Seabed vibration elbow solid-liquid two-phase flow erosion corrosion coupling analysis method and system

Abstract

The invention belongs to the technical field of ocean engineering, and discloses a seabed vibration elbow solid-liquid two-phase flow erosion corrosion coupling analysis method and system. The method comprises the following steps: establishing a three-dimensional fine model of a local bent pipe section; constructing a flow accelerated corrosion model by using a mass transfer equation and a solubility equation to calculate a flow accelerated corrosion rate; an E / CRC particle erosive wear model is introduced to calculate the erosive wear rate of particles to the wall surface of the pipeline; an erosion-corrosion coupling model is constructed based on the electrochemical corrosion secondary current model to simulate the erosion corrosion process of solid-liquid two-phase flow in the vibration pipeline, and an erosion corrosion coupling response rule in the vibration elbow is obtained. Compared with an original analysis method which only considers erosion wear, the erosion corrosion rate calculation precision is improved by 36%, the simulation result and experiment comparison error is reduced to be within 20%, and technical support is provided for accurate analysis of pipeline damage under the erosion corrosion coupling effect.

Description

Technical Field

[0001] The invention belongs to the field of marine engineering technology, and in particular relates to a method and system for analyzing coupled erosion and corrosion of solid-liquid two-phase flow in a submarine vibrating elbow. Background Art

[0002] Erosion-corrosion inside submarine elbows is a complex mechanism under the coupling effect of solid-liquid two-phase flow erosion and electrochemical corrosion of the pipe wall. Existing research focuses on the numerical simulation analysis of mechanical erosion and wear of pipe walls by flowing particles, but fails to combine the solid-liquid two-phase flow characteristics in the pipe and the erosion-corrosion coupling effect, which greatly limits its application in engineering. In addition, pipeline vibration in the actual marine environment will aggravate erosion and corrosion, causing thinning and degradation of pipeline materials to produce more complex forms of damage and rupture. However, the current simulation and analysis method of erosion-corrosion characteristics in vibrating pipes does not take into account the vibration characteristics of the pipeline structure, and there is no basis for setting the pipeline vibration operating parameters. It is difficult to explain the effect of vibration on erosion-corrosion of solid-liquid two-phase flow in elbows, and it is impossible to accurately simulate the erosion-corrosion process of solid-liquid two-phase flow in vibrating elbows. Summary of the invention

[0003] In order to overcome the problems existing in the related art, the disclosed embodiments of the present invention provide a method and system for coupling analysis of erosion and corrosion of solid-liquid two-phase flow in a submarine vibrating elbow.

[0004] The technical solution is as follows: A coupled analysis method for erosion-corrosion of solid-liquid two-phase flow in a submarine vibrating elbow comprises the following steps: S1, construct a two-dimensional curved pipeline model, consider the influence of internal flow and external seawater pressure as well as pipeline displacement deformation on the flow in the pipe, conduct modal analysis of the liquid-filled pipeline, set pipeline vibration operating parameters according to the modal analysis results, and establish a three-dimensional fine model of the local curved pipe section; S2, using the mass transfer equation and solubility equation, construct a simulation model of flow-accelerated corrosion in pipes and calculate the flow-accelerated corrosion rate inside the elbow; S3, introduce the E / CRC particle erosion wear model to calculate the erosion wear rate of particles on the pipe wall; S4, based on the electrochemical corrosion secondary current model, the erosion-corrosion coupling model is constructed to simulate the erosion-corrosion process of solid-liquid two-phase flow in the vibrating pipeline and obtain the erosion-corrosion coupling response law in the vibrating elbow.

[0005] In step S1, the pipeline vibration condition parameters are set according to the modal analysis results, and a three-dimensional fine model of the local elbow section is established, including: expressing the pipeline vibration condition in the form of simple harmonic vibration, and establishing the periodic vibration displacement of the three-dimensional fine model of the local elbow section, the expression is: ; In the formula, is the vibration displacement, in mm; is the amplitude, in mm; is the angular frequency, in rad / s, and its relationship with the vibration frequency is , is the frequency, in Hz; For time, is the initial phase angle, defined as 0.

[0006] In step S2, a flow-accelerated corrosion simulation model is constructed using the mass transfer equation and the solubility equation to calculate the flow-accelerated corrosion rate inside the elbow, including: using flow-accelerated corrosion FAC to calculate the flow-accelerated corrosion rate at different flow rates and temperatures, and analyzing the relationship between the fluid flow wall shear stress and the corrosion rate.

[0007] Furthermore, the flow accelerated corrosion rate in the pipe at different flow rates and temperatures is calculated, including: (1) Electrochemical dissolution of the matrix iron, formation of oxide film, and dissolution of the oxide film under flow state; (2) Comprehensively considering the influence of the above processes, the above processes occur near the wall of the pipeline under the flow state, and the flow accelerated corrosion rate in the pipe at different flow rates and temperatures is calculated. The FAC corrosion rate is expressed as: ; In the formula, is the flow accelerated corrosion rate, in mm·y -1 ; is the solubility of the soluble iron-containing component, is the mass transfer coefficient. Considering the influence of flow characteristics, the mass transfer coefficient of the corrosive medium at the wall is related to the flow velocity. is the porosity of the oxide layer, is the diffusion coefficient; is the oxide layer thickness, in m.

