A composite dynamic choke rotary shaft magnetic fluid seal for a pump

Abstract

The application discloses a composite dynamic resistance flow rotary shaft magnetic fluid sealing device for a pump, which comprises a sealing space formed between a pump cover and a pump shaft, a magnetic fluid sealing unit, a magnetic fluid active recovery unit and a flexible dynamic resistance flow unit are arranged in the sealing space, the magnetic fluid sealing unit comprises a plurality of pole shoes arranged in an axial direction, an inner ring of the pole shoe is provided with pole teeth, and a magnetic fluid is filled in a gap between the pole teeth and a shaft sleeve; the magnetic fluid active recovery unit comprises a magnetic fluid recovery disc fixedly arranged on the pump shaft, and a resistance flow gap is arranged between a left end surface of the magnetic fluid recovery disc and a right end surface of a rightmost pole shoe; a liquid storage groove is arranged on the left end surface of the magnetic fluid recovery disc; and the flexible dynamic resistance flow unit comprises an annular liquid resistance groove arranged on the left end surface of the magnetic fluid recovery disc, and an annular flexible resistance flow air bag is arranged in the liquid resistance groove. The application can effectively buffer medium impact, block the erosion of high-speed liquid flow to the sealing system, and avoid sealing failure caused by liquid flow scouring.

Description

Technical Field

[0001] This invention relates to the field of pump sealing technology, and specifically to a composite dynamic flow-blocking rotary shaft magnetohydrodynamic sealing device for pumps. Background Technology

[0002] Pumps, as a general-purpose fluid transport and energy conversion device, are widely used in key fields such as water conservancy and hydropower, petrochemicals, marine power, and aerospace. Pump equipment itself must possess extremely strong environmental adaptability, capable of stable operation under harsh conditions such as high-speed operation, multiphase media (e.g., gas-containing, solid-containing, or gas-liquid-solid mixtures), pressure pulsation, and complex vibrations. The rotary shaft sealing system, as a core component ensuring stable pump operation, directly determines the pump's volumetric efficiency, operational reliability, and maintenance cycle. Currently, the petrochemical, water supply and drainage, shipbuilding, and nuclear power industries are continuously increasing their requirements for the adaptability and durability of pump sealing technology. Traditional sealing methods are no longer sufficient to meet the needs of high-end pump equipment, especially in liquid media environments (such as water, oil, and chemical media), where the quality of the seal directly restricts the overall operating performance and total life-cycle cost of the pump.

[0003] Currently, traditional pump sealing methods (such as packing seals and mechanical seals) have significant shortcomings under complex operating conditions: Packing seals wear out quickly, leak a lot, and require frequent maintenance; mechanical seals, although performing well, are prone to end face wear, thermal cracking, or even sudden failure in environments with particulate media, severe vibration, or frequent start-stop cycles, making it difficult to meet the long-term stable operation requirements of high-end pumps.

[0004] While magnetohydrodynamic (MHD) seals offer advantages such as non-contact operation and zero leakage, and have been validated in high-end fields like vacuum sealing and precision instruments, they are susceptible to the effects of high-speed water flow, pressure pulsation, and vibration in environments where liquid media are pumped. For example... Figure 1 The diagram shows a multi-stage annular magnetic circuit layout used in traditional magnetohydrodynamic (MHD) seals. It relies on permanent magnets and magnetically conductive pole pieces to form a stable radial magnetic field within the sealing gap, confining the MHD between the shaft and the magnetic poles to form a liquid film barrier, achieving a non-contact seal. While this type of structure offers reliable sealing performance under normal pressure and low-scouring conditions, it is prone to problems such as emulsification of the MHD, interface instability, and liquid film rupture and leakage under harsh conditions involving high-speed rotation of fluid machinery, multiphase media scouring, and pressure pulsation. The magnetic media is rapidly depleted, and the magnetic response characteristics decay quickly, making it difficult to maintain long-term sealing capabilities. Both seal life and reliability are significantly limited, failing to meet the engineering requirements of modern equipment for high-reliability, long-life seals.

