Submerged pump

Abstract

The invention discloses a submerged pump, and particularly relates to the technical field of delivery pumps, the submerged pump comprises a motor, a pump body, a pump shaft and an impeller assembly, and the pump shaft and the impeller assembly are located in the pump body; a shell of the motor is directly connected with the upper portion of the pump body, static seal is formed between the shell of the motor and the pump body, one end of the pump shaft is directly connected with the output end of the motor, the other end of the pump shaft is connected with the impeller assembly in an interference fit mode, and the pump shaft is not provided with a submerged bearing. The submerged pump solves the technical problem that in the prior art, a submerged pump in a lead-bismuth reactor is poor in vibration and noise reduction effect, and the submerged pump is low in noise and compact in structure.

Description

Technical Field

[0001] The invention relates to the technical field of delivery pumps, and in particular to a submersible pump. Background Art

[0002] As an important liquid conveying device, submersible pumps have important applications in various fields, especially in the field of advanced nuclear energy system technology. As a key equipment for circulating cooling liquid in liquid metal reactors, submersible pumps are of great significance in the research and development of liquid metal reactors.

[0003] As the core key equipment for transporting high-temperature media in liquid metal reactors, the submersible pump is a circulating pump for high-temperature liquid metal. In the long-term operation, low vibration and noise and long life and corrosion resistance are the key core indicators. Due to the complex flow interaction between high-density high-temperature liquid metal and the flow-through parts, the flow-through parts of the high-temperature liquid metal circulation pump have short corrosion failure life and high vibration and noise problems that need to be solved urgently.

[0004] The vibration and noise generated by the submersible pump during operation will cause damage to the equipment. On the one hand, it will cause fatigue damage to the impeller and guide vane, reduced bearing life, mechanical seal failure and other faults. On the other hand, it will radiate to the upstream and downstream system equipment, causing unstable operation or failure of other equipment in the system, seriously affecting the stability and safety of the unit operation. In addition to the vibration caused by installation or structural failure, the unbalanced pump rotor system, the mechanical excitation caused by the misalignment of the motor and pump shaft, and the hydraulic excitation caused by the complex flow inside the flow-through parts are all important reasons for the vibration and noise of the pump.

[0005] Existing rotor system dynamic balancing technology, motor and pump shaft flexible connection and other measures can reduce structural vibration and noise, and meet the basic safety operation requirements of pump equipment in relevant standards, but the technology is complex, the assembly process is demanding, the economic cost is high, and the mechanical excitation cannot be completely eliminated; at the same time, due to the complex internal flow of the submerged pump, the hydraulic excitation is difficult to accurately predict and effectively control, which leads to poor vibration and noise reduction effects. Especially in lead-bismuth reactors that use high-density and high-temperature liquid metal as cooling liquid, the submerged pumps used in the existing technology have even less ideal vibration and noise reduction effects. Summary of the invention

[0006] The purpose of the present invention is to solve the technical problem that the vibration and noise reduction effect of the submerged pump in the lead-bismuth reactor in the prior art is not good. The present invention provides the following technical solutions:

[0007] A submersible pump comprises a motor, a pump body, a pump shaft and an impeller assembly, wherein the pump shaft and the impeller assembly are located inside the pump body; the outer casing of the motor is directly connected to the upper part of the pump body and a static seal is formed between the outer casing of the motor and the pump body; one end of the pump shaft is directly connected to the output end of the motor, and the other end is connected to the impeller assembly by interference fit.

[0008] Furthermore, no submersible bearing is installed on the pump shaft.

[0009] A submersible pump further comprises a flow guide assembly, wherein the flow guide assembly is fixedly arranged inside the pump body and is spaced below the impeller assembly.

[0010] Furthermore, the guide assembly includes a fixing member and a plurality of guide vanes, all of the guide vanes are evenly distributed on the periphery of the fixing member, and one side of the guide vane is fixedly connected to the inner cavity of the pump body, and the other side is fixedly connected to the fixing member.

