A variable-frequency speed-regulating starting feed water pump for a nuclear power plant

Abstract

The present invention relates to the technical field of nuclear power feed water pumps, and discloses a variable frequency speed regulation type starting feed water pump for nuclear power plants, which includes a pump body, a drive shaft arranged inside the pump body, a speed regulation motor arranged at one end of the drive shaft, an auxiliary water conveyance assembly arranged on one side of the pump body, and a multi-stage impeller mechanism and an adjustment assembly arranged inside the pump body. A main water inlet and a main water outlet are provided at the top of the pump body. Through the provided auxiliary water conveyance assembly and multi-stage impeller mechanism, water flows into the front cavity from the main water inlet. The speed regulation motor runs at a low speed and drives the front impeller main body and multiple rear impellers to rotate inside the pump body through the drive shaft. When the front impeller main body rotates, the water flow can be divided into two parts and conveyed in two directions through the provided inner discharge blades and outer discharge blades, making the water flow rate and pressure more stable, reducing the impact on key equipment, better adapting to different working conditions requirements, and achieving the effect of improving the stability and reliability of the system.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear power feed water pumps, in particular to a variable frequency speed regulation type starting feed water pump for a nuclear power station. Background Art

[0002] The startup feedwater pump in a nuclear power plant is an important auxiliary equipment, used to provide deoxygenated water to the steam generator during unit startup, shutdown and low-load operation to ensure a stable water supply for the primary coolant. The application of variable frequency speed regulation technology enables the startup feedwater pump to flexibly adjust the speed according to the actual working conditions, which not only improves the working efficiency of the pump, but also significantly reduces energy consumption and prolongs the service life of the equipment, which plays an important role in improving the overall operational reliability and economy of the nuclear power plant.

[0003] The patent publication number CN102606485A discloses a start-up feedwater pump for a nuclear power plant, including a stator component, a rotor component, two sets of mechanical seals, a mechanical seal flushing pipe and a bearing component. The stator component includes a pump body and a balance water pipe, and the rotor component includes a pump shaft, an impeller, an intermediate sealing sleeve, a rear sealing sleeve and a sleeve nut. The bearing component includes a front bearing, a rear bearing, an intermediate throttling bushing and a rear throttling bushing. The pump body is an axially split structure and is divided into a lower pump body at the bottom and an upper pump cover at the top through a horizontal center plane. The lower pump body and the upper pump cover are connected as a whole by a plurality of clamping bolts; the inner cavity of the pump body is provided with the first to fifth pressure water chambers in the low-pressure zone and the sixth to ninth pressure water chambers in the high-pressure zone. The balance water pipe is connected between the inlet and outlet located at the front and rear parts of the pump body; the impeller is composed of a nine-stage impeller, and the two sets of mechanical seals are respectively installed at the front and rear ends of the pump body; the mechanical seal flushing pipe is led out from the outlet of the first-stage pressure water chamber and connected to the two sets of mechanical seals respectively.

[0004] The prior art has the following defects:

[0005] Unable to smoothly convert efficiency between low speed and high speed: The internal fluid dynamic characteristics and mechanical structure of the existing starting water pump perform differently at different speeds. The impeller and guide vane cannot effectively guide the water flow at low speed, resulting in reduced efficiency. When the speed changes, the efficiency curve of the pump will change suddenly or decrease, resulting in unstable water flow and affecting the normal operation of the system. This uneven change in efficiency will also increase energy consumption, increase equipment wear, and reduce safety and reliability. Therefore, it is necessary to set up a structure that can convert efficiency between low speed and high speed. At low speed, water is delivered by a single-stage water pump. During the process of increasing the speed, it is gradually converted to a multi-stage water pump to deliver water, so that the water flow and pressure are more stable, reducing the impact on key equipment, and better adapting to different working conditions. Requirements, to achieve the effect of improving system stability and reliability.