[0005] To this end, this application proposes a composite sealing device that integrates a flexible dynamic flow-blocking structure and a magnetohydrodynamic self-recovery function, which significantly improves the stability and long-term effectiveness of the sealing system under complex working conditions such as high-speed operation of pumps, multiphase flow, vibration and shock, and provides a more reliable, efficient and engineering-applicable new solution for rotary shaft seals of high-end pumps. Summary of the Invention

[0006] The purpose of this invention is to provide a composite dynamic flow-blocking rotary shaft magnetohydrodynamic sealing device for pumps, which at least partially solves one of the technical problems in related technologies.

[0007] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: A composite dynamic flow-blocking rotary shaft magnetofluid sealing device for pumps includes a sealing space formed between a pump cover and a pump shaft. A magnetofluid sealing unit is provided in the sealing space. The magnetofluid sealing unit includes a bushing fixedly fitted outside the pump shaft. Multiple pole shoes are arranged along the axial direction outside the bushing. Permanent magnets are installed between adjacent pole shoes. The outer ring of the pole shoes is sealed and fixedly connected to the pump cover. The inner ring of the pole shoes is provided with pole teeth, and the pole teeth are clearance-fitted with the bushing. Magnetofluid is filled in the gap between the pole teeth and the bushing to form a magnetofluid sealing ring. The sealed space is also equipped with a magnetic fluid active recovery unit, which includes a magnetic fluid recovery disc fixedly sleeved on the outside of the pump shaft. The magnetic fluid recovery disc is located on the side close to the impeller. The end face of the magnetic fluid recovery disc away from the impeller is the left end face. There is a flow-blocking gap between the left end face of the magnetic fluid recovery disc and the right end face of the rightmost pole shoe. One or more liquid storage tanks are arranged on the left end face of the magnetic fluid recovery disc and / or the right end face of the rightmost pole shoe. The sealed space is also equipped with a flexible dynamic flow-blocking unit. The flexible dynamic flow-blocking unit includes an annular liquid-blocking groove set on the left end face of the magnetic fluid recovery tray. The position of the liquid-blocking groove corresponds to the magnetic fluid sealing ring, and the left side of the liquid-blocking groove is set as an opening. An annular flexible flow-blocking airbag is installed in the liquid-blocking groove. The inner ring of the flexible flow-blocking airbag is fixedly connected to the inner ring of the liquid-blocking groove, and the left side of the flexible flow-blocking airbag extends out of the opening of the liquid-blocking groove. The rightmost pole tooth of the rightmost pole shoe is the last stage pole tooth. The flexible flow-blocking airbag and the magnetic fluid at the last stage pole tooth form a dynamic flow-blocking cooperation. When the pump shaft rotates at high speed, the flexible flow-blocking airbag expands radially under the action of centrifugal force, and forms a flexible sealing barrier by adhering to the magnetofluid at the last stage pole tooth; when the pump shaft stops or slows down, the centrifugal force disappears, and the flexible flow-blocking airbag retracts radially by its own elasticity and separates from the magnetofluid at the last stage pole tooth.

[0008] Furthermore, the flow-blocking gap is 0.05-0.2 mm.

[0009] Furthermore, the last stage of the pole tooth in the rightmost pole shoe is located radially outside the liquid-blocking groove and the flexible flow-blocking airbag.

[0010] Furthermore, the bushing has a stepped structure, including a large-diameter section and a small-diameter section, with a stepped surface formed between the large-diameter section and the small-diameter section; wherein the small-diameter section is located on the side closer to the magnetofluid recovery disk; A left pole shoe is provided corresponding to the large diameter segment, and a right pole shoe is provided corresponding to the small diameter segment.

[0011] Furthermore, the right pole shoe also has pole teeth on the side that mates with the stepped surface.

[0012] Furthermore, the pole teeth are single-sided trapezoidal pole tooth structures.

[0013] Furthermore, the liquid storage tank is an annular liquid storage tank, and one or more annular liquid storage tanks are arranged radially along the magnetohydrodynamic recovery disc.

[0014] Furthermore, the cross-section of the annular liquid storage tank is serrated, and the tips of the serrations are inclined towards the outer ring.

[0015] Furthermore, a magnetic retaining ring is provided on the left side of the leftmost pole shoe, and the magnetic retaining ring is fixedly connected to the pump cover.

[0016] Furthermore, the permanent magnet is placed axially along the N and S poles.

