A method for simulating erosion of a pump casing coating

Abstract

The application relates to a pump shell coating erosion corrosion simulation method, and belongs to the field of multi-physical field coupling numerical simulation, and comprises the following steps: constructing a three-dimensional fluid domain geometric model of a turbine pump; carrying out grid division on the three-dimensional fluid domain geometric model and setting a boundary condition; coupling calculation of mechanical wear and electrochemical corrosion; according to the calculated erosion corrosion rate, predicting the erosion life of the inner wall coating of the pump shell, and / or formulating an operation condition suitable for the inner wall coating of the pump shell, and / or formulating a coating thickness scheme of the inner wall coating of the pump shell. Through the construction of the finite element simulation model of the multi-physical field coupling, the application quantitatively analyzes the influence of the erosion speed, the erosion angle and the sand carrying amount on the erosion corrosion behavior of the coating, reveals the material loss mechanism under the synergistic action of the sand erosion and the electrochemical corrosion, accurately predicts the evolution law of the coating damage, and thus provides a reliable theoretical basis for the failure prediction and design optimization of the anticorrosion coating of the inner wall of the volute.

Description

Technical Field

[0001] This invention relates to the field of multiphysics coupling numerical simulation technology, specifically to a simulation method for erosion corrosion of pump casing coatings by multi-field coupling of erosion and electrochemical corrosion, which is applied to the damage prediction of the inner wall coating of turbine pumps in important plant water systems of nuclear power plants under the combined effects of erosion and electrochemical corrosion. Background Technology

[0002] The critical plant water system (SEC) is a dedicated safety auxiliary system for nuclear power plants, used to safely transfer the heat load of the nuclear island equipment cooling water system (RRI) to seawater, ensuring the thermal safety of the nuclear power plant under normal and accident operating conditions. Because the SEC turbopump continuously transports seawater, its volute inner wall coating material faces two severe damaging environments: water erosion and electrochemical corrosion. Firstly, solid particles such as quartz sand in seawater impact the inner wall with the high-speed fluid, causing mechanical wear; secondly, the high concentration of Cl in seawater... - Plasma-induced electrochemical corrosion exists. A significant synergistic acceleration effect exists between these two damage mechanisms; that is, the total material loss is far greater than the sum of mechanical wear and electrochemical corrosion alone, exhibiting a nonlinear synergistic enhancement characteristic. However, the existing technology has the following drawbacks: 1. Limitations of single-physics simulation: Traditional scouring simulations often use computational fluid dynamics-discrete phase model (CFD-DPM) methods, while corrosion simulations often use electrochemical models. The two are independent of each other and lack effective data coupling with physical mechanisms, which cannot truly reflect the synergistic process of scouring and corrosion.

[0003] 2. Linearization Deficiencies of Existing Coupling Methods: Existing technologies, exemplified by Chinese patent CN112255088A, while considering both erosion and electrochemical factors, essentially simplify the electrochemical influence into a correction coefficient or linear term superimposed on the erosion model. This linearization method fails to capture the nonlinear synergistic enhancement effect between erosion and corrosion, especially under harsh conditions such as high flow velocities, large angles, and high sand content, resulting in significant deviations between predicted and actual conditions.

[0004] 3. Ignoring the feedback effect of morphology evolution: Existing models are usually unidirectional calculations, that is, they only consider the effects of fluid and particles on the wall surface, ignoring the feedback effect of the evolution of wall surface morphology such as pitting and scratches on the local flow field and particle motion trajectory as erosion and corrosion proceed, resulting in insufficient accuracy of long-term damage prediction.

[0005] Therefore, developing a simulation method that can realistically reflect the nonlinear synergistic effect of erosion and electrochemical corrosion and dynamically predict the evolution of coating damage is of great significance for life prediction and coating design optimization of key equipment in nuclear power plants. Summary of the Invention

[0006] The purpose of this invention is to address the problem in existing technologies that cannot quantify and predict the nonlinear synergistic enhancement effect between scouring and corrosion. This invention provides a simulation method for scouring and corrosion of pump casing coatings using a multi-field coupled scouring and electrochemical corrosion model. This method constructs a multi-physics coupled finite element simulation model to quantify and analyze the influence of scouring velocity, scouring angle, and sand carrying capacity on the scouring and corrosion behavior of the coating. It reveals the material loss mechanism under the synergistic effect of silt scouring and electrochemical corrosion, accurately predicts the evolution of coating damage, and thus provides a reliable theoretical basis for failure prediction and design optimization of anti-corrosion coatings on the inner wall of the vortex casing.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A simulation method for erosion corrosion of pump casing coatings involving multi-field coupling of erosion and electrochemical corrosion includes the following steps: S1. Construct a three-dimensional fluid domain geometric model of the turbopump; S2. Mesh the three-dimensional fluid domain geometry model and set boundary conditions; S3. Using computational fluid dynamics software and a turbulence model, perform steady-state or transient simulations of the flow field inside the pump to obtain the velocity distribution, streamline morphology, and pressure distribution characteristics of the flow field; S4. Using the Eulerian-Lagrange method, the motion trajectory and velocity distribution of particles in the pump are simulated through a discrete phase model to obtain the motion trajectory and velocity distribution of particles of different sizes in the flow field, and to identify dangerous areas and weak points of erosion. S5. Perform coupled calculations of mechanical wear and electrochemical corrosion, specifically including: S5.1. Calculate the mechanical wear rate using a wear rate model. ; S5.2. Calculate the electrochemical corrosion rate based on the electrochemical kinetic equations and considering the effect of flow rate. ; S5.3. Calculate the erosion rate The rate of erosion corrosion is determined by the rate of mechanical wear. Electrochemical corrosion rate and the incremental interaction between mechanical wear and electrochemical corrosion It consists of three parts: In the formula, the interaction increment The calculation formula is in the form of a product of polynomial functions with separate variables: In the formula, The scouring corrosion synergistic material coefficient is determined by the material's inherent properties and is obtained through scouring corrosion coupling experiments. It is used to characterize the additional damage rate caused by the synergistic effect of scouring and electrochemical corrosion on the inner wall coating of the pump casing. For particle impact velocity, This represents the particle volume fraction. The impact angle of the particles; , , These are the particle impact velocities. Impact angle of particles and particle volume fraction The dimensionless function, in polynomial form, describes the nonlinear influence of each factor on the synergistic effect, and its form is: in, Represents particle impact velocity Particle volume fraction or particle impact angle ; , , ,…, The coefficients are obtained by fitting multiple nonlinear regression to the data from the scouring corrosion coupling experiment. S6. Based on the calculated erosion corrosion rate Predict the erosion life of the pump casing inner wall coating, and / or formulate suitable operating conditions for the pump casing inner wall coating, and / or formulate a coating thickness scheme for the pump casing inner wall coating.

