Field Coupling Method Research Articles

Performance evaluation of cold plasma and h-BN nano-lubricant multi-field coupling assisted micro-milling of aluminum alloy 6061-T651

Micro-milling has been employed in various fields due to its efficiency, flexibility, material, and structural versatility in the machining of small and high-quality parts. However, when micro-milling highly plastic aluminum alloys, it is difficult to produce a smooth surface due to the easy sticking of tools. To solve this problem, a multi-energy field coupling method of adding nano-lubricant to the micro-milling area by minimum quantity lubrication (MQL) and modifying the aluminum alloy by cold plasma (CP) was introduced. In this paper, the experiments of CP and h-BN nano-lubricant minimum quantity lubrication (NMQL) multi-field coupling assisted (CPNMQL) micro-milling of aluminum alloy 6061-T65 were carried out to analyze 3D surface roughness (Sa), tool texture, milling forces (Fx and Fy), and surface morphology. The results revealed that the CP could increase the surface microhardness and improve material removal rate; Cottonseed oil with h-BN nanoparticles exhibited superior lubricating properties; The milling forces Fx and Fy were significantly reduced; Sa (0.029 µm) under CPNMQL condition decreased by 60 %, 72.1 %, 27.5 %, and 53.2 % comparing to dry (0.104 µm), NMQL (0.04 µm), and CP (0.062 µm) conditions. In addition, the smallest and most uniform tool mark texture height and depth of 0.038 µm was obtained under CPNMQL condition, a 76.3 % reduction over dry condition.

Structure optimization design of gasket test rig based on response surface model

In order to enhance the temperature regulation response speed of the gasket test rig and reduce the hysteresis of the temperature control system, structural optimization is implemented in the hardware part of the test rig. Firstly, a multi-physical field coupling method is employed for comprehensive performance testing of high-temperature and high-pressure gaskets, establishing a heat-fluid-solid coupling simulation and analysis model based on ANSYS. Then, internal temperature distribution of the gasket test device is calculated considering initial and boundary conditions. Next, data is collected using Latin hypercube sampling method, and optimal structural parameter combinations are determined through a multi-objective optimization approach utilizing response surface method and improved genetic algorithm. Finally, collected data is further utilized with response surface method and improved genetic algorithm multi-objective optimization technique to obtain optimal structural parameter combinations for the gasket test device which are verified by heat-fluid-solid coupling simulation. The temperatures tested before and after optimization are analyzed for comparison purposes. The results demonstrate that optimized gasket test rig significantly enhances its temperature control performance.

Numerical Computation of Temperature Rise of Gas‐Insulated Transmission Lines Considering Thermal Properties of Insulating Gas

Accurate temperature rise prediction of the gas‐insulated transmission lines (GIL) can help to lower the cost of equipment through optimization design. To investigate the temperature rise of GIL and the heat transfer efficiency of new eco‐friendly insulating gas, the electromagnetic‐thermal‐fluid field coupling method that considers the thermal properties of solid and gaseous media is proposed. The finite element method is applied to solve the eddy‐current field and obtain the Joule loss of the conductive rod and the enclosure accurately. The GIL temperature distribution of different insulating gases is computed based on their thermophysical parameters. The heat transfer efficiency is found to be positively correlated with gas density, constant pressure heat capacity and thermal conductivity. A parameter that characterizes the heat transfer efficiency of the insulating gas is defined, such that a larger value indicates a higher heat transfer efficiency. This parameter helps to quickly determine the heat transfer capacity of new eco‐friendly insulating gas, and facilitate the optimal design of GIL equipment. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

Design and optimization of superconducting CUSP electromagnetic field structure based on a COMSOL-GMDH-MOSO hybrid strategy

