Multistage centrifugal pump axial force balancing mechanism and multistage centrifugal pump

Abstract

The application discloses a kind of multistage centrifugal pump axial force balancing mechanism and multistage centrifugal pump, multistage centrifugal pump axial force balancing mechanism includes pump shaft assembly, bearing seat, first balancing component and second balancing component, one end of pump shaft assembly is provided with last stage impeller, bearing seat is movably sleeved in the outside of pump shaft assembly, stop piece is arranged between bearing seat and pump shaft assembly, first balancing component is fixedly sleeved in the outside of pump shaft assembly, pressure relief passage is arranged between the outside wall of first balancing component and the inner side wall of bearing seat, first balancing component is arranged in the side of stop piece close to last stage impeller, and adjustable balance chamber is formed between stop piece and first balancing component, second balancing component is fixedly sleeved in the end of pump shaft assembly away from last stage impeller, and located in the outside of bearing seat, second balancing component forms adjustable gap with stop piece, so, the application can significantly improve the elimination effect of axial force, while simple structure, can greatly improve the compactness of multistage pump.

Description

Technical Field

[0001] This application relates to the field of centrifugal pump technology, and further to an axial force balancing mechanism for a multi-stage centrifugal pump and a multi-stage centrifugal pump. Background Technology

[0002] A multistage pump is a type of centrifugal pump that achieves high-pressure output by combining multiple centrifugal impellers. It generates centrifugal force through the rotation of the impellers, thereby energizing the fluid, and gradually increasing the pressure and energy of the liquid through a multi-stage series connection. Multistage pumps are commonly used in applications requiring high head, such as urban water supply, hydraulic engineering, and fire protection engineering. The design of multistage pumps makes them highly efficient, energy-saving, and space-saving. They typically consist of an inlet section, outlet section, intermediate section, impeller, balancing system, stuffing box, guide vanes, gland, and bearings. Multistage pumps can transport clean water or other liquid chemicals, with the medium temperature generally not exceeding 80 degrees Celsius. In terms of applications, multistage pumps are widely used in water supply and drainage systems in mines, factories, and cities, as well as various industrial applications requiring high-pressure output. Their high efficiency and reliability make them an ideal choice in many industrial sectors.

[0003] Axial force in a multistage pump refers to the axial force acting on the rotor during pump operation due to liquid flow and the asymmetry of the pump's internal structure. These forces can cause axial movement of the rotor, as well as rotor movement towards the suction inlet, resulting in vibration and potentially damaging the pump body due to impeller wear ring friction, thus affecting the pump's normal operation and lifespan. Therefore, to eliminate the adverse effects of axial force on multistage pumps, many manufacturers employ back-to-back impeller designs or independent axial force balancing devices. However, existing axial force elimination methods are ineffective, leaving a significant amount of axial force unresolved, and their complex designs lead to excessively large dimensions.

[0004] Therefore, the present invention aims to provide an axial force balancing mechanism for a multi-stage centrifugal pump and a multi-stage centrifugal pump to solve the above-mentioned technical problems. Summary of the Invention

[0005] To address the aforementioned technical problems, the purpose of this application is to provide an axial force balancing mechanism for a multi-stage centrifugal pump and a multi-stage centrifugal pump. The first balancing component eliminates axial force by reducing pressure and abutting against a stop, while the second balancing component further eliminates axial force by abutting against a stop. This significantly improves the axial force elimination effect and has a simple structure, reducing the adverse impact of the balancing mechanism on the size of the multi-stage pump.

