A simulation method for erosion profile evolution of solid particles in a turbulent field

Abstract

The application belongs to the field of computer simulation, and discloses a simulation method for erosion and wear profile evolution of solid particles in a turbulent field, which adopts finite element analysis technology to simulate the evolution process of the wall surface of a hydraulic element caused by the erosion and wear of solid particles in a turbulent field; the method comprises the following steps: 1) determining the initial boundary conditions of the flow field and the initial state of particles at the inlet; 2) solving the flow velocity, pressure, Reynolds stress and other parameters at each point in the turbulent flow field; 3) solving the random motion trajectory of a large number of solid particles in the turbulent flow field; 4) counting the collision information between the particles and the wall surface of the flow field, solving the material removal rate of the impacted wall surface, and solving the shape of the impacted wall surface within a given time; 5) according to the calculation results, updating the boundary of the flow field, repeating steps 2) to 4), until the desired total simulation time or the final wear profile is reached. Compared with the prior art, the application has the advantage of accurate calculation results.

Description

A simulation method for the evolution of solid particle erosion wear profile in turbulent flow fields Technical Field

[0001] This invention belongs to the field of physics simulation and relates to a simulation method for the evolution of erosion wear, specifically a simulation method for the evolution of the erosion wear profile of solid particles in a turbulent flow field. Background Technology

[0002] Research on solid particle erosion wear can be traced back to 1876. During the construction of the Brooklyn Bridge, Roebling used granite slabs instead of metal plates as reflectors, improving the service life of the sand-collecting equipment (McCullough D. The Great Bridge: The Epic Story of the Building of the Brooklyn Bridge [M]. Simon and Schuster, 2012). Based on engineering practice, Wahl proposed that particle impact velocity and impact angle are key factors affecting erosion wear (Wahl H, Hartstein FO C. Strahlverschleiß:zusammenfassende Darstellung heutiger Erkenntnisse und praktischerAbwehrmethoden [M]. Franckh, 1946).By the mid-20th century, with the development of erosion wear theory and turbulent particle diffusion models, erosion prediction of hydraulic and pneumatic components became possible. This led to the development of predictions for turbine blades (Hamed AA, Tabakoff W, Rivir RB, et al. Turbine blade surface deterioration by erosion[J]. Journal of turbomachinery, 2005, 127(3): 445-452), pump bodies (Zhong Y, Minemura K. Measurement of erosion due to particle impingement and numerical prediction of wear in pump casing[J]. wear, 1996, 199(1): 36-44.), pipes (Njobuenwu DO, Fairweather M. Modelling of pipe bend erosion by diluteparticle suspensions[J]. Computers&Chemical Engineering, 2012, 42: 235-247.), and valves (Zhang K, Yao J, Jiang T. Degradation assessment and life prediction of This paper discusses the theoretical study of erosion wear in electro-hydraulic servo valves under erosion wear [J]. Engineering failure analysis, 2014, 36: 284-300. Most studies focus on determining the wear location and predicting the initial wear removal rate, proposing improvement measures based on the calculation results; however, they neglect the calculation of the wear profile evolution process, failing to assess the evolution of component structure and performance during erosion wear.

[0003] In existing studies on erosion wear, the calculation of particle trajectory and erosion wear rate usually relies on commercial computational fluid dynamics software. Due to the lag in software development and considerations for improving computational efficiency, many mainstream computational fluid dynamics software do not consider some complex and critical models. For example, in FLUENT's solid particle and wall collision model, the squeeze film effect is not considered. The squeeze film is a liquid film that has a buffering effect on approaching particles. Clark quantitatively analyzed the influence of the squeeze film in the liquid medium on the erosion of solid particles. If the squeeze film effect is not considered, the theoretical model results are significantly different from the experimental erosion wear rate, especially for the erosion of small particles (Clark HM I. The influence of the squeeze film in slurry erosion[J]. Wear, 256.9 (2004) 918-926.). Furthermore, the temporal and spatial correlation of turbulent eddies is crucial for calculating particle trajectories (Balachandar S, Eaton J K. Turbulent dispersed multiphase flow[J]. Annual review of fluid mechanics,2010, 42: 111-133.), which is also not explicitly stated in FLUENT. Summary of the Invention

