Method and apparatus for polishing the inner surface of a variable diameter elbow

Abstract

The application discloses a variable-diameter elbow inner surface polishing and strengthening method and device, and relates to the field of polishing equipment.The device comprises a variable-diameter elbow and piston cylinders arranged at both ends of the variable-diameter elbow, wherein the piston cylinders are divided into a left piston cylinder and a right piston cylinder; a piston one, a piston two and a piston three are arranged in the left piston cylinder, the piston one is arranged in the left piston cylinder alone, and the piston two and the piston three are arranged in the left piston cylinder oppositely; a water inlet and an abrasive inlet are further arranged on the left piston cylinder; a piston four, a piston five and a piston six are arranged in the right piston cylinder, the piston six is arranged in the right piston cylinder alone, and the piston four and the piston five are arranged in the right piston cylinder oppositely; a water outlet and an abrasive outlet are further arranged on the right piston cylinder; a die is arranged in the variable-diameter elbow, and the shape of the die is shaped according to the shape of the variable-diameter elbow; and the radial section width between the variable-diameter elbow and the die is controlled by the die, so that uniform polishing is realized.

Description

Technical Field

[0001] This invention relates to the field of polishing equipment, specifically to a method and apparatus for polishing and strengthening the inner surface of a variable diameter bent pipe. Background Technology

[0002] For bends, especially variable diameter bends, polishing and strengthening of the inner surface are necessary to achieve the required machining accuracy. However, the small aperture and long internal depth of bends make polishing and strengthening of the inner surface particularly difficult. Therefore, there is an urgent need for a device to polish and strengthen the inner surface of variable diameter bends.

[0003] Cavitation technology creates vapor bubbles or gas-filled cavitation cavities by lowering the internal pressure of a fluid below its saturated vapor pressure. The localized high pressure generated by the collapse of these cavitation bubbles can mechanically impact the material surface, further inducing plastic deformation and thus increasing the material's strength. Furthermore, the instantaneous high temperature generated during cavitation collapse can trigger a thermal effect on the material surface, promoting changes in its microstructure and contributing to material strengthening.

[0004] Chinese Patent Publication No. CN118404414A, entitled "A Magnetic Grinding Apparatus and Method for Processing the Inner Surface of a Conduit," discloses a grinding apparatus for processing the inner surface of a conduit. The apparatus includes a base, a robotic arm mounted on the base, a fixed clamping component, and a polishing mechanism on the robotic arm. The polishing mechanism includes a base located at the gripper of the robotic arm, and a connecting seat detachably mounted on the base and fixed to the gripper. This apparatus can achieve precision grinding to remove defects from the inner surface of the conduit, reducing the manufacturing and maintenance costs of grinding the inner wall of the pipe. However, this equipment can only polish the inner surface of the pipe; further surface strengthening is still required to improve the mechanical properties of the pipe.

[0005] Chinese Patent Publication No. CN115741486B, entitled "Ultrasonic-Assisted Nanoabrasive Water Jet Composite Polishing Device and Method for the Inner Surface of Grooved Heat Pipes," discloses an ultrasonic-assisted nanoabrasive water jet composite polishing device for the inner surface of grooved heat pipes. This device includes a driving device, a spraying device, an ultrasonic device, and an ultrasonic polishing platform. The driving device is connected to the spraying device and drives it to rotate eccentrically. The spraying device forms a polishing slurry to polish the inner surface of the grooved heat pipe. The ultrasonic device is fixed on the ultrasonic polishing platform to achieve efficient composite polishing of the surface to be processed on the grooved heat pipe. It can achieve the removal of trace amounts of material and provides stable polishing results. However, when processing variable-diameter bends, because the diameter of the bend changes in the cross-sectional direction, the water jet accumulates in the deeper recesses, causing cavitation bubbles to collapse before reaching the inner wall surface, ultimately resulting in uneven polishing enhancement when processing variable-diameter bends. Summary of the Invention

[0006] The purpose of this invention is to provide a method and apparatus for polishing and strengthening the inner surface of a variable diameter bent pipe, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a variable diameter bend inner surface polishing and strengthening device, comprising a variable diameter bend and piston cylinders located at both ends of the variable diameter bend, wherein the piston cylinders are divided into a left piston cylinder and a right piston cylinder;

[0008] The left piston cylinder is equipped with piston one, piston two, and piston three. Piston one is arranged alone in the left piston cylinder, while piston two and piston three are arranged opposite each other in the left piston cylinder. The left piston cylinder is also equipped with a water inlet and an abrasive inlet.