[0006] To achieve the above objectives, this application provides an axial force balancing mechanism for a multi-stage centrifugal pump, comprising:

[0007] A pump shaft assembly, wherein a final stage impeller is provided at one end of the pump shaft assembly;

[0008] A bearing housing is movably sleeved on the outside of the pump shaft assembly to allow the pump shaft assembly to rotate relative to the bearing housing, and a stop is provided between the bearing housing and the pump shaft assembly;

[0009] The first balancing component is sleeved and fixed on the outside of the pump shaft assembly and disposed inside the bearing housing. A pressure reducing channel is provided between the outer side wall of the first balancing component and the inner side wall of the bearing housing. The first balancing component is disposed on the side of the stop member near the last stage impeller and an adjustable balancing chamber is formed between the stop member and the first balancing component. The adjustable balancing chamber is connected to the pressure reducing channel and the pump inlet of the bearing housing.

[0010] The second balancing assembly is sleeved and fixed at the end of the pump shaft assembly away from the final stage impeller and located on the outside of the bearing housing. An adjustable clearance is formed between the second balancing assembly and the stop member.

[0011] The pump shaft assembly is adapted to move along the extension direction of the bearing housing to adjust the size of the adjustable balance chamber and the adjustable gap.

[0012] In some embodiments, the stop is sleeved on the outside of the pump shaft assembly and is connected and fixed to the inner sidewall of the bearing housing;

[0013] A first flow channel is provided on the side of the stop member near the second balance component, and a second flow channel is provided on the inner side wall of the stop member, which is connected to the first flow channel. The first flow channel is used to allow liquid to flow in, so as to form a liquid film between the second balance component and the bearing seat.

[0014] In some embodiments, the first balancing assembly includes a balancing drum and a first thrust disc, the balancing drum being sleeved and fixed to the outside of the pump shaft assembly;

[0015] The balancing drum has a mounting groove on the side away from the final stage impeller that mates with the first thrust plate to fix the first thrust plate on the balancing drum. The first thrust plate is correspondingly arranged with the stop to form the adjustable gap.

[0016] In some embodiments, the second balancing assembly includes a mounting base and a second thrust disk, the mounting base being sleeved and fixed to the outer side of the pump shaft assembly at the end away from the final stage impeller;

[0017] The mounting base has an inner groove on the side near the stop member that mates with the second thrust plate to fix the second thrust plate on the mounting base. The second thrust plate and the stop member are arranged correspondingly to form the adjustable balance chamber.

[0018] In some embodiments, the pump shaft assembly includes a drive shaft and a bushing, the bushing being fitted and fixed to the outside of the drive shaft and correspondingly disposed with the stop member;

[0019] The sides of the balance drum and the mounting base that are close to each other are respectively connected to the two ends of the bushing in the extension direction.

[0020] In some embodiments, a labyrinthine sealing groove is provided on the outer wall of the balancing drum to form the pressure relief channel.

[0021] In some embodiments, the stop member includes a first bearing and a second bearing in sequence in the direction close to the last stage impeller, and the first bearing and the second bearing are each provided with the first guide groove and the second guide groove;

[0022] The second guide groove of the first bearing is connected to the first guide groove of the second bearing.

[0023] In some embodiments, the first thrust plate, the second thrust plate, and the stop are made of the same material.

[0024] In some embodiments, the size of the adjustable gap is 0.5mm-1mm.

[0025] A multistage centrifugal pump, comprising any of the above-described axial force balancing mechanisms for a multistage centrifugal pump.

[0026] Compared with the prior art, the axial force balancing mechanism and multistage centrifugal pump provided in this application have the following advantages:

[0027] 1. The present invention provides an axial force balancing mechanism for a multi-stage centrifugal pump. An adjustable balancing chamber is formed between a first balancing component and a stop, and an adjustable gap is formed between a second balancing component and a stop. When the balancing mechanism is in different working states, the size of the adjustable balancing chamber and the adjustable gap can be adjusted with the movement of the pump shaft assembly. When operating under rated conditions or low head conditions, the axial force is shared by the first and second balancing components. The first balancing component eliminates most of the axial force by forming a pressure difference, while the second balancing component eliminates the remaining axial force by contacting and squeezing the stop. When operating under high head conditions, the axial force is shared by the first balancing component. While eliminating most of the axial force through the pressure difference, the first balancing component can also eliminate the remaining axial force by contacting and squeezing the stop, thereby significantly improving the axial force balancing effect. It can be seen that only the first balancing component, the second balancing component, and the stop are needed to achieve axial force balancing, which can significantly reduce the number of parts and the design difficulty and versatility of the balancing device. Moreover, the balancing mechanism can withstand axial forces in two opposite directions, effectively reducing the axial dimension of the adjustable balancing chamber, thereby ensuring the compactness of the multi-stage pump.

