Nuclear main pump with low pressure pulsation performance

Abstract

The utility model discloses a nuclear main pump with low pressure pulsation performance belongs to nuclear main pump design technical field, including pump shell main part, guide vane body, impeller and pump shaft, and the fluid chamber that has the intercommunication arrangement with the bottom of pump shell main part in guide vane body, the pump shaft is along vertical and is in proper order and is penetrated the pump shell main part with the guide vane body, and with the impeller fixed connection, the pump shell main part has the throttling sealing portion, the buffer cavity portion and the mechanical seal portion in proper order along the direction of being close to guide vane body, the buffer cavity portion is linked together with the fluid chamber through the throttling sealing portion, and the buffer cavity portion outside is equipped with the inflation unit for filling into the buffer cavity portion with the pressure inert gas. The utility model utilizes the compressibility of inert gas, offsets and reduces the pressure pulsation of pump export, and then reduces the fluid noise and mechanical vibration noise of nuclear main pump.

Description

Technical Field

[0001] This utility model relates to the field of nuclear main pump design technology, and in particular to a nuclear main pump with low pressure pulsation performance. Background Technology

[0002] Using liquid metal as a coolant for nuclear reactors is a development trend for underwater nuclear power platforms, characterized by its small size, good thermal conductivity, high thermal efficiency, and high power output. The main nuclear pump, which drives the circulation of high-temperature liquid metal inside the reactor, is one of the core power components of the nuclear reactor.

[0003] Nuclear main pumps fall under the category of centrifugal pumps, but their technical parameters and performance requirements are much higher than those of common industrial centrifugal pumps. In particular, to meet the low-noise and low-vibration requirements of underwater nuclear power platforms, the nuclear main pump needs to operate stably with low noise and low vibration at 450 degrees Celsius. However, due to the relative motion between the blades and guide vanes, the pump inevitably experiences "dynamic-static interference" when transporting liquid, resulting in pressure pulsations at the pump outlet. These pressure pulsations generate fluid noise and excite mechanical (pipeline and pump) vibration noise, increasing the noise sources. Therefore, there is an urgent need to develop a nuclear main pump with low pressure pulsation performance to facilitate its use on underwater nuclear power platforms and meet the expected safety requirements. Utility Model Content

[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing a nuclear main pump with low pressure pulsation performance. This reduces the fluid noise of the nuclear main pump and the mechanical vibration noise generated by the fluid pressure pulsation by reducing the pump outlet pressure pulsation.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A nuclear main pump with low-pressure pulsation performance includes a pump casing body, a guide vane body, an impeller, and a pump shaft. The guide vane body is sealed to the pump casing body. A fluid chamber communicating with the bottom of the pump casing body is located inside the guide vane body. The pump shaft passes through the pump casing body and the guide vane body vertically and is fixedly connected to the impeller. The pump casing body has a throttling seal, a buffer chamber, and a mechanical seal in sequence along the direction close to the guide vane body. The throttling seal is used to achieve throttling sealing between the pump casing body and the pump shaft. The mechanical seal is used to achieve rotational sealing between the pump casing body and the pump shaft. The buffer chamber is connected to the fluid chamber via the throttling seal. An inflation unit for filling the buffer chamber with pressurized inert gas is provided on the outside of the buffer chamber. A throttling seal, a buffer chamber, and a mechanical seal are arranged axially on the pump casing. The buffer chamber is equipped with an inert gas filling unit. The fluid leaking into the buffer chamber from the throttling seal and the inert gas filling the buffer chamber form a dynamic pressure balance. Because the gas has strong compressibility, the gas volume shrinks or expands with the pressure pulsation of the fluid chamber, thereby effectively reducing the pressure pulsation value and reducing the fluid noise and mechanical vibration noise caused by pressure fluctuations.

[0006] The guide vane body has a radial bearing on its inner side, which is used to realize the rotational connection between the guide vane body and the pump shaft.

