Cavity filter tip structure optimization method

Abstract

The invention discloses a cavity filter tip structure optimization method, which comprises the following steps of: scanning a cavity cigarette filter tip to obtain an overall data file of the cavity cigarette filter tip, constructing an overall cavity filter tip model, performing geometric repair, and reversely reconstructing the model; the pressure and speed of the cavity filter tip under different flue gas inlet conditions are measured through experiments, and simulation boundary conditions are obtained; the method comprises the following steps: constructing an integral cavity filter finite element model in a full proportion, and performing finite element analogue simulation calculation on a smoke flowing process in a cavity cigarette filter to obtain pressure distribution in the filter; segmenting the model to obtain a local fiber model, combining to obtain the internal pressure distribution of the filter tip, calculating to obtain the boundary condition of the local model, taking the boundary condition as the initial condition of the flow field simulation calculation of the local model, and simulating to obtain the influence of the porosity of the tipping paper and the cavity on the smoke flow; and analyzing parameters of the local fiber simulation model to obtain optimal cavity filter tip structure parameters. The method has the advantages of high geometric model reduction degree, low manual experiment cost and shortened experiment time consumption.

Description

Technical Field

[0001] This invention relates to the field of cigarette technology, and in particular to a method for optimizing the structure of a cavity filter tip. Background Technology

[0002] Smoking has always been a globally significant issue. Studies show that mainstream cigarette smoke contains over 4,000 harmful chemicals, forming a complex aerosol composed of particulate matter, various gases, and organic vapors. This directly impacts the health of smokers and those around them, causing respiratory illnesses, heart disease, and high blood pressure. Globally, there are 1.1 billion smokers, and this number continues to grow. To effectively reduce the health hazards of cigarette smoking, improvements can be made in two main ways: optimizing the tobacco blend and modifying the filter structure. Cigarette filters, acting as a bridge between the cigarette and the smoker, effectively filter out some harmful substances in the smoke, representing the most direct physical method for reducing tar and harm. Currently, mainstream cigarette filters include ordinary single filters, composite filters, grooved filters, and cavity filters.

[0003] Currently, research on cigarette filters mainly employs experimental and numerical simulation methods. For newly designed cigarette filter structures, experimental methods require large-scale sample comparisons and extensive data collection and analysis, resulting in high economic and time costs. Numerical simulation methods are less expensive than experimental methods, but the complex geometry of cellulose acetate makes it difficult to construct a complete model for flow field simulation. Many studies currently use simplified porous media models to analyze the flow field and filtration characteristics of cigarette filters. This method can be used to study the overall combustion temperature distribution of cigarettes and the overall filtration performance of cigarette filters. However, because the crisscrossing distribution of cellulose acetate in the filter directly affects the internal flow field, the simplified porous media model cannot reflect the influence of fibers on the smoke flow characteristics, leading to low reliability of the obtained data on the cavity filter structure. Summary of the Invention

[0004] To address the problems in the background art, this invention provides a method for optimizing the structure of a cavity filter tip, which can solve the problems of low geometric model fidelity, high cost of manual experiments, and long experimental time in existing cigarette design models.

[0005] This invention provides a method for optimizing the structure of a cavity filter tip, comprising:

[0006] S1: Scan the hollow cigarette filter to obtain the overall data file of the hollow cigarette filter and then construct the overall hollow filter scanning model;

[0007] S2: Geometric repair is performed based on the constructed overall cavity filter scanning model, and the cellulose acetate model is obtained by reverse reconstruction;

[0008] S3: Experimental measurements were performed on the cavity filter under different flue gas inlet conditions to obtain boundary conditions;

[0009] S4: Construct a full-scale finite element model of the overall cavity filter based on the actual size of the cigarette filter. Combine the boundary conditions obtained in S3 to perform finite element simulation of the smoke flow process inside the cavity cigarette filter and calculate the internal pressure distribution of the filter.