[0028] 2. The present invention provides an axial force balancing mechanism for a multi-stage centrifugal pump, wherein a first guide groove and a second guide groove are provided on the stop member. The first guide groove can form a liquid film between the second balancing component and the end face of the stop member. This liquid film can reduce the direct contact between the two, prevent dry friction, protect the components from damage, ensure the smooth operation of the equipment, reduce wear and extend service life. Similarly, the second guide groove can guide the liquid to the bearing and the bushing to play the role of lubrication, cooling and preventing dry friction.

[0029] 3. The axial force balancing mechanism for a multi-stage centrifugal pump provided by the present invention has a bushing sleeve fitted on the outside of the transmission shaft, and the bushing sleeve and the stop are correspondingly arranged, which can provide radial support for the transmission shaft, provide higher stability and support for the high-speed rotating transmission shaft, and ensure that the transmission shaft has good coaxiality during operation. Attached Figure Description

[0030] The preferred embodiments will now be described in a clear and easy-to-understand manner, in conjunction with the accompanying drawings, to further explain the above-mentioned characteristics, technical features, advantages, and implementation methods of this application.

[0031] Figure 1 This is a schematic diagram of the axial force balancing mechanism for a multi-stage centrifugal pump provided by the present invention;

[0032] Figure 2 This is a schematic diagram of the structure of the first balancing component provided by the present invention;

[0033] Figure 3 This is a schematic diagram of the structure of the second balancing component provided by the present invention;

[0034] Figure 4 This is a schematic diagram of the bearing structure provided by the present invention.

[0035] Explanation of icon numbers:

[0036] Bearing housing 1, first bearing 11, second bearing 12, first guide groove 13, second guide groove 14, first balancing assembly 2, adjustable balancing chamber 21, balancing drum 22, labyrinth-shaped sealing groove 221, first thrust plate 23, second balancing assembly 3, adjustable clearance 31, mounting base 32, second thrust plate 33, drive shaft 41, bushing 42. Detailed Implementation

[0037] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the specific implementation methods of this application will be described below with reference to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings and other implementation methods can be obtained based on these drawings without creative effort.

[0038] To keep the drawings concise, each drawing only schematically shows the parts relevant to the application; these do not represent the actual structure of the product. Furthermore, for ease of understanding, in some drawings, only one of components with the same structure or function is schematically shown, or only one is labeled. In this document, "one" can mean not only "only one" but also "more than one."

[0039] It should also be further understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0040] In this document, 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 fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0041] In the description of this application, 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", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0042] Furthermore, in the description of this application, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0043] The principle of a multistage centrifugal pump is based on the Navier-Stokes equations (NS equations) in fluid mechanics. It utilizes multiple impellers and guide vanes (also called guide vanes or baffles) inside the pump casing to continuously accelerate and pressurize the liquid as it passes through the pump. When the electric motor drives the pump shaft to rotate, the impellers rotate accordingly, converting mechanical energy into the kinetic and potential energy of the liquid. Upon entering the first-stage impeller, the liquid is accelerated, and some of its kinetic energy is converted into pressure energy. It then flows into the guide vanes, which redistribute the liquid's kinetic energy, reduce eddy current losses, and guide the liquid to the next stage impeller. This process is repeated between each impeller and guide vane stage; with each stage, the liquid pressure increases, ultimately achieving high-lift delivery. The design of multistage centrifugal pumps allows each stage to effectively increase the liquid's energy, making them extremely useful in applications requiring high lift.