[0007] The pump housing body is provided with a thrust bearing, which is located on the side of the mechanical seal away from the buffer cavity, and is used to provide a thrust force to the pump shaft that acts in the opposite direction to the axial force of the fluid.

[0008] The buffer cavity is equipped with several thermal barrier ring plates, each of which is axially spaced and sleeved on the outside of the pump shaft and fixedly connected to the inner wall of the buffer cavity. The thermal barrier ring plates effectively isolate the heat radiation generated by the high-temperature medium below them, ensuring that the mechanical seal, thrust bearing, and motor can operate stably at their respective allowable operating temperatures.

[0009] The heat barrier ring plate has a conical structure, and the inner ring of the heat barrier ring plate is located on the side close to the mechanical seal.

[0010] The inflation unit includes an inflation connector, an inflation solenoid valve, and an inert gas tank. The inflation connector is fixed to the outside of the pump housing body and connected to the buffer cavity. The inert gas tank is connected to the inflation connector via an inflation pipeline. The inflation solenoid valve is installed on the inflation pipeline.

[0011] The inflation unit also includes a flow sensor and an opening regulating valve. The opening regulating valve and the flow sensor are installed sequentially on the inflation pipeline on the outlet side of the inflation solenoid valve along the gas transmission direction. The opening regulating valve is connected to the flow sensor via a controller. The controller is configured to control the opening of the opening regulating valve according to the set flow rate of the flow sensor.

[0012] The buffer cavity is equipped with a liquid level sensor, which is connected to the inflation solenoid valve via a controller. The controller is configured to control the inflation solenoid valve to open for the first time and remain open for a set time when the liquid level in the buffer cavity is detected by the liquid level sensor to exceed a set minimum threshold.

[0013] The controller is configured to open the inflation solenoid valve and replenish the buffer cavity with inert gas when the liquid level sensor detects that the fluid level in the buffer cavity exceeds a set maximum threshold.

[0014] This utility model has the following beneficial effects: By axially arranging a throttling sealing part, a buffer cavity part, and a mechanical seal part on the pump casing body, and providing an inert gas filling unit on the buffer cavity part, the fluid leaking into the buffer cavity from the throttling sealing part and the inert gas filling the buffer cavity form a dynamic pressure balance. Because the gas has strong compressibility, the volume of the gas filling it decreases or expands with the pressure pulsation of the fluid chamber, thereby offsetting and reducing the magnitude of the pressure pulsation, and effectively reducing the fluid noise and mechanical vibration noise generated by the pressure pulsation. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this utility model and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the structure of this utility model; Figure 2 This is a schematic diagram of the structure of the buffer cavity in this utility model; Figure 3 This is a schematic diagram of the mechanical seal part in this utility model; Figure 4 This is a schematic diagram of the thrust bearing portion in this utility model; Figure 5 A comparative schematic diagram of pressure pulsation after the main nuclear pump is started; Figure 5(a) shows the pressure fluctuation curve of the existing nuclear main pump during operation over time. Figure 5 (b) shows the pressure fluctuation curve of the main pump in the core of this invention during operation as a function of time.

