Simulation method of macro-micro coupling pollution of coal mine material induced airflow transfer point

Abstract

This invention discloses a simulation calculation method for macro- and micro-scale coupled pollution at coal material induced airflow transfer points, comprising the following steps: S1: Constructing a three-dimensional model of an open underground transfer point and a flow field calculation grid; S2: Establishing a macro- and micro-scale separation strategy for solid materials; S3: Calculating macroscopic coal flow motion and spatial porosity based on the discrete element method; S4: Calculating fine dust diffusion based on a fluid dynamics discrete phase model; S5: Performing asynchronous coupled calculations of fluid and discrete element methods, which can avoid simulation result distortion and the problem of coupled simulation easily leading to grids exceeding 100 million and calculation divergence.

Description

Technical Field

[0001] This invention relates to the field of dust simulation technology, specifically to a simulation calculation method for macro- and micro-coupling pollution at coal and mineral material induced airflow transfer points. Background Technology

[0002] Conveyor belt transfer points in coal mines are typically located in enclosed, narrow, and confined roadways, making them major sources of mine dust pollution. Under high-throughput transport conditions, large quantities of coal fall at high speeds under gravity, generating not only fine coal dust through collisions but, more importantly, the large coal flows forcefully displace and carry away surrounding air during their descent, creating a unique and powerful "induced draft." This induced draft, combined with the existing ventilation in the underground roadways, forms a violent dust jet in open or semi-open spaces without feed chutes, leading to the widespread and disorderly diffusion of highly respirable dust within the roadways.

[0003] Currently, simulations of dust at transfer points face a severe "cross-scale computing power paradox." If only pure computational fluid dynamics (CFD) software is used, although the calculation speed is fast, it cannot realistically simulate the "induced airflow" generated by the compression of air by large volumes of solid coal, resulting in low simulated wind speeds and severely distorted dust dispersion trajectories.

[0004] To address this issue, the conventional approach is to use fluid dynamics software and discrete element method (CFD-DEM) software in combination. However, in engineering-scale mine models, forcibly including large coal chunks (centimeter-scale) and fine dust (micrometer-scale) simultaneously in the DEM software for contact mechanics calculations, the fundamental algorithmic rule that "the mesh must be larger than the particles" leads to an exponential explosion in the number of contact retrieval meshes (easily exceeding 100 million). This not only causes instantaneous memory overflow on ordinary workstations but also results in the equations diverging and collapsing due to severe porosity fluctuations. Therefore, a coupled research technique is urgently needed that can realistically reproduce the physical mechanism of induced wind, ensure high computational stability, and guide the design of physical dust control equipment. Summary of the Invention

[0005] This invention aims to solve the technical problems existing in the prior art. In particular, it innovatively proposes a simulation calculation method for macro- and micro-coupling pollution at the coal and mineral material induced airflow transfer point, which can avoid the distortion of simulation results and the problems of coupled simulation easily leading to grids exceeding 100 million and calculation divergence.

[0006] To achieve the above objectives, this invention provides a simulation calculation method for macro- and micro-coupling pollution at coal material induced airflow transfer points, comprising the following steps:

[0007] S1: Construct a 3D model of the open transfer point in the well and a mesh for flow field calculation;

[0008] A three-dimensional solid model of an open transfer point without a guide chute, including the upper and lower level belt conveyors and confined roadways in a coal mine, is obtained. The internal connected fluid space is extracted and meshed to establish a computational fluid dynamics flow field calculation mesh.

[0009] S2: Establish macro- and micro-scale separation strategies for solid materials;

[0010] Set particle size classification threshold The dispersed solid media in the fluid domain inside the tunnel are divided into particles with a diameter greater than [missing information]. Large coal materials with macroscopic phases and particle sizes smaller than The microscopic phase of fine dust;

[0011] S3: Calculation of macroscopic coal flow motion and spatial porosity based on the discrete element method;

[0012] S4: Calculation of fine dust diffusion based on a discrete phase model of fluid dynamics; in computational fluid dynamics software, combined with the boundary conditions of ventilation velocity in underground roadways, a real-time porosity factor is introduced. With momentum transfer source term The Navier-Stokes governing equations are used, and the discrete phase model is activated. The motion trajectory of the fine dust microphase is generated and calculated using dimensionality reduction tracking technology.