As the semiconductor industry gains momentum, there is a significant focus on producing high-quality silicon wafers with larger diameters. However, the preparation of major-diameter, high-quality silicon single-crystal has encountered challenges such as intense convection inside the melt and high oxygen impurity concentration at the interface between the fluid and solid phases. To tackle these problems, the external superconducting CUSP electromagnetic field structure was designed to optimize the crystal growth parameters. A hybrid strategy of the multiphysics field coupling method, Group Method of Data Handling (GMDH) type neural network identification, and the Multiple Objective Snake Optimizer (MOSO) algorithm was proposed to optimize the superconducting CUSP electromagnetic field structure. A two-dimensional axisymmetric model was established for 18-inch silicon single-crystal preparation using the Magnet system Applied Czochralski (MCZ) method. The amount of longitudinal plies of superconducting CUSP electromagnetic field coils, coil spacing, and the thickness of magnetic shields were selected as design variables, and the radial electromagnetic induction intensity at the graphite crucible inner wall and the superconducting magnet volume were used as dual objective functions. The required samples for GMDH training were provided by COMSOL Multiphysics (COMSOL) numerical calculations, and polynomial mathematical equations were established with the radial electromagnetic induction intensity at the graphite crucible inner wall and the superconducting magnet volume as the dual objective functions. Then the Pareto optimal solution for the electromagnetic field structure design variables was obtained using the dual objective function optimized by MOSO. With the hybrid strategy, numerical simulations and theoretical analysis of the crystal preparation process parameters under the effect of the superconducting electromagnetic field with the optimal structure were carried out. The results displayed that the added superconducting CUSP electromagnetic field reduced the crystal radial and axial thermal gradients and greatly suppressed the melt convection. As a result, the heat distribution inside the hot fused silicon was more even, the thermal gradient at the solid–liquid interface was reduced by 68.4%, and the oxygen impurity content was reduced by 82.1%, which effectively improved the crystal quality. The thermal field simulation results verified that the proposed hybrid strategy provided a new numerical calculation method for obtaining the optimal superconducting electromagnetic field structure.

The magnetic field design of a solenoid for the cold-cathode Penning ion source of a miniature neutron tube

A high-yield and beam-stable neutron tube can be applied in many fields. It is of great significance to the optimal external magnetic field intensity of the cold-cathode Penning ion source (PIS) and precisely controls the movement of deuterium (D), tritium (T) ions and electrons in the source of the neutron tubes. A cold-cathode PIS is designed based on the solenoidal magnetic field to obtain better uniformity of the magnetic field and higher yield of the neutron tube. The degree of magnetic field uniformity among the magnetic block, double magnetic rings and solenoidal ion sources is compared using finite element simulation methods. Using drift diffusion approximation and a magnetic field coupling method, the plasma distribution of hydrogen and the relationship between plasma density and magnetic field intensity at 0.06 Pa pressure and a solenoid magnetic field are obtained. The results show that the solenoidal ion source has the most uniform magnetic field distribution. The optimum magnetic field strength of about 0.1 T is obtained in the ion source at an excitation voltage of 1 V. The maximum average number density of monatomic hydrogen ions (H+) is 1 × 108 m−3, and an ion-beam current of about 14.51 μA is formed under the −5000 V extraction field. The study of the solenoidal magnetic field contributes to the understanding of the particle dynamics within the PIS and provides a reference for the further improvement of the source performance of the neutron tube in the future.

Rotor Design and Optimization of High-Speed Surface-Mounted Permanent Magnet Motor Based on the Multi-Physical Field Coupling Method

Rotor Design and Optimization of High-Speed Surface-Mounted Permanent Magnet Motor Based on the Multi-Physical Field Coupling Method

Coupling Analysis of Electromagnetic Vibration and Noise of FeCo-Based Permanent-Magnet Synchronous Motor

Addressing the problem of the vibration and noise of a permanent-magnet synchronous motor (PMSM), this paper optimizes the structure of a permanent-magnet motor rotator, introduces the electromagnetic-structure-acoustic coupling calculation model, and optimizes the motor rotator to reduce the vibration and noise of a permanent-magnet motor. Using the theory of Maxwell’s stress equation, the radial electromagnetic force on the stator teeth of the permanent-magnet motor is deduced and analyzed, and the correctness of the analysis calculation is verified by using the finite element multi-physical field coupling method. Based on the deduced analytical expression of the radial electromagnetic force, the sources of the radial electromagnetic force for each order and the frequency of the permanent-magnet motor are summarized. A 12-slot, 8-pole, permanent-magnet motor is taken as an example. A calculation model considering the spatial distribution of the radial electromagnetic force and the electromagnetic vibration of an iron-cobalt-based stator is established. The harmonic response of the electromagnetic vibration of the motor is analyzed, and a modal analysis is carried out. The optimized acceleration vibration noise cascade of the FeCo-based permanent-magnet drive motor under load is given. The correctness and validity of the theoretical derivation and simulation are verified by experiments.

