An axial force balancing mechanism for a supercritical boiler feed water pump

Abstract

This invention discloses an axial force balancing mechanism for a supercritical boiler feedwater pump, relating to the field of feedwater pumps. It includes a pump body, a rotor, an inlet module, and a discharge module, as well as a pressurizing section, a balancing section, and a buffer section. The pressurizing section includes multiple impellers fixedly connected to the rotor and a pressurizing channel formed within the pump body. The balancing section includes a balancing chamber formed within the discharge module, containing a balancing disc fixedly connected to the rotor. The side of the balancing chamber away from the impellers is connected to the inlet module via a balancing pipe. The buffer section includes a buffer tank located outside the pump body, connected to a control component. The control component is connected to both the buffer pipe and the balancing pipe, with the buffer pipe connected to the side of the balancing chamber closest to the impellers. This mechanism rapidly establishes a balancing force during pump startup and quickly releases pressure during shutdown, solving the problem of rotor movement and wear caused by the lag in transient balancing force during pump startup and shutdown.

Description

Technical Field

[0001] This invention relates to the field of feedwater pumps, and more specifically, to an axial force balancing mechanism for feedwater pumps used in supercritical boilers. Background Technology

[0002] Supercritical power generation technology is currently the mainstream technology in the field of thermal power generation, possessing significant advantages such as high power generation efficiency, low energy consumption, and clean and environmentally friendly operation. It is a core technological support for ensuring the safe and stable supply of national power. As a key auxiliary equipment in supercritical thermal power generating units, the supercritical boiler feedwater pump primarily undertakes the important function of supplying high-temperature and high-pressure feedwater to the boiler. Its operational reliability and stability directly affect the safe, efficient, and continuous operation of the entire generating unit. Supercritical boiler feedwater pumps are typically multi-stage centrifugal structures, operating under harsh conditions of high temperature, high pressure, and high speed. The pressure of the working medium inside the pump far exceeds the critical pressure of water, and the temperature is within the supercritical operating range. During the operation of the feedwater pump, due to the fixed pressure difference between the inlet and outlet of each impeller stage, the rotor assembly generates a continuous and large axial force. This axial force is characterized by large amplitude, sensitivity to operating condition fluctuations, and significant transient changes.

[0003] The axial force balancing mechanism is a core component of supercritical boiler feedwater pumps. Its function is to counteract the axial thrust on the rotor assembly in real time, maintain the stability of the rotor's axial position inside the pump body, and avoid problems such as rubbing between moving and stationary parts, bearing overload damage, and excessive pump body vibration caused by axial force imbalance. It is crucial to ensure the structural safety, service life, and working efficiency of the feedwater pump. During the entire life cycle of the supercritical boiler feedwater pump, transient processes such as start-up, shutdown, and switching between different operating conditions will cause rapid changes in axial force, which places extremely high demands on the response characteristics, adjustment accuracy, and adaptability of the axial force balancing mechanism.

[0004] In existing technologies, mechanical axial force balancing mechanisms using a balance disc and a balance pipe are commonly employed. These mechanisms utilize the pressure difference between the balance chamber and the pump inlet side to create a counterbalancing force, thereby offsetting the axial thrust generated by the impeller. While such mechanisms can achieve dynamic axial force balance during steady-state operation, they suffer from insurmountable technical defects during the instantaneous startup and shutdown of the water pump. During pump startup, the axial force generated by the impeller's progressive pressurization increases rapidly, while the high-pressure medium needs to flow into the balance chamber with a delay through the flow channel. This causes the formation of the balancing force to lag behind the increase in axial force, making the rotor prone to axial movement towards the impeller side. This leads to impact and wear between the balance disc and the balance ring. When the pump stops, the axial force generated by the impeller disappears instantaneously, but high-pressure medium remains in the balance chamber, making the balancing force much greater than the instantaneous axial force. This causes the rotor to violently move in the opposite direction, easily resulting in impact and wear between the balance disc and the pump body. In severe cases, this can lead to pump body seal failure. Summary of the Invention

[0005] In order to overcome the above-mentioned defects of the prior art, the present invention provides an axial force balancing mechanism for a supercritical boiler feedwater pump to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: an axial force balancing mechanism for a supercritical boiler feedwater pump, comprising a pump body, a rotor, an inlet module and a discharge module, and further comprising:

