A physical simulation experimental device for underground coal fire radiation smoldering

Abstract

The present application discloses a physical similarity simulation experimental device for underground coal fire radiation smoldering, which belongs to the field of coal fire smoldering. The device's heat radiation mechanism is set on the top of the experimental box; the gas supply mechanism is connected to the experimental box, used to mix different gas mixtures and deliver them to the experimental box, and can adjust the positive and negative pressure of the experimental box; the gas concentration monitoring mechanism is connected to the experimental box, used to monitor the volume concentration of various gases in the experimental box in real time; the coal sample is placed in the sample placement box, which is placed on the top of the weight monitoring mechanism; the upper part of the weight monitoring mechanism and the sample placement box are placed in the inner cavity of the experimental box and are located below the heat radiation mechanism; the temperature monitoring mechanism includes a thermometer and a temperature data acquisition instrument; the heat radiation, gas supply, gas concentration monitoring, weight monitoring mechanism and temperature data acquisition instrument are all electrically connected to the data processing and control mechanism. The present application can solve the problem that there is currently little research on the parameters of the conditions for the ignition of coal fire smoldering in the air and the laws of the smoldering spread.

Description

Technical Field

[0001] The present application relates to the technical field of coal fire smoldering research, and in particular to a physical similarity simulation experimental device for underground coal fire radiation smoldering. Background Art

[0002] Coal, the core pillar of the energy system, is subject to spontaneous combustion during mining, leading to resource waste, ecological damage, and public health threats. Jurassic-Permian coal seams, particularly those found in some regions, are characterized by low metamorphic levels (dominated by long-flame and non-caking coals) and shallow depths (50-80 meters). These seams are prone to spontaneous combustion, creating fragmented goafs beneath the seams. These areas allow the remaining loose coal to come into contact with oxygen, leading to fermentation and smoldering. Even when there is no coal nearby, heat radiation from burning coal piles can ignite adjacent coal masses, causing contactless smoldering and spreading, leading to widespread underground coalfield fires.

[0003] In a closed environment and under oxygen-deficient conditions, the coal-oxygen reaction continuously releases heat to form a temperature gradient, driving gases (CO2 / CO / CH4) to migrate to the surface through cracks, producing a "chimney effect". The combustion center is initially under negative pressure, and turns to positive pressure during the peak smoldering period, exacerbating gas diffusion. Smoldering disasters are highly concealed, easy to rekindle, and difficult to control. They need to be prevented and controlled, so the process needs to be studied.

[0004] However, there is little research on the parameters of coal fire smoldering ignition conditions and the smoldering spread rules. The key parameter system for smoldering ignition is missing, which makes it impossible to effectively prevent and control smoldering. Summary of the Invention

[0005] The embodiment of the present application provides a physical similarity simulation experimental device for underground coal fire radiation smoldering, which can solve the problem that there is currently little research on the parameters for the ignition conditions and smoldering spread laws of coal fire smoldering in the air, and the key parameter system for smoldering in the air is missing, resulting in the inability to effectively prevent and control coal fire smoldering.

[0006] In order to achieve the above-mentioned purpose, the technical solution of the embodiment of the present invention is:

[0007] The embodiment of the present invention provides an underground coal fire radiation smoldering physical similarity simulation experimental device, which includes an experimental box, a heat radiation mechanism, a gas supply mechanism, a gas concentration monitoring mechanism, a sample placement box, a weight monitoring mechanism, a temperature monitoring mechanism, and a data processing and control mechanism;

[0008] The heat radiation mechanism is arranged on the top of the experimental box;

[0009] The gas supply mechanism is in communication with the experimental box, and is used to mix and deliver different gas mixtures to the experimental box, and is capable of adjusting the positive and negative pressures of the experimental box;

[0010] The gas concentration monitoring mechanism is connected to the experimental box and is used to monitor the volume concentration of various gases in the experimental box in real time;

[0011] The coal sample is placed in the sample placement box, which is placed on top of the weight monitoring mechanism;

[0012] The upper portion of the weight monitoring mechanism and the sample placement box are placed in the inner cavity of the experimental box and below the heat radiation mechanism;

[0013] The temperature monitoring mechanism includes a thermometer and a temperature data acquisition instrument;

[0014] The thermometers include a plurality of thermometers, all electrically connected to the temperature data acquisition instrument, and divided into N groups, with M thermometers in each group;

[0015] A first group of thermometers is arranged at a preset height H from the upper surface of the sample placement box, and the second to N groups of thermometers are arranged in sequence from the reference surface to the bottom surface at an axial spacing distance h, with the upper surface of the sample placement box as the reference surface;

[0016] The thermometers in each layer are arranged in a circular array of equal arcs around the central axis of the sample placement box, and the tops of the M thermometers are sequentially moved from the center of the sample placement box toward the outer wall by A times the preset distance k, where A is a natural number, k= , where L is the distance from the center of the sample box to the outer wall where the thermometer is set. The length of the last thermometer extending into the sample box;

[0017] The heat radiation mechanism, the gas supply mechanism, the gas concentration monitoring mechanism, the weight monitoring mechanism and the temperature data acquisition instrument are all electrically connected to the data processing and control mechanism.

[0018] In a possible implementation, the thermometers are divided into five groups, each group consisting of four thermometers, and the top ends of the four thermometers are sequentially moved clockwise from the center of the sample placement box toward the outer wall by A times the preset distance k;

[0019] Assume that the center position of the plane where the fifth group of thermometers of the sample placement box is located is the coordinate origin, the position of the thermometer at the top of each group located at the center of the placement box is the OX axis, the direction perpendicular to the OX axis is the OY axis, and the vertically upward direction is the OZ axis, and establish an OXYZ axis coordinate system;

[0020] The temperature data matrix T of the multiple thermometers inserted into the coal samples in the sample placement box is:

[0021] ;

[0022] The time matrix t when the multiple thermometers reach their highest temperature is:

[0023] ;

[0024] The time matrix t of the radial propagation kcm of the coal fire smoldering in each group of the pyrometers rd-1 for:

[0025] ;

[0026] Velocity matrix v of radial propagation kcm of coal fire smoldering rd-1 for:

[0027] ;

[0028] Average speed of radial propagation of coal fire smoldering kcm for:

[0029] ;

[0030] The time matrix t of the radial propagation of 2 kcm of coal fire smoldering in each group of the pyrometers rd-2 for:

[0031] ;

[0032] Velocity matrix v for radial propagation of coal fire smoldering at 2 kcm rd-2 for:

[0033] ;

[0034] The average speed of the smoldering coal fire spreading radially at 2 kcm for:

[0035] ;

[0036] The time matrix t of the radial propagation of coal fire smoldering 3 kcm in each group of the pyrometers rd-3 for:

[0037] ;

[0038] Velocity matrix v of coal fire smoldering radial propagation 3 kcm rd-3 for:

[0039] ;

[0040] The average speed of the smoldering coal fire spreading radially at 3 kcm for:

[0041] ;

[0042] Average speed of radial propagation of smoldering coal fire for:

[0043] ;

[0044] The time matrix t of the axial propagation of coal fire smoldering and the axial spacing distance h ad-1 for:

[0045] ;

[0046] The velocity matrix v of the axial propagation of coal fire smoldering at the axial spacing h ad-1 for:

[0047] ;

[0048] The average velocity of axial propagation of coal fire smoldering at an axial distance h for:

[0049] ;

[0050] The time matrix t of the axial propagation of coal fire smoldering twice the axial spacing distance of 2h ad-2 for:

[0051] ;

[0052] The velocity matrix v of the axial propagation of coal fire smoldering twice the axial spacing distance 2h ad-2 for:

[0053] ;

[0054] The average speed of coal fire smoldering axial propagation twice the axial distance for 2 hours for:

[0055] ;

[0056] The time matrix t of the axial propagation of coal fire smoldering three times the axial separation distance of 3h ad-3 for:

[0057] ;

[0058] The velocity matrix v of the axial propagation of coal fire smoldering three times the axial separation distance 3h ad-3 for:

[0059] ;

[0060] The average speed of coal fire smoldering axial propagation three times the axial separation distance for 3 hours for:

[0061] ;

[0062] Average axial propagation velocity of smoldering coal fire for:

[0063] .

[0064] In a possible implementation, the gas supply mechanism includes a gas cylinder, a gas proportioning instrument, an air inlet pipe, an air delivery pump, an electronic flow meter, an air suction pump, and a gas pressure sensor;

[0065] The gas cylinders include a plurality of gas cylinders, each containing different gases;

[0066] Each of the gas cylinders is connected to the gas inlet of the gas proportioning instrument through a gas delivery pipe;

[0067] The gas outlet of the gas proportioning instrument is connected to one end of the gas inlet pipe;

[0068] The other end of the air inlet pipe is connected to the experimental box;

[0069] The air supply pump and the electronic flow meter are sequentially arranged on the air intake pipe;

[0070] The suction pump is arranged on the top of the experimental box and is connected to the experimental box and the gas concentration monitoring mechanism;

[0071] The gas pressure sensor is arranged in the experimental box;

[0072] The gas proportioning instrument, the air supply pump, the air suction pump and the gas pressure sensor are all electrically connected to the data processing and control mechanism.

[0073] In one possible implementation, the weight monitoring mechanism includes a lifting structure, a weight sensor, a fireproof and heat-insulating layer, and a bracket;

[0074] The weight sensor is arranged on the lifting structure;

[0075] The temperature data collector is arranged on the weight sensor;

[0076] The fireproof and heat-insulating layer is provided on the temperature data acquisition instrument;

[0077] The bottom end of the bracket is inserted into the weight sensor, and the top end is placed on the sample placement box;

[0078] The weight sensor, the lifting structure and the temperature data collector are all electrically connected to a data processing and control mechanism.

[0079] In a possible implementation, the underground coal fire radiation smoldering physical similarity simulation experimental device further includes a settlement height monitoring mechanism;

[0080] The settlement height monitoring mechanism is provided on the side wall of the sample placement box, and is used to monitor the real-time settlement height of the coal sample when the coal sample is burning;

[0081] The settlement height monitoring mechanism is electrically connected to the data processing and control mechanism.

[0082] In a possible implementation, the relationship between the smoldering settling height of the coal sample, the thermal radiation power, and the porosity of the coal sample is:

[0083] ;

[0084] Where h is the smoldering settlement height of the coal sample, ξ is the correction coefficient, W is the thermal radiation power, is the porosity of the coal sample, is the correction factor.

