Oil-immersed cooling underwater frequency converter temperature field simulation analysis method and system

Abstract

The invention belongs to the technical field of underwater cooling and thermal management, and particularly relates to an oil-immersed cooling underwater frequency converter temperature field simulation method and system, and the method comprises the steps: building a geometric model of an underwater frequency converter and an internal fluid domain model of the underwater frequency converter; carrying out grid division on a solid grid and a fluid domain of the underwater frequency converter model, and setting material attributes; setting a contact type and a friction condition between objects in the underwater frequency converter; the environment temperature of the underwater frequency converter, the convection coefficient of a shell and seawater, the natural convection and heat transfer coefficient of internal oil and the thermal load of each heating module are set, and the overall heat dissipation performance is verified and optimized through simulation. The technical problems that in the prior art, due to the fact that the thickness of a shell of a pressure-resistant cabin is large, the heat conduction path is long, the heat dissipation efficiency is low, and local overheating is caused due to the fact that the pressure-resistant cabin cannot adapt to water temperature changes and complex distribution of heating devices are solved; the heat dissipation simulation accuracy is improved; and the overall heat dissipation performance is optimized.

Description

Technical Field

[0001] The present invention belongs to the technical field of underwater cooling and thermal management, and in particular, relates to a temperature field simulation analysis method and system for an underwater frequency converter with oil immersion cooling. Background Art

[0002] In modern underwater equipment, the inverter is one of the core components, mainly responsible for regulating electrical energy to drive the normal operation of underwater motors. However, the particularity of the underwater environment places higher requirements on the heat dissipation of the inverter. The existing underwater inverter housing usually adopts a pressure-resistant cabin design to cope with the high-pressure environment of the deep sea. Although this pressure-resistant cabin design can effectively protect the internal components of the equipment from the external high pressure, due to the large thickness of the shell, the heat conduction path through the shell is long, resulting in low heat dissipation efficiency.

[0003] Existing heat dissipation methods mainly rely on attaching internal heat-generating devices directly to the pressure-resistant cabin shell, and dissipating heat through direct contact between the shell and the external water body. This heat dissipation effect depends on the thermal conductivity of the shell material. However, the shell is thick, and the heat needs to pass through a long conduction path to be transferred to the water body, so the heat transfer efficiency is low. In addition, when there are many heat-generating components inside the inverter and they are unevenly distributed, heat is easy to accumulate in the equipment, resulting in local overheating, further increasing the heat load of the equipment.

[0004] In addition, the water temperature in the underwater environment varies significantly due to factors such as depth, season and geographical location. It is difficult for traditional heat dissipation methods to maintain stable heat dissipation performance under different water temperature conditions. Especially when working for a long time in the deep sea, changes in external water temperature may significantly affect the heat dissipation efficiency. In an environment where high temperature is used for a long time, the electronic components of the underwater inverter may suffer from performance degradation, shortened lifespan, and even equipment failure due to continuous high temperature.

[0005] In summary, the main problems of the existing technology include: the pressure cabin shell is thick, resulting in a long heat conduction path and low heat dissipation efficiency; the water temperature changes significantly, and the traditional heat dissipation method is difficult to adapt to complex working conditions; the distribution of heating components is complex, the heat dissipation path is not ideal, and it is easy to cause local overheating. In response to these problems, it is necessary to further explore and optimize the heat dissipation solution to improve the overall heat dissipation performance and reliability of the underwater inverter. Summary of the invention

[0006] In view of the defects of the prior art, the present invention proposes a temperature field simulation and analysis method and system for an underwater inverter with oil-immersed cooling. The analysis is based on the heat dissipation insulating oil filled inside the underwater inverter, and the internal heat flow of the underwater inverter is simulated by optimizing modeling and simulation technology to improve the accuracy of the heat dissipation performance simulation and the overall heat dissipation effect.

[0007] In one aspect, the present invention provides a method for simulating and analyzing the temperature field of an underwater frequency converter with oil immersion cooling, the method comprising:

[0008] Step 1: Establish the geometric model of the underwater inverter and its internal fluid domain model;

[0009] Step 2: Mesh the solid mesh and fluid domain of the underwater inverter model and set the material properties;

[0010] Step 3: Set the contact type and friction conditions between the objects inside the underwater inverter;

[0011] Step 4: Set the ambient temperature of the underwater inverter, the convection coefficient between the shell and seawater, the natural convection and heat transfer coefficient of the internal oil, and the heat load of each heating module, and verify and optimize the overall heat dissipation performance through simulation.

[0012] Further, step 1 comprises:

[0013] Step 1.1: Construct the geometric model of the underwater frequency converter according to the simplification principle;

[0014] Step 1.2: According to the structure of the internal non-pressure-bearing shell and shielded shell of the inverter, determine the fluid domain boundary of the insulating oil inside the inverter, set the contact surface between the fluid domain and the simplified key components, and establish the internal fluid domain model.

[0015] Furthermore, in step 1.1, the simplification principles include: ignoring non-critical components, maintaining the structural features of critical components, and adjusting the size and shape of components.

[0016] Further, step 2 includes:

[0017] Step 2.1: Use hexahedral meshing for the shell of the underwater inverter, and use tetrahedral meshing for the internal key modules of the underwater inverter;

[0018] Step 2.2: Use tetrahedral mesh pairs to divide the fluid domain filled with insulating oil inside the shell;

[0019] Step 2.3: Define the overall structural materials of the subsea drive according to the pressure and temperature loads it will withstand in the deep sea environment.

[0020] Further, step 3 includes:

[0021] Step 3.1: Identify potential contact surfaces based on the geometric structure of each heat generating module inside the inverter and label the contact type for each contact surface;

[0022] Step 3.2: Set the contact stiffness parameters for each contact surface and set the friction coefficient for the contact surface with sliding potential;

[0023] Step 3.3: Set the thermal contact impedance and heat dissipation coefficient for the contact surface between each heating module and the heat dissipation insulating oil.

