Multi-stage centrifugal pump

Abstract

The invention provides a multi-stage centrifugal pump which comprises a pump body, a balance drum, a rotating shaft and a balance assembly, the rotating shaft penetrates through the pump body, and the balance drum is arranged on the outer side of the rotating shaft in a sleeving mode; the balance assembly comprises an adjustable balance drum sleeve and an adjustable stator sleeve, the balance drum is sleeved with the adjustable balance drum sleeve, the pump body is sleeved with the adjustable stator sleeve, and the adjustable balance drum sleeve and the adjustable stator sleeve are in coaxial clearance fit; a containing cavity is formed in the pump body, a fixing ring is arranged in the containing cavity and arranged on the outer side of the rotating shaft in a sleeving mode, one end of the fixing ring abuts against the balance drum, a communicating suction inlet communicating with the containing cavity is formed in the pump body, and the communicating suction inlet is used for enabling fluid in the containing cavity to flow back to an inlet of the pump body; the adjustable balancing drum sleeve and the balancing drum are configured to be capable of being detached along with the rotating shaft so as to adjust the thickness of the adjustable balancing drum sleeve and the thickness of the adjustable stator sleeve, and therefore the gap between the adjustable balancing drum sleeve and the adjustable stator sleeve can meet the requirement.

Description

Technical Field

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

[0002] Axial force balance is a core challenge in the design of multistage centrifugal pumps, and related faults account for more than 80% of all failures in multistage pumps, seriously affecting the operational stability of the equipment.

[0003] In the existing technology, the axial force balancing device consisting of a balance drum and a balance sleeve is the most widely used. It generates a reverse balancing force by using the cross-sectional area of ​​the balance drum and the pressure difference between the two ends to counteract the axial force generated when the impeller is working. However, uncertainties such as inter-stage leakage during the operation of multi-stage pumps can easily lead to errors in the calculation of axial force, which makes it difficult to design the size of the balance drum accurately.

[0004] In actual research and development, it is usually necessary to first select approximate dimensions based on experience, and then determine the final specifications through repeated experiments and adjustments. This not only significantly increases the product manufacturing cost, but also significantly extends the research and development cycle.

[0005] Based on this, the inventors of this application propose a multi-stage centrifugal pump in order to solve one or more of the aforementioned technical problems. Summary of the Invention

[0006] The present invention solves the above-mentioned technical problems through the following technical solution: This invention provides a multistage centrifugal pump, comprising: The pump body, the balance drum, the rotating shaft, and the balance assembly are provided, wherein the rotating shaft passes through the pump body and the balance drum is sleeved on the outside of the rotating shaft; The balancing assembly includes an adjustable balancing drum sleeve and an adjustable stator sleeve. The adjustable balancing drum sleeve is sleeved on the outside of the balancing drum, and the adjustable stator sleeve is sleeved on the pump body. The adjustable balancing drum sleeve and the adjustable stator sleeve are coaxially clearance-fitted. The pump body has a receiving cavity, and a fixing ring is provided inside the receiving cavity. The fixing ring is sleeved on the outside of the rotating shaft and one end abuts against the balance drum. The pump body has a connecting suction port that communicates with the receiving cavity. The connecting suction port is used to return the fluid in the receiving cavity to the pump body inlet. The adjustable balance drum sleeve and the balance drum are configured to be detached together with the rotating shaft to adjust the thickness of the adjustable balance drum sleeve and the adjustable stator sleeve, thereby ensuring that the gap between the adjustable balance drum sleeve and the adjustable stator sleeve meets the requirements.

[0007] According to one embodiment of the present invention, the thickness calculation formula of the adjustable balancing drum sleeve is as follows: h = R1 - R0; F2=Δp(R1 2 -R3 2 )π; F2 = F1 - ΔF; Wherein, F2 is the balancing force generated by the pressure difference Δp at both ends of the balancing drum; F1 is the axial force generated by the impeller when the pump body is working; ΔF is the residual axial force; R1 is the radius of the outer diameter of the adjustable balancing drum sleeve; R0 is the outer diameter radius of the balancing drum; and R3 is the radius of the final stage impeller hub.

[0008] According to one embodiment of the present invention, the adjustable balance drum sleeve has a plurality of first grooves along its axial direction on its outer side, and the adjustable stator sleeve has a plurality of second grooves corresponding to the first grooves along its axial direction on its inner side.