[0017] Reference numerals in the attached drawings: 1. Impeller; 2. Guide vane; 3. Pump casing body; 4. Pump shaft; 5. Throttling seal; 501. Throttling bushing; 502. Throttling shaft sleeve; 6. Buffer chamber; 7. Mechanical seal; 8. Air charging unit; 801. Air charging solenoid valve; 802. Opening adjustment valve; 803. Flow sensor; 804. Exhaust valve; 9. Radial bearing; 10. Thrust bearing; 11. Thermal barrier ring; 12. Liquid level sensor. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. The components of the embodiments of this utility model described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0019] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0020] In the description of this utility model, it should be understood that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the utility model product is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used to facilitate the description of this utility model and to simplify the description, and are not intended to indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0021] like Figure 1As shown, this utility model provides a nuclear main pump with low pressure pulsation performance, including a pump casing body 3, a guide vane body 2, an impeller 1, and a pump shaft 4. The guide vane body 2 is sealed to the pump casing body 3, and a fluid chamber communicating with the bottom of the pump casing body 3 is located inside the guide vane body 2. Specifically, the bottom opening of the guide vane body 2 forms the pump inlet of the nuclear main pump, and the outer bottom opening of the pump casing body 3 forms the pump outlet of the nuclear main pump. The pump shaft 4 vertically passes through the pump casing body 3 and the guide vane body 2 in sequence, and is fixedly connected to the impeller 1. The pump casing body 3, along the direction near the guide vane body 2, sequentially includes a throttling seal 5, a buffer cavity 6, and a mechanical seal 7. Specifically, the throttling seal 5 is used to achieve throttling sealing between the pump casing body 3 and the pump shaft 4, including a throttling bushing 502 fixed on the pump shaft 4 and a throttling bushing 501 fixed inside the pump casing body 3. The mechanical seal 7 is used to achieve rotational sealing between the pump casing body 3 and the pump shaft 4. Specifically, the mechanical seal 7 in this solution adopts a double-end mechanical seal, as shown in the diagram. Figure 3 As shown, its structure is the same as the existing double-end mechanical seal structure, and will not be described in detail. The buffer chamber 6 is connected to the fluid chamber via the throttling seal 5. An inflation unit 8 for filling pressurized inert gas into the buffer chamber 6 is provided on the outside of the buffer chamber 6. After the nuclear main pump starts, under the high pressure at the pump outlet, the high-temperature molten metal permeates into the buffer chamber through the throttling gap between the throttling bushing 501 and the throttling shaft sleeve 502. At the same time, inert gas is filled into the buffer chamber by the inflation unit 8. As the amount of liquid leaking into the buffer chamber increases, the pressure of the inert gas increases until the pressure of the gas is close to the pressure of the liquid, forming a dynamic pressure balance. With the pressure pulsation generated by the liquid in the fluid chamber, the pressure pulsation is transmitted into the buffer chamber, and the volume of the gas filled into the buffer chamber shrinks or expands accordingly, thereby offsetting and reducing the pressure pulsation value to a certain extent. Figure 5 As shown, during the operation of the nuclear main pump with a buffer chamber, its pressure pulsation value ( Figure 5 (b) was reduced to the original ( Figure 5 The pressure is below 1 / 5, thus effectively reducing fluid noise and mechanical vibration noise caused by pressure pulsation.

[0022] Further preferred, such as Figure 1 As shown, the guide vane body 2 has a radial bearing 9 on its inner side. The radial bearing 9 is used to realize the rotational connection between the guide vane body 2 and the pump shaft 4 to ensure the stability of the transmission between the pump shaft 4 and the guide vane body 2. The pump housing body 3 is provided with a thrust bearing 10. The thrust bearing 10 is located on the side of the mechanical seal 7 away from the buffer cavity 6, and is used to provide a thrust force to the pump shaft 4 in the opposite direction to the axial force of the fluid. Specifically, in this solution, the thrust bearing 10 adopts the following... Figure 4The Mitchell thrust bearing shown has the same structure as existing thrust bearings, so it will not be described in detail.

[0023] It is worth noting that, such as Figure 2 As shown, the pump casing body 3 is divided into a lower pump casing, a middle pump casing, and an upper pump casing from bottom to top. The lower pump casing and the middle pump casing are sealed together, and the middle pump casing and the upper pump casing are sealed together. The pump outlet is located outside the lower pump casing. The bottom of the lower pump casing has a first through-hole for the pump shaft 4 to pass through. The throttling bushing 501 is fixed inside the first through-hole. The top of the lower casing forms a buffer groove. The middle pump casing has a cylindrical inner cavity. The bottom of the upper pump casing is a flange face. After the three pump casings are connected, the flange face, the cylindrical inner cavity, and the buffer groove together form a buffer cavity part 6 with a regular shape (cylindrical). The middle of the flange face has a second through-hole for the pump shaft 4 to pass through. The double-end mechanical seal is fixed on the second through-hole. The top opening of the upper pump casing is provided and connected to the pump shaft 4 through a Mitchell thrust bearing.

