Coal seam pulse fracturing anti-reflection gas extraction device capable of being dynamically regulated and controlled

Abstract

The invention discloses a coal seam pulse fracturing anti-reflection gas extraction device capable of being dynamically regulated and controlled. The coal seam pulse fracturing anti-reflection gas extraction device comprises a sleeve which can be arranged on the ground surface and extend to a coal seam area; a pulse generator and an extraction device are arranged on the two sides of the ground above the drill hole, and a controller is arranged between the pulse generator and the extraction device. A nested valve body is vertically assembled in the sleeve in the axial direction of the sleeve, and a packer is arranged outside the nested valve body. The outer side wall of the packer and the inner side wall of the casing pipe slide in a sealed mode. A set of variable nozzles are arranged on the outer circumferential side wall of the nested valve body in the radial direction of the nested valve body. According to the pulse fracturing system with the intelligent regulation and control function, the limitation that traditional pulse parameters cannot be adjusted after being preset is broken through, and pulse parameter combination is dynamically optimized through real-time feedback of the sensing probe; a variable nozzle structure is further adopted, the cross sectional area of the nozzle is dynamically adjusted according to different coal seams, and underground fast and accurate energy regulation and efficient utilization are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of coal rock permeability enhancement and gas extraction, and specifically relates to a coal seam pulse fracturing permeability enhancement and gas extraction device that can be dynamically controlled. Background Art

[0002] Efficient coal seam gas extraction is key to ensuring safe coal mine production and realizing gas resource utilization. However, most coal seams in my country have low permeability and high adsorption, which severely restricts gas extraction efficiency. Currently, the most commonly used gas extraction methods include hydraulic fracturing, deep-hole blasting, hydraulic slotting, and protective layer mining. However, these technologies have significant limitations: hydraulic fracturing can easily cause water locks, blocking gas migration pathways; deep-hole blasting makes explosive delivery difficult; hydraulic slotting is less effective in soft coal seams and is not suitable for downward drilling due to slag removal issues; and protective layer mining is not suitable for single-seam mining.

[0003] While existing pulse fracturing technology can induce fatigue damage in the coal mass through periodic load disturbances, increasing fracture density, it generally lacks dynamic control capabilities: fracturing parameters are fixed during operation and cannot be adaptively optimized based on real-time geological responses downhole. This results in low energy utilization and a limited permeability range. Furthermore, existing hydraulic pulse fracturing and permeability enhancement devices are independent of gas extraction devices. Operations must first be completed with the hydraulic pulse fracturing and permeability enhancement device, and then the extraction device must be switched to perform extraction. This fragmented process is inefficient and time-consuming.

[0004] Even though some equipment adopts an integrated design, the nozzle compatible with the extraction device still needs to be replaced after the coal seam is fractured and permeable. The replacement process not only leads to the risk of gas leakage, but also causes process interruption, significantly extending the operation time.

[0005] Therefore, it is necessary to provide a coal seam pulse fracturing and permeability enhancement gas extraction device that can be dynamically controlled to solve the problems raised in the above background technology. Summary of the Invention

[0006] To achieve the above objectives, the present invention provides the following technical solutions: a dynamically adjustable coal seam pulse fracturing and permeability enhancement gas extraction device, comprising a casing that can be placed on the surface and extended into the coal seam area; a pulse generator and an extraction device are provided on both sides of the ground above the borehole, and a controller is provided between the pulse generator and the extraction device; A nested valve body is vertically installed inside the casing along its axial direction, and a packer is arranged outside the nested valve body; the outer wall of the packer slides in a sealed manner with the inner wall of the casing; The outer circumferential side wall of the nested valve body is provided with a group of variable nozzles along its radial direction.

[0007] Furthermore, preferably, the casing is provided with extraction holes corresponding to the coal seam area along the circumferential radial direction.

[0008] Furthermore, preferably, a drive assembly is provided outside the nested valve body, and the drive assembly is fixedly connected to the packer; a distance meter is also provided outside the nested valve body.

[0009] Furthermore, as a preference, the nested valve body comprises an outer fixed valve sleeve, a middle rotary valve core and an inner drive shaft which are arranged in sequence from the outside to the inside, the outer fixed valve sleeve is fixed to the inner drive shaft, the middle rotary valve core is sealingly and rotatably connected between the outer fixed valve sleeve and the inner drive shaft, the outer fixed valve sleeve is provided with a group of extraction ports corresponding to the variable nozzles along the circumferential radial direction, and each of the variable nozzles is sealed and connected to the extraction port.

