Method and system for simulating motion of bubbles in transformer oil by considering multi-physics field coupling

Abstract

The invention discloses a method and a system for simulating bubble motion in transformer oil by considering multi-physics field coupling, and the method comprises the steps: fusing an energy equation into a mass conservation and momentum conservation equation, and constructing a multi-physics field model which considers the coupling of an electric field, a thermal field and a flow field; introducing a k-epsilon turbulence model into the multi-physics field model to obtain a first optimized multi-physics field model; the k-epsilon turbulence model is an oil flow model in a large transformer; introducing a phase field method into the first optimized multi-physics field model to obtain a second optimized multi-physics field model; various forces of bubble motion are introduced into the second optimized multi-physics field model, and a third optimized multi-physics field model is obtained; and performing parameter solving on the third optimized multi-physical field model to obtain the movement process of the bubbles in the transformer oil. According to the invention, a multi-physical field model considering coupling of an electric field, a thermal field and a flow field is constructed, and comprehensive and accurate simulation of bubble motion in transformer oil is realized.

Description

Technical Field

[0001] The invention relates to the technical field of simulation of bubble movement in transformer oil, and in particular to a method and system for simulating bubble movement in transformer oil considering multi-physical field coupling. Background Art

[0002] During the long-term operation of the transformer, due to the occurrence of partial discharge, overheating and other faults, the transformer oil will crack and produce bubbles. This phenomenon not only affects the normal operation of the transformer, but more seriously may cause insulation breakdown, resulting in major safety hazards and economic losses. In terms of experimental research, current experimental research mainly uses the oil bubble injection method to observe the dynamic changes of bubbles, but this method is significantly different from the motion characteristics of suspended bubbles in oil-paper insulation under actual working conditions. In terms of simulation research, existing simulations mostly use a single physical field to study the movement of bubbles, but the formation and movement of bubbles involves a complex multi-physical field coupling process, including the interaction of electric fields, temperature fields, fluid dynamics and other aspects. However, the existing simulation method does not take into account the multi-physical field coupling effect, resulting in inaccurate simulation of bubble movement in transformer oil and other problems.

[0003] In view of this, this application is hereby filed. Summary of the invention

[0004] The technical problem to be solved by the present invention is that the existing simulation methods mostly use a single physical field to study the movement law of bubbles, but the formation and movement of bubbles involve a complex multi-physical field coupling process. The existing methods do not consider the multi-physical field coupling effect, resulting in inaccurate simulation of bubble movement in transformer oil and other problems. The purpose of the present invention is to provide a method and system for simulating bubble movement in transformer oil considering multi-physical field coupling. The present invention constructs a multi-physical field model considering the coupling of electric field, thermal field and flow field, and realizes a comprehensive and accurate simulation of bubble movement in transformer oil.

[0005] The present invention is achieved through the following technical solutions:

[0006] In a first aspect, the present invention provides a method for simulating bubble motion in transformer oil considering multi-physical field coupling, the method comprising:

[0007] Integrate the energy equation into the mass conservation and momentum conservation equations, and construct a multi-physics model that considers the coupling of electric field, thermal field and flow field;

[0008] The k-ε turbulence model is introduced into the multi-physics field model to obtain the first optimized multi-physics field model; the k-ε turbulence model is an oil flow model in a large transformer;

[0009] Introducing the phase field method into the first optimized multi-physics field model to obtain a second optimized multi-physics field model;

[0010] Various forces of bubble motion are introduced into the second optimized multi-physics model to obtain a third optimized multi-physics model;

[0011] The parameters of the third optimized multi-physics field model are solved to obtain the bubble movement process in the transformer oil.

[0012] Furthermore, the expression of the multi-physics model is:

[0013]

[0014] PρRT

[0015]

[0016] Where ρ is the fluid density; t is the time; v is the velocity; p is the pressure; μ is the fluid dynamic viscosity; g is the gravitational acceleration; F is the volume force (buoyancy, electromagnetic force, etc.); E is the total energy; kef f is the effective thermal conductivity; T is the temperature; Sh is the volume heat source; R is the molar gas constant; ρ 0 is the liquid density at the reference pressure; n is the density index; κ is the bulk modulus under pressure; κ 0 is the bulk modulus at reference pressure; is the differential operator.

