A hydraulically sealed, speed-limited rotating hydraulic jet self-advancing drill bit

Abstract

The present invention relates to a hydraulically sealed, speed-limited rotating hydraulic jet self-feeding drill bit, which mainly includes a rotating drill bit, a rotating shaft, a shell and a base. The front end of the rotating shaft is connected to the rotating drill bit, and the rear part is placed in the shell. The rear end of the shell is connected to the base. The rotating head is arranged with a central spray hole, an intermediate spray hole and a rotating spray hole. The central spray hole is mainly used for breaking rocks; the intermediate spray holes are located on both sides of the central hole and have a certain opening angle, which are mainly used for breaking rocks and expanding holes to increase the area of ​​the drill hole; the rotating spray holes are located at both ends of the outer side of the rotating head and have a certain inclination angle and center distance, which are mainly used to generate rotational torque and expand holes. A speed-limiting hole is drilled in the middle of the rotating shaft, and four self-feeding holes are arranged on the base to provide self-feeding force for drilling, and further expand holes and discharge slag. The present invention uses hydraulic gap sealing, has a simple structure, small size, and has the characteristics of self-rotation, self-feeding and self-speed limiting.

Description

Technical Field

[0001] The invention relates to a hydraulic jet self-propelled drill bit, which is suitable for radial drilling of tree-shaped boreholes in coal seams with low air permeability in underground coal seams. Background Art

[0002] Coalbed methane is an efficient and clean energy source and one of the emerging industries with huge development space in the energy industry. As a green and low-carbon energy source, coalbed methane is an important supplement to conventional natural gas. my country is rich in coalbed methane resources. The development and utilization of coalbed methane is of great significance to promoting coal mine safety, filling the gap between natural gas supply and demand, and reducing carbon emissions. my country's coal mines are extending deeper year by year. The development of coalbed methane is characterized by low pressure, low permeability, and low saturation. The development is difficult, the coalbed methane extraction efficiency is low, and the safe and efficient mining of coalbed methane and coal is restricted. Traditional single drilling, dense drilling, hydraulic cutting and other technologies increase permeability unevenly, with a small range and low extraction efficiency. Therefore, some scholars have proposed the technology of tree-like drilling to increase the permeability of coal seams, that is, on the basis of the original gas extraction mother hole, a self-propelled rotary drill bit is used through a very small radius diverter to radially drill multiple tree-like branch boreholes in a unit of the coal seam perpendicular to the mother hole, so as to achieve the purpose of uniformly increasing the permeability of the coal seam and increasing the gas extraction volume.

[0003] The existing rotary drill bits are mainly used in the oil field. The radial horizontal well jet drill bits used in this field are applied to the tree-like drilling technology in coal mines. However, there are still the following problems: (1) The drill bit is large in size and has a large radius of curvature in the coal seam, which does not meet the requirements of the extremely small radius diverter in the coal seam, such as the "Self-propelled jet drill bit for radial horizontal wells" published in the Chinese patent document CN210858591U. (2) The existing rotary jet drill bits have a complex structure, are difficult to disassemble, and have a short service life, such as the "Self-rotating cavitation jet drill bit with micro-tooth for self-propelled water jet rock breaking drilling" published in the patent document CN114541973A. (3) Most of the existing rotary jet drill bits cannot limit the speed, and the rotary drill bits with speed limiting function are large in size and complex in structure, such as the "Magnetic Speed ​​Limiting Self-Rotating Sprinkler" published in patent document CN214210966U and the "Permanent Magnetic Turbine Braking Speed ​​Limiting and Non-Contact Gap Sealed High-Pressure Water Rotating Sprinkler" published in patent document CN202199453U; (4) The self-advancing force generated by the drill bit is small and cannot overcome the friction resistance in the borehole to advance forward, such as the "A Pulse Cavitation Porous Jet Nozzle" published in patent document CN102434102A. Summary of the invention

[0004] The purpose of the present invention is to improve the shortcomings of the existing self-propelled rotary water jet drill bit, and to provide a hydraulically sealed speed-limited rotary hydraulic jet self-propelled drill bit suitable for tree-shaped drilling, which reduces the size of the drill bit, simplifies the structure, increases the speed-limiting effect, and improves the self-propelling force.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A hydraulically sealed, speed-limited, rotating, hydraulic jet self-propelled drill bit comprises a rotating drill bit, a rotating shaft, a housing and a base. The rotating shaft capable of rotating therein is installed in the housing, the rear end of the housing is connected to the base via threads, and the rear end of the base can be connected to a high-pressure hose; the head of the rotating shaft is connected to the rotating drill bit via threads, and a fluid channel is provided inside the rotating shaft, which communicates with the fluid channels in the rotating drill bit and the base.

