Superconducting direct current induction heating apparatus, superconducting coil and method for optimizing a core structure

Abstract

This application relates to an optimization method for a superconducting DC induction heating device, a superconducting coil, and a core structure. The superconducting DC induction heating device uses a core assembly coaxially and symmetrically arranged with a high-temperature superconducting magnet. A central circular core guides the vertical magnetic field to both heating stations, forming a dual-station heating structure, significantly improving magnetic field utilization and heating efficiency. The movable core allows for flexible adjustment of the magnetic field gap width at each heating station, and the segmented cores can independently adjust the local magnetic field strength, achieving both uniform heating of the heated component and gradient heating requirements, adapting to different metal heat treatment processes. The optimization method of this application uses a combination of parametric scanning and finite element analysis to screen for the optimal parameter combination, achieving synergistic optimization of the core structure parameters and superconducting coil parameters. The experimental verification phase uses heating time and central magnetic field strength as core indicators. The optimized device can significantly shorten the metal heating cycle and significantly improve energy efficiency.

Description

Technical Field

[0001] This application relates to the field of induction heating technology, and in particular to superconducting DC induction heating equipment, superconducting coils, and methods for optimizing core structures. Background Technology

[0002] In the metal heat treatment industry, traditional metal heating methods mainly include combustion heating and resistance heating. These methods suffer from low energy efficiency, high energy consumption, slow heating speed, and serious pollution. Although traditional induction heating improves the heating effect to some extent by relying on the principle of electromagnetic induction, it is limited by the resistance loss of copper coils, resulting in an energy efficiency of less than 50% for industrial frequency furnaces. It also suffers from poor heating uniformity, making it difficult to meet the high-precision heating requirements of high-end manufacturing.

[0003] The development of high-temperature superconducting magnet technology has made it possible to upgrade induction heating technology. It utilizes superconducting materials with critical temperatures above the liquid nitrogen temperature range to achieve zero-resistance conductivity and perfect diamagnetism, reducing refrigeration costs and expanding the application scenarios of strong magnetic fields. However, in existing technologies that apply superconducting magnets to induction heating, the magnets mostly adopt a single coil structure without a dedicated iron core magnetic guiding structure, resulting in low magnetic field utilization. Furthermore, there is a lack of systematic optimization methods for superconducting coil and iron core structures, making it impossible to achieve a comprehensive balance between magnetic field strength, heating efficiency, and equipment mechanical strength. Problems such as low heating efficiency and lack of clear constraints on parameter design still exist, making it difficult to take full advantage of the high field strength of superconducting magnets. Summary of the Invention

[0004] This application provides a superconducting DC induction heating device that forms a high-efficiency heating station through a dedicated iron core magnetic structure. It also proposes an optimization method for the superconducting coil and iron core structure to achieve precise design and synergistic optimization of parameters, thereby significantly improving the heating efficiency of metals.

[0005] On the one hand, this application provides a superconducting DC induction heating device, including a high-temperature superconducting magnet and an iron core assembly. The iron core assembly and the high-temperature superconducting magnet are coaxially arranged and symmetrically arranged along the central axis of the high-temperature superconducting magnet. The iron core assembly and the high-temperature superconducting magnet cooperate to form a stable magnetic circuit, ensuring the efficient conduction and utilization of the magnetic field. The core assembly includes a central circular core, an upper core, a lower core, side cores, and a movable core. These core components work together to guide the magnetic field and create the heating station. The specific structural connections are as follows: The central circular iron core is inserted through the central hole of the high-temperature superconducting magnet, providing the main conduction path for the vertical magnetic field generated by the high-temperature superconducting magnet, and is the core component of the magnetic circuit; The upper iron core is connected to the upper end of the middle circular iron core, and the lower iron core is connected to the lower end of the middle circular iron core. The upper iron core, the lower iron core, and the middle circular iron core together form a central magnetic guiding structure, which restricts the direction of magnetic field transmission. The side cores consist of two parts, symmetrically distributed on the left and right sides of the high-temperature superconducting magnet. Each side core is connected to the corresponding side of the lower core. The side cores provide an extension path for the central magnetic field to conduct to both sides, thus achieving a two-sided distribution of the magnetic field. The movable iron core consists of two parts, symmetrically distributed on the left and right sides of the upper iron core, located above the corresponding side iron cores. Each movable iron core forms a heating station between itself and the upper iron core. The metal rod or other workpiece to be heated is placed in the heating station. The central circular iron core guides the vertical magnetic field generated by the high-temperature superconducting magnet to both sides to the heating station, thereby achieving induction heating of the workpiece using electromagnetic induction. The movable iron core can move closer to or further away from the upper iron core to adjust the air gap width of the magnetic field in the heating station, thereby controlling the magnetic field strength of the heating station to adapt to different heating requirements.

[0006] In one possible design, the movable iron core comprises multiple segmented iron cores, each of which can individually move closer to or further away from the upper iron core to adjust the local air gap magnetic field strength of the heating station. This independent adjustment design of the segmented iron cores allows for precise control of the local magnetic field within the heating station, ensuring both uniform heating of the workpiece and meeting the process requirements of gradient heating, thus improving the equipment's adaptability.