[0010] S5: The reconstructed cellulose acetate model is segmented to obtain a local fiber model. The internal pressure distribution of the filter is obtained, and the boundary conditions of the local fiber model are calculated.

[0011] S6: Use the boundary conditions of the local fiber model as the initial conditions for the flow field simulation calculation of the local fiber model, and obtain the parameters of the local fiber simulation model through simulation.

[0012] S7: Analyze the parameters of the local fiber simulation model to obtain the optimal cavity filter structure parameters.

[0013] This invention proposes a method for optimizing the structure of a cavity filter tip. The method involves geometric modeling based on a scanned file of the cavity filter tip, and experimentally measuring the boundary conditions of the overall model to analyze the overall cigarette filter tip pressure distribution and obtain precise local pressure. Using this as boundary condition, flow field simulation is performed on a local cellulose acetate model to obtain the influence of the cavity and the porosity of the tipping paper on the smoke flow. This addresses the problems of low geometric model fidelity, high cost of manual experiments, and long experimental time in existing cigarette design models.

[0014] Furthermore, Micro-CT scanning technology was used to scan the cavity cigarette filter to obtain the overall STL file of the cavity cigarette filter.

[0015] Furthermore, the Micro-CT scanning precision is 2.95μm, and it performs partitioned scanning, and the scan results are stitched together to obtain the final filter STL model.

[0016] Furthermore, the geometric repair refers to repairing geometric defects in the overall data file, including self-intersections, non-manifold edges, highly refractive edges, nails, small components, small channels, and small holes.

[0017] Furthermore, S3 specifically involves two experiments conducted using the velocity distribution function: ISO suction mode velocity v = 0.61sin(πt / 2) and HCI suction mode velocity v = 0.96sin(πt / 2). The boundary conditions were measured using a smoke extraction machine and a piezoresistive meter.

[0018] Furthermore, the boundary conditions in S3 include the filter outlet pressure and velocity.

[0019] Furthermore, in S4, the finite element model of the integral cavity filter includes a laminar flow model, a porous media model, and a component transport model.

[0020] Furthermore, the simulation in S4 uses a simplified porous medium model to perform multi-physics fluid-structure interaction simulation, which yields the flow field distribution and pressure distribution inside the filter nozzle. The pressure distribution law inside the cavity filter nozzle is obtained by analyzing the axial and radial pressure changes at various locations inside the filter nozzle.

[0021] Furthermore, the parameters of the local fiber simulation model obtained in S6 include: the influence of cavity shape on flue gas flow, the influence of cavity shape on flue gas filtration, the influence of splicing paper porosity on flue gas flow, and the influence of splicing paper porosity on flue gas filtration.

[0022] Furthermore, the specific process of S7 is as follows: analyze the influence of cavity shape and splicing paper porosity on flue gas flow and flue gas filtration, change cavity shape and splicing paper porosity to obtain flue gas flow conditions inside cavity filter under different structures, and then compare and analyze to obtain the optimal cavity filter structure.

[0023] Beneficial effects

[0024] This invention proposes a method for optimizing the structure of a cavity filter tip. The method involves geometric modeling based on a scanned file of the cavity filter tip, and experimentally measuring the boundary conditions of the overall model to analyze the overall cigarette filter tip pressure distribution and obtain precise local pressure. Using this as boundary condition, flow field simulation is performed on a local cellulose acetate model to obtain the influence of the cavity and the porosity of the tipping paper on the smoke flow. This addresses the problems of low geometric model fidelity, high cost of manual experiments, and long experimental time in existing cigarette design models. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a flowchart of the cavity filter flow field simulation method provided in the embodiments of the present invention;

[0027] Figure 2 The Micro-CT scan point cloud STL model of the hollow cigarette filter provided in this embodiment of the invention, wherein: Figure 2 (a) is a partial view of the axial section of the model; Figure 2 (b) A schematic diagram of the selected cross-section for the model; Figure 2 (c) is a partial view of the radial section of the model;

