Experimental System and Method for Monitoring Flow Field and Gas Migration in Goaf Area of ​​Coal Mine Working Face

Abstract

This invention proposes an experimental system and method for monitoring the flow field and gas migration in the goaf of a coal mine working face. The experimental system includes a goaf model of the coal mine working face, a flow field control device, a gas extraction control device, a gas flow field monitoring device, and a control system. The flow field control device includes a fan for introducing fresh airflow and coloring units for coloring the fresh airflow and the gas in the goaf, respectively. The goaf buried pipe, coal seam extraction pipe, and high-level borehole extraction pipe of the gas extraction control device are connected to three sets of extraction devices. The gas flow field monitoring device includes gas concentration monitors and flow meters installed on each buried pipe and extraction pipe, as well as gas concentration sensors and wind speed sensors buried inside the goaf, for recording flow field data. This invention is a comprehensive experimental system integrating three-dimensional fracture field of the goaf, real-time monitoring of multiple parameters, and visualization of gas migration, presenting the entire process of gas migration in the goaf in a physical form through visualization and full-area monitoring.

Description

[0001] This invention belongs to the technical field of coal mine goaf, specifically relating to an experimental system and method for monitoring the flow field and gas migration in the goaf of a coal mine working face. Background Technology

[0002] After coal mining, the overlying strata in the goaf collapse, forming caving zones, fracture zones, and tortuous subsidence zones from bottom to top. Gas released from the desorbed residual coal diffuses and migrates under the influence of airflow, causing localized gas accumulation in the goaf. Current methods are insufficient for comprehensive monitoring of gas concentration in the goaf. U-shaped ventilation, as the most common working face layout, directly affects gas accumulation and migration patterns due to the airflow volume in its intake roadway and the complex fracture field formed within the goaf. Current research on the dynamic distribution of gas in the goaf mainly relies on numerical simulations and localized underground measurements.

[0003] CN202310443103.4 discloses a gas monitoring system for coal mine goaf areas, which establishes a three-dimensional model of the goaf area. Although this model can construct a theoretical flow field, it is limited by the simplification of boundary conditions and the accuracy of the turbulence model. It lacks the geometric restoration of the pore structure of the collapsed rock mass in the goaf area, making it difficult to restore the unsteady gas diffusion characteristics in the porous media of the real goaf area, and in particular, it cannot intuitively present the gas migration trajectory. CN202311316576.4 discloses a joint experimental platform for fracture field-flow field-gas concentration field in mining space, which can directly establish the direct connection between fracture field, flow field and gas concentration field in mining space. On this basis, it can study the wind speed and pressure distribution law and gas migration law under different ventilation, leak plugging, gas outburst and nitrogen injection conditions. However, it cannot realize the synchronous visualization and comparison of the movement path of multi-component gases (such as fresh air flow / gas).

[0004] In addition, for on-site monitoring, the space for underground sensors is limited, making it impossible to achieve full coverage of the goaf. Existing technologies can only obtain data on air volume, pressure, and gas concentration at a certain point, which is insufficient to reflect the dynamic distribution characteristics of gas in the entire area, resulting in blind spots in gas monitoring. Summary of the Invention

[0005] To address the technical problems existing in the prior art, the first aspect of the present invention is to provide an experimental system for monitoring the flow field and gas migration in the goaf of a coal mine working face. The second aspect of the present invention is to provide an experimental method based on the aforementioned experimental system for monitoring the flow field and gas migration in the goaf of a coal mine working face.