[0024] Further, step 4 includes:

[0025] Step 4.1: According to the seawater temperature at the working depth of the underwater inverter, set the external ambient temperature of the housing and the thermal convection parameters between the housing and the seawater;

[0026] Step 4.2: Based on the power loss of each heat-generating module, calculate the thermal power of each module and apply it as a thermal load to the simulation model;

[0027] Step 4.3: Set the thermal convection conditions between the housing of the underwater inverter and the seawater;

[0028] Step 4.4: Set the natural convection coefficient of the oil inside the underwater inverter and the heat transfer coefficient between the oil and each heating module;

[0029] Step 4.5: Apply all calculated heat loads and boundary conditions to the simulation model. Observe the heat flow path and overall temperature distribution through preliminary simulation to check for local overheating or uneven cooling. If so, adjust the heat load or convection parameters to optimize the model.

[0030] Furthermore, in step 1.1, the simplified underwater frequency converter includes a housing and a main heat-generating module inside the housing, wherein the main heat-generating module includes an inverter unit module, a reactor module, a control box module and a phase-shifting transformer.

[0031] Furthermore, in step 1, the internal fluid domain model of the underwater frequency converter is a three-dimensional structure in which the heat dissipating insulating oil is filled inside the shell of the underwater frequency converter.

[0032] Furthermore, the simulation model of the underwater frequency converter in step 4.5 is determined by the following formula:

[0033]

[0034] Where: ρ represents the material density (kg / m3); C p represents specific heat capacity (J / kg·℃); T represents temperature field (℃); k represents thermal conductivity (W / m·℃); P loss,i represents the power loss of the i-th heat generating module (W); V i represents the volume of the i-th heating module (m3); h sea represents the convective heat transfer coefficient between the shell and seawater (W / m2·℃); T shell Indicates the shell temperature (℃); T sea Indicates seawater temperature (℃); R th,jrepresents the thermal contact impedance between the jth heating module and the oil (℃ / W); T module represents the temperature of the jth heating module (℃); T oil Indicates oil temperature (℃).

[0035] On the other hand, the present invention also provides a temperature field simulation and analysis system for an underwater frequency converter with oil immersion cooling, comprising:

[0036] The geometric modeling module is used to establish the geometric model of the underwater frequency converter and its internal fluid domain model;

[0037] The meshing and material property setting module is used to mesh the solid and fluid domains of the underwater inverter and set the corresponding material properties;

[0038] The contact definition module is used to set the contact type and friction conditions between objects inside the underwater inverter;

[0039] The boundary condition setting and simulation module is used to set the ambient temperature of the underwater inverter, the convection coefficient between the shell and seawater, the natural convection and heat transfer coefficient of the internal oil, and the heat load of each heating module, and verify and optimize the overall heat dissipation performance through simulation.

[0040] The beneficial effects of the present invention are:

[0041] First, the method of the present invention establishes a geometric model and a fluid domain model of the underwater frequency converter, performs precise mesh division and material property setting, and combines the optimization of contact type and friction conditions to achieve accurate simulation of the natural convection of the internal oil and the thermal load of each heating module, thereby effectively improving the accuracy of the heat dissipation performance simulation, optimizing the overall heat dissipation effect, and ensuring the stable operation of the underwater frequency converter.

[0042] Second, in the preferred implementation, the method of the present invention uses the simplification principle to effectively remove non-critical components in the geometric modeling process and retain the structural characteristics of critical components, thereby simplifying the model complexity, reducing the consumption of computing resources and simulation time. At the same time, the size and shape of components are reasonably adjusted, and the fluid domain boundary setting is optimized to ensure that the simulation results have high accuracy and engineering feasibility, and improve the consistency of modeling efficiency and simulation effect.

[0043] Third, in the preferred implementation, the method of the present invention adopts a combination of hexahedron and tetrahedron grids through the grid division strategy of the shell and the internal key modules, which improves the adaptability and computational stability of the model grid and ensures the accuracy and efficiency in the simulation process. At the same time, the reasonable grid division of the fluid domain and the precise definition of material properties under deep-sea environmental conditions help to more realistically reflect the thermodynamic behavior of the underwater frequency converter under actual working conditions and optimize the reliability and accuracy of the simulation results.

[0044] Fourth, in the preferred implementation, the method of the present invention improves the accuracy of the heat conduction path by accurately identifying the contact surface of the heating module and marking the contact type. At the same time, the appropriate contact stiffness and friction coefficient are set for each contact surface, the mechanical stability between the modules is optimized, and the overall thermal management effect is further enhanced by setting the thermal contact impedance and heat dissipation coefficient of the oil contact surface, ensuring efficient heat transfer and heat dissipation performance, and improving the stable operation capability of the inverter in the deep sea environment.

[0045] Fifth, in the preferred implementation, the method of the present invention accurately simulates the heat conduction and heat dissipation behavior of the inverter under deep sea conditions by comprehensively setting the seawater environment temperature and the heat load of each heating module. By carefully adjusting the heat convection conditions between the shell and the seawater and the natural convection and heat transfer coefficient of the oil, a more optimized temperature distribution and uniform heat flow path are achieved, reducing the risk of local overheating.

[0046] Sixth, in the preferred implementation, the method of the present invention uses the three-dimensional structure of the heat dissipation insulating oil filled inside the shell of the underwater frequency converter as the analysis basis, and realizes the simulation and evaluation of the heat dissipation performance inside the frequency converter. By filling the heat dissipation insulating oil, the fluid forms a stable circulation inside the shell, effectively taking away the heat generated inside the frequency converter, reducing the temperature of the equipment and extending the service life. At the same time, the insulating oil also provides excellent electrical insulation performance, avoiding the occurrence of electrical short circuits and arc phenomena, and ensuring the safe operation of the equipment.

