A method for analyzing leakage performance of a mechanical seal of a residual heat removal pump

Abstract

The present application relates to a kind of residual heat exhaust pump mechanical seal leakage performance analysis method.The method includes the following steps: generating residual heat exhaust pump and its mechanical seal three-dimensional model.Volume extraction is carried out on three-dimensional model, to generate the fluid domain of solid domain.Non-structured grid division processing is carried out on solid domain and fluid domain.In three-dimensional model after grid division processing, to pump domain, to obtain the pressure boundary and temperature boundary of mechanical seal domain for conjugate heat transfer calculation.According to the pressure boundary and temperature boundary of mechanical seal domain, to obtain the fluid pressure and solid temperature of mechanical seal domain related components for the conjugate heat transfer calculation of mechanical seal domain.According to the fluid pressure and solid temperature of mechanical seal domain related components, to obtain the maximum gap data between dynamic ring and static ring in mechanical seal domain for heat-fluid-solid coupling analysis.The maximum gap data is used as leakage channel width, to obtain the leakage rate of residual heat exhaust pump mechanical seal.

Description

Technical Field

[0001] This invention relates to the field of mechanical seal performance analysis technology, and in particular to a method for analyzing the leakage performance of a mechanical seal in a waste heat discharge pump. Background Technology

[0002] Residual heat removal (RRA) pumps are a crucial component of the residual heat removal system in pressurized water reactor nuclear power plants, responsible for ensuring the normal circulation of coolant during reactor maintenance or malfunctions. This function is critical to the safe operation of nuclear power plants, especially in high-temperature and high-pressure environments, where RRA pumps must possess reliable performance to prevent potential safety hazards. Because RRA pumps transport highly radioactive coolant, leaks in the mechanical seals can not only lead to coolant leakage but also potentially cause radioactive contamination, severely impacting the safety and economic efficiency of the nuclear power plant. Mechanical seals are widely used in rotating machinery due to their reliable structure, long service life, and low leakage characteristics, especially in applications requiring high sealing performance and reliability.

[0003] However, research on the leakage performance of mechanical seals for RRA pumps is relatively limited, especially in three-dimensional thermo-fluid-structure interaction environments. Existing studies often focus on the analysis of single factors, lacking a systematic approach to comprehensively evaluate the performance of mechanical seals under complex operating conditions. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for analyzing the leakage performance of a mechanical seal in a waste heat discharge pump.

[0005] The technical solution adopted by this invention to solve its technical problem is: a method for analyzing the leakage performance of a waste heat discharge pump mechanical seal, the method comprising the following steps:

[0006] S1. Generate a three-dimensional model of the waste heat discharge pump and its mechanical seal;

[0007] S2. Extract volume from the three-dimensional model to generate a fluid domain within a solid domain, wherein the solid domain includes a pump domain and a mechanical seal domain.

[0008] S3. Perform unstructured mesh generation on the solid domain and the fluid domain;

[0009] S4. In the three-dimensional model after mesh generation, perform conjugate heat transfer calculations on the pump domain to obtain the pressure boundary and temperature boundary of the mechanical seal domain.

[0010] S5. In the three-dimensional model after mesh generation, conjugate heat transfer calculations are performed on the mechanical seal domain based on the pressure and temperature boundaries of the mechanical seal domain to obtain the fluid pressure and solid temperature of the relevant components of the mechanical seal domain.

[0011] S6. Perform a thermo-fluid-structure interaction analysis based on the fluid pressure and solid temperature of the relevant components in the mechanical seal domain to obtain the maximum gap data between the dynamic ring and the stationary ring in the mechanical seal domain.

[0012] S7. The maximum gap data is used as the leakage channel width, and the leakage rate of the mechanical seal of the waste heat discharge pump is calculated accordingly.

[0013] Furthermore, in the waste heat discharge pump mechanical seal leakage performance analysis method of the present invention, in step S1, the three-dimensional model includes a pump casing, impeller, pump shaft, mechanical seal housing, dynamic ring, stationary ring, and stationary ring seat; wherein, the main structural parameters of the impeller include impeller inlet diameter, impeller outlet diameter, hub diameter, number of blades, blade outlet angle, and blade wrap angle, and the main structural parameters of the mechanical seal include sealing end face inner diameter, sealing end face outer diameter, and sealing end face balance diameter.

[0014] Furthermore, in the waste heat discharge pump mechanical seal leakage performance analysis method of the present invention, step S4 includes:

[0015] In the 3D model after mesh generation, the inlet pressure, inlet temperature and outlet flow boundary conditions of the pump domain are determined, and the mass conservation equation, momentum conservation equation and energy conservation equation are solved based on the SIMPLEC algorithm to obtain the pressure boundary and temperature boundary of the mechanical seal domain.