[0009] The right piston cylinder is equipped with piston four, piston five and piston six. Piston six is ​​set separately in the right piston cylinder. Piston four and piston five are arranged opposite to each other in the right piston cylinder. The right piston cylinder is also equipped with a water outlet and an abrasive outlet.

[0010] The variable diameter bend is equipped with a mold, the shape of which is modeled after the shape of the variable diameter bend. The gap between the inner wall of the variable diameter bend and the outer wall of the mold increases as the inner diameter of the variable diameter bend decreases.

[0011] Preferably, valve one is provided in the water inlet and valve two is provided in the abrasive inlet.

[0012] Preferably, the left piston cylinder is fixedly connected to the flange two on the reducing bend via flange one, and a sealing flange five is provided between flange one and flange two.

[0013] Preferably, the right piston cylinder is fixedly connected to flange three on the reducing bend via flange four.

[0014] Preferably, valve three is provided in the water outlet and valve four is provided in the abrasive outlet.

[0015] Preferably, the flange five is fixedly connected to the root of the mold, and a through hole is provided on the flange five.

[0016] A method for polishing and strengthening the inner surface of a variable diameter bent pipe includes the following steps:

[0017] S1. Drive piston one to its maximum stroke via an external controller, between the water inlet and the abrasive inlet, and drive piston six to its maximum stroke, between the water outlet and the abrasive outlet.

[0018] S2. Open the control valves 2 and 4 of the abrasive flow inlet and outlet pipes. Under the action of the external supply equipment, the abrasive flow enters the working chamber of the left piston cylinder from the abrasive flow inlet and enters the gap between the variable diameter bend and the mold. During the flow of the abrasive flow, the inner surface of the variable diameter bend is polished. Finally, under the action of pressure, the excess abrasive flow is discharged through the abrasive flow outlet.

[0019] S3. Close control valves two and four of the abrasive flow inlet and outlet pipes to stop the abrasive flow injection;

[0020] S4. Drive the piston to move to the minimum stroke position through the external controller, open the control valve of the water inlet pipe to inject water into the working chamber of the left piston cylinder;

[0021] S5. At this time, piston one and piston six are at their minimum stroke, so that the working chamber volume of the left and right piston cylinders is as large as possible. After injecting an appropriate volume of internal water, piston one and piston six reciprocate in the same direction and at the same frequency. When piston one compresses to its minimum stroke, piston six simultaneously stretches to its maximum stroke. When piston one stretches to its maximum stroke, piston six simultaneously compresses to its minimum stroke. In the left piston cylinder, piston two and piston three reciprocate in the same direction and at the same frequency, and in the right piston cylinder, piston four and piston five reciprocate in the same direction and at the same frequency, so that the internal water flow and abrasive flow are mixed evenly.

[0022] S6. Then open the control valve of the abrasive outlet pipe to discharge part of the mixture;

[0023] S7. With piston one at its minimum stroke and all other pistons at their maximum stroke, open control valve one of the water inlet pipe, fill the pipe with water, and then close all valves.

[0024] S8. Control the piston to move in six directions to the minimum stroke, and control the pistons two, three, four and five to move synchronously to the minimum stroke, so as to reduce the pressure in the working chambers of the left and right piston cylinders and the variable diameter bend to below the saturated vapor pressure, thereby generating cavitation bubbles through cavitation.

[0025] S9. After piston one reaches the minimum stroke and piston six reaches the minimum stroke, control all pistons to move to the maximum stroke again. At this time, the pressure increases, causing the cavitation bubbles to collapse and release energy, so that the abrasive flow and water flow interact to strengthen the inner surface.

[0026] S10. Control all pistons to repeat the above movements. During the piston compression movement to the minimum stroke, cavitation bubbles are generated. During the piston extension movement to the maximum stroke, the cavitation bubbles collapse, thus strengthening the inner surface.

