Multi-stage centrifugal pump capable of improving cavitation performance

Abstract

The invention discloses a multi-stage centrifugal pump capable of improving cavitation performance, which comprises a pump body, the bottom of the pump body is a suction section, the upper part of the pump body is an extrusion section, a pump shaft is arranged in the pump body, an impeller is arranged on the pump shaft, and the impeller is fixed at the inlet end part of the pump shaft through an impeller nut; an impeller sleeve is arranged at the inlet position of the impeller; a bearing body is arranged outside the impeller sleeve; a bearing seat is arranged outside the bearing body; and the bearing seat is connected with the suction section. The multi-stage centrifugal pump solves the problem that rib plates on the bearing and the bearing frame in an existing multi-stage centrifugal pump block an inlet runner, and the cavitation performance of the multi-stage centrifugal pump is improved.

Description

Technical Field

[0001] This invention relates to multistage centrifugal pumps, and more specifically, to a multistage centrifugal pump with improved cavitation performance. Background Technology

[0002] Multistage centrifugal pumps are mainly used for conveying and pressurizing clean water. Their traditional structure is as follows: Figure 1 As shown, Figure 1 The middle arrow indicates the direction of water flow. Water is drawn in from the bottom suction section 1 and discharged from the top discharge section 2. The main components include: motor frame 3, pump body 4, coupling 5, pump shaft 6, impeller 7, sealing ring 8, lock nut 9, shaft sleeve 10, and bearing 11, etc. The lower bearing 11 is usually a sliding bearing, which is installed in the inlet of the suction section 1 and is crucial for the stable operation of the centrifugal pump.

[0003] like Figure 2 The bearing structure of the suction section 1 shown has a bushing 10 mounted on the pump shaft 6, and a bearing 11 mounted inside the bearing bracket 12. There is a clearance between the bearing 11 and the bushing 10. Lubricating water enters from below and flows out from above through the clearance. Figure 2 As indicated by the middle arrow, the ribs on bearing 11 and bearing housing 12 block the inlet flow channel, leading to increased flow velocity and decreased inlet pressure, which adversely affects cavitation performance. This adverse factor urgently needs to be addressed for applications requiring high cavitation performance.

[0004] Existing patent applications, such as patent application number 201720463040.9, disclose a single-stage vertical centrifugal pump, comprising a pump body, a pump cover, a bearing housing, and a motor connected sequentially from bottom to top. The pump body contains a pump shaft, one end of which is equipped with an impeller. The other end of the pump shaft passes through the pump cover and bearing housing and is connected to the motor shaft. A sealing assembly is provided between the pump shaft and the pump cover, and a bearing assembly is provided between the pump shaft and the bearing housing. This utility model has advantages such as compact structure, small footprint, and safe and reliable operation. However, the aforementioned patent technology targets a single-stage centrifugal pump with only one impeller and an inducer wheel in front of it, resulting in a relatively complex structure. This patent technology targets a multi-stage centrifugal pump with multiple impellers and no inducer wheel, resulting in a relatively simple structure. The methods for improving cavitation resistance are different: the above-mentioned patented technology adds an inducer 17 to the impeller inlet, and increases the pump inlet pressure by the rotation of the inducer to improve cavitation resistance; while this patented technology eliminates the bearing, bushing and stiffener in the impeller inlet suction section to reduce the loss of inlet water pressure, so that the impeller inlet can maintain a certain pressure, thereby improving cavitation resistance.

[0005] Patent application number 201720845993.1 discloses a cavitation breaking device for a vehicle-mounted fire pump, comprising an impeller, an inducer wheel, a drive shaft, and a positioning assembly. The inducer wheel includes a hollow shaft and multiple helical blades. The first end of the hollow shaft is cylindrical, and the second end is frustum-shaped. The multiple helical blades are evenly distributed on the outer surface of the second end of the hollow shaft. The hollow shaft is sleeved on and fixedly connected to the drive shaft. The impeller is sleeved on and fixedly connected to the drive shaft. The positioning assembly is connected to the drive shaft. The first end of the hollow shaft is adjacent to the end of the impeller, and the second end of the hollow shaft is adjacent to the positioning assembly. This utility model's cavitation breaking device for a vehicle-mounted fire pump has a simple structure, is easy to install, effectively prevents cavitation, and effectively increases the suction head of the vehicle-mounted fire pump. Both the aforementioned patented technology and this patented technology involve adding an inducer wheel at the inlet of the impeller, but the structures are slightly different: the inducer wheel of the aforementioned patented technology includes a hollow wheel shaft and multiple spiral blades, which provides a stronger boost to the inlet water flow.