[0007] In one possible design, each segment of the iron core is threaded onto a corresponding lead screw, and each lead screw has a manual handle connected to its end via a bearing seat. By manually rotating the handle, the lead screw is rotated. Utilizing the threaded engagement between the lead screw and the segment of the iron core, the rotational motion of the lead screw is converted into the linear motion of the segment of the iron core, enabling precise movement of the segment of the iron core towards or away from the upper iron core. This adjustment method is simple in structure, convenient to operate, and has high adjustment accuracy, effectively controlling changes in the air gap width of the magnetic field.

[0008] In one possible design, the thickness of both the upper and lower iron cores is greater than the thickness of the workpiece being heated. This ensures that the upper and lower iron cores can provide comprehensive magnetic field coverage for the heating station, avoiding uneven magnetic field distribution due to insufficient iron core thickness. This ensures that all parts of the workpiece being heated can be effectively heated, improving heating uniformity.

[0009] In one possible design, the high-temperature superconducting magnet includes a Dewar, a cold shield, a coil assembly, and a cooling assembly. The Dewar and the cold shield are sealed together to provide a sealed, low-temperature operating environment for the coil assembly and prevent cold leakage. The cooling assembly is conductively connected to the cold shield and the coil assembly, continuously providing cooling to both, ensuring the thermal radiation insulation effect of the cold shield and the superconducting characteristics of the coil assembly, enabling the coil assembly to achieve zero-resistance conduction, reducing energy loss, and fully utilizing the high field strength advantage of the high-temperature superconducting magnet.

[0010] On the other hand, this application also provides a method for optimizing the structure of a superconducting coil and its core, applied to the aforementioned superconducting DC induction heating device, comprising the following steps: S1. Based on the design parameters such as superconducting coil current, air gap magnetic field spacing, upper core thickness, lower core thickness, side core thickness, middle circular core diameter, high-temperature superconducting tape material, high-temperature superconducting tape usage, number of coil axial winding layers, and room temperature hole inner diameter of high-temperature superconducting magnet, a complete simulation model of superconducting coil and core structure is constructed, laying the model foundation for subsequent multiphysics field analysis and parameter optimization. S2. Based on the simulation model, a three-field coupled equation system of electromagnetic field, temperature field, and electromagnetic force is constructed by combining Maxwell's equations, the heat conduction equation, and the electromagnetic force formula, forming a three-field coupled model. This model realizes the coordinated analysis of electromagnetic field, temperature field, and electromagnetic force, and for the first time achieves the direct quantification of the stress distribution of the iron core by electromagnetic force. It breaks through the limitation of traditional design that only focuses on a single physical field, and can more comprehensively reflect the working status of the equipment. S3. Based on the three-field coupling model, simulation analysis was used to screen out the primary influencing parameters that have the main impact on the central magnetic field strength and heating time. The primary influencing parameters include the number of turns of the superconducting coil, the operating current of the superconducting coil, the ratio of the diameter of the middle circular iron core to the width of the air gap, and the ratio of the thickness of the lower iron core to the thickness of the upper iron core. By focusing on the core influencing parameters, the workload of subsequent parameter optimization is reduced and the optimization efficiency is improved. S4. Based on the first influencing parameter, combined with the structural limitations, operational requirements and safe operation requirements of the equipment, determine the boundary conditions and optimization range of the core structure parameters and superconducting coil parameters, and provide clear constraint standards for parameter selection; S5. With the shortest heating time as the core optimization objective and the constraints of ensuring that the mechanical strength of the iron core and the critical current density of the coil do not exceed the limits, a multi-objective optimization model is established. Among them, ensuring that the mechanical strength of the iron core does not exceed the limits is determined by comparing the stress value calculated by electromagnetic force with the yield strength of the material. Ensuring that the critical current density of the coil does not exceed the limits can effectively prevent the coil from failing and ensure the safe and stable operation of the equipment. S6. By combining parametric scanning and finite element analysis, an initial parameter combination mesh is generated using orthogonal experimental design. The optimal solution that satisfies the boundary conditions, optimization range, and constraint conditions is iteratively screened to determine the best combination of core structure parameters and superconducting coil parameters. This method realizes the global optimization search of superconducting coil and core structure parameters and can find the optimal parameter matching scheme under multiple constraints. S7. Establish an optimized model of the superconducting coil and core structure based on the best combination, and conduct actual heating tests to verify the model, ensuring its practicality and accuracy, and providing reliable parameter basis for the actual production and application of the equipment.

[0011] In one possible design, the boundary condition is that the central magnetic field strength Br ≥ 0.5T. This condition ensures that the heating station has sufficient magnetic field strength to meet the requirements of rapid metal heating. The optimization range is: 2100N < number of turns n of the superconducting coil < 3300N, 160A < operating current I of the superconducting coil < 320A, 2.8 < diameter D of the middle circular iron core / air gap width L < 3.2, 1.1 < thickness H1 of the lower iron core / thickness H2 of the upper iron core < 1.2. This optimization range was determined by simulation analysis and equipment structural constraints, taking into account magnetic field strength, heating efficiency, equipment mechanical strength, and manufacturing cost, and represents the optimal range for parameter design.