[0028] Figure 3 The hollow cigarette filter tip partial sampling fiber geometric model provided in the embodiment of the present invention, wherein: Figure 3 (a) is a radial cross-sectional view of the filter tip; Figure 3 (b) is a radial cross-sectional view of a 1 / 4 filter tip; Figure 3 (c) is a radial cross-sectional view of a 1 / 8 filter tip; Figure 3 (d) is the radial cross-section of a 1 / 12 filter tip. Figure 1 / 36 Radial section view of the filter tip; Figure 3 (e) 1 / 12 Filter Tip Radial Section Figure 1 / 36 Radial section view of the filter tip;

[0029] Figure 4 This is a geometric model of an integral cavity cigarette filter provided in an embodiment of the present invention;

[0030] Figure 5 The finite element model of the porous media model of the integral cavity cigarette filter provided in the embodiment of the present invention;

[0031] Figure 6 The simulation results of the porous media model of the integral cavity cigarette filter provided in the embodiments of the present invention are as follows: Figure 6 (a) shows the velocity distribution diagram; Figure 6 (b) is a pressure distribution diagram;

[0032] Figure 7 The pressure distribution of cellulose acetate inside the porous media model of the integral cavity cigarette filter provided in this embodiment of the invention, wherein: Figure 7 (a) shows the axial pressure variation at different radius positions of the filter tip; Figure 7 (b) shows the radial pressure variation at different height positions of the filter tip;

[0033] Figure 8 The partially cavity cigarette filter provided in this embodiment of the invention does not consider the porosity of the splicing paper (i.e., the porosity is 0) and the finite element model of the smoke flow in the cavity, wherein: Figure 8 (a) is a local geometric model that does not take into account the porosity of the splicing paper and the 1 / 36 cavity; Figure 8 (b) is a schematic diagram of the mesh generation for a 1 / 36 local model;

[0034] Figure 9 For the partially cavity cigarette filter provided in the embodiments of the present invention, a finite element model considering the porosity of the splicing paper and the smoke flow in the cavity is provided, wherein: Figure 9 (a) Considering the porosity of the splicing paper and the local geometric model of cavity 1 / 36; Figure 9 (b) Schematic diagram of mesh generation for the local model considering splicing paper porosity and cavity 1 / 36;

[0035] Figure 10 The embodiments of the present invention provide the effects of porosity of the nozzle paper in a partially cavity cigarette filter and the cavity on the flow velocity of smoke; wherein: Figure 10 (a) is a schematic diagram that does not consider the effect of splicing paper porosity and cavity on flue gas flow velocity; Figure 10 (b) Schematic diagram considering the effect of splicing paper porosity and cavity on flue gas flow velocity;

[0036] Figure 11 The following is a schematic diagram illustrating the influence of the porosity of the splicing paper and the cavity on the pressure distribution of cellulose acetate in a cigarette filter tip with a partial cavity, provided in an embodiment of the present invention; wherein: (a) is a schematic diagram without considering the influence of the splicing paper porosity and the cavity on the pressure distribution of cellulose acetate; (b) is a schematic diagram considering the influence of the splicing paper porosity and the cavity on the pressure distribution of cellulose acetate.

[0037] In the diagram: 1-Tipping paper, 2-Cellulose acetate, 3-Air inlet, 4-Cavity, 5-Fluorite outlet, 6-Fluorite inlet. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0039] Example 1

[0040] like Figure 1 As shown, this embodiment provides a method for optimizing the structure of a cavity filter tip, including:

[0041] S1: Scan the hollow cigarette filter to obtain the overall data file of the hollow cigarette filter, and then construct the overall hollow filter scanning model. Specifically, Micro-CT scanning technology is used to scan the hollow cigarette filter to obtain the overall STL file of the hollow cigarette filter; the scanning accuracy of Micro-CT is 2.95μm, and it is performed in sections. The scan results are then stitched together to obtain the final filter STL model.

