A double-suction centrifugal pump with a built-in driving mechanism

Abstract

The application provides a double-suction centrifugal pump with a built-in driving mechanism, and belongs to the field of fluid delivery and special motor combination. The application comprises a split pump shell, an impeller, a pump shaft and a built-in driving mechanism. The pump shaft is fixed inside the pump shell, and two impellers are symmetrically sleeved on the pump shaft and can rotate around the pump shaft. The built-in driving mechanism is an axial flux motor structure, comprising a magnet and an induction coil. The induction coil is fixed on the pump shaft and located between the two impellers, and the magnet is embedded in each of the two impellers. A rotating alternating magnetic field is generated by electrifying the induction coil, which drives the impellers with the magnets on both sides to rotate synchronously around the stationary pump shaft, so as to realize the delivery of fluid. The application realizes the self-balancing of axial magnetic force, significantly reduces the axial load of the water-lubricated bearing, and prolongs the service life of the bearing and the whole machine.

Description

Technical Field

[0001] This invention relates to the field of centrifugal pumps, and particularly to a double-suction centrifugal pump with a built-in drive mechanism. Background Technology

[0002] Double-suction centrifugal pumps, as core equipment for high-flow-rate fluid transportation, are widely used in municipal water supply, industrial circulation, agricultural irrigation, and ship ballast. Their typical structure includes a pump body, pump cover, impeller, pump shaft, and external drive motor. The pump shaft is supported at both ends by bearing housings and is dynamically and statically isolated from the pump casing by mechanical seals. Torque is transmitted between the motor output shaft and the pump shaft via a coupling. While this classic transmission method has been validated through long-term engineering, several structural bottlenecks have gradually emerged under conditions of limited space, high leakage prevention requirements, and frequent maintenance, as detailed below:

[0003] First, the external radial flux motor needs to be placed on one side of the pump body, and the two are connected by a coupling. A common base is also required to ensure alignment accuracy. For high-flow double-suction pumps, the motor power is often hundreds of kilowatts, and the motor body length can be more than one meter. In addition to the coupling cover, base and maintenance passage, the axial footprint of the entire pump set often exceeds three meters, making it difficult to arrange in compact places such as ship engine rooms and underground pumping stations.

[0004] Secondly, in traditional designs, the pump shaft rotates at high speed, requiring dynamic sealing structures such as mechanical seals or packing seals where the shaft exits the pump casing. The lifespan of the dynamic and static rings of a mechanical seal is typically only 8,000 to 15,000 hours under high-speed friction and media corrosion, and it is extremely sensitive to installation alignment accuracy. Once the seal fails, high-pressure fluid will leak outwards along the axial direction, causing not only media loss but also potentially equipment shutdown and even safety accidents. For applications involving the transport of toxic, flammable, or valuable media, the leakage risk of dynamic seals is even more unacceptable.

[0005] Third, although traditional double-suction pumps theoretically offset most of the hydraulic axial force through their double-suction structure, the axial force on the motor side (such as the magnetic pull of the radial flux motor and the additional bending moment of the coupling) still needs to be borne by the thrust bearing. High-thrust bearings have complex structures, high costs, and significant temperature rise under high-speed conditions, which limits the increase in pump speed and power density.

[0006] Fourth, the motor, coupling, bearing housing and pump body are manufactured and installed independently. On-site, multiple processes such as alignment, coupling debugging and seal pre-tightening are required, which results in a long installation cycle and high skill requirements for personnel. During later maintenance, any failure in any part may affect the whole system, resulting in high maintenance costs.

[0007] To address these issues, the industry has attempted to shorten the axial dimension by bringing the motor closer to the pump body, for example, by using a direct-drive structure to eliminate the coupling or placing the disc motor at the end of the pump shaft. However, these improvements have not addressed the root cause: the motor stator and rotor remain exposed outside the pump body, limiting volume reduction; the pump shaft continues to rotate, and the dynamic seal cannot be completely eliminated; the enormous unidirectional axial magnetic pull introduced by the single-sided disc motor actually exacerbates the bearing load; and if the drive structure is completely embedded in the fluid, magnet corrosion and stator insulation failure become new technical obstacles. Therefore, how to achieve ultimate integration of the pump and motor while simultaneously ensuring corrosion protection, axial force balance, and high-reliability assembly has become a pressing technical challenge in the field of double-suction centrifugal pumps. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a double-suction centrifugal pump with a built-in drive mechanism. By adopting a built-in axial flux motor topology, the induction coil is fixed to the stationary pump shaft and placed between the two impellers. The magnet is embedded in the two impellers. After being energized, a rotating alternating magnetic field is generated to directly drive the impellers to rotate, thereby realizing the integration of the pump and the motor. The overall size is only equivalent to the pump body of a traditional double-suction pump. It does not require a common base or centering, and eliminates the bearing housing and external motor drive of traditional pump sets.

[0009] The present invention achieves the above-mentioned technical objectives through the following technical means.