[0012] In one possible design, the parametric scan in step S6 includes univariate simulation analysis. The basic conditions for the univariate simulation analysis are a superconducting coil current of 300A, an air gap magnetic field spacing of 540mm, and a high-temperature superconducting tape usage of 11km. By controlling a single variable and fixing other parameters, the influence of each parameter on the air gap center magnetic field can be accurately determined, providing a precise theoretical basis for parameter optimization.

[0013] In one possible design, univariate simulation analysis includes: keeping the diameter of the central circular core constant, changing the thickness of the upper, lower, and side cores and analyzing their impact on the central magnetic field of the air gap; keeping the core thickness constant, changing the diameter of the central circular core and analyzing its impact on the central magnetic field of the air gap; keeping the diameter of the central circular core and the amount of strip material constant, adjusting the height of the winding area and analyzing its impact on the central magnetic field of the air gap; keeping the amount of strip material and the height of the winding area constant, adjusting the axial offset of the coil and analyzing its impact on the central magnetic field of the air gap and the electromagnetic force of the coil assembly. Through multi-dimensional univariate analysis, the influence characteristics of core structural parameters on the magnetic field can be fully understood.

[0014] In one possible design, the axial offset of the coil can be adjusted within the range of 0-80mm, with an optimal offset of 40mm upward along the axial direction. This optimal offset is determined by simulation analysis. At this point, the magnetic field strength at the center of the air gap is slightly increased, and the downward electromagnetic force on the coil is significantly reduced. This effectively reduces the risk of deformation of the coil assembly due to electromagnetic force, while ensuring a safe distance between the coil and the Dewar, thus improving the structural stability of the equipment.

[0015] In one possible design, the experimental verification in step S7 uses the heating time of the metal rod to be heated and the central magnetic field strength as verification indicators. By actually measuring the core indicators, the effectiveness of the optimized model can be intuitively judged, ensuring that the optimized parameter combination can achieve a dual improvement in magnetic field strength and heating efficiency.

[0016] The beneficial effects of this application are as follows: The superconducting DC induction heating device of this application arranges the iron core assembly and the high-temperature superconducting magnet coaxially and symmetrically. The vertical magnetic field is guided to the heating stations on both sides by the central circular iron core, forming a dual-station heating structure, which greatly improves the magnetic field utilization and heating efficiency. The movable iron core can flexibly adjust the air gap width of the magnetic field at the heating station, and the segmented iron core can independently adjust the local magnetic field strength. It can achieve uniform heating of the heated parts and meet the requirements of gradient heating, and is suitable for different metal heat treatment processes.

[0017] The optimization method in this application constructs a three-field coupled model of electromagnetic field, temperature field, and electromagnetic force, realizing the collaborative analysis of multiple physical fields. Since the electromagnetic field acts on the aluminum rod, causing Joule heating and raising its temperature to the required heating temperature, the temperature change of the aluminum rod will in turn affect its electromagnetic properties (electrical conductivity, thermal conductivity, and stress distribution), thereby altering the electromagnetic field distribution. The electromagnetic field acts on the coil assembly itself, causing it to bear electromagnetic force and resulting in microscopic deformation. This microscopic deformation of the coil assembly affects the electromagnetic field distribution, thus affecting the heating efficiency. Simultaneously, the electromagnetic field acts on the iron core, causing it to bear electromagnetic force and altering the stress distribution of the iron core. This stress change causes microscopic deformation and magnetic circuit changes in the iron core, which in turn affect the electromagnetic field distribution, thus affecting the heating efficiency. This step uses a simulation model of the superconducting coil and iron core as a carrier to fuse the three classic physical equations describing the electromagnetic field, temperature field, and electromagnetic force field through key coupling terms. This enables the direct quantification of the effects of electromagnetic force on the deformation of the coil assembly and iron core, temperature on the change of the electromagnetic properties of the aluminum rod, and the effect of the deformation of the coil assembly and iron core on the electromagnetic field distribution. This allows subsequent parameter optimization to better align with the physical laws of actual equipment operation. Through simulation analysis of the coupled model, the primary influencing parameters that have a core impact on the central magnetic field strength and heating time can be accurately identified, avoiding blind analysis and improving optimization efficiency.

[0018] By selecting the primary influencing parameters, the core direction of parameter design was clarified, optimization efficiency was improved, and the determined boundary conditions and optimization range provided clear standards for equipment parameter design, avoiding blind design.

[0019] The optimization method uses a combination of parametric scanning and finite element analysis to screen the optimal combination of parameters, achieving synergistic optimization of core structure parameters and superconducting coil parameters, taking into account heating efficiency, equipment mechanical strength and operational safety. The experimental verification stage uses heating time and central magnetic field strength as core indicators to ensure the practicality of the optimization model. The optimized equipment can significantly shorten the metal heating cycle and significantly improve energy efficiency.

