A numerical simulation method for determining the shape and size of a silo arch

Abstract

The present application relates to the technical field of silo numerical simulation, in particular to a numerical simulation method for determining the shape and size of a silo arch. First, a finite element method (FEM) numerical model is established relative to the silo, the flow state of particles with different parameters inside the silo is simulated by computer, then the positions, shapes and sizes prone to arching are found by using the simulation results, and finally new design charts are obtained, including different discharge port sizes corresponding to different particle sizes, shapes, silo shapes and other parameters, to guide silo technical improvement and design. The present application establishes a FEM numerical simulation model matching the actual project for calculation, which can quickly and accurately simulate the flow state of particles inside the silo and realize the visualization of the results, so that the flow state of particles inside the silo can be clearly observed. By using this mechanism model research method, the basic principles of particle flow in silo discharge can be better understood, so that the arching problem can be solved from the root cause.

Description

Technical Field

[0001] This invention relates to the field of numerical simulation technology for silos, and in particular to a numerical simulation method for determining the shape and size of the silo arch. Background Technology

[0002] Silos are crucial equipment in powder processing, serving not only as storage devices but also as feeders to other equipment. To maintain stable feeding, mass flow is typically designed for silos. However, in actual production, due to the characteristics of the particles themselves, as well as the silo structure and wall friction, funnel flow can easily occur, leading to unstable flow and even material arching and blockage. Arching frequently occurs during unloading, causing reduced production capacity and even serious safety accidents. Its occurrence is unpredictable and irregular, and the silo structure prevents operators from visually observing the internal particle flow. Furthermore, prevention lacks standardized theoretical support, relying primarily on worker experience for rectification and maintenance. When arching occurs, timely breaking is necessary. Existing methods often involve manual tapping, adding vibration devices, or air blowing. These methods are sometimes insufficient to resolve the problem promptly, and manual tapping is time-consuming, labor-intensive, and poses safety hazards. Summary of the Invention

[0003] The purpose of this invention is to address the problems existing in the background technology by proposing a numerical simulation method for determining the shape and size of the silo material arch.

[0004] The technical solution of the present invention, a numerical simulation method for determining the shape and size of a silo arch, includes the following specific steps:

[0005] S1. Establish a numerical simulation model of the silo;

[0006] S2. Based on the numerical simulation model in S1, the flow state of particles with different parameters inside the silo is simulated using FEM finite element software.

[0007] S3. Use numerical simulation results to find the parts, shapes and sizes that are prone to arching;

[0008] S4. Optimize the silo structure based on the simulation results obtained in S3;

[0009] S5. Re-enter the optimized silo structure from S4 into the FEM finite element software to verify whether the results meet the expected requirements; if not, repeat S2-S5 until the output results meet the expected requirements.

[0010] In S1, the silo structure and dimensions are systematically measured and a model is built based on the construction drawings.

[0011] Preferably, in S1, the structural dimensions model of the silo is built using the modeling module of Abaqus or Solidworks software.

[0012] Preferably, the FEM (Finite Element Method) computer software used in S2 is Abaqus; the silo model established in S1 is directly imported into the Abaqus software.

[0013] S2 uses the Euler finite element method for numerical simulation, and its governing equations are as follows:

[0014] Conservation of mass:

[0015]

[0016] Conservation of momentum:

[0017]

[0018] Energy conservation:

[0019]

[0020]

[0021] Where ρ is the bulk density of the material, v represents the flow velocity, σ represents the stress tensor, and ∈ is equivalent to the internal energy per unit volume.

[0022] Preferably, in S2, the Mohr-Coulomb elastoplastic model is used to describe the cohesive flow behavior of bulk materials in the silo; the elastic behavior of the material is described using Young's modulus and Poisson's ratio.

[0023]

[0024] σ ij It is the total stress. It is elastic strain. It is a fourth-order elastic tensor;

[0025] Regarding the yield condition:

[0026] R mc q-ptanφ-c=0

[0027]

[0028] The stress p is given by the following formula

[0029]

[0030] And the equivalent stress q

[0031]

[0032] Where S ij It is deviation stress. The internal friction angle c is the material cohesion. Θ is the polar angle of deviation, given by cos(3Θ)=(r / q). 3 definition;

[0033]

[0034] in

[0035]

[0036] Where ψ is the material expansion angle, c0 represents cohesion; ε = 0.1 represents the eccentricity of all simulated flow potentials; furthermore, e is determined by the internal friction angle, i.e.

[0037] The results output by the FEM finite element software in S2 include particle flow velocity, pressure distribution table, and particle flow images and videos.

[0038] A database of particle flow results in silos is generated based on particle velocity and pressure distribution tables.

[0039] Based on the data from the silo particle flow results database, silo optimization charts are generated. These charts are then used to technically upgrade existing silos or optimize the design of new silos.

[0040] A visualization system for the state of particle flow in silos is generated based on particle flow images and videos, which displays the state of particle flow through visualization.