[0042] In this implementation, the Micro-CT scanning equipment used was the nanoVoxel 3502E open-tube transmission high-resolution CT system, operating at 80kV, with a pixel matrix of 1920×1536, a maximum testable sample size of 450mm×350mm, and a maximum resolution of 0.5μm. The selected equipment, based on the VG Studio MAX platform, performed 3D visualization processing on the acquired DICOM image data files. A precise and complete point cloud data model of the filter tip (including states such as cellulose acetate bending, entanglement, suspension, and aggregation) was established through methods such as setting the normal direction, constructing a coordinate system, image fusion, region growing, threshold segmentation based on image grayscale, and 3D transformation. The scanning accuracy was 2.95μm. The scanning process employed a technique of scanning in sections and then stitching them together to form the point cloud STL model of the hollow cigarette filter tip, as shown below. Figure 2 (a)- Figure 2 As shown in (c).

[0043] S2: Geometric repair is performed based on the constructed overall cavity filter scanning model, and the cellulose acetate model is obtained by reverse reconstruction.

[0044] In practice, based on the extracted point cloud STL model, geometric repair and reconstruction are performed using the industrial modeling software Geomagic Design X and Geomagic Wrap. This primarily repairs geometric defects appearing in the point cloud STL geometric file, including self-intersections, non-manifold edges, highly refractive edges, nail-like structures, small components, small channels, and small holes. The point cloud STL file is then converted into an STP solid model. To simplify the model, this embodiment ultimately transforms the curved surface model of the cigarette filter and its internal acetate filaments into a 3D solid CAD model. The hollow cigarette filter is segmented, and considering computational costs and time, a 1 / 36 scale geometric model is ultimately used as the flow field simulation geometric model. The local geometric model of the hollow cigarette filter is shown below. Figure 3 (a)- Figure 3 As shown in (e).

[0045] S3: Experimental measurements were performed on the cavity filter under different flue gas inlet conditions to obtain the boundary conditions. The boundary conditions include the filter outlet pressure and velocity.

[0046] Specifically, two experiments were conducted using the velocity distribution function v = 0.61sin(πt / 2) for ISO suction mode and v = 0.96sin(πt / 2) for HCI suction mode. The boundary conditions were measured using a smoke extraction machine and a piezoresistive meter. The boundary conditions included the filter outlet boundary pressure and velocity magnitude.

[0047] S4: Construct a full-scale finite element model of the overall cavity filter based on the actual size of the cigarette filter. Combine the boundary conditions obtained in S3 to perform finite element simulation of the smoke flow process inside the cavity cigarette filter and calculate the internal pressure distribution of the filter.

[0048] In practice, the finite element method (FEM) simulation of the smoke flow process inside the cavity cigarette filter is performed using the CFD simulation software ANSYS Fluent. The main modules involved include laminar flow model, porous medium model, and component transport model. The smoke flow inside the cigarette filter should follow the continuity equation and momentum equation.

[0049]

[0050]

[0051] In the formula, ρ is the fluid density; u, v, and w are the velocity components in the x, y, and z directions, respectively; t is time; and S is the mass source term. σ represents velocity; σ represents pressure. For Hamiltonian operators; Let represent the vector sum of gravity and external forces.

[0052] Because cigarette smoke is a highly complex aerosol, its flow within a cigarette filter is a dynamic process. Parameters such as smoke velocity, temperature, and the number of smoke particles are constantly changing, making it virtually impossible to realistically simulate the flow of cigarette smoke within a filter. Therefore, when establishing the cigarette filter model, the following assumptions are made regarding the flow of smoke within the filter:

[0053] (a) It is assumed that cellulose acetate for cigarette filters is an isotropic, porous medium with uniform pore size;

[0054] (b) The cigarette filter has very low resistance and the density of the smoke changes little during the inhalation process. It is assumed that the smoke is an incompressible fluid.

