Numerical simulation method under fully-mechanized excavation face turbulence air chamber control-dry purification technology

Abstract

The invention discloses a numerical simulation method under a fully-mechanized excavation face turbulence air chamber control-dry purification technology. Carrying out numerical simulation through a k-epsilon mathematical model and a DPM mathematical model, and describing the fluid motion of the fully mechanized excavation face by using an Euler method. Establishing a mathematical model, and simulating the dust diffusion process of the fully-mechanized excavation face. Through numerical simulation of the heading machine, the diffusion condition of dust under the action of airflow disturbance is studied, and a guarantee is provided for providing more reasonable dust falling measures.

Description

Technical Field

[0001] The present invention belongs to the technical field of fluid mechanics in coal mines, and in particular to the technical field of numerical simulation method under turbulent air chamber control-dry purification technology for comprehensive excavation faces. Background Art

[0002] In recent years, with the continuous increase in the intensity of coal mining and the increasing mechanization and automation of mining technology, problems such as natural disasters in mines have become increasingly prominent, especially the coal dust pollution problem at the bottom of the mine. According to on-site measurements, without taking any dust prevention measures, the dust concentration of the fully-mechanized excavation face can generally reach 2000-4000mg / m 3 The instantaneous dust concentration of the operation can be as high as 6000mg / m 3 , seriously exceeding the relevant provisions of the Coal Mine Safety Regulations. Long-term exposure of miners to a high concentration of dust pollution in the working environment can cause fibrotic changes in their lung tissue, which is known as pneumoconiosis.

[0003] The existing numerical simulation research is generally aimed at the distribution and pollution of dust with wind flow in coal mining operations. There is a lack of research on the dust removal effect of special dust prevention equipment deployed in fully mechanized excavation working faces. Summary of the invention

[0004] The present invention aims to solve the technical problems existing in the prior art. The present invention provides a numerical simulation method for the arrangement of dust prevention equipment in a comprehensive excavation face, and in particular relates to a numerical simulation method for turbulent air chamber control-dry purification technology in a comprehensive excavation face. To solve the above problems, the scheme of the present invention includes the following steps:

[0005] Step 1: Use SolidWorks software to build a proportional geometric model. The model is drawn according to the requirements. The geometric model consists of the working space of the working face, hydraulic support, coal mining machine, and scraper conveyor. The length, width, and height of the working space are: 50m×5m×3.5m;

[0006] Step 2: Import the file into Mesh, and use tetrahedral mesh to divide the mesh according to the curvature size of the mesh and the minimum size between adjacent meshes. At the same time, set 4 mesh schemes with different mesh sizes and perform mesh independence test to ensure that the best mesh scheme is used during calculation;

[0007] Step 3: 10 measuring points are selected at equal intervals at the breathing zone height of the workers' working area of ​​the working face to obtain the wind flow velocity, and the wind flow velocity is used as a verification parameter for the grid independence test; four grid schemes are compared, and the grid division scheme when the calculation results no longer change is used as the final grid scheme;

[0008] Step 4: Import the final mesh solution into Fluent. First, adjust the scale to ensure that the size of the physical model is consistent with the actual size and check the mesh quality.

[0009] Step 5: First open the steady-state environment in Fluent and enable the k-ε model;

[0010] Step 6: Set the initial conditions of the wind flow and simulate the wind flow. After the calculation is completed, export the data and case files of the wind flow field;

[0011] Step 6: Import the exported wind flow field data and case files into Fluent again, convert the steady-state environment into a transient environment, and set the gravity acceleration according to the model direction;

[0012] Step 7: Open the discrete phase model and determine the coordinates of an injection point;

[0013] Step 8. Select the dust generation mode and direction, and set parameters such as mass flow rate and pressure;

[0014] Step 9. Set the DPM wall condition and select escape;

[0015] Step 10. Open the Autosave tab and set the automatic save time interval based on the simulation time.