[0007] The booster unit includes multiple impellers fixedly connected to the rotor, and also includes a booster channel opened in the pump body;

[0008] Balancing section: It includes a balancing chamber opened in the discharge module, the balancing chamber is provided with a balancing disc fixedly connected to the rotor, and the side of the balancing chamber away from the impeller is connected to the inlet module through a balancing pipe;

[0009] Buffer section: It includes a receiving cavity disposed in the pump body, the receiving cavity is provided with a buffer tank, the buffer tank is connected to a control component, one side of the control component is connected to a buffer pipe, the other side of the control component is connected to a balance pipe, the buffer pipe is connected to the side of the balance cavity near the impeller, and the control component can selectively connect the buffer tank to the buffer pipe or the balance pipe according to the movement trend of the rotor when the pump body starts and stops.

[0010] Preferably, the impeller at the end is connected to the side of the balance chamber near the impeller via a pressurization channel, and the control component is fixedly connected to the receiving chamber.

[0011] Preferably, a balancing ring is provided on the side of the balancing chamber near the impeller, and a balancing gap exists between the balancing ring and the rotor.

[0012] Preferably, a control block is slidably connected within the control assembly, and a synchronizing rod is fixedly connected to one end of the control block. The free end of the synchronizing rod passes through the control assembly and is rotatably connected to the rotor via a slip ring.

[0013] Preferably, a pressure plate is slidably connected inside the buffer tank, the lower end of the pressure plate is connected to the bottom of the buffer tank through an elastic element, and the upper side of the buffer tank is connected to the control component through a connecting pipe.

[0014] Preferably, the control block has a first through slot that can communicate with the buffer tube, and the control block has a second through slot that can communicate with the balance tube.

[0015] Preferably, the extension direction of the first through slot is consistent with the rotor axis, and the free end of the first through slot is connected to the side where the buffer tube in the control component is located. The extension direction of the second through slot is consistent with the rotor radially, and the free end of the second through slot is connected to the side where the balance tube in the control component is located.

[0016] Preferably, the control component is provided with a first one-way valve with its opening facing the balance pipe at the connection point with the balance pipe, and the balance chamber is provided with a second one-way valve with its opening facing the balance chamber at the connection point with the pressurization channel.

[0017] Preferably, the control component includes a first baffle that is fixedly connected to the control block, and the first baffle can block the balance tube.

[0018] Preferably, the control assembly includes a slide rod fixedly connected to the control block, and the free end of the slide rod is fixedly connected to a second baffle, which can block the buffer tube.

[0019] The technical effects and advantages of this invention are as follows:

[0020] 1. This invention achieves precise dynamic compensation of axial force during the transient process of starting and stopping the water pump by coordinating the buffer section and the control component. When the water pump starts, the control component responds to the axial movement of the rotor, connects the buffer tank and the high-pressure side of the balance chamber, and uses the high-pressure medium pre-stored in the buffer tank to instantly establish a balance force, effectively making up for the defect of pressure build-up lag in the main channel, and avoiding the impact and wear of the balance disc and balance ring caused by the rotor moving towards the impeller side at the moment of start-up.

[0021] 2. This invention achieves rapid pressure balance when the water pump stops by coordinating the buffer section and the control component. When the water pump stops, the control component moves in the opposite direction with the rotor, connecting the buffer tank and the low-pressure side of the balance chamber, quickly balancing the pressure difference on both sides of the balance disc, eliminating the reverse impact caused by the residual balancing force, preventing severe collision and rubbing between the balance disc and the pump body end cover, and significantly improving the shutdown safety and structural durability of the unit.

[0022] 3. This invention, through the dynamic throttling design of the first and second baffles within the control assembly, can linearly adjust the flow rate and pressure of the buffer tank replenishing or depressurizing the balance chamber according to the magnitude of rotor axial movement. During startup, as the axial force gradually increases, the compensation balancing force increases synchronously and smoothly by adjusting the flow area of ​​the buffer pipe through the second baffle. During shutdown, the pressure on the low-pressure side of the balance chamber decreases synchronously with the depressurization on the high-pressure side by adjusting the flow area of ​​the balance pipe through the first baffle. This dynamic adjustment mechanism ensures real-time matching between the balancing force and the axial force throughout the entire transient process, eliminates the driving force of rotor axial movement, and greatly improves the response characteristics and working condition adaptability of the axial force balancing mechanism. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the pump body of the present invention.

