Pressure-difference self-adaptive anti-backflow self-cleaning reaming and slotting jet device and control method

Abstract

The application relates to the technical field of fluidizers, and discloses a differential pressure self-adaptive backflow prevention self-cleaning reaming and slotting fluidizer and a control method, which solve the problem of nozzle head and internal flow channel blockage caused by coal powder slurry backflow in a hole after the existing fluidizer is stopped. The fluidizer comprises a connecting joint, a fluidizer main body and a nozzle assembly, a differential pressure self-adaptive opening and closing mechanism is arranged in the flow guide channel of the fluidizer main body, the mechanism comprises a guide sleeve, a valve seat, a sliding valve core and a return spring, the valve core and the valve seat cooperatively form a backflow prevention sealing mechanism, when high-pressure water supply is performed, the forward water pressure overcomes the elastic force to push the valve core to move forward to open the flow channel and perform normal jetting operation; when the water supply is stopped, the valve core is reset backward under the joint action of the elastic force of the return spring and the reverse fluid pressure in the hole, and tightly presses the valve seat to realize automatic blockage and sealing, the coal powder slurry backflow is blocked, the cumbersome steps of frequent tripping and cleaning are eliminated, and the construction continuity and the service life of the equipment are improved.

Description

Technical Field

[0001] This application relates to the field of jet ejector technology, specifically to a differential pressure adaptive anti-backflow self-cleaning orifice-expanding and slotting jet ejector and its control method. Background Technology

[0002] In coal mine underground gas control, erosion control, and coal seam permeability enhancement projects, high-pressure water jet reaming and slotting technology is commonly used. This technology utilizes a reaming and slotting jetter connected to the front end of the drill pipe. High-pressure water from a high-pressure pump station flows through the jetter's internal channels and nozzles to form a high-speed jet, eroding and fracturing the coal seam wall to increase coal seam permeability and improve the effectiveness of subsequent hydraulic fracturing. Current reaming and slotting jetters mainly consist of a connector, a main body, and a nozzle; the internal channels are open and continuous during operation.

[0003] This open-channel structure has certain limitations in actual construction operations. When the reaming operation is completed in a phase or the pump is temporarily stopped, the high-pressure water pressure inside the ejector drops rapidly, while a large amount of high-concentration slurry composed of accumulated water, broken coal powder, and rock powder remains inside the borehole. At this time, the residual fluid pressure inside the borehole is higher than the pressure inside the ejector. Driven by this reverse pressure difference, the coal powder slurry inside the borehole will flow back into the internal channel of the ejector along the nozzle.

[0004] Since the nozzle orifice diameter of the jet injector is usually only one to three millimeters and the internal space is narrow, fine coal powder that flows in back into the nozzle is prone to deposit and accumulate at the nozzle outlet and the corner of the internal flow channel, which in turn causes flow channel blockage.

[0005] If the equipment becomes internally blocked, restarting the high-pressure pump will result in reduced jet pressure, jet deflection, or even complete failure to produce water, making it impossible to continue the borehole reaming operation. In this situation, on-site personnel must stop work, completely remove the long drill rod from the borehole, disassemble and clear the blockage in the jet injector before drilling can resume. This reactive drill-removal and blockage-clearing operation consumes a significant amount of auxiliary time, reducing the continuity and efficiency of deep hole reaming and trenching operations.

[0006] Meanwhile, frequent backflow of coal dust particles can also cause abrasive wear on internal equipment components, shortening their service life. Although some existing equipment attempts to introduce conventional one-way valve structures to prevent backflow, conventional valve bodies are difficult to adapt to the high abrasion, high solids content slurry, and frequent start-stop conditions in underground coal mines, and are prone to jamming failure and poor sealing.

[0007] Therefore, this application proposes a differential pressure adaptive anti-backflow self-cleaning orifice-expanding and slotting jet injector and control method to overcome the shortcomings of the prior art. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this application provides a differential pressure adaptive anti-backflow self-cleaning borehole-expanding and slotting jet and its control method. This solves the problem that in existing borehole-expanding and slotting jets, residual water and coal powder slurry in the borehole can easily backflow after the pump stops, causing blockage of the nozzle head and internal flow channels, requiring frequent drilling and cleaning, and causing equipment wear.

