Novel immersion type multi-stage centrifugal pump

Abstract

The invention relates to the technical field of fluid conveying equipment, in particular to a novel immersion type multi-stage centrifugal pump which comprises a pump body, and the pump body is provided with a water inlet used for liquid inflow and a water outlet used for liquid outflow. And the impeller is arranged in the pump body and is used for carrying out multi-stage pressurization on the liquid. And the pump shaft is in transmission connection with the impeller. The pump head is connected with the pump body, and the pump shaft penetrates through the pump head. And a composite non-contact sealing structure for axially sealing the pump shaft is arranged in the pump head. Medium flowing is slowed down through the fluid dynamic pressure sealing principle, media are thrown out through centrifugal force and are secondarily blocked, the problem that a traditional mechanical seal loses efficacy under the working conditions of special media and frequent starting and stopping is solved, the reliability and stability of equipment are improved, and the mechanical seal is suitable for complex working conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fluid machinery, in particular to a new type of immersed multistage centrifugal pump. BACKGROUND

[0002] The immersed multistage centrifugal pump is a fluid conveying device widely used in industrial fields, and the axial sealing design has an important influence on the overall performance of the pump. The axial sealing of the immersed multistage centrifugal pump on the market currently adopts a mechanical seal structure, which relies on the axial adhesion of the dynamic ring and the static ring to achieve sealing, and provides pre-tightening force through a spring and an auxiliary sealing ring to maintain the sealing effect. The mechanical seal has obvious advantages, such as excellent sealing performance, low leakage rate, long service life, and low friction power consumption, and has been widely used in the immersed centrifugal pump industry.

[0003] However, in the actual application process of the mechanical seal, some limitations also appear. First, the mechanical seal is sensitive to the characteristics of the medium, especially when the medium contains solid particles, easily crystallized substances or corrosive components, which can easily cause wear or failure of the sealing surface. Second, the mechanical seal needs to keep the liquid in the pump sufficient, otherwise dry friction will cause damage to the sealing surface, thereby causing leakage problems. In addition, under the condition of frequent start-stop, the mechanical seal may be broken due to pressure impact or the rubber part may be permanently deformed. Finally, for special media such as easy crystallization, easy adsorption or high viscosity, the mechanical seal has certain challenges in long-term sealing, which may increase the risk of leakage. These limitations have potential impact on the reliability and stability of the immersed multistage centrifugal pump.

[0004] In view of the above problems, the present application proposes a new type of immersed multistage centrifugal pump. SUMMARY

[0005] The purpose of the present application is to provide a new type of immersed multistage centrifugal pump to solve the problem that the existing mechanical seal structure is prone to failure when handling complex media. The traditional contact type mechanical seal is abandoned, and a multi-stage collaborative composite non-contact sealing structure is adopted, thereby significantly improving the reliability, stability and service life of the pump under complex working conditions.

[0006] An immersed multistage centrifugal pump, comprising: A pump body having a water inlet for liquid inflow and a water outlet for liquid outflow.

[0007] An impeller arranged inside the pump body for multi-stage pressurization of the liquid.

[0008] A pump shaft in transmission connection with the impeller, and A pump head connected with the pump body, and the pump shaft passes through the pump head.

[0009] The pump head is provided with a composite non-contact sealing structure for axially sealing the pump shaft.

[0010] The composite non-contact sealing structure comprises: A first-stage gap sealing assembly, which comprises a bushing fixedly connected inside the pump head, the pump shaft passing through the inner hole of the bushing, a radial gap being formed between the inner hole of the bushing and the outer surface of the pump shaft, and a plurality of bushing annular grooves being distributed on the inner hole wall of the bushing along the axial direction of the pump shaft, the radial gap and the plurality of bushing annular grooves together constituting a flow resistance passage for fluid to achieve pressure drop and blockage of initial leakage.

[0011] A second-stage axial blocking sealing assembly, which comprises a first shaft seal installed along the axial direction of the pump shaft and rotating synchronously with the pump shaft, the first shaft seal being used for axially blocking the medium and for radially throwing out the blocked medium, and the lower end of the first shaft seal being further provided with a shaft seal annular groove for radially blocking the medium again after being thrown out.

[0012] Further, the composite non-contact sealing structure further comprises: A third-stage auxiliary sealing assembly, which comprises a second shaft seal installed along the axial direction of the pump shaft and rotating synchronously with the pump shaft.

[0013] Further, the second shaft seal is a flexible sealing member made of rubber, which is tightly pressed into and fixed on the outer surface of the pump shaft in an interference fit manner, and the structural size and material properties of the second shaft seal are designed to form a sealing fit with the pump shaft and the inner cavity of the pump head, so as to cooperate with the first two-stage sealing assembly to axially seal.