[0024] Figure 2 This is a schematic diagram of the pressurization section and the balancing section in this invention.

[0025] Figure 3 This is a schematic diagram of the structure of the balance tube and balance cavity in this invention.

[0026] Figure 4 This is a schematic diagram of the structure of the buffer section and the balance cavity in this invention.

[0027] Figure 5 For the present invention Figure 4 A magnified view of A in the middle.

[0028] Figure 6 This is a schematic diagram of the balance tube and control components.

[0029] Figure 7 This is a schematic diagram of the structure within the control component of the present invention.

[0030] Figure 8 This is a schematic diagram of the structure of the first through groove and the second through groove in this invention.

[0031] In the picture:

[0032] 1. Pump body; 12. Rotor; 13. Inlet module; 14. Discharge module;

[0033] 2. Pressure boosting section; 21. Impeller; 22. Pressure boosting channel;

[0034] 3. Balancing section; 31. Balancing chamber; 32. Balancing disc; 33. Balancing tube; 34. Balancing ring;

[0035] 4. Buffer section; 41. Buffer tank; 42. Control assembly; 43. Buffer tube; 44. Control block; 45. Synchronizing rod; 46. Pressure plate; 47. Elastic element; 48. Connecting pipe; 49. First through groove; 410. Second through groove; 411. First check valve; 412. First baffle; 413. Second baffle; 414. Slide rod; 415. Slip ring; 416. Second check valve; 417. Receiving cavity. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0037] Example 1

[0038] In the existing technology, a mechanical axial force balancing mechanism using a balance disc 32 and a balance pipe 33 is employed. When the pump starts, the axial force generated by the impeller 21 increasing in pressure step by step increases rapidly. However, the high-pressure medium needs to flow into the balance chamber 31 through the flow channel with a delay, causing the formation of the balancing force to lag behind the increase in axial force. The rotor 12 is prone to axial movement towards the impeller 21 side, causing impact and wear between the balance disc 32 and the balance ring 34. When the pump stops, the axial force generated by the impeller 21 disappears instantaneously, but high-pressure medium remains in the balance chamber 31, making the balancing force much greater than the instantaneous axial force. The rotor 12 moves violently in the opposite direction, which can easily cause impact and wear between the balance disc 32 and the pump body 1. In severe cases, it can lead to the failure of the pump body 1 seal.

[0039] To resolve the above technical issues, please refer to Figures 1 to 8 As shown, the first embodiment of the present invention provides an axial force balancing mechanism for a supercritical boiler feedwater pump, including a pump body 1, a rotor 12, an inlet module 13 and a discharge module 14, and further including:

[0040] The booster unit 2 includes multiple impellers 21 fixedly connected to the rotor 12, and a booster channel 22 opened in the pump body 1. When the rotor 12 rotates, the impellers 21 rotate synchronously at high speed with the rotor 12. The medium inside the impeller 21 rotates together under the drive of the blades. Under the action of centrifugal force, the medium is quickly thrown to the outer edge of the impeller 21, which significantly increases the medium flow rate and pressure at the outer edge of the impeller 21. After the medium is thrown out, a local negative pressure zone is formed in the center of the impeller 21. Its pressure is much lower than the medium pressure in the pump suction pipe. Under the pressure difference between the external atmospheric pressure and the negative pressure in the center of the impeller 21, the medium in the suction pipe is continuously pressed into the impeller 21. With the continuous rotation of the rotor 12 and the impeller 21, the medium is continuously sucked in and transported. The pressurized medium flows into the next impeller 21 through the booster channel 22, realizing step-by-step pressurization.

