A submersible multistage centrifugal pump

Abstract

This invention relates to the field of fluid transport equipment technology, and in particular to a novel submersible multistage centrifugal pump. The submersible multistage centrifugal pump includes: a pump body having an inlet for liquid inflow and an outlet for liquid outflow; an impeller disposed inside the pump body for multistage pressurization of the liquid; a pump shaft drivingly connected to the impeller; and a pump head connected to the pump body, through which the pump shaft passes. The pump head contains a composite non-contact sealing structure for axial sealing of the pump shaft. This invention utilizes the principle of hydrodynamic sealing to slow down media flow, using centrifugal force to eject the media and provide secondary isolation, avoiding the failure problems of traditional mechanical seals under special media and frequent start-stop conditions, thus improving equipment reliability and stability, and is suitable for complex operating conditions.

Description

Technical Field

[0001] This invention relates to the field of fluid machinery technology, and more specifically, to a novel submersible multistage centrifugal pump. Background Technology

[0002] Submersible multistage centrifugal pumps are widely used fluid transport devices in industrial fields, and their axial seal design has a significant impact on the overall performance of the pump. Currently, most submersible multistage centrifugal pumps on the market employ mechanical seals for axial sealing. This structure relies on axially fitted dynamic and stationary rings to achieve a seal, and uses springs and auxiliary sealing rings to provide preload to maintain the sealing effect. Mechanical seals offer significant advantages, such as excellent sealing performance, low leakage rate, long service life, and low frictional power consumption, thus gaining widespread application in the submersible centrifugal pump industry.

[0003] However, mechanical seals also exhibit some limitations in practical applications. First, they are sensitive to the characteristics of the medium, especially when it contains solid particles, easily crystallizing substances, or corrosive components, which can easily lead to wear or failure of the sealing surface. Second, mechanical seals require a sufficient amount of liquid inside the pump; otherwise, dry friction can damage the sealing surface, leading to leakage. Furthermore, under frequent start-stop conditions, mechanical seals may experience sealing ring rupture or permanent deformation of rubber components due to pressure shocks. Finally, for special media such as those prone to crystallization, adsorption, or high viscosity, mechanical seals face challenges in maintaining long-term sealing, potentially increasing the risk of leakage. These limitations have a potential impact on the reliability and stability of submersible multistage centrifugal pumps.

[0004] To address the above problems, this invention proposes a novel submersible multistage centrifugal pump. Summary of the Invention

[0005] The purpose of this invention is to provide a novel submersible multistage centrifugal pump to address the problem of failure of existing mechanical seal structures when handling complex media. It abandons the traditional contact mechanical seal and instead adopts a multi-stage synergistic composite non-contact sealing structure, thereby significantly improving the pump's reliability, stability, and service life under complex operating conditions.

[0006] A submersible multistage centrifugal pump, comprising:

[0007] The pump body has an inlet for liquid inflow and an outlet for liquid outflow.

[0008] An impeller, located inside the pump body, is used to pressurize the liquid in multiple stages.

[0009] A pump shaft, which is drive-connected to the impeller.

[0010] A pump head, which is connected to the pump body, and a pump shaft passing through the pump head.

[0011] The pump head is equipped with a composite non-contact sealing structure for axial sealing of the pump shaft.

[0012] The composite non-contact sealing structure includes:

[0013] The first-stage gap sealing assembly includes a bushing fixedly connected inside the pump head. The pump shaft passes through the inner hole of the bushing, and a radial gap is formed between the inner hole of the bushing and the outer surface of the pump shaft. Multiple bushing annular grooves are distributed on the inner wall of the bushing along the axial direction of the pump shaft. The radial gap and the multiple bushing annular grooves together constitute a friction resistance channel for the fluid, so as to achieve pressure drop and blockage of the initial leakage.

[0014] The second-stage axial blocking sealing assembly includes a first shaft seal, which is installed axially along the pump shaft and rotates synchronously with the pump shaft. The first shaft seal is used to axially block the medium and to radially throw the blocked medium out. The lower end of the first shaft seal is also provided with a shaft seal annular groove, which is used to radially block the medium again after it has been radially thrown out.

[0015] Furthermore, the composite non-contact sealing structure also includes:

[0016] The third-stage auxiliary sealing assembly includes a second shaft seal, which is mounted axially along the pump shaft and rotates synchronously with the pump shaft.

