Display method of vortex structure in cold state and combustion flow field

Abstract

The invention discloses a display method for a vortex structure in a cold state and a combustion flow field, and relates to the technical field of fluid display. Generating a laser sheet light source according to the vortex structure characteristic parameters; tracking particles are selected and generated based on the vortex structure characteristic parameters; scattering tracking particles in the to-be-detected area; acquiring an image of the to-be-detected area according to the vortex structure characteristic parameters; and processing the image of the to-be-detected area, and displaying the vortex structure. The vortex structure display method is divided into six systematic steps of obtaining vortex structure characteristic parameters, generating a laser sheet light source, selecting and generating tracking particles, scattering the tracking particles, collecting an image and processing the image, and the vortex structure characteristic parameters penetrate through the whole process to form a complete and correlated technical scheme. The problems that a traditional display method is large in parameter setting randomness and all steps are lack of coordination are solved, and clear display of internal and external forms of the vortex structure and accurate capture of dynamic characteristics are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of fluid display, in particular to a method for displaying vortex structures in cold and combustion flow fields. Background Art

[0002] The observation and analysis of vortex structures in flow fields are of great significance to the optimization of combustion processes, fluid dynamics research, and combustion equipment design. The methods commonly used for macroscopic display of cold and burning flow fields include the smoke flow method and the schlieren method. The smoke flow method is mainly suitable for flow observation in wind tunnels and is not very suitable for combustion flow fields, especially in open spaces. The schlieren method is suitable for cold and burning flow fields, and can capture the fluid flow state and flame morphology in real time. However, when vortex structures exist in the flow field, only vortex clusters can be displayed, and their internal and external structures cannot be distinguished. Therefore, a display method suitable for vortex structures in cold and burning flow fields is needed to solve the problem that it is difficult to distinguish their internal and external structures using the schlieren method. Summary of the Invention

[0003] In view of the above-mentioned problems, the present invention is proposed.

[0004] Therefore, the present invention provides a method for displaying vortex structures in cold and burning flow fields, which can solve the problems mentioned in the background technology.

[0005] To solve the above technical problems, the present invention provides the following technical solutions: a method for displaying vortex structures in cold and combustion flow fields, comprising: obtaining characteristic parameters of the vortex structure; generating a laser sheet light source according to the characteristic parameters of the vortex structure; selecting and generating tracking particles based on the characteristic parameters of the vortex structure; scattering the tracking particles in the area to be measured; collecting an image of the area to be measured according to the characteristic parameters of the vortex structure; processing the image of the area to be measured to display the vortex structure.

[0006] As a preferred solution of the method for displaying vortex structures in cold and combustion flow fields described in the present invention, the method of obtaining characteristic parameters of the vortex structure includes: determining the type of flow field to be measured; obtaining flow characteristic data of the flow field to be measured; and analyzing the characteristic parameters of the vortex structure based on the flow characteristic data.

[0007] As a preferred solution of the method for displaying vortex structures in cold and combustion flow fields described in the present invention, generating a laser sheet light source according to the characteristic parameters of the vortex structure includes: selecting a laser based on the characteristic parameters of the vortex structure; adjusting the output parameters of the laser according to the characteristic parameters of the vortex structure; and converting the light output of the laser into a laser sheet light source through an optical system.

[0008] As a preferred solution of the method for displaying vortex structures in cold and combustion flow fields described in the present invention, the method of selecting and generating tracking particles based on the characteristic parameters of the vortex structure includes: analyzing the environmental parameters of the area to be measured according to the characteristic parameters of the vortex structure; determining the characteristic parameters of the particles based on the environmental parameters; selecting the type of tracking particles according to the characteristic parameters of the particles; and generating the tracking particles using a particle generating device corresponding to the type of tracking particles. The beneficial effects of this preferred technical solution are: through a systematic process of analyzing the environmental parameters of the area to be measured, determining the characteristic parameters of the particles, selecting the type of tracking particles, and generating tracking particles using a corresponding device, the problems of large arbitrariness in the selection of tracking particles and unstable particle performance in different flow field environments in traditional methods are solved, ensuring that the tracking particles in different areas to be measured have good flow field following and scattering characteristics, and providing basic conditions for clearly displaying the vortex structure.

[0009] As a preferred solution of the method for displaying vortex structures in cold and combustion flow fields described in the present invention, the method comprises: scattering the tracking particles in the area to be measured includes: determining the distribution area of ​​the vortex structure in the area to be measured according to the characteristic parameters of the vortex structure; starting the laser sheet light source; adjusting the position of the laser sheet light source according to the characteristic parameters of the vortex structure; determining the scattering parameters of the tracking particles according to the characteristic parameters of the vortex structure; controlling the particle conveying system to introduce the tracking particles into the vortex structure distribution area of ​​the area to be measured; and monitoring the distribution state of the tracking particles in the area to be measured. The beneficial effects of this preferred technical solution are: by accurately determining the vortex structure distribution area, scientifically adjusting the position of the laser sheet light source, reasonably setting the tracking particle scattering parameters and monitoring the distribution state in real time, the problems of uneven particle scattering and inaccurate observation area in the traditional method are solved, ensuring that the tracking particles can be evenly distributed in the vortex structure area, and improving the clarity and accuracy of the vortex structure display.

