Permanent magnet variable frequency self-suction multi-stage centrifugal pump

Abstract

The application relates to the technical field of multistage centrifugal pumps, and discloses a permanent-magnet variable-frequency self-suction multistage centrifugal pump. The application comprises a permanent-magnet variable-frequency motor and a pump body provided with a water inlet and a water outlet, a guide vane group composed of an inlet guide vane and a plurality of impeller guide vanes is fixedly arranged in the pump body, a rotor fixedly connected with an output shaft of the permanent-magnet variable-frequency motor is rotatably arranged in the guide vane group, and an impeller fixedly connected with the rotor is arranged in each of the plurality of impeller guide vanes; a pressure cavity is formed between the guide vane group and the pump body, a backflow port for communicating the pressure cavity is arranged on the inlet guide vane, and a control valve is arranged in the backflow port. The structural relationship between the pump body and the guide vane group is improved, so that a composite pressure cavity is formed between the pump body and the guide vane group, the backflow port and the control valve are arranged between the pressure cavity and the inlet guide vane, a flow guarantee mechanism is formed, the total output flow of the centrifugal pump is ensured to be higher than the minimum continuous flow, and the cavitation at the inlet of the first-stage impeller is avoided from the root.

Description

Technical Field

[0001] This invention relates to the field of multistage centrifugal pump technology, and in particular to a permanent magnet variable frequency self-priming multistage centrifugal pump. Background Technology

[0002] Self-priming multistage centrifugal pumps, as a type of high-efficiency fluid transport equipment, ingeniously integrate self-priming functionality with multistage pressurization technology. Their core feature lies in the series connection of multiple specially designed first-stage impellers equipped with inducer wheels or special anti-cavitation structures. This allows for rapid self-priming, followed by a gradual increase in liquid pressure, ultimately achieving a head and outlet pressure far exceeding that of a single-stage centrifugal pump. This meets the demands of high-lift, stable water supply for applications such as high-rise building water supply and industrial processes.

[0003] However, in actual operation, the performance and reliability of this pump type are heavily constrained by the stability of the inlet operating conditions (water supply). Any abnormal fluctuations or malfunctions in the water supply pipeline (such as filter / screen blockage, valves not fully open, or foreign objects in the pipeline) will cause a sharp decrease in the effective net positive suction head (NPSHa) of the centrifugal pump. Because the pressure inside the centrifugal pump increases progressively from the inlet to the outlet, the inlet region of the first-stage impeller becomes the "weakest link" in the entire pump system with the lowest pressure. When the pressure here drops below the saturated vapor pressure of the pumped liquid, severe cavitation will occur.

[0004] Cavitation not only produces severe vibrations and noise, indicating abnormal equipment operation, but also causes continuous corrosive damage to the impeller (especially the first-stage impeller) material, leading to decreased efficiency and performance degradation, ultimately significantly shortening the service life of the centrifugal pump and increasing maintenance costs.

[0005] Therefore, it is necessary to propose a permanent magnet variable frequency self-priming multistage centrifugal pump that can better adapt to fluctuations in water supply pipelines. Summary of the Invention

[0006] To solve the above-mentioned technical problems, the present invention provides a permanent magnet variable frequency self-priming multistage centrifugal pump.

[0007] The present invention is achieved by the following technical solution: a permanent magnet variable frequency motor and a pump body with an inlet and an outlet. A guide vane group consisting of an inlet guide vane and multiple impeller guide vanes is fixedly installed inside the pump body. A rotor fixedly connected to the output shaft of the permanent magnet variable frequency motor is rotatably installed inside the guide vane group. Impellers fixedly connected to the rotor are installed inside the multiple impeller guide vanes.

[0008] A pressure chamber is formed between the guide vane assembly and the pump body. A return port for connecting the pressure chamber is provided on the inlet guide vane. A control valve is provided in the return port. The control valve includes a stop block provided on the inlet guide vane. A valve body is slidably provided on the stop block. A first spring with both ends abutting against the two is sleeved on the valve body.