[0044] In multistage centrifugal pumps, when liquid flows through the impeller, an axial force is generated pointing towards the low-pressure area due to the pressure difference before and after the impeller. Existing axial force elimination mechanisms in multistage centrifugal pumps have poor axial force elimination effects, leaving a significant amount of axial force uneliminated, and their complex designs result in excessively large dimensions.

[0045] In response, this invention provides an axial force balancing mechanism for a multi-stage centrifugal pump, which improves the axial force balancing effect while reducing the adverse effects of the balancing mechanism on the size of the multi-stage centrifugal pump, thus meeting the need for miniaturization of the multi-stage centrifugal pump.

[0046] For details, please refer to the instruction manual appendix. Figures 1 to 4An axial force balancing mechanism for a multi-stage centrifugal pump includes a pump shaft assembly, a bearing housing 1, a first balancing component 2, and a second balancing component 3. One end of the pump shaft assembly is fitted with a final-stage impeller. A bearing housing 1 is movably mounted on the outside of the pump shaft assembly, allowing the pump shaft assembly to rotate relative to the bearing housing 1, thereby driving the final-stage impeller to rotate. A stop is also provided between the pump shaft assembly and the bearing housing 1. Correspondingly, a first balancing component 2 is fixedly sleeved on the outer side of the pump shaft assembly. This first balancing component 2 is located inside the bearing housing 1, and its outer side wall forms a pressure-reducing channel with the inner side wall of the bearing housing 1. Furthermore, the first balancing component 2 is positioned near the stop near the final-stage impeller, and a gap is provided between the first balancing component 2 and the stop, forming an adjustable balancing chamber 21. This adjustable balancing chamber 21 communicates with the pressure-reducing channel and the pump inlet.

[0047] In addition, a second balancing component 3 is fixedly fitted at the other end of the pump shaft assembly away from the final stage impeller. The second balancing component 3 is located outside the bearing housing 1 and is spaced apart from the stop member to form an adjustable gap 31 between the second balancing component 3 and the stop member.

[0048] Additionally, one end of the pump shaft assembly passes through the bearing housing 1. The pump shaft assembly can move as needed along the extension direction of the bearing housing 1 to adjust the size of the adjustable balance chamber 21 and the adjustable clearance 31, thereby achieving pump balance control. Generally, the pump shaft assembly will move relative to the extension direction of the bearing housing 1 under the action of axial force and pressure difference during operation.

[0049] The specific principle of balancing axial force in actual use is as follows: High-pressure fluid enters the adjustable balancing chamber 21 through the pressure-reducing channel. The pressure-reducing channel can reduce the pressure of the high-pressure fluid, creating a pressure difference between the two ends of the first balancing component 2 (the pressure on the side of the first balancing component 2 away from the final impeller is higher than the pressure on the side away from the final impeller). This pressure difference generates an upward force, thereby eliminating part of the axial force. See the attached diagram in the instruction manual. Figure 1 When the multistage centrifugal pump operates at its rated condition or at a lower head, the first balancing assembly 2 and the second balancing assembly 3 jointly bear the axial force under this condition. When the multistage centrifugal pump operates at its rated condition or at a lower head, the pressure difference of the first balancing assembly 2 is less than the magnitude of the axial force, causing the axial force to drive the pump shaft assembly downwards to reduce the adjustable clearance 31 and increase the adjustable balancing chamber 21, until the second balancing assembly 3 and the end of the stop member away from the last stage impeller are fully in contact and pressed together. At this time, the stop member can provide an upward supporting force to the second balancing assembly 3, that is, to provide an upward supporting force to the pump shaft assembly, thereby further balancing the axial force (that is, balancing the part of the axial force that was not balanced by the first balancing assembly 2).

