Double-shell multi-stage centrifugal pump

Abstract

The utility model discloses a double-shell multistage centrifugal pump, an inner shell is formed by enclosing a first shell and a second shell which are detachable and is arranged in an outer shell, a rotor part is arranged in the inner shell, and the first shell and the second shell are detached, so that the whole rotor part can be taken out and is convenient to disassemble, assemble and maintain; a first-stage impeller in the rotor component is composed of double-suction impellers, the inlet flow speed of fluid can be reduced so as to improve the cavitation resistance, then the first-stage impeller is matched with a first set of impellers and a second set of impellers which are composed of symmetrically-distributed single-suction impellers, the hydraulic loss in the pump can be reduced, and therefore the overall efficiency of the pump is improved, and the axial force is balanced; a transition flow channel formed in the inner shell is of a symmetrical double-volute structure, the structure is simple, the casting cost is low, fluid can be evenly distributed into the two volutes, radial force is effectively reduced and balanced, noise and vibration of the pump are reduced, non-uniformity of fluid flowing is reduced, and the efficiency of the pump and the operation stability and reliability of the pump are improved.

Description

Technical Field

[0001] This utility model relates to the field of centrifugal pump technology, specifically to a double-casing multistage centrifugal pump. Background Technology

[0002] Multistage centrifugal pumps are mainly used to transport high-temperature, high-pressure, easily crystallizing, and highly corrosive chemical media. They typically employ a segmental multistage pump design, such as the double-casing multistage centrifugal pump disclosed in Chinese Patent No. CN 213298290 U. This pump features a segmental pump core and a cylindrical outer casing. Both the suction and discharge pipes are vertically upward, and the pump is supported horizontally along its centerline. The casing sealing ring is embedded in the middle section and spot-welded. After dynamic balancing, the rotor assembly is sequentially fitted with guide vanes and the middle section, secured with connecting screws. The suction section and rear pump cover are positioned using a stop and fixed with connecting screws, forming a unified assembly with the rotor for easy disassembly and maintenance. However, in the aforementioned double-casing multistage pump, the impellers are arranged in the same direction, resulting in low overall pump efficiency and poor cavitation performance.

[0003] Based on this, Chinese patent application CN 118242314 A discloses a dual-casing multistage centrifugal pump. The pump casing includes a base shell and a first-stage guide impeller assembly and a second-stage guide impeller assembly arranged back-to-back. Both the first-stage and second-stage guide impeller assemblies include two or more guide impellers. The two axial end faces of the guide impellers are respectively provided with a forward flow channel and a reverse flow channel. Adjacent forward and reverse flow channels are connected step-by-step in the axial direction and each includes four volutes spaced circumferentially along the guide impeller. The first-stage guide impeller assembly also includes an outlet guide vane for connecting to the impeller outlet and having four volutes spaced circumferentially along its length. The base shell is provided with four transition flow channels. One end of each of the four transition flow channels is connected to one of the four volutes of the outlet guide vane, and the other end is used to connect to the inlet of the first-stage impeller corresponding to the second-stage guide impeller assembly, thereby achieving high head performance of the multistage centrifugal pump.

[0004] However, in the dual-casing multistage centrifugal pump provided by the above solution, the transition channel adopts a 4-volute structure, which is complex. This not only increases the manufacturing and assembly cost, but also makes the flow path of the fluid in the transition channel more complex, increases the fluid resistance, thereby reducing the hydraulic efficiency of the pump, increasing the risk of cavitation in the pump, and causing uneven radial force distribution in the pump.

[0005] Therefore, how to simplify the structure of multistage centrifugal pumps, making them easy to manufacture, disassemble, and maintain, while effectively balancing axial and radial forces and improving their cavitation resistance and efficiency, has become a problem that needs to be solved in this field. Utility Model Content

[0006] In view of the shortcomings of the existing technology, the purpose of this utility model is to provide a double-casing multistage centrifugal pump with a simple structure that is easy to disassemble and maintain, so as to effectively balance axial force and radial force, and improve cavitation resistance and efficiency.

[0007] To achieve the above objectives, the present invention provides a dual-casing multistage centrifugal pump, comprising a casing, a core assembly and a rotor assembly disposed within the casing, and a suction flange and a discharge flange connecting the casing.

[0008] The core package component includes an inner shell, which is formed by a detachable first shell and a second shell. The first shell and the second shell cooperate to form a transition channel within the inner shell. The transition channel is configured as a symmetrical double-volute structure, with short transition channels formed on both sides and a long transition channel formed in the middle region.