[0047] Seventh, the system of the present invention integrates geometric modeling, meshing, contact definition and boundary condition setting functions, and provides an integrated temperature field simulation analysis solution. Through modular design, users can efficiently complete the entire process from modeling to simulation optimization, significantly improving simulation accuracy and efficiency. At the same time, the system helps to quickly discover and solve heat dissipation problems, improve the heat dissipation performance and operational reliability of underwater inverters, and meet actual engineering needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a flow chart of the temperature field simulation analysis method of the oil-immersed cooling underwater frequency converter of the present invention;

[0049] Figure 2 1 is an initial appearance structure and a simplified appearance structure diagram of the underwater frequency converter housing of an embodiment of the present invention;

[0050] Figure 3 1. The complete internal component structure and simplified internal component structure diagram of the underwater frequency converter according to the embodiment of the present invention;

[0051] Figure 4 is a schematic diagram of a geometric model of an underwater frequency converter not filled with insulating oil and filled with insulating oil according to an embodiment of the present invention;

[0052] Figure 5 is a structural diagram of the hexahedral mesh of the shell and the tetrahedral mesh of the internal module of an embodiment of the present invention;

[0053] Figure 6 is a tetrahedral mesh division structure diagram of a fluid domain in an embodiment of the present invention;

[0054] Figure 7 It is a schematic diagram of the material assignment of the housing and internal structure of an embodiment of the present invention and the heat dissipation type insulating oil;

[0055] Figure 8 is a schematic diagram of the contact binding definition between the inverter unit module and the housing according to an embodiment of the present invention;

[0056] Fig. 9 is a schematic diagram of contact definition between a reactor module and a fluid domain according to an embodiment of the present invention;

[0057] Fig.10 is a schematic diagram of contact definition between a phase-shifting transformer and a bottom of an oil tank according to an embodiment of the present invention;

[0058] Fig.11 1 is a diagram of four main heat generation modules of the underwater frequency converter according to an embodiment of the present invention and their corresponding power loss;

[0059] Fig.12 is a schematic diagram of seawater convection boundary loading according to an embodiment of the present invention;

[0060] Fig.13 is a schematic diagram of oil convection boundary loading according to an embodiment of the present invention;

[0061] Fig.14 is a schematic diagram of applying thermal load to an internal module of an underwater frequency converter according to an embodiment of the present invention;

[0062] Fig.15 It is a schematic diagram of the temperature field distribution inside the underwater frequency converter of an embodiment of the present invention. DETAILED DESCRIPTION

[0063] In order to enable those skilled in the art to better understand the technical solution of the present application, the present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0064] In the description of this application, the terms "first", "second", and "third" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance; the term "plurality" refers to two or more, unless otherwise expressly defined. Terms such as "installed", "connected", "connected", and "fixed" should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; "connected" can be a direct connection or an indirect connection through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0065] In the description of the present application, it should be understood that the directions or positional relationships indicated by the terms "up", "down", "left", "right", "front", "back", etc. are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or unit referred to must have a specific direction, be constructed and operated in a specific orientation, and therefore, should not be understood as a limitation on the present application.

[0066] In the description of this specification, the description of the terms "one embodiment / method", "some embodiments / methods", "specific embodiments / methods", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment / method or example are included in at least one embodiment / method or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment / method or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments / methods or examples in a suitable manner.

[0067] As the instruction manual Figure 1 The purpose of the present invention is to provide a method for simulating and analyzing the temperature field of an underwater frequency converter with oil immersion cooling, the method comprising:

[0068] Step 1: Establish the geometric model of the underwater inverter and its internal fluid domain model.

[0069] The purpose of step 1 is to accurately reflect the structural characteristics and internal heat exchange environment of the underwater frequency converter during the simulation process of temperature field analysis, so as to improve the accuracy of simulation analysis. Due to the complex internal structure and numerous components of the underwater frequency converter, directly using a complete geometric model for simulation will greatly increase the computational burden and may affect the stability of the results. Therefore, the present invention retains the geometric and thermal characteristics of key components by reasonably simplifying the geometric model. The interior of the underwater frequency converter is filled with heat-dissipating insulating oil, which is used to cool the main heat-generating components. Based on this, a fluid domain model is constructed to simulate the natural convection and heat conduction of the heat-dissipating insulating oil, thereby providing a reliable basis for subsequent temperature field analysis.

[0070] The geometric model of the subsea inverter can be designed using SolidWorks, AutoCAD or CATIA software, and the internal fluid domain model can be modeled using fluid simulation software (such as Fluent or Star-CCM+).

[0071] Step 1 specifically includes:

[0072] Step 1.1: Construct the geometric model of the underwater inverter according to the simplification principle.

[0073] The simplification principle includes: ignoring non-critical components, maintaining the structural features of critical components, and adjusting the size and shape of components. Based on the simplification principle, the geometric model construction process of the underwater inverter is as follows:

[0074] First, the main structural components of the underwater inverter are determined. The underwater inverter includes non-pressure-bearing shell, shielded shell, pressure compensation device, inverter unit module, reactor module, phase-shifting transformer, control box module, frame circuit breaker and other components. The non-pressure-bearing shell is used to provide protection and support. The shielded shell is used to separate the strong and weak electricity partitions to prevent electromagnetic interference. The pressure compensation device is used to adjust the internal pressure so that the internal system is balanced with the external pressure of the deep sea. The inverter unit module is used to convert DC power into AC power to drive the underwater motor to run, and is the main source of heat for power conversion. The reactor module is used to limit current mutations, reduce electromagnetic interference and grid harmonics, and maintain the electrical stability of the system. The phase-shifting transformer is used to reduce the impact of harmonics through phase-shifting control, optimize power transmission efficiency and reduce power loss. The control box module is used to integrate various control circuits and signal processing units to ensure the precise control and monitoring functions of the system. The frame circuit breaker is used to provide overload and short-circuit protection to ensure the safe operation of the underwater inverter. Among them, the inverter unit module and the reactor module are the main sources of heat, with high heat dissipation requirements, which directly affect the temperature field distribution of the entire system. The phase-shifting transformer has a significant impact on the power quality by changing the phase. Its heat comes from conversion loss, and effective heat dissipation must be ensured under high load. The control box module generates relatively low heat, but due to its high integration, local overheating can easily affect system stability, so proper heat dissipation design is required. The main function of the frame circuit breaker is circuit protection. Its heat mainly accumulates when the opening and closing actions are frequent, so it is necessary to ensure that its heat does not affect the surrounding modules.