[0017] The beneficial effects of this invention are: 1. This invention designs a flexible dynamic flow-blocking unit. The flexible flow-blocking airbag can adaptively deform with the rotation speed to achieve dynamic adaptation under varying operating conditions. It can effectively buffer the impact of the medium, block the erosion of the sealing system by high-speed liquid flow, and avoid sealing failure caused by liquid flow scouring. At the same time, it compensates for pressure fluctuations through flexible deformation, reduces problems such as magnetofluid emulsification and interface instability, enhances the anti-interference ability of the sealing system, adapts to the sealing requirements under different rotation speeds, and can also assist in the autonomous recovery of magnetofluid, reducing magnetofluid loss and emulsification problems.

[0018] Meanwhile, a magnetic fluid active recovery unit was designed to work in conjunction with a flexible dynamic flow-blocking unit. Relying on centrifugal force and pressure difference, the medium in the sealed gap is constrained and the leaked magnetic fluid is recovered and reused, reducing material consumption and maintenance costs, and avoiding noise and leakage problems caused by high-speed jets.

[0019] 2. The magnetic fluid sealing unit of the present invention optimizes the magnetic circuit layout and adopts a single-sided trapezoidal pole tooth structure, which improves the magnetic field utilization and medium constraint capability, adapts to complex working conditions such as variable speed and variable load, and maintains the stability of the sealing liquid film.

[0020] 3. This invention forms a modular coaxial nested structure, which can be directly integrated and installed at the shaft end of the hydraulic pump body. It seamlessly adapts to the pump body impeller, pump casing, and bearing housing without requiring significant modifications to the main pump structure or the addition of an additional drive device. This reduces maintenance costs, improves overall operating efficiency, and ensures long-term stable operation of the sealing system. The device's shaft sleeve is coaxially fixed to the pump shaft. The magnetic circuit assembly, flexible flow-blocking airbag, and magnetofluid recovery disc are sequentially assembled axially, precisely fitting with the pump cover to form a complete sealed chamber. The overall structure is compact, with minimal axial space occupation.

[0021] The components of this invention are coaxially nested and assembled with an axial limiting step and a radial positioning structure. This ensures the coaxiality and rotational accuracy of the sealing device and the pump body, avoiding additional installation errors. It also places the flexible flow blocking, magnetic fluid sealing, and active recovery functional units on the leakage path of the high-pressure medium inside the pump. This allows for direct dynamic isolation and active magnetic fluid recovery of the medium leaking from the pump cavity, effectively suppressing leakage at the pump shaft end. This significantly improves the sealing reliability and operational stability of the pump body, providing a reliable sealing guarantee for the long-term operation of pump equipment under liquid medium conditions.

[0022] 4. The sealing device of the present invention can be directly adapted to the installation requirements of pump shafts of different specifications. It has good versatility and engineering applicability and can be widely used in rotary shaft sealing applications of various pumps such as centrifugal pumps, axial flow pumps, mixed flow pumps, and positive displacement pumps, providing reliable technical support for pump equipment to achieve high efficiency, long service life and low leakage operation. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of a traditional magnetohydrodynamic seal; Figure 2 This is a three-dimensional structural schematic diagram of the present invention; Figure 3 This is the front view of the present invention; Figure 4 yes Figure 3 A sectional view; Figure 5 This is a partial enlarged view of the flexible flow-blocking airbag portion of the present invention; Figure 6 This is a schematic diagram of the invention assembled on a pump; Figure 7 This is a schematic diagram illustrating the overall working principle of the present invention; Figure 8 yes Figure 7 An enlarged schematic diagram illustrating the working principle of the intermediate liquid storage tank; Figure 9 yes Figure 7 An enlarged schematic diagram of the working principle at point A.

[0024] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the invention. To better illustrate this embodiment, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0026] like Figures 2 to 6 As shown, this embodiment discloses a composite dynamic flow-blocking rotary shaft magnetic fluid sealing device for horizontal pumps, including a sealing space formed between the pump cover 8 and the pump shaft 7, and a magnetic fluid sealing unit, a magnetic fluid active recovery unit and a flexible dynamic flow-blocking unit are provided in the sealing space.

[0027] The specific structures of the magnetohydrodynamic sealing unit, the magnetohydrodynamic active recovery unit, and the flexible dynamic flow-blocking unit are described below. The left-right direction is defined by the axial direction of the pump shaft 7, and the right side is defined by the side where the impeller 9 is located.