[0006] In this embodiment of the invention, the experimental system for monitoring the flow field and gas migration in the goaf of a coal mine working face includes a goaf model, a flow field control device, a gas extraction control device, a gas flow field monitoring device, and a control system. The goaf model includes the coal body in front of the working face, the goaf located behind the coal body in front of the working face, and a roadway with an intake airway and a return airway located between the coal body in front of the working face and the goaf. The flow field control device includes a fan for introducing fresh air into the intake airway, an air volume sensor for monitoring the air volume of the fresh air in the intake airway, and coloring units for coloring the fresh air entering the intake airway and the gas in the goaf, respectively. The control system adjusts the air supply of the fan according to the reading of the air volume sensor. The gas extraction control device includes a goaf pipe buried in the goaf, a coal seam extraction pipe connected to the coal seam extraction borehole in front of the working face, and a gas extraction pipe connected to the goaf. The system consists of a high-level directional borehole connected to a high-level borehole extraction pipe. The goaf buried pipe, coal seam extraction pipe, and high-level borehole extraction pipe are respectively connected to the first, second, and third extraction devices. Pressure sensors are installed on the goaf buried pipe, coal seam extraction pipe, and high-level borehole extraction pipe. The control system adjusts the extraction negative pressure of the first, second, and third extraction devices according to the readings of the pressure sensors on the goaf buried pipe, coal seam extraction pipe, and high-level borehole extraction pipe. The gas flow field monitoring device includes a gas concentration monitor and a flow meter installed on the goaf buried pipe, coal seam extraction pipe, and high-level borehole extraction pipe. The gas flow field monitoring device also includes multiple sets of gas concentration sensors and wind speed sensors buried inside the goaf. The signal output terminals of each gas concentration monitor, flow meter, gas concentration sensor, and wind speed sensor are connected to the input terminal of the control system to record flow field data.

[0007] The experimental method of this invention is based on the above-mentioned experimental system for monitoring the flow field and gas migration in the goaf of a coal mine working face. The experimental method includes the following steps: adjusting the air intake of the roadway, the negative pressure of the goaf buried pipe extraction, the negative pressure of the high-level borehole extraction pipe, and the number of high-level borehole extraction pipes; the gas concentration sensor and wind speed sensor buried in the goaf transmit the monitoring data to the control system; after the control system preprocesses the data, it calculates the grid gas concentration matrix / wind speed matrix to obtain the corresponding gas concentration / wind speed distribution cloud map; finally, the gas concentration / wind speed distribution cloud map is displayed through the output layer.

[0008] Compared with the prior art, the advantages of the superior technical solution of the present invention include: 1. This invention is a comprehensive experimental system that integrates three-dimensional fracture field of goaf, real-time monitoring of multiple parameters and visualization of gas migration. It presents the entire process of gas migration in goaf in a physical way. Through visualization and full-area monitoring, it can provide early warning of the risk of gas exceeding the limit and reduce safety accidents.

[0009] 2. This invention achieves real-time visualization of gas migration paths by setting coloring units to color fresh airflow and gas separately. It allows for intuitive comparison of the differences in diffusion, mixing, and migration paths of different gases (such as fresh airflow / gas) within the goaf model of a coal mine working face, providing direct evidence for optimizing roadway ventilation and gas extraction parameters, such as identifying gas accumulation areas.

[0010] 3. This invention embeds multiple sets of gas concentration sensors and wind speed sensors inside the goaf to form a high-density monitoring grid; and reconstructs the gas distribution model of the entire area by using real-time data (pressure, flow rate, concentration) from the three extraction systems of the goaf buried pipe, coal seam extraction pipe, and high-level borehole extraction pipe, combined with the dynamic feedback adjustment of the control system.

[0011] 4. The control system of the present invention dynamically adjusts the negative pressure and extraction volume of the three sets of ventilation devices based on the real-time data of the pressure sensors, flow meters and gas concentration monitors of each extraction pipeline, thereby improving the efficiency of gas control, avoiding gas accumulation caused by insufficient negative pressure, reducing the risk of gas exceeding limits, reducing the cost of gas control, and enhancing the self-adaptive capability of the extraction system.

[0012] 5. This invention obtains the distribution field of gas concentration and wind speed in the goaf by weighted averaging of data measured by gas concentration sensor / wind speed sensor, and generates the corresponding gas concentration / wind speed distribution cloud map.

[0013] 6. This invention takes the minimum gas concentration in the goaf as the objective function, analyzes the interaction of parameters such as roadway air intake, negative pressure of buried pipe drainage in the goaf, negative pressure of high-level borehole drainage pipe, and number of high-level borehole drainage pipes, constructs a response surface model, quickly solves the optimal parameter combination, forms the best gas drainage scheme, and reduces the gas concentration in the goaf. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the experimental system for monitoring the flow field and gas migration in the goaf of a coal mine working face, as described in this embodiment.

[0015] Figure 2 This is a top view schematic diagram of the goaf model of the coal mine working face in the embodiment.

[0016] Figure 3 yes Figure 1 A schematic diagram of the layout of extraction holes on the goaf wall at point A.