[0085] In a possible implementation, the underground coal fire radiation smoldering physical similarity simulation experimental device further includes an acoustic emission monitoring mechanism;

[0086] The acoustic emission monitoring mechanism includes a microphone and an acoustic wave data collector;

[0087] The number and location of the microphones are consistent with the location of the thermometer;

[0088] The plurality of microphones are electrically connected to the acoustic wave data acquisition instrument;

[0089] The acoustic wave data collector is electrically connected to the data processing and control mechanism.

[0090] In a possible implementation, when the coal sample is smoldering, the relationship between acoustic emission and coal sample temperature is:

[0091] ;

[0092] Where AE(T) is the acoustic emission signal, A and B are empirical coefficients, k1 and k2 are the exponential coefficients of the coal sample, T is the temperature of the coal sample, T0 is the initial temperature of the coal sample, α is the enhancement factor of the temperature change rate on the acoustic emission signal AE(T), T c is the critical temperature of the coal sample. In a possible implementation, the gas concentration monitoring mechanism monitors the oxygen volume concentration in the experimental box in real time;

[0093] The heat release rate during the smoldering process of the coal sample is:

[0094] ;

[0095] Where HRR is the heat release rate of the coal sample, △ is the oxygen consumption rate, A is the cross-sectional area of ​​the sample placement box, is the oxygen volume concentration at the first time point, is the oxygen volume concentration at the second time point, and t1 is the difference between the second time point and the first time point;

[0096] The total heat released during the smoldering process of the coal sample is:

[0097] ;

[0098] Where THR is the total heat release of the coal sample, t end is the smoldering extinguishing time of the coal sample.

[0099] In a possible implementation, the gas concentration monitoring mechanism monitors the CO2 volume concentration and CO volume concentration in the experimental box in real time;

[0100] The smoldering efficiency of the coal sample is:

[0101] ;

[0102] Where η is the smoldering efficiency of the coal sample, is the CO2 production rate, is the CO2 volume concentration at the third time point, is the CO2 volume concentration at the fourth time point, t2 is the difference between the fourth time point and the third time point, is the carbon monoxide production rate, is the CO volume concentration at the fifth time point, is the CO volume concentration at the sixth time point, and t3 is the difference between the sixth time point and the fifth time point.

[0103] One or more technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages:

[0104] The embodiment of the present application provides an experimental device for simulating the physical similarity of underground coal fire radiation smoldering. The thermal radiation mechanism is arranged on the top of the experimental box. The thermal radiation mechanism is regulated to obtain different radiation powers and different thermal energies. The thermal radiation mechanism is at a certain distance from the sample placement box. It can simulate the scene of non-contact smoldering spread of underground coal combustion heat radiation igniting adjacent coal bodies through the air, and can test the ignition temperature of coal samples under different thermal radiation conditions. Coal samples of different particle sizes are placed in the sample placement box. The conditions for cold wall extinguishing of coal samples of different particle sizes under self-sustaining smoldering and non-self-sustaining smoldering can also be studied, and the smoldering ignition time and ignition temperature of the coal samples can be analyzed. The gas supply mechanism mixes different gas mixtures and delivers them to the experimental box. It can also adjust the positive and negative pressures of the experimental box to simulate the underground environment where the coal samples are located. It can also simulate the chimney effect of the negative pressure in the coal sample combustion center turning into positive pressure. The device of the embodiment of the present application can simulate a real underground coal seam environment. The heat radiation mechanism, gas supply mechanism, gas concentration monitoring mechanism, weight monitoring mechanism, and temperature data acquisition instrument are all electrically connected to the data processing and control mechanism. Temperature, gas volume concentration, and mass data can be analyzed in real time to build a parameter database, filling the gap in the missing key parameter system for remote ignition. It can be directly used to establish a prevention and control model, reducing resource waste and ecological damage. The thermometers are arranged at preset heights and in a circular array, capable of monitoring temperature gradient changes in real time, systematically studying the radial and axial propagation characteristics and spread patterns of smoldering, quantifying the core parameters of remote ignition, revealing the full cycle pattern of smoldering from initiation to extinction, reducing the risk of re-ignition, and establishing a feasible prevention and control foundation. BRIEF DESCRIPTION OF THE DRAWINGS

[0105] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments of the present invention. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0106] Figure 1 A schematic diagram of the structure of a physical similarity simulation experimental device for underground coal fire radiation smoldering provided in an embodiment of the present application;

[0107] Figure 2 Partial schematic diagram of the heat radiation mechanism provided in the embodiment of the present application Figure 1 ;

[0108] Figure 3 Partial schematic diagram of the heat radiation mechanism provided in the embodiment of the present application Figure 2 ;

[0109] Figure 4 A schematic diagram of the structure of the gas supply mechanism provided in an embodiment of the present application;

[0110] Figure 5 A schematic diagram of the structure of a gas concentration monitoring mechanism provided in an embodiment of the present application;

[0111] Figure 6 A schematic diagram of the structure of the weight monitoring mechanism provided in an embodiment of the present application;

[0112] Figure 7 Schematic diagram of the structure of the temperature monitoring mechanism provided in the embodiment of the present application Figure 1 ;

[0113] Figure 8 Schematic diagram of the structure of the temperature monitoring mechanism provided in the embodiment of the present application Figure 2 ;

[0114] Figure 9 A schematic diagram of the structure of a settlement height monitoring mechanism provided in an embodiment of the present application;

[0115] Figure 10 A schematic diagram of the structure of the infrared camera monitoring mechanism provided in an embodiment of the present application;

[0116] Figure 11 A schematic diagram of the structure of the experimental box provided in the embodiment of the present application;

[0117] Figure 12 The cold wall quenching effect of coal samples after radiation smoldering at different particle sizes and different thermal radiation intensities provided in the embodiments of the present application;

[0118] Figure 13 The coal sample with a particle size of 0.1-0.5 mm provided in the embodiment of this application is 5kW / m 2 The temperature measured by the thermocouple below changes with time.

[0119] Figure 14 The coal sample with a particle size of 0.1-0.5 mm provided in the embodiment of this application is 5kW / m 2 The infrared picture at a certain moment is measured by the infrared camera.

[0120] Icons: 1-experimental box; 2-heat radiation mechanism; 21-radiation cone; 22-radiation shielding plate; 23-rotating structure; 24-heat flow meter; 25-temperature measuring thermocouple; 3-gas supply mechanism; 31-gas cylinder; 32-gas supply pipe; 33-gas proportioner; 34-inlet pipe; 35-gas supply pump; 36-electronic flow meter; 37-suction pump; 38-pressure reducing valve; 4-gas concentration monitoring mechanism; 41-gas supply pipe; 42-filter element; 43-water bath cooling box; 44-drying box; 45-gas concentration sensor group; 5-sample placement box; 51-card slot; 6-weight monitoring mechanism; 61-lifting structure; 62-weight sensor; 63-fireproof and heat-insulating layer; 64-bracket; 641-first vertical pole ;642-horizontal board;65-placing box;7-temperature monitoring mechanism;71-thermometer;72-temperature data acquisition instrument;8-data processing and control mechanism;9-sedimentation height monitoring mechanism;91-horizontal bar;92-second vertical bar;93-displacement sensor;A-acoustic emission monitoring mechanism;A1-microphone;A2-acoustic wave data acquisition instrument;B-infrared camera monitoring mechanism;B1-infrared camera;B2-secondary circulating water cooling layer;B3-insulation layer;B4-primary circulating water cooling layer;B5-insulation layer;C-temperature and humidity sensor;D-gas pressure sensor;T1-first group of thermocouples;T2-second group of thermocouples;T3-third group of thermocouples;T4-fourth group of thermocouples;T5-fifth group of thermocouples. DETAILED DESCRIPTION

[0121] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0122] In the description of the embodiments of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. The terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance. In addition, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be a communication between the internal parts of two components. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present invention can be understood according to the specific circumstances.

[0123] Please refer to Figure 1 As shown, an embodiment of the present invention provides an underground coal fire radiation smoldering physical similarity simulation experimental device, including an experimental box 1, a heat radiation mechanism 2, a gas supply mechanism 3, a gas concentration monitoring mechanism 4, a sample placement box 5, a weight monitoring mechanism 6, a temperature monitoring mechanism 7 and a data processing and control mechanism 8.

[0124] like Figure 1 and Figure 11 As shown, the experimental chamber 1 comprises a chamber body, a door, and a door handle. The door is pivotally connected to the front of the chamber. The chamber is made of heat-resistant transparent tempered glass. Only the front side can be opened. Heat-resistant sealing strips are installed around the interior of the front to ensure a complete seal when the door is closed. The door handle is located on the chamber door for easy opening. The chamber body is provided with an air outlet on the top and an air inlet on the side.

[0125] The heat radiation mechanism 2 is disposed on the top of the experimental chamber 1. The gas supply mechanism 3 is connected to the experimental chamber 1 (specifically, the gas supply mechanism 3 is connected to the experimental chamber 1 through the air inlet), and is used to deliver different gas mixtures to the experimental chamber 1 and to adjust the positive and negative pressures of the experimental chamber 1.

[0126] In reality, some oxygen in underground coal seams is already consumed, resulting in abnormal oxygen concentrations. Smoldering or ignition from a distance is considered oxygen-depleted combustion. Furthermore, combustion produces carbon monoxide, carbon dioxide, and alkanes such as methane, ethane, ethylene, and acetylene, and coal combustion propagates through this gas mixture. Gas supply mechanism 3 can be configured with various gas mixtures, including oxygen-depleted environments, and those containing carbon monoxide, carbon dioxide, and alkanes such as methane, ethane, ethylene, and acetylene, thereby more accurately simulating the environment of underground coal seams.

[0127] The gas concentration monitoring mechanism 4 is connected to the experimental chamber 1 (specifically, through the gas outlet), and is used to monitor the volume concentration of various gases within the experimental chamber 1 in real time. A sample box 5 is placed inside the coal sample, which is placed on top of the weight monitoring mechanism 6. The upper portion of the weight monitoring mechanism 6 and the sample box 5 are placed within the interior of the experimental chamber 1 and below the heat radiation mechanism 2. The inner walls and bottom of the sample box 5 are covered with a 1cm thermal insulation layer, and the interior is wrapped with two layers of tin foil for further insulation. The coal sample is placed inside.

[0128] Temperature monitoring mechanism 7 includes a thermometer 71 and a temperature data acquisition device 72. The thermometers 71 are arranged in N groups, each with M thermometers, and are electrically connected to the temperature data acquisition device 72. Specifically, the thermometers 71 are electrically connected to the temperature data acquisition device 72 via a temperature data transmission line. The temperature data transmission line is high-temperature resistant.