[0013] S5: Performs asynchronous coupled computation of fluid and discrete elements.

[0014] In the above scheme, step S1 also includes:

[0015] S1-1: Draw a three-dimensional model of the transfer point using three-dimensional drawing software. The three-dimensional model of the transfer point includes the underground conveying equipment of the coal mine and the external air envelope domain corresponding to the restricted roadway.

[0016] S1-2: Solid regions are eliminated through Boolean operations, leaving only air-flowing and interconnected spaces to generate the fluid domain inside the tunnel.

[0017] S1-3: Import the 3D model of the transfer point into the mesh processing software to perform tetrahedral mesh generation of the fluid domain inside the tunnel, and export the flow field calculation mesh file.

[0018] In the above scheme, step S3 also includes:

[0019] S3-1: Create a geometric model of a single large coal block;

[0020] S3-2: Generate macroscopic phases of the large coal material with different particle sizes based on the uniform size distribution model, and calculate their falling trajectory; and during generation, generate large coal material according to the separation strategy established in step S2.

[0021] S3-3: Set the simulation mesh parameters based on the minimum particle size of large coal materials;

[0022] Set the mesh constraint law as follows ,in, The minimum particle size of large coal pieces. Define the size of the contact retrieval mesh for discrete element analysis; set the size of the contact retrieval mesh in the Simulator according to the mesh constraint rules so that the total number of meshes meets the set range;

[0023] Calculate the real-time porosity of large coal particles produced by fluid. With momentum transfer source term .

[0024] In the above scheme, step S4 also includes:

[0025] S4-1: Import the flow field calculation mesh file constructed in step S1 into the computational fluid dynamics software, and activate the real-time porosity calculation function in the governing equations. With momentum transfer source term The Navier-Stokes modified equations;

[0026] S4-2: Set the fluid domain boundary conditions in the discrete phase model;

[0027] S4-3: Establish a jet source representing fine dust based on a discrete phase model.

[0028] In the above scheme, the Navier-Stokes modified equation expression in step S4-1 is as follows:

[0029] Continuity equation: ;

[0030] Momentum conservation equation: ;

[0031] in, Represents porosity. Represents fluid density, Represents fluid velocity. For fluid pressure, For viscous stress, It is the acceleration due to gravity. For Hamiltonian operators;

[0032] The interphase momentum transfer source term The calculation is performed using the following formula:

[0033] ;

[0034] in, For the corresponding fluid mesh volume, This represents the total number of large coal particles present within the grid. For fluid to a single particle The sum of the applied forces.

[0035] In the above scheme: the boundary conditions mentioned in step S4-2 are: setting the fluid domain inside the tunnel as transient simulation and specifying the magnitude and direction of gravity; setting the air inlet as velocity-inlet, the air outlet as pressure-outlet, and other walls and equipment as walls.

[0036] In the above scheme: the jet source type in step S4-3 is selected as Cone, and the position is set above the impact point of the falling material; the particle size distribution of the fine dust is set using the Rosin-Rammler distribution function, and the core particle size range is set to less than 50μm; at the same time, the UnsteadyParticleTracking function is checked to process dust particles using computational encapsulation polymerization technology.

[0037] In the above scheme, step S5 includes:

[0038] S5-1: Establish a two-way data communication interface;

[0039] Set up a coupling script load_edem_coupling, import the set coupling script load_edem_coupling into the computational fluid dynamics software and connect it to the coupling port of the discrete element software; use the API coupling interface to establish bidirectional real-time communication between the computational fluid dynamics software and the discrete element software, enable transient calculation mode, and transfer the interphase momentum transfer source term and porosity generated by large coal materials as source terms to the fluid domain inside the roadway.

