Coal body permeability measuring device based on pulse pressure

Abstract

The utility model discloses a coal body permeability measuring device based on pulse pressure, which comprises an electric control device, a coal sample holder, a gas inlet system and a gas outlet system, a coal sample is clamped in the coal sample holder, the inlet end of the coal sample holder is connected with a main gas inlet pipe, the main gas inlet pipe is used for introducing gas into the coal sample and applying pulse pressure, and the gas inlet system is connected with the gas outlet system. A first pressure sensor is arranged on the main air inlet pipe; the upstream end of the main air inlet pipe is connected with a first pipeline and a second pipeline; the coal sample holder is connected with a confining pressure loading device and an axial pressure loading device; a first electronic flowmeter is arranged on the first pipeline; the second pipeline is connected with a pulse pressure generator, and a pulse pressure sensor and a pneumatic check valve are arranged on the second pipeline; a second pressure sensor and a second electronic flowmeter are arranged on the air outlet pipeline; in the experiment process, the pulse pressure generator can be adjusted to apply different pulse pressures to the coal sample, the permeability of the corresponding coal sample is observed, and the optimal pulse pressure is provided for gas extraction before coal mining, so that the relatively best gas extraction effect is realized.

Description

Technical Field

[0001] The utility model relates to the technical field of coal body permeability testing. Background Art

[0002] A large amount of gas is produced during the formation of coal. Gas is not only the cause of gas explosions and coal and gas outburst disasters, but also an efficient clean energy source. Understanding the flow law of gas in coal seams is the premise for reducing gas accidents and expanding gas utilization. The permeability of coal bodies is the key parameter that determines the flow law of gas, so it is very necessary to study the permeability of coal bodies.

[0003] As my country's coal mining gradually extends to deeper areas, ground stress gradually increases, coal seam permeability decreases, and the danger of coal and gas outbursts gradually increases, gas control faces a series of difficulties; during the mining process, the gas in the coal body will seep into the working face through the pores in the coal. If it is not properly controlled, it will also threaten the life and property of the workers. If the coalbed methane can be extracted and utilized, it can not only reduce the occurrence of disasters, but also improve the overall mining efficiency of the coal seam and promote the development of economic benefits. Research on the seepage characteristics of coalbed gas extraction is of great significance to the reasonable design of extraction technology and the improvement of gas extraction effect.

[0004] Improving the permeability of coal bodies can improve the efficiency of gas extraction and enhance the safety of coal seam mining after extraction. The applicant has studied various coal seam permeability enhancement methods and found that applying pulse pressure to coal seams can enhance their permeability. What kind of pulse pressure should be applied to a specific coal seam to achieve the best permeability of the coal seam has direct guiding significance for gas extraction practice. Utility Model Content

[0005] The utility model aims to provide a coal body permeability measuring device based on pulse pressure, which provides a basis for determining the best pulse pressure for a specific coal seam through experiments to improve the permeability of the coal seam as much as possible.

[0006] To achieve the above-mentioned purpose, the coal permeability measuring device based on pulse pressure of the utility model comprises an electric control device, a coal sample holder, an air intake system and an air outlet system.

[0007] The coal sample is clamped in the coal sample holder, and the inlet end of the coal sample holder is connected to a main air intake pipe, which is used to introduce gas into the coal sample and apply pulse pressure, and a first pressure sensor is provided on the main air intake pipe; the upstream end of the main air intake pipe is connected to a first pipeline and a second pipeline; the coal sample holder is connected to a confining pressure loading device and an axial pressure loading device;

[0008] The first pipeline is connected to a gas cylinder, a gas pressure regulating valve is provided at the gas outlet of the gas cylinder, and a first electronic flow meter is provided on the first pipeline;

[0009] The second pipeline is connected to a pulse pressure generator, and a pulse pressure sensor and a pneumatic check valve are arranged on the second pipeline;

[0010] The outlet end of the coal sample holder is connected to a gas outlet pipeline, and the gas outlet pipeline is connected to a gas collecting and processing device, and the gas collecting and processing device is used to collect and process the gas discharged from the gas outlet pipeline; a second pressure sensor and a second electronic flow meter are provided on the gas outlet pipeline;

[0011] The electronic control device is connected to the first pressure sensor, the first electronic flow meter, the pulse pressure generator, the pulse pressure sensor, the second pressure sensor and the second electronic flow meter, and is connected to a display screen.

