A self-cleaning ballast water filter

Abstract

This invention relates to the field of ship ballast water treatment technology, specifically to a self-cleaning ballast water filter, comprising a housing, an inner filter basket and an outer filter basket coaxially nested within the housing, a drive mechanism, and a paired cleaning module and a suction module. The inner filter basket has a larger mesh size than the outer filter basket, allowing the filtered water to pass through both layers of filter screens before being discharged. The drive mechanism drives the two filter baskets to rotate in the same direction at a differential speed via a planetary gear set. The nozzle of the cleaning module abuts against the outer wall of the filter basket via a spring preload, and the suction tube of the suction module abuts against the inner wall of the filter basket via a spring preload; both are offset circumferentially. The nozzle can be switched between a pressurized water source and a pressurized air source to achieve alternating water washing and air washing. This invention combines graded filtration with an inner and outer clamping cleaning system using a double-layer differential speed filter basket, achieving online self-cleaning of the filter screen without shutting down the system, thus improving filtration efficiency and cleaning reliability.

Description

Technical Field

[0001] This invention relates to the field of ship ballast water treatment technology, and specifically to a self-cleaning ballast water filter. Background Technology

[0002] Ships need to inject or discharge seawater through ballast tanks to maintain hull stability during navigation. The transfer of ballast water between different sea areas can carry invasive marine life and sediment, posing a threat to the ecological environment of the discharge site. According to the International Maritime Organization's Ballast Water Management Convention, ships must treat ballast water to meet discharge standards. Filtration is a crucial component of ballast water treatment systems, used to intercept plankton, silt, and suspended solids in the water.

[0003] Existing ballast water filtration devices mostly employ fixed filter screens or single-layer rotating filter basket structures. After a period of operation, fixed filter screens accumulate a large amount of impurities on their surface, leading to a continuous increase in filtration resistance. This necessitates frequent shutdowns for manual cleaning or complete filter screen replacement, resulting in high maintenance costs and disruption to normal ship operations. While single-layer rotating filter baskets can achieve a certain degree of online cleaning in conjunction with cleaning devices, their single-stage filtration accuracy is limited. When faced with impurities in ballast water with a wide range of particle sizes, fine particles easily penetrate the filter screen, while coarse impurities easily clog the screen surface in a short time, making it difficult to simultaneously achieve filtration efficiency and cleaning effect.

[0004] Based on the above, this application proposes a self-cleaning ballast water filter that can effectively solve the above problems. Summary of the Invention

[0005] To address the challenge of balancing filtration accuracy and online cleaning capability in existing ballast water filtration devices, this application proposes a self-cleaning ballast water filter.

[0006] A self-cleaning ballast water filter, comprising:

[0007] The housing has an inlet and an outlet, and the side wall of the housing has a sewage outlet.

[0008] An inner filter basket and an outer filter basket are coaxially nested inside the housing. The mesh size of the inner filter basket is larger than that of the outer filter basket. A water inlet pipe extends from the water inlet into the housing and into the internal space of the inner filter basket. The filtered water flows through the inner filter basket and the outer filter basket in sequence and is discharged from the water outlet.

[0009] A drive mechanism, disposed on the housing, drives the inner filter basket and the outer filter basket to rotate in the same direction but at different speeds, wherein the inner filter basket rotates at a higher speed than the outer filter basket; and

[0010] A cleaning module and a suction module are provided in pairs corresponding to the inner filter basket and the outer filter basket, respectively. The cleaning module includes a nozzle facing the outer wall of the corresponding filter basket, and the suction module includes a suction pipe facing the inner wall of the corresponding filter basket. The nozzle is connected to an external cleaning source through a distribution main pipeline, and the suction pipe is connected to a suction pump through a collection main pipeline. The sewage outlet is connected to the inlet of the suction pump.

[0011] By setting up coaxial nested inner and outer filter baskets with the inner basket having a larger aperture than the outer basket, the water to be filtered undergoes two stages of filtration—coarse filtration and fine filtration—from the inner basket to the outer basket. This improves filtration accuracy while reducing the load on a single filter screen. The two filter baskets are rotated in the same direction at different speeds by a drive mechanism, and a cleaning module and a suction module are set up in pairs. The nozzle sprays cleaning medium from the outer wall surface, and the suction pipe sucks up the loose material from the inner wall surface, achieving a balance between multi-stage filtration and online cleaning without shutting down the system.

[0012] In one embodiment, the drive mechanism includes a drive motor and a planetary gear set. The planetary gear set includes a sun gear, planet gears, a planet carrier, and a ring gear. The ring gear is fixedly connected to the housing. The sun gear is connected to the output shaft of the drive motor and drives the inner filter basket to rotate. The planet carrier is connected to the outer filter basket via a hollow tube shaft and drives the outer filter basket to rotate. The hollow tube shaft is coaxially sleeved on the outside of the inner filter basket's rotating shaft. The lower end of the hollow tube shaft is fixedly connected to the planet carrier, and the upper end is connected to the bottom plate of the outer filter basket via a flange. At least two sets of radial support bearings are axially spaced between the inner filter basket's rotating shaft and the hollow tube shaft. By distributing the output of a single motor into two outputs with different speeds through the planetary gear set, and utilizing the kinematic relationship of a fixed ring gear and a sun gear input, the output speed of the planet carrier is lower than the input speed of the sun gear. This allows the inner and outer filter baskets to rotate in the same direction at different speeds with a single power source, simplifying the drive system structure and reducing potential sources of failure. The hollow tube shaft is coaxially sleeved on the outside of the inner filter basket shaft, which allows the two shafts to share the same axial space, reducing the radial dimension of the transmission system. The two sets of radial support bearings are arranged at intervals along the axial direction, ensuring the coaxiality and radial stiffness of the two shafts when rotating at different speeds.

[0013] In one embodiment, the cleaning module further includes a first elastic pre-tightening member, and the suction module further includes a second elastic pre-tightening member. The nozzle is mounted on the main distribution pipeline via the first elastic pre-tightening member, which is configured to allow the nozzle to elastically abut against the outer wall surface of the corresponding filter basket. The suction pipe is mounted on the main collection pipeline via the second elastic pre-tightening member, which is configured to allow the suction pipe to elastically abut against the inner wall surface of the corresponding filter basket. By using the elastic pre-tightening members to allow the nozzle and suction pipe to elastically fit against the outer and inner wall surfaces of the rotating filter basket, respectively, radial runout and manufacturing tolerances are compensated during the rotation of the filter basket. This ensures that the spraying of the cleaning medium and the suction of impurities always act on the area close to the mesh surface, improving the effective working area and efficiency of cleaning and suction.

[0014] In one embodiment, the top plate of the housing is provided with a first cleaning port and a second cleaning port. A pressurized water supply pipeline connected to an external pressurized water source enters the housing through the first cleaning port, and a pressurized air supply pipeline connected to an external pressurized air source enters the housing through the second cleaning port. A pressurized main pipeline is provided on the inner side of the top plate of the housing. The pressurized main pipeline is connected to both the pressurized water supply pipeline and the pressurized air supply pipeline. The pressurized main pipeline includes an external pressurized pipeline and an internal pressurized pipeline. The external pressurized pipeline and the internal pressurized pipeline are connected to each other through a connecting pipeline. The external pressurized pipeline is connected to the distribution main pipeline corresponding to the external filter basket, and the internal pressurized pipeline is connected to the distribution main pipeline corresponding to the internal filter basket. Valves are provided on the pressurized water supply pipeline and the pressurized air supply pipeline, respectively.

[0015] By setting two independent cleaning ports on the top plate of the housing, connecting the pressurized water source and the pressurized air source respectively, and setting a pressurized main pipeline system containing pressurized external pipeline and pressurized internal pipeline on the inner side of the top plate, pressurized water and compressed air can be independently and controllably supplied to the corresponding nozzles of the inner and outer filter baskets. By opening or closing the valves on their respective pipelines, the pressurized water flushing mode and compressed air purging mode can be flexibly switched. The design of both the pressurized external pipeline and the pressurized internal pipeline as annular pipelines ensures that each nozzle obtains uniform liquid or air supply pressure in the circumferential direction.