[0040] S5-2: Configure the coupling time step;

[0041] Integration time step in computational fluid dynamics software Time step of discrete element software The positive integer multiples of the dynamic matching ratio, and the dynamic matching ratio satisfies the constraints: ;

[0042] S5-3: Perform iterative calculations in a coupled environment;

[0043] Calculate the position and velocity of large coal particles, and calculate the real-time porosity of the current coal flow distribution. With momentum transfer source term and real-time porosity With momentum transfer source term The data is transferred to computational fluid dynamics software, where the Navier-Stokes equations are solved based on porosity and momentum transfer source terms. This process calculates the high-intensity induced wind flow field induced by coal flow and the fluid force exerted by the fluid on the coal particles. The fluid force is then fed back to discrete element software to adjust the trajectory of large coal particles. Simultaneously, the forces acting on fine dust particles in the flow field are calculated to simulate the spatial dispersion of fine dust particles under the combined effects of induced wind and roadway ventilation.

[0044] Export the flow field distribution data of the underground open space, extract the dust concentration cloud map data, and export the final falling trajectory and accumulation state of large coal materials to analyze the dispersion law of fine dust.

[0045] The above plan also includes:

[0046] S6: Design a dust control scheme based on simulation calculation results;

[0047] S6-1: Obtain the maximum induced wind speed at the material drop point from the simulation output of step S5. Perform verification;

[0048] S6-2: The maximum induced wind speed after verification Multiply by a safety factor to convert the control airflow of the dust control system;

[0049] S6-3: Calculate the rated negative pressure threshold of the external dust collector fan. ;

[0050] S6-4: Based on simulation results, extract the farthest three-dimensional boundary coordinates of the horizontal ejection of high-concentration respirable coal dust under the superposition of airflow, and design the shielding range and installation distance of the dustproof shielding device.

[0051] In the above scheme: during the verification in step S6-1, a two-way verification is performed based on Morrison's air balance theory and the following formula:

[0052] ;

[0053] in, This refers to the mass flow rate of large coal pieces. Due to the difference in elevation, For the equivalent diameter, For correction factor, The diameter of large coal particles. For the particle density of large coal materials, Density of the gaseous medium It is the acceleration due to gravity;

[0054] Step S6-3: Calculate the rated negative pressure threshold for air extraction. At that time, the rated negative pressure threshold of the external dust removal fan was derived by reverse derivation using the resistance equation of the tunnel pipeline system. ;

[0055] The specific derivation formula is as follows: ;

[0056] in, This is the system safety compensation coefficient. This is the sum of the frictional and local resistances of the dust cover and piping network. The fluid density is given.

[0057] In summary, the beneficial effects of this invention are:

[0058] 1. The macro- and micro-scale separation strategy for solid materials completely eliminates the computation of micron-sized dust in the discrete element method. Based on this, combined with the subsequently proposed mesh constraint law, the size of the discrete element mesh is strictly limited to 3 to 5 times the radius of the smallest large coal piece. The algorithm eliminates the distortion and oscillation of porosity within fluid micro-elements from the underlying algorithm, completely avoiding memory overflow and equation divergence caused by a mesh number of over 100 million, enabling ordinary industrial computers to run complex coal mine dust coupling simulations smoothly.

[0059] 2. Compared to traditional simplified models that do not consider material volume, this invention will include porosity. With momentum transfer source term The correction term is deeply embedded in the Navier-Stokes control equation, accurately reproducing the physical effects of "volume displacement" and "friction driving" on air when a large volume of coal falls. It truly restores the generation process of high-intensity induced airflow and the secondary dispersal effect of induced wind on the trajectory of fine dust in open space, which closely matches the complex and ever-changing real working conditions in coal mines.

[0060] 3. Based on high-fidelity flow field simulation data, the negative pressure of the dust removal fan can be derived by integrating the theoretical wind pressure equation, and the spatial layout of the external dustproof shielding device can be set in reverse with the dust diffusion boundary as the benchmark, providing a highly reliable and quantifiable engineering design method for the dust prevention system of the open transfer point in the coal mine. Attached Figure Description

[0061] Figure 1 This is the execution flowchart of the present invention.

[0062] Figure 2 This is a three-dimensional visualization diagram of the macroscopic material-driven induced wind field and the dispersion distribution of fine dust in the coupled field in this invention.