[0007] The middle part of the rotating shaft is located in the housing and is divided into a front section and a rear section, the front section is a cylinder, and the rear section is a conical cone with a taper of 3°~15°. An annular groove is arranged on the surface from the middle to the rear of the rotating shaft; and two speed limiting holes are arranged in the middle of a first annular groove on the conical cone, the center line of the speed limiting hole is perpendicular to the axis of the rotating shaft but does not intersect, and the center distance, that is, the vertical distance d2 between the axis of the speed limiting hole and the axis of the rotating shaft, is 1mm~4mm; there is a fluid channel in the middle of the rotating shaft, which is connected to the fluid channel in the rotating head and the fluid channel in the base.

[0008] A central nozzle is provided at the front end of the rotating head, the center line of the central nozzle is colinear with the axis of the rotating head, and intermediate nozzles are arranged on both sides of the central nozzle, the center lines of the two intermediate nozzles intersect with the axis of the rotating head to form an angle α, and are located in the same plane, α=15°~45°; two rotating nozzles are also provided on the rotating head, the plane where the center lines of the rotating nozzles are located is parallel to the plane where the axis is located and has a certain distance, this distance is the center distance d1, d1 is 3mm~10mm, and has a certain inclination angle β, β=15°~45°, the line connecting the outlets of the two rotating nozzles is perpendicular to the line connecting the outlets of the central nozzle and the intermediate nozzle; a cylindrical cavity is provided in the rotating head, the front end of the cavity (1) is connected to the central nozzle (27), the intermediate nozzle (26) and the rotating nozzle (28), and the rear end is connected to the rotating shaft flow channel.

[0009] In the above design, the couple generated by the two symmetrically distributed speed limiting holes is opposite to the torque generated by the two rotating holes on the rotating head, but the torque generated on the rotating shaft is smaller than the torque on the rotating head, thus playing a speed limiting role. When the fluid in the internal channel of the rotating shaft flows out through the speed limiting hole, the gap between the outside of the rotating shaft and the outer shell will be filled with fluid, and an annular water ring will be formed in the groove to play the role of a uniform gap liquid film and an annular liquid bearing.

[0010] Furthermore, the inside of the shell is a cavity similar to the outer contour of the rotating shaft, which is divided into a front cylindrical cavity and a truncated cone cavity. The length of the truncated cone cavity is longer than the length of the conical cone, so that the rotating shaft can move axially in the shell, and the front end is axially limited by the front end surface of the conical cone and the inner bottom surface of the truncated cone cavity at the front end, and the rear end surface of the conical cone is axially limited by the front end surface of the base at the rear end. That is, the conical cone in the middle of the rotating shaft is limited by the inner bottom in the shell and the front end surface of the base, so that the rotating shaft can only move axially between the two end surfaces.

[0011] Furthermore, a certain interval L is left between the rear of the rotating shaft and the bottom surface of the front cavity of the base, so that the fluid can flow into the gap between the rear end of the rotating shaft and the front end of the cylindrical cavity of the base to form a liquid film, L=2-3mm.

[0012] The above design, that is, the rear end face of the rotating shaft is not in direct contact with the bottom of the cylindrical cavity of the base, and there is a distance of 2~3mm between them. This distance is to allow the fluid to smoothly enter the gap between the rear end of the rotating shaft and the front end of the cylindrical cavity of the base to form a liquid film. When the rotating head drives the rotating shaft to rotate, it can be allowed to rotate between the gap liquid films, creating a low-damping environment, greatly reducing the torque required for the rotating head to rotate, and reducing the size of the drill bit. At the same time, the gap between the conical frustum and the shell will generate a backward force perpendicular to the area difference due to the liquid to balance the forward axial force, avoiding the rotating shaft from being stuck due to direct contact with the shell due to the forward axial force.

