Interference material efficiency evaluation method and system

Abstract

The invention discloses an interference material efficiency evaluation method and system. The method comprises the following steps: establishing an interference material concentration distribution prediction model in a smoke box environment, carrying out interference material particle concentration distribution numerical calculation according to the interference material concentration distribution prediction model, and extracting the interference material particle concentration in an optical channel from a calculation result; according to the single radiation transmission model of the interference material particles, calculating extinction efficiency factors and scattering efficiency factors of the interference material particles when electromagnetic waves with different incident angles and different wavelengths are incident; establishing an optical path GOA model of the interference material under real smoke screen particle concentration distribution, and substituting the particle radius of the interference material, the particle concentration of the interference material in an optical channel and extinction efficiency factors and scattering efficiency factors of the interference material particles when electromagnetic waves with different incident angles and different wavelengths are incident into the GOA model; and calculating to obtain the extinction effect of the interference material in the smoke box. According to the invention, interference effectiveness evaluation of non-uniform distribution of interference materials can be realized.

Description

Technical Field

[0001] The invention relates to a method and a system for evaluating the effectiveness of interference materials, and belongs to the technical field of smoke screen interference effectiveness evaluation. Background Art

[0002] The development of interference materials, smoke-generating equipment and devices cannot be separated from theoretical guidance, scientific experiments and the support of evaluation results. How to objectively and accurately evaluate the interference effectiveness of interference materials and smoke screens has become an important issue in the field of smoke screen technology. At present, the most widely used interference materials and smoke screen interference effectiveness evaluation methods are infrared spectroscopy, smoke box test method and field test method. The wide application of these evaluation methods provides important support for the development of the smoke screen field.

[0003] The infrared spectroscopy method requires a very small amount of interfering material sample (milligram level), has good test repeatability, fast analysis speed and simple operation. However, due to the large difference between this test method and the smoke screen release method of the interfering material, the measurement results are not very convincing in the evaluation of the material interference performance. It is currently commonly used for the characterization and selection of interfering materials in the scientific research stage. The mass extinction coefficient test value measured by infrared spectroscopy is much smaller than the result of the smoke box test method. In addition, the disadvantages of low light source intensity and large quantitative analysis error of infrared spectrometers also restrict the application of infrared spectroscopy in the evaluation of the interference performance of interfering materials.

[0004] The smoke box test method requires a small amount of interference material sample (gram level), and can measure the interference effect of each band (infrared, visible light, millimeter wave, etc.). The conditions are controllable when repeating the test, but due to the limitations of the smoke box size, stirring method, etc., it is impossible to ensure that the interference material is evenly distributed in the smoke box, and the measurement results are somewhat different from the interference effect of the actual application of the material. In addition, the premise of the Lambert-Beer law is that the absorbing material is evenly dispersed in the system. This law is actually not applicable to the case of uneven distribution of interference materials.

[0005] Field testing is the most reliable measurement method for evaluating the interference performance of materials. The test conditions are closest to the use environment of smoke-generating equipment and instruments, and it is a key means in the scientific research stage. However, field testing requires a lot of manpower and material resources, requires a large amount of interference material samples (kilogram level), and is affected by factors such as season and weather, and the test repeatability is poor.

[0006] In addition, these evaluation methods are not unified. The numerical deviations of the results obtained by various test methods such as infrared spectroscopy, smoke box test and field test are large, and it is difficult to verify the results obtained by multiple test methods with each other. Summary of the invention

[0007] The object of the present invention is to provide a method and system for evaluating the effectiveness of interference materials to solve one or more problems existing in the above-mentioned background technology.

[0008] To achieve the above object, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a method for evaluating the effectiveness of interference materials, comprising:

[0010] Establish a prediction model for the distribution of interference material particle concentration in a smoke box environment, perform numerical calculations on the distribution of interference material particle concentration based on the prediction model, and extract the concentration of interference material particles in the optical channel from the calculation results of the distribution of interference material particle concentration;

[0011] According to the single radiation transmission model of the interfering material particles, the extinction efficiency factor and scattering efficiency factor of the interfering material particles are calculated when electromagnetic waves with different incident angles and wavelengths are incident;

[0012] A GOA model of the optical path of interference materials under the actual concentration distribution of smoke particles is established. The radius of interference material particles, the concentration of interference material particles in the optical channel, and the extinction efficiency factor and scattering efficiency factor of interference material particles when electromagnetic waves of different incident angles and wavelengths are incident are substituted into the GOA model to calculate the transmittance and mass extinction coefficient of the interference material in the smoke box.

[0013] Furthermore, the interference material particle concentration distribution prediction model is established according to the following method:

[0014] A three-dimensional model of a smoke box is established. The inner wall of the smoke box is lined with an absorbing sponge cone, which is covered with glass fiber cloth. The internal size of the smoke box is equivalent to L×W×H, where L, W, and H are length, width, and height, respectively. Several optical channels are opened on the front and rear side walls of the smoke box. The center lines of the optical channels on the left and right sides are set at set intervals from the inner wall of the smoke box and between the center lines of adjacent optical channels, and the center lines of each optical channel have the same height. A nozzle for injecting interference materials is provided on the left or right wall of the smoke box. The nozzle is centered in the width direction and has the same height as the center line of the optical channel. The optical channel in the smoke box is segmented and modeled. Each optical channel is divided into n+2 segments, where n is a positive integer. The optical channel part inside the smoke box is divided into n segments on average, and the optical channel part of the absorbing sponge area on the front and rear sides of the smoke box is 1 segment each. Each optical channel is divided into n+2 segments of cylinders, and each segment of the cylinder creates a common circular surface at the junction of both ends to connect the fluid domain.

[0015] Three oscillating fans are installed inside the smoke box, with position coordinates of (L / 2, H, W / 2), (x, 0, W / 2), and (Lx, 0, W / 2). The fans are modeled and the established Fan model is placed in the fluid channel to calculate the fluid flow, and the pressure difference between the upstream and downstream of the blades at the set speed is obtained; the pressure difference between the upstream and downstream of the blades at the set speed is imported into the Fan model as the fan momentum source, and the lumped fan Fan model that combines the fan flow and pressure is obtained;

[0016] The overlapping grid method is used to simulate the air flow caused by fan stirring in the smoke box. The cutting body is selected as the grid unit type. The fan area where the fan rotates and revolves is set as the overlapping grid area. The smoke box area outside the fan area is used as the background grid to establish the overlapping area. The linear interpolation method is used for data interaction in the grid junction area, and the grid of the area enveloping the fan revolution range is encrypted.