[0028] The magnetohydrodynamic sealing unit includes a bushing 5 fixedly fitted onto the outside of the pump shaft 7. For connection, holes are drilled in the bushing 5 and the pump shaft 7, and bolts are used for fixing. The bushing 5 has a stepped structure, consisting of a large-diameter section on the left and a small-diameter section on the right, with a stepped surface between the two sections. Two pole shoes 3 are arranged axially along the outer edge of the bushing: a left pole shoe corresponding to the large-diameter section and a right pole shoe corresponding to the small-diameter section. The pole shoes 3 are made of a high-permeability material to converge and organize magnetic field lines, improving the gap magnetic field strength and utilization rate.

[0029] The outer ring of the left pole shoe is sealed and fixedly connected to the pump cover 8. The inner ring of the left pole shoe is provided with pole teeth, and the pole teeth are clearance-fitted with the large diameter section of the bushing 5. The outer ring of the right pole shoe is sealed and fixedly connected to the pump cover 8. The inner ring of the right pole shoe and the side of the right pole shoe that mates with the stepped surface are both provided with pole teeth. The pole teeth are clearance-fitted with the small diameter section of the bushing 5 and the stepped surface.

[0030] A permanent magnet 4 is installed between the two pole shoes 3. The permanent magnet 4 is placed axially with N and N poles, forming a uniform and stable radial and axial magnetic field in the sealing space between the pump shaft 7 and the pump cover 8. This firmly confines the magnetic fluid injected into the sealing space to the gap between the pole teeth and the shaft sleeve 5, forming a continuous and dense non-contact liquid film sealing barrier (magnetic fluid sealing ring). This fundamentally replaces the friction pair of traditional contact seals (such as mechanical seals and packing seals), achieving low-loss sealing. It retains the inherent advantages of magnetic fluid sealing, such as non-contact, low friction, and zero leakage, and is particularly suitable for pumping liquid media in applications where leakage requirements are stringent.

[0031] A magnetic blocking ring 1 is provided on the left side of the left pole shoe, and the magnetic blocking ring 1 is fixedly connected to the pump cover 8. The magnetic blocking ring 1 is made of non-magnetic material to prevent magnetic field leakage and reduce magnetic flux loss.

[0032] The magnetic fluid sealing unit of the present invention optimizes the magnetic circuit layout and adopts a single-sided trapezoidal pole tooth structure to improve the magnetic field utilization and medium constraint capability, adapt to complex working conditions such as variable speed and variable load, and maintain the stability of the sealing liquid film.

[0033] The magnetohydrodynamic (MHD) active recovery unit includes a MHD recovery disc 2 fixedly sleeved outside the pump shaft 7. Specifically, the MHD recovery disc 2 is connected to the pump shaft 7 via a key, allowing it to rotate together with the pump shaft 7. The MHD recovery disc 2 is located on the right side of the right pole shoe (i.e., closer to the impeller 9), and there is a 0.1mm flow-blocking gap between the left end face of the MHD recovery disc 2 and the right end face of the right pole shoe. This flow-blocking gap induces a capillary effect during operation, preventing MHD leakage and contact with the medium.

[0034] Multiple annular liquid storage tanks 21 are provided on the left end face of the magnetohydrodynamic (MHD) recovery disk 2. The multiple liquid storage tanks 21 are arranged at radial intervals along the MHD recovery disk to form a multi-level liquid storage structure. The cross-section of the liquid storage tanks 21 is serrated, and the tips of the serrations are inclined towards the outer ring of the MHD recovery disk 2.

[0035] The flexible dynamic flow-blocking unit includes an annular liquid-blocking groove 22 disposed on the left end face of the magnetic fluid recovery tray 2. The position of the liquid-blocking groove 22 corresponds to the magnetic fluid sealing ring, and the left side of the liquid-blocking groove 22 is provided as an opening. An annular flexible flow-blocking airbag 6 is installed inside the liquid-blocking groove 22. The inner ring of the flexible flow-blocking airbag 6 is fixedly connected to the inner ring of the liquid-blocking groove 22, and the left side part of the flexible flow-blocking airbag 6 extends out of the opening of the liquid-blocking groove 22.