[0017] Furthermore, the expression of the k-ε turbulence model is:

[0018]

[0019] Where: ρ is the fluid density; t is the time; G k , G b are the average velocity gradient and the turbulent kinetic energy generated by the buoyancy effect; Y M represents the effect of compressible turbulent pulsation expansion on the total dissipation rate; μt is the turbulent viscosity coefficient; C 1ε , C 2ε , C 3ε is the default value constant; the turbulent Prandtl number of turbulent kinetic energy k and dissipation rate ε is σk=1.0, σ ε =1.3;x i (i=1,2,3) represents three directions x, y, and z; μ is the dynamic viscosity of the fluid.

[0020] Furthermore, the phase field method uses φ∈[-1,1] to define the properties of two immiscible fluids. At the fluid interface, the function φ transitions from 1 to -1. In the phase field analysis, the Cahn-Hilliard equation is introduced to track the changes in the interface, comprehensively considering the effects of interfacial mobility and chemical potential.

[0021] Furthermore, the various forces of bubble motion include electric force, buoyancy, surface tension, gravity, drag, drag, and oil flow drag;

[0022] Among them, the electric field force and surface tension will cause the bubble to deform;

[0023] Buoyancy, gravity, drag, drag, and oil flow drag will cause the bubbles to move.

[0024] In a second aspect, the present invention provides a bubble movement observation system in transformer oil considering multi-physical field coupling, the system comprising an observation cavity, a high-voltage electrode, a ground electrode, an insulating cardboard, a near-infrared heating tube, an infrared temperature sensor, a three-way ball valve, a micro-injection pump, a high-speed camera and a computer;

[0025] The observation cavity is made of transparent acrylic plate and filled with transformer oil;

[0026] The high-voltage electrode and the grounding electrode are placed in the observation cavity, and insulating paperboard is added between the high-voltage electrode and the grounding electrode to simulate the actual transformer oil-paper insulation environment;

[0027] The near-infrared heating tube is installed above the observation cavity; the infrared temperature sensor is used to monitor the oil-paper insulation temperature in real time;

[0028] A three-way ball valve is connected to the bottom of the observation chamber; a microinjection pump is connected to the observation chamber through the three-way ball valve;

[0029] The high-speed camera is aimed at the observation cavity; the computer is electrically connected to the high-speed camera for data collection and analysis.

[0030] Furthermore, the insulating paperboard has a multi-layer structure, and the number of layers and the structure are adjusted to simulate oil-paper insulation systems of different thicknesses.

[0031] Furthermore, the power of the near-infrared heating tube is adjustable, and the heating temperature can be precisely controlled to simulate the temperature field distribution under different load conditions of the transformer;

[0032] The control system of the near-infrared heating tube and the infrared temperature sensor form a closed-loop control to achieve precise temperature regulation.

[0033] Furthermore, the microinjection pump is programmable and can simulate different bubble generation rates and sizes to study the movement characteristics of various bubble precipitation conditions.

[0034] Furthermore, the high-speed camera uses a high-frame-rate CMOS sensor, which can capture the bubble motion process at the microsecond level;

[0035] The computer is equipped with specialized data analysis software that can process images captured by high-speed cameras in real time, extract bubble motion parameters, and conduct real-time comparative analysis with theoretical predictions of multi-physics field models.

[0036] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0037] 1. The present invention considers the multi-physics field coupling simulation method of bubble motion in transformer oil. The present invention realizes a comprehensive and accurate simulation of bubble motion in transformer oil by constructing a multi-physics field model that considers the coupling of electric field, thermal field and flow field. The energy equation is added when solving the fluid motion, and the various forces on the bubble are comprehensively analyzed, including electric field force, buoyancy, resistance, surface tension, gravity, oil flow drag force and drag force, etc. This method that comprehensively considers the multi-physics field coupling effect makes the theoretical analysis of bubble motion closer to the actual situation and significantly improves the accuracy and practicality of the simulation.