[0017] Furthermore, two sets of grids were used for meshing the fan area and the smoke box area: 1.13 million grids on the fan surface and 5 million grids on the volume; 0.60 million grids on the smoke box surface and 3.23 million grids on the volume.

[0018] Furthermore, the interfering material is a spherical particle, and the single radiation transmission model of the spherical particle is established according to the following method:

[0019] A two-dimensional axisymmetric model of spherical particles is established, and a perfect matching layer is introduced on the boundary surface of the calculation area, so that the incident electromagnetic wave directly penetrates through the boundary surface into the perfect matching layer without being reflected on the boundary surface; mapped meshing is used in the perfect matching layer, and free tetrahedral meshing is used in the rest, with the maximum mesh size set to 1 / 5 of the wavelength of the incident electromagnetic wave;

[0020] According to the two-dimensional axisymmetric model of spherical particles, a single radiation transmission model of spherical particles is established.

[0021] Furthermore, the interfering particles are flake particles, and the single radiation transmission model of the flake particles is established according to the following method:

[0022] Establish a two-dimensional axisymmetric model of flake particles;

[0023] Through coordinate transformation, the plane electromagnetic wave background field with multi-angle incidence is loaded in the two-dimensional axisymmetric model of flake particles, and a single radiation transmission model of flake particles is established.

[0024] Furthermore, the loading of the plane electromagnetic wave background field incident at multiple angles in the two-dimensional axisymmetric model of the flake particles by coordinate transformation comprises:

[0025] The plane wave background field is:

[0026] (1)

[0027] In the formula, is the plane wave background field, is the background field in the z direction, is the wave vector, is the distance vector, For time, is the angular frequency, is an imaginary unit, is the natural logarithm;

[0028] Assuming the plane wave is in the xz plane, The angle with the z-axis is , the derivation process of parallel polarized light is the same as that of vertical polarized light. Consider the case of parallel polarized light incident:

[0029] (2)

[0030] In the formula, is the wave number, , is the speed of light, is the unit vector in the x direction, is the unit vector in the z direction, is the electric field strength;

[0031] Substituting equation (2) into equation (1), we get the plane wave background field:

[0032] (3)

[0033] In the formula, is the azimuth, ,and , , are the coordinates of the plane wave, is the length of the distance vector;

[0034] Expand the electromagnetic wave in plane wave and cylindrical coordinates as:

[0035] (4)

[0036] In the formula, is a first-order Bessel function, is the order;

[0037] The coordinate transformation formula from Cartesian coordinate system to cylindrical coordinate system is:

[0038] x ^ = 1 2 [ e i φ ( r ^ + i φ ^ ) + e − i φ ( r ^ − i φ ^ ) ] (5)

[0039] In the formula, for The unit vector of the direction, for Unit vector of direction;

[0040] Substituting equations (4) and (5) into equation (3), we obtain:

[0041] E b = E 0 e ikz cos θ { 1 2 cos θ ∑ m =−∞ ∞ [ ( − i ) m − 1 J m − 1 ( kr sin θ ) + ( − i ) m + 1 J m + 1 ( kr sin θ ) ] e − im φ r ^ − i 2 cos θ ∑ m =−∞ ∞ [( − i ) m − 1 J m − 1 ( kr sin θ ) − ( − i ) m + 1 J m + 1 ( kr sin θ )] e − im φ φ ^ + sin θ ∑ m =−∞ ∞ ( − i ) m J m ( kr sin θ ) e − im φ z ^ } (6)

[0042] After the above coordinate transformation, the loading of multi-angle incident plane wave background field in the two-dimensional axisymmetric model of flaky interference material is realized.

[0043] Furthermore, the interference material is a spherical particle, and a light path GOA model of the spherical interference material particles under the real concentration distribution is established to calculate the transmittance and mass extinction coefficient of the spherical interference material particles, including:

[0044] Establish a complete optical path GOA model for each optical channel, and divide the GOA model into n+2 segments, where the division of each segment is the same as the division of the optical channel;

[0045] Extracting the average concentration of spherical interfering material particles in each section of the optical channel from the calculation results of the spherical interfering material particle concentration distribution;

[0046] The radius of the spherical interference material particles, the average concentration of the spherical interference material particles in each section of the optical channel, and the extinction efficiency factor and scattering efficiency factor of the spherical particles when electromagnetic waves of different wavelengths are incident are substituted into the GOA model to calculate the transmittance and mass extinction coefficient of the spherical particle interference material in the entire optical channel.

[0047] Furthermore, the interference material is a flaky particle, and a light path GOA model of the flaky interference material particles under a real concentration distribution is established to calculate the transmittance and mass extinction coefficient of the flaky interference material particles, including:

[0048] Establish a complete optical path GOA model for each optical channel, and divide the GOA model into n+2 segments, where the division of each segment is the same as the division of the optical channel;

[0049] Each segment of the GOA model is evenly divided into several sub-segments, corresponding to several states of the flake particles at the particle concentration in the sub-segment when the electromagnetic wave is incident at different incident angles;

[0050] Extracting the average concentration of flake-like interfering material particles in each sub-segment of the optical channel from the calculated results of the flake-like interfering material particle concentration distribution;

[0051] The radius of the flaky interference material particles, the average concentration of the flaky interference material particles in each sub-segment of the optical channel, and the extinction efficiency factor and scattering efficiency factor of the flaky interference material particles in each sub-segment when electromagnetic waves of different wavelengths are incident are substituted into the GOA model to calculate the transmittance and mass extinction coefficient of the flaky particle interference material in the entire optical channel.

[0052] In a second aspect, the present invention provides an interference material effectiveness evaluation system, comprising:

[0053] A concentration distribution calculation module is used to establish a prediction model for the concentration distribution of interference material particles in a smoke box environment, perform numerical calculations on the concentration distribution of interference material particles according to the prediction model, and extract the concentration of interference material particles in the optical channel from the calculation results of the concentration distribution of interference material particles;

[0054] The particle extinction coefficient calculation module is used to calculate the extinction efficiency factor and scattering efficiency factor of the interfering material particles when electromagnetic waves of different incident angles and wavelengths are incident based on the single radiation transmission model of the interfering material particles;

[0055] The extinction performance calculation module is used to establish the optical path GOA model of the interference material under the real concentration distribution of the smoke particles. The radius of the interference material particles, the concentration of the interference material particles in the optical channel, and the extinction efficiency factor and scattering efficiency factor of the interference material particles when electromagnetic waves of different incident angles and wavelengths are incident are substituted into the GOA model to calculate the transmittance and mass extinction coefficient of the interference material in the smoke box.

