Interstage flow channel structure of multistage volute centrifugal pump

Abstract

The multistage volute centrifugal pump interstage flow channel structure comprises a pump shell which is horizontally and axially split, and an inner cavity of the pump shell comprises a plurality of interstage flow channels which are connected in series; the interstage flow channel comprises a pumping chamber, two symmetrical diffusion sections and a water outlet ring cavity; fluid is thrown out by the impeller to enter the pumping chamber, enters the two diffusion sections from the left horizontal position and the right horizontal position from the pumping chamber, spirally flows forwards in the diffusion sections in the circumferential direction and the axial direction, and enters the vertical extension sections at the tail ends of the diffusion sections after rotating by 90 degrees in the circumferential direction, and the vertical extension sections extend towards the water outlet ring cavity and are tangentially communicated with the water outlet ring cavity. The inner wall, corresponding to the water outlet ring cavity, of the pump shell is provided with two partition pieces extending into the water outlet ring cavity in a protruding mode, the two partition pieces are located on the same vertical face and are vertically opposite, the water outlet ring cavity is divided into a left semi-ring cavity and a right semi-ring cavity which are symmetrical, and the diffusion section communicates with the semi-ring cavities on the opposite sides in the left-right direction in a tangent mode. In the structure, fluid flows more smoothly and reasonably, the impact is small, the energy loss is low, and the efficiency is higher.

Description

Technical Field

[0001] The invention belongs to the technical field of centrifugal pumps in non-variable displacement pumps, and in particular relates to an inter-stage flow channel structure of a multi-stage volute centrifugal pump. Background Art

[0002] Multi-stage volute centrifugal pumps mostly adopt an axially split structure. The fluid is sucked in from the water inlet of the pump, and after being pressurized by the impellers at each stage, it is pumped out from the water outlet to achieve the purpose of conveying the fluid. When working, the impeller rotates at high speed, and the fluid is thrown to the outer edge of the impeller under the action of centrifugal force, and enters the water outlet ring cavity through the pressure chamber and the diffusion section. The water outlet ring cavity is also the water suction chamber of the lower impeller, and so on. Therefore, the internal cavity in the pump casing is actually connected by multiple interstage flow channels (also called transition flow channels). The interstage flow channels include the aforementioned pressure chamber, diffusion section and water outlet ring cavity. The pressure chamber is connected to the water outlet ring cavity (the water suction chamber of the lower impeller) through the diffusion section.

[0003] The water outlet ring cavity currently in use is circular, see Figure 7 , divided into an upper half and a lower half by left and right spacers 5 (the position of the spacers is shown in the figure, not a solid entity). The diffusers 3 are two symmetrical ones, starting from the left and right horizontal positions respectively. The fluid enters the diffuser 3 from the water pressure chamber 2, and flows in spirals along the circumferential and axial directions in the two diffusers 3. After turning a certain circumferential angle, each passes through a roughly vertical connecting flow channel with the same width as the diameter of the outlet ring cavity 4, allowing the fluid to enter the upper and lower halves of the outlet ring cavity 4 from the top and bottom of the outlet ring cavity 4 respectively, and be sucked into the next-stage impeller. Since the connecting flow channel is wide, in order to ensure the flow state of the fluid, a diverter rib 6 (the position of the diverter rib is shown in the figure, not a solid entity) is also provided in the middle of the connecting flow channel. The left and right spacers are arranged in the horizontal direction, perpendicular to the flow direction of the fluid. While being subjected to a large impact force, they disrupt the fluidity of the fluid, making it easy for vortices to form, resulting in large impact losses. As a suspended wall, the spacer is also easily damaged and deformed by the impact of the fluid. See also Figure 8 During manufacturing, the left and right spacers are arranged horizontally and located on the center open surface of the axially divided pump casing. They are separately manufactured parts and are assembled to the pump casing. The grooves and positioning pin holes for the spacers 5 (position diagram, not solid) must be processed and installed on the center open surfaces of the upper and lower shells for coordination and installation. To a certain extent, the integrity of the center open surface is destroyed and the effective sealing area on the center open surface is affected.