[0038] 2. The present invention considers the bubble movement observation system in transformer oil coupled with multiple physical fields. Corresponding to the simulation method, the observation system accurately simulates the complex physical environment of the actual working conditions of transformer oil-paper insulation through components such as high-voltage electrodes, near-infrared heating tubes, and insulating paperboard. The system uses a micro-injection pump to accurately control bubble generation, uses a high-speed camera to capture the bubble movement trajectory, and combines computer image processing technology to achieve accurate observation and quantitative analysis of the movement characteristics of bubbles under the action of multiple physical fields. This innovative experimental platform not only provides a reliable basis for verifying the multi-physical field coupling theoretical model, but also greatly improves the depth and accuracy of the study of bubble movement in transformer oil, and provides important technical support for optimizing transformer design and improving operational reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0040] Figure 1 A flow chart of a method for simulating bubble movement in transformer oil considering multi-physical field coupling of the present invention;

[0041] Figure 2 This is a schematic diagram of the structure of the bubble movement observation system in transformer oil considering multi-physical field coupling in the present invention.

[0042] Reference numerals and corresponding component names:

[0043] 1-Observation chamber, 2-high voltage electrode, 3-ground electrode, 4-insulating cardboard, 5-near infrared heating tube, 6-infrared temperature sensor, 7-three-way ball valve, 8-micro injection pump, 9-high-speed camera, 10-computer. DETAILED DESCRIPTION

[0044] Hereinafter, the term "include" or "may include" used in various embodiments of the present invention indicates the presence of the invented function, operation or element, and does not limit the addition of one or more functions, operations or elements. In addition, as used in various embodiments of the present invention, the terms "include", "have" and their cognates are intended only to indicate specific features, numbers, steps, operations, elements, components or combinations of the foregoing items, and should not be understood as first excluding the presence of one or more other features, numbers, steps, operations, elements, components or combinations of the foregoing items or the possibility of adding one or more features, numbers, steps, operations, elements, components or combinations of the foregoing items.

[0045] In various embodiments of the present invention, the expression "or" or "at least one of A or / and B" includes any combination or all combinations of the words listed at the same time. For example, the expression "A or B" or "at least one of A or / and B" may include A, may include B, or may include both A and B.

[0046] The expressions (such as "first", "second", etc.) used in various embodiments of the present invention may modify the various constituent elements in various embodiments, but may not limit the corresponding constituent elements. For example, the above expressions do not limit the order and / or importance of the elements. The above expressions are only used for the purpose of distinguishing an element from other elements. For example, the first user device and the second user device indicate different user devices, although both are user devices. For example, without departing from the scope of various embodiments of the present invention, the first element may be referred to as the second element, and similarly, the second element may also be referred to as the first element.

[0047] It should be noted that if it is described that one component element is “connected” to another component element, the first component element may be directly connected to the second component element, and a third component element may be “connected” between the first component element and the second component element. Conversely, when one component element is “directly connected” to another component element, it can be understood that there is no third component element between the first component element and the second component element.

[0048] The terms used in various embodiments of the present invention are only used for the purpose of describing specific embodiments and are not intended to limit various embodiments of the present invention. As used herein, the singular form is intended to also include the plural form, unless the context clearly indicates otherwise. Unless otherwise limited, all terms used here (including technical terms and scientific terms) have the same meaning as the meaning generally understood by those of ordinary skill in the art to which the various embodiments of the present invention belong. The terms (such as the terms defined in the dictionary generally used) will be interpreted as having the same meaning as the contextual meaning in the relevant technical field and will not be interpreted as having an idealized meaning or an overly formal meaning, unless clearly defined in various embodiments of the present invention.

[0049] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0050] The present invention is a new method and system that can comprehensively consider the multi-physics field coupling effect and accurately simulate the bubble movement in transformer oil. The key point of the present invention is to construct a multi-physics field coupling model that considers the thermal field and comprehensively analyzes the bubble force, and to design a set of electric, thermal and flow comprehensive bubble movement observation system including near-infrared heating tubes.

[0051] The present invention is no longer limited to the consideration of a single physical field, but comprehensively simulates the complex physical process in the actual operating environment of the transformer. It can make the study of bubble movement closer to reality, greatly improving the accuracy and practicality of the analysis results. At the same time, this invention can also be applied to other fields involving multi-physical field coupling, such as the study of microscopic particle movement in the insulating medium of other power equipment. This invention has no technical means that can be circumvented or replaced.

[0052] The design conception process of the method of the present invention is:

[0053] (1) The energy equation is integrated into the mass conservation and momentum conservation equations to obtain a multi-physics model that takes into account the coupling of electric field, thermal field and flow field (Formulas (1), (2), (3), (4), (5)). This basic model describes the basic behavior of the fluid, including continuity, momentum transfer and energy transfer.