[0009] When the pump body is unable to close the control valve due to insufficient water supply and the pressure in the pressure chamber weakens, the control valve opens, allowing the fluid in the pressure chamber to be diverted to the inlet guide vane through the return port, so that the pump body maintains a total output flow rate higher than the minimum continuous flow rate.

[0010] As a further improvement to the above solution, check valves are installed in both the inlet and outlet of the pump body.

[0011] As a further improvement to the above solution, the check valve includes a connecting ring, a plug valve is slidably installed inside the connecting ring, and a second spring is sleeved on the plug valve at both ends, which abuts against both of them.

[0012] As a further improvement to the above scheme, a pressure relief pipe is provided on the return port to connect the pressure chamber and the inlet guide vane. A telescopic frame for sealing both ends of the pressure relief pipe is rotatably installed on the return port. The top of the telescopic frame is rotatably connected to the check valve in the inlet. This allows the telescopic frame to tilt and the bottom of the telescopic frame to lift when the water supply in the pump body decreases and the valve moves back, thereby releasing the seal on both ends of the pressure relief pipe and completing the return of water in the pressure chamber in advance.

[0013] As a further improvement to the above scheme, a guide vane is also installed inside the inlet guide vane to guide the return water and prevent the return water from colliding with the water flowing into the inlet, which would cause turbulence and affect the conveying efficiency.

[0014] As a further improvement to the above scheme, two notches are provided on the deflector plate to avoid interfering with the tilting movement of the telescopic frame.

[0015] As a further improvement to the above solution, a through groove is provided at the bottom of the valve body to accommodate the pressure relief pipe, so that the pressure relief pipe will not restrict its lifting and opening, and at the same time, the pressure relief pipe can ensure the stability of its bottom end.

[0016] As a further improvement to the above solution, a pressure tank is installed at the outlet of the pump body. The installation height of the pressure tank is higher than the installation height of the check valve inside the outlet. This not only absorbs the water hammer impact generated when the centrifugal pump is shut down, but also allows the stored water to be released to replenish the system after the water supply fluctuates and the water flows back to replenish the inlet flow, thus preventing a sharp drop in the pressure of the water supply system.

[0017] As a further improvement to the above scheme, the pressure vessel includes a vessel body and a diaphragm disposed within the vessel body, with the diaphragm and the vessel body forming a gas chamber for filling with nitrogen.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] By improving the structural relationship between the pump body and the guide vane assembly, a composite pressure chamber is formed between them. A return port and a control valve are installed between the pressure chamber and the inlet guide vane, constituting a flow guarantee mechanism. When the water supply is insufficient or fluctuates, the pressure in the pressure chamber weakens, and the control valve opens the return port, diverting the fluid in the pressure chamber to the inlet guide vane. This ensures that the total output flow of the centrifugal pump is higher than the minimum continuous flow, fundamentally preventing cavitation at the inlet of the first-stage impeller. Furthermore, no electrical control components are required; the mechanical automatic control offers fast response and high reliability, reducing maintenance costs and ensuring stable operation of the centrifugal pump.

[0020] The check valve, telescopic frame, and pressure relief pipe at the inlet work together to form a linkage system for early warning and rapid pressure relief. When the water supply fluctuates, the plug valve of the check valve at the inlet moves back, causing the telescopic frame to tilt and release the blockage on the pressure relief pipe. This allows the fluid in the pressure chamber to enter the inlet guide vane in advance to relieve pressure, and allows the control valve to return in advance. This compensates for the response delay of the traditional mechanism and solves the problem of temporary cavitation of the guide vane group. At the same time, the guide plate guides the return water to avoid turbulence affecting the delivery efficiency.