[0041] Balance section 3 includes a balance chamber 31 located within the discharge module 14. The balance chamber 31 contains a balance disc 32 fixedly connected to the rotor 12. The final stage impeller 21 is connected to the side of the balance chamber 31 closest to the impeller 21 via a pressurization channel 22. The side of the balance chamber 31 furthest from the impeller 21 is connected to the inlet module 13 via a balance pipe 33. A balance ring 34 is located within the balance chamber 31 closest to the impeller 21. A balance gap exists between the balance ring 34 and the rotor 12. When the multi-stage impeller 21 operates, it generates a total axial thrust pointing towards the inlet side, causing the rotor 12 to tend to move towards the impeller 21. The high-pressure fluid from the outlet of the final stage impeller 21 enters the balance chamber 31 near the impeller 21 via the pressurization channel 22. The fluid acts on one side of the impeller 21 and on the inner end face of the balance disc 32; after the fluid is throttled and depressurized through the balance gap between the balance disc 32 and the balance ring 34, it enters the side of the balance chamber 31 away from the impeller 21; this side chamber is connected to the entry module 13 through the balance pipe 33, so that the outside of the balance chamber 31 is kept in a relatively low pressure state, thereby forming a stable pressure difference on the left and right sides of the balance disc 32. This pressure difference acts on the effective pressure bearing area of ​​the balance disc 32, generating a balancing force opposite to the direction of the axial force. When the pump body 1 is running in steady state, the balancing force and the axial thrust generated by the impeller 21 are close in magnitude and opposite in direction, canceling each other out, thereby limiting the axial movement of the rotor 12 and realizing the automatic balance of the axial force.

[0042] Buffer section 4: It includes a receiving cavity 417 disposed within the pump body 1, a buffer tank 41 disposed within the receiving cavity 417, the buffer tank 41 being connected to a control component 42, a buffer pipe 43 being connected to one side of the control component 42, and a balance pipe 33 being connected to the other side of the control component 42, the buffer pipe 43 being connected to the side of the balance cavity 31 near the impeller 21, the control component 42 being fixedly connected to the receiving cavity 417, and the control component 42 being able to selectively connect the buffer tank 41 to the buffer pipe 43 or the balance pipe 33 according to the movement trend of the rotor 12 when the pump body 1 starts and stops, the control component 42 being slidably connected to a control block 44, one end of the control block 44 being fixedly connected to a synchronizing rod 45, the free end of the synchronizing rod 45 passing through the control component 42 and connected to the rotor via a slip ring 415. Rotary connection 12, slip ring 415 is located outside pump body 1, sleeved on the outer shaft section of rotor 12 extending from pump body 1. Slip ring 415 is coaxially fixedly connected to rotor 12. An annular groove is provided on slip ring 415. Synchronizing rod 45 is rotatably connected to rotor 12 through the groove. The position where synchronizing rod 45 and slip ring 415 are rotatably connected is outside pump body 1, so there is no need to consider sealing issues. When the water pump is turned on, rotor 12 moves toward impeller 21 under the action of axial force. When the water pump is turned off, rotor 12 moves away from impeller 21 under the action of balancing force. Since rotor 12 and synchronizing rod 45 are rotatably connected through slip ring 415, when rotor 12 moves, it can drive control block 44 to move within control assembly 42 through synchronizing rod 45.

[0043] A pressure plate 46 is slidably connected inside the buffer tank 41. The lower end of the pressure plate 46 is connected to the bottom of the buffer tank 41 through an elastic element 47. The upper side of the buffer tank 41 is connected to the control component 42 through a connecting pipe 48. The buffer tank 41 stores a high-pressure medium to buffer the movement of the balance disc 32 when the water pump is turned on or off. In practical applications, the energy storage structure inside the buffer tank 41 is not limited to the mechanical elastic element 47. It can also adopt the commonly used pneumatic hydraulic accumulator structure in this field, which uses the expansion force of compressed gas to push the pressure plate 46 to meet the high-pressure energy storage requirements under supercritical conditions.

[0044] The control block 44 has a first through slot 49, the extension direction of which is consistent with the axial direction of the rotor 12. The first through slot 49 can communicate with the buffer pipe 43. The control block 44 also has a second through slot 410, the extension direction of which is consistent with the radial direction of the rotor 12. The second through slot 410 can communicate with the balance pipe 33. The first through slot 49 is not connected to the second through slot 410. When the water pump is turned on, the control block 44 moves towards the impeller 21 along with the rotor 12 via the synchronizing rod 45. The control block 44 drives the first through slot 49 to connect with the connecting pipe 48. Figure 4 and Figure 5 As shown, the free end of the first through slot 49 is connected to the side of the buffer pipe 43 in the control assembly 42, so that the buffer tank 41 is connected to the side of the balance chamber 31 near the impeller 21. When the water pump is turned off, the control block 44 moves with the rotor 12 away from the impeller 21 via the synchronizing rod 45. The control block 44 drives the second through slot 410 to connect with the balance pipe 33, as shown. Figure 7 As shown, the free end of the second through groove 410 is connected to the side where the balance tube 33 is located in the control component 42, so that the buffer tank 41 and the side of the balance chamber 31 away from the impeller 21 are connected.