[0017] The reference numerals in the accompanying drawings include: coal seam in front of the working face 11, goaf 12, caving zone 121, fracture zone 122, bending and subsidence zone 123, extraction hole 124, roadway 13, intake airway 131, return airway 132, fan 21, air volume sensor 22, coloring unit 23, first smoke generator 231, second smoke generator 232, embedded LED lighting strip 24, temperature and humidity control unit 25, steam generator 251, electric heating grid 252, temperature and humidity sensor 26, goaf buried pipe 31, coal seam extraction pipe 32, high-level borehole extraction pipe 33, first ventilation device 34, second ventilation device 35, third ventilation device 36, gas concentration monitor 41, flow meter 42, gas concentration sensor 43, wind speed sensor 44, upper corner gas concentration monitor 45, control system 50. Detailed Implementation

[0018] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Example

[0019] This embodiment provides an experimental system for monitoring the flow field and gas migration in the goaf of a coal mine working face, such as... Figure 1 and Figure 2 As shown, in a preferred embodiment, the experimental system includes a coal mine working face goaf model, a flow field control device, a gas extraction control device, a gas flow field monitoring device, and a control system 50.

[0020] In this invention, the goaf model of a coal mine working face includes a coal body 11 in front of the working face, a goaf 12 located behind the coal body 11, and a roadway 13 with an intake airway 131 and a return airway 132 located between the coal body 11 and the goaf 12. The coal body 11, the goaf 12, and the roadway 13 are all made of transparent material for visualization. The goaf 12 includes three overburden structures arranged from bottom to top: a caving zone 121, a fracture zone 122, and a bending subsidence zone 123. The roadway 13 encloses the coal body 11 in front of the working face from the left, rear, and right sides. The intake airway 131 and the return airway 132 are located on the left and right sides of the coal body in front and extend to the front side of the coal body 11 in front of the working face, respectively.

[0021] In this invention, the flow field control device includes a fan 21 (an axial flow micro fan 21) for introducing fresh air into the intake airway 131, an air volume sensor 22 for monitoring the air volume of the fresh air in the intake airway 131, and a coloring unit 23 for coloring the fresh air entering the intake airway 131 and the gas in the goaf 12, respectively. The signal output terminal of the air volume sensor 22 is connected to the air volume input terminal of the roadway 13 of the control system 50, and the air volume control terminal of the control system 50 is connected to the speed control terminal of the fan 21. The control system 50 adjusts the speed of the fan 21 according to the reading of the air volume sensor 22 to adjust the air supply volume, thereby adjusting the air volume of the roadway 13.

[0022] The coloring unit 23 includes a first smoke generator 231 and a second smoke generator 232. The first smoke generator 231 injects smoke of a first color, such as blue smoke, into the intake airway 131, with blue representing fresh airflow. The second smoke generator 232 injects smoke of a second color, such as red smoke, into the goaf 12, with red representing methane. For example, a first smoke generator 231 is installed behind the fan 21 to release blue smoke; two second smoke generators 232 are installed on the left side of the goaf 12, injecting red smoke into the goaf 12 through the wall openings. Preferably, embedded LED lighting strips are arranged in the goaf 12 to further improve the visualization of the flow field.

[0023] Preferably, the flow field control device further includes a temperature and humidity regulating unit 25 for regulating the temperature and humidity of the fresh airflow in the intake airway 131, and a temperature and humidity sensor 26 for monitoring the temperature and humidity of the fresh airflow in the intake airway 131. The control system 50 adjusts the temperature and humidity provided by the temperature and humidity regulating unit 25 according to the reading of the temperature and humidity sensor 26. Specifically, the temperature and humidity regulating unit 25 includes a steam generator 251 and an electric heating grid 252. The steam generator 251 is connected to the outlet of the blower 21 to regulate the humidity of the fresh airflow entering the intake airway 131. The electric heating grid 252 is located at the inlet of the intake airway 131 to regulate the temperature of the fresh airflow in the intake airway 131. The temperature and humidity sensor 26 and the airflow sensor 22 are sequentially located downstream of the electric heating grid 252. The control system 50 adjusts the steam volume of the steam generator 251 and the heat source temperature of the electric heating grid 252 according to the reading of the temperature and humidity sensor 26 to regulate the humidity and temperature of the intake air in the airway 13 (simulating the humid and hot environment of the working face).