[0075] Therefore, components with little impact on temperature field analysis, such as small connectors, fixed brackets and external pipelines, are ignored to reduce the complexity of the geometric model. These components have little impact on heat conduction, so their omission will not affect the simulation accuracy. In the process of model simplification, the main heat-generating modules include inverter unit module, reactor module, phase-shifting transformer and control box module, and their key geometric features are retained to ensure the reliability of simulation data. Appropriate size reduction or shape simplification is performed on the geometric features of the core heat-generating modules. Under the premise of keeping the thermal properties consistent with the actual situation, the details of the components are simplified to achieve higher computational efficiency in the simulation. For example, the components with complex structures such as reactor modules and control box modules are simplified into solid models suitable for temperature field analysis while maintaining the representativeness of their volume and position.

[0076] As the instruction manual Figure 2-3 , Figure 2 (a) in the figure shows the initial appearance structure of the housing 1 of the underwater inverter. The external pipes, brackets, valve bodies and other components are clearly visible. These components have little effect in the temperature field simulation and can be ignored when simplifying the model. Figure 2 (b) shows the simplified appearance structure of the housing 1, retaining the main structure of the housing 1 to provide necessary physical protection and support for the internal heat-generating components. Figure 3 (a) in the figure shows the complete internal component structure of the underwater inverter, including all core heat-generating modules and auxiliary components. Figure 3 (b) in the figure shows the simplified internal component structure of the underwater inverter, retaining the main heat-generating modules, including the inverter unit module 2, the reactor module 3, the control box module 4 and the phase-shifting transformer 5, and removing the minor components that do not affect the temperature field analysis.

[0077] Step 1.2: According to the structure of the internal non-pressure-bearing shell and shielded shell of the inverter, determine the fluid domain boundary of the insulating oil inside the inverter, set the contact surface between the fluid domain and the simplified key components, and establish the internal fluid domain model.

[0078] As the instruction manual Figure 4 , Figure 4 (a) is a schematic diagram of the underwater inverter geometric model without insulating oil filling. Figure 4 (b) is a schematic diagram of the underwater inverter geometric model filled with insulating oil. Figure 4 As can be seen from (b), the fluid domain boundary surrounds the key heat-generating modules such as the inverter unit module, reactor module, control box module and phase-shifting transformer. Through the contact surface between the fluid domain boundary and the key heat-generating modules, the insulating oil can absorb and conduct the heat generated by the modules, forming an internal natural convection heat dissipation effect. This design ensures the path for heat to be transferred from each heat-generating module to the casing.

[0079] Step 2: Mesh the solid mesh and fluid domain of the underwater inverter model and set the material properties.

[0080] Step 2 aims to achieve higher calculation accuracy and efficiency in the finite element analysis process by reasonably meshing the solid and fluid domains of the underwater inverter. At the same time, to ensure that the simulation results are consistent with the actual situation, the main materials of the structure are defined to reflect their real physical properties under different loads and temperature environments. These meshing and material property definitions provide a scientific and reliable basis for subsequent temperature field and mechanical analysis.

[0081] In this step, mainstream finite element simulation software (such as ANSYS and Abaqus) is used for meshing and material property setting.

[0082] Step 2 specifically includes:

[0083] Step 2.1: Use hexahedral meshing for the shell of the underwater inverter, and use tetrahedral meshing for the internal key modules of the underwater inverter.

[0084] It should be noted that the use of hexahedral meshes to divide the shell of the underwater inverter is because it can better adapt to large-area planar structures and improve the calculation efficiency of the shell of the underwater inverter. The mesh size of the shell of the underwater inverter is defined according to the actual dimensions of its length, width, and height. The use of tetrahedral meshes to divide the internal key modules of the underwater inverter is because the geometric shapes of the inverter unit, reactor module, phase-shifting transformer, and control box are complex and most of them bear loads. In order to ensure that the mesh density of the main internal heat-generating components is high enough, the heat generation and conduction details of each module can be more accurately captured during the simulation process. Selecting a smaller mesh size helps to improve the simulation accuracy of the local temperature field and ensure that the local heat flux density distribution can be accurately simulated.

[0085] As the instruction manual Figure 5 , Figure 5 The hexahedral mesh of the subsea inverter shell and the tetrahedral mesh of the internal module are shown. The shell mesh size is defined as 60mm based on its actual length, width and height, and the refined mesh size of the internal module is 40mm.

[0086] Step 2.2: Use tetrahedral mesh pairs to divide the fluid domain filled with insulating oil inside the shell.

[0087] As the instruction manual Figure 6 , Figure 6 The tetrahedral meshing of the fluid domain is shown, with an overall mesh size of 80 mm to balance computational complexity and simulation accuracy. The meshing scheme of the fluid domain takes into account the flow characteristics of the insulating oil and its effect on heat transfer efficiency.

[0088] Step 2.3: Define the overall structural materials of the subsea drive according to the pressure and temperature loads it will withstand in the deep sea environment.

[0089] In this application, the overall structural materials of the underwater inverter are 316L stainless steel, 980 steel (10CrNi5MoV) and TC4 titanium alloy. The material selection is allocated according to the environmental requirements and component functions as follows: 316L stainless steel is used for the shell of the underwater inverter, which can provide excellent corrosion resistance and mechanical strength, is suitable for long-term operation in deep-sea high-pressure environments, and has excellent heat dissipation performance. 980 steel (10CrNi5MoV) is used for internal pressure-bearing components and main structural supports. It has high strength and toughness and is suitable for maintaining stability under extreme pressure and impact loads. TC4 titanium alloy is used for key connecting components and some high-strength, lightweight modules. It combines high corrosion resistance and strength characteristics and is suitable for deep-sea applications that require lightweight design.

[0090] According to the requirements of the simulation analysis, the physical and mechanical properties of each material are provided, such as the material parameter Table 1, including density, thermal conductivity, Young's modulus, Poisson's ratio, yield strength, ultimate strength, thermal expansion coefficient, nonlinear tangent modulus, and specific heat capacity.