[0016] In one embodiment, each pair of nozzles and suction pipes corresponding to the same filter basket are offset circumferentially within the filter basket. The nozzles' contact positions on the outer wall of the corresponding filter basket and the suction pipes' contact positions on the inner wall of the corresponding filter basket have a circumferential offset angle greater than 0 degrees and not exceeding 45 degrees. By offsetting the same pair of nozzles and suction pipes circumferentially, the cleaning medium, after passing through the filter screen, must travel a certain arc length along the inner wall of the screen to reach the suction port, thereby generating a tangential flow component along the screen direction. This tangential component, superimposed on the wall motion generated by the rotation of the filter basket, causes each point on the screen passing through the cleaning area to alternately experience shearing forces with changing directions. Compared to the traditional radially aligned arrangement, which only provides normal impact force, this increases the tangential peeling capability for biofilm-like attachments spreading along the screen surface.

[0017] In one embodiment, the opening of the suction pipe is inclined relative to the radial direction of the corresponding filter basket, with the inclination direction consistent with the circumferential direction of the offset. The opening width of the suction pipe is greater than the outlet width of the nozzle, and the suction flow rate of the suction pump is not less than the ejection flow rate of the nozzle. By inclining the suction pipe opening in the same direction as the offset, the deflection loss when the oblique cleaning fluid reaches the suction port is reduced. The suction pipe opening width being greater than the nozzle outlet width matches the divergence characteristics of the oblique streamline, expanding the effective capture range. The constraint that the suction flow rate is not less than the nozzle flow rate ensures that the cleaning medium passing through the filter screen is concentrated and captured, preventing the cleaning medium from diluting and weakening the directional cleaning effect by diffusing into the gaps.

[0018] In one embodiment, a plurality of spiral guide vanes are connected to the outer wall surface of the inner filter basket. The spiral guide vanes rotate together with the inner filter basket. The spiral direction of the spiral guide vanes is set to push the fluid in the annular gap between the inner filter basket and the outer filter basket axially toward the bottom of the housing when rotating in the forward direction. The radial height of the spiral guide vanes is less than the smaller value of the compression stroke of the first elastic pretensioner and the second elastic pretensioner. The leading edge of the spiral guide vanes is chamfered. The spiral guide vanes rotate with the high-speed rotating inner basket, establishing an ordered spiral downward flow field in the annular gap. This throws heavy particles toward the outer basket wall under centrifugal force while simultaneously transporting them axially to the bottom collection area for discharge, reducing the particle load on the outer basket mesh and minimizing the sedimentation dead zone at the bottom of the gap. The vanes also act as reinforcing ribs, increasing the radial stiffness of the thin-walled basket to suppress deformation and vibration during high-speed rotation. The near-wall turbulence generated by the vane rotation increases the wall shear stress near the outer wall of the inner basket, increasing the hydraulic shear force that must be overcome for the initial adhesion of biological attachments. The radial height of the vanes is less than the compression stroke of the elastic pre-tightening element, and the leading edge is chamfered, allowing the vanes to briefly and smoothly push the elastic pre-tightening element away and then spring back to its original position when sweeping past a stationary nozzle or suction pipe, avoiding rigid collision interference between rotating and stationary components.

[0019] In one embodiment, the spiral guide vanes are uniformly distributed circumferentially on the outer wall of the inner filter basket. The radial height of the spiral guide vanes is less than half the width of the annular gap, and the angle between the spiral guide vanes and the outer wall of the inner filter basket is less than 45 degrees. The uniform circumferential distribution of the spiral guide vanes ensures that the spiral flow field in the annular gap is symmetrical and balanced in the circumferential direction, avoiding uneven particle deposition caused by excessively high or low local flow velocities. The radial height is limited to less than half the gap width, allowing free space for the cleaning module and filtered water to pass through on the outer side of the gap, achieving a balance between the guiding function and the filtration flux. The angle between the vanes and the outer wall is limited to less than 45 degrees, ensuring the axial transport component of the spiral flow.

[0020] In one embodiment, a control unit is further included. The drive motor is equipped with a frequency converter. The control unit is electrically connected to the frequency converter and the suction pump. The control unit is configured to control the frequency converter to execute an instantaneous reverse pulse sequence during the cleaning cycle. The instantaneous reverse pulse sequence includes, in sequence: a forward deceleration phase in which the drive motor is decelerated from forward rotation to a stop using a gradual acceleration and deceleration method; a reverse acceleration phase in which the drive motor is accelerated in the reverse direction to a speed lower than the normal forward rotation speed using a gradual acceleration and deceleration method; a reverse holding phase in which the reverse rotation is maintained for a preset duration; and a forward recovery phase in which the drive motor is restored to forward rotation using a gradual acceleration and deceleration method. The control unit is also configured to control the suction pump to run for a preset time before executing the instantaneous reverse pulse sequence. During constant rotation, the biofilm substrate attached to the mesh surface releases internal stress through the creep deformation of its viscoelastic matrix, thus ensuring its continued survival. The reversal pulse causes abrupt changes in the shear direction of the wall, and the creep elastic recovery stress accumulated in the substrate layer is superimposed in the same direction with the external reverse shear stress, causing the matrix to fatigue fracture and detach. Each stage adopts a gradual acceleration and deceleration method, so that the angular velocity of the planetary gear set approaches zero when the tooth surface switches, reducing the peak torque of the backlash impact. Before executing the reversal pulse, the suction pump is run in advance to discharge the sediment in the bottom collection area, reducing the amount of sediment that may be stirred up during the reversal due to the temporary reversal of the pumping direction of the spiral guide vanes.

[0021] In one embodiment, a sealing partition is provided inside the housing below the inner and outer filter baskets. The sealing partition and the bottom wall of the housing form a sealed gear cavity. The planetary gear set is encapsulated in the sealed gear cavity, which is filled with lubricating oil. The rotating shaft of the inner filter basket and the hollow tube shaft pass through the sealing partition, respectively. Two concentric labyrinth seal structures are provided at the passage of the sealing partition, wherein the outer labyrinth seal is disposed between the outer wall surface of the hollow tube shaft and the inner wall of the through hole of the sealing partition. Between the inner labyrinth seal, an inner labyrinth seal is disposed between the outer wall of the inner filter basket shaft and the inner wall of the hollow tube shaft; an axial gap is left between the bottom plate of the outer filter basket and the upper surface of the sealing partition to form a radially penetrating space; an annular sludge collection groove is provided in the area corresponding to the gap between the inner wall of the housing and the outer wall of the outer filter basket; several sludge discharge notches are evenly provided along the circumference of the outer edge of the bottom plate of the outer filter basket; the sludge discharge notches penetrate the thickness of the bottom plate and extend to the bottom end of the cylindrical wall of the outer filter basket; the annular sludge collection groove is connected to the sludge discharge outlet.

[0022] A sealing partition completely isolates the planetary gear set from the ballast water in the filtration area and fills it with lubricating oil, eliminating seawater corrosion of the gear surfaces and abrasive wear of suspended particles on the meshing surfaces. Two concentric labyrinth seal structures form multi-stage throttling channels between the outer wall of the hollow tube shaft and the inner wall of the partition through-hole, and between the outer wall of the inner filter basket shaft and the inner wall of the hollow tube shaft, respectively. This ensures that both the inner and outer coaxial shafts rotating at different speeds are isolated from the gear cavity through non-contact seals. The drain notch on the outer edge of the outer filter basket bottom plate allows impurities that settle in the annular gap to be radially thrown out by the centrifugal force generated by the rotation of the outer filter basket. These impurities fall through the drain notch into the radially penetrating space below the bottom plate and finally flow into the annular collection trough for discharge.