[0010] Furthermore, as a preference, water injection ports and gas collection ports are respectively provided on both sides of the upper end surface of the outer fixed valve sleeve along its axial direction; the water injection port is connected to the pulse generator through a high-pressure water pipe, and the gas collection port is connected to the extraction device through an extraction pipe; a gas flow rate-concentration sensor is provided on the outside of the extraction pipe near the borehole mouth; positioning holes are symmetrically provided on both sides of the water injection port and the gas collection port on the inner side of the outer fixed valve sleeve.

[0011] Furthermore, preferably, a sensor probe is provided along the radial direction of the outer circumferential side wall of the outer fixed valve sleeve.

[0012] Furthermore, as a preference, an L-shaped annular channel is opened inside the middle-layer rotary valve core; a through hole is opened in the radial direction of the outer circumferential side wall of the middle-layer rotary valve core; spring plungers are symmetrically arranged on both sides of the through hole; and a gear ring is fixedly arranged on the inner side of the lower end of the middle-layer rotary valve core.

[0013] Furthermore, preferably, a first drive motor and a drive gear are coaxially arranged from top to bottom inside the inner drive shaft, and a first reducer is arranged between the first drive motor and the drive gear; a group of planetary gears are distributed between the drive gear and the ring gear; each of the planetary gears is meshed with the drive gear and the ring gear; a shaft is fixed on each of the planetary gears, and the other end of the shaft is rotatably connected to a fixed frame embedded and fixed inside the inner drive shaft.

[0014] Further, as a preference, the variable nozzle includes a nozzle body and a nozzle head, one end of the nozzle body is fixedly connected to the outer fixed valve sleeve, and the other end thereof is fixedly connected to the nozzle head; an air collecting hole is vertically opened at the upper end of the nozzle body, and a filter is installed inside the air collecting hole; a group of ventilation channels are vertically opened inside the nozzle body along the circumference of the chamber below the collection hole; a one-way valve is coaxially arranged near one end of the collection hole in each ventilation channel; a second drive motor is offset inside the nozzle body, and the output shaft of the second drive motor is fixedly connected to the transmission shaft; a transmission screw is axially arranged inside the nozzle body, and a conical valve is provided on the transmission screw near one end of the nozzle head, and the transmission screw is meshed with the transmission shaft; the transmission screw and the transmission shaft are both sealed and arranged in the nozzle body.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The pulse fracturing system of the present invention has an intelligent control function, which breaks through the limitation that traditional pulse parameters cannot be adjusted after being preset. It dynamically optimizes the pulse parameter combination through real-time feedback from the sensor probe.

[0016] The present invention adopts a highly integrated, quickly disassembled downhole nested valve body, which solves the problems of traditional fracturing tools such as single function, bulky size, and difficulty in replacement and maintenance.

[0017] The present invention adopts a variable nozzle structure to dynamically adjust the nozzle cross-sectional area according to different coal seams, thereby realizing rapid and accurate energy regulation and efficient utilization underground; the variable nozzle has the dual functions of hydraulic pulse fracturing and gas extraction, and can directly switch to gas extraction operations without replacing the nozzle after hydraulic pulse fracturing to increase the permeability of the coal seam; this design not only ensures the continuity of the process and significantly saves operation time, but also effectively prevents gas leakage and comprehensively improves extraction efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic structural diagram of the nested valve body of the present invention; Figure 3 A half-sectional view of the structure of the nested valve body of the present invention; Figure 4 This is a schematic structural diagram of the middle-layer rotary valve core of the present invention; Figure 5 Schematic diagram of the structure of the spring plunger in the present invention; Figure 6 Schematic diagram of the structure of the adjustable nozzle in the present invention; Figure: 1, coal seam area; 2, borehole; 3, high-pressure water pump; 4, pulse generator; 5, extraction device; 6, controller; 7, casing; 71, extraction hole; 8, nested valve body; 81, inner drive shaft; 811, water injection port; 812, gas collection port; 813, extraction port; 82, middle rotary valve core; 821, through hole; 822, L-shaped annular channel; 83, outer fixed valve sleeve; 84, first drive motor; 85, first reducer; 86, drive gear; 87 , planetary gear; 88, fixed frame; 89, shaft; 9, variable nozzle; 91, nozzle body; 92, nozzle head; 93, one-way valve; 94, air collecting hole; 95, filter; 96, second drive motor; 97, ventilation channel; 98, transmission shaft; 99, transmission screw; 910, conical valve; 10, packer; 11, high-pressure water pipe; 12, extraction pipe; 13, spring plunger; 131, ball; 132, compression spring; 133, plunger; 14, ring gear. DETAILED DESCRIPTION