[0008] In step (1), the electrochemical dissolution of the matrix iron includes: the iron metal matrix in the flowing corrosive medium corrodes on the contact surface with the fluid, and the iron element reacts to generate ferrous ions. The FAC rate during the electrochemical dissolution of the matrix iron is expressed as: ; In the formula, is the reaction rate constant, is the concentration of soluble iron-containing components at the interface between the material surface and the solution, in mol·L -1 ; Solubility of soluble iron-containing components The expression is: ; In the formula, is the solubility product, in mol -2 ·L -2 ; The number of anions generated for a single electrolyte molecule, The number of cations generated for a single electrolyte molecule; The solubility is calculated based on the solubility product of the FeCO3 component of the oxide film. The solubility product of the iron-containing component is expressed as: ; In the formula, is the absolute temperature, in K; is the ionic strength, in mol·L -1 .

[0009] In step (1), the oxide film is generated, including: a part of the generated iron ions reacts to form an oxide film covering the surface of the substrate, and the other part diffuses into the mainstream area of ​​the fluid flow. The FAC rate of the oxide film generation process is expressed as: ; In the formula, is the concentration of soluble iron-containing components at the interface between the oxide layer and the solution, in mol·L -1 ; is the ratio of the iron ions involved in the formation of the oxide layer to the total iron ions produced by the matrix; is the diffusion coefficient of the iron-containing component involved in the reaction, in m 2 ·s -1 .

[0010] Furthermore, the oxide film dissolution under the flow state includes: the oxide film on the substrate surface is dissolved and diffused to the mainstream area under the influence of the flow, and is taken away from the reaction area with the flow. The FAC rate of the oxide film dissolution process under the flow state is expressed as follows: ; In the formula, is the concentration of iron components in the main flow area of ​​the solution, in mol·L -1 ; Mass transfer coefficient The expression is: ; In the formula, is the Reynolds number; is the characteristic length. For the flow in the pipe, the characteristic length is the inner diameter of the pipe, in meters; is the speed coefficient, , is the fluid wall friction velocity, in m·s -1 , is the average velocity of the fluid, in m·s -1 ; is a constant coefficient determined by experiments, with b ranging from 0.3 to 1 and c ranging from 0.33 to 0.4; is the Schmidt number, which indicates the relative thickness of the fluid dynamic boundary layer and the mass transfer layer; Diffusion coefficient The expression is: ; In the formula, is the Boltzmann constant, in J·K -1 ; is the dynamic viscosity of the fluid in the tube, in Pa·s; is the radius of the ions involved in diffusion in the solution, and its value is 0.078nm.

[0011] In step S3, the expression of the E / CRC particle erosion wear model is: ; ; In the formula, is the erosion model coefficient, is the particle shape factor, is the Brinell hardness of the wall material, is the speed index; is the velocity of the incident particle, in m·s -1 ; is the particle incident angle, in rad; is the particle incident angle function, which is used to characterize the effect of erosion angle on material wear rate.

[0012] In step S4, an erosion-corrosion coupling model is constructed based on the electrochemical corrosion secondary current model to simulate the erosion-corrosion process of solid-liquid two-phase flow in the vibrating pipeline, including: Under the combined action of erosion and electrochemical corrosion in liquid-solid two-phase flow, the specific expression of the total mass loss caused by material erosion corrosion is: ; In the formula, is the total mass loss due to erosion and corrosion, is the mass loss caused by pure erosion wear, is the mass loss caused by pure corrosion, The effect of particle erosion and wear on the electrochemical corrosion of materials; Under the conditions of liquid-solid two-phase flow erosion corrosion, the quantitative expression of erosion-promoted corrosion is: ; In the formula, The erosion damage effect of the oxide film. The erosion and wear of the oxide film by particles leads to further corrosion of the underlying metal surface. The increase in surface corrosion area caused by erosion pits leads to an increase in corrosion activity; is the ratio of the anode current density affected by particle impact, ranging from 0 to 1; are the anode current density under erosion and unaffected conditions, in A·m -2 ; is the surface area of ​​the affected area before the pit is created, It is the increased corrosion area on the material surface before and after erosion wear.

[0013] Another object of the present invention is to provide a coupled analysis system for erosion-corrosion of a submarine vibrating elbow solid-liquid two-phase flow, which implements the coupled analysis method for erosion-corrosion of a submarine vibrating elbow solid-liquid two-phase flow, and the system comprises: The module for establishing a three-dimensional fine model of a local bend section is used to construct a two-dimensional bend pipeline model, consider the influence of internal flow and external seawater pressure as well as pipeline displacement deformation on the flow in the pipe, conduct modal analysis of the liquid-filled pipeline, set pipeline vibration operating parameters according to the modal analysis results, and establish a three-dimensional fine model of the local bend section; The corrosion rate calculation module is used to construct a simulation model of flow-accelerated corrosion in pipes using the mass transfer equation and the solubility equation, and calculate the flow-accelerated corrosion rate in the elbow; The erosion wear rate calculation module is used to introduce the E / CRC particle erosion wear model to calculate the erosion wear rate of particles on the pipe wall; The erosion-corrosion coupling model building module is used to build an erosion-corrosion coupling model based on the electrochemical corrosion secondary current model, simulate the erosion-corrosion process of solid-liquid two-phase flow in a vibrating pipeline, and obtain the erosion-corrosion coupling response law in a vibrating elbow.