[0006] Patent application number 201922405442.5 discloses a single-stage, single-suction impeller inlet anti-clogging fastening structure, including a shaft, impeller, impeller retaining ring, and hexagonal head screw. The impeller is fitted onto the front of the shaft, with the inner hole of the impeller sleeve fitting with the outer circle of the shaft. An internally recessed threaded hole is formed at the shaft end face. A water-guiding surface is provided on the outer side of the impeller retaining ring. A through hole is provided in the center of the impeller retaining ring end face, and a countersunk hole is provided before the through hole. The countersunk hole size is slightly larger than the hexagonal head screw. The hexagonal head screw passes through the through hole in the impeller retaining ring and is screwed into the internally recessed threaded hole of the shaft head. The water-guiding surface on the outer side of the impeller retaining ring smoothly transitions to the curved surface of the impeller. The advantages of this invention are convenient installation and reliable structure, making the liquid flow more smoothly before entering the impeller channel, improving the flow pattern at the impeller inlet, reducing losses, thereby improving pump efficiency and enhancing cavitation performance. However, the aforementioned patented technology targets single-stage centrifugal pumps with only one impeller, equipped with a cylindrical head screw 4 and an impeller retaining ring 3, resulting in a relatively complex structure. This patented technology, on the other hand, targets multi-stage centrifugal pumps with multiple impellers, each equipped with a self-made internally threaded impeller nut, resulting in a relatively simple structure. The methods for improving cavitation resistance differ: the aforementioned patented technology replaces the cap-shaped nut 13, which can obstruct fluid flow, with a cylindrical head screw 4 and an impeller retaining ring 3 at the impeller inlet, thus improving cavitation resistance by allowing for smoother water flow; while this patented technology eliminates the traditionally designed bearings, bushings, and stiffeners in the impeller inlet suction section and adds a streamlined impeller nut to reduce inlet water pressure loss, allowing the impeller inlet to maintain a certain pressure, thereby improving cavitation resistance.

[0007] Patent application number 202521515158.2 discloses a self-ejecting structure for a centrifugal pump, including a casing, an inducer, an ejector, an impeller, and a main shaft. The casing is a hollow shell with an inlet and an outlet. The end of the main shaft extends into the casing. The impeller is sleeved on the outside of the main shaft and is located inside the casing. The inducer is connected to the end of the main shaft near the impeller. The ejector is sleeved on the outside of the inducer and connected to the inside of the casing. A jet channel is provided in the radial direction between the casing and the ejector. This solves the problem of cavitation in the inducer of the pump unit during high-speed rotation, which leads to reduced pump unit efficiency and vibration and noise. It achieves the technical effect of eliminating the leading-edge eddy current of the inducer, improving the cavitation performance of the inducer, and enhancing the pump unit's anti-cavitation capability. Both the aforementioned patented technology and this patented technology involve adding an inducer wheel at the impeller inlet, but with slight structural differences: the inducer wheel in the aforementioned patented technology includes a hub 21 and multiple spiral blades 22, providing a more powerful pressurization of the inlet water flow. Simultaneously, jet channels are provided radially between the casing 1 and the ejector 3. This solves the cavitation phenomenon that exists in the inducer wheel during high-speed rotation in existing technologies. Summary of the Invention

[0008] In view of the defects existing in the prior art, the purpose of this invention is to provide a multistage centrifugal pump with improved cavitation performance, which solves the problem of the bearing and bearing bracket ribs blocking the inlet flow channel in the existing multistage centrifugal pump, and improves the cavitation performance of the multistage centrifugal pump.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A multistage centrifugal pump for improving cavitation performance includes a pump body, the bottom of which is a suction section and the upper part is a discharge section. A pump shaft is provided inside the pump body, and an impeller is provided on the pump shaft.