[0009] The rotor component includes a pump shaft disposed in the inner housing and an impeller assembly disposed on the pump shaft. The impeller assembly includes a first-stage impeller distributed at the end of the transition channel, and a first group of impellers and a second group of impellers symmetrically distributed on both sides of the transition channel. A balancing drum is provided between the first group of impellers and the second group of impellers. The first-stage impeller is composed of a double-suction impeller. The first group of impellers and the second group of impellers are composed of a plurality of single-suction impellers with opposite suction ports. The suction ports of the first group of impellers face the first-stage impeller, and the suction ports of the second group of impellers face away from the first-stage impeller.

[0010] Furthermore, the outer casing includes an outer cylinder and a pump cover, the pump cover having a balance pipe extending to the suction flange.

[0011] Furthermore, the balancing drum is configured with a spiral sealing structure.

[0012] Furthermore, a weight-reducing cavity is formed in the inner shell corresponding to the middle region of the transition channel.

[0013] Furthermore, the cross-section of the transition channel is configured as rectangular, and the edges are configured as rounded corners.

[0014] Furthermore, a middle section is provided between adjacent impellers in the first group of impellers and the second group of impellers, and a first-stage sealing bushing is provided between the second-stage impeller in the first group of impellers that cooperates with the first-stage impeller and the first-stage impeller.

[0015] Furthermore, the final stage impeller in the second group of impellers is configured to be threadedly connected to the final stage impeller in the first group of impellers.

[0016] Furthermore, the pump shaft is provided with a retaining ring groove, and an impeller retaining ring is placed in the retaining ring groove. The pump shaft is connected to the impeller assembly by a key, and the impeller assembly is axially positioned by the impeller retaining ring.

[0017] Furthermore, the transition channels in the corresponding regions of the first group of impellers and the second group of impellers are configured as short transition channels, and the transition channel between the last stage impeller of the first group of impellers and the first stage impeller of the second group of impellers is configured as a long transition channel.

[0018] Furthermore, the length Y of the transition channel, the length X of the short transition channel, and the distance C between the last stage impeller of the first group of impellers and the first stage impeller of the second group of impellers are configured as Y = 4.5X + C.

[0019] The dual-casing multistage centrifugal pump provided by this utility model has an inner casing set inside the outer casing. The inner casing is formed by a detachable first casing and a second casing, and the rotor component is set inside the inner casing. This allows the rotor component to be removed as a whole for maintenance by separating the first casing and the second casing, making the dual-casing multistage centrifugal pump easy to disassemble and maintain.

[0020] Furthermore, the first-stage impeller in the rotor assembly is composed of a double-suction impeller. Under the same flow rate, the first-stage impeller can reduce the inlet velocity of the fluid to improve cavitation resistance. Combined with the first and second sets of impellers composed of symmetrically distributed single-suction impellers, it can reduce the hydraulic losses inside the pump, thereby improving the overall efficiency of the pump. A balancing drum is also provided between the first and second sets of impellers. When the fluid flows through the balancing drum, a pressure difference is generated before and after the balancing drum, thereby generating a force opposite to the axial force. This allows the first-stage impeller to effectively balance the axial force of this double-casing centrifugal pump in conjunction with the first and second sets of impellers.

[0021] Meanwhile, the transition channel formed inside the inner casing is a symmetrical double volute structure, which is simple in structure, has low casting cost, and simplifies the fluid flow path. After the fluid passes through the rotor components, the transition channel can evenly distribute the fluid into the two volutes, effectively reducing and balancing the radial force, reducing pump noise and vibration, and reducing the non-uniformity of fluid flow, further improving pump efficiency, thereby improving the operational stability and reliability of this double-casing centrifugal pump.

[0022] The inner casing, transition channel, first-stage impeller, first set of impellers, and second set of impellers thus form a double-casing multi-stage centrifugal pump that is easy to disassemble and maintain, effectively balances axial and radial forces, and improves cavitation resistance and efficiency. Attached Figure Description

[0023] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0024] Figure 1A schematic diagram of the overall structure of the double-casing multistage centrifugal pump provided by this utility model;

[0025] Figure 2 A cross-sectional view of the double-casing multistage centrifugal pump provided by this utility model;

[0026] Figure 3 This is a schematic diagram of the mating structure between the inner shell and the rotor component in this utility model;

[0027] Figure 4 This is a schematic diagram of the rotor component in this utility model;

[0028] Figure 5 and Figure 6 This is a schematic diagram of the transition channel in this utility model.