[0008] As one possible approach, in step S1, when constructing the three-dimensional fluid domain geometric model of the turbopump, the three-dimensional torsion pattern of the blades, the tip clearance, and the profile curvature of the volute tongue are preserved.

[0009] As one possible implementation method, step S2 specifically includes: S2.1. High-fidelity geometry reconstruction and fluid extraction for turbopumps: In 3D CAD software, the solid models of the impeller, volute and suction chamber of the turbopump are reconstructed, and the internal cavities of all flow components are extracted to generate the original fluid domain geometry. Using the impeller mechanical seal end face and the impeller outlet annular face as boundaries, a dynamic-static interface is constructed to divide the dynamic-static computational domains, thereby achieving topological separation of the dynamic-static computational domains; Extend the inlet and outlet boundaries; perform geometric cleanup and topology checks on the generated fluid domain; S2.2. Mesh Generation: A fully hexahedral structured mesh is used for the impeller fluid domain; the leading and trailing edges of the blades are adaptively refined with curvature, and the minimum mesh size is limited to 0.2 mm. An unstructured tetrahedral mesh was used for the static region of the volute; the maximum mesh size in the mainstream region of the volute was set to 3.0 mm; density boxes were set in the tongue region, and the local mesh size was refined to 0.5 mm. The near-wall boundary layer uses a prismatic layer mesh, with the first layer mesh height set to 0.035 mm; the total number of boundary layer layers is set to 3, and the interlayer growth rate is controlled at 1.15. S2.3. Set boundary conditions: Inlet boundary conditions: The pump suction inlet section is set as a velocity inlet, and the turbulence parameters are set based on the fully developed pipe flow turbulence theory, with the turbulence intensity set to 5%; Outlet boundary conditions: The pump outlet section is set as a pressure outlet, and the gauge pressure is set to 0 Pa; the backflow turbulence intensity is set to 5%; Solid wall boundary conditions: The contact boundary between the fluid and the solid surface is set as a solid wall and follows the no-slip condition; Discrete phase boundary conditions: The wall restitution coefficient model proposed for the collision between hard particles and metal walls is selected.

[0010] As one possible approach, in step S3, the computational fluid dynamics software is ANSYS Fluent, but not limited to it; the turbulence model is the k-ɛ turbulence model, but not limited to it.

[0011] As one possible approach, in step S4, the injection source of the discrete phase model adopts a surface injection type, and the injection source position is set at the inlet surface of the turbopump fluid domain. The initial velocity vector of the particles is set to be consistent with the velocity of the continuous phase fluid at the inlet, thus achieving slip-free injection, which is automatically given by the solver based on the inlet boundary conditions; the particle size distribution adopts a uniform particle size distribution.

[0012] As one possible approach, in step S4, the impact velocity and impact angle of the particles hitting the wall are calculated by combining the discrete phase model and the finite volume model with the wall erosion model. When simulating the motion trajectory and velocity distribution of the particles in the flow field, the effects of fluid drag, gravity, and buoyancy are considered. Based on particle dynamics theory, the solid phase pressure and solid phase viscosity are solved by solving the solid phase temperature equation to correct the motion trajectory and velocity of the particles.

[0013] As one possible approach, in step S5.1, the wear rate model is the Jana wear rate model, but it is not limited to this; the mechanical wear rate... Directly related to fluid dynamics parameters: In the formula, It is a dimensionless erosion rate, which is related to the material hardness and the particle impact angle. The dimensionless erosion rate is calculated using a dimensionless erosion rate model; the dimensionless erosion rate model is the Finnie dimensionless erosion rate model, but it is not limited to this; the Finnie dimensionless erosion rate model considers the particle rebound effect in the case of particle cutting wear on metal. In the formula, The erosion cutting material coefficient is used to characterize the ability of the coating on the inner wall of the pump casing to resist particle cutting wear. For metallic materials, the coefficient is selected through empirical values, while for ceramic materials, it is obtained through single-phase erosion experiments. Particle density; Vickers hardness of the material; The particle resilience coefficient is obtained by using the normal recovery coefficient. and tangential restitution coefficient Jointly determined; normal restoration coefficient and tangential restitution coefficient All are impact angles The function, i.e. , ;function and The parameters are defined by standard curves published in experimental data or literature. Furthermore, for different wall materials, the normal and tangential coefficient of restitution curves of the corresponding materials are used to accurately describe the momentum exchange characteristics at the boundary of different materials.

[0014] As one possible implementation method, step S5.2 specifically includes: The relationship between corrosion current and potential described by the Tafel equation is as follows: In the formula, This represents the corrosion current density under static conditions. Corrosion current density after taking into account the effect of flow rate; The velocity coefficient is related to the viscosity of the medium, and its value is determined by fitting experimental data. Its unit varies with the viscosity of the medium. Unit determined, ensuring The whole is dimensionless; Potential; The velocity index is dimensionless and is taken as 0.5 to 1.0 under turbulent conditions. Then, the electrochemical corrosion rate is obtained based on the electrochemical corrosion theory. .

[0015] As one possible approach, in step S5.3, The calibration was obtained through erosion corrosion coupling experiments, specifically including: Step 1: At different particle impact velocities Particle volume fraction and particle impact angle Erosion corrosion experiments were conducted on the inner wall coating of the pump casing under certain conditions to obtain the erosion corrosion rate; nonlinear regression and linear fitting were then performed based on the actual measured erosion corrosion rate data to determine the corrosion rate. , and The coefficient; Step 2, at the particle impact velocity Particle volume fraction and particle impact angle Erosion corrosion experiments were conducted on the inner wall coating of the pump casing under experimental conditions to obtain the erosion corrosion rate. ;Measuring the mechanical wear rate under the same hydrodynamic conditions but with suppressed electrochemical corrosion. ;Measure the electrochemical corrosion rate under the same electrochemical conditions but without particle erosion. ; Calculate the interaction increment : The particle impact velocity corresponding to the experimental conditions. Particle volume fraction and particle impact angle Substitution ;but The average value of the calculation results from multiple experimental operating points is taken as the final result. .

[0016] As one possible approach, in step S6, predicting the erosion life of the inner wall coating of the pump casing based on the erosion corrosion rate is specifically determined by: determining it based on the thickness of each local part of the inner wall coating of the pump casing and the total erosion rate of each local part. The specific operating conditions suitable for the inner wall coating of the pump casing are as follows: under a specific sand content, the turbine pump speed suitable for continuous operation of the turbine pump for a specific time without failure of the inner wall coating is determined based on the thickness of each local part of the inner wall coating of the pump casing and the total erosion rate of each local part under different speed conditions. The specific steps for determining the coating thickness scheme are as follows: under specific sand content and specific turbine pump operating speed conditions, the coating thickness of each local part of the pump casing inner wall is determined based on the total erosion rate.