[0012] The gas collection and processing device is a burner or a dilution and emission device; the burner is used to burn gas;

[0013] The dilution and discharge device comprises a dilution air pump, an air inlet of the dilution air pump is connected to a first inlet pipe and a second inlet pipe, and valves are respectively provided on the first inlet pipe and the second inlet pipe;

[0014] The first inlet pipe is used to connect the outlet pipe, and the second inlet pipe is connected to the ambient air; the outlet of the dilution air pump is connected to the discharge pipe, the discharge pipe is connected to the atmosphere, and the end of the discharge pipe is higher than the end of the second inlet pipe and is more than 10 meters away.

[0015] The coal sample holder comprises a cylinder, an air inlet end of the cylinder is provided with an air inlet plug, an air outlet end of the cylinder is threadedly connected with an air outlet cover, a loading shaft is slidably connected in the cylinder, the loading shaft is a three-section stepped shaft, and the three sections of the loading shaft are respectively a loading section, a pressure section and an extension section from inside to outside; the diameter of the loading section is larger than that of the pressure section, and the diameter of the pressure section is larger than that of the extension section; the loading section is used to press the coal sample in the axial direction; the extension section extends out of the air outlet cover and is in sliding sealing cooperation with the air outlet cover; the loading section is in sliding cooperation with the inner wall of the cylinder;

[0016] An air inlet cavity is provided at the inner end of the air inlet plug, and an air inlet orifice plate is provided at the inner end of the air inlet cavity, and the air inlet orifice plate is crimped to the air inlet end of the coal sample; the main air inlet pipe passes through the air inlet plug and communicates with the air inlet cavity, and an air inlet sealing ring is provided at the junction of the main air inlet pipe and the outer surface of the air inlet plug;

[0017] An air outlet cavity is provided at the inner end of the loading section, and an air outlet hole plate is provided at the inner end of the air outlet cavity, and the air outlet hole plate is crimped with the air outlet end of the coal sample; an air outlet pipeline passes through the loading shaft and communicates with the air outlet cavity, and an air outlet sealing ring is provided at the junction of the air outlet pipeline and the outer surface of the extended section of the loading shaft;

[0018] A confining pressure annular cavity is formed between the cylinder and the coal sample. A confining pressure loading port is provided on the cylinder. The confining pressure loading port is communicated with the confining pressure annular cavity and is connected to the confining pressure loading device. The confining pressure loading device is a high-pressure gas cylinder with a pressure regulating valve or a first gas pump.

[0019] An axial pressure annular cavity is provided between the pressure section and the inner wall of the cylinder, an axial pressure loading port is provided on the cylinder, the axial pressure loading port is communicated with the axial pressure annular cavity and is connected to the axial pressure loading device, and the axial pressure loading device is a high-pressure gas cylinder with a pressure regulating valve or a second gas pump;

[0020] A confining pressure sensor is provided on the connecting pipeline between the confining pressure loading device and the confining pressure annular cavity, and an axial pressure sensor is provided on the connecting pipeline between the axial pressure loading device and the axial pressure annular cavity. Both the confining pressure sensor and the axial pressure sensor are connected to the electronic control device.

[0021] The coal sample holder is arranged in a constant temperature device, and the constant temperature device is an electric thermostat or a constant temperature water bath.

[0022] A temperature sensor is arranged in the confining pressure annular cavity. The temperature sensor is connected with the coal sample and is used to measure the temperature of the coal sample and the confining pressure annular cavity. The temperature sensor is connected with the electric control device.