[0091] In Table 1, thermal conductivity is used to reflect the thermal conductivity of materials in deep-sea environments, especially 316L stainless steel and 980 steel are used in areas with high thermal conductivity requirements. Yield and ultimate strength are used to evaluate the structural stability of materials in high-pressure environments to prevent equipment from being damaged by external impacts. Thermal expansion coefficient is used to define the volume change of materials under temperature changes, with special attention paid to the effect of thermal expansion of heat-dissipating insulating oil on internal pressure and heat dissipation performance. These materials will be used in the simulation model to realistically reproduce the behavior of materials under deep-sea conditions:

[0092] Table 1

[0093]

[0094]

[0095] As the instruction manual Figure 7 , Figure 7 The schematic diagram of the material assignment of the underwater inverter housing and internal structure and heat dissipation insulating oil is shown. The green part represents the underwater inverter housing and internal structure, which are mainly used to provide mechanical strength and corrosion resistance to cope with the deep sea high pressure and seawater corrosion environment. These parts are responsible for protecting the internal components and stabilizing the entire device. The blue part represents the heat dissipation insulating oil filled in the housing, which is used to cool the internal heating components.

[0096] Step 3: Set the contact type and friction conditions between the objects inside the underwater inverter.

[0097] In the simulation analysis of underwater inverters, the contact and friction conditions between objects directly affect the accuracy of overall heat conduction and mechanical behavior. Considering the close connection and interaction between the components in the equipment, by setting appropriate contact and friction conditions, the heat conduction path, stress distribution and mechanical stability of each component under deep-sea high-pressure conditions can be realistically simulated. The purpose of step 3 is to optimize the simulation accuracy and ensure the accuracy of the model under different load conditions by setting the contact type and friction parameters between objects.

[0098] Step 3 specifically includes:

[0099] Step 3.1: Based on the geometric structure of each heat-generating module inside the inverter, identify potential contact surfaces and mark the contact type for each contact surface.

[0100] It should be noted that this step marks the contact type of each contact surface in the simulation software (such as ANSYS Workbench). For example: In ANSYS Workbench, users can use the "Contact Definition" tool to specify different contact types, such as "Rigid Contact", "Friction Contact" or "Frictionless Contact". ANSYS provides an automatic contact detection function that can quickly identify contact surfaces in the model and allow users to manually adjust contact properties to suit specific engineering needs.

[0101] Specifically, the contact parts of each heating module in the underwater frequency converter of the present invention include: the contact surface between the inverter unit module and the fixed bracket, the contact surface between the reactor module and the casing, the contact interface between the phase-shifting transformer and the heat dissipation insulating oil, etc. The contact surface between the inverter unit module and the fixed bracket mainly affects the structural stability and heat conduction path of the module. The contact surface between the reactor module and the casing affects the force distribution and heat dissipation efficiency of the casing. The contact interface between the phase-shifting transformer and the heat dissipation insulating oil needs to pay attention to heat conduction and heat exchange of the cooling medium. When marking the contact type, for tightly connected parts, it is marked as "rigid contact"; for parts that may slide relative to each other, it is marked as "sliding contact".

[0102] Step 3.2: Set the contact stiffness parameters for each contact surface and the friction coefficient for contact surfaces with sliding potential.

[0103] Setting the contact stiffness ensures that close-fitting components do not deform or move unreasonably under mechanical loads. The contact stiffness value is usually determined based on the material elastic modulus and geometric properties. For example, high stiffness values ​​should be set in areas where loads are transferred to critical structures to maintain system stability.

[0104] The friction coefficient for metal-to-metal contact is generally set between 0.2 and 0.3, and the specific value can be adjusted according to the actual working conditions, especially for parts that bear critical loads or high-frequency vibrations. If the contact surface is coated with lubricants or anti-corrosion coatings, the friction coefficient should be fine-tuned according to the material manual or experimental data.

[0105] Step 3.3: Set the thermal contact impedance and heat dissipation coefficient for the contact surface between each heating module and the heat dissipation insulating oil.

[0106] It should be noted that low thermal contact impedance is used for efficient heat conduction, while high thermal contact impedance simulates the thermal resistance effect of air gaps or non-close contact areas. This parameter needs to be determined based on the actual assembly accuracy and surface finish to simulate the thermal resistance effect. The heat dissipation coefficient should comprehensively consider the thermal conductivity, viscosity and fluid dynamics of the cooling medium to ensure that the simulation results are consistent with the actual performance. The embodiment of this application uses 20W / (m2·℃) to simulate the actual heat dissipation effect.

[0107] As the instruction manual Figure 8 , Figure 8 A schematic diagram showing the definition of the binding contact between the inverter unit module and the casing. Figure 8 The red area in the figure represents the contact surface between the geometric surface of the inverter unit module and the shell. These contact surfaces are usually set to be tightly combined to ensure that the module can be stably connected under mechanical loads and temperature changes, and to achieve effective force and heat transfer. The blue area represents the contact surface inside the corresponding shell, which is the other end of the contact setting. This target surface is the area that receives the mechanical load and heat conduction from the inverter unit. The binding contact type between the inverter unit module and the shell is set to "rigid contact" or "no slip contact". This setting ensures that there is no relative displacement between the inverter unit module and the shell, especially in terms of force and heat dissipation. The mechanical condition in the binding contact condition between the inverter unit module and the shell is set to have high contact stiffness, which can prevent the module from loosening or shifting in the deep sea high pressure environment. The thermal condition in the binding contact condition between the inverter unit module and the shell is set to a low thermal contact impedance value, which can ensure that the heat generated by the inverter unit can be quickly transferred to the shell.

[0108] As the instruction manual Fig. 9 , Fig. 9 Schematic diagram showing the contact definition between the reactor module and the fluid domain. Fig. 9The red area in the figure represents the contact surface between the reactor module and the fluid domain (heat dissipation insulating oil). This contact surface is a key area for heat conduction. The heat generated by the reactor module during operation will be transferred to the fluid domain through this surface. The blue area represents the fluid domain, which is the area where the heat dissipation insulating oil is located. The fluid domain further transfers the heat absorbed from the reactor module to other cooling paths, such as the casing, and finally dissipates it to the external environment through natural convection and thermal conductivity. The binding contact type between the reactor module and the fluid domain is set to "frictionless contact", which can simulate the fluidity of the heat dissipation insulating oil around the reactor module while ensuring realistic physical performance under force or environmental changes. The thermal conditions in the binding contact conditions between the reactor module and the fluid domain are set to a low thermal contact impedance value to maximize the heat conduction effect.