[0010] As a preferred embodiment of the method for displaying vortex structures in cold and combustion flow fields described in the present invention, the tracking particle types include liquid particles and solid particles. When the liquid particles are selected, the generation of the tracking particles includes: selecting silicone oil or olive oil as the liquid material; introducing the liquid material from the end of the atomizer; introducing a high-speed carrier gas flow at the bottom end of the atomizer, wherein the high-speed carrier gas flow is air or nitrogen; and adjusting the high-speed carrier gas flow velocity and the atomizer outlet diameter to generate the liquid particles.

[0011] As a preferred solution of the method for displaying vortex structures in cold and combustion flow fields described in the present invention, the tracking particle types include liquid particles and solid particles. When the solid particles are selected, the generation of the tracking particles includes: selecting silicon oxide, zirconium oxide or aluminum oxide as the solid material; filling the solid material in a solid particle generator; introducing fluidizing gas on one side of the solid particle generator, wherein the fluidizing gas is air or nitrogen; and controlling the flow rate of the fluidizing gas to generate the solid particles.

[0012] As a preferred embodiment of the method for displaying vortex structures in cold and combustion flow fields described in the present invention, the method includes: collecting images of the area to be measured according to the characteristic parameters of the vortex structure, including: setting imaging parameters of a high-speed camera according to the characteristic parameters of the vortex structure; adjusting the position of the high-speed camera to align with the area to be measured; and collecting an image sequence of the area to be measured. The beneficial effect of this preferred technical solution is that by setting the imaging parameters of the high-speed camera according to the characteristic parameters of the vortex structure, accurately adjusting the camera position, and collecting an image sequence of the target area, the problem of the traditional method of image acquisition parameter setting being highly empirical and difficult to capture dynamic vortex structures is solved, thereby achieving a complete record of the vortex structure evolution process and providing high-quality raw data for subsequent analysis.

[0013] As a preferred embodiment of the method for displaying vortex structures in cold and combustion flow fields described in the present invention, the method includes: acquiring an image of the area to be measured based on the characteristic parameters of the vortex structure; setting imaging parameters of a high-speed camera based on the characteristic parameters of the vortex structure; adjusting the position of the high-speed camera to align with the area to be measured; and acquiring a sequence of images of the area to be measured. The beneficial effects of this preferred technical solution are: by preprocessing the image, applying an enhancement method, using a vortex recognition algorithm to mark the vortex area, and organizing the image to display the vortex structure, the problems of strong subjectivity and poor display quality in vortex structure identification in traditional methods are resolved, thereby achieving objective identification and clear visualization of the vortex structure.

[0014] As a preferred solution of the method for displaying vortex structures in cold and combustion flow fields described in the present invention, the processing of the image of the area to be measured to display the vortex structure also includes: applying modal decomposition technology to process the image of the area to be measured; and constructing a three-dimensional model of the vortex structure based on the image of the area to be measured.

[0015] Beneficial effects of the present invention: The present invention solves the technical problem that the traditional smoke flow method and the schlieren method cannot clearly display the internal and external features of the vortex structure through the systematic parameter optimization design based on the characteristic parameters of the vortex structure. The present invention first establishes the correlation between the characteristic parameters of the vortex structure and the various parts of the system, so that the laser sheet light source parameters, the tracking particle selection and spreading method, the image acquisition parameters and the image processing method form a coordinated and consistent whole, and achieves a qualitative breakthrough in the following aspects: the link of obtaining the characteristic parameters of the vortex structure realizes the forward-looking analysis of the formation mechanism of the vortex structure, providing a scientific basis for the subsequent steps; the precise control of the laser sheet light source makes the light sheet thickness match the characteristic scale of the vortex structure, solving the problem that the traditional light source is difficult to clearly display vortex structures of different scales; the selection and generation process of the tracking particles takes into account the balance between the particle followability and scattering characteristics, overcoming the shortcoming of poor stability of traditional particles in high-temperature combustion flow fields; the precise control of the particle spreading link realizes the optimal distribution of particles in the vortex area; the precise matching of the image acquisition parameters with the characteristic frequency and speed of the vortex structure solves the problem of spatiotemporal resolution of capturing dynamic vortex structures; the innovative application of image processing and vortex recognition methods realizes the objective identification and visualization of vortex structures. In summary, the present invention can not only clearly display the internal and external morphology and dynamic evolution process of the vortex structure, but also extract the characteristic parameters of the vortex structure through quantitative analysis, providing an important tool for fluid dynamics research and combustion process optimization. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 This is a schematic diagram of the overall process of a method for displaying vortex structures in cold and burning flow fields proposed by the present invention;