[0019] See also Figures 1-6 In an embodiment of the present invention, a dynamically adjustable coal seam pulse fracturing and permeability enhancement gas extraction device includes a casing 7 that can be placed on the surface and extended to the coal seam area 1; a pulse generator 4 and an extraction device 5 are provided on both sides of the ground above a borehole 2, and a controller 6 is provided between the pulse generator 4 and the extraction device 5; A nested valve body 8 is vertically installed inside the casing 7 along its axial direction, and a packer 10 is provided outside the nested valve body 8; the outer wall of the packer 10 slides in a sealed manner with the inner wall of the casing 7; A group of variable nozzles 9 are provided along the radial direction of the outer circumferential side wall of the nested valve body 8 .

[0020] In this embodiment, the casing 7 is provided with extraction holes 71 corresponding to the coal seam area 1 along the circumferential radial direction, and each extraction hole 71 is arranged in a one-to-one correspondence with the nozzle of the variable nozzle 9; the hydraulic pulse is used to fracture and increase the permeability of the coal seam area 1 through the extraction hole 71, and the gas enters the variable nozzle 9 through the extraction hole 71.

[0021] As a preferred embodiment, a drive assembly is provided outside the nested valve body 8, and the drive assembly is fixedly connected to the packer 10; a distance meter is also provided outside the nested valve body 8. The distance meter is used to measure the distance between itself and the packer 10, and the drive assembly is used to drive the packer 10 to move along the axial direction of the casing 7 toward the bottom of the borehole 2 when the distance value measured by the distance meter is less than the preset distance value; it should be noted that the preset distance value can be selected according to actual conditions and needs; specifically, when the variable nozzle 9 is blocked by accumulated coal dust, the negative pressure suction force decreases, and the packer 10 is driven by gas to move upwards of the borehole 2. When the distance meter detects that the distance between itself and the packer 10 is less than the preset distance value, the drive assembly drives the packer 10 to move along the axial direction of the casing 7 toward the bottom of the borehole 2 to achieve the effect of instantaneous pressurization, thereby clearing the coal dust in the variable nozzle 9.

[0022] In this embodiment, the nested valve body 8 includes an outer fixed valve sleeve 83, a middle rotating valve core 82 and an inner driving shaft 81 arranged in sequence from the outside to the inside. The outer fixed valve sleeve 83 is fixed to the inner driving shaft 81, and the middle rotating valve core 82 is sealed and rotatably connected between the outer fixed valve sleeve 83 and the inner driving shaft 81. The outer fixed valve sleeve 83 is radially opened with a group of extraction ports 813 corresponding to the variable nozzles 9 along the circumference, and each variable nozzle 9 is sealed and connected to the extraction port 813.

[0023] In this embodiment, a water injection port 811 and a gas collection port 812 are respectively provided on both sides of the upper end surface of the outer fixed valve sleeve 83 along its axial direction. The water injection port 811 is connected to the pulse generator 4 through a high-pressure water pipe 11, and the gas collection port 812 is connected to the extraction device 5 through an extraction pipe 12; a gas flow rate-concentration sensor is provided on the outside of the extraction pipe 12 near the borehole mouth; positioning holes are symmetrically provided on both sides of the water injection port 811 and the gas collection port 812 on the inner side of the outer fixed valve sleeve 83, and the positioning holes are used to position the spring plunger 13.

[0024] In this embodiment, sensor probes are provided along the radial direction of the outer circumferential side wall of the outer fixed valve sleeve 83 , and the sensor probes are used to monitor downhole pressure, acoustic emission signals, microseismic signals and temperature.

[0025] As a preferred embodiment, the middle rotary valve core 82 defines an L-shaped annular channel 822. A through hole 821 is radially defined along the outer circumferential sidewall of the middle rotary valve core 82. Hydraulic pulses enter the L-shaped annular channel 822 through the water injection port 811 and are then delivered to the coal seam 1 through the variable nozzle 9 for fracturing and permeability enhancement. Spring plungers 13 are symmetrically positioned on either side of the through hole 821. These spring plungers 13 serve to position the middle rotary valve core 82. Initially, the through hole 821 of the middle rotary valve core 82 is connected to the water injection port. A gear ring 14 is fixedly mounted on the inner side of the lower end of the middle rotary valve core 82.

