Method for simulating transient vibration characteristics of umbrella skirt of composite insulator under strong wind

Abstract

The invention provides a composite insulator umbrella skirt vibration transient characteristic simulation method under strong wind, and relates to the technical field of high-voltage power transmission and transformation engineering, and the method comprises the steps: calculating the flow field distribution around a composite insulator and the stress distribution on the surface of an umbrella skirt in a strong wind region through employing a bidirectional fluid-solid coupling (FSI) method, and obtaining the transient vibration characteristic of the umbrella skirt of the composite insulator. By introducing the shear strain correction factor, the accuracy of the free shear flow of the fluid-solid boundary layer in the bidirectional fluid-solid coupling algorithm is improved, the service life of the composite insulator in the strong wind area is measured and calculated in combination with the stress-life curve of the composite insulator silicone rubber material, and a reliable theoretical basis is provided for actual engineering design.

Description

Technical Field

[0001] The invention relates to the technical field of high-voltage power transmission and transformation engineering, and in particular to a method for simulating the vibration transient characteristics of composite insulator sheds under strong winds. Background Art

[0002] The special natural conditions in the strong typhoon areas of the southeast coast and the sandy areas of the northwest region have put forward higher requirements for the safe operation of power transmission equipment. Operation experience shows that in strong wind weather, high-speed airflow will not only cause dynamic vibration to the composite insulator, but also may cause damage such as tearing of the shed structure, thereby significantly reducing its mechanical properties and insulation capacity. The damage of the shed will further lead to pollution accumulation, increase the risk of flashover, and threaten the safe and stable operation of the power system. Therefore, it is of great theoretical significance and engineering value to study the vibration and tearing mechanism of the composite insulator shed in a strong wind environment.

[0003] At present, the dynamic performance research of composite insulator sheds is mainly carried out through wind tunnel tests and static loading analysis. Although these methods reveal the mechanical properties of sheds to a certain extent, they have the following shortcomings: First, wind tunnel tests require the construction of complex experimental equipment, which has a long test cycle and high economic cost; second, the transient aerodynamic loads under actual strong wind conditions are relatively complex, and traditional static analysis is difficult to accurately simulate the actual vibration characteristics; third, the existing methods generally fail to combine the nonlinear characteristics of shed materials, and it is difficult to reflect the dynamic evolution process of shed tearing. Summary of the invention

[0004] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a method for simulating the transient characteristics of vibration of composite insulator sheds under strong winds, aiming to reduce expensive and time-consuming experiments, and quickly calculate the transient vibration characteristics of insulator sheds under different wind speed conditions through an independently designed efficient simulation program, and combine the stress-life curve of the silicone rubber material of the composite insulator to calculate the service life of the composite insulator in strong wind areas, so as to provide a reliable theoretical basis for practical engineering design.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A method for simulating the transient characteristics of composite insulator shed vibration under strong winds, comprising:

[0007] Based on the 3D modeling software, a 3D geometric model of the composite insulator is established according to the shed structure and size parameters of the composite insulator in actual operation, and the 3D geometric model is imported into the fluid simulation software and the calculation network is segmented;

[0008] Setting boundary conditions and initialization in fluid simulation software, and using an improved turbulence model by introducing a shear strain correction factor; the shear strain correction factor is used to adjust the imbalance phenomenon of turbulence generation and dissipation;

[0009] The dynamic grid technology is introduced to define the UDF function of composite insulator shed vibration and simulate the reciprocating vibration process of the shed in a strong wind environment.

[0010] The dynamic wind field simulation is carried out using the two-way fluid-solid coupling method to simulate the vibration response and aerodynamic load distribution of the shed under strong wind. The obtained dynamic pressure on the shed surface is used as the load condition and imported into the structural analysis module for transient stress solution to analyze the stress distribution, vibration deformation and stress state of key parts of the shed material in different time steps.

[0011] Combining the nonlinear characteristics of the shed material and the fracture mechanics model, the dynamic evolution of the stress aging process of the silicone rubber material of the shed is simulated. By analyzing the stress concentration area of ​​the shed under strong wind, the starting position and expansion path of the tearing are predicted, and the dynamic vibration characteristics and stress distribution cloud map of the shed are output.

[0012] Preferably, the computing network includes a composite insulator solid region, an air fluid region, and a fluid-solid interface region.

[0013] Preferably, setting boundary conditions and initializing in the fluid simulation software includes:

[0014] The fluid domain inlet is set as the velocity inlet boundary condition, the outlet is set as the pressure outlet boundary condition, the wall is set as the no-slip boundary condition, and the wall function is used to deal with the flow near the wall; when the flow field is initialized, the initial inlet velocity and turbulent kinetic energy are set at the flow field inlet as the benchmark.