[0018] Figure 2 Schematic diagram of an experimental system for a method of displaying vortex structures in cold and burning flow fields proposed by the present invention;

[0019] Figure 3 This is a display effect diagram of the vortex structure induced by the buoyancy convection of the jet flame boundary in a method for displaying the vortex structure in the cold state and combustion flow field proposed by the present invention;

[0020] Figure 4 This is a display effect diagram of the vortex structure in the cold flow field upstream of the flame, which is a recommendation of the display method of the vortex structure in the cold and burning flow fields proposed by the present invention. DETAILED DESCRIPTION

[0021] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, the following detailed description of the specific embodiments of the present invention is given in conjunction with the accompanying drawings. It is obvious that the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in this field without creative work should fall within the scope of protection of the present invention.

[0022] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0023] Example 1, with reference to Figure 1 and Figure 2 , as one embodiment of the present invention, provides a method for displaying vortex structures in cold and burning flow fields, comprising:

[0024] S100: Obtaining characteristic parameters of vortex structure;

[0025] S200: generating a laser sheet light source according to the characteristic parameters of the vortex structure;

[0026] S300: Selecting and generating tracking particles based on the characteristic parameters of the vortex structure;

[0027] S400: Spreading the tracking particles in the area to be measured;

[0028] S500: Acquire an image of the area to be measured according to the characteristic parameters of the vortex structure;

[0029] S600: Process the image to display the vortex structure.

[0030] It should be noted that the combustion flow fields in industrial combustion equipment and aircraft engines contain complex vortex structures, which significantly impact combustion efficiency, pollutant emissions, and combustion stability. Traditional smoke flow methods are primarily suitable for observing flow patterns in wind tunnels and are less suitable for combustion flow fields. While the schlieren method can be used for combustion flow fields, when vortex structures are present, it can only visualize vortex clusters and cannot distinguish the internal and external structures. Furthermore, the high temperatures present in combustion flow fields pose challenges to observation techniques, making conventional observation methods difficult to maintain stability and accuracy under these conditions.

[0031] Therefore, to address the aforementioned vortex structure observation issues, the present invention, through steps S100-S600, utilizes the principles of laser sheet illumination and tracking particle scattered light to achieve clear visualization of vortex structures in both cold and burning flow fields. Simultaneously, through real-time image acquisition with a high-speed camera, the evolution of vortex structures can be dynamically observed, providing strong support for flow field dynamics research. As a non-invasive measurement method, this invention does not interfere with the natural state of the flow field, and can obtain more accurate and reliable measurement results.

[0032] Example 2, reference Figure 1 , which is an embodiment of the present invention, provides a method for displaying vortex structures in cold and combustion flow fields based on the above embodiments.

[0033] In an embodiment of the present invention, obtaining characteristic parameters of the vortex structure in step S100 includes the following steps A1-A3:

[0034] A1: Determine the type of flow field to be measured;

[0035] A2: Obtain flow characteristic data of the flow field to be measured;

[0036] A3: Analyze the characteristic parameters of the vortex structure based on flow characteristics data.

[0037] Specifically, in A1, the flow field type must be determined based on the actual application scenario. Cold flow fields can be categorized as laminar or turbulent; combustion flow fields can be further subdivided into premixed combustion, diffusion combustion, and partially premixed combustion. The determination of the flow field type directly impacts the subsequent analysis of the characteristic parameters of the vortex structure.

[0038] Specifically, in A2, acquiring flow characteristic data for the flow field to be measured involves measuring or estimating basic parameters such as the Reynolds number, fluid density, viscosity, and velocity distribution. For combustion flow fields, additional combustion-related characteristic data such as flame propagation velocity, equivalence ratio, and heat release rate must also be acquired.

[0039] Specifically, in A3, the characteristic parameters of the vortex structure are analyzed based on the flow characteristic data, including its characteristic frequency, characteristic scale, generation location, and intensity. These parameters provide a foundation for subsequent steps, ensuring the rationality of laser sheet light source settings, tracking particle selection, and image acquisition parameters.

[0040] In an optional embodiment, the vortex structure characteristic parameters obtained in step S100 can also be obtained through computational fluid dynamics (CFD) methods, and vortex structure information that may exist in the flow field can be obtained through numerical simulation. Specifically, large eddy simulation (LES) or direct numerical simulation (DNS) methods can be used to capture the vortex generation, development, and dissipation processes in the flow field with high spatial and temporal accuracy, thereby predetermining the main characteristic parameters of the vortex structure.