[0023] In summary, this application includes at least one of the following beneficial technical effects:

[0024] 1. By setting up coaxial nested inner and outer filter baskets and making the mesh diameter of the inner filter basket larger than that of the outer filter basket, the water to be filtered flows from the inside to the outside, undergoing coarse filtration and fine filtration in sequence. This improves the filtration accuracy while dispersing the impurity load of the single-layer filter screen and reducing the risk of single-stage clogging.

[0025] 2. By setting up a planetary gear set and fixing the gear ring, with the sun gear driving the inner filter basket and the planetary carrier driving the outer filter basket through a hollow tube shaft, a single drive motor achieves the same-direction, different-speed rotation of the inner and outer filter baskets. This simplifies the drive system and ensures the differential speed relationship between the two filter baskets. The structure of the hollow tube shaft coaxially sleeved on the outside of the inner filter basket's rotating shaft reduces the radial space occupied by the entire transmission shaft system, and the radial support bearing ensures the coaxiality of the two shafts during differential rotation.

[0026] 3. By setting up elastic pre-tightening components, the nozzle and suction pipe are elastically pressed against and attached to the outer and inner walls of the rotating filter basket, respectively. This ensures that the cleaning module and suction module remain in close contact with the mesh surface during the rotation of the filter basket, compensating for manufacturing tolerances and radial runout, and guaranteeing the effectiveness of cleaning and suction.

[0027] 4. By offsetting the same pair of nozzles and suction pipes around the filter basket, the cleaning medium generates a tangential flow component along the mesh surface after passing through the filter screen. This component, combined with the wall motion of the rotating filter basket, forms an alternating shearing action, increasing the tangential peeling ability of biofilm-like attachments spread along the mesh surface.

[0028] 5. By setting spiral guide vanes on the outer wall of the inner filter basket, the centrifugal force and axial pumping effect generated by the vanes following the rotation of the inner filter basket are used to establish an ordered spiral downward flow field in the annular gap. This simultaneously achieves centrifugal separation and discharge of heavy particles, structural reinforcement of the thin-walled basket, improvement of the shear level in the near-wall region near the outer wall of the inner basket, and axial directional transport of the washed and peeled fragments.

[0029] 6. By setting the control unit to control the frequency converter to execute the instantaneous reverse pulse sequence during the cleaning cycle, the sudden change in the shear direction of the wall surface causes the creep strain accumulated in the biofilm basal layer to be superimposed with the reverse stress, resulting in fracture and shedding. Combined with the tangential peeling of the bias cleaning and the axial conveying of the spiral blades, a cleaning process with three stages of fracture, peeling and discharge are formed in sequence.

[0030] 7. By setting a sealing partition to encapsulate the planetary gear set in a sealed gear cavity filled with lubricating oil, the gear transmission system is completely isolated from the ballast water environment, eliminating the impact of seawater corrosion and abrasive wear on transmission accuracy and extending the service life of the drive mechanism.

[0031] 8. By setting a drain notch on the outer edge of the bottom plate of the outer filter basket and placing the annular sludge collection tank between the inner wall of the shell and the outer wall of the outer filter basket, the centrifugal force generated by the rotation of the outer filter basket is used to throw impurities from the bottom of the annular gap into the sludge collection tank through the drain notch. Combined with the pipeline transportation of the main collection pipeline and the negative pressure drainage of the suction pump, three sewage discharge paths are formed to work in concert: passive centrifugal discharge, active pipeline transportation, and negative pressure auxiliary drainage, which ensures the effective discharge of impurities of various particle sizes and shapes. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the overall structure of a self-cleaning ballast water filter provided in this application.

[0033] Figure 2 A cross-sectional schematic diagram of a self-cleaning ballast water filter provided in this application.

[0034] Figure 3 This is a schematic diagram of the cleaning module in a self-cleaning ballast water filter provided in this application.

[0035] Figure 4 An exploded view of the inner and outer filter baskets in a self-cleaning ballast water filter provided in this application.

[0036] Figure 5 This is a cross-sectional schematic diagram of a self-cleaning ballast water filter provided in this application without a cleaning module.

[0037] Figure 6 for Figure 5 Enlarged diagram of point A in the middle.

[0038] Figure 7 This is a schematic diagram of the sun gear, planet gears, and gear ring in a self-cleaning ballast water filter provided in this application.

[0039] Figure 8This is a schematic diagram showing the connection between the planetary carrier and the hollow tube shaft in a self-cleaning ballast water filter provided in this application.

[0040] Figure 9 This is a schematic diagram showing the arrangement of the cleaning module and suction module inside the inner and outer filter baskets of a self-cleaning ballast water filter provided in this application.

[0041] Figure 10 This application provides a control connection diagram for a self-cleaning ballast water filter.

[0042] Explanation of reference numerals in the attached figures:

[0043] 1. Housing; 10. Supporting foot; 11. Inlet; 12. Outlet; 13. Sewage outlet; 14. First cleaning port; 15. Second cleaning port; 16. Annular gap; 17. Sealing partition; 171. Labyrinth seal structure; 18. Sealing gear cavity; 181. Lubricating oil; 182. Oil pump; 1821. One-way valve; 183. Accumulator; 19. Annular sludge collection tank; 20. Viewing window; 2. Inner filter basket; 3. Outer filter basket; 31. Sewage discharge notch; 4. Inlet pipe; 5. Drive mechanism; 51. Drive motor; 511. Frequency converter; 52. Planetary gear set; 521. Sun gear; 52 2. Planetary gear; 523. Planetary carrier; 524. Gear ring; 53. Hollow tube shaft; 54. Radial support bearing; 6. Cleaning module; 61. Nozzle; 62. Main distribution pipeline; 63. First elastic preload; 64. Pressurized water pipeline; 65. Pressurized air pipeline; 66. Main pressurized pipeline; 661. External pressurized pipeline; 662. Internal pressurized pipeline; 663. Connecting pipeline; 67. Valve; 7. Suction module; 71. Suction pipe; 72. Main collection pipeline; 73. Suction pump; 74. Second elastic preload; 75. Collection tank; 8. Spiral guide vane; 81. Chamfer; 9. Control unit. Detailed Implementation

[0044] This application provides a self-cleaning ballast water filter, which is described below in conjunction with the appendix. Figure 1-10 This application will be described in further detail.

[0045] A self-cleaning ballast water filter includes a housing 1, an inner filter basket 2, an outer filter basket 3, a drive mechanism 5, a cleaning module 6, and a suction module 7.

[0046] In this embodiment, the shell 1 is a vertical cylindrical closed container. A water inlet 11 is provided on the top plate of the shell 1, and a water inlet pipe 4 is connected to the water inlet 11. A water outlet 12 is provided on the upper part of the side wall of the shell 1, and a sewage outlet 13 is provided on the lower part of the side wall of the shell 1. The height of the water outlet 12 is higher than that of the sewage outlet 13. A first cleaning port 14 and a second cleaning port 15 are also provided on the top plate of the shell 1 for external cleaning pipes to pass through and enter the interior of the shell 1.

[0047] The bottom of the housing 1 is provided with several support feet 10. The support feet 10 are evenly distributed along the outer circumference of the bottom wall of the housing 1. In this embodiment, the number of support feet 10 is preferably four, one of which is arranged every 90 degrees along the circumference. The support feet 10 are L-shaped or T-shaped steel structural members, and their upper ends are welded to the outer surface of the bottom wall of the housing 1. In this embodiment, full welding is preferably used to ensure the connection strength.

[0048] At least one viewing window 20 is provided on the side wall of the housing 1, allowing the operator to directly observe the state of the inner filter basket 2 and the outer filter basket 3 from the outside of the housing 1 through the viewing window 20. In this embodiment, the viewing window 20 is preferably tempered glass, and the number of viewing windows 20 is preferably two, symmetrically distributed along the circumference of the side wall of the housing 1, so as to observe the interior of the housing 1 from different angles.