[0020] The optimal axial offset of the coil determined in the optimization method reduces the electromagnetic force of the coil while increasing the magnetic field strength, effectively preventing coil deformation and improving the structural stability and service life of the equipment. The clear parameter optimization range also provides a reference for parameter matching of different specifications of heated parts, improving the adaptability of the equipment. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the overall structure of the superconducting DC induction heating device provided in the embodiments of this application; Figure 2 This is a schematic diagram of the structure of the movable iron core of the superconducting DC induction heating device provided in the embodiments of this application; Figure 3 This is a schematic diagram of the structure of the high-temperature superconducting magnet in the superconducting DC induction heating device provided in the embodiments of this application; Figure 4 An exploded view of the high-temperature superconducting magnet in the superconducting DC induction heating device provided in this application embodiment; Figure 5 A cross-sectional view of the high-temperature superconducting magnet in the superconducting DC induction heating device provided in this application embodiment; Figure 6 For simulation Figure 1 ; Figure 7 For simulation Figure 2 ; Figure 8 A magnetic field distribution diagram of a superconducting DC induction heating device provided in an embodiment of this application.

[0023] Figure label: 1. High-temperature superconducting magnet; 11. Dewar; 111. Dewar raised cover plate; 112. Dewar raised section; 113. Dewar lower cover plate; 114. Dewar upper cover plate; 115. Dewar inner cylinder; 116. Dewar outer cylinder; 117. Coil vertical pull rod; 118. Coil diagonal pull rod; 12. Cold shield; 121. Cold shield raised section; 122. Cold shield lower cover plate; 123. Cold shield inner cylinder; 124. Cold shield upper cover plate; 125. Cold shield outer cylinder ; 13. Coil assembly; 131. Cooling plate; 132. Coil; 133. Aluminum frame; 134. Stainless steel frame; 135. Through-pull rod; 14. Refrigeration assembly; 141. Refrigeration unit; 21. Middle round iron core; 22. Upper iron core; 23. Lower iron core; 24. Side iron core; 25. Movable iron core; 251. Segmented iron core; 3. Heating station; 4. Lead screw; 5. Bearing seat; 6. Manual handle; 7. Heated part. Detailed Implementation

[0024] The technical solutions of this application will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] The following is combined Figures 1-5 This application describes a superconducting DC induction heating device provided in its embodiments. The superconducting DC induction heating device includes a high-temperature superconducting magnet 1 and an iron core assembly. The iron core assembly is coaxially arranged with the high-temperature superconducting magnet 1 and symmetrically arranged along the central axis of the high-temperature superconducting magnet 1. The iron core assembly and the high-temperature superconducting magnet cooperate to form a stable magnetic circuit, ensuring efficient conduction and utilization of the magnetic field.

[0026] The core assembly includes a central circular core 21, an upper core 22, a lower core 23, side cores 24, and a movable core 25. The central circular core 21 passes through the central hole of the high-temperature superconducting magnet 1. The upper core 22 is fixedly connected to the upper end of the central circular core 21, and the lower core 23 is fixedly connected to the lower end of the central circular core 21. There are two side cores 24, symmetrically distributed on the left and right sides of the high-temperature superconducting magnet 1. The lower end of each side core 24 is fixedly connected to the corresponding side of the lower core 23 through a side plate and bolts. There are two movable iron cores 25, symmetrically distributed on the left and right sides of the upper iron core 22, and respectively located above the corresponding side iron cores 24. Each movable iron core 25 and the upper iron core 22 form a heating station 3. The heated part 7 is placed in the heating station 3. In this embodiment, the heated part 7 is an aluminum rod to be heated. The middle round iron core 21 guides the vertical magnetic field generated by the high temperature superconducting magnet 1 to the double heating station 3, and realizes the double-station induction heating of the aluminum rod by electromagnetic induction.

[0027] The movable iron core 25 can move closer to or further away from the upper iron core 22 to adjust the magnetic field gap width of the heating station 3, thereby controlling the magnetic field strength of the heating station 3 to adapt to different heating needs.

[0028] In some specific embodiments, the movable iron core 25 is divided into eight segmented iron cores 251. Each segmented iron core 251 is threaded onto a corresponding lead screw 4. The end of the lead screw 4 is connected to a manual handle 6 via a bearing seat 5. Rotating the manual handle 6 can drive the lead screw 4 to rotate, thereby driving the segmented iron core 251 to move closer to or further away from the upper iron core 22 individually. This allows for the control of the local air gap magnetic field strength in the heating station 3, meeting the uniform heating requirements of the aluminum rod. The independent adjustment design of the segmented iron cores 251 enables precise control of the local magnetic field within the heating station 3, ensuring both uniform heating of the heated component 7 and meeting the process requirements of gradient heating, thus improving the adaptability of the equipment.

[0029] The thickness of both the upper iron core 22 and the lower iron core 23 is greater than the diameter of the aluminum rod, ensuring that the upper iron core 22 and the lower iron core 23 can provide comprehensive magnetic field coverage for the heating station 3, ensuring that the magnetic field of the heating station 3 fully covers the aluminum rod, avoiding uneven magnetic field distribution due to insufficient iron core thickness, ensuring that all parts of the heated part 7 can be effectively heated, and improving heating uniformity.

