An analysis method for the influence of acceleration on the flow field of the insulator on the high-speed train roof

Abstract

The present invention discloses an analysis method for the influence of acceleration on the flow field of high-speed railway roof insulators, belonging to the technical field of high voltage and insulation. The method includes: based on finite element simulation, geometric modeling of the high-speed railway roof insulator model is carried out. Taking the atmospheric environment as the flow field and the high-speed railway insulator as the solid points, a flow field model and a solid motion model are established, and the geometric parameters of the high-speed railway and the insulator are set; different positions on the windward and leeward surfaces of the insulator are numbered and the flow field distribution around each solid point is updated; the finite element simulation method is used to set the material parameters of the model; the finite element simulation method is used to set the physical field, mesh generation and solution calculation of the model. The present invention draws the conclusion that the difference in the surface pressure and density distribution of the insulator under the condition of acceleration is greater than that under the condition of constant speed, which can be used to explore the flow field distribution law of the roof insulator and the flashover mechanism of the roof insulator during the start and brake of high-speed trains and the design of the high-speed railway roof flow field.

Description

Technical Field

[0001] The present invention belongs to the technical field of high voltage and insulation, and particularly relates to an analysis method for the influence of acceleration on the flow field of high-speed train roof insulators. Background Art

[0002] With the rapid development of high-speed trains, the current operating speed of high-speed trains has exceeded 300 km / h. The high-speed train roof insulator is a key device for high-voltage isolation of the car body and mechanical support of the pantograph. Its good insulation service performance is the basic condition for ensuring the safe operation of the train. The high-speed train roof insulator is inevitably affected by high-speed air flow during operation. When the high-speed train accelerates and starts or decelerates and stops, the distribution of the flow field on the surface of the high-speed train roof insulator is different from that in the constant-speed case. The flow field on the surface of the insulator may show a more complex distribution under acceleration and deceleration conditions of the high-speed train, which will have an important impact on the distribution of the flow velocity, air pressure, and density on the insulator surface, and will inevitably affect the external insulation discharge characteristics of the high-speed train roof.

[0003] In the prior art, domestic and foreign researchers have conducted a large number of studies on the gas discharge characteristics in the air flow environment, the surface discharge characteristics of insulators in the air flow environment, the surface flashover characteristics in the vacuum environment, the competition mechanism between gas discharge and surface flashover, and the flow field characteristics on the back of a solid moving rapidly, and have also obtained many results. However, there are few studies on the influence of acceleration during the operation of high-speed trains on the distribution characteristics of the flow field on the surface of roof insulators. Therefore, it is necessary to study the distribution characteristics of the air flow around the train and the insulator under different acceleration conditions, so as to provide a reference basis for the distribution law and design of the roof flow field and the flashover mechanism of the insulator during the start and deceleration of the train.

[0004] Based on this, the R & D personnel have proposed an analysis method for the influence of acceleration on the flow field of high-speed train roof insulators. Summary of the Invention

[0005] The purpose of the present invention is to provide an analysis method for the influence of acceleration on the flow field of high-speed train roof insulators, so as to solve the problem of insufficient research on the influence of acceleration during the operation of high-speed trains on the distribution characteristics of the flow field on the surface of roof insulators.

[0006] To solve the above problems, the technical solution of the present invention is as follows:

[0007] An analysis method for the influence of acceleration on the flow field of high-speed train roof insulators, the method is divided into the following steps:

[0008] Step S1: Based on finite element simulation, perform geometric modeling on the high-speed train roof insulator model. Taking the atmospheric environment as the flow field and the high-speed train insulator as the solid point, establish a flow field model and a solid motion model, and set the geometric parameters of the high-speed train and the insulator;

[0009] Step S2: As the high-speed rail insulator moves, number different positions on the windward and leeward sides of the insulator and update the flow field distribution around each solid point;

[0010] Mark different positions on the windward and leeward sides of the insulator:

[0011] When the train travels from right to left in the plane, due to the different flow field distributions on the surface of each insulator, mark the head of the windward side of the first insulator as 1, the root as 3, the head of the leeward side as 2, and the root as 4; mark the head of the windward side of the second insulator as 5, the root as 7, the head of the leeward side as 6, and the root as 8;

[0012] Step S3: Set material parameters based on finite element simulation;

[0013] Based on the material parameter settings in the finite element simulation, set the dynamic viscosity, density, Young's modulus, and Poisson's ratio of the corresponding regions;

[0014] Step S4: Perform physical field settings, mesh generation, and solution calculation in the finite element simulation;

[0015] The physical field settings include setting "solid mechanics", "laminar flow", and "global ordinary differential equations";

[0016] Calculation shows that: under positive acceleration conditions, the leeward side of the insulator is the weak position of the insulator; under negative acceleration conditions, the windward side of the insulator is the weak position of the insulator.