[0014] In combination with all the above technical solutions, the beneficial effects of the present invention are as follows: The present invention discloses a coupled analysis method for erosion-corrosion of solid-liquid two-phase flow in a vibrating seabed elbow. By combining the solid-liquid two-phase flow characteristics in the pipe and comprehensively considering the flow-accelerated corrosion, erosion wear and erosion wear-electrochemical corrosion coupling effects, the mass loss rate of the inner wall of the pipe under the combined action of corrosive flowing liquid and solid phase particles is simulated. Compared with the original analysis method that only considers erosion wear, the calculation accuracy of the erosion-corrosion rate is improved by 36%, and the error between the simulation results and the experiment is reduced to within 20%, providing technical support for the accurate analysis of pipeline damage under the coupled action of erosion-corrosion. The present invention simulates the erosion-corrosion process of solid-liquid two-phase flow in a vibrating pipe for the first time based on the vibration characteristics of the pipe structure, and clarifies the influence of vibration on the coupling of erosion-corrosion in the elbow pipe.

[0015] The present invention improves the calculation accuracy of erosion corrosion rate: the original analysis method only considers erosion wear. The present invention combines the solid-liquid two-phase flow characteristics in the pipe and considers flow-accelerated corrosion, erosion wear and erosion wear-electrochemical corrosion coupling effects. The calculation accuracy of erosion corrosion rate can be improved by 36%, which will help engineers and designers better evaluate the operating life and reliability of pipelines and reduce accident risks. Reduce costs and improve efficiency: Accurately predicting the erosion corrosion rate helps optimize maintenance plans and resource allocation, avoid excessive maintenance or unnecessary shutdowns, so as to reduce maintenance costs and improve production efficiency. In addition, the technical solution can also reduce test costs and time, making the engineering design and evaluation process more efficient. Improved erosion-corrosion coupling model of vibrating elbows: by introducing pipeline vibration and fine-tuning the modeling of key parts of the elbow, the improved erosion-corrosion coupling model can more accurately simulate the erosion-corrosion process of solid-liquid two-phase flow in vibrating elbows, and the error between the simulation results and the experiment is reduced to within 20%.

[0016] The present invention realizes the accurate characterization of erosion and corrosion of submarine pipelines: In the field of submarine oil and gas pipeline engineering, erosion and corrosion inside the pipeline will seriously affect the service life and operational safety of marine oil and gas pipelines. Existing studies only consider erosion and wear, and it is often difficult to accurately characterize the erosion and corrosion process inside the submarine pipeline, which greatly limits its engineering application. The present invention combines the solid-liquid two-phase flow characteristics in the pipe and comprehensively considers the flow-accelerated corrosion, erosion and wear, and erosion and wear-electrochemical corrosion coupling effects, so as to realize the accurate prediction of the mass loss rate of the inner wall of the pipeline under the joint action of corrosive flowing liquid and solid phase particles, and the calculation accuracy is improved by 36%. Consider the influence of pipeline vibration on the erosion and corrosion of submarine elbows: In the actual marine environment, pipeline vibration will aggravate erosion and corrosion, resulting in thinning and degradation of pipeline materials, resulting in more complex forms of damage and rupture. The present invention sets the pipeline vibration operating parameters according to the vibration characteristics of the pipeline structure, realizes the simulation of the erosion and corrosion process of solid-liquid two-phase flow in the vibrating pipeline, and improves the accuracy of model prediction.

[0017] The technical solution of the present invention comprehensively studies and solves the erosion corrosion of submarine elbow pipes from the theoretical and practical levels by considering the influence of pipeline structural parameters such as fluid dynamics, pipe diameter, and external factors such as pipeline vibration on the erosion corrosion in the pipe. In this process, the technical solution of the present invention focuses on comprehensively considering the factors affecting pipeline erosion corrosion and improving the accuracy and practicality of the prediction of the erosion corrosion coupling model. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings herein are incorporated in and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the description, serve to explain the principles of the present disclosure; Figure 1This is a flow chart of a method for analyzing the coupled erosion and corrosion of a subsea vibrating elbow solid-liquid two-phase flow provided by an embodiment of the present invention; Figure 2 is a schematic diagram of a simulation of the transverse simple harmonic vibration of a curved pipe section provided by an embodiment of the present invention; Figure 3 It is a schematic diagram of the erosion-enhanced corrosion mechanism under the erosion-corrosion of liquid-solid two-phase flow in a pipeline provided by an embodiment of the present invention; Figure 4 Schematic diagram of a coupled analysis system for solid-liquid two-phase flow erosion-corrosion of a submarine vibrating elbow provided by an embodiment of the present invention; Figure 5 This is a schematic diagram of fine modeling of a local curved pipe section of a pipeline provided by an embodiment of the present invention; Figure 6 A cloud diagram of the erosion wear rate distribution provided by an embodiment of the present invention; Figure 7 A cloud diagram of the total erosion-corrosion rate distribution provided by an embodiment of the present invention; Figure 8 A distribution diagram of erosion-corrosion rates in a static pipeline provided by an embodiment of the present invention; Fig. 9 The erosion corrosion rate distribution diagram in the pipe under the working condition of 1mm amplitude provided by the embodiment of the present invention; In the figure: 1. Module for establishing a three-dimensional fine model of a local curved pipe section; 2. Module for calculating the corrosion rate; 3. Module for calculating the erosion and wear rate; 4. Module for building an erosion-corrosion coupling model. DETAILED DESCRIPTION

[0019] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific implementation disclosed below.

