Visual online measurement method for complex vortex flow of vortex tube

Abstract

The invention provides a visual online measurement method for complex vortex flow of a vortex tube, solves the problems of low measurement precision and poor stability and reliability of a non-intrusive flow test technology, and carries out accurate inversion, identification and continuous correction on characteristic parameters of the vortex tube based on multi-source heterogeneous experimental test data; according to the characteristics that numerous hot spots in the vortex tube are distributed in a scattered mode and the positions of the hot spots are random, a vortex tube wall sound wave transceiver array arrangement scheme and an effective sound wave propagation path are constructed, and the visual measurement method for vortex tube complex vortex flow in any form is constructed based on the acoustic tomography technology. According to the method, the temperature distribution of gas in the vortex tube can be accurately inverted, a double-helix cold and hot air flow structure is indirectly described through a temperature field, the complex flow online inversion method based on digital twinning can overcome the defects in the prior art, and the method has the advantages of real-time online non-intrusive measurement and wide temperature measurement range.

Description

Technical Field

[0001] The invention belongs to a non-contact measurement method for complex energy separation and flow visualization of a vortex tube, and particularly relates to an online measurement method for complex vortex flow visualization of a vortex tube. Background Art

[0002] The vortex tube is a simple thermal device that can separate compressed gas into two streams of cold and hot air. It has no moving parts inside, a simple structure, and is easy to use. It has the advantages of small size, light weight, green working fluid, and no maintenance costs. The vortex tube has great development potential and broad development prospects in many fields such as refrigeration, heating, gas separation, air dehumidification, natural gas liquefaction, cryogenic biology, precision instruments, aerospace, etc. Although the vortex tube is widely used, its low energy separation efficiency has always restricted its continued development. Therefore, researchers from all over the world have carried out a lot of theoretical and experimental research on the energy separation mechanism and performance of the vortex tube. The vortex tube, which seems to have a very simple structure and operation, performs very complex three-dimensional motion inside, involving many interdisciplinary fields such as fluid mechanics, heat transfer, and thermodynamics. The complex three-dimensional strong vortex flow form in the vortex tube is the difficulty that limits the clear understanding of its energy separation mechanism, and clear temperature and velocity distribution and flow structure are essential to explain this phenomenon. Since Ranque invented the vortex tube, scholars have never stopped exploring its energy separation mechanism. However, due to the differences in the design structure, processing technology, material selection, working fluid use, etc. of the vortex tube, the results obtained so far have not been unified. So far, there is no clear and widely accepted understanding of its internal energy separation mechanism. With the continuous deepening of vortex tubes in industrial applications, people hope to have a deeper understanding of the energy separation mechanism and structural improvement of vortex tubes, so as to better understand the energy separation phenomenon of vortex tubes and guide the improvement of structures and optimization of performance through mechanisms, so as to innovate and realize the wider application of vortex tubes. However, the current experimental technology research on vortex tubes lags far behind the research on existing applications. Due to the lack of reliable flow field visualization instruments, the study of the changing laws of the energy separation effect caused by changes in vortex tube structures and working conditions has become extremely challenging.

[0003] In order to understand the flow pattern of the fluid in the vortex tube, some scholars have used transparent materials such as glass or resin to process and manufacture vortex tubes to achieve visualization of the internal field of the vortex tube. These tracer-based visualization studies help to initially understand the main flow patterns in the vortex tube. Due to the strong centrifugal force caused by strong swirl, it is often difficult for tracer particles to obtain accurate and stable flow traces. In addition, since visualization studies can only qualitatively describe the flow in the vortex tube, for more detailed data, such as pressure, temperature, velocity field distribution, etc., further in-depth research on measurement methods is needed.