[0041] In another optional embodiment, the characteristic parameters of the vortex structure obtained in step S100 can also be estimated based on an experimental database of similar flow fields. By querying experimental results under similar operating conditions, combining similarity theory and dimensionless analysis methods, a mapping relationship between the current flow field and known flow fields is established, thereby deducing the characteristic parameters of the vortex structure in the current flow field.

[0042] In an embodiment of the present invention, generating a laser sheet light source according to characteristic parameters of the vortex structure in step S200 includes the following steps B1-B3:

[0043] B1: Select laser based on vortex structure characteristic parameters;

[0044] B2: Adjust the output parameters of the laser according to the characteristic parameters of the vortex structure;

[0045] B3: The optical system converts the laser light output into a laser sheet light source.

[0046] Specifically, in step B1, the appropriate laser type is selected based on the characteristic scale and speed of the vortex structure. For small-scale, high-speed vortex structures, a high-power pulsed laser is required to provide sufficient scattered light intensity; for large-scale, low-speed vortex structures, a continuous laser can be used to achieve stable illumination conditions.

[0047] Specifically, in B2, laser parameters such as output power, wavelength, and pulse frequency are adjusted based on the scattering characteristics of the vortex structure. For example, for vortex structures in high-temperature combustion flow fields, the laser power needs to be appropriately increased to overcome the interference of thermal radiation background. For flow fields containing different particles, the laser wavelength needs to be selected to match the particle scattering characteristics.

[0048] Specifically, in B3, an optical system consisting of a cylindrical lens assembly, a beam expander, and a focusing lens converts a point laser source into a laser sheet. The optical system design ensures that the thickness of the resulting laser sheet is appropriate for the scale of the vortex structure to be observed, typically within the range of 0.2-1.0 mm, and that the intensity distribution of the laser sheet is uniform, with no noticeable areas of uneven brightness.

[0049] In an optional embodiment, the laser sheet light source in step S200 can also be generated using a wavelength-tunable laser system, which automatically selects the optimal wavelength based on the scattering characteristics of the tracked particle to achieve the best signal-to-noise ratio. This system adjusts the angle or temperature of the nonlinear crystal to change the laser output wavelength, thereby adapting to the optimal scattering wavelength of different tracked particles and improving image quality.

[0050] In another alternative embodiment, the laser sheet light source generated in step S200 can also be generated using a dual laser sheet light system. Two mutually perpendicular laser sheet light sources simultaneously illuminate the flow field, and combined with a dual-camera synchronous acquisition system, three-dimensional visualization of the vortex structure can be achieved. This method can more comprehensively capture the spatial distribution characteristics of the vortex structure.

[0051] In an embodiment of the present invention, selecting and generating tracking particles based on vortex structure characteristic parameters in step S300 includes the following steps C1-C4:

[0052] C1: Analyze the environmental parameters of the area to be measured based on the characteristic parameters of the vortex structure;

[0053] C2: Determine particle characteristic parameters based on environmental parameters;

[0054] C3: Select the tracking particle type based on the particle characteristic parameters;

[0055] C4: Generate tracking particles using a particle generation device corresponding to the tracking particle type.

[0056] Specifically, in C1, the environmental parameters of the area under test are analyzed, including the flow field temperature range, velocity distribution, medium composition, and pressure. For combustion flow fields, special parameters such as flame temperature and combustion product distribution also need to be considered. These environmental parameters directly influence the selection and generation of tracking particles.

[0057] Specifically, in C2, particle characteristic parameters are determined based on environmental parameters, primarily including particle density, particle size range, temperature resistance, and light scattering properties. Ideally, tracking particles should have good flow field tracking performance, meaning a sufficiently small Stokes number (typically less than 0.1) ensures that the particles can accurately follow the flow field without lag or inertial deviation.

[0058] Specifically, in C3, the most suitable tracking particle type is selected based on the particle's characteristic parameters. For low-temperature, cold flow fields, liquid particles such as silicone oil or olive oil droplets can be used; for high-temperature, combustion flow fields, heat-resistant solid particles such as zirconium oxide or aluminum oxide powder are required. The choice of tracking particles requires a balance between tracking performance and scattering intensity. Smaller particle size results in better tracking performance, but also weaker scattering intensity.

[0059] Specifically, in C4, corresponding particle generation devices are used for different tracking particle types. Liquid particles can be generated by an atomizer, while solid particles can be generated by a solid particle generator. The parameters of the particle generation device must be adjusted based on the previously determined particle characteristic parameters to ensure that the generated tracking particles meet the experimental requirements.

