vane of the water jet propulsion pump and transmit the photographed spatial guide vane image to the computer through an image acquisition card.

[0071] Step Six: ： Image data processing and flow field data acquisition of the V3V system: The computer processes the images of the space guide vane captured by the V3V camera array to obtain the velocity data of the tracer particles inside the space guide vane, and obtains the flow field data of the space guide vane based on the velocity data of the tracer particles inside the space guide vane.

[0072] In a preferred embodiment of the present invention, the step of the computer processing the image of the space guide vane captured by the V3V camera array to obtain the velocity data of the tracer particles in the space guide vane is specifically as follows: the computer sequentially performs image preprocessing, particle identification in the image, particle matching and spatial reconstruction, velocity synthesis calculation and velocity field spatial reconstruction, and velocity field postprocessing on the image of the space guide vane captured by the V3V camera array to obtain the velocity data of the tracer particles in the space guide vane.

[0073] In a preferred embodiment of the present invention, the step of obtaining the flow field data of the space guide vane body based on the velocity data of the tracer particles inside the space guide vane body specifically includes: calculating and analyzing the velocity data of the tracer particles inside the space guide vane body based on ParaView 5.10 and MATLAB to obtain the flow field data of the space guide vane body, and the flow field data includes the average flow field, the flow statistics, the transient flow field, the transient flow field feature extraction, and the flow field reconstruction.

[0074] Those skilled in the art should understand that variations can be implemented by combining existing technology with the above embodiments, which will not be elaborated here. Such variations do not affect the essence of the present invention, and will not be elaborated here either.

[0075] The preferred embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and the devices and structures not described in detail should be understood as being implemented in a conventional manner in the art. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the scope of the present invention. This does not affect the essential content of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the present invention's technical solutions still fall within the protection scope of the present invention.

Claims

1. A method for measuring the flow field of a spatial guide vane body based on V3V technology, applied to measuring the flow field of a spatial guide vane body in hydraulic machinery, characterized in that, Includes the following steps: A V3V measurement system is provided, comprising a V3V camera array, a camera optical three-dimensional coordinate frame, a laser light guide arm, an image acquisition card, a computer, a synchronizer, and a laser source. The V3V camera array is mounted on the camera optical three-dimensional coordinate frame and is communicatively connected to the computer via the image acquisition card. The laser source is connected to the laser light guide arm, and the synchronizer is connected to both the V3V camera array and the laser source. A calibration container filled with water is placed between the test area of ​​the space guide vane of the hydraulic machinery and the V3V camera array. A target disk is placed in the calibration container, and the target disk is aligned with the vertical projection plane of the test area of ​​the space guide vane. After adjusting the spatial position of the camera array so that the center of the V3V camera array coincides with the center of the target disk, the distance between the target disk and the V3V camera array is measured and recorded. Based on the test area of ​​the spatial guide vane of the hydraulic machinery, the thickness of the target disk calibration space is determined, and the position of each calibration section is determined based on the thickness of the target disk calibration space, and the thickness of the target disk calibration space is not less than the thickness of the test area of ​​the spatial guide vane. Adjust the camera parameters of the V3V camera array to achieve the preset requirements for saturation and image clarity of the calibration points on the target disk. After recording the camera parameters of the V3V camera array, move the target disk in the calibration container toward the direction of the space guide vane. Then, use the V3V camera array to take pictures of the target disk according to the position of the calibration section of the target disk, and transmit the pictures of the target disk to the computer through the image acquisition card. The computer evaluates the current position and camera parameters of the V3V camera array based on the image of the target disk captured by the V3V camera array. If the evaluation of the current position and camera parameters of the V3V camera array is valid, the flow field of the spatial guide vane of the hydraulic machinery is measured based on the current position and camera parameters of the V3V camera array. The step of measuring the flow field of the spatial guide vane of the hydraulic machinery based on the current position and camera parameters of the V3V camera array includes the steps of removing the calibration container and the target disk, and translating the V3V camera array on the camera optical three-dimensional coordinate frame.