[0029] Figure label:

[0030] 100. Outer casing; 110. Outer cylinder; 120. Pump cover; 130. Balance pipe;

[0031] 200. Core package component; 210. Inner shell; 211. First shell; 212. Second shell; 213. Weight reduction cavity; 220. Transition channel; 221. Short transition channel; 222. Long transition channel; 223. First stage channel;

[0032] 300. Rotor assembly; 310. Pump shaft; 320. Impeller assembly; 321. First stage impeller; 322. First group of impellers; 3221. Second stage impeller; 3222. First group of impellers and last stage impeller; 323. Second group of impellers; 3231. Second group of impellers and last stage impeller; 3232. Second group of impellers and first stage impeller; 324. Intermediate section; 325. First stage sealing bushing; 330. Balancing drum;

[0033] 400. Suction flange; 500. Extrusion flange. Detailed Implementation

[0034] To make the technical means, creative features, objectives and effects of this utility model easier to understand, the following description, in conjunction with specific illustrations, further elaborates on this utility model.

[0035] See Figure 1 and Figure 2 The illustration shows an example of a double-casing multistage centrifugal pump provided by this utility model.

[0036] As shown in the figure, the dual-casing multistage centrifugal pump in this example mainly includes a casing 100, a core assembly 200 and a rotor assembly 300 disposed in the casing 100, and a suction flange 400 and a discharge flange 500 connected to the casing 100.

[0037] The core assembly 200 includes an inner housing 210, which is formed by a detachable first housing 211 and a second housing 212. This allows the rotor assembly 300 to be removed as a whole for maintenance by separating the first housing 211 and the second housing 212, making this dual-housing multistage centrifugal pump easy to disassemble and maintain.

[0038] Meanwhile, the first housing 211 and the second housing 212 cooperate within the inner housing 210 to form a transition channel 220. The transition channel 220 is configured as a symmetrical double volute structure, with short transition channels 221 formed on both sides and a long transition channel 222 formed in the middle region. This makes the transition channel 220 simple in structure, with low casting cost, and also simplifies the fluid flow path. After the fluid passes through the rotor component 300, the transition channel 220 can evenly distribute the fluid into the two volutes, effectively reducing and balancing radial forces, reducing pump noise and vibration, and reducing the non-uniformity of fluid flow, thereby improving pump efficiency and improving the operational stability and reliability of this double-casing centrifugal pump.

[0039] Furthermore, the rotor component 300 includes a pump shaft 310 disposed in the inner housing 210 and an impeller assembly 320 disposed on the pump shaft 310. The impeller assembly 320 includes a first-stage impeller 321 distributed at the end of the corresponding transition channel 220, and a first set of impellers 322 and a second set of impellers 323 symmetrically distributed on both sides of the corresponding transition channel 220. The first-stage impeller 321 is composed of a double-suction impeller, which allows the first-stage impeller 321 to reduce the inlet velocity of the fluid at the same flow rate, thereby improving cavitation resistance. In terms of performance, the first impeller 322 and the second impeller 323 are composed of single-suction impellers with opposite suction inlets, which can reduce the hydraulic loss inside the pump and thus improve the overall efficiency of the pump. A balance drum 330 is also provided between the first impeller 322 and the second impeller 323. When the fluid flows through the balance drum, a pressure difference will be generated before and after the balance drum, thereby generating a force opposite to the axial force. This allows the first impeller 321 to work in conjunction with the first impeller 322 and the second impeller 323 to effectively balance the axial force of this double-casing centrifugal pump.

[0040] The inner casing 210, transition channel 220, first-stage impeller 321, first group of impellers 322 and second group of impellers 323 thus cooperate to realize that the double-casing multi-stage centrifugal pump is easy to disassemble and maintain, effectively balances axial and radial forces, and improves cavitation resistance and efficiency.

[0041] The outer shell 100 mainly includes an outer cylinder 110 and a pump cover 120. The outer cylinder 100 has a cavity inside that accommodates the core package component 200 and the rotor component 300, and the pump cover 120 is provided at the end of the outer cylinder 100 for sealing.