[0030] The high-temperature superconducting magnet 1 includes a Dewar 11, a cold shield 12, a coil assembly 13, and a cooling assembly 14. The Dewar 11 and the cold shield 12 are sealed together. The first-stage cold head of the cooling assembly 14 is conductively connected to the cold shield 12, and the second-stage cold head is conductively connected to the coil assembly 13, providing continuous cooling for the cold shield 12 and the coil assembly 13, ensuring the superconducting characteristics of the coil 132 in the coil assembly 13, and achieving zero-resistance conduction.

[0031] Specifically, the Dewar 11 includes a Dewar protrusion cover plate 111, a Dewar protrusion 112, a lower Dewar cover plate 113, an upper Dewar cover plate 114, an inner Dewar cylinder 115, an outer Dewar cylinder 116, a coil vertical tie rod 117, and a coil diagonal tie rod 118. The cooling shield 12 includes a cooling shield protrusion 121, a lower cooling shield cover plate 122, an inner cooling shield cylinder 123, an upper cooling shield cover plate 124, and an outer cooling shield cylinder 125. The coil assembly 13 includes a cooling plate 131, a coil 132, an aluminum frame 133, a stainless steel frame 134, and a through-type tie rod 135. The cooling assembly 14 includes a cooling unit 141, a primary cooling component, and a secondary cooling component.

[0032] The Dewar protrusion cover 111 and Dewar protrusion 112 are sealed with an O-ring, while the remaining components of the Dewar are sealed by welding. The primary cold head of the refrigerator 141 transfers cold energy starting from the primary cooling conductor, sequentially connecting to the cold shield protrusion 121, the cold shield outer cylinder 125, the cold shield lower cover 122, the cold shield upper cover 124, and finally to the cold shield inner cylinder 123. The main function of the cold shield 12 is to insulate the coil 132 from heat radiation, which helps maintain the low temperature of the coil 132. The secondary cold head of the refrigerator 141 transfers cold energy starting from the secondary cooling conductor, sequentially connecting to the cooling guide plate 131, the aluminum frame 133, and finally to the coil 132. The aluminum frame 133 and the stainless steel frame 134 are nested structures. Because aluminum has a high thermal conductivity, aluminum is used for cooling close to the coil 132 to promote temperature uniformity in the coil 132. The outer nested stainless steel frame 134 strengthens the coil assembly 13, preventing deformation of the coil 132 due to electromagnetic forces.

[0033] This application also provides an optimization method for the structure of a superconducting coil and its core, applied to the superconducting DC induction heating device described above, with the application scenario of heating aluminum rods with specifications of Φ486×1500mm and Φ410×1500mm. The optimization method includes the following steps: S1. Establish a simulation model of the superconducting coil and core structure: Based on the design parameters such as superconducting coil current of 300A, air gap magnetic field spacing of 540mm, upper core thickness of 530mm, lower core thickness of 600mm, side core thickness of 600mm, middle circular core diameter of 1500mm, high-temperature superconducting tape material of REBCO, high-temperature superconducting tape usage of 11km, axial winding layers of the coil of 320mm, and room temperature hole inner diameter of the high-temperature superconducting magnet of 1600mm, a simulation model is constructed.

[0034] S2. Construct a three-field coupling model: Based on the simulation model, combine Maxwell's equations, the heat conduction equations, and the electromagnetic force formula to construct a three-field coupling equation set of electromagnetic field, temperature field, and electromagnetic force, forming a three-field coupling model.

[0035] Specifically, based on the simulation model, a three-field coupling equation set of electromagnetic field, temperature field and electromagnetic force is constructed, and a three-field coupling model is formed between electromagnetic field and temperature field, temperature field and electromagnetic force, and electromagnetic field and electromagnetic force.

[0036] S3. Screening the primary influencing parameters: Based on the three-field coupling model, the primary influencing parameters on the central magnetic field strength and heating time are screened as follows: number of turns of the superconducting coil, operating current of the superconducting coil, ratio of the diameter of the middle circular iron core to the width of the air gap, and ratio of the thickness of the lower iron core to the thickness of the upper iron core.

[0037] S4. Determine the parameter boundary conditions and optimization range: The boundary condition is determined to be the central magnetic field strength Br≥0.5T, and the optimization range is: 2100N<n<3300N, 160A<I<320A, 2.8<D / L<3.2, 1.1

[0038] S5. Establish a multi-objective optimization model: With the shortest heating time of the aluminum rod as the optimization objective, and with the constraints of not exceeding the limits of the mechanical strength of the iron core and not exceeding the limits of the critical current density of the coil, establish a multi-objective optimization model.