[0017] As one possible approach, the simulation method further includes dynamic simulation considering surface morphology evolution: after obtaining the scouring corrosion rate distribution in step S6, the calculated wall wear amount is applied back to the three-dimensional fluid domain geometry model in step S2 through mesh deformation or dynamic mesh technology to update the wall morphology, and steps S3-S5 are repeated, thereby realizing dynamic simulation considering morphology evolution and further improving long-term prediction accuracy.

[0018] Compared with the prior art, the present invention has the following beneficial technical effects: 1. By constructing a calculation model for erosion corrosion rate that includes mechanical wear rate, electrochemical corrosion rate, and their interactive increments, a multi-physics nonlinear coupling simulation of erosion and electrochemical corrosion was achieved. Specifically, this invention abandons the traditional linear superposition or simple correction methods and creatively introduces a separated variable polynomial interactive increment term related to impact velocity, impact angle, and particle concentration, and calibrates its coefficients experimentally. This technique can accurately capture the nonlinear synergistic enhancement effect between erosion and corrosion, solving the problem that existing technologies cannot accurately quantify this effect, and significantly improving the accuracy of corrosion simulation.

[0019] 2. High-fidelity geometric modeling, hybrid mesh generation, and fine boundary layer settings yielded high-precision flow field and particle trajectory simulation results. Specifically, this invention employs differentiated meshing strategies for the impeller and volute, and locally refines key areas such as the baffle and blade leading edge. Combined with reasonable boundary layer settings, this ensures that the complex turbulent structure, pressure gradient, and particle impact parameters within the pump can be accurately captured under acceptable computational resource consumption, providing an accurate data foundation for subsequent damage calculations.

[0020] 3. The simulation method of this invention can be directly applied to engineering practice, predicting coating life, guiding coating thickness design, and optimizing operating conditions. Specifically, by outputting the spatial distribution of erosion corrosion rate on the inner wall of the pump casing, high-risk areas can be quantitatively identified. Based on the damage rate under different rotational speeds and sand content, it provides a quantitative and reliable theoretical basis for the operation and maintenance decisions, coating material selection, and differentiated thickness design of SEC pumps in nuclear power plants, thereby extending equipment life, reducing maintenance costs, and improving the safety of nuclear power plant operation. Attached Figure Description

[0021] Figure 1 This is a flowchart of a simulation method for erosion corrosion of pump casing coatings using multi-field coupling of erosion and electrochemical corrosion, according to an embodiment of the present invention. Figure 2 Design diagram for the fluid domain model of a turbopump; Figure 3 This is a cross-sectional view of the inside of a turbopump; Figure 4This is a schematic diagram of the dynamic and static calculation domains of a turbopump. Figure 5 This is a schematic diagram of the calculation model for a turbopump. Figure 6 Finite element mesh diagram of the fluid domain of the turbopump; Figure 7 This is a contour map of the velocity distribution across the midsection of the turbopump. Figure 8 This is a diagram showing the absolute velocity distribution within the key flow channel of a turbopump. Figure 9 This is a cloud map showing the static pressure distribution within the turbopump. Figure 10 The plot shows the particle trajectory at an inlet velocity of 6.75 m / s, colored according to the particle residence time. Detailed Implementation

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0023] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0024] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments.

[0025] Example 1 This embodiment provides a simulation method for erosion corrosion of pump casing coatings involving multi-field coupling of erosion and electrochemical corrosion. The process is as follows: Figure 1 As shown. This embodiment uses a turbine pump in a critical plant water system (SEC) of a nuclear power plant as an example. The inner wall of the pump casing is coated with an anti-corrosion coating. The main solid particles in seawater are quartz sand. The simulation process specifically includes the following steps.

[0026] S1. Turbopump Geometric Modeling A turbopump mainly consists of the following components: pump body, impeller, inlet section, and outlet section, such as... Figure 2As shown. The core object of CFD analysis is the negative space of fluid flow. Fluid domain modeling is the foundation for constructing numerical mathematical and physical models. This invention adopts a "bottom-up" modeling strategy, constructing a high-fidelity three-dimensional computational domain by extracting the internal flow space of the pump body, impeller, and auxiliary pipelines. The specific modeling process and key processing strategies are as follows.

[0027] High-fidelity geometric reconstruction and fluid extraction of turbopumps: Based on hydraulic design drawings, the solid models of the turbopump impeller, volute, and suction chamber are accurately reconstructed in 3D CAD software. During this process, key hydraulic characteristics such as the three-dimensional torsion of the blades, the blade tip clearance, and the profile curvature of the volute tongue are strictly preserved, as these characteristics directly determine the shear strength of the flow field and the erosion trajectory of particles.

[0028] Subsequently, using the difference or fill functions in Boolean operations, the internal cavities of all flow components are extracted to generate the original fluid domain geometry, ensuring that the fluid domain's topology is closed and has no overlapping surfaces. The internal cross-sectional view of the turbopump is shown below. Figure 3 As shown; To address the typical rotor-stator interference problem in turbopumps, the computational domain must be divided into a "rotating domain" and a "stationary domain" based on the physical properties of the flow. A cylindrical or rotating interface is constructed, bounded by the impeller mechanical seal end face and the impeller outlet annular surface. The divided dynamic and static computational domains are as follows: Figure 4 As shown, the topological separation of the dynamic and static computational domains is achieved. This interface is the basis for realizing the multi-reference frame model, ensuring that the momentum equation and turbulent physical quantities can satisfy flux conservation in different coordinate systems, thereby accurately simulating the centrifugal force field generated by the impeller rotation and its unsteady disturbance to the stationary volute.

[0029] To eliminate the influence of non-physical boundary conditions on the core flow field and to solve the common convergence problem in the calculation of strong swirling flow fields, this model has undergone special extension treatment of the inlet and outlet boundaries.

[0030] Inlet extension: The suction section is extended upstream by 2 times the pipe diameter to eliminate the false uniformity caused by the inlet boundary setting, so that the fluid has enough space to develop into a turbulent velocity profile that conforms to physical laws before entering the impeller, while avoiding the upstream potential flow effect generated by the impeller rotation from interfering with the numerical stability of the inlet boundary.