[0013] Furthermore, the surface of the housing is provided with two symmetrical leakage holes, and the center lines of the leakage holes are perpendicular to the axis of the housing. Preferably, the leakage holes are located near the rear end of the rotating shaft conical cone, so that the size of the rearward effect between the axial force and the conical cone gap can be dynamically adjusted by the size of the area of ​​the leakage holes blocked by the rear end of the rotating shaft conical cone, so that the front and rear end surfaces of the rotating shaft conical cone do not contact the housing and the base.

[0014] Furthermore, the base is cylindrical, with a front cavity at the front for accommodating the rear of the rotating shaft, and a fluid channel at the rear, the diameter of the fluid channel is the same as the diameter of the flow channel in the rotating shaft; four evenly arranged rear nozzles are opened at the rear end of the base, which form a certain angle γ with the axis of the base, and the γ is between 10° and 30°. The rear end of the base is connected to the high-pressure hose through a thread.

[0015] The overall length of the drill bit ranges from 60 mm to 140 mm, and the outer diameter ranges from 8 mm to 30 mm.

[0016] The advantages of the present invention include at least the following:

[0017] 1. The rotary drill bit is small in size, simple in structure, and each part is easy to disassemble.

[0018] 2. The drill bit is equipped with two middle nozzles with a certain opening angle. When jetting, it can produce radial tensile damage to the rock mass, which can expand the drilling area and improve the drilling efficiency.

[0019] 3. The rotating nozzle of this drill bit has a certain inclination angle, which generates a tangential destructive force on the rock mass while generating a rotating torque, effectively crushing the rock and expanding the drilling area.

[0020] 4. This drill bit generates a liquid film through the gap between the rotating shaft and the housing and the base to form a hydraulic intermittent seal. On the one hand, the hydraulic gap seal allows a certain amount of leakage. On the other hand, the gap liquid film allows the rotating shaft to rotate in the low-damping liquid film, reducing the friction torque of the rotating shaft, reducing the torque required for rotation, and improving the energy utilization rate of the water jet.

[0021] 5. The speed limiting hole arranged on the conical truncated cone of the rotating shaft of the drill bit provides a liquid film for the gap and plays a role in speed limiting.

[0022] 6. Four backward nozzles with a certain angle to the axis are axially arranged at the rear of the base of the drill bit, which provide self-advance force for the drill bit and play the role of slag removal and drilling hole trimming. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of a small-sized hydraulically sealed, speed-limited rotating hydraulic jet self-propelled drill bit for tree-shaped drilling of the present invention;

[0024] Figure 2 yes Figure 1 Left view of the middle rotating head;

[0025] Figure 3 yes Figure 2 A-direction view;

[0026] Figure 4 It is a front view of the rotating shaft of a small-sized hydraulically sealed, speed-limited rotating hydraulic jet self-propelled drill bit for tree-shaped drilling of the present invention;

[0027] Figure 5 yes Figure 4 BB section view;

[0028] Figure 6 It is a front view of the base of a small-sized hydraulically sealed, speed-limited rotating hydraulic jet self-propelled drill bit for tree-shaped drilling of the present invention;

[0029] Figure 7 yes Figure 6 CC section view;

[0030] Figure 8 yes Figure 6 Right view of .

[0031] Description of Figure Numbers:

[0032] 1. Cavity, 2. Rotating head, 3. Rotating shaft head, 4. Rotating shaft, 5. Inner bottom, 6. Front end of conical cone, 7. First annular groove, 8. Shell, 9. Gap between conical cone and shell, 10. Drain hole, 11. Gap between rear end of rotating shaft and base, 12. Rear of shell, 13. Base, 14. Rear nozzle, 15. Fluid channel in base, 16. Bottom of front cavity of base, 17. Rear end of rotating shaft, 18. Rear end of rotating shaft, 19. Front face of base, 20. Rear end of conical cone, 21. Conical cone, 22. Speed ​​limiting hole, 23. Annular groove, 24. Gap in front of rotating shaft, 25. Internal flow channel of rotating shaft, 26. Intermediate nozzle, 27. Center nozzle, 28. Rotating nozzle. DETAILED DESCRIPTION

[0033] The following is combined with Figures 1 to 8 The implementation method of the small-size hydraulic seal speed-limited rotating hydraulic jet self-propelled drill bit for tree-shaped drilling is further described as follows:

[0034] Combination Figures 1 to 8 As shown, a small-sized hydraulically sealed, speed-limited rotating hydraulic jet self-propelled drill bit for tree-shaped drilling provided in this embodiment includes a rotating head 2, a rotating shaft 4, a housing 8 and a base 13. The overall length of the drill bit ranges from 60 mm to 140 mm, and the outer diameter ranges from 8 mm to 30 mm.