[0011] Furthermore, the impeller assembly includes an impeller and a plurality of blades evenly distributed on the upper surface of the impeller, and the impeller is connected to the pump shaft through a tapered shaft interference fit.

[0012] A liquid outlet is provided at the bottom of the pump body; a plurality of liquid inlet channels are provided on the outer circumference of the pump body along the radial direction of the pump body, one end of the liquid inlet channel is connected to the outside of the pump body, and the other end extends to above the impeller assembly.

[0013] The diameter of the pump shaft is set in a gradient, and the diameter of the pump shaft gradually decreases from the end connected to the motor to the end connected to the impeller assembly.

[0014] The number of the liquid inlet channels is n, the number of the blades is greater than or equal to n+1, the number of the guide vanes and the number of the blades are mutually prime numbers, wherein n is greater than or equal to 1.

[0015] The pump shaft and the impeller are installed by cold installation; when the material expansion coefficient of the pump shaft is at least one order of magnitude higher than the material expansion coefficient of the impeller, when the pump shaft and the impeller are installed, the ratio of the interference amount to the assembly clearance is (1.8-2):1.

[0016] The pump body comprises an upper shell and a lower shell, and the inner wall of the upper shell is connected to the outer wall of the lower shell in a stepped sealing manner.

[0017] The present invention has the following advantages:

[0018] (1) The present invention eliminates the coupling and directly connects the pump shaft to the output end of the motor, thereby eliminating the coupling, eliminating the mechanical excitation of the pump rotor system, breaking the traditional complex rotor system composition of the pump, and simplifying the rotor system composition, thereby improving system reliability, making the operation more stable, and reducing vibration and noise levels.

[0019] (2) The present invention connects the motor and the pump body by adopting a static seal, thereby replacing the mechanical seal commonly used in the prior art and directly eliminating the noise and vibration caused by the mechanical seal.

[0020] (3) The present invention eliminates the submerged bearing used in the prior art to reduce pump shaft vibration and adopts a cantilever pump shaft. Compared with the prior art, the present invention eliminates the submerged bearing and adopts a structural design with a large cantilever ratio, thereby simplifying the structural design of the submerged pump, reducing maintenance costs, improving the bending and torsional strength of the pump shaft, reducing the rotation deviation of the pump, improving the running stability of the pump, and effectively reducing the vibration and noise of the pump.

[0021] (4) The present invention discloses a condition regarding the number of liquid inlet channels, the number of impellers, and the number of guide vanes. When the number of liquid inlet channels is n, the number of blades is greater than or equal to n+1, the number of guide vanes and the number of blades are mutually prime numbers, and n is greater than or equal to 1, it can meet the conditions for reducing hydraulic excitation, reducing resonance, and thus reducing noise.

[0022] (5) The present invention provides a brand-new design structure of a submersible pump, which eliminates the vibration and noise of the submersible pump from both mechanical excitation and hydraulic excitation by eliminating the coupling and submersible bearing, changing the connection mode between the pump body and the motor to a static seal, and optimizing the number of liquid inlet channels, impellers and guide vanes, thereby providing a submersible pump with low vibration and noise.

[0023] (6) The submersible pump provided by the present invention not only achieves the technical effect of vibration reduction and noise reduction by eliminating the coupling and the submersible bearing and changing the connection method between the pump body and the motor to a static seal, but also simplifies the structure of the submersible pump and makes the layout reasonable, making the structure of the submersible pump more miniaturized, thereby realizing a miniaturized design of the submersible pump. When applied to a lead-bismuth reactor, it is beneficial to realize a miniaturized design of the reactor body. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural schematic diagram of the present invention;

[0025] Figure 2 This is an enlarged view of point A.

[0026] In the figure: 1. motor, 2. pump body, 21. upper shell, 22. lower shell, 3. pump shaft, 4. impeller assembly, 41. impeller, 42. blades, 5. guide assembly, 51. fixing part, 52. guide vane, 6. liquid outlet, 7. liquid inlet channel. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0028] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents some embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0029] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features and technical solutions in the embodiments may be combined with each other.