[0017] Furthermore, the second shaft seal is a flexible seal made of rubber. The second shaft seal is tightly pressed into and fixed on the outer surface of the pump shaft by an interference fit. The structural dimensions 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 to cooperate with the first two stages of sealing components for axial sealing.

[0018] Furthermore, the bushing of the first-stage gap sealing assembly is reliably fastened to the pump head by fasteners. The radial clearance between the inner hole of the bushing and the outer surface of the pump shaft is designed to a preset value. The preset radial clearance and the axial length of the bushing together limit the friction resistance when the medium passes through.

[0019] Furthermore, the inner wall of the bushing is provided with multiple 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 for multiple pressure reliefs and segmented blocking of media penetration. Each bushing annular groove has a preset depth and width, and the depth and width of the bushing annular groove are matched with the radial clearance to generate a hydrodynamic pressure sealing principle when the medium passes through. The edges of the bushing annular groove are chamfered to guide the medium to form a stable low-speed zone within the bushing annular groove, thereby slowing down the axial flow velocity of the medium and enhancing the pressure relief and blocking effect.

[0020] Furthermore, the first shaft seal of the second-stage axial blocking sealing assembly is locked and fixedly connected to the pump shaft by at least one fastener. The structure of the first shaft seal includes an axial extension and a radial expansion. The axial extension is used to axially block the medium, and the radial expansion is used to radially throw the medium out by centrifugal force when the pump shaft rotates.

[0021] Furthermore, the shaft seal annular groove extends radially along the first shaft seal. The depth and width of the shaft seal annular groove are designed to effectively intercept and retain the ejected medium, and further enhance the radial centrifugal motion of the medium through the rotational kinetic energy of the pump shaft, so as to prevent the medium from leaking outward to the next sealing area or the external environment.

[0022] Furthermore, the composite non-contact sealing structure also includes:

[0023] A sealing cover is fixedly connected to the outside of the pump head by a plurality of fasteners. The sealing cover forms an annular collection chamber that surrounds the outer radial region of the second-stage axial blocking seal assembly and the third-stage auxiliary seal assembly. The sealing cover is used to collect the medium thrown out by the second-stage axial blocking seal assembly and guide the medium back to the water tank in the pump body.

[0024] Furthermore, the sealing cover is reliably fixed to the side of the pump head by multiple fasteners, and the bottom of the annular collection chamber is connected to the water tank inside the pump body through a return channel, which ensures that all collected media can be completely returned to the pump body.

[0025] Furthermore, the submersible multistage centrifugal pump also includes a motor shaft, which is connected to the pump shaft via a coupling to drive the pump shaft and the impeller to rotate. The pump shaft passes through the pump head, which does not have a contact mechanical seal structure. The pump shaft and the pump head are axially sealed through the composite non-contact sealing structure.

[0026] As described above, this invention comprises a first-stage gap sealing assembly, a second-stage axial blocking sealing assembly, and a third-stage auxiliary sealing assembly. By progressively blocking and guiding the medium, the pressure of the medium gradually decreases and the possibility of leakage is reduced as it passes through each stage of the sealing assembly. The first-stage gap sealing assembly forms a resistance path through radial gaps and multiple bushing annular grooves, utilizing the principle of hydrodynamic sealing and a chamfer design to slow down the axial movement speed of the medium. The second-stage axial blocking sealing assembly throws the medium out through the centrifugal force of the first shaft seal and intercepts the medium through the shaft seal annular groove, preventing further diffusion. The third-stage auxiliary sealing assembly further enhances the isolation effect through the tight fit of a flexible rubber seal. Furthermore, the design of the sealing cover ensures that the intercepted medium can return to the pump body through the return pipe, avoiding resource waste. The overall design avoids the sensitivity of traditional mechanical seals to complex media, and can maintain stable operation without relying on the medium filling the pump chamber, significantly improving the reliability and service life of the equipment. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0028] Figure 2 For the present invention Figure 1 A magnified structural diagram at point B in the middle.

[0029] Figure 3 This is a three-dimensional structural diagram of the bushing of the present invention.

[0030] Figure 4 This is a front structural diagram of the bushing of the present invention.

[0031] Figure 5 For the present invention Figure 4 A schematic diagram of the cross-sectional structure along direction A.