[0035] The rotating shaft 4 is installed in the housing 8 and can rotate therein. The rear part 12 of the housing is connected to the base 13 through threads, and the rear end of the base can be connected to a high-pressure hose. The rotating shaft head 3 is connected to the rotating head 2 through threads, and the rotating shaft 4 is provided with a rotating shaft internal flow channel 25, which is connected to the rotating head cylindrical cavity 1 and the fluid channel 15 in the base.

[0036] The following is a detailed description of the specific structure of each part:

[0037] The rotating head 2 is provided with a central nozzle 27 in front. Figure 2 and Figure 3 As shown, the center line of the central nozzle 27 is colinear with the axis of the rotating head 2, and intermediate nozzles 26 are arranged on both sides of the central nozzle 27. The center lines of the two intermediate nozzles 26 intersect with the axis of the rotating head 2 to form a certain angle α and are in the same plane. Figure 2 As shown, the two intermediate nozzles 26 are located above and below the central nozzle 27, and there is an angle between the axis of the intermediate nozzle 26 and the axis of the central nozzle 27. Figure 3 In the equation, α=15°~45°.

[0038] The rotating head 2 is designed with two rotating nozzles 28 on the outside. The plane where the center line of the rotating nozzle is located is parallel to the plane where the axis is located and has a certain distance, which is the center distance d1, d1 = 3mm~10mm. The two rotating nozzles 28 have a certain inclination angle β, and the line connecting the outlets of the two rotating nozzles 28 is perpendicular to the line connecting the outlets of the center nozzle 27 and the middle nozzle 26. Figure 2 As shown, the rotating nozzle is located at the left and right outlets of the central nozzle and is in the same horizontal line as the central nozzle. The angle formed by the axis of the rotating nozzle 28 and the axis of the central nozzle 27 is β, β=15°~45°.

[0039] The rotating head 2 has a cylindrical cavity 1 in it, the front end of the cavity 1 is communicated with the central nozzle 27, the middle nozzle 26 and the rotating nozzle 28, and the rear end of the cavity 1 is communicated with the internal flow channel 25 of the rotating shaft.

[0040] The middle part of the rotating shaft 4 is located in the housing 8, and is divided into a front section and a rear section. The front section is the rotating shaft head 3, and the rear section is a conical truncated cone 21, and the taper range is 3° to 15°. The conical truncated cone 21 is limited by the inner bottom 5 in the housing 8 and the front end surface 19 of the base, so that the rotating shaft 4 can only move axially between the two end surfaces. Figure 1 shown.