[0009] To achieve the above objectives, this application provides the following technical solution:

[0010] A differential pressure adaptive anti-backflow self-cleaning orifice-expanding grooving jet ejector includes a connecting joint and an ejector body with a through-flow channel, the connecting joint being fixedly connected to the tail end of the ejector body; it also includes: The differential pressure adaptive opening and closing mechanism is set in the flow guide channel. The differential pressure adaptive opening and closing mechanism includes a guide sleeve and a valve seat fixedly connected to the inner wall of the flow guide channel, a valve core slidably connected in the guide sleeve, and a return spring sleeved in the flow guide channel with its two ends abutting against the guide sleeve and the valve core respectively. The anti-backflow sealing mechanism is composed of a valve core and a valve seat. The end of the valve core facing the valve seat has a sealing surface, and the area where the sealing surface and the valve seat surface are in contact is the anti-backflow sealing area. The nozzle assembly includes a nozzle seat fixedly connected to the front end of the ejector body, and a nozzle head fixedly connected to the nozzle seat with its front end face open to form a nozzle outlet.

[0011] Preferably, the valve core includes a front head and a rod connected to the rear side of the front head, the sealing surface is located on the front head, the return spring is sleeved on the outside of the rod, and the end of the rod away from the front head is slidably inserted into the inner cavity of the guide sleeve.

[0012] Preferably, the ejector body has a guide hole on the inner wall between the valve seat and the nozzle seat, and the guide channel is connected to the inside of the nozzle seat through the guide hole; further, there are multiple guide holes, and the multiple guide holes are distributed in an array structure.

[0013] Preferably, the sealing surface has a conical surface structure, and the inner wall of the valve seat has a conical concave surface structure, with the sealing surface and the inner wall of the valve seat having the same and compatible taper.

[0014] Preferably, the outer wall surface of the tail end of the connector is provided with a threaded structure, which is configured to be fixedly connected to the external drill rod thread, and the other end of the drill rod is connected to the external high-pressure water supply system pipeline.

[0015] Preferably, the nozzle head has an internal flow channel, and the cross-sectional area of ​​the internal flow channel gradually decreases along the direction toward the nozzle outlet.

[0016] Preferably, the central axis of the connecting joint, the central axis of the ejector body, the sliding central axis of the valve core, and the central axis of the nozzle head are on the same straight line.

[0017] Preferably, the return spring is a helical compression spring, and the inner wall of the guide sleeve protrudes inward to form an annular stepped surface, with one end of the return spring abutting against the annular stepped surface.

[0018] This application also provides a control method for the above-mentioned differential pressure adaptive anti-backflow self-cleaning orifice-expanding and slotting jet, including the following steps: The jetting device, connected to the drill rod, is inserted entirely into a pre-drilled hole inside the outer coal seam. Start the high-pressure water supply system, and the high-pressure water flows through the drill rod and connecting joint into the guide channel of the jet ejector body; The positive pressure of the high-pressure water in the flow channel overcomes the elastic force of the reset spring in the differential pressure adaptive opening and closing mechanism. The high-pressure water pushes the valve core, which is slidably connected in the guide sleeve, to move forward, causing the sealing surface on the valve core to disengage from the valve seat, and the anti-backflow sealing mechanism is in the conducting and opening state. High-pressure water flows into the nozzle seat of the nozzle assembly along the guide channel and is ejected outward at high speed from the nozzle outlet at the front end of the nozzle head; The high-speed water jet ejected from the nozzle outlet directly impacts the coal seam on the borehole wall, eroding, cutting and breaking the original coal body, forming a borehole expansion cavity around the borehole, and the water flow directly washes the guide channel and its internal area when water is supplied and sprayed. When the high-pressure water supply system stops supplying water, the positive water pressure in the flow channel disappears, and the valve core slides back to its original position under the elastic force of the return spring. The sealing surface is then pressed against the valve seat, and the anti-backflow sealing mechanism closes. The water and coal powder slurry formed by the mixed water flow of the crushed coal in the borehole and the expansion slot flowed in reverse from the nozzle outlet, and generated reverse backflow pressure on the front end face of the valve core. Under the combined action of reverse flow pressure and return spring force, the valve core is pressed tightly against the valve seat, forming a compressed seal in the check seal area.