[0056] Compared with the prior art, the beneficial technical effects achieved by the present invention are:

[0057] The present invention establishes a particle concentration distribution prediction model for a confined space, calculates the particle concentration distribution value in the confined space, establishes a particle single radiation transmission model of two types of flake and spherical particles according to the actual morphology of the interference material, calculates the extinction efficiency factor and scattering efficiency factor of the particles when electromagnetic waves of different incident angles and wavelengths are incident, establishes a geometric optics approximation model under the actual concentration distribution of smoke particles, substitutes the concentration distribution of the interference material and the extinction efficiency factor and scattering efficiency factor of the interference material particles into the geometric optics approximation model, calculates the extinction effect simulation value of the interference material, and realizes the interference effectiveness evaluation under the condition of uneven distribution of the interference material. Through simulation, the number of experiments can be reduced, time and material costs can be saved, the interference material effectiveness evaluation experiment and the interference material effectiveness evaluation result based on simulation can be mutually verified, and the joint effectiveness evaluation of the interference material can be realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 A flow chart of a method for evaluating the effectiveness of interference materials according to an embodiment of the present invention;

[0059] Figure 2 A schematic diagram of a three-dimensional model of a cigarette box established in an embodiment of the present invention;

[0060] Figure 3 (a) is the topological structure diagram of each optical channel in the fluid domain;

[0061] Figure 3 (b) Figure 3 (a) Local detail diagram;

[0062] Figure 4 This is the parameter diagram of the KDS-310 oscillating fan installed inside the smoke box;

[0063] Figure 5 This is the geometric model diagram of the KDS-310 oscillating fan blade;

[0064] Figure 6 This is the initial position diagram of the overlapping grids of the three fans;

[0065] Figure 7 This is the overlapped grid computational domain diagram around the top fan;

[0066] Figure 8 The size and position relationship diagram of the fan encryption domain;

[0067] Fig. 9 The position relationship diagram of the fan encrypted domain and the overlapping grid of the fan area, where (a) is the front view and (b) is the three-dimensional diagram;

[0068] Fig.10 (a) is a comparison of the fan encryption domain and the surrounding grid size;

[0069] Fig.10 (b) Fig.10 (a) Local detail diagram;

[0070] Fig.11 The mesh division of the fan and the smoke box, where (a) is the fan surface mesh; (b) is the fan body mesh; (c) is the smoke box surface mesh; (d) is the smoke box body mesh;

[0071] Fig.12 (a) is a three-dimensional geometric model diagram of flake particles;

[0072] Fig.12 (b) is the three-dimensional geometric model of spherical particles;

[0073] Fig.13 (a) is a two-dimensional axisymmetric model diagram of a spherical particle;

[0074] Fig.13 (b) is the mesh division diagram of the spherical particle model;

[0075] Fig.14 This is a model diagram of a flake particle;

[0076] Fig.15 (a) is the complex refractive index curve of the flake particle interference material;

[0077] Fig.15 (b) is the complex refractive index curve of the spherical particle interference material;

[0078] Fig.16 (a) is the plane wave background field diagram of the vertical incident electromagnetic wave with a wavelength of 11 μm;

[0079] Fig.16 (b) is the plane wave background field diagram of electromagnetic wave with wavelength of 11μm incident at 45°;

[0080] Fig.17 (a) is the GOA model diagram under the ideal uniform distribution of spherical smoke particles;

[0081] Fig.17 (b) is the mesh division diagram of the GOA model under the ideal uniform distribution of spherical smoke particles;

[0082] Fig.17 (c) is the segmented GOA model diagram under the ideal uniform distribution of sheet smoke particles;

[0083] Fig.18 (a) is the GOA model diagram under the actual concentration distribution of spherical smoke particles;

[0084] Fig.18 (b) is the GOA model diagram under the actual concentration distribution of sheet smoke particles;

[0085] Fig.19 are the simulated values ​​of transmittance of flake copper powder and ultrafine graphite interference materials, where (a) to (d) are the simulated values ​​of transmittance of flake copper powder interference materials at 0.4~0.8μm, 1~3μm, 3~5μm and 8~14μm, respectively, and (e) to (h) are the simulated values ​​of transmittance of ultrafine graphite interference materials at 0.4~0.8μm, 1~3μm, 3~5μm and 8~14μm, respectively. DETAILED DESCRIPTION

[0086] The present invention will be further described below in conjunction with specific examples. The following examples are only used to more clearly illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention.

[0087] like Figure 1 As shown, an embodiment of the present invention provides a method for evaluating the effectiveness of interference materials, comprising:

[0088] Step 1, establishing a prediction model for the concentration distribution of interference material particles in a smoke box environment, performing numerical calculations on the concentration distribution of interference material particles according to the prediction model, and extracting the concentration of interference material particles in the optical channel from the calculation results of the concentration distribution of interference material particles;

[0089] (1) Smoke box modeling

[0090] The smoke box test system consists of a smoke box, a smoke interference performance test instrument, three KDS-310 oscillating fans and an online particle concentration monitoring device. Figure 2 is the three-dimensional model of the cigarette box. Table 1 shows the size parameters of the cigarette box. The origin of the coordinates in the table is Figure 2 The end point pointed by the arrow in the three-dimensional model of the smoke box. The inner wall of the smoke box is made of stainless steel plate and lined with absorbing sponge cones. It can be regarded as a microwave darkroom to eliminate the influence of random reflection of incident electromagnetic waves on the inner wall of the smoke box. In order to prevent interfering materials from entering the absorbing sponge during the experiment, the absorbing sponge is covered with glass fiber cloth. Excluding the thickness of the absorbing sponge on the inner wall of the smoke box, the internal size of the smoke box is equivalent to 3.69m×1.49m×3.00m, and the volume is 16.49m 3 .like Figure 2 As shown in the figure, the side wall of the smoke box has an optical channel for the smoke interference performance test instrument, which is 1.10m away from the bottom of the smoke box. The particle concentration distribution prediction model is implemented using Simcenter STAR-CCM+13 software.