[0109] As the instruction manual Fig.10 , Fig.10 Schematic diagram showing the contact definition between the phase-shifting transformer and the tank bottom. Fig.10 The red area in the figure represents the contact surface between the phase-shifting transformer and the bottom of the oil tank. This contact surface is the main supporting area for the phase-shifting transformer and must be able to effectively transfer mechanical loads and participate in the heat conduction process. The blue area represents the structure on which the phase-shifting transformer relies, which bears the weight and heat conduction load from the transformer, and further transfers the heat to the heat-dissipating insulating oil in the oil tank, and then dissipates it to the external environment. The binding contact type between the phase-shifting transformer and the bottom of the oil tank is set to "rigid contact" or "fixed contact". This is because the phase-shifting transformer is subject to greater external pressure and vibration in the deep-sea environment. This setting can ensure that the phase-shifting transformer remains stable during operation without displacement or sliding. The phase-shifting transformer generates heat during operation and conducts it through the contact surface with the bottom of the oil tank. Therefore, the thermal condition thermal contact impedance in the binding contact condition between the phase-shifting transformer and the bottom of the oil tank is set according to the material properties. A lower thermal resistance value helps the heat to be efficiently transferred to the bottom of the oil tank and dispersed and cooled by the oil.

[0110] Step 4: Set the ambient temperature of the underwater inverter, the convection coefficient between the shell and seawater, the natural convection and heat transfer coefficient of the internal oil, and the heat load of each heating module, and verify and optimize the overall heat dissipation performance through simulation.

[0111] The purpose of step 4 is to establish an accurate heat conduction and convection model to ensure that the heat dissipation effect of the underwater inverter in the actual operating environment can be accurately simulated and optimized. By reasonably setting the external environmental conditions and internal heat load parameters, the temperature distribution of the equipment can be predicted, potential overheating areas can be identified, and effective design adjustments can be made to improve the heat dissipation performance.

[0112] Step 4 specifically includes:

[0113] Step 4.1: According to the seawater temperature at the working depth of the underwater inverter, set the external ambient temperature of the housing and the thermal convection parameters between the housing and the seawater.

[0114] The ambient temperature outside the housing is set according to the actual seawater temperature of the deep sea environment where the underwater inverter is located. This temperature value will affect the heat convection process between the housing and the surrounding seawater, and thus affect the heat dissipation efficiency. According to the actual seawater temperature of the simulation environment, the convection heat transfer coefficient between the housing and the seawater is set. This parameter simulates the heat exchange process between the seawater and the housing to ensure that the heat can be efficiently dissipated from the housing to the surrounding seawater. The heat convection parameters can be adjusted according to the different simulated water depths and flow rates to reflect the actual seawater's cooling capacity for the equipment.

[0115] Step 4.2: Based on the power loss of each heat-generating module, calculate the thermal power of each module and apply it as a thermal load to the simulation model.

[0116] The thermal power of each module is determined by the following formula:

[0117]

[0118] Where: Q represents the thermal power input per unit volume; P represents the total power loss of the module; V represents the volume of the module.

[0119] It should be noted that the power loss of each heating module is a known parameter, usually provided by the module manufacturer. The thermal power of each module is converted into a heat load using formula (1), and the heat load is distributed to each heating module (such as inverter unit, reactor, etc.) to ensure that the heat distribution conforms to the actual usage and accurately reflects the heat input of the heat source.

[0120] As the instruction manual Fig.11 , Fig.11 The four main heat-generating modules in the underwater inverter and their corresponding power losses are shown. The power loss of the inverter module and phase-shifting transformer is 4.286kW, the power loss of the reactor module is 3kW, and the power loss of the control box module is 150W.

[0121] Step 4.3: Set the thermal convection condition between the housing of the submersible inverter and the seawater.

[0122] For example, based on the seawater temperature of 10°C, the heat flux coefficient is set to 500W / (m2·°C) to truly simulate the cooling effect of seawater on the shell. The convection coefficient can be adjusted according to different water depths and water flow speeds to ensure that the simulation model can truly reproduce the heat exchange behavior between the shell and seawater.

[0123] As the instruction manual Fig.12 , Fig.12This is a schematic diagram of seawater convection boundary loading. The seawater ambient temperature marked in the figure is 10°C, which is the reference temperature when the equipment exchanges heat with the surrounding seawater in a deep-sea environment. The marked seawater convection parameter is 500W / (m2·℃), which indicates the intensity of thermal convection between the shell and the surrounding seawater. The yellow area indicates the heat dissipation effect of the equipment shell in contact with seawater. The convection coefficient of 500W / (m2·℃) shows that the inverter design has taken into account the demand for efficient heat dissipation under deep-sea conditions. The uniform distribution of colors shown in the figure represents that the shell has a consistent temperature gradient at the set time point, which means that the inverter can effectively manage internal heat and maintain a stable temperature field through thermal convection between the shell and seawater under deep-sea conditions.

[0124] Step 4.4: Set the natural convection coefficient of the oil inside the underwater inverter and the heat transfer coefficient between the oil and each heating module.

[0125] In this application, since there is no active convection equipment inside the inverter, the natural convection of the oil is caused by the density difference of the oil. For example, the convection coefficient is set to 20W / (m2·℃) to reflect the natural flow and heat exchange behavior of the oil under the temperature gradient. By defining the heat transfer coefficient between the oil and each heating module, it is ensured that the heat dissipation insulating oil can effectively absorb and disperse heat, and the thermal conductivity of the heat dissipation insulating oil is used for calculation to maintain the accuracy of the heat conduction process.

[0126] As the instruction manual Fig.13 , Fig.13 Schematic diagram of oil convection boundary loading. Fig.13 The heat input of internal modules (such as inverter units, reactors, phase-shifting transformers, control boxes, etc.) is shown in the figure. The marked yellow areas represent the heat load of each module, and the heat input parameters given in the legend are 32°C and 0.025W / (m2·℃). This setting shows the heat generated continuously by each heat-generating module during operation and is used to simulate the overall temperature field distribution. The color scale at the bottom (from 7500 to 30000kW / m3) indicates the temperature gradient in different areas, reflecting the distribution of heat throughout the system. Darker colors represent areas of higher heat generation, which usually correspond to major heat-generating components.