[0024] In a further preferred embodiment, the buffer cavity 6 is provided with a plurality of heat barrier ring plates 11, each of which is axially spaced and sleeved on the outside of the pump shaft 4 and fixedly connected to the inner wall of the buffer cavity 6. In this embodiment, there are four heat barrier ring plates 11, which are made of insulating materials with low thermal conductivity, such as aluminum silicate cotton board, vacuum insulation board, ceramic fiber board, etc. The heat barrier ring plates 11 effectively isolate the heat radiation generated by the high-temperature medium below the heat barrier ring plates 11 through their insulation properties, thereby ensuring that the mechanical seal 7, the thrust bearing 10 and the motor can operate stably at the allowable operating temperature of their respective components.

[0025] More preferably, the heat barrier ring plate 11 has a conical structure. Specifically, the inner ring of the heat barrier ring plate 11 is located on the side close to the mechanical seal part 7. Through the conical design, the area facing the high-temperature medium is larger, thereby reflecting more heat radiation.

[0026] like Figure 2As shown, in this scheme, the inflation unit 8 includes an inflation connector, an inflation solenoid valve 801, and an inert gas tank. The inflation connector is fixed to the outside of the pump housing body and connected to the buffer cavity 6. The inert gas tank is connected to the inflation connector via an inflation pipeline. The inflation solenoid valve 801 is installed on the inflation pipeline. Furthermore, the inflation unit 8 also includes a flow sensor 803 and an opening adjustment valve 802. The opening adjustment valve 802 and the flow sensor 803 are sequentially installed on the inflation solenoid valve 801 along the gas transmission direction. On the gas filling pipeline on the outlet side, the opening regulating valve 802 is communicatively connected to the flow sensor 803 via a controller. The controller is configured to control the opening of the opening regulating valve 802 according to the set flow rate of the flow sensor 803, so that the gas filling unit 8 fills the buffer cavity 6 with inert gas at a constant flow rate. The amount of inert gas filled into the buffer cavity 6 to buffer pressure pulsation is calculated based on the gas filling time. In this scheme, the inert gas is a protective gas used to protect the high-temperature liquid metal from oxidation, and argon is preferred.

[0027] Preferably, in order to avoid the heat barrier ring plate 11 affecting the inflation speed of the inflation unit 8, the installation height of the heat barrier ring plate 11 should be higher than the height of the inflation joint.

[0028] More preferably, a liquid level sensor 12 is provided inside the buffer cavity 6. The liquid level sensor 12 is a high-temperature resistant sensor and can be sealed and installed on the middle pump housing via a transmitter. The liquid level sensor 12 is communicatively connected to the inflation solenoid valve 801 via a controller. The controller is configured to control the inflation solenoid valve 801 to open for the first time and remain open for a set time when the liquid level sensor 12 detects that the fluid level in the buffer cavity 6 exceeds a set minimum threshold, so as to fill the buffer cavity 6 with a certain amount of inert gas.

[0029] To protect the gas filling unit 8, the controller is configured to open the gas filling solenoid valve and add inert gas to the buffer chamber 6 when the liquid level sensor 12 detects that the fluid level in the buffer chamber 6 exceeds the set maximum threshold. It is worth noting that the above controller can be a PLC controller. Preferably, the maximum threshold is less than the vertical height between the gas filling connector and the connection between the buffer chamber 6 and the connection between the buffer chamber 6 and the throttling seal 5. When the high-temperature metal liquid level in the buffer chamber 6 exceeds the maximum threshold, it proves that there is a leak in the buffer chamber 6. Inert gas is added in time to maintain the normal operation of the nuclear main pump. The nuclear main pump is then overhauled after the entire nuclear reactor is shut down.