[0019] This application provides a differential pressure adaptive anti-backflow self-cleaning orifice-expanding grooving jet and its control method. It has the following beneficial effects: 1. Preventing backflow of pulverized coal slurry fundamentally solves the blockage problem. This application achieves automatic control of the flow channel by setting a differential pressure adaptive opening and closing mechanism consisting of a valve core, valve seat, and return spring inside the ejector body. After the water supply stops, the return spring drives the valve core to reset, and at the same time, the reverse pressure in the borehole will further press the sealing surface of the valve core tightly against the valve seat, forming a reliable blockage and preventing the slurry containing a large number of pulverized coal particles in the borehole from flowing back into the flow channel and nozzle assembly. This solves the technical problem of nozzle and flow channel blockage caused by backflow in the prior art.

[0020] 2. Improved construction continuity and reduced auxiliary operation time and labor intensity. By avoiding blockage caused by backflow, the jet ejector of this application does not require frequent manual cleaning of the drill rod after completing one hole enlargement operation and stopping the pump, as is the case with existing technologies. This allows the hole enlargement and trenching operations to be carried out continuously and stably, reducing the time spent on auxiliary operations such as rod removal, blockage clearing, and resetting. The effect is more obvious in long-distance drilling construction, thereby improving the overall construction efficiency and reducing the labor intensity of on-site personnel.

[0021] 3. The anti-backflow sealing mechanism of this application not only prevents blockage but, more importantly, prevents highly abrasive coal dust particles from entering the ejector, reducing the erosion and wear on key components such as the valve core sealing surface, valve seat, guide hole, and nozzle head internal flow channel caused by the high-pressure water flow. Simultaneously, the opening and closing mechanism is a purely mechanical structure, independent of external electrical control systems, and its simple structure results in a low failure rate under the complex conditions of high humidity and high dust in underground coal mines, thus improving the overall operational reliability and service life of the device. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure of this application; Figure 2 This is a cross-sectional view of the differential pressure adaptive opening and closing mechanism of this application; Figure 3 This is a schematic diagram illustrating the anti-backflow working principle of this application; Figure 4 This is a schematic diagram of the field application status of this application.

[0023] Among them, 1. Connecting joint; 2. Jet ejector body; 31. Valve core; 32. Valve seat; 33. Guide sleeve; 34. Return spring; 35. Sealing surface; 36. Guide hole; 4. Anti-backflow sealing mechanism; 51. Nozzle seat; 52. Nozzle head; 6. Guide channel; 9. Drill hole; 10. Coal body; 11. Accumulated water and coal powder slurry; 12. Nozzle outlet; 13. Anti-backflow sealing area; 14. Drill rod; 15. High-pressure water supply system; 16. Enlarged hole cavity; 17. Coal seam. Detailed Implementation

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

[0025] Please see Figure 1-4This application provides a differential pressure adaptive anti-backflow self-cleaning reamer with enlarged orifice and groove, including a connecting joint 1 and a jet body 2 with an internal through-flow channel 6. This through-flow channel design can reduce the pressure loss along the flow path during high-pressure fluid transmission. The connecting joint 1 is fixedly connected to the tail end of the jet body 2, providing a stable support foundation for the entire device and a high-pressure sealed water inlet.

[0026] It also includes: a differential pressure adaptive opening and closing mechanism, which serves as the core control unit for achieving fully automatic flow channel opening and closing. It is located in the flow channel 6, utilizing the internal space of the main body without increasing the volume of external equipment, thus ensuring the compactness of the overall shape of the jet injector.