[0016] Furthermore, in the waste heat discharge pump mechanical seal leakage performance analysis method of the present invention, step S5 includes:

[0017] In the 3D model after mesh generation, the flow rate and pressure boundary conditions of the cooling water in the fusible body and the cooling water in the sealing cavity of the mechanical seal domain are determined according to the pressure boundary and temperature boundary of the mechanical seal domain. The mass conservation equation, momentum conservation equation and energy conservation equation are solved based on the SIMPLEC algorithm to obtain the fluid pressure and solid temperature of the relevant components of the mechanical seal domain.

[0018] Furthermore, in the waste heat discharge pump mechanical seal leakage performance analysis method of the present invention, the fluid pressure and solid temperature of the relevant components of the mechanical seal domain include the fluid pressure of the contact surface of the bushing, rotating ring, stationary ring and stationary ring seat and the cooling water of the sealing cavity of the mechanical seal domain, as well as the temperature data of the bushing, rotating ring, stationary ring and stationary ring seat.

[0019] Furthermore, in the waste heat discharge pump mechanical seal leakage performance analysis method of the present invention, step S5 includes:

[0020] The frictional heat flux density q of the thermal boundary condition is set between the end faces of the moving ring and the stationary ring. FIt is calculated using the following formula:

[0021] q F =fp c v

[0022] Where f is the coefficient of friction; p c is the specific pressure at the sealed end face; v is the average velocity at the end face.

[0023] Furthermore, in the waste heat discharge pump mechanical seal leakage performance analysis method of the present invention, step S6 includes:

[0024] The fluid pressure and solid temperature data of the relevant components of the mechanical seal domain are transferred to the structural analysis module through the External Data module. Circumferential constraints and spring support constraints are applied to the stationary ring seat, and fixed constraints are applied to the pump domain connection surface. Moreover, in the structural analysis module, a static solver is used to perform stress, strain, and deformation analysis on the dynamic ring, stationary ring, stationary ring seat, and bushing of the mechanical seal to obtain the maximum gap data between the dynamic ring and the stationary ring in the mechanical seal domain.

[0025] Furthermore, in the waste heat discharge pump mechanical seal leakage performance analysis method of the present invention, step S2 includes:

[0026] The fluid domains of the pump domain and the mechanical seal domain are determined by a volume extraction method; wherein, the fluid domain of the pump domain is the water flow domain when the waste heat discharge pump is working, and the fluid domain of the mechanical seal domain includes the cooling water flow domain of the plenum and the cooling water flow domain of the sealing cavity.

[0027] Furthermore, in the waste heat discharge pump mechanical seal leakage performance analysis method of the present invention, step S3 includes:

[0028] In the unstructured mesh generation process of the solid domain and the fluid domain, the y+ value of the fluid boundary layer of the pump domain is set to be within 1, and the y+ value of the fluid domain of the mechanical seal domain is set to be within an allowable range based on 30, so as to achieve densification processing at the mechanical seal surface, near the impeller and in small flow channels; where the y+ value represents the dimensionless distance in the normal direction of the wall.

[0029] Furthermore, in the waste heat discharge pump mechanical seal leakage performance analysis method of the present invention, step S7 includes:

[0030] Using the maximum gap data as the width of the leakage channel, the leakage rate Q of the waste heat discharge pump mechanical seal is calculated using the following Mayer leakage rate empirical formula:

[0031]

[0032] Among them, D oΔp is the outer diameter of the sealing end face, Δp is the differential pressure of the sealing fluid, S is the gap balance coefficient, h is the end face gap, and p is the outer diameter of the sealing end face. c It is the specific pressure of the sealing end face, p c =Bp+p s B is the balance coefficient. p is the fluid medium pressure acting on the moving and stationary rings. s It is the spring ratio, D i It is the inner diameter of the sealing end face, D b It is the equilibrium diameter.

[0033] The leakage performance analysis method for the mechanical seal of the waste heat recovery pump (RRA) of this invention has the following beneficial effects: By comprehensively considering the coupling effects of heat, fluid, and solid, this invention can accurately assess the leakage performance of the mechanical seal of the RRA pump, providing a scientific basis for the safe operation of the RRA pump. This is not only of great significance for its structural design and optimization, but also helps to improve the safety and reliability of nuclear power plants. It can effectively reduce safety hazards caused by leakage, reduce maintenance costs, and extend the service life of equipment, thereby improving overall economic benefits. Attached Figure Description

[0034] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0035] Figure 1 This is a flowchart illustrating the method for analyzing the leakage performance of a waste heat discharge pump mechanical seal provided in an embodiment of the present invention.