[0041] The portion of the rotating shaft 4 located inside the housing 8 has annular grooves 23 evenly arranged on the surface, and the distance between the annular grooves 23 is between 3 and 8 mm. Among them, the depth of the first annular groove 7 at the front end of the conical truncated cone 21 is greater than the depth of other grooves on the surface, and two speed limiting holes 22 with axes perpendicular to the axis of the rotating shaft 4 and a certain center distance are symmetrically arranged in the middle of the first annular groove 7. The center line of the speed limiting hole 22 is perpendicular to the axis of the rotating shaft 4 but does not intersect, and the center distance or the vertical distance d2 between the axis of the speed limiting hole 22 and the axis of the rotating shaft 4 is 1 mm to 4 mm, such as Figure 4 and Figure 5. The couple generated by the two symmetrically distributed speed limiting holes 22 is opposite to the couple torque generated by the two rotating nozzles 28 on the rotating head 2, but the couple torque generated on the rotating shaft 4 is smaller than the couple torque on the rotating head 2, thereby playing a role in speed limiting. When the fluid in the internal flow channel 25 of the rotating shaft flows out through the speed limiting hole 22, the conical truncated cone 21 between the outside of the rotating shaft 4 and the shell 8 and the shell gap 9, the gap 11 between the rear end of the rotating shaft and the base, and the gap 24 at the front of the rotating shaft will be filled with fluid, and an annular water ring will be formed in the annular groove 23 to play the role of uniform gap liquid film and annular liquid bearing. In addition, the rear end face 17 of the rotating shaft is not in direct contact with the bottom 16 of the front cavity of the base, and there is a gap of 2mm~3mm between them. This distance is to allow the fluid to smoothly enter the rear end 18 of the rotating shaft and the gap 11 between the rear end of the rotating shaft and the base in the front cavity of the base to form a liquid film. When the rotating head 2 drives the rotating shaft 4 to rotate, it can be allowed to rotate between the uniform gap liquid film, creating a low-damping environment, greatly reducing the torque required for the rotation of the rotating head 2, and reducing the size of the drill bit. At the same time, the liquid in the gap 9 between the conical cone and the shell will generate a backward force perpendicular to the area difference between the two bottom surfaces of the conical cone 21 to balance the forward axial force, thereby preventing the rotating shaft 4 from being stuck due to direct contact with the shell 8 due to the forward axial force.

[0042] The rotating shaft 4 has an internal flow channel 25 which communicates with the cavity 1 and the fluid channel 15 in the base. The diameter of the internal flow channel 25 is between 3 mm and 10 mm, which is the same as the diameter of the fluid channel in the base 13 and the rotary drill bit.

[0043] The interior of the shell 8 is a cavity similar to the outer contour of the rotating shaft 4. The diameters of the front cylindrical and truncated cone shaped cavities are slightly larger than the diameters of the two parts of the rotating shaft 4, while the diameter of the cylindrical cavity of the rear part 12 of the shell is equal to the bottom diameter of the cavity of the conical cone 21. Two symmetrical leakage holes 10 with center lines perpendicular to the axis of the shell are designed on the surface of the shell 8. The leakage hole 10 is preferably located near the rear end 20 of the conical cone. The function is to dynamically adjust the axial force and the size of the backward force between the conical cone and the shell gap 9 by the size of the area of ​​the leakage hole 10 blocked by the rear end 20 of the conical cone, so that the rear end 20 of the conical cone and the front end 6 of the conical cone do not contact the shell 8 and the front end surface 19 of the base.

[0044] The base 13 is composed of two cylinders. Figure 6~Figure 8As shown, a front cavity of the base is formed in the cylinder at the front end, and the diameter of the front cavity of the base is larger than the outer diameter of the rear end 18 of the rotating shaft, and accommodates the rear end 18 of the rotating shaft. A fluid channel 15 in the base is formed in the cylinder at the rear end, and the diameter of the fluid channel 15 in the base is the same as the diameter of the internal flow channel 25 of the rotating shaft. The rear end of the base is also provided with four evenly arranged backward nozzles 14 that form a certain angle γ with the axis of the base, γ=10°~30°. The backward nozzle 14 provides self-advance force for drilling, and further expands the hole and discharges slag. The rear end of the base is designed with an external thread for connection with a high-pressure hose.

[0045] The following is a further description of the above drill bit structure in combination with the working principle:

[0046] When the high-pressure hose is connected to the rear end of the base 13, the pump station is started. At this time, high-pressure water will first be ejected from the four circumferentially arranged rear nozzles 14 on the base to generate self-propelling force. At the same time, the high-pressure water will enter the internal flow channel 25 of the rotating shaft and pass through the gap between the rotating shaft 4 and the base 13 to enter the gap 11 between the rotating shaft and the base to generate a liquid film. Due to the action of axial force, the front end 6 of the conical cone will directly contact the inner bottom 5 in the outer shell 8. At this time, the fluid will be ejected through the speed limiting hole 22 on the rotating shaft 4, part of which enters the gap 24 in the front of the rotating shaft, and the other part enters the gap 9 between the conical cone and the outer shell. The kinetic energy of the high-pressure water is converted into pressure energy in the gap, generating a backward force perpendicular to the area difference between the two bottom surfaces of the conical cone 21. In addition, at the beginning, the rear end face 20 of the conical cone does not completely block the leakage hole 10 on the outer shell 8, and the flow rate of high-pressure water flowing out from the gap 11 between the rear end of the rotating shaft and the base to the leakage hole 10 increases, and the axial force decreases. By reasonably designing the taper of the conical cone 21, the axial force and the backward force between the conical cone and the outer shell gap 9 can be balanced, so that the rotating shaft 4 rotates in the liquid film gap, greatly reducing the rotational friction torque.