[0010] A double-suction centrifugal pump with a built-in drive mechanism includes a split pump casing, impellers, a pump shaft and a built-in drive mechanism. The pump shaft is fixed inside the pump casing, and the two impellers are symmetrically sleeved on the pump shaft and can rotate around the pump shaft.

[0011] The built-in drive mechanism is an axial flux motor structure, including a magnet and an induction coil. The induction coil is fixed on the pump shaft and located between two impellers, and magnets are embedded in the two impellers respectively.

[0012] By energizing the induction coil to generate a rotating alternating magnetic field, the impellers with magnets on both sides are driven to rotate synchronously around the stationary pump shaft to achieve fluid transport.

[0013] Furthermore, the pump shaft is provided with flat shafts at both ends to prevent rotation, and the pump housing is provided with slots that match the flat shafts. The flat shafts at both ends of the pump shaft are placed in the slots, and the pump shaft and the pump housing are connected by axial limiting pins to restrict the axial movement of the pump shaft.

[0014] Furthermore, the induction coil is mounted on the stator support, and a flat-face fit structure is provided between the stator support and the pump shaft to limit the circumferential rotation of the induction coil; the part of the stator support wrapped by the induction coil is embedded with soft magnetic composite material to optimize the magnetic circuit.

[0015] Furthermore, the induction coil is provided with a first isolation layer, which is a metal shield or a waterproof insulating resin potting layer; the magnet is provided with a second isolation layer, which is an impeller shield plate integrally formed with the impeller; the first isolation layer and the second isolation layer are arranged opposite to each other, forming an axial working gap between them, which also serves as a flow channel for the magnetic circuit working air gap and the pumping medium.

[0016] Furthermore, the impeller is provided with a bearing housing inside, and the impeller is supported on the pump shaft by a water-lubricated bearing installed in the bearing housing; the impeller is provided with a lubrication and cooling channel, which connects the inside of the bearing housing with the outside of the impeller, and is used to introduce the pumping medium into the water-lubricated bearing for lubrication, and to collect the cooling medium flowing through the surface of the induction coil into the water-lubricated bearing, forming a composite circulation loop integrating cooling and lubrication.

[0017] Furthermore, the impeller is provided with a first channel and a second channel, and the bearing housing has a first through hole and a second through hole; fluid flows into the interior of the water-lubricated bearing through the first channel and the first through hole; fluid from the gap between the two impellers enters the interior of the water-lubricated bearing after being cooled by the surface of the induction coil, and the fluid inside the water-lubricated bearing flows out through the second through hole and the second channel, forming a compound circulation loop.

[0018] Furthermore, a synchronous fitting structure is provided on the opposite end faces of the two impellers for synchronous rotation of the two impellers; an annular groove is also provided on the opposite end faces of the two impellers for decelerating and reducing the pressure of the high-pressure fluid entering the gap between the two impellers.

[0019] Furthermore, the pump shaft is provided with a wiring channel inside, through which the wire powered by the induction coil passes to the outside of the pump casing; one or both ends of the wiring channel extend to the outside of the pump casing and are connected to a power controller; shaft sealing rings are provided at the points where the pump shaft passes through the pump casing for static sealing.

[0020] Furthermore, it also includes an automatic exhaust mechanism, which includes an exhaust port, an exhaust pipe, a four-way pipe and an automatic exhaust device disposed on the pump casing. The automatic exhaust device connects the high-pressure zone and two low-pressure zones inside the pump casing through the four-way pipe and the exhaust pipe. A check valve is provided on the exhaust pipe connecting the low-pressure zones.

[0021] The beneficial effects of this invention are as follows:

[0022] 1. The double-suction centrifugal pump with built-in drive mechanism described in this invention adopts a built-in axial flux motor topology, in which the induction coil is fixed to the stationary pump shaft and placed between the two impellers, and the magnet is embedded in the two impellers. After being energized, a rotating alternating magnetic field is generated to directly drive the impeller to rotate, thereby achieving a high degree of integration between the pump and the motor. The overall volume is only equivalent to the pump body of a traditional double-suction pump. It does not require a common base or centering, and eliminates the bearing housing and external motor drive of traditional pump sets.

[0023] 2. The double-suction centrifugal pump with built-in drive mechanism described in this invention uses a stator assembly fixed in the middle of the pump shaft and rotors installed on both sides of the stator assembly. The rotors are mounted on the impellers. This symmetrical axial magnetic flux structure makes the axial electromagnetic attraction force generated by the middle stator assembly on the two impellers equal in magnitude and opposite in direction, and naturally cancels out on the pump shaft. This achieves self-balancing of axial magnetic pull, significantly reduces the axial load on the water-lubricated bearing, and extends the service life of the bearing and the whole machine.

[0024] 3. The double-suction centrifugal pump with built-in drive mechanism described in this invention forms a simply supported beam structure by rigidly fixing both ends of the pump shaft in the pump casing. Only a static sealing structure such as a shaft sealing ring is needed where the shaft passes through the casing, thereby completely eliminating the dynamic seal and achieving high reliability and zero leakage of the pump unit from the root.