[0004] At present, there are two main methods for obtaining the three-dimensional flow field in the vortex tube: contact measurement and non-contact measurement. Contact measurement generally uses instruments such as pitot tubes, thermocouples and hot wire anemometers to perform invasive experimental measurements on the main channel of the vortex tube, which can obtain quantitative information on the velocity field, pressure field and temperature field. Due to the limited size of the vortex tube, invasive probe measurement will cause certain interference to the internal flow field of the vortex tube, and most of the working conditions are relatively simple, and the velocity of the entire field cannot be obtained, and it is difficult to analyze the mechanism of flow structure changes with working conditions. Non-contact measurement includes infrared measurement, particle imaging technology and laser Doppler velocimetry. This non-invasive measurement can avoid interference with the flow field and has high measurement accuracy. However, non-contact measurement technology requires the use of tracer particles to complete the experiment, so the tracking and scattering of the tracer particles are relatively high. In addition, the density of particles entrained by the fluid is significantly different from the density of the fluid, and it is impossible to completely follow the fluid 100%. The particle velocity is more or less different from the flow velocity, which is the primary error of the laser velocimeter. At the same time, due to the refraction of light on the circular wall of the vortex tube and the high centrifugal force, the tracer particles in this non-contact measurement will be thrown to the tube wall immediately after entering the tube, making it impossible for the camera (or probe) to capture particle information, resulting in unstable tracer particle tracking and unreliable flow field tracking traces. Finally, this measurement method can generally only measure the internal flow field of the vortex tube under low-pressure inlet conditions, and other auxiliary instruments are required to measure static pressure, which has great limitations.

[0005] Intrusive probe measurement technology obtains the distribution of pressure field, velocity field and temperature field by drilling holes on the pipe wall. Although it is widely used, it will damage the pipe wall to a certain extent and is difficult to apply to small vortex tubes. In order to obtain richer and more accurate flow field information, small-size vortex tube experimental technology based on non-invasive testing technology is of great significance. Although experimental testing technologies represented by particle imaging and laser phase Doppler velocimetry are relatively mature and will help the study of internal flow in vortex tubes, particle imaging velocimetry and laser phase Doppler velocimetry are relatively expensive and difficult to promote. In the future, it is necessary to further develop convenient and low-cost flow visualization test methods to assist in the in-depth exploration of the complex flow mechanism and energy separation mechanism of vortex tubes. Summary of the invention

[0006] The present invention constructs a visualization measurement method for complex vortex flow in a vortex tube based on acoustic tomography technology. The method has the advantages of not contacting the complex flow inside the vortex tube, a wide temperature measurement range, a large measurement area, and real-time online measurement. The temperature testing method based on acoustic tomography can accurately invert the temperature distribution of the gas in the vortex tube, and then indirectly characterize the double-helix hot and cold air flow structure through the temperature field. This method can overcome the shortcomings of the prior art and has attractive application prospects for the visualization of complex flow fields in vortex tubes.

[0007] In view of this, the present invention provides a method for visualizing online measurement of complex vortex flow in a vortex tube, comprising the following basic operating steps:

[0008] S1: Establish accurate identification and testing methods for characteristic parameters of vortex tubes;

[0009] S2: Considering the scattered distribution of many hot spots in the vortex tube and the randomness of their locations, a layout scheme of the acoustic wave transceiver array on the wall of the vortex tube and an effective acoustic wave propagation path are constructed;

[0010] S3: Aiming at the non-uniform temperature distribution inside the vortex tube, a temperature field tomography algorithm considering the sound ray bending effect is established based on the forward unfolding sound ray tracing technology;

[0011] S4: Under the premise of meeting the measurement accuracy, establish a method to simplify the acoustic wave transceiver and fully verify the layout plan of the transceiver array;

[0012] S5: Deeply integrate acoustic tomography experimental data, flow physics models and machine learning algorithms to construct a digital twin method for online inversion of vortex tube flow that integrates measurement and calculation, structure and effect, and achieves high-fidelity mirroring and low-latency visualization of complex vortices in vortex tubes.

[0013] Furthermore, in step S1, a method for accurately identifying and testing characteristic parameters of a vortex tube is established, which specifically includes the following steps:

[0014] Step 1-1: Conduct sensitivity analysis on the characteristic parameters of complex vortex dynamics of the vortex tube, arrange sensors based on the optimal layout technology of complex measuring points, improve the density of sensor information and reduce the redundancy of information;

[0015] Steps 1-2: By arranging different types of sensors at the same measuring point and different types of sensors at different measuring points, it is possible to perceive the complex flow inside the vortex tube more accurately and meticulously from different angles and dimensions.