[0063] Figure 3 This is a comparison diagram of the flow field velocity vectors of the technical solution of this invention and traditional simulation methods, wherein... Figure 3 (a) is the velocity vector diagram of the bidirectional coupled simulated state flow field of this invention. Figure 3 (b) is the velocity vector diagram of the flow field using the traditional CFD simulation method. Detailed Implementation

[0064] The present invention will be further described below with reference to the embodiments and accompanying drawings:

[0065] like Figure 1 As shown, a simulation calculation method for macro- and micro-coupling pollution at coal material induced airflow transfer points includes the following steps:

[0066] S1: Construct a 3D model of the open transfer point in the well and a mesh for flow field calculation;

[0067] A three-dimensional solid model of an open transfer point without a guide chute, including the upper and lower level belt conveyors and confined roadways in a coal mine, is obtained. The internal connected fluid space is extracted and meshed to establish a computational fluid dynamics (CFD) flow field calculation mesh.

[0068] The specific steps are as follows:

[0069] S1-1: Draw a 3D model of the transfer point using 3D drawing software;

[0070] The three-dimensional model of the transfer point includes the underground conveying equipment of the coal mine and the external air envelope corresponding to the confined roadway. The three-dimensional drawing software in this embodiment is Solidworks. The underground conveying equipment of the coal mine includes the scraper conveyor and belt conveyor that are connected to each other, and the scraper conveyor, belt conveyor and confined roadway form an open transfer point three-dimensional model without a guide chute.

[0071] S1-2: Obtain the 3D model of the transfer point and extract the internal connected fluid space;

[0072] Solid regions are eliminated using Boolean operations, leaving only interconnected spaces where air can flow, to generate the fluid domain inside the tunnel. The inlet of the fluid domain inside the tunnel is set to Velocity-inlet to simulate real ventilation, and the outlet is set to PressureOutlet to prevent backflow and divergence in the calculation. The 3D model of the transfer point is exported in .xt format.

[0073] S1-3: Grid division;

[0074] The 3D model of the transfer point is imported into the mesh processing software to perform tetrahedral mesh generation of the fluid domain inside the tunnel, ensuring that the proportion of mesh orthogonal quality greater than 0.4 accounts for more than 99%, and the flow field calculation mesh file is exported; the mesh processing software in this embodiment is ICEM, and the flow field calculation mesh file is in mesh format;

[0075] S2: Establish macro- and micro-scale separation strategies for solid materials;

[0076] Set particle size classification thresholds based on actual working conditions. The dispersed solid media in the fluid domain inside the tunnel are divided into particles with a diameter greater than [missing information]. Large coal materials with macroscopic phases and particle sizes smaller than The microscopic phase of fine dust;

[0077] S3: Calculate macroscopic coal flow motion and spatial porosity based on the discrete element method (DEM); In the discrete element software, generate macroscopic phases of the large coal material with different particle sizes based on a uniform size distribution model to truly reflect the physical conditions of random mixing of coal blocks underground, and calculate their falling trajectory.

[0078] The specific steps are as follows:

[0079] S3-1: Create a geometric model of a single large coal block;

[0080] Select the ore for 3D scanning, and import the 3D scan file into the discrete element method software. The 3D scan file is an STL file, and the discrete element method software in this embodiment is EDEM.

[0081] Under the Bulk Material command, create Partical particles, then click the Add Multi-Sphere command to display the outline mesh using Templates, generating multi-particles that precisely fill the model shape.

[0082] Set equipment material properties;

[0083] In the Size Distribution command, set the coal proportion; in the Equipment Material command, set the equipment material property to steel; set Poisson's Ratio to 0.3, Solids Density to 7800 kg / m3, Shear Modulus to 7e+10 Pa, and configure the contact interaction between the coal and the equipment.

[0084] S3-2: Generate macroscopic phases of the large coal material with different particle sizes based on the uniform size distribution model to truly reflect the physical conditions of random mixing of coal blocks underground, and calculate their falling trajectory; and generate large coal material blocks according to the separation strategy established in step S2.

[0085] Specifically, a particle factory is set up to generate only large coal particles with a diameter of 30mm-60mm, and the proportion of large coal particles of each size is set in SizeDistribution to reproduce the real material.

[0086] S3-3: Set the simulation mesh parameters based on the minimum particle size of large coal materials;

[0087] The mesh constraint rules are determined as follows: ,in, The minimum particle size of large coal pieces. The size of the discrete element contact retrieval grid is set to 3 to 5 times the minimum radius of the large material.