[0042] Furthermore, the outer cylinder 110 is provided with an intake flange 400 and an outlet flange 500 that connect the internal core package component 200 and the rotor component 300. Preferably, the intake flange 400 and the outlet flange 500 are arranged side by side above the outer cylinder 110, and the intake flange 400 is located at the end of the outer cylinder 110, so that the intake flange 400 can cooperate with the rotor component 300 located inside the outer cylinder 110. Fluid enters the rotor component 300 from the intake flange 400, and is discharged from the outlet flange 500 after being pressurized by the rotation of the rotor component 300.

[0043] To facilitate disassembly and maintenance of the rotor assembly 300, the core package 200 inside the outer shell 100 mainly includes an inner shell 210. The rotor assembly 300 is placed in the inner shell 210, so that the inner shell 210 and the outer shell 100 cooperate to form a double shell. After the pump cover 120 is removed from the outer shell 100, the inner shell 210 can be directly pulled out from the outer shell 100 as a whole, which is convenient for disassembly and maintenance.

[0044] Furthermore, combined Figure 3 The inner shell 210 is formed by a detachable first shell 211 and a second shell 212. The first shell 211 and the second shell 212 are symmetrically distributed in the upper and lower regions of the outer shell 100 and are configured as a horizontal split structure, so that after the first shell 211 and the second shell 212 are separated, the rotor component 300 can be directly removed from the inner shell 210, which facilitates the maintenance of the rotor component 300.

[0045] In order to enable the inner housing 210 to cooperate with the rotor component 300, and to form a smooth and simple flow path when the fluid rotates through the rotor component 300 in the inner housing 210, the first housing 211 and the second housing 212 cooperate to form a transition channel 220 in the inner housing 210. The transition channel 220 is configured as a symmetrical double volute structure, so that when the fluid rotates through the rotor component 300, the transition channel 220 can guide the fluid to be evenly distributed into the two volutes, effectively reducing and balancing the radial force.

[0046] In conjunction with this, Figure 1 and Figure 2 The rotor component 300 is disposed in the inner housing 210, including the pump shaft 310 and the impeller assembly 320 disposed on the pump shaft 310. The impeller assembly 320 is distributed in cooperation with the transition flow channel 220 to guide the fluid to flow uniformly.

[0047] Specifically, the pump shaft 310 is provided with a retaining ring groove, in which an impeller retaining ring is placed. The pump shaft 310 is connected to the impeller assembly 320 by a key, and the impeller assembly 320 is axially positioned by the impeller retaining ring, so as to ensure a stable connection between the pump shaft 310 and the impeller assembly 320.

[0048] Furthermore, the impeller assembly 320 includes a first-stage impeller 321, a first group of impellers 322, and a second group of impellers 323. The first-stage impeller 321 is distributed at the end of the corresponding transition channel 220 and corresponds to the inlet flange 400, so that the fluid enters the first-stage impeller 321 from the inlet flange 400 and is pressurized by the rotation of the first-stage impeller 321.

[0049] Meanwhile, the first set of impellers 322 and the second set of impellers 323 are symmetrically distributed on both sides of the corresponding transition channel 220, and the outlet of the first set of impellers 322 corresponds to the outlet of the first stage impeller 321, so that after the fluid flows out of the first stage impeller 321, it enters the first set of impellers 322, and then flows out of the first set of impellers 322 and enters the second set of impellers 323, so that the first stage impeller 321, the first set of impellers 322 and the second set of impellers 323 work together to continuously drive the fluid to rotate and pressurize, and then discharge it from the discharge flange 500.

[0050] As a result, the pressures on both sides of the impeller assembly 320 are different, forming a low-pressure area at the suction flange 400 and a high-pressure area at the inlet of the second impeller 323. The inlet end of the second impeller 323 is equipped with a mechanical seal. In order to reduce the pressure in the sealing cavity, the pump cover 120 is also equipped with a balance pipe 130. One end of the balance pipe 130 extends through the pump cover 120 to the inlet of the second impeller 323, and the other end extends to the suction flange 400, so that the balance pipe 130 forms a fluid channel, which can effectively balance the pressure in the high-pressure area, thereby reducing the pressure in the sealing cavity.

[0051] Furthermore, combined Figure 4 The first-stage impeller 321 is composed of double-suction impellers. The first group of impellers 322 and the second group of impellers 323 are composed of several single-suction impellers with opposite suction ports. The suction ports of the single-suction impellers of the first group of impellers 322 face the first-stage impeller 321, while the suction ports of the single-suction impellers of the second group of impellers 323 face away from the first-stage impeller 321. This allows the fluid to enter the first-stage impeller 321 first. The double-suction impellers can reduce the inlet velocity of the fluid, thereby reducing the pressure of the fluid at the inlet of the first-stage impeller 321 and reducing the occurrence of cavitation.