[0004] To address the aforementioned issues, this invention provides a simulation method for the evolution of solid particle erosion wear profiles in turbulent flow fields. This method is primarily used for erosion prediction of hydraulic and pneumatic components. It provides numerical calculation models for particle trajectories and erosion wear rates, taking into account factors such as the aforementioned squeeze film effect and the temporal and spatial correlation of turbulent eddies.

[0005] The technical solution of the present invention is as follows:

[0006] A simulation method for the evolution of solid particle erosion wear profiles in a turbulent flow field includes the following steps:

[0007] Step 1: Determine the initial boundary conditions of the flow field and the initial state of the particles at the inlet;

[0008] Step 2: Solve for the velocity and pressure parameters at each point in the turbulent flow field;

[0009] Step 3: Solve for the random trajectories of a large number of solid particles in the turbulent flow field;

[0010] Step 4: Collect data on the collision between particles and the flow field wall, calculate the material removal rate of the impacted wall, and calculate the shape of the impacted wall within a given time period.

[0011] Step 5: Based on the calculation results, update the flow field boundary and repeat steps 2 to 4 until the desired total simulation time or final wear profile is achieved.

[0012] Further, step one specifically involves placing a certain number of particles at the inlet of the flow field, and using the actual measured pressure and flow velocity at the inlet and outlet of the flow field as boundary conditions.

[0013] Furthermore, step two also includes solving the effect of random velocity fluctuations of the fluid on solid particles in the flow field. Specifically, the Reynolds stress model is used to solve the turbulent flow field to obtain the anisotropic distribution law of velocity fluctuations in space.

[0014] Furthermore, based on the assumption that the spatial distribution of Reynolds stress is anisotropic, a Reynolds stress model is adopted, and commercial CFD software is used to solve the flow field. The flow field data obtained by the CFD software is then substituted into a self-developed numerical calculation program for later use. The flow data includes flow field pressure, average velocity in three spatial directions, six Reynolds stresses, turbulent kinetic energy k value, and turbulent kinetic energy dissipation rate ε value.

[0015] Furthermore, in step three, Newton's laws of motion are used to calculate the random trajectories of a large number of solid particles in the turbulent field. The solution for the solid particle trajectories is divided into discrete time steps. The particle motion state at a certain time t can be obtained from the previous time step. The motion state is obtained.

[0016] Furthermore, the discrete time step Δt is taken as the minimum value of the Kolmogorov characteristic length of the turbulent eddy and the velocity gradient distribution length, i.e.

[0017]

[0018] in, The Kolmogorov characteristic length of the turbulent eddy; The Kolmogorov characteristic time corresponds to the duration of the turbulent eddy. Let be the fluid velocity vector at the location of the particle. For particle velocity vectors, The maximum feature length is set to limit the maximum distance a particle can travel within a time step.

[0019] Furthermore, in step four, considering the squeezing oil film effect, the actual normal velocity of the particles impacting the wall surface... The normal velocity of particles impacting the wall when the squeezing oil film effect is not considered. The ratio, i.e., the squeeze film factor Represented as

[0020]

[0021]

[0022] in, Density of solid particles; For fluid density; μ is a constant; μ is the fluid viscosity. It is a constant. The diameter is the solid particle diameter.