[0129] like Figure 1 and Figure 7 As shown, the first group of thermometers 71 is set at a preset height H from the upper surface of the sample placement box 5 (because in the experiment, the coal sample is filled in the sample placement box 5 until the upper surface of the coal sample is flush with the upper surface of the sample placement box 5, so the first group of thermometers 71 is set at the preset height H from the upper surface of the coal sample). With the upper surface of the sample placement box 5 (i.e. the upper surface of the coal sample) as the reference surface, the second to Nth groups of thermometers 71 are sequentially set from the reference surface to the bottom surface with an axial spacing of h. Figure 8 As shown, each layer of thermometers 71 is arranged in a circular array of equal arcs around the central axis of the sample placement box 5, and the top ends of the M thermometers 71 are sequentially moved from the center of the sample placement box 5 toward the outer wall by A times the preset distance k, where A is a natural number (i.e., A is a multiple of 0, 1, 2, 3, etc.), and k= , where L is the distance from the center of the sample placement box 5 to the outer wall where the thermometer 71 is set, The length of the last thermometer 71 extending into the sample placement box 5. The cross section of the sample placement box 5 can be rectangular or circular. The embodiment of the present application provides a schematic diagram of a structure in which the cross section of the sample placement box 5 is rectangular.

[0130] Example, combined Figure 1 、 Figure 7 and Figure 8As shown, the sample storage box 5 provided in the embodiment of the present application is a rectangular parallelepiped with a square cross-section. The thermometer 71 is a twenty-element thermocouple, each electrically connected to a temperature data acquisition device 72. The thermocouples are arranged in five groups of four. In practice, mounting brackets for the thermometers 71 are provided on the upper, lower, and left sides of the sample storage box 5. The thermometers 71 are K-type thermocouples with a diameter of 1 mm. Mounting holes with a diameter of 1.1 mm are provided on the upper, lower, and left sides of the sample storage box 5. These mounting holes allow the thermocouples to pass through and secure them in place.

[0131] The first group of thermocouples T1 is set at a distance of 0.5 cm from the upper surface of the sample placement box 5 (i.e., the upper surface of the coal sample). Taking the upper surface of the sample placement box 5 (i.e., the upper surface of the coal sample) as the reference plane, the second to fifth groups of thermocouples are sequentially set from the reference plane to the bottom surface with an axial spacing of 1 cm, that is, the second group of thermocouples T2 is set at the upper surface of the sample placement box 5 (i.e., the upper surface of the coal sample), the third group of thermocouples T3 is set 1 cm axially below the second group of thermocouples (i.e., below the upper surface of the coal sample), the fourth group of thermocouples T4 is set 2 cm axially below the second group of thermocouples (i.e., below the upper surface of the coal sample), and the fifth group of thermocouples T5 is set 3 cm axially below the second group of thermocouples (i.e., below the upper surface of the coal sample).

[0132] The installation method of the thermometer 71 provided in the embodiment of the present application can obtain the ignition temperature and ignition time of the coal sample from smoldering to burning by setting the first set of thermometers 71 at a preset height H from the upper surface of the sample placement box 5 and the second set of thermometers 71 on the upper surface of the sample placement box 5. Figure 13 In the embodiment of the present application, the upper surface of the coal sample is 2.5 cm away from the bottom surface of the heat radiation mechanism 2, and the first set of thermocouples T1 is 2 cm away from the bottom surface of the heat radiation mechanism 2. The first set of thermocouples T1 is exposed to the air. Figure 13 The black line in the middle is the curve of the temperature change of the first group of thermocouple T1 over time. Figure 13 The red line in the middle is the curve of the temperature change of the second group of thermocouples T2 over time. The second group of thermocouples T2 is the temperature at the upper surface of the coal sample. During the heating process of the heat radiation mechanism 2, the temperature of the first group of thermocouples T1 and the second group of thermocouples T2 will rise. If the coal sample is not burning, the coal sample will not affect the first group of thermocouples T1 and the second group of thermocouples T2. The temperature of the first group of thermocouples T1 and the second group of thermocouples T2 will rise to a certain level and then stop rising. The curve of the temperature change over time of the first group of thermocouples T1 and the second group of thermocouples T2 does not change suddenly. The curve of the temperature change over time will continue in a straight line in a direction nearly parallel to the horizontal axis at this temperature. If the coal sample burns, the first group of thermocouples T1 will rise rapidly at the smoldering ignition temperature of the coal sample ( Figure 13 The second set of thermocouples T2 will also rise rapidly at the smoldering ignition temperature of the coal sample (point E in the middle). Figure 13The coal sample ignition temperature can be obtained by combining points E and F. The horizontal axis corresponding to the ignition temperature is the ignition time.

[0133] The axial placement distance of the thermocouples provided in the embodiment of the present application can ensure a reasonable experimental time. The twenty thermocouples provided can ensure a reasonable axial placement distance and accurately measure the required data while not occupying too much space in the sample placement box 5, thereby ensuring measurement accuracy.

[0134] If the first set of thermocouples T1 is farther from the coal sample and closer to the heat radiation mechanism 2, the heat transferred to the first set of thermocouples T1 by the combustion of the coal sample is less, and the heat transferred to the first set of thermocouples T1 by the heat radiation mechanism 2 is more. Then, when the coal burns, it is difficult to determine whether it is the combustion of the coal sample or the heat provided by the heat radiation mechanism 2, and thus it is difficult to determine the ignition temperature of the coal sample through the first set of thermocouples T1. If the first set of thermocouples T1 is closer to the coal sample and farther from the heat radiation mechanism 2, the temperature curves of the first set of thermocouples T1 and the second set of thermocouples T2 over time are less distinguishable, which is not conducive to combining the first set of thermocouples T1 and the second set of thermocouples T2 to obtain the ignition temperature and ignition time.

[0135] The first group of thermocouples T1 is set at 0.5 cm from the upper surface of the sample placement box 5 (the bottom surface of the heat radiation mechanism 2 is 2.5 cm away from the upper surface of the sample placement box 5). The curve of the temperature change of the first group of thermocouples T1 over time can clearly show that the ignition temperature of the coal sample combustion suddenly increases, which is quite different from the temperature provided by the heat radiation mechanism 2. Therefore, the ignition temperature and ignition time of the coal sample combustion can be accurately judged by combining the first group of thermocouples T1 and the second group of thermocouples T2.

[0136] In addition, combined Figure 13 It can be seen that the second group of thermocouples T2 ( Figure 13 The curve of the temperature change of the second group of thermocouples T2 over time is red), the third group of thermocouples T3 ( Figure 13 The curve of the temperature change of the third group of thermocouples T3 over time is blue), the fourth group of thermocouples T4 ( Figure 13 The temperature curve of the fourth group of thermocouples T4 over time is green) and the fifth group of thermocouples T5 ( Figure 13 The curve of the temperature change of the fifth group of thermocouples T5 over time is purple). Through the second to fourth groups of thermocouples, the relationship between the coal sample combustion collapse rate and the combustion temperature and combustion time can be studied. Specifically, Figure 13As shown, the temperature measured by the second set of thermocouples T2 gradually rises and then falls, and the curve fluctuates. This is because the second set of thermocouples is set on the upper surface of the coal sample. After the coal sample burns, the ash sinks and collapses. Therefore, the distance between the second set of thermocouples and the burning coal sample increases, and the temperature measured by the second set of thermocouples gradually decreases. As the ash sinks and collapses, the curve fluctuates. Similarly, the curve of the coal sample temperature and time measured by the third set of thermocouples first rises, then falls, and then fluctuates. However, the fourth and fifth sets of thermocouples do not fluctuate because they are set at a lower position. The temperature and time curves measured by the fourth and fifth sets of thermocouples can be used to determine the time when the coal sample completes combustion.

[0137] The length of the thermocouple probe in the embodiment of the present application is 2 cm, which can prevent the high temperature of the heat radiation mechanism 2 from damaging the thermocouple adapter. Specifically, the length of the thermocouple probe in the embodiment of the present application is 2 cm. Figure 8 As shown, the sample placement box 5 is a rectangular parallelepiped with a square cross-section, and the side length of the square is 8 cm. The thermocouple at the top is located at the center of the sample placement box 5, and its length extending into the sample placement box 5 is 4 cm. The remaining 16 cm of the thermocouple including the adapter is located outside the sample placement box 5. The remaining thermocouples on the same layer are located outside the sample placement box 5 for a longer length, that is, all thermocouple adapters are less affected by the thermal energy of the heat radiation mechanism 2. Therefore, the thermocouple probe of the embodiment of the present application is longer, which can prevent the heat radiation mechanism 2 from damaging the thermocouple due to high temperature.

[0138] Furthermore, each layer of thermocouples is arranged in a circular array of equal arcs around the central axis of the sample placement box 5 (eg Figure 8 As shown, the arc between adjacent thermocouples is π / 2), and the top ends of the four thermocouples move sequentially from the center of the sample placement box 5 toward the outer wall by a preset distance k= = 0 times, 1 times, 2 times and 3 times of 1cm. Figure 8 As shown, the top of the first thermocouple on the right moves toward the outer wall. , that is, the top of the first thermocouple is located at the center of the sample placement box 5, and the top of the second thermocouple on the lower side moves toward the outer wall , the top of the third thermocouple on the left moves toward the outer wall , the top of the fourth thermocouple on the upper side moves toward the outer wall .

[0139] The heat radiation mechanism 2 , the gas supply mechanism 3 , the gas concentration monitoring mechanism 4 , the weight monitoring mechanism 6 and the temperature data acquisition device 72 are all electrically connected to the data processing and control mechanism 8 .

[0140] The data processing and control mechanism 8 includes a computer module. This module contains built-in data monitoring and calculation software. The data monitoring software monitors the gas composition, gas volume concentration, radiation power, radiation distance, weight change of the coal sample during combustion, and the temperature measured by various thermometers 71 within the experimental chamber 1 in real time, and transmits the monitored data to the data calculation software. The data calculation software then performs calculations on the acquired data. The data processing and control mechanism 8 integrates all parameters for optimized analysis and control, avoiding data silos.