[0030] It should be noted that similar numbers and letters represent similar items in the following figures, so once an item is defined in one figure, it does not need to be further defined and explained in the subsequent figures. In the description of the present invention, it should be noted that the orientation or position relationship indicated by the terms "upper", "lower", etc. is based on the orientation or position relationship shown in the drawings, or the orientation or position relationship in which the product of the invention is usually placed when in use, or the orientation or position relationship commonly understood by those skilled in the art. Such terms are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0031] A submersible pump comprises a motor 1, a pump body 2, a pump shaft 3 and an impeller assembly 4, wherein the pump shaft 3 and the impeller assembly 4 are located inside the pump body 2; the housing of the motor 1 is directly connected to the upper part of the pump body 2 and a static seal is formed between the housing of the motor 1 and the pump body 2; one end of the pump shaft 3 is directly connected to the output end of the motor 1, and the other end is connected to the impeller assembly 4 by interference fit. No submersible bearing is installed on the pump shaft 3.

[0032] The upper part of the pump body 2 is fixedly connected to the outer shell of the motor 1 by bolts, so that the shell of the motor 1 is directly fixedly connected to the outer shell of the pump body 2. Compared with the prior art, the traditional mechanical seal has a complex structure, many wearing parts, high cost, complex installation and replacement, and difficulty in handling accidents. And when the natural frequency of the mechanical seal is close to the operating frequency of the pump shaft 3, it is easy to cause resonance, resulting in accelerated seal wear or fatigue damage and high vibration noise. The present invention changes the structure of the pump body 2 from a mechanical seal to a static seal, which greatly reduces the risk of leakage and is suitable for conveying special media such as radioactive liquids; at the same time, it reduces the number of components of the submersible pump, simplifies the maintenance process, and reduces maintenance costs.

[0033] At the same time, one end of the pump shaft 3 is directly connected to the output end of the motor 1, and there is no coupling between the pump shaft 3 and the motor 1. By eliminating the coupling used for connecting the motor 1 and the pump shaft 3, a coaxial structure in which the motor 1 and the pump share the same pump shaft 3 is proposed. The direct coupling of the pump and the motor 1 makes the structure more compact, reduces mechanical losses, and runs more stably, achieving the purpose of reducing vibration and noise levels. The traditional coupling has a complex structure and high cost. During installation, the concentricity of the motor 1 shaft and the pump shaft 3 needs to be strictly adjusted, otherwise it is easy to generate vibration and impact, resulting in high vibration and noise.

[0034] Furthermore, the pump shaft described in the present invention is not equipped with a submerged bearing. In the prior art, a submerged bearing is usually installed at one end of the pump shaft under the liquid, while the pump shaft of the present invention is equipped with a submerged bearing, eliminating the submerged bearing and adopting a structural design with a large cantilever ratio, thereby simplifying the structural design of the submerged pump, reducing maintenance costs, improving the bending and torsional strength of the pump shaft, reducing the rotation deviation of the pump, improving the running stability of the pump, and effectively reducing the vibration and noise of the pump. In addition, since the bearing part of the traditional submerged pump is located in the conveying medium, it cannot provide good cooling and lubrication for conveying special media such as high-temperature liquid metals, and is easily corroded and worn by the medium. These problems will cause the bearing to be unable to withstand the rotation of the pump normally, thereby causing unbalanced rotor movement, and then causing increased vibration and noise of the pump. The present invention further reduces the vibration and noise caused by unbalanced rotor movement by eliminating the submerged bearing.

[0035] In the present invention, a large cantilever ratio design is adopted to ensure that after the submerged bearing is eliminated, the same transmission power is still guaranteed under the condition of reduced noise. Cantilever ratio = cantilever length / motor bearing support distance. Specifically, in the prior art, the cantilever ratio of the submerged pump equipped with the submerged bearing is between 1.1-1.5. Under the same conditions, the cantilever ratio of the present invention is designed to be 1.6-3.0, which reduces the noise while meeting the same power as the prior art.