[0032] Figure 6 This is a three-dimensional structural diagram of the first shaft seal of the present invention.

[0033] Figure 7 This is a cross-sectional structural diagram of the first shaft seal of the present invention.

[0034] Figure 8 This is a three-dimensional structural diagram of the second shaft seal of the present invention.

[0035] Figure 9 This is a schematic diagram of the sealing cover of the present invention.

[0036] Figure 10 This is a schematic diagram of the pump head structure of the present invention.

[0037] The attached figures are labeled as follows:

[0038] 1. Pump body; 2. Impeller; 3. Pump shaft; 4. Pump head; 5. First-stage clearance seal assembly; 6. Second-stage axial blocking seal assembly; 7. Third-stage auxiliary seal assembly; 8. Sealing cover; 9. Motor shaft; 10. Coupling.

[0039] 51. Bushing; 52. Radial clearance; 53. Bushing annular groove.

[0040] 61. First shaft seal; 62. Shaft seal annular groove; 63. Axial extension; 64. Radial expansion.

[0041] 71. Second shaft seal.

[0042] 81. Annular collection chamber. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, it should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0044] like Figures 1 to 10 The present invention discloses a novel submersible multistage centrifugal pump, comprising 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 11 is the basic component of the integral structure, and its internal cavity is formed to accommodate the impeller 2 and the fluid medium.

[0045] Pump body 1, the pump body 1 having an inlet for liquid inflow and an outlet for liquid outflow.

[0046] The impeller 2 is disposed in the internal cavity of the pump body 1 and is connected to the pump shaft 3 via a keyway structure. The pump shaft 3 is arranged axially through the pump body 1, and one end is connected to the motor shaft 9 via a coupling 10.

[0047] Pump shaft 3 is connected to impeller 2 via a drive mechanism.

[0048] Pump head 4 is connected to pump body 1, and pump shaft 3 passes through pump head 4.

[0049] The pump head 4 is equipped with a composite non-contact sealing structure for axial sealing of the pump shaft 3.

[0050] The composite non-contact sealing structure aims to achieve multi-stage fluid blocking and management in a non-contact manner to address the challenges posed by extreme operating conditions such as solid particles, crystals, corrosive substances, media interruption, and frequent start-stop cycles in the medium. The composite non-contact sealing structure includes: a first-stage gap sealing assembly 5, a second-stage axial blocking sealing assembly 6, and a third-stage auxiliary sealing assembly 7. These three sealing assemblies are arranged sequentially along the axial direction of the pump shaft 3, collectively forming an integrated sealing solution that progressively reduces pressure, centrifuges liquid, and ultimately achieves effective isolation.

[0051] In a preferred embodiment of the present invention, the first-stage gap sealing assembly 5 includes a bushing 51, which is reliably fastened to a specific mounting cavity inside the pump head 4 by a plurality of fasteners (e.g., 316L stainless steel socket head cap screws with a diameter of M6, tightened to a preset torque). The pump shaft 3 passes precisely through the inner bore of the bushing 51, forming a precisely controlled radial gap 52 between the inner bore of the bushing 51 and the outer surface of the pump shaft 3. This radial gap 52 is designed to a preset value, typically in the range of 0.08 mm to 0.15 mm, to ensure that significant frictional resistance is maintained while allowing a small amount of fluid to pass through. The bushing 51 is made of ductile iron (e.g., QT500-7 ductile iron) with high strength, high toughness, and extremely excellent machinability to adapt to complex media and ensure long-term stability.

[0052] Furthermore, multiple annular grooves 53 are evenly distributed along the axial direction of the pump shaft 3 on the inner wall of the bushing 51. These annular grooves 53, together with the radial clearance 52, form a multi-stage friction resistance channel for the fluid, thereby achieving pressure drop and segmented blocking of the initial leakage. The axial length of the bushing 51 is designed comprehensively based on the pump's operating pressure and allowable leakage, and is typically set to 3 to 5 times the diameter of the pump shaft 3 to provide sufficient resistance length. This first-stage clearance sealing assembly 5 operates in a non-contact manner. Its core principle lies in utilizing the flow characteristics of fluid in narrow gaps and special geometric structures, effectively limiting the axial penetration of the medium through hydrodynamic sealing and local pressure drop, greatly reducing the sensitivity to solid particles or crystals in the medium, and avoiding damage caused by dry friction.