[0054] (2) In order to more accurately describe the complex turbulence effects, the k-ε turbulence model (Formulas (6) and (7)) is introduced on the basis of Formulas (1), (2), (3), (4) and (5). This expands the basic equations and adds the description of the turbulent kinetic energy k and the turbulent dissipation rate ε, so that the model can better simulate the turbulent characteristics in high Reynolds number flows.

[0055] (3) In order to more accurately describe the dynamic behavior of the gas-liquid interface, especially to deal with complex interface topological changes (such as the splitting and merging of bubbles), the phase field method (Equations (16) to (19)) is introduced (in fact, a variable φ and an equation (18) are added). The phase field method provides a continuous method to describe the evolution of the interface by introducing φ and equation (18), enabling the model to better capture complex physical phenomena.

[0056] (4) In order to fully consider the various forces that affect the motion of the bubble, equations (8) to (15) are introduced as source terms of the above equations ((1), (2), (3), (4), (5), (6), (7), (18), a total of 8 equations and 8 unknowns: pressure, temperature, velocity, energy, density, k and ε, phase field variable φ). These equations describe the various forces acting on the bubble.

[0057] Example 1

[0058] like Figure 1 As shown, the present invention considers a method for simulating bubble movement in transformer oil with multi-physical field coupling, and the method comprises:

[0059] Step 1: Integrate the energy equation into the mass conservation and momentum conservation equations to construct a multi-physics model that considers the coupling of electric field, thermal field and flow field;

[0060] This is because transformer oil faces complex interactions of multiple physical fields in actual operation, including electric field, thermal field and flow field. Therefore, it is necessary to study the movement law of bubbles in oil based on a multi-physics field model that couples the three fields of electricity, heat and flow.

[0061] Specifically, the oil flow in large transformers can be described by turbulence models, and transformer oil can generally be regarded as an incompressible fluid. Transformer oil satisfies the three laws of conservation of mass, conservation of momentum, and conservation of energy during the flow process. That is, based on the existing technology, the energy equation is integrated into the mass conservation and momentum conservation equations, and the expression of the multi-physics field model is obtained as follows:

[0062]

[0063] Where ρ is the fluid density; t is the time; v is the velocity; p is the pressure; μ is the fluid dynamic viscosity; g is the gravitational acceleration; F is the volume force (buoyancy, electromagnetic force, etc.); E is the total energy; kef f is the effective thermal conductivity; T is the temperature; Sh is the volume heat source;

[0064] In addition, the solution model contains the gas state equation and the liquid state equation, which are as follows:

[0065] P=ρRT(4)

[0066]

[0067] Where R is the molar gas constant; ρ 0 is the liquid density at the reference pressure; n is the density index; κ is the bulk modulus under pressure; κ0 is the bulk modulus at the reference pressure; is the differential operator;

[0068] Step 2, introducing a k-ε turbulence model into the multi-physics field model to obtain a first optimized multi-physics field model; the k-ε turbulence model is an oil flow model in a large transformer;

[0069] Specifically, the expression of the k-ε turbulence model is:

[0070]

[0071] Where: ρ is the fluid density; t is the time; G k , G b are the average velocity gradient and the turbulent kinetic energy generated by the buoyancy effect; Y M represents the effect of compressible turbulent pulsation expansion on the total dissipation rate; μt is the turbulent viscosity coefficient; C 1ε , C 2ε , C 3ε is the default value constant; the turbulent Prandtl number of turbulent kinetic energy k and dissipation rate ε is σk=1.0, σ ε =1.3;x i (i=1,2,3) represents three directions x, y, and z; μ is the dynamic viscosity of the fluid.

[0072] Step 3, introducing the phase field method into the first optimized multi-physics field model to obtain a second optimized multi-physics field model;

[0073] The above model contains gas and liquid phases and belongs to a two-phase flow model. This technical solution adopts the phase field method to solve it, and uses φ∈[-1,1] to define the properties of two immiscible fluids, where φ=1 is defined as fluid A in the two-phase flow, and φ=-1 is defined as fluid B. At the fluid interface, the function φ transitions from 1 to -1. Then, in any volume unit of the two-phase flow, the volume fractions VA and VB of the A and B phases satisfy:

[0074]

[0075] The dielectric constant ε, density ρ, and dynamic viscosity μ of the AB two-phase interface can be calculated by the following formula:

[0076]

[0077] In phase field analysis, the Cahn-Hilliard equation is usually introduced to track the changes in the interface. Considering the effects of interface mobility and chemical potential, the Cahn-Hilliard equation can be expressed as follows:

[0078]

[0079] Where: γ is the interface mobility; G is the chemical potential; δ is the interface capillary thickness.