[0052] Next, the fluid flows out from the first impeller 321 and then enters the first impeller 322 and the second impeller 323 in sequence. Since the first impeller 322 and the second impeller 323 are symmetrically distributed and have opposite suction ports, the first impeller 322 and the second impeller 323 will generate opposite axial forces, thereby achieving axial force self-balancing of the pump.

[0053] Specifically, adjacent single-suction impellers in the first group of impellers 322 and the second group of impellers 323 are separated by a middle section 324. A first-stage sealing bushing 325 is provided between the second-stage impeller 3221 (the first-stage impeller of the first group of impellers 322) that cooperates with the first-stage impeller 321 in the first group of impellers 322 and the first-stage impeller 321. The first-stage sealing bushing 325 separates the second-stage impeller 3221 from the first-stage impeller 321, so that the middle section 324 and the first-stage sealing bushing 325 can cooperate to prevent the fluid at the outlet end of the upper impeller from flowing directly into the inlet of the lower impeller. The fluid can enter the lower impeller through the transition channel 220. At the same time, the middle section 324 and the first-stage sealing bushing 325 can also play a wear-resistant role, avoiding direct contact damage between the impeller and the pump body, and making replacement convenient.

[0054] Therefore, combined Figure 4 The arrow points to the direction of the fluid flow path. Along the fluid flow path, each impeller in the impeller assembly 320 forms a first-stage impeller 321, a second-stage impeller 3221, ..., an Nth-stage impeller (i.e., the last-stage impeller of the second group of impellers 3231). The fluid flows evenly through each impeller and is pressurized before being discharged from the discharge flange 500.

[0055] The second impeller 3231 and the first impeller 3222 are connected by a threaded connection, which makes the second impeller 3231 and the first impeller 3222 tightly connected and not prone to leakage.

[0056] Furthermore, combined Figure 2 Between the first impeller 322 and the second impeller 323, i.e., between the last stage impeller 3222 of the first impeller and the last stage impeller 3231 of the second impeller, a balance drum 330 is provided. The balance drum 330 is configured as a spiral sealing structure. Compared with the existing labyrinth seal, the leakage is small, and the spiral seal is a non-contact seal with a long service life and low installation accuracy requirements.

[0057] Meanwhile, when the fluid flows through the balance drum 330, the rotation of the first set of impellers 322 and the second set of impellers 323 will drive the fluid to rotate synchronously around the balance drum 330, thereby generating a pressure difference before and after the balance drum 330, generating a force opposite to the axial force, further balancing the axial force of the pump. This can prevent the pump shaft 310 from bending or deforming under the action of axial force, thereby protecting the mechanical parts of the pump, extending the service life of the pump, and improving the operating efficiency and stability of the pump.

[0058] The combination of the first-stage impeller 321, the first set of impellers 322, and the second set of impellers 323 can reduce the risk of cavitation while effectively balancing axial forces.

[0059] Combination Figure 5 and Figure 6In order to enable the impeller assembly 320 to cooperate with the transition channel 220, and to enable the transition channel 220 to guide the fluid to enter the first impeller 321, the first group of impellers 322 and the second group of impellers 323 evenly, short transition channels 221 are formed on both sides of the transition channel 220. The short transition channels 221 are configured as a continuous spiral structure. The first group of impellers 322 and the second group of impellers 323 are respectively distributed in the short transition channels 221, so that the short transition channels 221 can guide the fluid to flow between the multiple single-suction impellers in the first group of impellers 322 and the second group of impellers 323.

[0060] Furthermore, the short transition channels 221 on both sides cooperate to form a symmetrical double volute structure, which allows the short transition channels 221 to evenly distribute the fluid into the two volutes, effectively reducing and balancing the radial force and improving the pump efficiency.

[0061] Meanwhile, a long transition channel 222 is formed in the middle region of the transition channel 220. The long transition channel 222 is configured to connect the outlet of the first impeller 322 and the inlet of the second impeller 323, so that the long transition channel 222 can guide the fluid from the outlet of the first impeller 322 into the inlet of the second impeller 323, thereby realizing the continuous flow of fluid in the impeller assembly 320, reducing flow loss and improving pump efficiency.