[0039] S6. Screening the optimal combination of parameters: Based on the conditions of a superconducting coil current of 300A, an air gap magnetic field spacing of 540mm, and a high-temperature superconducting tape usage of 11km, a single-variable simulation analysis was conducted. The effects of core thickness, diameter of the central circular core, height of the winding area, and axial offset of the coil on the magnetic field at the center of the air gap were analyzed in turn. The optimal offset of the coil along the axial direction was determined to be 40mm upward. Combined with finite element analysis, an orthogonal experimental design was used to generate an initial parameter combination mesh, and the optimal combination of parameters that satisfies all constraints was iteratively screened.

[0040] The univariate simulation analysis is detailed below: Keeping the diameter of the central circular iron core constant, the thicknesses of the upper, lower, and side iron cores were varied, and their impact on the central magnetic field of the air gap was analyzed. Similarly, keeping the core thickness constant, the diameter of the central circular iron core was varied, and its impact on the central magnetic field of the air gap was analyzed. Furthermore, keeping the diameter of the central circular iron core and the amount of strip material constant, the height of the winding area was adjusted, and its impact on the central magnetic field of the air gap was analyzed. Finally, keeping the amount of strip material and the height of the winding area constant, the axial offset of the coil was adjusted, and its impact on the central magnetic field of the air gap and the electromagnetic force of the coil was analyzed. Through multi-dimensional univariate analysis, the influence characteristics of the core structural parameters on the magnetic field were comprehensively understood.

[0041] S7. Experimental Verification: Based on the optimal combination of parameters, an optimization model is established. Actual heating tests are conducted using aluminum rods with diameters of 486×1500mm and 410×1500mm as the heating objects. The heating time of the aluminum rods and the central magnetic field strength of heating station 3 are used as verification indicators.

[0042] In this embodiment, step S6 specifically includes: S61. Keep the diameter of the middle round iron core unchanged, and change the thickness of the upper iron core (base 530mm), the thickness of the lower iron core (base 600mm) and the thickness of the side iron core (base 600mm), with an adjustment range of ±100mm.

[0043] Result: Reference Figure 6 ​As shown, between -100 and +100 mm, the magnetic field at the fixed core end (i.e., the magnetic field at both ends of the upper core) decreases significantly, while the magnetic field at the air gap center is at its maximum at approximately position 0, meaning that the magnetic field at the air gap center is at its maximum when the base size remains unchanged.

[0044] S62. Based on step S61, keep the amount of high-temperature superconducting tape used in the superconducting coil unchanged at 11km, and keep the thickness of the upper iron core, lower iron core and side iron core unchanged, and change the diameter of the middle round iron core, with an adjustment range of 1500-1800mm.

[0045] Result: Reference Figure 7 As shown, the diameter of the circular iron core is between 1500-1800 mm, and the magnetic field at the center of the air gap increases significantly. Due to mechanical limitations, the maximum inner diameter of the high-temperature superconducting magnet can only be 1600 mm. At this point, the maximum magnetic field at the center of the air gap is 0.55 T, which meets the design requirements.

[0046] S63. Based on step S62, keep the diameter of the central round iron core unchanged and keep the amount of high-temperature superconducting tape used in the coil unchanged at 11km. Adjust the height of the winding area (i.e., the number of axial layers) within a range of 200-400mm (base winding height 320mm).

[0047] Results: As the winding height increases, the magnetic field at the center of the air gap decreases slightly (20 Gs).

[0048] Analysis: Considering both heat conduction and curing, a greater strip winding height and a smaller radial layer count are more conducive to paraffin impregnation. Furthermore, a thinner strip radially results in better heat conduction. Considering both winding height and heat conduction efficiency, the winding height should be kept constant.

[0049] S64. Based on step S63, keep the amount of high-temperature superconducting tape used in the coil unchanged at 11km and keep the winding height unchanged at 320mm. The coil position is shifted upward along the axial direction, with an adjustment range of 0-80mm (0 is the mid-plane).

[0050] Results: As the upward offset distance of the coil increases, the magnetic field increases slightly (50Gs at 80mm). In addition, the downward electromagnetic force of the coil assembly is reduced by about 4 tons. Considering that the minimum distance between the coil and the Dewar is about 240mm, the maximum upward offset of the coil is 40mm. This can reduce the force on the coil assembly and the coil tie rod, which is beneficial to improving the structural stability of the coil assembly.

[0051] Final results: 1. Keeping other conditions unchanged, we optimized the core size parameters, coil position parameters, and size parameters to find the optimal parameter combination to ensure the maximum magnetic field at the air gap center; 2. According to the principle of induction heating, the larger the magnetic field, the shorter the time to heat to the required heating temperature and the higher the heating efficiency.

[0052] To further verify the optimization method of this application, multiple embodiments and comparative examples were set up for the experiment. Some core parameters and experimental results are shown in the table below:

[0053] In Examples 1-4 and Comparative Examples 1-3, an aluminum rod with a diameter of 486 mm and a length of 1500 mm was heated to 500°C.