[0091] Table 1 Smoke box size parameters

[0092] parameter Size (L×W×H or coordinates) Smoke box size 3690 mm×1490 mm×3000 mm Nozzle location (3690, 1100, 745) Fan 1 (1845, 3000, 745) Fan 2 (900, 0, 745) Fan 3 (2790, 0, 745)

[0093] like Figure 2 As shown in the figure, there are 8 optical channels inside the smoke box for testing the interference effect of smoke screen on electromagnetic waves. The center line of each channel is 145, 400, 600, 400, 600, 400, 600, 400, 145 mm away from the left and right walls and the center line of the adjacent channel, and the height of the center line of the optical channel is 1100 mm. In addition to the absorbing sponge, the outside of the smoke box is also covered with insulation material, so that the thickness of the front and rear side walls of the smoke box is 305 mm respectively, and the length of the optical channel inside the smoke box is 1490 mm, so the total length of the optical channel is 2100 mm. A nozzle for spraying interference material is set at one end of the length direction of the smoke box. The nozzle has a diameter of 12 mm, is centered in the width direction, and has a height of 1100 mm, which is consistent with the height of the center line of the optical channel.

[0094] When modeling the smoke box, the resolution is 10mm per interval, and each interval is divided into 5 grids. In order to facilitate the subsequent extraction of the particle concentration distribution of each segment in the direction of the optical channel, the optical channel with a length of 1490mm inside the smoke box is divided into 10 segments for modeling, and each segment is 149mm long. This geometric model is the fluid domain for fluid analysis, and it is somewhat different from the actual geometric model entity in terms of topological relationship. Each optical channel is divided into multiple cylinders, which are relatively independent geometrically; however, in the fluid domain, each segment of the cylinder needs to create a common circular surface at the junction of both ends to connect the fluid domain. Figure 3 The topological structure and local details of each optical channel in the fluid domain.

[0095] (2) Fan modeling

[0096] like Figure 2 As shown, three KDS-310 oscillating fans numbered 1 to 3 are installed inside the smoke box to stir and disperse the interfering materials sprayed into the smoke box. Fans 2 and 3 are installed on the center line of the bottom of the smoke box (in the length direction), and fan 1 is installed at the top center. Figure 4 This is a schematic diagram of the KDS-310 oscillating fan. The motor shaft is tilted at an angle of 30°. The motor is an AC / DC brushed motor with a rated operating voltage of 48V, a rotation speed of 1450r / min, and an orbital speed of 6.11r / min.

[0097] In order to capture the dynamic process of the fan rotating at high speed in the smoke box, transient calculations need to be performed. This transient calculation is mainly to capture the airflow state in the smoke box space, rather than the rotation of the fan itself; and the peripheral linear speed of the fan is too large. In order to improve the calculation accuracy and prevent calculation divergence, a very small time step needs to be set, which requires a very large amount of calculation, which is very uneconomical for solving the overall transient. Therefore, the fan model should be simplified. Before simplifying the fan model, the MRF model and the fan momentum source model need to be calculated for the flow characteristics of the fan to obtain the relationship between the fan flow and pressure at a specific speed.

[0098] After the fan is modeled, it is placed in the fluid channel and fluid flow calculation (CFD) is performed to obtain the pressure difference between the upstream and downstream of the blades at a speed of 1450r / min (normal operating condition of the fan). The fan movement is simplified through the pressure difference data. Figure 5 The geometric model is established based on the KDS-310 oscillating fan blade data.

[0099] When the fan performance curve is obtained and the precise geometric shape of the fan has no effect on the calculation results, the simplified fan model (Fan model) is used to simplify the fan model. The KDS-310 oscillating fan is an axial flow fan, and the inflow and outflow directions of the airflow are the same, that is, it flows along the fan axis. The present invention uses the fan momentum source model (Fan Momentum Source) provided by the fluid software to establish the axial flow fan Fan model, imports the pressure difference between the upstream and downstream of the blade at a speed of 1450r / min obtained by CFD calculation, and imports it into the Fan model as the fan momentum source to establish a lumped fan Fan model that combines the flow rate and pressure of the fan. In the Fan model, the fan is modeled as a volume area, and when the airflow passes through this area, it will cause a pressure jump upstream and downstream of the fan. In the calculation, the fan area does not move like a real fan, which can greatly reduce the amount of calculation. In addition, the Fan model can also simulate the vortex introduced by the fan and calculate the vortex velocity downstream of the fan.

[0100] The fan area and the smoke box area belong to different areas, and the fan area has the rotation and revolution of the fan, which requires separate mesh encryption to improve the calculation accuracy. Therefore, the overlapping mesh model is used to overlap the two. Overlapping meshes are used to discretize the computational domain with multiple different meshes. These meshes can overlap each other in any way. They are widely used in dealing with multiple or moving objects and CFD simulation optimization research. The principle of the overlapping mesh method is to divide the multi-motion area into several sub-areas, each sub-area generates a set of meshes independently, and there are no less than 4 layers of meshes in an overlapping state at the boundary. The meshes at the boundary between each sub-area are interpolated to exchange data and finally realize the calculation of fluid motion. The independent meshes of each sub-area can be relatively displaced without constraints. The overlapping domain and the background domain are connected through hole excision and unit recognition. The hole excision process divides the mesh into active units and inactive units. Unit recognition can determine the corresponding contribution unit for the interpolation unit.

[0101] The initial positions of the 3 fan overlapping grids are as follows Figure 6 As shown in the figure, the overlapping grid method is used to simulate the air flow caused by fan stirring in the smoke box. The grid unit type is selected as a cutting body, and the fan area with fan rotation and revolution is set as an overlapping grid area. The smoke box area outside the fan area is used as the background grid to establish an overlapping area. The linear interpolation method is used for data interaction in the grid intersection area. Taking the top fan as an example, the overlapping grid calculation domain around it is as follows Figure 7 shown.

[0102] (3) Grid division

[0103] In CFD simulation, although a convergent numerical solution can be obtained by continuously encrypting the grid, encrypting the grid on a global scale will lead to insufficient computer computing performance and excessive computing time. Therefore, it is particularly important to encrypt the grid locally. In the method of the present invention, the area around the fan contains all changes and refinements to the grid, so it is necessary to encrypt the volume surrounding the fan locally. Figure 8 The size and position relationship of the fan encryption domain, Fig. 9 The positional relationship between the fan encryption domain and the overlapping grid of the fan area.