[0050] When the multistage centrifugal pump operates at high head, the pressure difference of the first balancing assembly 2 is greater than the magnitude of the axial force. This pressure difference causes the pump shaft assembly to move upward, increasing the adjustable clearance 31 and decreasing the adjustable balancing chamber 21, until the first balancing assembly 2 and the end of the stop member furthest from the last stage impeller are fully in contact and pressed together. The stop member provides a downward supporting force to the first balancing assembly 2, which in turn provides a downward supporting force to the pump shaft assembly, thus achieving axial force balance. Under this condition, the stop member does not support the first balancing assembly 2; therefore, the axial force balance is entirely borne by the first balancing assembly 2.

[0051] Compared to existing axial force elimination methods, the axial force balancing mechanism for a multi-stage centrifugal pump provided in this embodiment not only eliminates part of the axial force through pressure difference, but also further eliminates the remaining axial force through the stop and the first balancing component 2 or the second balancing component 3. This effectively balances the axial force under both low and high head conditions. Furthermore, this embodiment has a simple structure, requires fewer components, and significantly reduces the space occupied by the axial force balancing mechanism, thereby reducing the size of the multi-stage centrifugal pump.

[0052] In one embodiment, see the appendix to the specification. Figure 1 This embodiment further describes the pump shaft assembly. The pump shaft assembly includes a drive shaft 41 and a bushing 42. The bushing 42 is fitted and fixed to the outside of the drive shaft 41 and is correspondingly arranged with a stop member. One end of the drive shaft 41 is provided with a final-stage impeller. The two ends of the bushing 42 extending in the direction of extension are respectively connected to the sides of the first balancing assembly 2 and the second balancing assembly 3 that are close to each other.

[0053] Furthermore, the stop is sleeved on the outside of the pump shaft assembly, that is, on the outside of the pump shaft 41, and is fixed on the inner wall of the bearing seat 1.

[0054] Understandably, the bushing 42 and the stop can provide radial support for the drive shaft 41, ensuring good coaxiality of the pump shaft during operation and providing higher stability and support for the high-speed rotating rotor.

[0055] Furthermore, see the appendix to the instruction manual. Figure 2 The first balancing assembly 2 consists of a balancing drum 22 and a first thrust disc 23, wherein the balancing drum 22 is fixedly sleeved on the outside of the bushing 42. At the end of the balancing drum 22 furthest from the final stage impeller, a mounting groove matching the first thrust disc 23 is provided; this mounting groove is used to fix the first thrust disc 23 onto the balancing drum 22. The first thrust disc 23 and the stop member are correspondingly arranged, forming an adjustable balancing chamber 21 between them.

[0056] The second balancing assembly 3 consists of a mounting base 32 and a second thrust disc 33. The mounting base 32 is fixed to the exterior of the pump shaft assembly at the end away from the final stage impeller. On the side of the mounting base 32 near the stop member, there is an inner groove adapted to the second thrust disc 33, which securely mounts the second thrust disc 33 within the mounting base 32. Furthermore, the second thrust disc 33 is disposed opposite to the stop member, forming an adjustable gap 31 between them.

[0057] Understandably, please refer to the instruction manual appendix. Figure 1 A mounting groove is located in the middle of the balance drum 22, allowing the inner ring of the balance drum 22 to connect with one end of the bushing 42. A first thrust disc 23, located within the mounting groove, corresponds to a stop. Correspondingly, an inner groove is located in the middle of the mounting base 32, allowing the inner ring of the mounting base 32 to connect with the other end of the bushing 42. A second thrust disc 33, located within the inner groove, corresponds to a stop. Therefore, when the drive shaft 41 moves, the drive shaft 41, bushing 42, first balance assembly 2, and second balance assembly 3 move synchronously relative to the stop.

[0058] There are various ways to connect the bushing 42, the balance drum 22, and the mounting base 32 to the drive shaft 41. Generally, they can be fixed by a flat key connection. All of these are within the scope of protection of this invention and will not be described in detail here.