[0024] In this invention, the gas extraction control device includes a goaf pipe 31 buried in the goaf 12, a coal seam extraction pipe 32 connected to a coal seam extraction borehole of the coal body 11 in front of the working face, and a high-level borehole extraction pipe 33 connected to a high-level directional borehole of the goaf 12. The goaf pipe 31, the coal seam extraction pipe 32, and the high-level borehole extraction pipe 33 are respectively connected to a first ventilation device 34, a second ventilation device 35, and a third ventilation device 36. Pressure sensors are provided on the goaf pipe 31, the coal seam extraction pipe 32, and the high-level borehole extraction pipe 33. The control system 50 adjusts the extraction negative pressure of the first ventilation device 34, the second ventilation device 35, and the third ventilation device 36 according to the readings of the pressure sensors on the goaf pipe 31, the coal seam extraction pipe 32, and the high-level borehole extraction pipe 33.

[0025] The outlets of the goaf buried pipe 31, the coal seam extraction pipe 32, and the high-level borehole extraction pipe 33 are located near the return airway 132. For example, the goaf buried pipe 31 is inserted into the caving zone 121 from the right side and buried within it; the coal seam extraction pipe 32 is inserted into the coal body 11 in front of the working face from the right side; and the high-level directional extraction area is located in the fracture zone 122 and extends from front to back. Several extraction holes 124 are provided at different positions on the goaf wall 12, with the number of extraction holes 124 exceeding the number of high-level borehole extraction pipes 33. The high-level borehole extraction pipes 33 extend into the fracture zone 122 through the extraction holes 124 on the goaf wall 12. Figure 3 As shown, twelve extraction holes 124 are arranged in a matrix. Multiple (e.g., three) high-level drilling extraction pipes 33 can be connected to extraction holes 124 at different positions to study the impact of different extraction positions on the gas control effect of goaf 12.

[0026] In this invention, the gas flow field monitoring device includes a gas concentration monitor 41 and a flow meter 42 installed on the goaf buried pipe 31, the coal seam extraction pipe 32, and the high-level borehole extraction pipe 33. The gas flow field monitoring device also includes multiple sets of wireless gas concentration sensors 43 and wind speed sensors 44 buried inside the goaf 12 (specifically, multiple sets of gas concentration sensors 43 and wind speed sensors 44 are arranged in a matrix in the three zones of the collapse zone 121, the fracture zone 122, and the bending and subsidence zone 123). The signal output terminals of each gas concentration monitor 41, flow meter 42, gas concentration sensor 43, and wind speed sensor 44 are respectively connected to the input terminal of the control system 50 for recording flow field data.

[0027] The gas flow field monitoring device also includes a gas concentration monitor 45 located at the upper corner of the working face outside the goaf model 12. The signal output terminal of the upper corner gas concentration monitor 45 is connected to the control system 50. In actual field operations, a gas concentration monitor 41 is also installed at the upper corner of the working face to monitor the gas concentration at that location, as relevant safety regulations stipulate that the gas concentration at the upper corner must not exceed 1%. This application sets up a gas concentration monitor 41 at the upper corner to better convert the monitoring data into actual field data. Example

[0028] This embodiment provides an experimental method for monitoring the flow field and gas migration in the goaf of a coal mine working face based on the experimental system of Embodiment 1. The experimental system of Embodiment 1 can carry out three physical similarity experiments, including: airflow migration and gas concentration distribution experiments in the goaf of the working face, gas extraction experiments in the goaf, and coal seam gas extraction experiments.

[0029] The experiment on airflow migration and gas concentration distribution in the goaf of the working face is as follows: The embedded LED lighting strip is turned on, and the blower 21 is started to inject fresh air into the intake airway 131. The speed of the blower 21 is adjusted according to the reading of the airflow sensor 22 to regulate the airflow in the intake airway 131. After the airflow in the intake airway 131 stabilizes, the steam generator 251 and the electric heating grid 252 are started to control the temperature and humidity of the fresh airflow. The steam volume and heat source temperature are adjusted according to the temperature and humidity sensor 26 to regulate the intake air humidity and temperature. The first smoke generator 231 continuously supplies blue smoke into the intake airway 131; the first exhaust device 34 and the third exhaust device 36 are activated, and the extraction negative pressure is adjusted according to the pressure sensors built into the goaf buried pipe 31 and the high-level borehole extraction pipe 33 to control the gas concentration in the goaf; two second smoke generators 232 are activated, continuously injecting red smoke into the goaf 12, and gas concentration data and wind speed data at different spatial locations are obtained through the gas concentration sensor 43 and wind speed sensor 44 inside the goaf 12. All the aforementioned measurement data are transmitted to the control system 50 via a wireless network.

