A structure for localized ventilation in underground mines to prevent the spread of fire smoke

Abstract

The application discloses a kind of underground local ventilation fire hazard smoke spread structure, including ventilation pipeline, the inside surface of the ventilation pipeline is provided with variable diameter part, variable diameter part includes the elastic tube wall being arranged in the inside of ventilation pipeline and the heat conduction alloy part being arranged in the outside of ventilation pipeline, cavity is arranged between elastic tube wall and heat conduction alloy part, heated expansion part is arranged in cavity, heated expansion part expands and props open elastic tube wall at medium temperature, reduce the pipe diameter at variable diameter part, the inside lower part of ventilation pipeline is close to variable diameter part and is provided with dust outlet, dust hopper is provided in the lower side of dust outlet, dust outlet is arranged in the downstream side of variable diameter part in the air flow direction of the inside of ventilation pipeline;Heated expansion part further expands and makes elastic tube wall further deformation to close ventilation pipeline at high temperature.The structure does not need external energy, simple structure, easy to maintain, maintenance cost is lower, and the dependence degree of electrical equipment is low, not easy to fail, strong stability.

Description

Technical Field

[0001] This invention relates to the field of underground ventilation technology, specifically to an underground local ventilation structure for preventing the spread of fire smoke. Background Technology

[0002] With the increasing complexity of underground working environments such as mines and tunnels, fire prevention has become a core challenge in safety management. Toxic fumes and high-temperature particles generated by fires spread rapidly in ventilation ducts, posing a risk of asphyxiation and potentially igniting adjacent areas, causing secondary disasters.

[0003] While traditional ventilation systems possess basic dust removal and airflow control functions, they have significant shortcomings in fire conditions, making it difficult to achieve the dual protection goals of dynamic smoke suppression and active fire isolation.

[0004] Existing underground ventilation and fire prevention methods typically employ fixed fire dampers or flame-retardant coatings, relying on the inherent fire-resistant properties of the materials (such as ceramic fiberboard and fire-resistant gypsum) to delay the spread of fire, but failing to completely block the spread of fire and smoke. Methods using sensors to monitor fire and trigger the closure of electric / pneumatic valves require external control systems and energy supplies; underground fires may be accompanied by power outages, easily leading to system failure. Therefore, we propose a localized underground ventilation structure to prevent the spread of fire and smoke. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the existing defects and provide a local ventilation structure for preventing the spread of fire smoke in underground mines. This structure can block the spread of fire and isolate the passage of smoke. It does not require external energy, has a simple structure, is easy to maintain, has low maintenance costs, low dependence on electrical equipment, is not prone to failure, and has strong stability. It can effectively solve the problems in the background technology.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a structure for preventing the spread of fire smoke in underground local ventilation systems, comprising a ventilation duct, wherein a diameter-changing section is provided on the inner surface of the ventilation duct, the diameter-changing section comprising an elastic pipe wall disposed on the inner side of the ventilation duct and a heat-conducting alloy section disposed on the outer side of the ventilation duct, a cavity being provided between the elastic pipe wall and the heat-conducting alloy section, and a thermal expansion section being provided within the cavity, the thermal expansion section expanding and expanding the elastic pipe wall at medium temperature, reducing the pipe diameter at the diameter-changing section, a dust discharge port being provided on the lower inner side of the ventilation duct near the diameter-changing section, a dust collection hopper being provided below the dust discharge port, the dust discharge port being located on the downstream side of the diameter-changing section in the airflow direction inside the ventilation duct; the thermal expansion section further expanding at high temperature causes the elastic pipe wall to further deform and seal the ventilation duct.

[0007] In a preferred embodiment of the present invention, the thermally expanded portion is an expansion material layer.

[0008] As a preferred embodiment of the present invention, the ventilation duct is provided with an upwardly bent portion, which is located above the dust discharge port.

[0009] As a preferred embodiment of the present invention, the dust collection hopper is shaped like a sieve, and a dust discharge box is connected to the bottom of the dust collection hopper. A dust outlet is provided on one side of the lower part of the dust discharge box, and a drive motor is installed on the outer surface of the other side of the lower part of the dust discharge box. The output shaft of the drive motor passes through the inner side of the lower part of the dust discharge box and is connected to the rotating shaft through a coupling. A spiral pusher plate is installed on the rotating shaft.

[0010] As a preferred embodiment of the present invention, a plurality of atomizing nozzles are uniformly arranged on the upper inner side of the ventilation duct.