[0021] The pressure tank, with its special structure and installation height, achieves a dual function. During normal operation, excess water flows into the tank for storage; when fluctuations in water supply cause a decrease in outlet pressure, the water in the tank is quickly released to replenish pressure, preventing a sudden drop in the water supply system pressure. When the centrifugal pump is shut down, the diaphragm inside the tank absorbs water hammer energy through elastic deformation, buffering pressure fluctuations, protecting the centrifugal pump, valves, and pipelines, extending system life, and reducing maintenance costs. Attached Figure Description

[0022] Figure 1 This is a schematic diagram showing the overall structure of the permanent magnet variable frequency self-priming multistage centrifugal pump of the present invention;

[0023] Figure 2 This is a disassembled view of the permanent magnet variable frequency self-priming multistage centrifugal pump of the present invention;

[0024] Figure 3 This is a side plan sectional view of the permanent magnet variable frequency self-priming multistage centrifugal pump of the present invention;

[0025] Figure 4 for Figure 3 A diagram showing the pump body section;

[0026] Figure 5 This is a disassembled view of the permanent magnet variable frequency self-priming multistage centrifugal pump of the present invention;

[0027] Figure 6 This is a cross-sectional view of the permanent magnet variable frequency self-priming multistage centrifugal pump of the present invention;

[0028] Figure 7 This is a breakdown diagram of the guide vane assembly;

[0029] Figure 8This is a cross-sectional view of the inlet guide vane and check valve.

[0030] Figure 9 This is a cross-sectional view of the pump body and guide vane assembly.

[0031] Figure 10 This is a cross-sectional view of the imported guide vane.

[0032] Explanation of key symbols:

[0033] 1. Permanent magnet variable frequency motor; 2. Pump body; 201. Inlet; 202. Outlet; 203. Discharge port; 3. Guide vane assembly; 301. Inlet guide vane; 3011. Return port; 3012. Guide plate; 302. Impeller guide vane; 3021. Discharge port; 4. Rotor; 5. Impeller; 6. Pressure chamber; 7. Check valve; 701. Connecting ring; 702. Plug valve; 703. Second spring; 8. Control valve; 801. Abutment block; 802. Valve body; 8021. Through groove; 803. First spring; 9. Telescopic frame; 10. Pressure relief pipe; 11. Pressure tank; 1101. Tank body; 1102. Diaphragm; 1103. Air chamber; 12. Pressure sensor. Detailed Implementation

[0034] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments.

[0035] Please combine Figures 1 to 10 The permanent magnet variable frequency self-priming multistage centrifugal pump includes: a permanent magnet variable frequency motor 1 and a pump body 2 with an inlet 201 and an outlet 202. The pump body 2 is also provided with a discharge port 203 below the inlet 201. The discharge port 203 can be used to discharge water and sediment accumulated in the pump body 2. The outlet 202 of the pump body 2 is a detachable multi-port pipe. A pressure sensor 12 is also provided on the multi-port pipe. The pressure sensor 12 is used to detect the pressure in the outlet 202. When the pressure in the outlet 202 is too high, the pump body is triggered to stop, thus protecting the entire system. The pump body 2 is fixedly connected to the output flange of the permanent magnet variable frequency motor 1 by bolts. The bottom of the permanent magnet variable frequency motor 1 is fixedly installed with a base, and the base is provided with a shell covering the pump body. Inside the pump body 2, a guide vane group 3 is fixedly installed, consisting of an inlet guide vane 301 and multiple impeller guide vanes 302. The last impeller guide vane 302 is provided with multiple outlets 3021 arranged in a ring, thereby connecting the impeller guide vane 302 and the pressure chamber 6. The rotor 4, which is fixedly connected to the output shaft of the permanent magnet variable frequency motor 1, is rotatably installed inside the guide vane group 3. Each of the multiple impeller guide vanes 302 is provided with an impeller 5, which is fixedly connected to the rotor 4.

[0036] Please combine Figure 6A pressure chamber 6 is formed between the guide vane assembly 3 and the pump body 2. A return port 3011 for connecting the pressure chamber 6 is provided on the inlet guide vane 301. A control valve 8 is provided in the return port 3011. The control valve 8 includes a block 801 fixedly installed on the guide plate 3012 inside the inlet guide vane 301. A valve body 802 is slidably installed on the block 801. A first spring 803 with both ends abutting against the two is sleeved on the valve body 802.