[0016] In steps 1-3, the experimental data, fast Fourier transform and wavelet algorithm are deeply integrated with machine learning methods, and multi-source data segmentation and noise reduction technology are used to reduce the deviation caused by poor data quality from the source, and the reliability time-frequency analysis of the measured vortex tube flow data is performed.

[0017] Furthermore, in step S2, a vortex tube wall acoustic wave transceiver array arrangement scheme and an effective acoustic wave propagation path are constructed, and the specific steps are as follows:

[0018] Step 2-1, design different vortex tube wall acoustic wave transceiver array layout schemes;

[0019] Step 2-2: Establish a data acquisition and transmission system to transmit the vortex tube acoustic tomography test data to the upper virtual machine virtual experiment system in real time;

[0020] Step 2-3: Use measured data and acoustic simulation to determine the effective sound wave propagation path between the transceiver that transmits the sound wave and other transceivers that receive the sound wave.

[0021] Furthermore, in step S3, a temperature field tomography algorithm taking into account the sound ray bending effect is established based on the forward unfolding sound ray tracing technology, including the following steps:

[0022] Step 3-1: According to the functional relationship between the sound velocity distribution of the vortex tube and the sound wave propagation time of each path, a temperature field forward problem model is established, and then an algorithm for the inverse problem of the temperature field based on acoustic tomography is constructed;

[0023] Step 3-2: Establish a temperature field reconstruction algorithm based on triangle forward expansion ray tracing and least squares method to construct a two-dimensional temperature field that takes into account the bending effect of the ray;

[0024] Step 3-3: Establish the tetrahedron forward unfolding sound ray tracking technology to realize the reconstruction of the three-dimensional non-uniform temperature field taking into account the sound ray bending effect, and improve the reconstruction accuracy of the three-dimensional non-uniform temperature field.

[0025] Furthermore, in step S4, a method for establishing a simplified acoustic wave transceiver array layout scheme comprises the following steps:

[0026] Step 4-1, reconstruct the corresponding temperature distribution based on different transceiver numbers, positions and effective sound wave propagation path selection methods;

[0027] Step 4-2: Determine the method of streamlining the acoustic wave transceiver while meeting the measurement accuracy, and verify the feasibility of the transceiver array layout solution.

[0028] Furthermore, in step S5, a digital twin method for online inversion of vortex tube flow with “measurement and calculation fusion, structure and effect integration” is constructed, and the detailed steps are as follows:

[0029] Step 5-1, through collection, field testing and the above-mentioned vortex tube characteristic parameter inversion methods, the initial and boundary conditions, fluid physical parameters and experimental conditions required for constructing the vortex tube three-dimensional vortex flow numerical model are obtained, and then the vortex tube flow visualization digital twin model is constructed;

[0030] Step 5-2: Integrate acoustic tomography experimental data and machine learning methods to construct a full-domain, cross-scale, high-fidelity, and dynamic online simulation method for vortex flow in vortex tubes based on mechanism constraints;

[0031] Step 5-3: Based on a specific discrete scale, a cross-scale flow simulation method that embeds multi-scale physical processes is directly constructed in the discrete space. The large-scale and small-scale vortex distribution characteristics inside the vortex tube are automatically and efficiently characterized according to actual needs, and the fidelity of the virtual-real image of the complex flow in the vortex tube is improved from the perspective of "measurement fusion".

[0032] Step 5-4 combines model reduction technology and machine learning methods to greatly simplify the calculation process of complex eddy flow fields, evolving numerical simulations of tens of minutes or even hundreds of hours into a response efficiency of seconds, thus achieving online simulation of multi-scale vortex structures.

[0033] Compared with the prior art, the method for visualizing online measurement of complex vortex flow in a vortex tube described in the present invention proposes a non-invasive testing technology for visualizing vortex flow in a vortex tube based on acoustic tomography, and accurately inverts complex vortex fields based on the digital twin method of "measurement and calculation fusion, structure and effect integration". It has the following advantages and innovations in overcoming the reliability and convenience problems existing in traditional contact and non-contact measurement technologies:

[0034] (1) Different from the traditional contact and non-contact measurement technologies, the present invention takes a different approach by introducing acoustic tomography technology based on acoustic temperature measurement. By arranging an acoustic transceiver to measure the sound wave propagation velocity in the medium, the temperature distribution inside the vortex tube is inverted, and the double-helix hot and cold airflow structure is accurately measured indirectly through the temperature field.