[0025] 4. The double-suction centrifugal pump with built-in drive mechanism described in this invention uses a metal shield or resin potting layer outside the induction coil as the first isolation layer and an impeller shield plate integrally formed with the impeller outside the magnet as the second isolation layer. An axial working gap is formed between the two isolation layers. This gap also serves as the flow channel between the working air gap of the magnetic circuit and the pumping medium. This achieves the spatial overlap of the double anti-corrosion isolation and the working air gap, which not only ensures the long-term reliable operation of the magnet and the induction coil in corrosive media, but also maintains the effective air gap required for electromagnetic work, thus taking into account both high energy efficiency and high protection.

[0026] 5. The double-suction centrifugal pump with built-in drive mechanism described in this invention, by setting a water-lubricated bearing inside the impeller and opening a lubrication and cooling flow channel on the impeller connecting the inside and outside of the bearing housing, uses the pressure difference between the impeller inlet and outlet to introduce the pumping medium into the bearing for lubrication, and at the same time, the cooling medium flowing through the surface of the induction coil is collected into the bearing, forming a composite circulation loop integrating cooling and lubrication. This enables the motor and bearing to operate reliably under high power density without the need for an external cooling and lubrication system, simplifying the overall structure and reducing operating energy consumption.

[0027] 6. The double-suction centrifugal pump with built-in drive mechanism described in this invention pre-assembles the pump shaft, induction coil, water-lubricated bearing and impellers on both sides into a core module, and with the upper and lower split pump casing, only the core module needs to be put in or taken out as a whole during assembly or overhaul, thereby achieving rapid assembly and maintenance, and significantly reducing the difficulty and cost of manufacturing and maintenance.

[0028] 7. The double-suction centrifugal pump with built-in drive mechanism described in this invention ensures strict synchronous rotation of the two impellers under electromagnetic drive force by setting a synchronous cooperation structure on the opposite end faces of the two impellers; at the same time, by setting an annular groove on the opposite end faces of the two impellers, the high-pressure fluid entering the impeller gap is decelerated and depressurized, thereby realizing the stability of synchronous operation of the two rotors and the hydraulic impact protection of the stator assembly, reducing pump vibration and extending the stator insulation life. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are some embodiments of the present invention. For those skilled in the art, it is obvious that other drawings can be obtained from these drawings without creative effort.

[0030] Figure 1 This is an external view of the double-suction centrifugal pump with built-in drive mechanism described in this invention.

[0031] Figure 2 This is a front view sectional view of the dual-suction pump described in this invention.

[0032] Figure 3 This is a cross-sectional view of the pump shaft and impeller as described in this invention.

[0033] Figure 4 This is a schematic diagram of the installation of the lower pump body and pump shaft according to the present invention.

[0034] Figure 5 This is a schematic diagram of the impeller installation and positioning assembly according to the present invention.

[0035] Figure 6 This is a diagram of the impeller structure described in this invention.

[0036] Figure 7 This is a schematic diagram of the stator fixing assembly according to the present invention.

[0037] Figure 8 This is a schematic diagram of the cooling channel and bearing lubrication described in this invention.

[0038] In the picture:

[0039] 1-Pump body; 1a-Stepped groove of pump body; 1b-Stepped groove of pump body; 1c-Stepped end face of pump body; 1d-Slot; 2-Shaft sealing ring; 3-Induction coil; 4-Stator limiting ring; 4a-First end face; 4b-Second end face; 4c-Third end face; 4d-Inner flat surface of stator limiting ring; 5-Pump shaft; 5a-Flat shaft; 5b-Stepped end face; 5c-Sealing ring groove; 5d-Way routing channel; 5e-Pump shaft through hole; 5f-Anti-rotation outer flat surface ; 5g - Pump shaft center groove; 6 - Pump cover; 7 - Exhaust port; 8 - Exhaust pipe; 9 - Four-way pipe; 10 - Exhaust device; 11 - Magnet; 12 - Left impeller; 12a - Left impeller annular groove; 12b - Left impeller synchronous groove; 12c - Left impeller bearing seat groove; 12d - Left impeller limiting key; 12e - Second channel; 12f - First channel; 12g - Left end face of the inner ring of the left impeller; 12h - Left impeller magnet groove; 13 - Right impeller; 13a-Right impeller annular groove; 13b-Right impeller synchronous key; 13c-Right impeller bearing housing groove; 14-Stator bracket; 14a-Stator bracket channel; 14b-Stator bracket inner flat surface; 15-Bearing housing; 15a-Bearing housing key; 15b-Bearing housing inner side wall; 15c-First through hole; 15d-Second through hole; 16-Bearing bush; 16a-Bearing bush first end face; 16b-Bearing bush second end face; 17-Bearing Inner sleeve; 17a-First end face of bearing inner sleeve; 17b-Protruding key of bearing inner sleeve; 17c-Second end face of bearing inner sleeve; 17d-Groove of bearing inner sleeve; 17e-Outer flat surface of bearing inner sleeve; 18-Pump shaft sleeve; 18a-Protruding key of pump shaft sleeve; 18b-First end face of pump shaft sleeve; 18c-Groove of pump shaft sleeve; 19-Limiting sleeve; 19a-Protruding key of limiting sleeve; 20-Impeller limiting inner ring; 20a-Protruding key of impeller limiting inner ring; 21-Impeller shielding plate. Detailed Implementation