[0011] As a preferred embodiment of the present invention, the thermal expansion part is a shape memory alloy spring.

[0012] As a preferred embodiment of the present invention, a cavity is provided on the inner side of the thermally conductive alloy part, and a heating component is disposed in the cavity.

[0013] As a preferred embodiment of the present invention, an elastic dust filter is provided on the inner side of the ventilation duct, and the elastic dust filter is located on the upstream side of the diameter change section in the airflow direction inside the ventilation duct.

[0014] As a preferred embodiment of the present invention, a fixing rod is provided in the middle of the elastic dust filter, and the two ends of the fixing rod are fixedly disposed on the inner surface of the ventilation duct; a slider is provided at the end of the elastic dust filter, and a groove corresponding to the slider is opened on the inner surface of the ventilation duct, and the slider is slidably disposed in the groove.

[0015] As a preferred embodiment of the present invention, a hinge rod is hinged to one side surface of the slider facing the variable diameter section, and the other end of the hinge rod is hinged to the side surface of the elastic tube wall.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This structure is mainly used for local ventilation and fire prevention in underground chambers, such as equipment chambers and safety chambers, with ventilation ducts used to ventilate the chambers. At least one diameter-changing section is provided within the ventilation duct, which can be located near areas prone to fire. In the early stages of a fire, heat is transferred to the thermal expansion section through the ventilation duct and the heat-conducting alloy section. The thermal expansion section expands due to heat, reducing the diameter of the diameter-changing section. The ventilation duct relies on external equipment such as fans for continuous ventilation. When air flows to the reduced diameter-changing section, the wind speed accelerates, the static pressure decreases, and a local low-pressure turbulent zone is formed. Large dust particles in the smoke generated by the fire will be difficult to change direction with the airflow due to inertia, and will be captured and collected by impacting the pipe wall surface. They will then enter the dust collection hopper through the dust outlet and be collected. At the same time, the low-pressure zone promotes the collision and aggregation of small particles into larger particles, improving the capture of harmful particles in the smoke. When a fire spreads to or occurs at the diameter change section, the dust exhaust port will expand further, causing the elastic pipe wall to deform further, thereby sealing the ventilation duct, blocking the spread of fire, and isolating the passage of smoke. This structure requires no external power source, is simple in structure, easy to maintain, has low maintenance costs, low dependence on electrical equipment, is not prone to failure, and has strong stability. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the present invention;

[0018] Figure 2 This is a schematic diagram of the state at medium temperature in this invention;

[0019] Figure 3 This is a schematic diagram of the state of the present invention at high temperature;

[0020] Figure 4 This is a schematic diagram of another embodiment of the present invention;

[0021] Figure 5 This is a schematic diagram of the state during heating according to another embodiment of the present invention;

[0022] Figure 6 This is a schematic diagram of the cross-sectional structure of the present invention.

[0023] In the diagram: 1. Ventilation duct, 2. Variable diameter section, 21. Thermally conductive alloy section, 22. Thermal expansion section, 23. Elastic pipe wall, 24. Expansion material layer, 25. Memory alloy spring, 3. Dust outlet, 4. Dust collection hopper, 5. Bending section, 6. Dust collection box, 7. Drive motor, 8. Atomizing nozzle, 9. Elastic dust filter, 10. Fixing rod, 11. Slider, 12. Hinge rod, 13. Heating component, 14. Dust concentration sensor. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Please see Figure 1-6 The present invention provides a technical solution: a structure for preventing the spread of fire smoke in underground local ventilation, including a ventilation duct 1 for ventilating underground chambers, equipment chambers, safety chambers, etc. The inner surface of the ventilation duct 1 is provided with at least one section of variable diameter 2, which can be located near a place where fire is likely to occur.

[0026] The variable diameter section 2 includes an elastic tube wall 23 disposed inside the ventilation duct 1 and a heat-conducting alloy section 21 disposed outside the ventilation duct 1. The elastic tube wall 23 can be made of materials with good elasticity and high temperature resistance, such as borosilicate rubber or silicone rubber, or metal corrugated pipes such as 310S stainless steel corrugated pipes, which can be deformed and have good recovery properties.

[0027] When using metal corrugated pipes, a layer of thermally expandable silicone can be applied to the surface of the metal corrugated pipe. This silicone can expand and deform when heated, allowing multiple metal corrugated pipes to expand and fill the gaps through the thermally expandable silicone layer, thereby improving the barrier effect against flue gas.