[0036] The flexible flow-restricting airbag 6 is made of a highly elastic, media-resistant (water, oil, chemical media-resistant), and aging-resistant flexible material, and is integrally embedded in the liquid-restricting groove 22. It can rotate synchronously with the pump shaft 7 and the magnetofluid recovery disc 2. During pump operation, the volume of the flexible flow-restricting airbag 6 changes dynamically under the action of centrifugal force, forming a flow-restricting effect that adapts to the rotational speed, effectively buffering the impact of pressure pulsation, high-speed scouring, and shaft vibration caused by the liquid medium in the pump on the magnetofluid interface; when the pump stops, the flexible flow-restricting airbag 6 restores its deformation and autonomously recovers the detached magnetofluid.

[0037] Simultaneously, an anti-interference limiting structure is installed. The rightmost pole tooth in the right pole shoe is the last stage pole tooth 31. The position of the last stage pole tooth 31 is on the radial outer side of the liquid-blocking groove 22 and the flexible flow-blocking airbag 6, forming a differentiated height layout. Furthermore, the outer ring end face of the liquid-blocking groove 22 physically limits the maximum expansion deformation of the airbag, constraining the deformation range of the flexible material and ensuring the safety and stability of the flexible flow-blocking airbag 6 and the entire sealing structure under long-term pump start-up and shutdown, variable speed operation, and complex hydraulic conditions.

[0038] Workbench simulations show that at a rotation speed of 7000 r / min, the maximum radial deformation of the flexible flow-blocking airbag 6 can reach 0.298 mm, which can stably form a continuous fit with the magnetofluid adsorbed at the last stage pole tooth 31 in the right pole shoe, thus constructing a complete flexible sealing barrier.

[0039] like Figures 7 to 9 As shown, the working principle of this invention is as follows: To address the two core problems of magnetohydrodynamic (MHD) seals on pump shafts in liquid media—emulsion instability at the MHD interface and leakage of MHD fluid—this invention employs a combined sealing structure of a flexible flow-blocking airbag 6 and a rigid MHD fluid recovery disc 2. This structure constructs an integrated sealing system that features dynamic flow blocking, multi-stage interception, active recovery, and anti-interference protection. By relying on structural synergy and adaptive operating conditions, it achieves stable sealing under multiple operating conditions.

[0040] During normal high-speed operation of the pump, the flexible flow-blocking airbag 6, which rotates synchronously with the pump shaft 7, expands radially under centrifugal force, forming a continuous flexible sealing barrier with the magnetofluid at the last stage pole tooth 31 in the right pole shoe. This effectively prevents high-pressure water from directly impacting the magnetofluid interface, inhibits media erosion and vibration-induced magnetofluid emulsification and interface instability, and blocks liquid media from intruding into the seal. A small flow-blocking gap is set between the magnetofluid recovery disc 2 and the right pole shoe, forming a capillary liquid barrier based on capillary effect and pressure difference, preventing water from penetrating the gap and intruding into the sealing area, thus achieving physical isolation between the medium and the magnetofluid. A small amount of leaked magnetofluid entering the gap is captured and buffered step by step by the multi-stage liquid storage tanks 21 arranged on the magnetofluid recovery disc 2. The centrifugal blocking effect of the sawtooth structure prevents the magnetofluid from further spreading and contaminating the medium, completing multi-stage interception and protection.

[0041] Furthermore, the expanding flexible flow-restricting airbag 6 can discharge water accumulated in the gap between the pole shoe and the magnetohydrodynamic recovery disc 2, further enhancing the media isolation effect. The specific principle is as follows: When the pump is stopped, due to capillary action, some liquid media will be adsorbed and remain in the narrow gap between the magnetohydrodynamic recovery disc 2 and the right pole shoe. When the pump starts and enters the working state, the flexible flow-restricting airbag 6, which rotates synchronously with the pump shaft 7, undergoes radial elastic expansion under the action of centrifugal force, and its volume increases significantly. During the expansion process, the flexible flow-restricting airbag 6 will form a dual synergistic effect inside the flow-restricting gap: on the one hand, the radial displacement of the flexible flow-restricting airbag 6 will generate direct radial and axial pushing force on the water accumulated in the flow-restricting gap, driving the liquid to flow outward along the gap; on the other hand, the core area inside the device has good sealing performance, and the expansion of the flexible flow-restricting airbag 6 will compress the limited space in the flow-restricting gap, causing the local pressure to rise and forming an outward pressure difference, further promoting the rapid discharge of accumulated water. Under the combined effect of physical pushing and pressure difference, the water accumulated in the flow-blocking gap is completely removed, effectively eliminating liquid accumulation and preventing direct contact between the liquid medium and the magnetic fluid. This suppresses the problems of magnetic fluid emulsification and interface instability from the source, further enhancing the medium isolation effect.