[0017] Furthermore, the specific steps in Step S1 are: According to the actual shape and size of the high-speed rail and the insulator, construct a simple geometric model and set the geometric parameters of the high-speed rail and the insulator;

[0018] The specific dimensions are: the length of the air domain is 650m, the height is 150m; the size of the high-speed rail is 60m×30m; the size of the insulator is 10m×10m, and the distance between insulators is 30m; the head and tail of the high-speed rail are U-shaped.

[0019] Furthermore, the material parameters in Step S3 are:

[0020] The laminar flow material during the operation of the high-speed rail is air, and the dynamic viscosity is set as a function of temperature eta(T), and the density is set as a function of pressure and temperature rho(pA, T);

[0021] The material of the high-speed rail is aluminum alloy, with a density of 3900 kg / m3, a Young's modulus of 300e9 pa, and a Poisson's ratio of 0.222;

[0022] The material of the insulator is quartz glass, with a density of 2203 kg / m3, a Young's modulus of 73.1e9 pa, and a Poisson's ratio of 0.17.

[0023] Further, the specific setting process in step S4 is as follows:

[0024] In the "laminar flow" physical field, set the "inlet" boundary condition at one end of the air domain, set the air pressure value and suppress backflow, and set the "outlet" boundary condition at the other end to form the air domain circulation.

[0025] In the "solid mechanics" physical field, add the "acceleration" boundary condition, and keep the other boundary conditions default.

[0026] The mesh division includes mesh division of the high-speed rail insulator and air. In this embodiment, the complete mesh contains 5,115 elements.

[0027] Use the moving mesh technology to solve the problem of large mesh deformation caused by fluid-structure interaction during the high-speed operation of the train; set the solution step size to 0.1 s and the solution time to 6 s, select the fully coupled calculation mode, select automatic mesh rezoning, and enable Anderson acceleration in the transient solver to start the calculation.

[0028] Further, the specific calculation result in step S4 is as follows: Compared with the constant speed condition, the difference in the flow velocity distribution on the insulator surface is greater under positive and negative acceleration conditions. The difference in the flow velocity distribution on the insulator surface under positive and negative acceleration conditions is about 1.57 - 1.86 times that under the constant speed condition.

[0029] The beneficial effects of the present invention are as follows:

[0030] (1) Based on finite element simulation, the present invention conducts geometric modeling of the high-speed rail roof insulator model, takes the atmospheric environment as the flow field, takes the high-speed rail insulator as the solid point, establishes the flow field model and the solid motion model, and sets the geometric parameters of the high-speed rail and the insulator; numbers different positions on the windward and leeward sides of the insulator and updates the flow field distribution around each solid point; uses the finite element simulation method to set the material parameters of the model; uses the finite element simulation method to set the physical field, mesh division and solution calculation of the model. The simulation results can provide a reference basis for exploring the influence characteristics of acceleration on gas-solid interface discharge in the airflow environment.

[0031] (2) The present invention simultaneously considers the acceleration direction and magnitude, compares the flow field distribution on the insulator surface under the acceleration condition with that under the constant speed condition, analyzes the changes in velocity, pressure, and density of the flow field on the insulator surface under different acceleration conditions, and draws the conclusion that the difference in the flow velocity distribution on the insulator surface under positive and negative acceleration conditions is approximately 1.57 - 1.86 times that under the constant speed condition. This parameter can be used to analyze the influence characteristics of acceleration on the flow field of the high-speed rail roof insulator, providing an important reference basis for exploring the flow field distribution law of the roof insulator, the flashover mechanism of the roof insulator, and the design of the high-speed rail roof flow field when the high-speed train starts and brakes. Description of the Drawings

[0032] Figure 1 It is a flowchart of an analysis method for the influence of acceleration on the flow field of a high-speed rail roof insulator;

[0033] Figure 2 It is a geometric model diagram of the high-speed rail insulator in the embodiment;

[0034] Figure 3 It is a flow field velocity distribution point diagram of point No. 3 selected in the embodiment;

[0035] Figure 4 It is a flow field pressure distribution point diagram of point No. 3 selected in the embodiment;

[0036] Figure 5 It is a flow field density distribution point diagram of point No. 3 selected in the embodiment. Detailed Embodiment

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0038] Therefore, the detailed description of the embodiments of the present invention provided in the drawings below is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Embodiment

[0039] As Figure 1 shown, an analysis method for the influence of acceleration on the flow field of a high-speed rail roof insulator specifically includes the following steps.