[0027] The differential pressure adaptive opening and closing mechanism includes a guide sleeve 33 and a valve seat 32 fixedly connected to the inner wall of the flow channel 6, a valve core 31 slidably connected in the guide sleeve 33, and a return spring 34 sleeved in the flow channel 6 with its two ends abutting against the guide sleeve 33 and the valve core 31 respectively. The above components together constitute a purely mechanical pressure response module that can operate sensitively and stably in harsh downhole conditions without relying on any external electronic sensors or electric drive.

[0028] The backflow prevention sealing mechanism 4 is crucial in quickly establishing a safety barrier to block harmful external impurities when water supply is interrupted. It consists of a valve core 31 and a valve seat 32. The linear sliding displacement of the valve core 31 converts friction into a strong end-face contact clamping force. The end of the valve core 31 facing the valve seat 32 has a sealing surface 35, which has undergone high-precision wear-resistant hardening treatment and can resist the scouring and erosion of high-pressure sand-containing water flow for a long time. The contact area between the sealing surface 35 and the surface of the valve seat 32 is a backflow prevention sealing area 13, which forms a tight, seamless barrier, cutting off the flow path of accumulated water and coal powder slurry 11 backflow into the equipment.

[0029] The nozzle assembly, as the final execution end that converts the hydrostatic pressure of high-pressure fluid into high-speed cutting kinetic energy, includes a nozzle seat 51 fixedly connected to the front end of the jet body 2. It not only plays a secondary rectification role for the water flowing out of the internal channel, but also provides a sturdy mounting base for the front end components, and a nozzle head 52 fixedly connected to the nozzle seat 51 with its front end face open to form the nozzle outlet 12. This further accelerates the fluid through the narrow aperture, forming a concentrated water jet with erosion capability.

[0030] The valve core 31 includes a front head and a rod connected to the rear side of the front head. This streamlined stepped design, which is larger at the front and smaller at the back, helps to significantly reduce the local eddies and fluid resistance generated when the water flows around the valve core 31. The sealing surface 35 is located on the front head, giving it a wider force-bearing area. It can directly meet the backflow pressure from the reverse flow of fluid from the borehole 9 to enhance the self-sealing effect. The return spring 34 is sleeved on the outside of the rod. Through the rigid internal support of the middle rod, it prevents the return spring 34 from radially bending or becoming unstable and stuck during high-frequency compression and rebound cycles. The end of the rod away from the front head is slidably inserted into the internal cavity of the guide sleeve 33. The inner wall of the guide sleeve 33 limits the rod, ensuring that the valve core 31 always maintains a stable axial linear motion trajectory when subjected to severe water flow impact.

[0031] The ejector body 2 has flow guide holes 36 on its inner wall between the valve seat 32 and the nozzle seat 51. These flow guide holes 36 form a dedicated channel for the high-pressure main body after the valve core 31 is opened, and achieve self-cleaning of surface deposits when the fluid passes through at high speed. The flow guide channel 6 is connected to the inside of the nozzle seat 51 through the flow guide holes 36, so that the high-pressure water flow that crosses the sealing surface 35 can flow smoothly into the front spray area without obstruction, eliminating dead corners in the internal water flow circulation.

[0032] The number of guide holes 36 is multiple, which increases the overall flow cross-sectional area to meet the stringent power requirements of high flow rate and high pressure jet for deep hole excavation operations in coal mines. The multiple guide holes 36 are distributed in an array structure. This uniform and symmetrical geometric arrangement ensures the balance and stability of the hydraulic pressure field inside the main body and avoids lateral damage to internal components due to eccentric load.

[0033] The sealing surface 35 has a conical structure, which utilizes the wedge-shaped pressure increase principle of the inclined surface of the cone to amplify the limited axial thrust of the return spring 34 into a sealing clamping force perpendicular to the contact surface. The inner wall of the valve seat 32 has a conical concave surface structure. The inclination angle of this concave surface is calculated and processed to map and match the contour features of the valve core 31 and the sealing surface 35. The sealing surface 35 and the inner wall of the valve seat 32 have the same taper and are compatible, thereby ensuring that the two can form a full contact and tight seal from surface to surface when the system is closed, eliminating tiny leakage gaps.