[0020] The innovation of the present invention is that the present invention combines the flow accelerated corrosion model, the erosion wear model and the erosion wear-electrochemical corrosion coupling effect to establish a prediction model for the erosion corrosion rate of liquid-solid two-phase flow in the pipeline, simulates the mass loss rate of the inner wall of the pipeline under the combined action of corrosive flowing liquid and solid phase particles, and realizes accurate characterization of pipeline damage under the erosion corrosion coupling. Based on the vibration characteristics of the pipeline structure, the erosion corrosion process of the solid-liquid two-phase flow in the vibrating pipeline is simulated, and the influence of vibration on the erosion corrosion coupling in the elbow pipe is clarified, filling the gap in the field of erosion corrosion research of submarine vibrating elbow pipes.

[0021] Embodiment 1, as Figure 1As shown, the method for analyzing the erosion-corrosion coupling of solid-liquid two-phase flow in a submarine vibrating elbow provided by an embodiment of the present invention overcomes the difficulty of the existing submarine elbow erosion analysis method in accurately characterizing the erosion-corrosion coupling effect of the vibrating pipeline, and specifically includes: S1, construct a two-dimensional curved pipeline model, consider the influence of internal flow and external seawater pressure as well as pipeline displacement deformation on the flow in the pipe, conduct modal analysis of the liquid-filled pipeline, set pipeline vibration operating parameters according to the modal analysis results, and establish a three-dimensional fine model of the local curved pipe section; The present invention considers the large aspect ratio structural characteristics of the pipeline, converts the three-dimensional pipeline and the fluid in the pipeline into a two-dimensional curve form, and constructs a two-dimensional beam unit curved pipeline model. S2, using the mass transfer equation and solubility equation, construct a simulation model of flow-accelerated corrosion in pipes and calculate the flow-accelerated corrosion rate inside the elbow; The present invention considers the promoting effect of the flow of corrosive fluid in the tube on the corrosion reaction in the wall boundary layer, and constructs it based on the flow field characteristics of the tube using the mass transfer equation and the solubility equation; S3, introduce the E / CRC particle erosion wear model to calculate the erosion wear rate of particles on the pipe wall; After analyzing the fluid flow model in the tube and constructing the particle motion equation to characterize the particle trajectory, the E / CRC particle erosion and wear model is introduced; S4, based on the electrochemical corrosion secondary current model, the erosion-corrosion coupling model is constructed to simulate the erosion-corrosion process of solid-liquid two-phase flow in the vibrating pipeline and obtain the erosion-corrosion coupling response law in the vibrating elbow.

[0022] Example 2, as a specific implementation of the present invention, the method for coupling erosion-corrosion analysis of solid-liquid two-phase flow in a submarine vibrating elbow provided by the embodiment of the present invention includes the following technical features.

[0023] In step S1, the pipeline vibration operating parameters are set according to the modal analysis results, and a three-dimensional fine model of the local elbow section is established, including: Vibration is a common problem in marine pipelines. It can affect the flow state of the flowing medium in the pipeline and change the frequency and intensity of the collision between the flowing particles and the pipe wall. The high turbulence intensity and particle erosion in the vibrating pipeline will aggravate the erosion corrosion. Since the present invention focuses on the flow field in the pipeline and its erosion corrosion effect, and the actual pipeline vibration has complex characteristics, the pipeline vibration condition is considered as a simple harmonic vibration form. The schematic diagram of the transverse simple harmonic vibration of the bend section is shown in Figure 2 , its periodic vibration displacement expression is as follows: ; In the formula, is the vibration displacement, in mm; is the amplitude, in mm; is the angular frequency, in rad / s, and its relationship with the vibration frequency is , is the frequency, in Hz; For time, is the initial phase angle, defined as 0.

[0024] In step S2, the flow accelerated corrosion model is constructed using the mass transfer equation and the solubility equation to calculate the flow accelerated corrosion rate, including: To analyze the erosion corrosion of multiphase flow in pipes, it is necessary to first clarify the corrosion mechanism under single-phase flow conditions. The present invention uses the computational fluid dynamics (CFD) method to simulate the problem of flow-promoted corrosion in pipes, calculates the flow accelerated corrosion rate in pipes at different flow rates and temperatures based on flow accelerated corrosion (FAC), and explores the relationship between the shear stress of the fluid flow wall and the corrosion rate.

[0025] The FAC process can be divided into: electrochemical dissolution of matrix iron; oxide film formation; oxide film dissolution under flow state.

[0026] Electrochemical dissolution of matrix iron: The iron metal matrix in the flowing corrosive medium corrodes on the surface in contact with the fluid, and the iron reacts to generate ferrous ions. The FAC rate in this process can be expressed as: ; In the formula, is the reaction rate constant, is the concentration of soluble iron-containing components at the interface between the material surface and the solution, in mol·L -1 ; Solubility of soluble iron-containing components The expression is: ; In the formula, is the solubility product, in mol -2 ·L -2 ; The number of anions generated for a single electrolyte molecule, The number of cations generated for a single electrolyte molecule; The solubility is calculated based on the solubility product of the FeCO3 component of the oxide film. The solubility product of the iron-containing component (FeCO3) is expressed as: ; In the formula, is the absolute temperature, in K; is the ionic strength, in mol·L -1 .