[0060] In an optional embodiment, fluorescent particles can be used as tracking particles in step S300. These particles emit fluorescence at a specific wavelength when illuminated by laser light. By installing a corresponding bandpass filter in front of the image acquisition system, background scattered and reflected light can be filtered out, allowing only the fluorescent signal to be received. This significantly improves the signal-to-noise ratio of the image, making it particularly suitable for complex flow environments with strong background interference.

[0061] In another alternative embodiment, the tracking particles generated in step S300 can also be generated using electrospray technology to generate nanoscale charged droplets. This method applies a high voltage to the capillary tip, causing the liquid to be atomized into extremely small charged droplets under the action of the electric field. The particle size can be controlled within the range of 50-500 nanometers, with excellent flow field tracking performance, making it suitable for observing tiny vortex structures.

[0062] In an embodiment of the present invention, spreading tracking particles in the area to be measured in step S400 includes the following steps D1-D6:

[0063] D1: Determine the distribution area of ​​the vortex structure in the area to be measured based on the characteristic parameters of the vortex structure;

[0064] D2: Start the laser sheet light source;

[0065] D3: Adjust the position of the laser light source according to the characteristic parameters of the vortex structure;

[0066] D4: Determine the spreading parameters of tracking particles based on the characteristic parameters of the vortex structure;

[0067] D5: Control the particle delivery system to introduce tracking particles into the vortex structure distribution area of ​​the area to be measured;

[0068] D6: Monitor the distribution of tracking particles in the area to be tested.

[0069] Specifically, in D1, preliminary flow field analysis or preliminary experiments are used to determine the spatial region where vortex structures are likely to appear. For jet flames, vortex structures typically form downstream of the flame tip; for propulsion flames, the focus is primarily on the upstream region of the flame root. Accurately determining the distribution of vortex structures helps optimize subsequent observation strategies.

[0070] Specifically, in steps D2-D3, the laser sheet light source is activated and adjusted to align the laser sheet light plane with the main plane of the vortex structure. For axisymmetric flow fields, the laser sheet light is typically perpendicular to the main axis of the flow. For complex three-dimensional flow fields, multi-angle scanning is required to determine the optimal observation plane.

[0071] Specifically, in D4, the tracking particle distribution parameters, including particle concentration, distribution position, and distribution method, are determined based on the characteristic parameters of the vortex structure. The particle concentration needs to be sufficient to clearly display the vortex structure, but not too high to cause mutual obstruction or interfere with the characteristics of the flow field itself.

[0072] Specifically, in the D5, tracking particles are introduced into the measurement area via a particle delivery system. For combustion flow fields, particles are typically introduced into the fuel jet or ambient air; for cold flow fields, particles can be introduced directly upstream of the observation area. The particle delivery system must be designed to ensure uniform particle distribution, preventing aggregation or sedimentation during delivery.

[0073] Specifically, in the D6, a high-speed camera monitors the distribution of particles within the test area in real time, ensuring that there are no obvious blank areas within the particle field and that the particle distribution density is moderate, clearly showing the boundaries and internal features of the vortex structure. If monitoring reveals uneven particle distribution, the parameters of the particle delivery system are adjusted until the ideal state is achieved.

[0074] In an optional embodiment, the tracking particle release in step S400 can also employ a pulsed particle release strategy. Based on the periodic characteristics of the vortex structure, tracking particles are released at specific times to enhance the visualization of the vortex structure. This approach is particularly suitable for vortex structures with strong periodicity and high predictability, such as Karman vortex streets or vortex structures caused by periodic combustion instabilities.

[0075] In another alternative embodiment, tracking particle distribution in step S400 can also utilize a multi-point injection system, simultaneously introducing tracking particles at different locations within the flow field to ensure uniform particle distribution throughout the observation area. This approach is suitable for large-scale observation areas or flow fields with complex geometries, effectively avoiding uneven particle distribution caused by sedimentation or diffusion during particle transport.

[0076] In an embodiment of the present invention, collecting an image of the area to be measured according to the characteristic parameters of the vortex structure in step S500 includes the following steps E1-E3:

[0077] E1: Setting the imaging parameters of the high-speed camera according to the characteristic parameters of the vortex structure;

[0078] E2: Adjust the position of the high-speed camera to the area to be measured;

[0079] E3: Collect an image sequence of the area to be tested.

[0080] Specifically, in E1, the high-speed camera's frame rate and exposure time are set based on the vortex structure's characteristic frequency and velocity. The frame rate setting must adhere to the Nyquist sampling theorem, meaning it should be greater than twice the vortex structure's characteristic frequency to fully capture the dynamic evolution of the vortex structure. The exposure time is set based on the maximum velocity of the tracked particles to avoid motion blur during the exposure period.

[0081] Specifically, in E2, the high-speed camera's position is adjusted so that its field of view covers the entire vortex distribution area, while ensuring that the camera lens axis is perpendicular to the laser sheet's optical plane to obtain the clearest scattering image. The camera's magnification must be set based on the characteristic scale of the vortex structure, ensuring both sufficient resolution of the vortex structure in the image and a field of view that fully encompasses the entire vortex structure.