[0028] As a heat transfer medium in a fire, the thermally conductive alloy part 21 needs to achieve rapid thermal response and high-temperature structural stability. It can be made of AA6061-T6 aluminum alloy or C18200 chromium zirconium copper alloy with high thermal conductivity.

[0029] A cavity is provided between the elastic tube wall 23 and the heat-conducting alloy part 21. A thermal expansion part 22 is installed within the cavity. At medium temperatures (80-150℃), the thermal expansion part 22 expands and stretches the elastic tube wall 23, reducing the diameter of the pipe at the reducing section 2. In the early stages of a fire, heat is transferred to the thermal expansion part 22 through the ventilation duct 1 and the heat-conducting alloy part 21, causing the thermal expansion part 22 to expand and reduce the diameter of the reducing section 2. Specifically, after the thermal expansion part 22 expands, it, in conjunction with the elastic tube wall 23, forms a shape with a small inner diameter in the middle and large inner diameters on both sides. At this time, the inner diameter of the reducing section gradually decreases and then gradually increases along the airflow direction. The ventilation duct 1 relies on external equipment such as fans for continuous ventilation. When the air flows to the reduced-diameter section 2, the wind speed accelerates, the static pressure decreases, and a local low-pressure turbulent zone is formed. Large dust particles in the smoke generated by the fire are difficult to change direction with the airflow due to inertia and are captured and collected by impacting the surface of the tube wall. At the same time, the reduced diameter of the reducing section 2 can also limit the oxygen supply to the fire area and suppress the fire.

[0030] A dust discharge port 3 is provided on the lower inner side of the ventilation duct 1 near the diameter change section 2. A dust collection hopper 4 is provided below the dust discharge port 3. The dust discharge port 3 is located on the downstream side of the ventilation duct 1 in the direction of air flow relative to the diameter change section 2. Large dust particles are more likely to enter the dust collection hopper 4 through the dust discharge port 3 and be collected when the wind speed decreases and the static pressure increases in the low-pressure turbulent flow zone. At the same time, the low-pressure zone will promote the collision and aggregation of small particles into larger particles, thereby improving the capture of harmful particles in the flue gas.

[0031] When the fire spreads to the diameter change section 2 or a fire occurs at the diameter change section 2, the thermal expansion section 22 will expand further, causing the elastic pipe wall 23 to deform further. When the thermal expansion section 22 is at a high temperature (≥200℃), it will expand further, causing the elastic pipe wall 23 to deform further, sealing the ventilation duct 1, blocking the spread of the fire, and isolating the passage of smoke.

[0032] Three to eight sets of reducing sections 2 are arranged on the inner circumference of the ventilation duct 1. The radial cross-sectional shape of the expanding section 2 is fan-shaped. When the multiple sets of reducing sections 2 expand at high temperature, they can surround each other to form a complete circle and seal the duct. The axial positions of the multiple sets of reducing sections 2 can be staggered so that the multiple sets of reducing sections 2 can squeeze each other to seal the duct when they expand at high temperature.

[0033] This structure requires no external energy source, is simple in design, easy to maintain, has low maintenance costs, low dependence on electrical equipment, is not prone to failure, and is highly stable.

[0034] In a preferred embodiment, the thermal expansion part 22 is an expansion material layer 24, such as a paraffin-graphite composite phase change material or expanded graphite. The expansion temperature of expanded graphite is 200°C, and its volume expands by 150-300 times at high temperatures. When the fire spreads to the diameter change part 2, it can completely seal the ventilation duct 1.

[0035] In a preferred embodiment, the ventilation duct 1 is provided with an upwardly bent section 5, which is located above the dust outlet 3. By providing the upwardly bent section 5, dust, smoke and other particles passing through the reduced diameter section 2 can more easily impact the duct wall and fall into the dust collection hopper 4.

[0036] Alternatively, the lower inner wall of the bend 5 is inclined toward the diameter-changing section 2, with the inclination direction being upward. This increases the resistance to the upward flow of dust, smoke, and other particles that impact the pipe wall at that location, resulting in a better anti-spreading effect for dust and smoke.

[0037] In a preferred embodiment, the dust collection hopper 4 is shaped like a sieve, with a large opening at the top connecting to the dust collection port 3 and a small opening at the bottom, facilitating dust collection. A piezoelectric ceramic vibrator can be installed on the upper inner wall of the dust collection hopper 4 to periodically generate 20kHz high-frequency vibrations to prevent caking.