[0027] Oxide film formation: Part of the generated iron ions react to form an oxide film covering the surface of the substrate, and the other part diffuses to the main area of ​​fluid flow (mainstream area). The FAC rate in this process can be expressed as: ; In the formula, is the concentration of soluble iron-containing components at the interface between the oxide layer and the solution, in mol·L -1 ; is the ratio of the iron ions involved in the formation of the oxide layer to the total iron ions produced by the matrix; is the diffusion coefficient of the iron-containing component involved in the reaction, in m 2 ·s -1 .

[0028] Dissolution of oxide film under flow state: The oxide film on the substrate surface is dissolved and diffused to the mainstream area under the influence of flow, and is carried away from the reaction area with the flow. The FAC rate in this process can be expressed as follows: ; In the formula, is the concentration of iron components in the main flow area of ​​the solution, in mol·L -1 ; Mass transfer coefficient The expression is: ; In the formula, is the Reynolds number; is the characteristic length. For the flow in the pipe, the characteristic length is the inner diameter of the pipe, in meters; is the speed coefficient, , is the fluid wall friction velocity, in m·s -1 , is the average velocity of the fluid, in m·s -1 ; is a constant coefficient determined by experiments, with b ranging from 0.3 to 1 and c ranging from 0.33 to 0.4; is the Schmidt number, which indicates the relative thickness of the fluid dynamic boundary layer and the mass transfer layer; Diffusion coefficient The expression is: ; In the formula, is the Boltzmann constant, in J·K -1 ; is the dynamic viscosity of the fluid in the tube, in Pa·s; is the radius of the ions involved in diffusion in the solution, and its value is 0.078nm.

[0029] The present invention innovatively proposes that, considering the influence of the above three processes comprehensively, assuming that the above processes occur near the wall of the pipeline under the flow state, the FAC corrosion rate can be expressed as: ; In the formula, is the flow accelerated corrosion rate, in mm·y -1 ; is the solubility of the soluble iron-containing component, is the mass transfer coefficient. Considering the influence of flow characteristics, the mass transfer coefficient of the corrosive medium at the wall is related to the flow velocity. is the porosity of the oxide layer, is the diffusion coefficient; is the oxide layer thickness, in m.

[0030] In step S3, the E / CRC particle erosion wear model is introduced to calculate the erosion wear rate of particles on the pipeline wall, including: The particle movement is driven by the flowing liquid in the tube. The CFD method is used to analyze the fluid flow in the tube. After completing the analysis of the flow field and solving the discrete phase particle motion equation, it is necessary to associate the calculated impact velocity, angle, position and other information when the particles hit the material surface with the erosion damage prediction model to obtain the material erosion damage rate.

[0031] Since pipeline steel is a tough material, the present invention adopts the E / CRC particle erosion wear model. The erosion rate is defined according to the ratio of the mass of the material removed by surface erosion to the mass of the incident particles: ; ; In the formula, is the erosion model coefficient, is the particle shape factor, is the Brinell hardness of the wall material, is the speed index; is the velocity of the incident particle, in m·s -1 ; is the particle incident angle, in rad; is the particle incident angle function, which is used to characterize the effect of erosion angle on material wear rate.

[0032] In step S4, constructing an erosion-corrosion coupling model based on the electrochemical corrosion secondary current model to simulate the erosion-corrosion process of solid-liquid two-phase flow in the vibrating pipeline includes: Erosion corrosion is the result of the interaction between mechanical erosion and electrochemical corrosion. There are many influencing factors, and the degree of damage to the material under the coupling of erosion wear and electrochemical corrosion is usually greater than the simple superposition of the two, which is more harmful in actual engineering. Therefore, based on the secondary current distribution of electrochemical corrosion and the dynamic Hertz contact mechanics theory, the erosion-electrochemical corrosion coupling relationship equation is introduced into the numerical model to calculate the material mass loss caused by the coupling of the two on the pipe wall.

[0033] Under the combined effects of erosion and electrochemical corrosion in liquid-solid two-phase flow, the total mass loss caused by material erosion corrosion can be specifically expressed as follows: ; In the formula, is the total mass loss due to erosion and corrosion, is the mass loss caused by pure erosion wear, is the mass loss caused by pure corrosion, The effect of particle erosion and wear on the electrochemical corrosion of materials; The present invention innovatively proposes that under the conditions of liquid-solid two-phase flow erosion corrosion, the location where the material is subjected to high-frequency particle impact often produces a higher anode current density, thereby causing more serious corrosion damage at the material erosion location. Figure 3 This is a schematic diagram of the erosion-enhanced corrosion mechanism under liquid-solid two-phase flow erosion corrosion in pipelines. The erosion-enhanced corrosion can be quantitatively expressed as follows: ; In the formula, The erosion damage effect of the oxide film. The erosion and wear of the oxide film by particles leads to further corrosion of the underlying metal surface. The increase in surface corrosion area caused by erosion pits leads to an increase in corrosion activity; is the ratio of the anode current density affected by particle impact, ranging from 0 to 1; are the anode current density under erosion and unaffected conditions, in A·m -2 ; is the surface area of ​​the affected area before the pit is created, It is the increased corrosion area on the material surface before and after erosion wear.