[0015] Preferably, the control equation of the improved turbulence model is:

[0016]

[0017] G ω * =β shear ·G ω

[0018] Where k represents the turbulent kinetic energy, which represents the time-averaged change in turbulent velocity per unit mass of fluid. ω represents the turbulent frequency, which represents the dissipation rate of turbulent kinetic energy. ρ represents the fluid density, u represents the velocity vector of the fluid, and x represents the velocity of the fluid. i Indicates the specific coordinate direction (for a three-dimensional model, it is one of the x, y, and z directions in the rectangular coordinate system), G k represents the amount of turbulent kinetic energy generated due to the mean velocity gradient, Gω represents the amount of turbulence frequency ω, Γ k and Γ ω represent the effective diffusion rates of k and ω, respectively, and Y k and Y ω represents the dissipation of k and ω due to turbulence, β shear is the shear strain correction factor.

[0019] Preferably, the dynamic mesh technology is used to transfer the deformation of the insulator shed to the improved turbulence model in real time after each iterative solution, so as to re-perform mesh division at the fluid-solid boundary.

[0020] Preferably, the bidirectional fluid-solid coupling calculation method used is:

[0021] When the improved turbulence model reaches convergence each time it is calculated, the stress data of the fluid-solid interface is transferred to the transient structure module for solution using the coupling component to obtain the incremental displacement of the solid area. The incremental displacement is then transferred back to the improved turbulence model through the coupling component to change the original flow field distribution.

[0022] Preferably, the stress-fatigue curve of the silicone rubber material used in the fracture mechanics model is obtained from a preset experiment to reflect the fatigue law of the shed material under the application of long-term wind load.

[0023] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0024] 1. The present invention provides a method for simulating the transient characteristics of vibration of composite insulator sheds under strong winds. The calculation model improves the original fluid model. For the bidirectional fluid-solid coupling calculation method adopted in the present invention, a shear strain rate correction factor is introduced to improve the numerical simulation accuracy of the flow field and the solid interface near the wall.

[0025] 2. The bidirectional fluid-solid coupling calculation method adopted in the present invention can obtain the real-time shed stress distribution and transient vibration characteristics of the composite insulator shed under strong wind disturbance, which truly reflects the wind-induced vibration characteristics of the composite insulator shed under actual working conditions.

[0026] 3. The present invention fully considers the nonlinear characteristics of the silicone rubber material of the composite insulator shed and reflects the real evolution process of the shed tearing behavior.

[0027] 4. The present invention provides a method for simulating the transient characteristics of vibration of composite insulator sheds under strong winds, which can accurately simulate the vibration response and stress distribution process of the sheds under strong winds, overcomes the problems of long test cycle, insufficient simulation accuracy, and failure to analyze the dynamic deformation of the sheds in traditional methods, and provides an effective solution for the design optimization and engineering application of composite insulators. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0029] Figure 1 A flow chart of a method provided by an embodiment of the present invention;

[0030] Figure 2 A schematic diagram of a technical route provided for an embodiment of the present invention;

[0031] Figure 3 A schematic diagram of a bidirectional fluid-solid coupling simulation calculation method provided by an embodiment of the present invention;

[0032] Figure 4 A three-dimensional model diagram of a composite insulator provided in an embodiment of the present invention;

[0033] Figure 5 A diagram showing deformation results of a composite insulator under simulated wind erosion provided by an embodiment of the present invention;

[0034] Figure 6 A diagram showing stress distribution results of a composite insulator under simulated wind erosion provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] The purpose of the present invention is to provide a method for simulating the transient vibration characteristics of composite insulator sheds under strong winds, aiming to reduce expensive and time-consuming experiments, quickly calculate the transient vibration characteristics of insulator sheds under different wind speed conditions through an independently designed high-efficiency simulation program, and calculate the service life of composite insulators in strong wind areas in combination with the stress-life curve of the silicone rubber material of the composite insulator, so as to provide a reliable theoretical basis for practical engineering design.