[0059] In one embodiment, see the appendix to the specification. Figure 1 and Figure 4 This embodiment provides a specific structure for a stop member. A first guide groove 13 is provided at the end of the stop member near the second balancing component 3, and the first guide groove 13 is located at the end of the stop member. When the axial force balancing mechanism is working, fluid, under the action of a centrifugal pump, can enter between the second balancing component 3 and the stop member through the first guide groove 13, thereby forming a liquid film between the second thrust disc 33 and the stop member. This reduces friction, decreases wear, and extends the service life of the components. Furthermore, the liquid film can absorb and carry away the heat generated by friction, preventing overheating.

[0060] Alternatively, preferably, a first guide groove 13 is also provided at the end of the stop member near the last stage impeller to form a liquid film between the stop member and the first balancing assembly 2. Correspondingly, a second guide groove 14 is provided on the inner sidewall of the stop member, which communicates with the first guide groove 13. The second guide groove 14 can introduce liquid between the stop member and the bushing 42 for lubrication and cooling between the bearing and the bushing 42, and to prevent dry friction.

[0061] Furthermore, this embodiment provides a further description of the stop component. The stop component includes a first bearing 11 and a second bearing 12, which are arranged sequentially in the direction close to the final stage impeller. Correspondingly, a first guide groove 13 is formed at one end of the first bearing 11 and the second bearing 12 that is far apart from each other. Additionally, a second guide groove 14 is provided on the inner wall of both the first bearing 11 and the second bearing 12, and these second guide grooves communicate with the first guide grooves 13 on the corresponding bearings.

[0062] Preferably, the second guide groove 14 of the first bearing 11 is also connected to the second guide groove 14 of the second bearing 12 to allow liquid to flow in the balancing mechanism.

[0063] In addition, the first thrust plate 23, the second thrust plate 33 and the stop are made of the same material, all of which are made of hard wear-resistant alloy to ensure the service life of the balancing mechanism.

[0064] The adjustable gap 31 is set to 0.5mm-1mm, which greatly reduces the axial dimension of the balance chamber, making the axial dimension of the equipment more compact.

[0065] In one embodiment, see the appendix to the specification. Figure 2 A labyrinth-shaped sealing groove 221 is provided on the outer wall of the balance drum 22. The labyrinth-shaped sealing groove 221 extends along the circumference and length of the balance drum 22 to form a pressure-reducing channel between the balance drum 22 and the bearing housing 1. Preferably, the labyrinth-shaped sealing groove can be configured as a toothed groove to further improve the pressure-reducing effect of the pressure-reducing channel.

[0066] In one embodiment, this embodiment provides a multistage centrifugal pump, including an axial force balancing mechanism for a multistage centrifugal pump as described in any of the above embodiments. The multistage centrifugal pump provided in this embodiment can effectively balance axial forces through the cooperation of the first balancing component 2, the second balancing component 3, and the stop component. This reduces axial movement of the pump shaft assembly, improves the pump's operational stability, and also reduces wear between the second balancing component 3 and the stop component, extending the service life of the second balancing component 3. Furthermore, balancing axial forces can reduce failures such as shaft breakage caused by axial force imbalance, thereby improving the stability and reliability of the multistage pump.