[0034] Embodiment 3, as Figure 4 As shown, the solid-liquid two-phase flow erosion-corrosion coupling analysis system for a submarine vibrating elbow provided by an embodiment of the present invention comprises: The local bend section three-dimensional fine model building module 1 is used to build a two-dimensional bend pipeline model, consider the influence of internal flow and external seawater pressure and pipeline displacement deformation on the flow in the pipe, perform modal analysis of the liquid-filled pipeline, set pipeline vibration operating parameters according to the modal analysis results, and build a three-dimensional fine model of the local bend section; The corrosion rate calculation module 2 is used to construct a simulation model of flow-accelerated corrosion in the pipe by using the mass transfer equation and the solubility equation, and calculate the flow-accelerated corrosion rate in the elbow; The erosion wear rate calculation module 3 is used to introduce the E / CRC particle erosion wear model to calculate the erosion wear rate of particles on the pipe wall; The erosion-corrosion coupling model construction module 4 is used to construct the erosion-corrosion coupling model based on the electrochemical corrosion secondary current model, simulate the erosion-corrosion process of solid-liquid two-phase flow in the vibrating pipeline, and obtain the erosion-corrosion coupling response law in the vibrating elbow.

[0035] Example 4, as another embodiment of the present invention, the method for coupling analysis of erosion and corrosion of solid-liquid two-phase flow in a submarine vibrating elbow provided by the embodiment of the present invention includes: Step 1: Construct a two-dimensional curved pipeline model of beam elements, consider the influence of internal flow, external seawater pressure and pipeline displacement deformation on the flow in the pipe, couple the flow in the pipe with the pipeline structure response, perform modal analysis on the curved pipeline, set the pipeline vibration operating parameters according to the modal analysis results, and establish a three-dimensional fine model of the local curved section.

[0036] Step 2: Use the RANS turbulence model to simulate the turbulence in the tube based on the turbulent kinetic energy and specific dissipation rate and apply it to the particle flow to calculate the flow field characteristics of the flow in the tube. Use the mass transfer equation and solubility equation for secondary development to construct a flow accelerated corrosion model to calculate the flow accelerated corrosion amount and flow accelerated corrosion rate of the liquid phase in the tube.

[0037] Step 3: Based on the Euler-Lagrangian method, a particle motion differential equation is constructed in the time domain to characterize the particle trajectory in the liquid flow field. The discrete phase model is used to solve the motion trajectory of each particle in the pipeline, and the position, velocity, and angle of attack when it collides with the wall are obtained. According to the calculation results, the mirror reflection (Bounce) equation is used to obtain information such as the rebound angle and velocity after the particle hits the pipeline wall, so as to describe the movement behavior of the particle after colliding with the wall boundary. The erosion rate of the particle on the pipeline wall is calculated by introducing the E / CRC particle erosion wear model.

[0038] Step 4. Based on the secondary current distribution theory of electrochemical corrosion of pipeline materials, the diffusion, electromigration and convection of ions in the liquid phase in the pipe are considered. The current expression in the electrolyte is constructed based on the conservation of mass in the electrolyte, and the boundary conditions required for solving the electrochemical polarization equation between the electrode and the electrolyte are solved. The dynamic Hertz contact mechanics theory describing the contact between the sphere and the wall is introduced to obtain the relevant parameters of the particle erosion pits. Secondary development is carried out considering the increase in corrosion activity caused by the deformation of the particle impacting the wall. The erosion-corrosion coupling equation is constructed and a numerical model is introduced to calculate the erosion-corrosion coupling rate.

[0039] Step 5, combining flow-accelerated corrosion, particle erosion wear model and electrochemical corrosion secondary current model, simulate the erosion-corrosion process of solid-liquid two-phase flow in the vibrating pipeline based on the erosion-corrosion coupling effect, and clarify the erosion-corrosion response law in the vibrating elbow.

[0040] The submarine pipeline erosion-corrosion analysis method provided by the embodiment of the present invention can be applied to the coupled numerical analysis process of erosion-corrosion of solid-liquid two-phase flow in submarine vibrating elbow pipes.

[0041] Taking a 90° submarine elbow structure as an example, the solid-liquid two-phase flow erosion-corrosion coupling analysis method of submarine vibration elbow disclosed in the present invention is implemented. First, a beam unit two-dimensional elbow pipeline model is constructed, and static analysis is performed considering the internal flow and external seawater pressure. The modal analysis calculation of the elbow is performed using the method of the present invention. The local elbow section of the elbow pipeline is finely modeled. Figure 5 The structural parameters of the submarine pipeline are shown in Table 1. Based on the modal analysis results, the pipeline vibration condition is set, and the "deformation geometry" function is used to apply a lateral vibration displacement that changes periodically over time to the pipeline. The flow field model, particle properties and electrochemical parameters in the pipe are set. The particle diameter used is 400 μm, and the inlet mass flow rate is 400 g·s -1 The two ends of the whole pipeline are fixed constraints, and the inlet velocity is 4m·s -1 , the flow boundary condition is that the outlet pressure is 1.5Mpa.