[0014] Further, the bushing of the first-stage gap sealing assembly is reliably fastened to the pump head by fasteners, and the radial gap between the inner hole of the bushing and the outer surface of the pump shaft is designed to be a preset value, the preset radial gap and the axial length of the bushing together defining the flow resistance when the medium passes through.

[0015] Further, the inner hole wall of the bushing is provided with a plurality of bushing annular grooves distributed along the axial direction of the pump shaft, the bushing annular grooves are equidistantly distributed along the axial direction of the pump shaft, and are used for multiple pressure relief and segmented blocking of the medium; each bushing annular groove has a preset depth and width, the depth and width of the bushing annular groove are matched with the radial gap to generate a fluid dynamic pressure sealing principle when the medium passes through, and the edges of the bushing annular groove are chamfered to guide the medium to form a stable low-speed area in the bushing annular groove, so as to slow down the axial flow speed of the medium and enhance the pressure relief and blocking effect.

[0016] Further, the first shaft seal of the second-stage axial blocking sealing assembly is locked and fixedly connected with the pump shaft through at least one fastener, the structure of the first shaft seal comprises an axial extension part and a radial outward expansion part, the axial extension part is used for axial blocking of the medium, and the radial outward expansion part is used for radially throwing out the medium by centrifugal force when the pump shaft rotates.

[0017] Further, the shaft seal annular groove extends along the radial direction of the first shaft seal, and the depth and width of the shaft seal annular groove are designed to be able to effectively intercept and retain the thrown-out medium, and further enhance the radial centrifugal motion of the medium by the rotational kinetic energy of the pump shaft, so as to avoid leakage of the medium to the outside of the next-stage sealing area or the external environment.

[0018] Further, the composite non-contact sealing structure further comprises: A sealing cover is fixedly connected to the outer side of the pump head through a plurality of fasteners, the sealing cover forms an annular collection chamber, the annular collection chamber surrounds the outer radial area of the second-stage axial blocking sealing assembly and the third-stage auxiliary sealing assembly, the sealing cover is used for collecting the medium thrown out by the second-stage axial blocking sealing assembly and guiding the medium to flow back to the water tank in the pump body.

[0019] Further, the sealing cover is reliably fixed to the side surface of the pump head through a plurality of fasteners, the bottom of the annular collection chamber is connected to the water tank in the pump body through a backflow channel, and the backflow channel ensures that all the collected medium can completely flow back to the pump body.

[0020] Further, the immersed multistage centrifugal pump further comprises a motor shaft, the motor shaft is connected with the pump shaft through a shaft coupling to drive the pump shaft and the impeller to rotate, the pump shaft passes through the pump head, the pump head is not provided with a contact type mechanical sealing structure, and the pump shaft and the pump head are axially sealed through the composite non-contact sealing structure.

[0021] From the above, the first gap sealing assembly, the second axial blocking sealing assembly and the third auxiliary sealing assembly are arranged, the medium is gradually blocked and guided, the pressure of the medium is gradually reduced and the possibility of leakage is reduced when passing through each sealing assembly. The first gap sealing assembly forms a resistance path through the radial gap and the plurality of bushing annular grooves, and the axial movement speed of the medium is slowed down by using the fluid dynamic pressure sealing principle and the chamfer design; the second axial blocking sealing assembly is thrown out by the centrifugal force of the first shaft seal, and the medium is intercepted by the shaft seal annular groove to avoid further diffusion; the third auxiliary sealing assembly further enhances the isolation effect by the close fitting of the flexible sealing element made of rubber material. In addition, the design of the sealing cover ensures that the intercepted medium can return to the pump body through the return pipeline, avoiding resource waste. The overall design avoids the sensitivity problem of traditional mechanical seals to complex media, and can maintain stable operation without relying on the medium filling the pump cavity, significantly improving the reliability and service life of the equipment. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is a schematic diagram of the overall structure of the application.

[0023] Figure 2 It is a schematic diagram of the overall structure of the application. Figure 1 It is a schematic diagram of the overall structure of the application.

[0024] Figure 3 It is a schematic diagram of the overall structure of the application.

[0025] Figure 4 It is a schematic diagram of the overall structure of the application.

[0026] Figure 5 It is a schematic diagram of the overall structure of the application. Figure 4 It is a schematic diagram of the overall structure of the application.

[0027] Figure 6 It is a schematic diagram of the overall structure of the application.