[0009] According to one embodiment of the present invention, the balancing drum is provided with a final stage impeller on the side away from the receiving cavity, and the first groove and the second groove are both arranged inclined toward the final stage impeller.

[0010] According to one embodiment of the present invention, along the axial direction of the adjustable balancing drum sleeve, the first grooves of different depths, widths and tilt angles are arranged alternately. Along the axial direction of the adjustable stator sleeve, the second grooves of different depths, widths and tilt angles are arranged alternately.

[0011] According to one embodiment of the present invention, both the first groove and the second groove are annular grooves.

[0012] According to one embodiment of the present invention, an annular positioning groove is provided on the rotating shaft, and an annular mating groove is provided between the side of the balance drum facing the accommodating cavity and the rotating shaft; The inner side of the fixing ring is provided with a first protrusion that fits into the annular positioning groove, and the side end of the fixing ring is provided with a second protrusion that fits into the annular mating groove.

[0013] According to one embodiment of the present invention, the adjustable balancing drum sleeve and the balancing drum are fastened together by a first fastener; The adjustable stator sleeve is fastened to the pump body by a second fastener.

[0014] According to one embodiment of the present invention, the first fastener and the second fastener are threaded connectors.

[0015] According to one embodiment of the present invention, the gap between the adjustable balance drum sleeve and the adjustable stator sleeve is 0.15mm to 0.3mm.

[0016] The positive and progressive effects of this invention are as follows: This invention relates to a multi-stage centrifugal pump, which achieves effective axial force balance by setting up a balancing assembly consisting of a matching adjustable balancing drum sleeve and an adjustable stator sleeve. This assembly, along with a fixing ring fitted onto the rotating shaft and pressing against the balancing drum, and a connecting suction port communicating with the pump body cavity, allows for efficient axial force balance. Furthermore, the adjustable balancing drum sleeve and the balancing drum can be disassembled along with the rotating shaft, eliminating the need to redesign and manufacture the pump body and balancing drum. Residual axial force can be adjusted simply by replacing the adjustable balancing drum sleeve and the adjustable stator sleeve with appropriately sized ones, without disassembling the pump body and rotor components. This significantly reduces the product development and manufacturing costs of the multi-stage centrifugal pump and shortens the production cycle. Attached Figure Description

[0017] The above and other features, properties and advantages of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings and embodiments, wherein: Figure 1 This is a cross-sectional view of the multi-stage centrifugal pump of the present invention at one angle; Figure 2 This is a schematic diagram showing the layout of the second groove on the inner surface of the adjustable stator sleeve or the first groove on the outer surface of the adjustable balance drum sleeve.

[0018] 1. Pump body; 11. Receiving cavity; 12. Retaining ring; 121. First protrusion; 122. Second protrusion; 13. Connecting suction inlet; 2. Balancing drum; 21. Annular mating groove; 3. Rotating shaft; 31. Annular positioning groove; 4. Balancing assembly; 41. Adjustable balancing drum sleeve; 411. First groove; 412. First fastener; 42. Adjustable stator sleeve; 421. Second groove; 422. Second fastener; 5. Final stage impeller. Detailed Implementation

[0019] The present invention will be further described below with reference to specific embodiments and accompanying drawings. More details are set forth in the following description in order to provide a full understanding of the present invention. However, the present invention can obviously be implemented in many other ways different from those described herein. Those skilled in the art can make similar extensions and derivations based on actual application situations without departing from the spirit of the present invention. Therefore, the scope of protection of the present invention should not be limited by the content of this specific embodiment.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0021] As a key fluid transport device in the industrial field, especially in nuclear power integrated small reactor systems, the axial force balancing effect of multistage centrifugal pumps directly determines their operational stability, service life and safety reliability. However, traditional axial force balancing devices suffer from technical pain points such as large dimensional calculation errors, the need to redesign and manufacture the pump body and balancing drum during adjustment, high R&D costs and long development cycles due to factors such as interstage leakage.

[0022] Based on this, please refer to Figure 1 and Figure 2 This application proposes a multistage centrifugal pump, including a pump body 1, a balance drum 2, a rotating shaft 3 and a balance assembly 4. The rotating shaft 3 passes through the pump body 1, and the balance drum 2 is sleeved on the outside of the rotating shaft 3. The balance drum 2 and the rotating shaft 3 are interference fit, and the balance drum 2 rotates coaxially and at the same speed as the rotating shaft 3.