[0047] If the backward axial force is too large, the rear end face 20 of the conical cone will be in direct contact with the front end face 19 of the base. At this time, the leakage hole 10 and the gap 9 between the conical cone and the outer shell are all connected, the leakage flow in the gap 9 between the conical cone and the outer shell increases, and the backward force in the gap decreases, which causes the rotating shaft 4 to lose contact with the base 13. Therefore, the rotating shaft 4 controls the axial force and the backward force in the gap 9 between the conical cone and the outer shell by blocking the area of ​​the leakage hole 10 with the rear end face 20 of the conical cone to dynamically adjust the position of the rotating shaft 4, so that it is always in a suspended state without contact with the outer shell 8 and the base 13, avoiding jamming and excessive rotational friction.

[0048] After high-pressure water enters the drill bit, since the internal flow channel 25 of the rotating shaft is connected to the cavity 1 in the rotating head, the high-pressure water jet is ejected through the nozzle on the rotating head 2, rotating and crushing the rock while drilling. Among them, the fluid ejected from the center hole is mainly used for rock breaking. The fluid ejected through the two middle nozzles 26 can produce radial tensile damage to the rock mass during the jet due to the middle nozzle 26 having a certain opening angle, which can expand the drilling area and improve the drilling efficiency. The water jetted through the rotating nozzle 28, due to the arrangement position and inclination angle of the rotating nozzle 28, generates a tangential destructive force on the rock mass while generating a rotating torque, effectively crushing the rock and expanding the drilling area.

[0049] The above description is only an illustrative specific implementation manner of the present invention and is not intended to limit the scope of the present invention. Modifications and changes to some technical features based on the technology and solutions disclosed in the present invention are all within the protection scope of the present invention.

Claims

1. A hydraulically sealed, speed-limited rotating hydraulic jet self-propelled drill bit, comprising a rotating head (2), a rotating shaft (4), a housing (8) and a base (13); the rotating shaft (4) is installed in the housing (8), and the rear portion (12) of the housing is connected to the base (13); the rotating shaft head (3) is connected to the rotating head (2), and the rear portion (18) of the rotating shaft is located in the front cavity of the base (13); the characteristics are: The middle of the rotating shaft (4) is located in the housing (8) and is divided into a front section and a rear section, the front section is a cylinder, and the rear section is a conical cone (21) with a taper of 3° to 15°; an annular groove is arranged on the surface from the middle to the rear of the rotating shaft (4); and at least two speed limiting holes (22) are arranged in the middle of a first annular groove (7) on the conical cone (21), the center line of the speed limiting hole (22) is perpendicular to the axis of the rotating shaft (4) but does not intersect, and the vertical distance d2 between the axis of the speed limiting hole and the axis of the rotating shaft is 1 mm to 4 mm; the middle of the rotating shaft (4) is provided with an internal flow channel (25) of the rotating shaft, which is communicated with the fluid channel in the rotating head and the fluid channel (15) in the base; A central nozzle (27) is provided at the front end of the rotating head (2), the center line of the central nozzle (27) is colinear with the axis of the rotating head (2), and intermediate nozzles (26) are arranged on both sides of the central nozzle (27), the center lines of the two intermediate nozzles (26) intersect with the axis of the rotating head (2) to form an angle α, and are located in the same plane, α=15°~45°; the rotating head is also provided with two rotating nozzles (28), the plane where the center lines of the rotating nozzles (28) are located is parallel to the axis of the rotating head The two planes are parallel and separated by a certain center distance d1, d1=3mm~10mm, and have a certain inclination angle β, β=15°~45°, and the line connecting the outlets of the two rotating nozzles (28) is perpendicular to the line connecting the outlets of the central nozzle (27) and the intermediate nozzle (26); the rotating head (2) has a cylindrical cavity (1), the front end of the cavity (1) is connected to the central nozzle (27), the intermediate nozzle (26) and the rotating nozzle (28), and the rear end is connected to the internal flow channel (25) of the rotating shaft; The couple generated by the two symmetrically distributed speed limiting holes (22) on the rotating shaft is opposite to the couple torque generated by the two rotating nozzles (28) on the rotating head, but the couple torque generated on the rotating shaft is smaller than the couple torque on the rotating head, which plays a role in speed limiting. At the same time, when the fluid in the internal channel of the rotating shaft flows out through the speed limiting holes, the gap between the outside of the rotating shaft and the outer shell is filled with fluid, and an annular water ring is formed in the annular groove to play the role of a uniform gap liquid film and an annular liquid bearing.