[0023] The utility model has the following advantages:

[0024] The utility model can introduce gas into the coal sample through a gas cylinder, discharge the gas passing through the coal sample through an outlet pipe, obtain the permeability of the coal sample through a first electronic flowmeter and a second electronic flowmeter, and during the experiment, the pulse pressure generator can be adjusted to apply different pulse pressures to the coal sample and observe the corresponding permeability of the coal sample (the smaller the difference between the first electronic flowmeter and the second electronic flowmeter, the better the permeability of the coal sample), thereby providing a basis for obtaining the best pulse pressure for a specific coal seam (the coal sample is sampled from a specific coal seam), facilitating staff to study the relationship between the pulse pressure characteristics and the permeability of the coal sample, and providing specific operational guidance for gas extraction before coal mining (providing the best pulse pressure to achieve the relatively best gas extraction effect).

[0025] The pneumatic check valve can prevent the gas in the first pipeline from entering the second pipeline, thereby avoiding experimental errors.

[0026] Both the burner and the dilution and emission device can be used to effectively treat the gas emitted by the experiment. When the burner is used, the gas emitted during the experiment is directly burned and will not cause any harm. When the dilution and emission device is used, the dilution air pump simultaneously inhales the gas in the gas outlet pipeline and the ambient air. By adjusting the opening degree of the valves on the first inlet pipe and the second inlet pipe, the ratio of the gas inhaled by the dilution air pump and the ambient air can be adjusted, thereby greatly reducing the gas emission concentration and ensuring that the gas emission concentration is within a safe range.

[0027] The coal sample holder has a compact structure and is convenient for applying axial pressure and confining pressure to the coal sample to simulate the actual stress condition of the coal seam.

[0028] The setting of the air inlet cavity and the air inlet orifice plate can make the air inlet pass through the coal sample more evenly, avoid the phenomenon that the air inlet passes through the coal sample near the axis of the coal sample, make the coal sample be subjected to a more uniform pulse air inlet pressure, and thus better simulate the coal seam permeability phenomenon under pulse conditions, which helps to improve the accuracy of the measurement. The air inlet orifice plate has two functions, one is to serve as a protective structure for the air inlet cavity, and the other is to serve as a structure for pressing the coal sample. The setting of the air outlet cavity and the air outlet orifice plate allows the gas at various locations of the coal sample outlet end to flow out of the coal sample more smoothly.

[0029] The temperature sensor is connected to the electric control device, and the electric control device can adjust the working state of the thermostat according to the signal of the temperature sensor, so as to better control the temperature. If the temperature of the coal sample and the confining pressure annular cavity is lower than the predetermined value, the thermostat can be adjusted to provide a temperature higher than the predetermined value. When the temperature of the coal sample and the confining pressure annular cavity is equal to the predetermined value, the thermostat is adjusted to provide a temperature equal to the predetermined value. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a structural schematic diagram of the utility model.

[0031] Figure 2 It is a structural schematic diagram of the coal sample holder.

[0032] Figure 3 It is a structural schematic diagram of the dilution discharge device.

[0033] Figure 4 It is the electric control structure diagram of the utility model. DETAILED DESCRIPTION

[0034] like Figures 1 to 4 As shown, the coal permeability measuring device based on pulse pressure of the utility model comprises an electric control device 1, a coal sample holder 2, an air intake system and an air outlet system, and the electric control device 1 is preferably an industrial control computer;

[0035] A coal sample 3 is clamped in the coal sample holder 2. The inlet end of the coal sample holder 2 is connected to a main air intake pipe 4, which is used to introduce gas into the coal sample 3 and apply pulse pressure. A first pressure sensor 5 is provided on the main air intake pipe 4. A first pipeline 6 and a second pipeline 7 are connected to the upstream end of the main air intake pipe 4. The coal sample holder 2 is connected to a confining pressure loading device 8 and an axial pressure loading device 9.