[0027] S11. Then open the control valve four of the abrasive outlet pipe. Under control, piston one and piston six reciprocate in the same direction and frequency to discharge the mixture, complete the strengthening, and remove the reducing bend.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] 1. This invention manufactures specific molds for different variable-diameter bends to control the radial cross-sectional area between the bend and the mold to increase as the inner diameter of the bend decreases. This increase in the radial cross-sectional area between the bend and the mold ensures that the abrasive flow has the same velocity and pressure at any point on the inner surface. Ultimately, this results in a uniform force exerted by the abrasive flow on the inner surface of the bend, preventing significant stress concentration in certain parts of the pipe and achieving uniform polishing of the inner surface.

[0030] 2. This invention changes the volume of the working chamber, the variable-diameter bend, and the mold gap by controlling the closing degree of different pistons, and processes a specific mold to ultimately achieve uniform flow of abrasive material within the variable-diameter bend. This avoids the problems of incomplete processing on one side or over-processing on the other side of the inner surface of the bend in traditional polishing, enabling polishing of the inner surface of the variable-diameter bend in both radial and axial directions, thus improving the polishing efficiency of the variable-diameter bend surface.

[0031] 3. This invention uses a controller to drive different pistons in a regular reciprocating motion, changing the pressure in the working chamber and generating negative pressure to achieve cavitation. As the volume of the closed working chamber increases, the liquid pressure drops to below the saturated vapor pressure, thus initiating cavitation and generating bubbles. When the piston compresses, the pressure inside the closed working chamber increases, causing the bubbles to collapse. Through the regular reciprocating motion of the piston, a cycle of cavitation initiation, development, and collapse is achieved within the working chamber. When the pressure on the upper surface of the inner wall of the variable-diameter bend reaches the cavitation collapse pressure, the bubbles collapse and release enormous energy. Utilizing the water flow, abrasive flow, and the high-energy released by cavitation collapse, microscopic pits on the inner surface of the bend are filled and minor imperfections are removed. Further strengthening can be achieved after the initial polishing of the bend, realizing integrated polishing and strengthening.

[0032] 4. This invention utilizes the high-energy and impact generated by the collapse of cavitation bubbles in the cavitation effect to process the inner surface of the variable-diameter bend, effectively re-polishing the inner surface. Compared to traditional polishing, it achieves better surface quality and lower surface roughness. Simultaneously, since the abrasive flow is difficult to vent all at once, the abrasive flow, under the force generated by cavitation bubble collapse, impacts and strengthens the inner surface of the bend, striking it with higher speed and kinetic energy. This allows the cavitation effect and abrasive flow polishing to work together, further enhancing the microscopic strengthening effect of the surface. This can further reduce potentially harmful deformations such as microcracks, improving the overall performance of the variable-diameter bend. Attached Figure Description

[0033] Figure 1 This is the overall system diagram of the present invention;

[0034] Figure 2 It is an enlarged view of the connection between the cavity, the mold, and the variable-diameter bend to be processed;

[0035] Figure 3 It is a structural diagram of the mold;

[0036] Figure 4 yes Figure 1 Internal piston and valve structure diagram of the piston cylinder during internal polishing operation;

[0037] Figure 5 yes Figure 1 Diagram of the piston and valve structure inside the piston cylinder during the abrasive flow discharge after the polishing work is completed;

[0038] Figure 6 yes Figure 1 The diagram shows the internal structure of the piston and valves of the piston cylinder in the initial state when the device is performing surface strengthening work.

[0039] Figure 7 yes Figure 1 The diagram shows the internal piston and valve structure of the piston cylinder during the intermediate state of the surface strengthening process of the device shown.

[0040] In the diagram: 1. Piston 1; 2. Piston 2; 3. Piston 3; 4. Valve 1; 5. Valve 2; 6. Water inlet; 7. Abrasive inlet; 8. Flange 1; 9. Flange 2; 10. Mold; 11. Reducing bend; 12. Flange 3; 13. Flange 4; 14. Valve 3; 15. Water outlet; 16. Abrasive outlet; 17. Valve 4; 18. Piston 4; 19. Piston 5; 20. Piston 6; 21. Flange 5; 22-1. Left piston cylinder; 22-2. Right piston cylinder; 23. Water flow; 24. Abrasive flow; 25. Cavitation; 26. Maximum stroke of piston 1; 27. Minimum stroke of piston 1; 28. Minimum stroke of piston 2; 29. ​​Maximum stroke of piston 2; 30. Minimum stroke of piston 6; 31. Maximum stroke of piston 6; 32. Maximum stroke of piston 4; 33. Minimum stroke of piston 4. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0042] Please see Figures 1 to 5The present invention provides a technical solution: a polishing and strengthening device for the inner surface of a variable diameter bend, comprising a variable diameter bend 11 and piston cylinders located at both ends of the variable diameter bend 11. The piston cylinders are divided into a left piston cylinder 22-1 and a right piston cylinder 22-2. The left piston cylinder 22-1 is larger than the right piston cylinder 22-2. The end of the variable diameter bend 11 with a larger radial cross-sectional area is the inlet end, which is connected to the left piston cylinder 22-1, and the end with a smaller radial cross-sectional area is the outlet end, which is connected to the right piston cylinder 22-2.