[0030] Gas extraction experiment in goaf 12: Twelve extraction holes 124 are provided at the front end of the fracture zone 122 near the return airway 132. Multiple high-level drilled extraction pipes 33 can extend into the goaf 12 through the extraction holes 124. The remaining extraction holes 124 without high-level drilled extraction pipes 33 are blocked with sealing plugs. With the third ventilation device 36, the extraction negative pressure is adjusted. The effects of different extraction depths, extraction positions and extraction negative pressures on the gas concentration distribution in goaf 12 can be studied.

[0031] During experiments on airflow and gas concentration distribution in the goaf and gas extraction in goaf 12, the following parameters are adjusted: roadway air intake (adjusted by fan 21), negative pressure of goaf buried pipe extraction (adjusted by first extraction device 34), negative pressure of high-level borehole extraction pipe (adjusted by third extraction device 36), and position of high-level borehole extraction pipe. The control system 50 includes a multi-layer sensor with an input layer, a hidden layer, and an output layer. Gas concentration sensor 43 and wind speed sensor 44, buried in goaf 12, transmit monitoring data to the input layer of the control system 50. The input layer transmits the data to the hidden layer. After preprocessing the data, the hidden layer uses a spatial interpolation algorithm to calculate the grid gas concentration matrix / wind speed matrix using inverse distance weighting, obtaining the corresponding gas concentration / wind speed distribution cloud map. Finally, the output layer displays the gas concentration / wind speed distribution cloud map.

[0032] The specific method for calculating the grid gas concentration matrix / wind speed matrix using the spatial interpolation algorithm for inverse distance weighting is as follows: , In the formula: Points to be estimated x The predicted value is 0, where n is the total number of gas concentration sensors / wind speed sensors. z ( x i ) is the first i Data measured by a gas concentration sensor / wind speed sensor This is the weighted value of the data measured by the i-th gas concentration sensor / wind speed sensor. d ( x 0, x i ) is the point to be estimated and the first i The distance between the gas concentration sensor / wind speed sensor p It is the power exponent (usually taken as 1 to 3). It can be calculated using the formula above. d It is the distance (to any point to be estimated) x (the distance between 0 and a certain sensor i), for example p If the value is 2, the result can be calculated. .

[0033] Based on the aforementioned gas concentration distribution cloud map, the control system 50 uses the lowest gas concentration in the goaf 12 as the standard and calls the response surface methodology to analyze the interactive effects of roadway air intake, goaf buried pipe extraction negative pressure, high-level borehole extraction pipe negative pressure, and high-level borehole extraction pipe position on the goaf gas concentration. Order: The air intake volume of the tunnel shall be recorded as... x 1. The negative pressure of buried pipe extraction in the goaf is recorded as: x 2. The negative pressure of the high-level borehole extraction pipe is recorded as... x3. The location of the high-level borehole extraction pipe is recorded as follows: x 4 (i.e., the distance between the high-level borehole extraction pipe and the upper corner of the working face is) x 4. Preferably, the vertical distance between the high-level borehole extraction pipe position and the upper corner of the working face is... x 4); The objective function for establishing the response surface model is expressed as a quadratic polynomial: , In the formula: Y This represents the system's response value, i.e., the gas concentration in the goaf. Indicates the first i One influencing factor ( x 1 represents the air intake volume of the tunnel. x 2 represents the negative pressure for drainage via buried pipes in the goaf. x 3 represents the negative pressure in the high-level borehole extraction pipe. x 4 indicates the location of the high-level borehole extraction pipe. β 0 is a constant term; β i The coefficient of the linear term; β ii The coefficient of the quadratic term; β ij These are the coefficients of the interaction term; ε The error term is represented by ; k is 4. The response surface model can be estimated from the experimental data through regression fitting. Specifically, based on the experimental data, the response surface method can establish the design matrix X corresponding to the objective function, where X is composed of all influencing factors. Construct it, and then use the least squares method. Solve β 0、 β i , β ii , β ij Error term ε The difference between the experimentally measured value and the value predicted by the objective function.