2. The method for measuring the flow field of a spatial guide vane based on V3V technology as described in claim 1, characterized in that, The specific steps for measuring the flow field of the spatial guide vane of a hydraulic machine based on the current position and camera parameters of the V3V camera array include: Remove the calibration container and the target disk, and adjust the optical part by installing a bulk light source in the optical path of the laser light source to expand the laser emitted by the laser light source into a laser bulk light source that can cover and illuminate the flow field of the space guide vane; The V3V camera array is translated on the camera optical three-dimensional coordinate frame to adjust the distance between the V3V camera array and the test area of ​​the space guide vane so that it is equal to the distance between the recorded target disk and the V3V camera array; The pre-mixed tracer particle suspension is added to the flow channel of the hydraulic machine, and the hydraulic machine is started. Set the laser intensity of the laser source and the measurement and shooting parameters of the synchronizer; The V3V camera array is used to photograph the spatial guide vane of the hydraulic machinery, and the captured images of the spatial guide vane are transmitted to the computer through the image acquisition card; The computer processes images of the space guide vane captured by the V3V camera array to obtain velocity data of tracer particles within the space guide vane, and obtains flow field data of the space guide vane based on the velocity data of the tracer particles within the space guide vane.

3. The method for measuring the flow field of a spatial guide vane based on V3V technology as described in claim 2, characterized in that, The volume light source adjustment optics unit includes two lenses.

4. The method for measuring the flow field of a spatial guide vane based on V3V technology as described in claim 2, characterized in that, The tracer particles are fluorescent particles.

5. The method for measuring the flow field of a spatial guide vane based on V3V technology as described in claim 2, characterized in that, The step of translating the V3V camera array on the camera optical three-dimensional coordinate frame to adjust the distance between the V3V camera array and the test area of ​​the space guide vane so that it is equal to the distance between the recorded target disk and the V3V camera array also includes the step of calibrating the position of the V3V camera array using a camera calibration laser. The specific steps for calibrating the position of the V3V camera array using a camera calibration laser include: The camera calibration laser calibration is used to ensure that the central area of ​​the flow channel captured by the V3V camera array is aligned with the camera optical axis of the V3V camera array. The camera calibration laser calibration is used to make the imaging plane of the V3V camera array parallel to the plane of the area to be measured of the space guide vane. The camera calibration laser calibration ensures that the imaging surface of the V3V camera array covers the entire flow channel of the space guide vane.

6. The method for measuring the flow field of a spatial guide vane based on V3V technology as described in claim 2, characterized in that, The synchronizer measures the following shooting parameters: pulse repetition frequency, laser pulse delay time, exposure time, and frame span time of the captured image.

7. The method for measuring the flow field of a spatial guide vane based on V3V technology as described in claim 2, characterized in that, The specific steps for the computer to process images of the space guide vane captured by the V3V camera array to obtain velocity data of tracer particles within the space guide vane are as follows: The computer sequentially performs image preprocessing, particle identification, particle matching and spatial reconstruction, velocity synthesis calculation and velocity field spatial reconstruction, and velocity field post-processing on the images of the space guide vane captured by the V3V camera array to obtain velocity data of the tracer particles in the space guide vane.

8. The method for measuring the flow field of a spatial guide vane based on V3V technology as described in claim 2, characterized in that, The specific steps for obtaining the flow field data of the space guide vane body based on the velocity data of tracer particles inside the space guide vane body are as follows: Based on ParaView 5.10 and MATLAB, the velocity data of tracer particles in the space guide vane are calculated and analyzed to obtain the flow field data of the space guide vane. The flow field data includes the average flow field, the flow statistics, the transient flow field, the transient flow field feature extraction, and the flow field reconstruction.

9. The method for measuring the flow field of a space guide vane based on V3V technology as described in claim 1, characterized in that, Both the calibration container and the space guide vane are made of acrylic.

10. The method for measuring the flow field of a space guide vane body based on V3V technology as described in claim 1, characterized in that, The specific steps for evaluating the current position and camera parameters of the V3V camera array using a computer based on images of the target disk captured by the V3V camera array are as follows: The computer is used to determine whether the target center trajectory line, linear magnification, and warping error of the three cameras of the V3V camera array meet the preset requirements based on the images of the target disk captured by the V3V camera array. If the preset requirements are met, the current position of the V3V camera array and the camera parameters are evaluated as valid. If the preset requirements are not met, the current position and camera parameters of the V3V camera array are evaluated as invalid, and the process returns to adjusting the camera parameters of the V3V camera array so that the saturation and image clarity of the calibration points on the target disk meet the preset requirements.

Images