[0035] (2) Different from the existing flow measurement technology that only passively uses test data, the present invention adopts an innovative method of virtual-real interaction to construct a vortex tube flow digital twin, actively coupling experimental test data, physical models and artificial intelligence methods; based on the big data generated by acoustic tomography tests, the characteristic parameters of the vortex tube are continuously corrected, thereby realizing the hyper-realistic dynamic simulation mapping of the vortex tube entity in the digital space, making the invisible and intangible complex airflow vortex "transparently visualized".

[0036] (3) Different from the traditional flow visualization that relies only on a single hardware measurement technology, the present invention is based on the innovative idea of ​​"combining software and hardware", bidirectionally linking the physical entity with the digital virtual twin, interacting in real time and running synchronously; through machine learning methods, the high-precision simulation of the complex multi-scale turbulence process of the vortex tube is accelerated, making it possible to transmit two-way information between the field measured data and the simulation data in seconds, and then timely interpret and integrate the experimental test data, realizing the vortex tube flow visualization inversion process with self-learning, self-updating, self-feedback and self-evolution capabilities. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a schematic diagram of the vortex flow in a vortex tube according to an embodiment of the method of the present invention.

[0038] Figure 2This is a flow chart of a method for visualizing online measurement of complex vortex flow in a vortex tube according to the present invention.

[0039] Figure 3 The figure is a schematic diagram of the arrangement scheme of the acoustic wave signal transceiver of the acoustic tomography system of the method of the present invention.

[0040] Figure 4 This is a flow chart of acoustic tomography test data acquisition and transmission in the method of the present invention.

[0041] Figure 5 The figure is a schematic diagram of the effective sound wave path between the transceivers of the acoustic tomography system of the method of the present invention.

[0042] Figure 6 This is a flow chart of vortex tube flow visualization based on digital twin virtual-reality interaction of the method of the present invention. DETAILED DESCRIPTION

[0043] The following is a detailed description of an embodiment of the present invention in conjunction with the accompanying drawings. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.

[0044] This embodiment is described based on a typical vortex flow scenario inside a vortex tube. Figure 1 A method for visualizing online measurement of complex vortex flow in a vortex tube according to the present invention is shown in FIG. Figure 2 As shown, the following steps are included:

[0045] S1: Establish a method for accurately identifying and testing characteristic parameters of a vortex tube, which specifically includes the following steps:

[0046] Step 1-1: Conduct sensitivity analysis on the characteristic parameters of complex vortex dynamics of the vortex tube, arrange sensors based on the optimal layout technology of complex measuring points, improve the density of sensor information and reduce the redundancy of information;

[0047] Steps 1-2: By arranging different types of sensors at the same measuring point and different types of sensors at different measuring points, it is possible to perceive the complex flow inside the vortex tube more accurately and meticulously from different angles and dimensions.

[0048] In steps 1-3, the experimental data, fast Fourier transform and wavelet algorithm are deeply integrated with machine learning methods, and multi-source data segmentation and noise reduction technology are used to reduce the deviation caused by poor data quality from the source, and the reliability time-frequency analysis of the measured vortex tube flow data is performed.

[0049] S2: In view of the scattered distribution of many hot spots in the vortex tube and the random characteristics of the location of the hot spots, a layout scheme of the vortex tube wall acoustic wave transceiver array and an effective acoustic wave propagation path are constructed. The specific steps are as follows:

[0050] Step 2-1, such as Figure 3 As shown, different arrangements of vortex tube wall acoustic wave transceiver arrays are designed;

[0051] Step 2-2, such as Figure 4 As shown, a data acquisition and transmission system is established to transmit the vortex tube acoustic tomography test data to the upper virtual machine virtual experiment system in real time;

[0052] Step 2-3, through measured data and acoustic simulation, the effective sound wave propagation path between the transceiver that transmits the sound wave and other transceivers that receive the sound wave is determined, such as Figure 5 shown.