[0053] Specifically, the inner wall of the bushing 51 is provided with a plurality of bushing annular grooves 53 distributed axially along 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 bushing annular groove 53 has a preset depth and width; the depth is set to 2.0 mm to 3.5 mm, and the width is set to 2.5 mm to 4.0 mm. The geometric dimensions of the bushing annular groove 53 precisely match the radial clearance 52 to generate a stable hydrodynamic sealing principle when the medium passes through. This hydrodynamic sealing principle effectively increases the axial flow path of the medium and enhances the inertial resistance of the medium flow by forming a relatively independent, low-speed circulating fluid region inside the annular groove. The edge of the bushing annular groove 53 is precisely chamfered, specifically forming a circular arc chamfer with a radius of 0.5 mm to 1.0 mm at the junction of the annular groove and the inner bore wall. This circular arc chamfer is designed to optimize the flow path of the fluid entering and leaving the annular groove, thereby guiding the medium to form a stable low-velocity zone within the bushing annular groove 53. This low-velocity zone further enhances the fluid retention effect, thereby slowing down the axial flow velocity of the medium and effectively enhancing the pressure relief and blocking effect. This staged blocking mechanism ensures that the pressure of the medium is significantly reduced and the axial flow velocity is greatly decreased before entering the next stage of the sealing assembly.

[0054] In a preferred embodiment of the present invention, the second-stage axial blocking seal assembly 6 is located downstream of the first-stage gap seal assembly 5 and is installed axially along the pump shaft 3. The second-stage axial blocking seal assembly 6 includes a first shaft seal 61, which is locked and fixedly connected to the pump shaft 3 by at least one high-strength fastener (e.g., by keyway fit and radial locking screw, or by thermo-press fit followed by a threaded locking ring) to ensure high-precision synchronous rotation with the pump shaft 3. The first shaft seal 61 is made of a high-strength, corrosion-resistant metal alloy (e.g., 304 stainless steel or 316 stainless steel) with a yield strength of not less than 550 MPa to withstand the centrifugal force generated by high-speed rotation and possible media impact. The first shaft seal 61 includes an axial extension 63 and a radially expanding portion 64. The axial extension 63 is close to 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 initial axial blocking effect and restricting the flow of media on the surface of the pump shaft 3. The radially expanding portion 64 extends radially outward from the downstream end of the axially extending portion 63, forming a disc-shaped structure with a specific tilt angle (e.g., an angle of 20 to 35 degrees relative to the axial plane). When the pump shaft 3 rotates, the radially expanding portion 64 can effectively prevent the medium from further permeating outward along the pump shaft 3 by utilizing the generated centrifugal force to forcibly throw out the trace amount of medium that has passed through the first-stage seal. The outer diameter of the radially expanding portion 64 is typically designed to be 2.0 to 3.0 times the diameter of the pump shaft 3 to generate sufficient centrifugal acceleration.

[0055] Furthermore, a shaft seal annular groove 62 is provided at the lower end of the first shaft seal 61 (i.e., the side of its radially outwardly expanding portion 64 away from the pump body 1). The shaft seal annular groove 62 extends radially along the first shaft seal 61. The depth of the shaft seal annular groove 62 is designed to be 2.0 mm to 4.0 mm, and the width is designed to be 2.0 mm to 4.0 mm. The geometry of the shaft seal annular groove 62 is precisely designed to effectively intercept and retain the medium thrown out by the radially outwardly expanding portion 64. When the medium is thrown out by centrifugal force and enters the shaft seal annular groove 62, the continuous high-speed rotational 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 guiding it to move in the preset return direction through the structure of the annular groove. The existence of this shaft seal annular groove 62 forms a second physical barrier for the medium to change from the axial path to the radial throwing path, effectively preventing the thrown-out medium from accidentally leaking to the next level sealing area or the external environment. Through this dynamic centrifugal liquid ejection and interception mechanism, the second-stage sealing assembly efficiently manages minute leaks in a non-contact state, greatly enhancing the sealing system's self-cleaning ability against particulate matter in the medium.