[0141] The embodiment of the present application provides an experimental device for simulating the physical similarity of underground coal fire radiation smoldering. The heat radiation mechanism 2 is arranged on the top of the experimental box 1. The heat radiation mechanism 2 is controlled to obtain different radiation powers and different thermal energies. The heat radiation mechanism 2 is at a certain distance from the sample placement box 5. It can simulate the scene of non-contact smoldering spread of underground coal combustion heat radiation igniting adjacent coal bodies through the air, and can test the ignition temperature of coal samples under different heat radiation conditions. Coal samples of different particle sizes are placed in the sample placement box 5. The conditions of cold wall extinguishing of coal samples of different particle sizes under self-sustaining smoldering and non-self-sustaining smoldering can also be studied, and the smoldering ignition time and ignition temperature of coal samples can be analyzed. The gas supply mechanism 3 mixes different gas mixtures and delivers them to the experimental box 1. It can also adjust the positive and negative pressures of the experimental box 1 to simulate the underground environment of the coal sample in the experimental box 1. It can also simulate the chimney effect of the negative pressure in the coal sample combustion center turning into positive pressure. The device of the embodiment of the present application can simulate a real underground coal seam environment. The heat radiation mechanism 2, gas supply mechanism 3, gas concentration monitoring mechanism 4, weight monitoring mechanism 6, and temperature data acquisition device 72 are all electrically connected to the data processing and control mechanism 8. Temperature, gas volume concentration, and mass data can be analyzed in real time to construct a parameter database, filling the gap in the missing key parameter system for remote ignition. It can be directly used to establish a prevention and control model, reducing resource waste and ecological damage. Thermometers 71 are arranged at a preset height and in a circular array, capable of real-time monitoring of temperature gradient changes, systematically studying the radial and axial propagation characteristics and spread patterns of smoldering, quantifying the core parameters of remote ignition, revealing the full cycle of smoldering from initiation to extinction, reducing the risk of re-ignition, and establishing a practical prevention and control foundation.

[0142] Furthermore, if Figure 1 、 Figure 7 and Figure 8 As shown, the thermometers 71 are divided into five groups, each group consisting of four, i.e., there are 20 thermometers 71. The top ends of the four thermometers 71 are sequentially moved clockwise from the center of the sample placement box 5 toward the outer wall by A times the preset distance k, with the first thermometer 71 located on the right. The thermometers 71 may be K-type thermocouples.

[0143] Continue to refer to Figure 1 、 Figure 7 and Figure 8As shown, the center position of the plane where the fifth group of thermometers 71 of the sample placement box 5 are located is set as the coordinate origin, the position of the thermometer 71 at the top of each group located at the center of the placement box is taken as the OX axis, the direction perpendicular to the OX axis is taken as the OY axis, and the vertical upward direction is taken as the OZ axis, and an OXYZ axis coordinate system is established.

[0144] The temperature data matrix T of the multiple thermometers 71 inserted into the coal sample in the sample placement box 5 (the temperature data matrix does not use the data of the first group of thermometers 71 because they are exposed to the air) is:

[0145] .

[0146] The time matrix t when the multiple thermometers 71 reach their maximum temperature is:

[0147] .

[0148] Specifically, Figure 13 In the figure, the curve of the temperature change of the second group of thermocouple T2 over time is red, and the temperature and time corresponding to the highest peak of the red line; the curve of the temperature change of the third group of thermocouple T3 over time is blue, and the temperature and time corresponding to the highest peak of the blue line; the curve of the temperature change of the fourth group of thermocouple T4 over time is green, and the temperature and time corresponding to the highest peak of the green line; the curve of the temperature change of the fifth group of thermocouple T5 over time is purple, and the temperature and time corresponding to the highest peak of the purple line. The above temperature data matrix and time matrix can be obtained.

[0149] The time matrix t of the radial propagation kcm of coal fire smoldering in each layer where the pyrometers 71 are located rd-1 for:

[0150] .

[0151] Velocity matrix v of radial propagation kcm of coal fire smoldering rd-1 for:

[0152] .

[0153] Average speed of radial propagation of coal fire smoldering kcm for:

[0154] .

[0155] The time matrix t of the radial propagation of coal fire smoldering 2 kcm in each layer where the temperature measuring device 71 is located rd-2 for:

[0156] .

[0157] Velocity matrix v for radial propagation of coal fire smoldering at 2 kcmrd-2 for:

[0158] .

[0159] The average speed of the smoldering coal fire spreading radially at 2 kcm for:

[0160] .

[0161] The time matrix t of the radial propagation of coal fire smoldering 3 kcm in each layer where the temperature measuring device 71 is located rd-3 for:

[0162] .

[0163] Velocity matrix v of coal fire smoldering radial propagation 3 kcm rd-3 for:

[0164] .

[0165] The average speed of the smoldering coal fire spreading radially at 3 kcm for:

[0166] .

[0167] Average speed of radial propagation of smoldering coal fire for:

[0168] .

[0169] The time matrix t of the axial propagation of coal fire smoldering and the axial spacing distance h ad-1 for:

[0170] .

[0171] The velocity matrix v of the axial propagation of coal fire smoldering at the axial spacing h ad-1 for:

[0172] .

[0173] The average velocity of axial propagation of coal fire smoldering at an axial distance h for:

[0174] .

[0175] The time matrix t of the axial propagation of coal fire smoldering twice the axial spacing distance of 2h ad-2 for:

[0176] .

[0177] The velocity matrix v of the axial propagation of coal fire smoldering twice the axial spacing distance 2h ad-2 for:

[0178] .

[0179] The average speed of coal fire smoldering axial propagation twice the axial distance for 2 hours for:

[0180] .

[0181] The time matrix t of the axial propagation of coal fire smoldering three times the axial separation distance of 3h ad-3 for:

[0182] .

[0183] The velocity matrix v of the axial propagation of coal fire smoldering three times the axial separation distance 3h ad-3 for:

[0184] .

[0185] The average speed of coal fire smoldering axial propagation three times the axial separation distance for 3 hours for:

[0186] .

[0187] Average axial propagation velocity of smoldering coal fire for:

[0188] .

[0189] By calculating the average radial and axial velocities of the coal fire smoldering, the radial and axial propagation velocities of the coal fire smoldering can be accurately obtained.

[0190] Specifically, when the sample placement box 5 of the embodiment of the present application is a rectangular parallelepiped with a square cross section and a side length of 8 cm, the upper surface of the sample placement box 5 (i.e., the upper surface of the coal sample) is used as the reference plane, the second to fifth groups of thermocouples are sequentially arranged from the reference plane to the bottom surface with an axial spacing of 1 cm, and the top of the first thermocouple on the right side is moved toward the outer wall. , that is, the top of the first thermocouple is located at the center of the sample placement box 5, and the top of the second thermocouple on the lower side moves toward the outer wall , the top of the third thermocouple on the left moves toward the outer wall , the top of the fourth thermocouple on the upper side moves toward the outer wall When the coordinate system is set as OX, the center position of the plane where the fifth group of thermometers 71 of the sample placement box 5 is located is set as the coordinate origin, the position of the thermometer 71 at the top of each group located in the center of the placement box is set as the OX axis, the direction perpendicular to the OX axis is set as the OY axis, and the vertical upward direction is set as the OZ axis to establish an OXYZ axis coordinate system.

[0191] The temperature data matrix T of the multiple thermometers 71 inserted into the coal sample in the sample placement box 5 is:

[0192] .

[0193] The time matrix t when the multiple thermometers 71 reach their maximum temperature is:

[0194] .

[0195] The time matrix t of the radial spread of coal fire smoldering 1 cm in each layer where the temperature measuring device 71 is located rd-1 for:

[0196] .

[0197] Velocity matrix v of the radial propagation of coal fire smoldering 1 cm rd-1 for:

[0198] .

[0199] The average speed of the smoldering coal fire spreading 1 cm in the radial direction for:

[0200] .

[0201] The time matrix t of the radial spread of coal fire smoldering 2 cm in each layer where the temperature measuring device 71 is located rd-2 for:

[0202] .

[0203] Velocity matrix v of the radial propagation of coal fire smoldering 2 cm rd-2 for:

[0204] .

[0205] The average speed of the smoldering coal fire spreading 2 cm in the radial direction for:

[0206] .

[0207] The time matrix t of the radial spread of coal fire smoldering 3 cm in each layer where the temperature measuring device 71 is located rd-3 for:

[0208] .

[0209] Velocity matrix v of the radial propagation of coal fire smoldering 3 cm rd-3 for:

[0210] .

[0211] The average speed of the smoldering coal fire spreading 3 cm in the radial direction for:

[0212] .

[0213] Average speed of radial propagation of smoldering coal fire for:

[0214] .

[0215] The time matrix t of the axial propagation of coal fire smoldering with an axial spacing of 1 cm ad-1 for:

[0216] .

[0217] The velocity matrix v of the axial propagation of coal fire smoldering with an axial spacing of 1 cm ad-1 for:

[0218] .

[0219] Average velocity of axial propagation of coal fire smoldering at an axial distance of 1 cm for:

[0220] .

[0221] The time matrix t for the axial propagation of coal fire smoldering at twice the axial spacing of 2 cm ad-2 for:

[0222] .

[0223] The velocity matrix v of the axial propagation of coal fire smoldering at twice the axial spacing of 2 cm ad-2 for:

[0224] .

[0225] The average speed of coal fire smoldering axial propagation at twice the axial distance of 2 cm for:

[0226] .

[0227] The time matrix t for the axial propagation of coal fire smoldering three times the axial spacing distance of 3 cm ad-3 for:

[0228] .

[0229] The velocity matrix v of the axial propagation of coal fire smoldering three times the axial spacing distance of 3 cm ad-3 for:

[0230] .

[0231] The average speed of coal fire smoldering axial propagation three times the axial spacing of 3cm for:

[0232] .

[0233] Average axial propagation velocity of smoldering coal fire for:

[0234] .

[0235] The calculation method provided in the embodiments of this application quantifies the smoldering spread pattern through a velocity matrix and average velocity formula, accurately analyzing the propagation characteristics of smoldering at different radial distances and axial depths, and predicting the fire zone expansion path. The velocity data matrix can be integrated into the data processing and control mechanism 8 to generate a smoldering propagation model, providing a parameter basis for the design of underground fire zone isolation zones and reducing the risk of re-ignition. Providing data from both axial and radial dimensions fills the gap in the missing key parameter system for airborne smoldering, improving the repeatability of the experiment and the feasibility of prevention and control. The calculation of the average velocity provides a more accurate estimate of the smoldering propagation velocity.

[0236] like Figure 2 and Figure 3 As shown, the heat radiation mechanism 2 includes a radiation cone 21 , a radiation shielding plate 22 , a rotating structure 23 and a heat flux meter 24 .

[0237] The top of the radiation cone 21 is set at the top of the experimental box 1. The radiation shielding plate 22 is set at the bottom of the radiation cone 21. The rotating structure 23 is connected to the radiation shielding plate 22 and can drive the radiation shielding plate 22 to rotate. The measuring end of the heat flux meter 24 is set at the lower part of the experimental box 1 and is connected to the water source. Before the formal experiment, the heat flux meter 24 needs to be calibrated by opening the box. The radiation cone 21 is set in a frustum shape, with an electric heating tube inside. By adjusting the power of the heating tube, the thermal radiation intensity can be accurately controlled, and a thermal radiation intensity of up to 60kW / m² can be uniformly generated. Three temperature measuring thermocouples 25 are attached to the top of the radiation cone 21. The temperature measuring thermocouples 25 are electrically connected to the data processing and control mechanism 8. The data processing and control mechanism 8 controls the thermal radiation intensity of the radiation cone 21 to achieve closed-loop control of the thermal radiation intensity.