[0041] A silo arching prediction and early warning system was built by combining particle flow images and videos with a database of particle flow results in silos; this system can predict and warn of arching phenomena in the material flow within silos.

[0042] Preferably, the expected requirements in S5 are set as follows: feeding efficiency increased by 20%, equipment energy consumption decreased by 10%, and the number of bridging events decreased by 20%.

[0043] Compared with the prior art, the present invention has the following beneficial technical effects:

[0044] This invention uses numerical simulation to study particle flow inside silos, thereby predicting the shape, size, and location of material arching that may occur inside the silos, and optimizing the shape and structure of the silos to solve the problem of arching.

[0045] This invention calculates the flow state of different materials in silos under various working conditions, improves the accuracy of predicting silo flow problems such as arching and collapse, realizes the function of early prediction and warning, and to a certain extent provides feasible technical transformation or design solutions, reducing the time and cost of technical transformation, while also avoiding problems such as errors caused by manual measurement. Attached Figure Description

[0046] Figure 1 This is a flowchart illustrating the technical process of the present invention.

[0047] Figure 2 This is a schematic diagram of the structure and dimensions of a cement plant silo equipment in an embodiment of the present invention;

[0048] Figure 3 This is a diagram of the internal pressure distribution of the silo obtained using the FEM numerical simulation method in an embodiment of the present invention.

[0049] Figure 4 This is a comparison diagram of the internal pressure distribution of the silo after improvement using the FEM numerical simulation method in an embodiment of the present invention;

[0050] Figure 5 This is a graph showing the change in silo weight during the unloading process, obtained using the FEM numerical simulation method in an embodiment of the present invention. Detailed Implementation

[0051] A numerical simulation method for determining the shape and size of the silo arch includes the following specific steps:

[0052] S1. Systematically measure the structure and dimensions of the silo and, in conjunction with the construction drawings, use the built-in drawing module of Abaqus or Solidworks software to create a numerical simulation model of the silo.

[0053] S2. Based on the numerical simulation model in S1, the flow state of particles with different parameters inside the silo is simulated using Abaqus software.

[0054] After importing the silo model into the Abaqus software, use the Property module to set material properties and define them on each component. The defined material properties include basic physical properties, mechanical properties, thermodynamic properties, etc. Then use the Create Section button to define the cross-sectional properties of materials for different structures. After completing the material property definition, set the calculation steps. Note that after building the model, you need to add an Eulerian structure to cover the entire model, and create a solid structure inside the silo model. Fill the interior of the silo and couple it to the Eulerian structure to complete the material placement process.

[0055] First, use the Step module to define the calculation steps, including information such as calculation duration, number of calculation steps, and the results to be output;

[0056] Then, the field variable output and historical variable output, interaction property settings, contact relationship settings, gravity load definition, boundary condition settings, symmetry / antisymmetry / completely fixed settings, displacement / rotation angle settings, velocity and rotation speed settings are set in sequence to determine the necessary boundary conditions for numerical simulation.

[0057] Next, use the Mesh module to mesh the internal structure of the model. First, the mesh type needs to be determined, choosing an appropriate type based on the specific structure and computational requirements. After determining the mesh type, the mesh size needs to be determined, specifying the mesh density and shape at different locations. Typically, a holistic meshing method is used to draw the mesh for the entire structure. For simple model structures, default settings are sufficient. After the mesh is drawn, the mesh quality check function can be used to inspect and optimize the mesh quality.

[0058] Finally, a new calculation program can be created using the Job module to simulate the operating conditions of the silo under different working conditions.

[0059] S3. Use numerical simulation results to find the parts, shapes and sizes that are prone to arching;

[0060] S4. Optimize the silo structure based on the simulation results obtained in S3;

[0061] S5. Re-enter the optimized silo structure from S4 into the FEM finite element software to verify whether the results meet the expected requirements; if not, repeat S2-S5 until the output results meet the expected requirements.

[0062] Example 1

[0063] Based on the flow stabilization silo structure used in a cement plant, an FEM numerical simulation model was established. The equipment dimensions and schematic diagram are shown below. Figure 2 As shown.

[0064] Table 1. Dimensions of Silo Equipment in a Cement Plant

[0065]

[0066]

[0067] The numerical simulation model of the steady-flow chamber uses a thin shell of iron, 1 mm thick, as its outer wall. The parameter values ​​are as follows:

[0068] Density: 7800 kg / m³ 3

[0069] Young's modulus E: 388 GPa

[0070] Poisson's ratio: 0.25;

[0071] Coefficient of friction: 0.3 (the internal slice partition wall surface is a frictionless wall surface)

[0072] Numerical simulations were conducted using different parameter values ​​to study the various effects on particle flow characteristics. To ensure the accuracy of the numerical simulations, a three-dimensional finite element model was rebuilt in the software. The basic parameters used in the particle simulation are shown in the table below.