[0036] Figure 2 This is a simplified schematic diagram of the RRA pump and its matching mechanical seal provided in an embodiment of the present invention;

[0037] Figure 3 This is a schematic diagram of the fluid domain of the RRA pump and mechanical seal provided in an embodiment of the present invention;

[0038] Figure 4 This is a schematic diagram of the main boundary conditions of the mechanical seal model provided in the embodiments of the present invention;

[0039] Figure 5 This is a schematic diagram of mechanical seal constraints and loads provided in an embodiment of the present invention;

[0040] Figure 6 These are schematic diagrams of the grid provided in the embodiments of the present invention (a) pump grid diagram; b) mechanical seal grid diagram;

[0041] Figure 7 This is a diagram showing the change in leakage gap at the outlet of the leakage channel provided in an embodiment of the present invention.

[0042] Labeling Explanation: 1. Inlet Flange; 2. Pump Casing; 3. Outlet Flange; 4. Pump Cover; 5. Pump Shaft; 6. Impeller Nut; 7. Impeller; 8. Shaft Sleeve; 9. Mechanical Seal Housing; 10. Mechanical Seal Shaft Sleeve; 11. Rotating Ring; 12. Stationary Ring; 13. Stationary Ring Seat; 14. Gland Cooling Water; 15. Sealing Chamber Cooling Water; 16. Gland Cooling Water Inlet; 17. Gland Cooling Water Outlet; 18. Sealing Chamber Cooling Water Inlet; 19. Sealing Chamber Cooling Water Outlet; 20. RRA Pump and Inlet Section; 21. RRA Pump Impeller Section; 22. RRA Pump Outlet Section; 23. Gland Cooling Water Flow Area; 24. Sealing Chamber Cooling Water Flow Area; 25. Fixed constraint; 26. Fluid pressure load; 27. Circumferential constraint; 28. Spring support; A. Mechanical seal and pump cover connection surface; B. Mechanical seal and shaft sleeve connection surface (x direction); C. Mechanical seal and shaft connection surface; D. Mechanical seal and shaft sleeve connection surface (z direction); W1. Mechanical seal housing wall connected to the pump area; W2. Mechanical seal housing wall (top); W3. Mechanical seal housing wall (right); W4. Rotating ring inner wall; W5. Mechanical seal shaft sleeve outer wall; W6. Stationary ring seat inner wall; W7. Stationary ring inner wall; WR. Rotating and stationary ring end face contact surface (rotating ring); WS. Rotating and stationary ring end face contact surface (stationary ring). Detailed Implementation

[0043] To provide a clearer understanding of the technical features, objectives, and effects of this invention, the specific embodiments of the invention are now described in detail with reference to the accompanying drawings. It should be noted in the following description that SpaceClaim and SolidWorks are two different modeling software programs. Specific modeling methods / processes can be found in related technologies. In this application, the solid domain is obtained through modeling in SolidWorks, and the fluid domain is obtained through volume extraction operations in SpaceClaim. FLUENT Meshing is a dedicated meshing tool provided by AnsysFLUENT, used to provide high-quality meshes for computational fluid dynamics; workbench is an integrated platform of the Ansys software suite, where structural static analysis is performed through the Static Structural module in workbench. External Data: A module in workbench used to import external data into the simulation workflow. Engineering Data: A module in workbench used to define the material properties and engineering data required for the simulation. Realizedk-ε,SST k-ω: The name of the turbulence equation. Materials: A module in Ansys FLUENT for setting material properties. Sweep: A method of mesh generation. The SIMPLEC algorithm, short for Semi-Implicit Method for Pressure-Linked Equations-C, is a numerical method in computational fluid dynamics (CFD) for solving flow field problems. It is an improvement upon the SIMPLE algorithm. It enhances the pressure-velocity coupling method by introducing a correction function to increase convergence speed.

[0044] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0045] In a preferred embodiment, reference Figure 1 The method for analyzing the leakage performance of the mechanical seal of the waste heat discharge pump in this embodiment includes the following steps:

[0046] S1. Generate a 3D model of the waste heat discharge pump and its mechanical seal. Specifically, a 3D model of the waste heat discharge pump and its mechanical seal can be constructed and generated using SolidWorks modeling software. It can be understood that in step S1, the 3D model includes key components such as the pump casing, impeller, pump shaft, mechanical seal housing, dynamic ring, stationary ring, and stationary ring seat. The main structural parameters of the impeller include the impeller inlet diameter, impeller outlet diameter, hub diameter, number of blades, blade outlet angle, and blade wrap angle. The main structural parameters of the mechanical seal include the inner diameter of the sealing end face, the outer diameter of the sealing end face, and the balanced diameter of the sealing end face.