[0042] Table 1 Structural parameters of submarine pipeline

[0043] Figure 6 is the erosion wear rate distribution cloud map, Figure 7 is the total erosion-corrosion rate distribution cloud map. Figure 6 It can be seen that the erosion wear is most serious on the outer side of the downstream bend section and on the outer side of the connection with the outlet straight pipe. Figure 7 It can be seen that the distribution of the total erosion corrosion rate on the inner wall of the pipeline is similar to that of the erosion wear rate, but its overall rate is higher on the outer side of the elbow (average 500 μg·h -1 cm -2), the maximum value is still distributed in the outer area where the downstream of the elbow is connected with the outlet straight pipe section. Figure 6 and Figure 7 The erosion rate value at the position of the maximum erosion corrosion rate of the middle elbow is compared with the total erosion corrosion rate value. The erosion wear in the mass loss at this position only accounts for 64% of the total erosion corrosion. Compared with the original analysis method that only considers erosion wear, the calculation accuracy of the erosion corrosion rate is improved by 36%, and the error between the simulation results and the experiment is reduced to within 20%. This shows that the material quality loss caused by corrosion cannot be ignored, and the damage mechanism of the pipeline wall where the quality loss is serious is affected by mechanical erosion and electrochemical corrosion.

[0044] Figure 8 is the erosion corrosion rate distribution diagram in the static pipeline. Fig. 9 This is the distribution diagram of the erosion corrosion rate in the pipe under the condition of 1mm amplitude. Figure 8 , Fig. 9 It can be seen that the erosion corrosion distribution in the pipe changes from uniform distribution on the outside of the elbow in static state to concentrated distribution on the downstream of the elbow in vibration state, which means that vibration not only significantly changes the distribution of erosion corrosion on the pipe wall, but also affects the erosion rate. Fig. 9 It can be seen that the maximum erosion corrosion rate (455.33 μg·h -1 cm -2 ) is when there is no vibration (189.1μg·h -1 cm -2 ), the serious erosion and corrosion parts of the vibrating pipeline are still the parts with severe particle erosion and wear. Although the increase of turbulence intensity in the vibrating pipe can lead to the improvement of near-wall corrosion mass transfer efficiency, the main reason for the significant increase in the maximum erosion and corrosion rate is the erosion-enhanced corrosion effect.

[0045] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principles of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for coupling erosion-corrosion analysis of solid-liquid two-phase flow in a submarine vibrating elbow, characterized in that: The method comprises the following steps: S1, construct a two-dimensional curved pipeline model, consider the influence of internal flow and external seawater pressure as well as pipeline displacement deformation on the flow in the pipe, conduct modal analysis of the liquid-filled pipeline, set pipeline vibration operating parameters according to the modal analysis results, and establish a three-dimensional fine model of the local curved pipe section; S2, using the mass transfer equation and solubility equation, construct a simulation model of flow-accelerated corrosion in pipes and calculate the flow-accelerated corrosion rate inside the elbow; S3, introduce the E / CRC particle erosion wear model to calculate the erosion wear rate of particles on the pipe wall; S4, based on the electrochemical corrosion secondary current model, the erosion-corrosion coupling model is constructed to simulate the erosion-corrosion process of solid-liquid two-phase flow in the vibrating pipeline and obtain the erosion-corrosion coupling response law in the vibrating elbow.

2. The method for coupling erosion-corrosion analysis of solid-liquid two-phase flow in a submarine vibrating elbow according to claim 1 is characterized in that: In step S1, the pipeline vibration condition parameters are set according to the modal analysis results, and a three-dimensional fine model of the local elbow section is established, including: expressing the pipeline vibration condition in the form of simple harmonic vibration, and establishing the periodic vibration displacement of the three-dimensional fine model of the local elbow section, the expression is: ； In the formula, is the vibration displacement, is the amplitude, is the angular frequency, For time, is the initial phase angle.

3. The method for coupling erosion-corrosion analysis of solid-liquid two-phase flow in a submarine vibrating elbow according to claim 1 is characterized in that: In step S2, a flow-accelerated corrosion simulation model is constructed using the mass transfer equation and the solubility equation to calculate the flow-accelerated corrosion rate inside the elbow, including: using flow-accelerated corrosion FAC to calculate the flow-accelerated corrosion rate at different flow rates and temperatures, and analyzing the relationship between the fluid flow wall shear stress and the corrosion rate.

4. The method for coupling erosion-corrosion analysis of solid-liquid two-phase flow in a submarine vibrating elbow according to claim 3 is characterized in that: Calculate the flow accelerated corrosion rate in pipes at different flow rates and temperatures, including: (1) Electrochemical dissolution of the matrix iron, formation of oxide film, and dissolution of the oxide film under flow state; (2) Comprehensively considering the influence of the above processes, the above processes occur near the wall of the pipeline under the flow state, and the flow accelerated corrosion rate in the pipe at different flow rates and temperatures is calculated. The FAC corrosion rate is expressed as: ； In the formula, The flow accelerates the corrosion rate. is the solubility of the soluble iron-containing component, is the mass transfer coefficient, is the porosity of the oxide layer, is the diffusion coefficient; is the oxide layer thickness.