[0030] For the aforementioned nuclear main pump, before commissioning, the volume of inert gas in the buffer chamber 6 that would bring the main pump to a theoretical dynamic equilibrium state is estimated in advance. Relevant control parameters are then set in the controller. These parameters include the minimum threshold, maximum threshold, and normal liquid level of the level sensor 12, the set flow rate Q of the flow sensor 803, and the initial opening duration t of the charging solenoid valve 801. The normal liquid level, the set flow rate Q of the flow sensor, and the initial opening duration t of the charging solenoid valve are calculated based on the estimated volume of inert gas in the buffer chamber 6. The specific calculation process is as follows: The volume occupied by the inert gas (argon) in the buffer cavity 6 can be calculated according to the regular cylindrical structure, V=πr 2 H and r are the inner diameter values ​​of the middle pump casing, and H is the estimated height value occupied by the inert gas in the buffer chamber 6; for example Figure 2 As shown, the liquid level of the high-temperature liquid metal corresponding to the estimated height value H is recorded as the normal liquid level value; according to the ideal gas law, the estimated number of moles of argon in the buffer chamber is n=PV / RT, where P is the average pressure value of the pump outlet of the nuclear main pump, T is the estimated Kelvin temperature of the liquid metal in the buffer chamber, and P and T can be obtained from the historical operating data of the nuclear main pump and the nuclear reactor cooling cycle system. R is the ideal gas constant, with a value of 8.314 J / (mol·K); further, the mass of argon to be charged into the buffer chamber is m=nM, where M is the molar mass of argon, with a value of 40 g / mol; then, according to the volume formulas V=m / ρ and V=Qt, the relationship between the duration t of the first opening of the charging solenoid valve 801 and the set flow rate Q of the flow sensor 803 is obtained as t=m / (ρQ), where ρ is the density of argon at room temperature, with a value of 1.784 x 10⁻⁶. 3 g / ml; then by determining the specific value of one parameter (such as the set flow rate Q of the flow sensor 803), the value of another parameter (such as the duration t of the first opening of the inflation solenoid valve 801) can be obtained.

[0031] After the main nuclear pump is put into use, its specific operating procedures are as follows: Before the cooling circulation system of the nuclear reactor is put into operation, argon gas is introduced into the main nuclear pump and related pipelines for protection; before starting the main nuclear pump, a priming operation is performed, and the exhaust valve 804 on the pump casing body 3 is opened simultaneously, preferably, as follows: Figure 2As shown, the exhaust valve 804 corresponds to the position of the gas filling connector, allowing gas to be discharged from the buffer chamber 6. After the priming pump is completed, the exhaust valve 804 is closed, and the main core pump is turned on. Under normal operation of the main core pump, high-temperature liquid metal enters the buffer chamber 6 through the throttling seal 5. When the liquid level sensor 12 detects that the liquid level of the high-temperature liquid metal in the buffer chamber 6 exceeds the set minimum threshold, the controller controls the opening of the gas filling solenoid valve 801 and the opening adjustment valve 802, and maintains the argon gas delivery flow rate at Q to the buffer chamber 6. The internal filling time is t. After closing the filling solenoid valve 801 and the opening adjustment valve 802, the buffer chamber 6 is in a dynamic balance between high-temperature liquid metal and argon. When the liquid level sensor 12 detects that the liquid level of the high-temperature liquid metal in the buffer chamber 6 exceeds the set maximum threshold, the controller controls the opening of the filling solenoid valve 801 and the opening adjustment valve 802 to replenish argon until the liquid level sensor 12 detects that the liquid level of the high-temperature liquid metal in the buffer chamber 6 is lower than the normal liquid level value, and repeats this step to ensure the normal operation of the nuclear main pump.