[0047] S2. Perform volume extraction on the 3D model to generate the fluid domain of the solid domain, which includes the pump domain and the mechanical seal domain. Specifically, in step S2, the fluid domains of the pump domain and the mechanical seal domain are determined by the volume extraction method. The fluid domain of the pump domain is the water flow domain during the operation of the waste heat discharge pump, and the fluid domain of the mechanical seal domain includes the cooling water flow domain of the plenum and the cooling water flow domain of the sealing cavity. For example, volume extraction can be performed in SpaceClaim to generate the fluid domains of the pump domain and the mechanical seal domain.

[0048] S3. Perform unstructured mesh generation on the solid and fluid domains. In step S3, during the unstructured mesh generation of the solid and fluid domains, the y+ value is set to within 1 for the fluid boundary layer of the pump domain, and within an allowable range of 30 for the fluid domain of the mechanical seal domain. This achieves mesh refinement at the mechanical seal surface, near the impeller, and in small flow channels. The y+ value represents the dimensionless distance in the wall normal direction, primarily used in boundary layer analysis in fluid mechanics to determine if the mesh resolution is sufficiently fine. Reasonably controlling the y+ value can balance computational accuracy and efficiency, and is a crucial step in mesh generation and simulation verification. In other words, the mesh generation process can also further refine the mesh at the mechanical seal surface, near the impeller, and in small flow channels. In this embodiment, to better capture complex physical phenomena and improve computational accuracy in engineering simulation calculations, it is necessary to generate a finer mesh for a certain region. In this scheme, the mechanical seal surface, impeller, and small flow channels are areas of particular interest. For example, the y+ value of the fluid domain in the mechanical seal region can be controlled to be around 30, such as 28, 29, 30, 31, 32, 29.4, 29.8, 30.3, 30.5, 30.7, etc. For example, the solid region and fluid domain of the RRA pump can be unstructured and meshed using FLUENT Meshing, with further meshing applied to the mechanical seal surface, near the impeller, and in small flow channels.

[0049] It should be noted that in this embodiment, mesh generation is a fundamental step in computational fluid dynamics physics simulation. These mesh elements are used for numerically solving partial differential equations. Mesh generation directly determines the accuracy, stability, and efficiency of the calculation. A reasonable mesh generation is a key step for successful simulation.

[0050] S4. In the meshed 3D model, perform conjugate heat transfer calculations on the pump domain to obtain the pressure and temperature boundaries of the mechanical seal domain. In some embodiments, step S4 includes: determining the inlet pressure, inlet temperature, and outlet flow rate boundary conditions of the pump domain in the meshed 3D model. For example, the inlet pressure, temperature, and outlet flow rate boundary conditions can be set in FLUENT. Then, solve the mass conservation equation, momentum conservation equation, and energy conservation equation based on the SIMPLEC algorithm to obtain the pressure and temperature boundaries of the mechanical seal domain. It can be understood that the conjugate heat transfer calculation of the pump domain in this step obtains the pressure and temperature boundaries of the mechanical seal domain by obtaining the internal flow field and temperature distribution of the pump. Since the pump domain and the mechanical seal domain are connected, but are calculated separately in this application, it is necessary to transfer the pressure and temperature data at the boundaries.

[0051] S5. In the 3D model after mesh generation, conjugate heat transfer calculations are performed on the mechanical seal domain based on its pressure and temperature boundaries to obtain the fluid pressure and solid temperature of the relevant components. It can be understood that the fluid pressure and solid temperature of the relevant components include the fluid pressure at the contact surfaces of the bushing, rotating ring, stationary ring and stationary ring seat, and cooling water in the sealing cavity, as well as the temperature data of the bushing, rotating ring, stationary ring and stationary ring seat.

[0052] S6. Perform a thermo-fluid-structure interaction analysis based on the fluid pressure and solid temperature of the relevant components in the mechanical seal domain to obtain the maximum gap data between the dynamic ring and the stationary ring in the mechanical seal domain.

[0053] S7. Using the maximum gap data as the leakage channel width, the leakage rate of the waste heat discharge pump mechanical seal is calculated. That is, the maximum gap data obtained in step S6 is used as the width of the leakage channel (i.e., the assumption of equal thickness), and then the leakage rate of the mechanical seal is calculated according to a specific empirical formula for leakage rate.

[0054] This embodiment, by comprehensively considering the coupling effects of heat, fluid, and solid, can accurately assess the leakage performance of the RRA pump mechanical seal, providing a scientific basis for the safe operation of the RRA pump. This is not only significant for its structural design and optimization but also contributes to improving the safety and reliability of nuclear power plants. It can effectively reduce safety hazards caused by leakage, decrease maintenance costs, and extend the service life of equipment, thereby improving overall economic benefits.

[0055] In some embodiments, step S5 includes: in the meshed 3D model, determining the flow rate and pressure boundary conditions of the plenum cooling water and sealing cavity cooling water of the mechanical seal domain based on the pressure and temperature boundaries of the mechanical seal domain. For example, the flow rate and pressure boundary conditions of the plenum cooling water and sealing cavity cooling water can be set in FLUENT. Then, the mass conservation equation, momentum conservation equation, and energy conservation equation are solved based on the SIMPLEC algorithm to obtain the fluid pressure and solid temperature of the relevant components of the mechanical seal domain.