[0026] In this embodiment, a first drive motor 84 and a drive gear 86 are coaxially arranged from top to bottom inside the inner drive shaft 81, and a first reducer 85 is arranged between the first drive motor 84 and the drive gear 86; a group of planetary gears 87 are distributed between the drive gear 86 and the ring gear 14; each planetary gear 87 is meshed with the drive gear 86 and the ring gear 14; a shaft 89 is fixed on each planetary gear 87, and the other end of the shaft 89 is rotatably connected to a fixing frame 88 embedded and fixed inside the inner drive shaft 81. The first drive motor 84 drives the drive gear 86 to rotate through the first reducer 85. The planetary gears 87 engage with the drive gear 86 and the ring gear 14 to drive the ring gear 14 to rotate, thereby driving the middle layer rotary valve core 82 to rotate, and switching between hydraulic pulse fracturing and gas extraction. The variable nozzle 9 has the dual functions of hydraulic pulse fracturing and gas extraction. After hydraulic pulse fracturing and gas extraction in the coal seam area 1, it can be directly converted to gas extraction without replacing the nozzle. This design not only ensures the continuity of the process and significantly saves operation time, but also effectively prevents gas leakage and comprehensively improves extraction efficiency. The device can monitor the extraction status for a long time. If the extraction effect decreases significantly in the later stage, the controller can determine whether it is necessary to restart the pulse enhancement operation. When the pulse operation is restarted, the hydraulic pulse can clean the coal dust in the adjustable nozzle to prevent blockage during gas extraction.

[0027] In this embodiment, the variable nozzle 9 includes a nozzle body 91 and a nozzle head 92. One end of the nozzle body 91 is fixedly connected to the outer fixed valve sleeve 83, and the other end is fixedly connected to the nozzle head 92. A gas collecting hole 94 is vertically opened at the upper end of the nozzle body 91, and a filter 95 is installed inside the gas collecting hole 94. The filter 95 is used to filter the coal dust in the gas. A group of ventilation channels 97 are vertically opened inside the nozzle body 91 along the circumference of the chamber below the collection hole 94. A one-way valve 93 is coaxially arranged near one end of the collection hole 94 in each ventilation channel 97. The one-way valve 93 only allows gas to pass from top to bottom and blocks the hydraulic pulse. A second drive motor 96 is offset within the nozzle body 91, with its output shaft fixedly connected to a transmission shaft 98. A drive screw 99 is axially disposed within the nozzle body 91. A conical valve 910 is disposed at one end of the drive screw 99 near the nozzle head 92, and a drive screw 95 engages with the transmission shaft 94. Both the drive screw 99 and the transmission shaft 94 are sealed within the nozzle body 91. The controller 6 controls the operation of the second drive motor 99, driving the transmission shaft 94 to rotate. The transmission shaft 94, through engagement with the drive screw 99, converts its own rotational motion into axial movement of the drive screw 99, thereby driving the conical valve 96 to move horizontally.

[0028] Specifically, drilling and positioning: Drilling is carried out to the target coal seam 1 to locate the area requiring permeability enhancement.

[0029] Equipment installation: Insert the casing 7 into the borehole 2, lower the nested valve body 8 with the packer 10 into the target section, and connect the surface pulse generator 4, controller 6 and extraction device 5.

[0030] Initial parameter setting: Set the initial pulse parameters (frequency, pressure, etc.) and extraction parameters based on geological data and engineering experience.

[0031] Start fracturing and monitoring: Start the pulse generator 4, and the hydraulic pulse enters the nested valve body 8 through the high-pressure water pipe 11. The hydraulic pulse is transmitted to the target coal seam area 1 through the variable nozzle 9 to perform fracturing and permeability enhancement on the target coal seam area 1; the sensor probe monitors the downhole pressure, acoustic emission signal, microseismic signal and temperature in real time.