[0011] The impeller is fixed to the inlet end of the pump shaft by an impeller nut;

[0012] An impeller sleeve is provided at the inlet position of the impeller;

[0013] The impeller sleeve is provided with a bearing body on its exterior;

[0014] The bearing body is provided with a bearing seat on its exterior.

[0015] The bearing housing is connected to the suction section.

[0016] Preferably, the impeller and the impeller sleeve are interference fit, with a fit tolerance of S7 / h6;

[0017] The impeller sleeve and the bearing body are fitted with a clearance fit, with a fit tolerance of F8 / h7.

[0018] The bearing body and the bearing housing are interference fit, with a fit tolerance of S7 / h6;

[0019] The bearing housing is connected to the suction section by a screw assembly.

[0020] Preferably, the impeller sleeve is assembled onto the impeller using a heat-fitting process, and is heated before assembly.

[0021] The bearing body is assembled onto the bearing seat using a cryogenic assembly process, where it is shrunk by freezing.

[0022] Preferably, the impeller sleeve has 2 to 6 disassembly screw holes on the end face facing the outlet side of the suction section;

[0023] The dimensions of the disassembly screw holes are M5~M10.

[0024] Preferably, each end face of the impeller sleeve has two chamfers, and the chamfers have a size of c×45°;

[0025] c = 0.5~2mm.

[0026] Preferably, the inner circular side surface of the bearing body has multiple arc-shaped longitudinal grooves evenly distributed along the circumferential direction of the inner circle.

[0027] The trenches have a depth e = 0.2~1.0mm, an arc radius R = 5~30mm, and a number of 8~48 trenches.

[0028] Preferably, the upper and lower parts of the inner cylindrical surface of the bearing body are each provided with a chamfer, and the chamfer has a size of c×45°;

[0029] c = 0.5~2mm.

[0030] Preferably, the bearing housing has 4 to 10 mounting through holes;

[0031] The diameter of the mounting through hole is d = 6~25mm.

[0032] Preferably, the number of screw assemblies is the same as the number of mounting through holes;

[0033] The screw assembly includes a screw, a flat washer, and a spring washer.

[0034] Preferably, the impeller sleeve and the bearing body are made of different wear-resistant alloy materials.

[0035] This invention provides a multi-stage centrifugal pump with improved cavitation performance. Firstly, it simplifies the suction section structure and improves fluid efficiency: It eliminates the bearings, bushings, and locking nuts found in existing suction sections, as well as the sealing ring, reducing mechanical friction losses and leakage risks. It also optimizes the impeller inlet position, creating a smoother flow path transition with the suction section outlet, reducing turbulence losses and ensuring stable pressure when water enters the impeller, thus significantly improving cavitation performance. Secondly, it enhances the integrated bearing support and sealing design: The design of the mating parts between the impeller inlet and suction section outlet positions is modified, adding components such as an impeller sleeve, bearing housing, bearing seat, impeller nut, and screw assembly. Through the precise fit between the impeller sleeve and bearing housing, it achieves the dual functions of bearing support and sealing ring leakage control. This design not only improves the rotor's dynamic stability and reduces vibration but also optimizes sealing performance, reduces leakage rate, and extends pump service life. The first-stage impeller sealing ring section has both bearing support positioning and sealing ring leakage control functions.

[0036] In summary, this invention ensures unobstructed suction inlet for multi-stage centrifugal pumps, maintaining appropriate pressure at the impeller inlet and thus improving cavitation performance. Furthermore, the combination of the impeller sleeve and bearing housing integrates the functions of bearing support and leakage control via the sealing ring. This results in smoother flow channels, reduced hydraulic losses, and increased efficiency. Superior cavitation performance makes it suitable for more demanding operating conditions (such as high temperature and high suction pressure). Lower maintenance costs, fewer vulnerable parts, and improved reliability are also achieved. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of an existing multistage centrifugal pump;