[0127] Step 4.5: Apply all calculated heat loads and boundary conditions to the simulation model. Observe the heat flow path and overall temperature distribution through preliminary simulation to check for local overheating or uneven cooling. If so, adjust the heat load or convection parameters to optimize the model.

[0128] The simulation model of heat transfer of the underwater inverter is expressed by the following formula:

[0129]

[0130] Where: ρ represents the material density (kg / m3); C p represents specific heat capacity (J / kg·℃); T represents temperature field (℃); k represents thermal conductivity (W / m·℃); P loss,i represents the power loss of the i-th heat generating module (W); V i represents the volume of the i-th heating module (m3); h sea represents the convective heat transfer coefficient between the shell and seawater (W / m2·℃); T shell Indicates the shell temperature (℃); T sea Indicates seawater temperature (℃); R th,j represents the thermal contact impedance between the jth heating module and the oil (℃ / W); T module represents the temperature of the jth heating module (℃); T oil Indicates oil temperature (℃).

[0131] Specifically, The temperature change rate is described, indicating the transient thermal behavior of the subsea inverter.

[0132] represents heat transfer by conduction, using the thermal conductivity k to describe the diffusion of the temperature gradient. The heat conduction term is determined by the following equation:

[0133]

[0134] In the heat conduction In the temperature gradient They represent the rate of change of temperature in the x, y, and z directions, respectively. These gradients are used to calculate how heat is transferred and diffused in space.

[0135] It represents the summary of the power loss of all n heat generation modules (such as inverter units, reactors, control modules, etc.) converted into volume heat source generation rate, reflecting that the power loss of the heat generation module is converted into heat and applied to the system. sea (T shell -T sea ) represents the convective heat transfer between the shell and the seawater, reflecting the heat exchange between the shell and the surrounding seawater. Represents the heat transfer between each heating module and the oil through the thermal contact impedance R th,j To calculate heat flow, temperature difference (T module -T oil ) drives the heat flow from the heating module to the oil, reflecting the contact interface characteristics between the module and the oil.

[0136] In step 4.5, the process of optimizing the model includes:

[0137] S1: Identify local overheating areas: Analyze the temperature field and locate areas with excessively high temperatures through simulation results. Check whether these areas are located around heat-generating modules or at bottlenecks in the heat flow path.

[0138] S2: Adjust heat load distribution: If the temperature of a heating module is too high, its heat load needs to be redistributed to optimize the heat source distribution for more uniform heat dissipation. The location of the heating module or the heat dissipation design can be adjusted based on the specific heat load analysis.

[0139] S3: Optimize the convection heat transfer coefficient: For the convection heat transfer between the shell and the seawater, the convection coefficient h can be optimized by adjusting the seawater flow rate or depth conditions. sea , increasing the seawater flow rate or using high-efficiency heat dissipation coatings can improve the heat exchange efficiency.

[0140] S4: Adjust material properties: Consider replacing the original materials with materials with better thermal conductivity, especially in key parts of the housing and heat-generating modules to enhance the overall heat dissipation effect.

[0141] S5: Optimize geometry: Check the geometry, especially the internal flow channel design, to ensure that there are no obvious obstructions or dead zones in the oil flow path. The flow channel can be redesigned to enhance the natural convection capacity of the oil and ensure that heat is quickly transferred to the heat dissipation housing.

[0142] S6: Use multiple simulation iterations: gradually adjust each parameter and perform multiple simulation iterations to verify the effect of each adjustment. After each simulation, analyze the new temperature field and heat flow path until a uniform temperature distribution and optimal heat dissipation performance are achieved.

[0143] Instructions attached Fig.14 , Fig.14The schematic diagram of heat load application for each internal component. The heat input of each module is represented by different symbols and thermal power density, as follows: A: inverter unit module 36640W / m3, B: inverter unit module 37000W / m3, C: inverter unit module 58250W / m3, D: reactor module 14290W / m3, E: control box module 7070W / m3, F: phase-shifting transformer 12869W / m3, these values ​​represent the heat generated by each module during operation. The three modules of inverter unit module (A, B, C) have high thermal power density and are distributed in the upper and middle areas of the equipment. This means that these modules are the main source of heat and place high demands on the cooling system. In particular, the thermal power density of 58250W / m3 requires focus on cooling effect and rapid dispersion of heat. The reactor module (D) is located in the middle area, with a thermal power density of 14290W / m3. Although the heat generation is relatively low, it still needs to be effectively dissipated through natural convection and oil cooling systems. Control box module (E): The thermal power density is 7070W / m3, the heat generation is less, and it is distributed in the lower area of ​​​​the equipment. The thermal management requirements of this module are relatively low, but the temperature still needs to be kept stable to ensure the normal operation of the circuit. Phase-shifting transformer (F): Located in the lower area, the thermal power density is 12869W / m3, and temperature control is required through the oil cooling system to prevent temperature rise from affecting the performance of the transformer.

[0144] Instructions attached Fig.15 , Fig.15 The temperature field distribution inside the underwater inverter is shown, and different colors are used to represent the temperature gradient of each area. The color gradually transitions from blue (low temperature area) to red (high temperature area), which intuitively reflects the heat distribution inside the equipment. The inverter unit module and the upper structure at the top clearly show a higher temperature, and the color is close to red. This shows that these components are the main source of heat, the heat is concentrated, and special attention needs to be paid to the cooling design to avoid local overheating of the equipment. The lower area in the figure, especially the reactor and the phase-shifting transformer, has a relatively uniform temperature distribution of blue or green, indicating that these components have good heat dissipation and the heat has been effectively dispersed by the cooling system.

[0145] Another object of the present invention is to provide a temperature field simulation and analysis system for an underwater frequency converter with oil immersion cooling, the system comprising:

[0146] The geometric modeling module is used to establish the geometric model of the underwater frequency converter and its internal fluid domain model.

[0147] The meshing and material property setting module is used to mesh the solid and fluid domains of the underwater frequency converter and set the corresponding material properties.

[0148] The contact definition module is used to set the contact type and friction conditions between objects inside the underwater inverter.

[0149] The boundary condition setting and simulation module is used to set the ambient temperature of the underwater inverter, the convection coefficient between the shell and seawater, the natural convection and heat transfer coefficient of the internal oil, and the heat load of each heating module, and verify and optimize the overall heat dissipation performance through simulation.