[0006] Insufficient water conveyance capacity when used as a standby pump: When the existing starting feed pump is used as a standby pump, its water flow rate and pressure are both lower than the design values, unable to meet the needs of the nuclear reactor cooling system. When the main pump fails or is under maintenance, it cannot replace the function of the main pump in a timely or complete manner, affecting the safe operation of the system, and further affecting the efficiency and stability of the generator, resulting in reactor shutdown or reduced load operation, and affecting the power generation capacity of the nuclear power plant. Therefore, a reflux structure needs to be added to improve the water conveyance capacity of the pump when the starting feed pump is used as a standby pump. When the main pump fails or is under maintenance, it can quickly and smoothly take over the task, reduce the system response time, improve safety, and achieve the effect of improving water conveyance efficiency and stability. Summary of the Invention

[0007] In view of the problems in the prior art such as the inability to smoothly transition the efficiency between low speed and high speed and insufficient water conveyance capacity when used as a standby pump, a variable frequency speed regulation type starting feed pump for nuclear power plants is proposed.

[0008] This application provides a variable frequency speed regulation type starting feed pump for nuclear power plants, and its purpose is: through the set auxiliary water conveyance component and multi-stage impeller mechanism, the single-stage water pump conveys water at low speed, and during the process of increasing the rotational speed, it gradually changes to the multi-stage water pump for water conveyance, making the water flow rate and pressure more stable, achieving the effect of improving the stability and reliability of the system. Through the set auxiliary water conveyance component and adjustment component, when the main pump fails or is under maintenance, it can quickly and smoothly take over the task, achieving the effect of improving water conveyance efficiency and stability.

[0009] The technical solution of the present invention is: A variable frequency speed regulation type starting feed pump for nuclear power plants, including a pump body, a drive shaft arranged inside the pump body, a speed regulation motor arranged at one end of the drive shaft, an auxiliary water conveyance component arranged on one side of the pump body, and a multi-stage impeller mechanism and an adjustment component arranged inside the pump body. A main water inlet and a main water outlet are opened at the top of the pump body. The adjustment component is used to adjust the water flow direction. The multi-stage impeller mechanism includes a pre-impeller component arranged between the pump body and the drive shaft and a plurality of rear impellers. A plurality of sealing rings are fixedly installed inside the pump body. A cavity component is arranged between the pre-impeller component, the plurality of rear impellers and the pump body;

[0010] The pre-impeller component includes a pre-sealing block fixedly installed on the inner wall of the pump body and a pre-impeller main body fixedly installed on the outer wall of the drive shaft. The inner wall of the pre-sealing block is rotationally connected to the outer wall of the drive shaft, and the outer wall of the pre-impeller main body is rotationally connected to the inner wall of the pump body. A plurality of support columns are fixedly connected to the outer wall of the pre-impeller main body close to the pre-sealing block, and inner discharge blades and outer discharge blades are fixedly connected to the outer walls of the plurality of support columns.

[0011] With the above solution, by means of the set front impeller assembly, when the speed-regulating motor runs at a low speed to drive the rotation of the front impeller body, the water flow can be divided into two parts and transported in two directions through the set inner discharge blades and outer discharge blades. One part of the water flow is transported by the outer discharge blades to the auxiliary water delivery assembly, and the other part of the water flow is transported by the inner discharge blades to the cavity where the rear impeller is located. Thus, the efficiency between low speed and high speed can be transformed. At low speed, the water is delivered by a single-stage water pump. During the process of increasing the rotational speed, it gradually changes to the water delivery by a multi-stage water pump, making the water flow and pressure more stable, reducing the impact on key equipment, better adapting to the requirements of different working conditions, and achieving the effect of improving the stability and reliability of the system.

[0012] Further, the cavity assembly includes a front cavity, an intermediate cavity, and a rear cavity opened inside the pump body. The front cavity is arranged between the front sealing block and the front impeller body. The intermediate cavity is arranged between the front impeller body and multiple rear impellers. The rear cavity is arranged between the rear impeller and the adjustment assembly.

[0013] Further, both the inner discharge blades and the outer discharge blades are arranged inside the front cavity. When multiple inner discharge blades rotate, they can transport the water flow in the front cavity to the intermediate cavity. When multiple outer discharge blades rotate, they can transport the water flow in the front cavity to the auxiliary water delivery assembly.