[0045] The control component 42 is provided with a first check valve 411 with its opening facing the balance pipe 33 at the connection point with the balance pipe 33. The first check valve 411 can effectively prevent the medium in the balance pipe 33 from flowing back into the buffer tank 41. The balance chamber 31 is provided with a second check valve 416 with its opening facing the balance chamber 31 at the connection point with the boosting channel 22. The second check valve 416 can prevent the high-pressure medium flowing into the balance chamber 31 from flowing back into the boosting channel 22 during the start-up phase of the pump body 1.

[0046] During use, the elastic element 47 is in a compressed and energy-storing state, with the initial state as follows: Figure 4 and Figure 5As shown, the connecting pipe 48 is blocked by the control block 44. The connecting pipe 48 is located between the first through groove 49 and the second through groove 410. When the water pump is turned on, the water pump drives multiple impellers 21 to rotate through the rotor 12. The axial force generated by the impellers 21 increasing in pressure step by step increases rapidly. Due to the pressure difference, the axial force acts on the rotor 12, causing the rotor 12 to move towards the impellers 21. The high-pressure medium needs to flow into the balance chamber 31 through the pressurization channel 22 after a delay. At this time, the rotor 12 drives the control block 44 to move towards the impellers 21 within the control assembly 42 through the synchronous rod 45. The control block 44 drives the first through groove 49 to connect with the connecting pipe 48. Figure 4 and Figure 5As shown, the free end of the first through groove 49 is connected to the side of the buffer tube 43 in the control assembly 42, so that the buffer tank 41 is connected to the side of the balance chamber 31 near the impeller 21. Under the reset action of the elastic element 47, the high-pressure medium in the buffer tank 41 is pushed by the pressure plate 46. The high-pressure medium enters the first through groove 49 through the connecting pipe 48. After flowing into the first through groove 49, the high-pressure medium enters the side of the balance chamber 31 near the impeller 21 through the buffer tube 43. At this time, although the high-pressure medium in the pump body 1 does not enter the balance chamber 31, the high-pressure medium in the buffer tank 41 enters the side of the balance chamber 31 near the impeller 21, thereby generating a balancing force opposite to the axial force. This effectively prevents the balance disc 32 from shifting towards the impeller 21 at the moment the pump body 1 is turned on. As the rotor 12 rotates, the impeller 21 rotates synchronously at high speed. The medium inside the impeller 21 rotates together under the drive of the blades. Under the action of centrifugal force, the medium is quickly thrown towards the outer edge of the impeller 21, causing the medium velocity and pressure at the outer edge of the impeller 21 to increase significantly. After the medium is thrown out, a local negative pressure zone will be formed at the center of the impeller 21. Its pressure is much lower than the medium pressure in the pump suction pipe. Under the pressure difference between the external atmospheric pressure and the negative pressure at the center of the impeller 21, the medium in the suction pipe is continuously forced into the impeller 21. With the continuous rotation of the rotor 12 and the impeller 21, The medium is continuously drawn in and transported. After being pressurized, the medium flows into the next stage impeller 21 through the pressurization channel 22, achieving step-by-step pressurization. The high-pressure medium after step-by-step pressurization enters the discharge module 14, and simultaneously enters the balance chamber 31 near the impeller 21 through the final stage impeller 21 and the pressurization channel 22, acting on the inner end face of the balance disk 32. The fluid is then throttled and depressurized through the balance gap between the balance disk 32 and the balance ring 34, and enters the balance chamber 31 away from the impeller 21. This side chamber is connected to the entry module 13 through the balance pipe 33, keeping the outside of the balance chamber 31 in a relatively low-pressure state, thereby forming a stable pressure on the left and right sides of the balance disk 32. A constant pressure difference acts on the effective bearing area of ​​the balance disc 32, generating a balancing force opposite to the direction of the axial force. Under the action of this balancing force, the pump body 1 gradually enters steady-state operation. The balancing force and the axial thrust generated by the impeller 21 are close in magnitude but opposite in direction, thus canceling each other out and limiting the axial movement of the rotor 12. During the above process, the high-pressure medium generated by the pump body 1 enters the balance chamber 31 and participates in the axial force balance. Meanwhile, the buffer tank 41 remains in communication with the balance chamber 31. The high-pressure medium in the balance chamber 31 flows back to the buffer tank 41 through the buffer pipe 43 and the first through groove 49 to replenish the high-pressure medium in the buffer tank 41.