[0023] Furthermore, in step five, the wear profile is updated by transforming the profile of the eroded surface into several straight lines of equal length joined end to end, with the length denoted as . ,but Erosion wear amount corresponding to each straight line segment within a time period for:

[0024]

[0025] The depth h of the endpoint movement is represented as:

[0026]

[0027] in, m is the target density; The number of solid particles impacting the straight segment within a given time period; Let D be the amount of material removed by the i-th particle impacting the wall, and D be the diameter of the sliding valve. Then, move the endpoints of each straight line segment at the same end into the wall along the vertical direction to form new nodes, and connect the new nodes with straight line segments to form a new profile.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] 1. A simulation method for the evolution of solid particle erosion wear profile in turbulent flow field is proposed, which can obtain the wear profile of the flow field boundary after a certain time.

[0030] 2. By using the Reynolds stress model (RSM) to solve the turbulent flow field, the anisotropic distribution of velocity fluctuations in space can be obtained, thus obtaining a flow field velocity fluctuation situation that is more consistent with the time situation.

[0031] 3. Since the calculation method based on the Kolmogorov characteristic length of turbulent eddies is only applicable to high Reynolds number or large-size flow fields, the time step of particle trajectory solving in this patent does not use the Kolmogorov characteristic length of turbulent eddies, but is based on the flow field velocity gradient as small as possible; thus avoiding large errors or even mistakes in small-size low Reynolds number flow fields (upstream flow fields).

[0032] 4. In liquid media, when solid particles impact the material surface, due to the inertia and viscosity of the liquid, a high-pressure liquid film is formed between two close surfaces, which hinders the movement of the particles and changes the speed and angle of the particles impacting the wall. This patent takes into account the squeezing oil film effect when solid particles collide with the flow field wall, which improves the accuracy of calculating information such as the speed and angle of small-sized particles impacting the wall. Attached Figure Description

[0033] To more clearly illustrate the technical solutions of the embodiments of this invention, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0034] Figure 1 is a flowchart of a simulation method for the evolution of solid particle erosion wear profile in a turbulent flow field according to the present invention.

[0035] Figure 2 is a schematic diagram of the principle of the erosion wear profile update method of the present invention. Detailed Implementation

[0036] This section describes embodiments of the present invention, used to explain and illustrate the technical solutions of the present invention. Unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0037] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating directions or positional relationships, are given in the accompanying drawings and are used only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or device referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include more than one of those features. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0038] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integrated connection; they can refer to a mechanical connection or a point connection; they can refer to a direct connection or a connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0039] A simulation method for the evolution of solid particle erosion wear profiles in a turbulent flow field includes the following steps:

[0040] Step 1: Determine the initial boundary conditions of the flow field and the initial state of the particles at the inlet;

[0041] Step 2: Solve for the velocity and pressure parameters at each point in the turbulent flow field;

[0042] Step 3: Solve for the random trajectories of a large number of solid particles in the turbulent flow field;

[0043] Step 4: Collect data on the collision between particles and the flow field wall, calculate the material removal rate of the impacted wall, and calculate the shape of the impacted wall within a given time period.

[0044] Step 5: Based on the calculation results, update the flow field boundary and repeat steps 2 to 4 until the desired total simulation time or final wear profile is achieved.

[0045] Step one specifically involves placing a certain number of particles at the inlet of the flow field, and using the actual measured pressure and flow velocity at the inlet and outlet of the flow field as boundary conditions.

[0046] Step two also includes solving the effect of random velocity fluctuations of the fluid on solid particles in the flow field. Specifically, the Reynolds stress model is used to solve the turbulent flow field to obtain the anisotropic distribution law of velocity fluctuations in space.

[0047] Based on the assumption that the spatial distribution of Reynolds stress is anisotropic, a Reynolds stress model is adopted, and commercial CFD software is used to solve the flow field. The flow field data obtained by the CFD software is then substituted into a self-developed numerical calculation program for later use. The flow data includes flow field pressure, average velocity in three spatial directions, six Reynolds stresses, turbulent kinetic energy k value, and turbulent kinetic energy dissipation rate ε value.