[0043] In this embodiment, the left piston cylinder 22-1 is provided with piston 1, piston 2, and piston 3. Piston 1 is arranged alone in the left piston cylinder 22-1, while piston 2 and piston 3 are arranged opposite to each other in the left piston cylinder 22-1. The left piston cylinder 22-1 is also provided with a water inlet 6 and an abrasive inlet 7. The central axes of piston 1 and flange 8 are collinear. The axial length of piston 1 is greater than the axial length of piston 2 and piston 3. The size of piston 1 is greater than that of piston 2 and piston 3. Piston 2 and piston 3 have the same structure and are located on both sides perpendicular to the axis of piston 1, and are arranged symmetrically with respect to the central axis of piston 1.

[0044] In this embodiment, the right piston cylinder 22-2 is provided with piston four 18, piston five 19 and piston six 20. Piston six 20 is separately arranged in the right piston cylinder 22-2. Piston four 18 and piston five 19 are arranged opposite to each other in the right piston cylinder 22-2. The right piston cylinder 22-2 is also provided with a water outlet 15 and an abrasive outlet 16. The right piston cylinder 22-2 and the left piston cylinder 22-1 have the same structure, with only a difference in size.

[0045] In this embodiment, a mold 10 is provided inside the variable diameter bend 11. The shape of the mold 10 is processed according to the shape of the variable diameter bend 11. The gap width between the inner wall of the variable diameter bend 11 and the outer wall of the mold 10 increases as the inner diameter of the variable diameter bend 11 decreases.

[0046] In this embodiment, valve 4 is provided in the water inlet 6, and valve 5 is provided in the abrasive inlet 7.

[0047] In this embodiment, the left piston cylinder 22-1 is fixedly connected to the flange 29 on the reducing bend 11 via flange 18, and a sealing flange 5 21 is provided between flange 18 and flange 29. The right piston cylinder 22-2 is fixedly connected to the flange 3 12 on the reducing bend 11 via flange 4 13.

[0048] In this embodiment, taking the left piston cylinder 22-1 as an example, when the variable diameter bend 11 is fixed and valves 4 and 5 are closed, pistons 1, 2, and 3 enclose the piston cylinder into a closed working chamber. Each piston is tightly sealed to the inner wall of its corresponding through hole and can reciprocate along the inner wall of the through hole, moving closer to or away from the working chamber, ultimately reducing or increasing the volume of the working chamber.

[0049] In this embodiment, piston 1 can extend into the working chamber. The maximum stroke 26 is located between the water inlet 6 and the abrasive inlet 7, and the minimum stroke 27 is located inside the working chamber. Piston 2 and piston 3 have the same stroke. If the maximum stroke 29 of piston 2 does not exceed the maximum position of its through hole, it cannot extend into the working chamber. The minimum stroke 28 of piston 2 is inside the copper tube.

[0050] In this embodiment, the three pistons of the left piston cylinder 22-1 and the two valves of the right piston cylinder 22-2 are all driven independently by an external controller (the controller is omitted in the figure). The controller independently drives the three pistons to move and the two valves to open and close.

[0051] In this embodiment, the piston moves under the drive of the controller, which can reduce or increase the volume of the working chamber. Taking the left piston cylinder 22-1 as an example, when the piston moves to its maximum stroke 26, it can extend into the working chamber, reducing the volume of the working chamber; when the piston moves to its minimum stroke 27, the volume of the working chamber increases. By changing the volume of the working chamber, the pressure within the working chamber can be changed.

[0052] In this embodiment, valve 3 14 is provided in the water outlet 15, and valve 4 17 is provided in the abrasive outlet 16.

[0053] In this embodiment, the flange 21 is fixedly connected to the root of the mold 10, and a through hole is provided on the flange 21.