[0104] In addition, when transitioning from fine grid to coarse grid, in order to avoid large calculation errors, the transition from dense to sparse grid should be as slow as possible. To this end, the mesh is encrypted in the area of ​​the fan's revolution range. Fig.10 Size comparison and local details of the fan encrypted domain and surrounding mesh.

[0105] The present invention mainly has two calculation domains: the fan area and the smoke box area, including the fan real performance calculation and the smoke box flow calculation, so two sets of grids are designed during mesh division. The number of fan surface grids is 1.13 million, and the number of volume grids is 5 million; the number of smoke box surface grids is 600,000, and the number of volume grids is 3.23 million. Fig.11 shown.

[0106] According to the smoke box test conditions, the operation conditions of the air compressor and the fan are distinguished, and the smoke box flow calculation is divided into five stages: −15~0, 1~15, 16~30, 31~60, and 61~90s. The flow field, streamlines and velocity vectors in the smoke box model at different stages are analyzed, and the concentration distribution data of the interfering materials in the smoke box are calculated.

[0107] Step 2, according to the single radiation transmission model of the interfering material particles, calculate the extinction efficiency factor and scattering efficiency factor of the interfering material particles when electromagnetic waves with different incident angles and different wavelengths are incident;

[0108] (1) Computational object modeling

[0109] Combined with Mie scattering theory, the extinction ability of flake and spherical particles is numerically calculated by the GOA method. According to the actual test results, the initial conditions of flake and spherical particles are set as shown in Table 2. Fig.12 The three-dimensional geometric model of the two particles. The particle multiple scattering radiation transmission model was modeled using COMSOL Multiphysics® 5.6 software.

[0110] Table 2 Physical parameters of flake and spherical particles

[0111]

[0112] In the GOA method, the unit size of the finite element model is required to be no larger than 1 / 5 of the wavelength of the incident electromagnetic wave. For spherical particles, a two-dimensional axisymmetric simplified model of spherical particles is used, and a perfectly matched layer (PML) is used to connect each unit, such as Fig.13 shown.

[0113] Fig.13 In (a), the perfect matching layer refers to the introduction of a virtual anisotropic lossy medium near the boundary surface of the computational region. The medium has exactly the same wave impedance as the medium of the adjacent computational region. The incident electromagnetic wave can directly penetrate through the interface and enter the PML without being reflected on the interface. As an absorbing boundary, the PML can eliminate the influence of reflection and make the computational region space completely match other adjacent computational regions. It is often used to simulate infinite domains. Fig.13 (b) is the meshing of the spherical particle model. Mapped meshing is used in PML to improve the boundary absorption performance, and free tetrahedral meshing is used in the rest of the model. The maximum mesh size is set to 1 / 5 of the wavelength of the incident electromagnetic wave.

[0114] Flaky particles can be directly modeled, and finite element models such as Fig.14 shown.

[0115] (2) Complex refractive index of interfering materials

[0116] The complex refractive index (m=n+ik), also known as the optical constant, is a basic physical parameter that describes the law of electromagnetic wave radiation transmission in the medium. It is the premise and basis for studying the radiation transmission characteristics of the medium. In the field of smoke research, the Mie scattering method, T matrix method, FDTD method, finite element method and other computational models and methods for studying the extinction performance of smoke particles all require the necessary physical parameter of the complex refractive index. The real part n of the complex refractive index is the scattering coefficient, which represents the propagation speed of the electromagnetic wave in the medium; the imaginary part k is the absorption coefficient, which represents the attenuation law of the electromagnetic wave in the medium. It can be seen that the complex refractive index is not a constant, but a function that changes with the wavelength of the incident electromagnetic wave.

[0117] The ellipsometer is used to obtain the ellipsometric parameters of the sample by ellipsometry, and the dispersion model is established to fit the scattering coefficient and the absorption coefficient, and then the complex refractive index of the sample can be determined. Specifically, the sheet and spherical interference materials are directly pressed under 10MPa using an infrared tablet press, and the complex refractive index is measured by ellipsometry. Fig.15 It is the complex refractive index curve of the flake and spherical interference material.

[0118] from Fig.15The particle complex refractive index is extracted when electromagnetic waves are incident at 0.6μm, 2μm, 4μm and 11μm (the central spectrum wavelength of the radiometer), as shown in Table 3. The particle complex refractive index is used to calculate the actual values ​​of the extinction efficiency factor and the scattering efficiency factor.

[0119] Table 3 Complex refractive index of particles when electromagnetic waves of 0.6 μm, 2 μm, 4 μm and 11 μm are incident

[0120]

[0121] (3) Particle single radiation transfer model

[0122] Electromagnetic scattering calculations of particles with continuous rotational symmetry (spherical interfering material particles) can be performed in a two-dimensional axisymmetric model without the need to build a three-dimensional model, which can significantly reduce the time required for calculations.

[0123] For flake particles, the incident plane electromagnetic wave in the smoke can have multiple angles, but in a 2D axisymmetric model, the background field cannot be set as a plane wave propagating in any direction because it will destroy the rotational symmetry of the model along the symmetry axis. Through coordinate transformation, the loading of the plane wave background field can be realized in a 2D axisymmetric model, including:

[0124] The general plane wave background field is:

[0125] (1)

[0126] In the formula, is the plane wave background field, is the background field in the z direction, is the wave vector (also called the wave number vector), is the distance vector, For time, is the angular frequency, is an imaginary unit, is the natural logarithm.

[0127] Without loss of generality, assuming that the plane wave is in the xz plane, The angle with the z-axis is The derivation process of parallel polarized light is the same as that of vertical polarized light. Here we consider the case of incident parallel polarized light:

[0128] (2)

[0129] In the formula, is the wave number, , is the speed of light, is the unit vector in the x direction, is the unit vector in the z direction, is the electric field strength.

[0130] Combining equations (1) and (2), the plane wave background field is:

[0131] (3)

[0132] In the formula, is the azimuth, ,and , , are the coordinates of the plane wave, is the length of the distance vector.