[0048] In step three, Newton's laws of motion are used to calculate the random trajectories of a large number of solid particles in the turbulent field. The solution for the solid particle trajectories is divided into discrete time steps. The particle motion state at a certain time t can be obtained from the previous time step. The motion state is obtained.

[0049] The discrete time step Δt is taken as the minimum value of the Kolmogorov characteristic length of the turbulent eddy and the length of the velocity gradient distribution, i.e.

[0050]

[0051] in, The Kolmogorov characteristic length of the turbulent eddy; The Kolmogorov characteristic time corresponds to the duration of the turbulent eddy. Let be the fluid velocity vector at the location of the particle. For particle velocity vectors, The maximum feature length is set to limit the maximum distance a particle can travel within a time step.

[0052] In step four, considering the squeezing oil film effect, the actual normal velocity of the particles impacting the wall is... The normal velocity of particles impacting the wall when the squeezing oil film effect is not considered. The ratio, i.e., the squeeze film factor Represented as

[0053]

[0054]

[0055] in, Density of solid particles; For fluid density; μ is a constant; μ is the fluid viscosity. It is a constant. The diameter is the solid particle diameter.

[0056] In step five, the wear profile is updated by transforming the profile of the eroded surface into several straight lines of equal length joined end to end, with the length denoted as . ,but Erosion wear amount corresponding to each straight line segment within a time period for:

[0057]

[0058] The depth h of the endpoint movement is represented as:

[0059]

[0060] in, m is the target density; The number of solid particles impacting the straight segment within a given time period; Let D be the amount of material removed by the i-th particle impacting the wall, and D be the diameter of the sliding valve. Then, move the endpoints of each straight line segment at the same end into the wall along the vertical direction to form new nodes, and connect the new nodes with straight line segments to form a new profile.

[0061] The following is another embodiment of the present invention.

[0062] A simulation method for the evolution of solid particle erosion wear profile in a turbulent field, employing finite element analysis technology, simulates the wall evolution process of hydraulic components caused by solid particle erosion wear in a turbulent field, characterized by the following steps:

[0063] 1) Determine the initial boundary conditions of the flow field and the initial state of the particles at the inlet;

[0064] 2) Solve for parameters such as velocity, pressure, and Reynolds stress at various points in the turbulent flow field;

[0065] 3) Solve for the random trajectories of a large number of solid particles in a turbulent flow field;

[0066] 4) Collect statistics on the collision information between particles and the flow field wall, solve for the material removal rate of the impacted wall, and solve for the shape of the impacted wall within a given time.

[0067] 5) Based on the calculation results, update the flow field boundary and repeat steps 2)-4) until the desired total simulation time or final wear profile is reached.

[0068] The flow field is a turbulent flow field, and the influence of random velocity fluctuations of the fluid on solid particles in the flow field cannot be ignored.

[0069] Used to obtain the anisotropic distribution pattern of velocity fluctuations in space.

[0070] The time discretization method is used to solve the motion trajectory of solid particles in the flow field.

[0071] The time step for solving the particle trajectory should not be the Kolmogorov characteristic length of the turbulent eddy, but should be as small as possible based on the velocity gradient of the flow field. This is because the calculation method based on the Kolmogorov characteristic length of the turbulent eddy is only applicable to high Reynolds number or large-size flow fields, while it has large errors or even mistakes when used for small-size low Reynolds number flow fields (upstream flow fields).

[0072] It is necessary to consider the autocorrelation of the evolution of turbulent eddies over time and the spatial correlation between turbulent eddies. This is because the motion of solid particles may be affected by the same turbulent eddy in several consecutive time steps. The current state of the turbulent eddy is affected by the state of the previous time step, which leads to the evolution of the velocity fluctuation value corresponding to a specific turbulent eddy having temporal inheritance. Moreover, solid particles will pass through different turbulent eddies during their motion. Classical experimental results show that the velocity fluctuations generated by turbulent eddies are spatially correlated.