[0054] In Example 1, the number of turns n of the superconducting coil in the high-temperature superconducting magnet is 3200 turns (meets design requirements; more turns result in a stronger magnetic field, but also higher cost and structural limitations must be considered). The operating current I of the superconducting coil is 180 amperes (meets design requirements; a higher current results in a stronger magnetic field, but cannot exceed the critical current of the strip material used in the coil). The diameter D of the middle circular iron core is 1500 mm (smaller than the inner diameter of the room-temperature hole in the high-temperature superconducting magnet). The air gap width L is 530 mm (the distance between the upper iron core side end face and the movable iron core side end face, which is larger than the diameter of the aluminum rod). The thickness H1 of the lower iron core is... The diameter of the upper iron core is 600mm, and the thickness of the upper iron core is 530mm (greater than the diameter of the aluminum rod, to ensure that the magnetic field area covers the aluminum rod). The ratio of the diameter of the middle circular iron core D to the width of the air gap L is 2.83 (meets the design requirements), and the ratio of the thickness of the lower iron core H1 to the thickness of the upper iron core H2 is 1.13 (meets the design requirements). Ultimately, the central magnetic field strength Br of the air gap is 0.51T (meets the design requirements, and the central axis of the air gap coincides with the central axis of the aluminum rod). Under this magnetic field strength, heating an aluminum rod with a diameter of Φ486×1500mm to the required heating temperature takes only 13 minutes, greatly improving the heating efficiency.

[0055] In Examples 2-4, the number of turns n of the superconducting coil, the operating current I of the superconducting coil, the ratio D / L of the diameter D of the middle circular iron core to the width L of the air gap, and the ratio H1 / H2 of the thickness H1 of the lower iron core to the thickness H2 of the upper iron core all meet the design requirements. Ultimately, the central magnetic field strength of the air gap can be higher than 0.5T, and heating a Φ486×1500mm aluminum rod to the required heating temperature takes less than 14 minutes, greatly improving the heating efficiency.

[0056] In Comparative Example 1, the number of turns n of the superconducting coil is 1900, which does not meet the design requirements. It takes 17 minutes to heat an aluminum rod with a diameter of 486×1500mm to the required heating temperature, which significantly reduces the efficiency.

[0057] In Comparative Example 2, the ratio of the diameter D of the central circular iron core to the width L of the air gap, D / L, is 2.5, which does not meet the design requirements. The time required to heat an aluminum rod with a diameter of 486×1500mm to the required heating temperature is 15.5 minutes, which significantly reduces the efficiency.

[0058] In Comparative Example 3, the ratio of the thickness H1 of the lower iron core to the thickness H2 of the upper iron core, H1 / H2, is 1.23, which does not meet the design requirements. The time required to heat an aluminum rod with a diameter of 486×1500mm to a temperature of 500°C is 14.5 minutes, which significantly reduces the efficiency.

[0059] In Examples 5-8 and Comparative Examples 4-6, an aluminum rod with a diameter of 410 mm and a length of 1500 mm was heated to 500°C.

[0060] Similarly, in Examples 5-8, the number of turns n of the superconducting coil, the operating current I of the superconducting coil, the ratio D / L of the diameter D of the middle circular iron core to the width L of the air gap, and the ratio H1 / H2 of the thickness H1 of the lower iron core to the thickness H2 of the upper iron core all meet the design requirements. Ultimately, the central magnetic field strength of the air gap can reach 0.5T, and heating a Φ410×1500mm aluminum rod to the required heating temperature takes less than 9.5 minutes, greatly improving the heating efficiency.

[0061] In Comparative Example 4, the number of turns n of the superconducting coil is 1900, which does not meet the design requirements. It takes 12 minutes to heat an aluminum rod with a diameter of 410×1500mm to the required heating temperature, which significantly reduces the efficiency.

[0062] In Comparative Example 5, the ratio of the diameter D of the central circular iron core to the width L of the air gap, D / L, is 2.5, which does not meet the design requirements. It takes 10 minutes to heat an aluminum rod with a diameter of 410×1500mm to the required heating temperature, which significantly reduces the efficiency.

[0063] In Comparative Example 6, the ratio of the thickness H1 of the lower iron core to the thickness H2 of the upper iron core, H1 / H2, is 1.23, which does not meet the design requirements. It takes 10 minutes to heat an aluminum rod with a diameter of 410×1500mm to the required heating temperature, which significantly reduces the efficiency.

[0064] Meanwhile, referring to the data from Examples 1-4 or Examples 5-8, under the condition that the aluminum rod size is the same, the larger the product of the number of turns n of the superconducting coil and the operating current I of the superconducting coil, the shorter the heating time of the aluminum rod.

[0065] Meanwhile, referring to the data from Examples 1 and 5, with other parameters remaining unchanged, the smaller the size of the aluminum rod, the shorter the heating time of the aluminum rod.

[0066] Therefore, the optimization method of this application achieves synergistic optimization of core structure parameters and superconducting coil parameters, taking into account heating efficiency, equipment mechanical strength and operational safety.