[0037] When the water supply to the pump body 2 is insufficient, causing the pressure in the pressure chamber 6 to weaken and fail to close the control valve 8, the control valve 8 opens, allowing the fluid in the pressure chamber 6 to be diverted through the return port 3011 to the inlet guide vane 301, so that the pump body 2 maintains a total output flow rate higher than the minimum continuous flow rate.

[0038] Through the above technical solution, by improving the structural relationship between the pump body 2 and the guide vane assembly 3, a composite pressure chamber 6 is formed between them. A return port 3011 and a control valve 8 are installed between the pressure chamber 6 and the inlet guide vane 301, constituting a flow guarantee mechanism. When the water supply is insufficient or fluctuates, the pressure in the pressure chamber 6 decreases, and the control valve 8 opens the return port 3011, diverting the fluid in the pressure chamber 6 to the inlet guide vane 301, ensuring that the total output flow of the centrifugal pump is higher than the minimum continuous flow, thus preventing cavitation at the inlet of the first-stage impeller 5 from the root cause. Furthermore, no electrical control components are required; the mechanical automatic control has a fast response and high reliability, reducing maintenance costs and ensuring stable operation of the centrifugal pump.

[0039] Please combine Figure 3 , Figure 4 as well as Figure 8 Check valves 7 are installed in both the inlet 201 and outlet 202 of the pump body 2. The check valve 7 includes a connecting ring 701, and a plug valve 702 is slidably installed in the connecting ring 701. A second spring 703 is sleeved on the plug valve 702, with both ends abutting against the two.

[0040] Please combine Figures 8 to 10 A pressure relief pipe 10 is provided on the return port 3011, connecting the pressure chamber 6 and the inlet guide vane 301. The middle part of the pressure relief pipe 10 is provided with two through holes. The fluid in the pressure chamber 6 can enter the pressure relief pipe 10 through the through holes and be discharged into the inlet guide vane 301 from both ends. A telescopic frame 9 for sealing both ends of the pressure relief pipe 10 is rotatably provided on the return port 3011. The telescopic frame 9 consists of two sleeves connected by a connecting shaft and two telescopic strips slidably installed in the sleeves. The two sleeves are rotatably connected to the check valve 7 in the inlet 201 through the connecting shaft. The two telescopic strips are rotatably connected to the return port 3011. This causes the water supply in the pump body 2 to decrease, causing the valve 702 to move back, which drives the telescopic frame 9 to tilt and the bottom end of the telescopic frame 9 to lift up, thereby releasing the seal on both ends of the pressure relief pipe 10 and completing the return of water in the pressure chamber 6 in advance.

[0041] Through the above technical solution, the check valve 7 of the inlet 201, the telescopic frame 9 and the pressure relief pipe 10 work together to form a linkage system for early warning and rapid pressure relief. When the water supply fluctuates, the plug valve 702 of the check valve 7 of the inlet 201 moves back, causing the telescopic frame 9 to tilt, releasing the blockage on the pressure relief pipe 10, allowing the fluid in the pressure chamber 6 to enter the inlet guide vane 301 in advance to relieve pressure, allowing the control valve 8 to return in advance, making up for the response delay of the traditional mechanism and solving the problem of temporary cavitation of the guide vane group 3.

[0042] Please combine Figures 4 to 8 The inlet guide vane 301 is also equipped with a flow guide plate 3012, which is used to guide the return water body to avoid the return water body from colliding with the water body flowing into the inlet 201, which would cause turbulence and affect the conveying efficiency. At the same time, when the flow guide plate 3012 is used in conjunction with the check valve 7 in the inlet 201, it can filter impurities in the fluid entering the pump body 2.

[0043] Please combine Figures 8 to 10 The guide plate 3012 is provided with two notches to avoid interfering with the tilting movement of the telescopic frame 9.

[0044] Please combine Figure 10 The bottom of the valve body 802 is provided with a through groove 8021 for adapting to the pressure relief pipe 10, so that the pressure relief pipe 10 is not restricted from opening and closing, and the bottom of the pressure relief pipe 10 can be kept stable.