Research on Low-Frequency Noise Control Based on Fractal Coiled Acoustic Metamaterials

In this paper, a self-similar fractal coiled acoustic metamaterial is designed for the low-frequency noise control problem by combining a perforated plate and a coiled back cavity structure. Based on the multiphysics field coupling method and thermoviscous acoustic theory, the effect of structural parameter changes on the sound absorption performance of the metamaterial structure is investigated using finite element analysis. The sound energy dissipation mechanism of the metamaterial structure is studied. Finally, 3D printing technology is used to prepare the metamaterial model structure, and the low-frequency sound absorption performance of the metamaterial structure is tested through structural sound absorption performance experiments, which verify that the metamaterial has subwavelength sound absorption performance.

Full‐time domain deformation characteristics of water drop on sheds edge causing insulation failure of large‐diameter composite post insulators under heavy rainfall

Insulation failures caused by water drops deformation on insulator sheds edge greatly threaten the stable operation of power grid. However, only few studies have focused on water drops deformation characteristics on insulator sheds edge. In this paper, full-time domain deformation of water drop was defined. The rain tests were performed to study the deformation of water drops and obtain water drops parameters under DC voltage. The water drops deformation parameter was selected according to the state of water drops when arc is generated. A fluid-electric field coupling method is employed to establish simulation model to study the influence of water drops initial diameter, initial mass flow rate, DC voltage, and conductivity on water drops deformation. It is indicated that water drops maximum deformation length before first break in simulation is in good consistency with that obtained from rain tests. The water drops initial diameter, initial mass flow rate, and DC voltage significantly influence the deformation of water drops on sheds edge. Moreover, the water drops may even bridge adjacent sheds in some cases. In contrast, the effect of water drops conductivity on the water drops deformation is not apparent.

Numerical simulation of the condensation process in high voltage switchgear based on the temperature and humidity distribution

The condensation on solid materials surface inside switchgear is an important reason threatening its safety and reliability. The formation of condensation is closely related to the temperature and humidity distribution inside the switchgear. A 3-D simplified finite element calculation model for the switchgear is established, including the bus bar, the wall bushing, the circuit breaker, the cables and other key components. Based on the electromagnetic-temperature-humidity multi-physical field coupling method, the temperature distribution inside the switchgear are calculated when the operating current flows through the bus-bar. Furthermore, the humidity diffusion process is also calculated when the relative humidity of external environment was 0.8, and the relative humidity inside the switchgear is obtained. The calculation results show that the surface humidity of the contact box of the circuit breaker is the highest whereas the temperature is the lowest, which is the location where the condensation is easy to occur.

The Optimization Design of Sound Arrester for the Dry Type Air Core Smoothing Reactor Based on the Multi‐Physical Field Coupling Method

In this paper, according to the parameters of the dry type air core smoothing reactor, the stress‐sound field and fluid‐temperature field coupling simulation model is established, the detailed temperature field and sound field distribution are obtained, and the influence law of sound arrester on the sound pressure level and temperature rise are analyzed. It can be found that the temperature rise of encapsulation coils are significantly increased when adding the sound arrester, and the reasons are given by analyzing the fluid velocity in the air ducts. Meanwhile, the optimization design method about sound arrester is proposed based on the orthogonal experiment design and finite element method. The influence curve and contribution rate of sound arrester on the pressure level and temperature rise are analyzed, and the optimal structural parameters of the sound arrester are obtained. The results show that the optimization method can significantly reduce the temperature rise and sound pressure level simultaneously, and improving the operational reliability of the smoothing reactor. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Corrosion Failure and Electrochemical Corrosion Behavior of Coiled Tubing

Coiled tubing (CT) is known to be susceptible to corrosion due to the complexity of wellbore environment and limited material selection. Since the weld seam (WS) and the base metal (BM) of CT are different in composition and microstructure, WS material usually shows very different (lower) corrosion resistance compared with BM. To better understand the corrosion-related behaviors of CT materials and the mechanism behind them, the WS and BM samples were directly processed from a finished product of CT, and a series of electrochemical experiments were conducted in laboratory conditions to study the corrosion behaviors of both WS and BM materials. The results showed that the corrosion potentials of BM and WS under the condition of 60 °C and saturated CO2 increased by 57.1% and 41.6%, respectively, comparing with the condition of no CO2 presence. Also the corrosion current of the WS was found to be 14 times of the BM’s. A corrosion model was established assuming the principles of galvanic couple corrosion applied on the working conditions of CT. The surface morphologies of the samples were analyzed by the multi-physical field coupling method. The results showed a very good consistence between the corrosion model and the experimental data. Meanwhile, this model was also used to evaluate the impacts of the welding reinforcement, the area ratio of WS and BM, and the material defects on their corrosion rates. The results indicated that the area ratio of WS and BM is in direct proportional to the corrosion rate, and the other two parameters showed very little effect.