[0055] Finite element model of integral cavity filter tip as follows Figure 4 As shown, the overall length of the hollow filter tip is 28mm, the cavity 4 is 7mm long, the radius of cellulose acetate 2 is 3.15mm, the radius of cavity 4 is 2.48mm, and the thickness of the tipping paper 1 is 0.1mm. A polyhedral mesh was used during mesh generation to reduce the number of meshes while ensuring mesh quality, thus lowering computational costs. Three boundary layers were drawn on the walls and interfaces. The overall porous media model of the hollow cigarette filter tip is shown in the finite element model. Figure 5 As shown.

[0056] This simulation of the overall hollow cigarette filter flow field uses a steady-state approach. Since the smoke is an incompressible fluid, a pressure-based solver is used in this embodiment. Simple calculations of the flow velocity at the filter intake end show that its Reynolds number is less than 3000, indicating that the smoke flow within the filter is laminar. Therefore, a laminar model is selected for simulation. Furthermore, since the smoke contains multiple components, a species transport model is used to analyze the variations of these components in the filter flow. When setting up the fluid domain, the tipping paper and cellulose acetate sections are designed as porous media.

[0057] The simulation employs a velocity-pressure coupling method, selecting the SIMPLE algorithm. This algorithm calculates the pressure field based on an interlaced mesh, thereby solving the momentum equation. In the microdispersion scheme options, the gradient term finite difference method uses the Least-Squares Cell-Based method to prevent spurious diffusion during the calculation, resulting in more accurate results. The pressure term finite difference method uses the PRESTO! method. To achieve more reliable accuracy in the simulation, a second-order upwind scheme is used for the momentum equation. The convergence limit of the continuity equation and the residuals of each component is set to 10⁻⁶ to determine convergence, ensuring the accuracy and precision of the calculation.

[0058] This step primarily involves modeling based on the actual dimensions of a cigarette filter, using a simplified porous media model for multiphysics fluid-structure interaction simulation to obtain the internal flow field and pressure distribution of the filter. The axial and radial pressure variations at various locations within the filter are analyzed to determine the pressure distribution within the cavity filter. The results are as follows: Figure 6 (a) Figure 6 (b) Figure 7 (a) Figure 7 As shown in (b).

[0059] S5: The reconstructed cellulose acetate model is segmented to obtain a local fiber model. The internal pressure distribution of the filter is obtained by combining the segments, and the boundary conditions of the local fiber model are calculated.

[0060] In practice, the massive amount of geometric model data obtained from MicroCT scanning results in high computational costs. Therefore, the reconstructed cellulose acetate model is segmented to obtain local fiber models. Flow field simulations are then performed on these local fiber models to analyze and compare the effects of splicing paper porosity and cavity size parameters on flue gas flow. Based on the pressure distribution results in S4 and the analysis of the internal pressure distribution pattern of the cavity filter, the simulation boundary conditions for the local fiber model of the cavity filter are determined. A local fiber model with a thickness of 0.22 mm is selected as the research object, Z = 0 mm is defined as the pressure outlet, and the pressure outlet pressure is set to P.outlet =-90Pa, define Z=0.22mm as the pressure inlet, set the pressure inlet pressure to Pinlet=0Pa, and determine the pressure inlet (divided into cavity and cellulose acetate parts) based on the pressure distribution law and the local fiber model of the cavity filter. The pressure in the cavity part remains uniform, and the root mean square average is taken; the pressure at the cellulose acetate part varies more, and the weighted average is taken. Whether the porosity of the splicing paper is considered in the local cavity cigarette filter, and the finite element model of the smoke flow in the cavity, are as follows. Figure 8 (a) Figure 8 (b) Figure 9 (a) Figure 9 As shown in (b).

[0061] S6: The boundary conditions of the local fiber model are used as the initial conditions for the flow field simulation calculation of the local fiber model, and the parameters of the local fiber simulation model are obtained through simulation. The parameters obtained from the simulation include: the influence of cavity shape on flue gas flow, the influence of cavity shape on flue gas filtration, the influence of splicing paper porosity on flue gas flow, and the influence of splicing paper porosity on flue gas filtration.