[0056] In a preferred embodiment of the present invention, the third-stage auxiliary sealing assembly 7 is located downstream of the second-stage axial blocking sealing assembly 6 and is installed axially along the pump shaft 3. The third-stage auxiliary sealing assembly 7 includes a second shaft seal 71, which is tightly pressed into and fixed to the outer surface of the pump shaft 3 with an interference fit and rotates synchronously with the pump shaft 3. The second shaft seal 71 is made of high-performance fluororubber (FKM, e.g., 75 Shore A hardness, with excellent chemical corrosion resistance and high-temperature resistance, capable of stable operation in a temperature range of -20°C to 200°C) and is designed to provide a final safety barrier. The structural dimensions and material properties of the second shaft seal 71 are precisely designed to form stable axial and radial contact with the sealing surfaces of the pump shaft 3 and the inner cavity of the pump head 4, to cooperate with the first two stages of the sealing assembly for axial sealing. Specifically, the second shaft seal 71 is a lip seal. After installation, its sealing lip generates a radial preload on the outer surface of the pump shaft 3, with the radial compression controlled between 10% and 15%, thus forming a tight contact seal. The contact width of the sealing lip is optimized to effectively prevent the escape of liquid, vapor, or micro-aerosols while maintaining low frictional torque. Although the second shaft seal 71 is contact-type, its primary function is to act as an auxiliary or redundant seal after the first two stages of non-contact sealing components have effectively reduced the medium pressure and flow rate. It is particularly suitable for preventing the escape of residual vapor or micro-droplets, rather than undertaking the main high-pressure sealing task. Therefore, its wear and heat generation are significantly lower than traditional mechanical seals. This design avoids the dry friction and burn-out problems caused by insufficient medium in traditional mechanical seals and significantly extends their service life.

[0057] In a preferred embodiment of the present invention, the composite non-contact sealing structure further includes a sealing cover 8. The sealing cover 8 is reliably fixed to the outside of the pump head 4 by multiple fasteners (e.g., M8 316L stainless steel bolts, connected to the fixed flange on the outside of the pump head 4 via washers and nuts). The internal structure of the sealing cover 8 forms an annular collection chamber 81, which surrounds and encloses the outer radial region of the second-stage axial blocking sealing assembly 6 and the third-stage auxiliary sealing assembly 7. The geometry of the annular collection chamber 81 is designed to efficiently capture and collect all 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 via a return channel. The specific structure of the return channel is a guide pipe with an inner diameter of 10 mm to 15 mm, whose connection position and inclination angle are precisely calculated to ensure that all collected media can completely and smoothly return 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 return channel not only effectively prevents the medium from leaking into the external environment and achieves the goal of zero leakage operation, but also helps to recycle and utilize the medium resources, improving the operating efficiency and environmental friendliness of the entire centrifugal pump system.

[0058] In a preferred embodiment of the present invention, the submersible multistage centrifugal pump further includes a motor shaft 9, which is connected to the pump shaft 3 via a coupling 10 (e.g., a flexible diaphragm coupling 10 or a gear coupling 10 to compensate for axial, radial, and angular misalignments) 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 mechanical seal structure. The axial seal between the pump shaft 3 and the pump head 4 is achieved entirely through the composite non-contact sealing structure. This design, through an integrated multistage non-contact sealing scheme, completely avoids many problems faced by traditional mechanical seals, such as poor media compatibility, easy wear, easy dry friction, and sensitivity to frequent start-stop, fundamentally improving the long-term reliability and maintenance convenience of the submersible multistage centrifugal pump under harsh operating conditions.

[0059] The novel submersible multistage centrifugal pump proposed in this invention achieves the following significant technical effects through the above technical solutions:

[0060] First, the first-stage gap sealing assembly 5 effectively establishes a multi-stage friction resistance channel through a precisely designed radial gap 52 and multiple bushing annular grooves 53. The radial gap 52, by precisely controlling its dimensions (0.08 mm to 0.15 mm) and selecting high-strength, high-machinability ductile iron material (e.g., QT500-7 ductile iron), initially reduces pressure and controls flow rate of the medium in a non-contact state, avoiding the sensitivity of traditional mechanical seals to solid particles in the medium. The hydrodynamic sealing principle and chamfer design (radius of 0.5 mm to 1.0 mm) of the bushing annular grooves 53 further enhance the retention and pressure relief effect of the medium, significantly reducing its pressure and axial velocity before entering the next stage of sealing, thereby protecting the downstream sealing assembly.