[0036] The first pipeline 6 is connected to a gas cylinder 10, a gas pressure regulating valve 11 is provided at the gas outlet of the gas cylinder 10, and a first electronic flow meter 12 is provided on the first pipeline 6;

[0037] The second pipeline 7 is connected to a pulse pressure generator 13, and a pulse pressure sensor 14 and a pneumatic check valve 15 are provided on the second pipeline 7;

[0038] The outlet end of the coal sample holder 2 is connected to a gas outlet pipeline 16, and the gas outlet pipeline 16 is connected to a gas collecting and processing device 17, and the gas collecting and processing device 17 is used to collect and process the gas discharged from the gas outlet pipeline 16; the gas outlet pipeline 16 is provided with a second pressure sensor 18 and a second electronic flow meter 19;

[0039] The electronic control device 1 is connected to the first pressure sensor 5 , the first electronic flow meter 12 , the pulse pressure generator 13 , the pulse pressure sensor 14 , the second pressure sensor 18 and the second electronic flow meter 19 , and is connected to a display screen 20 .

[0040] The utility model can introduce gas into the coal sample 3 through the gas cylinder 10, discharge the gas passing through the coal sample 3 through the gas outlet pipe 16, and obtain the permeability of the coal sample 3 through the first electronic flowmeter 12 and the second electronic flowmeter 19. During the experiment, the pulse pressure generator 13 can be adjusted to apply different pulse pressures to the coal sample 3 and observe the corresponding permeability performance of the coal sample 3 (the smaller the difference between the first electronic flowmeter 12 and the second electronic flowmeter 19, the better the permeability of the coal sample 3), thereby providing a basis for obtaining the optimal pulse pressure (including pressure peak and valley values ​​and pulse frequency) for a specific coal seam (the coal sample 3 is sampled from a specific coal seam), facilitating the staff to study the relationship between the pulse pressure characteristics and the permeability of the coal sample 3, and providing specific operational guidance for gas extraction before coal mining (providing the optimal pulse pressure to achieve the relatively best gas extraction effect).

[0041] The pneumatic check valve 15 can prevent the gas in the first pipeline 6 from entering the second pipeline 7, thereby avoiding experimental errors.

[0042] The gas collection and processing device 17 is a burner or a dilution and emission device; the burner is used to burn gas;

[0043] The dilution and discharge device comprises a dilution air pump 21, the air inlet of the dilution air pump 21 is connected to a first inlet pipe 22 and a second inlet pipe 23, and valves 24 are respectively provided on the first inlet pipe 22 and the second inlet pipe 23;

[0044] The first inlet pipe 22 is used to connect to the outlet pipe 16, and the second inlet pipe 23 is connected to the ambient air; the outlet of the dilution air pump 21 is connected to the exhaust pipe 25, and the exhaust pipe 25 is connected to the atmosphere. The end of the exhaust pipe 25 is higher than the end of the second inlet pipe 23 and is more than 10 meters away.

[0045] Both the burner and the dilution and emission device can be used to effectively treat the gas emitted by the experiment. When the burner is used, the gas emitted during the experiment is directly burned and no harm is caused. When the dilution and emission device is used, the dilution air pump 21 simultaneously inhales the gas in the gas outlet pipeline 16 and the ambient air. By adjusting the opening degree of the valve 24 on the first inlet pipe 22 and the second inlet pipe 23, the ratio of the gas gas inhaled by the dilution air pump 21 and the ambient air can be adjusted, thereby greatly reducing the gas emission concentration and ensuring that the gas emission concentration is in a safe range.