[0053] S3: Aiming at the non-uniform temperature distribution characteristics inside the vortex tube, a temperature field tomography algorithm considering the sound ray bending effect is established based on the forward expansion sound ray tracing technology, including the following steps:

[0054] Step 3-1: According to the functional relationship between the sound velocity distribution of the vortex tube and the sound wave propagation time of each path, a temperature field forward problem model is established, and then an algorithm for the inverse problem of the temperature field based on acoustic tomography is constructed;

[0055] Step 3-2: Establish a temperature field reconstruction algorithm based on triangle forward expansion ray tracing and least squares method to construct a two-dimensional temperature field that takes into account the bending effect of the ray;

[0056] Step 3-3: Establish the tetrahedron forward unfolding sound ray tracking technology to realize the reconstruction of the three-dimensional non-uniform temperature field taking into account the sound ray bending effect, and improve the reconstruction accuracy of the three-dimensional non-uniform temperature field.

[0057] S4: Under the premise of meeting the measurement accuracy, establish a method to simplify the acoustic wave transceiver and fully verify the layout plan of the transceiver array. The steps are as follows:

[0058] Step 4-1, reconstruct the corresponding temperature distribution based on different transceiver numbers, positions and effective sound wave propagation path selection methods;

[0059] Step 4-2: Determine the method of streamlining the acoustic wave transceiver while meeting the measurement accuracy, and verify the feasibility of the transceiver array layout solution.

[0060] S5: Figure 6 , deeply integrate acoustic tomography experimental data, flow physics model and machine learning algorithm, build a "measurement and calculation fusion, structure and effect integration" vortex tube flow online inversion digital twin method, realize high-fidelity mirroring and low-latency visualization of complex vortices in vortex tubes, the detailed steps are as follows:

[0061] Step 5-1, through collection, field testing and the above-mentioned vortex tube characteristic parameter inversion methods, the initial and boundary conditions, fluid physical parameters and experimental conditions required for constructing the vortex tube three-dimensional vortex flow numerical model are obtained, and then the vortex tube flow visualization digital twin model is constructed;

[0062] Step 5-2: Integrate acoustic tomography experimental data and machine learning methods to construct a full-domain, cross-scale, high-fidelity, and dynamic online simulation method for vortex flow in vortex tubes based on mechanism constraints;

[0063] Step 5-3: Based on a specific discrete scale, a cross-scale flow simulation method that embeds multi-scale physical processes is directly constructed in the discrete space. The large-scale and small-scale vortex distribution characteristics inside the vortex tube are automatically and efficiently characterized according to actual needs, and the fidelity of the virtual-real image of the complex flow in the vortex tube is improved from the perspective of "measurement fusion".

[0064] Step 5-4 combines model reduction technology and machine learning methods to greatly simplify the calculation process of complex eddy flow fields, evolving numerical simulations of tens of minutes or even hundreds of hours into a response efficiency of seconds, thus achieving online simulation of multi-scale vortex structures.

[0065] The above-described embodiment is only a preferred solution of the present invention, but it is not intended to limit the present invention. A person skilled in the relevant technical field may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. A method for visualizing online measurement of complex vortex flow in a vortex tube, characterized in that: The non-intrusive testing technology based on acoustic tomography is used to invert the complex flow of the vortex tube online, including the following steps: S1: Establish accurate identification and testing methods for characteristic parameters of vortex tubes; S2: Considering the scattered distribution of many hot spots in the vortex tube and the randomness of their locations, a layout scheme of the acoustic wave transceiver array on the wall of the vortex tube and an effective acoustic wave propagation path are constructed; S3: Aiming at the non-uniform temperature distribution inside the vortex tube, a temperature field tomography algorithm considering the sound ray bending effect is established based on the forward unfolding sound ray tracing technology; S4: Under the premise of meeting the measurement accuracy, establish a method to simplify the acoustic wave transceiver and fully verify the layout plan of the transceiver array; S5: Deeply integrate acoustic tomography experimental data, flow physics models and machine learning algorithms to construct a digital twin method for online inversion of vortex tube flow that integrates measurement and calculation, structure and effect, and achieves high-fidelity mirroring and low-latency visualization of complex vortices in vortex tubes.