[0238] The heat radiation mechanism 2 provided in the embodiment of the present application has a radiation cone 21 fixed to the top of the experimental box 1, which generates heat radiation with adjustable intensity, accurately simulates the heat radiation intensity of air-fired ignition, and adjusts the heat radiation intensity to test the ignition threshold of different heat radiation intensities. The radiation shielding plate 22 is located at the bottom of the radiation cone 21 and its position is adjusted by a rotating structure 23. The rotating structure 23 can be a motor, and the output shaft of the motor is connected to the bottom of the radiation shielding plate 22. The rotation of the motor drives the radiation shielding plate 22 to rotate. The area of ​​the radiation shielding plate 22 is greater than or equal to the bottom area of ​​the radiation cone 21 and is made of non-water-cooled stainless steel. During the pre-experiment preparation stage and the post-experiment completion stage, when heat radiation is not required, the radiation shielding layer is rotated to the bottom of the radiation cone 21 to block heat radiation. During the experiment, when heat radiation is required, the radiation shielding layer is rotated away from the bottom of the radiation cone 21 to allow the heat radiation to propagate downward.

[0239] The heat flux meter 24 is set at the lower part of the experimental box 1 and connected to the water circulation to prevent the heat flux meter 24 from short-circuiting and measure the heat flux density in real time. The data of the heat flux meter 24 is input into the data processing control mechanism 8 to optimize the thermal power setting and reduce experimental errors.

[0240] like Figure 1 、 4 As shown in Figure 11, the gas supply mechanism 3 includes a gas cylinder 31, a gas proportioning device 33, an air inlet pipe 34, an air pump 35, an electronic flowmeter 36, an air suction pump 37, and a gas pressure sensor D. There are multiple gas cylinders 31, and different gases are placed in the multiple gas cylinders 31. For example, oxygen and substances such as carbon monoxide, carbon dioxide, methane, ethane, ethylene, and acetylene generated after the coal sample is heated can be placed in the multiple gas cylinders 31 respectively, so that the gas supply mechanism 3 can configure different gas mixtures including an oxygen-depleted environment containing carbon monoxide, carbon dioxide, and substances such as methane, ethane, ethylene, and acetylene, thereby simulating the different gases generated during the oxidation and heating process of the coal sample. The different gases generated also affect the combustion conditions during the thermal radiation process. Of course, other gases can also be included according to actual conditions.

[0241] Each gas cylinder 31 is connected to the air inlet of the gas proportioner 33 through the air supply pipe 32. A pressure reducing valve 38 is provided on the air supply pipe 32. The air outlet of the gas proportioner 33 is connected to one end of the air inlet pipe 34. The other end of the air inlet pipe 34 is connected to the experimental box 1. The air supply pump 35 and the electronic flow meter 36 are arranged on the air inlet pipe 34 in sequence. The air suction pump 37 is arranged at the top of the experimental box 1 and is connected to the experimental box 1 and the gas concentration monitoring mechanism 4. The gas pressure sensor D is arranged in the experimental box 1. The gas proportioner 33, the air supply pump 35, the air suction pump 37 and the gas pressure sensor D are all electrically connected to the data processing and control mechanism 8.

[0242] The gas supply mechanism 3 provided in the embodiment of the present application has multiple gas cylinders 31 containing different gases, and all of them are connected to the air inlet of the gas proportioning instrument 33 through the air supply pipe 32, so as to supply different gases to the gas proportioning instrument 33. After the data processing and control mechanism 8 adjusts the gas proportioning instrument 33 to obtain the required mixed gas, the required mixed gas is sent into the experimental box 1 through the air inlet pipe 34. It can reproduce the oxygen-deficient environment of the underground fire area and support the test of the effect of different O2 volume concentrations on smoldering. The pressure in the experimental box 1 is measured by the gas pressure sensor D and the data is transmitted to the data processing and control mechanism 8. The data processing and control mechanism 8 adjusts the air supply volume of the air supply pump 35 and the air suction volume of the air suction pump 37 at the top of the box to adjust the positive and negative pressure in the experimental box 1, simulating the dynamics of "negative pressure to positive pressure in the combustion center", thereby simulating the actual "chimney effect" and improving the authenticity of the experiment. The electronic flow meter 36 measures the gas flow in real time and transmits the data to the data processing and control mechanism 8.

[0243] like Figure 5 As shown, the gas concentration monitoring mechanism 4 includes a gas pipe 41, a filter element 42, a water bath cooling box 43, a drying box 44, and a gas concentration sensor group 45. One end of the gas pipe 41 is connected to the experimental box 1, and the other end is connected to the input port of the water bath cooling box 43.

[0244] A multi-stage filter element 42 is sequentially arranged on the gas delivery pipe 41. Figure 5 A schematic diagram illustrates a structure in which two stages of filter elements 42 are sequentially installed on a gas transmission pipe 41. The number of filter elements 42 can be adjusted based on actual needs. The output of a water bath cooling chamber 43 is connected to the input of a drying chamber 44. The output of the drying chamber 44 is connected to a gas concentration sensor group 45. The gas concentration sensor group 45 is electrically connected to the data processing and control unit 8 via a gas concentration information transmission line. The gas concentration sensor group 45 includes an oxygen gas concentration sensor, a carbon monoxide gas concentration sensor, and a carbon dioxide gas concentration sensor.

[0245] The gas concentration monitoring mechanism 4 provided in the embodiment of the present application extracts combustion gas from the experimental chamber 1 via an air pump 37 (here, the air pump 37 also serves to provide power for the exhaust of combustion gas) and is transported to a gas pipe 41. A multi-stage filter element 42 on the gas pipe 41 removes particulate matter (if the filter element 42 is two-stage, the first-stage filter element 42 can initially remove smoke and unburned carbon particles from the combustion gas to prevent clogging or contamination of subsequent analytical instruments. The second-stage filter element 42 can further remove small particulate matter from the combustion gas, ensuring that there are no particulate matter in the combustion gas). The gas enters a water bath cooling box 43 for cooling, reducing the high-temperature combustion gas to room temperature, and then passes through a drying box 44 for dehydration and drying. Finally, a gas concentration sensor group 45 monitors gas volume concentration data and can detect the volume concentrations of oxygen, carbon monoxide, and carbon dioxide in the combustion gas with a response time of ≤3.5 seconds and an accuracy of 0.1%. The data is transmitted to a data processing and control mechanism 8. It can ensure accurate measurement of gas volume concentration, and the multi-stage filter element 42 removes particulate matter, which can extend the life of the sensor and support long-term monitoring of the entire smoldering cycle.

[0246] like Figure 6 As shown, the weight monitoring mechanism 6 includes a lifting structure 61, a weight sensor 62, a fireproof and heat-insulating layer 63 and a bracket 64. The weight sensor 62 is arranged on the lifting structure 61, and the lifting structure 61 can be a hydraulic lift, a jack, etc. The temperature data collector 72 is arranged on the weight sensor 62. The fireproof and heat-insulating layer 63 is arranged on the temperature data collector 72. The bottom end of the bracket 64 is inserted into the weight sensor 62, and the sample placement box 5 is placed on the top end. The weight sensor 62, the lifting structure 61 and the temperature data collector 72 are all electrically connected to the data processing and control mechanism 8 through a data transmission line, and can transmit the weight data and temperature data of the coal sample to the data processing and control mechanism 8 in real time, and can record, calculate and transmit the weight loss and weight loss rate of the coal sample during the smoldering process in real time.

[0247] The weight monitoring mechanism 6 and the lifting structure 61 provided in the embodiment of the present application can adjust the distance between the sample storage box 5 and the heat radiation mechanism 2. In practice, the data cable of the temperature data acquisition device 72 is connected to the thermometer 71. If the temperature data acquisition device 72 is installed externally, the weight of the temperature data acquisition device 72 (including the connecting data cable) will affect the measured weight of the coal sample in the sample storage box 5. However, if the temperature data acquisition device (including the connecting data cable) is placed on the weight sensor 62, the weight of the temperature data acquisition device 72 (including the connecting data cable) will not affect the measured weight of the coal sample in the sample storage box 5.

[0248] The weight sensor 62 is mounted on the lifting structure 61. The fireproof insulation layer 63 can isolate the heat and ensure that the temperature data collector 72 set below it is not affected by the temperature. The temperature data collector 72 is placed on the weight sensor 62 and can collect the temperature data of the thermometer 71. The bracket 64 includes a first vertical rod 641 and a horizontal plate 642. The horizontal plate 642 is square, such as Figure 1 and Figure 7 As shown, a rectangular slot 51 is provided at the bottom of the sample storage box 5. This slot 51 mates with a horizontal plate 642, securing the sample storage box 5 to the bracket 64 through the horizontal plate 642 and the slot 51, providing excellent fixation and load-bearing properties. The weight sensor 62 features an automatic calibration function to ensure the accuracy of the measured data. A storage box 65 is also provided below the lifting structure 61 to increase the overall height of the weight monitoring mechanism 6.

[0249] The present invention quantifies coal sample mass loss and correlates it with smoldering progress, providing data for calculating combustion rate. The fireproof design ensures reliability at high temperatures and reduces the risk of equipment damage.

[0250] like Figure 9 As shown, the underground coal fire radiant smoldering physical simulation experimental apparatus provided in this embodiment of the present application further includes a settlement height monitoring mechanism 9. Settlement height monitoring mechanism 9 is disposed on the side wall of the sample placement box 5 and is used to monitor the real-time settlement height of the coal sample as it burns. Settlement height monitoring mechanism 9 is electrically connected to the data processing and control mechanism 8.

[0251] The settlement height monitoring mechanism 9 provided in this embodiment is mounted on the side wall of the sample storage box 5. As the coal sample burns, it monitors the real-time settlement height of the coal sample. This data is transmitted in real time to the data processing and control mechanism 8, which displays a real-time settlement curve, capturing physical changes in the coal sample (such as collapse) and calculating the settlement rate, providing early warning of settlement risks and improving experimental safety.

[0252] Continue to refer to Figure 9 As shown, the sedimentation height monitoring mechanism 9 includes a cross bar 91, a second vertical bar 92 and a displacement sensor 93. The cross bar 91 and the second vertical bar 92 are arranged perpendicular to each other. The displacement sensor 93 is arranged on the second vertical bar 92 and is located on the side wall of the sample placement box 5. The displacement sensor 93 is electrically connected to the data processing and control mechanism 8. The displacement sensor 93 measures the sedimentation displacement, and the data is input into the data processing and control mechanism 8 to calculate the sedimentation rate. The sedimentation height monitoring mechanism 9 provided in the embodiment of the present application can accurately monitor tiny sedimentations (millimeter level), simplify the installation structure, and reduce maintenance costs.