[0036] A submersible pump further includes a flow guide assembly 5, which is fixedly arranged inside the pump body 2 and spaced below the impeller assembly 4. Further, the flow guide assembly 5 includes a fixing member 51 and a plurality of guide vanes 52, all of which are evenly distributed on the periphery of the fixing member 51, and one side of the guide vane 52 is fixedly connected to the inner wall of the pump body 2, and the other side is fixedly connected to the fixing member 51. The flow guide assembly 5 is used to converge the flowing liquid, and disperse the hydraulic excitation of the flowing liquid through the guide vanes 52, thereby reducing the radial force, thereby reducing the resonance and reducing the noise of the pump.

[0037] Furthermore, the impeller assembly 4 includes an impeller 41 and a plurality of blades 42 evenly distributed on the upper surface of the impeller 41, and the impeller 41 is connected with one end of the pump shaft 3 by interference fit. The impeller assembly 4 can rotate in the pump body 2 along with the rotation of the pump shaft 3, and the blades 42 are evenly distributed on the outer surface of the impeller 41, and each blade 42 is arranged along the flow direction of the liquid. Preferably, the fixing member 51 and the impeller 41 are arranged at intervals and together form a flame-shaped structural setting (that is, the spatial guide vane is adapted to the shape of the impeller and the two are arranged in a flame-shaped setting). This structural setting can make the liquid flow evenly when flowing through the impeller assembly 4 and the guide vane 52 assembly, reduce the backflow vortex in the flow channel, reduce the radial force of the impeller 41, and then reduce the pressure pulsation inside the pump, and improve the vibration reduction and noise reduction effect.

[0038] Furthermore, the number of the liquid inlet channels 7 is n, the number of the blades 42 is greater than or equal to n+1, the number of the guide vanes and the number of the blades are mutually prime numbers, and the greatest common divisor of the number of the guide vanes and the number of the blades is 1, where n is greater than or equal to 1.

[0039] In the above scheme, when the number of the liquid inlet channels 7 is n, the number of the blades 42 is greater than or equal to n+1, the number of the guide vanes 52 and the number of the blades 42 are prime numbers to each other, and when n is greater than or equal to 1, it can reduce hydraulic excitation, reduce resonance, and thus reduce noise. The specific reasons are as follows:

[0040] The number of blades and the number of guide vanes are combined in a prime number combination to avoid the coincidence of the impeller's rotation frequency and the mechanical natural frequency of the guide vanes, thereby reducing the vibration amplitude. On the other hand, by increasing or decreasing the number of blades and the number of liquid inlet channels, the uniformity of the pressure distribution of the flow at the impeller outlet is improved, the vortex and flow separation in the flow channel are reduced, and the amplitude of a single pressure fluctuation is reduced, thereby reducing noise and vibration.

[0041] In one embodiment, the number of liquid inlet channels 7 is 4, the number of blades 42 is 6, and the number of guide vanes 52 is 7. By adjusting the quantitative relationship among the liquid inlet channels 7, the impeller 41, and the guide vanes 52, the technical effect of reducing hydraulic excitation and thus reducing noise is achieved.

[0042] A liquid outlet 6 is provided at the bottom of the pump body 2; a plurality of liquid inlet channels 7 are provided on the outer periphery of the pump body 2 along the radial direction of the pump body 2, one end of the liquid inlet channel 7 is connected to the outside of the pump body 2, and the other end extends to the top of the impeller assembly 4. The liquid inlet of the liquid inlet channel 7 of the present invention is arranged on the outer periphery of the pump body 2, the liquid outlet 6 is arranged at the bottom of the pump body 2, and the liquid inlet of each liquid inlet channel 7 is higher than the liquid outlet 6, forming a top-in and bottom-out structural mode. Different from the bottom-in and top-out mode of the submersible pump commonly used in the prior art, the bottom-in and top-out structural mode combined with the structural arrangement of the impeller assembly 4 and the guide assembly 5 is more conducive to reducing hydraulic excitation, thereby reducing the noise of the submersible pump.