2. The method for visualizing online measurement of complex vortex flow in a vortex tube according to claim 1, characterized in that: In step S1, a method for accurately identifying and testing characteristic parameters of a vortex tube is established, which specifically includes the following steps: Step 1-1: Conduct sensitivity analysis on the characteristic parameters of complex vortex dynamics of the vortex tube, arrange sensors based on the optimal layout technology of complex measuring points, improve the density of sensor information and reduce the redundancy of information; Steps 1-2: By arranging different types of sensors at the same measuring point and different types of sensors at different measuring points, it is possible to perceive the complex flow inside the vortex tube more accurately and meticulously from different angles and dimensions. In steps 1-3, the experimental data, fast Fourier transform and wavelet algorithm are deeply integrated with machine learning methods, and multi-source data segmentation and noise reduction technology are used to reduce the deviation caused by poor data quality from the source, and the reliability time-frequency analysis of the measured vortex tube flow data is performed.

3. The method for visualizing online measurement of complex vortex flow in a vortex tube according to claim 1, characterized in that: In step S2, a layout scheme of the vortex tube wall acoustic wave transceiver array and an effective acoustic wave propagation path are constructed, and the specific steps are as follows: Step 2-1, design different vortex tube wall acoustic wave transceiver array layout schemes; Step 2-2: Establish a data acquisition and transmission system to transmit the vortex tube acoustic tomography test data to the upper virtual machine virtual experiment system in real time; Step 2-3: Use measured data and acoustic simulation to determine the effective sound wave propagation path between the transceiver that transmits the sound wave and other transceivers that receive the sound wave.

4. The method for visualizing online measurement of complex vortex flow in a vortex tube according to claim 1, characterized in that: In step S3, a temperature field tomography algorithm taking into account the sound ray bending effect is established based on the forward unfolding sound ray tracing technology, including the following steps: Step 3-1: According to the functional relationship between the sound velocity distribution of the vortex tube and the sound wave propagation time of each path, a temperature field forward problem model is established, and then an algorithm for the inverse problem of the temperature field based on acoustic tomography is constructed; Step 3-2: Establish a temperature field reconstruction algorithm based on triangle forward expansion ray tracing and least squares method to construct a two-dimensional temperature field that takes into account the bending effect of the ray; Step 3-3: Establish the tetrahedron forward unfolding sound ray tracking technology to realize the reconstruction of the three-dimensional non-uniform temperature field taking into account the sound ray bending effect, and improve the reconstruction accuracy of the three-dimensional non-uniform temperature field.

5. The method for visualizing online measurement of complex vortex flow in a vortex tube according to claim 1, characterized in that: In step S4, a method for establishing a simplified acoustic wave transceiver array layout scheme is as follows: Step 4-1, reconstruct the corresponding temperature distribution based on different transceiver numbers, positions and effective sound wave propagation path selection methods; Step 4-2: Determine the method of streamlining the acoustic wave transceiver while meeting the measurement accuracy, and verify the feasibility of the transceiver array layout solution.

6. The method for visualizing online measurement of complex vortex flow in a vortex tube according to claim 1, characterized in that: In step S5, a digital twin method for online inversion of vortex tube flow with "measurement and calculation fusion, structure and effect integration" is constructed, and the detailed steps are as follows: Step 5-1, through collection, field testing and the above-mentioned vortex tube characteristic parameter inversion methods, the initial and boundary conditions, fluid physical parameters and experimental conditions required for constructing the vortex tube three-dimensional vortex flow numerical model are obtained, and then the vortex tube flow visualization digital twin model is constructed; Step 5-2: Integrate acoustic tomography experimental data and machine learning methods to construct a full-domain, cross-scale, high-fidelity, and dynamic online simulation method for vortex flow in vortex tubes based on mechanism constraints; Step 5-3: Based on a specific discrete scale, a cross-scale flow simulation method that embeds multi-scale physical processes is directly constructed in discrete space. The large-scale and small-scale vortex distribution characteristics inside the vortex tube are automatically and efficiently characterized according to actual needs, and the fidelity of the virtual-real image of the complex flow in the vortex tube is improved from the perspective of "measurement fusion"; Step 5-4 combines model reduction technology and machine learning methods to greatly simplify the calculation process of complex eddy flow fields, evolving numerical simulations of tens of minutes or even hundreds of hours into a response efficiency of seconds, thus achieving online simulation of multi-scale vortex structures.

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