[0056] In some embodiments, step S5 further includes: setting a heat flux boundary condition between the moving ring end face and the stationary ring end face, wherein the frictional heat flux density q of the heat flux boundary condition is... F It is calculated using the following formula:

[0057] q F =fp c v

[0058] Where f is the coefficient of friction. c It is the specific pressure at the sealed end face. v is the average velocity at the end face.

[0059] Based on the above embodiments, step S6 includes: transferring the fluid pressure and solid temperature data of the relevant components of the mechanical seal domain to the structural analysis module through the External Data module, applying circumferential constraints and spring support constraints to the stationary ring seat, and applying fixed constraints to the pump domain connection surface. Furthermore, in the structural analysis module, a statics solver is used to perform stress, strain, and deformation analysis on the dynamic ring, stationary ring, stationary ring seat, and bushing of the mechanical seal to obtain the maximum gap data between the dynamic and stationary rings in the mechanical seal domain. In other words, fluid pressure and temperature data can be imported into Workbench and transferred to the structural analysis module through the external data module to analyze the stress, strain, and deformation of the mechanical seal. It can be understood that in this embodiment, applying constraints is a crucial step in ensuring the accuracy and reliability of the calculation results in structural mechanics simulation. The role of constraints is to define the boundary conditions of the structure, enabling it to correctly simulate the stress and deformation conditions in the actual environment during simulation. For example, if an object is firmly fixed by a support, the structural analysis assumes that the degrees of freedom of all nodes at the fixed end are restricted, thus requiring the addition of fully fixed constraints.

[0060] In some embodiments, step S7 includes: using the maximum gap data as the width of the leakage channel, and calculating the leakage rate Q of the waste heat discharge pump mechanical seal using the following Mayer leakage rate empirical formula:

[0061]

[0062] Among them, D oΔp is the outer diameter of the sealing end face, Δp is the differential pressure of the sealing fluid, S is the gap balance coefficient, h is the end face gap, and p is the outer diameter of the sealing end face. c It is the specific pressure of the sealing end face, p c =Bp+p s B is the balance coefficient. p is the fluid medium pressure acting on the moving and stationary rings. s It is the spring ratio, D i It is the inner diameter of the sealing end face, D b This is the balance diameter. Equal thickness of the leakage path assumes that the width of the leakage path is consistent throughout the entire leakage path, i.e., it is the maximum gap data between the moving and stationary rings. Because the calculated leakage path widths are inconsistent, for a conservative assessment, considering the worst-case scenario, the maximum gap data is selected as the leakage path width. This can help improve the safety and reliability of nuclear power plants. It can effectively reduce safety hazards caused by leaks, reduce maintenance costs, and extend the service life of equipment, thereby improving overall economic benefits.

[0063] refer to Figures 2 to 7 In one specific embodiment, this example uses a thermal-fluid-structure interaction (TFI) method for analyzing the leakage performance of an RRA pump's mechanical seal. This method involves establishing a three-dimensional model of the RRA pump and its associated mechanical seal, performing conjugate heat transfer calculations to obtain the internal flow field and temperature distribution of the pump, and then transferring the obtained pressure and temperature boundary conditions to the mechanical seal domain for analysis. Specifically, the mechanical seal leakage performance analysis method includes defining the geometric parameters of each key component, including the impeller inlet diameter, impeller outlet diameter, hub diameter, number of blades, blade outlet angle, inner diameter of the sealing end face, outer diameter, and balance diameter. Based on the design requirements of the RRA pump, the geometric parameters of the key parts of the pump impeller are constructed as shown in Table 1, and the geometric parameters of the key parts of the mechanical seal are constructed as shown in Table 2.

[0064] Table 1 Main structural parameters of the internal impeller of the RRA pump

[0065]

[0066] Table 2 Main Structural Parameters of Mechanical Seals for RRA Pumps

[0067]

[0068] A three-dimensional geometric model of the RRA pump and its mechanical seal was constructed using SolidWorks software. The geometric model includes the main components of the pump, such as the inlet flange, outlet flange, pump casing, pump cover, impeller, pump shaft, impeller nut, and shaft sleeve, as well as the main components of the mechanical seal, such as the mechanical seal housing, mechanical seal shaft sleeve, rotating ring, stationary ring, and stationary ring seat.