[0040] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0041] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "axial," "radial," "vertical," "horizontal," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0042] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0043] Example 1

[0044] like Figure 1 As shown, the double-suction centrifugal pump with built-in drive mechanism of the present invention has a nearly symmetrical horizontal structure, with the left end A being the inlet and the right end B being the outlet. The pump casing adopts a horizontal split structure, consisting of the pump body 1 and the pump cover 6 fastened together along the horizontal split surface. After precision machining, a sealing gasket is sandwiched or coated with sealant on the split surface, and then it is fastened with high-strength bolts arranged circumferentially around the perimeter, thus forming a high-pressure resistant sealed cavity. The biggest difference between the double-suction centrifugal pump with built-in drive mechanism of the present invention and the traditional double-suction centrifugal pump is that it adopts a built-in drive mechanism, with the motor drive located inside the pump body. Its size is only a part of the pump body of a traditional double-suction centrifugal pump. This embodiment eliminates the need for external motors, common bases, couplings, and bearing housings, etc. The overall volume is only equivalent to the pump body part of a traditional pump set, making the structure extremely compact.

[0045] The double-suction centrifugal pump with a built-in drive mechanism of the present invention includes a split pump casing, impellers, a pump shaft 5, and a built-in drive mechanism. The pump shaft 5 is fixed inside the pump casing, and two impellers are symmetrically mounted on the pump shaft 5 and can rotate around the pump shaft 5. The pump shaft 5 is horizontally arranged along the center line of the pump cavity, and its two ends are respectively inserted into corresponding mounting holes in the pump casing, and remain absolutely stationary in the working state. The two impellers are symmetrically mounted on the pump shaft 5 and can rotate around the pump shaft 5. The built-in drive mechanism includes a stator assembly and a rotor assembly mounted on the impellers. The two impellers are a left impeller 12 and a right impeller 13.

[0046] like Figure 2 , Figure 3 and Figure 4 As shown in the embodiment, the pump shaft 5 has flat shafts 5a at both ends. The cross-section of the flat shafts 5a is rectangular or double D-shaped, forming a surface contact anti-rotation fit with the corresponding slots 1d on the pump casing. Stepped end faces 5b are machined on both ends of the pump shaft 5. These stepped end faces 5b abut against the stepped grooves 1a on the pump casing, forming an axial limiting structure. Simultaneously, sealing ring grooves 5c are machined near the casing penetration area at both ends of the pump shaft 5. The shaft sealing ring 2 is installed in the sealing ring grooves 5c, forming a static seal. When the pump body 1 and pump cover 6 are closed and tightened, the pump shaft 5 is completely positioned radially and axially, effectively eliminating the risk of slippage and movement of the pump shaft 5 under complex hydraulic conditions. A wiring channel 5d is provided inside the pump shaft 5 along its centerline. One or both ends of the wiring channel 5d extend to the outside of the pump body for threading the wires that power the induction coil 3. A pump shaft through hole 5e is also provided in the middle of the pump shaft 5. The pump shaft through hole 5e is perpendicularly connected to the wiring channel 5d, allowing the wires to be led out from inside the pump shaft 5 and connected to an external power controller. Water-resistant sealing material is filled between the wires and the through hole wall to ensure insulation reliability under long-term immersion conditions.

[0047] like Figure 2 , Figure 3 and Figure 7 As shown, the stator assembly includes a stator bracket 14, an induction coil 3, and a stator limiting ring 4. The stator bracket 14 is fixedly mounted on the pump shaft 5 and located between the left impeller 12 and the right impeller 13. The stator bracket 14 is made of non-magnetic metal or high-strength engineering plastic. The inner sidewall of the stator bracket 14 is provided with an inner flat surface 14b, which cooperates with the anti-rotation outer flat surface 5f on the pump shaft 5, thereby restricting the circumferential rotation of the stator bracket 14. Several coil slots are evenly distributed circumferentially on the stator bracket 14. The induction coil 3 is wound with rectangular flat copper wire and arranged tightly in the slots in a brick-like manner to push the slot fill factor to the limit. The coil winding uses water-resistant insulated wires such as cross-linked polyethylene (XLPE) or nylon sheath to adapt to the working conditions of long-term immersion in the pumping medium.

[0048] To further optimize the magnetic circuit, soft magnetic composite materials (SMCs) are embedded inside the part of the stator support 14 that is wrapped by the induction coil 3. Soft magnetic composite materials are made by coating the surface of high-voltage iron powder with a nanoscale insulating film, and then pressing it into various complex three-dimensional shapes under extremely high pressure, much like pressing a pill. The embedding method involves first creating a sufficiently deep groove on one side of the stator support 14 that is wrapped by the induction coil 3, then placing the soft magnetic composite material of a specific shape into the groove, and finally completely sealing the soft magnetic composite material with a suitable shielding plate using welding or other processes. This utilizes its isotropic magnetic permeability, extremely low high-frequency eddy current losses, and the near-net-shape engineering characteristics of powder metallurgy to optimize the torsional magnetic circuit distribution and significantly improve the overall electromagnetic efficiency of the dual-rotor motor.