[0016] Step 11: Set the Time Step Size and Number of Time Steps to select an appropriate simulation duration while ensuring simulation accuracy.

[0017] Step 12: Import the automatically saved data file and case file into CFD-Post, and analyze the wind flow trajectory diagram, wind flow cloud diagram, dust space-time evolution diagram, dust concentration distribution XY plane diagram, and dust concentration distribution ZX plane diagram in CFD-Post.

[0018] The present invention provides a numerical simulation method for turbulent air chamber control-dry purification technology of a comprehensive excavation face, and numerical simulation is performed through the k-ε mathematical model and the DPM mathematical model. First, the wind flow is regarded as a continuous phase, and the Euler method is used to describe the fluid motion of the comprehensive excavation working face. After that, the dust particles are regarded as discrete phases, and a mathematical model is established using the Euler-Lagrange method to simulate the dust diffusion process of the comprehensive excavation working face: During the excavation process of the comprehensive excavation working face provided by the present invention, the diffusion of dust under the action of wind flow disturbance is studied by numerically simulating the tunneling machine, so as to provide a guarantee for proposing more reasonable dust reduction measures, and provide theoretical guidance for dust prevention and control and mine environmental protection, which has very important practical significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the flow chart of numerical simulation of air flow and dust in fully mechanized excavation working face;

[0020] Figure 2 It is a geometric model diagram;

[0021] Figure 3 Grid division diagram;

[0022] Figure 4 is the grid independence test diagram;

[0023] Figure 5 Wind flow streamline diagram;

[0024] Figure 6 Dust spatiotemporal evolution diagram;

[0025] Figure 7 Dust concentration distribution XY plane diagram;

[0026] Figure 8 Dust concentration distribution ZY plane diagram. DETAILED DESCRIPTION

[0027] Step 1: Use SolidWorks software to build a proportional geometric model. The model is drawn according to the requirements. The geometric model consists of the working space of the working face, hydraulic support, coal mining machine, and scraper conveyor. The length, width, and height of the working space are: 50m×5m×3.5m;

[0028] Step 2: Import the file into Mesh, and use tetrahedral mesh to divide the mesh according to the curvature size of the mesh and the minimum size between adjacent meshes. At the same time, set 4 mesh schemes with different mesh sizes and perform mesh independence test to ensure that the best mesh scheme is used during calculation;

[0029] Step 3: 10 measuring points are selected at equal intervals at the breathing zone height of the workers' working area of ​​the working face to obtain the wind flow velocity, and the wind flow velocity is used as a verification parameter for the grid independence test; four grid schemes are compared, and the grid division scheme when the calculation results no longer change is used as the final grid scheme;

[0030] Step 4: Import the final mesh solution into Fluent. First, adjust the scale to ensure that the size of the physical model is consistent with the actual size and check the mesh quality.

[0031] Step 5: First open the steady-state environment in Fluent and enable the k-ε model;

[0032] Step 6: Set the initial conditions of the wind flow and simulate the wind flow. After the calculation is completed, export the data and case files of the wind flow field;

[0033] Step 6: Import the exported wind flow field data and case files into Fluent again, convert the steady-state environment into a transient environment, and set the gravity acceleration according to the model direction;

[0034] Step 7: Open the discrete phase model and determine the coordinates of an injection point;

[0035] Step 8. Select the dust generation mode and direction, and set parameters such as mass flow rate and pressure;

[0036] Step 9. Set the DPM wall condition and select escape;

[0037] Step 10. Open the Autosave tab and set the automatic save time interval based on the simulation time.

[0038] Step 11: Set the Time Step Size and Number of Time Steps to select an appropriate simulation duration while ensuring simulation accuracy.

[0039] Step 12: Import the automatically saved data file and case file into CFD-Post, and analyze the wind flow trajectory diagram, wind flow cloud diagram, dust space-time evolution diagram, dust concentration distribution XY plane diagram, and dust concentration distribution ZX plane diagram in CFD-Post.