[0031] Outlet Extension: Extend the outlet downstream by three times the pipe diameter. Because the fluid at the turbopump outlet carries strong residual swirling and complex secondary flow structures, directly cutting it off at the volute outlet results in a non-zero flow field gradient, violating the assumption of the "pressure outlet" boundary regarding fully developed flow. This can lead to external fluid being drawn back into the computational domain during calculations, forming a backflow, and consequently causing residual oscillations or even computational divergence. For example... Figure 5As shown, the establishment of the extension section provides physical space for the dissipation and rectification of the swirling flow, ensuring that the flow at the outlet boundary has been restored to a unidirectional flow, thereby greatly improving the robustness of numerical calculations.

[0032] Finally, the generated fluid domain is geometrically cleaned and topologically checked: tiny features that have a negligible impact on the flow field but would severely degrade the mesh quality are removed. At the same time, the "interference check" tool is used to ensure that there is no geometric overlap between the rotating and stationary domains, and to verify that the normal vectors of all surfaces point into the fluid. This achieves model cleaning and integrity verification, ultimately forming a watertight, topologically valid computational model suitable for high-quality mesh generation.

[0033] S2. Mesh Generation and Boundary Condition Setting S2.1 Mesh Generation Considering the high torsion of the turbine pump impeller flow channel and the geometric complexity of the volute tongue region, this invention adopts a "block-coupled" hybrid mesh strategy, uses ANSYS Fluent software for mesh generation, and employs differentiated discretization schemes for different computational domains to balance computational accuracy and resource consumption.

[0034] As the core working component, the rotating impeller exhibits drastic changes in flow field gradient. To ensure the accuracy of the rotating flow field solution and reduce numerical pseudo-diffusion, a fully hexahedral structured mesh is used for the impeller fluid domain. Curvature adaptive refinement is applied to the leading and trailing edges of the blades, with a minimum mesh size limited to 0.2 mm to accurately capture flow separation and wake structures. The unstructured mesh in the stationary domain of the volute contains complex double logarithmic spiral tongues and diffuser sections. A highly adaptable unstructured tetrahedral mesh is used, combined with prism layer technology, with the maximum mesh size in the volute's main flow region set at 3.0 mm.

[0035] Densification of critical areas: Density boxes are set in the tongue region, and the local mesh size is refined to 0.5 mm to capture the pressure gradient abrupt change when the high-speed jet impacts the tongue.

[0036] Near-wall boundary layer for coordination The turbulence model requires generating high-quality prismatic layer meshes on all solid wall surfaces to resolve the viscous sublayer within the boundary layer. This is based on the Reynolds number. And the theoretical estimation of the first layer mesh height using the flat plate boundary layer theory ( The setting is 0.035 mm, which ensures dimensionless wall distances over the vast majority of the wall surface area. Value control at Within the viscous sublayer, the total number of boundary layers was set to 3, with the interlayer growth rate strictly controlled at 1.15 to ensure a smooth transition in volume ratio between the boundary layer mesh and the tetrahedral mesh in the mainstream region. After mesh generation, a global check was performed using orthogonal quality and skewness as core indicators. The final mesh quality statistics are shown in Table 1.

[0037] Table 1. Statistics and Evaluation of Global Grid Quality To eliminate the interference of mesh quantity on numerical solutions, this invention establishes three sets of mesh models with different densities: coarse, medium, and fine, under the same boundary conditions ( Steady-state calculations were performed. The verification results are shown in Table 2 below.

[0038] Table 2. Statistics of Mesh Independence Verification Data Table 2 shows that the efficiency change is significant when the number of grid cells increases from 1.85 million to 3.24 million, indicating that the coarse grid failed to fully resolve the flow field details. When the number of grid cells is further increased to 5.12 million, the efficiency change is within 0.2%, which meets the grid independence requirement. Considering both computational accuracy and time cost, Grid 3 takes more than twice as long as Grid 2. Therefore, Grid 2 was ultimately selected for subsequent particle erosion calculations. The grid was divided as follows: Figure 6 As shown.

[0039] S2.2. Setting up the physical model and boundary conditions (1) Properties of multiphase flow materials Continuous phase: Water is assumed to be an incompressible Newtonian fluid, and its physical properties are based on ambient temperature and pressure. )set up.

[0040] Discrete phase: Quartz sand is mainly composed of quartz and feldspar, with high hardness and many angular features. In this simulation, the particles are simplified to spherical rigid particles, and the main physical parameters are shown in Table 3.

[0041] Table 3. Physical parameter settings for discrete phase particles (2) Configuration of the jet source In the discrete phase model, the configuration of the injection source directly determines the initial distribution and dynamic characteristics of particles in the flow field. This embodiment, focusing on the flow characteristics at the turbine pump inlet, sets the following parameters: The injection source adopts a surface injection type, and the injection source position is set at the inlet face of the fluid domain of the turbopump. This setting can simulate the process of particles entering the pump channel uniformly with the water flow, which is consistent with the entry mode of suspended sediment in actual working conditions. To ensure that the momentum exchange between the discrete and continuous phases at the inlet conforms to physical reality, the initial velocity vector of the particles is set to be consistent with the velocity of the continuous phase fluid at the inlet, thus achieving slip-free injection. This vector is automatically assigned by the solver based on the inlet boundary conditions. A uniform particle size distribution is adopted. The set values ​​for different sand concentration conditions are detailed in Table 4 below.

[0042] Table 4. DPM injection parameter settings under different sediment concentration conditions In the surface jetting settings of ANSYS Fluent software, the total mass flow rate calculated above needs to be set to... Enter the total mass flow rate option, and the solver will automatically allocate the injection flux for each particle flow based on the area of ​​the inlet grid surface.

[0043] To ensure the convergence and accuracy of particle trajectory calculations within complex tortuous flow channels, the maximum number of tracking steps is set to 50,000 to prevent premature termination of tracking due to excessively long paths in strong swirling regions. A step size factor of 5 is set to balance the accuracy and numerical stability of the trajectory calculation.

[0044] (3) Boundary condition settings Boundary conditions are the boundary conditions of the governing equations, and their physical reality directly determines the accuracy of the flow field solution. In this embodiment, based on the actual operating environment and fluid dynamics characteristics of the turbopump, the following boundary conditions are adopted: Inlet boundary conditions: The pump suction inlet section is set as a velocity inlet. This boundary type allows direct specification of the velocity vector and turbulence scalar of the fluid entering the computational domain, and is suitable for mass flow control of incompressible flows.

[0045] The turbulence parameters are set based on the fully developed theory of pipe turbulence, with the inlet turbulence intensity ( ) and hydraulic diameter ( The settings are as follows: turbulence intensity is set to 5%. This is based on an empirical formula. It is estimated that the intensity of fully developed pipe flow at high Reynolds numbers is typically between 3% and 5%. Considering the disturbances from bends and valves in the pipeline before the pump, 5% is taken as a conservative estimate for moderate turbulence.