[0004] There is also a transition channel structure of a multi-stage centrifugal pump disclosed in CN107035720A, which uses a separate expansion section and connects to a fully spiral water outlet ring cavity, making the pump structure compact and the fluid stable. However, it is not suitable for the aforementioned symmetrical expansion section form. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the technical problem to be solved by the present invention is to provide an interstage flow channel structure of a multi-stage volute centrifugal pump to avoid the problems of unstable flow state of the fluid in the interstage flow channel (water outlet ring cavity), possible vortex and large fluid energy loss, thereby achieving the effect of reducing energy loss and improving efficiency.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions: A multi-stage volute centrifugal pump interstage flow channel structure, including a horizontally axially split pump casing, an inner cavity is formed in the pump casing, and the inner cavity includes a plurality of interstage flow channels connected in series; the interstage flow channel includes a pressure water chamber, a diffusion section and a water outlet annular cavity, and the diffusion sections are two symmetrical ones; the fluid is thrown out by an impeller and enters the pressure water chamber, and enters the two diffusion sections from the pressure water chamber from the left and right horizontal positions respectively, flows forward in a spiral shape along the circumferential direction and the axial direction in the diffusion section, and enters the vertical extension section at the end of the diffusion section after a 90° circumferential rotation, and the vertical extension section extends toward the water outlet annular cavity and is tangentially connected to the water outlet annular cavity; a protrusion on the inner wall of the pump casing corresponding to the water outlet annular cavity is provided with two spacers extending into the water outlet annular cavity, and the two spacers are located on the same vertical plane and are opposite to each other up and down, and the water outlet annular cavity is divided into two symmetrical left and right semi-annular cavities, and the diffusion section is tangentially connected to the semi-annular cavity on the opposite side in the left and right directions.

[0007] To further improve the above technical solution, the width of the vertical extension section corresponds to the radius of the water outlet annular cavity.

[0008] Furthermore, the spacer and the axially split half of the pump casing are an integrally formed structure.

[0009] Furthermore, the end of the diffusion section is connected to the vertical extension section through a smooth transition of a 90° arc section.

[0010] Compared with the prior art, the present invention has the following beneficial effects: The multi-stage volute centrifugal pump interstage flow channel structure of the present invention is that when the impeller rotates, the fluid is sucked into the upper water outlet ring cavity by the impeller, and then thrown out by the impeller to the water pressure chamber and divided into two diffusion sections. In the circumferential direction, the fluid flows in the two diffusion sections in a spiral shape along the circumferential direction and the axial direction respectively. The end of the diffusion section is tangent to the semi-ring cavity of the water outlet ring cavity on the opposite side through the vertical extension section. The fluid is tangentially introduced into the (lower) water outlet ring cavity and is quickly sucked into the next-stage impeller in the left and right halves of the water outlet ring cavity respectively. The flow is smoother and more reasonable, the probability of vortexes appearing in the water outlet ring cavity is greatly reduced, the loss is smaller under small flow conditions, and the efficiency is higher.

[0011] The spacer is arranged in the vertical direction, parallel to the direction of the fluid entering the water outlet annular cavity, dividing the water outlet annular cavity into two vertical halves, which conforms to the flow law, has small impact, less disturbance, and reduces fluid energy loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1A schematic structural diagram of a multi-stage volute centrifugal pump according to an embodiment; Figure 2 for Figure 1 Bottom view of Figure 3 for Figure 1 Stereoscopic image of Figure 4 for Figure 3 Middle AA section (only the axially split upper pump casing is shown); Figure 5 This is a schematic diagram of the interstage flow passage structure of a multi-stage volute centrifugal pump of an embodiment, in which the interstage flow passage space is converted into a physical expression; Figure 6 for Figure 5 Front view of the interstage flow passage space entity expression; Figure 7 A schematic diagram of the entity expression of the interstage flow channel structure mentioned in the background technology; Figure 8 A schematic diagram of the installation position of the spacer mentioned in the background technology; Among them, there are a pump casing 1, a water pressure chamber 2, a diffusion section 3, an arc section 31, a vertical extension section 32, a water outlet annular cavity 4, a semi-annular cavity 41, a spacer 5, and a diverter rib 6. DETAILED DESCRIPTION

[0013] The specific implementation modes of the present invention will be further described in detail below in conjunction with the accompanying drawings.

[0014] See also Figure 1-Figure 6 A multi-stage volute centrifugal pump inter-stage flow channel structure of a specific embodiment includes a horizontally axially split pump casing 1, the pump casing 1 has a water inlet and a water outlet, the first stage inside the water inlet is a double-suction impeller, water is sucked on both sides and thrown out to the three-stage series-connected single-suction impellers in the same direction for step-by-step pressurization, and then the water is discharged to the suction chamber of the three-stage series-connected single-suction impeller in the opposite direction, and then the water is pumped out from the water outlet after step-by-step pressurization through the three-stage series-connected single-suction impeller in the opposite direction.