[0043] The diameter of the pump shaft 3 is set in a gradient, and the diameter of the pump shaft 3 gradually decreases from the end connected to the motor 1 to the end connected to the impeller assembly 4.

[0044] The pump body 2 includes an upper shell 21 and a lower shell 22, and the inner wall of the upper shell 21 is connected to the outer wall of the lower shell 22 in a stepped sealing manner. Specifically, the inner wall of the upper shell 21 is arranged in a stepped concave manner, and the outer wall of the lower shell 22 is arranged in a stepped convex manner. The upper shell 21 and the lower shell 22 are matched in a stepped sealing manner and then sealed and fixed by welding.

[0045] The pump shaft 3 and the impeller 41 are installed by cold installation; when the material expansion coefficient of the pump shaft 3 is at least one order of magnitude higher than the material expansion coefficient of the impeller 41, when the pump shaft 3 and the impeller 41 are installed, the ratio of the interference amount to the assembly clearance is (1.8-2):1.

[0046] Specifically, the pump shaft 3 and the impeller 41 are installed by the cold installation method. The pump shaft 3 needs to be low-temperature cooled by cooling, and then the impeller 41 at room temperature is installed on the shaft neck of the pump shaft 3 with a taper (the taper ratio can be selected between 1:30 and 1:100). Finally, an external force is applied through the shaft head locking nut to press the impeller 41 onto the pump shaft 3, and the impeller 41 is locked and fixed to complete the installation of the impeller 41 and the pump shaft 3. When the pump shaft 3 is low-temperature cooled, the cooling temperature needs to be regulated. The specific control temperature calculation formula of the cold installation method is as follows:

[0047] ΔT=(δ+Δ) / (α*D)

[0048] Wherein δ is the interference, Δ is the assembly clearance, α is the linear expansion coefficient of the material, and D is the matching shaft diameter. In order to simplify the calculation and ensure that the impeller 41 and the pump shaft 3 meet the requirements of the installation process when they are installed by the cold installation method, the present invention provides the following solution: when the material expansion coefficient of the pump shaft 3 is at least one order of magnitude higher than the material expansion coefficient of the impeller 41, the ratio of the interference to the assembly clearance is (1.8-2):1.

[0049] In this embodiment, the material of the pump shaft 3 is stainless steel, and the thermal expansion coefficient of stainless steel is 10 -5 / ℃ order of magnitude, the impeller 41 adopts a new ceramic material (such as MAX phase material) with a thermal expansion coefficient of 10 -6 / ℃ order of magnitude, there is an order of magnitude difference between the two. When the material expansion coefficient of the pump shaft 3 is at least one order of magnitude higher than the material expansion coefficient of the impeller 41, the interference is 0.03mm. According to the ratio relationship provided by the present invention, the assembly clearance is directly selected as 0.015mm. The specific control temperature of the cold installation method is calculated by the above formula.

[0050] When the pump shaft 3 and the impeller 41 are installed by the cold installation method, the ratio of the interference amount and the assembly clearance can be directly used to obtain the value of the other data when one of the data is determined, and this value relationship between the interference amount and the assembly clearance can meet the installation requirements of the pump shaft 3 and the impeller 41, so that the contact surfaces of the two are closely fitted, without stress concentration and cracking risks, and can achieve the assembly process requirements. The calculation process and the convenience of operation are simplified.

[0051] In this embodiment, the interference is 0.03 mm. According to the ratio provided by the present invention, the assembly clearance is directly selected to be 0.015 mm, and the linear expansion coefficient is 5.0*10 -6 / ℃, with a shaft diameter of 50mm, it is directly obtained through calculation that under the condition of room temperature of 15℃, the cooling temperature of the pump shaft 3 is -195℃. After cooling the pump shaft 3 at -195℃ for 20min, it is installed with the impeller 41. After testing, it meets the installation requirements.