[0049] The induction coil 3 is encased in an independent metal shield or a waterproof insulating resin potting layer, forming a first isolation layer with double anti-corrosion protection. Several stator support channels 14a are also evenly distributed circumferentially on the stator support 14. The stator support channels 14a are connected to the pump shaft through hole 5e, providing space for the wires to be threaded through.

[0050] The axial positioning of the stator assembly is achieved collaboratively by the stator limiting ring 4 and the bearing inner sleeve 17. For example... Figure 3 and Figure 7 As shown, the bearing inner sleeve 17 is fitted onto the pump shaft 5. One end of the bearing inner sleeve 17 has a bearing inner sleeve key 17b, which is embedded in the central groove 5g of the pump shaft to prevent rotation of the bearing inner sleeve 17 relative to the pump shaft 5. Simultaneously, the outer flat surface 17e of the bearing inner sleeve and the anti-rotation outer flat surface 5f of the pump shaft are in the same circumferential orientation, ensuring the continuity of the flat surface fit. The stator limiting ring 4 is fitted onto the pump shaft 5 and located between the bearing inner sleeve 17 and the stator bracket 14. The first end face 4a on one side of the stator limiting ring 4 abuts against the second end face 17c of the bearing inner sleeve, while the second end face 4b and the third end face 4c on the other side of the stator limiting ring 4 respectively fit against the inner end face of the stator bracket 14. The inner flat surface 4d of the stator limiting ring engages with the anti-rotation outer flat surface 5f of the pump shaft to prevent rotation. The stator bracket 14 is positioned between the two bearing inner sleeves 17, achieving axial positioning of the stator assembly.

[0051] Since the left impeller 12 and the right impeller 13 have the same structure, the description will take the left impeller 12 as an example. Figure 2 , Figure 3 , Figure 5 and Figure 6As shown, for ease of description, the left impeller 12 is considered as part of the left rotor assembly. The left rotor assembly includes the left impeller 12, magnet 11, impeller shield 21, bearing housing 15, bearing bush 16, bearing inner sleeve 17, impeller limiting inner ring 20, and limiting sleeve 19. The left impeller 12 is integrally molded using high-performance engineering plastics (such as polyphenylene sulfide PPS or polyphenylene sulfide PPE / PPO) through injection molding, exhibiting excellent corrosion resistance, mechanical strength, and dimensional stability. The magnet 11 is made of high-energy-product permanent magnet materials such as neodymium iron boron (NdFeB) and is embedded in the left impeller magnet slot 12h through insert injection molding. The side of the magnet 11 closest to the induction coil 3 is completely sealed by the impeller shield 21, which is integrally molded with the impeller. The thickness of the impeller shield 21 is optimized through electromagnetic design, minimizing its thickness while ensuring structural strength, in order to shorten the non-working air gap in the magnetic circuit. The outer surface of the impeller shield 21 is flush with the side of the impeller and is polished to form a smooth end face. The magnet 11 is completely sealed inside the plastic impeller, utilizing its strong magnetism while fundamentally solving the corrosion problem, forming a second isolation layer with double anti-corrosion isolation. The shield or resin layer outside the induction coil 3 is positioned opposite to the impeller shield 21 on the impeller, forming an axial working magnetic gap between them. The axial dimension of the magnetic gap is usually controlled within the range of 0.5mm to 2.0mm, and the specific value needs to be determined comprehensively based on the electromagnetic thrust, machining accuracy, and thermal deformation characteristics of the plastic impeller. If the magnetic gap is too small, assembly will be difficult and the risk of thermal deformation will increase; if the magnetic gap is too large, leakage flux will increase and electromagnetic efficiency will decrease. In the magnetic gap, the pumping medium can form a thin liquid film, which not only has a cooling effect but also suppresses rotor vibration through fluid damping effect.

[0052] The pump shaft sleeve 18 is fitted onto the pump shaft 5 and located between the impeller limiting inner ring 20 and the pump casing. Its outer wall is machined with a pump shaft sleeve key 18a, which is embedded in the stepped groove 1b of the pump body, thereby restricting the circumferential rotation of the pump shaft sleeve 18 relative to the pump casing. The first end face 18b of the pump shaft sleeve abuts against the stepped end face 1c of the pump body, forming an axial positioning reference. The inner hole of the pump shaft sleeve 18 and the pump shaft 5 typically use a clearance fit or transition fit. The recommended fit tolerance zone is H7 / h6 or H7 / k6 to ensure convenient assembly while maintaining sufficient coaxiality. The right end face of the pump shaft sleeve 18 (near the impeller) abuts against the left end face of the limiting sleeve 19. The impeller limiting inner ring 20 is embedded in the left end inner hole of the left impeller 12. The impeller limiting inner ring protrusion 20a is embedded in the left impeller limiting concave key 12d and abuts against the left end face 12g of the left impeller inner ring, realizing the synchronous rotation of the impeller limiting inner ring 20 and the left impeller 12. The left end of the impeller limiting inner ring 20 is opposite to the limiting sleeve 19, with an axial gap of 0.1mm to 0.3mm between them. This gap provides compensation space for the thermal expansion of the impeller and the hydraulic axial displacement, and is filled by the pumping medium to form a lubricating film. The limiting sleeve 19 is fixed to the pump shaft sleeve 18 by the cooperation of the limiting sleeve protrusion 19a and the pump shaft sleeve groove 18c. The pump shaft sleeve 18 is circumferentially fixed by the pump shaft sleeve protrusion 18a being embedded in the pump body stepped groove 1b, and axially positioned by the abutment of the first end face 18b of the pump shaft sleeve and the stepped end face 1c of the pump body. The axial position of the left impeller on the pump shaft 5 is defined, while allowing it to rotate freely.