[0253] Optionally, the relationship between the smoldering coal sample's settling height, thermal radiation power, and coal sample porosity is:

[0254] .

[0255] Where h is the smoldering settlement height of the coal sample, ξ is the correction coefficient, W is the thermal radiation power, is the porosity of the coal sample, is the correction factor.

[0256] The relationship formula in the embodiment of this application quantifies the sedimentation behavior of coal samples under the action of thermal radiation, relates physical changes to smoldering conditions, and solves the problem of the unclear physical mechanism of the continuous heat release and temperature gradient formed by the coal-oxygen reaction under oxygen-deficient conditions. For example, the porosity of the coal sample The product of the inverse of and the thermal radiation power W directly reflects the subsidence height, helping to predict the risk of coal sample collapse. This relationship is adaptable to different coal qualities (such as long flame coal), and outputs subsidence height data for assessing coal pile stability and reducing the incidence of collapse accidents during underground fire zone management. From the perspectives of thermodynamics (thermal radiation power) and materials science (coal sample porosity), it provides key parameters for simulating real-world underground environments, enhancing the effectiveness of prevention and control measures.

[0257] like Figure 7 and Figure 8 As shown, the underground coal fire radiation smoldering physical similarity simulation experimental device also includes an acoustic emission monitoring mechanism A. The acoustic emission monitoring mechanism A includes a microphone A1 and an acoustic wave data collector A2. Microphone A1 is a capacitor microphone packaged in ceramic, or a 1 / 4 high-temperature resistant free-field polarization microphone, which can withstand a high temperature of 1200°C. A support frame for fixing the microphone A1 is provided on the side of the sample placement box 5. The number and setting position of the microphone A1 are consistent with the setting position of the thermometer 71 (for example, the thermocouples include twenty, divided into five groups, four in each group, and placed next to the right side of the thermocouple). Multiple microphones A1 are electrically connected to the acoustic wave data collector A2. The acoustic wave data collector A2 is electrically connected to the data processing and control mechanism 8, and the microphone A1 collects the acoustic emission signal and transmits it to the acoustic wave data collector A2. The acoustic wave data collector A2 transmits the data to the data processing and control mechanism 8.

[0258] The acoustic emission monitoring mechanism A provided in this embodiment provides non-contact monitoring (e.g., cracking sound) and enhances early warning capabilities. Its position is consistent with that of the thermometer 71, ensuring spatial alignment of acoustic and thermal data and improving analysis accuracy.

[0259] Acoustic wave data acquisition instrument A2 is placed to the left of weight sensor 62 (in this case, temperature data acquisition instrument 72 is placed to the right of weight sensor 62 to maintain weight balance). Its weight is calculated together with the sample box 5, thermocouple, and acoustic wave data transmission cable. In practice, the data cable of acoustic wave data acquisition instrument A2 is connected to microphone A1. If acoustic wave data acquisition instrument A2 is placed externally, the weight of acoustic wave data acquisition instrument A2 (including the connecting data cable) will affect the measured weight of the coal sample in the sample box 5. However, if acoustic wave data acquisition instrument A2 (including the connecting data cable) is placed entirely on weight sensor 62, the weight of acoustic wave data acquisition instrument A2 (including the connecting data cable) will not affect the measured weight of the coal sample in the sample box 5.

[0260] Microphone A1 can be used in conjunction with thermometer 71 to analyze the propagation characteristics of the coal sample during its smoldering spread. By collecting information such as the acoustic emission amplitude and duration, the sonic boom generated by the smoldering coal sample can be analyzed. Based on the sonic boom state, the smoldering location and smoldering spread pattern of the coal sample can be analyzed.

[0261] Optionally, when the coal sample is smoldering, the relationship between acoustic emission and coal sample temperature is:

[0262] .

[0263] Wherein, AE (T) is the acoustic emission signal, A and B are empirical coefficients, which are related to the moisture, ash, volatile matter and fixed carbon content of the coal sample and need to be calibrated, k1 and k2 are the exponential coefficients of the coal sample, which reflect the pyrolysis reaction kinetics of the coal sample, T is the coal sample temperature, unit is K, T0 is the initial temperature of the coal sample, unit is K, α is the enhancement factor of the temperature change rate on the acoustic emission signal AE (T), which is related to the thermal radiation power received by the coal sample, T c It is the critical temperature of the coal sample, which is related to the pyrolysis characteristics of the coal type, and the unit is K.

[0264] The relationship between acoustic emission and coal sample temperature provided in the embodiment of the present application establishes an exponential correlation between acoustic emission and temperature, which can be used to determine the critical temperature of the coal sample at T c Early warning of smoldering peaks nearby addresses the hidden nature of smoldering hazards. Using empirical coefficients A and B and an enhancement factor α, a formula calibrates the acoustic emission responses of different coal types, assisting the data processing and control mechanism 8 in identifying early smoldering (e.g., the enhancement of acoustic emissions by the temperature change rate dT / dt), reducing missed detections and enhancing monitoring reliability. From an acoustic monitoring perspective, this provides a non-invasive early warning method, filling the gap in real-time response parameters in the study of spread patterns. Furthermore, segmented calculations ensure continuity of measurement data and establish a relationship between the spread of smoldering in coal samples and acoustic emissions. By integrating temperature measurement data with acoustic emission data, the relationship between the spread of smoldering in coal samples and acoustic emissions is determined, and a mathematical model of the smoldering propagation rate and heat flux density is constructed.

[0265] Furthermore, the center position of the plane where the fifth group of microphones A1 of the sample placement box 5 is located is set as the coordinate origin, the position of the microphone A1 with the top of each group located at the center of the sample placement box 5 is set as the OM axis, the direction perpendicular to the OM axis is set as the ON axis, and the vertical upward direction is set as the OS axis, to establish an OMNS axis coordinate system.

[0266] The acoustic emission data matrix AE of the multiple microphones A1 arranged in the sample placement box 5 is:

[0267] .

[0268] The acoustic emission data matrix of the present embodiment provides spatially distributed acoustic emission data, resolving the issue of unclear gas diffusion mechanisms. Combined with the temperature data matrix, it can analyze acoustic emission hotspots (e.g., matrix elements AE{ij} corresponding to specific coordinate points), integrate spatially distributed data, and optimize the analysis of radial and axial propagation patterns of smoldering coal samples. The acoustic emission data matrix can be input into the data processing and control mechanism 8 to generate an acoustic-thermal coupling model of smoldering propagation, helping to identify gas migration paths under the "chimney effect." This enables multidimensional analysis, enhances the comprehensiveness of monitoring from a data science perspective, and provides spatial dimension parameters for prevention and control (e.g., isolation zone optimization).

[0269] The experimental device for simulating the smoldering radiative combustion of an underground coal fire provided in this embodiment of the present invention also includes an infrared camera monitoring mechanism B. This mechanism B is located at the bottom of the heat radiation mechanism 2 and is electrically connected to the data processing and control mechanism 8. Infrared camera B1 captures real-time infrared images of the coal sample's temperature distribution. This data is then fed into the data processing and control mechanism 8, which visualizes the temperature field (e.g., identifying hot spots). This helps resolve the issue of unclear patterns in the spread of smoldering.

[0270] like Figure 12 As shown, coal samples with different thermal radiation intensities and particle sizes have different cold wall quenching effects after combustion. Combined with the surface temperature distribution images of the coal samples from the infrared camera monitoring mechanism B, the cold wall quenching effects of the coal samples can be accurately analyzed. Clearly determining the thermal radiation power of the coal samples in the three states of unburned, smoldering, and open flame, and transmitting this data to the data processing and control mechanism 8, can break down data silos.

[0271] like Figure 10As shown, infrared camera monitoring mechanism B includes an infrared camera B1, a secondary circulating water cooling layer B2, a thermal insulation layer B3, a primary circulating water cooling layer B4, and a thermal insulation layer B5. Infrared camera B1 is electrically connected to data processing and control mechanism 8. The secondary circulating water cooling layer B2 is located outside infrared camera B1. The thermal insulation layer B3 is located outside the secondary circulating water cooling layer B2. The primary circulating water cooling layer B4 is located outside the thermal insulation layer B3. The thermal insulation layer B5 is located outside the primary circulating water cooling layer B4.

[0272] Infrared camera B1 captures infrared radiation from the coal-oxygen reaction, capturing the surface temperature distribution and flame propagation of the coal sample, including changes during flame formation, expansion, and extinction. This provides crucial visualization data for studying smoldering behavior under coal thermal radiation. The camera is surrounded by a secondary circulating water cooling layer B2, an insulation layer B3, a primary circulating water cooling layer B4, and a thermal insulation layer B5 (from inside to outside). The thermal insulation layer B5 isolates heat from the heat radiation mechanism 2. The primary circulating water cooling layer B4 is connected to a water source, dissipating any heat that cannot be isolated through the circulating water cooling layer. The thermal insulation layer B3 maintains stable temperature. The secondary circulating water cooling layer B2 is connected to a water source, providing additional cooling in addition to the primary cooling, preventing damage from high temperatures and protecting the infrared camera B1 from high temperatures (such as near the radiation cone 21), ensuring long-term stability. The multi-layer design optimizes thermal management and enhances image quality.

[0273] The infrared camera B1 can also capture the changes in the voids on the coal sample surface, and obtain the relationship between the void ratio and the settling height of the coal sample, as well as a comprehensive analysis of the relationship between the settling height, thermal radiation intensity and particle size of the coal sample.

[0274] The experimental device provided in the embodiment of the present application can also be used to study the cold wall extinguishing in combination with infrared data. Figure 12 As shown, the coal sample with small particle size of 0.1-0.5mm is at 5kW / m 2 Under low thermal radiation intensity, the surrounding area is basically not burned, and as the thermal radiation power increases, the cold wall suffocation effect becomes weaker and weaker, and the surrounding area of ​​the coal sample can be completely burned. Figure 14 The infrared image of a certain moment measured by the infrared camera B1 is shown in the figure. The middle temperature is EP1, and the surrounding temperatures are L1, L2, L3 and L4. It can be directly displayed by Figure 14 It can be seen that the temperature in the center is significantly higher than the surrounding temperature, demonstrating a cold wall suffocation effect. Because coal is a good conductor of heat, small coal particles can dissipate heat. Larger coal particles transfer heat outward. Therefore, under the same thermal radiation intensity, larger coal particle size results in a weaker cold wall suffocation effect. By studying the cold wall suffocation effect of coal samples, it is possible to promptly break up the surrounding coal into small pieces to serve as a barrier during coal seam combustion, preventing the spread of fire and reducing the amount of earthwork used in the project.