[0040] Furthermore, the mathematical model for numerical simulation of a turbulent air chamber control-dry purification technology for a fully mechanized excavation face is as follows:

[0041] Since the Re of the fully mechanized excavation face is generally greater than 1×10 6 , the wind flow state is turbulent. The wind flow-dust migration process in the comprehensive excavation face is very complicated, and the specific equation is:

[0042] (1) Continuity equation:

[0043]

[0044] Where: ρ-density (kg·m -3 ); x-coordinate (m); u-velocity vector (m·s -1 );t-time(s);i-tensor index symbol.

[0045] (2) Standard equation

[0046] Turbulent pulsation kinetic energy equation:

[0047]

[0048] The turbulent pulsation kinetic energy dissipation rate equation is:

[0049]

[0050]

[0051] Where: k is the turbulent kinetic energy, m 2 / s 2 ; G k -The coefficient of the change rate of turbulent kinetic energy affected by the change of shear force, [kg·(s -3 ·m -1 )]; G b - turbulent kinetic energy caused by buoyancy effects; C 1ε , C 2ε , σ ε , σ k - constant; μ eff is the viscosity coefficient; a k is the inverse of the effective Prandtl value of turbulent kinetic energy, which is taken as 1.0; ε is the turbulent kinetic energy, m 2 / s 3 ; j is the tensor index symbol.

[0052] The particle phase force balance equation is as follows:

[0053]

[0054] In the formula, m p -Dust mass (mg); u p -Dust migration speed (m·s -1 ) ;∑F-the combined force on the dust (N); F d - Resistance to dust (N); F g - Gravity of dust (N); F f -Buoyancy of dust (N); F X -Other forces acting on the dust, (N);

[0055] In order to fully consider the coupling characteristics of airflow and dust, a mathematical model was established using the Euler-Lagrange equation in the discrete phase model. A large number of particles were tracked and their motion was described in the computational flow field. ANSYS Fluent predicts the motion trajectory by integrating the equilibrium forces on the discrete phase particles, which can be solved by writing it into the differential equation of the force of the integrated particles in Lagrangian coordinates.

[0056] The equilibrium equation of the particle interaction force is:

[0057]

[0058] τ r is the droplet or particle relaxation time, and its formula is:

[0059]

[0060] C d is the drag coefficient; d p is the particle size, C d The expression is:

[0061]

[0062]

Claims

1. A numerical simulation method for turbulent air chamber control-dry purification technology in a fully mechanized excavation face, characterized in that: The numerical simulation method of wind-borne dust under the turbulent air chamber control-dry purification system of the fully mechanized excavation working face under consideration includes the following steps: (a) Based on the shape and size of the required physical model, use SolidWorks to build a proportional physical model and save it as an IGES file. Import the IGES file into the Geometry window in ANSYS and generate a Geometry file. Check whether the entities are consistent with the entities divided in the SolidWorks model. Name the imported model in a standardized way and set the computational domain in Geometry to the fluid domain. Save and close the Geometry window and update the operation under the Geometry tree. (b) Import the file into Mesh and mesh it using tetrahedral meshing based on the mesh curvature size and the minimum size between adjacent meshes. Perform an independence test on the four mesh sizes and then export the file as a Mesh file, naming them A, B, C, and D respectively. (c) Import the mesh files of four different mesh sizes into Fluent and perform calculation settings. Ten equally spaced measurement points at the breathing zone height of the workers on the working face are used to obtain the wind velocity. The wind velocity is used as the verification parameter for the mesh independence test. Starting from Group B, the mesh density is continuously increased. In subsequent calculations, the number of calculated meshes at which the calculation results no longer change is used as the mesh number benchmark, and this number of meshes is used as the final mesh solution. (d) First, open the steady-state environment in Fluent, enable the k-ε model, set the initial conditions for the wind flow, and iterate the wind flow simulation for 500 steps; After the calculation is completed, export the data and case files of the wind flow field; (e) First, open the steady-state environment in Fluent, open the DPM model, and set the boundary condition parameters and dust source parameters for the model. After the parameters are set, perform a 10-second transient simulation on the working surface. (f) Set up automatic saving of data and case data files as required to facilitate subsequent data processing. After initialization, set the simulation time and step size as required. After the simulation is completed, export the data and case files, and export the XML file of dust particles. Import the data file and XML file into CFD-POST to view the simulation of the comprehensive excavation site.