[0014] With the above solution, through the set cavity assembly, the water flow in the front cavity is divided into two parts. One part of the water flow is transported to the auxiliary water delivery assembly, and the other part of the water flow is transported to the intermediate cavity. The water flow transported to the auxiliary water delivery assembly forms a single-stage water pump and is then transported to the rear cavity. The water flow transported to the intermediate cavity forms a multi-stage water pump. When the rotational speed of the speed-regulating motor becomes faster, the intermediate cavity is connected to the rear cavity through the adjustment assembly, which is suitable for the requirements of high-pressure feed water in nuclear power plants.

[0015] Further, the auxiliary water delivery assembly includes an auxiliary water inlet connecting pipe communicated with the front cavity, and an auxiliary water discharge connecting pipe communicated with the rear cavity. An auxiliary water delivery pipe is communicated between the auxiliary water inlet connecting pipe and the auxiliary water discharge connecting pipe.

[0016] Further, a water delivery auger is rotatably connected to the inner wall of the auxiliary water delivery pipe, and an auxiliary driving motor is fixedly connected to one end of the water delivery auger.

[0017] With the above solution, through the set auxiliary water delivery assembly, the water flow in the front cavity enters the auxiliary water delivery pipe through the auxiliary water inlet connecting pipe. At this time, the auxiliary driving motor runs forward, and the power output by the auxiliary driving motor drives the water delivery auger to rotate, driving the water flow in the auxiliary water delivery pipe to the auxiliary water discharge connecting pipe and entering the rear cavity, and finally discharging from the main water discharge port. Thus, a single-stage water pump is formed. The single-stage water pump has a higher efficiency during low-speed startup and can quickly reach a stable operating state.

[0018] Furthermore, the adjustment assembly includes a rear sealing block fixedly mounted on the inner wall of the pump body, the outer wall of the rear sealing block is fixedly connected with a plurality of evenly distributed shrinkage tubes, the interior of the shrinkage tube is slidably connected with a push rod, and a shrinkage spring is fixedly connected between the push rod and the shrinkage tube.

[0019] Furthermore, the adjustment assembly also includes a plurality of evenly distributed second gaskets fixedly mounted on the inner wall of the pump body, the end of the push rod away from the shrinkage tube is fixedly connected to the first gasket, a hollow sealing block is arranged between the plurality of second gaskets and the plurality of first gaskets, and the hollow sealing block is rotatably sleeved on the outer wall of the drive shaft.

[0020] Furthermore, the inner wall of the hollow sealing block is fixedly connected to a plurality of inclined sliding cylinders, and the inner walls of the plurality of inclined sliding cylinders are rollingly connected to gravity balls. When the hollow sealing block rotates with the drive shaft, the gravity balls will move from one end of the inclined sliding cylinder close to the drive shaft to the end away from the drive shaft under the action of centrifugal force.

[0021] By adopting the above scheme, through the setting of the adjustment component, when the speed of the speed regulating motor is slow, the hollow sealing block is resisted by the push rod and the contraction spring in the contraction cylinder, thereby closing the middle cavity and the rear cavity; when the speed of the speed regulating motor becomes faster, the gravity ball inside the hollow sealing block moves from the end of the inclined sliding cylinder close to the drive shaft to the end away from the drive shaft under the action of centrifugal force, and squeezes the hollow sealing block under the impact of the water flow, so that the hollow sealing block approaches the contraction cylinder, thereby connecting the middle cavity and the rear cavity, thereby regulating the direction of the water flow.

[0022] Beneficial effects of the present invention:

[0023] Through the auxiliary water delivery component and the multi-stage impeller mechanism, water flows from the main water inlet into the front cavity. The speed regulating motor runs at a low speed and drives the front impeller body and multiple rear impellers to rotate inside the pump body through the driving shaft. When the front impeller body rotates, the inner row blades and outer row blades can be used to divide the water flow into two parts and transport them in two directions. A part of the water flow is blocked by the outer row blades at the outer ring of the front cavity, close to the auxiliary water inlet connecting pipe, and is transported to the rear cavity by the auxiliary water delivery component, and finally discharged from the main drain port, thereby forming a single-stage water pump. The single-stage water pump has a higher efficiency when starting at a low speed and can quickly reach a stable operating state. Another part of the water flow is transported to the inner ring of the front cavity by the inner row blades and enters the middle cavity. Under the regulation of the regulating component, the middle cavity is connected with the rear cavity and finally discharged from the main drain port, thereby forming a multi-stage water pump, which makes the water flow and pressure more stable, reduces the impact on key equipment, better adapts to different working conditions, and achieves the effect of improving system stability and reliability.