[0046] Outlet boundary conditions: The pump outlet section is set as a pressure outlet, and the gauge pressure is set to 0 Pa. Since the outlet section has been extended downstream by 5 times the pipe diameter during geometric modeling, the flow at the outlet section is fully developed, and the pressure gradient is close to zero. Setting the gauge pressure to 0 Pa means that this section is directly discharged into the atmosphere, serving as a reference point for the entire pressure field and does not affect the head calculation. Backflow is set to a backflow turbulence intensity of 5%. The backflow direction is perpendicular to the boundary. This prevents non-physical numerical errors from being drawn in from outside the computational domain, enhancing computational stability, especially in the early stages of iteration or when local backflow exists.

[0047] Solid wall boundary conditions: The contact boundary between the fluid and the solid surface is set as a solid wall and follows the no-slip condition, that is, the relative velocity of the fluid at the wall is zero; according to the motion state of the component, it is divided into stationary wall and rotating wall.

[0048] The stationary wall includes the suction chamber, volute, and inlet / outlet extensions. Its motion type is stationary wall. Roughness is set to 0. Assuming the wall is hydraulically smooth, the influence of micro-roughness on flow friction is ignored; the focus is on pressure drag caused by macroscopic geometry. The rotating wall includes impeller blades, hub, and cover plate. Its motion type is moving wall. The motion reference frame is rotational, relative to adjacent grid regions. The impeller wall moves with the rotating fluid domain; its velocity relative to the rotating coordinate system is 0, but it has a tangential velocity relative to the absolutely stationary coordinate system. This setup ensures efficient work transfer between the blades and the fluid. The rotational speed is 980 rpm, and the angular velocity... The value is 102.6 rad / s, and the rotation axis is the Z-axis.

[0049] Discrete phase boundary conditions: In discrete phase simulation, the collision process between particles and the inner wall of the pump involves complex kinetic energy dissipation; in order to accurately simulate the secondary bouncing trajectory of quartz sand particles in the flow channel and their momentum transfer to the wall, a reasonable coefficient of restitution must be set.

[0050] This embodiment uses the classic wall restitution coefficient model developed by Frederic et al. for the collision of hard particles with metal walls. This model sets the restitution coefficient as a function of the particle impact angle, which can better simulate the motion characteristics of quartz sand in the complex flow channel of a turbopump.

[0051] S3. In ANSYS Fluent software, the k-ɛ turbulence model is used to perform steady-state or transient simulations of the flow field inside the pump to obtain detailed flow field distribution and pressure distribution characteristics, including velocity distribution, pressure distribution and streamline morphology; Mass continuity equation: Momentum conservation equation: The k-ɛ turbulence model is: Specifically, for turbopumps under rated operating conditions ( We perform post-processing analysis on the steady-state flow field under the condition of ), focusing on analyzing the evolution of the internal velocity and pressure fields, and identifying unstable flow characteristics that may lead to increased local erosion.

[0052] Figure 7 The absolute velocity vector distribution of the pump body's intermediate cross section (Z=0 plane) is shown: the fluid enters the impeller inlet uniformly at a velocity of about 6.75 m / s, with smooth streamlines and no obvious pre-swirl or separation vortices; after entering the impeller, the absolute velocity increases rapidly in the radial direction due to the work done by the centrifugal force of the blades; the absolute velocity reaches its peak at the impeller outlet, at about 39.8 m / s, and this high-velocity region is a high-risk source of erosion; the high-speed fluid carries solid particles and throws them out with huge tangential momentum, directly bombarding the volute wall.

[0053] Figure 8 The diagram shows the absolute velocity distribution within the key flow channel. By capturing detailed velocity field data, the momentum transfer process and local flow characteristics of the fluid can be analyzed in depth. The following features can be observed from the vector diagram: Inlet flow regime and angle of attack characteristics: Axial inflow: In the suction chamber region, the fluid velocity vector is mainly expressed as the axial component. The direction is parallel to the rotation axis; the vector distribution is uniform, and no obvious pre-swirl or large-scale backflow is observed, indicating that the suction chamber design is reasonable and can provide stable inflow conditions for the impeller; the relative velocity vector at the leading edge of the blade is basically consistent with the tangential direction of the blade rib line, indicating that under rated operating conditions, the fluid has no impact inflow and the impact loss is small, which is conducive to suppressing the initial cavitation at the inlet. Internal flow and energy transfer within the impeller are influenced by centrifugal Coriolis forces: After the fluid enters the impeller channel, the velocity vector direction is significantly deflected under the combined action of centrifugal and Coriolis forces, gradually changing from axial to a composite direction of radial and tangential. The vector direction of the fluid velocity strictly conforms to the blade profile distribution, reflecting the constraint and guiding effect of the blades on the fluid. The vector modulus near the pressure surface of the blade is slightly smaller than that near the suction surface, but the directional consistency is better. This tangential flow vector closely adhering to the wall means that particles mainly undergo small-angle abrasion inside the channel, rather than direct impact.

[0054] The distribution of the pressure field reflects the pump's work capacity, and local low-pressure areas are a key basis for judging whether cavitation has occurred. Figure 9This is a static pressure distribution cloud map. From the inlet to the outlet, the total pressure of the fluid shows a monotonically increasing trend. This physically verifies that the impeller, as a power-generating component, effectively converts shaft power into the mechanical energy of the fluid, achieving continuous energy injection. At the impeller outlet, the fluid gains extremely high absolute velocity. According to Bernoulli's equation, given the increase in total energy, the high kinetic energy component leads to a relatively low local static pressure at this point. At this time, the fluid energy mainly exists in the form of kinetic energy and has not yet been fully converted into easily transportable pressure energy. This explains why the static pressure at the impeller outlet is not the highest value across the entire field, and why there is a local low-pressure zone at the trailing edge of the blade suction surface.

[0055] S4. Using the Eulerian-Lagrange method, the motion trajectory and velocity distribution of particles within the pump are simulated through a discrete phase model. This yields the motion trajectory and velocity distribution of particles of different sizes in the flow field under seawater conditions, identifying hazardous areas and weak points prone to erosion. The impact velocity and impact angle of particles striking the wall are calculated using a combination of the discrete phase model, the finite volume model, and the wall erosion model, serving as the basis for quantitative analysis of mechanical wear rates.