[0275] The experimental device for simulating the smoldering radiative combustion of an underground coal fire provided in the present embodiment also includes a temperature and humidity sensor C. The temperature and humidity sensor C is disposed within the experimental chamber 1 and is electrically connected to the data processing and control mechanism 8. The temperature and humidity sensor C monitors temperature and humidity data in real time and transmits the data to the data processing and control mechanism 8. This provides environmental parameters, which can be used to calibrate the gas concentration monitoring mechanism 4, improving overall accuracy. Furthermore, the data transmitted from the temperature and humidity sensor C to the data processing and control mechanism 8 enables analysis of how the overall temperature and humidity within the experimental chamber 1 change with thermal radiation intensity and time.

[0276] Furthermore, the gas concentration monitoring mechanism 4 monitors the oxygen volume concentration in the experimental box 1 in real time.

[0277] The heat release rate during the smoldering process of the coal sample is:

[0278] .

[0279] Where HRR is the heat release rate of the coal sample, in KW, is the oxygen consumption rate, in g / s, 13.1 is the heat released per gram of oxygen consumed, and A is the cross-sectional area of ​​the sample placement box 5, in m 2 , is the oxygen volume concentration at the first time point, is the oxygen volume concentration at the second time point, and t1 is the difference between the second time point and the first time point.

[0280] The total heat released during the smoldering of the coal sample is:

[0281] .

[0282] Where THR is the total heat release of the coal sample, in kW / m 2 , t end It is the time when the smoldering of the coal sample is extinguished.

[0283] The formula in this embodiment calculates HRR and THR in real time based on oxygen concentration changes, directly addressing the under-researched nature of the smoldering process and quantifying heat release data. THR can be used to assess total smoldering energy loss, providing a basis for the dosage of extinguishing agents (such as nitrogen injection), guiding the allocation of prevention and control resources, and reducing resource waste.

[0284] Furthermore, the gas concentration monitoring mechanism 4 monitors the CO 2 volume concentration and the CO volume concentration in the experimental box 1 in real time.

[0285] The smoldering efficiency of the coal sample is:

[0286] .

[0287] Where η is the smoldering efficiency of the coal sample, is the CO2 production rate, is the CO2 volume concentration at the third time point, is the CO2 volume concentration at the fourth time point, t2 is the difference between the fourth time point and the third time point, is the carbon monoxide production rate, is the CO volume concentration at the fifth time point, is the CO volume concentration at the sixth time point, and t3 is the difference between the sixth time point and the fifth time point.

[0288] The formula provided in the embodiments of this application quantifies the chemical efficiency of smoldering based on the CO2 and CO production rates, addressing the lack of parameters for remote ignition and assessing combustion efficiency. For example, a low η value indicates incomplete combustion, providing guidance for optimizing gas supply (e.g., increasing oxygen concentration). The output η parameter can be used to assess gaseous pollutant emissions and has potential applications in environmental protection.

[0289] A specific experimental method for a physical similarity simulation experimental device for underground coal fire radiation smoldering based on an embodiment of the present application is provided herein.

[0290] 1. Prepare coal samples with particle sizes of 0.1-0.5 mm, 1-3 mm, and 7-10 mm, and measure the moisture, ash, volatile matter, and fixed carbon content of the coal samples using industrial analyzers.

[0291] 2. Open the heat radiation mechanism 2, gas supply mechanism 3, gas concentration monitoring mechanism 4, weight monitoring mechanism 6, temperature monitoring mechanism 7, settlement height monitoring mechanism 9, infrared camera monitoring mechanism B, temperature and humidity sensor C, acoustic emission monitoring mechanism A, and data processing and control mechanism 8 in sequence to test the airtightness of the experimental chamber 1 (positive and negative pressure environments) to ensure that each mechanism is working smoothly.

[0292] 3. Calibrate the thermal radiation intensity at different positions at the same temperature. Regulate the radiation temperature using the radiation cone 21 in the thermal radiation mechanism 2. Measure the thermal radiation intensity using the heat flux meter 24. Regulate the height of the sample placement box 5 using the lifting structure 61. Continue measuring the thermal radiation intensity to obtain the thermal radiation intensity at different positions and temperatures, and record it in the data processing and control mechanism 8.

[0293] 4. Place a 0.1-0.5mm coal sample in the sample placement box 5. Initially set the distance between the sample placement box 5 and the radiation cone 21 to 2.5cm. Use the gas proportioning instrument 33 to prepare the gas environment in the experimental box 1 to a 21% nitrogen and oxygen mixture. Use the air supply pump 35 and the air suction pump 37 to control the gas pressure in the experimental box 1 to 101.325kPa. Use the data processing and control mechanism 8 to control the thermal radiation intensity of the radiation cone 21 to 5kW / m 2 , start the experiment.

[0294] 5. Assume that the center of the plane where the fifth group of thermometers 71 of the sample placement box 5 is located is the coordinate origin, the position of each group of thermometers 71 at the center of the placement box is the OX axis, the direction perpendicular to the OX axis is the OY axis, and the vertically upward direction is the OZ axis. Establish the OXYZ axis coordinate system (the data of the first layer thermocouple T1 is not included):

[0295] The temperature data matrix T of the multiple thermometers 71 inserted into the coal sample in the sample placement box 5 is:

[0296] .

[0297] The time matrix t when the multiple thermometers 71 reach their maximum temperature is:

[0298] .

[0299] The time matrix t of the radial spread of coal fire smoldering 1 cm in each layer where the temperature measuring device 71 is located rd-1 for:

[0300] .

[0301] Velocity matrix v of the radial propagation of coal fire smoldering 1 cm rd-1 for:

[0302] .

[0303] The average speed of the smoldering coal fire spreading 1 cm in the radial direction for:

[0304] .

[0305] The time matrix t of the radial spread of coal fire smoldering 2 cm in each layer where the temperature measuring device 71 is located rd-2 for:

[0306] .

[0307] Velocity matrix v of the radial propagation of coal fire smoldering 2 cm rd-2 for:

[0308] .

[0309] The average speed of the smoldering coal fire spreading 2 cm in the radial direction for:

[0310] .

[0311] The time matrix t of the radial propagation of coal fire smoldering 3 kcm in each layer where the temperature measuring device 71 is located rd-3 for:

[0312] .

[0313] Velocity matrix v of the radial propagation of coal fire smoldering 3 cm rd-3 for:

[0314] .

[0315] The average speed of the smoldering coal fire spreading 3 cm in the radial direction for:

[0316] .

[0317] Average speed of radial propagation of smoldering coal fire for:

[0318] .

[0319] The time matrix t of the axial propagation of coal fire smoldering with an axial spacing of 1 cm ad-1 for:

[0320] .

[0321] The velocity matrix v of the axial propagation of coal fire smoldering with an axial spacing of 1 cm ad-1 for:

[0322] .

[0323] Average velocity of axial propagation of coal fire smoldering at an axial distance of 1 cm for:

[0324] .

[0325] The time matrix t for the axial propagation of coal fire smoldering at twice the axial spacing of 2 cm ad-2 for:

[0326] .

[0327] The velocity matrix v of the axial propagation of coal fire smoldering at twice the axial spacing of 2 cm ad-2 for:

[0328] .

[0329] The average speed of coal fire smoldering axial propagation at twice the axial distance of 2 cm for:

[0330] .

[0331] The time matrix t for the axial propagation of coal fire smoldering three times the axial spacing distance of 3 cm ad-3 for:

[0332] .

[0333] The velocity matrix v of the axial propagation of coal fire smoldering three times the axial spacing distance of 3 cm ad-3 for:

[0334] .

[0335] The average speed of coal fire smoldering axial propagation three times the axial spacing of 3cm for:

[0336] .

[0337] Average axial propagation velocity of smoldering coal fire for:

[0338]

[0339] When the coal sample is smoldering, the relationship between acoustic emission and coal sample temperature is:

[0340] .

[0341] Wherein, AE (T) is the acoustic emission signal, A and B are empirical coefficients, which are related to the moisture, ash, volatile matter and fixed carbon content of the coal sample and need to be calibrated, k1 and k2 are the exponential coefficients of the coal sample, which reflect the pyrolysis reaction kinetics of the coal sample, T is the coal sample temperature, unit is K, T0 is the initial temperature of the coal sample, unit is K, α is the enhancement factor of the temperature change rate on the acoustic emission signal AE (T), which is related to the thermal radiation power received by the coal sample, T c It is the critical temperature of the coal sample, which is related to the pyrolysis characteristics of the coal type, and the unit is K.

[0342] 6. Set the center of the plane where the fifth microphone group A1 of the sample storage box 5 is located as the coordinate origin, the position of each microphone group A1 at the center of the sample storage box 5 as the OM axis, the direction perpendicular to the OM axis as the ON axis, and the vertically upward direction as the OS axis to establish the OMNS axis coordinate system.

[0343] The acoustic emission data matrix AE of the multiple microphones A1 arranged in the sample placement box 5 is:

[0344] .

[0345] The microphone A1 is close to the thermocouple and can be approximately at the same position. The radial and axial propagation laws of the coal sample smoldering are analyzed by combining the acoustic emission signals at different positions of the sample placement box 5 with the temperature data of the thermocouple.

[0346] Microphone A1 can be used in conjunction with thermocouples to analyze the propagation characteristics of coal sample smoldering during its spread. By collecting information such as acoustic emission amplitude and duration, the sonic boom generated by the smoldering coal sample can be analyzed. Based on the sonic boom state, the smoldering location and spread of the coal sample can be determined.

[0347] 7. The settlement height of the coal sample during smoldering is measured by the settlement height monitoring mechanism 9. The relationship between the settlement height of the smoldering coal sample, the thermal radiation power and the porosity of the coal sample is:

[0348] .

[0349] Where h is the smoldering settlement height of the coal sample, ξ is the correction coefficient, W is the thermal radiation power, is the porosity of the coal sample, is the correction factor.

[0350] 8. The above data are recorded in the data processing and control mechanism 8. The gas environment and gas pressure in the experimental box 1 are regulated by the data processing and control mechanism 8. The experimental measurement is repeated to obtain the radiation smoldering spread law of the underground coal fire.