[0053] The synchronous rotation of the left impeller 12 and the right impeller 13 is achieved through a synchronous connection structure. Several left impeller synchronous grooves 12b are evenly distributed circumferentially on the end face of the left impeller 12 facing the right impeller 13, while a right impeller synchronous key 13b is machined on the corresponding end face of the right impeller 13. The right impeller synchronous key 13b is embedded in the left impeller synchronous grooves 12b, forming a circumferential meshing, ensuring that the two impellers maintain strict synchronization under the action of electromagnetic driving force. Furthermore, left impeller annular grooves 12a and 13a are respectively machined on the opposite end faces of the left impeller 12 and the right impeller 13. These annular grooves 12a and 13a are used to decelerate and reduce the pressure of the high-pressure fluid entering the gap between the two impellers, reducing the direct impact of the high-speed fluid on the central stator assembly, and simultaneously guiding the fluid to flow towards the cooling and lubrication channels at an appropriate speed.

[0054] like Figure 3 , Figure 5 and Figure 6As shown, the impeller is rotatably supported on the pump shaft 5 via a water-lubricated bearing system. Taking the left impeller 12 as an example, a bearing housing 15 is embedded in its right end. The bearing housing 15 has an L-shaped cross-section design, and its outer wall is machined with a bearing housing key 15a. The bearing housing key 15a is embedded in the left impeller bearing housing groove 12c, so that the bearing housing 15 and the left impeller 12 form a synchronously rotating whole. Inside the bearing housing 15, a bearing bush 16 and a bearing inner sleeve 17 are installed in sequence, and the three together form the friction pair of the water-lubricated bearing. The bearing bush 16 is made of high-performance ceramic materials such as silicon carbide, which has wear resistance and corrosion resistance; the bearing inner sleeve 17 is fitted on the pump shaft 5 and remains stationary. The bearing inner sleeve protrusion key 17b is embedded in the middle groove 5g of the pump shaft to achieve circumferential anti-rotation; the first end face 17a of the bearing inner sleeve abuts against the second end face 16b of the bearing bush, forming an inner axial reference; the second end face 17c of the bearing inner sleeve abuts against the first end face 4a of the stator limiting ring, while the other end face (second end face 4b and third end face 4c) of the stator limiting ring 4 is in contact with the end face of the stator support 14. Thus, a continuous axial force transmission chain is formed from the stator support 14 through the stator limiting ring 4, the bearing inner sleeve 17, the bearing bush 16 to the bearing seat 15, ultimately transmitting the electromagnetic axial force and the hydraulic axial force to the pump casing, ensuring the axial stability of the rotor assembly under complex working conditions.

[0055] It should be noted that the mating end faces should be finely ground before assembly, and the surface roughness Ra should be controlled within the range of 0.8μm to 1.6μm to reduce local stress concentration when the end faces are in contact. At the same time, it is recommended to apply a small amount of water-resistant grease between the mating surfaces to reduce initial dry friction and prevent adhesion after long-term standing.

[0056] The bearing housing 15 has a first through hole 15c and a second through hole 15d on its side wall, which are respectively connected to the first channel 12f and the second channel 12e of the left impeller, forming inlet and outlet channels for the cooling and lubricating medium. A lubricating water groove is also provided inside the bearing housing 15, which communicates with the second through hole 15d to ensure that the cooling medium can fully wet the friction interface between the bearing bush 16 and the bearing inner sleeve 17. The first end face 16a of the bearing bush abuts against the inner wall 15b of the bearing housing, and the first end face 17a of the bearing inner sleeve abuts against the second end face 16b of the bearing bush, thereby limiting the axial displacement range of the bearing bush 16. The bearing inner sleeve 17 is also machined with a bearing inner sleeve groove 17d, which is evenly distributed circumferentially to increase the flow cross-sectional area of ​​the cooling medium and improve lubrication uniformity.

[0057] This embodiment adopts an axial flux motor topology with a central single stator and dual rotors on both sides, completely integrating the motor drive function within the pump body chamber. When the external power controller supplies three-phase alternating current to the induction coil 3, the induction coil 3 generates a rotating alternating magnetic field. The alternating magnetic field passes through the impeller shield plate 21 via the air gap and acts on the magnet 11, generating an electromagnetic torque on the magnet 11. This torque drives the left impeller 12 and the right impeller 13 to rotate synchronously around the stationary pump shaft 5, thereby achieving fluid transport.