[0032] Dynamic Control: Controller 6 analyzes real-time data (fracture propagation morphology and pressure response characteristics) and automatically adjusts hydraulic pulse parameters based on the analysis results and pre-set optimization objectives. For example, it increases peak pressure when encountering hard coal and reduces frequency when cracks are rapidly expanding to prevent overextension. A one-way valve 93 interrupts the hydraulic pulse. The variable nozzle 9 dynamically adjusts its nozzle cross-sectional area based on the coal seam. Controller 6 controls the operation of the second drive motor 96, which rotates the drive shaft 98. The drive shaft 98, meshing with the drive screw 99, converts its rotational motion into axial movement, which in turn drives the conical valve 910 horizontally. When encountering hard and brittle coal seams, the conical valve 910 moves toward the nozzle, reducing the nozzle cross-sectional area, increasing the jet velocity, and enhancing rock breaking capability. When encountering broken and soft coal seams, the conical valve 910 moves away from the nozzle, increasing the nozzle cross-sectional area and increasing the fracture extension radius.

[0033] Pulse fracturing cycle: Multiple rounds of pulse action with different parameters are carried out to gradually optimize the permeability enhancement effect based on the control results.

[0034] Switching to Drainage: After achieving the fracturing and permeability enhancement target, the operating mode is manually switched to drainage mode. The controller 6 activates the first drive motor 84, which drives the drive gear 86. The planetary gears 87 mesh with the drive gear 86 and the ring gear 14, driving the ring gear 14 to rotate, thereby rotating the middle rotary valve core 82. Simultaneously, the compression spring 132 within the spring plunger 13 contracts, and the ball 131 retracts into the plunger 133. When the middle rotary valve core 82 rotates 180°, the first drive motor 84 stops. Simultaneously, the spring plunger 13 releases the compression spring 132, pushing the ball 131 into the positioning hole and locking the middle rotary valve core 82 in place. During the rotation of the middle rotary valve core 82, residual water in the L-shaped annular channel 822 flows out of the variable nozzle 9. A small amount of water remains in the L-shaped annular channel 822, which can absorb coal dust during gas drainage. The controller 6 controls the operation of the second drive motor 96, driving the transmission shaft 98 to rotate. The transmission shaft 98, through engagement with the transmission screw 99, converts its own rotational motion into axial movement of the transmission screw 99, thereby driving the conical valve 910 to move horizontally, driving the conical valve 910 to move toward the side close to the nozzle to seal the nozzle. The one-way valve 93 only allows gas to pass from top to bottom, and the gas enters the variable nozzle 9 through the ventilation channel 97. The flow rate-gas concentration sensor monitors the gas in the extraction pipe 12 in real time. The controller 6 dynamically adjusts the negative pressure of the extraction device according to the changes in gas flow rate and concentration, and increases the extraction negative pressure when the gas flow rate is low or the gas outflow is large. When a large gas outflow is detected, controller 6 controls the second drive motor 96 to operate, driving the drive shaft 98 to rotate. Drive shaft 98, through engagement with drive screw 99, converts its own rotational motion into axial movement of the drive screw 99, thereby driving conical valve 910 to move horizontally, moving it away from the nozzle, releasing the nozzle seal and allowing gas to enter the variable nozzle 9 simultaneously through the nozzle and vent channel 97. When the variable nozzle 9 is clogged with accumulated coal dust, the negative suction force decreases, and the packer 10 is driven by the gas upward toward the borehole 2. When the rangefinder detects that the distance between itself and the packer 10 is less than a preset distance, the drive assembly drives the packer 10 axially along the casing 7 toward the bottom of the borehole 2, achieving a transient pressurization effect and clearing the coal dust from the variable nozzle 9. If the extraction pipe 12 becomes clogged, backwash mode is activated, and cleaning fluid is reversely injected from the extraction pipe 12 into the L-shaped annular channel 822.

[0035] Long-term drainage and monitoring: The device can monitor the drainage status over time. If the drainage effect decreases significantly, the controller 6 can determine whether to restart the pulse permeability enhancement process. When the pulse process is restarted, the hydraulic pulse can clear the coal dust in the adjustable nozzle 9 to prevent blockage during gas drainage.

[0036] The above is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A dynamically adjustable coal seam pulse fracturing and permeability enhancement gas extraction device, characterized by: It includes a casing (7) that can be placed on the ground surface and extended to the coal seam area (1); a pulse generator (4) and an extraction device (5) are provided on both sides of the ground above the borehole (2); a controller (6) is provided between the pulse generator (4) and the extraction device (5); A nested valve body (8) is vertically mounted inside the casing (7) along its axial direction, and a packer (10) is arranged outside the nested valve body (8); the outer wall of the packer (10) slides in a sealed manner with the inner wall of the casing (7); A group of variable nozzles (9) are provided along the radial direction of the outer circumferential side wall of the nested valve body (8).