[0023] The balancing assembly 4 includes an adjustable balancing drum sleeve 41 and an adjustable stator sleeve 42. The adjustable balancing drum sleeve 41 is fitted outside the balancing drum 2, and the adjustable stator sleeve 42 is fitted onto the pump body 1. The adjustable balancing drum sleeve 41 and the adjustable stator sleeve 42 are coaxially fitted with a clearance fit. The pump body 1 has a receiving cavity 11, and a fixing ring 12 is provided inside the receiving cavity 11. The fixing ring 12 is fitted outside the rotating shaft 3 and one end presses against the balancing drum 2. The pump body 1 has a connecting suction port 13 that communicates with the receiving cavity 11. The connecting suction port 13 is used to return the fluid in the receiving cavity 11 to the inlet of the pump body 1. The adjustable balancing drum sleeve 41 and the balancing drum 2 are configured to be detached together with the rotating shaft 3 to adjust the thickness of the adjustable balancing drum sleeve 41 and the adjustable stator sleeve 42, thereby ensuring that the clearance between the adjustable balancing drum sleeve 41 and the adjustable stator sleeve 42 meets the requirements.

[0024] By setting up an adjustable balance drum sleeve 41 and an adjustable stator sleeve 42 to form a balance component 4, and cooperating with the fixing ring 12 sleeved on the rotating shaft 3 and pressing against the balance drum 2, and the connecting suction port 13 connected to the receiving cavity 11 of the pump body 1, the axial force is effectively balanced. At the same time, the adjustable balance drum sleeve 41 and the balance drum 2 can be disassembled together with the rotating shaft 3, without the need to redesign and manufacture the pump body 1 and the balance drum 2. The residual axial force can be adjusted simply by replacing the adjustable balance drum sleeve 41 and the adjustable stator sleeve 42 of the appropriate size. There is no need to disassemble the pump body 1 and the rotor components, which greatly reduces the product development and manufacturing cost of multi-stage centrifugal pumps and shortens the production cycle.

[0025] like Figure 1 As shown, a final stage impeller 5 is provided on the outer side of the balance drum 2 away from the fixed ring 12. The final stage impeller 5 is sleeved on the rotating shaft 3 and presses against the balance drum 2 at one end. The axial movement of the balance drum 2 is restricted by the cooperation of the final stage impeller 5 and the fixed ring 12.

[0026] To improve the connection stability between the fixed ring 12 and the balance drum 2, an annular positioning groove 31 is provided on the rotating shaft 3, and an annular mating groove 21 is provided between the side of the balance drum 2 facing the accommodating cavity 11 and the rotating shaft 3; the inner side of the fixed ring 12 is provided with a first protrusion 121 that fits into the annular positioning groove 31, and the side end of the fixed ring 12 is provided with a second protrusion 122 that fits into the annular mating groove 21.

[0027] By engaging the first protrusion 121 and the second protrusion 122 with the annular positioning groove 31 and the annular mating groove 21 respectively, the balance drum 2 can be precisely axially limited, preventing axial movement of the balance drum 2 during pump body 1 operation and ensuring the stability of axial force balance. It also restricts the circumferential rotation of the balance drum 2, preventing relative sliding between the balance drum 2 and the rotating shaft 3, reducing wear between them, and extending the service life of both the rotating shaft 3 and the balance drum 2. Furthermore, the interlocking positioning structure facilitates easy installation and disassembly, making subsequent maintenance and parts replacement convenient.

[0028] The adjustable balance drum sleeve 41 and the adjustable stator sleeve 42 are fastened to the balance drum 2 by the first fastener 412; the adjustable stator sleeve 42 is fastened to the pump body 1 by the second fastener 422.

[0029] Both the first fastener 412 and the second fastener 422 can be threaded fasteners, such as bolts or screws, and there is no limitation on them.

[0030] Threaded fasteners were chosen as the first fastener 412 and the second fastener 422 because they offer high connection strength and precise positioning, effectively ensuring the connection stability between the adjustable balance drum sleeve 41 and the balance drum 2, as well as between the adjustable stator sleeve 42 and the pump body 1, preventing loosening due to vibration during high-speed operation of the pump body 1. Furthermore, the threaded connection is easy to disassemble and install, requiring no specialized tools, allowing technicians to quickly replace and adjust the balance assembly 4, thus improving the maintenance efficiency of the pump body 1. Moreover, the high standardization of threaded fasteners and their low procurement and replacement costs further reduce the maintenance costs of the pump body 1.