[0034] The outer wall surface of the tail end of the connecting joint 1 is provided with a threaded structure, which adopts wear-resistant pipe threads that meet the high strength standards for mining, so as to facilitate quick and reliable connection operations for underground workers in harsh environments. The threaded structure is set to be fixedly connected to the external drill rod 14, ensuring the structural rigidity of the tool when transmitting the rotation torque of the drilling rig, while maintaining the high pressure watertightness inside the system. The other end of the drill rod 14 is connected to the external high pressure water supply system 15 pipeline, thereby establishing a continuous and pressurized fluid power source for the entire hole enlargement and slotting equipment.

[0035] The nozzle head 52 has an internal flow channel. The internal flow channel curve has been optimized through in-depth simulation of fluid dynamics to reduce the frictional energy loss between the fluid and the wall. The cross-sectional area of ​​the internal flow channel gradually decreases along the direction towards the nozzle outlet 12. This convergent structure continuously and strongly compresses the water flowing through it, so that the water bursts out with jet speed and rock-breaking kinetic energy the instant it leaves the outlet.

[0036] The central axis of the connecting joint 1, the central axis of the ejector body 2, the sliding central axis of the valve core 31, and the central axis of the nozzle head 52 are all on the same straight line. This multi-axis concentric linear overall layout design can not only guide the high-speed jet to pass smoothly and avoid internal fluid deviation, but also eliminate the overall equipment vibration caused by asymmetric water flow excitation and improve the targeting accuracy of jet orifice expansion.

[0037] The return spring 34 is a helical compression spring made of high-strength, fatigue-resistant alloy spring steel, ensuring that its elastic performance does not decrease after tens of millions of high-frequency opening and closing cycles. The inner wall of the guide sleeve 33 protrudes inward to form an annular stepped surface. This stepped surface serves as a sturdy base, not only enhancing the structural rigidity of the guide sleeve 33 itself, but also providing a flat and stable force-bearing end face for the return spring 34. One end of the return spring 34 abuts against the annular stepped surface, while the other end continuously acts on the sliding valve core 31, ensuring that the equipment can output a constant and reliable return thrust each time the water pressure is reduced, so as to quickly complete the backflow prevention and sealing action.

[0038] Please see Figure 1-4 The control method for a differential pressure adaptive anti-backflow self-cleaning orifice-expanding and slotting jet nozzle provided in this application includes the following steps: The jetting device, connected to the drill rod 14, is inserted into the pre-drilled hole 9 inside the outer coal seam 17. During this stage, the equipment is in a pressureless and static state, which completes the initial spatial positioning and delivery for subsequent hydraulic cutting operations.

[0039] The high-pressure water supply system 15 is started, and the main pump station on the ground or underground begins to output working fluid with high kinetic energy. The high-pressure water flows through the drill pipe 14 and the connecting joint 1 into the guide channel 6 of the jet body 2. The fluid quickly builds pressure in the closed pipeline and fills the entire internal space, ready to trigger the mechanical response of the core mechanism.

[0040] The positive pressure of the high-pressure water in the flow channel 6 overcomes the elastic force of the return spring 34 in the differential pressure adaptive opening and closing mechanism. At this time, the forward thrust generated by the water force is much greater than the spring preload and the frictional resistance of the moving parts. The high-pressure water pushes the valve core 31, which is slidably connected in the guide sleeve 33, to move forward. The valve core 31 makes a smooth axial linear movement under the limit of the guide sleeve 33, avoiding the deflection caused by the water flow impact. This causes the sealing surface 35 on the valve core 31 to separate from the valve seat 32, breaking the original blocking state and allowing the internal fluid path to be completely unobstructed. The anti-backflow sealing mechanism 4 is in the open state. At this time, the equipment automatically switches from the sealing defense mode to the high-flow full-speed jet working mode.

[0041] High-pressure water flows into the nozzle seat 51 of the nozzle assembly through the guide channel 6. The fluid undergoes preliminary rectification and convergence here, and the flow becomes more stable and orderly. It is then ejected outward at high speed from the nozzle outlet 12 at the front end of the nozzle head 52. Potential energy is converted into kinetic energy at this moment, forming a slender water column with penetrating power.