[0047] Then, when the rotor 12 drives the balance disc 32 to move to the initial position, the rotor 12 drives the control block 44 and the first through slot 49 to move to the initial position through the synchronous rod 45. At this time, under the obstruction of the control block 44, the connecting pipe 48 on the buffer tank 41 is no longer connected to the control component 42, realizing accurate dynamic compensation of axial force during the instantaneous start-stop process of the water pump. When the water pump starts, the control component 42 responds to the axial movement of the rotor 12, connects the buffer tank 41 and the high-pressure side of the balance chamber 31, and uses the high-pressure medium pre-stored in the buffer tank 41 to instantly establish a balance force, effectively making up for the defect of pressure lag in the main channel, and avoiding the impact and wear of the balance disc 32 and the balance ring 34 caused by the rotor 12 moving towards the impeller 21 side at the moment of start-up.

[0048] When the water pump is shut off, the axial force generated by the impeller 21 disappears instantaneously due to the loss of power from the rotor 12. High-pressure medium remains in the balance chamber 31, causing the balancing force to be much greater than the instantaneous axial force. The rotor 12 then moves away from the impeller 21. The rotor 12, via the synchronizing rod 45, drives the control block 44 to move synchronously. The control block 44 then connects the second through slot 410 to the balance pipe 33. Figure 7 As shown, the free end of the second channel 410 is connected to the side of the control assembly 42 where the balance pipe 33 is located, so that the buffer tank 41 and the side of the balance chamber 31 away from the impeller 21 are connected. At this time, the balance pipe 33 is connected to the high-pressure medium in the buffer tank 41. The high-pressure medium flows into the side of the balance chamber 31 away from the impeller 21 through the balance pipe 33. Because the control assembly 42 is provided with a first one-way valve 411 with its opening facing the balance pipe 33 at the connection point, the first one-way valve 411 can effectively prevent the medium in the balance pipe 33 from flowing back into the buffer tank 41, so that the pressure difference on both sides of the balance chamber 31 is close, which can effectively prevent the residual balancing force from driving the balance disc 3. 2. As the pressure difference on both sides of the balance chamber 31 gradually balances, the rotor 12 drives the balance disc 32 back to the initial position. The rotor 12 drives the control block 44 back to the initial position through the synchronous rod 45, so that the buffer tank 41 and the balance chamber 31 are no longer connected, realizing rapid pressure balance when the water pump stops. When the water pump stops, the control component 42 moves in the opposite direction with the rotor 12, connecting the buffer tank 41 and the low-pressure side of the balance chamber 31, quickly balancing the pressure difference on both sides of the balance disc 32, eliminating the reverse impact caused by the residual balancing force, preventing the balance disc 32 from violently rubbing against the pump body 1 end cover, and significantly improving the shutdown safety and structural durability of the unit.

[0049] Example 2

[0050] As can be seen from the above embodiments, when the pump body 1 is turned on, the medium is pressurized step by step by the impeller 21. Before the high-pressure medium enters the balance chamber 31, the axial force is a gradually increasing process. If the high-pressure medium in the buffer tank 41 is a constant value, the rotor 12 will still drive the balance disc 32 to move due to the change in axial force, and the balance disc 32 still has the risk of impact wear. Similarly, when the water pump is turned off, as the high-pressure medium on the side of the balance chamber 31 near the impeller 21 flows into the side of the balance chamber 31 away from the impeller 21, the pressure on the side of the balance chamber 31 near the impeller 21 will gradually decrease. If the high-pressure medium in the buffer tank 41 is a constant value, as the pressure on the side of the balance chamber 31 near the impeller 21 decreases while the pressure on the other side is constant, the rotor 12 will still drive the balance disc 32 to move, and the balance disc 32 still has the risk of impact wear.