[0034] The desired optimal effect is to achieve the lowest possible methane concentration in the goaf. Based on the objective function for goaf methane concentration, the optimal combination of roadway air intake, goaf buried pipe extraction negative pressure, high-level borehole extraction pipe negative pressure, and high-level borehole extraction pipe position is obtained (through genetic algorithms, gradient descent methods, etc.) to achieve the lowest methane concentration in the goaf. This results in the optimal methane extraction optimization scheme.

[0035] Coal seam gas extraction experiment: A coal seam extraction pipe 32 is arranged along the coal seam direction via boreholes. The extraction pipe 32 is equipped with a gas concentration monitor 41 and a flow meter 42, and is connected to a second ventilation device 35. During the experiment, the air intake of roadway 13, the negative pressure of the goaf buried pipe 31, the negative pressure of the high-level borehole extraction pipe 33, and the position of the high-level borehole extraction pipe 33 are adjusted to the aforementioned optimal gas extraction scheme. By activating the second ventilation device 35, the purpose of extracting coal seam gas and adjusting the extraction negative pressure can be achieved. The second ventilation device 35, the gas concentration monitor 41, and the flow meter 42 on the coal seam extraction pipe 32 are all connected to the control system 50, which can transmit monitoring data and negative pressure values ​​to the control system 50.

[0036] It should be noted that this application can achieve real-time visualization of gas migration paths by using a high-resolution imaging device (such as a high-definition camera) set outside the goaf model of the coal mine working face.

[0037] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. An experimental system for monitoring the flow field and gas migration in the goaf of a coal mine working face, characterized in that, This includes a coal mine working face goaf model, flow field control device, gas extraction control device, gas flow field monitoring device, and control system; The coal mine working face goaf model includes the coal body in front of the working face, the goaf located behind the coal body in front of the working face, and the roadway with intake and return airways located between the coal body in front of the working face and the goaf. The flow field control device includes a fan for introducing fresh air into the intake airway, an air volume sensor for monitoring the air volume of fresh air in the intake airway, and a coloring unit for coloring the fresh air entering the intake airway and the gas in the goaf, respectively. The control system adjusts the air supply of the fan according to the reading of the air volume sensor. The gas extraction control device includes a goaf buried pipe embedded in the goaf, a coal seam extraction pipe connected to a coal seam extraction borehole in the coal body ahead of the working face, and a high-level borehole extraction pipe connected to the high-level directional extraction area of ​​the goaf. The goaf buried pipe, the coal seam extraction pipe, and the high-level borehole extraction pipe are respectively connected to a first ventilation device, a second ventilation device, and a third ventilation device. Pressure sensors are installed on the goaf buried pipe, the coal seam extraction pipe, and the high-level borehole extraction pipe. The control system adjusts the extraction negative pressure of the first ventilation device, the second ventilation device, and the third ventilation device according to the readings of the pressure sensors on the goaf buried pipe, the coal seam extraction pipe, and the high-level borehole extraction pipe. The gas flow field monitoring device includes a gas concentration monitor and a flow meter installed on the buried pipe in the goaf, the coal seam extraction pipe and the high-level borehole extraction pipe. The gas flow field monitoring device also includes multiple sets of gas concentration sensors and wind speed sensors buried inside the goaf. The signal output terminals of each gas concentration monitor, flow meter, gas concentration sensor and wind speed sensor are respectively connected to the input terminal of the control system to record flow field data.

2. The experimental system for monitoring the flow field and gas migration in the goaf of a coal mine working face according to claim 1, characterized in that, The flow field control device also includes a temperature and humidity regulating unit for adjusting the temperature and humidity of the fresh airflow in the intake airway, and a temperature and humidity sensor for monitoring the temperature and humidity of the fresh airflow in the intake airway. The control system adjusts the temperature and humidity provided by the temperature and humidity regulating unit according to the readings of the temperature and humidity sensor.

3. The experimental system for monitoring the flow field and gas migration in the goaf of a coal mine working face according to claim 2, characterized in that, The temperature and humidity control unit includes a steam generator and an electric heating grid. The steam generator is connected to a fan to regulate the humidity of the fresh air entering the air intake lane. The electric heating grid is installed in the air intake lane to regulate the temperature of the fresh air entering the air intake lane. The control system adjusts the steam output of the steam generator and the heat source temperature of the electric heating grid according to the readings of the temperature and humidity sensors.