[0049] In this embodiment, both the inner filter basket 2 and the outer filter basket 3 are cylindrical mesh basket structures, coaxially nested inside the housing 1. The outer filter basket 3 is fitted onto the outside of the inner filter basket 2, forming an annular gap 16 between them. The mesh aperture of the inner filter basket 2 is larger than that of the outer filter basket 3. The inlet pipe 4 extends downward from the inlet 11 through the internal space of the housing 1 and into the internal space of the inner filter basket 2. The ballast water to be filtered is injected into the inner filter basket 2 through the inlet pipe 4, first passing through the mesh surface of the inner filter basket 2 from the inside out and entering the annular gap 16 to complete coarse filtration, and then continuing to pass through the mesh surface of the outer filter basket 3 from the inside out and entering the space between the outer filter basket 3 and the housing 1 to complete fine filtration. The filtered water is discharged from the outlet 12. Gradient grading filtration is achieved through the two-stage filter baskets with different pore sizes, so that the inner filter basket 2 undertakes the coarse filtration task of intercepting large particulate impurities, and the outer filter basket 3 undertakes the fine filtration task of intercepting fine particulate impurities. Each of the two filter screens bears the impurity load matched to its pore size. In this embodiment, the mesh size of the inner filter basket 2 is preferably 200-500 micrometers, and the mesh size of the outer filter basket 3 is preferably 25-50 micrometers. The inner filter basket 2 is responsible for coarse filtration, and the impurity particles intercepted on its mesh surface are relatively large and have weak adhesion. The higher rotation speed increases the wall shear stress on the mesh surface of the inner filter basket 2, which is conducive to the large particles of impurities falling off the mesh surface under the combined action of centrifugal force and shear force and being thrown into the annular gap 16 between the inner filter basket 2 and the outer filter basket 3. The outer filter basket 3 is responsible for fine filtration, and its mesh size is relatively small. The lower rotation speed reduces the risk of fine particles of impurities embedding into the mesh under the action of centrifugal force. At the same time, the rotation speed difference between the two baskets causes the fluid in the annular gap 16 to generate relative shear motion, which is beneficial to prevent impurities from depositing in the annular gap 16.

[0050] In this embodiment, the drive mechanism 5 includes a drive motor 51 and a planetary gear set 52. The drive motor 51 is mounted on the bottom plate of the housing 1 and faces the external space, with its output shaft passing through the bottom plate and extending into the interior of the housing 1. The planetary gear set 52 includes a sun gear 521, several planet gears 522, a planet carrier 523, and a ring gear 524. The ring gear 524 is fixedly connected to the housing 1 and remains stationary. The sun gear 521 is coaxially connected to the output shaft of the drive motor 51. The sun gear 521 is also connected to the rotating shaft of the inner filter basket 2, and when the drive motor 51 operates, the sun gear 521 drives the inner filter basket 2 to rotate. Several planet gears 522 mesh between the sun gear 521 and the ring gear 524, and the planet gears 522 are mounted on the planet carrier 523. The planet carrier 523 is connected to the bottom plate of the outer filter basket 3 through a hollow tube shaft 53, driving the outer filter basket 3 to rotate.

[0051] Specifically, the hollow tube shaft 53 is a hollow tubular structure, coaxially sleeved on the outside of the rotating shaft of the inner filter basket 2. The lower end of the hollow tube shaft 53 is fixedly connected to the planetary carrier 523, and the upper end is connected to the bottom plate of the outer filter basket 3 via a flange. At least two sets of radial support bearings 54 are axially spaced between the rotating shaft of the inner filter basket 2 and the hollow tube shaft 53. The radial support bearings 54 constrain the two shafts to share the same axis, while allowing the two shafts to rotate freely at different speeds. In this embodiment, the number of radial support bearings 54 is preferably two sets. Since the gear ring 524 is fixed, based on the kinematic relationship of the planetary gear system, the output speed of the planetary carrier 523 is lower than the input speed of the sun gear 521 and the rotation direction is the same, that is, the inner filter basket 2 rotates at a higher speed while the outer filter basket 3 rotates in the same direction at a lower speed. The drive motor 51 is equipped with a frequency converter 511, which can control the speed and rotation direction of the drive motor 51. In this embodiment, the number of planetary gears 522 is preferably four, and the radial support bearings 54 are preferably deep groove ball bearings.

[0052] In this embodiment, a cleaning module 6 and a suction module 7 are respectively provided in pairs for the inner filter basket 2 and the outer filter basket 3. The cleaning module 6 is suspended and fixed to the pressurization main pipeline 66 via the distribution main pipeline 62. The pressurization main pipeline 66 is fixedly installed inside the top plate of the housing 1. Therefore, the cleaning module 6 remains stationary and does not rotate with the top plate of the housing 1 as the final fixed base. The suction module 7 extends downward via the collection main pipeline 72. The lower end of the collection main pipeline 72 is fixed to the upper surface of the sealing partition 17. Therefore, the suction module 7 remains stationary and does not rotate with the sealing partition 17 as the final fixed base.

[0053] Specifically, the cleaning module 6 includes a nozzle 61 and a first elastic pre-tightening member 63. The nozzle 61 is mounted on the main distribution pipeline 62 via the first elastic pre-tightening member 63. Specifically, the main distribution pipeline 62 is a rigid pipeline, with its upper end rigidly connected to the main pressurization pipeline 66 and its lower end extending to the height of the outer wall of the corresponding filter basket. The fixed end of the first elastic pre-tightening member 63 is fixed to the main distribution pipeline 62, and its movable end is connected to the nozzle 61, applying an elastic clamping force to the nozzle 61 in the radial direction, pointing towards the outer wall of the filter basket. The reaction force of the elastic pre-tightening is transmitted through the main distribution pipeline 62 to the main pressurization pipeline 66, and then from the main pressurization pipeline 66 to the top plate of the housing 1.

[0054] Specifically, the suction module 7 includes a suction pipe 71 and a second elastic pre-tightening member 74. The suction pipe 71 is mounted on the main collection pipeline 72 via the second elastic pre-tightening member 74. Specifically, the main collection pipeline 72 is a rigid pipeline that extends axially downward and passes through the bottom plate of the corresponding filter basket. The fixed end of the second elastic pre-tightening member 74 is fixed to the main collection pipeline 72, and the movable end is connected to the suction pipe 71, applying an elastic clamping force to the suction pipe 71 in the radial direction, pointing towards the inner wall of the filter basket. The reaction force of the elastic pre-tightening is transmitted through the main collection pipeline 72 to the pipeline labyrinth seal at the bottom plate crossing and the fixed support at the lower end of the main collection pipeline, and finally to the sealing partition 17 or the housing 1.

[0055] Specifically, in this embodiment, both the first elastic pretensioner 63 and the second elastic pretensioner 74 are preferably springs. The compression stroke of the first elastic pretensioner 63 is preferably 8mm to 15mm, and the compression stroke of the second elastic pretensioner 74 is preferably 8mm to 15mm.