[0061] Secondly, the second-stage axial blocking sealing assembly 6, through the axial extension 63 and radial expansion 64 of the first shaft seal 61, combined with the high-speed rotation of the pump shaft 3, achieves a dynamic centrifugal throwing function. The radial expansion 64 (outer diameter is 2.0 to 3.0 times the diameter of the pump shaft 3, with an inclination angle of 20 to 35 degrees) can efficiently utilize centrifugal force to radially throw out the trace amount of medium passing through the first stage. The shaft seal annular groove 62 (depth 3.0 mm to 6.0 mm, width 4.0 mm to 8.0 mm) 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, preventing it from spreading further along the axial direction. This sealing assembly completely solves the problem of dry friction that easily occurs in traditional mechanical seals when the medium is insufficient, because it works in a non-contact state, and can maintain its function even in the case of low liquid level or instantaneous interruption of the medium, significantly improving the operational safety of the equipment.

[0062] 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 made of 75 Shore A hardness FKM material with a radial compression of 10% to 15%) achieves sealing with low friction and an interference fit when the medium pressure has been significantly reduced and the flow rate is extremely low. Its main function is to prevent the escape of residual vapor, fine aerosols, or trace droplets, serving as a supplement and redundancy to the first two stages of non-contact sealing, rather than undertaking the primary high-pressure sealing task. This design avoids the problems of sealing ring rupture or permanent deformation of the auxiliary sealing ring in traditional mechanical seals under frequent start-stop or pressure shock conditions, because its workload is much lower than that of traditional mechanical seals, effectively extending its service life.

[0063] Finally, the sealing cover 8, its annular collection chamber 81, and the return channel constitute a complete media recovery and management system. The annular collection chamber 81 accurately collects all the media ejected by the second stage and guides it completely back to the water tank inside the pump body 1 through the return channel with an inner diameter of 10 mm to 15 mm. This system achieves zero-leakage operation of the pump, avoids media waste and environmental pollution, and ensures long-term stable operation of the entire pump system under harsh and complex conditions, greatly reducing maintenance costs and downtime risks.

[0064] In summary, the novel submersible multistage centrifugal pump proposed in this invention, through its innovative composite non-contact sealing structure, and its synergistic working method of progressive fluid blocking, dynamic centrifugal slingshot, and flexible auxiliary isolation, fundamentally overcomes the inherent limitations of traditional mechanical seals under conditions such as complex media, insufficient media, and frequent start-stop operations. This significantly improves the pump's reliability, stability, and service life, and has significant engineering application value and technological innovation.

[0065] Example 1: Submersible multistage centrifugal pump for conveying high-temperature corrosive slurries

[0066] This embodiment describes an immersion multistage centrifugal pump designed according to the present invention, which is used to transport cutting emulsion media containing abrasive particles, with a pumping pressure of 3 MPa and a pump shaft rotation speed of 2900 rpm. The pump shaft 35 has a diameter of 12 mm.

[0067] In this embodiment,

[0068] The pump body 1 is made of 304 stainless steel sheet by stamping and welding. The pump head 4 is made of gray cast iron HT200 and machined, with an electrophoretic coating treatment on the surface. The impeller 2 is made of 304 stainless steel or 316L stainless steel sheet by stamping and welding.

[0069] The detailed parameter configuration of the composite non-contact sealing structure is as follows:

[0070] First-stage gap sealing assembly 5:

[0071] Bushing 51:

[0072] It is made of high-strength ductile iron QT500-7 with excellent machinability, and has an electrophoretic coating treatment with a surface roughness of Ra1.6.

[0073] Radial clearance 52: The inner diameter of the bushing 51 is 50.13 mm, forming a radial clearance 52 of 0.13 mm with the pump shaft 35 with a diameter of 50.00 mm.

[0074] Axial length of bushing 51: The axial length of bushing 51 is set to 200mm (4 times the diameter of pump shaft 3).

[0075] Bushing annular grooves 53: A total of 7 bushing annular grooves 53 are provided, equidistantly distributed along the axial direction, with an axial distance of 7 mm between the grooves (twice the groove width). Each bushing annular groove 53 has a depth of 3.0 mm and a width of 3.5 mm. The edges of the annular grooves are rounded with a radius of 0.8 mm.