4. The experimental system for monitoring the flow field and gas migration in the goaf of a coal mine working face according to claim 1, characterized in that, The coloring unit includes a first smoke generator and a second smoke generator. The first smoke generator is used to inject smoke of a first color into the intake airway to represent fresh airflow, and the second smoke generator is used to inject smoke of a second color into the goaf to represent gas. The second color is different from the first color.

5. The experimental system for monitoring the flow field and gas migration in the goaf of a coal mine working face according to claim 1, characterized in that, The gas flow field monitoring device also includes a gas concentration monitor located at the upper corner of the working face, and the signal output terminal of the upper corner gas concentration monitor is connected to the control system.

6. The experimental system for monitoring the flow field and gas migration in the goaf of a coal mine working face according to claim 1, characterized in that, The goaf includes three overlying rock structures arranged from bottom to top: a caving zone, a fracture zone, and a flexural subsidence zone; and / or embedded LED lighting strips are arranged within the goaf.

7. The experimental system for monitoring the flow field and gas migration in the goaf of a coal mine working face according to claim 6, characterized in that, The outlets of the goaf buried pipe, coal seam extraction pipe and high-level borehole extraction pipe are close to the return airway; and / or the goaf buried pipe is buried in the caving zone, and the high-level directional extraction area is located in the fracture zone. And / or a number of extraction holes are provided at different positions on the goaf wall, the number of extraction holes being greater than the number of high-level borehole extraction pipes, the high-level borehole extraction pipes extending into the fracture zone through the extraction holes on the goaf wall.

8. The experimental method for monitoring the flow field and gas migration in the goaf of a coal mine working face based on any one of claims 1-7, characterized in that, Includes the following steps: Adjust the air intake of the roadway, the negative pressure of the buried pipe extraction in the goaf, the negative pressure of the high-level borehole extraction pipe, and the position of the high-level borehole extraction pipe. Gas concentration sensors and wind speed sensors buried in the goaf transmit monitoring data to the control system. After data preprocessing, the control system calculates the grid gas concentration matrix / wind speed matrix to obtain the corresponding gas concentration / wind speed distribution cloud map. Finally, the gas concentration / wind speed distribution cloud map is displayed through the output layer.

9. The experimental method according to claim 8, characterized in that, The specific method for calculating the grid gas concentration matrix / wind speed matrix is ​​as follows: ， In the formula: Points to be estimated x The predicted value is 0, where n is the total number of gas concentration sensors / wind speed sensors. z ( x i ) is the first i Data measured by a gas concentration sensor / wind speed sensor This is the weighted value of the data measured by the i-th gas concentration sensor / wind speed sensor. d ( x 0, x i ) is the point to be estimated and the first i The distance between the gas concentration sensor / wind speed sensor p It is a power exponent.

10. The experimental method according to claim 9, characterized in that, Based on the gas concentration distribution cloud map, the control system uses the lowest gas concentration in the goaf as the standard and calls the response surface methodology to analyze the interactive effects of roadway air intake, goaf buried pipe extraction negative pressure, high-level borehole extraction pipe negative pressure, and high-level borehole extraction pipe position on the goaf gas concentration. Order: The air intake volume of the tunnel shall be recorded as... x 1. The negative pressure of buried pipe extraction in the goaf is recorded as: x 2. The negative pressure of the high-level borehole extraction pipe is recorded as... x 3. The location of the high-level borehole extraction pipe is recorded as follows: x 4; The objective function for establishing the response surface model is: ， In the formula: Y This represents the system's response value, i.e., the gas concentration in the goaf. Indicates the first i One influencing factor; β 0 is a constant term; β i The coefficient of the linear term; β ii The coefficient of the quadratic term; β ij The coefficients of the interaction term; ε This is the error term; k is 4; Based on the aforementioned objective function, the optimal combination of roadway air intake, goaf buried pipe extraction negative pressure, high-level borehole extraction pipe negative pressure, and high-level borehole extraction pipe position is obtained to achieve the lowest gas concentration in the goaf, thus forming the optimal gas extraction scheme.

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