[0133] Expand the electromagnetic wave in plane wave and cylindrical coordinates as:

[0134] (4)

[0135] In the formula, is a first-order Bessel function, is the order. The coordinate transformation formula from Cartesian coordinate system to cylindrical coordinate system is:

[0136] x ^ = 1 2 [ e i φ ( r ^ + i φ ^ ) + e − i φ ( r ^ − i φ ^ ) ] (5)

[0137] In the formula, for The unit vector of the direction, for The unit vector of the direction.

[0138] Combining the above formulas, we can get:

[0139] E b = E 0 e ikz cos θ { 1 2 cos θ ∑ m =−∞ ∞ [ ( − i ) m − 1 J m − 1 ( kr sin θ ) + ( − i ) m + 1 J m + 1 ( kr sin θ ) ] e − im φ r ^ − i 2 cos θ ∑ m =−∞ ∞ [( − i ) m − 1 J m − 1 ( kr sin θ ) − ( − i ) m + 1 J m + 1 ( kr sin θ )] e − im φ φ ^ + sin θ ∑ m =−∞ ∞ ( − i ) m J m ( kr sin θ ) e − im φ z ^ } (6).

[0140] The above derivation converts the plane wave background field into a sum of infinite azimuthal moduli (i.e., the order of the Bessel function), where the cylindrical modulus is , indicating that a two-dimensional axisymmetric simulation can be performed. and negative There is only a phase factor difference between them, so the summation of the background field only needs to be calculated from =0 to =N. For example, the background field The components can be written as:

[0141] E r = 1 2 E 0 e ikz cos θ cos θ ∑ m = 0 ∞ χ ( m )[( − i ) m − 1 J m − 1 ( kr sin θ ) + ( − i ) m + 1 J m + 1 ( kr sin θ )] cos( m φ ) r ^ (7)

[0142] In the formula, is a step function, =0, =1; >0, =2. Although is an infinite series, but if the particle size is comparable to the wavelength, The result will converge after a finite number of terms. Therefore, define N=4, and take the incident electromagnetic wave with a wavelength of 11μm as an example, the background field obtained is as follows Fig.16 As shown, (a) is the plane wave background field when the electromagnetic wave is incident vertically, and (b) is the plane wave background field when the electromagnetic wave is incident at 45°.

[0143] After the above coordinate transformation, the loading of multi-angle incident plane wave background field in the two-dimensional axisymmetric model of flaky interference material was realized, and a particle single radiation transmission model was established, which can be used to calculate the extinction cross section, scattering cross section, extinction efficiency factor and scattering efficiency factor of the particles.

[0144] For centrosymmetric spherical interfering material particles, the radiation transmission model can be directly established.

[0145] Step 3, establish a GOA model of the optical path of the interference material under the real concentration distribution of the smoke particles, substitute the radius of the interference material particles, the concentration of the interference material particles in the optical channel, and the extinction efficiency factor and scattering efficiency factor of the interference material particles when electromagnetic waves of different incident angles and wavelengths are incident into the GOA model, and calculate the transmittance and mass extinction coefficient of the interference material in the smoke box;

[0146] (1) GOA model under ideal uniform distribution of smoke particles

[0147] The GOA method is used to model electromagnetic wave propagation when the wavelength is smaller than the size of the smallest geometric entity in the model.

[0148] Assume that the flake and spherical interference materials in the smoke box do not settle and are in an ideal uniform distribution. For the spherical particles under the ideal uniform distribution of smoke particles, electromagnetic waves from different incident directions have no effect on their extinction effect. Therefore, it is only necessary to establish a complete optical path GOA model with a length of 2100mm, such as Fig.17 (a) As shown. The GOA method does not have strict requirements on the grid size, so it is sufficient to select the light path area to automatically divide the tetrahedron units, such as Fig.17 (b) as shown.

[0149] Substituting the scattering particle radius, scattering particle density (i.e., particle concentration), extinction efficiency factor, and scattering efficiency factor in the optical channel into the GOA model, the extinction performance of the interfering material in the smoke box can be calculated. The extinction efficiency factor and scattering efficiency factor are calculated using the particle single radiation transmission model, and the particle concentration is obtained from the numerical analysis results of the concentration distribution of the interfering material in the smoke box environment.

[0150] For the flake particles under the ideal uniform distribution of smoke particles, the GOA model needs to be segmented because the particles have different absorption and scattering efficiencies for incident electromagnetic waves at different angles. In reality, the orientation of particles in all directions is evenly distributed. This method simplifies it into four cases: the incident angles of the electromagnetic wave and the normal to the particle normal plane are 0°, 30°, 60° and 90° (i.e., the four postures of the particle: vertical incidence of the electromagnetic wave to parallel incidence of the electromagnetic wave). Therefore, the light path can be evenly divided into four parts. Under the premise of setting the same concentration, each part uses the particle extinction efficiency factor and scattering efficiency factor of different incident angles. The segmentation of the model is used to replace the orientation of particles in all directions in reality. Fig.17 (c) is a schematic diagram of the segmented GOA model.

[0151] (2) GOA model under the actual concentration distribution of smoke particles

[0152] Based on the GOA model under ideal uniform distribution of smoke particles, a GOA model under real concentration distribution of smoke particles is constructed.

[0153] Calculations are carried out on the distribution models of flake and spherical interference materials under the actual concentration of smoke particles to evaluate their interference effectiveness.

[0154] For spherical particle interference materials, the following steps are included:

[0155] Step 3011, establishing a complete optical path GOA model for each optical channel, dividing the GOA model into n+2 segments, and the division of each segment is the same as the division of the optical channel;

[0156] Each optical channel in the smoke box is divided into 12 sections, the two ends of the absorbing sponge area are each 1 section, and the 1490mm inner area of ​​the middle smoke box is divided into 10 sections. The GOA model is divided into 12 sections, and the division of each section is the same as the optical channel. Fig.18 (a) is the GOA model under the actual concentration distribution of spherical smoke particles.

[0157] Step 3012, extracting the average concentration of the spherical interfering material particles in each section of the optical channel from the calculation result of the concentration distribution of the spherical interfering material particles;

[0158] The average concentration of interfering materials in each optical channel is extracted from the numerical analysis results of the interfering material concentration distribution in the smoke box environment for GOA model calculation.

[0159] Step 3013, substitute the radius of the spherical interference material particles, the average concentration of the spherical interference material particles in each section of the optical channel, and the extinction efficiency factor and scattering efficiency factor of the spherical particles when electromagnetic waves of different wavelengths are incident into the GOA model to calculate the transmittance and mass extinction coefficient of the spherical particle interference material in the entire optical channel.