[0056] Specifically, in addition to the water inlet 11, the top plate of the casing 1 also has a first cleaning port 14 and a second cleaning port 15. A pressurized water supply pipeline 64 and a pressurized air supply pipeline 65 pass through the first cleaning port 14 and the second cleaning port 15 respectively and enter the interior of the casing 1. The pressurized water supply pipeline 64 is connected to an external pressurized water pump as a pressurized water source, and the pressurized air supply pipeline 65 is connected to an external air compressor as a pressurized air source. Both the pressurized water supply pipeline 64 and the pressurized air supply pipeline 65 are equipped with valves 67. By opening or closing the corresponding valves 67, the air washing mode or the water washing mode can be selected. A pressurized main pipeline 66 is fixedly installed on the side wall of the top plate of the casing 1 facing the interior of the casing 1. The pressurized main pipeline 66 is connected to both the pressurized water supply pipeline 64 and the pressurized air supply pipeline 65. The pressurized main pipeline 66 includes an external pressurized pipeline 661 and an internal pressurized pipeline 662. The external pressurized pipeline 661 corresponds to the external filter basket 3, and the internal pressurized pipeline 662 corresponds to the internal filter basket 2. Both are annular pipelines and are interconnected through a connecting pipeline 663. The external pressurized pipeline 661 is connected to the main distribution pipeline 62 of each nozzle 61 corresponding to the external filter basket 3, and the internal pressurized pipeline 662 is connected to the main distribution pipeline 62 of each nozzle 61 corresponding to the internal filter basket 2. The annular pipeline design ensures that each nozzle 61 receives a uniform liquid or gas supply pressure in the circumferential direction. When valve 67, which connects to the pressurized water source, is opened, pressurized water flows sequentially through pressurized water supply pipeline 64, pressurized main pipeline 66, and distribution main pipeline 62 to each nozzle 61, and is sprayed onto the outer wall of the filter basket to wash the mesh surface; when valve 67, which connects to the pressurized air source, is opened, compressed air flows through the same pipeline system to each nozzle 61 and is sprayed out at high speed, using air pressure to impact the outer wall of the mesh surface and blow off the attached material.

[0057] Specifically, all suction pipes 71 corresponding to the same filter basket are interconnected through a main collection pipe 72 corresponding to that filter basket. The main collection pipe 72 corresponding to the inner filter basket 2 and the main collection pipe 72 corresponding to the outer filter basket 3 extend downward along the axial direction, pass through the bottom plate of the inner filter basket 2 or the bottom plate of the outer filter basket 3, and enter the annular sludge collection groove 19 between the inner wall of the housing 1 and the outer wall of the outer filter basket 3. A sludge discharge outlet 13 is provided on the side wall of the housing 1 at the position corresponding to the annular sludge collection groove 19. A suction pump 73 located outside the housing 1 is connected to the sludge discharge outlet 13 through a pipe. The main collection pipe 72 consists of cylindrical pipe sections that pass through the bottom plates of the inner filter basket 2 and the outer filter basket 3. Each crossing point is equipped with a pipe labyrinth seal, formed by multiple annular protrusions on the outer wall of the pipe and corresponding annular grooves on the inner wall of the bottom plate's through-hole, creating a multi-stage throttling channel. This ensures a non-contact seal between the stationary pipe and the rotating bottom plate, allowing the bottom plate to rotate freely with the filter basket while preventing water leakage along the pipe crossing points in the filtration area. In this embodiment, the suction pump 73 is preferably a self-priming centrifugal pump.

[0058] In this embodiment, each pair of nozzles 61 and suction pipes 71 corresponding to the same filter basket are offset circumferentially within the filter basket. That is, the contact position of the nozzle 61 on the outer wall of the filter basket and the contact position of the suction pipe 71 on the inner wall of the same filter basket are not directly opposite each other in the circumferential direction, and there is a circumferential offset angle between them. In this embodiment, the offset angle is set to 25 to 35 degrees. The opening of the suction pipe 71 is inclined relative to the radial direction of the corresponding filter basket, so that the normal direction of the opening surface of the suction pipe 71 is deflected towards the circumferential side indicated by the offset angle, and the inclination direction is consistent with the offset circumferential direction. The opening width of the suction pipe 71 is greater than the outlet width of the nozzle 61 to cover the range of oblique streamline divergence caused by the offset. The suction flow rate of the suction pump 73 is set to be not less than the ejection flow rate of the nozzle 61 to ensure that the cleaning medium flow passing through the filter screen is concentrated and captured by the suction pipe 71. When pressurized water or compressed air is ejected from nozzle 61 and passes through the mesh, the medium travels along the inner wall of the mesh for a certain arc length before entering the suction pipe 71, because the suction pipe 71 is not directly opposite the radial direction of nozzle 61 but is biased to one side. This results in the cleaning flow passing through the mesh having both a normal component perpendicular to the mesh and a tangential component traveling along the mesh.

[0059] In this embodiment, a plurality of spiral guide vanes 8 are fixedly connected to the outer wall of the inner filter basket 2. The spiral guide vanes 8 are connected to the outer wall of the inner filter basket 2 by continuous welding or integrally formed with the basket body; in this embodiment, continuous welding is preferred. The spiral guide vanes 8 are evenly distributed along the circumferential direction of the outer wall of the inner filter basket 2, and in this embodiment, 4 to 6 vanes are provided. The spiral guide vanes 8 rotate together with the inner filter basket 2. The spiral direction of the spiral guide vanes 8 is set so that when the drive motor 51 rotates in the forward direction, the vanes push the fluid in the annular gap 16 axially toward the bottom of the housing 1. The radial height of the spiral guide vanes 8 is less than half the width of the annular gap 16; in this embodiment, the radial height is approximately 30% of the width of the annular gap 16. The radial height of the spiral guide vanes 8 is also less than the value of the smaller compression stroke of the first elastic pre-tightening member 63 and the second elastic pre-tightening member 74. The leading edge of the spiral guide vanes 8 is provided with a rounded chamfer 81. The angle between the spiral guide vanes 8 and the outer wall of the inner filter basket 2, i.e., the spiral angle, is set to 15 degrees to 30 degrees. When the leading edge of the spiral guide vane 8 sweeps across the circumferential position of the nozzle 61 or suction pipe 71 during rotation, the chamfered surface 81 of the leading edge of the vane first contacts the abutment end of the elastic pretensioner and smoothly pushes it away radially. After the vane passes, the elastic pretensioner rebounds, causing the nozzle 61 or suction pipe 71 to return to its working position against the mesh surface. Because the vane thickness is very small relative to the circumferential spacing, the time taken for a single sweep is extremely short, and the interval between adjacent vanes is much greater than the rebound time of the elastic pretensioner. The elastic pretensioner is completely reset before the next vane arrives. In this embodiment, the width of the annular gap 16 is preferably 15mm to 40mm.

[0060] Specifically, as the helical guide vanes 8 rotate at high speed with the inner filter basket 2, a helical flow field is established in the annular gap 16. In this flow field, fluid particles are radially propelled by centrifugal force and axially propelled by the helical surface of the blades. Heavy particles in the annular gap 16 migrate towards the inner wall of the outer filter basket 3 under the action of centrifugal force, and are transported to the bottom along the inner wall of the outer filter basket 3 under the influence of the axial component of the helical flow. The helical guide vanes 8 also act as reinforcing ribs for the thin-walled inner filter basket 2, improving the radial stiffness of the basket under rotational and differential pressure loads. When the blades rotate, leading-edge separation vortices and wake turbulence are generated near the outer wall of the inner filter basket 2, increasing the shear level in the near-wall region.

[0061] In this embodiment, the filter also includes a control unit 9. The control unit 9 is electrically connected to the frequency converter 511 and the suction pump 73. The control unit 9 is configured to control the frequency converter 511 to execute an instantaneous reverse pulse sequence during the cleaning cycle. The sequence includes the following stages in sequence: First, a forward deceleration stage, in which the control unit 9 instructs the frequency converter 511 to gradually decelerate the drive motor 51 from the normal forward speed to a stop in a gradual acceleration and deceleration manner. This stage ensures that the angular velocity of the planetary gear set 52 approaches zero when the tooth surface transitions from the forward drive surface to the reverse drive surface near the zero speed crossing. Second, a reverse acceleration stage, in which the control unit 9 instructs the frequency converter 511 to accelerate the drive motor 51 in the reverse direction to a target reverse speed in a gradual acceleration and deceleration manner. This target reverse speed is lower than the normal forward speed. Then, a reverse holding stage, in which the reverse rotation is maintained for a preset duration. Finally, a forward recovery stage, in which the control unit 9 instructs the frequency converter 511 to gradually accelerate the drive motor 51 from the reverse rotation to the normal forward speed after stopping in a gradual acceleration and deceleration manner. Before executing the instantaneous reversal pulse sequence, the control unit 9 first controls the suction pump 73 to run for a preset time to pre-pump the impurities that have been deposited in the dirt collection area at the bottom of the housing 1, so as to reduce the amount of sediment that may be stirred up during the reversal due to the temporary change in the pumping direction of the spiral guide vane 8.