[0031] like Figure 1As shown, when the multistage centrifugal pump is working, the impeller will generate an axial force F1 towards the inlet side of the pump body 1 due to the fluid pressure difference. In order to counteract this axial force, this application provides an adjustable balance drum sleeve 41 on the outside of the balance drum 2 and an adjustable stator sleeve 42 on the side of the pump body 1. The two are coaxially fitted with a clearance to form a pressure difference adjustment structure. The pressure difference is formed at both ends of the balance drum 2 due to the fluid flow. Combined with the effective cross-sectional area formed by the adjustable balance drum sleeve 41 and the hub radius of the last stage impeller 5, an axial balance force F2 opposite to the direction of the axial force F1 is generated. This balance force counteracts most of the axial force of the impeller, and only the residual axial force ΔF of the resultant force is retained and borne by the pump body 1, thereby achieving the balance of the axial force on the pump body 1.

[0032] Please continue to refer to Figure 1 The adjustable stator sleeve 42 and the adjustable balance drum sleeve 41 are fitted with a clearance, with a clearance value of 0.15mm-0.3mm. The 0.15mm-0.3mm range is a set value based on engineering experience and can be adjusted according to actual needs.

[0033] The formula for calculating the thickness of the adjustable balance drum sleeve 41 is as follows: h = R1 - R0; F2=Δp(R1 2 -R3 2 )π; F2 = F1 - ΔF; Wherein, F2 is the balancing force generated by the pressure difference Δp at both ends of the balance drum 2; F1 is the axial force generated by the impeller when the pump body 1 is working; ΔF is the residual axial force; R1 is the radius of the outer diameter of the adjustable balance drum sleeve 41; R0 is the outer diameter radius of the balance drum 2; and R3 is the radius of the hub of the final stage impeller 5.

[0034] When it is necessary to adjust the residual axial force ΔF of a multi-stage centrifugal pump, the value of h can be calculated based on the required balancing force F2, and then the thickness of the adjustable stator sleeve 42 can be calculated. Then, the rotating shaft 3, along with the balancing drum 2, is removed from the pump body 1, and an adjustable balancing drum sleeve 41 of suitable thickness is selected for replacement. Since the balancing drum 2 has been removed, there is sufficient space to disassemble and replace the adjustable stator sleeve 42. After both the adjustable balancing drum sleeve 41 and the adjustable stator sleeve 42 have been replaced, the balancing drum 2 can be reassembled. The entire process does not require remanufacturing the pump body 1 and the balancing drum 2; only the adjustable balancing drum sleeve 41 and the adjustable stator sleeve 42 need to be adjusted, significantly reducing product manufacturing costs and cycle time.

[0035] Please refer to Figure 2 The adjustable balance drum sleeve 41 has multiple first grooves 411 on its outer side along its axial direction, and the adjustable stator sleeve 42 has multiple second grooves 421 on its inner side along its axial direction corresponding to the first grooves 411.

[0036] Specifically, the first groove 411 and the second groove 421 are both arranged inclined toward the last stage impeller 5.

[0037] The first groove 411 and the second groove 421 can not only reduce the leakage of the gap between the adjustable balance drum sleeve 41 and the adjustable stator sleeve 42, but also increase the fluid resistance, thereby reducing the axial length dimension.

[0038] Furthermore, along the axial direction of the adjustable balance drum sleeve 41, first grooves 411 of different depths, widths and tilt angles are arranged alternately; along the axial direction of the adjustable stator sleeve 42, second grooves 421 of different depths, widths and tilt angles are arranged alternately.

[0039] By arranging grooves of different depths, widths, and inclination angles at staggered intervals along the axial direction, a gradient fluid resistance distribution can be formed based on the differences in fluid pressure and velocity at different axial positions within the pump body 1. Compared to grooves of uniform specifications, this allows for more precise control of pressure changes within the gaps, achieving better leakage control and pressure difference regulation.

[0040] Moreover, the differentiated groove layout can disperse the impact of fluid on the balancing component 4, reduce local wear at the groove, extend the service life of the adjustable balancing drum sleeve 41 and the adjustable stator sleeve 42, and improve the durability of the balancing component 4.

[0041] In summary, the multi-stage centrifugal pump proposed in this application does not require remanufacturing the pump body 1 and the balance drum 2 when the residual axial force of the pump needs to be adjusted. Only the dimensions of the adjustable balance drum sleeve 41 and the adjustable stator sleeve 42 need to be adjusted, which can significantly reduce the product manufacturing cost and manufacturing cycle.