[0037] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] Figure 1 A flow chart of a method provided by an embodiment of the present invention, such as Figure 1 As shown, the present invention provides a method for simulating the transient characteristics of composite insulator shed vibration under strong winds, comprising:

[0039] Step 100: Based on the 3D modeling software, a 3D geometric model of the composite insulator is established according to the shed structure and size parameters of the composite insulator in actual operation, and the 3D geometric model is imported into the fluid simulation software and the calculation network is segmented;

[0040] Step 200: setting boundary conditions and initializing in the fluid simulation software, and using the improved turbulence model by introducing a shear strain correction factor; the shear strain correction factor is used to adjust the imbalance phenomenon of turbulence generation and dissipation;

[0041] Step 300: Introduce the dynamic grid technology, define the UDF function of the composite insulator shed vibration, and simulate the reciprocating vibration process of the shed in a strong wind environment;

[0042] Step 400: a dynamic wind field simulation is performed using a bidirectional fluid-solid coupling method to simulate the vibration response and aerodynamic load distribution of the shed under strong wind, and the obtained dynamic pressure on the shed surface is used as a load condition and imported into a structural analysis module to perform transient stress solution, and the stress distribution, vibration deformation and stress state of key parts of the shed material in different time steps are analyzed;

[0043] Step 500: Combining the nonlinear characteristics of the shed material and the fracture mechanics model, the dynamic evolution of the stress aging process of the shed silicone rubber material is simulated, and the starting position and expansion path of the tearing are predicted by analyzing the stress concentration area of ​​the shed under strong wind, and the dynamic vibration characteristics and stress distribution cloud map of the shed are output.

[0044] Specifically, Figure 2 As shown, the specific process of this embodiment is as follows:

[0045] Process 1: Based on the shed structure and size parameters of the composite insulator in actual operation, use 3D modeling software (such as SolidWorks) to build a 3D model of the composite insulator (such as Figure 4 As shown in the figure, the geometric model is imported into the fluid simulation software and the computational network is divided. The geometric model and mesh include the composite insulator solid region, air fluid region, and fluid-solid interface region. A three-dimensional (3D) bidirectional fluid-solid coupling simulation model is established using the finite volume method (FVM). The computational process is as follows: Figure 3 shown.

[0046] Process 2: Define the fluid parameters under strong wind environment in the computational domain, set the inlet wind speed and turbulence model, and simulate the dynamic flow field of air under strong wind. Define the shed material properties as an elastic body model, and set the shed boundary conditions (such as fixed support) and fluid domain outlet conditions. Introduce dynamic wind load to ensure that the simulation model can truly reflect the dynamic airflow and shed surface load characteristics caused by strong wind.

[0047] Process 3: Introduce dynamic grid technology, define the UDF function of composite insulator shed vibration, and simulate the reciprocating vibration process of the shed in a strong wind environment.

[0048] Process 4: Use the two-way fluid-solid coupling method to perform dynamic wind field simulation through FLUENT software to simulate the vibration response and aerodynamic load distribution of the shed under strong wind. The obtained dynamic pressure on the shed surface is used as the load condition and imported into the structural analysis module for transient stress solution to analyze the stress distribution, vibration deformation and stress state of key parts of the shed material in different time steps.

[0049] Process 5: Combine the nonlinear characteristics of the shed material and the fracture mechanics model to simulate the dynamic evolution of the stress aging process of the shed silicone rubber material. By analyzing the stress concentration area of ​​the shed under strong wind, the starting position and expansion path of the tearing are predicted. Figure 5 and Figure 6 As shown in the figure, the dynamic vibration characteristics and stress distribution cloud diagram of the shed are output, providing reference data for the optimization design of the shed in actual engineering applications.

[0050] In the second process, the fluid domain inlet is set as a velocity inlet boundary condition, the outlet is set as a pressure outlet boundary condition, the wall is set as a no-slip boundary condition, and the wall function is used to process the flow near the wall. When the flow field is initialized, the initial inlet velocity and turbulent kinetic energy are set at the flow field inlet as a reference.

[0051] In the second process, the calculation model used by the fluid module is the improved k-ω turbulence model. By introducing the shear strain correction factor, the accuracy of the model in predicting free shear flow is improved. Its control equation is:

[0052]

[0053] G ω * =β shear ·G ω

[0054] In these equations, k represents the turbulent kinetic energy, which represents the time-averaged change in turbulent velocity per unit mass of fluid. ω represents the turbulent frequency, which represents the rate at which turbulent kinetic energy is dissipated. ρ represents the fluid density, u represents the velocity vector of the fluid, and x represents the velocity of the fluid. iIndicates the specific coordinate direction, G k represents the amount of turbulent kinetic energy generated due to the mean velocity gradient, G ω represents the amount of turbulence frequency ω, Γ k and Γ ω represent the effective diffusion rates of k and ω, respectively, and Y k and Y ω represents the dissipation of k and ω due to turbulence. shear It is the shear strain correction factor introduced by the present invention in order to accurately calculate the wind load distribution at the fluid-solid interface.