2. The hydraulically sealed, speed-controlled rotatable hydraulic jet self-advancing drill bit according to claim 1, characterized in that: The depth of the first annular groove (7) at the front end of the conical truncated cone (21) is greater than the depth of the other annular grooves, and the speed limiting hole (22) is arranged in the first annular groove (7).

3. The hydraulically sealed, speed-controlled rotatable hydraulic jet self-advancing drill bit according to claim 1, characterized in that: The second annular groove (23) has a depth of 0.5 mm to 1.5 mm and a spacing of 3 mm to 8 mm.

4. The hydraulically sealed, speed-limited rotatable hydraulic jet self-advancing drill bit according to claim 1, 2 or 3, characterized in that: The interior of the housing (8) is a cavity having a similar outer contour to the rotating shaft (4), which is divided into a front cylindrical cavity and a truncated cone-shaped cavity. The length of the truncated cone-shaped cavity is longer than the length of the conical cone (21), so that the rotating shaft (4) can move axially in the housing (8), and the front end surface of the conical cone (21) cooperates with the inner bottom surface of the truncated cone-shaped cavity to perform axial positioning at the front end, and the rear end surface of the conical cone (21) cooperates with the front end surface of the base (13) to perform axial positioning at the rear end.

5. The hydraulically sealed, speed-limited rotatable hydraulic jet self-advancing drill bit according to claim 1, 2 or 3, characterized in that: A certain distance L is left between the rear portion (18) of the rotating shaft and the bottom surface of the front cavity of the base (13), allowing fluid to flow into the gap between the rear end of the rotating shaft and the front end of the cylindrical cavity of the base to form a liquid film, L = 2-3 mm.

6. The hydraulically sealed, speed-limited rotatable hydraulic jet self-advancing drill bit according to claim 1, 2 or 3, characterized in that: Two symmetrical leakage holes (10) are provided on the surface of the outer shell (8), and the center lines of the leakage holes (10) are perpendicular to the axis of the outer shell (8).

7. The hydraulically sealed, speed-controlled rotatable hydraulic jet self-advancing drill bit according to claim 6, characterized in that: The leakage hole (10) is located near the rear end of the conical cone of the rotating shaft, so that the size of the area of ​​the leakage hole blocked by the rear end of the conical cone of the rotating shaft is dynamically adjusted to adjust the size of the backward action between the axial force and the conical cone gap, so that the front and rear end surfaces of the conical cone of the rotating shaft do not contact the housing and the base.

8. The hydraulically sealed, speed-controlled rotatable hydraulic jet self-advancing drill bit according to claim 1, 2 or 3, characterized in that: The base (13) is cylindrical, with a front cavity at the front for accommodating the rear part (18) of the rotating shaft, and a base internal fluid channel (15) at the rear, wherein the diameter of the base internal fluid channel (15) is the same as the diameter of the internal flow channel (25) of the rotating shaft; and the rear end of the base (13) is provided with four rearward nozzles (14) evenly arranged in the circumference and forming an angle γ with the axis of the base (13), γ=10°~30°.

9. The hydraulic seal speed-limited rotatable hydraulic jet self-advancing drill bit according to claim 1, 2 or 3, characterized in that: The diameter of the flow channel (25) inside the rotating shaft is between 3 mm and 10 mm.

10. The hydraulic seal speed-controlled rotatable hydraulic jet self-advancing drill bit according to claim 1, 2 or 3, characterized in that: The overall length of the drill bit ranges from 60 mm to 140 mm, and the outer diameter ranges from 8 mm to 30 mm.

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