[0160] For the flake interference material under the real concentration distribution of smoke particles, the GOA model needs to be segmented because the absorption and scattering efficiency of flake particles to incident electromagnetic waves at different angles are different. Under the premise of maintaining the above segmentation, each segment of the GOA model is further divided into four segments, corresponding to the four particle postures under the particle concentration of the segment when the electromagnetic wave is incident at 0°, 30°, 60° and 90°, and the particle extinction efficiency factor and scattering efficiency factor at each incident angle are input at the same time. Fig.18 (b) is the GOA model under the actual concentration distribution of sheet smoke particles.

[0161] The radius of the flaky interference material particles (radius in the radial direction), the average concentration of the flaky interference material particles in each sub-segment of the optical channel, and the extinction efficiency factor and scattering efficiency factor of the flaky particles in each sub-segment when electromagnetic waves of different wavelengths are incident are substituted into the GOA model under the actual concentration distribution of the flaky particles to calculate the transmittance and mass extinction coefficient of the flaky interference material in the entire optical channel.

[0162] The following is an example of interference materials such as copper flake powder (flake) and ultrafine graphite (spherical):

[0163] According to the numerical analysis results of the particle concentration distribution in the smoke box, combined with the extinction efficiency factor and scattering efficiency factor calculated by the particle single radiation transmission model, the effectiveness of the flake copper powder and ultrafine graphite interference materials was evaluated. The results are as follows:

[0164] The simulated transmittance values ​​of flake copper powder and ultrafine graphite interference materials at 0.4~0.8μm, 1~3μm, 3~5μm and 8~14μm are as follows Fig.19 Table 4 shows the comparison between the simulated and experimental values ​​of the mass extinction coefficients of the flake copper powder and ultrafine graphite interference materials.

[0165] Table 4 Comparison of simulated and experimental values ​​of mass extinction coefficient of flake copper powder and ultrafine graphite interference materials

[0166]

[0167] Depend on Fig.19 It can be seen that the simulated transmittance of ultrafine graphite is better than that of flake copper powder, which is consistent with the experimental results. As can be seen from Table 4, the simulated values ​​of mass extinction coefficient of ultrafine graphite and flake copper powder are close to the experimental values, and the simulation results are generally good, with the error within an acceptable range.

[0168] In another embodiment, the present invention further provides an interference material effectiveness evaluation system, comprising:

[0169] A concentration distribution calculation module is used to establish a prediction model for the concentration distribution of interference material particles in a smoke box environment, perform numerical calculations on the concentration distribution of interference material particles according to the prediction model, and extract the concentration of interference material particles in the optical channel from the calculation results of the concentration distribution of interference material particles;

[0170] The particle extinction coefficient calculation module is used to calculate the extinction efficiency factor and scattering efficiency factor of the interfering material particles when electromagnetic waves of different incident angles and wavelengths are incident based on the single radiation transmission model of the interfering material particles;

[0171] The extinction performance calculation module is used to establish the optical path GOA model of the interference material under the real concentration distribution of the smoke particles. The radius of the interference material particles, the concentration of the interference material particles in the optical channel, and the extinction efficiency factor and scattering efficiency factor of the interference material particles when electromagnetic waves of different incident angles and wavelengths are incident are substituted into the GOA model to calculate the transmittance and mass extinction coefficient of the interference material in the smoke box.

[0172] The present invention calculates the particle concentration distribution in a confined space by numerical calculation and the particle multiple scattered radiation transmission, calculates the extinction efficiency factor and the scattering efficiency factor by the particle single radiation transmission, and finally establishes a geometric optical approximation model under the real concentration distribution of smoke particles. The extinction effect of the interfering material in the smoke box can be obtained by calculating the concentration distribution of the interfering material in the smoke box and the material parameters.

[0173] The present invention has been disclosed above with preferred embodiments, but they are not intended to limit the present invention. Any technical solutions obtained by adopting equivalent replacement or equivalent transformation solutions fall within the protection scope of the present invention.

Claims

1. A method for evaluating the effectiveness of interference materials, characterized in that: include: Establish a prediction model for the distribution of interference material particle concentration in a smoke box environment, perform numerical calculations on the distribution of interference material particle concentration based on the prediction model, and extract the concentration of interference material particles in the optical channel from the calculation results of the distribution of interference material particle concentration; According to the single radiation transmission model of the interfering material particles, the extinction efficiency factor and scattering efficiency factor of the interfering material particles are calculated when electromagnetic waves with different incident angles and wavelengths are incident; A GOA model of the optical path of interference materials under the actual concentration distribution of smoke particles is established. The radius of interference material particles, the concentration of interference material particles in the optical channel, and the extinction efficiency factor and scattering efficiency factor of interference material particles when electromagnetic waves of different incident angles and wavelengths are incident are substituted into the GOA model to calculate the transmittance and mass extinction coefficient of the interference material in the smoke box.

2. The interference material effectiveness evaluation method according to claim 1, characterized in that: The interfering material particle concentration distribution prediction model is established according to the following method: A three-dimensional model of a smoke box is established. The inner wall of the smoke box is lined with an absorbing sponge cone, which is covered with glass fiber cloth. The internal size of the smoke box is equivalent to L×W×H, where L, W, and H are length, width, and height, respectively. Several optical channels are opened on the front and rear side walls of the smoke box. The center lines of the optical channels on the left and right sides are set at set intervals from the inner wall of the smoke box and between the center lines of adjacent optical channels, and the center lines of each optical channel have the same height. A nozzle for injecting interference materials is provided on the left or right wall of the smoke box. The nozzle is centered in the width direction and has the same height as the center line of the optical channel. The optical channel in the smoke box is segmented and modeled. Each optical channel is divided into n+2 segments, where n is a positive integer. The optical channel part inside the smoke box is divided into n segments on average, and the optical channel part of the absorbing sponge area on the front and rear sides of the smoke box is 1 segment each. Each optical channel is divided into n+2 segments of cylinders, and each segment of the cylinder creates a common circular surface at the junction of both ends to connect the fluid domain. Three oscillating fans are installed inside the smoke box, with position coordinates of (L / 2, H, W / 2), (x, 0, W / 2), and (Lx, 0, W / 2). The fans are modeled and the established Fan model is placed in the fluid channel to calculate the fluid flow, and the pressure difference between the upstream and downstream of the blades at the set speed is obtained; the pressure difference between the upstream and downstream of the blades at the set speed is imported into the Fan model as the fan momentum source, and the lumped fan Fan model that combines the fan flow and pressure is obtained; The overlapping grid method is used to simulate the air flow caused by fan stirring in the smoke box. The cutting body is selected as the grid unit type. The fan area where the fan rotates and revolves is set as the overlapping grid area. The smoke box area outside the fan area is used as the background grid to establish the overlapping area. The linear interpolation method is used for data interaction in the grid junction area, and the grid of the area enveloping the fan revolution range is encrypted.