[0080] Step 4, introducing various forces of bubble motion into the second optimized multi-physics field model to obtain a third optimized multi-physics field model;

[0081] Bubbles in oil are affected by multiple forces during their movement, including electric field force, buoyancy, surface tension, gravity, resistance, drag force and oil flow drag force. Electric field force and surface tension cause bubble deformation, while buoyancy, gravity, resistance, drag force and oil flow drag force cause bubbles to move.

[0082] The expression of the electric field force is:

[0083]

[0084] T m is the Maxwell stress tensor. In the electrostatic field solution, T m It can be expressed by the electric field strength E and the electric displacement vector D:

[0085]

[0086] The buoyancy expression is:

[0087] FVBρg(10)

[0088] The resistance expression is:

[0089]

[0090] The expression of surface tension is:

[0091]

[0092] The gravity expression is:

[0093] FeVBρ1g(13) The oil flow drag force expression is:

[0094] The drag force expression of FP / v(14) is:

[0095] F=AS(15)

[0096] Where: V b is the bubble volume; φ is the electric potential; r s is the contact radius; C D is the resistance coefficient; ρ 1 is the air density; ks t is the curvature of the gas-liquid interface; σ is the bubble surface tension coefficient; A is the drag coefficient; S is the wake area; P is the external oil pump power. D Related to the shape of an object and its surface characteristics.

[0097] Step 5, solving the parameters of the third optimized multi-physics field model to obtain the bubble movement process in the transformer oil.

[0098] In this embodiment, the most commonly used solution method for the complex multi-physics field coupling problem of multiple equations and multiple variables in the model is to use the finite element method or finite volume method of commercial software to solve the parameters, thereby simulating the movement process of bubbles in transformer oil.

[0099] The present invention realizes a comprehensive and accurate simulation of bubble movement in transformer oil by constructing a multi-physics field model that considers the coupling of electric field, thermal field and flow field. The energy equation is added when solving the fluid movement, and the various forces on the bubble are comprehensively analyzed, including electric field force, buoyancy, resistance, surface tension, gravity, oil flow drag force and drag force, etc. This method of comprehensively considering the coupling effect of multiple physical fields makes the theoretical analysis of bubble movement closer to the actual situation and significantly improves the accuracy and practicality of the simulation.

[0100] Example 2

[0101] like Figure 2 As shown, the difference between this embodiment and embodiment 1 is that this embodiment provides an observation system for bubble movement in transformer oil considering multi-physical field coupling, and the system is based on the simulation method for bubble movement in transformer oil considering multi-physical field coupling of embodiment 1.

[0102] The system includes an observation chamber 1, a high-voltage electrode 2, a ground electrode 3, an insulating cardboard 4, a near-infrared heating tube 5, an infrared temperature sensor 6, a three-way ball valve 7, a micro-injection pump 8, a high-speed camera 9 and a computer 10;

[0103] The observation cavity 1 is made of a transparent acrylic plate and filled with transformer oil;

[0104] The high voltage electrode 2 and the ground electrode 3 are placed in the observation cavity 1, and an insulating paperboard 4 is added between the high voltage electrode 2 and the ground electrode 3 to simulate the actual transformer oil-paper insulation environment;

[0105] The near-infrared heating tube 5 is installed above the observation cavity 1; the infrared temperature sensor 6 is used to monitor the oil-paper insulation temperature in real time;

[0106] The three-way ball valve 7 is connected to the bottom of the observation chamber 1; the microinjection pump 8 is connected to the observation chamber 1 through the three-way ball valve 7;

[0107] The high-speed camera 9 is aimed at the observation cavity 1; the computer 10 is electrically connected to the high-speed camera 9 for data collection and analysis.

[0108] In this embodiment, the insulating paperboard 4 is a multi-layer structure, and the number of layers and the structure are adjusted to simulate oil-paper insulation systems of different thicknesses.