2. The numerical simulation method for turbulent air chamber control-dry purification technology according to claim 1 is characterized in that: In step (a): SolidWorks software is used to establish a proportional geometric model. The model is drawn according to the requirements. The geometric model consists of a working space on the working face, a tunnel boring machine, a dry dust removal fan, and a turbulent air chamber generator. The length, width, and height of the working space are 50m×5m×3.5m respectively.

3. The numerical simulation method for turbulent air chamber control-dry purification technology of fully mechanized excavation face according to claim 1 is characterized in that: In step (b): grid division of different sizes is performed. The quality of the simulation calculation grid directly determines the accuracy of the numerical simulation results. The numbers of the four groups of grids A, B, C, and D are 2,431,157, 2,882,014, 3,205,276, and 3,944,842, respectively. The four groups of grids are reasonable in type, appropriate in density, and of high quality. Most of the quality is between good and excellent, which fully meets the requirements of numerical simulation and can be used for numerical simulation.

4. The numerical simulation method for turbulent air chamber control-dry purification technology of fully mechanized excavation face according to claim 1 is characterized in that: In step (c), a sampling point was selected every 5 meters. To reduce the risk of dust to humans, three measurements were taken at each sampling point to obtain the average value. The values ​​of Groups A and B fluctuated significantly, but starting from Group B, the simulation results remained essentially unchanged as the number of grid cells increased. Considering calculation speed and accuracy, Group B was the optimal choice for the simulation.

5. The numerical simulation method for turbulent air chamber control-dry purification technology of fully mechanized excavation face according to claim 1 is characterized in that: In step (d): (1) Set the fluid domain to a steady-state simulation and specify the magnitude and direction of gravity; (2) Set the compressed air cylinder as the air outlet, set the dry dust removal fan as the air outlet, and set the turbulent air chamber generator as the air outlet; (3) Set the air inlet to inlet-velocity and the air outlet to outletpressure; (4) Set the air inlet speed to 2.4 m / s, the turbulence intensity to 4.3%, and the hydraulic diameter to 3.4 m; (5) Initialize the fluid domain; (6) Iterate 500 steps under steady-state conditions and export the data and case files after the calculation is completed.

6. The numerical simulation method for turbulent air chamber control-dry purification technology according to claim 1 is characterized in that: In step (e): (1) Convert the steady-state simulation to a transient simulation and enable the discrete phase model; (2) Set the spray material to coal-hv; (3) Set the dust generating point and dust generating direction according to the coordinates of the tunnel boring machine, set the mass flow rate to 0.048 kg / s, and the dust generating time to 10 s; (4) Boundary condition setting: The surface of the exhaust tube is set as the capture surface, where the dust moves to be captured, and the wall condition is set to escape; (5) Simulate 10s in transient environment, set Time Step Size to 0.01s, and Number of Time Steps to 1000.

7. The numerical simulation method for turbulent air chamber control-dry purification technology of fully mechanized excavation face according to claim 1 is characterized in that: In step (e): import the automatically saved data file and case file into CFD-Post, and analyze the wind flow trajectory diagram, wind flow cloud diagram, dust spatiotemporal evolution diagram, dust concentration distribution XY plane diagram, and dust concentration distribution ZX plane diagram in CFD-Post.

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