[0038] The dust collection hopper 4 is connected to a dust discharge box 6 below. A dust outlet is provided on one side of the lower part of the dust discharge box 6. A drive motor 7 is installed on the outer surface of the other side of the lower part of the dust discharge box 6. The output shaft of the drive motor 7 passes through the inner side of the lower part of the dust discharge box 6 and is connected to the rotating shaft through a coupling. A spiral pusher plate is installed on the rotating shaft. The drive motor 7 drives the spiral pusher plate to rotate through the rotating shaft, which can push the dust accumulated at the bottom of the dust discharge box 6 out of the dust outlet to the outside, thereby centrally treating it.

[0039] The spiral pusher plate is made of tungsten carbide coated steel plate, with surface hardness increased to HRC65 or higher, and its service life can be extended by 3 times.

[0040] In a preferred embodiment, a plurality of atomizing nozzles 8 are uniformly arranged on the upper inner side of the ventilation duct 1. The nozzles 8 can be located in the middle of the variable diameter section 2 or on the downstream side of the variable diameter section 2, above the dust discharge port 3. The nozzles 8 are connected to external water pumps, water storage equipment, water delivery pipes, etc. Atomized droplets (such as water or chemical solutions) are sprayed into the high-speed airflow through the nozzles 8. After the droplets collide with dust, smoke and other particles, the dust is adsorbed through inertial collision, diffusion and interception mechanisms to form a "liquid-solid mixture". When the mixture flows into the expansion section, the flow velocity decreases and the static pressure recovers. The droplets carry the dust and settle at the dust discharge port 3, which can further enhance the dust removal effect.

[0041] Furthermore, nozzle 8 employs dual-fluid atomization technology, mixing compressed air and water for spraying to avoid clogging. Simultaneously, a nanobubble generator produces bubbles with a diameter of <100nm, enhancing the PM2.5 capture efficiency.

[0042] In a preferred embodiment, the thermal expansion portion 22 is a shape memory alloy spring 25, which can be selected from CuZnAl shape memory alloy or NiTi-based shape memory alloy, preferably NiTi-based shape memory alloy, which has strong corrosion resistance, good high-temperature stability, and is suitable for high-temperature areas underground, while also exhibiting high shape recovery strain. The shape memory alloy spring 25 deforms the thermal expansion portion 22 at high temperatures, and in conjunction with the elastic pipe wall 23, it can quickly restore the shape and inner diameter of the variable diameter portion 2 inside the ventilation duct 1 after the fire is extinguished, achieving normal ventilation and ensuring airflow within the chamber.

[0043] Optionally, multiple diameter-changing sections 2 can be installed in the ventilation duct 1. The thermal expansion sections 22 at each diameter-changing section 2 can be the same or different. For example, in areas prone to fire or where it is easy to maintain and replace the thermal expansion sections 22, expanded graphite can be installed. Its excellent expansion capacity can seal the duct, and it can quickly expand and deform to seal the ventilation duct in the event of a fire, thus preventing the spread of the fire. In areas where fires are not likely to occur or where maintenance and replacement are difficult, or where the dust concentration is high, a recoverable expansion material such as a shape memory alloy spring 25 can be used. By changing the pipe diameter, it can quickly remove dust when the dust concentration is high or when a large amount of smoke is generated by a fire, thus reducing the damage caused by smoke. After the dust concentration decreases or the fire is extinguished, it can return to its original state and maintain normal ventilation.

[0044] In locations where only dust removal is required, a reducing section 2 can be installed at the bottom. This allows dust passing through the reduced-diameter section 2 to more easily enter the low-pressure turbulent zone at the dust outlet 3, and thus more easily enter the dust collection hopper 4, thereby improving the dust removal effect.

[0045] In a preferred embodiment, a cavity is provided inside the thermally conductive alloy part 21, and a heating component 13 is provided inside the cavity. The heating component 13 can be a commonly used resistance heating wire or a plate heater, etc. The shape memory alloy spring 25 is deformed by the active heating of the heating component 13, which, together with the elastic tube wall 23, reduces the inner diameter of the variable diameter part 2. When the dust concentration in the ventilation duct 1 is high and continued ventilation will affect the air quality in the chamber, the dust removal effect at the variable diameter part 2 is improved, which is conducive to improving the air quality in the well. At the same time, when the dust concentration is low, the pipe diameter is restored, the ventilation volume is increased, and the ventilation quality in the well is maintained.