[0054] In this embodiment, the reducing elbow 11 is tightly fitted to the piston cylinder and the mold 10. The outlet flange 8 of the left piston cylinder 22-1 is fixedly connected to the flange 9 of the reducing elbow 11 and the flange 21 of the mold by bolts. A sealing rubber ring 1 is installed between flange 8 and flange 21, and a sealing rubber ring 2 is installed between flange 21 and flange 9. The inner diameters of sealing rubber rings 1 and 2 are the same as those of flanges 8, 9, and 21. Similarly, a sealing rubber ring 3 is installed between the inlet flange 13 of the right piston cylinder 22-2 and the flange 12 of the reducing elbow 11. The inner diameter of sealing rubber ring 3 is the same as that of flanges 13 and 12. After the reducing pipe 11, the mold 10, and the left piston cylinder 22-1 and the right piston cylinder 22-2 are fixed by the flange, the left piston cylinder 22-1, the right piston cylinder 22-2 and the reducing pipe 11 are interconnected by the sealing rubber ring one, the sealing rubber ring two and the sealing rubber ring three, forming a closed sealing space.

[0055] In this embodiment, the inner diameter of flange 21, which is machined at the end of mold 11, is the same as that of flange 8 and flange 9. Four brackets are machined at equal angles on the inner diameter of flange 21 and welded to connect and fix mold 10.

[0056] In this embodiment, the flange 21 and the mold 10 have the same length on their upper axial surfaces. The mold 10 is installed at the axial center of the inner diameter of the flange 21. The mold 10 is specifically machined to ensure that the radial cross-sectional area between the variable diameter bend 11 and the mold 10 increases as the inner diameter of the variable diameter bend 11 decreases. This ensures that the abrasive flow 24 has the same speed and pressure when passing through the variable diameter bend, and the same force on its inner surface.

[0057] Working principle: First, the left piston cylinder 22-1, the right piston cylinder 22-2, the variable diameter bend 11 and the mold 10 are fixedly connected and assembled.

[0058] like Figure 4 As shown, after assembly, the polishing and strengthening device for the inner surface of the reducing bend 11 begins operation. Piston 1 moves to its maximum stroke 26 under the drive of the controller, and piston 20 moves to its maximum stroke 31 under the drive of the controller. Valve 5 at the abrasive inlet 7 and valve 14 at the abrasive outlet 16 open. Under high pressure, the abrasive flow 24 enters the space between the reducing bend 11 and the mold 10 through the abrasive inlet 7 for polishing, and finally exits from the abrasive outlet 16. During the polishing process, both pistons 1 and 20 are at their maximum stroke positions, minimizing the working chamber volume and avoiding obstruction of the abrasive flow 24, thus improving polishing efficiency.

[0059] Because the mold 10 is individually manufactured for different reducing pipes 11, it ensures that the radial cross-sectional area between the reducing pipe and the mold increases as the inner diameter of the reducing pipe 11 decreases. The pressure distribution of the abrasive flow 24 inside the reducing pipe 11 tends to be uniform, avoiding localized accumulation or excessively high flow rates, thus achieving uniform polishing of the inner wall. Furthermore, as fluid mechanics dictates, the velocity and pressure of the abrasive flow 24 tend to remain constant within the pipe, preventing large localized stress concentrations in certain parts of the pipe that could lead to uneven polishing or damage to the inner wall. By introducing a specifically processed mold, the uniformity and quality of the inner surface polishing are improved.

[0060] like Figure 5 As shown, after polishing the inner wall of the variable-diameter bend 11, a large amount of abrasive flow 24 remains in the gap between the working chamber and the inner wall of the bend. The abrasive flow 24 is then discharged. Valves 2 (5), 3 (14), and 4 (17) are closed to stop the injection and discharge of the abrasive flow. Pistons 1 (1) and 6 (20) move to their minimum stroke position under the drive of the controller. Pistons 2 (2), 3 (3), 4 (18), and 5 (19) continue to reciprocate relative to each other, improving the fluidity of the subsequently injected water and achieving a better discharge effect for the abrasive flow 24.