[0351] Figure 12 The figure shows the cold wall extinguishing effect of coal samples with different particle sizes after radiation smoldering. It can be seen from the figure that in coal samples with the same particle size, the greater the thermal radiation intensity, the less obvious the cold wall extinguishing effect of the coal sample; under the same radiation intensity, the larger the coal sample particle size, the less obvious the cold wall extinguishing effect. Figure 13 The coal sample with particle size of 0.1-0.5 mm is shown at 5 kW / m 2 From the thermocouple data, we can analyze that the ignition time of the coal sample is 2370s and the ignition temperature is 233.7℃.

[0352] The experimental device of the embodiment of the present application can also study the smoldering state of the coal sample after being irradiated for a fixed time, determine the minimum thermal radiation intensity of the coal sample when it is non-combustible and smoldering, and the critical thermal radiation intensity when smoldering turns to open flame.

[0353] The device of the embodiment of the present application can simulate the real environment of underground coal fire radiation smoldering (oxygen concentration, gas pressure and thermal radiation intensity), obtain the measurement of parameters such as coal fire smoldering remote ignition conditions, gas generation law, heat release rate, total heat release amount, thermal radiation intensity required for smoldering to open flame, and smoldering spread law under different particle sizes, different gas concentrations, different atmospheric pressures and different radiation powers, and at the same time can study the spread law of coal sample smoldering process in combination with acoustic emission technology, derive the relationship between the length of the cold wall extinguishing wall of coal sample and the coal sample particle size and thermal radiation intensity, clarify the spread law of coal sample under self-sustaining smoldering and non-self-sustaining smoldering, and fill the gap in the research on the conditions and spread law of underground coal fire smoldering remote ignition. It solves the problem that the development and evolution of underground coal fire radiation smoldering is difficult to study and provides theoretical guidance for the active prevention and control of underground coal fire smoldering disasters.

[0354] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other. Each embodiment focuses on the differences from other embodiments.

[0355] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit the present application. Although the present application has been described in detail with reference to the aforementioned embodiments, a person of ordinary skill in the art should understand that the technical solutions described in the aforementioned embodiments can still be modified, or some or all of the technical features therein can be replaced by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present application.

Claims

1. An underground coal fire radiation smoldering physical similarity simulation experimental device, characterized in that: It includes an experimental box, a heat radiation mechanism, a gas supply mechanism, a gas concentration monitoring mechanism, a sample placement box, a weight monitoring mechanism, a temperature monitoring mechanism and a data processing and control mechanism; The heat radiation mechanism is arranged on the top of the experimental box; The gas supply mechanism is in communication with the experimental box, and is used to mix and deliver different gas mixtures to the experimental box, and is capable of adjusting the positive and negative pressures of the experimental box; The gas concentration monitoring mechanism is in communication with the experimental box; The coal sample is placed in the sample placement box, which is placed on top of the weight monitoring mechanism; The upper portion of the weight monitoring mechanism and the sample placement box are placed in the inner cavity of the experimental box and below the heat radiation mechanism; The temperature monitoring mechanism includes a thermometer and a temperature data acquisition instrument; The thermometers include a plurality of thermometers, all electrically connected to the temperature data acquisition instrument, and divided into N groups, with M thermometers in each group; A first group of thermometers is arranged at a preset height H from the upper surface of the sample placement box, and the second to N groups of thermometers are arranged in sequence from the reference surface to the bottom surface at an axial spacing distance h, with the upper surface of the sample placement box as the reference surface; The thermometers in each layer are arranged in a circular array of equal arcs around the central axis of the sample placement box, and the tops of the M thermometers are sequentially moved from the center of the sample placement box toward the outer wall by A times the preset distance k, where A is a natural number, k= , where L is the distance from the center of the sample box to the outer wall where the thermometer is set, and l is the length of the last thermometer extending into the sample box; The heat radiation mechanism, the gas supply mechanism, the gas concentration monitoring mechanism, the weight monitoring mechanism and the temperature data acquisition device are all electrically connected to the data processing and control mechanism; The gas supply mechanism includes a gas cylinder, a gas proportioning instrument, an air inlet pipe, an air delivery pump, an electronic flow meter, an air suction pump and a gas pressure sensor; The gas cylinders include a plurality of gas cylinders, each containing different gases; Each of the gas cylinders is connected to the gas inlet of the gas proportioning instrument through a gas supply pipe; The gas outlet of the gas proportioning instrument is connected to one end of the gas inlet pipe; The other end of the air inlet pipe is connected to the experimental box; The air supply pump and the electronic flow meter are sequentially arranged on the air intake pipe; The suction pump is arranged on the top of the experimental box and is connected to the experimental box and the gas concentration monitoring mechanism; The gas pressure sensor is arranged in the experimental box; The gas proportioning instrument, the air supply pump, the air suction pump and the gas pressure sensor are all electrically connected to the data processing and control mechanism; The weight monitoring mechanism includes a lifting structure, a weight sensor, a fireproof and heat-insulating layer, and a bracket; The weight sensor is arranged on the lifting structure; The temperature data collector is arranged on the weight sensor; The fireproof and heat-insulating layer is provided on the temperature data acquisition instrument; The bottom end of the bracket is inserted into the weight sensor, and the top end is placed on the sample placement box; The weight sensor, the lifting structure and the temperature data collector are all electrically connected to a data processing and control mechanism.

2. The underground coal fire radiation smoldering physical similarity simulation experimental device according to claim 1 is characterized in that: The thermometers are divided into five groups, each group consists of four thermometers, and the top ends of the four thermometers are moved in an orderly clockwise direction from the center of the sample placement box toward the outer wall by A times the preset distance k; Assume that the center position of the plane where the fifth group of thermometers of the sample placement box is located is the coordinate origin, the position of the thermometer at the top of each group located at the center of the placement box is the OX axis, the direction perpendicular to the OX axis is the OY axis, and the vertically upward direction is the OZ axis, and establish an OXYZ axis coordinate system; The temperature data matrix T of the multiple thermometers inserted into the coal samples in the sample placement box is: ； The time matrix t when the multiple thermometers reach their highest temperature is: ； The time matrix t of the radial propagation kcm of the coal fire smoldering in each group of the pyrometers rd-1 for: ； Velocity matrix v of radial propagation kcm of coal fire smoldering rd-1 for: ； Average speed of radial propagation of coal fire smoldering kcm for: ； The time matrix t of the radial propagation of 2 kcm of coal fire smoldering in each group of the pyrometers rd-2 for: ； Velocity matrix v for radial propagation of coal fire smoldering at 2 kcm rd-2 for: ； The average speed of the smoldering coal fire spreading radially at 2 kcm for: ； The time matrix t of the radial propagation of coal fire smoldering 3 kcm in each group of the pyrometers rd-3 for: ； Velocity matrix v of coal fire smoldering radial propagation 3 kcm rd-3 for: ； The average speed of the smoldering coal fire spreading radially at 3 kcm for: ； Average speed of radial propagation of smoldering coal fire for: ； The time matrix t of the axial propagation of coal fire smoldering and the axial spacing distance h ad-1 for: ； The velocity matrix v of the axial propagation of coal fire smoldering at the axial spacing h ad-1 for: ； The average velocity of axial propagation of coal fire smoldering at an axial distance h for: ； The time matrix t of the axial propagation of coal fire smoldering twice the axial spacing distance of 2h ad-2 for: ； The velocity matrix v of the axial propagation of coal fire smoldering twice the axial spacing distance 2h ad-2 for: ； The average speed of coal fire smoldering axial propagation twice the axial distance for 2 hours for: ； The time matrix t of the axial propagation of coal fire smoldering three times the axial separation distance of 3h ad-3 for: ； The velocity matrix v of the axial propagation of coal fire smoldering three times the axial separation distance 3h ad-3 for: ； The average speed of coal fire smoldering axial propagation three times the axial separation distance for 3 hours for: ； Average axial propagation velocity of smoldering coal fire for: 。 3. The underground coal fire radiation smoldering physical similarity simulation experimental device according to claim 1 is characterized in that: It also includes a settlement height monitoring agency; The settlement height monitoring mechanism is provided on the side wall of the sample placement box, and is used to monitor the real-time settlement height of the coal sample when the coal sample is burning; The settlement height monitoring mechanism is electrically connected to the data processing and control mechanism.

4. The underground coal fire radiation smoldering physical similarity simulation experimental device according to claim 3 is characterized in that: The relationship between the smoldering settlement height of the coal sample, the thermal radiation power and the porosity of the coal sample is: ； Where h is the smoldering settlement height of the coal sample, ξ is the correction coefficient, W is the thermal radiation power, is the porosity of the coal sample, is the correction factor.

5. The underground coal fire radiation smoldering physical similarity simulation experimental device according to claim 1 is characterized in that: It also includes acoustic emission monitoring agencies; The acoustic emission monitoring mechanism includes a microphone and an acoustic wave data collector; The number and location of the microphones are consistent with the location of the thermometer; The plurality of microphones are electrically connected to the acoustic wave data acquisition instrument; The acoustic wave data collector is electrically connected to the data processing and control mechanism.

6. The underground coal fire radiation smoldering physical similarity simulation experimental device according to claim 5 is characterized in that: When the coal sample is smoldering, the relationship between acoustic emission and coal sample temperature is: ； Where AE(T) is the acoustic emission signal, A and B are empirical coefficients, k1 and k2 are the exponential coefficients of the coal sample, T is the temperature of the coal sample, T0 is the initial temperature of the coal sample, α is the enhancement factor of the temperature change rate on the acoustic emission signal AE(T), T c is the critical temperature of the coal sample.

7. The underground coal fire radiation smoldering physical similarity simulation experimental device according to claim 1 is characterized in that: The gas concentration monitoring mechanism monitors the oxygen volume concentration in the experimental box in real time; The heat release rate during the smoldering process of the coal sample is: ； Where HRR is the heat release rate of the coal sample, △ is the oxygen consumption rate, A is the cross-sectional area of ​​the sample placement box, is the oxygen volume concentration at the first time point, is the oxygen volume concentration at the second time point, and t1 is the difference between the second time point and the first time point; The total heat released during the smoldering process of the coal sample is: ； Where THR is the total heat release of the coal sample, t end is the smoldering extinguishing time of the coal sample.

8. The underground coal fire radiation smoldering physical similarity simulation experimental device according to claim 1 is characterized in that: The gas concentration monitoring mechanism monitors the CO2 volume concentration and CO volume concentration in the experimental box in real time; The smoldering efficiency of the coal sample is: ； Where η is the smoldering efficiency of the coal sample, is the CO2 production rate, is the CO2 volume concentration at the third time point, is the CO2 volume concentration at the fourth time point, t2 is the difference between the fourth time point and the third time point, is the carbon monoxide production rate, is the CO volume concentration at the fifth time point, is the CO volume concentration at the sixth time point, and t3 is the difference between the sixth time point and the fifth time point.

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