[0082] Specifically, in E3, a high-speed camera is activated to capture a sequence of images of the area to be measured. The acquisition duration must cover the complete lifecycle of multiple vortex structures to facilitate subsequent analysis of their dynamic characteristics. Image quality must be monitored in real time throughout the acquisition process to ensure accurate focus, appropriate brightness, and clear contrast.

[0083] In an alternative embodiment, the image acquisition in step S500 can also be performed using a dual-camera stereo imaging system. Two calibrated high-speed cameras simultaneously capture the flow field from different angles, and the three-dimensional spatial distribution of the vortex structure is reconstructed using the principle of parallax. This method overcomes the limitations of single-plane observation and obtains complete spatial information about the vortex structure.

[0084] In another alternative embodiment, the image acquisition in step S500 can also utilize synchronized triggering of a high-speed camera and a laser system to precisely capture the vortex structure at a specific moment. By precisely synchronizing the exposure time of the high-speed camera with the emission time of the pulsed laser, high signal-to-noise ratio images can be obtained within an extremely short exposure time, making it suitable for observing vortex structures in high-speed flow fields.

[0085] In an embodiment of the present invention, processing the image of the area to be measured and displaying the vortex structure in step S600 includes the following steps F1-F4:

[0086] F1: Preprocess the image of the area to be tested;

[0087] F2: Apply image enhancement methods to process the image of the area to be measured;

[0088] F3: Use vortex recognition method to mark the vortex area in the image of the area to be measured;

[0089] F4: The image of the tissue area to be tested shows a vortex structure.

[0090] Specifically, in F1, the original image is preprocessed, including background removal, noise filtering, and geometric correction. Background removal is achieved by capturing a particle-free background image and then subtracting it from the original image. Noise filtering can use methods such as Gaussian filtering and median filtering. Geometric correction is used to eliminate image distortion caused by camera lens distortion and viewing angle.

[0091] Specifically, in F2, image enhancement methods are applied to the preprocessed image to improve the visibility and boundary clarity of the vortex structure. Common image enhancement methods include histogram equalization, adaptive contrast enhancement, and edge sharpening. For areas with uneven particle density, a local adaptive enhancement algorithm can be used, applying different enhancement parameters to different areas.

[0092] Specifically, in F3, vortex identification methods are used to identify and mark vortex regions in the enhanced image. Vortex identification methods can be based on particle distribution pattern analysis, detecting the rotational characteristics of the particle velocity field or the vorticity distribution to determine the location and boundaries of vortex structures. The output of this step is typically an image with vortex regions marked, facilitating subsequent analysis and visualization.

[0093] Specifically, in F4, the processed image sequence is organized in chronological order to form a continuous display of the dynamic evolution of the vortex structure. Various visualization methods can be used, such as pseudo-color display, 3D reconstruction, or animation sequence, to intuitively show the vortex structure's morphology, intensity, and evolution process.

[0094] In an optional embodiment, the image processing in step S600 can also employ intrinsic mode decomposition (POD) technology to extract the primary spatial modes and temporal coefficients of the vortex structure from the image sequence, enabling quantitative analysis of the vortex structure's dynamic characteristics. This method can identify dominant structures and periodic features in the flow field and is suitable for analyzing multi-scale vortex structures in complex flow fields.

[0095] In another optional embodiment, the image processing in step S600 can also use particle image velocimetry (PIV) technology to obtain the instantaneous velocity distribution of the flow field by calculating the particle displacement field between consecutive image frames, and then calculate the characteristic quantities of the vortex structure such as the vortex field and the strain rate field, thereby achieving an in-depth analysis of the dynamic mechanism of the vortex structure.

[0096] In addition, processing the image to display the vortex structure in step S600 may further include the following steps G1-G2:

[0097] G1: Apply modal decomposition technology to process the image of the area to be measured;

[0098] G2: Construct a three-dimensional model of the vortex structure based on the image of the area to be measured.

[0099] Specifically, in G1, modal decomposition techniques such as proper mode decomposition (POD), dynamic mode decomposition (DMD), or wavelet decomposition are applied to decompose the vortex structure into modal combinations of different spatiotemporal scales. These modes can reveal the energy distribution, temporal evolution characteristics, and spatial interaction mechanisms of the vortex structure, providing a quantitative basis for studying the physical mechanisms of vortex structures.

[0100] Specifically, G2 constructs a three-dimensional model of the vortex structure based on the processed image sequence. For single-plane observation data, the 3D structure can be inferred by assuming the vortex structure has a certain symmetry (such as axisymmetry or plane symmetry). For multi-plane or stereo imaging data, the 3D model can be directly constructed using computer graphics methods such as volume rendering or isosurface extraction, achieving comprehensive visualization of the vortex structure.