[0067] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0068] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0069] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between components; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0070] In this application, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0071] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A superconducting DC induction heating device, characterized in that, The system includes a high-temperature superconducting magnet and a core assembly. The core assembly is coaxially arranged with the high-temperature superconducting magnet and symmetrically arranged along the central axis of the high-temperature superconducting magnet. The core assembly includes: An intermediate circular iron core is inserted through the central hole of the high-temperature superconducting magnet. The upper iron core is connected to the upper end of the intermediate circular iron core; The lower iron core is connected to the lower end of the intermediate circular iron core; The side cores include two side cores, which are symmetrically distributed on the left and right sides of the high-temperature superconducting magnet, and each side core is connected to the corresponding side of the lower core. The movable iron core comprises two movable iron cores, symmetrically distributed on the left and right sides of the upper iron core, respectively located above the corresponding side iron cores. Each movable iron core forms a heating station between itself and the upper iron core. The middle circular iron core guides the vertical magnetic field generated by the high-temperature superconducting magnet to the heating station on both sides. The movable iron core can move closer to or further away from the upper iron core to adjust the air gap width of the magnetic field at the heating station.

2. The superconducting DC induction heating device according to claim 1, characterized in that, The movable iron core includes multiple segmented iron cores, each of which can individually move closer to or further away from the upper iron core to adjust the local air gap magnetic field strength of the heating station.

3. The superconducting DC induction heating device according to claim 1, characterized in that, The thickness of both the upper and lower iron cores is greater than the thickness of the heated component.

4. The superconducting DC induction heating device according to claim 1, characterized in that, The high-temperature superconducting magnet includes a Dewar, a cold shield, a coil assembly, and a cooling assembly. The Dewar is sealed to the cold shield, and the cooling assembly is conductively connected to the cold shield and the coil assembly, respectively.

5. A method for optimizing the structure of a superconducting coil and its core, applied to the superconducting DC induction heating device according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Establish a simulation model of the superconducting coil and core structure. The design parameters of the simulation model include superconducting coil current, air gap magnetic field spacing, upper core thickness, lower core thickness, side core thickness, middle circular core diameter, high-temperature superconducting tape material, high-temperature superconducting tape usage, number of coil axial winding layers, and room temperature hole inner diameter of the high-temperature superconducting magnet. S2. Based on the simulation model, combine Maxwell's equations, the heat conduction equations, and the electromagnetic force formula to construct a three-field coupled equation set of electromagnetic field-temperature field-electromagnetic force, forming a three-field coupled model. S3. Based on the three-field coupling model, the first influencing parameters that have the main impact on the central magnetic field strength and heating time are selected. The first influencing parameters include the number of turns of the superconducting coil, the operating current of the superconducting coil, the ratio of the diameter of the middle circular iron core to the width of the air gap, and the ratio of the thickness of the lower iron core to the thickness of the upper iron core. S4. Based on the first influencing parameter, determine the boundary conditions and optimization range of the core structure parameters and superconducting coil parameters; S5. Establish a multi-objective optimization model with the shortest heating time as the optimization objective and the constraints being that the mechanical strength of the iron core and the critical current density of the coil do not exceed the limits. S6. By combining parametric scanning and finite element analysis, an initial parameter combination mesh is generated using orthogonal experimental design. The optimal solution that satisfies the boundary conditions, optimization range, and constraint conditions is iteratively screened to determine the best combination of core structure parameters and superconducting coil parameters. S7. Based on the optimal combination, establish an optimized model of the superconducting coil and core structure, and conduct experimental verification.

6. The method for optimizing the superconducting coil and core structure according to claim 5, characterized in that, The boundary condition is that the central magnetic field strength Br ≥ 0.5T, and the optimization range is: 2100N < number of turns of the superconducting coil n < 3300N, 160A < operating current of the superconducting coil I < 320A, 2.8 < diameter of the middle circular iron core D / air gap width L < 3.2, 1.1 < thickness of the lower iron core H1 / thickness of the upper iron core H2 < 1.

2.

7. The method for optimizing the superconducting coil and core structure according to claim 6, characterized in that, The parametric scanning described in step S6 includes univariate simulation analysis. The basic conditions for the univariate simulation analysis are a superconducting coil current of 300A, an air gap magnetic field spacing of 540mm, and a high-temperature superconducting tape usage of 11km.

8. The method for optimizing the superconducting coil and core structure according to claim 7, characterized in that, The univariate simulation analysis includes: keeping the diameter of the central circular iron core constant, changing the thickness of the upper iron core, lower iron core, and side iron core and analyzing the impact on the central magnetic field of the air gap; keeping the iron core thickness constant, changing the diameter of the central circular iron core and analyzing the impact on the central magnetic field of the air gap; keeping the diameter of the central circular iron core and the amount of strip material constant, adjusting the height of the winding area and analyzing the impact on the central magnetic field of the air gap; keeping the amount of strip material and the height of the winding area constant, adjusting the axial offset of the coil and analyzing the impact on the central magnetic field of the air gap and the electromagnetic force of the coil assembly.

9. The method for optimizing the superconducting coil and core structure according to claim 8, characterized in that, The adjustment range of the axial offset of the coil is 0-80mm, and the optimal offset is 40mm upward along the axial direction.

10. The method for optimizing the superconducting coil and core structure according to claim 5, characterized in that, The experimental verification described in step S7 uses the heating time of the metal rod to be heated and the central magnetic field strength as verification indicators.

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