[0088] The contact retrieval grid size in the Simulator is set according to the grid constraint law so that the total number of cells (Approx. Number of Cells) meets the set range;

[0089] In this embodiment, the contact retrieval grid size (Cell Size) is set to 700, so that the total number of grids (Approx.Number of Cells) is stabilized at around 17650. This geometric constraint eliminates porosity oscillations within the fluid micro-element, completely avoiding memory overflow caused by blindly performing cross-scale calculations. This ensures that when bidirectionally coupling with the computational fluid dynamics software Fluent is performed subsequently, there will be no "improperlist" list overflow error caused by porosity distortion.

[0090] Calculate the real-time porosity of large coal particles produced by fluid. With momentum transfer source term ;

[0091] S4: Calculation of fine dust diffusion based on the discrete phase fluid dynamics model (CFD-DPM);

[0092] In computational fluid dynamics software, the boundary condition of ventilation velocity in underground roadways is incorporated, including real-time porosity. With momentum transfer source term The Navier-Stokes governing equations are used to represent the intense displacement and dragging effect of high-flux coal flow on air.

[0093] Simultaneously, the discrete phase model (DPM) is activated, and the motion trajectory of the microscopic phase of fine dust is generated and calculated using dimensionality reduction tracking technology;

[0094] The specific steps are as follows:

[0095] S4-1: Import the flow field calculation mesh file constructed in step S1 into the computational fluid dynamics software (Fluent), and activate the real-time porosity calculation function in the governing equations. With momentum transfer source term The Navier-Stokes modified equations;

[0096] The Navier-Stokes correction equation is expressed as follows:

[0097] Continuity equation:

[0098] Momentum conservation equation:

[0099] in, Represents porosity. Represents fluid density, Represents fluid velocity. For fluid pressure, For viscous stress, It is the acceleration due to gravity. For Hamiltonian operators;

[0100] The momentum transfer source term The calculation method is as follows: calculate the total volume average of the forces exerted by a large coal particle group on the airflow within a single fluid grid, and its mathematical expression is:

[0101] ;

[0102] in, For the corresponding fluid mesh volume, This represents the total number of large coal particles present within the grid. For fluid to a single particle The sum of the applied forces.

[0103] S4-2: Set the fluid domain boundary conditions in the discrete phase model as follows:

[0104] The fluid domain inside the tunnel is set as a transient simulation and the magnitude and direction of gravity are specified; the air inlet is set as a velocity-inlet, the air outlet is set as a pressure-outlet, and other walls and equipment are set as walls.

[0105] S4-3: Establish a jet source representing fine dust based on the discrete phase model (DPM);

[0106] The injection source type is selected as Cone, and its position is set above the impact point of the falling material. The particle size distribution of the fine dust is set using the Rosin-Rammler distribution function, and the particle size range of the fine dust is set to 6μm~80μm to represent the high-risk respirable dust in coal mines, with the core particle size range set to less than 50μm. At the same time, the UnsteadyParticleTracking function is selected to use computational parcel aggregation technology to process dust particles, thereby reducing the amount of trajectory tracking computation in the fluid domain.

[0107] S5: Perform asynchronous coupled computation of fluid and discrete elements;

[0108] A two-way data communication interface was established between computational fluid dynamics software and discrete element method software; data was exchanged in real time between the two software programs to simulate the interaction between "coal flow movement" and "air flow"; and the flow field distribution and dust concentration cloud map data of the underground open space were output.

[0109] The specific steps are as follows:

[0110] S5-1: Establish a two-way data communication interface;

[0111] Set up the coupling script load_edem_coupling, import the set coupling script load_edem_coupling into the computational fluid dynamics software Fluent, and activate the coupling port of the discrete element method software EDEM; use the API coupling interface file to establish bidirectional real-time communication between the computational fluid dynamics software and the discrete element method software, enable transient calculation mode, and pass the resistance and volume effect of large materials on airflow as source terms to the fluid domain.