[0042] When the pump stops or slows down, the centrifugal force disappears, and the flexible flow-blocking airbag 6 rapidly retracts radially due to its own elasticity, causing the liquid-blocking groove 22 inside the magnetic fluid recovery disc 2 to expand instantly and form a local negative pressure. Driven by the pressure difference, the leaked magnetic fluid retained in each level of the liquid storage tank 21 is drawn back along the gap and automatically flows back to the main sealing area of ​​the pole tooth, realizing the active recovery and recycling of magnetic fluid without manual intervention, effectively reducing magnetic fluid loss, extending the service life of the seal, and solving the problem of sealing performance degradation caused by media loss.

[0043] At the same time, the magnetic fluid recovery disk 2 is used to physically constrain the maximum expansion deformation of the flexible flow-blocking airbag 6, so as to avoid mechanical friction and wear failure caused by excessive deformation of the airbag adhering to the pole teeth, and ensure the structural safety and operational stability of the flexible component and the entire sealing system in the long term.

[0044] This invention achieves a magnetic fluid anti-emulsification, anti-leakage, recyclable, and long-life sealing effect through the coordinated operation of flexible flow-blocking airbags, capillary gap liquid isolation, multi-stage liquid storage interception, shutdown negative pressure recovery, and anti-interference limit. It is suitable for the long-term reliable operation requirements of hydraulic machinery under liquid media conditions.

[0045] This invention effectively solves the problems of emulsification instability and gap leakage at the magnetohydrodynamic interface, significantly reduces media loss, and improves the stability and service life of the seal. At the same time, it constructs an all-condition adaptive sealing protection system that can accurately adapt to complex liquid conditions with varying speeds and loads, which is of great value in improving the reliability and engineering applicability of hydraulic mechanical seals.

[0046] This invention integrates dynamic flow obstruction, multi-stage interception, negative pressure recovery, and structural protection into a unified design. It can adapt to different operating conditions and the changes in the sealing flow state during the transition between operating conditions in real time, effectively ensuring the safety and structural stability of the hydraulic machinery. It is of great significance for promoting the engineering application of magnetohydrodynamic sealing technology in the field of fluid machinery.

[0047] Furthermore, the present invention forms a modular coaxial nested structure that can be directly integrated and installed at the shaft end of the hydraulic mechanical pump body, achieving seamless adaptation with the pump body impeller, pump casing and bearing seat. It does not require major modifications to the main structure of the pump body, nor does it require additional drive devices, which can reduce operation and maintenance costs, improve overall operating efficiency, and ensure long-term stable operation of the sealing system.

[0048] This invention can also be applied to vertical or inclined pump scenarios. It only requires removing the serrated liquid storage tank 21 on the magnetic fluid recovery plate 2 and machining a liquid storage tank structure of the same specifications on the side wall surface of the gap between the right pole shoe and the magnetic fluid recovery plate 2. This can achieve effective retention and recovery of magnetic fluid, ensuring that the device can stably perform its sealing function under different installation postures. It is perfectly adapted to the installation and operation requirements of various pump types and has good working condition adaptability.

[0049] The above embodiments are only used to illustrate and not limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention without departing from the spirit and scope of the present invention. Any modifications or partial substitutions should be covered within the scope of the claims of the present invention.

[0050] If the terms "first" or "second" are used in this document to define components, those skilled in the art should know that the use of "first" or "second" is merely for the convenience of describing the invention and simplifying the description, and unless otherwise stated, the above terms have no special meaning.

[0051] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0052] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" 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 based on the specific circumstances.