5. The method for coupling erosion-corrosion analysis of solid-liquid two-phase flow in a submarine vibrating elbow according to claim 4 is characterized in that: In step (1), the electrochemical dissolution of the matrix iron includes: the iron metal matrix in the flowing corrosive medium corrodes on the contact surface with the fluid, and the iron element reacts to generate ferrous ions. The FAC rate during the electrochemical dissolution of the matrix iron is expressed as: ； In the formula, is the reaction rate constant, is the concentration of soluble iron-containing components at the interface between the material surface and the solution; Solubility of soluble iron-containing components The expression is: ； In the formula, is the solubility product, The number of anions generated for a single electrolyte molecule, The number of cations generated for a single electrolyte molecule; The solubility is calculated based on the solubility product of the FeCO3 component of the oxide film. The solubility product of the iron-containing component is expressed as: ； In the formula, is the absolute temperature, is the ionic strength.

6. The method for coupling erosion-corrosion analysis of solid-liquid two-phase flow in a submarine vibrating elbow according to claim 5 is characterized in that: In step (1), the oxide film is generated, including: a part of the generated iron ions reacts to form an oxide film covering the surface of the substrate, and the other part diffuses into the mainstream area of ​​the fluid flow. The FAC rate of the oxide film generation process is expressed as: ； In the formula, is the concentration of soluble iron-containing components at the interface between the oxide layer surface and the solution, is the ratio of the iron ions involved in the formation of the oxide layer to the total iron ions produced by the matrix; is the diffusion coefficient of the iron-containing component involved in the reaction.

7. The method for coupling erosion-corrosion analysis of solid-liquid two-phase flow in a submarine vibrating elbow according to claim 6 is characterized in that: The oxide film dissolution under the flow state includes: the oxide film on the substrate surface is dissolved and diffused to the mainstream area under the influence of the flow, and is taken away from the reaction area with the flow. The FAC rate of the oxide film dissolution process under the flow state is expressed as follows: ； In the formula, is the concentration of iron-containing components in the main flow area of ​​the solution; Mass transfer coefficient The expression is: ； In the formula, is the Reynolds number; is the characteristic length; is the speed coefficient, , is the fluid wall friction velocity, is the average velocity of the fluid; is a constant coefficient determined experimentally, is the Schmidt number; Diffusion coefficient The expression is: ； In the formula, is the Boltzmann constant, is the dynamic viscosity of the fluid in the tube, is the radius of the ion involved in diffusion in the solution.

8. The method for coupling erosion-corrosion analysis of solid-liquid two-phase flow in a submarine vibrating elbow according to claim 4 is characterized in that: In step S3, the expression of the E / CRC particle erosion wear model is: ； ； In the formula, is the erosion model coefficient, is the particle shape factor, is the Brinell hardness of the wall material, is the speed index; is the magnitude of the incident particle velocity; is the particle incident angle; is the particle incident angle function, which is used to characterize the effect of erosion angle on material wear rate.

9. The method for coupling erosion-corrosion analysis of solid-liquid two-phase flow in a submarine vibrating elbow according to claim 1 is characterized in that: In step S4, an erosion-corrosion coupling model is constructed based on the electrochemical corrosion secondary current model to simulate the erosion-corrosion process of solid-liquid two-phase flow in the vibrating pipeline, including: Under the combined action of erosion and electrochemical corrosion in liquid-solid two-phase flow, the specific expression of the total mass loss caused by material erosion corrosion is: ； In the formula, is the total mass loss due to erosion and corrosion, is the mass loss caused by pure erosion wear, is the mass loss caused by pure corrosion, The effect of particle erosion and wear on the electrochemical corrosion of materials; Under the conditions of liquid-solid two-phase flow erosion corrosion, the quantitative expression of erosion-promoted corrosion is: ； In the formula, is the erosion damage effect of the oxide film, The increase in surface corrosion area caused by erosion pits leads to an increase in corrosion activity; is the proportion of anode current density affected by particle impact; are the anode current density under erosion and unaffected conditions, respectively; is the surface area of ​​the affected area before the pit is created, It is the increased corrosion area on the material surface before and after erosion wear.

10. A coupled analysis system for erosion and corrosion of solid-liquid two-phase flow in a submarine vibrating elbow, characterized in that: The system implements the method for coupling analysis of solid-liquid two-phase flow erosion and corrosion of a submarine vibrating elbow as claimed in any one of claims 1 to 9, and the system comprises: A local bend section three-dimensional fine model building module (1) is used to build a two-dimensional bend pipeline model, consider the influence of internal flow and external seawater pressure and pipeline displacement deformation on the flow in the pipe, perform modal analysis of the liquid-filled pipeline, set pipeline vibration operating parameters according to the modal analysis results, and build a local bend section three-dimensional fine model; The corrosion rate calculation module (2) is used to construct a simulation model of flow-accelerated corrosion in the pipe by using the mass transfer equation and the solubility equation, and calculate the flow-accelerated corrosion rate in the elbow; An erosion wear rate calculation module (3) is used to introduce the E / CRC particle erosion wear model to calculate the erosion wear rate of particles on the pipe wall; The erosion-corrosion coupling model building module (4) is used to build an erosion-corrosion coupling model based on the electrochemical corrosion secondary current model, simulate the erosion-corrosion process of solid-liquid two-phase flow in the vibrating pipeline, and obtain the erosion-corrosion coupling response law in the vibrating elbow.

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