[0073] Table 2 Mechanical Performance Parameters of Granular Materials

[0074] Cement particles 1642 13.9 0.211 26.1

[0075] After applying the model in this invention to the set parameters, various results can be output. To address the problem of silo arching, pressure distribution is used as an example here. Figure 3 A cross-sectional view of the silo's center during the unloading process is shown, illustrating the changes in pressure distribution within the silo. Darker colors represent lower pressure, while lighter colors represent higher pressure. The image reveals areas of higher pressure forming arches at the silo's hopper bends and in the lower chute, indicating a large accumulation of particles and slower flow velocity. It is evident that more than one arch exists within the hopper.

[0076] To address the arching problem currently existing in silos, this invention analyzes existing results and finds that arching is most likely to occur at the bends in the hopper. Modifying this area can reduce arching. Therefore, this invention utilizes the ease of parameter adjustment in FEM numerical simulation to modify the silo shape and performs multiple sets of calculations using the same parameters to obtain results. Figure 4 The figure illustrates the flow patterns observed in silos at three different angles. As the silo angle increases, the pressure distribution inside the hopper becomes more uniform, the arching structure becomes less pronounced, and the flow exhibits minimal fluctuations. Therefore, it is concluded that increasing the hopper angle can significantly resolve the arching problem.

[0077] Figure 5 The figure shows the unloading speed of the hopper at different hopper angles. As can be seen from the figure, the unloading speed increases and the unloading becomes more stable with the increase of the hopper angle. This indicates that increasing the hopper angle can increase unloading efficiency and reduce the impact of arching on unloading, achieving stable material supply. Using this invention can shorten the original technical modification experiment and design time to 2 days, greatly guiding the direction of technical modification and reducing errors caused by insufficient experience of personnel, thus saving costs.

[0078] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited thereto. Various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention.

Claims

1. A numerical simulation method for determining the shape and size of a silo arch, characterized in that, The specific steps include the following: S1. Establish a numerical simulation model of the silo; S2. Based on the numerical simulation model in S1, the flow state of particles with different parameters inside the silo is simulated using FEM finite element software. S2 uses the Mohr-Coulomb elastoplastic model to describe the cohesive flow behavior of bulk materials in silos; the elastic behavior of the material is described using Young's modulus and Poisson's ratio. ； It is the total stress. It is elastic strain. It is a fourth-order elastic tensor; Regarding the yield condition: ； The first invariant of stress p is given by the following formula: ； And the first invariant of equivalent force is q: ； in It is deviation stress. It is the internal friction angle. It is the cohesive force of materials. It is the polar angle of deviation, from definition; ； in ； in, It is the material expansion angle. Represents cohesion; The eccentricity represents the flow potential in all simulations; furthermore, e is determined by the internal friction angle, i.e. ; S3. Use numerical simulation results to find the parts, shapes and sizes that are prone to arching; S4. Optimize the silo structure based on the simulation results obtained in S3; S5. Re-enter the optimized silo structure from S4 into the FEM finite element software to verify whether the results meet the expected requirements; if not, repeat S2-S5 until the output results meet the expected requirements.

2. The numerical simulation method for determining the shape and size of the silo arch according to claim 1, characterized in that, In S1, the silo structure and dimensions are systematically measured and a model is built based on the construction drawings.

3. The numerical simulation method for determining the shape and size of the silo arch according to claim 2, characterized in that, In S1, use the modeling module of Abaqus or Solidworks software to create a structural dimension model of the silo.

4. The numerical simulation method for determining the shape and size of the silo arch according to claim 1, characterized in that, The FEM (Finite Element Method) software used in S2 is Abaqus; the silo model created in S1 is directly imported into the Abaqus software.

5. The numerical simulation method for determining the shape and size of the silo arch according to claim 1, characterized in that, S2 uses the Euler finite element method for numerical simulation, and its governing equations are as follows: Conservation of mass: ； Conservation of momentum: ； Energy conservation: ； in, It is the bulk density of the material. Indicates flow rate, ϵ represents the stress tensor, which is equivalent to the internal energy per unit volume.

6. The numerical simulation method for determining the shape and size of the silo arch according to claim 1, characterized in that, The results output by the FEM finite element software in S2 include particle flow velocity, mass flow rate, pressure distribution table, and images and videos of particle flow characteristics. A database of particle flow results in silos is generated based on particle velocity and pressure distribution tables. Based on the data from the silo particle flow results database, silo optimization charts are generated. These charts are then used to technically upgrade existing silos or optimize the design of new silos.

7. The numerical simulation method for determining the shape and size of the silo arch according to claim 6, characterized in that, A visualization system for the state of particle flow in silos is generated based on particle flow images and videos, and the state of particle flow is displayed through the visualization system. A silo arching prediction and early warning system was built by combining particle flow images and videos with a database of particle flow results in silos; this system can predict and warn of arching phenomena in the material flow within silos.

8. The numerical simulation method for determining the shape and size of the silo arch according to claim 1, characterized in that, The expected requirements for S5 are a 20% increase in feeding efficiency, a 10% decrease in equipment energy consumption, and a 20% decrease in the number of bridging events.

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