[0062] Furthermore, the transition channel 220 has a rectangular cross-section and rounded edges to form a smooth flow channel, which can effectively reduce the non-uniformity of fluid flow, reduce turbulence, thereby reducing hydraulic losses and improving pump efficiency.

[0063] As a preferred configuration, combined with Figure 6 The length Y of the long transition channel 222 and the length X of the short transition channel 221, as well as the distance C from the outlet of the first impeller 322 to the inlet of the second impeller 323 (the distance between the last stage impeller 3222 of the first impeller group and the first stage impeller 3232 of the second impeller group), are matched and configured as Y = 4.5X + C, so that the long transition channel 222 and the short transition channel 221 can be precisely distributed and cooperate with each other to guide the fluid to flow continuously and uniformly between the impeller assemblies 3.

[0064] Specifically, in combination Figure 5 and Figure 6Along the fluid flow path, the transition channel 220 forms a first-stage channel 223 at the first-stage impeller 321, and second-stage channels corresponding to the second and third-stage impellers are formed at the first group of impellers 322 and the second group of impellers 323, respectively; third-stage channels corresponding to the third and fourth-stage impellers, ... and N-1-stage channels corresponding to the (N-1)th and Nth-stage impellers, respectively. The channels in the regions corresponding to the first group of impellers 322 and the second group of impellers 323 are short transition channels. The first group of impellers has a final-stage impeller 3222, and the second group of impellers has a first-stage impeller 3232. The flow channel between them is a long transition channel, which allows the fluid to first enter the first-stage impeller 321 from the suction flange 400. The first-stage impeller 321 drives the fluid to rotate, increasing the fluid's kinetic and potential energy. After the fluid flows out, the first-stage flow channel 223 guides the fluid into the first set of impellers 322. The fluid is then rotated and pressurized by the impeller corresponding to the first set of impellers 322 and flows out. Then, it flows from the outlet of the first set of impellers 322 into the suction port of the second set of impellers 323 through the long transition channel. Finally, it is rotated and pressurized by the impeller corresponding to the second set of impellers 322 and flows out through the discharge flange 500.

[0065] As an example, in this instance, the first group of impellers 322 and the second group of impellers 323 in the impeller assembly 320 each include five single-suction impellers and are symmetrically distributed. Correspondingly, the transition flow channel 220 includes ten flow channels corresponding to the single-suction impellers in the first group of impellers 322 and the second group of impellers 323.

[0066] The second to fifth stage flow channels in the region corresponding to the first group of impellers 322, and the seventh to tenth stage flow channels in the region corresponding to the second group of impellers 323 are configured as short transition flow channels, while the sixth stage flow channel between the last stage impeller 3222 (i.e., the sixth stage impeller) of the first group of impellers and the first stage impeller 3232 (i.e., the seventh stage impeller) of the second group of impellers is configured as a long transition flow channel.

[0067] Thus, under a given pressure, the fluid enters the inner casing 210 through the suction flange 400. After its kinetic and potential energy is increased by the first-stage impeller 321 of the rotor assembly 300, it passes through the first-stage flow channel 223, where most of its kinetic energy is converted into potential energy. Next, the fluid enters the second-stage impeller of the first group of impellers 322 through the first-stage flow channel 223, and then flows through the second to fifth-stage flow channels of the first group of impellers 322 for pressurization. Subsequently, the fluid enters the suction port of the second group of impellers 323 through the sixth-stage flow channel, i.e., the long transition flow channel, and then enters the seventh-stage impeller. It then flows through the seventh to tenth-stage flow channels of the second group of impellers 323 for pressurization, and finally exits through the discharge flange 500.

[0068] The transition channel 220 and impeller assembly 320 thus form a cooperative system that guides the fluid to flow evenly through each impeller. The first-stage impeller 321 reduces the inlet velocity of the fluid, thereby reducing the pressure at the fluid inlet and reducing cavitation. During the flow process, the transition channel 220 reduces hydraulic losses, balances radial forces, and improves pump efficiency. At the same time, the first set of impellers 322 and the second set of impellers 323, which are opposite to each other at the suction inlet, can achieve self-balancing of axial forces.

[0069] Furthermore, in order to reduce the weight of the pump and facilitate its disassembly and assembly, a weight-reducing cavity 213 is provided inside the inner housing 210. The weight-reducing cavity 213 is configured as a hollow structure to reduce the amount of material used in the inner housing 210, thereby reducing the overall weight of the pump and facilitating the disassembly and assembly of the inner housing 210 and the movement of the pump body.