[0024] Through the provided multi-stage impeller mechanism and adjustment component, when the speed of the speed-regulating motor increases, the gravity balls inside the hollow sealing block move from the end close to the drive shaft of the inclined sliding cylinder to the end far from the drive shaft under the action of centrifugal force, and under the impact of water flow, they squeeze the hollow sealing block, causing the hollow sealing block to approach the contraction cylinder. As a result, the intermediate cavity communicates with the rear cavity, and the water flow in the intermediate cavity flows into the rear cavity. At this time, the auxiliary drive motor is turned off, and the water flow in the auxiliary water delivery pipe stops flowing. The water flow can only flow through the intermediate cavity and finally be discharged from the main drain port, thus forming a multi-stage water pump. The multi-stage water pump can achieve a relatively high lift and is suitable for the high-pressure water supply requirements in nuclear power plants.

[0025] Through the provided auxiliary water delivery component and adjustment component, when used as a standby pump and the multi-stage water pump at this time cannot meet the needs of the nuclear reactor cooling system, the auxiliary drive motor can be operated in reverse to return part of the water flow in the rear cavity to the front cavity through the auxiliary water delivery pipe. The return can increase the inlet pressure of the feed water pump, reduce the risk of cavitation, and improve the reliability of the entire system. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the overall structure of the feed water pump of the present invention;

[0027] Figure 2 Top view of the overall structure of the feed water pump of the present invention;

[0028] Figure 3 Schematic diagram of the structure at the main water inlet and main drain port of the present invention;

[0029] Figure 4 Front view of the structure at the multi-stage impeller mechanism of the present invention;

[0030] Figure 5 Schematic diagram of the structure at the front impeller assembly of the present invention;

[0031] Figure 6 Schematic diagram of the structure at the rear impeller of the present invention;

[0032] Figure 7 Schematic diagram of the structure at the cavity assembly of the present invention;

[0033] Figure 8 Schematic diagram of the structure at the auxiliary water delivery component of the present invention;

[0034] Figure 9 Front view of the structure at the rear cavity of the present invention;

[0035] Figure 10 For the present invention Figure 9 Schematic diagram of the enlarged structure at A in the present invention;

[0036] Figure 11Schematic diagram of the structure at the hollow sealing block of the present invention.

[0037] In the figure:

[0038] 1. Pump body; 2. Driving shaft; 3. Speed-regulating motor; 4. Auxiliary water delivery assembly; 41. Auxiliary water inlet connecting pipe; 42. Auxiliary water delivery pipe; 43. Water delivery auger; 44. Auxiliary water discharge connecting pipe; 45. Auxiliary driving motor; 5. Main water inlet; 6. Main water discharge; 7. Multi-stage impeller mechanism; 71. Front impeller assembly; 711. Front sealing block; 712. Front impeller main body; 713. Support column; 714. Inner discharge blade; 715. Outer discharge blade; 72. Rear impeller; 73. Sealing ring; 74. Cavity assembly; 741. Front cavity; 742. Intermediate cavity; 743. Rear cavity; 8. Adjusting assembly; 81. Rear sealing block; 82. Shrinkage cylinder; 83. Shrinkage spring; 84. Push rod; 85. First gasket; 86. Second gasket; 87. Hollow sealing block; 88. Inclined sliding cylinder; 89. Gravity ball. Detailed implementation manners

[0039] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following will give a detailed description of the specific implementation manners of the present invention with reference to the accompanying drawings of the specification.