[0028] Figure 7 It is a schematic diagram of the overall structure of the application.

[0029] Figure 8 It is a schematic diagram of the overall structure of the application.

[0030] Figure 9 It is a schematic diagram of the overall structure of the application.

[0031] Figure 10 It is a schematic diagram of the overall structure of the application.

[0032] The reference signs are as follows: 1, pump body; 2, impeller; 3, pump shaft; 4, pump head; 5, first stage gap sealing assembly; 6, second stage axial blocking sealing assembly; 7, third stage auxiliary sealing assembly; 8, sealing cover; 9, motor shaft; 10, coupling.

[0033] 51, bushing; 52, radial gap; 53, bushing annular groove.

[0034] 61, first shaft seal; 62, shaft seal annular groove; 63, axial extension; 64, radial expansion.

[0035] 71, second shaft seal.

[0036] 81, annular collection chamber. DETAILED DESCRIPTION

[0037] To make the objectives, technical solutions and advantages of the present application clearer, further detailed description will be given below with the aid of drawings and examples. However, it should be understood that the specific examples described herein are only used to explain the present application and are not used to limit the scope of the present application. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present application.

[0038] As Figures 1 to 10 shown in the present application, a new type of immersed multistage centrifugal pump includes a pump body 1, an impeller 2, a pump shaft 3, a pump head 4, and a composite non-contact sealing structure. The pump body 1 is a basic component of the overall structure, and a cavity is formed inside for accommodating the impeller 2 and the fluid medium.

[0039] The pump body 1 has a water inlet for liquid inflow and a water outlet for liquid outflow.

[0040] The impeller 2 is arranged in the internal cavity of the pump body 1 and is drivingly connected to the pump shaft 3 through a key groove structure. The pump shaft 3 is arranged along the axial direction of the pump body 1 and is connected to the motor shaft 9 through the coupling 10.

[0041] The pump shaft 3 is drivingly connected to the impeller 2.

[0042] The pump head 4 is connected to the pump body 1, and the pump shaft 3 passes through the pump head 4.

[0043] The pump head 4 is provided with a composite non-contact sealing structure for axially sealing the pump shaft 3.

[0044] The composite non-contact sealing structure aims to achieve multi-stage fluid blocking and management in a non-contact manner to cope with challenges brought by solid particles, crystalline substances, corrosive substances, medium interruption and frequent start-stop in the medium. The composite non-contact sealing structure comprises a first-stage gap sealing assembly 5, a second-stage axial blocking sealing assembly 6 and a third-stage auxiliary sealing assembly 7. The three-stage sealing assemblies are arranged in sequence along the axial direction of the pump shaft 3 and jointly constitute an integrated sealing scheme of gradually reducing pressure, centrifugally throwing liquid and finally achieving effective isolation.

[0045] As a preferred embodiment of the present application, the first-stage gap sealing assembly 5 comprises a bushing 51 which is reliably fastened to a specific mounting cavity inside the pump head 4 through a plurality of fasteners (for example, M6-diameter 316L stainless steel hexagonal socket screws fastened through a preset torque). The pump shaft 3 precisely passes through the inner hole of the bushing 51, and a precisely controlled radial gap 52 is formed between the inner hole of the bushing 51 and the outer surface of the pump shaft 3. The radial gap 52 is designed to have a preset value, which is usually in the range of 0.08 mm to 0.15 mm, to ensure that a significant flow resistance is maintained while allowing a small amount of fluid to pass through. The bushing 51 is made of ductile iron material (for example, QT500-7 ductile iron material) which has high strength, high toughness and excellent machining performance to adapt to complex media and ensure long-term stability.

[0046] Further, a plurality of bushing annular grooves 53 are uniformly distributed on the inner hole wall of the bushing 51 along the axial direction of the pump shaft 3, which together with the radial gap 52 forms a multi-stage flow resistance channel for fluid to achieve pressure drop and segmented blocking of the initial leakage. The axial length of the bushing 51 is designed according to the operating pressure of the pump and the allowable leakage, and is usually set to 3 to 5 times the diameter of the pump shaft 3 to provide sufficient resistance length. The first-stage gap sealing assembly 5 works in a non-contact manner, and its core principle is to utilize the flow characteristics of fluid in a narrow gap and special geometry to effectively limit the axial penetration of the medium by fluid dynamic pressure sealing and local pressure drop, greatly reducing the sensitivity to solid particles or crystalline substances in the medium and avoiding damage caused by dry friction.