[0015] The inner cavity of the pump casing 1 includes a plurality of interstage flow passages connected in series; the interstage flow passages include a water pressure chamber 2, a diffuser section 3 and a water outlet annular cavity 4, and there are two symmetrical diffuser sections 3; the fluid is thrown out by the impeller (not shown in the figure) and enters the water pressure chamber 2, and enters the two diffuser sections 3 from the left and right horizontal positions of the water pressure chamber 2, and flows forward in a spiral shape along the circumferential and axial directions in the diffuser section 3, and the cross-sectional area of ​​the diffuser section 3 gradually increases. After rotating 90° circumferentially, the fluid enters the vertical extension section 32 at the end of the diffuser section 3, and the vertical extension section 32 extends toward the water outlet annular cavity 4 and is tangentially connected to the water outlet annular cavity 4.

[0016] The inner wall of the pump housing 1 corresponding to the water outlet ring cavity 4 is provided with two spacers 5 ( Figure 5 , Figure 6 The two spacers 5 are located on the same vertical plane and face each other up and down, dividing the outlet annular cavity 4 into two symmetrical left and right semi-annular cavities 41. After the diffusion section 3 extends 90° in a spiral shape along the circumferential and axial directions, it is tangentially connected to the semi-annular cavity 41 on the opposite side in the left and right directions through the vertical extension section 32 at the end.

[0017] The spacer 5 and the axially split half of the pump housing 1 are an integrally formed structure, specifically, an integrally cast structure.

[0018] The interstage flow channel structure of the multi-stage volute centrifugal pump of the embodiment, when working, the impeller rotates, the fluid is sucked into the upper water outlet annular cavity 4 by the impeller, and then thrown out by the impeller to the water pressure chamber 2, and divided into two diffusion sections 3, the circumferential direction, the fluid flows in the two diffusion sections 3 in a spiral shape along the circumferential direction and the axial direction, the end of the diffusion section 3 is tangent to the semi-annular cavity 41 of the opposite side water outlet annular cavity 4 through the vertical extension section 32, and the fluid is tangentially introduced into the (lower) water outlet annular cavity 4. In implementation, the water outlet annular cavity 4 is slightly larger than the outer diameter of the impeller mouth ring, and the fluid flows vertically after passing through the two diffusion sections 3, and enters the water outlet annular cavity 4 from top to bottom, and is quickly sucked into the next stage impeller in the left and right halves of the water outlet annular cavity 4, respectively, so that the flow is smoother and more reasonable, the probability of vortex appearing in the water outlet annular cavity 4 is greatly reduced, the loss is smaller in the small flow condition, and the efficiency is higher. The spacer 5 is arranged in the vertical direction, parallel to the direction of the fluid entering the water outlet annular cavity 4, and divides the water outlet annular cavity 4 into two vertical halves, which conforms to the flow law, has small impact, less disturbance, and reduces fluid energy loss.

[0019] The width of the vertical extension section 32 corresponds to the radius of the water outlet annular cavity 4. The end of the diffusion section 3 is smoothly connected to the vertical extension section 32 through a 90° arc section 31. This can further avoid fluid energy loss and improve efficiency. The width of the vertical extension section 32 is smaller, so there is no need to Figure 8 The diverter rib 6 shown is easy to manufacture and reduces the difficulty of sand cleaning during casting.

[0020] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. An interstage flow passage structure of a multi-stage volute centrifugal pump, comprising a pump casing that is horizontally axially split, an inner cavity is formed in the pump casing, and the inner cavity comprises a plurality of interstage flow passages connected in series; Features: The interstage flow passage includes a pressure water chamber, a diffusion section and a water outlet annular cavity, and the diffusion sections are two symmetrical ones. The fluid is thrown out by the impeller and enters the pressure water chamber. From the pressure water chamber, the fluid enters the two diffusion sections from the left and right horizontal positions, flows forward in a spiral shape along the circumferential and axial directions in the diffusion section, and after turning 90 degrees in the circumferential direction, enters the vertical extension section at the end of the diffusion section. The vertical extension section extends toward the water outlet annular cavity and is tangentially connected to the water outlet annular cavity. The inner wall protrusion of the pump casing corresponding to the water outlet ring cavity is provided with two spacers extending into the water outlet ring cavity. The two spacers are located on the same vertical plane and opposite to each other up and down, dividing the water outlet ring cavity into two symmetrical left and right semi-ring cavities. The diffusion section is tangentially connected to the semi-ring cavities on the opposite sides in the left and right directions.

2. According to claim 1, a multi-stage volute centrifugal pump interstage flow channel structure, Features: The width of the vertical extension section corresponds to the radius of the water outlet annular cavity.

3. According to the inter-stage flow channel structure of a multi-stage volute centrifugal pump according to claim 1 or 2, Features: The partition is an integrally formed structure with the axially split half of the pump casing.

4. According to claim 1, a multi-stage volute centrifugal pump interstage flow channel structure, Features: The end of the diffusion section is connected to the vertical extension section through a smooth transition of a 90° arc section.

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