[0112] S5-2: Configure the coupling time step;

[0113] Integration time step in the computational fluid dynamics software Fluent The time step of the discrete element method software EDEM The positive integer multiples of the dynamic matching ratio, and the dynamic matching ratio satisfies the constraints: ;

[0114] In this embodiment, the overall simulation time is set to 10 seconds, and the time step of the discrete element method software EDEM is [missing information]. Set to 0.0001, the integration time step in the computational fluid dynamics software Fluent. Set to 0.001, time step to 10000, and maximum iteration to 20; simultaneously enable Unsteady Particle Tracking to ensure real-time updates of dust source items within each time step.

[0115] S5-3: Perform iterative calculations in a coupled environment;

[0116] Calculate the position and velocity of large coal particles, and calculate the porosity of the current coal flow distribution in real time. With momentum transfer source term and real-time porosity With momentum transfer source term Transferred to computational fluid dynamics software;

[0117] Computational fluid dynamics software receives porosity With momentum transfer source term Subsequently, based on porosity and momentum transfer source terms, the Navier-Stokes equations are solved to calculate the high-intensity induced wind flow field induced by coal flow and the fluid forces such as drag and buoyancy on coal particles. The fluid forces are then fed back to the discrete element software to adjust the trajectory of large coal materials. At the same time, the forces on fine dust are calculated in the flow field to simulate the spatial dispersion of fine dust under the superposition of induced wind and roadway ventilation.

[0118] The flow field distribution data of the underground open space was exported from computational fluid dynamics software, dust concentration cloud map data was extracted, and the final falling trajectory and accumulation state of large coal materials were exported from discrete element method software to analyze the emission law of fine dust.

[0119] The analysis of the dispersion law of fine dust includes: comparing the internal pressure field and outlet velocity field of the feed chute under two states: open coupling and closed coupling (independent CFD), and quantifying the impact of the induced wind generated by the falling of large pieces of material on the escape flux of fine dust.

[0120] S6: Design a dust control scheme based on simulation calculation results;

[0121] This method is applicable to physical dust control projects;

[0122] S6-1: Obtain the maximum induced wind speed at the material drop point from the simulation output of step S5. Perform verification;

[0123] Based on Morrison's air balance theory, the maximum induced wind speed at the material drop point is extracted from the simulation output of step S5. Perform two-way verification using the following formula:

[0124] ;

[0125] in, This refers to the mass flow rate of large coal pieces. Due to the difference in elevation, For the equivalent diameter, For correction factor, The diameter of large coal particles. For the particle density of large coal materials, Density of the gaseous medium It is the acceleration due to gravity;

[0126] S6-2: The maximum induced wind speed after verification Multiply by a safety factor to convert the air volume into the control air volume of the dust control system, ensuring that the exhaust capacity covers the most unfavorable operating conditions;

[0127] S6-3: Calculate the rated negative pressure threshold of the external dust collector fan. ;

[0128] By combining the resistance equation of the tunnel pipeline system, the rated negative pressure threshold of the external dust removal fan is derived in reverse. ;

[0129] The specific derivation formula is as follows: ;

[0130] in, This is the system safety compensation coefficient. This is the sum of the frictional and local resistances of the dust cover and piping network. For fluid density;

[0131] S6-4: Based on simulation results, extract the farthest three-dimensional boundary coordinates of the horizontal ejection of high-concentration respirable coal dust under the superposition of airflow, and design the shielding range and installation distance of the dustproof shielding device;

[0132] Among them, the dustproof shielding device is a suspended dustproof baffle or dustproof soft curtain. The farthest three-dimensional boundary coordinates of the horizontal projection of high-concentration respirable coal dust under the superposition of airflow are extracted. Using this as the envelope criterion, the drooping depth and installation distance of the external suspended dustproof baffle or dustproof soft curtain are designed in reverse to achieve precise customization of dustproof hardware.