[0047] Specifically, the inner hole wall of the bushing 51 is provided with a plurality of bushing annular grooves 53 distributed along the axial direction of the pump shaft 3. The bushing annular grooves 53 are equidistantly distributed along the axial direction of the pump shaft 3, for example, 2 to 6 bushing annular grooves 53 are provided within the effective sealing length of the bushing 51, and the axial distance between each bushing annular groove 53 is 1.5 to 2.5 times the width of the bushing annular groove 53. Each of the bushing annular grooves 53 has a predetermined depth and width, the depth of the bushing annular groove 53 is set to 2.0 to 3.5 mm, and the width is set to 2.5 to 4.0 mm. The geometric size of the bushing annular groove 53 is precisely matched with the radial gap 52 to generate a stable fluid dynamic pressure sealing principle when the medium passes. The fluid dynamic pressure sealing principle effectively increases the axial flow path of the medium by forming a relatively independent, low-speed circulating fluid area inside the annular groove, and improves the inertial resistance of the medium flow. The edge of the bushing annular groove 53 is precisely chamfered, and the chamfering is specifically a circular arc chamfer with a radius of 0.5 to 1.0 mm formed at the connection between the annular groove and the inner hole wall. The design of the circular arc chamfer aims to optimize the flow lines when the fluid enters and exits the annular groove, thereby guiding the medium to form a stable low-speed area in the bushing annular groove 53, which further enhances the fluid retention effect, thereby slowing down the axial flow speed of the medium and effectively enhancing the pressure relief blocking effect. The hierarchical blocking mechanism ensures that the pressure of the medium has been significantly reduced and the axial flow speed has been greatly reduced before entering the next level of sealing assembly.

[0048] As a preferred embodiment of the present application, the second stage axial blocking seal assembly 6 is installed immediately downstream of the first stage gap seal assembly 5 along the axial direction of the pump shaft 3. The second stage axial blocking seal assembly 6 comprises a first shaft seal 61, which is fixedly connected with the pump shaft 3 by at least one high-strength fastener (for example, by a keyway fit and a radial locking screw, or by a thermal press fit followed by a threaded locking ring), ensuring synchronous high-precision rotation with the pump shaft 3. The first shaft seal 61 is made of a high-strength, corrosion-resistant metal alloy (for example, 304 stainless steel or 316 stainless steel) with a yield strength of not less than 550 MPa, capable of withstanding the centrifugal force generated by high-speed rotation and possible medium impact. The structure of the first shaft seal 61 includes an axial extension 63 and a radial outward expansion 64. The axial extension 63 is in close contact with the pump shaft 3, and its axial length is designed to be 0.5 to 1.0 times the diameter of the pump shaft 3, providing an initial axial blocking effect and limiting the flow of medium on the surface of the pump shaft 3. The radial outward expansion 64 extends radially outward from the downstream end of the axial extension 63, forming a disc-shaped structure with a specific inclination angle (for example, 20 to 35 degrees relative to the axial plane). When the pump shaft 3 rotates, the radial outward expansion 64 can use the generated centrifugal force to forcibly throw out the small amount of medium passing through the first stage seal in the radial direction, effectively preventing the medium from further penetrating along the pump shaft 3. The outer diameter of the radial outward expansion 64 is typically designed to be 2.0 to 3.0 times the diameter of the pump shaft 3 to generate sufficient centrifugal acceleration.

[0049] Further, the lower end of the first shaft seal 61 (i.e., the side of the radial outward expansion 64 away from the pump body 1) is also provided with a shaft seal annular groove 62. The shaft seal annular groove 62 extends along the radial direction of the first shaft seal 61. The depth of the shaft seal annular groove 62 is designed to be 2.0 to 4.0 mm, and the width is designed to be 2.0 to 4.0 mm. The geometric size of the shaft seal annular groove 62 is accurately designed to effectively intercept and retain the medium thrown out by the radial outward expansion 64. When the medium is thrown out by the centrifugal force and enters the shaft seal annular groove 62, the continuous high-speed rotation kinetic energy of the pump shaft 3 will further enhance the radial centrifugal motion of the medium in the annular groove, causing the medium to continuously accumulate on the outer wall of the annular groove and move in the pre-set return direction through the structure of the annular groove. The presence of this shaft seal annular groove 62 forms a second physical barrier for the medium to change from an axial path to a radial throw-out path, effectively preventing accidental leakage of the thrown-out medium to the next stage seal area or the external environment. Through this dynamic centrifugal liquid throwing and interception mechanism, the second stage seal assembly efficiently manages the small amount of leakage in a non-contact state, greatly enhancing the self-cleaning ability of the sealing system for particulate matter in the medium.