[0061] Open valve 4 at water inlet 6 to inject water flow 23 into the gap between the working chamber, the reducing pipe 11, and the mold 10. After injecting an appropriate volume of liquid, pistons 1 and 6 reciprocate regularly under the drive of the controller. When piston 1 reaches its maximum stroke 26, piston 6 20 is at its minimum stroke 30. When piston 1 reaches its minimum stroke 27, piston 6 20 is at its maximum stroke 31, so that the abrasive flow 24 in the gap between the working chamber, the reducing pipe 11, and the mold 10 mixes with the injected liquid. Finally, pistons 1 and 6 20 stop moving, valve 4 is closed, and valve 4 17 at water outlet 15 is opened to discharge the abrasive flow 24 and the liquid.

[0062] like Figure 6 and Figure 7As shown, the abrasive flow applied during polishing is difficult to discharge all at once. At this point, the remaining abrasive flow 24, driven by the high-energy release from the collapse of cavitation bubbles 25 and the interaction between the water flow 23 and the inner wall of the bend, performs a surface strengthening process on the inner wall. Valve 17 is closed, and piston 1 is controlled to its minimum stroke 27. The remaining pistons move to their maximum stroke under the control of the controller. Valve 4 of the water inlet pipe is opened, filling the gap between the working chamber and the reducing bend 11 and the mold 10 with liquid. Valve 4 is then closed. The actuators of all pistons are activated, causing all pistons to move simultaneously to their minimum stroke, and then simultaneously to their maximum stroke, continuing this reciprocating motion to repeatedly change the volume of the enclosed space. As the enclosed space is stretched outwards, when the pressure drops below the liquid's saturated vapor pressure, cavitation occurs, precipitating cavitation bubbles 25 from the liquid, which further develop and expand as the volume increases. When the volume of the enclosed space decreases, the internal pressure increases, causing the generated cavitation bubbles 25 to collapse and release high-energy deposits. This results in microscopic compression deformation, filling microscopic pits on the surface and removing minor imperfections, thereby strengthening the inner wall of the bent pipe. The instantaneous shock wave generated by the collapse of the cavitation bubbles 25 not only acts directly on the inner surface of the bent pipe but also drives the abrasive flow 24 to impact the inner surface at a higher speed and kinetic energy. This allows the cavitation effect and the polishing effect of the abrasive flow 24 to work together, further enhancing the microscopic strengthening effect of the surface.

[0063] Due to the different radial cross-sections of the reducing bend 11, to achieve a uniform surface strengthening effect, during installation, the reducing bend 11 is fixedly connected to the inlet end with the larger cross-sectional area and the left piston cylinder 22-1, while the outlet end with the smaller radial cross-sectional area is fixedly connected to the right piston cylinder 22-2. The left piston cylinder 22-1 is larger than the right piston cylinder 22-2. The piston 1 is larger than the piston 6 20. Therefore, during volume alternation, the left piston cylinder 22-1 generates more cavitation bubbles than the right piston cylinder 22-2. When the cavitation bubbles collapse on the inner surface of the bend under the piston's push, the number of cavitation bubbles 25 at the bend inlet end is greater than at the outlet end. Therefore, the inlet end with the larger radial cross-sectional area receives a greater force than the outlet end with the smaller cross-sectional area, thus preventing uneven strengthening.

[0064] When the inner wall of the reducing bend 11 is polished and strengthened to the desired effect, the driver stops and the piston is reset. The valve 18 of the water outlet 15 is opened to release the water flow 23 and the abrasive flow 24. The bolts are loosened, and the reducing bend 11 and the mold 10 are removed to complete the polishing.

[0065] A method for polishing and strengthening the inner surface of a variable diameter bent pipe includes the following steps:

[0066] S1. Drive piston 1 to its maximum stroke 26 via an external controller, which is between water inlet 6 and abrasive inlet 7. Drive piston 6 20 to its maximum stroke 31, which is between water outlet 15 and abrasive outlet 16.

[0067] S2. Open the control valves 25 and 417 of the abrasive flow inlet 7 and abrasive flow outlet 16 pipelines. Under the action of the external supply equipment, the abrasive flow 24 enters the working chamber of the left piston cylinder 22-1 from the abrasive flow inlet 7 and enters the gap between the variable diameter bend 11 and the mold 10. During the flow of the abrasive flow 24, the inner surface of the variable diameter bend 11 is polished. Finally, under the action of pressure, the excess abrasive flow 24 is discharged through the abrasive flow outlet 16.