[0051] To resolve the above technical issues, please refer to Figures 1 to 8 As shown, the control component 42 is provided with a first baffle 412 fixedly connected to the control block 44. The first baffle 412 can block the balance tube 33. The control component 42 is provided with a slide rod 414 fixedly connected to the control block 44. The free end of the slide rod 414 is fixedly connected to a second baffle 413. The second baffle 413 can block the buffer tube 43. The function of the first baffle 412 and the second baffle 413 is to form a throttling regulation by changing the flow area. When the fluid passes through the narrow channel formed by the baffle, the mechanical energy is irreversibly lost due to vortices, friction and local resistance. The smaller the flow area, the greater the local resistance and throttling pressure drop, thereby realizing the dynamic regulation of the pressure of the medium flowing into the balance chamber 31.

[0052] As can be seen from the above embodiments, when the water pump is first started, the rotor 12 and impeller 21 rotate at extremely low speeds, the centrifugal force on the medium is weak, and it is impossible to form effective pressurization. The pressure difference between the inlet and outlet of impeller 21 is small. As the rotational speed increases, the work done by impeller 21 on the medium increases, and the medium begins to flow towards the outer edge of impeller 21 under the action of centrifugal force. An initial pressure difference is formed at the inlet and outlet of a single-stage impeller 21. Since the water pump is a multi-stage series structure, the medium is pressurized by the previous stage and then enters the next stage for pressurization. The pressure difference of each stage is superimposed, and the total axial force shows a steady upward trend as the rotational speed increases. When the rotational speed approaches the rated value, the flow channel inside the pump is completely filled with liquid, the outlet pressure of impeller 21 rises rapidly, and the pressure difference between the inlet and outlet of each stage impeller 21 increases. The axial force increases rapidly, becoming the sum of the axial thrust of all impellers 21. During the rising phase of the axial force, it acts on the rotor 12, which in turn drives the control block 44 to move towards the impeller 21 via the synchronizing rod 45. The control block 44 then drives the second baffle 413 to move via the slide rod 414, gradually reducing the area of ​​the connection between the second baffle 413 and the buffer tube 43 and the control assembly 42. This means the flow cross-section of the buffer medium gradually increases. According to fluid mechanics principles, the increase in the flow cross-section leads to a reduction in local resistance and throttling pressure drop at that point. This allows the high-pressure medium in the buffer tank 41 to flow into the balance chamber 31 near the impeller 21 with less pressure loss. Therefore, as the rotational speed and axial force increase, the fluid pressure flowing into the balance chamber 31 also increases synchronously and steadily, generating an increasing balancing force that dynamically matches the axial force. This eliminates the driving force that caused the rotor 12 to drive the balance disc 32 to move towards the impeller 21.

[0053] When the motor of pump body 1 is de-energized, the impeller 21 stops working instantly. The axial thrust generated by the pressure difference of the multi-stage impeller 21 rapidly decays to near zero. However, the side of the balance chamber 31 near the impeller 21 is still filled with the high-pressure medium before shutdown. This high-pressure medium cannot be released instantly, and the two sides of the balance disc 32 still maintain a large pressure difference. Under the action of this pressure difference, the balance force is instantly maintained at a peak level close to the rated operating condition, which is much greater than the axial thrust that has disappeared. The high-pressure medium in the balance chamber 31 can only be throttled and depressurized through the small balance gap between the balance disc 32 and the balance ring 34, and then slowly discharged to the low-pressure side of the module 13 through the balance pipe 33. The pressure discharge speed is slow and the path is long.

[0054] As described above, when the water pump is shut off, the rotor 12 moves away from the impeller 21 under the action of the residual balancing force. The rotor 12 drives the control block 44 to move synchronously away from the impeller 21. At this time, the control block 44 drives the second channel 410 to replenish the high-pressure medium in the buffer tank 41 to the side of the balance chamber 31 away from the impeller 21. Simultaneously, the control block 44 drives the first baffle 412 to begin blocking the connection between the balance pipe 33 and the control component 42. The first baffle 412 acts as a throttling device, causing the discharge cross-section of the balance pipe 33 to gradually decrease. According to the principles of fluid mechanics, the reduction in the discharge cross-section leads to a sharp increase in the local resistance of the fluid flowing out of the chamber, forming a strong back pressure effect.