Thermoelastic vibration analysis of disc brake based on multi-physical field coupling method

Thermoelastic vibration is the main cause of brake jitter and noise, including significant fluctuations in temperature, thermal stress, structure size and braking moment. In order to improve the reliability of thermoelastic vibration results, a multi-physical field coupling modeling method is proposed in this paper, which can realize the simultaneous calculation of temperature field, stress field and air flow field. Firstly, the theoretical analysis of the whole braking coupling process and feasibility analysis is carried out. Secondly, ABAQUS solid model and FLUENT fluid model are established respectively, and MPCCI is used to share the parameters of the two models, including temperature, node displacement and heat transfer coefficient. Finally, different paths are constructed to study the fluctuation of thermoelastic parameters in different directions. The research conclusion of thermoelastic vibration can provide important basis for optimization of brake NVH (Noise Vibration and Harshness).

Research on Temperature Rise Calculation of the Large Synchronous Compensator in UHVDC System

In order to study the temperature distribution characteristics of stator and stator winding of large dual-water internal cooling synchronous compensator. According to the fluid-solid multi-physical field coupling method, a three-dimensional calculation model of large-scale dual-water internal cooling synchronous compensator is established. Considering the complexity of the stator slot structure and the high requirement for computer performance, the simplified equivalent treatment of the stator slot structure is made. Then, based on the fluid-temperature coupled heat transfer theory, the temperature distribution is solved by finite element method with the loss of stator core and stator coil as heat source. Finally, the accuracy of temperature distribution and simplified equivalent model is verified by steady-state temperature field analysis method.

Study on laser-stricken damage to alumina ceramic layer of different surface roughness

This study examines the laser-stricken damage to different alumina ceramic surfaces of different roughness through multi-physical field coupling simulations and laser-striking experiments. The surfaces of different morphologies can be described by waves of different frequencies and amplitudes, and the waves which are discretized can be described by rectangular microstructures of different heights. In this paper, we found that the reaction of roughness surfaces to gauss lasers stricken on them could be simulated by the reaction of rectangular microstructures of different heights to laser strike. The simulation was carried out through the multi-physical field coupling method. The distribution of temperature and stress on rectangular microstructure were examined after being treated by high energy laser. It was found that overhigh temperature and stress were the main causes of laser-stricken damage, but there existed a critical rectangular column height value. The microstructure became increasingly prone to damage and fall-off with the increase of the rectangular column’s height, but it became decreasingly prone to damage after the rectangular column reached the critical value. In the experiments, seven roughness zones of alumina ceramic layer were chosen as sample surfaces for laser-striking experiment. The results showed that there was a critical roughness value at a fixed laser energy density. As a result, the amount of particles falling off the surfaces caused by laser strike was rising when the roughness was increasing. However, the amount of particles falling off the surfaces was decreasing after roughness reached the critical value. The critical rectangular column height value in the simulation corresponded to the critical roughness value in the experiment. Therefore, an appropriate selection of roughness is an important factor for obtaining high laser-stricken damage threshold.

Research on cavitation acoustic characteristics of centrifugal pump based on fluid-acoustic field coupling method

In order to study the change rules of interior acoustic field with the development of cavitation, this article presented a method that through comparing the experiment results with numerical simula...

Power Transformer Spatial Acoustic Radiation Characteristics Analysis under Multiple Operating Conditions

Spatial acoustic radiation characteristics analysis is the precondition of reducing the noise influence of outdoor power transformer while multi-physical field coupling method can be applied to quantify and reveal these acoustic characteristics of a running power transformer. In this study, based on the theoretical analysis about noise generation and dissemination process, an acoustic radiation model about oil-immersed power transformer was established and verified with field test data in time and frequency domain. Then, far-field analysis and directivity analysis were accomplished to characterize acoustic field of power transformer under multiple operating conditions. Finally, the acoustic radiation influence on potential surrounding buildings were analyzed and discussed. The visual results and conclusion provide acoustic guide for the optimal planning and design about both power substation and ambient buildings.