[0062] In practical implementation, the simplified conditions in the flow field simulation of the local fiber model are the same as those in the overall porous media model in the previous section. It is assumed that the flue gas is an incompressible fluid and that there is no material or heat exchange between the inner and outer boundaries and the outside world. In this step, two comparative simulations were performed on the local cavity filter model. The difference lies in whether or not the influence of the porosity of the splicing paper and the cavity was considered. During the meshing process, since the fiber surface is irregularly shaped, tetrahedral meshes were selected to improve the mesh quality, and three boundary layers were drawn on the walls and interfaces.

[0063] This calculation aims to dynamically analyze the flow of flue gas within a filter during the standard suction phase using numerical simulation. Therefore, a transient solution was selected in the simulation solver settings. Since flue gas is an incompressible fluid, a pressure-based solver was employed. Calculations of the flow velocity at the filter intake end show a Reynolds number less than 3000, indicating laminar flow within the filter. Therefore, a laminar model was chosen for simulation. Furthermore, given the presence of multiple components in the flue gas, a species transport model was used to analyze the variations in these components during filter flow. Additionally, due to issues such as geometric shape loss during MicroCT and geometric reverse modeling, errors were introduced compared to the actual fiber model. To compensate for these errors, a porous media model was introduced, setting the fluid domain as a porous medium to improve realism and reduce errors. After considering the porosity of the tipping paper and the cavity, the numerical simulation boundary settings are the same as above. The difference lies in the cavity and tipping paper sections. The cavity section is the flue gas fluid domain, while the tipping paper section is simplified as a porous medium region with a porosity set to 0.99. The entire surface of the tipping paper is set as a pressure inlet, allowing air to enter the filter through the tipping paper, thus cooling the mainstream flue gas.

[0064] This calculation employs the SIMPLEC algorithm, a velocity-pressure coupling method, which primarily calculates the pressure field based on an interlaced grid to solve the momentum equation. In the microdispersion scheme options, the gradient term finite difference method uses the Least-Squares Cell-Based method to prevent spurious diffusion during the calculation, resulting in more accurate results. The pressure term finite difference method uses the PRESTO! method. To achieve more reliable simulation accuracy, a second-order upwind scheme is used for the momentum equation. The convergence limits of the continuity equation and the residuals of each component are set to 10⁻⁶ to determine convergence, ensuring accuracy and precision. Since the actual inhalation time is 2 seconds, only the local fiber model flow field results within 2 seconds need to be calculated. In this embodiment, the time step is set to 0.01 seconds, requiring a total of 200 calculation steps.

[0065] This step mainly relies on the pressure distribution pattern obtained in S4 and the boundary conditions of the local fiber model calculated in S5. These are used as the initial conditions for the flow field simulation calculation of the local fiber model. The simulation results show the influence of the porosity and cavity of the splicing paper on the flue gas flow. Figure 10 (a) Figure 10 (b) Figure 11 (a) Figure 11 As shown in (b).

[0066] S7: Analyze the flow field of the local fiber simulation model to obtain the optimal cavity filter structure parameters, including cavity shape and splicing paper porosity.

[0067] In practice, the influence of cavity shape and filter tip porosity on flue gas flow and filtration is analyzed. By changing the cavity shape and filter tip porosity, the flue gas flow inside the cavity filter tip under different structures is obtained. The simulation method is the same as the above steps, so as to obtain the optimal cavity filter tip structure through comparative analysis.

[0068] This invention proposes a method for optimizing the structure of a cavity filter tip. The method involves geometric modeling based on a scanned file of the cavity filter tip, and experimentally measuring the boundary conditions of the overall model to analyze the overall cigarette filter tip pressure distribution and obtain precise local pressure. Using this as boundary condition, flow field simulation is performed on a local cellulose acetate model to obtain the influence of the cavity and the porosity of the tipping paper on the smoke flow. This addresses the problems of low geometric model fidelity, high cost of manual experiments, and long experimental time in existing cigarette design models.