[0073] When solid particles collide with the flow field wall, the squeezing oil film effect should be considered. This is because, in a liquid medium, when solid particles impact the material surface, due to the inertia and viscosity of the liquid, a high-pressure liquid film is formed between two closely spaced surfaces, which hinders the movement of the particles and changes the velocity and angle of the particles impacting the wall. This squeezing film effect has a more significant impact on the movement of small-sized particles.

[0074] Based on the impact angle, velocity, and impact probability of solid particles, the material removal rate of the eroded surface can be calculated using the Forder erosion wear model.

[0075] When calculating the material removal rate, secondary erosion caused by the breakage of solid particles during impact should be taken into account.

[0076] This invention provides a simulation method for the evolution of solid particle erosion wear profiles in a turbulent flow field, as shown in Figure 1, including the following steps:

[0077] 1) Determine the initial boundary conditions of the flow field and the initial state of the particles at the inlet. Place a certain number of particles at the inlet of the flow field; define the boundary conditions such as pressure and velocity at the inlet and outlet of the flow field.

[0078] 2) Solve for parameters such as velocity, pressure, and Reynolds stress at various points in the turbulent flow field. Based on the assumption that the spatial distribution of Reynolds stress (velocity fluctuations) is anisotropic, the Reynolds stress model (RSM) is adopted, and the flow field is solved using commercial CFD software. The flow field data obtained by the CFD software (including flow field pressure, average velocity in three directions, six Reynolds stresses, turbulent kinetic energy k value, and turbulent kinetic energy dissipation rate ε value) are then substituted into a self-developed numerical calculation program for later use.

[0079] 3) Solve for the random trajectories of a large number of solid particles in a turbulent flow field. The motion of the particles in the flow field obeys Newton's laws of motion, and...

[0080] (1)

[0081] in, Mass of solid particles; Particle velocity; For steady-state drag force; Forces related to gravitational acceleration include the weight of solid particles and the buoyancy they experience; For pressure gradient force; For lift; This is to add mass force.

[0082] The solution to the trajectory of solid particles is divided into discrete time steps; the particle's motion state at a certain time t can be obtained from the previous time step. The motion state is obtained, and we have

[0083] (2)

[0084] (3)

[0085] in, For solid particles in The acceleration at time step. The discrete time step is taken as the minimum of the Kolmogorov characteristic length of the turbulent eddy and the length of the velocity gradient distribution, which gives us...

[0086] (4)

[0087] Based on the Frenkieel function (Berlemont A, Desjonqueres P, Gouesbet G. Particle Lagrangian simulation in turbulent flows[J]. International Journal of Multiphase Flow, 1990, 16(1): 19-34), the autocorrelation of turbulent eddies is considered.

[0088] 4) Collect statistical information on the collisions between particles and the flow field wall, calculate the material removal rate of the impacted wall, and determine the shape of the impacted wall within a given time interval. Consider the squeezing oil film effect and the actual normal velocity of the particles impacting the wall. The normal velocity of particles impacting the wall when the squeezing oil film effect is not considered. The ratio (i.e., the squeeze film factor F) is expressed as

[0089] (5)

[0090] (6)

[0091] Based on the erosion wear model summarized by Order (Forder A, Thew M, Harrison D. Anumerical investigation of solid particle erosion experienced within oilfield control valves[J]. Wear, 1998, 216(2): 184-193.), the erosion wear rate W was calculated.

[0092] As shown in Figure 2, the contour of the eroded surface is transformed into several straight line segments of equal length connected end to end. The erosion wear volume corresponding to each straight line segment within a time period is

[0093] (7)

[0094] Where m is The number of solid particles impacting the straight segment within a given time period; Let h be the mass of material removed due to the impact of the i-th particle on the wall. Then, move the endpoints of each straight line segment at the same end into the wall along the vertical direction to form new nodes. Connect the new nodes with straight line segments to form a new profile; the depth h of the endpoint movement is denoted as h.