[0055] In particular, the traditional k-ω turbulence model has large prediction errors in strong shear flow or eddy flow areas because the generation term G in the turbulence frequency control equation ω It is assumed that turbulent dissipation increases linearly with the generation of turbulent kinetic energy, but in reality, the high shear effect causes the dissipation rate to lag behind the generation of turbulent kinetic energy. By introducing a dynamic turbulent kinetic energy dissipation correction term, the numerical simulation accuracy of the flow field and the solid interface near the wall is improved.

[0056] The present invention adds a shear strain rate correction factor β to the traditional turbulent kinetic energy dissipation term. shear , which is used to adjust the dissipation level in the high turbulent kinetic energy region. The modified ω control equation is

[0057] G ω * =β shear *G ω

[0058] β shear =1+C shear *S 2

[0059]

[0060] Where S is the shear strain rate, S ij is the symmetric part of the velocity gradient, C shear is the control parameter.

[0061] When β shear > 1, corresponding to the high shear region, the generated term G ω is appropriately enhanced, and the reaction turbulence is rapidly generated; when β shear →1, corresponding to the low shear region, the generated term remains in its original form and no additional correction is introduced.

[0062] Generally speaking, higher shear strain rates correspond to the fluid-solid boundary layer, turbulent core, or near the fluid separation point because the turbulent kinetic energy generated in these regions is higher.

[0063] Regarding whether the area corresponding to the grid is a high shear area, the present invention independently writes a user-defined function (UserDefined Function). By setting a threshold, the high shear area in the flow field can be automatically marked and identified without explicitly marking the high shear area. By dynamically calculating the correction factor of the S value, precise control of the turbulence generation in different areas of the flow field can be achieved.

[0064] Correction factor β shear The imbalance phenomenon of turbulence generation and dissipation has been adjusted, which can more accurately describe the turbulent behavior in the high shear area, effectively avoid the excessive growth of the turbulence frequency ω, reduce the overestimation of turbulent kinetic energy in the calculation, and significantly improve the accuracy of turbulence frequency and aerodynamic load distribution in the edge area of ​​the umbrella skirt.

[0065] The dynamic mesh technology used in the process three can transfer the deformation of the insulator shed to the fluid module in real time after each iterative solution, and re-divide the mesh at the fluid-solid boundary to make the calculation results more consistent with engineering practice.

[0066] In the process 4, a bidirectional fluid-solid coupling calculation method is used. After each calculation of the fluid module reaches convergence, the coupling component transmits the stress data of the fluid-solid interface to the transient structure module for solution, and obtains the incremental displacement of the solid area. The incremental displacement is then transmitted back to the fluid module through the coupling component to change the original flow field distribution.

[0067] In the process five, the stress-fatigue curve (SN curve) of the silicone rubber material used in the fracture mechanics model is obtained through experiments, which can accurately reflect the fatigue law of the shed material under long-term wind load.

[0068] Specifically, the method for simulating the transient characteristics of composite insulator shed vibration under strong wind provided by the embodiment of the present invention adopts a bidirectional fluid-solid coupling method and performs dynamic wind field simulation through CFD software to simulate the vibration response and aerodynamic load distribution of the shed under strong wind. Combined with the nonlinear characteristics of the shed material and the fracture mechanics model, the process of stress fatigue failure of the shed material is analyzed.

[0069] Specifically, the steps of this embodiment are as follows:

[0070] Step 1: The present invention selects a composite insulator widely used in 750kV ultra-high voltage DC transmission lines, the product model is FXBZ-±800-320-EE. Since the composite insulator is large in size and has a repeated arrangement of large and small shed skirts, in order to reduce unnecessary calculations, Figure 4As shown in the figure, short samples of five large and five small composite insulators with a total of ten shed lengths were taken for simulation. The diameter of the small shed is 180mm and the diameter of the large shed is 220mm. The total number of nodes and units in the mesh of the fluid calculation domain is 238,896, and the total number of units is 1,357,566. The total number of nodes and units in the mesh of the solid calculation domain is 405,319, and the total number of units is 270,012.

[0071] Step 2: Define the boundary type for numerical simulation:

[0072] The velocity inlet and pressure outlet boundary conditions are defined in the fluid domain. The initial velocity is set to 45 m / s, and the no-slip boundary condition is used for the fluid-solid wall.

[0073] Write a custom user function (UDF) for the shear strain rate correction factor, and compile the defined UDF through the Compiled UDFs panel provided by the FLUENT software to dynamically connect to the FLUENT solver.

[0074] The standard k-ω turbulence model is selected as the turbulence model to calculate the flow field and pressure field variables and extract the velocity and stress parameters of the solid-fluid contact surface.