[0046] The coal sample holder 2 comprises a cylinder 26, an air inlet end of the cylinder 26 is provided with an air inlet end plug 27, an air outlet end of the cylinder 26 is threadedly connected with an air outlet end cover 28, a loading shaft is slidably connected inside the cylinder 26, and the loading shaft is a three-section stepped shaft, and the three sections of the loading shaft are respectively a loading section 29, a pressure section 30 and an extension section 31 from inside to outside; the diameter of the loading section 29 is larger than that of the pressure section 30, and the diameter of the pressure section 30 is larger than that of the extension section 31; the loading section 29 is used to press the coal sample 3 in the axial direction; the extension section 31 extends out of the air outlet end cover 28 and is slidably sealed with the air outlet end cover 28; the loading section 29 is slidably matched with the inner wall of the cylinder 26;

[0047] An air inlet cavity 32 is provided at the inner end of the air inlet plug 27, and an air inlet orifice plate 33 is provided at the inner end of the air inlet cavity 32, and the air inlet orifice plate 33 is crimped with the air inlet end of the coal sample 3; the main air inlet pipe 4 passes through the air inlet plug 27 and communicates with the air inlet cavity 32, and an air inlet sealing ring is provided at the junction of the main air inlet pipe 4 and the outer surface of the air inlet plug 27; a first sealing groove is provided in the outer surface of the air inlet plug 27, and a compression sealing ring (air inlet sealing ring) that holds the main air inlet pipe 4 is embedded in the first sealing groove

[0048] The inner end of the loading section 29 is provided with an air outlet cavity 34, and the inner end of the air outlet cavity 34 is provided with an air outlet plate 35, and the air outlet plate 35 is crimped with the air outlet end of the coal sample 3; the air outlet pipeline 16 passes through the loading shaft and communicates with the air outlet cavity 34, and an air outlet sealing ring is provided at the junction of the air outlet pipeline 16 and the outer surface of the extension section 31 of the loading shaft; the outer surface of the extension section 31 of the loading shaft is concavely provided with a second sealing groove, and a compression sealing ring (air outlet sealing ring) that holds the air outlet pipeline 16 is embedded in the second sealing groove. The sealing ring is conventional technology, and the figure does not show the air inlet sealing ring and the air outlet sealing ring.

[0049] A confining pressure annular cavity 36 is formed between the cylinder 26 and the coal sample 3. A confining pressure loading port 37 is provided on the cylinder 26. The confining pressure loading port 37 is communicated with the confining pressure annular cavity 36 and is connected to the confining pressure loading device 8. The confining pressure loading device 8 is a high-pressure gas cylinder (such as a nitrogen gas cylinder) with a pressure regulating valve or a first gas pump.

[0050] An axial pressure annular cavity 38 is provided between the pressure section 30 and the inner wall of the cylinder 26. An axial pressure loading port 39 is provided on the cylinder 26. The axial pressure loading port 39 is communicated with the axial pressure annular cavity 38 and is connected to the axial pressure loading device 9. The axial pressure loading device 9 is a high-pressure gas cylinder (such as a nitrogen gas cylinder) with a pressure regulating valve or a second gas pump.

[0051] A confining pressure sensor 40 is provided on the connecting pipeline between the confining pressure loading device 8 and the confining pressure annular cavity 36 , and an axial pressure sensor 41 is provided on the connecting pipeline between the axial pressure loading device 9 and the axial pressure annular cavity 38 . Both the confining pressure sensor 40 and the axial pressure sensor 41 are connected to the electronic control device 1 .

[0052] The coal sample holder 2 has a compact structure and is convenient for applying axial pressure and confining pressure to the coal sample 3 to simulate the actual stress condition of the coal seam.

[0053] The setting of the air inlet cavity 32 and the air inlet orifice plate 33 can make the air inlet pass through the coal sample 3 more evenly, avoid the phenomenon that the air inlet is concentrated near the axis of the coal sample 3 and pass through the coal sample 3, so that the coal sample 3 is subjected to a more uniform pulse air inlet pressure, thereby better simulating the coal seam permeability phenomenon under pulse conditions, which helps to improve the accuracy of the measurement. The air inlet orifice plate 33 has two functions, one is to serve as a protective structure for the air inlet cavity 32, and the other is to serve as a structure for pressing the coal sample 3. The setting of the air outlet cavity 34 and the air outlet orifice plate 35 allows the gas at each outlet end of the coal sample 3 to flow out of the coal sample 3 more smoothly.