[0046] Optionally, PM2.5 / PM10 online monitoring instruments or dust concentration sensors 14 can be installed before and after the diameter change section of the ventilation duct 1 to provide real-time feedback data to an external PLC controller. A fuzzy PID control algorithm is used to dynamically adjust the water spray volume of the atomizing nozzle 8 and the heating temperature of the heating component 13 according to the dust concentration change rate.

[0047] An optional technical solution is that an elastic dust filter 9 is provided on the inner side of the ventilation duct 1. The elastic dust filter 9 can be selected as high-strength polyester fiber or PTFE (polytetrafluoroethylene) membrane filter material. The elastic dust filter 9 is located on the upstream side of the variable diameter part 2 in the air flow direction on the inner side of the ventilation duct 1, and is used to filter dust and the like.

[0048] Optionally, a fixing rod 10 is provided in the middle of the elastic dust filter 9, and the two ends of the fixing rod 10 are fixedly disposed on the inner surface of the ventilation duct 1; a slider 11 is provided at the end of the elastic dust filter 9, and a groove corresponding to the slider 11 is opened on the inner surface of the ventilation duct 1, in which the slider 11 slides. The elastic dust filter 9 has a small pore size (1-10 μm), which can filter larger dust particles. When a large number of dust particles accumulate on the elastic dust filter 9, its pores become blocked, the overall wind resistance of the elastic dust filter 9 increases, and it deforms. Since the middle of the elastic dust filter 9 is fixed by the fixing rod 10, and the ends (at least the upper and lower ends) slide in the groove through the slider 11, it will move towards the diameter-changing part 2 after the wind resistance increases. A pressure sensor, piezoelectric switch, or proximity switch is installed on the inner wall of the chute near the variable diameter section 2 or on the side of the slider 11 facing the variable diameter section 2. When there is a lot of dust on the elastic dust filter 9, the overall wind resistance increases, and the slider 11 tends to move towards the variable diameter section 2, the pressure sensor, piezoelectric switch, or proximity switch is triggered, thereby opening the heating component 13. This causes the shape memory alloy spring 25 inside the variable diameter section 2 to deform due to heat, and the elastic tube wall 23 to expand, reducing the inner diameter of the variable diameter section 2. This improves the dust removal effect at that location and enables automatic dust removal when the dust concentration is high.

[0049] The heating element 13, drive motor 7, water pump, fan, and pressure sensor, piezoelectric switch, or proximity switch are all electrically connected to an external controller and powered by an external power supply. The controller is preferably a commonly used microcontroller or PLC controller, such as an Arduino series microcontroller or a Siemens S7 series PLC controller. The controller controls all the above electronic components using methods commonly used in the prior art.

[0050] Furthermore, a hinge rod 12 is hinged to one side of the slider 11 facing the variable diameter section 2. The other end of the hinge rod 12 is hinged to the side surface of the elastic tube wall 23. When the variable diameter section 2 expands, the elastic tube wall 23 bulges towards the center of the pipe, causing the hinge rod 12 to move. The slider 11 can be pushed away from the variable diameter section 2 by the hinge rod 12. The middle part of the elastic dust filter 9 is fixed by the fixing rod 10, so that its end is deformed away from the variable diameter section 2. The elastic dust filter 9 is stretched and deformed, and its aperture is enlarged. Large dust particles that are blocked in the aperture enter the variable diameter section where the pipe diameter is reduced through the elastic dust filter 9. Under the condition of increased wind speed and decreased static pressure, it combines with the water mist sprayed by the atomizing nozzle 8, and then enters the position of the bend 5 and collides with the inclined tube wall. After that, it falls from the dust outlet 3 into the dust collection hopper to complete the collection of dust. After a period of time (5-15 minutes), the heating component 13 is turned off, and the hinge rod 12 drives the slider 11 back to its original position, restoring the elastic dust filter 9 to its original state. This allows for automatic cleaning and collection of dust on the elastic dust filter 9, maintaining the filtration effect of dust in the pipe and thus improving the air quality inside the chamber.

[0051] The controller, heating component 13, drive motor 7, water pump, fan, pressure sensor or piezoelectric switch or proximity switch used in this application are all commonly used electronic components in the prior art. Their specific structure, working principle, control method and circuit connection are all known technologies and will not be described in detail here.