[0040] Step S1: Based on finite element simulation, conduct geometric modeling of the high-speed rail roof insulator model. Taking the atmospheric environment as the flow field and the high-speed rail insulator as the solid points, establish a flow field model and a solid motion model, and set the geometric parameters of the high-speed rail and the insulator;

[0041] According to the actual shape and size of the high-speed rail and the insulator, construct a simple geometric model, as Figure 2 shown, and set the geometric parameters of the high-speed rail and the insulator.

[0042] In this embodiment, the length of the air domain is 650m, the height is 150m; the size of the high-speed rail is 60m×30m; the size of the insulator is 10m×10m, and the distance between insulators is 30m; the heads and tails of the high-speed rail are U-shaped.

[0043] Step S2: As the high-speed rail insulator moves, number different positions on the windward and leeward sides of the insulator and update the flow field distribution around each solid point;

[0044] For the convenience of analysis and explanation, label different positions on the windward and leeward sides of the insulator: when the train travels from right to left in the plane, due to the different flow field distributions on the surface of each insulator, label the head of the windward side of the first insulator as 1, the root as 3, the head of the leeward side as 2, and the root as 4; label the head of the windward side of the second insulator as 5, the root as 7, the head of the leeward side as 6, and the root as 8.

[0045] Step S3: Based on finite element simulation, set the material parameters;

[0046] Based on the material parameter settings in finite element simulation, set the dynamic viscosity, density, Young's modulus, and Poisson's ratio of the corresponding regions.

[0047] The laminar flow material during the operation of the high-speed rail is air, and the dynamic viscosity is set as a function of temperature eta(T), and the density is set as a function of pressure and temperature rho(pA, T).

[0048] The material of the high-speed rail is aluminum alloy, with a density of 3900 kg / m3, a Young's modulus of 300e9 pa, and a Poisson's ratio of 0.222;

[0049] The material of the insulator is quartz glass, with a density of 2203 kg / m3, a Young's modulus of 73.1e9 pa, and a Poisson's ratio of 0.17.

[0050] Step S4: In finite element simulation, conduct physical field settings, mesh generation, and solution calculations.

[0051] The physical field settings include setting "solid mechanics", "laminar flow", and "global ordinary differential equations";

[0052] Among them, in the "laminar flow" physical field, an "inlet" boundary condition is set at one end of the air domain, the air pressure value is set and the backflow is suppressed, and an "outlet" boundary condition is set at the other end to form the circulation of the air domain.

[0053] In the "solid mechanics" physical field, an "acceleration" boundary condition is added, and the remaining boundary conditions are kept default.

[0054] The mesh generation includes meshing the high-speed rail insulator and the air. In this embodiment, the complete mesh contains 5,115 elements.

[0055] The moving mesh technique is used to solve the problem of large mesh deformation caused by fluid-structure interaction during the high-speed operation of the train; the solution step size is set to 0.1 s and the solution time is set to 6 s. The fully coupled calculation mode is selected, and the automatic mesh rezoning is selected. Anderson acceleration is enabled in the transient solver, and then the calculation can be started.

[0056] Figure 3 It is the flow field velocity distribution dot diagram of point 3 of the model at t = 5 s calculated through the above steps.

[0057] It can be clearly seen that the velocity at this point of the insulator shows a linear upward trend before 5 s, and the velocity slightly decreases at 5 s but still shows an upward trend as a whole.

[0058] Figure 4 It is the flow field pressure distribution dot diagram of point 3 of the model at t = 5 s calculated through the above steps.

[0059] Different from the velocity distribution dot diagram, the pressure distribution dot diagram shows a slow upward trend. Similarly, the pressure drops briefly at 5 s, which corresponds to the velocity distribution dot diagram, but the pressure shows an upward trend as a whole.

[0060] Figure 5 It is the flow field density distribution dot diagram of point 3 of the model at t = 5 s calculated through the above steps.

[0061] The density distribution dot diagram is basically the same as the pressure distribution dot diagram, and the density change is positively correlated with the pressure change.

[0062] In summary, it can be seen that: under the condition of positive acceleration, the leeward side of the insulator is the weak position of the insulator; under the condition of negative acceleration, the windward side of the insulator is the weak position of the insulator.