An overlapping domain decomposition based near-far field coupling method for wave structure interaction simulations

This paper presents a newly developed Overlapping Domain Decomposition (ODD) method, which forms the basis of a near-far field coupling solver for a wide range of wave-structure interaction problems. In this method, the computational domain is decomposed into near and far fields which are then modeled separately by solving the viscous Navier-Stokes equations (NSE) and the Potential Laplacian equation (PLE) respectively. A Finite volume method (FVM) is adopted to discretize both the NS and PL equations. The free surface problem is solved in both domains but using totally different strategies. In the potential domain, a moving mesh free surface tracking method is adopted where arbitrary polyhedral mesh adapts to the time-varying shape of the interface using vertex-based automatic mesh motion solver. Meanwhile, at the free surface, the boundary conditions are formulated using an ordinary differential equation (ODE) derived from the Bernoulli's equation. In the viscous domain, however, the volume of fluid (VOF) method is used to predict the location of free surface. The novelty of the reported method lies in two-folds. First, the introduction of the so called overlapped buffer zone eliminates the need of performing time costing iterative schemes in the non-overlapping domain decomposition methods to ensure the matching of free surface elevation at the domain boundaries. The concept of a buffer zone is borrowed from the relaxation zone technique which is commonly used near the inlet to ensure a stable wave generation or near the outlet to absorb the reflected waves in numerical wave simulations. Second, an in-house developed OVERSET method is adopted for the viscous domain solver to handle large object displacement in the case of an extreme event. The proposed method has been implemented in the OpenFOAM platform (foam-extend-3.1). To validate the method, the propagation of a solitary wave is first simulated and the resulting wave parameters are compared with the corresponding analytical, as well as pure VOF solution. Meanwhile, a comparison of the CPU time between the single domain approach and the current method has been provided. Next, the measured wave impact loading for a single body which is partially submerged will be used to further test the method. Last but not least, the method is applied to simulate the spilling wave breaking near the beach. Various numerical examples presented in the paper demonstrate the accuracy and efficiency of the proposed method. Towards the end, computation of a sinking semi-submersible platform will be presented to demonstrate further the capability of the method.

Electromagnetic-Thermal-Flow Field Coupling Simulation of 12-kV Medium-Voltage Switchgear

Long-term heating and excessive temperature rise will significantly affect the electrical and insulation performance of electric power equipment, causing the potential security risk. In this paper, the temperature rise situation under normal operation of a 12-kV medium voltage switchgear is studied through modeling and simulation method. First, in the simulation analysis of the whole switchgear, based on the theory of eddy-current field, gas flow field, and temperature field, the temperature rise distribution of the switchgear under the condition of natural convection and forced convection is simulated and analyzed. Then, several improvement methods are taken to reduce the temperature rise that emerges in the switchgear, including using spring contact finger structure to replace flexible connection structure, and also the optimization scheme of vacuum circuit breaker (VCB) pole and current transformer (CT). Then, simulation and research of different improvement schemes are conducted based on the electromagnetic-thermal-flow field coupling method. The simulation results of whole switchgear show that the above coupling method is very useful for the calculation of temperature rise. The simulation results also show that the spring contact structure is beneficial to reduce the temperature rise of vacuum interrupter and mechanical connection part. After the modification of design, the temperature rise conditions of the VCB pole and CT are significantly improved.

Non-contact resistance and capacitance on-line measurement of lubrication oil film in rolling element bearing employing an electric field coupling method

Abstract The lubrication condition of a radially loaded rolling element bearing mainly depends on the continuity of the oil film between friction pairs, which is critical for highly reliable electromechanical systems. To achieve the continuous online monitoring of the lubricating condition of the bearing oil film, a non-contact measuring method for both the oil film capacitance and resistance, which can be used to detect oil deterioration and film damage, is proposed. The method is implemented by measuring the complex impedance of the oil film using two electric field coupling paths instead of slip rings, thus avoiding mechanical contact with the rotating parts directly. This paper provides the equivalent circuit of the lubrication structure in the bearing and the operational principle, algorithm, and circuit implementation of the non-contact measurement. Verification experiments were carried out for a practical rotary mechanical system, obtaining the capacitance in the range of 50–300 pF and the resistance in the range of 50 kΩ–2 MΩ with error less than 15%, which is sufficient for practical on-line lubrication monitoring. The proposed method has a wide range of applications in high-reliability, high-speed, and precise suspension systems.