[0052] All parts not disclosed in this invention are prior art, and their specific structures, materials, and working principles will not be described in detail. Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A fire smoke propagation preventing structure for local ventilation in a mine, comprising a ventilation duct (1), characterized in that: The inner side surface of the ventilation duct (1) is provided with a variable diameter part (2), the variable diameter part (2) comprises an elastic pipe wall (23) arranged on the inner side of the ventilation duct (1) and a heat-conducting alloy part (21) arranged on the outer side of the ventilation duct (1), a cavity is arranged between the elastic pipe wall (23) and the heat-conducting alloy part (21), a heat expansion part (22) is arranged in the cavity, the heat expansion part (22) expands to support the elastic pipe wall (23) at medium temperature, reduces the pipe diameter at the variable diameter part (2), and cooperates with the elastic pipe wall (23) to form a shape with small intermediate inner diameter and large two-side inner diameter, at this time, the inner diameter of the variable diameter part (2) gradually decreases and then gradually increases along the air flow direction, when the air flows to the reduced variable diameter part (2), the wind speed increases and the static pressure decreases, forming a local low-pressure turbulent flow area, promoting the collision and aggregation of micro-particles into larger particles. A dust discharge port (3) is arranged on the inner side of the ventilation duct (1) near the variable diameter part (2), a dust collecting hopper (4) is arranged on the lower side of the dust discharge port (3), the dust discharge port (3) is arranged on the downstream side of the variable diameter part (2) in the air flow direction on the inner side of the ventilation duct (1), the wind speed of the large particle dust decreases and the static pressure increases after passing through the low-pressure turbulent flow area, and the large particle dust is collected in the dust collecting hopper (4) through the dust discharge port (3); an upwardly bent bending part (5) is arranged on the ventilation duct (1), the bending part (5) is arranged above the dust discharge port (3); the heat expansion part (22) further expands at high temperature to further deform the elastic pipe wall (23) to close the ventilation duct (1).

2. The mine local ventilation fire smoke spread prevention structure according to claim 1, characterized in that: The heat expansion part (22) is an expansion material layer (24).

3. The mine fire-prevention and smoke propagation prevention structure with local ventilation according to claim 1, characterized in that: The dust collecting hopper (4) is in the shape of a tower, a dust discharge box (6) is communicated below the dust collecting hopper (4), a dust outlet is arranged on one side of the lower part of the dust discharge box (6), a driving motor (7) is mounted on the outer side surface of the other side of the lower part of the dust discharge box (6), the output shaft of the driving motor (7) penetrates into the inner side of the lower part of the dust discharge box (6) and is connected with a rotating shaft through a shaft coupling, and a spiral pushing plate is mounted on the rotating shaft.

4. The mine fire-prevention and smoke propagation prevention structure with local ventilation according to claim 1, characterized in that: A plurality of atomizing nozzles (8) are uniformly arranged on the inner side of the upper part of the ventilation duct (1).

5. The mine fire-prevention and smoke propagation prevention structure with local ventilation according to claim 1, characterized in that: The heat expansion part (22) is a memory alloy spring (25).

6. A downhole localised ventilation fire-smoke spread prevention structure according to claim 5, characterised in that: A cavity is formed in the inner side of the heat-conducting alloy part (21), and a heating assembly (13) is arranged in the cavity.

7. A downhole localised ventilation fire-smoke spread prevention structure according to claim 6, characterised in that: An elastic dust filter screen (9) is arranged on the inner side of the ventilation duct (1), and the elastic dust filter screen (9) is arranged on the upstream side of the variable diameter part (2) in the air flow direction on the inner side of the ventilation duct (1).

8. A downhole localised ventilation fire-smoke spread prevention structure according to claim 7, characterised in that: A fixed rod (10) is arranged on the middle part of the elastic dust filter screen (9), and both ends of the fixed rod (10) are fixedly arranged on the inner side surface of the ventilation duct (1); a sliding block (11) is arranged on the end part of the elastic dust filter screen (9), and a sliding groove corresponding to the sliding block (11) is formed in the inner side surface of the ventilation duct (1), and the sliding block (11) is slidingly arranged in the sliding groove.

9. A downhole localised ventilation fire-smoke spread prevention structure according to claim 8, characterised in that: A hinged rod (12) is hingedly arranged on one side surface of the sliding block (11) facing the variable diameter part (2), and the other end of the hinged rod (12) is hingedly connected with the side surface of the elastic pipe wall (23).

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