[0040] Referring to Figure 1 - Figure 11 , a variable-frequency speed-regulating starting feed water pump for a nuclear power plant is provided, which includes a pump body 1, a driving shaft 2 arranged inside the pump body 1, a speed-regulating motor 3 arranged at one end of the driving shaft 2, an auxiliary water delivery assembly 4 arranged on one side of the pump body 1, and a multi-stage impeller mechanism 7 and an adjusting assembly 8 arranged inside the pump body 1. A main water inlet 5 and a main water discharge 6 are opened at the top of the pump body 1. The adjusting assembly 8 is used to adjust the water flow direction. The multi-stage impeller mechanism 7 includes a front impeller assembly 71 arranged between the pump body 1 and the driving shaft 2 and a plurality of rear impellers 72. A plurality of sealing rings 73 are fixedly installed inside the pump body 1. A cavity assembly 74 is arranged between the front impeller assembly 71, the plurality of rear impellers 72 and the pump body 1.

[0041] Referring to Figure 4 - Figure 7 , the front impeller assembly 71 includes a front sealing block 711 fixedly installed on the inner wall of the pump body 1 and a front impeller main body 712 fixedly installed on the outer wall of the driving shaft 2. The inner wall of the front sealing block 711 is rotatably connected to the outer wall of the driving shaft 2, and the outer wall of the front impeller main body 712 is rotatably connected to the inner wall of the pump body 1. A plurality of support columns 713 are fixedly connected to the outer wall of the front impeller main body 712 close to the front sealing block 711. Inner discharge blades 714 and outer discharge blades 715 are fixedly connected to the outer walls of the plurality of support columns 713.

[0042] Specifically, multiple rear impellers 72 can be provided. The sealing ring 73 is arranged inside the pump body 1 to seal the connection between the front impeller main body 712 and the multiple rear impellers 72. The multiple inner discharge vanes 714 and outer discharge vanes 715 are evenly distributed on the front impeller main body 712 and are connected by the support columns 713. The function of the front sealing block 711 is to seal one end of the pump body 1 and form a water conveyance cavity between it and the front impeller main body 712.

[0043] With the provided front impeller assembly 71, when the speed-regulating motor 3 runs at a low speed and drives the front impeller main body 712 to rotate, the water flow can be divided into two parts and conveyed in two directions through the provided inner discharge vanes 714 and outer discharge vanes 715. One part of the water flow is conveyed to the auxiliary water conveyance assembly 4 by the outer discharge vanes 715, and the other part of the water flow is conveyed to the cavity where the rear impellers 72 are located by the inner discharge vanes 714. Thus, the efficiency between low speed and high speed can be transformed. At low speed, water is conveyed by a single-stage water pump. During the process of increasing the rotational speed, it is gradually transformed into water conveyance by a multi-stage water pump, making the water flow rate and pressure more stable, reducing the impact on key equipment, better adapting to the requirements of different working conditions, and achieving the effect of improving the stability and reliability of the system.

[0044] Refer to Figure 7 - Figure 8 The cavity assembly 74 includes a front cavity 741, an intermediate cavity 742, and a rear cavity 743 opened inside the pump body 1. The front cavity 741 is arranged between the front sealing block 711 and the front impeller main body 712. The intermediate cavity 742 is arranged between the front impeller main body 712 and the multiple rear impellers 72. The rear cavity 743 is arranged between the rear impellers 72 and the adjustment assembly 8. The inner discharge vanes 714 and outer discharge vanes 715 are both arranged inside the front cavity 741. When the multiple inner discharge vanes 714 rotate, they can convey the water flow in the front cavity 741 to the intermediate cavity 742, and when the multiple outer discharge vanes 715 rotate, they can convey the water flow in the front cavity 741 to the auxiliary water conveyance assembly 4.

[0045] With the provided cavity assembly 74, the water flow in the front cavity 741 is divided into two parts. One part of the water flow is conveyed to the auxiliary water conveyance assembly 4, and the other part of the water flow is conveyed to the intermediate cavity 742. The water flow conveyed to the auxiliary water conveyance assembly 4 forms a single-stage water pump and is then conveyed to the rear cavity 743. The water flow conveyed to the intermediate cavity 742 forms a multi-stage water pump. When the rotational speed of the speed-regulating motor 3 becomes faster, the intermediate cavity 742 is connected to the rear cavity 743 through the adjustment assembly 8, which is suitable for the high-pressure feed water requirements in nuclear power plants.