[0042] The high-speed water jet ejected from nozzle outlet 12 directly impacts the coal seam 17 on the borehole wall of borehole 9. The water hammer effect and shear force act instantly on the coal-rock interface, eroding, cutting and breaking the original coal body 10, destroying the original structural stress of the coal body 10, causing it to peel off and disintegrate over a large area, forming a borehole expansion cavity 16 around borehole 9, increasing the pressure relief space and permeability of coal seam 17. Moreover, when water is supplied and sprayed, the water flow directly washes the guide channel 6 and its internal area. This accompanying self-cleaning effect removes fine particles that may be attached to the inner wall, maintaining the long-term cleanliness of the flow channel.

[0043] When the high-pressure water supply system 15 stops supplying water, the hole expansion operation is temporarily completed or an emergency shutdown occurs, the power source of the system is instantly cut off, the positive water pressure in the flow channel 6 disappears, and the key hydraulic support that maintains the valve core 31 in the open state rapidly decreases to zero. Under the elastic force of the return spring 34, the valve core 31 slides back to reset. The compressed return spring 34 quickly releases the accumulated elastic potential energy, driving the valve core 31 to return quickly. The sealing surface 35 fits against the valve seat 32, and the two make rigid contact instantly, initially cutting off the exchange channel of internal and external fluids. The anti-backflow sealing mechanism 4 closes, and the equipment accurately returns to the initial defense and blocking state by relying on the pure mechanical structure.

[0044] The water and coal powder slurry 11 formed by the mixed water flow of the crushed coal body 10 in the borehole 9 and the enlarged cavity 16 flowed back from the nozzle outlet 12. Due to the high residual hydrostatic pressure in the external space, the high-concentration suspended slurry attempted to flow back along the original path and generated reverse backflow pressure on the front end face of the valve core 31. This destructive water pressure that attempted to invade became an external auxiliary force to enhance the internal sealing performance.

[0045] Under the combined action of reverse backflow pressure and the elastic force of the return spring 34, the superposition of internal and external double locking forces improves the pressure resistance and leakage resistance of the mechanism. The valve core 31 presses tightly against the valve seat 32, increasing the squeezing friction between the contact surfaces, eliminating tiny leakage gaps, and forming a tight seal in the check seal area 13, building a solid barrier and achieving the anti-blocking and flow-stopping effect without manual intervention.

Claims

1. A differential pressure adaptive anti-backflow self-cleaning orifice-expanding grooving jet ejector, comprising a connecting joint (1) and an ejector body (2) with an internally connected flow guide channel (6), wherein the connecting joint (1) is fixedly connected to the tail end of the ejector body (2); characterized in that, Also includes: The differential pressure adaptive opening and closing mechanism is disposed in the flow channel (6). The differential pressure adaptive opening and closing mechanism includes a guide sleeve (33) and a valve seat (32) fixedly connected to the inner wall of the flow channel (6), a valve core (31) slidably connected in the guide sleeve (33), and a return spring (34) sleeved in the flow channel (6) and whose two ends respectively abut against the guide sleeve (33) and the valve core (31). The anti-backflow sealing mechanism (4) is formed by the valve core (31) and the valve seat (32). The valve core (31) has a sealing surface (35) at one end facing the valve seat (32). The anti-backflow sealing area (13) is where the sealing surface (35) and the surface of the valve seat (32) are in contact. The nozzle assembly includes a nozzle seat (51) fixedly connected to the front end of the jet body (2), and a nozzle head (52) fixedly connected to the nozzle seat (51) and having its front end face open to form a nozzle outlet (12).

2. The differential pressure adaptive anti-backflow self-cleaning orifice-expanding and slotting jet jet according to claim 1, characterized in that: The valve core (31) includes a front end head and a rod body connected to the rear side of the front end head. The sealing surface (35) is located on the front end head. The return spring (34) is sleeved on the outside of the rod body. The end of the rod body away from the front end head is slidably inserted into the internal cavity of the guide sleeve (33).