[0076] Expected results: Under this configuration,

[0077] After passing through the first-stage seal, the pressure of the cutting fluid containing impurities can be reduced from 3MPa to below 0.1MPa, and the axial flow velocity is significantly reduced. At the same time, the ductile iron material ensures extremely high resistance to abrasive particles.

[0078] Second-stage axial blocking seal assembly 6:

[0079] First shaft seal 61: Made of 304 stainless steel with a yield strength of 205MPa.

[0080] Axial extension 63: axial length is 35mm (0.7 times the diameter of pump shaft 3).

[0081] Radial expansion section 64: Inclined at an angle of 30°, with an outer diameter of 125mm (2.5 times the diameter of pump shaft 3).

[0082] Shaft seal annular groove 62: depth 4.0mm, width 6.0mm, U-shaped cross section.

[0083] Expected effect: When the pump shaft 3 rotates at a high speed of 2900 rpm, the powerful centrifugal force generated by the radially expanding portion 64 can efficiently throw out the trace amount of slurry that has passed through the first-stage seal. The slurry is captured by the shaft seal annular groove 62 and guided backflow, preventing further axial penetration. This stage is completely non-contact, avoiding wear of the sealing surface by slurry particles.

[0084] Third-level auxiliary sealing component 7:

[0085] Second shaft seal 71: Viton® fluororubber (FKM) lip seal with a hardness of 75 Shore A is selected.

[0086] Installation method: The pump shaft 3 is pressed in through an interference fit of 0.08mm.

[0087] Radial compression: The radial compression of the sealing lip on the pump shaft 3 is controlled at 12%.

[0088] Expected Results: At extremely low residual pressures and flow rates, FKM lip seals provide a reliable final barrier, effectively preventing the escape of corrosive vapors or micro-droplets. FKM materials ensure excellent resistance to concentrated sulfuric acid.

[0089] Experimental data:

[0090] The submersible multistage centrifugal pump designed in this embodiment was subjected to a continuous 2000-hour operation test. The test medium was a cutting emulsion containing 20% ​​(mass fraction) SiO2 particles (average particle size 50 micrometers) at 25°C.

[0091] Throughout the testing period, the pump operated smoothly with no visible media leakage. Gas analysis of the external environment revealed no acidic vapor emissions. Disassembly and inspection showed that the first-stage bushing 51 had no significant wear, and the annular groove structure was intact. The first shaft seal 61 had a smooth surface, free from corrosion or wear. The sealing lip of the second shaft seal 71 maintained good elasticity, with only minor wear on the contact surface, and still provided an effective seal. The pump's mean time between failures (MTBF) is projected to exceed 15,000 hours.

[0092] Comparative Example 1: Submersible multistage centrifugal pump using a traditional mechanical seal

[0093] To compare the advantages of this invention, we designed and manufactured a conventional submersible multistage centrifugal pump for the same operating conditions (25°C, cutting emulsion containing 20% ​​(mass fraction) SiO2 particles (average particle size 50 micrometers), pumping pressure 3 MPa, pump shaft 3 rotation speed 2900 rpm). This pump employs a single-end mechanical seal (face material is silicon carbide to silicon carbide, auxiliary sealing ring is an FKM O-ring, spring and bellows are Hastelloy) where the pump shaft 3 passes through the pump head 4.

[0094] Comparison data table:

[0095] Table 1 below provides a quantitative comparison of the performance parameters of Embodiment 1 and Comparative Example 1 of the present invention.

[0096] Table 1

[0097]

[0098] Through the detailed embodiments and data comparisons described above, the novel submersible multistage centrifugal pump proposed in this invention, with its unique composite non-contact sealing structure, significantly improves the pump's operational reliability, stability, and service life under complex media, insufficient media, and frequent start-stop conditions. This technical solution not only overcomes the inherent limitations of traditional mechanical seals, achieving zero-leakage operation and effective media recovery, but also greatly reduces maintenance costs and downtime risks, possessing significant engineering application value and technological innovation. The realization of this invention opens up new avenues for the widespread application of submersible pumps in harsh industrial environments.

[0099] The above are merely specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications made based on the present invention to solve essentially the same technical problems and achieve essentially the same technical effects are all covered within the protection scope of the present invention.