[0109] In this embodiment, the power of the near-infrared heating tube 5 is adjustable, and the heating temperature can be accurately controlled to simulate the temperature field distribution under different load conditions of the transformer;

[0110] The control system of the near-infrared heating tube 5 and the infrared temperature sensor 6 form a closed-loop control to achieve precise temperature regulation.

[0111] In this embodiment, the microinjection pump 8 is programmable and can simulate different bubble generation rates and sizes to study the movement characteristics of various bubble precipitation conditions.

[0112] In this embodiment, the high-speed camera 9 uses a high-frame-rate CMOS sensor, which can capture the bubble movement process at the microsecond level;

[0113] The computer 10 is equipped with special data analysis software, which can process the images collected by the high-speed camera 9 in real time, extract bubble motion parameters, and perform real-time comparative analysis with theoretical predictions of the multi-physics field model.

[0114] In specific implementation, based on this observation system, the experimental steps are as follows:

[0115] System preparation: Check the connections of each component and ensure that the transformer oil in observation chamber 1 reaches the predetermined liquid level.

[0116] Establishing an electric field: applying a preset voltage through the high-voltage electrode 2 and the ground electrode 3 to establish an electric field environment simulating the actual operation of the transformer.

[0117] Temperature control: start the near-infrared heating tube 5 and use the infrared temperature sensor to monitor the oil temperature until it reaches a preset temperature value.

[0118] Bubble injection: Use the microinjection pump 8 to inject bubbles of a specific size and quantity into the observation cavity 1 to simulate the gas precipitation process in the transformer oil.

[0119] Data collection: Start the high-speed camera 9 to capture the movement of the bubbles under the action of the electric heating field. At the same time, record the parameters such as the electric field strength and oil temperature.

[0120] Image processing and analysis: The images captured by the high-speed camera 9 are transmitted to the computer 10, and the bubble motion trajectory is extracted using a dedicated image processing software.

[0121] Data analysis: Based on the extracted bubble motion trajectory, analyze the motion characteristics of the bubble under different electric field strengths, temperatures and oil flow velocities, such as speed, acceleration, trajectory shape, etc.

[0122] Model Validation and Optimization: Compare experimental data with theoretical predictions of multi-physics coupled models to verify model accuracy and optimize models as needed.

[0123] Corresponding to the method for simulating the movement of bubbles in transformer oil considering multi-physical field coupling in Example 1, the bubble movement observation system in transformer oil considering multi-physical field coupling provided in this embodiment accurately simulates the complex physical environment of the actual working conditions of transformer oil-paper insulation through components such as high-voltage electrode 2, near-infrared heating tube 5, and insulating paperboard 4. The system uses a micro-injection pump to accurately control bubble generation, uses a high-speed camera to capture the bubble movement trajectory, and combines computer image processing technology to achieve accurate observation and quantitative analysis of the movement characteristics of bubbles under the action of multi-physical fields. This innovative experimental platform not only provides a reliable basis for verifying the multi-physical field coupling theoretical model, but also greatly improves the depth and accuracy of the study of bubble movement in transformer oil, and provides important technical support for optimizing transformer design and improving operational reliability.

[0124] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0125] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0126] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0127] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0128] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for simulating bubble motion in transformer oil considering multi-physics field coupling, characterized in that: The method includes: Integrate the energy equation into the mass conservation and momentum conservation equations, and construct a multi-physics model that considers the coupling of electric field, thermal field and flow field; Introducing a k-ε turbulence model into the multi-physics field model to obtain a first optimized multi-physics field model; the k-ε turbulence model is an oil flow model in a large transformer; Introducing the phase field method into the first optimized multi-physics field model to obtain a second optimized multi-physics field model; Introducing various forces of bubble motion into the second optimized multi-physics field model to obtain a third optimized multi-physics field model; The parameters of the third optimized multi-physics field model are solved to obtain the bubble movement process in the transformer oil.

2. The method for simulating bubble movement in transformer oil considering multi-physical field coupling according to claim 1, characterized in that: The expression of the multi-physics model is: PρRT Where ρ is the fluid density; t is the time; v is the velocity; p is the pressure; μ is the fluid dynamic viscosity; g is the gravitational acceleration; F is the volume force; E is the total energy; kef f is the effective thermal conductivity; T is the temperature; Sh is the volume heat source; R is the molar gas constant; ρ0 is the liquid density at the reference pressure; n is the density index; κ is the bulk modulus under pressure; κ0 is the bulk modulus at the reference pressure; is the differential operator.