[0050] As a preferred embodiment of the present application, the third stage auxiliary seal assembly 7 is installed immediately downstream of the second stage axial blocking seal assembly 6 along the axial direction of the pump shaft 3. The third stage auxiliary seal assembly 7 comprises a second shaft seal 71 which is tightly pressed and fixed on the outer surface of the pump shaft 3 in an interference fit and rotates synchronously with the pump shaft 3. The second shaft seal 71 is made of a flexible seal of high performance fluorine rubber (FKM, for example, 75 Shore A hardness, with excellent chemical corrosion resistance and high temperature resistance, and can work stably in the temperature range of -20°C to 200°C) and is designed to provide the last safety barrier. The structural size and material properties of the second shaft seal 71 are precisely designed to form stable axial and radial contact with the sealing surface of the pump shaft 3 and the inner cavity of the pump head 4 to cooperate with the previous two stage seal assemblies for axial sealing. Specifically, the second shaft seal 71 is a lip seal, and the sealing lip of the second shaft seal 71 generates a radial pre-tightening force on the outer surface of the pump shaft 3 after installation, and the radial compression amount is controlled between 10% and 15%, thereby forming a tight contact seal. The contact width of the sealing lip is optimally designed to effectively prevent the escape of liquid, vapor or fine aerosol while maintaining low friction torque. Although the second shaft seal 71 is a contact seal, its main function is to serve as an auxiliary or redundant seal after the effective reduction of medium pressure and flow by the previous two stage non-contact seal assemblies, especially for preventing the escape of residual vapor or fine droplets, rather than assuming the main high pressure sealing task, so its wear and heat generation are significantly lower than that of the conventional mechanical seal. This design avoids the problem of dry friction and burning of the conventional mechanical seal due to insufficient medium, and significantly prolongs the service life.

[0051] As a preferred embodiment of the present application, the composite non-contact sealing structure further comprises a sealing cover 8. The sealing cover 8 is reliably fixed and connected to the outside of the pump head 4 by a plurality of fasteners (for example, 316L stainless steel bolts with M8, connected to the fixed flange outside the pump head 4 through a washer and a nut). The internal structure of the sealing cover 8 forms an annular collection chamber 81 which surrounds and encloses the outer radial area of the second-stage axial blocking sealing assembly 6 and the third-stage auxiliary sealing assembly 7. The annular collection chamber 81 is designed to efficiently capture and converge all the media ejected by the second-stage axial blocking sealing assembly 6. The bottom of the annular collection chamber 81 is reliably connected to the water tank inside the pump body 1 through a backflow channel. The specific structure of the backflow channel is a flow guide pipe with an inner diameter of 10-15 mm, and its connection position and inclination angle are accurately calculated to ensure that all the collected media can be completely and smoothly backflowed to the water tank inside the pump body 1 by gravity or a slight pressure difference. The design of the sealing cover 8 and the backflow channel not only effectively prevents the leakage of media to the external environment, achieving the goal of zero leakage operation, but also helps to recycle the media resources, improving the operation efficiency and environmental friendliness of the entire centrifugal pump system.

[0052] As a preferred embodiment of the present application, the immersed multi-stage centrifugal pump further comprises a motor shaft 9 connected to the pump shaft 3 through a shaft coupling 10 (for example, a flexible diaphragm coupling 10 or a gear coupling 10 to compensate for axial, radial and angular deviations) to drive the pump shaft 3 and the impeller 2 to rotate. The pump shaft 3 passes through the pump head 4 which does not have any contact type mechanical sealing structure. The axial sealing between the pump shaft 3 and the pump head 4 is completely realized by the composite non-contact sealing structure. This design completely avoids the problems of poor media compatibility, easy wear, easy dry friction and sensitivity to frequent start-stop of traditional mechanical seals through integrated multi-stage non-contact sealing scheme, fundamentally improving the long-term reliability and maintenance convenience of the immersed multi-stage centrifugal pump under harsh working conditions.

[0053] The new immersed multi-stage centrifugal pump proposed in the present application achieves the following significant technical effects through the above technical solutions: Firstly, the first stage gap sealing assembly 5 effectively establishes multi-stage resistance passage by precisely designed radial gap 52 and multiple bushing annular grooves 53. The radial gap 52, by precisely controlling its size (0.08mm to 0.15mm) and selecting high-strength, excellent mechanical processing performance of ductile iron material (for example: QT500-7 ductile iron material), performs initial pressure reduction and flow rate control on the medium in a non-contact state, avoiding the sensitivity of traditional mechanical seals to solid particles in the medium. The fluid dynamic pressure sealing principle and chamfer design (circular chamfer radius 0.5mm to 1.0mm) of the bushing annular groove 53 further enhance the medium retention and pressure relief effect, so that the pressure and axial flow rate of the medium are significantly reduced before entering the next stage of sealing, thereby protecting the downstream sealing assembly.