[0062] Specifically, in this embodiment, the control unit 9 is preferably a programmable logic controller.

[0063] Specifically, in this embodiment, the gradual acceleration / deceleration method is preferably an S-shaped acceleration / deceleration curve, in which the angular acceleration during the acceleration / deceleration process approaches zero at the beginning and end and smoothly transitions in the middle period, which is different from the linear acceleration / deceleration method with abrupt changes in angular acceleration; the forward normal speed is the steady-state operating speed of the drive motor 51 under filtration conditions, and the speed of the inner filter basket 2 is preferably 200 to 400 revolutions per minute; the target reverse speed is preferably 30% to 50% of the forward normal speed; the duration of the forward deceleration phase is preferably 1 to 2 seconds, the duration of the reverse acceleration phase is preferably 0.5 to 1 second, the preset duration of the reverse holding phase is preferably 0.5 to 3 seconds, the duration of the forward recovery phase is preferably 1 to 2 seconds, the total duration of the entire instantaneous reverse pulse sequence is preferably 4 to 8 seconds, and the execution interval between two adjacent instantaneous reverse pulse sequences is preferably 10 to 30 minutes; the preset time for the control unit 9 to control the operation of the suction pump 73 before executing the instantaneous reverse pulse sequence is preferably 3 to 5 seconds.

[0064] In this embodiment, a sealing partition 17 is provided inside the housing 1 below the inner filter basket 2 and the outer filter basket 3. The sealing partition 17 is a horizontally arranged plate structure, and its outer edge is sealed to the inner wall of the housing 1. The sealing partition 17 and the bottom wall of the housing 1 form a closed sealed gear cavity 18. The planetary gear set 52 is entirely encapsulated in this sealed gear cavity 18. The sealed gear cavity 18 is filled with lubricating oil 181, and in this embodiment, a biodegradable lubricating oil 181 that meets the environmental protection requirements for ships is preferably used.

[0065] Specifically, a hollow tube shaft 53 is fitted over the rotating shaft of the inner filter basket 2. The rotating shaft of the inner filter basket 2 and the hollow tube shaft 53 pass through the sealing partition 17 and enter the sealing gear cavity 18 to connect with the corresponding components of the planetary gear set 52. After passing through the inner cavity of the hollow tube shaft 53, the rotating shaft of the inner filter basket 2 connects to the sun gear 521, and after passing through the sealing partition 17, the hollow tube shaft 53 connects to the planet carrier 523. Two concentric labyrinth seal structures 171 are provided at the passage of the sealing partition 17. The outer labyrinth seal is located between the outer wall of the hollow tube shaft 53 and the inner wall of the through hole of the sealing partition 17. It is formed by multiple annular protrusions on the outer wall of the hollow tube shaft 53 and corresponding annular grooves on the inner wall of the through hole of the sealing partition 17, which are interlocked with a small gap to form a multi-stage throttling channel. The inner labyrinth seal is located between the outer wall of the inner filter basket 2's rotating shaft and the inner wall of the hollow tube shaft 53. It is formed by multiple annular protrusions on the outer wall of the rotating shaft and corresponding annular grooves on the inner wall of the hollow tube shaft 53, which are interlocked with a small gap to form a multi-stage throttling channel. Both labyrinth seal structures 171 are non-contact seals, with no friction or wear parts, and independently seal the two coaxial shafts rotating at different speeds.

[0066] Specifically, an oil pump 182 is installed inside the sealed gear cavity 18. The oil pump 182 is connected to the output shaft of the drive motor 51 and is driven by the drive motor 51 when it rotates in the forward direction without the need for an additional power source. A one-way valve 1821 is provided at the outlet of the oil pump 182. When the drive motor 51 rotates in the forward direction, the oil pump 182 pumps lubricating oil 181 into the sealed gear cavity 18 to maintain the oil pressure inside the cavity; when the drive motor 51 rotates in the reverse direction, during the execution of the instantaneous reverse pulse sequence, the oil pump 182 runs in reverse, but the one-way valve 1821 closes to prevent the lubricating oil 181 from being drawn out.

[0067] Specifically, an accumulator 183 is also provided inside the sealed gear cavity 18. During normal operation, the accumulator 183 is pressurized and stored by the oil pump 182. During the reverse pulse, the one-way valve 1821 closes and the oil pump 182 stops forward output for a short period of time, releasing the stored pressure energy to maintain the oil pressure inside the cavity higher than the water pressure in the filtration area above the sealing partition 17. The oil pump 182 and the accumulator 183 together ensure that the sealed gear cavity 18 is always kept at a slightly positive pressure state higher than the water pressure in the filtration area, so that the pressure gradient direction in each throttling gap of the labyrinth seal structure 171 is from the oil cavity side to the seawater side. Even if a small amount of leakage occurs, it is the lubricating oil 181 that seeps out to the filtration side rather than seawater entering the sealed gear cavity 18.

[0068] Specifically, an annular sludge collection trough 19 is provided above the sealing partition 17. The annular sludge collection trough 19 is located at the bottom between the inner wall of the housing 1 and the outer wall of the outer filter basket 3, on the upper surface of the sealing partition 17. It is used to collect impurity particles discharged through the drain opening 31 of the bottom plate of the outer filter basket 3, the suction sludge collected by the main pipeline 72, and suspended impurities brought in by negative pressure drainage. Several drain openings 31 are evenly provided around the circumference of the outer edge of the bottom plate of the outer filter basket 3. The drain openings 31 penetrate the thickness of the bottom plate and extend to the bottom end of the cylindrical wall of the outer filter basket 3. When the outer filter basket 3 rotates, the impurities on the upper surface of the bottom plate are discharged into the radially penetrating space below the bottom plate under the action of centrifugal force through the drain openings 31, and flow into the annular sludge collection trough 19 through this space. The annular sludge collection trough 19 is connected to the drain outlet 13 on the side wall of the housing 1 through a pipeline. When the suction pump 73 is running, it draws out the impurity mixture in the annular sludge collection trough 19 through the drain outlet 13. The annular sludge collection trough 19 is located above the sealing partition 17 and is completely spatially separated from the sealing gear cavity 18 below the sealing partition 17. The sewage discharge channel does not pass through the sealing gear cavity 18. In this embodiment, the number of sewage discharge notches 31 is preferably 6, which are evenly distributed along the circumference.

[0069] Furthermore, when the suction pump 73 is running, a local negative pressure is formed at the opening of the suction pipe 71, which draws the impurities that fall off the mesh surface under the cleaning action, along with the cleaning medium, through the collection main pipeline 72 to the annular sludge collection tank 19, and finally discharges them from the sewage outlet 13.

[0070] Furthermore, the sewage outlet 13 is connected to the inlet of the suction pump 73 via a sewage pipe. The outlet of the suction pump 73 is connected to a collection tank 75. The collection tank 75 is preferably a closed pressure vessel for collecting the discharged sewage.