[0055] Under the dual effects of liquid replenishment and pressurization, and throttling and limiting discharge, the pressure on the side of the balance chamber 31 away from the impeller 21 rapidly increases, quickly catching up with the residual high pressure on the side closer to the impeller 21. As the residual pressure on the high-pressure side slowly releases, the rotor 12 moves back, and the first baffle 412 gradually opens, causing the pressure on both sides of the balance chamber 31 to decrease synchronously and steadily. This effectively avoids the situation where the balance disc 32 violently moves in the opposite direction and rubs against each other due to excessive pressure difference on both sides of the balance chamber 31. This dynamic adjustment mechanism ensures the real-time matching of the balancing force and the axial force throughout the entire transient process, eliminates the driving force of the rotor 12's movement, and greatly improves the response characteristics and working condition adaptability of the axial force balancing mechanism.

[0056] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An axial force balancing mechanism for a supercritical boiler feedwater pump, comprising a pump body, a rotor, an inlet module, and a discharge module, characterized in that, Also includes: The booster unit includes multiple impellers fixedly connected to the rotor, and also includes a booster channel opened in the pump body; Balancing section: It includes a balancing chamber opened in the discharge module, the balancing chamber is provided with a balancing disc fixedly connected to the rotor, and the side of the balancing chamber away from the impeller is connected to the inlet module through a balancing pipe; Buffer section: It includes a receiving cavity disposed in the pump body, the receiving cavity is provided with a buffer tank, the buffer tank is connected to a control component, one side of the control component is connected to a buffer pipe, the other side of the control component is connected to a balance pipe, the buffer pipe is connected to the side of the balance cavity near the impeller, and the control component can selectively connect the buffer tank to the buffer pipe or the balance pipe according to the movement trend of the rotor when the pump body starts and stops.

2. The axial force balancing mechanism for a supercritical boiler feedwater pump according to claim 1, characterized in that, The impeller at the end is connected to the side of the balance chamber near the impeller via a pressurization channel, and the control component is fixedly connected to the receiving chamber.

3. The axial force balancing mechanism for a supercritical boiler feedwater pump according to claim 1, characterized in that, A balance ring is provided on the side of the balance chamber near the impeller, and a balance gap exists between the balance ring and the rotor.

4. The axial force balancing mechanism for a supercritical boiler feedwater pump according to claim 1, characterized in that, A control block is slidably connected within the control assembly. A synchronizing rod is fixedly connected to one end of the control block. The free end of the synchronizing rod passes through the control assembly and is rotatably connected to the rotor via a slip ring.

5. The axial force balancing mechanism for a supercritical boiler feedwater pump according to claim 1, characterized in that, A pressure plate is slidably connected inside the buffer tank. The lower end of the pressure plate is connected to the bottom of the buffer tank through an elastic element. The upper side of the buffer tank is connected to the control component through a connecting pipe.

6. The axial force balancing mechanism for a supercritical boiler feedwater pump according to claim 5, characterized in that, The control block has a first through slot that can communicate with the buffer tube, and the control block has a second through slot that can communicate with the balance tube.

7. The axial force balancing mechanism for a supercritical boiler feedwater pump according to claim 1, characterized in that, The first through slot extends in the same direction as the rotor axis, and the free end of the first through slot is connected to the side where the buffer tube in the control assembly is located. The second through slot extends in the same direction as the rotor radially, and the free end of the second through slot is connected to the side where the balance tube in the control assembly is located.

8. The axial force balancing mechanism for a supercritical boiler feedwater pump according to claim 7, characterized in that, The control component is provided with a first one-way valve with its opening facing the balance pipe at the connection point with the balance pipe, and the balance chamber is provided with a second one-way valve with its opening facing the balance chamber at the connection point with the pressurization channel.

9. The axial force balancing mechanism for a supercritical boiler feedwater pump according to claim 1, characterized in that, The control component is provided with a first baffle that is fixedly connected to the control block, and the first baffle can block the balance tube.

10. The axial force balancing mechanism for a supercritical boiler feedwater pump according to claim 9, characterized in that, The control assembly includes a slide rod that is fixedly connected to the control block. The free end of the slide rod is fixedly connected to a second baffle, which can block the buffer tube.

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