[0054] Secondly, the second stage axial blocking sealing assembly 6 realizes dynamic centrifugal liquid throwing function through the axial extension 63 and radial expansion 64 of the first shaft seal 61 combined with the direct rotation of the pump shaft 3. The radial expansion 64 (the outer diameter is 2.0 to 3.0 times the diameter of the pump shaft 3, and the inclination angle is 20 to 35 degrees) can efficiently utilize centrifugal force to throw out the trace amount of medium passing through the first stage in the radial direction. The shaft seal annular groove 62 (depth 3.0mm to 6.0mm, width 4.0mm to 8.0mm) precisely intercepts the thrown-out medium and further promotes the radial centrifugal motion of the medium through the rotational kinetic energy of the pump shaft 3, avoiding its further diffusion in the axial direction. This stage sealing assembly completely solves the problem of dry friction of traditional mechanical seals in the case of insufficient medium, because it works in a non-contact state, even in the case of low liquid level or transient interruption of the medium, it can maintain its function, significantly improving the operation safety of the equipment.

[0055] Furthermore, the third stage auxiliary sealing assembly 7 provides a flexible and reliable final isolation barrier. The second shaft seal 71 (using a lip seal of FKM material with a hardness of 75 Shore A, with a radial compression amount of 10% to 15%) realizes sealing in a low-friction, interference fit manner in the case of significantly reduced medium pressure and extremely small flow rate. Its main function is to prevent the escape of residual steam, fine aerosol or trace amount of liquid droplets, serving as a supplement and redundancy to the previous two stages of non-contact sealing, rather than bearing the main high-pressure sealing task. This design avoids the problem of sealing ring rupture or permanent deformation of auxiliary sealing ring of traditional mechanical seals in the case of frequent start-stop or pressure impact working conditions, because its working load is much lower than that of traditional mechanical seals, effectively prolonging the service life.

[0056] Finally, the sealing cover 8 and its annular collection chamber 81 and reflux passage constitute a perfect medium recycling and management system. The annular collection chamber 81 precisely collects all the medium thrown out by the second stage and completely guides the medium back to the water tank in the pump body 1 through the reflux passage with an inner diameter of 10-15 mm. This system realizes zero leakage operation of the pump, avoids medium waste and environmental pollution, and ensures long-term stable operation of the entire pump system under harsh and complex working conditions, greatly reducing maintenance cost and downtime risk.

[0057] In summary, the new type of immersed multistage centrifugal pump proposed in the application fundamentally overcomes the inherent limitations of traditional mechanical seals in complex media, insufficient media and frequent start-stop working conditions through the synergistic working mode of step-by-step fluid blocking, dynamic centrifugal liquid throwing and flexible auxiliary isolation, significantly improves the reliability, stability and service life of the pump, and has important engineering application value and technical innovation.

[0058] Example 1: Immersed multistage centrifugal pump for high-temperature corrosive slurry conveying This example describes an immersed multistage centrifugal pump designed according to the application, which is used to convey cutting emulsion medium containing abrasive particles, with a pumping pressure of 3 MPa and a pump shaft 3 speed of 2900 rpm. The pump shaft 35 diameter is 12 mm.

[0059] In this example, The pump body 1 is made of 304 stainless steel sheet stamping and welding process, and the pump head 4 is made of gray cast iron HT200 casting and processing, with surface electrophoretic coating treatment. The impeller 2 is made of 304 stainless steel or 316L stainless steel sheet stamping and welding.

[0060] The detailed parameter configuration of the composite non-contact sealing structure is as follows: First stage gap sealing assembly 5: Bushing 51: High-strength nodular cast iron material QT500-7 with excellent machining performance is selected, and the surface is treated with electrophoretic coating, with a surface roughness Ra1.6.

[0061] Radial gap 52: The inner diameter of the bushing 51 is 50.13 mm, forming a radial gap 52 of 0.13 mm with the pump shaft 35 with a diameter of 50.00 mm.

[0062] Axial length of bushing 51: The axial length of the bushing 51 is set to 200 mm (4 times the diameter of the pump shaft 3).

[0063] Bushing annular groove 53: 7 bushing annular grooves 53 are provided, equidistantly distributed along the axial direction, and the axial distance between grooves is 7 mm (2 times the groove width). The depth of each bushing annular groove 53 is 3.0 mm, and the width is 3.5 mm. The annular groove edge is chamfered with a radius of 0.8 mm.