[0046] Refer to Figure 8, the auxiliary water delivery component 4 includes an auxiliary water inlet connecting pipe 41 communicating with the front chamber 741 and an auxiliary water discharge connecting pipe 44 communicating with the rear chamber 743. An auxiliary water delivery pipe 42 is communicated between the auxiliary water inlet connecting pipe 41 and the auxiliary water discharge connecting pipe 44. A water delivery auger 43 is rotatably connected to the inner wall of the auxiliary water delivery pipe 42. One end of the water delivery auger 43 is fixedly connected to an auxiliary drive motor 45.

[0047] Through the arranged auxiliary water delivery component 4, the water flow in the front chamber 741 enters the auxiliary water delivery pipe 42 through the auxiliary water inlet connecting pipe 41. At this time, the auxiliary drive motor 45 runs forward, and the power output by the auxiliary drive motor 45 drives the water delivery auger 43 to rotate, driving the water flow in the auxiliary water delivery pipe 42 to the auxiliary water discharge connecting pipe 44 and entering the rear chamber 743, and finally discharging from the main drain port 6, thus forming a single-stage water pump. The single-stage water pump has a high efficiency when starting at a low speed and can quickly reach a stable operating state.

[0048] Refer to Figure 9 - Figure 11 , the adjusting component 8 includes a rear sealing block 81 fixedly installed on the inner wall of the pump body 1. A plurality of uniformly distributed shrinkage cylinders 82 are fixedly connected to the outer wall of the rear sealing block 81. A push rod 84 is slidably connected inside the shrinkage cylinder 82. A shrinkage spring 83 is fixedly connected between the push rod 84 and the shrinkage cylinder 82. The adjusting component 8 further includes a plurality of uniformly distributed second gaskets 86 fixedly installed on the inner wall of the pump body 1. One end of the push rod 84 away from the shrinkage cylinder 82 is fixedly connected to a first gasket 85. A hollow sealing block 87 is arranged between the plurality of second gaskets 86 and the plurality of first gaskets 85. The hollow sealing block 87 is rotatably sleeved on the outer wall of the drive shaft 2. A plurality of inclined sliding cylinders 88 are fixedly connected to the inner wall of the hollow sealing block 87. Gravity balls 89 are rollably connected to the inner walls of the plurality of inclined sliding cylinders 88. When the hollow sealing block 87 rotates with the drive shaft 2, the gravity balls 89 will move from one end of the inclined sliding cylinder 88 close to the drive shaft 2 to the end away from the drive shaft 2 under the action of centrifugal force.

[0049] Specifically, the hollow sealing block 87 is sleeved on the outer wall of the drive shaft 2 and rotates with the drive shaft 2. At the same time, the hollow sealing block 87 can slide on the drive shaft 2 under the action of centrifugal force and water pressure. First gaskets 85 and second gaskets 86 are arranged on both sides of the hollow sealing block 87. The function of the gaskets is to prevent the hollow sealing block 87 from being stuck and unable to move, and can reduce the friction between the hollow sealing block 87 and the inside of the pump body 1 or the push rod 84.

[0050] Through the provided adjusting component 8, when the speed of the speed-regulating motor 3 is relatively slow, the hollow sealing block 87 is resisted by the push rod 84 and the compression spring 83 in the contraction cylinder 82, thereby closing the intermediate cavity 742 and the rear cavity 743. When the speed of the speed-regulating motor 3 becomes faster, the gravity balls 89 inside the hollow sealing block 87 move from one end of the inclined sliding cylinder 88 close to the driving shaft 2 to the end far from the driving shaft 2 under the action of centrifugal force, and under the impact of water flow, they squeeze the hollow sealing block 87, causing the hollow sealing block 87 to approach the contraction cylinder 82. Thus, the intermediate cavity 742 and the rear cavity 743 are connected, playing a role in adjusting the water flow direction.