[0038] Figure 2 yes Figure 1 An enlarged view of position A in the middle;

[0039] Figure 3 This is a schematic diagram of the structure of the multi-stage centrifugal pump of the present invention;

[0040] Figure 4 yes Figure 1 An enlarged view of position B in the middle;

[0041] Figure 5 This is a schematic diagram of the impeller sleeve in the multi-stage centrifugal pump of the present invention, wherein (a) is a front view and (b) is a sectional view;

[0042] Figure 6 This is a schematic diagram of the bearing body and bearing seat in the multi-stage centrifugal pump of the present invention, wherein (a) is the front view and (b) is the top view;

[0043] Figure 7 yes Figure 6 An enlarged diagram of position C in the middle. Detailed Implementation

[0044] To better understand the above-mentioned technical solutions of the present invention, the technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0045] Combination Figure 3 and Figure 4 As shown, this invention provides a multi-stage centrifugal pump with improved cavitation performance, including a pump body 4, with a suction section 1 at the bottom and a discharge section 2 at the top. A pump shaft 6 is disposed in the middle of the pump body 4, and an impeller 7 is mounted on the pump shaft 6. The above is the prior art and will not be described in detail here. Unlike the prior art, in the multi-stage centrifugal pump of this invention, the impeller 7 is fixed to the inlet end of the pump shaft 6 by an impeller nut 13; an impeller sleeve 14 is assembled at the inlet position of the impeller 7, and the impeller 7 and the impeller sleeve 14 are interference fit; a bearing body 15 is assembled on the outside of the impeller sleeve 14, and the impeller sleeve 14 and the bearing body 15 are clearance fit; a bearing seat 16 is assembled on the outside of the bearing body 15, and the bearing body 15 and the bearing seat 16 are interference fit; the bearing seat 16 is connected and fixed to the suction section 1 by a screw assembly 17. This ensures unobstructed flow at the intake of section 1, allowing water to maintain appropriate pressure at the impeller 7 inlet, thus improving cavitation performance. Furthermore, the fit between the impeller sleeve 14 and the bearing housing 15 combines the functions of bearing support and leakage control by the original sealing ring. Figure 3 The arrows in the diagram indicate the direction of water flow. The main stream entering from the suction section 1 flows upward through the inlet of the impeller 7, then flows back through the gap between the impeller sleeve 14 and the bearing body 15 before merging with the main stream.

[0046] The impeller 7 and the impeller sleeve 14 are interference fit with a tolerance of S7 / h6. After the impeller sleeve 14 is heated and expanded, it is hot-fitted onto the inlet of the impeller 7.

[0047] The impeller sleeve 14 and the bearing housing 15 are made of different wear-resistant alloy materials. The impeller sleeve 14 and the bearing housing 15 are clearance fit with a fit tolerance of F8 / h7, and an appropriate fit clearance is maintained.

[0048] The bearing body 15 and the bearing housing 16 are interference fit with a tolerance of S7 / h6. The bearing body 15 shrinks in size after freezing and is then assembled onto the bearing housing 16.

[0049] Combination Figure 1 and Figure 3 As shown, the present invention uses an impeller nut 13 installed at the end of the pump shaft 6 to press the impeller 7, while also wrapping the end of the pump shaft 6 and having a guiding effect, resulting in a larger axial dimension. In contrast, the traditional locking nut is penetrated by the pump shaft and only presses the impeller, resulting in a smaller axial dimension.

[0050] Combination Figure 5As shown, 4 to 6 disassembly screw holes 1401 are provided on the end face of the impeller sleeve 14 facing the outlet side of the suction section 1. The size of the disassembly screw holes 1401 is M5 to M10, which are used to replace and disassemble the impeller sleeve 14 during maintenance.

[0051] The impeller sleeve 14 has two chamfers on its upper and lower end faces. The chamfer size is c×45°, where c=0.5~2mm, to facilitate assembly.

[0052] The impeller sleeve 14 serves as the positioning element for the entire pump shaft 6, preventing radial wobble, and also functions as the original sealing ring, controlling fluid leakage.