[0042] In the description of the embodiments of this application, unless otherwise expressly specified and limited, the technical terms such as "installation", "connection", "joining", and "fixing" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can also refer to mechanical connections. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0043] This application uses specific terms to describe embodiments of the application. Terms such as "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic associated with at least one embodiment of the application. Therefore, it should be emphasized and noted that references to "an embodiment," "one embodiment," or "an alternative embodiment" in different locations throughout this specification do not necessarily refer to the same embodiment. Furthermore, certain features, structures, or characteristics in one or more embodiments of the application can be appropriately combined.

[0044] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any variations and modifications can be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, any modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the invention, fall within the protection scope defined by the claims of the present invention.

Claims

1. A multistage centrifugal pump, characterized in that, include: The pump body, the balance drum, the rotating shaft, and the balance assembly are provided, wherein the rotating shaft passes through the pump body and the balance drum is sleeved on the outside of the rotating shaft; The balancing assembly includes an adjustable balancing drum sleeve and an adjustable stator sleeve. The adjustable balancing drum sleeve is sleeved on the outside of the balancing drum, and the adjustable stator sleeve is sleeved on the pump body. The adjustable balancing drum sleeve and the adjustable stator sleeve are coaxially clearance-fitted. The pump body has a receiving cavity, and a fixing ring is provided inside the receiving cavity. The fixing ring is sleeved on the outside of the rotating shaft and one end abuts against the balance drum. The pump body has a connecting suction port that communicates with the receiving cavity. The connecting suction port is used to return the fluid in the receiving cavity to the pump body inlet. The adjustable balance drum sleeve and the balance drum are configured to be detached together with the rotating shaft to adjust the thickness of the adjustable balance drum sleeve and the adjustable stator sleeve, thereby ensuring that the gap between the adjustable balance drum sleeve and the adjustable stator sleeve meets the requirements.

2. The multistage centrifugal pump according to claim 1, characterized in that, The formula for calculating the thickness of the adjustable balancing drum sleeve is as follows: h = R1 - R0; F2=Δp(R1 2 -R3 2 )π; F2 = F1 - ΔF; Wherein, F2 is the balancing force generated by the pressure difference Δp at both ends of the balancing drum; F1 is the axial force generated by the impeller when the pump body is working; ΔF is the residual axial force; R1 is the radius of the outer diameter of the adjustable balancing drum sleeve; R0 is the outer diameter radius of the balancing drum; and R3 is the radius of the final stage impeller hub.

3. The multistage centrifugal pump according to claim 1, characterized in that, The adjustable balance drum sleeve has multiple first grooves along its axial direction on its outer side, and the adjustable stator sleeve has multiple second grooves along its axial direction corresponding to the first grooves on its inner side.

4. The multistage centrifugal pump according to claim 3, characterized in that, The balancing drum has a final impeller on the side away from the accommodating cavity, and the first groove and the second groove are both arranged inclined toward the final impeller.

5. The multistage centrifugal pump according to claim 4, characterized in that, Along the axial direction of the adjustable balancing drum sleeve, the first grooves of different depths, widths and tilt angles are arranged alternately. Along the axial direction of the adjustable stator sleeve, the second grooves of different depths, widths and tilt angles are arranged alternately.

6. The multistage centrifugal pump according to claim 4, characterized in that, Both the first groove and the second groove are annular grooves.

7. The multistage centrifugal pump according to claim 1, characterized in that, The rotating shaft is provided with an annular positioning groove, and the side of the balance drum facing the accommodating cavity is provided with an annular mating groove between it and the rotating shaft; The inner side of the fixing ring is provided with a first protrusion that fits into the annular positioning groove, and the side end of the fixing ring is provided with a second protrusion that fits into the annular mating groove.

8. The multistage centrifugal pump according to claim 1, characterized in that, The adjustable balance drum sleeve is fastened to the balance drum by a first fastener; The adjustable stator sleeve is fastened to the pump body by a second fastener.

9. The multistage centrifugal pump according to claim 8, characterized in that, The first fastener and the second fastener are threaded connectors.

10. The multistage centrifugal pump according to claim 1, characterized in that, The gap between the adjustable balance drum sleeve and the adjustable stator sleeve is 0.15mm~0.3mm.

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