[0101] In summary, the method for displaying vortex structures in cold and burning flow fields, provided by this invention, achieves high-precision visualization of vortex structures through a systematic process for acquiring characteristic parameters of vortex structures, optimizing laser sheet light source and tracking particle selection, precisely controlling the tracking particle distribution process, scientifically setting image acquisition parameters, and employing advanced image processing techniques. This method is applicable to a variety of flow field environments and can clearly display the internal and external characteristics of vortex structures, providing an important visualization tool for fluid dynamics and combustion science research.

[0102] Example 3, reference Figures 2 to 4 , which is an embodiment of the present invention, is different from the previous two embodiments in that, based on the previous embodiment, a method for displaying vortex structures in cold and combustion flow fields is performed through a display system for vortex structures in cold and combustion flow fields.

[0103] like Figure 2 As shown in the figure, this flow field visualization system primarily consists of a particle tracking component and an image acquisition component. Tracking particles can be either liquid (silicone oil, olive oil, etc.) or solid (silicon oxide, zirconium oxide, aluminum oxide, etc.) particles, with a micron size. They are generated by a glass atomizer or a solid particle generator, mixed with air in a mixing chamber, and then introduced into the flow field to be measured. This system primarily utilizes the particle's tracking ability. The image acquisition system includes a laser sheet system and a high-speed camera. A laser beam is transformed through a set of lenses into a light sheet approximately 0.5 mm thick, illuminating a specific plane in the flow field. The high-speed camera then captures the image.

[0104] The implementation steps are as follows:

[0105] (1) Generate a laser sheet light source with a thickness of no more than 0.5 mm. The function of the light sheet is to illuminate the tracking particles on a certain plane within the area to be measured. Therefore, the light source must be of high intensity. Ordinary white light sources are not suitable due to their low brightness. This system uses a laser with a higher light intensity as the light source, such as a continuous laser with a wavelength of 532 nm. The laser point light source passes through a set of cylindrical mirrors to form a laser sheet light source with a thickness of no more than 0.5 mm.

[0106] (2) Produce tracking particles with a particle size of no more than 10 microns. If liquid particles are used, silicone oil or olive oil can be selected. The above liquid is introduced from the end of the glass nebulizer, and a high-speed carrier gas flow is introduced at the bottom of the glass nebulizer. Non-toxic and non-polluting inert gases such as air or nitrogen can be used. The shearing effect of the high-speed carrier gas flow at the outlet of the nebulizer can be used to produce particles with uniform particle size. The particle size of the tracking particles mainly depends on the outlet diameter of the glass nebulizer. If solid particles are used, solid powders such as silicon oxide, zirconium oxide, and aluminum oxide can be selected. A certain amount of solid powder is filled in the solid particle generator, which accounts for about 1 / 3 of the volume of the internal cavity of the solid particle generator. Fluidizing gas is introduced on one side of the generator. Non-toxic and non-polluting inert gases such as air or nitrogen can be used. After the fluidizing gas is fully mixed with some solid particles, the air flow carries the solid particles into the test area. The particle size of the solid tracking particles mainly depends on the particle size of the solid powder.

[0107] (3) Spread tracking particles in the area to be tested. After turning on the laser and illuminating the area to be tested with a light sheet, the tracking particles are introduced into the area to be tested. The concentration of particles in the area to be tested is observed using a high-speed camera. This method does not have strict requirements on the particle concentration, as long as there are no obvious blank areas in the particle field.

[0108] (4) Image acquisition: Adjust the camera frame rate and exposure time according to the actual flow velocity in the cold or burning flow field to clearly capture the vortex structure in the flow field.

[0109] The above system is used to capture the vortex structure in the flow field to test its effectiveness. The application scenarios are as follows:

[0110] Figure 3This is an application case of the jet flame combustion flow field. The flame oscillation or flickering phenomenon is a type of flame instability, which refers to the periodic changes in flame height, width and brightness over time. This phenomenon is mainly due to the buoyancy convection-induced Rayleigh-Taylor instability and Kelvin-Helmholtz instability at the interface between the high-temperature burned gas and the environment around the flame surface. In fluid mechanics, Rayleigh-Taylor instability refers to the instability phenomenon that occurs at the interface when a light fluid propels toward a heavy fluid. Kelvin-Helmholtz instability is a shear layer instability caused by velocity difference. It occurs at the interface of the same fluid or two fluids. When the shear layer develops to a certain position, it becomes unstable, thereby generating a wavy vortex structure. Figure 3 The oscillation (or flickering) phenomenon of laminar jet diffusion flame is shown. It can be seen that a symmetrical large-scale vortex structure appears downstream of the flame tip due to buoyancy convection. This structure is clearly presented, and the movement law of the vortex structure can be further obtained through statistics.