3. The method for simulating bubble movement in transformer oil considering multi-physical field coupling according to claim 1, characterized in that: The expression of the k-ε turbulence model is: Where: ρ is the fluid density; t is the time; G k , G b are the average velocity gradient and the turbulent kinetic energy generated by the buoyancy effect; Y M represents the effect of compressible turbulent pulsation expansion on the total dissipation rate; μt is the turbulent viscosity coefficient; C 1ε , C 2ε , C 3ε is the default value constant; the turbulent Prandtl number of turbulent kinetic energy k and dissipation rate ε is σk=1.0, σ ε =1.3;x i , i=1,2,3, representing three directions x, y, z; μ is the dynamic viscosity of the fluid.

4. The method for simulating bubble movement in transformer oil considering multi-physical field coupling according to claim 1, characterized in that: The phase field method uses φ∈[-1,1] to define the properties of two immiscible fluids. At the fluid interface, the function φ transitions from 1 to -1. In the phase field analysis, the Cahn-Hilliard equation is introduced to track the changes in the interface, comprehensively considering the effects of interface mobility and chemical potential.

5. The method for simulating bubble movement in transformer oil considering multi-physical field coupling according to claim 1, characterized in that: The various forces that affect bubble motion include electric force, buoyancy, surface tension, gravity, drag, and oil flow drag; Wherein, the electric field force and surface tension will cause the bubble to deform; The buoyancy, gravity, drag, drag and oil flow drag will cause the bubbles to move.

6. An observation system based on the method for simulating bubble motion in transformer oil considering multi-physical field coupling as claimed in any one of claims 1 to 5, characterized in that: The system comprises an observation chamber (1), a high-voltage electrode (2), a ground electrode (3), an insulating paperboard (4), a near-infrared heating tube (5), an infrared temperature sensor (6), a three-way ball valve (7), a microinjection pump (8), a high-speed camera (9) and a computer (10); The observation cavity (1) is made of a transparent acrylic plate and is filled with transformer oil; The high-voltage electrode (2) and the grounding electrode (3) are placed in the observation cavity (1), and an insulating paperboard (4) is added between the high-voltage electrode (2) and the grounding electrode (3) to simulate the actual transformer oil-paper insulation environment; The near-infrared heating tube (5) is installed above the observation cavity (1); the infrared temperature sensor (6) is used to monitor the oil-paper insulation temperature in real time; The three-way ball valve (7) is connected to the bottom of the observation chamber (1); the microinjection pump (8) is connected to the observation chamber (1) through the three-way ball valve (7); The high-speed camera (9) is aimed at the observation cavity (1); the computer (10) is electrically connected to the high-speed camera (9) for data collection and analysis.

7. The bubble movement observation system in transformer oil considering multi-physical field coupling according to claim 6 is characterized in that: The insulating paperboard (4) is a multi-layer structure, and the number of layers and the structure are adjusted to simulate oil-paper insulation systems of different thicknesses.

8. The bubble movement observation system in transformer oil considering multi-physical field coupling according to claim 6, characterized in that: The power of the near-infrared heating tube (5) is adjustable, and the heating temperature can be controlled to simulate the temperature field distribution under different load conditions of the transformer; The control system of the near-infrared heating tube (5) and the infrared temperature sensor (6) form a closed-loop control to achieve temperature regulation.

9. The bubble movement observation system in transformer oil considering multi-physical field coupling according to claim 6, characterized in that: The microinjection pump (8) is programmable and can simulate different bubble generation rates and sizes to study the movement characteristics of various bubble precipitation conditions.

10. The bubble movement observation system in transformer oil considering multi-physical field coupling according to claim 6, characterized in that: The high-speed camera (9) uses a high-frame-rate CMOS sensor and is capable of capturing the bubble movement process at the microsecond level; The computer (10) is equipped with special data analysis software, which can process the images collected by the high-speed camera (9) in real time, extract bubble motion parameters, and perform real-time comparative analysis with the theoretical predictions of the multi-physics field model.

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