[0052] The working principle of the present invention is: the motor 1 is operated, because the motor 1 is coaxial with the pump shaft 3, the operation of the motor 1 directly drives the rotation of the pump shaft 3; the rotation of the pump shaft 3 drives the rotation of the impeller assembly 4, which makes the liquid outside the pump body 2 flow into the pump body 2 through each liquid inlet channel 7 under the action of the pressure difference (when applied in the lead-bismuth reactor, the liquid outside the pump body 2 is liquid lead-bismuth), because the liquid inlet channel 7 extends to the top of the impeller assembly 4, so the liquid flows into the impeller assembly 4 for confluence, and the impeller 41 rotates, and under the action of the blades 42, it continues to flow downward into the guide assembly 5, passes through the guide assembly 5. Confluence is performed at the guide assembly 5 and hydraulic excitation is reduced, and then it flows out of the pump body 2 along the liquid outlet 6.

[0053] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A submersible pump, characterized in that: The pump comprises a motor (1), a pump body (2), a pump shaft (3) and an impeller assembly (4); the pump shaft (3) and the impeller assembly (4) are located inside the pump body (2); the outer shell of the motor (1) is directly connected to the upper part of the pump body (2) so that a static seal is formed between the outer shell of the motor (1) and the pump body (2); one end of the pump shaft (3) is directly connected to the output end of the motor (1), and the other end is connected to the impeller assembly (4) by interference fit.

2. A submersible pump according to claim 1, characterized in that: No submerged bearing is installed on the pump shaft (3).

3. A submersible pump according to claim 1, characterized in that: It also comprises a flow guide assembly (5), wherein the flow guide assembly (5) is fixedly arranged inside the pump body (2) and is arranged at intervals below the impeller assembly (4).

4. A submersible pump according to claim 3, characterized in that: The flow guide assembly (5) comprises a fixing member (51) and a plurality of guide vanes (52), wherein all the guide vanes (52) are evenly distributed on the periphery of the fixing member (51), and one side of the guide vane (52) is fixedly connected to the inner cavity of the pump body (2), and the other side is fixedly connected to the fixing member (51).

5. A submersible pump according to claim 4, characterized in that: The impeller assembly (4) comprises an impeller (41) and a plurality of blades (42) evenly distributed on the upper surface of the impeller (41); the impeller (41) is connected to one end of the pump shaft (3) through a tapered shaft interference fit.

6. A submersible pump according to claim 5, characterized in that: A liquid outlet (6) is provided at the bottom of the pump body (2); a plurality of liquid inlet channels (7) are provided on the outer periphery of the pump body (2) along the radial direction of the pump body (2); one end of the liquid inlet channel (7) is connected to the outside of the pump body (2), and the other end extends to the top of the impeller assembly (4).

7. A submersible pump according to claim 1, characterized in that: The diameter of the pump shaft (3) is arranged in a gradient, and the diameter of the pump shaft (3) gradually decreases from the end connected to the motor (1) to the end connected to the impeller assembly (4).

8. A submersible pump according to claim 6, characterized in that: The number of the liquid inlet channels (7) is n, the number of the blades (42) is greater than or equal to n+1, the number of the guide vanes (52) and the number of the blades (42) are mutually prime numbers, wherein n is greater than or equal to 1.

9. A submersible pump according to claim 5, characterized in that: The pump shaft (3) and the impeller (41) are installed by a cold installation method; when the material expansion coefficient of the pump shaft (3) is at least one order of magnitude higher than the material expansion coefficient of the impeller (41), when the pump shaft (3) and the impeller (41) are installed, the ratio of the interference amount to the assembly clearance is (1.8-2):

1.

10. A submersible pump according to claim 5, characterized in that: The pump body (2) comprises an upper shell (21) and a lower shell (22), and the inner wall of the upper shell (21) is connected to the outer wall of the lower shell (22) in a stepped sealing manner.

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