[0064] Expected effect: In this configuration, The cutting fluid containing impurities can be reduced from 3 MPa to below 0.1 MPa after passing through the first-stage seal, and the axial flow rate is significantly reduced, while the ductile cast iron material ensures high resistance to abrasive particles.

[0065] Second-stage axial blocking seal assembly 6: First shaft seal 61: made of 304 stainless steel material, with a yield strength of 205 MPa.

[0066] Axial extension 63: axial length of 35 mm (0.7 times the diameter of pump shaft 3).

[0067] Radial outward expansion 64: inclination angle of 30°, outer diameter of 125 mm (2.5 times the diameter of pump shaft 3).

[0068] Shaft seal annular groove 62: depth of 4.0 mm, width of 6.0 mm, U-shaped cross-section.

[0069] Expected effect: When the pump shaft 3 rotates at a high speed of 2900 rpm, the strong centrifugal force generated by the radial outward expansion 64 can efficiently throw out the trace amount of slurry passing through the first-stage seal. The slurry is captured and guided back by the shaft seal annular groove 62, preventing further axial penetration. This stage is completely non-contact, avoiding wear of the sealing surface by slurry particles.

[0070] Third-stage auxiliary seal assembly 7: Second shaft seal 71: Viton® fluororubber (FKM) lip seal with a hardness of 75 Shore A is selected.

[0071] Installation method: pressed into the pump shaft 3 by an interference fit of 0.08 mm.

[0072] Radial compression amount: the radial compression amount of the sealing lip to the pump shaft 3 is controlled at 12%.

[0073] Expected effect: Under extremely low residual pressure and flow, the FKM lip seal provides a reliable final isolation, effectively preventing the escape of corrosive steam or tiny droplets. The FKM material ensures good resistance to concentrated sulfuric acid.

[0074] Experimental data: The designed immersed multi-stage centrifugal pump in this embodiment was tested for 2000 hours continuously, and the testing medium was cutting emulsion with 20% (mass fraction) SiO2 particles (average particle size 50 microns) at 25°C.

[0075] During the whole test period, the pump ran smoothly without visible medium leakage. The external environment of the pump was detected by a gas analyzer, and no acidic vapor was detected. Disassembly inspection found that the surface of the first stage bushing 51 had no obvious wear, and the annular groove structure was intact. The surface of the first shaft seal 61 was smooth, without corrosion or wear marks. The sealing lip of the second shaft seal 71 remained good elasticity, with slight wear on the contact surface, which could still effectively seal. The mean time between failures (MTBF) of the pump was predicted to be more than 15000 hours.

[0076] Comparative Example 1: Immersed multi-stage centrifugal pump with traditional mechanical seal In order to compare the advantages of the present application, a traditional immersed multi-stage centrifugal pump was designed and manufactured for the same working conditions (cutting emulsion with 20% (mass fraction) SiO2 particles (average particle size 50 microns) at 25°C, pumping pressure 3 MPa, and pump shaft 3 rotating at 2900 rpm). The pump used a single-end mechanical seal (silicon carbide against silicon carbide, FKM O-ring as auxiliary seal ring, and hastelloy spring and bellows) at the position where the pump shaft 3 passed through the pump head 4.

[0077] Comparison data table: The performance parameters of Example 1 and Comparative Example 1 of the present application are quantitatively compared in Table 1 below.

[0078] Table 1 Through the above detailed examples and data comparison, the new type of immersed multi-stage centrifugal pump proposed in the present application significantly improves the running reliability, stability and service life of the pump under complex medium, insufficient medium and frequent start-stop conditions, thanks to its unique composite non-contact sealing structure. This technical solution not only overcomes the inherent limitations of traditional mechanical seals, realizes zero leakage operation and effective recovery of medium, but also greatly reduces maintenance costs and downtime risks, and has great engineering application value and technical innovation. The realization of the present application opens up a new way for the wide application of immersed pumps in harsh industrial environments.

[0079] The above is only a specific embodiment of the present application, but the technical features of the present application are not limited thereto. Any simple change, equivalent replacement or modification made on the basis of the present application to solve the same technical problem and achieve the same technical effect is covered by the protection scope of the present application.