[0032] During normal operation of the nuclear main pump, the pressure pulsation generated by the impeller 1 and guide vane 2 is transmitted from the fluid chamber to the buffer chamber 6 through the throttling gap of the throttling seal 5, and finally to the inert gas compressed in the buffer chamber 6. Because the gas has strong compressibility, the pressure pulsation of the entire fluid chamber is effectively reduced by the shrinking and expanding of the inert gas volume in the buffer chamber 6, thereby reducing the fluid noise and the mechanical vibration noise generated by the nuclear main pump.

[0033] The above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A nuclear main pump with low pressure pulsation performance, comprising a pump casing body, a guide vane body, an impeller, and a pump shaft, wherein the guide vane body is sealed to the pump casing body, and the guide vane body has a fluid chamber communicating with the bottom of the pump casing body; the pump shaft vertically passes through the pump casing body and the guide vane body sequentially, and is fixedly connected to the impeller, characterized in that, The pump casing body has a throttling seal, a buffer chamber, and a mechanical seal in sequence along the direction close to the guide vane. The throttling seal is used to achieve throttling sealing between the pump casing body and the pump shaft. The mechanical seal is used to achieve rotational sealing between the pump casing body and the pump shaft. The buffer chamber is connected to the fluid chamber through the throttling seal. An air filling unit is provided on the outside of the buffer chamber for filling the buffer chamber with pressurized inert gas.

2. A nuclear main pump with low pressure pulsation performance according to claim 1, characterized in that, The guide vane body has a radial bearing on its inner side, which is used to realize the rotational connection between the guide vane body and the pump shaft.

3. A nuclear main pump with low pressure pulsation performance according to claim 1 or 2, characterized in that, The pump housing body is provided with a thrust bearing, which is located on the side of the mechanical seal away from the buffer cavity, and is used to provide a thrust force to the pump shaft that acts in the opposite direction to the axial force of the fluid.

4. A nuclear main pump with low pressure pulsation performance according to claim 1, characterized in that, The buffer cavity is provided with a number of thermal barrier ring plates, each of which is axially spaced and sleeved on the outside of the pump shaft and fixedly connected to the inner wall of the buffer cavity.

5. A nuclear main pump with low pressure pulsation performance according to claim 4, characterized in that, The heat barrier ring plate has a conical structure, and the inner ring of the heat barrier ring plate is located on the side close to the mechanical seal.

6. A nuclear main pump with low pressure pulsation performance according to claim 1, 4, or 5, characterized in that, The inflation unit includes an inflation connector, an inflation solenoid valve, and an inert gas tank. The inflation connector is fixed to the outside of the pump housing body and connected to the buffer cavity. The inert gas tank is connected to the inflation connector via an inflation pipeline. The inflation solenoid valve is installed on the inflation pipeline.

7. A nuclear main pump with low pressure pulsation performance according to claim 6, characterized in that, The inflation unit also includes a flow sensor and an opening regulating valve. The opening regulating valve and the flow sensor are installed sequentially on the inflation pipeline on the outlet side of the inflation solenoid valve along the gas transmission direction. The opening regulating valve is connected to the flow sensor via a controller. The controller is configured to control the opening of the opening regulating valve according to the set flow rate of the flow sensor.

8. A nuclear main pump with low pressure pulsation performance according to claim 7, characterized in that, The buffer cavity is equipped with a liquid level sensor, which is connected to the inflation solenoid valve via a controller. The controller is configured to control the inflation solenoid valve to open for the first time and remain open for a set time when the liquid level in the buffer cavity is detected by the liquid level sensor to exceed a set minimum threshold.

9. A nuclear main pump with low pressure pulsation performance according to claim 8, characterized in that, The controller is configured to open the inflation solenoid valve and replenish the buffer cavity with inert gas when the liquid level sensor detects that the fluid level in the buffer cavity exceeds a set maximum threshold.

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