[0054] The coal sample holder 2 is arranged in a constant temperature device, which is an electric thermostat or a constant temperature water bath. A temperature sensor is arranged in the confining pressure annular cavity 36, which is connected to the coal sample 3 and used to measure the temperature of the coal sample 3 and the confining pressure annular cavity 36, and the temperature sensor is connected to the electric control device 1.

[0055] The temperature sensor is connected to the electronic control device 1, and the electronic control device 1 can adjust the working state of the thermostat according to the signal of the temperature sensor, so as to better control the temperature. For example, when the temperature of the coal sample 3 and the confining pressure annular cavity 36 is lower than the predetermined value, the thermostat can be adjusted to provide a temperature higher than the predetermined value. When the temperature of the coal sample 3 and the confining pressure annular cavity 36 is equal to the predetermined value, the thermostat is adjusted to provide a temperature equal to the predetermined value.

[0056] Before the experiment, a coal sample 3 is made from coal collected from the simulated coal seam. A rubber sleeve is preferably put on the circumferential surface of the coal sample 3 (the rubber sleeve is a conventional technology, not shown in the figure, and is used to prevent circumferential gas leakage of the coal sample 3), and then placed in the inner cavity of the cylinder 26 of the coal sample holder 2; the various components of the utility model are connected, and the axial pressure loading device 9 and the confining pressure loading device 8 are connected. The coal sample holder 2 is kept at a constant predetermined temperature by a constant temperature device to simulate the temperature of the actual coal seam.

[0057] The confining pressure loading device 8 is operated to apply confining pressure for simulating the actual coal seam confining pressure condition to the coal sample 3 through the confining pressure annular cavity 36 , and the axial pressure loading device 9 is operated to apply axial pressure for simulating the actual coal seam axial pressure condition to the coal sample 3 through the axial pressure annular cavity 38 .

[0058] Open the gas cylinder 10, and adjust the outlet pressure through the gas pressure regulating valve 11. Open the pulse pressure generator 13, and apply pulse pressure to the coal sample 3 through the second pipeline 7 and the main air inlet pipe 4. Observe and record the air inlet flow monitored by the first electronic flowmeter 12 and the air outlet flow monitored by the second electronic flowmeter 19 under this pulse pressure. Replace the parameters of the pulse pressure output by the pulse pressure generator 13 through the electronic control device 1, and obtain the pulse pressure parameters with the best permeability of the coal sample 3 through experiments. According to the seepage characteristics of the coal sample 3 under this optimal pulse pressure parameter, predict the gas flow rate during the actual coal seam pulse pressure permeability enhancement, match the corresponding gas extraction equipment, and achieve the relatively best extraction effect.

[0059] The above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention is described in detail with reference to the above embodiments, those skilled in the art should understand that the present invention can still be modified or replaced by equivalents. Any modification or partial replacement that does not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A coal permeability measuring device based on pulse pressure, comprising an electric control device, a coal sample holder, an air intake system and an air outlet system, characterized in that: The coal sample is clamped in the coal sample holder, and the inlet end of the coal sample holder is connected to a main air intake pipe, which is used to introduce gas into the coal sample and apply pulse pressure, and a first pressure sensor is provided on the main air intake pipe; the upstream end of the main air intake pipe is connected to a first pipeline and a second pipeline; the coal sample holder is connected to a confining pressure loading device and an axial pressure loading device; The first pipeline is connected to a gas cylinder, a gas pressure regulating valve is provided at the gas outlet of the gas cylinder, and a first electronic flow meter is provided on the first pipeline; The second pipeline is connected to a pulse pressure generator, and a pulse pressure sensor and a pneumatic check valve are arranged on the second pipeline; The outlet end of the coal sample holder is connected to a gas outlet pipeline, and the gas outlet pipeline is connected to a gas collecting and processing device, and the gas collecting and processing device is used to collect and process the gas discharged from the gas outlet pipeline; a second pressure sensor and a second electronic flow meter are provided on the gas outlet pipeline; The electronic control device is connected to the first pressure sensor, the first electronic flow meter, the pulse pressure generator, the pulse pressure sensor, the second pressure sensor and the second electronic flow meter, and is connected to a display screen.