[0069] Fluid domains were generated through volume extraction using SpaceClaim. The pump domain's fluid domain comprised the water flow domain during pump operation, while the mechanical seal domain comprised the cooling water flow domains of the plenum and the sealing cavity. The fluid and solid domains shared a topology. Unstructured meshing of the RRA pump's solid and fluid domains was performed using FLUENT Meshing. Refinement was applied near the mechanical seal surface, impeller, and small flow channels. For the fluid boundary layer of the pump domain, the y+ value was controlled to be less than 1, and for the fluid domain of the mechanical seal domain, the y+ value was controlled to be around 30. The pump domain mesh file was then imported into FLUENT.

[0070] It is understandable that shared topology is a geometric processing method in computational simulation, used to handle the connection relationship between multiple adjacent or contacting geometries. Here, it is to ensure that the interface mesh of the solid domain and the fluid domain has consistent node relationships when meshing.

[0071] In the viscous module of FLUENT, select the SST k-ω turbulence model. In Materials, set the material parameters for the solid material inlet flange, outlet flange, pump casing, pump cover, impeller, pump shaft, and fluid material water, as shown in Table 3 of Solid Material Parameters.

[0072] Table 3 Physical property parameters of solid materials in the pump area

[0073]

[0074] As is understandable, in ANSYS FLUENT, the viscous module is used to describe the internal viscosity of fluids and the energy dissipation associated with turbulence. Here, an appropriate flow model can be selected based on the actual situation, including laminar flow, turbulent flow, and transitional flow models.

[0075] It is understandable that the pump domain inlet boundary condition is set to a pressure inlet, with the pressure inlet set to the fluid pressure of 28 bar during pump operation, and the inlet temperature set to the fluid temperature of 403.15 K during pump operation. The pump domain outlet boundary condition is set to a flow outlet, with the flow outlet set to the pump's operating flow rate of 160 m³ / h. 3 The impeller region is set with a rotating coordinate system and a rotational speed of 1495 r / min. The wall temperature boundary condition in contact with air is set as a convective boundary condition, and the convective heat transfer coefficient with air is set to 10 W / (m²). 2 •K). Conjugate heat transfer calculations for the pump domain were performed in FLUENT, and the mass, momentum, and energy conservation equations were solved using the SIMPLEC algorithm.

[0076] The fluid mass conservation equation is:

[0077]

[0078] Where ρ is the fluid density, u is the fluid velocity vector, and t is time.

[0079] The momentum conservation equation for the fluid region is:

[0080]

[0081] Where μ is the dynamic viscosity of the fluid, and P is the pressure.

[0082] The energy conservation equation for the fluid region is:

[0083]

[0084] Among them, c p is the specific heat capacity of the fluid, T is the fluid temperature, and k is the thermal conductivity of the fluid.

[0085] The energy conservation equation for the solid region is:

[0086]

[0087] Among them, c p is the specific heat capacity of the solid, T is the temperature of the solid, k is the thermal conductivity of the solid, and Q is the energy source term of the solid.

[0088] Export the temperature and pressure data of the four surfaces A, B, C, and D where the pump cover, bushing, shaft, and mechanical seal of the RRA pump meet in the pump domain using FLUENT. Import the mechanical seal domain mesh file into FLUENT, select the Realized k-ε turbulence equation in the viscous module of FLUENT, and set the material parameters of the bushing, rotating ring, stationary ring, and stationary ring seat, as shown in Table 4.

[0089] Table 4 Physical property parameters of solid materials in the mechanical seal area

[0090]

[0091] The boundary conditions for the mechanical seal domain are set as follows: sealing cavity cooling water mass flow rate inlet, pump connection domain pressure inlet, and plenum cooling water pressure inlet; plenum cooling water mass flow rate outlet and sealing cavity cooling water pressure outlet. Specifically, the sealing cavity cooling water inlet mass flow rate is set to 0.6 kg / s; the sealing cavity cooling water pressure inlet is set to the pressure at interface D between the mechanical seal domain and the pump domain; the plenum cooling water inlet pressure is set to 13 bar; the sealing cavity cooling water outlet pressure is set to the pressure at the interface between the mechanical seal domain and the pump domain minus 2.23 bar; and the plenum cooling water outlet mass flow rate is set to 0.21 kg / s.

[0092] like Figure 3As shown, the mechanical seal shell walls W2 and W3 are set as convective boundary conditions, and the convective heat transfer coefficient with air is set to 10 W / (m²). 2 gK); the inner wall surface W4 of the moving ring and the outer wall surface W5 of the mechanical seal bushing are given as convective boundary conditions, and the convective heat transfer coefficient with air is set to 40 W / (m). 2 gK); The inner wall surfaces W6 and W7 of the stationary ring are given as convective boundary conditions, and the convective heat transfer coefficient with air is set to 30 W / (m²). 2 gK); The temperature boundary conditions of the four surfaces A, B, C, and D of the pump cover, bushing, and shaft mating of the RRA pump in the mechanical seal and pump domain are given as the temperature data calculated by the pump domain; the thermal flow boundary condition is defined between the dynamic ring end face WR and the static ring end face WS. Figure 3 In the diagram, AA refers to the cross-section, specifically the cross-sections at points 18 and 19 in the two left-hand diagrams, and the cross-sections at points 17 and 16 in the two right-hand diagrams. The frictional heat flux density qF is calculated using the formula:

[0093] q F =fp c v

[0094] Where f is the coefficient of friction, taken as 0.1; p c It is the end face specific pressure, p c =p s +pgK; K is the balance coefficient of the mechanical seal. A is the area of ​​the fluid medium; An is the area of ​​the sealed end face; v is the average velocity of the end face. n is the average radius of the sealing ring end face; n is the rotational speed; p is the fluid medium pressure acting on the moving and stationary rings. s It is the spring pressure, taken as 2.57 bar.

[0095] The mass, momentum, and energy conservation equations were solved using FLUENT's SIMPLEC algorithm, and the fluid pressures at the contact surfaces of the bushing, rotating ring, stationary ring and stationary ring seat, and cooling water in the sealing cavity, as well as the temperature data of the bushing, rotating ring, stationary ring and stationary ring seat, were derived.

[0096] In Workbench, a fluid-structure interaction analysis platform was built. In Engineering Data, the material parameters of the bushing, dynamic ring, stationary ring, and stationary ring seat were added as shown in Table 5.

[0097] Table 5. Physical properties of solid materials in fluid-structure interaction analysis.

[0098]

[0099] The mesh is generated using the Sweep method. The structural statics simulation uses a structural solver, requiring a mesh type based on solid mechanics. Meshes generated from heat transfer simulations are typically unsuitable for direct mechanical analysis; therefore, the Sweep method is necessary. Fluid pressure and solid temperature data are imported into Static Structural using the External Data module for structural analysis of the mechanical seal. Fixed constraints are applied to the pump domain connection surface D, and circumferential and spring support constraints are applied to the stationary ring seat. The deformations of the sealing end faces of the dynamic and stationary rings are then obtained. Figure 7 As shown, the maximum gap at the outlet of the leakage channel appears around 120° circumferentially, with a gap value of 1.24 μm. Taking the maximum gap as the diameter of the leakage channel, and assuming the leakage channel is of uniform thickness, the leakage rate is calculated using the Mayer empirical formula for leakage rate, yielding a leakage rate of 1.18 × 10⁻³ ml / s, equivalent to 1.41 drops per minute. It can be predicted that during the operation of the RRA pump, almost no leakage of cooling water from the mechanical seal into the sealing chamber will be observed, consistent with the actual operating conditions of a certain nuclear power plant.

[0100] This embodiment, by comprehensively considering the coupling effects of heat, fluid, and solid, can accurately assess the leakage performance of the RRA pump mechanical seal, providing a scientific basis for the safe operation of the RRA pump. This is not only significant for its structural design and optimization but also contributes to improving the safety and reliability of nuclear power plants. It can effectively reduce safety hazards caused by leakage, decrease maintenance costs, and extend the service life of equipment, thereby improving overall economic benefits.

[0101] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0102] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented directly by hardware, a software module executed by a processor, or a combination of both. The software module can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0103] It is understood that the above embodiments only illustrate preferred embodiments of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can freely combine the above technical features without departing from the concept of the present invention, and can also make several modifications and improvements, all of which fall within the protection scope of the present invention. Therefore, all equivalent transformations and modifications made with respect to the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A method for analyzing the leakage performance of a mechanical seal in a waste heat discharge pump, characterized in that, The method includes the following steps: S1. Generate a three-dimensional model of the waste heat discharge pump and its mechanical seal; S2. Extract volume from the three-dimensional model to generate a fluid domain within a solid domain, wherein the solid domain includes a pump domain and a mechanical seal domain. S3. Perform unstructured mesh generation on the solid domain and the fluid domain; S4. In the three-dimensional model after mesh generation, perform conjugate heat transfer calculations on the pump domain to obtain the pressure boundary and temperature boundary of the mechanical seal domain. S5. In the three-dimensional model after mesh generation, conjugate heat transfer calculations are performed on the mechanical seal domain based on the pressure and temperature boundaries of the mechanical seal domain to obtain the fluid pressure and solid temperature of the relevant components of the mechanical seal domain. S6. Perform a thermo-fluid-structure interaction analysis based on the fluid pressure and solid temperature of the relevant components in the mechanical seal domain to obtain the maximum gap data between the dynamic ring and the stationary ring in the mechanical seal domain. S7. The maximum gap data is used as the leakage channel width, and the leakage rate of the mechanical seal of the waste heat discharge pump is calculated accordingly.