[0056] Specifically, the fluid is treated as a continuous phase, and the Eulerian method is used for solving the problem. The particles, treated as a discrete phase, are tracked using the Lagrangian method to trace the motion of individual particles. This method is suitable for sparse flows with a particle volume fraction of less than 10%. The particle's trajectory in the flow field is controlled by a combination of fluid drag, centrifugal force, Coriolis force, and its own inertia. In this embodiment, the effects of fluid drag, gravity, and buoyancy are comprehensively considered.

[0057] In the momentum equation, the interparticle-particle interaction forces are ultimately reflected in the properties of the solid phase, such as solid phase pressure and solid phase viscosity. Based on particle dynamics theory, by solving the solid phase temperature equation, the solid phase pressure and solid phase viscosity can be solved to characterize the rheological behavior of the particle phase and improve the stability of the two-phase solution, thus obtaining a more reliable particle distribution field.

[0058] The solid-phase temperature equation is: Formula for solving solid phase pressure: Formula for calculating solid viscosity: Figure 10 The three-dimensional motion trajectory of sand particles with an inlet velocity of 6.75 m / s within the pump is shown. The particle trajectory distribution reveals that after entering through the inlet, the particles acquire tangential velocity under the action of the impeller blades, exhibiting a distinct rotational motion characteristic. Most particles move along the main flow zone, largely consistent with the fluid streamlines, exhibiting a spiral upward motion trajectory within the impeller channel.

[0059] S5. Erosion Corrosion Simulation Calculation S5.1. To quantitatively calculate the mechanical wear rate of particles on the wall surface. The mechanical wear rate was obtained using the Jana wear rate model. ; Jana wear rate model considers mechanical wear rate Defined as the mass loss of material per unit area per unit time, and expressed as a function of particle impact velocity. Particle volume fraction and particle impact angle The function; mechanical wear rate Directly related to fluid dynamics parameters: In the formula, mechanical wear rate The unit is meters per second (m / s) m / s In engineering applications, it is often converted to millimeters per year (mm / a), and the conversion relationship is 1. m / s =3.1536×10 10 mm / a Particle volume fraction , defined as the ratio of particle volume to the total volume of the mixture, is dimensionless; particle impact velocity. The unit is m / s ; It is a dimensionless erosion rate, which is related to the material hardness and the particle impact angle, and is dimensionless.

[0060] Dimensionless erosion rate The Finnie dimensionless erosion rate model was used to calculate the wear rate of metals by rigid particles, taking into account the particle rebound effect. In the formula, The erosion cutting material coefficient is used to characterize the ability of the coating on the inner wall of the pump casing to resist particle cutting wear. It is dimensionless, and the empirical value range for metallic materials is 0.01 to 0.05. For ceramic materials, it is obtained through single-phase erosion test calibration. Particle density, unit: kg / m 3 Impact angle of particles The unit is degrees (°). Vickers hardness of the material, in Pa; The particle resilience coefficient is dimensionless, and its value is expressed through the normal restitution coefficient. and tangential restitution coefficient Jointly determined; normal restoration coefficient and tangential restitution coefficient All are impact angles The function, i.e. , For quartz sand particles as a discrete phase, the function and The parameters are defined using experimental data or publicly available standard curves. Furthermore, for different wall materials, the normal and tangential coefficients of restitution curves corresponding to the materials are used to accurately describe the momentum exchange characteristics at the boundaries of different materials.

[0061] S5.2. Based on the electrochemical kinetic equations and considering the effect of flow rate, calculate the electrochemical corrosion rate; whereby the relationship between corrosion current and potential described by the Tafel equation is: In the formula, This represents the corrosion current density under static conditions, in units of... or 1 ; Corrosion current density after taking into account the effect of flow rate, in units of or 1 ; and The units should be consistent. The velocity coefficient is related to the viscosity of the medium. Its value and unit are determined by fitting experimental data, and its unit is derived from the potential. Confirm, ensure The whole is dimensionless; Potential, measured in volts (V). The velocity index is dimensionless and is typically taken as 0.5 to 1.0 under turbulent conditions. Then, the electrochemical corrosion rate is obtained based on the electrochemical corrosion theory. .

[0062] S5.3. Calculate the erosion corrosion rate The erosion corrosion rate is determined by the rate of mechanical wear alone. Individual electrochemical corrosion rate and the incremental interaction between mechanical wear and electrochemical corrosion It consists of three parts: In the formula, mechanical wear rate The unit is meters per second (m / s) m / s In engineering applications, it is often converted to millimeters per year (mm / a), and the conversion relationship is 1. m / s =3.1536×10 10 mm / a Electrochemical corrosion rate The unit is meters per second (m / s) m / s In engineering applications, it is often converted to millimeters per year (mm / a), and the conversion relationship is 1. m / s =3.1536×10 10 mm / a ; Erosion corrosion rate The unit is meters per second (m / s) m / s In engineering applications, it is often converted to millimeters per year (mm / a), and the conversion relationship is 1. m / s =3.1536×10 10 mm / a ; Interaction Increment The unit is meters per second (m / s) m / s In engineering applications, it is often converted to millimeters per year (mm / a), and the conversion relationship is 1. m / s =3.1536×10 10 mm / a ; , , , The units should be kept consistent.

[0063] Interaction Increment It is the core term characterizing the nonlinear synergistic enhancement effect between mechanical wear and electrochemical corrosion, and its calculation formula is a polynomial function product of a set of separated variables: In the formula, The synergistic material coefficient for erosion corrosion is determined by the material's inherent properties and is obtained through erosion corrosion coupling experiments. It characterizes the additional damage rate caused by the synergistic effect of erosion and electrochemical corrosion on the inner wall coating of the pump casing, and is expressed in m / s. In engineering applications, it is often converted to [missing value]. mm / a The conversion relationship is as follows: 1 m / s = 3.1536 × 10 10 mm / a ); , , Let be dimensionless functions representing particle impact velocity, particle impact angle, and particle volume fraction, respectively. These functions, in polynomial form, describe the nonlinear influence of each factor on the synergistic effect, and their form is: in, Represents particle impact velocity Particle volume fraction or particle impact angle ; , , ,…, The coefficients are obtained by fitting the erosion corrosion rate data obtained through erosion corrosion coupling experiments using multivariate nonlinear regression. Their dimensions are determined based on the dimensions of the independent variables to ensure that each term of the polynomial is dimensionless, thereby... The whole is dimensionless; constant term a 0 reflects the residual effect that may exist when the factor approaches zero; typically n Choose 2 or 3. Unlike existing technologies that use a single constant or linear term to characterize the synergistic effect, the polynomial form of this invention can accurately capture nonlinear physical phenomena such as "the interaction effect is not significant at low speeds, but increases exponentially after exceeding the speed threshold," and has stronger fitting ability and physical interpretability.