[0058] This embodiment utilizes the pumping medium itself to construct a cooling and lubrication composite circulation loop that requires no external auxiliary systems. Taking the left side as an example, its working process is as follows:

[0059] When the pump starts running, a portion of the low-pressure fluid enters the water-lubricated bearing directly through the flow channel a formed by the first channel 12f and the first through hole 15c, lubricating the friction interface between the bearing bush 16 and the bearing inner sleeve 17. Simultaneously, a small portion of the high-pressure fluid at the impeller outlet enters the central region through the gap between the two impellers. The high-speed fluid first undergoes deceleration and expansion through the annular groove 12a of the left impeller and the annular groove 13a of the right impeller, resulting in a reduced flow velocity and restored static pressure. It then flows relatively smoothly over the outer surface of the induction coil 3, absorbing the heat generated by the induction coil 3 and the iron core, thus completing the cooling function. The cooled fluid continues to pass through the axial gap between the first and second isolation layers, forming the flow channel d. The fluid in the axial gap not only carries away heat but also possesses a certain dynamic pressure due to its high flow velocity, generating a slight hydrodynamic pressure support effect on the rotor.

[0060] The lubricating fluid from flow channel a and the cooling fluid from flow channel d converge inside the bearing housing 15, jointly providing sufficient lubrication to the water-lubricated bearing. After absorbing frictional heat, the temperature rises, and finally flows out through flow channel e, formed by the second through hole 15d and the second channel 12e, mixing with the newly entering low-pressure fluid and participating in the above cycle again. This forms an integrated cooling and lubrication compound circulation loop a→d→e→a. This loop is driven entirely by the pressure difference between the impeller inlet and outlet, requiring no additional cooling or lubrication pump, resulting in a simple structure and reliable operation.

[0061] like Figures 2-7As shown, the drive and hydraulic core components of this embodiment can be pre-assembled into a highly integrated core module. The assembly sequence is as follows: First, the induction coil 3, stator bracket 14, and stator limiting ring 4 are installed in the middle of the pump shaft 5; then, the pump shaft sleeve 18, limiting sleeve 19, impeller limiting inner ring 20, bearing inner sleeve 17, bearing bush 16, and bearing seat 15 are sequentially fitted onto both ends of the pump shaft 5; then, the left impeller 12 and the right impeller 13 are fitted onto the pump shaft 5 from both sides, so that the right impeller synchronous protrusion key 13b is embedded into the left impeller synchronous groove 12b to complete the synchronous connection; finally, the magnet 11 is embedded into the left impeller magnet groove 12h through an insert injection molding process and sealed by the impeller shielding plate 21.

[0062] After the core package module is assembled, it is inserted into the lower half of the pump body 1, aligning the flat shaft 5a with the slot 1d on the pump body 1, and the stepped end face 5b is inserted into the stepped slot 1a of the pump body. Then, the pump cover 6 is fastened, so that the corresponding structure on the pump cover 6 presses the two ends of the pump shaft 5 tightly. Finally, the outer bolts are inserted to secure the pump body 1 and the pump cover 6, thus completing the assembly. During maintenance, simply loosen the bolts and lift the pump cover 6 to remove the entire core package module at once, enabling rapid maintenance.

[0063] like Figure 1 and Figure 2 As shown, in another embodiment of the present invention, the pump body 1 is provided with an exhaust port 7 at its top, and the exhaust port 7 is connected to a four-way pipe 9 through an exhaust pipe 8. The other three ports of the four-way pipe 9 are respectively connected to an automatic exhaust device 10 and an exhaust pipe 8 leading to two low-pressure water inlet zones inside the pump body 1. A check valve is provided on the exhaust pipe 8 connecting the low-pressure zones to prevent backflow of fluid from the high-pressure zone to the low-pressure zone. This exhaust mechanism can simultaneously discharge accumulated air from the high-pressure outlet zone and the two low-pressure water inlet zones, solving the inconvenience of traditional automatic exhaust valves that can only discharge gas from the high-pressure zone, while requiring manual unscrewing of the plug to discharge gas from the low-pressure zone, and avoiding the problem of liquid overflowing from the pump and contaminating the equipment surface during exhaust.

[0064] Example 2

[0065] The main difference between this embodiment and Embodiment 1 lies in the external protection of the induction coil 3. In Embodiment 1, the induction coil 3 is encased in a separate metal shield; however, in this embodiment, the induction coil 3 and its windings are integrally potted with waterproof insulating resin to form a dense, seamless insulating layer. The resin potting layer can be made of water-resistant insulating materials such as epoxy resin or polyurethane. Before potting, the induction coil 3 needs to undergo vacuum impregnation to remove internal air bubbles. After potting, it is cured at room temperature or under heating conditions. Compared to the metal shield, resin potting has advantages such as lighter weight, no risk of electrochemical corrosion, and better adaptability to complex shapes, but its heat dissipation performance is slightly inferior, making it suitable for operating conditions with low medium temperature or low power density. Both protection methods can be selected according to the specific application environment, and both can achieve effective corrosion protection and isolation on the stator side.