[0069] It is understood that the same or similar parts in the above embodiments can be referred to each other, and the contents not described in detail in some embodiments can be referred to the same or similar contents in other embodiments.

[0070] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for optimizing the structure of a cavity filter tip, characterized in that, include: S1: Scan the hollow cigarette filter to obtain the overall data file of the hollow cigarette filter and then construct the overall hollow filter scanning model; S2: Geometric repair is performed based on the constructed overall cavity filter scanning model, and the cellulose acetate model is obtained by reverse reconstruction; S3: Experimental measurements were conducted on the cavity filter under different flue gas inlet conditions to obtain boundary conditions; S4: Construct a full-scale finite element model of the overall cavity filter based on the actual size of the cigarette filter. Combine the boundary conditions obtained in S3 to perform finite element simulation of the smoke flow process inside the cavity cigarette filter, and then calculate the pressure distribution inside the filter. S5: The reconstructed cellulose acetate model is segmented to obtain a local fiber model. The internal pressure distribution of the filter is obtained, and the boundary conditions of the local fiber model are calculated. S6: Use the boundary conditions of the local fiber model as the initial conditions for the flow field simulation calculation of the local fiber model, and obtain the parameters of the local fiber simulation model through simulation. S7: Analyze the parameters of the local fiber simulation model to obtain the optimal cavity filter structure parameters.

2. The method for optimizing the structure of a cavity filter tip according to claim 1, characterized in that, Micro-CT scanning technology was used to scan the hollow cigarette filter to obtain the overall STL file of the hollow cigarette filter.

3. The method for optimizing the structure of a cavity filter tip according to claim 2, characterized in that, Micro-CT has a scanning precision of 2.95μm. It performs partitioned scanning and stitches the scanning results to obtain the final filter STL model.

4. The method for optimizing the structure of a cavity filter tip according to claim 1, characterized in that, The geometric repair refers to repairing geometric defects in the overall data file, including self-intersections, non-manifold edges, highly refractive edges, nails, small components, small channels, and small holes.

5. The method for optimizing the structure of a cavity filter tip according to claim 1, characterized in that, S3 specifically refers to the following: The flue gas inlet conditions include two experiments conducted according to the velocity distribution function: ISO suction mode velocity v = 0.61sin(πt / 2) and HCI suction mode velocity v = 0.96sin(πt / 2). The boundary conditions are measured using a smoke extraction machine and a piezoresistive meter.

6. The method for optimizing the structure of a cavity filter tip according to claim 1, characterized in that, The boundary conditions in S3 include the filter outlet pressure and velocity.

7. The method for optimizing the structure of a cavity filter tip according to claim 1, characterized in that, In S4, the finite element model of the integral cavity filter includes a laminar flow model, a porous media model, and a component transport model.

8. The method for optimizing the structure of a cavity filter tip according to claim 1, characterized in that, In S4, a simplified model of porous media is used for multi-physics fluid-structure interaction simulation to obtain the flow field distribution and pressure distribution inside the filter nozzle. The pressure distribution law inside the cavity filter nozzle is obtained by analyzing the pressure changes along the axial and radial directions at various positions inside the filter nozzle.

9. The method for optimizing the structure of a cavity filter tip according to claim 1, characterized in that, The parameters of the local fiber simulation model obtained in S6 include: the influence of cavity shape on flue gas flow, the influence of cavity shape on flue gas filtration, the influence of splicing paper porosity on flue gas flow, and the influence of splicing paper porosity on flue gas filtration.

10. The method for optimizing the structure of a cavity filter tip according to claim 9, characterized in that, The specific process of S7 is as follows: analyze the influence of cavity shape and splicing paper porosity on flue gas flow and flue gas filtration, change cavity shape and splicing paper porosity to obtain flue gas flow conditions inside cavity filter under different structures, and then compare and analyze to obtain the optimal cavity filter structure.

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