2. The dynamically controllable coal seam pulse fracturing and permeability enhancement gas extraction device according to claim 1, characterized in that: The casing (7) is provided with extraction holes (71) corresponding to the coal seam area (1) along the circumference radial direction.

3. The dynamically controllable coal seam pulse fracturing and permeability enhancement gas extraction device according to claim 1, characterized in that: A drive assembly is provided outside the nested valve body (8), and the drive assembly is fixedly connected to the packer (10); a distance meter is also provided outside the nested valve body (8).

4. The dynamically controllable coal seam pulse fracturing and permeability enhancement gas extraction device according to claim 1, characterized in that: The nested valve body (8) comprises an outer fixed valve sleeve (83), a middle rotating valve core (82) and an inner driving shaft (81) which are arranged in sequence from the outside to the inside. The outer fixed valve sleeve (83) is fixed to the inner driving shaft (81). The middle rotating valve core (82) is sealingly rotatably connected between the outer fixed valve sleeve (83) and the inner driving shaft (81). The outer fixed valve sleeve (83) is provided with a group of extraction ports (813) corresponding to the variable nozzles (9) along the circumference radial direction. Each of the variable nozzles (9) is sealed and connected to the extraction port (813).

5. The dynamically controllable coal seam pulse fracturing and permeability enhancement gas extraction device according to claim 4, characterized in that: A water injection port (811) and a gas collection port (812) are respectively provided on both sides of the upper end surface of the outer fixed valve sleeve (83) along its axial direction. The water injection port (811) is connected to the pulse generator (4) through a high-pressure water pipe (11), and the gas collection port (812) is connected to the extraction device (5) through an extraction pipe (12); a gas flow rate-concentration sensor is provided on the outside of the extraction pipe (12) near the borehole orifice; and positioning holes are symmetrically provided on both sides of the water injection port (811) and the gas collection port (812) inside the outer fixed valve sleeve (83).

6. The dynamically controllable coal seam pulse fracturing and permeability enhancement gas extraction device according to claim 5, characterized in that: A sensor probe is provided along the radial direction of the outer circumferential side wall of the outer fixed valve sleeve (83).

7. The dynamically controllable coal seam pulse fracturing and permeability enhancement gas extraction device according to claim 4, characterized in that: An L-shaped annular channel (822) is provided inside the middle rotary valve core (82); a through hole (821) is provided along the radial direction of the outer circumferential side wall of the middle rotary valve core (82); spring plungers (13) are symmetrically provided on both sides of the through hole (821); and a gear ring (14) is fixedly provided on the inner side of the lower end of the middle rotary valve core (82).

8. The dynamically controllable coal seam pulse fracturing and permeability enhancement gas extraction device according to claim 7, characterized in that: A first drive motor (84) and a drive gear (86) are coaxially arranged from top to bottom inside the inner drive shaft (81), and a first reducer (85) is arranged between the first drive motor (84) and the drive gear (86); a group of planetary gears (87) are distributed between the drive gear (86) and the ring gear (14); each of the planetary gears (87) is meshed with the drive gear (86) and the ring gear (14); a shaft (89) is fixed on each of the planetary gears (87), and the other end of the shaft (89) is rotatably connected to a fixing frame (88) embedded and fixed inside the inner drive shaft (81).

9. The dynamically controllable coal seam pulse fracturing and permeability enhancement gas extraction device according to claim 5, characterized in that: The variable nozzle (9) comprises a nozzle body (91) and a nozzle head (92), one end of the nozzle body (91) is fixedly connected to the outer fixed valve sleeve (83), and the other end thereof is fixedly connected to the nozzle head (92); an air collecting hole (94) is vertically opened at the upper end of the nozzle body (91), and a filter screen (95) is installed inside the air collecting hole (94); a group of ventilation channels (97) are vertically opened inside the nozzle body (91) along the circumference of the chamber below the collection hole (94); the inside of each ventilation channel (97) is close to the collection hole (94) A one-way valve (93) is coaxially arranged at one end; a second drive motor (96) is offset in the nozzle body (91), and the output shaft of the second drive motor (96) is fixedly connected to the transmission shaft (98); a transmission screw (99) is axially arranged inside the nozzle body (91), a conical valve (910) is arranged at one end of the transmission screw (99) close to the nozzle head (92), and the transmission screw (95) is meshed with the transmission shaft (94); the transmission screw (99) and the transmission shaft (94) are both sealed and arranged in the nozzle body (91).

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