[0068] S3. Close control valves 2.5 and 4.17 of the abrasive flow inlet 7 and abrasive flow outlet 16 pipelines to stop the filling of abrasive flow 24;

[0069] S4. Drive the piston-1 to the minimum stroke position 27 through the external controller, open the control valve-4 of the water inlet 6 pipe to inject water into the working chamber of the left piston cylinder 22-1;

[0070] S5. At this time, piston 1 is at the minimum stroke 27 and piston 6 is at the minimum stroke 30, so that the working chamber volume of the left piston cylinder 22-1 and the right piston cylinder 22-2 is as large as possible. After injecting an appropriate volume of internal water flow 23, piston 1 and piston 6 reciprocate in the same direction and at the same frequency. When piston 1 compresses to the minimum stroke 27, piston 6 simultaneously stretches to the maximum stroke 31. When piston 1 stretches to the maximum stroke 26, piston 6 simultaneously compresses to the minimum stroke 30. In the left piston cylinder 22-1, piston 2 and piston 3 reciprocate in the same direction and at the same frequency. In the right piston cylinder 22-2, piston 4 18 and piston 5 19 reciprocate in the same direction and at the same frequency, so that the internal water flow 23 and abrasive flow 24 are mixed evenly.

[0071] S6. Then open the control valve 17 of the abrasive outlet 16 pipe to discharge part of the mixture;

[0072] S7. Control piston 1 to be at the minimum stroke 27, and all other pistons to be at the maximum stroke. Open control valve 4 of water inlet 6 pipe, fill water flow 23, and then close all valves.

[0073] S8. Control piston six 20 to move to the minimum stroke 30, and control piston two 2, piston three 3, piston four 18, and piston five 19 to move synchronously to the minimum stroke, so as to reduce the pressure in the working chamber of the left piston cylinder 22-1 and the right piston cylinder 22-2 and the variable diameter bend 11 to below the saturated vapor pressure, thereby generating cavitation bubbles 25 through cavitation.

[0074] S9. After piston 1 reaches the minimum stroke 27 and piston 6 reaches the minimum stroke 30, all pistons are controlled to move to the maximum stroke again. At this time, the pressure increases, causing the cavitation bubble 25 to collapse and release energy, so that the abrasive flow 24 and the water flow 23 interact to strengthen the inner surface.

[0075] S10. Control all pistons to repeat the above movements. During the piston compression movement to the minimum stroke, cavitation bubbles 25 are generated. During the piston extension movement to the maximum stroke, cavitation bubbles 25 collapse, thus strengthening the inner surface.

[0076] S11. Then open the control valve 17 of the abrasive outlet 16 pipe. Under control, piston 1 and piston 6 reciprocate in the same direction and frequency to discharge the mixture, complete the strengthening, and remove the reducer bend.

[0077] As is known from common technical knowledge, this invention can be implemented through other embodiments that do not depart from its spirit or essential characteristics. Therefore, the disclosed embodiments described above are merely illustrative and not exhaustive. All modifications within the scope of this invention or its equivalents are included in this invention.