[0070] Preferably, the weight reduction chamber 213 is located in the middle region of the corresponding transition channel 220 to balance the center of gravity of the pump, reduce vibration and noise, and at the same time not affect the arrangement of the impeller assembly 320. As an example, the weight reduction chamber 213 can be formed by extending the transition channel 220 outward from the inner shell 210 to form an inner shell 210 with equal wall thickness.

[0071] In some embodiments, the weight reduction chamber 213 is configured in a streamlined shape to reduce fluid resistance in the transition channel 220, reduce hydraulic losses, and improve pump efficiency.

[0072] The dual-casing centrifugal pump provided by the present invention uses a detachable inner casing 210 to cooperate with the rotor component 300, so that the rotor component 300 can be removed as a whole, which is convenient for disassembly and maintenance. The transition flow channel 220 and the impeller assembly 320 simplify the fluid flow path, reduce hydraulic losses and improve pump efficiency. Furthermore, the first impeller 321 of the impeller assembly 320, together with the first group of impellers 322 and the second group of impellers 323, reduces the risk of cavitation while effectively balancing axial force.

[0073] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that this utility model is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this utility model. Various changes and modifications can be made to this utility model without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection of this utility model is defined by the appended claims and their equivalents.

Claims

1. A dual-casing multistage centrifugal pump, comprising a casing, a core assembly and a rotor assembly disposed within the casing, and a suction flange and a discharge flange connecting the casing, characterized in that, The core package component includes an inner shell, which is formed by a detachable first shell and a second shell. The first shell and the second shell cooperate to form a transition channel within the inner shell. The transition channel is configured as a symmetrical double-volute structure, with short transition channels formed on both sides and a long transition channel formed in the middle region. The rotor component includes a pump shaft disposed in the inner housing and an impeller assembly disposed on the pump shaft. The impeller assembly includes a first-stage impeller distributed at the end of the transition channel, and a first group of impellers and a second group of impellers symmetrically distributed on both sides of the transition channel. A balancing drum is provided between the first group of impellers and the second group of impellers. The first-stage impeller is composed of a double-suction impeller. The first group of impellers and the second group of impellers are composed of a plurality of single-suction impellers with opposite suction ports. The suction ports of the first group of impellers face the first-stage impeller, and the suction ports of the second group of impellers face away from the first-stage impeller.

2. The dual-casing multistage centrifugal pump according to claim 1, characterized in that, The outer casing includes an outer cylinder and a pump cover, the pump cover having a balance pipe extending to the suction flange.

3. The dual-casing multistage centrifugal pump according to claim 1, characterized in that, The balancing drum is configured with a spiral sealing structure.

4. The dual-casing multistage centrifugal pump according to claim 1, characterized in that, A weight-reducing cavity is formed in the middle region of the inner shell corresponding to the transition channel.

5. The dual-casing multistage centrifugal pump according to claim 1, characterized in that, The transition channel has a rectangular cross-section and rounded edges.

6. The dual-casing multistage centrifugal pump according to claim 1, characterized in that, A middle section is provided between adjacent impellers in the first group of impellers and the second group of impellers, and a first-stage sealing bushing is provided between the second-stage impeller in the first group of impellers that cooperates with the first-stage impeller and the first-stage impeller.

7. The dual-casing multistage centrifugal pump according to claim 1, characterized in that, The last stage impeller in the second group of impellers is connected to the last stage impeller in the first group of impellers by a threaded connection.

8. The dual-casing multistage centrifugal pump according to claim 1, characterized in that, The pump shaft is provided with a retaining ring groove, and an impeller retaining ring is placed in the retaining ring groove. The pump shaft is connected to the impeller assembly by a key, and the impeller assembly is axially positioned by the impeller retaining ring.

9. The dual-casing multistage centrifugal pump according to claim 1, characterized in that, The transition channels in the corresponding regions of the first group of impellers and the second group of impellers are configured as short transition channels, and the transition channel between the last stage impeller of the first group of impellers and the first stage impeller of the second group of impellers is configured as a long transition channel.

10. The dual-casing multistage centrifugal pump according to claim 9, characterized in that, The length Y of the transition channel, the length X of the short transition channel, and the distance C between the last stage impeller of the first group of impellers and the first stage impeller of the second group of impellers are configured such that Y = 4.5X + C.

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