3. The differential pressure adaptive anti-backflow self-cleaning orifice-expanding and slotting jet jet according to claim 2, characterized in that: The jet ejector body (2) has a guide hole (36) on the inner wall between the valve seat (32) and the nozzle seat (51), and the guide channel (6) is connected to the inside of the nozzle seat (51) through the guide hole (36).

4. The differential pressure adaptive anti-backflow self-cleaning orifice-expanding and slotting jet jet according to claim 3, characterized in that: The number of the flow guide holes (36) is multiple, and the multiple flow guide holes (36) are distributed in an array structure.

5. The differential pressure adaptive anti-backflow self-cleaning orifice-expanding and slotting jet jet according to claim 1, characterized in that: The sealing surface (35) has a conical surface structure, and the inner wall of the valve seat (32) has a conical concave surface structure. The sealing surface (35) and the inner wall of the valve seat (32) have the same taper and are compatible.

6. The differential pressure adaptive anti-backflow self-cleaning orifice-expanding and slotting jet jet according to claim 1, characterized in that: The outer wall surface of the tail end of the connecting joint (1) is provided with a threaded structure, which is configured to be threadedly fixedly connected to the external drill rod (14), and the other end of the drill rod (14) is connected to the external high-pressure water supply system (15) pipeline.

7. The differential pressure adaptive anti-backflow self-cleaning orifice-expanding and slotting jet jet according to claim 1, characterized in that: The nozzle head (52) has an internal flow channel, and the cross-sectional area of ​​the internal flow channel gradually decreases along the direction toward the nozzle outlet (12).

8. The differential pressure adaptive anti-backflow self-cleaning orifice-expanding and slotting jet jet according to claim 1, characterized in that: The central axis of the connecting joint (1), the central axis of the ejector body (2), the sliding central axis of the valve core (31), and the central axis of the nozzle head (52) are on the same straight line.

9. The differential pressure adaptive anti-backflow self-cleaning orifice-expanding and slotting jet jet according to claim 1, characterized in that: The reset spring (34) is a helical compression spring. The inner wall of the guide sleeve (33) protrudes inward to form an annular step surface. One end of the reset spring (34) abuts against the annular step surface.

10. A control method for the differential pressure adaptive anti-backflow self-cleaning orifice-expanding and slotting jet jet according to any one of claims 1 to 9, characterized in that, Includes the following steps: The jetting device connected to the drill rod (14) is inserted as a whole into the pre-drilled hole (9) inside the outer coal seam (17); Start the high-pressure water supply system (15), and the high-pressure water flows through the drill rod (14) and the connecting joint (1) into the guide channel (6) of the jet body (2); The positive pressure of the high-pressure water in the flow channel (6) overcomes the elastic force of the reset spring (34) in the differential pressure adaptive opening and closing mechanism. The high-pressure water pushes the valve core (31) slidably connected in the guide sleeve (33) to move forward, so that the sealing surface (35) on the valve core (31) is separated from the valve seat (32), and the anti-backflow sealing mechanism (4) is in the conducting open state. High-pressure water flows into the nozzle seat (51) of the nozzle assembly through the guide channel (6) and is ejected outward at high speed from the nozzle outlet (12) at the front end of the nozzle head (52); The high-speed water jet ejected from the nozzle outlet (12) directly impacts the coal seam (17) on the borehole wall (9), eroding, cutting and breaking the original coal body (10), forming an enlarged cavity (16) around the borehole (9), and the water flow directly washes the guide channel (6) and its internal area when water is supplied and sprayed. The high-pressure water supply system (15) stops supplying water, the positive water pressure in the flow channel (6) disappears, the valve core (31) slides back to reset under the elastic force of the reset spring (34), the sealing surface (35) is attached to the valve seat (32), and the anti-backflow sealing mechanism (4) is closed. The accumulated water and coal powder slurry (11) formed by the mixed water flow of the broken coal body (10) in the borehole (9) and the expansion groove (16) flowed in the opposite direction from the nozzle outlet (12) and generated a reverse backflow pressure on the front end face of the valve core (31). Under the combined action of the reverse backflow pressure and the elastic force of the reset spring (34), the valve core (31) presses backward tightly onto the valve seat (32), forming a tight seal in the check seal area (13).

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