[0064] The calibration was obtained through a coupled scouring and corrosion test, and the specific steps are as follows: (1) Based on the actual working conditions of the turbopump, a test device for erosion corrosion of the inner wall of the turbopump under service conditions was built, and the substrate and ceramic coating materials were subjected to different particle impact velocities. Particle volume fraction and particle impact angle Erosion corrosion experiments were conducted under specific conditions to obtain the erosion corrosion rate; nonlinear regression and linear fitting were then performed based on the actual measured erosion corrosion rate data to determine the... , and coefficient , , ,…, ; (2) Research on the impact velocity of matrix and ceramic coating materials on particles Particle volume fraction and particle impact angle Erosion corrosion experiments were conducted under experimental conditions to obtain the erosion corrosion rate. ;Measuring the mechanical wear rate under the same hydrodynamic conditions but with suppressed electrochemical corrosion. ;Measure the electrochemical corrosion rate under the same electrochemical conditions but without particle erosion. ; Calculate the interaction increment : ; The particle impact velocity corresponding to the experimental conditions Particle volume fraction and particle impact angle Substitution ;but The average value of the calculation results from multiple experimental operating points is taken as the final result. .

[0065] Experimental verification shows that the simulation method of this invention can accurately reproduce the complex vortex and water flow impact phenomena within a turbopump. The calculation process exhibits stable data convergence and good mass conservation. This demonstrates that the simulation method can predict the actual wear and tear of the equipment, and its output data can directly provide a reliable basis for subsequent coating selection, thickness design, and maintenance cycles.

[0066] S6. Predict the erosion life of the pump casing inner wall coating based on the erosion corrosion rate, and / or formulate suitable operating conditions for the pump casing inner wall coating, and / or formulate a coating thickness scheme for the pump casing inner wall coating.

[0067] The prediction of the erosion life of the inner wall coating of the pump casing based on the erosion corrosion rate is specifically determined by the thickness of each local part of the coating and the total erosion rate of each local part.

[0068] The specific operating conditions suitable for the inner wall coating of the pump casing are as follows: under a specific sand content, the appropriate turbine pump speed is determined based on the thickness of each local part of the inner wall coating of the pump casing and the total erosion rate of each local part under different speed conditions, so that the inner wall coating of the pump casing does not fail.

[0069] The specific method for determining the coating thickness of the inner wall of the pump casing is as follows: under specific sand content and specific turbine pump operating speed conditions, the coating thickness of each local part of the inner wall of the pump casing is determined based on the total erosion rate under specific sand content and specific turbine pump operating conditions.

[0070] For example, based on extreme mass loss data of high-speed sand particles in high-risk areas, the annual single-sided thickness loss rate of the substrate and coating is calculated, the upper and lower boundaries of the erosion corrosion rate are clarified, and a local coating thickness design scheme for the turbopump under continuous operation for 12 months is proposed accordingly. The service performance and service life of the turbopump under sandy conditions are evaluated, providing a theoretical basis for the optimized design, material selection, and protective measures of the turbopump.

[0071] In this embodiment, the simulation method further includes dynamic simulation considering surface morphology evolution: after obtaining the erosion corrosion rate distribution in step S6, the calculated wall wear is fed back to the three-dimensional fluid domain geometry model in step S2 using mesh deformation or dynamic mesh technology to update the wall morphology, and steps S3-S5 are repeated, thereby achieving dynamic simulation considering morphology evolution and further improving long-term prediction accuracy. Through this iterative calculation, dynamic simulation of the feedback effect of wall morphology evolution on the fluid field and particle trajectory is realized.

[0072] In summary, the simulation method proposed in this embodiment can accurately predict the erosion corrosion behavior of the inner wall coating of the turbine pump, providing a quantitative basis for the life assessment and protection design of key nuclear power equipment.

[0073] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for simulating erosion corrosion of pump casing coating, characterized in that, Includes the following steps: S1. Construct a three-dimensional fluid domain geometric model of the turbopump; S2. Mesh the three-dimensional fluid domain geometry model and set boundary conditions; S3. Using computational fluid dynamics software and a turbulence model, perform steady-state or transient simulations of the flow field inside the pump to obtain the velocity distribution, streamline morphology, and pressure distribution characteristics of the flow field; S4. Using the Eulerian-Lagrange method, the motion trajectory and velocity distribution of particles in the pump are simulated through a discrete phase model to obtain the motion trajectory and velocity distribution of particles of different sizes in the flow field, and to identify dangerous areas and weak points of erosion. S5. Perform coupled calculations of mechanical wear and electrochemical corrosion, specifically including: S5.

1. Calculate the mechanical wear rate using a wear rate model. ; S5.

2. Calculate the electrochemical corrosion rate based on the electrochemical kinetic equations and considering the effect of flow rate. ; S5.

3. Calculate the erosion rate The rate of erosion corrosion is determined by the rate of mechanical wear. Electrochemical corrosion rate and the incremental interaction between mechanical wear and electrochemical corrosion It consists of three parts: In the formula, the interaction increment The calculation formula is in the form of a product of polynomial functions with separate variables: In the formula, The scouring corrosion synergistic material coefficient is determined by the material's inherent properties and is obtained through scouring corrosion coupling experiments. It is used to characterize the additional damage rate caused by the synergistic effect of scouring and electrochemical corrosion on the inner wall coating of the pump casing. For particle impact velocity, This represents the particle volume fraction. The impact angle of the particles; , , These are the particle impact velocities. Impact angle of particles and particle volume fraction The dimensionless function, in polynomial form, describes the nonlinear influence of each factor on the synergistic effect, and its form is: in, Represents particle impact velocity Particle volume fraction or particle impact angle ; , , ,…, The coefficients are obtained by fitting multiple nonlinear regression to the data from the scouring corrosion coupling experiment. S6. Based on the calculated erosion corrosion rate Predict the erosion life of the pump casing inner wall coating, and / or formulate suitable operating conditions for the pump casing inner wall coating, and / or formulate a coating thickness scheme for the pump casing inner wall coating.

2. The simulation method for erosion corrosion of pump casing coating according to claim 1, characterized in that, In step S1, when constructing the three-dimensional fluid domain geometric model of the turbopump, the three-dimensional torsion law of the blades, the tip clearance, and the profile curvature of the volute tongue are preserved.

3. The simulation method for erosion corrosion of pump casing coating according to claim 1, characterized in that, Step S2 specifically includes: S2.

1. High-fidelity geometry reconstruction and fluid extraction for turbopumps: In 3D CAD software, the solid models of the impeller, volute and suction chamber of the turbopump are reconstructed, and the internal cavities of all flow components are extracted to generate the original fluid domain geometry. Using the impeller mechanical seal end face and the impeller outlet annular face as boundaries, a dynamic-static interface is constructed to divide the dynamic-static computational domains, thereby achieving topological separation of the dynamic-static computational domains; Extend the inlet and outlet boundaries; perform geometric cleanup and topology checks on the generated fluid domain; S2.