[0071] The working principle of the self-cleaning ballast water filter provided in this application embodiment is as follows:

[0072] During normal filtration, the drive motor 51 rotates in the forward direction, driving the inner filter basket 2 to rotate at a higher speed and the outer filter basket 3 to rotate at a lower speed in the same direction via the planetary gear set 52. The ballast water to be filtered is injected into the inner filter basket 2 through the inlet pipe 4, passes through the inner filter basket 2 to complete coarse filtration, passes through the outer filter basket 3 to complete fine filtration, and is discharged from the outlet 12. During this period, the spiral guide vanes 8 continue to work, generating a spiral downward flow in the annular gap 16, which throws heavy particles in the water onto the wall of the outer filter basket 3 under the action of centrifugal force and transports them axially to the upper surface of the bottom plate of the outer filter basket 3. Then, the centrifugal force generated by the rotation of the bottom plate throws the impurities through the drain hole 31 into the radial through space below the bottom plate, and finally flows into the annular collection tank 19, reducing the particle load on the mesh surface of the outer filter basket 3. The planetary gear set 52 inside the sealed gear cavity 18 is always immersed in lubricating oil 181. When the drive motor 51 rotates in the forward direction, the oil pump 182 continuously pumps lubricating oil 181 into the sealed gear cavity 18. Together with the accumulator 183, the oil pressure inside the cavity is maintained higher than the water pressure in the filter area above the sealing partition 17. Two concentric labyrinth seal structures 171 isolate the ballast water from the sealed gear cavity 18, so that the transmission system operates in the lubricating oil environment and avoids direct contact with seawater.

[0073] During online cleaning, the air washing mode is entered by opening valve 67 connected to the pressurized air source, or the water washing mode is entered by opening valve 67 connected to the pressurized water source. In air washing mode, compressed air is ejected at high speed from nozzle 61 through pressurized air supply line 65, pressurized main line 66, and distribution main line 62, impacting the rotating mesh surface with dynamic pressure to blow off attached impurities. In water washing mode, pressurized water is ejected from nozzle 61 through pressurized water supply line 64, pressurized main line 66, and distribution main line 62 to wash the mesh surface. Since each pair of nozzles 61 and suction pipe 71 are offset in the circumferential direction, the cleaning medium travels obliquely along the mesh surface to the suction port after passing through the mesh holes, generating a combined effect of normal impact force and tangential shear force on the mesh surface. The normal component pushes out particles embedded in the mesh holes, while the tangential component applies a peeling force to the biofilm-like attachments spread along the mesh surface. The continuous rotation of the filter basket causes each point on the screen to pass through the cleaning zone sequentially. Combined with the tangential flow of the cleaning medium, the sections of the screen passing through the cleaning zone experience alternating shearing forces with changing directions. The suction pump 73 operates synchronously with the cleaning module 6, capturing and collecting the detached impurities and cleaning medium through the inclined suction pipe 71. This is then transported via the main collection pipe 72 to the annular collection tank 19 and finally discharged from the drain outlet 13. Because the suction flow rate of the suction pump 73 is not less than the ejection flow rate of the nozzle 61, the cleaning medium passing through the filter screen is effectively collected and does not diffuse into the annular gap 16.

[0074] During deep cleaning, control unit 9 triggers an instantaneous reverse pulse sequence during the cleaning cycle. First, control unit 9 controls suction pump 73 to run for a preset time to pre-extract impurities deposited in the annular collection tank 19, reducing the amount of deposits that might be stirred up during the subsequent reverse phase due to the temporary change in pumping direction of the spiral guide vanes 8. After pre-extraction, control unit 9 instructs inverter 511 to begin executing the instantaneous reverse pulse sequence. During the forward deceleration phase, inverter 511 gradually decelerates drive motor 51 from its normal forward speed to a stop using an S-shaped gradual acceleration / deceleration curve. This curve brings the angular acceleration near zero speed close to zero, keeping the backlash impact experienced by the planetary gear set 52 during the transition from the forward drive surface to the reverse drive surface at a low level. During the reverse acceleration phase, inverter 511 accelerates drive motor 51 in the reverse direction to a target reverse speed using an S-shaped gradual acceleration / deceleration curve. This target reverse speed is lower than the normal forward speed, causing both the inner filter basket 2 and the outer filter basket 3 to rotate in the opposite direction. During the reverse holding phase, the drive motor 51 maintains reverse rotation for a preset duration. During reverse rotation, the wall shear direction on the filter basket mesh is opposite to that during forward rotation. The biofilm substrate layer attached to the mesh accumulates internal strain along the forward direction through viscoelastic creep during constant forward rotation. When the shear direction changes abruptly, the creep elastic recovery stress in the substrate layer that has not yet relaxed is superimposed in the same direction with the external reverse shear stress, causing the actual stress borne locally by the substrate layer to exceed its adhesion strength, thus causing the biofilm matrix to break and detach. During this period, the pumping direction of the spiral guide vane 8 temporarily changes from downward to upward. However, since the sediment in the annular sludge collection tank 19 has been pre-discharged by the suction pump 73 before reversing, the amount of residual impurities that can be lifted is limited, and the particle size of these impurities is larger than the mesh size of the outer filter basket 3 and will not pass through the outer filter basket 3 into the effluent. At the same time, since the driving force of the filtration flow from the inside to the outside comes from the inlet and outlet pressure difference maintained by the inlet pump, this pressure difference is not affected by the change in the rotation direction of the filter basket, so the filtration function is not interrupted during the reverse rotation. During reverse rotation, the direction of centrifugal force at the drain notch 31 on the bottom plate of the outer filter basket 3 remains unchanged. Therefore, impurities that have settled on the surface of the bottom plate will continue to be flung out by centrifugal force through the drain notch 31, and the passive drain path remains effective during reverse rotation. In the sealed gear cavity 18, when the drive motor 51 rotates in reverse, the oil pump 182 runs in reverse, but the one-way valve 1821 closes to prevent the lubricating oil 181 from being back-drawn out. During this brief period, the accumulator 183 releases the stored pressure energy, maintaining the slightly positive pressure state in the cavity unaffected. After the reverse holding phase ends, the forward recovery phase begins. The frequency converter 511 uses an S-shaped gradual acceleration and deceleration curve to restore the drive motor 51 from reverse rotation to normal forward speed after stopping.After resuming forward rotation, the offset cleaning module 6, using tangential shear force, lifts the biofilm fragments that broke during the reversal phase but still remain on the mesh surface from the mesh and sweeps them towards the suction port. The spiral guide vanes 8, after resuming forward rotation, re-establish a downward-pumping spiral flow field, axially transporting the fragments entering the annular gap 16 to the upper surface of the bottom plate of the outer filter basket 3. These fragments are then thrown through the drain notch 31 into the radially penetrating space below the bottom plate, ultimately flowing into the annular collection tank 19 and being discharged by the continuously operating suction pump 73 through the drain outlet 13. Thus, the three stages of breakage, peeling, and discharge are sequentially connected, completing a full deep cleaning process. The instantaneous reversal pulse sequence is repeated at preset intervals, continuously removing biofilm substrate deposits that are difficult to remove with conventional online cleaning without stopping the machine or disassembling it.

[0075] Furthermore, during the cleaning of the outer filter basket 3, the nozzle 61 sprays cleaning media from the outer wall side of the outer filter basket 3, which passes through the mesh surface and enters the annular gap 16 side, where it is collected and captured by the suction pipe 71 located on the inner wall surface of the outer filter basket 3. During the cleaning process, a small amount of cleaning media that passes through the mesh surface and enters the annular gap 16 mixes with the water to be filtered and then passes through the outer filter basket 3 again with the filtered water flow into the outlet side. Since the cleaning media itself is clean pressurized water or air, it will not pollute the quality of the outlet water.