Claims

1. A device for polishing and strengthening the inner surface of a variable diameter bent pipe, characterized in that: It includes a variable diameter bend (11) and piston cylinders located at both ends of the variable diameter bend (11), the piston cylinders being divided into a left piston cylinder (22-1) and a right piston cylinder (22-2). The left piston cylinder (22-1) is provided with piston one (1), piston two (2) and piston three (3). Piston one (1) is arranged alone in the left piston cylinder (22-1), and piston two (2) and piston three (3) are arranged opposite to each other in the left piston cylinder (22-1). The left piston cylinder (22-1) is also provided with a water inlet (6) and an abrasive inlet (7). The right piston cylinder (22-2) is provided with piston four (18), piston five (19) and piston six (20). Piston six (20) is separately provided in the right piston cylinder (22-2). Piston four (18) and piston five (19) are arranged opposite to each other in the right piston cylinder (22-2). The right piston cylinder (22-2) is also provided with a water outlet (15) and an abrasive outlet (16). The variable diameter bend (11) is provided with a mold (10). The shape of the mold (10) is processed according to the shape of the variable diameter bend (11). The gap between the inner wall of the variable diameter bend (11) and the outer wall of the mold (10) increases as the inner diameter of the variable diameter bend (11) gradually decreases. The left piston cylinder (22-1) is fixedly connected to the flange two (9) on the reducing elbow (11) via flange one (8), and a sealing flange five (21) is provided between the flange one (8) and the flange two (9). The right piston cylinder (22-2) is fixedly connected to the flange three (12) on the reducing bend (11) via flange four (13); Includes the following steps: S1. Drive piston one (1) to the maximum stroke (26) of piston one through an external controller, between the water inlet (6) and the abrasive inlet (7), and drive piston six (20) to the maximum stroke (31) of piston six, between the water outlet (15) and the abrasive outlet (16); S2. Open the control valves 2 (5) and 4 (17) of the abrasive flow inlet (7) and abrasive flow outlet (16) pipelines. Under the action of the external supply equipment, the abrasive flow (24) enters the working chamber of the left piston cylinder (22-1) from the abrasive flow inlet (7) and enters the gap between the variable diameter bend (11) and the mold (10). During the flow of the abrasive flow (24), the inner surface of the variable diameter bend (11) is polished. Finally, under the action of pressure, the excess abrasive flow (24) is discharged through the abrasive flow outlet (16). S3. Close the control valves 2 (5) and 4 (17) of the abrasive flow inlet (7) and abrasive flow outlet (16) pipelines to stop the filling of abrasive flow (24); S4. Drive the piston (1) to the minimum stroke (27) of the piston by the external controller, open the control valve (4) of the water inlet (6) pipe to inject water into the working chamber of the left piston cylinder (22-1) (23). S5. At this time, piston one (1) is at the minimum stroke of piston one (27) and piston six (20) is at the minimum stroke of piston six (30), so that the working chamber volume of the left piston cylinder (22-1) and the right piston cylinder (22-2) is as large as possible. After injecting an appropriate volume of internal water flow (23), piston one (1) and piston six (20) reciprocate in the same direction and at the same frequency. When piston one (1) moves to the minimum stroke of piston one (27), piston six (20) moves to the maximum stroke of piston six (31) at the same time. When piston one (1) moves to the maximum stroke of piston one (26), piston six (20) moves to the minimum stroke of piston six (30) at the same time. In the left piston cylinder (22-1), piston two (2) and piston three (3) reciprocate in the same direction and at the same frequency. In the right piston cylinder (22-2), piston four (18) and piston five (19) reciprocate in the same direction and at the same frequency, so that the internal water flow (23) and abrasive flow (24) are mixed evenly. S6. Then open the control valve four (17) of the abrasive outlet (16) pipe to discharge part of the mixture; S7. Control piston one (1) to be at the minimum stroke (27) of piston one, and the rest of the pistons to be at the maximum stroke. Open the control valve one (4) of the water inlet (6) pipe, fill the water flow (23) and then close all valves. S8. Control piston six (20) to move to piston six minimum stroke (30), control piston two (2), piston three (3), piston four (18), and piston five (19) to move synchronously to minimum stroke, reduce the pressure in the working chamber of left piston cylinder (22-1) and right piston cylinder (22-2) and the variable diameter bend (11) to below saturated vapor pressure, thereby generating cavitation bubbles (25) through cavitation. S9. After piston one (1) to piston one minimum stroke (27) and piston six (20) to piston six minimum stroke (30), control all pistons to move to the maximum stroke again. At this time, the pressure increases, causing the cavitation bubble (25) to collapse and release energy, so that the abrasive flow (24) and the water flow (23) interact to strengthen the inner surface. S10. Control all pistons to repeat the above movement. During the piston movement to the minimum stroke, cavitation bubbles (25) are generated. During the piston movement to the maximum stroke, the cavitation bubbles (25) collapse, thus strengthening the inner surface. S11. Then open the control valve of the abrasive outlet (16) pipe (17), piston one (1) and piston six (20) reciprocate in the same direction and frequency under control, discharge the mixture, complete the strengthening, and remove the reducing bend.

2. The variable diameter bent pipe inner surface polishing and strengthening device according to claim 1, characterized in that: The water inlet (6) is equipped with valve one (4), and the abrasive inlet (7) is equipped with valve two (5).

3. The device for polishing and strengthening the inner surface of a variable diameter bent pipe according to claim 1, characterized in that: The water outlet (15) is equipped with valve three (14), and the abrasive outlet (16) is equipped with valve four (17).

4. The variable diameter bent pipe inner surface polishing and strengthening device according to claim 3, characterized in that: The flange five (21) is fixedly connected to the root of the mold (10), and a through hole is provided on the flange five (21).

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