[0053] Combination Figure 6 and Figure 7 As shown, multiple arc-shaped longitudinal grooves 1501 are evenly distributed along the circumference of the inner circle on the inner side surface of the bearing body 15 to dissipate frictional heat and improve the service life of the bearing body 15.

[0054] The depth of the groove 1501 is e=0.2~1.0mm, the radius of the arc is R=5~30mm, and the number is 8~48.

[0055] The upper and lower parts of the inner cylindrical surface of the bearing body 15 are each provided with a chamfer. The chamfer size is c×45°, where c=0.5~2mm, to facilitate assembly.

[0056] The bearing housing 16 is provided with 4 to 10 mounting through holes 1601, and the diameter of the mounting through holes 1601 is d=6~25mm.

[0057] The number of screw assemblies 17 is the same as the number of mounting through holes 1601, used to mount and fix the bearing housing 16 on the suction section 1.

[0058] The screw assembly 17 includes a screw, a flat washer, and a spring washer.

[0059] The multistage centrifugal pump of this invention is applicable to both vertical and horizontal installation methods.

[0060] Those skilled in the art should recognize that the above embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Any variations or modifications to the above embodiments that are within the spirit and essence of the present invention will fall within the scope of the claims of the present invention.

Claims

1. A multistage centrifugal pump for improving cavitation performance, comprising a pump body, wherein the bottom of the pump body is a suction section and the upper part is a discharge section, a pump shaft is provided inside the pump body, and an impeller is provided on the pump shaft, characterized in that: The impeller is fixed to the inlet end of the pump shaft by an impeller nut; An impeller sleeve is provided at the inlet position of the impeller; The impeller sleeve is provided with a bearing body on its exterior; The bearing body is provided with a bearing seat on its exterior. The bearing housing is connected to the suction section.

2. The multistage centrifugal pump for improving cavitation performance according to claim 1, characterized in that: The impeller and the impeller sleeve are interference fit, with a fit tolerance of S7 / h6; The impeller sleeve and the bearing body are fitted with a clearance fit, with a fit tolerance of F8 / h7. The bearing body and the bearing housing are interference fit, with a fit tolerance of S7 / h6; The bearing housing is connected to the suction section by a screw assembly.

3. The multistage centrifugal pump for improving cavitation performance according to claim 2, characterized in that: The impeller sleeve is assembled onto the impeller using a heat-fitting process, and is heated before being installed onto the impeller. The bearing body is assembled onto the bearing seat using a cryogenic assembly process, where it is shrunk by freezing.

4. The multistage centrifugal pump for improving cavitation performance according to claim 2, characterized in that: The impeller sleeve has 2 to 6 disassembly screw holes on the end face facing the outlet side of the suction section; The dimensions of the disassembly screw holes are M5~M10.

5. The multistage centrifugal pump for improving cavitation performance according to claim 2, characterized in that: The impeller sleeve has two chamfers on each end face, and the chamfer has a size of c×45°; c = 0.5~2mm.

6. The multistage centrifugal pump for improving cavitation performance according to claim 2, characterized in that: Multiple arc-shaped longitudinal grooves are evenly distributed on the inner circular side surface of the bearing body along the circumferential direction of the inner circle. The trenches have a depth e = 0.2~1.0mm, an arc radius R = 5~30mm, and a number of 8~48 trenches.

7. The multistage centrifugal pump for improving cavitation performance according to claim 2, characterized in that: The bearing body has a chamfer at the top and bottom of its inner cylindrical surface, and the chamfer has a size of c×45°. c = 0.5~2mm.

8. The multistage centrifugal pump for improving cavitation performance according to claim 2, characterized in that: The bearing housing is provided with 4 to 10 mounting through holes; The diameter of the mounting through hole is d = 6~25mm.

9. The multistage centrifugal pump with improved cavitation performance according to claim 8, characterized in that: The number of screw assemblies is the same as the number of mounting through holes; The screw assembly includes a screw, a flat washer, and a spring washer.

10. The multistage centrifugal pump for improving cavitation performance according to claim 2, characterized in that: The impeller sleeve and the bearing body are made of different wear-resistant alloy materials.

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