[0133] Figure 2 This is a three-dimensional visualization diagram of the macroscopic material-driven induced wind field and the dispersion distribution of fine dust in the coupled field in this invention. Figure 3 (a) is the velocity vector diagram of the bidirectional coupled simulated state flow field of this invention. Figure 3 (b) is the velocity vector diagram of the flow field using a traditional CFD simulation method, which uses only data from pure computational fluid dynamics software. Figure 3 (a) The airflow velocity streamlines around the transfer point are dense and the streamlines are in a cool color, indicating that the flow velocity in this area is extremely high. The fluid is ejected at high speed from the blue structure bundle on the left and after hitting the red structure on the right, it produces violent diffusion and mixing. That is, a highly destructive dust ejection phenomenon dominated by induced wind is formed around the material drop point. Figure 3(b) In the case of relatively sparse and smooth streamline distribution, and streamline color exhibiting a wide range of warm tones, then the contrast is... Figure 3 (a) and Figure 3 (b) It can be seen that: the airflow velocity around the transfer point simulated using the bidirectional coupling method of this invention (e.g., Figure 3 (a) shows that it is significantly higher than uncoupled traditional standalone CFD simulations. Figure 3 (b) fully verifies the high fidelity and effectiveness of this separated coupling model in reproducing complex mine displacement flow fields.

Claims

1. A simulation calculation method for coal mine material induced airflow transfer point macro-meso coupling pollution, characterized in that, Includes the following steps: S1: Construct a 3D model of the open transfer point in the well and a mesh for flow field calculation; A three-dimensional solid model of an open transfer point without a guide chute, including the upper and lower level belt conveyors and confined roadways in a coal mine, is obtained. The internal connected fluid space is extracted and meshed to establish a computational fluid dynamics flow field calculation mesh. S2: Establish macro- and micro-scale separation strategies for solid materials; Setting particle size classification threshold The bulk solid medium in the fluid domain inside the roadway is divided into a macroscopic phase of large coal material with a particle size greater than and a microscopic phase of fine dust with a particle size less than ​ S3: Calculation of macroscopic coal flow motion and spatial porosity based on the discrete element method; S3-1: Create a geometric model of a single large coal block; S3-2: Generate macroscopic phases of the large coal material with different particle sizes based on the uniform size distribution model, and calculate their falling trajectory; and during generation, generate large coal material according to the separation strategy established in step S2. S3-3: Set the simulation mesh parameters based on the minimum particle size of large coal materials; The grid constraint rule is set as wherein, is the minimum particle size of the bulk coal material, is the size of the discrete element contact search grid; the contact search grid size in the Simulator is set according to the grid constraint rule, so that the total number of grids meets the set range; Calculate the real-time porosity of large coal particles produced by fluid. With momentum transfer source term ; S4: Calculation of fine dust diffusion based on a discrete phase model of fluid dynamics; in computational fluid dynamics software, combined with the boundary conditions of ventilation velocity in underground roadways, a real-time porosity factor is introduced. With momentum transfer source term The Navier-Stokes governing equations are used, and the discrete phase model is activated. The motion trajectory of the fine dust microphase is generated and calculated using dimensionality reduction tracking technology. S4-1: Import the flow field calculation mesh file constructed in step S1 into the computational fluid dynamics software, and activate the real-time porosity calculation function in the governing equations. With momentum transfer source term The Navier-Stokes modified equations; The Navier-Stokes modified equation is expressed as follows: Continuity equation: ; Momentum conservation equation: ; in, Represents porosity. Represents fluid density, Represents fluid velocity. For fluid pressure, For viscous stress, It is the acceleration due to gravity. For Hamiltonian operators; The momentum transfer source term The calculation is performed using the following formula: ； in, For the corresponding fluid mesh volume, This represents the total number of large coal particles present within the grid. For fluid to a single particle The sum of the applied forces; S4-2: Set the fluid domain boundary conditions in the discrete phase model; S4-3: Establish a jet source representing fine dust based on a discrete phase model; S5: Performs asynchronous coupled computation of fluid and discrete elements.

2. The simulation calculation method for macro- and micro-coupling pollution at coal and mineral material induced airflow transfer points according to claim 1, characterized in that, Step S1 also includes: S1-1: Draw a 3D model of the transfer point using 3D drawing software; the 3D model of the transfer point includes the underground conveying equipment of the coal mine and the external air envelope domain corresponding to the confined roadway; S1-2: Solid regions are eliminated through Boolean operations, leaving only air-flowing and interconnected spaces to generate the fluid domain inside the tunnel. S1-3: Import the 3D model of the transfer point into the mesh processing software to perform tetrahedral mesh generation of the fluid domain inside the tunnel, and export the flow field calculation mesh file.