[0075] Set up dynamic mesh update: Enter the "Dynamic Mesh" window, select the area near the wind farm-insulator interface, set the update method to "Remeshing", and configure relevant parameters in "Dynamic Mesh Parameters" to ensure that the mesh is updated as the shed deforms.

[0076] Activate the bidirectional fluid-structure interaction module, dynamically link the velocity and stress parameters of the flow field to the transient structure module, and pass the shed shape variables obtained by transient structure calculation back to the fluid calculation module.

[0077] COUPLED is selected as the solution method for the algebraic equations, and the time step is set to 0.05s. The bidirectional fluid-solid coupling module is used to iteratively solve the calculation area until the set iteration accuracy is met (relative tolerance is less than 0.0001), and the fluid distribution, shed surface stress distribution and deformation characteristics of each time step are output.

[0078] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0079] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for simulating the transient characteristics of composite insulator shed vibration under strong winds, characterized in that: include: Based on the 3D modeling software, a 3D geometric model of the composite insulator is established according to the shed structure and size parameters of the composite insulator in actual operation, and the 3D geometric model is imported into the fluid simulation software and the calculation network is segmented; Setting boundary conditions and initialization in fluid simulation software, and using an improved turbulence model by introducing a shear strain correction factor; the shear strain correction factor is used to adjust the imbalance phenomenon of turbulence generation and dissipation; The dynamic grid technology is introduced to define the UDF function of composite insulator shed vibration and simulate the reciprocating vibration process of the shed in a strong wind environment. The dynamic wind field simulation is carried out using the two-way fluid-solid coupling method to simulate the vibration response and aerodynamic load distribution of the shed under strong wind. The obtained dynamic pressure on the shed surface is used as the load condition and imported into the structural analysis module for transient stress solution to analyze the stress distribution, vibration deformation and stress state of key parts of the shed material in different time steps. Combining the nonlinear characteristics of the shed material and the fracture mechanics model, the dynamic evolution of the stress aging process of the silicone rubber material of the shed is simulated. By analyzing the stress concentration area of ​​the shed under strong wind, the starting position and expansion path of the tearing are predicted, and the dynamic vibration characteristics and stress distribution cloud map of the shed are output.

2. The method for simulating the transient characteristics of composite insulator shed vibration under strong wind according to claim 1, characterized in that: The computational network includes a composite insulator solid region, an air fluid region, and a fluid-solid interface region.

3. The method for simulating the transient characteristics of composite insulator shed vibration under strong wind according to claim 1, characterized in that: Set boundary conditions and perform initialization in the fluid simulation software, including: The fluid domain inlet is set as the velocity inlet boundary condition, the outlet is set as the pressure outlet boundary condition, the wall is set as the no-slip boundary condition, and the wall function is used to deal with the flow near the wall; when the flow field is initialized, the initial inlet velocity and turbulent kinetic energy are set at the flow field inlet as the benchmark.

4. The method for simulating the transient characteristics of composite insulator shed vibration under strong wind according to claim 1, characterized in that: The control equation of the improved turbulence model is: G ω * =b shear ·G ω Where k represents the turbulent kinetic energy, which represents the time-averaged change in turbulent velocity per unit mass of fluid. ω represents the turbulent frequency, which represents the dissipation rate of turbulent kinetic energy. ρ represents the fluid density, u represents the velocity vector of the fluid, and x represents the velocity of the fluid. i Indicates the specific coordinate direction, G k represents the amount of turbulent kinetic energy generated due to the mean velocity gradient, G ω represents the amount of turbulence frequency ω, Γ k and Γ ω represent the effective diffusion rates of k and ω, respectively, and Y k and Y ω represents the dissipation of k and ω due to turbulence, β shear is the shear strain correction factor.

5. The method for simulating the transient characteristics of composite insulator shed vibration under strong wind according to claim 1, characterized in that: The dynamic mesh technology is used to transfer the deformation of the insulator shed to the improved turbulence model in real time after each iterative solution, so as to re-perform mesh division at the fluid-solid boundary.

6. The method for simulating the transient characteristics of composite insulator shed vibration under strong wind according to claim 1, characterized in that: The two-way fluid-structure coupling calculation method used is: When the improved turbulence model reaches convergence each time it is calculated, the stress data of the fluid-solid interface is transferred to the transient structure module for solution using the coupling component to obtain the incremental displacement of the solid area. The incremental displacement is then transferred back to the improved turbulence model through the coupling component to change the original flow field distribution.

7. The method for simulating the transient characteristics of composite insulator shed vibration under strong wind according to claim 1, characterized in that: The stress-fatigue curve of the silicone rubber material used in the fracture mechanics model is obtained from a preset experiment to reflect the fatigue law of the shed material under the application of long-term wind load.

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