[0076] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A self-cleaning ballast water filter, characterized in that, include: The housing (1) is provided with an inlet (11) and an outlet (12), and the side wall of the housing (1) is provided with a sewage outlet (13); An inner filter basket (2) and an outer filter basket (3) are coaxially nested inside the housing (1). The mesh size of the inner filter basket (2) is larger than that of the outer filter basket (3). A water inlet pipe (4) extends from the water inlet (11) into the interior space of the inner filter basket (2) of the housing (1). The filtered water flows through the inner filter basket (2) and the outer filter basket (3) in sequence and is discharged from the water outlet (12). A drive mechanism (5) is disposed on the housing (1). The drive mechanism (5) drives the inner filter basket (2) and the outer filter basket (3) to rotate in the same direction but at different speeds, wherein the speed of the inner filter basket (2) is higher than the speed of the outer filter basket (3); and A cleaning module (6) and a suction module (7) are provided in pairs corresponding to the inner filter basket (2) and the outer filter basket (3). The cleaning module (6) includes a nozzle (61) facing the outer wall of the corresponding filter basket. The suction module (7) includes a suction pipe (71) facing the inner wall of the corresponding filter basket. The nozzle (61) is connected to an external cleaning source through a distribution main pipeline (62). The suction pipe (71) is connected to a suction pump (73) through a collection main pipeline (72). The sewage outlet (13) is connected to the inlet of the suction pump (73).

2. The self-cleaning ballast water filter according to claim 1, characterized in that, The drive mechanism (5) includes a drive motor (51) and a planetary gear set (52). The planetary gear set (52) includes a sun gear (521), planet gears (522), a planet carrier (523), and a ring gear (524). The ring gear (524) is fixedly connected to the housing (1). The sun gear (521) is connected to the output shaft of the drive motor (51) and drives the inner filter basket (2) to rotate. The planet carrier (523) passes through a hollow... The tube shaft (53) is connected to the outer filter basket (3) and drives the outer filter basket (3) to rotate. The hollow tube shaft (53) is coaxially sleeved on the outside of the rotating shaft of the inner filter basket (2). The lower end of the hollow tube shaft (53) is fixedly connected to the planetary carrier (523), and the upper end is connected to the bottom plate of the outer filter basket (3). At least two sets of radial support bearings (54) are axially spaced between the rotating shaft of the inner filter basket (2) and the hollow tube shaft (53).

3. The self-cleaning ballast water filter according to claim 1, characterized in that, The cleaning module (6) further includes a first elastic pre-tightening member (63), and the suction module (7) further includes a second elastic pre-tightening member (74). The nozzle (61) is installed on the main distribution pipeline (62) via the first elastic pre-tightening member (63), and the first elastic pre-tightening member (63) is configured to allow the nozzle (61) to elastically abut against the outer wall surface of the corresponding filter basket. The suction pipe (71) is installed on the main collection pipeline (72) via the second elastic pre-tightening member (74), and the second elastic pre-tightening member (74) is configured to allow the suction pipe (71) to elastically abut against the inner wall surface of the corresponding filter basket.

4. A self-cleaning ballast water filter according to claim 1, characterized in that, The top plate of the housing (1) is provided with a first cleaning port (14) and a second cleaning port (15). A pressurized water supply pipeline (64) connected to an external pressurized water source passes through the first cleaning port (14) and enters the interior of the housing (1). A pressurized air supply pipeline (65) connected to an external pressurized air source passes through the second cleaning port (15) and enters the interior of the housing (1). The inner side of the top plate of the housing (1) is provided with a pressurized main pipeline (66). The pressurized main pipeline (66) is connected to both the pressurized water supply pipeline (64) and the pressurized air supply pipeline (65). The pressurized main pipeline (66) includes a pressurized external pipeline (661) and a pressurized internal pipeline (662). The pressurized external pipeline (661) and the pressurized internal pipeline (662) are interconnected by a connecting pipeline (663). The pressurized external pipeline (661) is connected to the distribution main pipeline (62) corresponding to the external filter basket (3). The pressurized internal pipeline (662) is connected to the distribution main pipeline (62) corresponding to the internal filter basket (2). Valves (67) are respectively provided on the pressurized water pipeline (64) and the pressurized gas pipeline (65).

5. A self-cleaning ballast water filter according to claim 3, characterized in that, Each pair of nozzles (61) and suction tubes (71) corresponding to the same filter basket are offset in the circumferential direction of the filter basket. The nozzles (61) at their abutting positions on the outer wall of the corresponding filter basket and the suction tubes (71) at their abutting positions on the inner wall of the corresponding filter basket have a circumferential offset angle, which is greater than 0 degrees and does not exceed 45 degrees.

6. A self-cleaning ballast water filter according to claim 5, characterized in that, The opening of the suction pipe (71) is inclined relative to the radial direction of the corresponding filter basket, and the inclination direction is consistent with the circumferential direction of the offset. The opening width of the suction pipe (71) is greater than the outlet width of the nozzle (61), and the suction flow rate of the suction pump (73) is not less than the ejection flow rate of the nozzle (61).

7. A self-cleaning ballast water filter according to claim 3, characterized in that, A plurality of spiral guide vanes (8) are connected to the outer wall surface of the inner filter basket (2). The spiral guide vanes (8) rotate together with the inner filter basket (2). The spiral direction of the spiral guide vanes (8) is set to push the fluid in the annular gap (16) between the inner filter basket (2) and the outer filter basket (3) axially toward the bottom of the housing (1) when rotating in the forward direction. The radial height of the spiral guide vanes (8) is less than the smaller value of the compression stroke of the first elastic pretensioner (63) and the second elastic pretensioner (74). The leading edge of the spiral guide vanes (8) is provided with a chamfer (81).

8. A self-cleaning ballast water filter according to claim 7, characterized in that, The spiral guide vanes (8) are evenly distributed along the circumference on the outer wall of the inner filter basket (2). The radial height of the spiral guide vanes (8) is less than half the width of the annular gap (16). The angle between the spiral guide vanes (8) and the outer wall of the inner filter basket (2) is less than 45 degrees.

9. A self-cleaning ballast water filter according to claim 2, characterized in that, It also includes a control unit (9), the drive motor (51) is equipped with a frequency converter (511), the control unit (9) is electrically connected to the frequency converter (511) and the suction pump (73), the control unit (9) is configured to control the frequency converter (511) to execute an instantaneous reverse pulse sequence during the cleaning cycle, the instantaneous reverse pulse sequence includes: a forward deceleration stage in which the drive motor (51) is decelerated from forward rotation to stop in a gradually accelerating manner, a reverse acceleration stage in which the drive motor (51) is accelerated in the reverse direction to a speed lower than the normal forward speed in a gradually accelerating manner, a reverse holding stage in which the reverse rotation is maintained for a preset time, and a forward recovery stage in which the drive motor (51) is restored to forward rotation in a gradually accelerating manner, the control unit (9) is also configured to control the suction pump (73) to run for a preset time before executing the instantaneous reverse pulse sequence.

10. A self-cleaning ballast water filter according to claim 2, characterized in that, Inside the housing (1), a sealing partition (17) is provided below the inner filter basket (2) and the outer filter basket (3). The sealing partition (17) and the bottom wall of the housing (1) form a sealed gear cavity (18). The planetary gear set (52) is encapsulated in the sealed gear cavity (18). The sealed gear cavity (18) is filled with lubricating oil (181). The rotating shaft of the inner filter basket (2) and the hollow tube shaft (53) pass through the sealing partition (17). Two concentric labyrinth seal structures (171) are provided at the passage of the sealing partition (17). The outer labyrinth seal is set on the outer wall surface of the hollow tube shaft (53) and the sealing partition (171). Between the inner walls of the through holes of 7), the inner labyrinth seal is set between the outer wall of the inner filter basket (2) shaft and the inner wall of the hollow tube shaft (53); the bottom plate of the outer filter basket (3) and the upper surface of the sealing partition (17) are left with a gap along the axial direction to form a radial through space. The area between the inner wall of the shell (1) and the outer wall of the outer filter basket (3) corresponding to the gap is provided with an annular dirt collection groove (19). The outer edge of the bottom plate of the outer filter basket (3) is provided with several sewage discharge notches (31) evenly along the circumference. The sewage discharge notches (31) penetrate the thickness of the bottom plate and extend to the bottom end of the cylindrical wall of the outer filter basket (3). The annular dirt collection groove (19) is connected to the sewage discharge outlet (13).

Images