2. The coal permeability measuring device based on pulse pressure according to claim 1, characterized in that: The gas collection and processing device is a burner or a dilution and emission device; the burner is used to burn gas; The dilution and discharge device comprises a dilution air pump, an air inlet of the dilution air pump is connected to a first inlet pipe and a second inlet pipe, and valves are respectively provided on the first inlet pipe and the second inlet pipe; The first inlet pipe is used to connect the outlet pipe, and the second inlet pipe is connected to the ambient air; the outlet of the dilution air pump is connected to the discharge pipe, the discharge pipe is connected to the atmosphere, and the end of the discharge pipe is higher than the end of the second inlet pipe and is more than 10 meters away.

3. The coal permeability measuring device based on pulse pressure according to claim 1, characterized in that: The coal sample holder comprises a cylinder, an air inlet end of the cylinder is provided with an air inlet plug, an air outlet end of the cylinder is threadedly connected with an air outlet cover, a loading shaft is slidably connected in the cylinder, the loading shaft is a three-section stepped shaft, and the three sections of the loading shaft are respectively a loading section, a pressure section and an extension section from inside to outside; the diameter of the loading section is larger than that of the pressure section, and the diameter of the pressure section is larger than that of the extension section; the loading section is used to press the coal sample in the axial direction; the extension section extends out of the air outlet cover and is in sliding sealing cooperation with the air outlet cover; the loading section is in sliding cooperation with the inner wall of the cylinder; An air inlet cavity is provided at the inner end of the air inlet plug, and an air inlet orifice plate is provided at the inner end of the air inlet cavity, and the air inlet orifice plate is crimped to the air inlet end of the coal sample; the main air inlet pipe passes through the air inlet plug and communicates with the air inlet cavity, and an air inlet sealing ring is provided at the junction of the main air inlet pipe and the outer surface of the air inlet plug; An air outlet cavity is provided at the inner end of the loading section, and an air outlet hole plate is provided at the inner end of the air outlet cavity, and the air outlet hole plate is crimped with the air outlet end of the coal sample; an air outlet pipeline passes through the loading shaft and communicates with the air outlet cavity, and an air outlet sealing ring is provided at the junction of the air outlet pipeline and the outer surface of the extended section of the loading shaft; A confining pressure annular cavity is formed between the cylinder and the coal sample. A confining pressure loading port is provided on the cylinder. The confining pressure loading port is communicated with the confining pressure annular cavity and is connected to the confining pressure loading device. The confining pressure loading device is a high-pressure gas cylinder with a pressure regulating valve or a first gas pump. An axial pressure annular cavity is provided between the pressure section and the inner wall of the cylinder, an axial pressure loading port is provided on the cylinder, the axial pressure loading port is communicated with the axial pressure annular cavity and is connected to the axial pressure loading device, and the axial pressure loading device is a high-pressure gas cylinder with a pressure regulating valve or a second gas pump; A confining pressure sensor is provided on the connecting pipeline between the confining pressure loading device and the confining pressure annular cavity, and an axial pressure sensor is provided on the connecting pipeline between the axial pressure loading device and the axial pressure annular cavity. Both the confining pressure sensor and the axial pressure sensor are connected to the electronic control device.

4. The coal permeability measuring device based on pulse pressure according to claim 3 is characterized in that: The coal sample holder is arranged in a constant temperature device, and the constant temperature device is an electric thermostat or a constant temperature water bath.

5. The coal permeability measuring device based on pulse pressure according to claim 3, characterized in that: A temperature sensor is arranged in the confining pressure annular cavity. The temperature sensor is connected with the coal sample and is used to measure the temperature of the coal sample and the confining pressure annular cavity. The temperature sensor is connected with the electric control device.

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