[0063] Compared with the constant speed condition, the difference in the surface flow velocity distribution of the insulator is greater under the conditions of positive and negative accelerations. The difference in the surface flow velocity distribution of the insulator under the conditions of positive and negative accelerations is about 1.57 - 1.86 times that under the constant speed condition.

[0064] The conclusion that the difference in the surface pressure and density distribution of the insulator under this acceleration condition is greater than that under the constant speed condition can provide a reference basis for the distribution law and design of the roof flow field and the flashover mechanism of the insulator under the conditions of train start-up and deceleration. Incorporating the surface pressure and density distribution of the insulator under the conditions of train start-up and deceleration into use at the design stage has extremely strong engineering significance.

Claims

1. An analysis method for the influence of acceleration on the flow field of high-speed train roof insulators, characterized in that: The method comprises the following steps: Step S1: Based on finite element simulation, geometric modeling of the high-speed rail roof insulator model is carried out. Taking the atmospheric environment as the flow field and the high-speed rail insulator as the solid point, a flow field model and a solid motion model are established, and the geometric parameters of the high-speed rail and the insulator are set; Step S2: As the high-speed rail insulator moves, different positions on the windward side and the leeward side of the insulator are numbered and the flow field distribution around each solid point is updated; Label different positions on the windward side and the leeward side of the insulator: When the train travels from right to left in the plane, due to the different flow field distributions on the surface of each insulator, the head of the windward side of the first insulator is labeled as 1, the root is labeled as 3, the head of the leeward side is labeled as 2, and the root is labeled as 4; the head of the windward side of the second insulator is labeled as 5, the root is labeled as 7, the head of the leeward side is labeled as 6, and the root is labeled as 8; Step S3: Material parameter settings are carried out based on finite element simulation; Based on the material parameter settings in finite element simulation, the dynamic viscosity, density, Young's modulus, and Poisson's ratio of the corresponding regions are set; Step S4: Physical field settings, mesh generation, and solution calculation are carried out in finite element simulation; The physical field settings include setting "solid mechanics", "laminar flow", and "global ordinary differential equations"; Compared with the constant speed condition, the difference in the flow velocity distribution on the surface of the insulator is greater under positive and negative acceleration conditions. The difference in the flow velocity distribution on the surface of the insulator under positive and negative acceleration conditions is 1.57 - 1.86 times that under the constant speed condition; It can be seen that: under positive acceleration conditions, the leeward side of the insulator is the weak position of the insulator; under negative acceleration conditions, the windward side of the insulator is the weak position of the insulator.

2. The analysis method for the influence of acceleration on the flow field of high-speed train roof insulators according to claim 1, characterized in that: The specific steps in Step S1 are: According to the actual shape and size of the high-speed rail and the insulator, a simple geometric model is constructed, and the geometric parameters of the high-speed rail and the insulator are set; The specific dimensions are: the length of the air domain is 650m, the height is 150m; the size of the high-speed rail is 60m×30m; the size of the insulator is 10m×10m, and the distance between insulators is 30m; the head and tail of the high-speed rail are U-shaped.

3. The analysis method for the influence of acceleration on the flow field of high-speed train roof insulators according to claim 1, characterized in that: The material parameters in Step S3 are: The laminar flow material during the operation of the high-speed rail is air. The dynamic viscosity is set as a function eta(T) of temperature, and the density is set as a function rho(pA, T) of pressure and temperature; The high-speed rail material is aluminum alloy, with a density of 3900 kg / m 3 , a Young's modulus of 300e9 pa, and a Poisson's ratio of 0.222; The insulator material is quartz glass with a density of 2203 kg / m 3 , Young's modulus of 73.1e9 pa, and Poisson's ratio of 0.

17.

4. The analysis method for the influence of acceleration on the flow field of high-speed train roof insulators according to claim 1, characterized in that: The specific setting process in Step S4 is: In the "laminar flow" physical field, an "inlet" boundary condition is set at one end of the air domain, the air pressure value is set and backflow is suppressed, and an "outlet" boundary condition is set at the other end to form the circulation of the air domain; In the "solid mechanics" physical field, an "acceleration" boundary condition is added, and the other boundary conditions remain default; Mesh generation includes mesh generation for the high-speed rail insulator and air. The complete mesh contains 5115 elements; The moving mesh technology is used to solve the problem of large mesh deformation caused by fluid-structure interaction during the high-speed operation of the train; the solution step size is set to 0.1s and the solution time is 6s. The fully coupled calculation mode is selected, automatic mesh rezoning is selected, and Anderson acceleration is enabled in the transient solver to start the calculation.

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