[0067] It should be noted that the above embodiments can be freely combined as needed. The above are merely preferred embodiments of this application. It should be pointed out that for those skilled in the art, several improvements and modifications can be made without departing from the principles of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A multi-stage centrifugal pump axial force balancing mechanism, characterized by, The utility model relates to a multi-stage centrifugal pump with adjustable balance, comprising: a pump shaft assembly provided with a last-stage impeller at one end thereof; a bearing seat movably sleeved outside the pump shaft assembly for rotation of the pump shaft assembly relative to the bearing seat, and a stopper provided between the bearing seat and the pump shaft assembly; a first balance assembly fixedly sleeved outside the pump shaft assembly and arranged inside the bearing seat, a pressure reduction channel being provided between the outer wall of the first balance assembly and the inner wall of the bearing seat, the first balance assembly being arranged at the side of the stopper close to the last-stage impeller and forming an adjustable balance chamber between the stopper and the first balance assembly, the adjustable balance chamber being in communication with the pressure reduction channel and the pump inlet of the bearing seat; a second balance assembly fixedly sleeved at the end of the pump shaft assembly away from the last-stage impeller and arranged outside the bearing seat, the second balance assembly forming an adjustable gap with the stopper; wherein the pump shaft assembly is adapted to move along the extension direction of the bearing seat to adjust the size of the adjustable balance chamber and the adjustable gap; when the multi-stage centrifugal pump is operated at rated working condition or lower head working condition, the axial force is shared by the first balance assembly and the second balance assembly, the first balance assembly eliminates most of the axial force by forming a pressure difference, and the second balance assembly eliminates the remaining axial force by being pressed in contact with the stopper; when the multi-stage centrifugal pump is operated at high head working condition, the axial force is completely borne by the first balance assembly, the first balance assembly eliminates most of the axial force by forming a pressure difference and also eliminates the remaining axial force by being pressed in contact with the stopper.

2. A multi-stage centrifugal pump axial thrust balancing mechanism according to claim 1, wherein, The stopper is sleeved outside the pump shaft assembly and fixedly connected with the inner wall of the bearing seat; the end of the stopper is provided with a first flow guide groove, and the inner wall of the stopper is provided with a second flow guide groove in communication with the first flow guide groove, the first flow guide groove being used for liquid flow to form a liquid film between the second balance assembly and the stopper.

3. A multi-stage centrifugal pump axial thrust balancing mechanism according to claim 2, wherein, The first balance assembly comprises a balance drum and a first thrust disc, and the balance drum is fixedly sleeved outside the pump shaft assembly; the side of the balance drum away from the last-stage impeller is provided with a mounting groove matched with the first thrust disc to fix the first thrust disc on the balance drum, and the first thrust disc is arranged in correspondence with the stopper to form the adjustable balance chamber.

4. A multi-stage centrifugal pump axial thrust balancing mechanism according to claim 3, wherein The second balance assembly comprises a mounting seat and a second thrust disc, and the mounting seat is fixedly sleeved outside the end of the pump shaft assembly away from the last-stage impeller; the side of the mounting seat close to the stopper is provided with an inner recess matched with the second thrust disc to fix the second thrust disc on the mounting seat, and the second thrust disc is arranged in correspondence with the stopper to form the adjustable gap.

5. A multi-stage centrifugal pump axial thrust balancing mechanism according to claim 4, wherein, The pump shaft assembly comprises a transmission shaft and a shaft sleeve fixedly sleeved outside the transmission shaft and arranged in correspondence with the stopper; The side of the balance drum and the mounting seat close to each other is connected with two ends of the shaft sleeve extension direction respectively.

6. A multi-stage centrifugal pump axial thrust balancing mechanism according to any one of claims 3-5, characterized in that, The outer side wall of the balance drum is provided with a labyrinth sealing groove to form the pressure reduction channel.

7. A multi-stage centrifugal pump axial thrust balancing mechanism according to claim 6, wherein, The stopper comprises a first bearing and a second bearing in sequence in the direction close to the last stage impeller, and the first bearing and the second bearing are provided with the first flow guide groove at the ends away from each other. The second flow guide groove is arranged on the inner wall of the first bearing and the second bearing and communicates with the corresponding first flow guide groove.

8. A multi-stage centrifugal pump axial thrust balancing mechanism according to claim 5, wherein, The material of the first thrust disc, the second thrust disc and the stopper is the same.

9. A multi-stage centrifugal pump axial thrust balancing mechanism according to any one of claims 1-5, characterized in that, The size of the adjustable gap is 0.5mm-1mm.

10. A multi-stage centrifugal pump characterized by, The multi-stage centrifugal pump axial force balancing mechanism comprises the adjustable gap.

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