[0111] Figure 4 This is an application case of cold flow field. Figure 4 As shown in the figure, the regular laminar jet upstream of the flame root produces a wavy structure (marked by the red circle) due to the KH instability, and the surrounding air is sucked into the central fuel jet. When the jet breakup position (marked by the red dotted line) is low, the particle concentration near the flame root is more uniform, indicating that the mixing degree of fuel and air is enhanced.

[0112] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for displaying vortex structures in cold and burning flow fields, characterized in that: include: Obtaining characteristic parameters of vortex structure; generating a laser sheet light source according to the characteristic parameters of the vortex structure; Selecting and generating tracking particles based on the characteristic parameters of the vortex structure; Spreading the tracking particles in the area to be measured; Collecting an image of the area to be measured according to the characteristic parameters of the vortex structure; The image of the area to be measured is processed to display the vortex structure.

2. The method for displaying vortex structures in cold and burning flow fields according to claim 1, characterized in that: The obtaining of characteristic parameters of the vortex structure comprises: Determine the type of flow field to be measured; Acquiring flow characteristic data of the flow field to be measured; Characteristic parameters of the vortex structure are analyzed based on the flow characteristic data.

3. The method for displaying vortex structures in cold and burning flow fields according to claim 2, characterized in that: Generating a laser sheet light source according to the characteristic parameters of the vortex structure includes: Selecting a laser based on the characteristic parameters of the vortex structure; adjusting the output parameters of the laser according to the characteristic parameters of the vortex structure; The light output of the laser is converted into a laser sheet light source by an optical system.

4. The method for displaying vortex structures in cold and burning flow fields according to claim 3, characterized in that: The selecting and generating tracking particles based on the characteristic parameters of the vortex structure includes: Analyzing the environmental parameters of the area to be measured according to the characteristic parameters of the vortex structure; determining particle characteristic parameters based on the environmental parameters; Selecting a tracking particle type according to the particle characteristic parameters; The tracking particles are generated using a particle generating device corresponding to the tracking particle type.

5. The method for displaying vortex structures in cold and burning flow fields according to claim 4, characterized in that: The spreading of the tracking particles in the area to be measured comprises: Determining the distribution area of ​​the vortex structure in the area to be measured according to the characteristic parameters of the vortex structure; Starting the laser sheet light source; adjusting the position of the laser sheet light source according to the characteristic parameters of the vortex structure; determining the spreading parameters of the tracking particles according to the characteristic parameters of the vortex structure; controlling a particle delivery system to introduce the tracking particles into the vortex structure distribution area of ​​the area to be measured; The distribution state of the tracking particles in the area to be measured is monitored.

6. The method for displaying vortex structures in cold and burning flow fields according to claim 5, characterized in that: The tracking particle types include liquid particles and solid particles. When the liquid particles are selected, generating the tracking particles includes: Choose silicone oil or olive oil as the liquid material; Passing the liquid material into the end of the atomizer; A high-speed carrier gas flow is introduced into the bottom end of the atomizer, wherein the high-speed carrier gas flow is air or nitrogen; The liquid particles are generated by adjusting the velocity of the high-speed carrier gas and the diameter of the atomizer outlet.

7. The method for displaying vortex structures in cold and burning flow fields according to claim 6, characterized in that: The tracking particle types include liquid particles and solid particles. When the solid particles are selected, generating the tracking particles includes: Select silicon oxide, zirconium oxide or aluminum oxide as the solid material; filling the solid material in a solid particle generator; A fluidizing gas is introduced into one side of the solid particle generator, wherein the fluidizing gas is air or nitrogen; The solid particles are generated by controlling the flow rate of the fluidizing gas.

8. The method for displaying vortex structures in cold and burning flow fields according to claim 7, characterized in that: The collecting of the image of the area to be measured according to the characteristic parameters of the vortex structure comprises: Setting imaging parameters of a high-speed camera according to the characteristic parameters of the vortex structure; Adjust the position of the high-speed camera to align with the area to be measured; An image sequence of the area to be measured is collected.

9. The method for displaying vortex structures in cold and burning flow fields according to claim 8, characterized in that: The processing of the image of the area to be measured to display the vortex structure includes: Preprocessing the image of the area to be measured; Applying an image enhancement method to process the image of the area to be measured; Marking a vortex region in the image of the area to be measured using a vortex recognition method; The image of the area to be tested is organized to show the vortex structure.

10. The method for displaying vortex structures in cold and burning flow fields according to claim 9, characterized in that: The processing of the image of the area to be measured to display the vortex structure further comprises: applying a modal decomposition technique to process the image of the area to be measured; A three-dimensional model of the vortex structure is constructed based on the image of the area to be measured.

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