[0051] During use, water flow enters the front cavity 741 from the main water inlet 5. The speed-regulating motor 3 runs at a low speed and drives the front impeller main body 712 and multiple rear impellers 72 to rotate inside the pump body 1 through the driving shaft 2. When the front impeller main body 712 rotates, through the provided inner discharge blades 714 and outer discharge blades 715, the water flow can be divided into two parts and transported in two directions. One part of the water flow is blocked by the outer discharge blades 715 on the outer circle of the front cavity 741, close to the auxiliary water inlet connecting pipe 41, and is transported to the rear cavity 743 by the auxiliary water conveying component 4 and finally discharged from the main drain outlet 6. Thus, a single-stage water pump is formed. The single-stage water pump has a higher efficiency during low-speed startup and can quickly reach a stable operating state; the other part of the water flow is transported by the inner discharge blades 714 to the inner circle of the front cavity 741 and enters the intermediate cavity 742. Under the adjustment of the adjusting component 8, the intermediate cavity 742 and the rear cavity 743 are connected and finally discharged from the main drain outlet 6. Thus, a multi-stage water pump is formed. The multi-stage water pump can achieve a higher head and is suitable for the high-pressure water supply requirements in nuclear power plants; when used as a standby pump, at this time, the multi-stage water pump cannot meet the needs of the nuclear reactor cooling system. The auxiliary driving motor 45 can be reversely operated to return part of the water flow in the rear cavity 743 to the front cavity 741 through the auxiliary water pipe 42. The reflux can increase the inlet pressure of the feed water pump, reduce the risk of cavitation, and improve the reliability of the entire system.

[0052] The working principle of the present invention:

[0053] When starting the feed water pump to operate, water flow enters the front cavity 741 from the main water inlet 5. The speed-regulating motor 3 runs at a low speed and drives the front impeller main body 712 and multiple rear impellers 72 to rotate inside the pump body 1 through the driving shaft 2.

[0054] When the front impeller body 712 rotates, the inner row blades 714 and the outer row blades 715 are arranged to divide the water flow into two parts and transport them in two directions. A part of the water flow is blocked by the outer row blades 715 at the outer ring of the front cavity 741, close to the auxiliary water inlet connecting pipe 41, and enters the auxiliary water delivery pipe 42 from the auxiliary water inlet connecting pipe 41. At this time, the auxiliary driving motor 45 is running in the forward direction, and the power output by the auxiliary driving motor 45 drives the water delivery auger 43 to rotate, driving the water flow in the auxiliary water delivery pipe 42 to the auxiliary drainage connecting pipe 44, and enters the rear cavity 743, and finally discharged from the main drainage port 6, thereby forming a single-stage water pump. The single-stage water pump has a higher efficiency when starting at a low speed and can quickly reach a stable operating state.

[0055] Another part of the water flow is transported by the inner row of blades 714 to the inner circle of the front cavity 741, and enters the intermediate cavity 742. After being transported by multiple rear impellers 72, it flows in the intermediate cavity 742 and finally reaches the side of the hollow sealing block 87 close to the rear impeller 72. When the speed of the speed regulating motor 3 is slow, the hollow sealing block 87 is resisted by the push rod 84 and the contraction spring 83 in the contraction tube 82, thereby closing the intermediate cavity 742 and the rear cavity 743.

[0056] When the speed of the speed regulating motor 3 becomes faster, the gravity ball 89 inside the hollow sealing block 87 moves from the end of the inclined slide tube 88 close to the drive shaft 2 to the end away from the drive shaft 2 under the action of centrifugal force, and squeezes the hollow sealing block 87 under the impact of the water flow, so that the hollow sealing block 87 approaches the contraction tube 82, thereby the intermediate cavity 742 is connected with the rear cavity 743, and the water flow in the intermediate cavity 742 flows into the rear cavity 743. At this time, the auxiliary drive motor 45 is turned off, and the water flow in the auxiliary water pipe 42 stops flowing. The water flow can only flow from the intermediate cavity 742 and is finally discharged from the main drain port 6, thereby forming a multi-stage water pump. The multi-stage water pump can achieve a higher head and is suitable for the needs of high-pressure water supply in nuclear power plants.