3. The simulation calculation method for macro- and micro-coupling pollution at coal and mineral material induced airflow transfer points according to claim 1, characterized in that, The boundary conditions described in step S4-2 are as follows: the fluid domain inside the tunnel is set to transient simulation and the magnitude and direction of gravity are specified; the air inlet is set as velocity-inlet, the air outlet is set as pressure-outlet, and other walls and equipment are set as walls.

4. The simulation calculation method for macro- and micro-coupling pollution at coal and mineral material induced airflow transfer points according to claim 1, characterized in that, In step S4-3, the jet source type is selected as Cone, and the position is set above the impact point of the falling material; the particle size distribution of the fine dust is set using the Rosin-Rammler distribution function, and the core particle size range is set to less than 50μm; at the same time, the UnsteadyParticleTracking function is checked to process the dust particles using computational encapsulation polymerization technology.

5. The simulation calculation method for macro- and micro-coupling pollution at coal and mineral material induced airflow transfer points according to claim 1, characterized in that, Step S5 includes: S5-1: Establish a two-way data communication interface; Set up a coupling script load_edem_coupling, import the set coupling script load_edem_coupling into the computational fluid dynamics software and connect it to the coupling port of the discrete element software; use the API coupling interface to establish bidirectional real-time communication between the computational fluid dynamics software and the discrete element software, enable transient calculation mode, and transfer the interphase momentum transfer source term and porosity generated by large coal materials as source terms to the fluid domain inside the roadway. S5-2: Configure the coupling time step; Integration time step in computational fluid dynamics software Time step of discrete element software The positive integer multiples of the dynamic matching ratio, and the dynamic matching ratio satisfies the constraints: ; S5-3: Perform iterative calculations in a coupled environment; Calculate the position and velocity of large coal particles, and calculate the real-time porosity of the current coal flow distribution. With momentum transfer source term and real-time porosity With momentum transfer source term The data is transferred to computational fluid dynamics software, where the Navier-Stokes equations are solved based on porosity and momentum transfer source terms. This process calculates the high-intensity induced wind flow field induced by coal flow and the fluid force exerted by the fluid on the coal particles. The fluid force is then fed back to discrete element software to adjust the trajectory of large coal particles. Simultaneously, the forces acting on fine dust particles in the flow field are calculated to simulate the spatial dispersion of fine dust particles under the combined effects of induced wind and roadway ventilation. Export the flow field distribution data of the underground open space, extract the dust concentration cloud map data, and export the final falling trajectory and accumulation state of large coal materials to analyze the dispersion law of fine dust.

6. The simulation calculation method for macro- and micro-coupling pollution at coal and mineral material induced airflow transfer points according to claim 1, characterized in that, Also includes: S6: Design a dust control scheme based on simulation calculation results; S6-1: Obtain the maximum induced wind speed at the material drop point from the simulation output of step S5. Perform verification; S6-2: The maximum induced wind speed after verification Multiply by a safety factor to convert the control airflow of the dust control system; S6-3: Calculate the rated negative pressure threshold of the external dust collector fan. ; S6-4: Based on simulation results, extract the farthest three-dimensional boundary coordinates of the horizontal ejection of high-concentration respirable coal dust under the superposition of airflow, and design the shielding range and installation distance of the dustproof shielding device.

7. The simulation calculation method for macro- and micro-coupling pollution at coal and mineral material induced airflow transfer points according to claim 6, characterized in that, During step S6-1, a two-way verification is performed based on Morrison's air balance theory, using the following formula: ； in, This refers to the mass flow rate of large coal pieces. Due to the difference in elevation, For the equivalent diameter, For correction factor, The diameter of large coal particles. For the particle density of large coal materials, Density of the gaseous medium It is the acceleration due to gravity; Step S6-3: Calculate the rated negative pressure threshold for air extraction. At that time, the rated negative pressure threshold of the external dust removal fan was derived by reverse derivation using the resistance equation of the tunnel pipeline system. ; The specific derivation formula is as follows: ; in, For system safety compensation coefficient, This is the sum of the frictional and local resistances of the dust cover and piping network. The fluid density is given.

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