Claims

1. An immersed multi-stage centrifugal pump, comprising: a pump body having a water inlet for liquid inflow and a water outlet for liquid outflow; an impeller arranged inside the pump body for multi-stage pressurization of the liquid; a pump shaft in driving connection with the impeller; and a pump head connected with the pump body, the pump shaft passing through the pump head; characterized in that the pump head is provided with a composite non-contact sealing structure for axial sealing of the pump shaft; the composite non-contact sealing structure comprising: a first-stage gap sealing assembly including a bushing fixedly connected inside the pump head, the pump shaft passing through an inner hole of the bushing, a radial gap being formed between the inner hole of the bushing and an outer surface of the pump shaft, and a plurality of bushing annular grooves being distributed along the axial direction of the pump shaft on the inner hole wall of the bushing, the radial gap and the plurality of bushing annular grooves together constituting a flow resistance passage for fluid to achieve pressure drop and blockage of initial leakage; a second-stage axial blockage sealing assembly including a first shaft seal installed along the axial direction of the pump shaft and rotating synchronously with the pump shaft, the first shaft seal being used for axial blockage of the medium and for radially throwing out the blocked medium, and the first shaft seal further being provided at a lower end thereof with a shaft seal annular groove for re-radial blockage of the medium after being thrown out radially.

2. A multi-stage centrifugal pump according to claim 1, wherein the composite non-contact sealing structure further comprising: a third-stage auxiliary sealing assembly including a second shaft seal installed along the axial direction of the pump shaft and rotating synchronously with the pump shaft.

3. A multi-stage centrifugal pump according to claim 2, wherein the second shaft seal being a flexible sealing member of rubber material, the second shaft seal being tightly pressed into and fixed on the outer surface of the pump shaft in an interference fit, the structure size and material properties of the second shaft seal being designed to form a sealing fit with the pump shaft and the inner cavity of the pump head, so as to cooperate with the first two-stage sealing assembly to achieve axial sealing.

4. A multi-stage centrifugal pump according to claim 1, wherein the bushing of the first-stage gap sealing assembly being reliably fastened to the pump head by fasteners, and the radial gap between the inner hole of the bushing and the outer surface of the pump shaft being designed to have a preset value, the radial gap and the axial length of the bushing together defining the flow resistance of the medium when passing through.

5. A multi-stage centrifugal pump according to claim 4, wherein the inner hole wall of the bushing being provided with a plurality of bushing annular grooves distributed along the axial direction of the pump shaft, the bushing annular grooves being equidistantly distributed along the axial direction of the pump shaft and used for multiple pressure relief and segmented blockage of the medium, each of the bushing annular grooves having a preset depth and width, the depth and width of the bushing annular grooves being matched with the radial gap to generate a fluid dynamic pressure sealing principle when the medium passes through, and edges of the bushing annular grooves being chamfered to guide the medium to form a stable low-speed zone in the bushing annular grooves, thereby slowing down the axial flow speed of the medium and enhancing the pressure relief and blockage effect.

6. A multi-stage centrifugal pump according to claim 1, wherein The first shaft seal of the second stage axial blocking seal assembly is locked and fixedly connected with the pump shaft by at least one fastener, and the first shaft seal has a structure comprising an axial extension part for axially blocking the medium and a radially outwardly expanded part for radially throwing the medium out by centrifugal force when the pump shaft rotates.

7. A multi-stage centrifugal pump according to claim 4, wherein The shaft seal annular groove extends along the radial direction of the first shaft seal, and the depth and width of the shaft seal annular groove are designed to effectively intercept and retain the thrown medium and further enhance the radial centrifugal movement of the medium by the rotational kinetic energy of the pump shaft to avoid the outward leakage of the medium to the next stage seal area or the external environment.

8. A multi-stage centrifugal pump according to claim 2, wherein The composite non-contact seal structure further comprises: A seal cover is fixedly connected to the outside of the pump head by a plurality of fasteners, and forms an annular collection chamber surrounding the outer radial area of the second stage axial blocking seal assembly and the third stage auxiliary seal assembly. The seal cover is used to collect the medium thrown by the second stage axial blocking seal assembly and guide the medium back to the water tank in the pump body.

9. A multi-stage centrifugal pump according to claim 8, wherein The seal cover is reliably fixed to the side of the pump head by a plurality of fasteners, the bottom of the annular collection chamber is connected to the water tank in the pump body through a backflow channel, and the backflow channel ensures that all collected medium can completely backflow to the pump body.

10. An immersed multi-stage centrifugal pump according to any of claims 1-9, characterized in that The immersed multistage centrifugal pump further comprises a motor shaft connected with the pump shaft through a shaft coupling to drive the pump shaft and the impeller to rotate, the pump shaft passes through the pump head, the pump head is not provided with a contact mechanical seal structure, and the pump shaft and the pump head are axially sealed through the composite non-contact seal structure.

Images