Claims

1. A composite dynamic flow-blocking rotary shaft magnetohydrodynamic sealing device for pumps, comprising a sealing space formed between the pump cover and the pump shaft, characterized in that: The sealed space is equipped with a magnetic fluid sealing unit, which includes a bushing fixedly fitted outside the pump shaft. Multiple pole shoes are arranged along the axial direction outside the bushing, and permanent magnets are installed between adjacent pole shoes. The outer ring of the pole shoe is sealed and fixedly connected to the pump cover. The inner ring of the pole shoe is provided with pole teeth, and the pole teeth are clearance-fitted with the bushing. Magnetic fluid is filled in the gap between the pole teeth and the bushing to form a magnetic fluid sealing ring. The sealed space is also equipped with a magnetic fluid active recovery unit, which includes a magnetic fluid recovery disc fixedly sleeved on the outside of the pump shaft. The magnetic fluid recovery disc is located on the side close to the impeller. The end face of the magnetic fluid recovery disc away from the impeller is the left end face. There is a flow-blocking gap between the left end face of the magnetic fluid recovery disc and the right end face of the rightmost pole shoe. One or more liquid storage tanks are arranged on the left end face of the magnetic fluid recovery disc and / or the right end face of the rightmost pole shoe. The sealed space is also equipped with a flexible dynamic flow-blocking unit. The flexible dynamic flow-blocking unit includes an annular liquid-blocking groove set on the left end face of the magnetic fluid recovery tray. The position of the liquid-blocking groove corresponds to the magnetic fluid sealing ring, and the left side of the liquid-blocking groove is set as an opening. An annular flexible flow-blocking airbag is installed in the liquid-blocking groove. The inner ring of the flexible flow-blocking airbag is fixedly connected to the inner ring of the liquid-blocking groove, and the left side of the flexible flow-blocking airbag extends out of the opening of the liquid-blocking groove. The rightmost pole tooth of the rightmost pole shoe is the last stage pole tooth. The flexible flow-blocking airbag and the magnetic fluid at the last stage pole tooth form a dynamic flow-blocking cooperation. When the pump shaft rotates at high speed, the flexible flow-blocking airbag expands radially under the action of centrifugal force, and forms a flexible sealing barrier by adhering to the magnetofluid at the last stage pole tooth; when the pump shaft stops or slows down, the centrifugal force disappears, and the flexible flow-blocking airbag retracts radially by its own elasticity and separates from the magnetofluid at the last stage pole tooth. The last stage of the pole tooth in the rightmost pole shoe is located radially outside the liquid-blocking groove and the flexible flow-blocking airbag; The liquid storage tank is an annular liquid storage tank, and one or more annular liquid storage tanks are arranged radially along the magnetohydrodynamic recovery disc; The cross-section of the annular liquid storage tank is serrated, and the tips of the serrations are inclined towards the outer ring.

2. The composite dynamic flow-blocking rotary shaft magnetohydrodynamic sealing device for pumps according to claim 1, characterized in that: The flow-blocking gap is 0.05-0.2mm.

3. The composite dynamic flow-blocking rotary shaft magnetohydrodynamic sealing device for pumps according to claim 1, characterized in that: The bushing has a stepped structure, including a large-diameter section and a small-diameter section, with a stepped surface between the large-diameter section and the small-diameter section; the small-diameter section is located on the side closer to the magnetofluid recovery disk; A left pole shoe is provided corresponding to the large diameter segment, and a right pole shoe is provided corresponding to the small diameter segment.

4. A composite dynamic flow-blocking rotary shaft magnetohydrodynamic sealing device for pumps according to claim 3, characterized in that: The right pole shoe also has pole teeth on the side that mates with the stepped surface.

5. A composite dynamic flow-blocking rotary shaft magnetohydrodynamic sealing device for pumps according to claim 1 or 4, characterized in that: The pole teeth are single-sided trapezoidal pole tooth structures.

6. The composite dynamic flow-blocking rotary shaft magnetohydrodynamic sealing device for pumps according to claim 1, characterized in that: A magnetic retaining ring is located on the left side of the leftmost pole shoe, and the magnetic retaining ring is fixedly connected to the pump cover.

7. A composite dynamic flow-blocking rotary shaft magnetohydrodynamic sealing device for pumps according to claim 1, characterized in that: The permanent magnet is placed along the N-S pole axis.

Images