[0150] The present invention uses precise modeling and optimized simulation to truly reproduce the natural convection behavior of the heat dissipation insulating oil filled inside the inverter, thereby improving the heat transfer efficiency. Appropriate thermal contact impedance and heat dissipation coefficient settings are adopted to ensure efficient heat conduction of the oil between the heating modules, optimize the overall temperature distribution, effectively reduce the risk of local overheating, and ensure the stable heat dissipation performance of the underwater inverter in the deep sea environment.

[0151] The above is only an embodiment of the present invention, and the common sense such as the known specific structure and characteristics in the scheme is not described in detail here. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive, and the scope of the present invention is defined by the attached claims rather than the above description, so it is intended to include all changes within the meaning and scope of the equivalent elements of the claims. Any figure mark in the claims should not be regarded as limiting the claims involved.

Claims

1. A method for simulating and analyzing the temperature field of an underwater frequency converter with oil immersion cooling, characterized in that: Methods include: Step 1: Establish the geometric model of the underwater inverter and its internal fluid domain model; Step 2: Mesh the solid mesh and fluid domain of the underwater inverter model and set the material properties; Step 3: Set the contact type and friction conditions between the objects inside the underwater inverter; Step 4: Set the ambient temperature of the underwater inverter, the convection coefficient between the shell and seawater, the natural convection and heat transfer coefficient of the internal oil, and the heat load of each heating module, and verify and optimize the overall heat dissipation performance through simulation.

2. The temperature field simulation analysis method of an oil-immersed cooling underwater frequency converter according to claim 1 is characterized in that: Step 1 includes: Step 1.1: Construct the geometric model of the underwater frequency converter according to the simplification principle; Step 1.2: According to the structure of the internal non-pressure-bearing shell and shielded shell of the inverter, determine the fluid domain boundary of the insulating oil inside the inverter, set the contact surface between the fluid domain and the simplified key components, and establish the internal fluid domain model.

3. The temperature field simulation analysis method of an oil-immersed cooling underwater frequency converter according to claim 2 is characterized in that: In step 1.1, the simplification principles include: ignoring non-critical components, maintaining the structural features of critical components, and adjusting the size and shape of components.

4. The temperature field simulation analysis method of an oil-immersed cooling underwater frequency converter according to claim 1 is characterized in that: Step 2 includes: Step 2.1: Use hexahedral meshing for the shell of the underwater inverter, and use tetrahedral meshing for the internal key modules of the underwater inverter; Step 2.2: Use tetrahedral mesh pairs to divide the fluid domain filled with insulating oil inside the shell; Step 2.3: Define the overall structural materials of the subsea drive according to the pressure and temperature loads it will withstand in the deep sea environment.

5. The temperature field simulation analysis method of an oil-immersed cooling underwater frequency converter according to claim 1 is characterized in that: Step 3 includes: Step 3.1: Identify potential contact surfaces based on the geometric structure of each heat generating module inside the inverter and label the contact type for each contact surface; Step 3.2: Set the contact stiffness parameters for each contact surface and set the friction coefficient for the contact surface with sliding potential; Step 3.3: Set the thermal contact impedance and heat dissipation coefficient for the contact surface between each heating module and the heat dissipation insulating oil.

6. The temperature field simulation analysis method of an oil-immersed cooling underwater frequency converter according to claim 1 is characterized in that: Step 4 includes: Step 4.1: According to the seawater temperature at the working depth of the underwater inverter, set the external ambient temperature of the housing and the thermal convection parameters between the housing and the seawater; Step 4.2: Based on the power loss of each heat-generating module, calculate the thermal power of each module and apply it as a thermal load to the simulation model; Step 4.3: Set the thermal convection conditions between the housing of the underwater inverter and the seawater; Step 4.4: Set the natural convection coefficient of the oil inside the underwater inverter and the heat transfer coefficient between the oil and each heating module; Step 4.5: Apply all calculated heat loads and boundary conditions to the simulation model. Observe the heat flow path and overall temperature distribution through preliminary simulation to check for local overheating or uneven cooling. If so, adjust the heat load or convection parameters to optimize the model.

7. The method for simulating and analyzing the temperature field of an oil-immersed cooling underwater frequency converter according to claim 2, characterized in that: In step 1.1, the simplified underwater frequency converter includes a housing and a main heat-generating module inside the housing. The main heat-generating module includes an inverter unit module, a reactor module, a control box module and a phase-shifting transformer.

8. The temperature field simulation analysis method of an oil-immersed cooling underwater frequency converter according to claim 1, characterized in that: In step 1, the internal fluid domain model of the underwater inverter is a three-dimensional structure in which the heat dissipation insulating oil is filled in the shell of the underwater inverter.

9. The temperature field simulation analysis method of an oil-immersed cooling underwater frequency converter according to claim 1, characterized in that: The simulation model of the underwater inverter in step 4.5 is determined by the following formula: Where: ρ represents the material density (kg / m 3 );C p represents specific heat capacity (J / kg·℃); T represents temperature field (℃); k represents thermal conductivity (W / m·℃); P loss,i represents the power loss of the i-th heat generating module (W); V i represents the volume of the i-th heating module (m 3 );h sea Indicates the convection heat transfer coefficient between the shell and seawater (W / m 2 ℃); T shell Indicates the shell temperature (℃); T sea Indicates seawater temperature (℃); R th,j represents the thermal contact impedance between the jth heating module and the oil (℃ / W); T module represents the temperature of the jth heating module (℃); T oil Indicates oil temperature (℃).

10. A temperature field simulation and analysis system for an underwater frequency converter with oil immersion cooling, characterized in that: include: The geometric modeling module is used to establish the geometric model of the underwater frequency converter and its internal fluid domain model; The meshing and material property setting module is used to mesh the solid and fluid domains of the underwater inverter and set the corresponding material properties; The contact definition module is used to set the contact type and friction conditions between objects inside the underwater inverter; The boundary condition setting and simulation module is used to set the ambient temperature of the underwater inverter, the convection coefficient between the shell and seawater, the natural convection and heat transfer coefficient of the internal oil, and the heat load of each heating module, and verify and optimize the overall heat dissipation performance through simulation.

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