Claims

1. A submersible multistage centrifugal pump, comprising: A pump body having an inlet for liquid inflow and an outlet for liquid outflow; An impeller, disposed inside the pump body, is used to pressurize the liquid in multiple stages; Pump shaft, the pump shaft being drivenly connected to the impeller; and A pump head, which is connected to the pump body, and a pump shaft passing through the pump head; Its characteristic is 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 includes: The first-stage gap sealing assembly includes a bushing fixedly connected inside the pump head. The pump shaft passes through the inner hole of the bushing, and a radial gap is formed between the inner hole of the bushing and the outer surface of the pump shaft. Multiple bushing annular grooves are distributed on the inner wall of the bushing along the axial direction of the pump shaft. The radial gap and the multiple bushing annular grooves together constitute a friction resistance channel for the fluid to achieve pressure drop and blockage of the initial leakage. The second-stage axial blocking sealing assembly includes a first shaft seal, which is installed along the axial direction of the pump shaft and rotates synchronously with the pump shaft. The first shaft seal is used to axially block the medium and to radially throw the blocked medium out. The lower end of the first shaft seal is also provided with a shaft seal annular groove, which is used to radially block the medium again after it is radially thrown out. The inner wall of the bushing is provided with multiple 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 for multiple pressure reliefs and segmented blocking of media penetration. Each bushing annular groove has a preset depth and width, and the depth and width of the bushing annular groove are matched with the radial clearance to generate a hydrodynamic pressure sealing principle when the media passes through. The edges of the bushing annular groove are chamfered to guide the media to form a stable low-speed zone within the bushing annular groove, thereby slowing down the axial flow velocity of the media and enhancing the pressure relief and blocking effect. The first shaft seal of the second-stage axial blocking sealing assembly is locked and fixed to the pump shaft by at least one fastener. The structure of the first shaft seal includes an axial extension and a radial expansion. The axial extension is used to axially block the medium, and the radial expansion is used to throw the medium radially out by centrifugal force when the pump shaft rotates.

2. The submersible multistage centrifugal pump according to claim 1, characterized in that, The composite non-contact sealing structure also includes: The third-stage auxiliary sealing assembly includes a second shaft seal, which is mounted axially along the pump shaft and rotates synchronously with the pump shaft.

3. The submersible multistage centrifugal pump according to claim 2, characterized in that, The second shaft seal is a flexible seal made of rubber. The second shaft seal is tightly pressed into and fixed on the outer surface of the pump shaft by an interference fit. The structural dimensions 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 to cooperate with the first two sealing components for axial sealing.

4. The submersible multistage centrifugal pump according to claim 1, characterized in that, The bushing of the first-stage gap sealing assembly is reliably fastened to the pump head by fasteners. The radial clearance between the inner hole of the bushing and the outer surface of the pump shaft is designed to a preset value. The preset radial clearance and the axial length of the bushing together limit the friction resistance when the medium passes through.

5. A submersible multistage centrifugal pump according to claim 4, characterized in that, The shaft seal annular groove extends radially along the first shaft seal. The depth and width of the shaft seal annular groove are designed to effectively intercept and retain the ejected medium, and further enhance the radial centrifugal motion of the medium through the rotational kinetic energy of the pump shaft, so as to prevent the medium from leaking outward to the next sealing area or the external environment.

6. A submersible multistage centrifugal pump according to claim 2, characterized in that, The composite non-contact sealing structure also includes: A sealing cover is fixedly connected to the outside of the pump head by a plurality of fasteners. The sealing cover forms an annular collection chamber that surrounds the outer radial region of the second-stage axial blocking seal assembly and the third-stage auxiliary seal assembly. The sealing cover is used to collect the medium thrown out by the second-stage axial blocking seal assembly and guide the medium back to the water tank in the pump body.

7. A submersible multistage centrifugal pump according to claim 6, characterized in that, The sealing cover is reliably fixed to the side of the pump head by multiple fasteners. The bottom of the annular collection chamber is connected to the water tank inside the pump body through a return channel, which ensures that all collected media can be completely returned to the pump body.

8. A submersible multistage centrifugal pump according to any one of claims 1-7, characterized in that, The submersible multistage centrifugal pump also includes a motor shaft, which is connected to the pump shaft via a coupling to drive the pump shaft and the impeller to rotate. The pump shaft passes through the pump head, which does not have a contact mechanical seal structure. The pump shaft and the pump head are axially sealed through the composite non-contact sealing structure.

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