2. The method for analyzing the leakage performance of the mechanical seal of the waste heat discharge pump according to claim 1, characterized in that, In step S1, the three-dimensional model includes a pump casing, impeller, pump shaft, mechanical seal housing, dynamic ring, stationary ring, and stationary ring seat; wherein, the main structural parameters of the impeller include impeller inlet diameter, impeller outlet diameter, hub diameter, number of blades, blade outlet angle, and blade wrap angle, and the main structural parameters of the mechanical seal include sealing end face inner diameter, sealing end face outer diameter, and sealing end face balance diameter.

3. The method for analyzing the leakage performance of the mechanical seal of the waste heat discharge pump according to claim 1, characterized in that, Step S4 includes: In the 3D model after mesh generation, the inlet pressure, inlet temperature and outlet flow boundary conditions of the pump domain are determined, and the mass conservation equation, momentum conservation equation and energy conservation equation are solved based on the SIMPLEC algorithm to obtain the pressure boundary and temperature boundary of the mechanical seal domain.

4. The method for analyzing the leakage performance of the mechanical seal of the waste heat discharge pump according to claim 1, characterized in that, Step S5 includes: In the 3D model after mesh generation, the flow rate and pressure boundary conditions of the cooling water in the fusible body and the cooling water in the sealing cavity of the mechanical seal domain are determined according to the pressure boundary and temperature boundary of the mechanical seal domain. The mass conservation equation, momentum conservation equation and energy conservation equation are solved based on the SIMPLEC algorithm to obtain the fluid pressure and solid temperature of the relevant components of the mechanical seal domain.

5. The method for analyzing the leakage performance of the mechanical seal of the waste heat discharge pump according to claim 1 or 4, characterized in that, The fluid pressure and solid temperature of the components related to the mechanical seal domain include the fluid pressure of the contact surfaces of the bushing, rotating ring, stationary ring and stationary ring seat and the cooling water in the sealing cavity of the mechanical seal domain, as well as the temperature data of the bushing, rotating ring, stationary ring and stationary ring seat.

6. The method for analyzing the leakage performance of the mechanical seal of the waste heat discharge pump according to claim 5, characterized in that, Step S5 includes: The frictional heat flux density q of the thermal boundary condition is set between the end faces of the moving ring and the stationary ring. F It is calculated using the following formula: q F =fp c v Where f is the coefficient of friction; p c is the specific pressure at the sealed end face; v is the average velocity at the end face.

7. The method for analyzing the leakage performance of the mechanical seal of the waste heat discharge pump according to claim 5, characterized in that, Step S6 includes: The fluid pressure and solid temperature data of the relevant components of the mechanical seal domain are transferred to the structural analysis module through the External Data module. Circumferential constraints and spring support constraints are applied to the stationary ring seat, and fixed constraints are applied to the pump domain connection surface. Moreover, in the structural analysis module, a static solver is used to perform stress, strain, and deformation analysis on the dynamic ring, stationary ring, stationary ring seat, and bushing of the mechanical seal to obtain the maximum gap data between the dynamic ring and the stationary ring in the mechanical seal domain.

8. The method for analyzing the leakage performance of the mechanical seal of the waste heat discharge pump according to claim 1, characterized in that, Step S2 includes: The fluid domains of the pump domain and the mechanical seal domain are determined by a volume extraction method; wherein, the fluid domain of the pump domain is the water flow domain when the waste heat discharge pump is working, and the fluid domain of the mechanical seal domain includes the cooling water flow domain of the plenum and the cooling water flow domain of the sealing cavity.

9. The method for analyzing the leakage performance of the mechanical seal of the waste heat discharge pump according to claim 1, characterized in that, Step S3 includes: In the unstructured mesh generation process of the solid domain and the fluid domain, the y+ value of the fluid boundary layer of the pump domain is set to be within 1, and the y+ value of the fluid domain of the mechanical seal domain is set to be within an allowable range based on 30, so as to achieve densification processing at the mechanical seal surface, near the impeller and in small flow channels; where the y+ value represents the dimensionless distance in the normal direction of the wall.

10. The method for analyzing the leakage performance of the mechanical seal of the waste heat discharge pump according to claim 1, characterized in that, Step S7 includes: Using the maximum gap data as the width of the leakage channel, the leakage rate Q of the waste heat discharge pump mechanical seal is calculated using the following Mayer leakage rate empirical formula: Among them, D o Δp is the outer diameter of the sealing end face, Δp is the differential pressure of the sealing fluid, S is the gap balance coefficient, h is the end face gap, and p is the outer diameter of the sealing end face. c It is the specific pressure of the sealing end face, p c =Bp+p s B is the balance coefficient. p is the fluid medium pressure acting on the moving and stationary rings. s It is the spring ratio, D i It is the inner diameter of the sealing end face, D b It is the equilibrium diameter.

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