[0095] (8)

[0096] In the formula, D is the diameter of the slide valve.

[0097] 5) Based on the calculation results, update the flow field boundary and repeat steps 2)-4) until the desired total simulation time or final wear profile is reached.

Claims

1. A simulation method for the evolution of solid particle erosion wear profiles in a turbulent flow field, characterized in that, Includes the following steps: Step 1: Determine the initial boundary conditions of the flow field and the initial state of the particles at the inlet. Step 2: Solve for the velocity and pressure parameters at various points in the turbulent flow field. Step 3: Solve for the random trajectories of a large number of solid particles in the turbulent flow field. Step 4: Statistically analyze the collision information between particles and the flow field wall, solve for the material removal rate of the impacted wall, and determine the shape of the impacted wall within a given time. Step 5: Update the flow field boundary based on the calculation results, and repeat steps 2 to 4 until the desired total simulation time or final wear profile is reached. In step 4, the squeezing oil film effect is considered, and the normal velocity of the particles actually impacting the wall is... The normal velocity of particles impacting the wall when the squeezing oil film effect is not considered. The ratio, i.e., the squeeze film factor Represented as in, Density of solid particles; For fluid density; μ is a constant; μ is the fluid viscosity. It is a constant. The diameter of the solid particles is given. In step five, the wear profile is updated, transforming the profile of the eroded surface into several straight segments of equal length joined end-to-end, with the length denoted as . ,but Erosion wear amount corresponding to each straight line segment within a time period for: The depth h of the endpoint movement is represented as: in, m is the target density; The number of solid particles impacting the straight segment within a given time period; Let D be the amount of material removed by the i-th particle impacting the wall, and D be the diameter of the sliding valve. Then, move the endpoints of each straight line segment at the same end into the wall along the vertical direction to form new nodes, and connect the new nodes with straight line segments to form a new profile.

2. The simulation method for the evolution of solid particle erosion wear profile in a turbulent field according to claim 1, characterized in that, Step one specifically involves placing a certain number of particles at the inlet of the flow field, and using the actual measured pressure and flow velocity at the inlet and outlet of the flow field as boundary conditions.

3. The simulation method for the evolution of solid particle erosion wear profile in a turbulent field according to claim 1, characterized in that, Step two also includes solving the effect of random velocity fluctuations of the fluid on solid particles in the flow field. Specifically, the Reynolds stress model is used to solve the turbulent flow field to obtain the anisotropic distribution law of velocity fluctuations in space.

4. The simulation method for the evolution of solid particle erosion wear profile in a turbulent field according to claim 3, characterized in that, Based on the assumption that the spatial distribution of Reynolds stress is anisotropic, a Reynolds stress model is adopted, and commercial CFD software is used to solve the flow field. The flow field data obtained by the CFD software is then substituted into a self-developed numerical calculation program for later use. The flow data includes flow field pressure, average velocity in three spatial directions, six Reynolds stresses, turbulent kinetic energy k value, and turbulent kinetic energy dissipation rate ε value.

5. The simulation method for the evolution of solid particle erosion wear profile in a turbulent field according to claim 1, characterized in that, In step three, Newton's laws of motion are used to calculate the random trajectories of a large number of solid particles in the turbulent field. The solution for the solid particle trajectories is divided into discrete time steps, where the particle motion state at a certain time t is passed through the previous time step. The motion state is obtained.

6. The simulation method for the evolution of solid particle erosion wear profile in a turbulent field according to claim 5, characterized in that, The discrete time step Δt is taken as the minimum value of the Kolmogorov characteristic length of the turbulent eddy and the length of the velocity gradient distribution, i.e. in, The Kolmogorov characteristic length of the turbulent eddy; The Kolmogorov characteristic time corresponds to the duration of the turbulent eddy. Let be the fluid velocity vector at the location of the particle. For particle velocity vectors, The maximum feature length is set to limit the maximum distance a particle can travel within a time step.

Images