[0045] Please combine Figure 3 A pressure tank 11 is installed on the outlet 202 of the pump body 2. The pressure tank 11 includes a tank body 1101 and a diaphragm 1102 installed inside the tank body 1101. A gas chamber 1103 for filling with nitrogen is formed between the diaphragm 1102 and the tank body 1101. The installation height of the pressure tank 11 is higher than the installation height of the check valve 7 inside the outlet 202. This not only absorbs the water hammer impact generated when the centrifugal pump is turned off, but also allows the stored water to be released to replenish the system after the water supply fluctuates and the water flows back to replenish the inlet flow, thus preventing a sharp drop in the pressure of the water supply system.

[0046] Through the above technical solution, pressure tank 11 achieves dual functions due to its special structure and installation height. During normal operation, excess water flows into the tank for storage; when fluctuations in water supply cause a decrease in outlet pressure, the water flow inside the tank is quickly released to replenish pressure, preventing a sudden drop in water supply system pressure. When the centrifugal pump is shut down, the diaphragm 1102 inside the tank absorbs water hammer energy through elastic deformation, buffering pressure fluctuations, protecting the centrifugal pump, valves, and pipelines, extending system life, and reducing maintenance costs.

[0047] The implementation principle of a permanent magnet variable frequency self-priming multistage centrifugal pump in this application embodiment is as follows:

[0048] After the permanent magnet variable frequency motor 1 starts, its output shaft drives the rotor 4 and multiple impellers 5 fixed on the rotor 4 to rotate synchronously. The fluid enters from the inlet 201 of the pump body 2, and under the guidance of the multiple impellers 5, it enters the pressure chamber 6 through the guide vane group 3. During this process, under the action of the centrifugal force generated by the rotation of the impellers 5, the fluid is pressurized step by step and discharged through the outlet 202.

[0049] At this time, the pressure chamber 6 formed between the guide vane assembly 3 and the pump body 2 maintains normal pressure. This pressure overcomes the elastic force of the first spring 803, causing the valve body 802 of the control valve 8 to press tightly against the return port 3011, thereby closing the return port 3011 and preventing fluid backflow in the pressure chamber 6. At the same time, the water flow pressure pushes the plug valve 702 of the check valve 7 in the inlet 201 and outlet 202 respectively, overcoming the elastic force of the second spring 703, so that the check valve 7 begins to open, ensuring that the fluid can flow normally in one direction. During this process, when the centrifugal pump pressure supply is sufficient, and the flow rate at the outlet of the water supply system is less than the centrifugal pump supply, part of the water flows into the pressure tank 11 for storage as a backup.

[0050] When the water supply is insufficient, the pressure in the pressure chamber 6 decreases until it can no longer press against the valve body 802 of the control valve 8, causing the return port 3011 to open. The fluid in the pressure chamber 6 is diverted to the inlet guide vane 301 through the return port 3011, thereby maintaining the flow rate in the centrifugal pump and ensuring that the total output flow rate in the pump body 2 is always higher than the minimum continuous flow rate.

[0051] However, the pressure reduction of the entire centrifugal pump caused by the fluctuation of water supply occurs in the following order: inlet guide vane 301, impeller guide vane 302, pressure chamber 6, and finally outlet 202. When the pressure in pressure chamber 6 decreases, it means that cavitation has occurred in guide vane group 3.

[0052] When the water supply decreases or fluctuates, the plug valve 702 of the check valve 7 inside the inlet 201 moves back under the elastic force of the second spring 703. Simultaneously, it tilts the telescopic frame 9, causing its bottom end to lift and releasing the blockage at both ends of the pressure relief pipe 10. This allows the fluid in the pressure chamber 6 to enter the inlet guide vane 301 through the pressure relief pipe 10 in advance to complete the pressure relief, thereby allowing the control valve 8 to open earlier and achieve fluid backflow, thus solving the temporary cavitation problem of the guide vane assembly 3 after flow fluctuations.

[0053] At the same time, the fluid stored in the pressure tank 11 can also replenish the reduced pressure at the outlet 202 caused by backflow.