[0066] It should be understood that although this specification is described according to various embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0067] The detailed descriptions listed above are merely specific illustrations of feasible embodiments of the present invention and are not intended to limit the scope of protection of the present invention. All equivalent embodiments or modifications made without departing from the spirit of the present invention should be included within the scope of protection of the present invention.

Claims

1. A double-suction centrifugal pump with a built-in drive mechanism, characterized in that, It includes a split pump casing, impellers, pump shaft (5) and built-in drive mechanism. The pump shaft (5) is fixed inside the pump casing. The two impellers are symmetrically sleeved on the pump shaft (5) and can rotate around the pump shaft (5). The built-in drive mechanism is an axial flux motor structure, including a magnet (11) and an induction coil (3). The induction coil (3) is fixed on the pump shaft (5) and located between two impellers, and the magnet (11) is embedded in each of the two impellers. By energizing the induction coil (3) to generate a rotating alternating magnetic field, the impellers with magnets (11) on both sides are driven to rotate synchronously around the stationary pump shaft (5) to achieve fluid transport.

2. The double-suction centrifugal pump with built-in drive mechanism according to claim 1, characterized in that, The pump shaft (5) has flat shafts (5a) at both ends to prevent rotation. The pump housing has a groove (1d) that matches the flat shaft (5a). The flat shafts (5a) at both ends of the pump shaft (5) are placed in the groove (1d). The pump shaft (5) and the pump housing are connected by an axial limiting pin to restrict the axial movement of the pump shaft (5).

3. The double-suction centrifugal pump with built-in drive mechanism according to claim 1, characterized in that, The induction coil (3) is mounted on the stator support (14). The stator support (14) and the pump shaft (5) are provided with a flat surface mating structure to limit the circumferential rotation of the induction coil (3). The part of the stator support (14) wrapped by the induction coil (3) is inlaid with soft magnetic composite material to optimize the magnetic circuit.

4. The double-suction centrifugal pump with built-in drive mechanism according to claim 1, characterized in that, The induction coil (3) is provided with a first isolation layer on the outside, which is a metal shield or a waterproof insulating resin potting layer; the magnet (11) is provided with a second isolation layer on the outside, which is an impeller shield plate (21) integrally formed with the impeller; the first isolation layer and the second isolation layer are arranged opposite to each other, and an axial working gap is formed between them. The axial working gap also serves as the flow channel between the magnetic circuit working air gap and the pumping medium.

5. The double-suction centrifugal pump with built-in drive mechanism according to claim 4, characterized in that, The impeller is provided with a bearing housing (15) inside. The impeller is supported on the pump shaft (5) by a water-lubricated bearing installed in the bearing housing (15). The impeller is provided with a lubrication and cooling channel, which connects the inside of the bearing housing (15) with the outside of the impeller. It is used to introduce the pumping medium into the water-lubricated bearing for lubrication and to collect the cooling medium flowing through the surface of the induction coil (3) into the water-lubricated bearing to form a composite circulation loop integrating cooling and lubrication.

6. The double-suction centrifugal pump with built-in drive mechanism according to claim 5, characterized in that, The impeller is provided with a first channel (12f) and a second channel (12e), and the bearing housing (15) has a first through hole (15c) and a second through hole (15d). Fluid flows into the water-lubricated bearing through the first channel (12f) and the first through hole (15c). Fluid from the gap between the two impellers is cooled by the surface of the induction coil (3) and enters the water-lubricated bearing. The fluid inside the water-lubricated bearing flows out through the second through hole (15d) and the second channel (12e) to form a compound circulation loop.

7. The double-suction centrifugal pump with built-in drive mechanism according to claim 1, characterized in that, The two impellers are provided with a synchronous fitting structure on their opposite end faces for synchronous rotation; the two impellers are also provided with annular grooves on their opposite end faces for decelerating and reducing the pressure of the high-pressure fluid entering the gap between the two impellers.

8. The double-suction centrifugal pump with built-in drive mechanism according to claim 1, characterized in that, The pump shaft (5) is provided with a wiring channel (5d) inside. The wires powered by the induction coil (3) pass through the wiring channel (5d) and lead out to the outside of the pump casing. One or both ends of the wiring channel (5d) extend to the outside of the pump casing and are connected to a power controller. Shaft sealing rings (2) are provided at the points where the pump shaft (5) passes through the pump casing for static sealing.

9. The double-suction centrifugal pump with built-in drive mechanism according to claim 1, characterized in that, It also includes an automatic exhaust mechanism, which includes an exhaust port (7), an exhaust pipe (8), a four-way pipe (9) and an automatic exhaust device (10) provided on the pump casing. The automatic exhaust device (10) connects the high-pressure zone of the pump casing cavity with two low-pressure zones through the four-way pipe (9) and the exhaust pipe (8). The exhaust pipe (8) connecting the low-pressure zones is provided with a check valve.

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