2. Mesh Generation: A fully hexahedral structured mesh is used for the impeller fluid domain; the leading and trailing edges of the blades are adaptively refined with curvature, and the minimum mesh size is limited to 0.2 mm. An unstructured tetrahedral mesh was used for the static region of the volute; the maximum mesh size in the mainstream region of the volute was set to 3.0 mm; density boxes were set in the tongue region, and the local mesh size was refined to 0.5 mm. The near-wall boundary layer uses a prismatic layer mesh, with the first layer mesh height set to 0.035 mm; the total number of boundary layer layers is set to 3, and the interlayer growth rate is controlled at 1.

15. S2.

3. Set boundary conditions: Inlet boundary conditions: The pump suction inlet section is set as a velocity inlet, and the turbulence parameters are set based on the fully developed pipe flow turbulence theory, with the turbulence intensity set to 5%; Outlet boundary conditions: The pump outlet section is set as a pressure outlet, and the gauge pressure is set to 0 Pa; the backflow turbulence intensity is set to 5%; Solid wall boundary conditions: The contact boundary between the fluid and the solid surface is set as a solid wall and follows the no-slip condition; Discrete phase boundary conditions: The wall restitution coefficient model proposed for the collision between hard particles and metal walls is selected.

4. The simulation method for erosion corrosion of pump casing coating according to claim 1, characterized in that, In step S4, the injection source of the discrete phase model adopts the surface injection type, and the injection source position is set at the inlet surface of the turbopump fluid domain; The initial velocity vector of the particles is set to be consistent with the velocity of the continuous phase fluid at the inlet, thus achieving slip-free injection, which is automatically given by the solver based on the inlet boundary conditions; the particle size distribution adopts a uniform particle size distribution.

5. The simulation method for erosion corrosion of pump casing coating according to claim 1, characterized in that, In step S4, the impact velocity and impact angle of the particles hitting the wall are calculated by combining the discrete phase model and the finite volume model with the wall erosion model. When simulating the motion trajectory and velocity distribution of the particles in the flow field, the effects of fluid drag, gravity and buoyancy are considered. Based on the particle dynamics theory, the solid phase pressure and solid phase viscosity are solved by solving the solid phase temperature equation to correct the motion trajectory and velocity of the particles.

6. The simulation method for erosion corrosion of pump casing coating according to claim 1, characterized in that, In step S5.1, the mechanical wear rate is... Directly related to fluid dynamics parameters: In the formula, It is a dimensionless erosion rate, which is related to the material hardness and the particle impact angle. The dimensionless erosion rate is calculated using a dimensionless erosion rate model, taking into account the particle rebound effect in the case of particle-induced metal cutting wear: In the formula, The erosion cutting material coefficient is used to characterize the ability of the coating on the inner wall of the pump casing to resist particle cutting wear. For metallic materials, the coefficient is selected through empirical values, while for ceramic materials, it is obtained through single-phase erosion experiments. Particle density; Vickers hardness of the material; The particle resilience coefficient is obtained by using the normal recovery coefficient. and tangential restitution coefficient Jointly determined; normal restoration coefficient and tangential restitution coefficient All are impact angles The function, i.e. , ;function and The parameters are defined using standard curves published in experimental data or literature, and for different wall materials, the normal and tangential coefficient of restitution curves corresponding to the material are used respectively.

7. The method for simulating erosion corrosion of pump casing coating according to claim 1, characterized in that, Step S5.2 specifically includes: The relationship between corrosion current and potential described by the Tafel equation is as follows: In the formula, This represents the corrosion current density under static conditions. Corrosion current density after taking into account the effect of flow rate; The velocity coefficient is related to the viscosity of the medium, and its value is determined by fitting experimental data. Its unit varies with the viscosity of the medium. Unit determined, ensuring The whole is dimensionless; Potential; The velocity index is dimensionless and is taken as 0.5 to 1.0 under turbulent conditions. Then, the electrochemical corrosion rate is obtained based on the electrochemical corrosion theory. .

8. The method for simulating erosion corrosion of pump casing coating according to claim 1, characterized in that, In step S5.3, The calibration was obtained through erosion corrosion coupling experiments, specifically including: Step 1: At different particle impact velocities Particle volume fraction and particle impact angle Erosion corrosion experiments were conducted on the inner wall coating of the pump casing under certain conditions to obtain the erosion corrosion rate; nonlinear regression and linear fitting were then performed based on the actual measured erosion corrosion rate data to determine the corrosion rate. , and The coefficient; Step 2, at the particle impact velocity Particle volume fraction and particle impact angle Erosion corrosion experiments were conducted on the inner wall coating of the pump casing under experimental conditions to obtain the erosion corrosion rate. ;Measuring the mechanical wear rate under the same hydrodynamic conditions but with suppressed electrochemical corrosion. ;Measure the electrochemical corrosion rate under the same electrochemical conditions but without particle erosion. ; Calculate the interaction increment : The particle impact velocity corresponding to the experimental conditions. Particle volume fraction and particle impact angle Substitution ;but The average value of the calculation results from multiple experimental operating points is taken as the final result. .

9. The simulation method for erosion corrosion of pump casing coating according to claim 1, characterized in that, In step S6, the prediction of the erosion life of the inner wall coating of the pump casing based on the erosion corrosion rate is specifically determined by: the thickness of each local part of the inner wall coating of the pump casing and the total erosion rate of each local part. The specific operating conditions suitable for the inner wall coating of the pump casing are as follows: under a specific sand content, the turbine pump speed suitable for continuous operation of the turbine pump for a specific time without failure of the inner wall coating is determined based on the thickness of each local part of the inner wall coating of the pump casing and the total erosion rate of each local part under different speed conditions. The specific steps for determining the coating thickness scheme are as follows: under specific sand content and specific turbine pump operating speed conditions, the coating thickness of each local part of the pump casing inner wall is determined based on the total erosion rate.

10. The method for simulating erosion corrosion of pump casing coating according to any one of claims 1-9, characterized in that, It also includes dynamic simulation that considers the evolution of surface morphology: after obtaining the scouring corrosion rate distribution in step S6, the calculated wall wear amount is fed back to the three-dimensional fluid domain geometry model in step S2 through mesh deformation or dynamic mesh technology to update the wall morphology, and steps S3-S5 are repeated, thereby realizing dynamic simulation that considers morphology evolution and further improving the long-term prediction accuracy.

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