[0054] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A permanent magnet variable frequency self-priming multistage centrifugal pump, comprising a permanent magnet variable frequency motor (1) and a pump body (2) having an inlet (201) and an outlet (202), wherein a guide vane assembly (3) consisting of an inlet guide vane (301) and multiple impeller guide vanes (302) is fixedly disposed within the pump body (2), wherein a rotor (4) fixedly connected to the output shaft of the permanent magnet variable frequency motor (1) is rotatably disposed within the guide vane assembly (3), and each of the multiple impeller guide vanes (302) is provided with an impeller (5) fixedly connected to the rotor (4), characterized in that: A pressure chamber (6) is formed between the guide vane assembly (3) and the pump body (2). A return port (3011) for connecting the pressure chamber (6) is provided on the inlet guide vane (301). A control valve (8) is provided in the return port (3011). The control valve (8) includes a stop block (801) provided on the inlet guide vane (301). A valve body (802) is slidably provided on the stop block (801). A first spring (803) with both ends abutting against the two is sleeved on the valve body (802). Check valves (7) are installed in both the inlet (201) and outlet (202) of the pump body (2). The return port (3011) is provided with a pressure relief pipe (10) that connects the pressure chamber (6) and the inlet guide vane (301). The return port (3011) is rotatably provided with a telescopic frame (9) for sealing both ends of the pressure relief pipe (10). The top of the telescopic frame (9) is rotatably connected to the check valve (7) in the water inlet (201). This causes the water supply in the pump body (2) to decrease, which causes the valve (702) to move back, thereby tilting the telescopic frame (9) and raising the bottom end of the telescopic frame (9) to release the sealing of both ends of the pressure relief pipe (10) and thus complete the return of water in the pressure chamber (6) in advance. When the pump body (2) is unable to close the control valve (8) due to insufficient water supply, the pressure in the pressure chamber (6) weakens and cannot be tightly closed. The control valve (8) opens, allowing the fluid in the pressure chamber (6) to be diverted to the inlet guide vane (301) through the return port (3011), so that the pump body (2) maintains a total output flow rate higher than the minimum continuous flow rate.

2. The permanent magnet variable frequency self-priming multistage centrifugal pump as described in claim 1, characterized in that, The check valve (7) includes a connecting ring (701), a plug valve (702) is slidably installed inside the connecting ring (701), and a second spring (703) is sleeved on the plug valve (702) with its two ends abutting against the two.

3. The permanent magnet variable frequency self-priming multistage centrifugal pump as described in claim 1, characterized in that, The inlet guide vane (301) is also equipped with a guide plate (3012) to guide the return water body and avoid the return water body from colliding with the water body flowing into the inlet (201) and causing turbulence that affects the conveying efficiency.

4. The permanent magnet variable frequency self-priming multistage centrifugal pump as described in claim 3, characterized in that, The guide plate (3012) is provided with two notches for avoiding the telescopic frame (9) so as to avoid interfering with the tilting movement of the telescopic frame (9).

5. The permanent magnet variable frequency self-priming multistage centrifugal pump as described in claim 1, characterized in that, The bottom of the valve body (802) is provided with a through groove (8021) for adapting the pressure relief pipe (10), so that the pressure relief pipe (10) will not restrict its lifting and opening, and at the same time, the pressure relief pipe (10) can ensure the stability of its bottom end.

6. The permanent magnet variable frequency self-priming multistage centrifugal pump as described in claim 1, characterized in that, A pressure tank (11) is installed on the outlet (202) of the pump body (2). The installation height of the pressure tank (11) is higher than the installation height of the check valve (7) inside the outlet (202). This not only absorbs the water hammer impact generated when the centrifugal pump is shut down, but also allows the stored water to be released to replenish the system after the water supply fluctuates and the water flows back to replenish the inlet flow, thus preventing the water supply system pressure from dropping sharply.

7. The permanent magnet variable frequency self-priming multistage centrifugal pump as described in claim 6, characterized in that, The pressure vessel (11) includes a vessel body (1101) and a diaphragm (1102) disposed within the vessel body (1101), wherein a gas chamber (1103) for filling with nitrogen is formed between the diaphragm (1102) and the vessel body (1101).

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