3. The interference material effectiveness evaluation method according to claim 2, characterized in that: Two sets of grids were used for meshing the fan area and the smoke box area: 1.13 million grids on the fan surface and 5 million grids on the volume; 0.60 million grids on the smoke box surface and 3.23 million grids on the volume.

4. The interference material effectiveness evaluation method according to claim 1, characterized in that: The interfering material is a spherical particle, and the single radiation transmission model of the spherical particle is established according to the following method: A two-dimensional axisymmetric model of spherical particles is established, and a perfect matching layer is introduced on the boundary surface of the calculation area, so that the incident electromagnetic wave directly penetrates through the boundary surface into the perfect matching layer without being reflected on the boundary surface; mapped meshing is used in the perfect matching layer, and free tetrahedral meshing is used in the rest, with the maximum mesh size set to 1 / 5 of the wavelength of the incident electromagnetic wave; According to the two-dimensional axisymmetric model of spherical particles, a single radiation transmission model of spherical particles is established.

5. The interference material effectiveness evaluation method according to claim 1, characterized in that: The interfering particles are flake particles, and the single radiation transmission model of flake particles is established according to the following method: Establish a two-dimensional axisymmetric model of flake particles; Through coordinate transformation, the plane electromagnetic wave background field with multi-angle incidence is loaded in the two-dimensional axisymmetric model of flake particles, and a single radiation transmission model of flake particles is established.

6. The method for evaluating the effectiveness of interference materials according to claim 5, characterized in that: The method of loading the plane electromagnetic wave background field incident at multiple angles in the two-dimensional axisymmetric model of the flake particles through coordinate transformation includes: The plane wave background field is: （1） In the formula, is the plane wave background field, is the background field in the z direction, is the wave vector, is the distance vector, For time, is the angular frequency, is an imaginary unit, is the natural logarithm; Assuming the plane wave is in the xz plane, The angle with the z-axis is θ. The derivation process of parallel polarized light is the same as that of vertical polarized light. Consider the case of parallel polarized light incident: （2） In the formula, is the wave number, , is the speed of light, is the unit vector in the x direction, is the unit vector in the z direction, is the electric field strength; Substituting equation (2) into equation (1), we get the plane wave background field: （3） In the formula, is the azimuth, ,and , , are the coordinates of the plane wave, is the length of the distance vector; Expand the electromagnetic wave in plane wave and cylindrical coordinates as: （4） In the formula, is a first-order Bessel function, is the order; The coordinate transformation formula from Cartesian coordinate system to cylindrical coordinate system is: （5） In the formula, for The unit vector of the direction, for Unit vector of direction; Substituting equations (4) and (5) into equation (3), we obtain: （6） After the above coordinate transformation, the loading of multi-angle incident plane wave background field in the two-dimensional axisymmetric model of flaky interference material is realized.

7. The interference material effectiveness evaluation method according to claim 2, characterized in that: The interference material is a spherical particle, and a light path GOA model of the spherical interference material particles under the real concentration distribution is established to calculate the transmittance and mass extinction coefficient of the spherical interference material particles, including: Establish a complete optical path GOA model for each optical channel, and divide the GOA model into n+2 segments, where the division of each segment is the same as the division of the optical channel; Extracting the average concentration of spherical interfering material particles in each section of the optical channel from the calculation results of the spherical interfering material particle concentration distribution; The radius of the spherical interference material particles, the average concentration of the spherical interference material particles in each section of the optical channel, and the extinction efficiency factor and scattering efficiency factor of the spherical particles when electromagnetic waves of different wavelengths are incident are substituted into the GOA model to calculate the transmittance and mass extinction coefficient of the spherical particle interference material in the entire optical channel.

8. The interference material effectiveness evaluation method according to claim 2, characterized in that: The interference material is a flake particle, and a light path GOA model of the flake interference material particles under the real concentration distribution is established to calculate the transmittance and mass extinction coefficient of the flake interference material particles, including: Establish a complete optical path GOA model for each optical channel, and divide the GOA model into n+2 segments, where the division of each segment is the same as the division of the optical channel; Each segment of the GOA model is evenly divided into several sub-segments, corresponding to several states of the flake particles at the particle concentration in the sub-segment when the electromagnetic wave is incident at different incident angles; Extracting the average concentration of flake-like interfering material particles in each sub-segment of the optical channel from the calculated results of the flake-like interfering material particle concentration distribution; The radius of the flaky interference material particles, the average concentration of the flaky interference material particles in each sub-segment of the optical channel, and the extinction efficiency factor and scattering efficiency factor of the flaky interference material particles in each sub-segment when electromagnetic waves of different wavelengths are incident are substituted into the GOA model to calculate the transmittance and mass extinction coefficient of the flaky particle interference material in the entire optical channel.

9. A system for evaluating the effectiveness of interference materials, characterized in that: include: A concentration distribution calculation module is used to establish a prediction model for the concentration distribution of interference material particles in a smoke box environment, perform numerical calculations on the concentration distribution of interference material particles according to the prediction model, and extract the concentration of interference material particles in the optical channel from the calculation results of the concentration distribution of interference material particles; The particle extinction coefficient calculation module is used to calculate the extinction efficiency factor and scattering efficiency factor of the interfering material particles when electromagnetic waves of different incident angles and wavelengths are incident based on the single radiation transmission model of the interfering material particles; The extinction performance calculation module is used to establish the optical path GOA model of the interference material under the real concentration distribution of the smoke particles. The radius of the interference material particles, the concentration of the interference material particles in the optical channel, and the extinction efficiency factor and scattering efficiency factor of the interference material particles when electromagnetic waves of different incident angles and wavelengths are incident are substituted into the GOA model to calculate the transmittance and mass extinction coefficient of the interference material in the smoke box.

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