[0057] When used as a backup pump, the multi-stage water pump at this time cannot meet the needs of the nuclear reactor cooling system. The auxiliary drive motor 45 can be operated in reverse to return part of the water in the rear cavity 743 to the front cavity 741 through the auxiliary water pipe 42. The reflux can increase the inlet pressure of the water pump, reduce the risk of cavitation, and improve the reliability of the entire system.

[0058] It should be noted that the above embodiments are only used to illustrate the technical solutions 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 solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A variable frequency speed regulating starting water pump for a nuclear power plant, comprising a pump body, a driving shaft arranged inside the pump body, a speed regulating motor arranged at one end of the driving shaft, an auxiliary water delivery component arranged at one side of the pump body, and a multi-stage impeller mechanism and an adjusting component arranged inside the pump body, wherein a main water inlet and a main drain are provided at the top of the pump body, and the adjusting component is used to adjust the flow direction of water, and is characterized in that: The multi-stage impeller mechanism comprises a front impeller assembly and a plurality of rear impellers arranged between the pump body and the drive shaft, a plurality of sealing rings are fixedly installed inside the pump body, and a cavity assembly is arranged between the front impeller assembly, the plurality of rear impellers and the pump body; The pre-impeller assembly comprises a pre-sealing block fixedly mounted on the inner wall of the pump body, and a pre-impeller body fixedly mounted on the outer wall of the drive shaft, the inner wall of the pre-sealing block is rotatably connected to the outer wall of the drive shaft, the outer wall of the pre-impeller body is rotatably connected to the inner wall of the pump body, a plurality of support columns are fixedly connected on the outer wall of the pre-impeller body close to the pre-sealing block, and the outer walls of the plurality of support columns are fixedly connected with inner row blades and outer row blades; The adjustment assembly comprises a rear sealing block fixedly mounted on the inner wall of the pump body, a plurality of uniformly distributed shrinking cylinders are fixedly connected to the outer wall of the rear sealing block, a push rod is slidably connected inside the shrinking cylinder, and a shrinking spring is fixedly connected between the push rod and the shrinking cylinder; The adjustment assembly also includes a plurality of evenly distributed second gaskets fixedly mounted on the inner wall of the pump body, the end of the push rod away from the shrinking tube is fixedly connected to the first gasket, a hollow sealing block is arranged between the plurality of second gaskets and the plurality of first gaskets, and the hollow sealing block is rotatably sleeved on the outer wall of the driving shaft; The inner wall of the hollow sealing block is fixedly connected with a plurality of inclined slide cylinders, and the inner walls of the plurality of inclined slide cylinders are rollingly connected with gravity balls. When the hollow sealing block rotates with the drive shaft, the gravity balls will move from one end of the inclined slide cylinder close to the drive shaft to the other end away from the drive shaft under the action of centrifugal force.

2. The variable frequency speed regulating starting water supply pump for a nuclear power plant according to claim 1, characterized in that: The cavity assembly includes a front cavity, an intermediate cavity and a rear cavity which are opened inside the pump body. The front cavity is arranged between the front sealing block and the front impeller body, the intermediate cavity is arranged between the front impeller body and multiple rear impellers, and the rear cavity is arranged between the rear impeller and the adjustment assembly.

3. The variable frequency speed regulating starting water supply pump for a nuclear power plant according to claim 2, characterized in that: The inner row blades and the outer row blades are both arranged inside the front cavity. When the multiple inner row blades rotate, the water flow in the front cavity can be transported to the middle cavity. When the multiple outer row blades rotate, the water flow in the front cavity can be transported to the auxiliary water delivery component.

4. The variable frequency speed regulating starting water pump for a nuclear power plant according to claim 3, characterized in that: The auxiliary water delivery assembly includes an auxiliary water inlet connecting pipe connected to the front cavity and an auxiliary drainage connecting pipe connected to the rear cavity. An auxiliary water delivery pipe is connected between the auxiliary water inlet connecting pipe and the auxiliary drainage connecting pipe.

5. The variable frequency speed regulating starting water pump for a nuclear power plant according to claim 4, characterized in that: The inner wall of the auxiliary water delivery pipe is rotatably connected to a water delivery auger, and one end of the water delivery auger is fixedly connected to an auxiliary driving motor.

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